Structural basis for the recognition of Asef by adenomatous polyposis coli
Structural basis for the recognition of Asef by adenomatous polyposis coli
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DOI：
10.1038/cr.2011.119
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发表时间：
2012-02-01
期刊：
影响因子：
44.1
通讯作者：
Wu, Geng
中科院分区：
文献类型：
--
作者：
Zhang, Zhenyi;Chen, Leyi;Wu, Geng
大肠腺瘤性息肉病（Adenomatous polyposis coli，APC）通过激活APC刺激的鸟嘌呤核苷酸交换因子（guanine nucleotide-exchange factor，GEF; Asef）来调节细胞-细胞粘附和细胞迁移，该因子通常通过其Src同源3（SH 3）和Dbl同源（DH）结构域之间的结合而被自抑制。APC激活的Asef刺激小的GTdR Cdc 42，这导致细胞间粘附减少和细胞迁移增强。在结直肠癌中，截短的APC组成性激活Asef并促进癌细胞迁移和血管生成。在这里，我们报告的人APC/Asef复合物的晶体结构。我们发现，犰狳重复结构域的APC使用一个高度保守的表面凹槽，以识别APC结合区（ABR）的Asef，其构象的变化显着结合APC。APC和Asef上用于复合物形成的关键残基被突变，并且通过结合和活性测定证明了它们的重要性。APC/Asef复合物与自身抑制的Asef的结构重叠表明APC和Asef之间的结合可能在Asef-DH结构域和APC之间产生空间冲突，这可能导致Asef的构象变化，从而刺激其GEF活性。因此，我们的结构阐明了APC识别Asef的分子机制，并为癌症药物干预提供了潜在的靶点。
Adenomatous polyposis coli (APC) regulates cell-cell adhesion and cell migration through activating the APC-stimulated guanine nucleotide-exchange factor (GEF; Asef), which is usually autoinhibited through the binding between its Src homology 3 (SH3) and Dbl homology (DH) domains. The APC-activated Asef stimulates the small GTPase Cdc42, which leads to decreased cell-cell adherence and enhanced cell migration. In colorectal cancers, truncated APC constitutively activates Asef and promotes cancer cell migration and angiogenesis. Here, we report crystal structures of the human APC/Asef complex. We find that the armadillo repeat domain of APC uses a highly conserved surface groove to recognize the APC-binding region (ABR) of Asef, conformation of which changes dramatically upon binding to APC. Key residues on APC and Asef for the complex formation were mutated and their importance was demonstrated by binding and activity assays. Structural superimposition of the APC/Asef complex with autoinhibited Asef suggests that the binding between APC and Asef might create a steric clash between Asef-DH domain and APC, which possibly leads to a conformational change in Asef that stimulates its GEF activity. Our structures thus elucidate the molecular mechanism of Asef recognition by APC, as well as provide a potential target for pharmaceutical intervention against cancers.