PI4P对细胞自噬的分子调控研究

细胞自噬异常与疾病密切相关，但其调控机制尚不清楚。前期结果发现诱导自噬后，果蝇PI4KIIα被招募到自噬体表面，促进PI4P合成，并招募效应分子Osbp和Cert。果蝇中有三种PI4Ks，我们发现缺失任意一个PI4K都会导致自噬异常，但受影响的阶段不同。PI4P磷酸酶Sac1缺失导致PI4P在自噬溶酶体表面积累。与酵母不同，我们发现果蝇Sac1缺失并不影响自噬溶酶体的形成，但抑制自噬底物的降解。自噬过程中Sac1始终定位于内质网，暗示其通过内质网-自噬溶酶体接触反式水解PI4P。为了研究PI4P调控细胞自噬的复杂模式，本项目将探究：1. Sac1是否通过内质网-自噬溶酶体接触调控自噬；2. PI4P的下游效应分子如何发挥作用；3. 三种PI4K各自如何调控自噬；4. PI4P与其它PIP如何协同调控细胞自噬过程。该项目的完成将更为全面和深入地揭示PI4P调控细胞自噬的机制，具有重要意义。

Malfunction of autophagy is closely related to many diseases, but its regulatory mechanism remains unclear. We previously found that upon autophagy induction, Drosophila Pi4KIIα was recruited to the surface of autophagosome/autolysosome, which promoted the synthesis of phosphatidylinositol 4 phosphate (PI4P) and recruited downstream effectors such as Osbp and Cert. There are three PI4Ks in flies. We found that the inhibition of any of them caused autophagy defects and each at distinct stages. Meantime, the absence of PI4P phosphatase Sac1 resulted in the accumulation of PI4P on the surface of autolysosome. Unlike yeast, we found that Sac1 deletion did not affect autolysosome formation in Drosophila, but inhibited the degradation of autophagy cargos. Moreover, Sac1 was located in endoplasmic reticulum (ER) during autophagy, suggesting that it hydrolyzes PI4P in trans through ER-autolysosome contract. To dissect the mechanisms underlying how PI4P regulates autophagy, we will answer following questions in this project. 1. Does Sac1 regulate autophagy through ER-autolysosome contact; 2. How do downstream effectors mediate the function of PI4P in regulating autophagy; 3. How does each of the three PI4Ks regulate autophagy; 4. How do PI4P and other PIPs coordinate to regulate autophagy process. The completion of this project will reveal a full image of how PI4P regulates autophagy.