Perspectives on the mitochondrial permeability transition

The permeability transition, a sudden permeability increase of the inner mitochondrial membrane that is greatly favored by Ca2+ accumulation, has puzzled mitochondrial scientists for more than 40 years. It is now recognized that this phenomenon is mediated by opening a high conductance channel (the mitochondrial permeability transition pore) whose open-closed transitions are highly regulated. Through the pore mitochondria may participate in intracellular signalling, and release proteins involved in amplification of the cell death cascade triggered by a variety of physiological and pathological stimuli. Yet, the basic questions of the molecular nature of the permeability transition pore, its physiological role and its very occurrence in vivo remain a matter of intense debate. This short review is meant to summarize our current views on the mitochondrial permeability transition, its perspectives, and our strategies to resolve at least some of the outstanding issues about its nature and function.