Mechanisms of Activation of NHE by Cell Shrinkage and by Calyculin A in Ehrlich Ascites Tumor Cells
| Autor: | S T Christensen, S F Pederson, Else K. Hoffmann, C Varming |
|---|---|
| Rok vydání: | 2002 |
| Předmět: |
Sodium-Hydrogen Exchangers
Myosin light-chain kinase Physiology SB 203580 Hypertonic Solutions Phosphatase Biophysics Biology Mechanotransduction Cellular Sensitivity and Specificity Calcium in biology chemistry.chemical_compound Osmotic Pressure Tumor Cells Cultured Animals Protein Isoforms Protein Phosphatase Inhibitor Carcinoma Ehrlich Tumor Oxazoles Protein Kinase C Protein kinase C Cell Size Sodium-Hydrogen Exchanger 3 Osmolar Concentration Cell Biology Hydrogen-Ion Concentration Molecular biology Culture Media Chelerythrine chemistry Marine Toxins Calyculin |
| Zdroj: | Journal of Membrane Biology. 189:67-81 |
| ISSN: | 1432-1424 0022-2631 |
| DOI: | 10.1007/s00232-001-0190-2 |
| Popis: | The Na+/H+ exchanger isoforms NHE1, NHE2, and NHE3 were all found to be expressed in Ehrlich ascites tumor cells, as evaluated by Western blotting and confocal microscopy. Under unstimulated conditions, NHE1 was found predominantly in the plasma membrane, NHE3 intracellularly, and NHE2 in both compartments. Osmotic cell shrinkage elicited a rapid intracellular alkalinization, the sensitivity of which to EIPA (IC50 0.19 microM) and HOE 642 (IC50 0.85 microM) indicated that it predominantly reflected activation of NHE1. NHE activation by osmotic shrinkage was inhibited by the protein kinase C inhibitors chelerythrine (IC50 12.5 microM), Gö 6850 (5 microM), and Gö 6976 (1 microM), and by the p38 MAPK inhibitor SB 203580 (10 microM). Furthermore, hypertonic cell shrinkage elicited a biphasic increase in p38 MAPK phosphorylation, with the first significant increase detectable 2 minutes after the hypertonic challenge. Neither myosin light chain kinase-specific concentrations of ML-7 (IC50 40 microM) nor ERK1/2 inhibition by PD 98059 (50 microM) had any effect on NHE activation. Under isotonic conditions, the serine/threonine protein phosphatase inhibitor calyculin A elicited an EIPA- and HOE 642-inhibitable intracellular alkalinization, indicating NHE1 activation. Similarly, shrinkage-induced NHE activation was potentiated by calyculin A. The calyculin A-induced alkalinization was not associated with an increase in the free, intracellular calcium concentration, but was abolished by chelerythrine. It is concluded that shrinkage-induced NHE activation is dependent on PKC and p38 MAPK, but not on MLCK or ERK1/2. NHE activity under both iso- and hypertonic conditions is increased by inhibition of serine/threonine phosphatases, and this effect appears to be PKC-dependent. |
| Databáze: | OpenAIRE |
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