Measurement of caspase activation in mammalian cell cultures

The majority of caspases, cysteine-dependent aspartate-directed proteases, being in their activated state are involved in regulation of apoptosis by cleaving protein substrates harboring specific target motifs. Basically all biochemical and morphological changes in an apoptotic cell, including cell shrinkage, chromatin condensation, DNA fragmentation, and plasma membrane blebbing, are consequence of caspase-mediated proteolysis. Thus, uncovering activities of unique caspases are key determinants of the apoptotic process. This chapter describes a set of experimental protocols available for characterization, quantification and inhibition of caspase activities in mammalian cell cultures, including immunoblotting, usage of synthetic substrates, flow cytometry, and microscopic techniques.