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. Author manuscript; available in PMC: 2014 May 1.
Published in final edited form as: Trends Biochem Sci. 2013 Mar 1;38(5):233–242. doi: 10.1016/j.tibs.2013.01.004

Figure 2. Energy sensing by AMPK and control of mTORC1.

Figure 2

AMP-activated protein kinase (AMPK) acts as a metabolic checkpoint under nutrient starvation conditions, translating signals to mTORC1 through direct phosphorylation of tuberous sclerosis complex 2 (TSC2) and Raptor and inhibiting cell growth. The phosphorylation of AMPK at threonine 172 by liver kinase B1 (LKB1) in the activation loop is essential for AMPK activation. LKB1 is in a complex with STRAD and MO25. AMPK phosphorylates and activates TSC1/2 by phosphorylating TSC2, which inhibits mTORC1. AMPK also phosphorylates regulatory-associated protein of mTOR (Raptor) in a parallel pathway on sites that induce Raptor-14-3-3 binding and inhibition of mTORC1. RTK denotes receptor tyrosine kinase. P represents phosphorylation.