Calpain

Calpain is a widely expressed cytosolic cysteine ​​protease; its substrate recognition sequences differ from those of caspases, and it exists as two isoforms (Calpain I and Calpain II) with distinct requirements for calcium ions. It is activated by elevated intracellular calcium concentrations; consequently, it becomes activated and participates in the process of cell death in various cell types exposed to apoptotic signals. However, calpain is not a prerequisite for all apoptotic events; for instance, while it is essential for specific instances of apoptosis induction in thymocytes and hepatocytes, it is not required for Fas-induced apoptosis in Jurkat cells. Furthermore, calpain-mediated proteolytic cleavage is implicated in both necrotic and apoptotic processes associated with neurodegenerative diseases, such as cerebral ischemia and Alzheimer's disease^[1].

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