Dynamin-dependent amino acid endocytosis activates mechanistic target of rapamycin complex 1 (mTORC1)
Dynamin-dependent amino acid endocytosis activates mechanistic target of rapamycin complex 1 (mTORC1)
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DOI：
10.1074/jbc.m117.776443
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发表时间：
2017-11-03
影响因子：
4.8
通讯作者：
Iwata, Hiroyuki
中科院分区：
文献类型：
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作者：
Shibutani, Shusaku;Okazaki, Hana;Iwata, Hiroyuki
雷帕霉素复合物1（mTORC 1）的机制靶点是蛋白质合成的主要调节剂，也是在各种条件下（包括癌症和衰老）修饰细胞代谢的潜在靶点。mTORC 1活性受细胞外氨基酸的可用性严格调节，先前的研究表明，细胞外液中的氨基酸被转运至溶酶体腔。在那里，氨基酸通过Rag GTP酶诱导细胞质mTORC 1向溶酶体的募集，然后通过脑中富集的小GT3 Ras同系物（Rheb）激活mTORC 1。然而，胞外氨基酸如何到达溶酶体腔并激活mTORC 1仍不清楚。在这里，我们表明，氨基酸的摄取动力蛋白依赖的内吞作用中起着至关重要的作用mTORC 1激活。我们发现，mTORC1失活时，内吞作用被抑制过表达的显性阴性形式的发动蛋白2或药理学抑制发动蛋白或网格蛋白。因此，发动蛋白抑制可抑制mTORC1向溶酶体的募集。通过放线菌酮暴露或Rag过表达增加细胞内氨基酸来挽救mTORC1的活性和溶酶体募集，表明氨基酸剥夺是mTORC1通过动力蛋白抑制失活的主要原因。我们进一步表明，内吞抑制不诱导自噬，即使mTORC 1失活是已知的强烈诱导自噬。这些发现为使用内吞抑制剂作为潜在药物开辟了新的前景，这些药物可以有效地抑制营养物质的利用并关闭激活mTORC 1的上游信号。
The mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of protein synthesis and potential target for modifying cellular metabolism in various conditions, including cancer and aging. mTORC1 activity is tightly regulated by the availability of extracellular amino acids, and previous studies have revealed that amino acids in the extracellular fluid are transported to the lysosomal lumen. There, amino acids induce recruitment of cytoplasmic mTORC1 to the lysosome by the Rag GTPases, followed by mTORC1 activation by the small GTPase Ras homolog enriched in brain (Rheb). However, how the extracellular amino acids reach the lysosomal lumen and activate mTORC1 remains unclear. Here, we show that amino acid uptake by dynamin-dependent endocytosis plays a critical role in mTORC1 activation. We found that mTORC1 is inactivated when endocytosis is inhibited by overexpression of a dominant-negative form of dynamin 2 or by pharmacological inhibition of dynamin or clathrin. Consistently, the recruitment of mTORC1 to the lysosome was suppressed by the dynamin inhibition. The activity and lysosomal recruitment of mTORC1 were rescued by increasing intracellular amino acids via cycloheximide exposure or by Rag overexpression, indicating that amino acid deprivation is the main cause of mTORC1 inactivation via the dynamin inhibition. We further show that endocytosis inhibition does not induce autophagy even though mTORC1 inactivation is known to strongly induce autophagy. These findings open new perspectives for the use of endocytosis inhibitors as potential agents that can effectively inhibit nutrient utilization and shut down the upstream signals that activate mTORC1.