Nutrient transport, membrane trfficking, and mTORC1 signaling at lysosomes.

描述(申请人提供)：细胞吞噬和吞噬的终末阶段，介导外源底物的吸收，以及自噬，介导细胞内底物的吞噬，涉及溶酶体对吞噬的货物的消化，并将分解代谢产物输出到细胞质中用于生物合成。尽管这些途径对于目标底物的去除具有关键作用，而且溶酶体介导的消化对于被吞噬物质的实际清除和回收很重要，但人们对被吞没货物的溶酶体加工和降解成分的出口是如何监管的知之甚少。我们发现，当内化的货物被降解时，吞噬小体分裂的程序需要mTORC1蛋白激酶和脂激酶PIKfyve，这让人想起最近描述的自噬溶酶体重组(ALR)程序，该程序在自噬过程中起着类似的作用。液泡分裂与营养恢复有关，后者将被吞噬的细胞从氨基酸或葡萄糖/丙酮酸饥饿的影响中解救出来，并重新激活mTORC1。重新激活的mTOR专门针对含有降解细胞的大溶酶体空泡招募，并控制它们的分裂。这项拟议的研究将确定作用于溶酶体的氨基酸和糖转运蛋白，这些转运蛋白介导营养恢复和mTORC1激活，并将确定控制溶酶体空泡分裂的mTOR和PIKfyve调节蛋白。

DESCRIPTION (provided by applicant): The end stages of the cellular engulfment mechanisms phagocytosis and entosis, which mediate the uptake of exogenous substrates, and autophagy, which mediates the engulfment of intracellular substrates, involve lysosomal digestion of engulfed cargo and export of catabolites to the cytosol for use in biosynthesis. Despite the critical role of these pathways for the removal of targeted substrates, and the importance lysosome- mediated digestion for the actual clearance and recycling of engulfed material, little is known about how the lysosomal processing of engulfed cargo and export of degraded components is regulated. We have found that the mTORC1 protein kinase, a regulator of mRNA translation and autophagy, and the lipid kinase PIKfyve, are required for a program of phagosome fission that shrinks large lysosomal vacuoles as internalized cargo is degraded, which reminiscent of the recently described autophagic lysosome reformation (ALR) program that functions similarly during autophagy. Vacuole fission is associated with nutrient recovery that rescues engulfing cells from the effects of amino acid or glucose/pyruvate starvation, and reactivates mTORC1. Reactivated mTOR recruits specifically to large lysosomal vacuoles harboring degrading cells and controls their fission. The proposed research will identify amino acid and sugar transporters acting at lysosomes that mediate nutrient recovery and mTORC1 activation, and will identify mTOR and PIKfyve-regulated proteins that control the fission of lysosomal vacuoles.