BCL-xL antagonizes the deleterious effects of KRAS on mitochondrial scaffolding
In addition to its canonical role as a regulator of mitochondrial outer membrane permeabilization, BCL-xL exerts diverse non canonical functions contributing to cancer cell aggressiveness. In particular it regulates KRAS intracellular activation levels. We herein explored the mechanistic basis for this effect by a spatially restricted biotin-labelling proteomic approach designed to characterize proteins whose proximity to KRAS, used as a bait, is BCL-xL dependant. BCL-xL loss relocalizes KRAS to the vicinity of mitochondrial proteins. Proximal proteins include the mitochondrial scaffold prohibitin 2 (PHB2), which also interacts with BCL-xL and the downregulation of which prevents BCL-xL sensitive effects of KRAS induced contacts between mitochondria and endosomes, and mitochondrial mass decrease. These results argue that BCL-xL prevents a negative feedback regulation of KRAS canonical signaling by KRAS interference with mitochondrial quality control.