Identification and characterization of Asef2, a guanine-nucleotide exchange factor specific for Rac1 and Cdc42
Identification and characterization of Asef2, a guanine-nucleotide exchange factor specific for Rac1 and Cdc42
复制标题
DOI：
10.1038/sj.onc.1210574
复制
发表时间：
2007-12-06
期刊：
影响因子：
8
通讯作者：
Akiyama, T.
中科院分区：
文献类型：
--
作者：
Kawasaki, Y.;Sagara, M.;Akiyama, T.
抑癌基因腺瘤性息肉病结肠(APC)在散发性和家族性结直肠癌中发生突变。APC与rac1特异性的鸟嘌呤核苷酸交换因子ASEF相互作用，除了DBL同源(DH)、Pleckstrin(PH)和Src同源3(SH3)结构域外，ASEF还包含一个APC结合区(ABR)。APC可刺激ASEF的全球环境基金活性，从而调节细胞的黏附和迁移。在这里，我们已经确定了第二个ASEF，称为ASEF2，它在结构和功能上与ASEF有显著的相似之处。我们发现Asef2的N端ABR和SH3结构域都负责其与APC的相互作用。当在HeLa细胞中表达时，缺乏ABR和SH3结构域的突变Asef2，Asef2-Delta ABR/SH3，诱导了rac1和CDc42活性形式的水平增加。全长Asef2与在结直肠肿瘤细胞中表达的截短突变体APC共转染时也显示出这种活性。与此一致的是，Asef2-Delta ABR/SH3或Asef2+截短突变体APC均可刺激MDCK细胞片状脂体的形成和HeLa细胞丝状足细胞的形成。此外，RNA干扰实验表明，Asef2是表达截短APC的结直肠癌细胞迁移所必需的。这些结果表明，与ASEF类似，ASEF2在细胞迁移中起重要作用，而截短突变体APC激活的ASEP2是结直肠肿瘤细胞异常迁移所必需的。
The tumor suppressor adenomatous polyposis coli (APC) is mutated in sporadic and familial colorectal tumors. APC interacts with the Rac1-specific guanine-nucleotide exchange factor (GEF) Asef, which contains an APC-binding region (ABR) in addition to Dbl homology (DH), Pleckstrin (PH) and Src homology 3 (SH3) domains. APC stimulates the GEF activity of Asef, and thereby regulates cell adhesion and migration. Here, we have identified a second Asef, termed Asef2, that shows significant structural and functional similarities to Asef. We found that both the N-terminal ABR and SH3 domains of Asef2 are responsible for its interaction with APC. When expressed in HeLa cells, a mutant Asef2 lacking the ABR and SH3 domains, Asef2-Delta ABR/SH3, induced increases in the levels of the active forms of Rac1 and Cdc42. Full-length Asef2 also showed this activity when co-transfected with truncated mutant APC expressed in colorectal tumor cells. Consistent with this, either Asef2-Delta ABR/SH3 or Asef2 plus truncated mutant APC stimulated lamellipodia formation in MDCK cells and filopodia formation in HeLa cells. Furthermore, RNA interference experiments showed that Asef2 is required for migration of colorectal tumor cells expressing truncated APC. These results suggest that similar to Asef, Asef2 plays an important role in cell migration, and that Asef2 activated by truncated mutant APC is required for aberrant migration of colorectal tumor cells.