HS1BP3 negatively regulates autophagy by modulation of phosphatidic acid levels

A fundamental question is how autophagosome formation is regulated. Here we show that the PX domain protein HS1BP3 is a negative regulator of autophagosome formation. HS1BP3 depletion increased the formation of LC3-positive autophagosomes and degradation of cargo both in human cell culture and in zebrafish. HS1BP3 is localized to ATG16L1- and ATG9-positive autophagosome precursors and we show that HS1BP3 binds phosphatidic acid (PA) through its PX domain. Furthermore, we find the total PA content of cells to be significantly upregulated in the absence of HS1BP3, as a result of increased activity of the PA-producing enzyme phospholipase D (PLD) and increased localization of PLD1 to ATG16L1-positive membranes. We propose that HS1BP3 regulates autophagy by modulating the PA content of the ATG16L1-positive autophagosome precursor membranes through PLD1 activity and localization. Our findings provide key insights into how autophagosome formation is regulated by a novel negative-feedback mech...自噬体形成的调控机制是领域内的核心科学问题。本研究证实，含PX结构域（PX domain）的蛋白HS1BP3是自噬体形成的负调控因子。在人类细胞培养体系与斑马鱼模型中，敲低HS1BP3可显著增加LC3阳性自噬体的形成量与底物降解水平。HS1BP3定位于ATG16L1与ATG9阳性的自噬体前体膜结构，且其可通过PX结构域结合磷脂酸（PA）。进一步研究发现，在HS1BP3缺失的细胞中，总磷脂酸水平显著上调，这一现象源于PA合成酶磷脂酶D（PLD）的活性增强，以及PLD1向ATG16L1阳性膜结构的募集增加。本研究提出，HS1BP3可通过调控PLD1的活性与膜定位，进而改变ATG16L1阳性自噬体前体膜的磷脂酸含量，从而实现对自噬过程的调控。本研究结果为自噬体形成的新型负反馈调控机制提供了关键理论依据。