title: NAADP controls cross-talk between distinct Ca2+ stores in the heart.
abstract: In cardiac muscle the sarcoplasmic reticulum (SR) plays a key role in the control of contraction, releasing Ca(2+) in response to Ca(2+) influx across the sarcolemma via voltage-gated Ca(2+) channels. Here we report evidence for an additional distinct Ca(2+) store and for actions of nicotinic acid adenine dinucleotide phosphate (NAADP) to mobilize Ca(2+) from this store, leading in turn to enhanced Ca(2+) loading of the SR. Photoreleased NAADP increased Ca(2+) transients accompanying stimulated action potentials in ventricular myocytes. The effects were prevented by bafilomycin A (an H(+)-ATPase inhibitor acting on acidic Ca(2+) stores), by desensitizing concentrations of NAADP, and by ryanodine and thapsigargin to suppress SR function. Bafilomycin A also suppressed staining of acidic stores with Lysotracker Red without affecting SR integrity. Cytosolic application of NAADP by means of its membrane permeant acetoxymethyl ester increased myocyte contraction and the frequency and amplitude of Ca(2+) sparks, and these effects were inhibited by bafilomycin A. Effects of NAADP were associated with an increase in SR Ca(2+) load and appeared to be regulated by beta-adrenoreceptor stimulation. The observations are consistent with a novel role for NAADP in cardiac muscle mediated by Ca(2+) release from bafilomycin-sensitive acidic stores, which in turn enhances SR Ca(2+) release by increasing SR Ca(2+) load.
authors: Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, United Kingdom.
authors: Andrew
authors: A
authors: Macgregor
authors: Michiko
authors: M
authors: Yamasaki
authors: Stevan
authors: S
authors: Rakovic
authors: Luke
authors: L
authors: Sanders
authors: Raman
authors: R
authors: Parkesh
authors: Grant C
authors: GC
authors: Churchill
authors: Antony
authors: A
authors: Galione
authors: Derek A
authors: DA
authors: Terrar
mesh_terms: D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects*; D018942:Macrolides / Q000494:pharmacology; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D009249:NADP / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism; D012433:Ryanodine / Q000494:pharmacology; D012508:Sarcolemma / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D004791:Enzyme Inhibitors; D018942:Macrolides; D011943:Receptors, Adrenergic, beta; C057620:bafilomycin A; D012433:Ryanodine; D009249:NADP; C024376:NAADP; D019284:Thapsigargin; D006180:Proton-Translocating ATPases; D002118:Calcium