The Roles of Lysosomes in Inflammation and Autoimmune Diseases.

International Reviews of Immunology, Early Online:1–17, 2014 C Informa Healthcare USA, Inc. Copyright ISSN: 0883-0185 print / 1563-5244 online DOI: 10.3109/08830185.2014.936587

REVIEW ARTICLE

The Roles of Lysosomes in Inflammation and Autoimmune Diseases

Int Rev Immunol Downloaded from informahealthcare.com by Universiteit Twente on 12/10/14 For personal use only.

Wei Ge,1,∗ Dongxu Li,2,∗ Yanpan Gao,1 and Xuetao Cao1 1

National Key Laboratory of Medical Molecular Biology & Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Dongdan Santiao 5 #, Dongcheng district, Beijing, China; 2 Key Laboratory of Structure-Based Drug Design & Discovery, Ministry of Education, School of Pharmaceutical Engineering, Shenyang Pharmaceutical University, Wenhua road 103 #, Shenhe district, Shenyang, China

Lysosomes perform a range of functions, some of which, such as degradation, are common to all cell types. Others, such as secretion or lysosomal exocytosis, are more specialised and tend to involve fusion of this organelle with the cell surface to release its contents. This review describes lysosomal regulation of the inflammatory glucocorticoid signaling pathways, and summarizes the roles of lysosomes in negatively or positively modulating the production of inflammatory cytokines. We also review the characteristic changes in lysosomal hydrolases and membrane proteins in common autoimmune diseases. Finally, future directions in lysosome research are proposed, with it being suggested that the role of lysosomes will continue to be of growing interest in immunity research. Keywords: autoimmune diseases, cytokines, inflammation, lysosome

INTRODUCTION Lysosome is an organelle of eukaryotic cells that is critically involved in the degradation of macromolecules mainly delivered by endocytosis and autophagocytosis. Degradation is achieved by more than 60 hydrolases sequestered by a single phospholipid bilayer. As early as 1979, it was reported that lysosomal enzymes can inactive the glucocorticoid receptor-Hsp90 complex by ‘changing’ this complex to a smaller form, preventing the interaction of GR and glucocorticoids. In 1997, Tanaka and Sakanaka found that glucocorticoids promoted lysosomal vacuolation in microglial cells, and that the GR mediated an increase in cytoplasmic vacuoles and a significant suppression of acid phosphatase activity. In 2011, it was reported that lysosomes modulate glucocorticoid signalling and the inflammatory response. These studies show that the lysosomal activity is negatively correlated with the anti-inflammatory effect of glucocorticoids, an effect which occurs through the glucocorticoids signalling pathway. Accepted 13 June 2014. ∗ These authors contributed equally to this work. Address correspondence to Dr. Wei Ge and Dr. Xuetao Cao, National Key Laboratory of Medical Molecular Biology & Department of Immunology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Dongdan Santiao 5 #, Dongcheng district, Beijing 100005, China. E-mail: [email protected] or [email protected]






W. Ge et al.

In addition to glucocorticoid receptor regulation, secretory lysosomes can secrete or degrade inflammatory cytokines to regulate the release of cytokines (eg. IL-1β, IL18 and TNF-α) in the immune response. Thus, lysosomes can both positively and negatively regulate inflammation. A feedback mechanism exists to adjust the balance of the inflammatory response in cells and organelles. Furthermore, the involvement of a lysosomal membrane protein (such as TMEM9B) in the activation of the NF-κB and MAPK pathways suggests that the lysosomal compartments may play a central role in the inflammatory signalling network. In this review, we discuss key recent findings in the field and highlight some of the areas in which lysosomes play a role in inflammation. We also reviewed the characteristic changes in lysosomal hydrolases and membrane proteins in common autoimmune diseases. Finally, future directions in lysosome research are proposed, with it being suggested that the role of lysosomes will continue to be of growing interest in immunity research. Lysosomes Degrade Glucocorticoid Receptors in Inflammatory Pathways As early as 1979, it was reported that lysosomal enzymes can inactive the glucocorticoid receptor (GR)-Hsp90 complex by ‘changing’ this complex to a smaller form, preventing the interaction of GR and glucocorticoids (GC) [1](BOX 1). BOX 1 Anti-inflammation Mechanism of Glucocorticoids Glucocorticoids (GCs), steroidal anti-inflammatory drugs, are widely used for the treatment of inflammation. Their anti-inflammatory effects are brought about by their binding to the GR. The GR-GC complex is able to shuttle between the nucleus and cytoplasm. In the inactive state, the GR forms a complex with Hsp90 and is localised in the cytoplasm. When it is activated by binding GCs, the GR-GC dissociates from the GR-Hsp90 complex with the conformational change in the GR, which enables GRGC to translocate into the nucleus [2]. As a transcription factor, the GR-GC complex plays an anti-inflammatory role via two major pathways: i) The GR-GC complex interacts with nuclear factor κB (NF-κB) and activating protein 1 (AP-1), downregulating the expression of pro-inflammatory genes, including IL-1β, IL-6 and TNF-α; ii) The GR-GC complex binds to glucocorticoid response elements (GRE) in the nucleus, upregulating the expression of anti-inflammatory genes, including lipocortin-1, β2adrenoceptor and annexin-1 [3, 4]. Both pathways ultimately act on the arachidonic acid metabolic pathways, leading to reduced expression of PLA-2 and COX-2, thus decreasing prostaglandin (PG) secretion and suppressing inflammation [5]. In 1997, Tanaka and Sakanaka found that GCs promoted lysosomal vacuolation in microglial cells, and that the GR mediated an increase in cytoplasmic vacuoles and a significant suppression of acid phosphatase activity [6]. Since acid phosphatase activity is characteristic of lysosomes, they proposed that lysosomes play a role in the GR-mediated anti-inflammation pathway. In 2011, He et al. demonstrated that lysosomes modulate GC signalling and the inflammatory response [7]. They found that lysosomes promote inflammation by fusing with autophagosomes and degrading the GR (Figure 1). In He’s study, chloroquine, a weak base, was used to inhibit the activity of lysosome by neutralising the acidic lysosomal enzymes. The combination of chloroquine and dexamethasone (Dex, a GC drug) significantly relieved symptoms of arthritis in a mouse model, indicating that combination therapy is more effective than Dex alone. Other lysosomal function inhibitors, such as the V-ATPase inhibitor bafilomycin A1, may also enhance the anti-inflammatory activity of Dex. Moreover, a knockdown International Reviews of Immunology


lysosome Inflammation Autoimmune Diseases



Figure 1. GR-GC plays an anti-inflammatory role via two pathways. First, by interacting with nuclear factor κB (NF-κB) and AP-1, GR-GC down-regulates the expression of pro-inflammatory cytokines, such as IL-1β, IL-6, and TNF-α. Second, by binding GRE of DNA in the nucleus, the GR-GC dimer up-regulates the expression of anti-inflammatory genes such as lipocortin-1, β2adrenoceptor and annexin1. Both pathways ultimately act on the arachidonic acid metabolic pathways, leading to the reduced expression of PLA-2 and COX-2, and decreased secretion of PGs, suppressing inflammation. But when GR is degraded through the lysosome-mediated autophagy pathway, the abundance of GR in cytoplasm is reduced, and subsequent GR-GC anti-inflammatory activity is inhibited.

of transcription factor EB (TFEB), a lysosomal biogenesis regulator [8], decreased the number of lysosomes in cells, subsequently increasing the concentration of GRs and the anti-inflammatory effect of Dex [7]. These studies show that the lysosomal activity is negatively correlated with the antiinflammatory effect of Dex, an effect which occurs through the GC signalling pathway (Figure 1). This provides the theoretical basis for developing anti-inflammatory medicine combinations that consist of a lysosomal inhibitor and GCs, in order to reduce the dose of GCs, minimise GC side effects, improve efficacy and overcome GCdrug resistance. There is therefore a clear clinical rationale for the development of lysosomal inhibitors. However, the dynamic regulating mechanism between lysosome function and the GC signalling pathway remains unclear. Lysosomes Regulate the Secretion of Inflammatory Cytokines In addition to GR regulation, secretory lysosomes can secrete or degrade inflammatory cytokines to regulate the immune response (Table 1). Secretory lysosomes can undergo regulated cytokine release in response to external stimuli, such as lipopolysaccharide (LPS) and ATP (reviewed in [9]). IL-1β and IL-18 Secretory lysosomes can either promote or suppress inflammation, depending on the stage of the inflammatory response (Figure 2). Pro-inflammatory effects occur primarily as a result of the exocytosis of IL-1β [10]; an inflammatory signal (such as LPS) C Informa Healthcare USA, Inc. Copyright



W. Ge et al.

TABLE 1.


Cytokines

Interactions between lysosome and cytokines. Interactions between lysosome and cytokines

Reference

IL-1β

Pro-IL-1β is transformed into IL-1β by caspase-1 by interacting with Rab39a in lysosomes. Active IL-1β is secreted by lysosome exocytosis.

[10, 14]

IL-18

Similarly to IL-1β, IL-18 can reach the extracellular space via secretory lysosomes. This process is regulated by extracellular calcium influx along the microtubular cytoskeleton.

[21, 22]

IL-6 IFN-β TNF-α

Lysosome-associated small RabGTPase Rab7b mediates inhibition of TLR4 and TLR 9 signaling, which downregulate LPS-induced production of TNF-α, IL-6 and IFN-β. IL-6 stimulation induces lysosome-dependent degradation of gp130, which is critical for the cessation of IL-6-mediated signaling. Hypoxia enhances lysosomal TNF-α degradation. Secretion of TNF-α may be localised to secretory lysosomes; TNF-α cytotoxic signaling induces lysosomalpermeabilisation.

[23, 30, 31, 33, 97]

IL-8

Lysosomal PGN processing is required for production of TNF-α in monocytes and for IL-8 production in neutrophils. Lysosomal hydrolase-modified LDL can trigger the expression of IL-8 in macrophages.

[38, 39]

TGF-β

SNX25 negatively regulates TGF-β signaling by enhancing the degradation of TGF-β receptor I. TGF-β1 increases its cellular expression of the receptor (integrin α5β1) by preventing integrin α5β1 degradation.

[36, 37]

promotes the synthesis and cytoplasmic accumulation of the IL-1β precursor (proIL-1β) which then translocates into secretory lysosomes together with caspase-1. This translocation requires a pH difference between the cytosol and the lysosomal lumen. Caspase-1 is responsible for the transformation of the pro-IL-1β into its mature form, with the prerequisite that caspase-1 must interact with Rab39a (BOX 2) [11]. BOX 2 Interleukin-1β Interleukin-1β (IL-1β), a potent pro-inflammatory cytokine, is the most studied member of the IL-1 family because of its role in mediating inflammatory and autoimmune diseases [12]. Most proteins that are secreted from the cell contain signal peptides that direct their transport to the plasma membrane through the endoplasmic reticulumGolgi pathway. However, certain proteins, such as IL-1β, do not contain signal peptides and are secreted by unconventional means. In the case of IL-1β, these include secretory lysosomes, microvesicle shedding, membrane transporters and multivesicular bodies (reviewed in [13]). Rab39a During an inflammatory response, Rab39a is a trafficking adaptor linking caspase1 to IL-1β secretion. Recombinant caspase-1 cleaves Rab39a at a highly-conserved cleavage site. Pro-inflammatory stimuli induce Rab39a expression, while Rab39a International Reviews of Immunology





Figure 2. The lysosome-mediated inflammatory pathways. Pro-inflammatory pathway: Exogenous ATP activates cell membrane P2×7 receptor resulting in K+ efflux. The consequent decrease in the concentration of intracellular K+ concentration promotes inflammasome assembly and activates iPLA2, involved in transforming pro-caspase-1 into caspase-1. Caspase-1 is transported to the lysosome lumen by an as-yet-unknown mechanism. In addition, decreased K+ concentration stimulates cytosolic phosphatidylcholine specific phospholipase C (PC-PLC), which activates Ca2+ pumps in the plasma membrane, resulting in the influx of Ca2+ . The increasing intracellular concentration of Ca2+ can activate cPLA2 that is suggested to promote the lysosome exocytosis process. A fraction of cytoplasmic pro-IL-1β and pro-caspase-1 colocalise in secretory lysosomes and are secreted together with lysosomal hydrolases such as cathepsin D. Anti-inflammatory pathway: some flightless (Flii) localises to lysosomes and is secreted through a lysosomal pathway. Flii can inhibit caspase-1 as a pseudosubstrate, suppressing caspase-1-mediated maturation of the cytokine pro-IL-1β to IL-1β in macrophages, thus reducing IL-1β secretion. In addition, secreted flightless dampens the production of pro-inflammation cytokines by binding to LPS.

knockdown reduced IL-1β secretion (though pro-IL-1β mRNA levels are unchanged). Rab39a regulates the activation of pro-IL-1β to give IL-1β, while the expression of TNF-α is unchanged. Therefore, Rab39a is specific for IL-1β secretion. In contrast, overexpression of Rab39a results in an increase in IL-1β secretion, while overexpression of a Rab39a construct lacking the caspase-1 cleavage site leads to an additional increase in IL-1β secretion. Therefore, cleavage of Rab39a by caspase-1 would appear to serve as a mechanism for inactivating Rab39a, thereby reducing levels of IL-1β secretion [11]. IL-1β and other lysosomal contents are released into the extracellular space after the fusion of lysosomes with the plasma membrane, which is driven by exogenous ATP and by hypotonic conditions [10]. In 2004, Andrei and his colleagues verified the molecular mechanism of lysosome-mediated IL-1β secretion [14] (Figure 2). They suggest that an increase in intracellular Ca2+ during the secretion process mobilises secretory lysosomes. This change occurs along microtubules close to the microtubule organizing center [15], and is proceeded by actin-based movement at the cell periphery, towards the docking site at the plasma membrane. A number of lysosomal membrane proteins, e.g. soluble N-ethylmaleimide–sensitive factor attachment protein receptors (SNARES) and the Rab-GTPase family, have a crucial role to play in C Informa Healthcare USA, Inc. Copyright




W. Ge et al.

intracellular protein movement [9–16] and fusion between secretory lysosomes and the plasma membrane [17, 18] during the course of lysosome exocytosis. In short, ATPinduced IL-1β processing occurs within the secretory lysosome, positively regulating inflammation. Do lysosomes always have a positive regulatory function in inflammationmediated processes? The findings of Li et al. suggest not, as they have found that lysosomes can negatively modulate inflammatory by secreting flightless [19]. Flightless, a member of the gelsolin superfamily of actin-remodelling proteins, inhibits caspase1 by acting as a pseudo-substrate. This prevents caspase-1-mediated maturation of the cytokine pro-IL-1β to IL-1β in macrophages, thus reducing IL-1β secretion (Figure 2). The observation that knockdown of endogenous flightless enhances caspase-1 activity, and its overexpression inhibits caspase-1 activity and IL-1β maturation [19] supports this. In 2012, Lei et al. discovered that some flightless localised to lysosomes and is secreted through a lysosomal pathway in fibroblasts and macrophages [20]. Secreted flightless inhibits the production of pro-inflammatory cytokines by binding to LPS (Figure 2). Moreover, LPS-stimulating macrophages or scratch-wounding fibroblasts can upregulate the secretion of flightless, which in turn may have a modifying effect on wound inflammation and inhibit excessive cytokine production [20]. Similar to IL-1β, the secretion of IL-18 in dendritic cells (DCs) is also mediated by secretory lysosomes and regulated by extracellular Ca2+ influx [21].The reorganisation of cytoskeletal proteins is fundamental to this calcium-dependent process. The role played by secretory lysosomes is evidenced by the observation that the release of the lysosomal enzyme cathepsin D is comparable to the secretion of IL-18 in natural killer/immature DC cocultures [22]. TNF-α The pro-inflammatory cytokine tumor necrosis factor alpha (TNF-α) can regulate both cell survival and cell death, and can be regulated by lysosomes. The fate of TNF-α depends on cellular oxygen levels [23]. It is not uncommon for inflamed lesions to become severely hypoxic due to the fact that hypoxia can generate inflammation [24]. In the case of normoxia TNF-α is conveyed from the early endosome to the secretory lysosomes via the lysosome, and finally to the plasma membrane. In the hypoxic inflammatory micro-environment, TNF-α moves from the membrane towards the lysosome, enhancing its degradation [23]. Nitza et al. found that levels of TNF-α mRNA are unchanged in hypoxia, but intracellular TNF-α protein levels are decreased, and its secretion in mouse peritoneal macrophages is suppressed. This suggests enhanced degradation of TNF-α protein in hypoxia [23]. Whilst the quantity of secreted TNF-α was unaffected by the addition of the lysosome inhibitor bafilomycin A1, the degradation of intracellular TNF-α was dose-dependently inhibited. However, this only occurred under hypoxia, from which it can be inferred that intracellular TNF-α is directed to the lysosomes from the early endosomes, to boost its degradation during hypoxia [23]. To the best of our knowledge, this is the first time it has been reported that secretion of TNF-α is localised to secretory lysosomes, though this intact pathway remains to be established. Bastow et al. found that the SNAREs superfamily members vesicle-associated membrane protein (VAMP7 and VAMP8) potentially mediate lysosomal exocytosis in hypertrophic chondrocytes [25]. This finding is intriguing in the context of osteoarthritis (OA). While severe synovial inflammation, such as that found in rheumatoid arthritis, is absent in OA, moderate levels of joint inflammation can be found. OA chondrocytes express inflammatory cytokines including IL-1, TNF-α and IL-6. Pushparaj et al. demonstrated that TNF-α colocalises with VAMP8-containing vesicles, and that in VAMP8-deficient macrophages, TNF-α release is inhibited [26]. TNF-α release in International Reviews of Immunology





macrophages and proper trafficking of secretory lysosomes for exocytosis both require the VAMP8 vesicle-associated-SNARE. Interestingly, the SNARE proteins VAMP7 and VAMP8 have previously been shown to mediate fusion of late endosomes and lysosomes, respectively [27, 28]. It is tempting to speculate that as VAMP8 and TNFα are colocalised in secretory lysosomes, there may be a lysosome-associated pathway mediating the secretion of TNF-α, as occurs for IL-1β. As explained above, in inflammation-induced hypoxia, lysosomes in the inflammatory cells increase TNFα degradation, thereby reducing its secretion and release. This reduces the proinflammatory effects of TNF-α. Furthermore, lysosomes are involved in inducing apoptosis in the TNF-α cytotoxic signalling cascade; this pathway triggers lysosomal permeabilisation, releasing the pro-apoptotic lysosomal protease cathepsin B into the cytosol. Thus, TNF-α sets a complex signalling network into action. This network, in which the lysosome has a key role, facilitates biological responses that range from apoptosis to inflammation. Further studies verified such conclusions at the molecular level: in 2008, Francis et al. identified the lysosomal transmembrane protein 9B (TMEM9B, an N-glycosylated protein) as an important component of the TNF signalling pathway and a module shared with the IL-1β and Toll-like receptor (TLR) pathways [29]. The fact that TMEM9B is crucial to the TNF-mediated activation of both the NF-κB and MAPK pathways, but is not a prerequisite for TNF- or Fas ligand-induced apoptosis, suggests that TMEM9B plays a specific role in inflammatory cytokine signaling [29]. The localisation of TMEM9B in lysosomes suggests that this organelle is involved in the regulation of signal transduction downstream of inflammatory receptors.

IL-6, IFN-β, TGF-β and IL-8 IL-6, probably the most extensively studied cytokine, is generally regarded as a pro-inflammatory factor. Lysosomes are involved in the production of IL-6 and its downstream signalling pathways. Wang et al. found that Rab7b (a lysosomeassociated small Rab GTPase) could serve as a negative regulator of TLR4 signalling in macrophages by accelerating lysosomal degradation of TLR4 and decreasing the plasma membrane TLR4 expression level [30]. This resulted in the hyposensitivity of macrophages to LPS stimuli and inactivated the MAPK, NF-κB, and IRF3 pathways, in turn down-regulating the LPS-induced production of TNF-α, IL-6 and IFN-β. Yao et al. reported that Rab7b functions as a negative regulator of intracellular-localised TLR9 signalling in macrophages by enhancing trafficking of TLR9 to the lysosome for degradation [31]. This led to the suppression of TLR9-triggered generation of proinflammatory cytokines such as TNF-α, IL-6, and IFN-β by impairing activation of MAPK and NF-κB pathways. Rab7b-mediated inhibition of TLR4 and TLR9 signalling may serve as a feedback mechanism to prevent excessive inflammatory responses. However, in some specific cells, Rab7 can also promote the production of IL-6. For example, Rab7b plays an important role in megakaryopoiesis by activating NF-κB and promoting IL-6 production [32]. The IL-6 receptor complex consists of two ligand-binding α subunits and two signal-transducing subunits known as gp130. Lysosomes can degrade gp130, reducing the net number of surface-bound gp130 molecules, thus reducing IL-6-dependent STAT3 activation and downstream gene expression [33]. Tanaka et al. reported that IL-6 stimulation induced lysosome-dependent degradation of gp130, which is critical for cessation of IL-6-mediated signaling [34]. Furthermore, a complex interaction of diverse cytokines, that crosstalk on numerous levels, is part of the inflammatory response. Simone et al. found that IL-1β and TNF-α induce gp130 internalisation and its subsequent lysosomal degradation [35]. Consequently, the potential additive C Informa Healthcare USA, Inc. Copyright




W. Ge et al.

pro-inflammatory effects of these cytokines are impeded by the inhibitory activity of IL-1β and TNF-α on IL-6 signalling. Lysosomes can block inflammatory signalling pathways by degrading cytokines’ receptors, which are regulated by certain intracellular protein. For example, TGF-β signalling is negatively regulated by the protein sorting nexin (SNX25), a member of the sorting nexin family, which performs cargo sorting and signalling functions within the endocytic network. Through clathrin-dependent endocytosis and subsequent lysosome degradation, SNX25 enhances the degradation of the TGF-β receptor I [36]. Inflammatory cytokines can also inhibit the lysosomal degradation of their own receptors. For example, TGF-β1 increases expression of its cellular receptor (integrin α5β1) by preventing lysosome-mediated integrin α5β1 degradation [37]. Some inflammatory stimuli, such as Bacillus anthracis peptidoglycan (PGN), must be processed by the lysosome in order to be identified by the corresponding receptors, as PGN itself is not a stimulus for the sensor [38]. Lysosomal enzymes degrade PGN to a simpler moiety that can be recognised by a cytoplasmic sensor, leading to subsequent production of TNFα in monocytes and IL-8 production in neutrophils [38]. Pro-inflammatory agents can also be regulated through extracellular secretion of lysosomal enzymes. For example, cultured macrophages can release lysosomal acid lipases in the presence of inflammatory stimuli. These produce morphologically-modified Low-Density Lipoprotein, known as hydrolase-modified Low-Density Lipoprotein [39], which was shown to initiate IL-8 expression in macrophages via activation of the p38 MAPK and NF-κB pathways [39]. In summary, lysosomes can both positively and negatively regulate inflammation. We speculate that a feedback mechanism exists to adjust the balance of the inflammatory response in cells and organelles. Following an inflammatory stimulus, lysosomal secretion of pro-inflammatory cytokines can promote inflammation. However, after prolonged or severe inflammation, lysosomes can inhibit inflammatory cytokine production. A balance of both regulatory roles in the inflammatory response enables the body to maintain a state of equilibrium. Inflammation is a protective response of organisms to pathogens, irritation or injury. Whereas restricted inflammation is beneficial, excessive or persistent inflammation incites tissue destruction and disease. A disturbed balance between the activation and inhibition of inflammatory pathways can set the stage for chronic inflammation, which is increasingly recognised as a key pathogenic component of autoimmune, metabolic, cardiovascular and neurodegenerative disorders [40]. Therefore, the positive and negative regulation of inflammation by “flexible” lysosomes plays a significant role in maintaining the pro/anti-inflammatory balance. Furthermore, the involvement of a lysosomal membrane protein (such as TMEM9B) in the activation of the NF-κB and MAPK pathways suggests that the lysosomal compartments may play a central role in the inflammatory signalling network. It is possible that lysosomes contain more membrane proteins associated with inflammation, which are involved in the regulation of intracellular signalling pathways. These proteins are potentially new drug targets for the development of anti-inflammatory combination treatments. Lysosome and Autoimmune Diseases The lysosomal compartment plays a central role in a variety of cellular pathways that are important for normal immune system function. For example, a functional lysosomal compartment is required to process and present antigens, allowing MHC-I and MHC-II to exert their immunomodulatory effects [41]. In autoimmune diseases, organisms produce autoantigens (such as nuclear antigens) that the immune system cannot distinguish from normal antigens. Lysosomal enzyme activity controls the generation of autoantigens. For example, lysosomal International Reviews of Immunology




a-galactosidase A (a-Gal-A) degrades lipid antigens to prevent their accumulation and activation of the self lipid-reactive and CD1d-restricted NKT cells. Deficiency in aGal-A causes aberrant accumulation of lipid antigens and activation of immature NKT cells, resulting in autoimmunity [42]. In the MHC-II-mediated autoantigen processing and presentation pathway, the lysosome is like a key signalling hub, where endocytic, exocytic and degradation pathways intersect (BOX 3) (Table 2).


BOX 3 MHC-II-mediated Autoantigen Presentation Pathway Within the lysosomes of antigen presenting cells (APCs, e.g. DCs), self-antigens are degraded into antigenic peptides by lysosomal proteases. After synthesis in the endoplasmic reticulum, MHC-II is associated with the invariant chain (Ii). On stimulation, it is targeted to lysosomes (here also called MHC-II compartments), where lysosomal cathepsin S degrade Ii, leading to MHC-II maturation (for details see [43, 44]). Newly-synthesised MHC-II binds antigenic peptides to form the MHC II-peptide complex on the lysosome membrane. MHC-II-containing lysosome exocytosis and fusion with the plasma membrane ultimately delivers the peptide-MHC II complexes to the cell surface [45]. Activated DCs express co-stimulatory molecules of MHC II (e.g. CD28, CD40L) and efficiently present autoantigen peptides to CD4+ helper T-cells. These then activate B cells to become plasma cells, which subsequently produce large amounts of autoantibodies [46]. Due to the loss of self-tolerance, the immune system processes and presents these autoantigens as usual, subsequently inducing the production of autoantibodies. The autoantibodies react with self-components which are often macromolecular complexes of proteins and nucleic acids, in the nucleus and cytoplasm to form immune complexes that can accumulate in the kidneys and other tissues and lead to autoimmune diseases [47]. The next section summarises the critical role of lysosomes in some common autoimmune diseases, including systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Lysosomes and SLE SLE is a multi-factorial disease characterised by autoimmune responses against selfantigens generated by dying cells. A deficiency in the clearance of apoptotic cells is thought to be one of the causes of SLE [48]. Apoptotic cells are engulfed by macrophages, and then transferred to lysosomes. Here, their components are degraded into amino acids, nucleotides, fatty acids and monosaccharides by lysosomal enzymes. For example, DNase II-like acid DNase and cathepsins degrade the nucleosomes of apoptotic cells [49]. If the degradation does not occur properly, dead cell components (especially the nucleosomal DNA) accumulate in the lysosomes, leading to the intracellular activation of the innate immune system to produce proinflammatory cytokines, such as IFN-β and TNF-α [50]. The increased levels of the pro-inflammatory cytokines are believed to play a role in the pathogenesis of SLE [51], so cytokines have been suggested as therapeutic targets in SLE (reviewed in [52]). Obvious changes take place in the lysosome membrane proteins and lysosomal enzymes in the pathogenesis of SLE, which provide some evidence for the role of lysosomes in the SLE pathogenesis. It has been proposed that a possible gauge for disease activity in patients with SLE, could be the manifestation of lysosomeassociated membrane proteins (LAMPs) on the surface of peripheral blood mononuclear cells (PBMCs) [53]. Shayman et al. discovered, cloned and characterised lysosomal phospholipase A2 (LPLA2) [54, 55]. They found that LPLA2 knockout mice, older than one year, have abnormal serologies, including anti-dsDNA antibodies, positive C Informa Healthcare USA, Inc. Copyright



Type 1 diabetes (T1D)

Graves’ disease

Sjögren’s syndrome (SjS)

Multiple sclerosis(MS)

Psoriasis

Rheumatic arthritis (RA)

Systemic lupus erythematosus (SLE)

Graves’ hyperthyroidism is accompanied by a general increase in the activity of the serum lysosomal glycolsidases. The Cathepsin L mRNA expression of peripheral CD8+ T cells from T1D model mice is significantly increased compared with that of control mice. Cathepsin S or cathepsin B deficiency in NOD mice leads to a decrease in T1D incidence, whereas deficiency in cathepsin L exhibit complete resistance to the disease. Cathepsin G activity is higher in PBMCs from T1D patients compared to controls. Cathepsin G is involved in proinsulin (autoantigen of T1D) processing.

Lysosomal degradation breakdown of dead cells leads to production of pro-inflammatory cytokines, such as IFN-β and TNF-α. Lysosome-localised TLRs mediate the production of IFN-α whichhas a crucial role in the pathogenesis of SLE. Cathepsin K is a critical protease in synovial fibroblast-mediated collagen degradation and is elevated in the serum of RA patients [50–53]. Cathepsin S is significantly upregulated in the synovial fluids from RA patients [59,60]. Cathepsin L has a significant impact on RA severity [63]. Lysosomal exoglycosidases participate in the destruction of the articular cartilage [65]. In psoratic epidermis, cathepsins L, B and D are partially processed to activated mature forms, where they are presented high percentage and difuse expression in psoriatic epidermis. The degradative capacity of cathepsin D is responsible for the disordered differentiation and scale formation characteristic of psoriasis. Cathepsin S upregulation in MS patients during the relapse state, in RNA form from peripheral blood leucocytes and in serum proteins. Cathepsins S and D exist from precursor to mature forms in the CD34+ hematopoietic stem cells (HSCs) and are markedly more abundant in the acute-MS group as compared to the stable-MS. Increased activities of lysosomal glycosidases and peptidases were found in leukocytes from subjects who had been suffering from SjS for more than 5 years. Cathepsin S and H activities are significantly higher in the SjS mouse model than in control lysates.

Negative role or characteristic change of lysosomal enzymes in these diseases

Lysosomes and autoimmune diseases.

Autoimmune diseases

TABLE 2.

[82–86]

[87, 88]

[89, 90]

DC-LAMP levels are higher in psoriasis vulgaris lesions.

The levels of Cathepsins S and D expression in the CD34+ HSCs.

Lysosomal β-glucuronidase and dipeptidyl peptidase I as SjS marker enzymes. Cathepsin S expression in tears represents a biomarker for diagnosis of SjS. The serum lysosomal glycolsidases activity. Inhibition of cathepsin L as a powerful therapeutic strategy for autoimmune diabetes. Cathepsin G inhibitor reduces proinsulin-reactive T cell activation.

[60, 61, 63, 69, 70, 73, 75]

Activity levels of lysosomal exoglycosidases and cathepsins K, S and L.

[94–96]

[91]

[50, 53, 57]

Reference

Expression of Lamps on PBMC surface. LPLA2 activity.

Diagnostic indicators and therapeutic targets






anti-nuclear antibodies, and high circulating immunoglobulin levels. They also develop lymphoid hypertrophy and glomerulonephritis. This autoimmune phenotype resembles SLE [56]. Thus, LPLA2 activity has been suggested as a diagnostic and therapeutic target for SLE patients [57]. IFN-α has a crucial role in the pathogenesis of SLE including direct and indirect effects on APCs, T cells and B cells (reviewed in [58]). The lysosome-localised TLRmediated innate immune pathways regulate the production of IFN-α, TLR7 and TLR9. They occur in an inactive state in the plasmacytoid DCs of the Golgi complex, and are cleaved and activated in the lysosomes by acidic proteases. They can thusly interact with nucleic acids (single-strand RNA in the case of TLR7, DNA in the case of TLR9) that specialised receptors, such as Fcγ receptors, present to lysosomal compartments [59]. Activated TLRs stimulate the production of IFN-α via the MyD88-dependent IRF5/IRF7 pathways. This IFN-α-inducing activity can be inhibited by lysosome inhibitors such as chloroquine or bafilomycin A, blocking the activation of TLR7 and TLR9 [47]. In summary, lysosomes are implicated in the promotion of MHC class II presentation of autoantigens, degradation of apoptotic cells and the production of cytokines in patients with SLE. Lysosomes and RA RA is an autoimmune disease with unknown etiology, but it is probably a result of loss of self-tolerance. One of the disease hallmarks of RA is progressive cartilage and bone destruction in the joints, which is caused by the increased activity of a huge number of proteases that are secreted by several cell types in arthritic joints, such as synovial fibroblasts and osteoclasts. Lysosomal cysteine cathepsins have been identified as proteases that could potentially be involved in the pathogenesis of RA. For example, cathepsin K is a critical protease in synovial fibroblast-mediated collagen degradation [60, 61]. Skoumal et al. demonstrated that cathepsin K is elevated in the serum of patients with RA [62]. Overexpression of cathepsin K in transgenic mice makes them susceptible to progressive synovitis, which results in degradation of articular cartilage and bone [63]. However, the results of Schurigt et al. also point to alternative cathepsin K–independent mechanisms for bone destruction. They studied the effect of cathepsin K knockout in human TNF-transgenic mice (hTNFtg mice). These mice are used as a model of human RA, and have chronic polyarthritis, similar to human RA, with spontaneously developing inflammation and bone destruction. Cathepsin K knockout partially inhibited, but did not prevent, arthritic bone resorption [64, 65]. Nonetheless, cathepsin K is a valuable parameter for the assessment of bone metabolism in patients with established RA. Pharmacological inhibitors of cathepsin K such as MK-0822 [66], L-006235 [67] and icariin [68], have been studied extensively for the purpose of preventing bone erosion and joint destruction in RA. Cathepsin S is integral to the processing of MHC class II–Ii in autoantigenpresenting cells, which produces class II molecules that are competent for binding antigenic peptides. Cathepsin S knockout mice had a decreased susceptibility to RA and presented reduced invariant chain processing in B cells and DCs alike [69]. Cathepsin S is significantly upregulated in the synovial fluids from RA patients, consistent with its crucial role in the MHC class II-mediated immune response [70]. Cathepsin S inhibitors show potential for use in the treatment of autoimmune diseases. For instance, Weidauer et al. described the efficient inhibition of cathepsins K and S by two gold derivatives (auranofin and gold thiomalate) [71]. CSI-75, a potent and selective cathepsin S inhibitor, suppressed clinical signs and symptoms in experimental models of RA [72]. C Informa Healthcare USA, Inc. Copyright




W. Ge et al.

The severity of antigen-induced arthritis (AIA, a Th cell-dependent RA model) is inhibited in cathepsin L knockout mice, as characterised by reduced swelling, decreased inflammation and bone destruction [73]. In this study, the researchers proposed that cathepsin L has a significant impact on RA severity by influencing the selection of Th cell population in the thymus, but it seems not to play any significant role in direct joint destruction. In 2004, Schedel et al. showed that ribozymes cleaving cathepsin L mRNA are able to both decrease the synthesis of cathepsin L and reduce the invasion of RASF (synovial fibroblasts) into cartilage and subsequent cartilage destruction [74]. By cleaving glycoside bonds in glycoproteins and proteoglycans, lysosomal exoglycosidases (including β-glucuronidase, β-galactosidase, hexosaminidase, α-mannosidase and α-fucosidase) contribute to the destruction of the articular cartilage [75]. The serum of patients with RA shows a notable increase in the activity of all exoglycosidases, and likewise almost all exoglycosidases (with the exception of β-galactosidase and α-mannosidase) show increased activity in synovial fluid, with hexosaminidase as the principal enzyme [75]. TNF-α is a major cytokine in the pathogenesis of RA, orchestrating synovial inflammation and bone degradation. For example, RA synovial fibroblasts are stimulated by TNF-α to multiply and generate chemokines, growth factors, proteinases and adhesion molecules and it is thusly vital to the RA disease process [76]. Autophagy is a lysosome-mediated catabolic process that is also involved in autoimmune diseases. Continuous removal of these proteins by the lysosome-autophagy and ubiquitinproteasome protein degradation pathways is necessary for survival of synovial fibroblasts. Both pathways are more active in RA synovial fibroblasts than inother fibroblasts [77]. In addition, Lin et al. verified the role of autophagy in joint destruction in RA [78]. They demonstrated that autophagy is activated by TNF-α in RA osteoclasts, and stimulates osteoclast differentiation and bone destruction. In contrast to their aforementioned role in promoting tissue damage in RA, lysosomes may also exert a protective role: human six-transmembrane epithelial antigen of prostate 4 (STEAP4), localised in lysosomes, is regulated by TNF-α in synovium, where it inhibits IL-6/IL-8 secretion and proliferation of fibroblast-like synoviocytes. These findings suggest that STEAP4 might potentially suppress the pathogenesis of TNF-α-induced RA [79]. During arthritis, the lysosomal membrane is altered, causing lysosomes to fuse with the cell membrane and extrude the aforementioned enzymes. Accordingly, recent drug development efforts have focused on enhancing lysosomal stability to prevent the release of these enzymes in order to reduce the pain suffered by RA patients [80, 81]. In summary, during the RA pathological process, a variety of active enzymes from the lysosome are secreted into the jointcavity, damaging articular cartilage. In contrast, some lysosomal proteins such as STEAP4 can suppress RA by inhibiting inflammatory cytokine production or the proliferation of fibroblast-like synoviocytes. Lysosomal Proteases in Some Common Autoimmune Diseases Lysosomal proteases (also known as cathepsins) have been shown to play a significant role in some common autoimmune diseases. Psoriasis is a chronic autoimmune skin disease characterised by epidermal hyperproliferation and infiltration of inflammatory leukocytes. In normal epidermis, cathepsins L, B and D exist in an inactive, precursor form. However, in psoriatic epidermis, these cathepsins are partially processed to activated enzymes. In view of their high percentage and diffuse expression in psoriatic epidermis, they may play a role in the pathogenesis of psoriasis [82]. The degradative capacity of cathepsin D is responsible for the disordered differentiation and scale formation characteristic of psoriasis [83]. Cathepsin S expression is upregulated in psoriatic keratinocytes, but not in International Reviews of Immunology





actinic keratosis. Keratinocytic cathepsin S expression is activated by the cytokines IFN-γ and TNF-a, T-cells and atopic dermatitis keratinocytes. Cathepsin S is involved in MHC class II expression and invariant chain (Ii) degradation in keratinocytes [84]. Compared with normal tissues, the levels of DC lysosome-associated membrane protein (DC-LAMP) are higher in psoriasis vulgaris lesions, which suggest lysosomes may be associated with the altered differentiation of keratynocytes in psoriasis [85, 86]. On the other hand, DC-LAMP is involved in the synthesis and intracellular transportation of the MHC-antigen complex of DCs and serves as a reliable DC maturation marker [85]. Multiple sclerosis (MS) is a central nervous system autoimmune disease characterised by inflammation, demyelination and neurodegeneration. Elevated cathepsin S levels have been observed in MS patients during the relapse state, in comparison with healthy individuals [87]. mRNA levels of cathepsin S were increased in peripheral blood leucocytes and protein levels were increased in serum, consistent with previous observations of raised cathepsin S levels in other autoimmune diseases [87]. Recently, a study revealed a correlation between cathepsin S and D expression and MS clinical stage [88]: both lysosomal proteases are in an undeveloped form in the CD34positive hematopoietic stem cells (HSCs) isolated from the peripheral blood of healthy persons, whereas the same cells from acute-MS patients consistently display mature enzymes. In addition, mature forms of both enzymes are markedly more abundant in HSCs from the acute-MS patients when compared to their stable-MS counterparts. Therefore, doctors can qualitatively assess cathepsin S and D expression in CD34+ HSCs for MS diagnostic purposes. Sjögren’s syndrome (SjS) is a chronic autoimmune disease characterised by lymphocytic infiltration and destruction of lacrimal glands and salivary glands. In the first 5 years after diagnosis, activity of the lysosomal peptidases (cathepsin B, cathepsin D, dipeptidyl peptidase I, and tripeptidyl peptidase I) and also of the lysosomal glycosidases(β-galactosidase, α-mannosidase, β-glucuronidase and βhexosaminidase) was elevated in the leukocytes of patients with SjS. This activity further intensified between 5 and 10 years after diagnosis [89]. Thus, lysosomal enzyme activities in the leukocytes of subjects with SjS appeared to shadow the state of the disease in the first 10 years. The changes in lysosomal enzyme activities indicate that these enzymes may play a role in SjS-associated tissue injury by accelerating the breakdown of glycoproteins in lysosomes [89]. Studies in an SjS mouse model revealed elevated cathepsin S and H activities in lysates, and increased cathepsin S levels in tears. This correlates with the initiation of SjS and may therefore provide a biomarker for the diagnosis of autoimmune dacryoadenitis in humans [90]. Graves’ disease is an autoimmune disorder typically characterised by hyperthyroidism. Graves’ hyperthyroidism is accompanied by a general increase in lysosomal glycolsidase activity in serum [91]. About 25 to 50% of patients with Graves’ disease suffer from Graves’ ophthalmopathy, a complex eye and orbital disorder that is uniquely linked to Graves’ hyperthyroidism. Lysosome-related genes, such as CLN2, CLN3, and HEXB, may be involved in the pathogenesis of adipose tissue hypertrophy in Graves’ ophthalmopathy [92]. Type 1 diabetes (T1D) is an autoimmune disease characterised by T cell-mediated destruction of pancreas islet β cells. The gene encoding the lysosomal membrane protein GIMAP5 is mutated in the BB rat model, resulting in a tendency to develop autoimmune T1D [93]. In peripheral CD8+ T cells from non-obese diabetic (NOD) mice which develop spontaneous T1D, cathepsin L mRNA levels are significantly increased compared with those of control mice [94]. The cytotoxic activity of CD8+ T cells against the islets in NOD mice with T1D may possibly be regulated by Cathepsin L [94]. Inhibition of cathepsin L has been demonstrated to be a new therapeutic strategy for C Informa Healthcare USA, Inc. Copyright




W. Ge et al.

autoimmune diabetes in vivo by the administration of siRNA targeting the cathepsin L gene [94]. In addition, a deficiency in cathepsin S or cathepsin B in NOD mice reduced the incidence of T1D. By contrast, a deficiency in cathepsin L imparted complete resistance to the disease [95]. Cathepsin L-deficient NOD mice are also CD4+ lymphopenic, and possess an altered ratio of regulatory to activated T cells [95]. Zhou et al. have suggested that cathepsin G plays a crucial role in processing proinsulin [96], one of the major autoantigens in T1D. Cathepsin G activity is higher in peripheral blood mononuclear cells from T1D patients compared to controls and a cathepsin G inhibitor reduced proinsulin-reactive T cell activation. In summary, changes in the activities of lysosomal proteases may result in impaired phago- or endocytosis, inadequate extracellular matrix turnover, and remodeling. This point towards the involvement of lysosomal enzymes in the pathogenesis of autoimmune diseases. Their roles in these diseases are not yet fully understood, but further study of their significance could point towards new approaches for treatment of these diseases. ACKNOWLEDGEMENTS W. Ge. and Y.-P. Gao are supported by National Natural Science Foundation of China (81373150). All authors declare that there is no conflict of interest. Declaration of Interest The authors report no conflict of interest. The authors alone are responsible for the content and writing of the article. REFERENCES [1] Carlstedt-Duke J, Wrange O, Dahlberg E, et al. Transformation of the glucocorticoid receptor in rat liver cytosol by lysosomal enzymes. J Biol Chem 1979;254:1537–1539. [2] Vandevyver S, Dejager L, Libert C. On the trail of the glucocorticoid receptor: into the nucleus and back. Traffic 2012;13:364–374. [3] Kassel O, Herrlich P. Crosstalk between the glucocorticoid receptor and other transcription factors: molecular aspects. Mol Cell Endocrinol 2007;275:13–29. [4] Vandevyver S, Dejager L, Tuckermann J, et al. New insights into the anti-inflammatory mechanisms of glucocorticoids: an emerging role for glucocorticoid-receptor-mediated transactivation. Endocrinology 2013;154:933–1007. [5] Rhen T, Cidlowski JA. Antiinflammatory action of glucocorticoids–new mechanisms for old drugs. N Engl J Med 2005;353:1711–1723. [6] Tanaka J, Fujita H, Matsuda S, et al. Glucocorticoid- and mineralocorticoid receptors in microglial cells: the two receptors mediate differential effects of corticosteroids. Glia 1997;20:23–37. [7] He Y, Xu Y, Zhang C, et al. Identification of a lysosomal pathway that modulates glucocorticoid signaling and the inflammatory response. Sci Signal 2011;4:ra44. doi: 10.1126/scisignal.2001450 [8] Settembre C, Fraldi A, Medina DL, et al. Signals from the lysosome: a control centre for cellular clearance and energy metabolism. Nat Rev Mol Cell Biol 2013;14:283–296. [9] Blott EJ, Griffiths GM. Secretory lysosomes. Nat Rev Mol Cell Biol 2002;3:122–131. [10] Andrei C, Dazzi C, Lotti L, et al. The secretory route of the leaderless protein interleukin 1beta involves exocytosis of endolysosome-related vesicles. Mol Biol Cell 1999;10:1463–1475. [11] Becker CE, Creagh EM, O’Neill LA. Rab39a binds caspase-1 and is required for caspase-1-dependent interleukin-1beta secretion. J Biol Chem 2009;284:34531–34537. [12] Dinarello CA. Immunological and inflammatory functions of the interleukin-1 family. Annu Rev Immunol 2009;27:519–550. [13] Eder C. Mechanisms of interleukin-1 beta release. Immunobiology 2009;214:543–553. [14] Andrei C, Margiocco P, Poggi A, et al. Phospholipases C and A2 control lysosome-mediated IL-1 beta secretion: implications for inflammatory processes. Proc Natl Acad Sci USA 2004;101:9745–9750. [15] Carta S, Tassi S, Semino C, et al. Histone deacetylase inhibitors prevent exocytosis of interleukin1beta-containing secretory lysosomes: role of microtubules. Blood 2006;108:1618–1626. International Reviews of Immunology





[16] Stow JL, Murray RZ. Intracellular trafficking and secretion of inflammatory cytokines. Cytokine Growth Factor Rev 2013;24:227–239. [17] Holt OJ, Gallo F, Griffiths GM. Regulating secretory lysosomes. J Biochem 2006;140:7–12. [18] Stow JL, Manderson AP, Murray RZ. SNAREing immunity: the role of SNAREs in the immune system. Nat Rev Immunol 2006;6:919–929. [19] Li J, Yin HL, Yuan J. Flightless-I regulates proinflammatory caspases by selectively modulating intracellular localization and caspase activity. J Cell Biol 2008;181:321–333. [20] Lei N, Franken L, Ruzehaji N, et al. Flightless, secreted through a late endosome/lysosome pathway, binds LPS and dampens cytokine secretion. J Cell Sci 2012;125:4288–4296. [21] Gardella S, Andrei C, Poggi A, et al. Control of interleukin-18 secretion by dendritic cells: role of calcium influxes. FEBS Lett 2000;481:245–248. [22] Semino C, Angelini G, Poggi A, et al. NK/iDC interaction results in IL-18 secretion by DCs at the synaptic cleft followed by NK cell activation and release of the DC maturation factor HMGB1. Blood 2005;106:609–616. [23] Lahat N, Rahat MA, Kinarty A, et al. Hypoxia enhances lysosomal TNF-alpha degradation in mouse peritoneal macrophages. Am J Physiol Cell Physiol 2008;295:C2–12. [24] Eltzschig HK, Carmeliet P. Hypoxia and inflammation. N Engl J Med 2011;364:656–665. [25] Bastow ER, Last K, Golub S, et al. Evidence for lysosomal exocytosis and release of aggrecandegrading hydrolases from hypertrophic chondrocytes, in vitro and in vivo. Biol Open 2012;1:318–328. [26] Pushparaj PN, Tay HK, Wang CC, et al. VAMP8 is essential in anaphylatoxin-induced degranulation, TNF-alpha secretion, peritonitis, and systemic inflammation. J Immunol 2009;183:1413– 1418. [27] Antonin W, Holroyd C, Tikkanen R, et al. The R-SNARE endobrevin/VAMP-8 mediates homotypic fusion of early endosomes and late endosomes. Mol Biol Cell 2000;11:3289–3298. [28] Advani RJ, Yang B, Prekeris R, et al. VAMP-7 mediates vesicular transport from endosomes to lysosomes. J Cell Biol 1999;146:765–776. [29] Dodeller F, Gottar M, Huesken D, et al. The lysosomal transmembrane protein 9B regulates the activity of inflammatory signaling pathways. J Biol Chem 2008;283:21487–21494. [30] Wang Y, Chen T, Han C, et al. Lysosome-associated small Rab GTPase Rab7b negatively regulates TLR4 signaling in macrophages by promoting lysosomal degradation of TLR4. Blood 2007;110:962–971. [31] Yao M, Liu X, Li D, et al. Late endosome/lysosome-localized Rab7b suppresses TLR9-initiated proinflammatory cytokine and type I IFN production in macrophages. J Immunol 2009;183:1751–1758. [32] He D, Chen T, Yang M, et al. Small Rab GTPase Rab7b promotes megakaryocytic differentiation by enhancing IL-6 production and STAT3-GATA-1 association. J Mol Med (Berl) 2011;89:137–150. [33] German CL, Sauer BM, Howe CL. The STAT3 beacon: IL-6 recurrently activates STAT 3 from endosomal structures. Exp Cell Res 2011;317:1955–1969. [34] Tanaka Y, Tanaka N, Saeki Y, et al. c-Cbl-dependent monoubiquitination and lysosomal degradation of gp130. Mol Cell Biol 2008;28:4805–4818. [35] Radtke S, Wuller ¨ S, Yang XP, et al. Cross-regulation of cytokine signalling: pro-inflammatory cytokines restrict IL-6 signalling through receptor internalisation and degradation. J Cell Sci 2010;123:947–959. [36] Hao X, Wang Y, Ren F, et al. SNX25 regulates TGF-beta signaling by enhancing the receptor degradation. Cell Signal 2011;23:935–946. [37] Tian H, Mythreye K, Golzio C, et al. Endoglin mediates fibronectin/alpha5beta1 integrin and TGFbeta pathway crosstalk in endothelial cells. EMBO J 2012;31:3885–3900. [38] Iyer JK, Khurana T, Langer M, et al. Inflammatory cytokine response to Bacillus anthracis peptidoglycan requires phagocytosis and lysosomal trafficking. Infect Immun 2010;78:2418–2428. [39] Hakala JK, Lindstedt KA, Kovanen PT, et al. Low-density lipoprotein modified by macrophagederived lysosomal hydrolases induces expression and secretion of IL-8 via p38 MAPK and NF-kappaB by human monocyte-derived macrophages. Arterioscler Thromb Vasc Biol 2006;26:2504–2509. [40] Chinenov Y, Gupte R, Rogatsky I. Nuclear receptors in inflammation control: repression by GR and beyond. Mol Cell Endocrinol 2013;380:55–64. [41] Castaneda JA, Lim MJ, Cooper JD, et al. Immune system irregularities in lysosomal storage disorders. Acta Neuropathol 2008;115:159–174. [42] Darmoise A, Teneberg S, Bouzonville L, et al. Lysosomal alpha-galactosidase controls the generation of self lipid antigens for natural killer T cells. Immunity 2010;33:216–228. [43] Hsing LC, Rudensky AY. The lysosomal cysteine proteases in MHC class II antigen presentation. Immunol Rev 2005;207:229–241. [44] Neefjes J, Jongsma ML, Paul P, et al. Towards a systems understanding of MHC class I and MHC class II antigen presentation. Nat Rev Immunol 2011;11:823–836. C Informa Healthcare USA, Inc. Copyright




W. Ge et al.

[45] Chow A, Toomre D, Garrett W, et al. Dendritic cell maturation triggers retrograde MHC class II transport from lysosomes to the plasma membrane. Nature 2002;418:988–994. [46] Kis-Toth K, Tsokos GC. Dendritic cell function in lupus: Independent contributors or victims of aberrant immune regulation. Autoimmunity 2010;43:121–130. [47] Marshak-Rothstein A. Toll-like receptors in systemic autoimmune disease. Nat Rev Immunol 2006;6:823–835. [48] Gaipl US, Kuhn A, Sheriff A, et al. Clearance of apoptotic cells in human SLE. Curr Dir Autoimmun 2006;9:173–187. [49] Odaka C, Mizuochi T. Role of macrophage lysosomal enzymes in the degradation of nucleosomes of apoptotic cells. J Immunol 1999;163:5346–5352. [50] Nagata S, Hanayama R, Kawane K. Autoimmunity and the clearance of dead cells. Cell 2010;140:619–630. [51] Su DL, Lu ZM, Shen MN, et al. Roles of pro- and anti-inflammatory cytokines in the pathogenesis of SLE. J Biomed Biotechnol 2012;2012:347141. [52] Ronnblom L, Elkon KB. Cytokines as therapeutic targets in SLE. Nat Rev Rheumatol 2010;6:339–347. [53] Holcombe RF, Baethge BA, Wolf RE, et al. Correlation of serum interleukin-8 and cell surface lysosome-associated membrane protein expression with clinical disease activity in systemic lupus erythematosus. Lupus 1994;3:97–102. [54] Hiraoka M, Abe A, Shayman JA. Cloning and characterization of a lysosomal phospholipase A2, 1-Oacylceramide synthase. J Biol Chem 2002;277:10090–10099. [55] Abe A, Shayman JA. Purification and characterization of 1-O-acylceramide synthase, a novel phospholipase A2 with transacylase activity. J Biol Chem 1998;273:8467–8474. [56] Shayman JA, Kelly R, Kollmeyer J, et al. Group XV phospholipase A(2), a lysosomal phospholipase A(2). Prog Lipid Res 2011;50:1–13. [57] Shayman JA, Abe A, Kelly R, et al., inventors; The Regents Of The University Of Michigan, assignee. Lysosomal phospholipase A2 (LPLA2) activity as a diagnostic and therapeutic target for identifying and treating systemic lupus erythematosis. United States patent US8052970 B2. 2009 Jun 30, 2009. [58] Banchereau J, Pascual V, Palucka AK. Autoimmunity through cytokine-induced dendritic cell activation. Immunity 2004;20:539–550. [59] Wallace DJ, Gudsoorkar VS, Weisman MH, et al. New insights into mechanisms of therapeutic effects of antimalarial agents in SLE. Nat Rev Rheumatol 2012;8:522–533. [60] Everts V, Hou WS, Rialland X, et al. Cathepsin K deficiency in pycnodysostosis results in accumulation of non-digested phagocytosed collagen in fibroblasts. Calcif Tissue Int 2003;73:380–386. [61] Hou WS, Li Z, Gordon RE, et al. Cathepsin k is a critical protease in synovial fibroblast-mediated collagen degradation. Am J Pathol 2001;159:2167–2177. [62] Skoumal M, Haberhauer G, Kolarz G, et al. Serum cathepsin K levels of patients with longstanding rheumatoid arthritis: correlation with radiological destruction. Arthritis Res Ther 2005;7:R65–70. [63] Morko J, Kiviranta R, Joronen K, et al. Spontaneous development of synovitis and cartilage degeneration in transgenic mice overexpressing cathepsin K. Arthritis Rheum 2005;52:3713–3717. [64] Schurigt U, Hummel KM, Petrow PK, et al. Cathepsin K deficiency partially inhibits, but does not prevent, bone destruction in human tumor necrosis factor-transgenic mice. Arthritis Rheum 2008;58:422–434. [65] Li P, Schwarz EM. The TNF-alpha transgenic mouse model of inflammatory arthritis. Springer Semin Immunopathol 2003;25:19–33. [66] Gauthier JY, Chauret N, Cromlish W, et al. The discovery of odanacatib (MK-0822), a selective inhibitor of cathepsin K. Bioorg Med Chem Lett 2008;18:923–928. [67] Svelander L, Erlandsson-Harris H, Astner L, et al. Inhibition of cathepsin K reduces bone erosion, cartilage degradation and inflammation evoked by collagen-induced arthritis in mice. Eur J Pharmacol 2009;613:155–162. [68] Sun P, Liu Y, Deng X, et al. An inhibitor of cathepsin K, icariin suppresses cartilage and bone degradation in mice of collagen-induced arthritis. Phytomedicine 2013;20:975–979. [69] Nakagawa TY, Brissette WH, Lira PD, et al. Impaired invariant chain degradation and antigen presentation and diminished collagen-induced arthritis in cathepsin S null mice. Immunity 1999;10:207–217. [70] Pozgan U, Caglic D, Rozman B, et al. Expression and activity profiling of selected cysteine cathepsins and matrix metalloproteinases in synovial fluids from patients with rheumatoid arthritis and osteoarthritis. Biol Chem 2010;391:571–579. [71] Weidauer E, Yasuda Y, Biswal BK, et al. Effects of disease-modifying anti-rheumatic drugs (DMARDs) on the activities of rheumatoid arthritis-associated cathepsins K and S. Biol Chem 2007;388: 331–336. [72] Baugh M, Black D, Westwood P, et al. Therapeutic dosing of an orally active, selective cathepsin S inhibitor suppresses disease in models of autoimmunity. J Autoimmun 2011;36:201–209. International Reviews of Immunology





[73] Schurigt U, Eilenstein R, Gajda M, et al. Decreased arthritis severity in cathepsin L-deficient mice is attributed to an impaired T helper cell compartment. Inflamm Res 2012;61:1021–1029. [74] Schedel J, Seemayer CA, Pap T, et al. Targeting cathepsin L (CL) by specific ribozymes decreases CL protein synthesis and cartilage destruction in rheumatoid arthritis. Gene Ther 2004;11:1040–1047. [75] Pancewicz S, Popko J, Rutkowski R, et al. Activity of lysosomal exoglycosidases in serum and synovial fluid in patients with chronic Lyme and rheumatoid arthritis. Scand J Infect Dis 2009;41:584–589. [76] Boyce BF, Li P, Yao Z, et al. TNF-alpha and pathologic bone resorption. Keio J Med 2005;54:127–131. [77] Connor AM, Mahomed N, Gandhi R, et al. TNFalpha modulates protein degradation pathways in rheumatoid arthritis synovial fibroblasts. Arthritis Res Ther 2012;14:R62. [78] Lin NY, Beyer C, Giessl A, et al. Autophagy regulates TNFalpha-mediated joint destruction in experimental arthritis. Ann Rheum Dis 2013;72:761–768. [79] Tanaka Y, Matsumoto I, Iwanami K, et al. Six-transmembrane epithelial antigen of prostate4 (STEAP4) is a tumor necrosis factor alpha-induced protein that regulates IL-6, IL-8, and cell proliferation in synovium from patients with rheumatoid arthritis. Mod Rheumatol 2012;22:128–136. [80] Vijayan V, Shyni GL, Helen A. Efficacy of Bacopa monniera (L.) Wettst in alleviating lysosomal instability in adjuvant-induced arthritis in rats. Inflammation 2011;34:630–638. [81] Ekambarama SP, Perumala SS, Subramanianb V. Strychnos potatorum Linn Seed Extract Enhances Lysosomal Membrane Stability and Collagen Formation in Freunds Complete Adjuvant-Induced Arthritic Rats. J Herbs Spices Med Plants 2011;17:392–402. [82] Kawada A, Hara K, Kominami E, et al. Processing of cathepsins L, B and D in psoriatic epidermis. Arch Dermatol Res 1997;289:87–93. [83] Abdou AG, Maraee AH, Shoeib MA, et al. Cathepsin D expression in chronic plaque psoriasis: an immunohistochemical study. Acta Dermatovenerol Croat 2011;19:143–149. [84] Schonefuss A, Wendt W, Schattling B, et al. Upregulation of cathepsin S in psoriatic keratinocytes. Exp Dermatol 2010;19:e80–88. [85] Higaki M, Higaki Y, Kawashima M. Increased expression of CD208 (DC-LAMP) in epidermal keratinocytes of psoriatic lesions. J Dermatol 2009;36:144–149. [86] Wei-yuan M, Wen-ting L, Chen Z, et al. Significance of DC-LAMP and DC-SIGN expression in psoriasis vulgaris lesions. Exp Mol Pathol 2011;91:461–465. [87] Haves-Zburof D, Paperna T, Gour-Lavie A, et al. Cathepsins and their endogenous inhibitors cystatins: expression and modulation in multiple sclerosis. J Cell Mol Med 2011;15:2421–2429. [88] Martino S, Montesano S, di Girolamo I, et al. Expression of cathepsins S and D signals a distinctive biochemical trait in CD34+ hematopoietic stem cells of relapsing-remitting multiple sclerosis patients. Mult Scler 2013;19:1443–1453. [89] Sohar N, Sohar I, Hammer H. Lysosomal enzyme activities: new potential markers for Sjogren’s syndrome. Clin Biochem 2005;38:1120–1126. [90] Li X, Wu K, Edman M, et al. Increased expression of cathepsins and obesity-induced proinflammatory cytokines in lacrimal glands of male NOD mouse. Invest Ophthalmol Vis Sci 2010;51:5019–5029. [91] Komosinska-Vassev K, Olczyk K, Kozma EM, et al. Graves’ disease-associated changes in the serum lysosomal glycosidases activity and the glycosaminoglycan content. Clin Chim Acta 2003;331:97–102. [92] Chen MH, Liao SL, Chen MH, et al. Lysosome-related genes are regulated in the orbital fat of patients with graves’ ophthalmopathy. Invest Ophthalmol Vis Sci 2008;49:4760–4764. [93] Wong VW, Saunders AE, Hutchings A, et al. The autoimmunity-related GIMAP5 GTPase is a lysosome-associated protein. Self Nonself 2010;1:259–268. [94] Yamada A, Ishimaru N, Arakaki R, et al. Cathepsin L inhibition prevents murine autoimmune diabetes via suppression of CD8(+) T cell activity. PLoS One 2010;5:e12894. [95] Hsing LC, Kirk EA, McMillen TS, et al. Roles for cathepsins S, L, and B in insulitis and diabetes in the NOD mouse. J Autoimmun 2010;34:96–104. [96] Zou F, Schafer N, Palesch D, et al. Regulation of cathepsin G reduces the activation of proinsulinreactive T cells from type 1 diabetes patients. PLoS One 2011;6:e22815. doi: 10.1371/journal. pone.0022815 [97] Werneburg N, Guicciardi ME, Yin XM, et al. TNF-alpha-mediated lysosomal permeabilization is FAN and caspase 8/Bid dependent. Am J Physiol Gastrointest Liver Physiol 2004;287:G436–443.

C Informa Healthcare USA, Inc. Copyright

Roles of A20 in autoimmune diseases.

Ubiquitin, lysosomes, and neurodegenerative diseases.

Preface. Lysosomes and lysosomal diseases.

Ubiquitin, lysosomes and neurodegenerative diseases.

Lysosomes and the connective tissue diseases.

[Pemphigoid diseases. Autoimmune diseases in the elderly].

Direct and indirect pathogenic roles of autoantibodies in systemic autoimmune diseases.

Role of transient receptor potential vanilloid 1 in inflammation and autoimmune diseases.

TH9 cell differentiation, transcriptional control and function in inflammation, autoimmune diseases and cancer.

HLA and autoimmune diseases.

Eosinophils in Autoimmune Diseases.

Malignancy in autoimmune diseases.

MicroRNAs in autoimmune diseases.

Headache in autoimmune diseases.

An analysis of FDA-approved drugs for inflammation and autoimmune diseases.

MicroRNAs: The Role in Autoimmune Inflammation.

Diagnosis of autoimmune diseases.

The emerging roles of GPRC5A in diseases.

The MicroRNA-21 in Autoimmune Diseases.

The dopaminergic system in autoimmune diseases.

Hypergammaglobulinaemia and autoimmune rheumatic diseases.

Mast cell and autoimmune diseases.

Epigenetics and Autoimmune Thyroid Diseases.

Prolactin, immunoregulation, and autoimmune diseases.