Functional analysis of domain structures of human hepatocyte growth factor

点击翻译按钮获取中文摘要

Human hepatocyte growth factor (hHGF) is a multi-functional protein. hHGF consists of characteristic structural domains ; it has four kringle domains in the heavy chain and a serine proteaselike domain in the light chain. To elucidate the role of these domain structures, we prepared mutant proteins lacking each of these domains and examined their biological activities for stimulation of hepatocyte DNA synthesis, inhibition of MethA cell growth and induction of MDCK cell dissociation. We also examined their interactions with the c-met/HGF receptor by displacement analysis and by analysis of levels of tyrosine phosphorylation. The mutant proteins lacking the Nterminal, the first kringle or the second kringle domain were not biologically effective and could not displace hHGF bound to the c-met/HGF receptor. The results indicate that these domains are necessary for the biological activities of hHGF mediated by binding to the c-met/HGF receptor. The mutant proteins lacking the third or fourth kringle domain moderately retained biological activities and the receptor binding. The relative levels of the tyrosine phosphorylation of the c-met/HGF receptor by these mutant proteins correlated well with the relative potencies of the biological activities when compared with the wild-type hHGF. The mutant protein lacking the light chain was not effective in the biological activities and tyrosine phosphorylation of the c-met/HGF receptor, but displaced hHGF bound to the c-met/HGF receptor. These results suggest that the heavy chain plays an important role in the interaction of hHGF with the c-met/HGF receptor and that the light chain is further required for the tyrosine phosphorylation of the c-met/HGF receptor.