“Apoptosis is the process of programmed cell death (PCD) that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation.
There are two kinds of apoptosis signal transduction pathways – the mitochondrial, or intrinsic pathway, and direct signal transduction pathway. Apoptosis via the intrinsic pathway is caused by release of mitochondrial intermembrane proteins and SMAC in to the cytosol. These proteins ultimately activate caspases, which in turn promote the programmed cell death. Direct signal transduction pathway relies on signals from outside of the cell. Specifically, TNF and Fas death receptors on the surface of cells activated by ligands and this leads to direct signal transduction pathway that can activate caspases.”
- Ouyang, L. et al., Cell Proliferat. 2012; 45(6): 487-498.