mu-Calpain mediated cleavage of the Na+/Ca2+ exchanger in isolated mitochondria under A23187 induced Ca2+ stimulation.
Treatment of bovine pulmonary artery smooth muscle mitochondria with the calcium ionophore, A23187 (0.2 microM) stimulates mu-calpain activity and subsequently cleaves Na(+)/Ca(2+) exchanger (NCX). Pretreatment of the A23187 treated mitochondria with the calpain inhibitors, calpeptin or MDL28170 or with Ca(2+) chelator, EGTA does not cleave NCX. Treatment of the mitochondria with A23187 increases Ca(2+) level in the mitochondria, which subsequently dissociates mu-calpain-calpastatin association leading to the activation of mu-calpain. Immunoblot study of the A23187 treated mitochondria with the NCX polyclonal antibody indicates the degradation of mitochondrial inner membrane NCX (110kDa) resulting in the doublet of approximately 54-56kDa NCX fragments. Moreover, in vitro cleavage of mitochondrial purified NCX by mitochondrial purified mu-calpain supports our conclusion. This cleavage of NCX may be interpreted as the main cause of Ca(2+) overload and could lay a key role in the activation of apoptotic process in pulmonary smooth muscle.
Kar
Pulak
P
Department of Biochemistry and Biophysics, University of Kalyani, Kalyani, West Bengal, India.
Chakraborti
Tapati
T
Samanta
Krishna
K
Chakraborti
Sajal
S
D000818:Animals; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism; D002154:Calpain / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D002417:Cattle; D004151:Dipeptides / Q000494:pharmacology; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D008931:Mitochondria, Muscle / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D010713:Phosphatidylcholines / Q000494:pharmacology; D010742:Phospholipid Ethers / Q000494:pharmacology; D011651:Pulmonary Artery / Q000187:drug effects / Q000502:physiology*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*
C052298:1,2-dihexadecyl-sn-glycero-3-phosphocholine; D002135:Calcium-Binding Proteins; D004151:Dipeptides; D010713:Phosphatidylcholines; D010742:Phospholipid Ethers; D019831:Sodium-Calcium Exchanger; C071482:calpeptin; D000001:Calcimycin; C033668:calpastatin; D002154:Calpain; C449002:mu-calpain; C017251:1,2-oleoylphosphatidylcholine; D002118:Calcium; C058076:calpain inhibitor III