The Journal of Membrane Biology

, Volume 195, Issue 1, pp 53–62 | Cite as

Is the Voltage Gate of Connexins CO2-sensitive? Cx45 Channels and Inhibition of Calmodulin Expression

  • C. Peracchia
  • K. C. Young
  • X. G. Wang
  • L. L. Peracchia
Article

Abstract

The sensitivity of Cx45 channels to CO2, transjunctional voltage (Vj) and inhibition of calmodulin (CaM) expression was tested in oocytes by dual voltage clamp. Cx45 channels are very sensitive to Vj and close with Vj preferentially by the slow gate, likely to be the same as the chemical gate. With a CO2-induced drop in junctional conductance (Gj), both the speed of Vj-dependent inactivation of junctional current (Ij) and Vj sensitivity increased. With 40-mV Vj-pulses, the τ of single exponential Ij decay reversibly decreased by ˜40% during CO2 application, and Gj steady state/Gj peak decreased multiphasically, indicating that both kinetics and Vj sensitivity of chemical/slow Vj gating are altered by changes in [H+]i and/or [Ca2+]i. CaM expression was inhibited with oligonucleotides antisense to CaM mRNA. With 15 min CO2, relative junctional conductance (Gjt/Gjt0) dropped to 0% in controls, but only by ˜17% in CaM-antisense oocytes. Similarly, Vj sensitivity was significantly lessened in CaM-antisense oocytes. The data indicate that both the speed and sensitivity of Vj-dependent inactivation of the junctional current of Cx45 channels are affected by CO2 application, and that CaM plays a key role in channel gating.

Keywords

Cell communication Connexins Gap junctions Calmodulin Channel gating CO2 Xenopus oocytes 

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Copyright information

© Springer-Verlag New York Inc. 2003

Authors and Affiliations

  • C. Peracchia
    • 1
  • K. C. Young
    • 1
  • X. G. Wang
    • 1
  • L. L. Peracchia
    • 1
  1. 1.Department of Pharmacology and PhysiologyUniversity of Rochester, School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642-8711USA

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