Apoptosis is a genetically programmed mechanism of cell death that can be triggered by a variety of external and internal stimuli. Studies over the past decade have clearly established that caspases, a highly specialized group of proteases, play a critical role in the execution phase of apoptosis. They are also responsible for causing many of the morphological changes associated with this process. At present, 14 caspase family members have been identified and are divided into three subgroups based on their preference for specific tetrapeptide motifs. Caspases are synthesized as inactive pro-caspases that are cleaved by upstream proteases for full activation.
Activated caspases cleave a variety of intracellular proteins that disrupt cell survival pathways and lead to eventual cell death.
Activation of caspases as a strategy in cancer therapy has gained much ground during the past decade, particularly for inducing cell death in tumors and in determining the efficacy of chemotherapeutic agents. On the other hand, apoptosis inhibitors are fast becoming pratical therapeutic agents for both acute and chronic neurodegenerative conditions. Over-activation of the caspase cascade is involved in neurodegenerative diseases such as Huntington's disease (HD) and Alzheimer's disease (AD). In HD, caspases cleave huntingtin and generate toxic protein fragments containing polyglutamine.
Several reports have indicated that caspases cleave β-amyloid precursor protein (APP) and presenilins (PS1 and SP2). APP cleavage by caspases may contribute towards Aβ toxicity, a common feature in AD.