Developmental control of cAMP-induced Ca super(2+)-influx by cGMP: influx is delayed and reduced in a cGMP-phosphodiesterase D deficient mutant of Dictyostelium discoideum

• Published in: Cell calcium (Edinburgh) Vol. 37; no. 1; pp. 57 - 67
• Main Authors: Lusche, Daniel F, Malchow, D
• Format: Journal Article
• Language: English
• Published: 01-01-2005
• Subjects: Dictyostelium discoideum
• ISSN: 0143-4160
• DOI: 10.1016/j.ceca.2004.06.005

It was previously shown that cGMP enhances cAMP-induced Ca super(2+)-influx in Dictyostelium discoideum. This finding is based on experiments done with strains defective in cGMP-hydrolysis, the streamer F cells. In this work, we show that these chemically mutagenized cells display different properties in their cAMP-induced light-scattering response and cAMP-induced Ca super(2+)-influx compared with a cGMP-phosphodiesterase knock-out strain, pdeD KO, generated by homologous recombination. PdeD KO cells possess a reduced Ca super(2+)-influx that is developmentally regulated. This finding contradicts the result of streamer F cells, where cAMP-induced Ca super(2+)-influx is prolonged and elevated. Both mutants, however, showed a three to four-fold delayed response to cAMP at 3-4 h of starvation. Thus, the consequence of an elevated cGMP concentration is a delay and an inhibition of Ca super(2+)-influx and not an enhancement. Results obtained with streamer F cells should therefore be interpreted with caution because the mutation(s) responsible for the divergent phenotype to pdeD KO cells has not been identified. We show by the use of membrane-permeant cGMP-analogues in wild type (wt) cells, permeabilized cells and measurements on isolated vesicles that the cause for the reduced Ca super(2+)-influx seems to be due to developmentally regulated Ca super(2+)-channel inhibition by cGMP.