Characterization of WAC interactions with R2TP and TTT chaperone complexes linking glucose and glutamine availability to mTORC1 activity.

TELO2-TTI1-TTI2 (TTT) and R2TP are multi-subunit chaperones that cooperate with HSP90 to assemble matured complexes of the PIKK family of kinases, including mTOR complex 1 (mTORC1). WAC, a protein previously implicated in transcription, H2B ubiquitination, and autophagy, was recently identified as a regulator of mTORC1 in response to glucose and glutamine availability, acting in concert with R2TP and TTT. However, the molecular basis of the interactions of WAC with R2TP and TTT and their role in mTORC1 regulation remains poorly defined. Here, we characterized the interactions of WAC with mTOR, R2TP, and TTT and how these are affected by nutrient conditions. Using purified proteins, we establish that WAC directly binds to mTOR-mLST8, R2TP, and TELO2, but not TTI1 and TTI2. In cells, WAC is part of complexes containing components of mTORC1, R2TP, and TTT, and these associations are modulated by nutrient availability. Notably, WAC and TELO2 strongly associate with mTOR under glucose and glutamine deprivation, and these interactions are weakened minutes after nutrient refeeding. These dynamics correlate with changes in mTORC1 activity. Transcriptomic and proteomic analysis shows that WAC, mTOR, R2TP, and TTT are co-expressed across several human cancers, supporting that WAC is part of a functional pathway with mTOR, R2TP, and TTT. Together, our findings reveal the formation and disassembly of a WAC complex with mTOR and TELO2 that contributes to regulate mTORC1 in response to glucose and glutamine availability.