Regulation of L-type calcium channels by protein tyrosine kinase and protein kinase C in cultured rat and human retinal pigment epithelial cells

FASEB J. 1997 Sep;11(11):859-67. doi: 10.1096/fasebj.11.11.9285484.


The effect of protein tyrosine kinases (PTKs) on L-type calcium channel currents was studied in cultured rat and human retinal pigment epithelial cells. Barium currents through L-type channels were measured in the perforated patch-clamp technique and identified by using the L-type calcium channel opener Bay K8644 (10(-6) M). Application of the PTK blockers genistein (5 x 10(-6) M) or lavendustin A (5 x 10(-6) M) led to a decrease of L-type currents. The inactive genistein analog daidzein (10(-5) M) showed no effect on calcium channels. Intracellular application of pp60(c-src) (30 U/ml) via the patch-pipette during the conventional whole-cell configuration led to an increase of L-type currents. The protein kinase A and protein kinase G blocker H9 (10(-6) M) showed no effect on L-type currents; genistein reduced the current in the presence of H9. The protein kinase C (PKC) blocker chelerythrine (10(-5) M) reduced the L-type current; additional inhibition of PTK by lavendustin showed an additional reduction of currents. Intracellular application of myristoylated PKC substrate (5 x 10(-5) M) for PKC inhibition led to a fast rundown of L-type current amplitudes. Intracellularly applied myristoylated PKC substrate (10(-4) M) together with pp60(c-src) showed no effect on L-type current. Up-regulation of PKC by 10(-6) M phorbol-12-myristate-13-acetate (PMA) had no effect on the L-type current amplitude. However, genistein in cells pretreated with PMA led to an increase of the L-type currents. Intracellular application of pp60(c-src) in PMA-treated cells led to a reduction of L-type currents. We conclude that in the resting cell, PTK and PKC regulate L-type calcium channels in an additive manner. L-type channels appeared as a site of integration of PTK activation and of PKC-dependent pathways. The activity of PKC determines whether PTK decreases or increases L-type channel activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium Channels / physiology*
  • Calcium Channels, L-Type
  • Cells, Cultured
  • Humans
  • Pigment Epithelium of Eye / metabolism*
  • Protein Kinase C / physiology*
  • Protein Serine-Threonine Kinases / metabolism
  • Protein-Tyrosine Kinases / physiology*
  • Proto-Oncogene Proteins pp60(c-src) / physiology
  • Rats
  • Tetradecanoylphorbol Acetate / pharmacology


  • Calcium Channels
  • Calcium Channels, L-Type
  • Protein-Tyrosine Kinases
  • Proto-Oncogene Proteins pp60(c-src)
  • Protein Serine-Threonine Kinases
  • Protein Kinase C
  • Tetradecanoylphorbol Acetate