ABSTRACT

The primary cilium (PC), a plasma membrane microtubule-based structure, is a sensor of extracellular chemical and mechanical stress stimuli. Upon ciliogenesis, the autophagy protein ATG16L1 and the ciliary protein IFT20 are co-transported to the PC. We demonstrated in a recent study that IFT20 and ATG16L1 interact in a multiprotein complex. This interaction is mediated by the ATG16L1 WD40 domain and an ATG16L1-binding motif newly identified in IFT20. ATG16L1-deficient cells are decorated by giant ciliary structures hallmarked by defects in PC-associated signaling. These structures uncommonly accumulate phosphatidylinositol-4,5-bisphosphate (PtdIns[4,5]P₂) while phosphatidylinositol-4-phosphate (PtdIns4P), a lipid normally concentrated in the PC, is excluded. We show that INPP5E, a phosphoinositide-associated phosphatase responsible for PtdIns4P generation, is a partner of ATG16L1 in this context. Perturbation of the ATG16L1-IFT20 complex alters INPP5E trafficking and proper function at the ciliary membrane. Altogether, these results reveal a novel autophagy-independent function of ATG16L1 that contributes to proper PC dynamics and function.

摘要

初级纤毛 (PC) 是一种基于质膜微管的结构，是细胞外化学和机械应力刺激的传感器。纤毛发生后，自噬蛋白 ATG16L1 和纤毛蛋白 IFT20 共同转运至 PC。我们在最近的一项研究中证明 IFT20 和 ATG16L1 在多蛋白复合物中相互作用。这种相互作用由 ATG16L1 WD40 结构域和 IFT20 中新发现的 ATG16L1 结合基序介导。ATG16L1 缺陷细胞由以 PC 相关信号缺陷为标志的巨大纤毛结构装饰。这些结构不常见地积聚 4,5-二磷酸磷脂酰肌醇 (PtdIns[4,5]P ₂) 而磷脂酰肌醇-4-磷酸 (PtdIns4P)，一种通常集中在 PC 中的脂质，被排除在外。我们表明，INPP5E 是一种负责 PtdIns4P 生成的磷酸肌醇相关磷酸酶，在这种情况下是 ATG16L1 的合作伙伴。ATG16L1-IFT20 复合物的扰动改变了 INPP5E 的运输和睫状膜的正常功能。总之，这些结果揭示了 ATG16L1 的一种新的不依赖自噬的功能，它有助于适当的 PC 动力学和功能。