Developmental control of cAMP-induced Ca2+-influx by cGMP: influx is delayed and reduced in a cGMP-phosphodiesterase D deficient mutant of Dictyostelium discoideum.
It was previously shown that cGMP enhances cAMP-induced Ca2+-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 Ca2+-influx compared with a cGMP-phosphodiesterase knock-out strain, pdeD KO, generated by homologous recombination. PdeD KO cells possess a reduced Ca2+-influx that is developmentally regulated. This finding contradicts the result of streamer F cells, where cAMP-induced Ca2+-influx is prolonged and elevated. Both mutants, however, showed a three to four-fold delayed response to cAMP at 3-4h of starvation. Thus, the consequence of an elevated cGMP concentration is a delay and an inhibition of Ca2+-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 Ca2+-influx seems to be due to developmentally regulated Ca2+-channel inhibition by cGMP.
Lusche
Daniel F
DF
Department of Biology, University of Konstanz, Universitaetsstr.10, D-78457 Konstanz, Germany. Daniel.Lusche@uni-konstanz.de
Malchow
D
D
D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000235:genetics*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism* / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism*; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D004023:Dictyostelium / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D045604:Extracellular Fluid / Q000187:drug effects / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010775:Photic Stimulation; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
D015220:Calcium Channels; D016718:Arachidonic Acid; D000242:Cyclic AMP; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D006152:Cyclic GMP; D002118:Calcium