Vital functions for lethal caspases.

Caspases are a family of cysteine proteases expressed as inactive zymogens in virtually all animal cells. These enzymes play a central role in most cell death pathways leading to apoptosis but growing evidences implicate caspases also in nonapoptotic functions. Several of these enzymes, activated in molecular platforms referred to as inflammasomes, play a role in innate immune response by processing some of the cytokines involved in inflammatory response. Caspases are requested for terminal differentiation of specific cell types, whether this differentiation process leads to enucleation or not. These enzymes play also a role in T and B lymphocyte proliferation and, in some circumstances, appear to be cytoprotective rather than cytotoxic. These pleiotropic functions implicate caspases in the control of life and death but the fine regulation of their dual effect remains poorly understood. The nonapoptotic functions of caspases implicate that cells can restrict the proteolytic activity of these enzymes to selected substrates. Deregulation of the pathways in which caspases exert these nonapoptotic functions is suspected to play a role in the pathophysiology of several human diseases.