Evidence for two intracellular calcium pools in Dictyostelium: the cAMP-induced calcium influx is directed into a NBD-Cl- and 2,5-di-(tert-butyl)1,4-hydroquinone-sensitive pool.
Signal transduction in Dictyostelium for oriented movement and differentiation involves a fine tuning of the cytosolic Ca2+ concentration. We have previously shown that cAMP binding to the cell surface receptor elicits two cellular events: (i) to enhance Ca2+ entry across the plasma membrane; (ii) to increase Ca2+ uptake into Ca(2+)-sequestering organelles. Here we used permeabilised cells to show that cAMP-induced Ca2+ uptake in these cells was sensitive to the Ca2+ transport ATPase blocker 2,5-di-(tert-butyl)-1,4-hydroquinone (BHQ) and the vacuolar H(+)-ATPase inhibitor NBD-Cl. By contrast, bafilomycin A1 and vanadate, inhibitors of Ca2+ uptake into acidosomes in Dictyostelium, did not reduce the cAMP-induced Ca2+ uptake of permeabilised cells. GTP gamma S served as a tool to measure Ins(1,4,5)P3- (InsP3)-sensitive Ca2+ release. Following NBD-Cl or BHQ treatment Ca2+ release was reversibly inhibited. We conclude that the cAMP-controlled Ca2+ influx is directed into a NBD-Cl and BHQ-sensitive compartment, which comprises the InsP3-releasable pool. The acidosomal Ca2+ store seems to provide for additional Ca2+ if required.
Flaadt
H
H
Fakultät fäur Biologie, Universität Konstanz, FRG.
Jaworski
E
E
Malchow
D
D
D009327:4-Chloro-7-nitrobenzofurazan / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002463:Cell Membrane Permeability / Q000187:drug effects; D000242:Cyclic AMP / Q000494:pharmacology; D004023:Dictyostelium / Q000187:drug effects / Q000378:metabolism*; D005372:Filipin / Q000494:pharmacology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006873:Hydroquinones / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects; D008954:Models, Biological; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors
D006873:Hydroquinones; C019359:2,5-di-tert-butylhydroquinone; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D005372:Filipin; D000242:Cyclic AMP; D006180:Proton-Translocating ATPases; D000252:Calcium-Transporting ATPases; D009327:4-Chloro-7-nitrobenzofurazan; D002118:Calcium