AMBRA1 controls antigen-driven activation and proliferation of naive T cells

AMBRA1 (activating molecule in Beclin1-regulated autophagy) is a member of the BECN1 (BECLIN1) protein complex, and it plays a role in autophagy, cell death, tumorigenesis and proliferation. We recently reported that on T-cell receptor (TCR) stimulation, AMBRA1 controlled both autophagy and the cell cycle with metabolic regulation. Accumulating evidence has shown that autophagy and metabolic control are pivotal for T-cell activation, clonal expansion and effector/memory cell fate decision. However, it is unknown whether AMBRA1 is involved in T-cell function under physiological conditions. We found that T cells in Ambra1-conditional knockout (cKO) mice induced an exacerbated graft versus host response when they were transplanted into allogeneic BALB/c mice. Furthermore, Ambra1-deficient T cells showed increased proliferation and cytotoxic capability toward specific antigens in response to in vivo stimulation using allogeneic spleen cells. This enhanced immune response mainly contributed to naive T-cell hyperactivity. The T-cell hyperactivity observed in this study was similar to those in some metabolic factor-deficient mice, but not those in other pro-autophagic factor-deficient mice. Under the static condition, however, naive T cells were reduced in Ambra1-cKO mice, the same as in pro-autophagic factor-deficient mice. Collectively, these results suggested that AMBRA1 was involved in regulating T cell-mediated immune responses through autophagy-dependent and -independent mechanisms.