Chang, S.-C. S.; Thorlacius, A.; Sundborger-Lunna, A.

Intrinsic apoptosis, or programmed cell death, is a vital response to stress and DNA damage in cells, and dysregulation of the intrinsic apoptotic pathway is common in multiple cancers. The release of pro-apoptotic factors from mitochondria by the protein Bax is preceded by changes in the lipid composition, and thereby, the membrane properties of the outer mitochondrial membrane. We find that the membrane remodeling protein endophilin B1 primes membranes rich in mitochondria-specific lipid cardiolipin for Bax-mediated permeabilization, and displays 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, and that a related protein, endophilin B2, is constitutively bound to healthy mitochondria.