Single Serine on TSC2 Exerts Biased Control over mTORC1 Activation by ERK1/2 but Not Akt

Abstract

The mammalian target of rapamycin complex 1 (mTORC1) is tightly controlled by tuberous sclerosis complex-2 (TSC2) that is regulated by phosphorylation from kinases responding to environmental cues. Protein kinase G specifically modifies serine-1365 (S1364, human), and its phosphorylation (or phosphomimetic SE mutant) potently blocks mTORC1 co-activation by pathological stress, while a phospho-silenced (SA) mutation does the opposite. Neither alter basal mTORC1 activity. Here we show S1365 exerts biased control over mTORC1 activity (S6K phosphorylation) modifying ERK1/2 but not Akt-dependent stimulation. Whereas mTORC1 activation by endothelin-1 is potently modified by S1365 status, insulin or PDGF stimulation are unaltered. TSC2-S1365 is also phosphorylated upon ET-1 but not insulin stimulation in a PKG-dependent manner, revealing intrinsic bias. Neither energy or nutrient modulation of mTORC1 are impacted by S1365. Consistent with these results, knock-in mice with either TSC2 SA or SE mutations develop identical obesity, glucose intolerance, and fatty liver disease from a high fat diet. Thus, S1365 provides an ERK1/2-selective mTORC1 control mechanism and a genetic means to modify pathological versus physiological mTOR stimuli.