Molecular basis for CPAP-tubulin interaction in controlling centriolar and ciliary length.
Molecular basis for CPAP-tubulin interaction in controlling centriolar and ciliary length.
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CPAP-微管蛋白相互作用控制中心粒和纤毛长度的分子基础
DOI：
10.1038/ncomms11874
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发表时间：
2016-06-16
影响因子：
16.6
通讯作者：
Li H
中科院分区：
文献类型：
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作者：
Zheng X;Ramani A;Soni K;Gottardo M;Zheng S;Ming Gooi L;Li W;Feng S;Mariappan A;Wason A;Widlund P;Pozniakovsky A;Poser I;Deng H;Ou G;Riparbelli M;Giuliano C;Hyman AA;Sattler M;Gopalakrishnan J;Li H
中心粒和纤毛是以微管为基础的结构，其精确的形成需要控制细胞质微管蛋白的掺入。细胞质微管蛋白是如何被识别为中心粒/纤毛微管的，目前仍知之甚少。中心体P4.1相关蛋白(CPAP)通过其PN2-3结构域与微管蛋白结合。在这里，我们证明了Pn2-3中的C端环螺旋以微管外表面的β-微管蛋白为靶标，而N端螺旋基序覆盖了微管的α-β表面的β-微管蛋白。通过这一过程，PN2-3与GTP-微管蛋白形成高亲和力的复合体，这对确定中心粒/纤毛微管的数量和长度至关重要。令人惊讶的是，PN2-3的两个不同的突变对中心粒/纤毛微管长度显示出相反的影响。CPAPF375A与微管蛋白的相互作用大大减少，导致较短的中心粒和纤毛显示双微管而不是三重微管。揭开β-微管蛋白聚合表面的CPAPEE343RR显示出轻微的微管结合亲和力降低，通过增强其结合的微管蛋白的动态释放而导致新形成的中心粒/纤毛微管的过度延长。因此，CPAP调节其结合微管蛋白的传递，以确定基于微管的细胞结构的大小，使用一种“离合器式”机制。
Centrioles and cilia are microtubule-based structures, whose precise formation requires controlled cytoplasmic tubulin incorporation. How cytoplasmic tubulin is recognized for centriolar/ciliary-microtubule construction remains poorly understood. Centrosomal-P4.1-associated-protein (CPAP) binds tubulin via its PN2-3 domain. Here, we show that a C-terminal loop-helix in PN2-3 targets β-tubulin at the microtubule outer surface, while an N-terminal helical motif caps microtubule’s α-β surface of β-tubulin. Through this, PN2-3 forms a high-affinity complex with GTP-tubulin, crucial for defining numbers and lengths of centriolar/ciliary-microtubules. Surprisingly, two distinct mutations in PN2-3 exhibit opposite effects on centriolar/ciliary-microtubule lengths. CPAPF375A, with strongly reduced tubulin interaction, causes shorter centrioles and cilia exhibiting doublet- instead of triplet-microtubules. CPAPEE343RRthat unmasks the β-tubulin polymerization surface displays slightly reduced tubulin-binding affinity inducing over-elongation of newly forming centriolar/ciliary-microtubules by enhanced dynamic release of its bound tubulin. Thus CPAP regulates delivery of its bound-tubulin to define the size of microtubule-based cellular structures using a ‘clutch-like’ mechanism.