Calpain inhibition: a therapeutic strategy targeting multiple disease states.
The calpains represent a well-conserved family of calcium-dependent cysteine proteases. They consist of several ubiquitous and tissue specific isoforms and exhibit broad substrate specificity influencing many aspects of cell physiology including migration, proliferation and apoptosis. Calpain activity in vivo is tightly regulated by its natural endogenous inhibitor calpastatin. Calpastatin specifically inhibits calpain and not other cysteine proteases by interaction with several sites on the calpain molecule. Inappropriate regulation of the calpain-calpastatin proteolytic system is associated with several important human pathological disorders including muscular dystrophy, cancer, Alzheimer's disease, neurological injury, ischaemia/reperfusion injury, atherosclerosis, diabetes and cataract formation. Recent advances in elucidating the tertiary structures of calpain 2 and its regulatory domain calpain 4, together with identification of new modes of regulating calpain activity provide new opportunities for the design of novel calpain inhibitors. Several classes of inhibitors, including peptidyl epoxide, aldehyde, and ketoamide inhibitors, targeting the active site have proven effective against the calpains and are in the process of evaluation in animal models of human disease. However, a major limitation to the clinical use of such inhibitors is their lack of specificity among cysteine proteases and other proteolytic enzymes. The development of a new class of calpain inhibitors that interact with domains outside of the catalytic site of calpain may provide greater specificity and therapeutic potential.
The Beaston Insititue for Cancer Research, Cancer Research UK, Glasgow G61 1BD, Scotland, UK. neil.carragher@astrazeneca.com
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D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism / Q000627:therapeutic use; D002154:Calpain / Q000037:antagonists & inhibitors* / Q000502:physiology; D015853:Cysteine Proteinase Inhibitors / Q000627:therapeutic use*; D006801:Humans
D002135:Calcium-Binding Proteins; D015853:Cysteine Proteinase Inhibitors; C033668:calpastatin; D002154:Calpain