Effects of protein kinase C on delayed rectifier K+ channel regulation by tyrosine kinase in rat retinal pigment epithelial cells.
OBJECTIVE
Investigation of the regulation of delayed rectifier potassium channels by protein kinases in retinal pigment epithelial (RPE) cells.


METHODS
Membrane currents of cultured RPE cells were measured in either the perforated-patch or whole-cell configuration of the patch-clamp technique.


RESULTS
Different potassium channel blockers from animal venoms (charybdotoxin, hanatoxin, agitoxin, tityustoxin) were used to identify the delayed rectifying outward current in RPE cells as current through potassium channels, mainly composed of Kv1.3 subunits. Extracellular application of a tyrosine kinase blocker, such as genistein (100 microM), lavendustin A (10 microM), or herbimycin A (4 microM), almost completely abolished the delayed rectifier currents. Intracellular application of the tyrosine kinase pp60(c-src) (30 U/mL) through a patch pipette led to an increase of the delayed rectifier current consistent with an activation of the delayed rectifier channels by src subtype tyrosine kinase. Inhibition (with 1 microM chelerythrine) or activation (with 1 microM phorbol ester PMA) of protein kinase C (PKC) did not change the activity of delayed rectifier channels. Inhibition of PKC also did not change the effect of tyrosine kinase inhibition of delayed rectifier currents. However, in cells with stimulated PKC, inhibition of tyrosine kinase by genistein led to an increase of delayed rectifier currents. Intracellular application of pp60(c-src) (30 U/mL) in cells with stimulated PKC led to inhibition of delayed rectifier currents. CONCLUSIONS. Tyrosine kinase, of the src family, can activate or inhibit delayed rectifier channels composed of Kv1.3 subunits in RPE cells. The activity of PKC determines whether tyrosine kinase activates or inhibits these K+ channels.
Strauss
Olaf
O
Institute for Clinical Physiology, Benjamin Franklin University Clinic, Free University of Berlin, Hindenburgdamm 30, 12200 Berlin, Germany. strauss@ukbf.fu-berlin.de
Rosenthal
Rita
R
Dey
Dennis
D
Beninde
Julia
J
Wollmann
Guido
G
Thieme
Hagen
H
Wiederholt
Michael
M
D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051664:Kv1.3 Potassium Channel; D018408:Patch-Clamp Techniques; D010857:Pigment Epithelium of Eye / Q000187:drug effects* / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000494:pharmacology*; D051381:Rats
D004791:Enzyme Inhibitors; C496975:Kcna3 protein, rat; D051664:Kv1.3 Potassium Channel; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011505:Protein-Tyrosine Kinases; D016392:Proto-Oncogene Proteins pp60(c-src); D011493:Protein Kinase C; D011188:Potassium