Molecular Mechanisms of Tissue Regeneration through the Conversion of HGF Receptor Signaling in Response of Injury

(1)LAR通过酪氨酸去磷酸化调节HGF/c-Met活化：通过细胞-细胞接触调节的细胞增殖抑制是正常细胞的基本特征。在以汇合细胞密度培养的肝细胞中，HGF 刺激诱导短暂的 c-Met 酪氨酸磷酸化，但未能诱导促有丝分裂反应。我们发现 LAR 在失活中发挥着决定性的作用，即通过物理相互作用使 c-Met 酪氨酸去磷酸化，这种作用特别发生在汇合条件下的肝细胞中。我们将这些结果发表在 J-Biol-Chem 281 : 8765 (2006) 上。 (2) HGF/c-Met 激活在胆汁淤积损伤中的生理意义：我们使用胆管结扎 (BDL) 手术技术在小鼠中诱导胆汁淤积状态。 BDL 手术后，肝脏中 HGF 和 c-Met mRNA 水平短暂升高。此外，我们获得的证据表明内源性 HGF 参与肝细胞细胞死亡（包括坏死和凋亡）的生理保护。我们将这些结果发表在Am-J-Physiol 292 : G639 (2007)中。 (3)仅表达突变c-Met (ΔJxt-Met)的敲入小鼠的产生：c-Met的近膜Ser-985的磷酸化状态在c-Met的激活中起功能调节作用。 c-Met 具有缺乏细胞质近膜区域的剪接变体 (ΔJxt-Met)。为了分析 ΔJxt-Met 的功能，我们生成了仅表达 ΔJxt 形式的 c-Met 的敲入小鼠。纯合突变小鼠在新生儿期死亡。目前正在进行病理分析。

(1) Regulation of HGF/c-Met activation through tyrosine dephosphrylation by LAR:Inhibition of cell proliferation regulated by cell-cell contact is a fundamental characteristic of normal cells. In hepatocytes cultured at a confluent cell density, HGF stimulation induced transient c-Met tyrosine phosphorylation and failed to induce mitogenic response. We found that LAR plays a definitive role in inactivation, i.e. tyrosine dephosphorylation of c-Met through their physical interaction, which specifically occurs in hepatocytes under confluent condition. We published these results in J-Biol-Chem 281 : 8765 (2006).(2) Physiological significance of HGF/c-Met activation in cholestatic injury:We used a surgical technique of bile duct ligation (BDL) to induce cholestatic conditions in mice. After the BDL surgery, HGF and c-Met mRNA levels transiently increased in livers. Furthmore, we obtained evidence that endogenous HGF is involved in the physiological protection of hepatocyte cell death including necrosis and apoptosis. We published these results in Am-J-Physiol 292 : G639 (2007).(3) Generation of knock-in mice expressing only mutated c-Met (ΔJxt-Met):The phosphorylation status of juxtamembrane Ser-985 of c-Met plays functional regulatory role in activation of c-Met. c-Met has a splice variant that lacks a cytoplasmic juxtamembrane region (ΔJxt-Met). To analyze the function of ΔJxt-Met, we generated knock-in mice expressing only ΔJxt form of c-Met. Homozygous mutant mice died during neonatal period. Pathological analysis is now in progress.