68 - Apoptosis

Abstract

This chapter discusses apoptosis, which is a program for cell deletion triggered by either physiological or noxious signals. The chapter discusses several related concepts, including morphological characterization of cell death, regulation of programmed cell death, roles of physiological cell death, and frontiers in the study of apoptosis. The wealth of information on cell deletion emphasizes the importance of cellular machinery, which is constitutively present in the cytoplasm and readily executes a cell death program. As opposed to previous perspective, RNA transcription and protein synthesis do not appear to be an essential characteristic for the action of the execution machinery in apoptosis. This indicates that cell death effectors are constitutively present, but repressed. Other stages of cell death like signaling or determination could be under transcriptional or translational control. It is not yet understood how Bcl-2 works and this protein has already revolutionized the understanding of cell death mechanisms. It is known that the so-called "proliferative" disorders could also originate by a reduction in cell death, independently of an increment in cell proliferation. The finding that Bcl-2 can partially protect against necrotic insults in addition to apoptosis implies that both processes could have more in common than previously thought. Important advances have been carried out in the molecular identification of the cell death machinery, for regulators and for effectors as well. The similarity of this program from worms to mammals has allowed the combination of forces for a faster understanding of cell deletion, and it highlights the importance of apoptosis in cell function.