A long-lasting potentiation of calmodulin-mediated chloride channel activity without a mediation of protein kinase C in Xenopus oocytes injected with rat brain mRNA.
When Xenopus oocytes injected with rat brain poly(A)+RNA were voltage-clamped in a recording solution containing Ca2+, a depolarization pulse induced a transient current, ICl(Ca), which reflects calmodulin-mediated opening of endogenous Cl- channels in response to a Ca2+ influx through Ca2+ channels of brain origin. ICl(Ca) could be repetitively observed with a steady amplitude over 1 h, whereas the response was greatly potentiated for more than 30 min after a brief stimulation of muscarinic or other Ca2(+)-mobilizing receptors. The enhancement of ICl(Ca) was mimicked by an injection of inositol-1,4,5-trisphosphate or by a treatment with A23187, but not affected by treatments that stimulate or inhibit protein kinase C activity. Isolated Ba2+ current flowing through voltage-sensitive Ca2+ channels was not augmented during the facilitation of ICl(Ca). These observations indicate that the endogenous calmodulin/Cl- channel system may memorize an over-threshold increase in the intracellular Ca2+ concentration and potentiate the Ca2(+)-sensitiveness of the Cl- channel. A long-lasting autoregulation of Ca2(+)-dependent ion channel activity is suggested.
Department of Pharmacology, Toyama Medical and Pharmaceutical University, Japan.
S
S
Kaneko
E
E
Doi
H
H
Watanabe
Y
Y
Nomura
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D005260:Female; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D007473:Ion Channels / Q000378:metabolism*; D007608:Kainic Acid / Q000494:pharmacology; D008564:Membrane Potentials; D009865:Oocytes / Q000378:metabolism; D011061:Poly A / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D012313:RNA / Q000378:metabolism*; D012333:RNA, Messenger; D051381:Rats; D012701:Serotonin / Q000494:pharmacology; D014982:Xenopus laevis
D015220:Calcium Channels; D002147:Calmodulin; D002712:Chlorides; D007473:Ion Channels; D012333:RNA, Messenger; D011061:Poly A; D001464:Barium; D012701:Serotonin; D000001:Calcimycin; D012313:RNA; D015544:Inositol 1,4,5-Trisphosphate; D011493:Protein Kinase C; D000109:Acetylcholine; D007608:Kainic Acid