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

描述（由申请人提供）：细胞吞噬机制的最后阶段吞噬和内吞，介导外源底物的摄取，以及自噬，介导细胞内底物的吞噬，包括溶酶体消化吞噬的货物，并将分解代谢物出口到细胞质中用于生物合成。尽管这些途径在清除目标底物中起着关键作用，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也很重要，但对于吞噬货物的溶酶体加工和降解成分的出口是如何被调节的，我们知之甚少。我们发现mRNA翻译和自噬的调节因子mTORC1蛋白激酶和脂质激酶PIKfyve是吞噬体分裂程序所必需的，当内化货物被降解时，吞噬体分裂程序会收缩大的溶酶体液泡，这让人想起最近描述的自噬溶酶体重组（ALR）程序，它在自噬过程中具有类似的功能。液泡裂变与营养恢复有关，营养恢复使被吞噬的细胞免于氨基酸或葡萄糖/丙酮酸饥饿的影响，并重新激活mTORC1。重新激活的mTOR特异性地招募容纳降解细胞的大溶酶体液泡并控制它们的裂变。拟议的研究将确定作用于溶酶体的氨基酸和糖转运体，介导营养恢复和mTORC1激活，并将确定控制溶酶体液泡裂变的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.