Yoon Mee-Sup, Son Kook, Arauz Edwin, Han Jung Min, Kim Sunghoon, Chen Jie
Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601 South Goodwin Avenue B107, Urbana, IL 61801, USA; Department of Molecular Medicine, School of Medicine, Gachon University, Incheon 406-840, Republic of Korea.
Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601 South Goodwin Avenue B107, Urbana, IL 61801, USA.
Cell Rep. 2016 Aug 9;16(6):1510-1517. doi: 10.1016/j.celrep.2016.07.008. Epub 2016 Jul 28.
Amino acid availability activates signaling by the mammalian target of rapamycin (mTOR) complex 1, mTORC1, a master regulator of cell growth. The class III PI-3-kinase Vps34 mediates amino acid signaling to mTORC1 by regulating lysosomal translocation and activation of the phospholipase PLD1. Here, we identify leucyl-tRNA synthetase (LRS) as a leucine sensor for the activation of Vps34-PLD1 upstream of mTORC1. LRS is necessary for amino acid-induced Vps34 activation, cellular PI(3)P level increase, PLD1 activation, and PLD1 lysosomal translocation. Leucine binding, but not tRNA charging activity of LRS, is required for this regulation. Moreover, LRS physically interacts with Vps34 in amino acid-stimulatable non-autophagic complexes. Finally, purified LRS protein activates Vps34 kinase in vitro in a leucine-dependent manner. Collectively, our findings provide compelling evidence for a direct role of LRS in amino acid activation of Vps34 via a non-canonical mechanism and fill a gap in the amino acid-sensing mTORC1 signaling network.
氨基酸的可利用性通过雷帕霉素哺乳动物靶蛋白（mTOR）复合物1（mTORC1，细胞生长的主要调节因子）激活信号传导。III类磷脂酰肌醇-3-激酶Vps34通过调节溶酶体易位和磷脂酶PLD1的激活，介导氨基酸向mTORC1的信号传导。在此，我们确定亮氨酰-tRNA合成酶（LRS）是mTORC1上游Vps34-PLD1激活的亮氨酸传感器。LRS是氨基酸诱导的Vps34激活、细胞磷脂酰肌醇-3-磷酸（PI(3)P）水平升高、PLD1激活和PLD1溶酶体易位所必需的。这种调节需要LRS的亮氨酸结合，但不需要其tRNA充电活性。此外，LRS在氨基酸可刺激的非自噬复合物中与Vps34发生物理相互作用。最后，纯化的LRS蛋白在体外以亮氨酸依赖的方式激活Vps34激酶。总的来说，我们的研究结果为LRS通过非经典机制在氨基酸激活Vps34中发挥直接作用提供了有力证据，并填补了氨基酸感应mTORC1信号网络中的一个空白。
