Thorlacius, A. | bioRxiv Science

bioRxiv2026

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.

biophysics↗

bioRxiv2024

Peripheral membrane protein endophilin B1 probes, perturbs and permeabilizes lipid bilayers

Bin/Amphiphysin/Rvs (BAR) domain containing proteins are cytosolic, peripheral membrane proteins that regulate the curvature of membranes in eukaryotic cells. BAR protein endophilin B1 plays a key role in multiple cellular processes critical for oncogenesis, including autophagy and apoptosis. Amphipathic regions in endophilin B1 drive membrane association and tubulation through membrane scaffolding. Our understanding of exactly how BAR proteins like endophilin B1 promote highly diverse intracellular membrane remodeling events in the cell is severely limited due to lack of high-resolution structural information. Here we present the highest resolution cryo-EM structure of a BAR protein to date and the first structures of a BAR protein bound to nanodiscs. Using neural networks, we can effectively sort particle species of different stoichiometries, revealing the tremendous flexibility of post-membrane binding, pre-polymer BAR dimer organization and membrane deformation. We also show that endophilin B1 efficiently permeabilizes negatively charged liposomes that contain mitochondria-specific lipid cardiolipin and propose a new model for Bax-mediated cell death.

biochemistry↗