Inactivation of calcium-activated chloride conductance in Xenopus oocytes: roles of calcium and protein kinase C

Rony Boton, Dafna Singer, Nathan Dascal*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Scopus citations

Abstract

Inactivation of Ca2+ -induced Cl- currents was studied in Xenopus oocytes using the two-electrode voltage-clamp technique. In oocytes permeabilized to Ca2+ by treatment with the ionophore A23187, Ca2+ influx caused by the addition of 2.5-5 mM Ca2+ to the extracellular solution elicited Cl- currents consisting of two components: a fast, transient one (Ifast) and a slow one (Islow). In response to a subsequent application of the same dose of Ca2+, Ifast and Islow were reduced (inactivation phenomenon). The inactivation did not depend on the direction of current flow, but did depend on the duration of the first exposure to Ca2+. The extent of inactivation of Ifast was more significant than that to Islow. Both Ifast and Islow fully recovered from inactivation in less than 30 min. Intracellular injections of 100-400 pmol CaCl2 evoked large inward currents but did not reduce the amplitude of currents evoked by Ca2+ influx. The activator of protein kinase C, β-phorbol dibutyrate, caused full inhibition of Ifast without any change in Islow. H-7 (1,5-isoquinolinesulfonyl-1,2 methylpiperazine), an inhibitor of protein kinases, strongly reduced the extent of inactivation. Our results suggest that elevation of intracellular Ca2+ by Ca2+ influx through the plasma membrane causes inactivation of the Ca2+ -dependent Cl- conductance via activation of a Ca2+ -dependent protein kinase, possibly protein kinase C, whereas Ca2+ arriving at the membrane from inside the cell does not initiate the processes leading to inactivation.

Original languageEnglish
Pages (from-to)1-6
Number of pages6
JournalPflugers Archiv European Journal of Physiology
Volume416
Issue number1-2
DOIs
StatePublished - Apr 1990

Keywords

  • Chloride channel
  • Inactivation
  • Protein kinase C
  • Xenopus oocyte

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