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Query: EC:2.7.10.1 (ERK)
 95,504 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have cloned a genomic region of the murine fibroblast growth factor (FGF) receptor 1 (FGFR1) gene that includes three alternative exons for the third immunoglobulinlike domain in the extracellular region of the receptor. The mRNA of one of these splice variants encodes a secreted receptor that lacks transmembrane and cytoplasmic sequences as well as a portion of the third immunoglobulinlike domain. Highest levels of mRNA encoding this variant were found in brain, skeletal muscle, and skin. We expressed this form of FGFR1 in CHO cells and showed that the recombinant secreted protein binds acidic FGF. We also discovered a novel alternative exon in the third immunoglobulinlike domain that encodes part of a transmembrane FGFR1 mRNA. This exon is highly homologous to the corresponding region of the keratinocyte growth factor receptor. Transcripts including this exon were present at highest levels in the skin. We cloned an FGFR1 cDNA which includes this exon and expressed this receptor variant in L6 rat skeletal muscle myoblasts. The new receptor variant had a 50-fold-lower affinity for basic FGF than does the published FGFR1 variant, whereas both forms of receptor bound acidic FGF with high affinity. These results show that the third immunoglobulinlike domain plays an important role in determining the binding specificities for different FGFs. Our data provide the first evidence that differential splicing in the extracellular region of a receptor gene generates receptor variants with different ligand-binding specificities.
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PMID:Differential splicing in the extracellular region of fibroblast growth factor receptor 1 generates receptor variants with different ligand-binding specificities. 130 95

Fibroblast growth factors (FGFs) can influence the growth and differentiation of cultured cells derived from neuroectoderm, ectoderm or mesenchyme. The FGFs interact with a family of at least four closely related receptor tyrosine kinases that are products of individual genes. To investigate the role of FGFs in the growth and differentiation of embryonic tissues and to determine whether the individual FGF receptor genes might have specific functions, we compared the localization of mRNA for two FGF receptor genes, FGFR1 (the flg gene product) and FGFR2 (the bek gene product), during limb formation and organogenesis in mouse embryos (E9.5-E16.5). Although the two genes were coexpressed in some tissues, the differential expression of FGFR1 and FGFR2 in most embryonic tissues was striking. FGFR1 was expressed diffusely in mesenchyme of limb buds, somites and organ rudiments. In contrast, FGFR2 was expressed predominantly in the epithelial cells of embryonic skin and of developing organs. The differential expression of FGFR1 and FGFR2 in mesenchyme and epithelium respectively, suggests the receptor genes are independently regulated and that they mediate different functions of FGFs during development.
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PMID:Two FGF receptor genes are differentially expressed in epithelial and mesenchymal tissues during limb formation and organogenesis in the mouse. 131 77

Binding of cellular growth factors to their receptors constitutes a highly specific interaction and the basis for cell and tissue-type specific growth and differentiation. A unique feature of fibroblast growth factor (FGF) receptors is the multitude of structural variants and an unprecedented degree of cross-reactivity between receptors and their various ligands. To examine receptor-ligand specificity within these families of growth factors and receptors, we used genetic engineering to substitute discrete regions between Bek/FGFR2 and the closely related keratinocyte growth factor receptor (KGFR). We demonstrate that a confined, 50 amino acid, variable region within the third immunoglobulin-like domain of Bek and KGFR exclusively determines their ligand binding specificities. Replacing the variable region of Bek/FGFR2 with the corresponding sequence of KGFR resulted in a chimeric receptor which bound KGF and had lost the capacity to bind basic FGF. We present evidence that the two variable sequences are encoded by two distinct exons that map close together in the mouse genome and follow a constant exon, suggesting that the two receptors were derived from a common gene by mutually exclusive alternative mRNA splicing. These results identify the C-terminal half of the third immunoglobulin-like domain of FGF receptors as a major determinant for ligand binding and present a novel genetic mechanism for altering receptor-ligand specificity and generating receptor diversity.
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PMID:A confined variable region confers ligand specificity on fibroblast growth factor receptors: implications for the origin of the immunoglobulin fold. 131 75

The bek gene encodes a member of the high-affinity fibroblast growth factor receptor family. The BEK/FGFR-2 receptor is a membrane-spanning tyrosine kinase with the typical features of FGF receptors. We have cloned a murine bek cDNA and expressed it in receptor-negative Chinese hamster ovary cells and in 32D myeloid cells. The BEK receptor expressed in Chinese hamster ovary cells binds acidic FGF, basic FGF, and Kaposi FGF equally well but does not bind keratinocyte growth factor or FGF-5 appreciably. Upon treatment with basic FGF or Kaposi FGF, the BEK receptor is phosphorylated and a mitogenic response is achieved. Heparan sulfate proteoglycans have been shown to play an obligate role in basic FGF binding to the high-affinity FLG receptor. Unlike the BEK-expressing Chinese hamster ovary cells, 32D cells expressing the BEK receptor require the addition of exogenous heparin in order to grow in the presence of basic FGF or Kaposi FGF. We show that the addition of heparin greatly enhances the binding of radio-labeled basic FGF to the receptor. Thus the BEK receptor, like FLG, also requires an interaction with heparan sulfate proteoglycans to facilitate binding to its ligands.
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PMID:Characterization of the murine BEK fibroblast growth factor (FGF) receptor: activation by three members of the FGF family and requirement for heparin. 137 95

Alternatively spliced variants of fibroblast growth factor receptor 1 mRNA are predicted to encode secreted forms and membrane-bound forms of receptors. The predicted amino acid sequences of these receptor variants differ in a portion of the extracellular region. In this study, we characterized the function of one of these splice variants which was predicted by its cDNA to be a secreted FGF receptor. We expressed this secreted form of the human FGFR1 (sFGFR1) in Chinese hamster ovary cells. The sFGFR1 protein oligomerized upon ligand binding. Surprisingly, the sFGFR1 preferentially bound basic FGF over acidic FGF. In cross-linking experiments, the sFGFR1 showed higher binding affinity for basic FGF (Kd approximately 30 nM) than for acidic FGF (Kd greater than 300 nM). These results suggest that this secreted form of FGF receptor has an unusual ligand binding specificity that may be important for its biological role in vivo.
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PMID:A naturally occurring secreted form of fibroblast growth factor (FGF) receptor 1 binds basic FGF in preference over acidic FGF. 137 91

Fibroblast growth factors (FGFs) and their receptors play an important role in cell growth, angiogenesis and embryonal development. Four distinct genes encoding fibroblast growth factor receptors (FGFRs) were identified: flg, encoding FGFR1, bek encoding FGFR2, and the genes for FGFR3 and FGFR4. Both FGFR2 and keratinocyte growth factor receptor (KGFR) are encoded by the same gene, bek. To study the regulation of expression of the FGF receptors we analysed the DNA sequence flanking the 5' region of the cDNA of murine FGFR2 to seek elements that control its transcription. A 5-kbp fragment containing the 5' end of the cDNA was isolated from mouse genomic library and used to map the promoter region. We found that the sequence encoding the 5' non-translated region of the FGFR2/KGFR cDNA contains an intron located 210 bp upstream from the translation start site. Using RNAase protection and primer extension, we identified the mRNA start 37 bp upstream from the beginning of the bek cDNA. The promoter activity was found to reside in a 1.3-kbp fragment upstream from the cDNA, and deletion mapping further localized the promoter to a 0.7-kbp fragment. The sequence of this region shows high G+C content (62%), which is particularly emphasized in the 200 bp upstream from the mRNA start (80% G+C). This region contains the CCGCCC, GGGCGG AND GGAGG motifs also found in promoters of other growth factor receptors. Neither TATA nor CAAT boxes were found near the RNA start site. The characterization of this promoter will allow studies of the regulation of expression of the FGFR2 during development and in pathophysiological states. The differences between the promoter sequence of the gene for FGFR2 (bek) and FGFR1 (flg) may explain their differential expression during development.
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PMID:Promoter region of the murine fibroblast growth factor receptor 2 (bek/KGFR) gene. 140 37

The BEK transmembrane protein tyrosine kinase is a receptor for both acidic and basic fibroblast growth factors. We identify several different transcripts which code for BEK-related proteins. These proteins differ from BEK in regions expected to control receptor activity. Thus, some of the proteins have altered extracellular, ligand-binding domains, and others an altered carboxy-terminal tail. Still other forms of BEK differ only in their juxtamembrane domains. Sequencing of parts of the BEK gene shows that alternative splicing of the premessenger can account for at least some of this diversity. In particular, an apparently tissue specific, mutually exclusive splicing of two internal exons permits both the previously described K-SAM mRNA and the BEK mRNA to be derived from the same premessenger.
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PMID:Multiple mRNAs code for proteins related to the BEK fibroblast growth factor receptor. 164 4

The aim of this work was to compare the distribution in organs of syngeneic mice sarcoma JWS and leukemia L-1210 cells previously labelled with sodium dichromate (Na2 51CrO4) and iododeoxyuridine (125IUDR) after i.v. transplantation. Also, the results obtained with both labels were compared. Both kinds of cells under study are trapped in lungs, but the number of trapped JWS cells is greater. L-1210 cells probably recirculate. The cells undergo extensive destruction during the first 3 days after transplantation. This kind of study requires the use of two markers: cytoplasmic and nuclear and careful analysis of radioactivity changes is also required to obtain proper conclusions.
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PMID:[Kinetics and distribution of transplanted sarcoma JWS and leukemia L1210 cells by intravenous route]. 182 78

The distribution of neoplastic--JWS sarcoma and lymphatic leukemia L-1210 cells after intravenous injection into allogeneic recipients is presented. Cells were labelled with two labels: cytoplasmic (sodium chromate-51CR) and nuclear (iododeoxyuridine-125IUDR). Radioactivity of blood, lungs, liver, spleen and kidneys was measured 90 minutes and 24 hours after cell transplantation. The pattern of cell trapping, destruction and elimination from the circulation was characteristic of cell line injected. Destruction and elimination processed faster in allogeneic system than in syngeneic one.
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PMID:[Distribution and elimination of transplanted sarcoma JWS and leukemia L1210 cells in allogeneic recipients--inbred C57BL mice by intravenous route]. 182 79

K-SAM gene was originally isolated as an amplified gene in a stomach cancer cell line by in-gel DNA renaturation method. K-SAM encodes a membrane receptor with tyrosine kinase and is often amplified in poorly differentiated type of stomach cancer, while c-ERBB-2 is often amplified in well differentiated type of stomach cancer. There are several forms of K-SAM mRNAs which are generated by alternative splicing, and two types of K-SAM protein without transmembrane region. The ligand of K-SAM is considered to be growth factor(s) belonging to fibroblast growth factor (FGF) or heparin binding growth factor (HBFG) family. We have also frequently found amplification of HST-1 or HSTF1 gene in esophageal cancer. HST-1 gene, originally found as a transforming gene, is located on human chromosome 11q13, and it locates 35 kbp apart from its related gene, INT-2. Neither of the genes was expressed even in cancer cells with the co-amplification. By cosmid walking, we have identified at least two genes, designated tentatively as EXP1 and EXP2, on the same amplicon as HST-1 and INT-2, and the mRNAs for EXP1 and EXP2 genes were increased in amounts proportional to the degree of amplification.
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PMID:Biological significance of gene amplification in carcinogenesis. 184 51


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