Dynamics of mitochondrial structure during apoptosis and the enigma of Opa1

The large scale remodeling of mitochondria during apoptosis is a necessary step for the complete release of cytochrome c has been a tenet since 2002. However, more recent findings strongly indicate that the large-scale remodeling previously described actually takes place after the release of cytochrome c and in a caspase-dependent manner, bringing into question whether mitochondria remodeling is necessary. In a more recent article, however, it was shown that a much more subtle form of remodeling is taking place which is only observable by electron tomography. In the Bcl-2 inhibitable Bax/Bak-dependent intrinsic pathway of apoptosis, the release of cytochrome c from mitochondria is a consequence of two carefully coordinated events: formation of outer membrane pores and opening of crista junctions triggered by Opal oligomer disassembly, and both steps are necessary for the complete release of cytochrome c. We review the recent literature pertaining to the coordinated release of cytochrome c during cell death. (C) 2009 Elsevier B.V. All rights reserved.