Wang Dakun, Li Zaibo, Messing Edward M, Wu Guan
Department of Urology, The James P. Wilmot Cancer Center, University of Rochester Medical Center, Rochester, New York 14642, USA.
J Biol Chem. 2002 Sep 27;277(39):36216-22. doi: 10.1074/jbc.M205111200. Epub 2002 Jul 29.
MET is a receptor protein-tyrosine kinase (RPTK) for hepatocyte growth factor (HGF), which is a multifunctional cytokine controlling cell growth, morphogenesis, and motility. MET overexpression has been identified in a variety of human cancers. Oncogenic missense mutations of the tyrosine kinase domain of the MET gene have been identified in human papillary renal cell carcinomas. In this study, RanBPM, also known as RanBP9, is identified as a novel interacting protein of MET through yeast two-hybrid screen. RanBPM contains a conserved SPRY (repeats in splA and RyR) domain. We demonstrate that RanBPM can interact with MET in vitro and in vivo, and the interaction can be strengthened by HGF stimulation. RanBPM interacts with the tyrosine kinase domain of MET through its SPRY domain. We show that RanBPM can induce GTP-Ras association and Erk phosphorylation and elevate serum response element-luciferase (SRE-LUC) expression, indicating that RanBPM can activate the Ras-Erk-SRE pathway. We demonstrate that RanBPM, which itself is not a guanine exchange protein, stimulates Ras activation by recruiting Sos. On the cellular level, A704 cells, a human renal carcinoma cell line, transfected with RanBPM exhibit increased migration ability. Our data suggest that RanBPM, functioning as an adaptor protein for the MET tyrosine kinase domain, can augment the HGF-MET signaling pathway and that RanBPM overexpression may cause constitutive activation of the Ras signaling pathway.
MET是肝细胞生长因子（HGF）的一种受体蛋白酪氨酸激酶（RPTK），HGF是一种控制细胞生长、形态发生和运动的多功能细胞因子。MET的过表达已在多种人类癌症中被发现。在人类乳头状肾细胞癌中已鉴定出MET基因酪氨酸激酶结构域的致癌错义突变。在本研究中，RanBPM，也称为RanBP9，通过酵母双杂交筛选被鉴定为MET的一种新型相互作用蛋白。RanBPM包含一个保守的SPRY（splA和RyR中的重复序列）结构域。我们证明RanBPM在体外和体内均可与MET相互作用，并且这种相互作用可被HGF刺激增强。RanBPM通过其SPRY结构域与MET的酪氨酸激酶结构域相互作用。我们表明RanBPM可诱导GTP-Ras结合和Erk磷酸化，并提高血清反应元件荧光素酶（SRE-LUC）的表达，表明RanBPM可激活Ras-Erk-SRE途径。我们证明本身并非鸟嘌呤交换蛋白的RanBPM通过招募Sos刺激Ras激活。在细胞水平上，转染了RanBPM的人肾癌细胞系A704细胞表现出增强的迁移能力。我们的数据表明，作为MET酪氨酸激酶结构域的衔接蛋白，RanBPM可增强HGF-MET信号通路，并且RanBPM的过表达可能导致Ras信号通路的组成性激活。
