TMEM55B contributes to lysosomal homeostasis and amino acid-induced mTORC1 activation
TMEM55B contributes to lysosomal homeostasis and amino acid-induced mTORC1 activation
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DOI：
10.1111/gtc.12583
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发表时间：
2018-06-01
期刊：
影响因子：
2.1
通讯作者：
Nakayama, Keiichi I.
中科院分区：
文献类型：
--
作者：
Hashimoto, Yutaka;Shirane, Michiko;Nakayama, Keiichi I.
雷帕霉素复合物 1 (mTORC1) 的哺乳动物/机械靶点对生长因子和营养可用性做出反应。氨基酸诱导 mTORC1 募集至溶酶体膜并随后激活，但这种激活的分子机制仍不清楚。我们现在已经研究了 TMEM55B（一种分子功能未知的溶酶体蛋白）在此过程中的作用，基于蛋白质组学和免疫荧光分析的结果表明，TMEM55B 与参与 mTORC1 激活的许多蛋白质相互作用，包括液泡型质子 ATP 酶 (V-ATPase) 和 Ragulator 复合物的成分。 溶酶体膜。与对照细胞相比，TMEM55B 耗尽的细胞中氨基酸诱导的 mTORC1 底物 S6K 和 4E-BP 磷酸化减弱。还发现 TMEM55B 的消耗会引起溶酶体应激，如转录因子 TFEB 易位至细胞核所示。此外，在TMEM55B耗尽的细胞中，V-ATP酶的V1结构域亚复合物向脂筏的募集被取消。总的来说，我们的结果表明 TMEM55B 有助于溶酶体膜脂筏中 V-ATP 酶复合物的组装以及随后 mTORC1 的激活。
Mammalian/mechanistic target of rapamycin complex 1 (mTORC1) responds to growth factors and nutrient availability. Amino acids induce the recruitment of mTORC1 to the lysosomal membrane and its consequent activation, but the molecular mechanism of such activation has remained unclear. We have now examined the role of TMEM55B, a lysosomal protein of unknown molecular function, in this process on the basis of the results of proteomics and immunofluorescence analyses showing that TMEM55B interacts with many proteins that participate in mTORC1 activation including components of the vacuolar-type proton ATPase (V-ATPase) and Ragulator complexes at the lysosomal membrane. The amino acid-induced phosphorylation of the mTORC1 substrates S6K and 4E-BP was attenuated in TMEM55B-depleted cells compared with control cells. Depletion of TMEM55B was also found to evoke lysosomal stress as showed by translocation of the transcription factor TFEB to the nucleus. Furthermore, recruitment of the V1 domain subcomplex of V-ATPase to lipid rafts was abrogated in TMEM55B-depleted cells. Collectively, our results suggest that TMEM55B contributes to assembly of the V-ATPase complex in lipid rafts of the lysosomal membrane and to subsequent activation of mTORC1.