Proteolysis in Apoptosis: Enzymes and Substrates

Publisher Summary This chapter discusses the major classes of proteases that have been ascribed roles in apoptosis and presents the evidence for their involvement in programmed cell death. Apoptosis or programmed cell death is a genetically controlled and highly regulated process through which multicellular organisms remove unwanted cells, and might be considered a specific form of terminal differentiation. It also occurs in response to a wide range of toxic stimuli. Apoptosis is important during embryogenesis, for homeostasis of tissue mass, and for prevention of disease. If apoptosis occurs too much, the results are impaired development or degenerative disease. On the other hand too little may also result in impaired development as well as tumor formation and sustained viral or bacterial infection. Unlike necrosis that results from plasma-membrane injury and causes cells to swell, apoptosis is characterized by cell shrinkage—the chromatin becomes pyknotic and may form crescent-shaped bodies along the nuclear envelope,—the nucleus may break up, the cell produces processes or buds, which often contain nuclear fragments, and the DNA is cleaved into intranucleosomal pieces giving rise to characteristic 185bp fragments.