Aging Institute, University of Pittsburgh School of Medicine and University of Pittsburgh Medical Center, Pittsburgh, PA, USA.
Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
Nature. 2022 Sep;609(7928):815-821. doi: 10.1038/s41586-022-05164-4. Epub 2022 Sep 7.
Lysosomal dysfunction has been increasingly linked to disease and normal ageing. Lysosomal membrane permeabilization (LMP), a hallmark of lysosome-related diseases, can be triggered by diverse cellular stressors. Given the damaging contents of lysosomes, LMP must be rapidly resolved, although the underlying mechanisms are poorly understood. Here, using an unbiased proteomic approach, we show that LMP stimulates a phosphoinositide-initiated membrane tethering and lipid transport (PITT) pathway for rapid lysosomal repair. Upon LMP, phosphatidylinositol-4 kinase type 2α (PI4K2A) accumulates rapidly on damaged lysosomes, generating high levels of the lipid messenger phosphatidylinositol-4-phosphate. Lysosomal phosphatidylinositol-4-phosphate in turn recruits multiple oxysterol-binding protein (OSBP)-related protein (ORP) family members, including ORP9, ORP10, ORP11 and OSBP, to orchestrate extensive new membrane contact sites between damaged lysosomes and the endoplasmic reticulum. The ORPs subsequently catalyse robust endoplasmic reticulum-to-lysosome transfer of phosphatidylserine and cholesterol to support rapid lysosomal repair. Finally, the lipid transfer protein ATG2 is also recruited to damaged lysosomes where its activity is potently stimulated by phosphatidylserine. Independent of macroautophagy, ATG2 mediates rapid membrane repair through direct lysosomal lipid transfer. Together, our findings identify that the PITT pathway maintains lysosomal membrane integrity, with important implications for numerous age-related diseases characterized by impaired lysosomal function.
溶酶体功能障碍与疾病和正常衰老的关系日益密切。溶酶体相关疾病的一个标志是溶酶体膜通透性增加（LMP），它可以被多种细胞应激源触发。鉴于溶酶体内容物的破坏性，LMP 必须迅速得到解决，尽管其潜在机制尚不清楚。在这里，我们使用一种无偏的蛋白质组学方法，表明 LMP 刺激了一种磷酸肌醇引发的膜连接和脂质转运（PITT）途径，用于快速溶酶体修复。在 LMP 后，磷脂酰肌醇-4 激酶 2α（PI4K2A）迅速积累在受损的溶酶体上，产生高水平的脂质信使磷脂酰肌醇-4-磷酸。溶酶体中的磷脂酰肌醇-4-磷酸反过来招募了多个甾醇结合蛋白（OSBP）相关蛋白（ORP）家族成员，包括 ORP9、ORP10、ORP11 和 OSBP，以协调受损溶酶体与内质网之间广泛的新膜接触位点。然后，ORPs 催化内质网到溶酶体的磷脂酰丝氨酸和胆固醇的大量转移，以支持快速的溶酶体修复。最后，脂质转移蛋白 ATG2 也被招募到受损的溶酶体上，其活性被磷脂酰丝氨酸强烈刺激。独立于巨自噬，ATG2 通过直接的溶酶体脂质转移来介导快速的膜修复。总之，我们的发现表明 PITT 途径维持了溶酶体膜的完整性，对许多以溶酶体功能受损为特征的与年龄相关的疾病具有重要意义。
