title: Ritonavir inhibition of calcium-activated neutral proteases.
abstract: Calpains (EC 3.4.22.17) are intracellular calcium-activated cysteine proteases that mediate tissue injury following post-ischemic and post-traumatic stress. Both human HIV protease and calpains share a similar secondary structure, where the active site is flanked by hydrophobic regions. The present study demonstrates that ritonavir, a hydrophobic HIV protease inhibitor, also inhibits calpain activity. In PC12 cell extracts assayed for calpain at maximal activity (2mM calcium), ritonavir exhibited competitive inhibition with a K(i) of 11+/-7.0 microM. Experiments with purified enzymes showed inhibition for both m- and mu-calpain isoforms (m-calpain, K(i)=9.2+/-1.2 microM; mu-calpain, K(i)=5.9+/-1.4 microM). Ritonavir also inhibited calcium-stimulated calpain activity in PC12 cells in situ. These results suggest that ritonavir or analogues of the drug should be investigated as cytoprotective agents in conditions where cell death or injury is mediated via calpain activation.
authors: Unit of Clinical and Biochemical Pharmacology, Laboratory of Clinical Studies, Division of Intramural Clinical and Biochemical Research, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892-1256, USA.
authors: Wenshuai
authors: W
authors: Wan
authors: Paolo B
authors: PB
authors: DePetrillo
mesh_terms: D000818:Animals; D002154:Calpain / Q000037:antagonists & inhibitors*; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D007700:Kinetics; D016716:PC12 Cells; D051381:Rats; D019438:Ritonavir / Q000494:pharmacology*
chemical_list: D017320:HIV Protease Inhibitors; D002154:Calpain; D019438:Ritonavir