IFT54 regulates IFT20 stability but is not essential for tubulin transport during ciliogenesis
IFT54 regulates IFT20 stability but is not essential for tubulin transport during ciliogenesis
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IFT54 调节 IFT20 稳定性，但对于纤毛发生过程中的微管蛋白运输不是必需的
DOI：
10.1007/s00018-017-2525-x
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发表时间：
2017
影响因子：
8
通讯作者：
Pan Junmin
中科院分区：
文献类型：
--
作者：
Zhu Xin;Liang Yinwen;Gao Feng;Pan Junmin
鞭毛内运输（IFT）是纤毛发生所必需的，通过使用IFT复合物作为货物适配器来运送纤毛成分。IFT54是IFT-B复合物的一个组成部分，也与细胞质微管（MTs）有关。IFT54的缺失损害纤毛组装和细胞质MT动力学。IFT54的n端钙钙蛋白同源（CH）结构域与微管蛋白/ mt相互作用，并被认为在纤毛发生过程中运输微管蛋白，而c端卷曲线圈（CC）结构域与IFT20结合。然而，这些结构域在体内的确切功能尚不清楚。我们发现，在衣藻中，IFT54的缺失完全阻断了纤毛的发生，但不影响纺锤体的形成和细胞周期的正常进程，即使IFT54与有丝分裂mt相互作用。有趣的是，缺乏CH结构域的IFT54允许适当的鞭毛组装。CH结构域是IFT54与轴素结合而不是与有丝分裂mt结合所必需的，并且还调节IFT54的鞭毛进口，而不是IFT81和IFT46。c端CC结构域对于IFT54结合IFT20，以及IFT54募集到基础体并整合到IFT复合物中至关重要。IFT54或CC结构域的完全缺失会破坏IFT20的稳定性。单独表达CC结构域的IFT54突变细胞挽救了IFT20的稳定性，并形成发育不全的鞭毛，同时积累了IFT- a组分IFT43和IFT- b组分IFT46，这表明IFT54也在鞭毛尖端的IFT翻转中起作用。
Intraflagellar transport (IFT) is required for ciliogenesis by ferrying ciliary components using IFT complexes as cargo adaptors. IFT54 is a component of the IFT-B complex and is also associated with cytoplasmic microtubules (MTs). Loss of IFT54 impairs cilia assembly as well as cytoplasmic MT dynamics. The N-terminal calponin homology (CH) domain of IFT54 interacts with tubulins/MTs and has been proposed to transport tubulin during ciliogenesis, whereas the C-terminal coiled-coil (CC) domain binds IFT20. However, the precise function of these domains in vivo is not well understood. We showed that inChlamydomonas, loss of IFT54 completely blocks ciliogenesis but does not affect spindle formation and proper cell cycle progression, even though IFT54 interacts with mitotic MTs. Interestingly, IFT54 lacking the CH domain allows proper flagellar assembly. The CH domain is required for the association of IFT54 with the axoneme but not with mitotic MTs, and also regulates the flagellar import of IFT54 but not IFT81 and IFT46. The C-terminal CC domain is essential for IFT54 to bind IFT20, and for its recruitment to the basal body and incorporation into IFT complexes. Complete loss of IFT54 or the CC domain destabilizes IFT20.ift54mutant cells expressing the CC domain alone rescue the stability of IFT20 and form stunted flagella with accumulation of both IFT-A component IFT43 and IFT-B component IFT46, indicating that IFT54 also functions in IFT turn-around at the flagellar tip.