Recent evidence has linked the lysosomal cholesterol accumulation in Niemann-Pick type C1 with anomalies associated with primary ciliogenesis. Here, we report that perturbed intracellular cholesterol distribution imposed by lysosomal cholesterol accumulation during TMEM135 depletion is closely associated with impaired ciliogenesis. TMEM135 depletion does not affect the formation of the basal body and the ciliary transition zone. TMEM135 depletion severely blunts Rab8 trafficking to the centrioles without affecting the centriolar localization of Rab11 and Rabin8, the upstream regulators of Rab8 activation. Although TMEM135 depletion prevents enhanced IFT20 localization at the centrioles, ciliary vesicle formation is not affected. Furthermore, enhanced IFT20 localization at the centrioles is dependent on Rab8 activation. Supplementation of cholesterol in complex with cyclodextrin rescues Rab8 trafficking to the centrioles and Rab8 activation, thereby recovering primary ciliogenesis in TMEM135-depleted cells. Taken together, our data suggest that TMEM135 depletion prevents ciliary vesicle elongation, a characteristic of impaired Rab8 function. Our study thus reveals a previously uncharacterized effect of erroneous intracellular cholesterol distribution on impairing Rab8 function and primary ciliogenesis.

中文翻译：

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TMEM135 通过调节细胞内胆固醇分布来调节原发性纤毛发生。

最近的证据已将 Niemann-Pick C1 型溶酶体胆固醇的积累与与原发性纤毛发生相关的异常联系起来。在这里，我们报告在 TMEM135 耗竭期间溶酶体胆固醇积累造成的细胞内胆固醇分布紊乱与纤毛发生受损密切相关。TMEM135 耗竭不影响基体和睫状体过渡区的形成。TMEM135 耗尽严重削弱了 Rab8 向中心粒的运输，而不影响 Rab8 激活的上游调节剂 Rab11 和 Rabin8 的中心粒定位。虽然 TMEM135 的消耗阻止了 IFT20 在中心粒的定位增强，但纤毛囊泡的形成不受影响。此外，增强的 IFT20 在中心粒的定位取决于 Rab8 的激活。补充与环糊精复合的胆固醇可挽救 Rab8 向中心粒的转运和 Rab8 激活，从而恢复 TMEM135 耗尽细胞中的初级纤毛发生。合在一起，我们的数据表明，TMEM135 的消耗阻止了睫状囊泡的伸长，这是 Rab8 功能受损的一个特征。因此，我们的研究揭示了错误的细胞内胆固醇分布对损害 Rab8 功能和原发性纤毛发生的先前未表征的影响。