NAADP activates a Ca2+ current that is dependent on F-actin cytoskeleton.
Nicotinic acid adenine dinucleotide phosphate (NAADP) is involved in the Ca2+ response observed at fertilization in several species, including starfish. In this study, we have employed Ca2+ imaging and the single-electrode voltage-clamp technique to investigate whether the NAADP-mediated Ca2+ entry discovered in our laboratory in starfish oocytes was underlain by a membrane current and whether the response to NAADP required an intact cytoskeleton. Uncaging of preinjected NAADP evoked a cortical Ca2+ flash that was followed by the spreading of the wave to the remainder of the cell. No Ca2+ increase was detected in Ca2+-free sea water. Under voltage-clamp conditions, the photoliberation of NAADP activated an inward rectifying membrane current, which reversed at potentials more positive than +50 mV and was abolished by removal of Ca2+ but not of Na+. The current was affected by preincubation with verapamil, SKF 96356, and thapsigargin but not by preinjection of heparin, 8-NH2- cyclic ADP-ribose, or both antagonists. The membrane current and the Ca2+ wave were inhibited by latrunculin-A and jasplakinolide, which depolymerize and stabilize actin cytoskeleton, respectively. These data offer the first demonstration that NAADP initiates a Ca2+ sweep by activating a Ca2+-permeable membrane current that requires an intact F-actin cytoskeleton as other Ca2+-permeable currents, such as ICRAC and IARC.
Moccia
Francesco
F
Laboratory of Cell Biology, Stazione Zoologica Anton Dohrn, Villa Comunale I-80121, Naples, Italy.
Lim
Dmitri
D
Nusco
Gilda A
GA
Ercolano
Emanuela
E
Santella
Luigia
L
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling; D002462:Cell Membrane / Q000502:physiology; D047630:Depsipeptides; D004553:Electric Conductivity; D008954:Models, Biological; D009249:NADP / Q000031:analogs & derivatives* / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010456:Peptides, Cyclic / Q000494:pharmacology; D013215:Starfish; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines
D019086:Bridged Bicyclo Compounds, Heterocyclic; D015220:Calcium Channels; D047630:Depsipeptides; D010456:Peptides, Cyclic; D013844:Thiazoles; D053778:Thiazolidines; C057531:jasplakinolide; D009249:NADP; C024376:NAADP; C037067:latrunculin A; D002118:Calcium