Asef2 functions as a Cdc42 exchange factor and is stimulated by the release of an autoinhibitory module from a concealed C-terminal activation element
Asef2 functions as a Cdc42 exchange factor and is stimulated by the release of an autoinhibitory module from a concealed C-terminal activation element
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DOI：
10.1128/mcb.01608-06
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发表时间：
2007-02-01
影响因子：
5.3
通讯作者：
Billadeau, Daniel D.
中科院分区：
文献类型：
--
作者：
Hamann, Michael J.;Lubking, Casey M.;Billadeau, Daniel D.
Asef（本文称为Asef 1）被鉴定为由腺瘤性结肠息肉病（APC）刺激的Rac 1特异性交换因子，有助于结直肠癌细胞转移。我们研究了Asef 2，Asef 1同源物具有类似的N-末端APC结合区（ABR）和Src同源3（SH 3）结构域。与以前的报道相反，我们发现Asef 1和Asef 2交换活性是Cdc 42特异性的。此外，Asef 2的ABR不独立地发挥作用，而是与SH 3结构域串联作用以结合APC。ABRSH 3还结合Asef 2的C-末端尾部，使其在蛋白质中起自抑制模块的作用。C-末端尾部的缺失并没有如预测的那样组成性地激活Asef 2;相反，增加Cdc 42 GDP/GTP交换需要保守的C-末端片段。因此，Asef 2活化涉及A-PC从C末端尾部释放ABRSH 3，导致Cdc 42交换。这些结果突出了一种新的交换因子调节机制，并建立Asef 1和Asef 2作为Cdc 42交换因子，为理解APC在建立细胞极性和迁移中的贡献提供了更合适的背景。
Asef (herein called Asef1) was identified as a Rac1-specific exchange factor stimulated by adenomatous polyposis coli (APC), contributing to colorectal cancer cell metastasis. We investigated Asef2, an Asef1 homologue having a similar N-terminal APC binding region (ABR) and Src-homology 3 (SH3) domain. Contrary to previous reports, we found that Asef1 and Asef2 exchange activity is Cdc42 specific. Moreover, the ABR of Asef2 did not function independently but acted in tandem with the SH3 domain to bind APC. The ABRSH3 also bound the C-terminal tail of Asef2, allowing it to function as an autoinhibitory module within the protein. Deletion of the C-terminal tail did not constitutively activate Asef2 as predicted; rather, a conserved C-terminal segment was required for augmented Cdc42 GDP/GTP exchange. Thus, Asef2 activation involves A-PC releasing the ABRSH3 from the C-terminal tail, resulting in Cdc42 exchange. These results highlight a novel exchange factor regulatory mechanism and establish Asef1 and Asef2 as Cdc42 exchange factors, providing a more appropriate context for understanding the contribution of APC in establishing cell polarity and migration.