磷脂酰肌醇3-磷酸酯(PI(3)P)在内吞作用中起重要作用,吞噬作用,和自噬。PI(3)P由III类磷脂酰肌醇3-激酶(PI3K)复合物的Vps34产生。Vps34-PI3K复合物可分为Vps34-PI3KII类(含有Vps38,内体)和Vps34-PI3KI类(含有Atg14,自噬小体)。大多数PI(3)Ps与内体膜相关。在酵母中,Vps34和PI(3)P的内体定位受到Vps21模块蛋白的严格调控。在酵母吞噬体组装位点(PAS)或哺乳动物omgasome,PI(3)P结合与磷酸肌醇(WIPI)蛋白相互作用的WD重复蛋白,以进一步招募两个缀合系统,Atg5-Atg12·Atg16和Atg8-PE(LC3-II),启动自噬。然而,自噬过程中PI(3)P的时空调控仍不清楚。因此,在这项研究中,我们确定了Vps21对自噬诱导后Vps8,Vps34,Atg21,Atg8和Atg16的定位和相互作用的影响。结果表明,Vps21是Vps8-Vps34和Vps34-Atg21在内体上的连续共定位和相互作用所必需的,PAS上的Atg21-Atg8/Atg16。除了破坏PI3K复合物II亚基Vps34和Vps38在内体的定位外,PI3K复合物I亚基Vps34和Atg14以及Atg21的定位部分从vps21º细胞中的PAS中断。vps21细胞中受损的PI3K-PI(3)P-Atg21-Atg16轴可能会延迟自噬,这与Atg21缺失时早期自噬的延迟一致。这项研究首次揭示了自噬中Vps21对PI3K-PI(3)P-Atg21-Atg16模块的上游顺序调节。
Phosphatidylinositol 3-phosphate (PI(3)P) serves important functions in endocytosis, phagocytosis, and autophagy. PI(3)P is generated by Vps34 of the class III phosphatidylinositol 3-kinase (PI3K) complex. The Vps34-PI3K complex can be divided into Vps34-PI3K class II (containing Vps38, endosomal) and Vps34-PI3K class I (containing Atg14, autophagosomal). Most PI(3)Ps are associated with endosomal membranes. In yeast, the endosomal localization of Vps34 and PI(3)P is tightly regulated by Vps21-module proteins. At yeast phagophore assembly site (PAS) or mammalian omegasomes, PI(3)P binds to WD-repeat protein interacting with phosphoinositide (WIPI) proteins to further recruit two conjugation systems, Atg5-Atg12·Atg16 and Atg8-PE (LC3-II), to initiate autophagy. However, the spatiotemporal regulation of PI(3)P during autophagy remains obscure. Therefore, in this study, we determined the effect of Vps21 on localization and interactions of Vps8, Vps34, Atg21, Atg8, and Atg16 upon autophagy induction. The results showed that Vps21 was required for successive colocalizations and interactions of Vps8-Vps34 and Vps34-Atg21 on endosomes, and Atg21-Atg8/Atg16 on the PAS. In addition to disrupted localization of the PI3K complex II subunits Vps34 and Vps38 on endosomes, the localization of the PI3K complex I subunits Vps34 and Atg14, as well as Atg21, was partly disrupted from the PAS in vps21∆ cells. The impaired PI3K-PI(3)P-Atg21-Atg16 axis in vps21∆ cells might delay autophagy, which is consistent with the delay of early autophagy when Atg21 was absent. This study provides the first insight into the upstream sequential regulation of the PI3K-PI(3)P-Atg21-Atg16 module by Vps21 in autophagy.