Involvement of protein tyrosine kinase in the InsP3-induced activation of Ca2+-dependent Cl- currents in cultured cells of the rat retinal pigment epithelium

J Membr Biol. 1999 Jun 1;169(3):141-53. doi: 10.1007/s002329900526.


This combined study of patch-clamp and intracellular Ca2+ ([Ca2+]i) measurement was undertaken in order to identify signaling pathways that lead to activation of Ca2+-dependent Cl- channels in cultured rat retinal pigment epithelial (RPE) cells. Intracellular application of InsP3 (10 microM) led to an increase in [Ca2+]i and activation of Cl- currents. In contrast, intracellular application of Ca2+ (10 microM) only induced transient activation of Cl- currents. After full activation by InsP3, currents were insensitive to removal of extracellular Ca2+ and to the blocker of ICRAC, La3+ (10 microM), despite the fact that both maneuvers led to a decline in [Ca2+]i. The InsP3-induced rise in Cl- conductance could be prevented either by thapsigargin-induced (1 microM) depletion of intracellular Ca2+ stores or by removal of Ca2+ prior to the experiment. The effect of InsP3 could be mimicked by intracellular application of the Ca2+-chelator BAPTA (10 mm). Block of PKC (chelerythrine, 1 microM) had no effect. Inhibition of Ca2+/calmodulin kinase (KN-63, KN-92; 5 microM) reduced Cl--conductance in 50% of the cells investigated without affecting [Ca2+]i. Inhibition of protein tyrosine kinase (50 microM tyrphostin 51, 5 microM genistein, 5 microM lavendustin) reduced an increase in [Ca2+]i and Cl- conductance. In summary, elevation of [Ca]i by InsP3 leads to activation of Cl- channels involving cytosolic Ca2+ stores and Ca2+ influx from extracellular space. Tyrosine kinases are essential for the Ca2+-independent maintenance of this conductance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / physiology*
  • Cells, Cultured
  • Chloride Channels / physiology*
  • Inositol Phosphates / physiology*
  • Ion Channel Gating / physiology*
  • Patch-Clamp Techniques
  • Pigment Epithelium of Eye / physiology*
  • Protein-Tyrosine Kinases / physiology*
  • Rats
  • Signal Transduction


  • Chloride Channels
  • Inositol Phosphates
  • Protein-Tyrosine Kinases
  • Calcium