Biochimica et BiophysicaActa, 1089(1991)244-246 '© 1991 ElsevierSciencePublishersB.V. 0167-4781/91/$03.50 ADONIS 0167478191001536
Two cDNAs encoding novel human FGF receptor Masaharu Seno, Reiko Sasada, Tatsuya Watanabe, Kaori lshimaru and Koichi Igarashi Biotechnology ResearchLaboratories, Researchand DecelopmentDicision, Takeda ChemicalIndustries, Ltd., Osaka (Japan) (Received21 January 1991) Keywords: FGF receptor;cDNA sequence;Tyrosinekinase; bek; fig; bfr; Solublereceptor;(Human) Two types of cDNAs encoding novel human FGF receptors were isolated. These two cDNAs were found to be closely related to the oucogene bek. Products from these genes were membrane-bound when their cDNAs were transiently expressed in COS cells, whereas products from the regions coding extracellular domains were free of membrane attachment and found in the culture medium.
Fibroblast growth factors (FGFs) are potent mitogens for a wide variety of cells derived from mesoderm and neuroectoderm, particularly endothelial cells (reviewed in Ref. 1). FGFs also induce differentiation of adipocytes and stimulate neurite outgrowth from neuronal cells and from PCI2 cells. Complementary DNA sequences for human F G F receptors have recently been reported [2-4]. These cDNAs are classified as members of the fig [2,5] and bek [2,6] families. Using a mixture of oligonucleotides (5'-ATrCTTATGCTTCCCGATCATI'/CTTCATCATT/CTCCA'UI'/CTC-3') designed from the amino acid sequence of chicken basic F G F receptor (529aa-541aa)  as a probe, we isolated two types of novel cDNA clones for the human F G F receptor from a human carcinoma cell line Kato-lll  eDNA library. These two cDNAs, 2.3 kb and 2.6 kb in length, were subeioned into the pUC plasmid vector to construct plasmids pTBI283 and pTB1284, respectively. The nucleotide sequence analyses showed these cDNAs to be closely related to bek rather than to fig and we named them bfr (bek related F G F receptor). The nucleotide sequence shown in Fig. 1 is bfr-I (pTB1284) composed of 2650 bp and bfr-1 encodes the protein, BFR-I, which consists of 769 amino acid residues. The other cDNA, bfr-2, composed of 2299 bp showed deletions from nt 134 to 478 and from nt 1309 to 1314 (underlined portions in Fig. 1), and a single base change of G to T at nt 1029 in the
The sequence data in this paper have been submitted to the EMBL Data Bank under accessionnumber XSfi191. Correspondence: M. Seno, BiotechaologyResearch Laboratories,
Research and Development Diviskm,Takeda Chemical Industries, Ltd., 2-17-85Juso-honmachi,Yodogawa-ku,Osaka 532, Japan.
bfr-I sequence. Hence, bfr-2 encodes the protein, BFR-2, composed of 652 amino acid residues in the same open reading frame as shown in bfr-1 (Fig. 1). The amino acid sequences of BFR-1, BFR-2, BEK and FLG were compared in Fig. 2. The differences between BFR-1 and BFR-2 mainly result from the deletion of the nucleotide sequences shown in Fig. 1. The similarities of amino acid sequences between BFR-I and BEK, and that between BFR-1 and FLG were calculated as 90.4% and 64.4%, respectively. From alignment of the amino acid sequences (Fig. 2), BFR-1 has an extracellular domain composed of three possible disulfide bridges (IgG-like domains ) and an acidic core sequence in its amino terminal side, a transmembrane region, and a tyrosine kinase domain divided by an insertion sequence as assigned in BEK and FLG . BFR-2 lacks the first IgG-like domain and the acidic core. The isolation of multiple cDNAs may imply the existence of the polymorphism in the F G F receptor, in the case of fig, polymorphism of this molecule has been recognized by review of independent reports [4,9]. The presence of polymorphism in the F G F receptor is consistent with the observation that FGFs cross-linked to two independent molecules of 145 kDa and 125 kDa . Such polymorphism may have resulted from alternative splicing or duplication of the gene. Nucleotide C at nt 1152 (Fig. 1) was replaced with A by site-directed mutation, which resulted in changing the tyrosine codon to a codon for termination of translation. By this mutation, bfr cDNAs were designed to code only extracellular domains, BFR-le~ and BFR-2e~. The cDNAs bfr-I and bfr-2, and their derivatives (bfr1~ and bfr-2ex) were linked to MuLV-LTR with SV40 ori to construct expression plasmids . Each result-
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