Lee Jae-Ho, Gao Chong Feng, Lee Chong Chou, Kim Myung Deok, Vande Woude George F
Department of Biochemistry, School of Medicine, Ajou University, Suwon 443-721, Korea.
Exp Mol Med. 2006 Oct 31;38(5):565-73. doi: 10.1038/emm.2006.66.
The Met tyrosine kinase receptor is a widely expressed molecule, which mediates pleiotropic cellular responses following activation by its ligand, hepatocyte growth factor/scatter factor (HGF/SF). Previously, one of the authors identified an alternatively spliced form of Met (Met-SM) that lacked a single exon of a 47-amino-acid segment in the juxtamembrane domain. Here we report that Met-SM is a potent transforming gene in NIH3T3 mouse fibroblast cells. Met-SM-transfected NIH3T3 cells show stronger foci-forming activity than wild type- Met-transfected ones. In addition, Met-SM-transfected NIH3T3 cells form colonies in soft agar and are tumorigenic in athymic nu/nu mice. Furthermore, HGF/SF significantly increases the focus-forming activity of Met-SM comparing to wild type Met. The amount of protein and of tyrosine kinase activity of Met-SM accumulates to a high level following HGF/SF treatment. The accumulation of Met-SM correlated well with its delayed ubiquitination and increased stability. These results are consistent with the important role of the juxtamembrane domain in protein stability of Met receptor and suggest that the alternatively-spliced form may contribute to the development and progression of human cancer.
Met酪氨酸激酶受体是一种广泛表达的分子，它在被其配体肝细胞生长因子/散射因子（HGF/SF）激活后介导多效性细胞反应。此前，本文作者之一鉴定出一种Met的可变剪接形式（Met-SM），其近膜结构域中缺少一个包含47个氨基酸片段的单一外显子。在此我们报告，Met-SM在NIH3T3小鼠成纤维细胞中是一种有效的转化基因。转染Met-SM的NIH3T3细胞比转染野生型Met的细胞表现出更强的集落形成活性。此外，转染Met-SM的NIH3T3细胞在软琼脂中形成菌落，并且在无胸腺裸鼠中具有致瘤性。此外，与野生型Met相比，HGF/SF显著增加了Met-SM的集落形成活性。HGF/SF处理后，Met-SM的蛋白量和酪氨酸激酶活性积累到高水平。Met-SM的积累与其延迟的泛素化和增加的稳定性密切相关。这些结果与近膜结构域在Met受体蛋白稳定性中的重要作用一致，并表明这种可变剪接形式可能有助于人类癌症的发生和发展。
