Structural and functional domains critical for constitutive activation of the HGF-receptor (Met).
Structural and functional domains critical for constitutive activation of the HGF-receptor (Met).
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发表时间：
1994-06
期刊：
影响因子：
8
通讯作者：
Z. Zhen;Silvia Giordano;P. Longati;Enzo Medico;M. Campiglio;P. M. Comoglio
中科院分区：
文献类型：
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作者：
Z. Zhen;Silvia Giordano;P. Longati;Enzo Medico;M. Campiglio;P. M. Comoglio
MET基因编码肝细胞生长因子的酪氨酸激酶受体，是一种潜在有害的癌基因，在相当一部分人类癌症中过表达。为了研究致癌激活的分子机制，分析了许多MET构建体的生物化学和生物学特性。天然异源二聚体受体（α β）、单独的β链以及激酶缺陷突变体在转染后不转化啮齿动物成纤维细胞。胞质结构域，截断直接低于跨膜区，获得组成型酪氨酸激酶活性在体内，产生的转化灶，并在裸鼠中致瘤。去除前39个氨基酸的质膜结构域导致在体内的组成型激活和转化潜力的损失，而不损害体外激酶活性。用5' TPR序列替换质膜结构域恢复了组成性激酶活化和转化性质。参与磷酸化后催化活性正调控的两个酪氨酸残基（HGF受体激酶结构域中的Y1234或Y1235）中的任一个的定点突变强烈损害TRP-MET转化潜力。这些数据表明：（1）截短的细胞质HGF受体具有组成性激酶活性并且是致癌的;（2）胞膜结构域的前39个氨基酸和（3）催化结构域中的调节酪氨酸是释放其转化潜力所必需的。
The MET gene, encoding the tyrosine kinase receptor for Hepatocyte Growth Factor, is a potentially harmful oncogene overexpressed in a significant fraction of human cancers. To study the molecular mechanisms responsible for oncogenic activation, the biochemical and biological properties of a number of MET constructs were analysed. The native heterodimeric receptor (alpha beta), the beta chain alone, as well as a kinase defective mutant did not transform rodent fibroblasts upon transfection. The cytoplasmic domain, truncated immediately below the transmembrane region, acquired constitutive tyrosine kinase activity in vivo, produced foci of transformation, and was tumorigenic in nude mice. Removal of the first 39 amino acids of the juxtamembrane domain resulted in loss of constitutive activation in vivo and transforming potential, without impairment of the in vitro kinase activity. Replacement of the juxtamembrane domain with 5' TPR sequences restored constitutive kinase activation and transforming properties. Site-directed mutagenesis of either of the two tyrosine residues involved in the positive regulation of the catalytic activity upon phosphorylation (Y1234 or Y1235 in the kinase domain of the HGF receptor), strongly impaired TRP-MET transforming potential. These data show that: (1) the truncated cytoplasmic HGF receptor has constitutive kinase activity and is oncogenic; (2) the first 39 amino acids of the juxtamembrane domain and (3) the regulatory tyrosines in the catalytic domain are required to unleash its transforming potential.