Abstract Glutamine addiction is a key metabolic vulnerability in cancer. However, the mechanisms governing the limited efficacy of glutamine metabolism inhibitor (GMI) monotherapy require further investigation. Via single-cell monitoring using a caspase-3 activity indicator, we identified SLC25A6 as a key mediator of GMI-induced apoptosis in colorectal cancer cells. SLC25A6 overexpression enhanced apoptosis both in vitro and in vivo. SLC25A6 promoted mitochondrial fragmentation and dysfunction and upregulated the expression of mitochondrial fission markers. Notably, mitofission inhibitors largely abolished SLC25A6-related mitochondrial dysfunction and intrinsic apoptosis. Mechanistically, SLC25A6 directly interacted with MIC60, competitively inhibiting MIC19 binding; both MIC60 and MIC19 are key components of the mitochondrial contact site and cristae organizing system (MICOS). The SLC25A6 T126A mutant failed to bind MIC60 and lost its ability to destabilize the MICOS complex and facilitate mitofission. Upregulation of SLC25A6 expression induced by the glutaminase inhibitor CB-839 sensitized cancer cells to the Bcl-2 inhibitor ABT-199. Combined CB-839 and ABT-199 treatment showed strong synergistic antitumor effects in colorectal cancer xenograft models. Our findings reveal a novel function of SLC25A6 that links metabolic stress to mitochondrial apoptosis via disruption of the MICOS complex. Combination treatments with mitochondrial apoptotic inducers represent a promising avenue for maximizing the efficacy of GMIs in cancer treatment.
Wang et al. (Thu,) studied this question.