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C-terminal truncated forms of Met, the hepatocyte growth factor receptor.

ABSTRACT: The MET proto-oncogene encodes a transmembrane tyrosine kinase of 190 kDa (p190MET), which has recently been identified as the receptor for hepatocyte growth factor/scatter factor. p190MET is a heterodimer composed of two disulfide-linked chains of 50 kDa (p50 alpha) and 145 kDa (p145 beta). We have produced four different monoclonal antibodies that are specific for the extracellular domain of the Met receptor. These antibodies immunoprecipitate with p190MET two additional Met proteins of 140 and 130 kDa. The first protein (p140MET) is membrane bound and is composed of an alpha chain (p50 alpha) and an 85-kDa C-terminal truncated beta chain (p85 beta). The second protein (p130MET) is released in the culture supernatant and consists of an alpha chain (p50 alpha) and a 75-kDa C-terminal truncated beta chain (p75 beta). Both truncated forms lack the tyrosine kinase domain. p140MET and p130MET are consistently detected in vivo, together with p190MET, in different cell lines or their culture supernatants. p140MET is preferentially localized at the cell surface, where it is present in roughly half the amount of p190MET. The two C-terminal truncated forms of the Met receptor are also found in stable transfectants expressing the full-length MET cDNA, thus showing that they originate from posttranslational proteolysis. This process is regulated by protein kinase C activation. Together, these data suggest that the production of the C-terminal truncated Met forms may have a physiological role in modulating the Met receptor function.

SUBMITTER: Prat M

PROVIDER: S-EPMC361753 | biostudies-other | 1991 Dec

REPOSITORIES: biostudies-other

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C-terminal truncated forms of Met, the hepatocyte growth factor receptor.

Prat M M Crepaldi T T Gandino L L Giordano S S Longati P P Comoglio P P

Molecular and cellular biology 19911201 12

The MET proto-oncogene encodes a transmembrane tyrosine kinase of 190 kDa (p190MET), which has recently been identified as the receptor for hepatocyte growth factor/scatter factor. p190MET is a heterodimer composed of two disulfide-linked chains of 50 kDa (p50 alpha) and 145 kDa (p145 beta). We have produced four different monoclonal antibodies that are specific for the extracellular domain of the Met receptor. These antibodies immunoprecipitate with p190MET two additional Met proteins of 140 an ...[more]

PMID: 1944272

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Project description:MET, the receptor for hepatocyte growth factor (HGF), is involved in wide variety of biological events and its aberrant activation is implicated in the pathogenesis of cancer. Especially, MET signaling is associated with resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs), key drugs in therapy of non-small cell lung cancer. MET has 11 potential N-glycosylation sites, however, the site-specific roles of N-glycans have not been elucidated. Here, we report that N-glycans regulate proteolytic processing of MET and HGF induced MET signaling, site specifically. N-glycosylation inhibitors suppressed processing and trafficking of endogenous MET in H1975 and EBC-1 lung cancer cells and exogenous MET in CHO cells. We purified the recombinant extracellular domain of human MET and determined the site-specific N-glycan structures and occupancy using nanoflow liquid chromatography-electrospray ionization mass spectrometry. The results indicated that most sites were fully glycosylated and the dominant population were complex-type which were rich in sialic acids and core fucoses. To examine the effects of N-glycan deletion of MET, we prepared endogenous-MET-knockout Flp-In CHO cells and transfected with series of N-glycan deletion mutants of MET. It was found that several N-glycans are implicated in processing of MET. It was also suggested that the N-glycans of -subunit of MET positively regulate HGF signaling, and the N-glycans of β-subunit negatively regulate HGF signaling. In all-N-glycan deletion mutant, processing and signaling were significantly suppressed. It was observed that the cell proliferation rate was suppressed in all-N-glycan deletion mutant, although the cell surface expression levels of MET were not completely diminished. We examined the HGF biding affinity for the recombinant extracellular domain of MET and found that peptide N-glycosidase F treatment did not affect the ligand binding affinity. It was suggested that N-glycans of MET affect the status and the function of the receptor site-specifically.

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C-terminal truncated forms of Met, the hepatocyte growth factor receptor.

Publications

C-terminal truncated forms of Met, the hepatocyte growth factor receptor.

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