A Xestospongin C-sensitive Ca(2+) store is required for cAMP-induced Ca(2+) influx and cAMP oscillations in Dictyostelium.
Xestospongin C (XeC) is known to bind to the inositol 1,4, 5-trisphosphate (IP(3))-sensitive store in mammalian cells and to inhibit IP(3)- and thapsigargin-induced Ca(2+) release. In this study we show that this is also true for Dictyostelium. In addition, XeC inhibited Ca(2+) uptake into purified vesicle fractions and induced Ca(2+) release. This suggests that, in the case of Dictyostelium, XeC opens rather than plugs the IP(3) receptor channel as was proposed for mammalian cells (Gafni, J., Munsch, J. A. , Lam, T. H., Catlin, M. C., Costa, L. G., Molinski, T. F., and Pessah, I. N. (1997) Neuron 19, 723-733). In order to elucidate the function of the XeC-sensitive Ca(2+) store in Dictyostelium during differentiation, we applied XeC to the cells and found that it caused a time-dependent increase of basal [Ca(2+)](i) and inhibited cAMP-induced Ca(2+) influx in single cells as well as in cell suspensions. Moreover, XeC blocked light scattering spikes and pulsatile cAMP signaling.
Schaloske
R
R
Faculty of Biology, University of Konstanz, Postfach 55 60, 78457 Konstanz, Germany. ralph.schaloske@uni-konstanz.de
Schlatterer
C
C
Malchow
D
D
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects; D002633:Chemotaxis / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism*; D004023:Dictyostelium / Q000187:drug effects / Q000378:metabolism*; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors; D047028:Macrocyclic Compounds; D010080:Oxazoles / Q000494:pharmacology*; D010507:Periodicity; D018160:Receptors, Cytoplasmic and Nuclear / Q000187:drug effects; D019284:Thapsigargin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D047028:Macrocyclic Compounds; D010080:Oxazoles; D018160:Receptors, Cytoplasmic and Nuclear; C108644:xestospongin A; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D002118:Calcium