The autophagy protein ATG16L1 cooperates with IFT20 and INPP5E to regulate the turnover of phosphoinositides at the primary cilium

Abstract : The primary cilium (PC) regulates signalization linked to external stress sensing. Previous works established a functional interplay between the PC and the autophagic machinery. When ciliogenesis is promoted by serum deprivation, the autophagy protein ATG16L1 and the ciliary protein IFT20 are co-transported to the PC. Here, we demonstrate that IFT20 and ATG16L1 are part of the same complex requiring the WD40 domain of ATG16L1 and a Y-E-F-I motif in IFT20. We show that ATG16L1-deficient cells exhibit aberrant ciliary structures, which accumulate PI4,5P2, whereas PI4P, a lipid normally concentrated in the PC, is absent. Finally, we demonstrate that INPP5E, a phosphoinositide-associated phosphatase responsible for PI4P generation, interacts with ATG16L1 and that a perturbation of the ATG16L1/IFT20 complex alters its trafficking to the PC. Altogether, our results reveal a function of ATG16L1 in ciliary lipid and protein trafficking, thus directly contributing to proper PC dynamics and functions.