Endophilin B1 primes mitochondria for execution

Intrinsic apoptosis, or programmed cell death, is a vital response to stress and DNA damage in cells, and dysregulation of this pathway is common in cancers. The release of pro-apoptotic factors from mitochondria by the pro-apoptotic protein Bax is preceded by changes in the membrane properties of the outer mitochondrial membrane. We find that the membrane remodeling protein endophilin B1 primes membranes rich in the mitochondria-specific lipid cardiolipin for Bax-mediated membrane permeabilization, via a dual regulatory mechanism. We also show evidence that endophilin B1 translocates to the surface of mitochondria to co-localize with Bax during apoptosis in situ , where it forms biomolecular condensates.