The mechanistic target of rapamycin (mTOR) is a kinase that functions in at least two complexes: rapamycin (RAPA)-sensitive mTORC1 and RAPA-insensitive mTORC2. These complexes play critical roles in myriad essential cellular functions. In dendritic cells (DC), targeting of mTORC1 using RAPA inhibits differentiation, maturation, and allostimulatory function; absence of mTORC2 in DC leads to an enhanced inflammatory profile. However, the allostimulatory role of mTORC2 in DC is undefined. In addition, while mTOR is an important metabolic regulator in DC, the role of mTORC2 in regulation of DC metabolism is unknown. To elucidate the role of mTORC2 in DC metabolism and alloimmunity, we generated novel mice deficient in mTORC2 (mTORC2^DC-/-) specifically in conventional CD11c+ DC. We hypothesized that ablation of mTORC2 in DC might alter metabolic activity resulting in augmented T cell responses and alloimmunity in vivo.

The glycolytic capacity and mitochondrial respiratory activity of wild-type and mTORC2^DC-/- generated from mouse BM were analyzed using a Seahorse XF Bioanalyzer. The role of mTORC2 in DC instigation of immune responses was investigated in vivo by: 1) intratumoral injection of mTORC2^DC-/- in a B16 melanoma model, and 2) determining the impact of mTORC2^DC-/- on in vivo alloreactive T cell responses and survival of mTORC2^DC-/- male>female skin and heterotopic heart allografts.

mTORC2^DC-/- exhibited increased glycolytic and mitochondrial metabolic activity and enhanced T cell allostimulatory function in vitro compared to control DC. In vivo, mTORC2^DC-/- retarded B16 melanoma growth by stimulating enhanced anti-tumor CTL responses, whereas mTORC2^DC-/- mice displayed enhanced alloreactive T cell responses and allografts from mTORC2^DC-/- donors were rejected in accelerated fashion.

These data reveal for the first time that mTORC2 negatively regulates conventional DC metabolism and DC promotion of T cell responses and graft rejection. Our studies suggest a link between mTORC2, DC metabolism, and allograft outcome that may provide a basis for therapeutic targeting of DC metabolism to regulate alloimmune responses.

CITATION INFORMATION: Watson A, Raïche-Regué D, Dai H, Fabian K, Delgoffe G, Storkus W, Thomson A. mTORC2 Negatively Regulates Dendritic Cell (DC) Metabolism and the Allostimulatory Function of Donor DCs in Organ Transplantation. Am J Transplant. 2016;16 (suppl 3).

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