Membrane Morphology and Function
Protein kinase C involvement in cell cycle modulation Alessandro Poli*1 , Sara Mongiorgi*, Lucio Cocco* and Matilde Y. Follo* *Cell Signaling Laboratory, Department of Biomedical Sciences (DIBINEM), University of Bologna, Italy
Biochemical Society Transactions
www.biochemsoctrans.org
Abstract Protein kinases C (PKCs) are a family of serine/threonine kinases which act as key regulators in cell cycle progression and differentiation. Studies of the involvement of PKCs in cell proliferation showed that their role is dependent on cell models, cell cycle phases, timing of activation and localization. Indeed, PKCs can positively and negatively act on it, regulating entry, progression and exit from the cell cycle. In particular, the targets of PKCs resulted to be some of the key proteins involved in the cell cycle including cyclins, cyclin-dependent kinases (Cdks), Cip/Kip inhibitors and lamins. Several findings described roles for PKCs in the regulation of G1 /S and G2 /M checkpoints. As a matter of fact, data from independent laboratories demonstrated PKC-related modulations of cyclins D, leading to effects on the G1 /S transition and differentiation of different cell lines. Moreover, interesting data were published on PKC-mediated phosphorylation of lamins. In addition, PKC isoenzymes can accumulate in the nuclei, attracted by different stimuli including diacylglycerol (DAG) fluctuations during cell cycle progression, and target lamins, leading to their disassembly at mitosis. In the present paper, we briefly review how PKCs could regulate cell proliferation and differentiation affecting different molecules related to cell cycle progression.
Protein kinase C family: classes, structure and maturation Protein kinases C (PKCs) are serine/threonine phosphotransferases which belong to the AGC family of protein kinases (cAMP-dependent, cGMP-dependent and protein kinases C) [1–3]. These molecules are involved in many cellular processes such as proliferation and cell cycle progression, differentiation, tumorigenesis and apoptosis through the transduction of the signals which promote phospholipid hydrolysis [1–7]. Ten PKC enzymes are known in mammalian cells and are divided into three classes on the basis of the differences in their domain composition, which indicate which cofactors they need for activation [1–3,8]. First, the conventional class is composed of four isoforms: PKCα, the two splicing variants PKCβI and PKCβII (which differ in their C-terminus by 43 amino acids) and PKCγ ; next are the four novel isoforms, PKCδ, PKCε, PKCη and PKCθ; finally, the atypical class refers to PKCζ and PKCι/λ [1,2,8] (Figure 1). All of these isoenzymes are characterized by conserved regions (C1–C4 domains) spaced out by variable regions (V1–V5); the N-terminal regulatory domain is different among various PKC classes and includes an autoinhibitory pseudosubstrate region and two membrane-targeting regions, C1 and C2 domains. On the other hand, PKC isoenzymes have a very conserved C-terminal catalytic domain containing a C3/ATP-binding domain and C4/kinase domain [1,2,8] (Figure 1). This Key words: cell cycle, G1 /S, G2 /M, phospholipase C, protein kinase C. Abbreviations: Cdk, cyclin-dependent kinase; DAG, diacylglycerol; HSP, heat-shock protein; MEL, murine erythroleukaemia cell line; PKC, protein kinase C; PLC, phospholipase C; PS, phosphatidylserine; SH, Src homology. 1 To whom correspondence should be addressed (email [email protected]).
Biochem. Soc. Trans. (2014) 42, 1471–1476; doi:10.1042/BST20140128
structure is kept together by a hinge region [1–3]. However, conventional isoforms contain classic C1 and C2 domains, which bind diacylglycerol (DAG) and anionic lipids in a Ca2 + -dependent manner respectively [1–3] (Figure 1). The production of these two molecules is linked to the activity of the phospholipase C (PLC) family, a class of enzyme which hydrolyses phosphatidylinositol 4,5-bisphosphate generating DAG and inositol 1,4,5-trisphosphate which, in turn, induces Ca2 + release from the endoplasmic reticulum. Moreover, phosphatidylserine (PS), which can be bound by the C2 domain, has been described as another important cofactor for activation and membrane translocation of these proteins. On the other hand, physiological activation of novel PKCs only requires DAG; indeed, these enzymes are not sensitive to Ca2 + due to the presence of a variant C2 domain, which lacks some key residues for Ca2 + binding. The C1 domain of conventional and novel classes is present as a tandem called C1A and C1B, which are able to bind not only DAG but also the powerful tumour-promoting phorbol esters [1,2,8]. Finally, atypical PKCs contain a different variant of the C1 domain, which is not sensitive to DAG or phorbol esters, and they lack a C2 domain. These molecules are regulated by protein–protein interactions mediated by a Phox/Bem1p (PB1) domain and a C-terminal postsynaptic density protein 95 (PSD95), Drosophila discs large tumour suppressor (Dlg1) and zonula occludens 1 (ZO-1) (PDZ) ligand motif, which control their functions in the cells [1,2,8] (Figure 1). In addition, two more PKC isoenzymes are known, PKCμ and PKCν, which are considered either to belong to a fourth class of PKCs or to be members of a different family called protein kinase D [9]. However, PKCs undergo a process of maturation characterized by a C The
C 2014 Biochemical Society Authors Journal compilation
1471
1472
Biochemical Society Transactions (2014) Volume 42, part 5
Figure 1 Structure of the three PKC classes Schematic representation of the primary structure of the three PKC classes. The common structure of PKC is characterized by conserved (C1–C4) and variable regions (V1–V5). At the N-terminus, PKCs present the regulatory domain, which is the most variable domain through the different classes. Indeed, if conventional and novel classes show a tandem C1 domain (red, C1A and C1B) able to bind DAG and phorbol esters, the atypical PKCs are characterized by an atypical domain not able to bind any of them. The C2 domain (yellow) is sensitive to Ca2 + only in conventional PKCs. Novel isoforms have a different C2 domain, not sensitive to Ca2 + , while the atypical isoforms lack this domain and possess a PB1 domain (blue), important for protein–protein interactions. A hinge region links the regulatory to the catalytic domain where PKCs present the three phosphorylation sites (activation loop, turn and hydrophobic motifs), which are fundamental for their maturation (C4 domain, blue/green). Finally, the C3/ATP-binding domain is located in the catalytic region of all three classes (orange).
series of ordered and constitutive phosphorylations, which lead the enzyme to a catalytically competent form ready to translocate to the membrane for activation [1]. This mechanism has been described in a remarkable report from Newton [1]. Briefly, newly synthesized PKCs are stabilized by the link with heat-shock protein 90 (HSP90) [10], which allows the first phosphorylation event by phosphoinositidedependent kinase-1 (PDK-1) on the activation loop situated in the catalytic domain [11,12]. Then, mammalian target of rapamycin complex 2 (mTORC2) promotes the second and third phosphorylation respectively on turn and hydrophobic motifs, leading to a fully mature and open form of the isoenzyme [13–15]. Here, DAG and Ca2 + recruit PKCs at the plasma membranes where they bind PS and, fully activated, they can phosphorylate their substrates [1,2,8,16]. Next, PKCs are dephosphorylated by the PH domain and leucine-rich repeat protein phosphatase (PHLPP) on the hydrophobic motif [17]; this event starts the process that drives PKCs to be totally dephosphorylated and degraded [1,2,8,16]. A partial inhibition of this is due to the binding with HSP70, which promotes a mechanism of rephosphorylation of PKCs and, then, their reactivation [18].
Mammalian cell cycle progression: cyclins, cyclin-dependent kinases, inhibitors The mammalian cell cycle has been already described in many articles (e.g. [19,20]) and only a brief portrait is given in the C The
C 2014 Biochemical Society Authors Journal compilation
present review. The cell cycle consists of a series of events that lead to DNA duplication and chromosome segregation into two new daughter cells [19,20]. These events have been commonly subdivided into four phases: a G1 -phase where cells start to prepare for DNA synthesis that takes place during the S-phase; then, a G2 -phase where cells prepare to divide; and finally, an M-phase (or mitosis) during which cell division in two novel cells occurs [19,20] (Figure 2). All of these steps are strictly controlled and regulated by proteins called cyclins, discovered for the first time by Evans et al. [21] thanks to pioneering studies on sea urchin oocytes (reviewed in [22]). Cyclins are proteins characterized by oscillations related to cell cycle progression, namely fluctuations of their expression and destruction generally induced by the ubiquitin-mediated system [21–23]. Through the years, our knowledge about these molecules has increased and they have been described as the regulatory partners of another important class of enzymes, the cyclin-dependent kinases (Cdks) [21–26]. These isoenzymes need to be complexed with cyclins to activate and phosphorylate their substrates, driving cell cycle progression [21–26]. Various classes and isoforms of cyclins and Cdks have been discovered and linked to the different phases of the cell cycle: entry and progression trough the G1 -phase is due to cyclin D (D1, D2 and D3)–Cdk4–Cdk6 complexes [21–26]. They lead to retinoblastoma protein (pRb) phosphorylation and, then, to the subsequent transactivation of the elongation factor 2 (E2F) and its targets genes. Next, together with cyclins
Membrane Morphology and Function
Figure 2 Cell cycle and PKCs Representation of the most important cell cycle events and of the involvement of some PKCs in their regulation. PKCα and PKCε are able to affect cyclins D1 and D3, leading to effects on the G1 /S-phase of the cell cycle and differentiation. An inhibitory role for PKCη has been described in down-modulation of the cyclin E–Cdk2 complex. Different regulations of cyclins A and E are linked to PKCδ activity. Finally, nuclear translocation of PKCα and PKCβII leads to lamin B1 phosphorylation in the G2 /M-phase. Opposite roles on p21/cip1 and p27/kip1 have been reported for PKCs.
E1–E2/Cdk2, they promote G1 /S transition [21–29]. At the end of the S-phase, cyclin A–Cdk2 complexes drive the cells to the early G2 -phase, where nuclear translocation of the cyclin B1–Cdk1 complex helps the cells to enter mitosis [21,22,24–28,30]. In addition, phosphorylation events can further regulate cyclin–Cdk complex activity [21–28,30]. Indeed, different kinases (Polo-like kinase 1, Cdk-activating kinases, Wee1) and phosphatases (Cdc25a/b/c) are known to play fundamental roles in cell cycle progression [21–28,30]. Finally, other molecules are involved in the regulation of cell proliferation including the Cip/Kip (p21 and p27) and Ink4 (p15 and p16) Cdk inhibitors, which inhibit cyclins and Cdks [31,32] (Figure 2).
PKC signalling and cell cycle Our knowledge of PKC involvement in cell proliferation and differentiation is very wide at the moment and, through the years, it has become clear that these effects are mostly context-dependent [33] (Figure 2). As a matter of fact, many studies found roles for PKCs in cell cycle machinery both as antiproliferative and growth-stimulatory enzymes [33].
Moreover, several findings showed different effects for a single PKC isoenzyme which can target more molecules and regulate various cell-cycle-related proteins depending on cell models, signalling environment and localization through the different cell cycle phases [33]. Indeed, PKC localization has been described as fundamental for their regulatory roles by different independent studies [2,33,34]. However, the control of cell proliferation by these isoenzymes is characterized by very complex processes affecting many proteins such as cyclins, Cdks, Cip/Kip inhibitors and nuclear lamins [33]. Both in vitro and in vivo evidences showed specific effects of PKC isoenzymes at G1 /S transition or G2 /M progression in multiple cell lines, affecting both cyclins and Cdk inhibitors [33,35–37] (Figure 2). Reports by Freya and colleagues indicated that activation of PKCs in intestinal crypt cell line led to cyclin D down-regulation, together with a different induction of p21/cip1 and p27/kip1 [38,39]. Moreover, the conventional PKCδ isoform has been described in regulation of cyclins A and E [39,40]. Studies on PKCη indicated that its association with cyclin E–Cdk2 inhibited Cdk2 activity through p21/cip1 phosphorylation [41]. On the other hand, Goss et al. [35] and Chen et al. [42] found roles for PKCβII at C The
C 2014 Biochemical Society Authors Journal compilation
1473
1474
Biochemical Society Transactions (2014) Volume 42, part 5
the G2 /M checkpoint, regulating lamin B1 phosphorylation and interacting with pericentrin (Figure 2).
Nuclear translocation of conventional PKCs leads to lamin B1 phosphorylation and G2 /M progression Different studies on the involvement of PKCs in G2 /M progression reported their capacity to phosphorylate lamin B1 after nuclear translocation [35–37]. Evidence was collected on different cell lines such as HL60 and murine erythroleukaemia (MEL) cell lines where PKCβII and PKCα respectively were described as able to accumulate into the nuclei during the G2 /M checkpoint. Here, they can phosphorylate lamin B1 driving its disassembly and entry into mitosis [35]. Chen et al. [35] showed that physiological DAG amount fluctuated during cell cycle progression, rising to a peak in G2 /M transition and returning to basal levels in the G1 -phase in HL60 cell line. These findings were supported by other studies on Swiss 3T3 and U937 cell lines [43,44]. Moreover, they showed, after nuclear isolation, that the DAG increase was sufficient to stimulate nuclear PKCβII translocation and lamin B1 phosphorylation. They also observed that isolated G2 /M nuclei contained an active phospholipase activity able to generate DAG in vitro. Then, treatment of HL60 cells with PLC inhibitors blocked their entry into G2 /M, therefore demonstrating an important role for nuclear PLCs in PKC nuclear translocation and cell cycle regulation [35]. Fiume et al. [37] proved that PKCα could phosphorylate lamin B1 in MEL. Synchronized cells in G2 /M were treated with several PKC inhibitors, but only Go6976, which is highly specific for PKCα [45], could effectively modulate cell cycle progression. This finding indicated a possible involvement of PKCs in this process. Moreover, experiment of RNAi techniques showed that PKCα, once in the nuclei, was able to phosphorylate lamin B1. PKCα nuclear translocation was linked with the activity of PLCβ1, which was almost completely located into the nuclei of this cell line. Indeed, silencing or inhibiting this PLC isoform led to a minor lamin B1 phosphorylation. This evidence supported the thesis of Chen et al. [35] and suggested that PLCβ1 was responsible for PKCs nuclear translocation.
PKCα-mediated regulation of cyclin D3 affects G1 /S transition Recently, we observed a new PKCα-mediated regulation of G1 /S transition in human erythroleukaemia cells (K562) through cyclin D3 modulation [46]. As reported by studies from our laboratory, PKCs are affected by nuclear PLCβ1 signalling, which, producing DAG, can modulate their activity. Hence, using K562 as a human cell line homologous with MEL, where previous studies were performed, we investigated the possible roles of the only two DAGdependent PKCs expressed in this cell model, PKCα and PKCβII [46]. Notably, overexpression of PLCβ1, performed C The
C 2014 Biochemical Society Authors Journal compilation
in G1 /S synchronized cells, led to a severe and peculiar decrease in PKCα levels, whereas PKCβII was not affected at all. This event was concomitant with an up-regulation of cyclin D3, which drove to a prolongation of the G1 /Sphase of the cell cycle and to a slower proliferation of K562 cells. The expression of other cyclins and Cdks, including cyclin A, cyclin E, Cdk4 and Cdk6, did not change. To understand whether PLCβ1 signalling was necessary in this process, we decided to overexpress a catalytic inactive mutant of the enzyme, which did not affect PKCα expression [47]. Finally, to mimic the effects of PLCβ1 overexpression, we transiently silenced PKCα, finding the same up-regulation of cyclin D3 and the same slower cell proliferation encountered in cells overexpressing PLCβ1. Therefore it was hypothesized a new mechanism through which PKCα higher activation, due to DAG increase by PLCβ1 activity, could lead to its faster degradation [1–3,16,48]. This fact was responsible of an important upmodulation of cyclin D3, which drove to a prolonged S-phase of the cell cycle and to a slower cell proliferation of K562 cell line.
Novel PKCε positively modulates cyclin D3 expression and myogenic differentiation A very different model was used by Gaboardi et al. [49] to study the effects of the novel PKCε activity on cyclin D3 during myoblast differentiation. Indeed, using the C2C12 cell line, they demonstrated the existence of a signalling network which linked PLCγ 1 and PKCε to the positive regulation of myogenin and cyclin D3, two proteins already reported to be fundamental for proliferation and differentiation of this cell line [47,50]. As PLCγ 1 activity rises during myogenic differentiation producing DAG [50], they screened the levels of all the conventional and novel PKC isoforms expressed in C2C12 during stimulation with insulin. Interestingly, they found that only PKCε and PKCη expression increased following PLCγ 1-related DAG production. Thanks to co-immunoprecipitation experiments, they also demonstrated that PKCε could co-interact with PLCγ 1 under both growing and differentiating conditions. This was confirmed by a GST pull-down assay, where they showed the ability of PKCε to bind the Src homology 2 (SH2)–SH2 and SH3 domains that are known to be located between X and Y catalytic domains of PLCγ 1. Moreover, immunocytochemistry experiments showed that the two proteins co-localized at the perinuclear Golgi apparatus. All together, these data suggested that PLCγ 1, by physical interaction, could stabilize and drive activation of PKCε. Finally, the kinase activity of this novel PKC isoform resulted fundamental in C2C12 myoblast differentiation: experiments performed using a maltose-binding protein (MBP) tag assay, RNAi techniques and kinase dead vectors showed effects of PKCε activity on cyclin D3 and myogenin expressions.
Conclusions The data reviewed in the present paper show several roles for PKCs in the cell cycle and cell differentiation. Therefore the
Membrane Morphology and Function
mechanisms by which PKCs can modulate cell proliferation are multiple and highly connected with the models, the cell cycle phases and the signalling environments [33]. In particular, many targets of PKCs have been discovered through the years, including cyclins, Cdks, cip/kip inhibitors and lamins [33]. As part of cell cycle regulation by PKCs, in the present paper, we reviewed the possibility of these isoenzymes to accumulate in the nuclei, thanks to different stimuli such as DAG fluctuations during cell cycle progression [35,43]. However, most of the literature focused on the roles of PKCs at G1 /S transition and, in particular, on their effects on cyclins D and Cip/Kip inhibitors [33,46]. Even if involvement of PKCs in mitosis has already been proposed [35–37,42], little is known about possible roles for these enzymes in the regulation of the G2 /M-related cyclins, including cyclin B1. This could be an important field of investigation for future studies, which will shed new light on PKC key regulatory roles in cell cycle progression.
Funding Our work is funded by the Italian Fondo per gli Investimenti della Ricerca di Base of the Ministero dell’Istruzione, dell’Univesita` e della Ricerca Scientifica (FIRB-MIUR).
References 1 Newton, A.C. (2010) Protein kinase C: poised to signal. Am. J. Physiol. Endocrinol. Metab. 298, E395–E402 CrossRef PubMed 2 Martelli, A.M., Faenza, I., Billi, A.M., Fala, F., Cocco, L. and Manzoli, L. (2003) Nuclear protein kinase C isoforms: key players in multiple cell functions? Histol. Histopathol. 18, 1301–1312 PubMed 3 Mellor, H. and Parker, P.J. (1998) The extended protein kinase C superfamily. Biochem. J. 332, 281–292 PubMed 4 Raimondi, C. and Falasca, M. (2012) Phosphoinositides signalling in cancer: focus on PI3K and PLC. Adv. Biol. Regul. 52, 166–182 CrossRef PubMed 5 Rhee, S.G. (2001) Regulation of phosphoinositide-specific phospholipase C. Annu. Rev. Biochem. 70, 281–312 CrossRef PubMed 6 Nishizuka, Y. (1992) Intracellular signaling by hydrolysis of phospholipids and activation of protein kinase C. Science 258, 607–614 CrossRef PubMed 7 Yang, Y.R., Follo, M.Y., Cocco, L. and Suh, P.G. (2013) The physiological roles of primary phospholipase C. Adv. Biol. Regul. 53, 232–241 CrossRef PubMed 8 Newton, A.C. (1995) Protein kinase C: structure, function, and regulation. J. Biol. Chem. 270 (48), 28495–28498 CrossRef PubMed 9 Rozengurt, E. (2011) Protein kinase D signaling: multiple biological functions in health and disease. Physiology 26, 23–33 CrossRef PubMed 10 Gould, C.M., Kannan, N., Taylor, S.S. and Newton, A.C. (2009) The chaperones Hsp90 and Cdc37 mediate the maturation and stabilization of protein kinase C through a conserved PXXP motif in the C-terminal tail. J. Biol. Chem. 284 (8), 4921–4935 CrossRef PubMed 11 Dutil, E.M., Toker, A. and Newton, A.C. (1998) Regulation of conventional protein kinase C isozymes by phosphoinositide-dependent kinase 1 (PDK-1). Curr. Biol. 8, 1366–1375 CrossRef PubMed 12 Le Good, J.A., Ziegler, W.H., Parekh, D.B., Alessi, D.R., Cohen, P. and Parker, P.J. (1998) Protein kinase C isotypes controlled by phosphoinositide 3-kinase through the protein kinase PDK1. Science 281, 2042–2045 CrossRef PubMed 13 Facchinetti, V., Ouyang, W., Wei, H., Soto, N., Lazorchak, A., Gould, C., Lowry, C., Newton, A.C., Mao, Y., Miao, R.Q. et al. (2008) The mammalian target of rapamycin complex 2 controls folding and stability of Akt and protein kinase C. EMBO J. 27, 1932–1943 CrossRef PubMed
14 Ikenoue, T., Inoki, K., Yang, Q., Zhou, X. and Guan, K.L. (2008) Essential function of TORC2 in PKC and Akt turn motif phosphorylation, maturation and signalling. EMBO J. 27, 1919–1931 CrossRef PubMed 15 Jacinto, E. and Lorberg, A. (2008) TOR regulation of AGC kinases in yeast and mammals. Biochem. J. 410, 19–37 CrossRef PubMed 16 Newton, A.C. (2001) Protein kinase C: structural and spatial regulation by phosphorylation, cofactors, and macromolecular interactions. Chem. Rev. 101, 2353–2364 CrossRef PubMed 17 Gao, T., Brognard, J. and Newton, A.C. (2008) The phosphatase PHLPP controls the cellular levels of protein kinase C. J. Biol. Chem. 283, 6300–6311 CrossRef PubMed 18 Gao, T. and Newton, A.C. (2006) Invariant Leu preceding turn motif phosphorylation site controls the interaction of protein kinase C with Hsp70. J. Biol. Chem. 281, 32461–32468 CrossRef PubMed 19 Grana, ˜ X. and Reddy, E.P. (1995) Cell cycle control in mammalian cells: role of cyclins, cyclin dependent kinases (CDKs), growth suppressor genes and cyclin-dependent kinase inhibitors (CKIs). Oncogene 11, 211–219 PubMed 20 Vermeulen, K., Van Bockstaele, D.R. and Berneman, Z.N. (2003) The cell cycle: a review of regulation, deregulation and therapeutic targets in cancer. Cell Prolif. 36, 131–149 CrossRef PubMed 21 Evans, T., Rosenthal, E.T., Youngblom, J., Distel, D. and Hunt, T. (1983) Cyclin: a protein specified by maternal mRNA in sea urchin eggs that is destroyed at each cleavage division. Cell 33, 389–396 CrossRef PubMed 22 Murray, A.W. (2004) Recycling the cell cycle: cyclins revisited. Cell 116, 221–234 CrossRef PubMed 23 Bloom, J. and Cross, F.R. (2007) Multiple levels of cyclin specificity in cell-cycle control. Nat. Rev. Mol. Cell Biol. 8, 149–160 CrossRef PubMed 24 Morgan, D.O. (1997) Cyclin-dependent kinases: engines, clocks and microprocessors. Annu. Rev. Cell Dev. Biol. 13, 261–291 CrossRef PubMed 25 Hochegger, H., Takeda, S. and Hunt, T. (2008) Cyclin-dependent kinases and cell-cycle transitions: does one fit all? Nat. Rev. Mol. Cell Biol. 9, 910–916 CrossRef PubMed 26 Harper, J.W. and Adams, P.D. (2001) Cyclin-dependent kinases. Chem. Rev. 101, 2511–2526 CrossRef PubMed 27 Weinberg, R.A. (1995) The retinoblastoma protein and cell cycle control. Cell 81, 323–330 CrossRef PubMed 28 Faenza, I., Matteucci, A., Manzoli, L., Billi, A.M., Aluigi, M., Peruzzi, D., Vitale, M., Castorina, S., Suh, P.G. and Cocco, L. (2000) A role for nuclear phospholipase C β 1 in cell cycle control. J. Biol. Chem. 275, 30520–30524 CrossRef PubMed 29 Gudas, J.M., Payton, M., Thukral, S., Chen, E., Bass, M., Robinson, M.O. and Coats, S. (1999) Cyclin E2, a novel G1 cyclin that binds Cdk2 and is aberrantly expressed in human cancers. Mol. Cell Biol. 19, 612–622 PubMed 30 Gavet, O. and Pines, J. (2010) Progressive activation of CyclinB1-Cdk1 coordinates entry to mitosis. Dev. Cell 18, 533–543 CrossRef PubMed 31 Coqueret, O. (2003) New roles for p21 and p27 cell-cycle inhibitors: a function for each cell compartment? Trends Cell Biol. 13 (2), 65–70 CrossRef PubMed 32 Canepa, ´ E.T., Scassa, M.E., Ceruti, J.M., Marazita, M.C., Carcagno, A.L., Sirkin, P.F. and Ogara, M.F. (2007) INK4 proteins, a family of mammalian CDK inhibitors with novel biological functions. IUBMB Life 59, 419–426 CrossRef PubMed 33 Black, A.R. and Black, J.D. (2012) Protein kinase C signaling and cell cycle regulation. Front. Immunol. 3, 423 PubMed 34 Irvine, R.F. (2003) Nuclear lipid signalling. Nat. Rev. Mol. Cell Biol. 4, 349–360 CrossRef PubMed 35 Goss, V.L., Hocevar, B.A., Thompson, L.J., Stratton, C.A., Burns, D.J. and Fields, A.P. (1994) Identification of nuclear β II protein kinase C as a mitotic lamin kinase. J. Biol. Chem. 269, 19074–19080 PubMed 36 Follo, M.Y., Faenza, I., Piazzi, M., Blalock, W.L., Manzoli, L., McCubrey, J.A. and Cocco, L. (2014) Nuclear PI-PLCβ1: an appraisal on targets and pathology. Adv. Biol. Regul. 54, 2–11 CrossRef PubMed 37 Fiume, R., Ramazzotti, G., Teti, G., Chiarini, F., Faenza, I., Mazzotti, G., Billi, A.M. and Cocco, L. (2009) Involvement of nuclear PLCβ1 in lamin B1 phosphorylation and G2/M cell cycle progression. FASEB J. 23, 957–966 CrossRef PubMed 38 Freya, M.R., Clarka, J.A., Leontievaa, O., Uronisa, J.M., Blacka, A.R. and Black, J.D. (2000) Protein kinase C signaling mediates a program of cell cycle withdrawal in the intestinal epithelium. J. Cell Biol. 151, 763–778 CrossRef PubMed C The
C 2014 Biochemical Society Authors Journal compilation
1475
1476
Biochemical Society Transactions (2014) Volume 42, part 5
39 Kitamura, K., Mizuno, K., Etoh, A., Akita, Y., Miyamoto, A., Nakayama, K. and Ohno, S. (2003) The second phase activation of protein kinase C delta at late G1 is required for DNA synthesis in serum-induced cell cycle progression. Genes Cells. 8, 311–324 CrossRef PubMed 40 Santiago-Walker, A.E., Fikaris, A.J., Kao, G.D., Brown, E.J., Kazanietz, M.G. and Meinkoth, J.L. (2005) Protein kinase C δ stimulates apoptosis by initiating G1 phase cell cycle progression and S phase arrest. J. Biol. Chem. 280, 32107–32114 CrossRef PubMed 41 Kashiwagi, M., Ohba, M., Watanabe, H., Ishino, K., Kasahara, K., Sanai, Y., Taya, Y. and Kuroki, T. (2000) PKCη associates with cyclin E/cdk2/p21 complex, phosphorylates p21 and inhibits cdk2 kinase in keratinocytes. Oncogene 19, 6334–6341 CrossRef PubMed 42 Chen, D., Purohit, A., Halilovic, E., Doxsey, S.J. and Newton, A.C. (2004) Centrosomal anchoring of protein kinase C βII by pericentrin controls microtubule organization, spindle function, and cytokinesis. J. Biol. Chem. 279, 4829–4839 CrossRef PubMed 43 Divecha, N., Banfic, ´ H. and Irvine, R.F. (1991) The polyphosphoinositide cycle exists in the nuclei of Swiss 3T3 cells under the control of a receptor (for IGF-I) in the plasma membrane, and stimulation of the cycle increases nuclear diacylglycerol and apparently induces translocation of protein kinase C to the nucleus. EMBO J. 10, 3207–3214 PubMed 44 Neri, L.M., Bortul, R., Borgatti, P., Tabellini, G., Baldini, G., Capitani, S. and Martelli, A.M. (2002) Proliferating or differentiating stimuli act on different lipid-dependent signaling pathways in nuclei of human leukemia cells. Mol. Biol. Cell 13, 947–964 CrossRef PubMed
C The
C 2014 Biochemical Society Authors Journal compilation
45 Wu-Zhang, A.X. and Newton, A.C. (2013) Protein kinase C pharmacology: refining the toolbox. Biochem. J. 452, 195–209 CrossRef PubMed 46 Poli, A., Faenza, I., Chiarini, F., Matteucci, A., McCubrey, J.A. and Cocco, L. (2013) K562 cell proliferation is modulated by PLCβ1 through a PKCα-mediated pathway. Cell Cycle 12, 1713–1721 CrossRef PubMed 47 Ramazzotti, G., Faenza, I., Gaboardi, G.C., Piazzi, M., Bavelloni, A., Fiume, R., Manzoli, L., Martelli, A.M. and Cocco, L. (2008) Catalytic activity of nuclear PLCβ1 is required for its signalling function during C2C12 differentiation. Cell. Signal. 20, 2013–2021 CrossRef PubMed 48 Lu, Z., Liu, D., Hornia, A., Wayne, D., Pagano, M. and Foster, A.D. (1998) Activation of protein kinase C triggers its ubiquitination and degradation. Mol. Cell. Biol. 18, 839–845 PubMed 49 Gaboardi, G.C., Ramazzotti, G., Bavelloni, A., Piazzi, M., Fiume, R., Billi, A.M., Matteucci, A., Faenza, I. and Cocco, L. (2009) A role for PKCε during C2C12 myogenic differentiation. Cell. Signal. 22, 629–635 CrossRef PubMed 50 Faenza, I., Ramazzotti, G., Bavelloni, A., Fiume, R., Gaboardi, G.C., Follo, M.Y., Gilmour, R.S., Martelli, A.M., Ravid, K. and Cocco, L. (2007) Inositide-dependent phospholipase C signaling mimics insulin in skeletal muscle differentiation by affecting specific regions of the cyclin D3 promoter. Endocrinology 148, 1108–1117 CrossRef PubMed
Received 6 May 2014 doi:10.1042/BST20140128
Protein kinase C involvement in cell cycle modulation Alessandro Poli*1 , Sara Mongiorgi*, Lucio Cocco* and Matilde Y. Follo* *Cell Signaling Laboratory, Department of Biomedical Sciences (DIBINEM), University of Bologna, Italy
Biochemical Society Transactions
www.biochemsoctrans.org
Abstract Protein kinases C (PKCs) are a family of serine/threonine kinases which act as key regulators in cell cycle progression and differentiation. Studies of the involvement of PKCs in cell proliferation showed that their role is dependent on cell models, cell cycle phases, timing of activation and localization. Indeed, PKCs can positively and negatively act on it, regulating entry, progression and exit from the cell cycle. In particular, the targets of PKCs resulted to be some of the key proteins involved in the cell cycle including cyclins, cyclin-dependent kinases (Cdks), Cip/Kip inhibitors and lamins. Several findings described roles for PKCs in the regulation of G1 /S and G2 /M checkpoints. As a matter of fact, data from independent laboratories demonstrated PKC-related modulations of cyclins D, leading to effects on the G1 /S transition and differentiation of different cell lines. Moreover, interesting data were published on PKC-mediated phosphorylation of lamins. In addition, PKC isoenzymes can accumulate in the nuclei, attracted by different stimuli including diacylglycerol (DAG) fluctuations during cell cycle progression, and target lamins, leading to their disassembly at mitosis. In the present paper, we briefly review how PKCs could regulate cell proliferation and differentiation affecting different molecules related to cell cycle progression.
Protein kinase C family: classes, structure and maturation Protein kinases C (PKCs) are serine/threonine phosphotransferases which belong to the AGC family of protein kinases (cAMP-dependent, cGMP-dependent and protein kinases C) [1–3]. These molecules are involved in many cellular processes such as proliferation and cell cycle progression, differentiation, tumorigenesis and apoptosis through the transduction of the signals which promote phospholipid hydrolysis [1–7]. Ten PKC enzymes are known in mammalian cells and are divided into three classes on the basis of the differences in their domain composition, which indicate which cofactors they need for activation [1–3,8]. First, the conventional class is composed of four isoforms: PKCα, the two splicing variants PKCβI and PKCβII (which differ in their C-terminus by 43 amino acids) and PKCγ ; next are the four novel isoforms, PKCδ, PKCε, PKCη and PKCθ; finally, the atypical class refers to PKCζ and PKCι/λ [1,2,8] (Figure 1). All of these isoenzymes are characterized by conserved regions (C1–C4 domains) spaced out by variable regions (V1–V5); the N-terminal regulatory domain is different among various PKC classes and includes an autoinhibitory pseudosubstrate region and two membrane-targeting regions, C1 and C2 domains. On the other hand, PKC isoenzymes have a very conserved C-terminal catalytic domain containing a C3/ATP-binding domain and C4/kinase domain [1,2,8] (Figure 1). This Key words: cell cycle, G1 /S, G2 /M, phospholipase C, protein kinase C. Abbreviations: Cdk, cyclin-dependent kinase; DAG, diacylglycerol; HSP, heat-shock protein; MEL, murine erythroleukaemia cell line; PKC, protein kinase C; PLC, phospholipase C; PS, phosphatidylserine; SH, Src homology. 1 To whom correspondence should be addressed (email [email protected]).
Biochem. Soc. Trans. (2014) 42, 1471–1476; doi:10.1042/BST20140128
structure is kept together by a hinge region [1–3]. However, conventional isoforms contain classic C1 and C2 domains, which bind diacylglycerol (DAG) and anionic lipids in a Ca2 + -dependent manner respectively [1–3] (Figure 1). The production of these two molecules is linked to the activity of the phospholipase C (PLC) family, a class of enzyme which hydrolyses phosphatidylinositol 4,5-bisphosphate generating DAG and inositol 1,4,5-trisphosphate which, in turn, induces Ca2 + release from the endoplasmic reticulum. Moreover, phosphatidylserine (PS), which can be bound by the C2 domain, has been described as another important cofactor for activation and membrane translocation of these proteins. On the other hand, physiological activation of novel PKCs only requires DAG; indeed, these enzymes are not sensitive to Ca2 + due to the presence of a variant C2 domain, which lacks some key residues for Ca2 + binding. The C1 domain of conventional and novel classes is present as a tandem called C1A and C1B, which are able to bind not only DAG but also the powerful tumour-promoting phorbol esters [1,2,8]. Finally, atypical PKCs contain a different variant of the C1 domain, which is not sensitive to DAG or phorbol esters, and they lack a C2 domain. These molecules are regulated by protein–protein interactions mediated by a Phox/Bem1p (PB1) domain and a C-terminal postsynaptic density protein 95 (PSD95), Drosophila discs large tumour suppressor (Dlg1) and zonula occludens 1 (ZO-1) (PDZ) ligand motif, which control their functions in the cells [1,2,8] (Figure 1). In addition, two more PKC isoenzymes are known, PKCμ and PKCν, which are considered either to belong to a fourth class of PKCs or to be members of a different family called protein kinase D [9]. However, PKCs undergo a process of maturation characterized by a C The
C 2014 Biochemical Society Authors Journal compilation
1471
1472
Biochemical Society Transactions (2014) Volume 42, part 5
Figure 1 Structure of the three PKC classes Schematic representation of the primary structure of the three PKC classes. The common structure of PKC is characterized by conserved (C1–C4) and variable regions (V1–V5). At the N-terminus, PKCs present the regulatory domain, which is the most variable domain through the different classes. Indeed, if conventional and novel classes show a tandem C1 domain (red, C1A and C1B) able to bind DAG and phorbol esters, the atypical PKCs are characterized by an atypical domain not able to bind any of them. The C2 domain (yellow) is sensitive to Ca2 + only in conventional PKCs. Novel isoforms have a different C2 domain, not sensitive to Ca2 + , while the atypical isoforms lack this domain and possess a PB1 domain (blue), important for protein–protein interactions. A hinge region links the regulatory to the catalytic domain where PKCs present the three phosphorylation sites (activation loop, turn and hydrophobic motifs), which are fundamental for their maturation (C4 domain, blue/green). Finally, the C3/ATP-binding domain is located in the catalytic region of all three classes (orange).
series of ordered and constitutive phosphorylations, which lead the enzyme to a catalytically competent form ready to translocate to the membrane for activation [1]. This mechanism has been described in a remarkable report from Newton [1]. Briefly, newly synthesized PKCs are stabilized by the link with heat-shock protein 90 (HSP90) [10], which allows the first phosphorylation event by phosphoinositidedependent kinase-1 (PDK-1) on the activation loop situated in the catalytic domain [11,12]. Then, mammalian target of rapamycin complex 2 (mTORC2) promotes the second and third phosphorylation respectively on turn and hydrophobic motifs, leading to a fully mature and open form of the isoenzyme [13–15]. Here, DAG and Ca2 + recruit PKCs at the plasma membranes where they bind PS and, fully activated, they can phosphorylate their substrates [1,2,8,16]. Next, PKCs are dephosphorylated by the PH domain and leucine-rich repeat protein phosphatase (PHLPP) on the hydrophobic motif [17]; this event starts the process that drives PKCs to be totally dephosphorylated and degraded [1,2,8,16]. A partial inhibition of this is due to the binding with HSP70, which promotes a mechanism of rephosphorylation of PKCs and, then, their reactivation [18].
Mammalian cell cycle progression: cyclins, cyclin-dependent kinases, inhibitors The mammalian cell cycle has been already described in many articles (e.g. [19,20]) and only a brief portrait is given in the C The
C 2014 Biochemical Society Authors Journal compilation
present review. The cell cycle consists of a series of events that lead to DNA duplication and chromosome segregation into two new daughter cells [19,20]. These events have been commonly subdivided into four phases: a G1 -phase where cells start to prepare for DNA synthesis that takes place during the S-phase; then, a G2 -phase where cells prepare to divide; and finally, an M-phase (or mitosis) during which cell division in two novel cells occurs [19,20] (Figure 2). All of these steps are strictly controlled and regulated by proteins called cyclins, discovered for the first time by Evans et al. [21] thanks to pioneering studies on sea urchin oocytes (reviewed in [22]). Cyclins are proteins characterized by oscillations related to cell cycle progression, namely fluctuations of their expression and destruction generally induced by the ubiquitin-mediated system [21–23]. Through the years, our knowledge about these molecules has increased and they have been described as the regulatory partners of another important class of enzymes, the cyclin-dependent kinases (Cdks) [21–26]. These isoenzymes need to be complexed with cyclins to activate and phosphorylate their substrates, driving cell cycle progression [21–26]. Various classes and isoforms of cyclins and Cdks have been discovered and linked to the different phases of the cell cycle: entry and progression trough the G1 -phase is due to cyclin D (D1, D2 and D3)–Cdk4–Cdk6 complexes [21–26]. They lead to retinoblastoma protein (pRb) phosphorylation and, then, to the subsequent transactivation of the elongation factor 2 (E2F) and its targets genes. Next, together with cyclins
Membrane Morphology and Function
Figure 2 Cell cycle and PKCs Representation of the most important cell cycle events and of the involvement of some PKCs in their regulation. PKCα and PKCε are able to affect cyclins D1 and D3, leading to effects on the G1 /S-phase of the cell cycle and differentiation. An inhibitory role for PKCη has been described in down-modulation of the cyclin E–Cdk2 complex. Different regulations of cyclins A and E are linked to PKCδ activity. Finally, nuclear translocation of PKCα and PKCβII leads to lamin B1 phosphorylation in the G2 /M-phase. Opposite roles on p21/cip1 and p27/kip1 have been reported for PKCs.
E1–E2/Cdk2, they promote G1 /S transition [21–29]. At the end of the S-phase, cyclin A–Cdk2 complexes drive the cells to the early G2 -phase, where nuclear translocation of the cyclin B1–Cdk1 complex helps the cells to enter mitosis [21,22,24–28,30]. In addition, phosphorylation events can further regulate cyclin–Cdk complex activity [21–28,30]. Indeed, different kinases (Polo-like kinase 1, Cdk-activating kinases, Wee1) and phosphatases (Cdc25a/b/c) are known to play fundamental roles in cell cycle progression [21–28,30]. Finally, other molecules are involved in the regulation of cell proliferation including the Cip/Kip (p21 and p27) and Ink4 (p15 and p16) Cdk inhibitors, which inhibit cyclins and Cdks [31,32] (Figure 2).
PKC signalling and cell cycle Our knowledge of PKC involvement in cell proliferation and differentiation is very wide at the moment and, through the years, it has become clear that these effects are mostly context-dependent [33] (Figure 2). As a matter of fact, many studies found roles for PKCs in cell cycle machinery both as antiproliferative and growth-stimulatory enzymes [33].
Moreover, several findings showed different effects for a single PKC isoenzyme which can target more molecules and regulate various cell-cycle-related proteins depending on cell models, signalling environment and localization through the different cell cycle phases [33]. Indeed, PKC localization has been described as fundamental for their regulatory roles by different independent studies [2,33,34]. However, the control of cell proliferation by these isoenzymes is characterized by very complex processes affecting many proteins such as cyclins, Cdks, Cip/Kip inhibitors and nuclear lamins [33]. Both in vitro and in vivo evidences showed specific effects of PKC isoenzymes at G1 /S transition or G2 /M progression in multiple cell lines, affecting both cyclins and Cdk inhibitors [33,35–37] (Figure 2). Reports by Freya and colleagues indicated that activation of PKCs in intestinal crypt cell line led to cyclin D down-regulation, together with a different induction of p21/cip1 and p27/kip1 [38,39]. Moreover, the conventional PKCδ isoform has been described in regulation of cyclins A and E [39,40]. Studies on PKCη indicated that its association with cyclin E–Cdk2 inhibited Cdk2 activity through p21/cip1 phosphorylation [41]. On the other hand, Goss et al. [35] and Chen et al. [42] found roles for PKCβII at C The
C 2014 Biochemical Society Authors Journal compilation
1473
1474
Biochemical Society Transactions (2014) Volume 42, part 5
the G2 /M checkpoint, regulating lamin B1 phosphorylation and interacting with pericentrin (Figure 2).
Nuclear translocation of conventional PKCs leads to lamin B1 phosphorylation and G2 /M progression Different studies on the involvement of PKCs in G2 /M progression reported their capacity to phosphorylate lamin B1 after nuclear translocation [35–37]. Evidence was collected on different cell lines such as HL60 and murine erythroleukaemia (MEL) cell lines where PKCβII and PKCα respectively were described as able to accumulate into the nuclei during the G2 /M checkpoint. Here, they can phosphorylate lamin B1 driving its disassembly and entry into mitosis [35]. Chen et al. [35] showed that physiological DAG amount fluctuated during cell cycle progression, rising to a peak in G2 /M transition and returning to basal levels in the G1 -phase in HL60 cell line. These findings were supported by other studies on Swiss 3T3 and U937 cell lines [43,44]. Moreover, they showed, after nuclear isolation, that the DAG increase was sufficient to stimulate nuclear PKCβII translocation and lamin B1 phosphorylation. They also observed that isolated G2 /M nuclei contained an active phospholipase activity able to generate DAG in vitro. Then, treatment of HL60 cells with PLC inhibitors blocked their entry into G2 /M, therefore demonstrating an important role for nuclear PLCs in PKC nuclear translocation and cell cycle regulation [35]. Fiume et al. [37] proved that PKCα could phosphorylate lamin B1 in MEL. Synchronized cells in G2 /M were treated with several PKC inhibitors, but only Go6976, which is highly specific for PKCα [45], could effectively modulate cell cycle progression. This finding indicated a possible involvement of PKCs in this process. Moreover, experiment of RNAi techniques showed that PKCα, once in the nuclei, was able to phosphorylate lamin B1. PKCα nuclear translocation was linked with the activity of PLCβ1, which was almost completely located into the nuclei of this cell line. Indeed, silencing or inhibiting this PLC isoform led to a minor lamin B1 phosphorylation. This evidence supported the thesis of Chen et al. [35] and suggested that PLCβ1 was responsible for PKCs nuclear translocation.
PKCα-mediated regulation of cyclin D3 affects G1 /S transition Recently, we observed a new PKCα-mediated regulation of G1 /S transition in human erythroleukaemia cells (K562) through cyclin D3 modulation [46]. As reported by studies from our laboratory, PKCs are affected by nuclear PLCβ1 signalling, which, producing DAG, can modulate their activity. Hence, using K562 as a human cell line homologous with MEL, where previous studies were performed, we investigated the possible roles of the only two DAGdependent PKCs expressed in this cell model, PKCα and PKCβII [46]. Notably, overexpression of PLCβ1, performed C The
C 2014 Biochemical Society Authors Journal compilation
in G1 /S synchronized cells, led to a severe and peculiar decrease in PKCα levels, whereas PKCβII was not affected at all. This event was concomitant with an up-regulation of cyclin D3, which drove to a prolongation of the G1 /Sphase of the cell cycle and to a slower proliferation of K562 cells. The expression of other cyclins and Cdks, including cyclin A, cyclin E, Cdk4 and Cdk6, did not change. To understand whether PLCβ1 signalling was necessary in this process, we decided to overexpress a catalytic inactive mutant of the enzyme, which did not affect PKCα expression [47]. Finally, to mimic the effects of PLCβ1 overexpression, we transiently silenced PKCα, finding the same up-regulation of cyclin D3 and the same slower cell proliferation encountered in cells overexpressing PLCβ1. Therefore it was hypothesized a new mechanism through which PKCα higher activation, due to DAG increase by PLCβ1 activity, could lead to its faster degradation [1–3,16,48]. This fact was responsible of an important upmodulation of cyclin D3, which drove to a prolonged S-phase of the cell cycle and to a slower cell proliferation of K562 cell line.
Novel PKCε positively modulates cyclin D3 expression and myogenic differentiation A very different model was used by Gaboardi et al. [49] to study the effects of the novel PKCε activity on cyclin D3 during myoblast differentiation. Indeed, using the C2C12 cell line, they demonstrated the existence of a signalling network which linked PLCγ 1 and PKCε to the positive regulation of myogenin and cyclin D3, two proteins already reported to be fundamental for proliferation and differentiation of this cell line [47,50]. As PLCγ 1 activity rises during myogenic differentiation producing DAG [50], they screened the levels of all the conventional and novel PKC isoforms expressed in C2C12 during stimulation with insulin. Interestingly, they found that only PKCε and PKCη expression increased following PLCγ 1-related DAG production. Thanks to co-immunoprecipitation experiments, they also demonstrated that PKCε could co-interact with PLCγ 1 under both growing and differentiating conditions. This was confirmed by a GST pull-down assay, where they showed the ability of PKCε to bind the Src homology 2 (SH2)–SH2 and SH3 domains that are known to be located between X and Y catalytic domains of PLCγ 1. Moreover, immunocytochemistry experiments showed that the two proteins co-localized at the perinuclear Golgi apparatus. All together, these data suggested that PLCγ 1, by physical interaction, could stabilize and drive activation of PKCε. Finally, the kinase activity of this novel PKC isoform resulted fundamental in C2C12 myoblast differentiation: experiments performed using a maltose-binding protein (MBP) tag assay, RNAi techniques and kinase dead vectors showed effects of PKCε activity on cyclin D3 and myogenin expressions.
Conclusions The data reviewed in the present paper show several roles for PKCs in the cell cycle and cell differentiation. Therefore the
Membrane Morphology and Function
mechanisms by which PKCs can modulate cell proliferation are multiple and highly connected with the models, the cell cycle phases and the signalling environments [33]. In particular, many targets of PKCs have been discovered through the years, including cyclins, Cdks, cip/kip inhibitors and lamins [33]. As part of cell cycle regulation by PKCs, in the present paper, we reviewed the possibility of these isoenzymes to accumulate in the nuclei, thanks to different stimuli such as DAG fluctuations during cell cycle progression [35,43]. However, most of the literature focused on the roles of PKCs at G1 /S transition and, in particular, on their effects on cyclins D and Cip/Kip inhibitors [33,46]. Even if involvement of PKCs in mitosis has already been proposed [35–37,42], little is known about possible roles for these enzymes in the regulation of the G2 /M-related cyclins, including cyclin B1. This could be an important field of investigation for future studies, which will shed new light on PKC key regulatory roles in cell cycle progression.
Funding Our work is funded by the Italian Fondo per gli Investimenti della Ricerca di Base of the Ministero dell’Istruzione, dell’Univesita` e della Ricerca Scientifica (FIRB-MIUR).
References 1 Newton, A.C. (2010) Protein kinase C: poised to signal. Am. J. Physiol. Endocrinol. Metab. 298, E395–E402 CrossRef PubMed 2 Martelli, A.M., Faenza, I., Billi, A.M., Fala, F., Cocco, L. and Manzoli, L. (2003) Nuclear protein kinase C isoforms: key players in multiple cell functions? Histol. Histopathol. 18, 1301–1312 PubMed 3 Mellor, H. and Parker, P.J. (1998) The extended protein kinase C superfamily. Biochem. J. 332, 281–292 PubMed 4 Raimondi, C. and Falasca, M. (2012) Phosphoinositides signalling in cancer: focus on PI3K and PLC. Adv. Biol. Regul. 52, 166–182 CrossRef PubMed 5 Rhee, S.G. (2001) Regulation of phosphoinositide-specific phospholipase C. Annu. Rev. Biochem. 70, 281–312 CrossRef PubMed 6 Nishizuka, Y. (1992) Intracellular signaling by hydrolysis of phospholipids and activation of protein kinase C. Science 258, 607–614 CrossRef PubMed 7 Yang, Y.R., Follo, M.Y., Cocco, L. and Suh, P.G. (2013) The physiological roles of primary phospholipase C. Adv. Biol. Regul. 53, 232–241 CrossRef PubMed 8 Newton, A.C. (1995) Protein kinase C: structure, function, and regulation. J. Biol. Chem. 270 (48), 28495–28498 CrossRef PubMed 9 Rozengurt, E. (2011) Protein kinase D signaling: multiple biological functions in health and disease. Physiology 26, 23–33 CrossRef PubMed 10 Gould, C.M., Kannan, N., Taylor, S.S. and Newton, A.C. (2009) The chaperones Hsp90 and Cdc37 mediate the maturation and stabilization of protein kinase C through a conserved PXXP motif in the C-terminal tail. J. Biol. Chem. 284 (8), 4921–4935 CrossRef PubMed 11 Dutil, E.M., Toker, A. and Newton, A.C. (1998) Regulation of conventional protein kinase C isozymes by phosphoinositide-dependent kinase 1 (PDK-1). Curr. Biol. 8, 1366–1375 CrossRef PubMed 12 Le Good, J.A., Ziegler, W.H., Parekh, D.B., Alessi, D.R., Cohen, P. and Parker, P.J. (1998) Protein kinase C isotypes controlled by phosphoinositide 3-kinase through the protein kinase PDK1. Science 281, 2042–2045 CrossRef PubMed 13 Facchinetti, V., Ouyang, W., Wei, H., Soto, N., Lazorchak, A., Gould, C., Lowry, C., Newton, A.C., Mao, Y., Miao, R.Q. et al. (2008) The mammalian target of rapamycin complex 2 controls folding and stability of Akt and protein kinase C. EMBO J. 27, 1932–1943 CrossRef PubMed
14 Ikenoue, T., Inoki, K., Yang, Q., Zhou, X. and Guan, K.L. (2008) Essential function of TORC2 in PKC and Akt turn motif phosphorylation, maturation and signalling. EMBO J. 27, 1919–1931 CrossRef PubMed 15 Jacinto, E. and Lorberg, A. (2008) TOR regulation of AGC kinases in yeast and mammals. Biochem. J. 410, 19–37 CrossRef PubMed 16 Newton, A.C. (2001) Protein kinase C: structural and spatial regulation by phosphorylation, cofactors, and macromolecular interactions. Chem. Rev. 101, 2353–2364 CrossRef PubMed 17 Gao, T., Brognard, J. and Newton, A.C. (2008) The phosphatase PHLPP controls the cellular levels of protein kinase C. J. Biol. Chem. 283, 6300–6311 CrossRef PubMed 18 Gao, T. and Newton, A.C. (2006) Invariant Leu preceding turn motif phosphorylation site controls the interaction of protein kinase C with Hsp70. J. Biol. Chem. 281, 32461–32468 CrossRef PubMed 19 Grana, ˜ X. and Reddy, E.P. (1995) Cell cycle control in mammalian cells: role of cyclins, cyclin dependent kinases (CDKs), growth suppressor genes and cyclin-dependent kinase inhibitors (CKIs). Oncogene 11, 211–219 PubMed 20 Vermeulen, K., Van Bockstaele, D.R. and Berneman, Z.N. (2003) The cell cycle: a review of regulation, deregulation and therapeutic targets in cancer. Cell Prolif. 36, 131–149 CrossRef PubMed 21 Evans, T., Rosenthal, E.T., Youngblom, J., Distel, D. and Hunt, T. (1983) Cyclin: a protein specified by maternal mRNA in sea urchin eggs that is destroyed at each cleavage division. Cell 33, 389–396 CrossRef PubMed 22 Murray, A.W. (2004) Recycling the cell cycle: cyclins revisited. Cell 116, 221–234 CrossRef PubMed 23 Bloom, J. and Cross, F.R. (2007) Multiple levels of cyclin specificity in cell-cycle control. Nat. Rev. Mol. Cell Biol. 8, 149–160 CrossRef PubMed 24 Morgan, D.O. (1997) Cyclin-dependent kinases: engines, clocks and microprocessors. Annu. Rev. Cell Dev. Biol. 13, 261–291 CrossRef PubMed 25 Hochegger, H., Takeda, S. and Hunt, T. (2008) Cyclin-dependent kinases and cell-cycle transitions: does one fit all? Nat. Rev. Mol. Cell Biol. 9, 910–916 CrossRef PubMed 26 Harper, J.W. and Adams, P.D. (2001) Cyclin-dependent kinases. Chem. Rev. 101, 2511–2526 CrossRef PubMed 27 Weinberg, R.A. (1995) The retinoblastoma protein and cell cycle control. Cell 81, 323–330 CrossRef PubMed 28 Faenza, I., Matteucci, A., Manzoli, L., Billi, A.M., Aluigi, M., Peruzzi, D., Vitale, M., Castorina, S., Suh, P.G. and Cocco, L. (2000) A role for nuclear phospholipase C β 1 in cell cycle control. J. Biol. Chem. 275, 30520–30524 CrossRef PubMed 29 Gudas, J.M., Payton, M., Thukral, S., Chen, E., Bass, M., Robinson, M.O. and Coats, S. (1999) Cyclin E2, a novel G1 cyclin that binds Cdk2 and is aberrantly expressed in human cancers. Mol. Cell Biol. 19, 612–622 PubMed 30 Gavet, O. and Pines, J. (2010) Progressive activation of CyclinB1-Cdk1 coordinates entry to mitosis. Dev. Cell 18, 533–543 CrossRef PubMed 31 Coqueret, O. (2003) New roles for p21 and p27 cell-cycle inhibitors: a function for each cell compartment? Trends Cell Biol. 13 (2), 65–70 CrossRef PubMed 32 Canepa, ´ E.T., Scassa, M.E., Ceruti, J.M., Marazita, M.C., Carcagno, A.L., Sirkin, P.F. and Ogara, M.F. (2007) INK4 proteins, a family of mammalian CDK inhibitors with novel biological functions. IUBMB Life 59, 419–426 CrossRef PubMed 33 Black, A.R. and Black, J.D. (2012) Protein kinase C signaling and cell cycle regulation. Front. Immunol. 3, 423 PubMed 34 Irvine, R.F. (2003) Nuclear lipid signalling. Nat. Rev. Mol. Cell Biol. 4, 349–360 CrossRef PubMed 35 Goss, V.L., Hocevar, B.A., Thompson, L.J., Stratton, C.A., Burns, D.J. and Fields, A.P. (1994) Identification of nuclear β II protein kinase C as a mitotic lamin kinase. J. Biol. Chem. 269, 19074–19080 PubMed 36 Follo, M.Y., Faenza, I., Piazzi, M., Blalock, W.L., Manzoli, L., McCubrey, J.A. and Cocco, L. (2014) Nuclear PI-PLCβ1: an appraisal on targets and pathology. Adv. Biol. Regul. 54, 2–11 CrossRef PubMed 37 Fiume, R., Ramazzotti, G., Teti, G., Chiarini, F., Faenza, I., Mazzotti, G., Billi, A.M. and Cocco, L. (2009) Involvement of nuclear PLCβ1 in lamin B1 phosphorylation and G2/M cell cycle progression. FASEB J. 23, 957–966 CrossRef PubMed 38 Freya, M.R., Clarka, J.A., Leontievaa, O., Uronisa, J.M., Blacka, A.R. and Black, J.D. (2000) Protein kinase C signaling mediates a program of cell cycle withdrawal in the intestinal epithelium. J. Cell Biol. 151, 763–778 CrossRef PubMed C The
C 2014 Biochemical Society Authors Journal compilation
1475
1476
Biochemical Society Transactions (2014) Volume 42, part 5
39 Kitamura, K., Mizuno, K., Etoh, A., Akita, Y., Miyamoto, A., Nakayama, K. and Ohno, S. (2003) The second phase activation of protein kinase C delta at late G1 is required for DNA synthesis in serum-induced cell cycle progression. Genes Cells. 8, 311–324 CrossRef PubMed 40 Santiago-Walker, A.E., Fikaris, A.J., Kao, G.D., Brown, E.J., Kazanietz, M.G. and Meinkoth, J.L. (2005) Protein kinase C δ stimulates apoptosis by initiating G1 phase cell cycle progression and S phase arrest. J. Biol. Chem. 280, 32107–32114 CrossRef PubMed 41 Kashiwagi, M., Ohba, M., Watanabe, H., Ishino, K., Kasahara, K., Sanai, Y., Taya, Y. and Kuroki, T. (2000) PKCη associates with cyclin E/cdk2/p21 complex, phosphorylates p21 and inhibits cdk2 kinase in keratinocytes. Oncogene 19, 6334–6341 CrossRef PubMed 42 Chen, D., Purohit, A., Halilovic, E., Doxsey, S.J. and Newton, A.C. (2004) Centrosomal anchoring of protein kinase C βII by pericentrin controls microtubule organization, spindle function, and cytokinesis. J. Biol. Chem. 279, 4829–4839 CrossRef PubMed 43 Divecha, N., Banfic, ´ H. and Irvine, R.F. (1991) The polyphosphoinositide cycle exists in the nuclei of Swiss 3T3 cells under the control of a receptor (for IGF-I) in the plasma membrane, and stimulation of the cycle increases nuclear diacylglycerol and apparently induces translocation of protein kinase C to the nucleus. EMBO J. 10, 3207–3214 PubMed 44 Neri, L.M., Bortul, R., Borgatti, P., Tabellini, G., Baldini, G., Capitani, S. and Martelli, A.M. (2002) Proliferating or differentiating stimuli act on different lipid-dependent signaling pathways in nuclei of human leukemia cells. Mol. Biol. Cell 13, 947–964 CrossRef PubMed
C The
C 2014 Biochemical Society Authors Journal compilation
45 Wu-Zhang, A.X. and Newton, A.C. (2013) Protein kinase C pharmacology: refining the toolbox. Biochem. J. 452, 195–209 CrossRef PubMed 46 Poli, A., Faenza, I., Chiarini, F., Matteucci, A., McCubrey, J.A. and Cocco, L. (2013) K562 cell proliferation is modulated by PLCβ1 through a PKCα-mediated pathway. Cell Cycle 12, 1713–1721 CrossRef PubMed 47 Ramazzotti, G., Faenza, I., Gaboardi, G.C., Piazzi, M., Bavelloni, A., Fiume, R., Manzoli, L., Martelli, A.M. and Cocco, L. (2008) Catalytic activity of nuclear PLCβ1 is required for its signalling function during C2C12 differentiation. Cell. Signal. 20, 2013–2021 CrossRef PubMed 48 Lu, Z., Liu, D., Hornia, A., Wayne, D., Pagano, M. and Foster, A.D. (1998) Activation of protein kinase C triggers its ubiquitination and degradation. Mol. Cell. Biol. 18, 839–845 PubMed 49 Gaboardi, G.C., Ramazzotti, G., Bavelloni, A., Piazzi, M., Fiume, R., Billi, A.M., Matteucci, A., Faenza, I. and Cocco, L. (2009) A role for PKCε during C2C12 myogenic differentiation. Cell. Signal. 22, 629–635 CrossRef PubMed 50 Faenza, I., Ramazzotti, G., Bavelloni, A., Fiume, R., Gaboardi, G.C., Follo, M.Y., Gilmour, R.S., Martelli, A.M., Ravid, K. and Cocco, L. (2007) Inositide-dependent phospholipase C signaling mimics insulin in skeletal muscle differentiation by affecting specific regions of the cyclin D3 promoter. Endocrinology 148, 1108–1117 CrossRef PubMed
Received 6 May 2014 doi:10.1042/BST20140128
