IMPLICATION OF MITOCHONDRIA IN APOPTOSIS

The induction phase of programmed cell death (PCD) or apoptosis is cha racterized by an extreme heterogeneity of potential PCD-triggering sig nal transduction pathways. During the subsequent effector phase, the n umerous PCD-inducing stimuli converge into a few stereotypical pathway s and cells pass a 'point of no return', thus becoming irreversibly co mmitted to death. Evidence is accumulating that cytoplasmic structures , including mitochondria, participate in the critical effector stage a nd that alterations usually considered to define apoptosis, as nuclear chromatolysis and cytolysis, have to be ascribed to the late degradat ion phase. We and others have recently shown that nuclear features of apoptosis are preceded by alterations in mitochondrial function and st ructure. The importance of these alterations for the apoptotic process and also the possible link between, these observations, the permeabil ity transition pore and the programmed cell death, are discussed.