cAMP-dependent protein kinase regulates inhibition of adenosine transport by ethanol.
Ethanol inhibits adenosine uptake, thereby increasing the concentration of extracellular adenosine. Elevation of extracellular adenosine increases intracellular cAMP concentration via activation of adenosine A2 receptors. Extracellular adenosine is also required for the subsequent development of ethanol-induced heterologous desensitization. Here we report that activation of cAMP-dependent protein kinase is necessary for inhibition of adenosine uptake by ethanol and for the consequent accumulation of extracellular adenosine. Ethanol does not inhibit adenosine uptake in mutants of the S49 cell line that lack receptor-stimulated cAMP production (unc cells) or cAMP-dependent protein kinase activity (kin- cells). Forskolin, which bypasses the receptor-coupling defect in unc cells to increase cAMP levels, restores inhibition of adenosine uptake by ethanol. In contrast, in kin- cells forskolin did not restore inhibition of adenosine uptake by ethanol, despite similar increases in cAMP levels. Taken together, these results suggest that cAMP-dependent protein kinase phosphorylates a component of the nucleoside transporter, thereby regulating the sensitivity of adenosine transport to ethanol.
Nagy
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Ernest Gallo Clinic and Research Center, University of California, San Francisco 94110.
Diamond
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Gordon
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D000241:Adenosine / Q000032:analysis / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000032:analysis / Q000096:biosynthesis; D000431:Ethanol / Q000494:pharmacology*; D010766:Phosphorylation; D011494:Protein Kinases / Q000502:physiology*; D014529:Uridine / Q000378:metabolism
D000431:Ethanol; D000242:Cyclic AMP; D011494:Protein Kinases; D000241:Adenosine; D014529:Uridine