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 stimF and K18 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. (C) 2003 Elsevier B.V All rights reserved.