Signal transduction pathways that regulate cell survival and cell death

Apoptosis or programmed cell death (PCD) is a physiological process critica l for organ development, tissue homeostasis and elimination of defective or potentially dangerous cells in complex organisms. Apoptosis permits cell d eath without a concomitant inflammatory response in the surrounding tissues . The process of apoptosis depends on the reception of multiple extracellul ar and intracellular signals, integration and amplification of these signal s by second messengers and finally, activation of the death effector protea ses, Defects in control of apoptotic pathways may contribute to a variety o f diseases including cancer, autoimmune and neurodegenerative conditions an d AIDS, While many components of the regulatory network controlling apoptos is have been defined, the mechanisms of action and patterns of interaction of these factors remain controversial. This article summarizes some of the known aspects of signaling pathways involved in apoptosis.