The mechanistic target of rapamycin (mTOR) is known to function in two complexes: mTOR complex 1 (mTORC1) and mTORC2. While the function of mTORC1 in dendritic cells (DCs) has been studied extensively, our group has only recently demonstrated mTORC2 deletion in DCs (TORC2^DC-/-) elicits an inflammatory phenotype and promotes allogeneic T effector cell activation. However, the underlying mechanism has not been resolved. In addition, the role of TORC2^DC-/- in transplantation has not been defined. We hypothesized TORC2^DC-/- would have altered metabolic activity, resulting in augmented antigen-specific T cell responses and accelerated graft rejection.

To study TORC2^DC-/- in transplantation, we used models in which TORC2 was deleted specifically in conventional CD11c⁺ DC in either skin graft donors or recipients . Graft survival was monitored; Banff rejection scoring was done by a blinded pathologist following immunohistochemical analysis. To ascertain if skin-resident TORC2^DC-/- could augment inflammatory responses, we performed a cell-mediated delayed-type hypersensitivity (DTH) assay. As mTORC2 has been implicated in cytoskeletal dynamics, we measured DC migration into secondary lymphoid tissue.

To elucidate the role of mTORC2 in regulating DC metabolism we analyzed the glycolytic capacity and mitochondrial respiration via extracellular flux. Mitochondrial mass and activity were determined via flow cytometry, and ATP production was measured.

We demonstrate, for the first time, TORC2^DC-/- in either skin graft donors or recipients accelerates rejection. TORC2^DC-/- mice also exhibit enhanced T cell and inflammatory monocytic infiltration in DTH responses. These effects are not due to differential migration of TORC2^DC-/- to secondary lymphoid tissue. TORC2^DC-/- utilize an altered metabolic program, wherein glycolytic function is enhanced as compared to wild-type (WT) DCs. This corresponds with increased viability of TORC2^DC-/- after stimulation, which may allow TORC2^DC-/- to persist in secondary lymphoid tissue longer than WT DCs. These findings reveal a novel role for mTORC2 in regulating DC immunometabolism, and may provide a basis for therapeutic targeting of DC metabolism to regulate immune responses in transplantation.

CITATION INFORMATION: Watson A., Dai H., Diaz-Perez J., Menk A., Killeen M., Delgoffe G., Mathers A., Thomson A. Glycolytic Bias in mTORC2-Deficient Dendritic Cells Potentiates Antigen-Specific Immunity and Accelerates Graft Rejection Am J Transplant. 2017;17 (suppl 3).

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