"Trojan" Methionine Probe Reveals PKM2 as a Methionine-Sensing Protein in the mTORC1 Pathway

Methionine (Met) plays a pivotal role in numerous cellular functions. Methionine restriction has been demonstrated to provide metabolic benefits in aging, obesity, diabetes and as an adjunct to cancer therapy. However, the methionine-sensing proteins and how cells directly sense the methionine level have remained elusive. In this study, we developed a photoaffinity analogue of methionine to capture proteins that specifically recognize and sense methionine in living cells. Using chemoproteomic profiling and biochemical validation, we found that PKM2 is a specific methionine sensor that transduces methionine availability signals through the interaction with the GATOR2 complex, which, in turn, modulates the downstream response of the mTORC1 pathway through a novel methionine-recognition pocket on PKM2. As our findings indicate that the sensing of methionine by PKM2 is independent of its enzymatic activity, we envision that disrupting the binding of methionine to PKM2 or stabilizing the PKM2-GATOR2 interaction would create a methionine pseudostarvation state in living cells, which holds promise as a novel therapeutic avenue that could emulate the physiological benefits of a methionine-restricted diet and circumvent the drawbacks of dietary methionine restriction.