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The Journal of Membrane Biology

, Volume 173, Issue 1, pp 39–46 | Cite as

Regulation of Lens rCx46-formed Hemichannels by Activation of Protein Kinase C, External Ca2+ and Protons

  • B.  Jedamzik
  • I.  Marten
  • A.  Ngezahayo
  • A.  Ernst
  • H.-A.  Kolb

Abstract.

Rodent lens connexin46 (rCx46) formed active voltage-dependent hemichannels when expressed in Xenopus oocytes. Time-dependent macroscopic currents were evoked upon depolarization. The observed two activation time constants were weakly voltage-dependent and in the order of hundreds of milliseconds and seconds, respectively. Occasionally, the macroscopic steady-state current and the corresponding current-voltage curve showed inactivation at high depolarizing voltages (>+50 mV). To account for the fast recovery from inactivation (<2 msec) favored by hyperpolarization, a four-state kinetic model (C 1 closed C 2 closed O open I inactivated ) is proposed. In the absence of inactivation, the macroscopic conductance decreased and inactivation became visible at voltages positive of +50 mV when the rCx46-expressing oocytes were treated with the protein-kinase-C-activators OAG or TPA, high external concentrations of Ca2+ or H+. However, the underlying mechanisms of OAG, H+ or Ca2+ action were different. While OAG did not alter the voltage-dependent activation of the rCx46-hemichannels, an increase in the external Ca2+ or H+ level shifted the voltage threshold for activation to more positive voltages. In contrast to Ca2+, protons were not effective in the physiological concentration range. We propose that under physiological conditions only external Ca2+ and intracellular PKC-dependent processes regulate rCx46 in the lens.

Key words: Ca2+— Connexin46 — Hemichannel activation — Inactivation — pH — OAG/TPA 

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Copyright information

© Springer-Verlag New York Inc. 2000

Authors and Affiliations

  • B.  Jedamzik
    • 1
  • I.  Marten
    • 1
  • A.  Ngezahayo
    • 1
  • A.  Ernst
    • 2
  • H.-A.  Kolb
    • 1
  1. 1.Institut für Biophysik, Universität Hannover, Herrenhäuserstr. 2, D-30419 Hannover, GermanyDE
  2. 2.HNO-Klinik, UKB Berlin, Rapsweg 55, D-12683 Berlin, GermanyDE

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