Cellular Aging: Cell Death

Many genes are now thought to function primarily in apoptosis. Most consist of families of genes whose different functions reflect the nuances of regulation of cell death. For instance, Fas is a member of a large family of receptor proteins. Caspases, a family including at least eleven enzymes, have evolved from a single caspase in a nematode worm. (Important enzymes are conserved from animal to animal throughout evolution. However, many amino acids may change and animals may keep more than one variant, splitting an original single enzyme into two related enzymes.) Other than the products of the genes mentioned above, there are inhibitors of cell death, such as Bcl-2, which is likewise a member of a family of genes. Since Bcl-2 must form dimers to function, the complexes that it forms with other family members may lead to inhibition or activation of apoptosis. Thus, some family members, such as bax, are proapoptotic. The activity of several genes specifically increases or decreases in apoptosis, but their specific function in apoptosis is not known.