Phosphatidic acid activates mTORC1 by displacing the inhibitor DEPTOR (1013.19)

Abstract

The lipid second messenger, phosphatidic acid (PA), is a critical mediator of mitogenic activation of the mammalian target of rapamycin complex 1 (mTORC1). Previously we showed that PA binds to mTOR and activates mTORC1, but the mechanism of this activation remains incompletely understood. Here we propose a novel mechanism of mTORC1 activation by PA. Using mass spectrometry analysis to identify mTOR interactions regulated by PA, followed by confirmation by co‐immunoprecipitation, we discovered that the interaction between mTOR and its inhibitor DEPTOR was disrupted by PA. Dissociation of DEPTOR by PA coincided with activation of mTORC1. Phospholipase D1 (PLD1) catalyzes the production of PA and is also an established mediator of mitogenic activation of mTORC1. Treatment of cells with phorbol myristate acetate and lysophosphatidic acid, known to activate PLD1, recapitulated the DEPTOR displacement and mTORC1 activation achieved with exogenous PA, and this effect was decreased by PLD1 inhibition. Furthermore, by examining a panel of PA molecules with various fatty acid chains, we found that only the PA species known to be produced by PLD displaced DEPTOR and activated mTORC1 both in vitro and in cells. Taken together, our results strongly suggest that PA produced by PLD1 regulates mTORC1 activity by displacing the inhibitor, DEPTOR.Grant Funding Source: Supported by NIH GM089771 and AR048914 grants to J. Chen.