Molecular Mechanisms for injury-dependent activation of c-Met, HGF receptor

点击翻译按钮获取中文摘要

In this project, we attempted to clarify the molecular mechanisms by which the tissues recognize their injured- or homeostatic states. We especially focused on the physiological changes of activation states of c-Met, the receptor for HGF and obtained the results as descried bellow 1〜4.1, (1) HGF readily induces cellular proliferation of primary hepatocytes when they are cultured at low cellular density, but in confluent cultures, HGF failed to show the effect. which was thought to mimic the response of parenchymal) hepatocytes in injured liver. In this system, we found that c-Met tyrosine autophosphorylation was down regulated in the confluent cells even after HGF-stimulation. (2) Oxidant stress causes arrest of cellular proliferation, and we found that the stress induced by hydrogen peroxide deprives cells of mitotic response to HGF, which was caused down regulation of c-Met activation through Ser985-phosphorylation on c-Met. (3) Primary hepatocytes could not proliferate in proline-free culture medium even after HGF-stimulation, while the c-Met and the associated signal transducers were readily activated.2, We successfully identified molecules responsible for 1,(1)〜 (3) as follows. (1) A tyrosine phosphatase LAR, which dephosphorylates c-Met in a cell density dependent way, (2) PKC enhances Ser985 phosphorylation and PP2A which targets phosphorylated Ser985 was suppressed by hydrogen peroxide-treatment, (3) Expression of CDK4 that trigger the cellular proliferation was suppressed under Pro-free medium.3, We established ES cells for construction of transgenic mouse carrying Ser985 deleted c-Met.