Highly proliferating cells are particularly dependent on glucose and glutamine for bioenergetics and to fuel biosynthesis of macromolecules. The signals that respond to the fluctuations of these nutrients and how they control metabolic pathways remain poorly understood. mTOR, as part of mTOR complex 1 (mTORC1), responds to amino acids and plays a central role in metabolism. On the other hand, little is known on how mTORC2, consisting of the core components mTOR, rictor, SIN1 and mLST8 is regulated and its metabolic functions. The phosphorylation of the mTORC2 substrate, Akt, is enhanced in cancer cells, suggesting that mTORC2 becomes deregulated during tumorigenesis. Here we found that the activity of mTORC2 is enhanced by diminishing glutamine-derived metabolites. mTORC2 activity is required by glutamine-requiring biosynthetic pathways such as the hexosamine biosynthetic pathway (HBP). Acute nutrient withdrawal augments Akt phosphorylation but does not affect GFAT1 expression. However, extreme starvation that eventually depletes intracellular glutamine metabolites inactivates mTORC2 and downregulates GFAT1 expression. Thus, while mTORC1 senses glutamine abundance to promote anabolism, mTORC2 responds to declining glutamine catabolites in order to restore metabolic homeostasis. Our findings uncover the role of mTORC2 in metabolic reprogramming and provide insights on more effective therapeutic strategies for glutamine-dependent tumors.
Citation Format: Estela Jacinto, Joseph Moloughney, Peter K. Kim, Nicole M. Vega-Cotto, Chang-Chih Wu, Thomas Lynch, Sisi Zhang, Matthew Adlam, Sai Guntaka, Po-Chien Chou, Joshua D. Rabinowitz, Guy Werlen. The mTORC2 target Akt is regulated in response to glutamine metabolite levels. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 21.