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

描述（由申请人提供）：细胞吞噬机制的终末阶段是吞噬作用和内吞作用（介导外源底物的摄取），以及自噬作用（介导细胞内底物的吞噬），涉及吞噬货物的溶酶体消化和钙转运蛋白输出至胞质溶胶用于生物合成。尽管这些途径对于去除靶向底物具有关键作用，并且溶酶体介导的消化对于吞噬物质的实际清除和再循环具有重要性，但关于如何调节吞噬货物的溶酶体加工和降解组分的输出知之甚少。我们已经发现，mTORC 1蛋白激酶，mRNA翻译和自噬的调节剂，和脂质激酶PIKfyve，是吞噬体分裂的程序所必需的，该程序随着内化的货物被降解而收缩大的溶酶体空泡，这让人想起最近描述的自噬溶酶体重组（ALR）程序，其在自噬过程中起类似的作用。胆固醇分裂与营养恢复有关，营养恢复将吞噬细胞从氨基酸或葡萄糖/丙酮酸饥饿的影响中拯救出来，并重新激活mTORC 1。重新激活的mTOR特异性地募集到容纳降解细胞的大溶酶体空泡并控制它们的分裂。拟议的研究将确定在溶酶体中作用的氨基酸和糖转运蛋白，介导营养恢复和mTORC 1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.