Mechanism of cAMP-induced H+-efflux ofDictyostelium cells: a role for fatty acids |
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Authors: | H Flaadt R Schaloske D Malchow |
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Institution: | (1) Faculty of Biology, University of Konstanz, D-78457 Konstanz, Germany;(2) Differentiation Epitheliale, Ecole Normale Superieure, 46 rue d'ulm, F-75005 Paris, France |
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Abstract: | AggregatingDictyostelium cells release protons when stimulated with cAMP. To find out whether the protons are generated by acidic vesicles or in the
cytosol, we permeabilized the cells and found that this did not alter the cAMP-response. Proton efflux in intact cells was
inhibited by preincubation with the V-type H+ ATPase inhibitor concanamycin A and with the plasma membrane H+ ATPase blocker miconazole. Surprisingly, miconazole also inhibited efflux in permeabilized cells, indicating that this type
of H+ ATPase is present on intracellular vesicles as well. Vesicular acidification was inhibited by miconazole and by concanamycin
A, suggesting that the acidic vesicles contain both V-type and P-type H+ ATPases. Moreover, concanamycin A and miconazole acted in concert, both in intact cells and in vesicles. The mechanism of
cAMP-induced Ca2+-fluxes involves phospholipase A2 activity. Fatty acids circumvent the plasma membrane and stimulate vesicular Ca2+-efflux. Here we show that arachidonic acid elicited H+-efflux not only from intact cells but also from acidic vesicles. The target of regulation by arachidonic acid seemed to be
the vesicular Ca2+-relase channel. |
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Keywords: | Acidic vesicles arachidonic acid Ca2+ transport concanamycin A H+-efflux miconazole |
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