No abstract

Kitamura, N. (1989) Biochem. Biophys. Res. Commun. 163, In the present study, we report the sequence of another cDNA clone for a shorter form of hHGF mRNA. Comparison of the sequence with that of the hHGF cDNA revealed that the two sequences are identical in their 5' ends up to 865 nucleotides downstream from the translation-initiation site, then completely diverge from each other. By Northern blot analysis, the hHGF-related 1.5-kb mRNA, which corresponded to the newly isolated cDNA variant, was identified in human placenta. Sequence analysis of a human genomic HGF clone showed that the diverged 3'-terminal portion of the mRNA is generated by alternative RNA-processing events utilizing a specific exon. The mRNA could encode a short hHGF molecule of 290 amino acids corresponding to the N-terminal portion of hHGF which consists of 728 amino acids. In order to examine the effect of the predicted translation product on hepatocyte growth, an expression plasmid for the cDNA variant was constructed and transfected into Cos cells. Immunoblotting analysis showed that the transfected Cos cells produced a protein of about 33 kDa. The protein product did not stimulate DNA synthesis by rat hepatocytes in primary culture.Hepatocyte growth factor (HGF) is a protein which stimulates the growth of adult rat hepatocytes in primary culture. HGF have been purified from the plasma of patients with fulminant hepatic failure [I], normal human plasma [2], rat platelet [3], and rabbit serum [2, 41. The purified HGF is a heterodimer consisting of heavy and light chains with molecular masses of about 65 kDa and 35 kDa, respectively. The entire amino acid sequences of human and rat HGF have been elucidated by sequence determinations of molecularly cloned cDNA [5 -81. The sequences showed that the heavy and light chains are produced from a single precursor by proteolytic processing. HGF consists of characteristic structural domains. One of these domains is four tandem repeats called kringles in the heavy chain region. The kringle structures are also present in several other proteins, such as plasminogen [9], prothrombin [lo], tissue plasminogen activator [I 11, urokinase [12], coagulation factor XI1 [I31 and apolipoprotein(a) [14]. The first kringle in plasminogen and the second kringle in

c-Met is a high-affinity receptor for hepatocyte growth factor (HGF) and plays a crucial role in embryonic development, as well as in the process of tissue repair. Overexpression and amplification of c-Met are often observed in various cancer tissues, especially in gastric carcinoma. It has, however, been unclear whether the overexpression leads to activation of the c-Met receptor. To address this point, we prepared an antibody (anti-phospho-Met) which specifically recognizes c-Met that is phosphorylated at Y1235, a major phosphorylation site of c-Met. Normal as well as cancerous gastric tissue was positive for anti-total-Met staining, whereas only cancerous tissue was strongly positive for anti-phospho-Met staining; cells near the basal layer were moderately positive, and the proliferative zone in normal tissue was only weakly positive. Among cancerous tissues from seven patients examined in the present study, those from six patients were strongly positive for phospho-Met staining. These results indicate that c-Met is actually activated in gastric carcinoma tissue, and may trigger proliferation/anti-apoptotic signals. (Cancer Sci 2004; 95: 803-808)

Hepatocyte growth factor (HGF) is secreted as an inactive single‐chain precursor from the producing cells, and normally remains in this form associated with the extracellular matrix. In response to tissue injury, the single‐chain precursor is converted to a biologically active heterodimer by a serine protease, the activity of which is induced in the injured tissue. We have previously identified HGF activator, a serum serine protease that activates single‐chain HGF. The sequence of HGF activator cDNA revealed that the HGF activator is homologous to blood‐coagulation factor XIIa. In this study, we found that coagulation factor XIIa has an ability to activate single‐chain HGF. Factor XIIa exhibited a significant level of HGF‐converting activity in the presence of dextran sulfate, although the specific activity of factor XIIa was slightly lower than that of the HGF activator. Since factor XIIa is activated during the initiation of contact activation induced by tissue injury, factor XIIa may function as an HGF‐converting enzyme together with HGF activator in the injured tissue. C1‐inhibitor, antithrombin III and α2‐antiplasmin, that regulate the blood‐clotting activity of factor XIIa, were also effective against the HGF‐converting activity of factor XIIa. Furthermore, factor XIIa was not active in the HGF‐converting activity in serum. Thus, the HGF‐converting activity of factor XIIa may be regulated by these serum inhibitors.

Hepatocyte growth factor (HGF) is secreted as an inactive single-chain precursor from the producing cells, and normally remains in this form associated with the extracellular matrix. In response to tissue injury, the single-chain precursor is converted to a biologically active heterodimer by a serine protease, the activity of which is induced in the injured tissue. We have previously identified HGF activator, a serum serine protease that activates single-chain HGF. The sequence of HGF activator cDNA revealed that the HGF activator is homologous to blood-coagulation factor XIIa. In this study, we found that coagulation factor XIIa has an ability to activate single-chain HGF. Factor XIIa exhibited a significant level of HGF-converting activity in the presence of dextran sulfate, although the specific activity of factor XIIa was slightly lower than that of the HGF activator. Since factor XIIa is activated during the initiation of contact activation induced by tissue injury, factor XIIa may function as an HGF-converting enzyme together with HGF activator in the injured tissue. C1-inhibitor, antithrombin III and alpha 2-antiplasmin, that regulate the blood-clotting activity of factor XIIa, were also effective against the HGF-converting activity of factor XIIa. Furthermore, factor XIIa was not active in the HGF-converting activity in serum. Thus, the HGF-converting activity of factor XIIa may be regulated by these serum inhibitors.