cADP-ribose potentiates cytosolic Ca2+ elevation and Ca2+ entry via L-type voltage-activated Ca2+ channels in NG108-15 neuronal cells.
The effects of cADP-ribose (cADPR), a metabolite of beta-NAD(+), on the elevation of cytoplasmic free Ca(2+) concentration ([Ca(2+)](i)) and Ca(2+) influx through voltage-activated Ca(2+) channels (VACCs) were studied in NG108-15 neuroblastomaxglioma hybrid cells. NG108-15 cells were pre-loaded with fura-2 and whole-cell patch-clamped. Application of cADPR through patch pipettes did not by itself trigger any [Ca(2+)](i) rise at the resting membrane potential. A rise in [Ca(2+)](i) was evoked upon sustained membrane depolarization, and was significantly larger in cADPR-infused cells than in non-infused cells. This potentiation in the [Ca(2+)](i) elevation was reproduced by infusion of beta-NAD(+), and was blocked by 8-bromo-cADPR and antagonized by external application of ryanodine or by pretreatment of cells with FK506. Nicotinamide inhibited beta-NAD(+)-induced, but not cADPR-elicited, potentiation. [Ca(2+)](i) increases or Ca(2+) influx, measured by Mn(2+) quenching, elicited by the same protocol of depolarization was blocked completely by nifedipine but not by omega-conotoxin. Ca(2+) influx in cADPR- or beta-NAD(+)-infused cells was steeper and greater than that in control cells, and was inhibited partly by ryanodine. In contrast, ryanodine accelerated Ca(2+) influx in non-infused cells. These results show that cADPR amplifies both depolarization-induced [Ca(2+)](i) increase and Ca(2+) influx through L-type VACCs. These results suggest that cADPR functions on ryanodine receptors as a direct agonist and also interacts with L-type VACCs as an indirect agonist, i.e. via a retrograde signal.
Hashii
M
M
Department of Biophysical Genetics, Kanazawa University Graduate School of Medicine, Kanazawa 920-8640, Japan. mhashii@pop.m.kanazawa-u.ac.jp
Minabe
Y
Y
Higashida
H
H
D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives* / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002478:Cells, Cultured; D036563:Cyclic ADP-Ribose; D003600:Cytosol / Q000378:metabolism; D015640:Ion Channel Gating; D008345:Manganese / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological; D009243:NAD / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism*; D009536:Niacinamide / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*; D016559:Tacrolimus / Q000494:pharmacology
D020746:Calcium Channels, L-Type; D019837:Ryanodine Receptor Calcium Release Channel; D009243:NAD; D036563:Cyclic ADP-Ribose; D012433:Ryanodine; D000246:Adenosine Diphosphate Ribose; D009536:Niacinamide; D008345:Manganese; D009543:Nifedipine; D002118:Calcium; D016559:Tacrolimus