Shrinkage-induced activation of Na+/H+ exchange in primary rat astrocytes: role of myosin light-chain kinase
| Autor: | Lamara D. Shrode, Robert W. Putnam, J. D. Klein, W. C. O'Neill |
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| Rok vydání: | 1995 |
| Předmět: |
Myosin light-chain kinase
Sodium-Hydrogen Exchangers Calmodulin Physiology Intracellular pH Trifluoperazine Rats Sprague-Dawley Adenosine Triphosphate Myosin medicine Cyclic AMP Animals Phosphorylation Myosin-Light-Chain Kinase Protein kinase C Cells Cultured Protein Kinase C biology Kinase Chemistry Cell Biology Adenosine Rats Biochemistry Astrocytes Biophysics biology.protein Calcium medicine.drug |
| Zdroj: | The American journal of physiology. 269(1 Pt 1) |
| ISSN: | 0002-9513 |
| Popis: | Primary rat astrocytes exposed to hyperosmotic solutions undergo Na(+)-dependent amiloride-sensitive alkalinization of 0.36 U [measured with the pH-sensitive fluorescent dye 2',7'-bis(carboxyethyl)-5(6)-carboxy-fluorescein], suggesting that shrinkage-induced alkalinization is due to activation of Na+/H+ exchange (NHE). Alkalinization is maintained for at least 20 min, and is readily reversible and ATP dependent. Hyperosmotic solutions produced no increase of intracellular Ca2+ or adenosine 3',5'-cyclic monophosphate (cAMP). Loading cells with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, a Ca2+ chelator, or depleting cells of protein kinase C (PKC) had no effect on activation of NHE. Thus shrinkage-induced activation of NHE does not involve cAMP, Ca2+, or PKC. However, ML-7, an inhibitor of myosin light-chain kinase (MLCK), inhibited shrinkage-induced activation with a half-maximal inhibition of 56 microM. This activation was also inhibited by 500 microM N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide, 100 microM chlorpromazine, and 50 microM trifluoperazine, all calmodulin inhibitors. Shrinkage increased the phosphorylation of an 18-kDa protein that colocalizes with myosin light chain. Our data suggest that shrinkage-induced activation of NHE in astrocytes occurs via a novel pathway involving activation of calmodulin-dependent MLCK and phosphorylation of myosin light chain. |
| Databáze: | OpenAIRE |
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