Journal article
Sphingosine differentially inhibits activation of the Na+/H+ exchanger by phorbol esters and growth factors
The Journal of biological chemistry, Vol.265(13), pp.7188-7194
05/05/1990
DOI: 10.1016/S0021-9258(19)39097-0
PMID: 2158991
Abstract
The role of protein kinase C in activation of the plasma membrane Na+/H+ exchanger was studied in cultured vascular smooth muscle cells. The basic lipid, sphingosine, was used to block enzymatic activity of protein kinase C. Na+/H+ exchange was activated by phorbol 12-myristate 13-acetate (PMA), diacylglycerols, platelet-derived growth factor (PDGF), thrombin, or by osmotically-induced cell shrinkage. Intracellular pH and Na+/H+ exchange activity were measured using the intracellular pH indicator, 2',7'-bis(carboxyethyl)-5(6) carboxyfluorescein. Acting alone, both crude sphingosine and pure, synthetic C18 D-(+)-erythro-sphingosine raised pHi in a dose-dependent manner (from 6.95 +/- 0.02 to 7.19 +/- 0.09 over 10 min for 10 microM sphingosine). This alkalinization was not due to Na+/H+ exchange as it was not altered by t-butylamiloride (50 microM) nor by replacement of the assay medium with a Na(+)-free solution. Sphingosine-induced alkalinization did not require protein kinase C activity, since it was fully intact in protein kinase C-depleted cells. It was also not due to a detergent action of sphingosine on the cell membrane, since both ionic and non-ionic detergents caused cell acidification. Rather, alkalinization induced by sphingosine appeared to be due to cellular uptake of NH3 groups since N-acetylsphingosine showed no alkalinization. After the initial cell alkalinization, cellular uptake of [3H]sphingosine continued slowly for up to 24 h. The ability of PMA or dioctanoylglycerol to activate Na+/H+ exchange fell to 20% of control after 24 h of sphingosine exposure. At all times, C11 and N-acetylsphingosine failed to block PMA-induced activation of the exchanger. Activation of the Na+/H+ exchanger by sucrose, which does not depend on protein kinase C activity, was unaffected by sphingosine. Activation of Na+/H+ exchange by thrombin and PDGF was partially inhibited by 30 and 20%, respectively. These data indicate that both thrombin and PDGF activate Na+/H+ exchange by pathway(s) that are primarily independent of protein kinase C.
Details
- Title: Subtitle
- Sphingosine differentially inhibits activation of the Na+/H+ exchanger by phorbol esters and growth factors
- Creators
- John H N Lowe - University of California, San FranciscoChou-Long Huang - University of California, San FranciscoHarlan E Ives - University of California, San Francisco
- Resource Type
- Journal article
- Publication Details
- The Journal of biological chemistry, Vol.265(13), pp.7188-7194
- DOI
- 10.1016/S0021-9258(19)39097-0
- PMID
- 2158991
- NLM abbreviation
- J Biol Chem
- ISSN
- 0021-9258
- eISSN
- 1083-351X
- Grant note
- DK-34127 / NIDDK NIH HHS HL41210 / NHLBI NIH HHS
- Language
- English
- Date published
- 05/05/1990
- Academic Unit
- Nephrology; Internal Medicine
- Record Identifier
- 9984359792002771
Metrics
11 Record Views