Ca2+ release triggered by nicotinate adenine dinucleotide phosphate in intact sea urchin eggs.
Nicotinate adenine dinucleotide phosphate (NAADP) was recently identified [Lee and Aarhus (1995) J. Biol. Chem. 270, 2152-2157; Chini, Beers and Dousa (1995) J. Biol. Chem. 270, 3116-3223] as a potent Ca(2+)-releasing agent in sea urchin egg homogenates. NAADP triggered Ca2+ release by a mechanism that was distinct from inositol 1,4,5-trisphosphate (InsP3)- and cyclic ADP-ribose (cADPR)-induced Ca2+ release. When NAADP was microinjected into intact sea urchin eggs it induced a dose-dependent increase in cytoplasmic free Ca2+ which was independent of the extracellular [Ca2+]. The Ca2+ waves elicited by microinjections of NAADP originated at the site of injection and swept across the cytosol. As previously found in sea urchin egg homogenates, NAADP-induced Ca2+ release in intact eggs was not blocked by heparin or by prior desensitization to InsP3 or cADPR. Thio-NADP, a specific inhibitor of the NAADP-induced Ca2+ release in sea urchin homogenates [Chini, Beers and Dousa (1995) J. Biol. Chem. 270, 3116-3223] blocked NAADP (but not InsP3 or cADPR) injection-induced Ca2+ release in intact sea urchin eggs. Finally, fertilization of sea urchin eggs abrogated subsequent NAADP-induced Ca2+ release, suggesting that the NAADP-sensitive Ca2+ pool may participate in the fertilization response. This study demonstrates that NAADP acts as a selective Ca(2+)-releasing agonist in intact cells.
Perez-Terzic
C M
CM
Department of Pharmacology, Mayo Clinic, Rochester, MN 55905, USA.
Chini
E N
EN
Shen
S S
SS
Dousa
T P
TP
Clapham
D E
DE
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005260:Female; D005306:Fertilization; D006493:Heparin / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D008845:Microinjections; D018613:Microscopy, Confocal; D009249:NADP / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D010063:Ovum / Q000187:drug effects / Q000378:metabolism*; D012617:Sea Urchins
D009249:NADP; C024376:NAADP; D015544:Inositol 1,4,5-Trisphosphate; D006493:Heparin; D002118:Calcium