Amplification of depolarization-induced and ryanodine-sensitive cytosolic Ca2+ elevation by synthetic carbocyclic analogs of cyclic ADP-ribose and their antagonistic effects in NG108-15 neuronal cells.
We synthesized analogs modified in the ribose unit (ribose linked to N1 of adenine) of cyclic ADP-ribose (cADPR), a Ca2+-mobilizing second messenger. The biological activities of these analogs were determined in NG108-15 neuroblastoma x glioma hybrid cells that were pre-loaded with fura-2 acetoxymethylester and subjected to whole-cell patch-clamp. Application of the hydrolysis-resistant cyclic ADP-carbocyclic-ribose (cADPcR) through patch pipettes potentiated elevation of the cytoplasmic free Ca2+ concentration ([Ca2+]i) at the depolarized membrane potential. The increase in [Ca2+]i evoked upon sustained membrane depolarization was significantly larger in cADPcR-infused cells than in non-infused cells and its degree was equivalent to or significantly greater than that induced by cADPR or beta-NAD+. 8-Chloro-cADPcR and two inosine congeners (cyclic IDP-carbocyclic-ribose and 8-bromo-cyclic IDP-carbocyclic-ribose) did not induce effects similar to those of cADPcR or cADPR. Instead, 8-chloro-cADPcR together with cADPR or cADPcR caused inhibition of the depolarization-induced [Ca2+]i increase as compared with either cADPR or cADPcR alone. These results demonstrated that our cADPR analogs have agonistic or antagonistic effects on the depolarization-induced [Ca2+]i increase and suggested the presence of functional reciprocal coupling between ryanodine receptors and voltage-activated Ca2+ channels via cADPR in mammalian neuronal cells.
Department of Biophysical Genetics, Kanazawa University Graduate School of Medicine, Kanazawa, Japan. mhashii@med.kanazawa-u.ac.jp
Minako
M
Hashii
Satoshi
S
Shuto
Masayoshi
M
Fukuoka
Takashi
T
Kudoh
Akira
A
Matsuda
Haruhiro
H
Higashida
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002460:Cell Line; D036563:Cyclic ADP-Ribose / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000494:pharmacology*; D003593:Cytoplasm / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D016257:Fura-2 / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000528:radiation effects; D051379:Mice; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009447:Neuroblastoma; D009474:Neurons / Q000187:drug effects* / Q000502:physiology / Q000528:radiation effects; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques / Q000379:methods; D012428:Ruthenium / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology*
D002121:Calcium Channel Blockers; C439996:cyclic ADP-carbocyclic-ribose; D036563:Cyclic ADP-Ribose; D012433:Ryanodine; D012428:Ruthenium; D009543:Nifedipine; D002118:Calcium; D016257:Fura-2