Cells receive signals from their environment telling them to stay alive. These signals go to the mitochondria, which actively removes a protein, Bax, which otherwise would kill the cell. The loss of survival signals leads to Bax accumulating on the mitochondria.
Barbara Schellenberg, Pengbo Wang, James A Keeble, Ricardo Rodriguez-Enriquez, Scott Walker, Thomas W Owens, Fiona Foster, Jolanta Tanianis-Hughes, Keith Brennan, Charles H Streuli, Andrew P Gilmore,
Molecular Cell 49(5):