Agonist-stimulated cyclic ADP ribose. Endogenous modulator of Ca(2+)-induced Ca2+ release in intestinal longitudinal muscle.
We have previously shown that agonist-induced Ca2+ mobilization in intestinal longitudinal muscle is mediated by ryanodine-sensitive, inositol 1,4,5-trisphosphate-insensitive sacroplasmic Ca2+ channels. Ca2+ release via these channels is triggered by agonist-stimulated Ca2+ influx and results in Ca(2+)-induced Ca2+ release. The present study examined whether cyclic ADP-ribose (cADPR) is synthesized in response to stimulation of longitudinal muscle by agonists and modulates the activity of Ca2+ release channels. Cyclic ADPR bound with high affinity to dispersed longitudinal muscle cells (IC50 1.9nM) and induced Ca2+ release (EC50 3.8 nM), increase in [Ca2+]i (EC50 2.0 nM), and contraction (EC50 1.1 nM); cADPR had no effect on circular muscle cells. The effects of cADPR were blocked by ruthenium red, dantrolene, and the specific antagonist, 8-amino-cADPR, and were augmented by caffeine but not affected by heparin. The binding of cADPR and its ability to stimulate Ca2+ release were dependent on the concentration of Ca2+. Cyclic ADPR was capable of stimulating Ca2+ release at subthreshold Ca2+ concentrations (25-100 nM) and of enhancing Ca(2+)-induced Ca2+ release. Longitudinal muscle extracts incubated with beta-NAD+ produced a time-dependent increase in Ca(2+)-mobilizing activity identified as authentic cADPR by blockade of Ca2+ release with 8-amino-cADPR and ruthenium red. Ca2+ mobilizing activity was increased by cholecystokinin octapeptide (CCK-8) in a concentration-dependent fashion. The increase induced by CCK-8 was suppressed by the CCK-A antagonist, L364,718, nifedipine, and guanyl-5'-yl thiophosphate. The study shows that ADP-ribosyl cyclase can be stimulated by agonists and that cADPR can act as an endogenous modulator of Ca(2+)-induced Ca2+ release.
Kuemmerle
J F
JF
Department of Medicine, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0711, USA.
Makhlouf
G M
GM
D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001570:Benzodiazepinones / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002463:Cell Membrane Permeability; D036563:Cyclic ADP-Ribose; D020109:Devazepide; D004305:Dose-Response Relationship, Drug; D006153:Guanosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism*; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D011817:Rabbits; D012430:Ruthenium Red / Q000494:pharmacology; D012844:Sincalide / Q000494:pharmacology; D013347:Subcellular Fractions / Q000378:metabolism; D013873:Thionucleotides / Q000494:pharmacology
D001570:Benzodiazepinones; D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D013873:Thionucleotides; D009243:NAD; D012430:Ruthenium Red; D036563:Cyclic ADP-Ribose; D006153:Guanosine Diphosphate; D000246:Adenosine Diphosphate Ribose; C023427:guanosine 5'-O-(2-thiodiphosphate); D006493:Heparin; D009543:Nifedipine; D020109:Devazepide; D012844:Sincalide; D002118:Calcium