Abstract
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.
MeSH terms
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Animals
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Calcimycin / pharmacology*
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Calcium / metabolism*
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Calcium-Binding Proteins / isolation & purification
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Calcium-Binding Proteins / metabolism
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Calpain / drug effects
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Calpain / isolation & purification
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Calpain / metabolism*
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Cattle
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Dipeptides / pharmacology
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Intracellular Membranes / drug effects
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Intracellular Membranes / metabolism
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Mitochondria, Muscle / drug effects
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Mitochondria, Muscle / metabolism*
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Mitochondria, Muscle / ultrastructure
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Mitochondrial Membranes / drug effects
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Mitochondrial Membranes / metabolism
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Muscle, Smooth, Vascular / drug effects
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Muscle, Smooth, Vascular / physiology*
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Phosphatidylcholines / pharmacology
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Phospholipid Ethers / pharmacology
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Pulmonary Artery / drug effects
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Pulmonary Artery / physiology*
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Sodium-Calcium Exchanger / metabolism*
Substances
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1,2-dihexadecyl-sn-glycero-3-phosphocholine
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Calcium-Binding Proteins
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Dipeptides
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Phosphatidylcholines
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Phospholipid Ethers
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Sodium-Calcium Exchanger
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calpeptin
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Calcimycin
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calpastatin
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Calpain
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mu-calpain
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1,2-oleoylphosphatidylcholine
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Calcium
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calpain inhibitor III