Structure of Crumbs tail in complex with the PALS1 PDZ-SH3-GK tandem reveals a highly specific assembly mechanism for the apical Crumbs complex
Structure of Crumbs tail in complex with the PALS1 PDZ-SH3-GK tandem reveals a highly specific assembly mechanism for the apical Crumbs complex
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DOI：
10.1073/pnas.1416515111
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发表时间：
2014-12-09
影响因子：
11.1
通讯作者：
Zhang, Mingjie
中科院分区：
文献类型：
--
作者：
Li, Youjun;Wei, Zhiyi;Zhang, Mingjie
Crumbs（Crb）复合物，由Crb，PALS 1和PATJ形成，在后生动物中是进化上保守的，并在极化上皮细胞的顶膜处充当主细胞生长和极性调节剂。Crb的细胞内功能，包括其与PALS 1的直接结合，是由Crb的高度保守的37个残基的胞质尾介导的。然而，控制高度特异性Crb-PALS 1复合物形成的机制基础尚不清楚，因为报道的Crb尾（Crb-CT）和PALS 1 PSD-95/DLG/ZO-1（PDZ）结构域之间的相互作用是弱的和混杂的。在这里，我们已经发现PALS 1的PDZ-Src同源3（SH 3）-鸟苷酸激酶（GK）串联体以70 nM的解离常数与Crb-CT结合，这类似于比PALS 1 PDZ-Crb-CT相互作用强100倍。PALS 1 PDZ-SH 3-GK-Crb-CT复合物的晶体结构显示，PDZ-SH 3-GK形成结构超模块，所有三个结构域都有助于与Crb的紧密结合。破坏PDZ-SH 3-GK超模块三级相互作用的突变削弱了PALS 1-Crb相互作用，并损害了Madin-Darby犬肾（MDCK）囊肿中PALS 1介导的极性建立。我们进一步表明，膜相关鸟苷酸激酶（MAGUKs）的其他成员（例如，CASK与neurexin结合）也需要它们的PDZ-SH 3-GK串联体的存在。
The Crumbs (Crb) complex, formed by Crb, PALS1, and PATJ, is evolutionarily conserved in metazoans and acts as a master cellgrowth and -polarity regulator at the apical membranes in polarized epithelia. Crb intracellular functions, including its direct binding to PALS1, are mediated by Crb's highly conserved 37-residue cytoplasmic tail. However, the mechanistic basis governing the highly specific Crb-PALS1 complex formation is unclear, as reported interaction between the Crb tail (Crb-CT) and PALS1 PSD-95/DLG/ZO-1 (PDZ) domain is weak and promiscuous. Here we have discovered that the PDZ-Src homolgy 3 (SH3)-Guanylate kinase (GK) tandem of PALS1 binds to Crb-CT with a dissociation constant of 70 nM, which is similar to 100-fold stronger than the PALS1 PDZ-Crb-CT interaction. The crystal structure of the PALS1 PDZ-SH3-GK-Crb-CT complex reveals that PDZ-SH3-GK forms a structural supramodule with all three domains contributing to the tight binding to Crb. Mutations disrupting the tertiary interactions of the PDZ-SH3-GK supramodule weaken the PALS1-Crb interaction and compromise PALS1-mediated polarity establishment in Madin-Darby canine kidney (MDCK) cysts. We further show that specific target binding of other members of membrane-associated guanylate kinases (MAGUKs) (e.g., CASK binding to neurexin) also requires the presence of their PDZ-SH3-GK tandems.