Chemoattractant-stimulated calcium influx in Dictyostelium discoideum does not depend on cGMP.
Chemoattractant stimulation of Dictyostelium cells leads to the opening of calcium channels in the plasma membrane, causing extracellular calcium to flux into the cell. The genetically uncharacterised mutants stmF and KI8 show strongly altered chemoattractant-stimulated cGMP responses. The aberrant calcium influx in these strains has provided evidence that the chemoattractant-stimulated calcium influx is potentiated by cGMP. We have tested this hypothesis in genetically defined mutants by measuring the calcium influx in a strain that lacks intracellular cGMP due to the disruption of two guanylyl cyclases, and in a strain with increased cGMP levels caused by the disruption of two cGMP-degrading phosphodiesterases. The results reveal that the calcium influx stimulated by cAMP or folic acid is essentially identical in these strains. We conclude that cGMP is not involved in chemoattractant-stimulated calcium influx.
Veltman
Douwe M
DM
GBB Research School, Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
De Boer
Jan Sietse
JS
Van Haastert
Peter J M
PJ
D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism*; D004023:Dictyostelium / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D005492:Folic Acid / Q000494:pharmacology; D017125:Genes, Protozoan; D007700:Kinetics; D009154:Mutation
D005492:Folic Acid; D000242:Cyclic AMP; D006152:Cyclic GMP