The Noxa/Mcl-1 axis regulates susceptibility to apoptosis under glucose limitation in dividing T cells

Throughout lymphocyte development, cellular persistence and expansion are tightly regulated by survival and apoptosis. Within the Bcl-2 family, distinct apoptogenic BH3-only members like Bid, Bim, and Puma appear to function in specific cell death pathways. We found that naive human T cells after mitogenic activation, apart from expected protective Bcl-2 members, also rapidly upregulate the BH3-only protein Noxa in a p53-independent fashion. The specific role of Noxa became apparent during glucose limitation and involves interaction with the labile Bcl-2 homolog Mcl-1. Knockdown of Noxa or Mcl-1 results in protection or susceptibility, respectively, to apoptosis induced by glucose deprivation. Declining Mcl-1 levels and apoptosis induction are inversely correlated to Noxa levels and prevented by readdition of glucose. We propose that the Noxa/Mcl-1 axis is an apoptosis rheostat in dividing cells, in a selective pathway that functions to restrain lymphocyte expansion and can be triggered by glucose deprivation.