Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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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)

Hepatocyte growth factor (HGF), a humoral mediator for regeneration of liver and kidney, possesses multiple biological activities. To investigate target cell specificity and to examine whether multiple actions of HGF are related to properties of the HGF receptor on target cells, we examined the effects of HGF on cell growth and motility and analyzed the HGF receptor in various species of cells. HGF stimulated growth and DNA synthesis of PAM212 (naturally immortalized mouse keratinocytes), Mv1Lu (mink lung epithelia), and A431 (human epidermoid carcinoma) cells, as well as mature hepatocytes, but inhibited those of IM-9 (human B-lymphoblasts). Conversely, HGF had a marked stimulatory effect on cell motility of MDCK (Mardin-Darby canine kidney epithelia) cells, but not on their growth. Also, HGF enhanced the motility of various species of cells, including A431, PAM212, HepG2 (human hepatoma), KB (human epidermoid carcinoma), and J-111 (human monocytes) cells. Scatchard analysis of 125I-HGF binding to hepatocytes indicated that the cells expressed both high- and low-affinity binding sites for HGF with Kd values of 23 and 260 pM, respectively. High-affinity HGF receptor with Kd values of 20-25 pM was detected at 40-720 sites/cell in MDCK, A431, PAM212, Lu99, and IM-9 cells, but not in fibroblasts and hematopoietic cells. In contrast, low-affinity binding sites were detected in all cell lines examined, even in those not responsive to HGF. Northern blots revealed that cells possessing a high-affinity HGF receptor expressed c-MET/HGF receptor mRNA. Therefore, HGF probably regulates both cell growth and motility of various types of epithelial cells and some types of mesenchymal cells. The multiple biological activities of HGF may be exerted through a high-affinity HGF receptor linked to multiple distinct intracellular signaling pathways.
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PMID:Regulation of cell growth and motility by hepatocyte growth factor and receptor expression in various cell species. 132 54

Hepatocyte growth factor (HGF), also known as scatter factor (SF), is a polypeptide which induces motility and/or mitogenesis in epithelial cells. The receptor for HGF/SF, p190MET, is a two-chain transmembrane tyrosine kinase encoded by the MET proto-oncogene. To identify the cytoplasmic effectors involved in signal transduction we have produced the human HGF/SF receptor in insect cells (Sf9) by means of a recombinant baculovirus. Two 170-kDa forms of the receptor were synthesized in Sf9 cells: the uncleaved single-chain precursor (which is by far the more abundant) and the proteolytically processed two-chain molecule. Both receptor species are phosphorylated on tyrosine in vivo and are active kinases in vitro. The recombinant receptor binds and phosphorylates in vitro four known cytoplasmic transducers containing src homology region 2 (SH2) domains: the 85-kDa subunit of phosphatidylinositol 3-kinase (Pl 3-kinase), rasGAP, phospholipase-C gamma (PLC-gamma), and p59Fyn, a tyrosine kinase of the src family. In all cases the association is strictly dependent on tyrosine phosphorylation of the receptor, indicating that it occurs via specific interaction with the SH2 domains. These results show that the HGF/SF receptor has the sequence requirements for binding a spectrum of cytoplasmic transducers whose different combinations in target cells may result in the observed pleiotropic biological response.
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PMID:Autophosphorylation promotes complex formation of recombinant hepatocyte growth factor receptor with cytoplasmic effectors containing SH2 domains. 132 86

The proto-oncogene c-MET encodes a transmembrane tyrosine kinase receptor for hepatocyte growth factor/scatter factor (HGF/SF). HGF/SF stimulates the proliferation and motility of various cell types. Because HGF/SF is also a melanocyte mitogen, we investigated the biological role of HGF/SF, including c-Met expression, activation and signal transduction, in normal and malignant human melanocytes. We show that HGF/SF is mitogenic in the presence of synergistic factors, such as basic fibroblast growth factor (bFGF) and mast cell growth factor (MGF) and that, by itself, it stimulates the motility of normal human melanocytes. The ligand also maintained high levels of tyrosinase activity and melanin content in theses cells. Signal transduction by HGF/SF included phosphorylation of tyrosyl residues on c-Met, a cascade of tyrosine phosphorylations on several other proteins and activation of microtubule-associated protein kinase/extracellular signal-regulated kinase. Met expression and activity are normal in human melanomas, and constitutive activity of HGF/SF in retrovirally infected autonomously proliferative mouse melanocytes is insufficient to confer the malignant phenotype. Our findings suggest that activation of Met in response to HGF/SF may contribute to malignant progression synergistically with the aberrant expression of bFGF in malignant melanocytes and that, in addition, the peptide may promote dispersion of factor-dependent melanocytes from early stages of primary melanomas to ectopic sites.
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PMID:Met and hepatocyte growth factor/scatter factor signal transduction in normal melanocytes and melanoma cells. 133 34

The receptor for Hepatocyte Growth Factor is a transmembrane tyrosine kinase encoded by the c-MET oncogene. We have previously shown that the Met protein is expressed in several human epithelial tissues. The receptor is barely detectable, however, in normal thyroids and in specimens from patients affected by non-neoplastic thyroid diseases. Now we report that the expression of the Met/HGF receptor is increased a hundred fold in 22 out of 41 human carcinomas derived from the thyroid follicular epithelium. A comprehensive analysis of 15 cases showed that the overexpressing carcinomas belong to histotype variants correlated with negative prognosis and in all but one case there were evidences of locally advanced disease and/or distant metastases. The 11 benign adenomas and the 5 medullary carcinomas tested were negative. Western blot analysis with monoclonal antibodies directed against either the intracellular or the extracellular receptor domains failed to reveal major structural alterations. Southern blot analysis also demonstrated that the c-MET gene was not amplified nor rearranged. These data suggest a role for the overexpression of c-MET oncogene in the pathogenesis and progression of thyroid tumors derived from the follicular epithelium.
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PMID:Overexpression of the c-MET/HGF receptor gene in human thyroid carcinomas. 133 53

The receptor for hepatocyte growth factor, also known as scatter factor (HGF/SF), has recently been identified as the 190-kDa heterodimeric tyrosine kinase encoded by the MET proto-oncogene (p190MET). The signaling pathway(s) triggered by HGF/SF are unknown. In A549 cells, a lung epithelial cell line, nanomolar concentrations of HGF/SF induced tyrosine phosphorylation of the p190MET receptor. The autophosphorylated receptor coprecipitated with phosphatidylinositol 3-kinase (PI 3-kinase) activity. In GTL16 cells, a cell line derived from a gastric carcinoma, the p190MET receptor, overexpressed and constitutively phosphorylated on tyrosine, coprecipitated with PI 3-kinase activity and with the 85-kDa PI 3-kinase subunit. In these cells activation of protein kinase C or the increase of intracellular [Ca2+] inhibits tyrosine phosphorylation of the p190MET receptor as well as the association with both PI 3-kinase activity and the 85-kDa subunit of the enzyme. In an in vitro assay, tyrosine phosphorylation of the immobilized p190MET receptor was required for binding of PI 3-kinase from cell lysates. These data strongly suggest that the signaling pathway activated by the HGF/SF receptor includes generation of D-3-phosphorylated inositol phospholipids.
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PMID:The tyrosine-phosphorylated hepatocyte growth factor/scatter factor receptor associates with phosphatidylinositol 3-kinase. 171 89

The MET oncogene encodes a transmembrane tyrosine kinase receptor. Recently, hepatocyte growth factor (HGF), a potent growth factor for hepatocytes involved in liver regeneration, has been proposed as a ligand. In this paper, the physiological role of the human Met/HGF receptor is investigated by studying its specific distribution in normal and neoplastic tissues. Northern blot analysis has shown that the MET gene is selectively expressed in several epithelial tissues. High levels of MET mRNA have been found in liver, gastrointestinal tract, thyroid and kidney. Western blot analysis has shown that the levels of the Met protein generally correspond to those of the mRNA. However, in the thyroid, where there is a high level of MET mRNA, the protein was barely detectable, suggesting translational or post-translational regulation. The protein was also detected in the brain. Normal or increased levels of MET mRNA and Met protein were consistently found in fresh samples of carcinomas as well as in epithelial tumor cell lines. In thyroid carcinomas of a specific histiotype the amount of Met protein, almost undetectable in the normal counterpart, was found to be increased more than 100-fold. The tissue distribution of the Met/HGF receptor indicates that this molecule is involved in growth control of epithelial cells other than hepatocytes and suggests that its increased expression may confer a growth advantage to neoplastic cells.
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PMID:Expression of the Met/HGF receptor in normal and neoplastic human tissues. 171 65

The human c-MET oncogene encodes a transmembrane tyrosine kinase (p190c-met) with structural and functional features of a growth-factor receptor. Monoclonal antibodies (MAbs) have been used to investigate the distribution of the c-Met protein in human normal and neoplastic tissues. By immunofluorescence microscopy homogeneous expression was detected in normal hepatocytes as well as in epithelial cells lining the stomach, the small and the large intestine. Positive staining was also found in epithelial cells of the endometrium and ovary, and in basal keratinocytes of esophagus and skin. By Northern blot analysis, high levels of c-met messenger RNA were detected in specimens of liver, gastro-intestinal tract and kidney. c-met-specific mRNA was also found in thyroid, pancreas and placenta, in which organs c-Met protein was barely detectable by immunofluorescence. The antibodies revealed expression of c-MET protein in hepatomas (11/14), carcinomas of colon and rectum (19/21), stomach (11/22), kidney (16/19), ovary (9/17) and skin (7/17). Carcinomas of the lung (13/20), thyroid (11/13) and pancreas (5/7) were also positive. In these last cases (lung, thyroid and pancreas) tumor cells were homogeneously stained by the antibodies, whereas in their normal counterparts staining was barely detectable. These data suggest that the receptor encoded by c-MET plays a physiological role in epithelial cell growth and that its expression is altered in human carcinomas.
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PMID:The receptor encoded by the human c-MET oncogene is expressed in hepatocytes, epithelial cells and solid tumors. 191 29

Hepatocyte growth factor (HGF) is a mesenchymal derived growth factor known to induce proliferation and "scattering" of epithelial and endothelial cells. Its receptor is the tyrosine kinase encoded by the c-MET protooncogene. Here we show that highly purified recombinant HGF stimulates hemopoietic progenitors to form colonies in vitro. In the presence of erythropoietin, picomolar concentrations of HGF induced the formation of erythroid burst-forming unit colonies from CD34-positive cells purified from human bone marrow, peripheral blood, or umbilical cord blood. The growth stimulatory activity was restricted to the erythroid lineage. HGF also stimulated the formation of multipotent CFU-GEMM colonies. This effect is synergized by stem cell factor, the ligand of the tyrosine kinase receptor encoded by the c-KIT protooncogene, which is active on early hemopoietic progenitors. By flow cytometry analysis, the receptor for HGF was found to be expressed on the cell surface in a fraction of CD34+ progenitors. Moreover, in situ hybridization experiments showed that HGF receptor mRNA is highly expressed in embryonic erythroid cells (megaloblasts). HGF mRNA was also found to be produced in the embryonal liver. These data show that HGF plays a direct role in the control of proliferation and differentiation of erythroid progenitors, and they suggest that it may be one of the long-sought mediators of paracrine interactions between stromal and hemopoietic cells within the hemopoietic microenvironment.
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PMID:Hepatocyte growth factor induces proliferation and differentiation of multipotent and erythroid hemopoietic progenitors. 752 22

Hepatocyte growth factor (scatter factor) and its receptor, the c-met proto-oncogene product (c-MET), have been implicated in embryogenesis, tissue reorganization, and tumor progression. Little is known, however, of the expression and functional significance of these molecules in prostatic cells and tissue. In this investigation, we assessed the expression of hepatocyte growth factor (HGF) and c-MET in prostatic tissues and cell lines and also determined the effect of purified recombinant HGF on cell proliferation and scattering of prostatic carcinoma cell lines. HGF was expressed by human prostatic stromal myofibroblasts in primary culture but not by three human prostatic carcinoma cell lines (LNCaP, DU 145, and PC-3) as assessed by Northern blot analysis. HGF was also detected by reverse transcriptase-polymerase chain reaction in both benign and malignant tissues from radical prostatectomy specimens. c-MET transcripts were identified by Northern blot in two androgen-insensitive human prostatic carcinoma cell lines (DU 145 and PC-3) but not the androgen-sensitive LNCaP cell line. Additional evidence of linkage of androgen responsiveness and c-MET was provided by experiments in which androgen deprivation of normal rat prostates via castration produced a marked up-regulation of c-MET expression as determined by Northern blot and immunohistochemistry. c-MET protein was detected by immunohistochemical analysis in a substantial percentage (58 of 128 or 45%) of prostatic carcinomas and was found more often in metastatic growths of human prostatic carcinoma (15 of 20 patients) compared with primary tumors (43 of 108 patients; P < 0.005). Moreover, in Dunning R-3327 rat prostatic carcinoma cell lines, c-MET expression was highest in the androgen-insensitive subline with the highest metastatic capacity. Purified recombinant human HGF induced dose-dependent cellular proliferation and scattering in the DU 145 carcinoma cell line. These data indicate that HGF may function in the prostate gland as a paracrine growth factor, with synthesis by stromal cells and with biological target cells being the epithelial cells. Expression of the HGF receptor, c-MET, is up-regulated by androgen deprivation and c-MET appears to be preferentially expressed on androgen-insensitive, metastatic cells, suggesting a possible linkage of c-MET expression with prostatic carcinoma progression.
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PMID:Hepatocyte growth factor and its receptor (c-MET) in prostatic carcinoma. 763 32

The pleiotropic effects (mitogenesis, motogenesis, and morphogenesis) elicited by hepatocyte growth factor/scatter factor (HGF/SF) are mediated by the activation of the tyrosine kinase receptor encoded by the MET proto-oncogene. Following autophosphorylation, the receptor associates with the p85/110 phosphatidylinositol (PI) 3-kinase complex in vivo and in vitro. By a combination of two complementary approaches, competition with synthetic phosphopeptides and association with Tyr-Phe receptor mutants, we have identified Y-1349 and Y-1356 in the HGF/SF receptor as the binding sites for PI 3-kinase. Y-1349VHV and Y-1356VNV do not conform to the canonical consensus sequence YXXM for PI 3-kinase binding and thus define YVXV as a novel recognition motif. Y-1349 and Y-1356 are located within the C-terminal portion of the HGF/SF receptor and are phosphorylation sites. The affinity of the N- and C-terminal src homology region 2 (SH2) domains of p85 for the phosphopeptides including Y-1349 and Y-1356 is 2 orders of magnitude lower than that measured for Y-751 in the platelet-derived growth factor receptor binding site. However, the closely spaced duplication of the novel recognition motif in the native HGF/SF receptor may allow binding with both SH2 domains of p85, thus generating an efficient docking site for PI 3-kinase. In agreement with this model, we have observed that a phosphopeptide including both Y-1349 and Y-1356 activates PI 3-kinase in vitro.
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PMID:A novel recognition motif for phosphatidylinositol 3-kinase binding mediates its association with the hepatocyte growth factor/scatter factor receptor. 768 41


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