Differences in the protein-kinase-A-dependent regulation of CFTR Cl- channels and Na+-K+ pumps in guinea-pig ventricular myocytes.
Protein-kinase-A- (PKA-) dependent regulation of cystic fibrosis transmembrane conductance regulator (CFTR) Cl- current (I(CFTR)) and Na+-K+ pump current (Ip) was studied in single guinea-pig ventricular myocytes. Both currents were measured simultaneously by means of whole-cell recording at 30 degrees C. The adenylyl cyclase activator forskolin was used to stimulate PKA activity. At -20 mV, forskolin (4 microM) induced a fast activation of I(CFTR) and a delayed stimulation of Ip. Despite the strikingly different time courses, however, the potency of the drug to regulate both currents was identical. Half-maximal activation of I(CFTR) and stimulation of Ip, respectively, were observed at 9.6 x 10(-8) M and 9.9 x 10(-8) M forskolin. Inclusion of a specific peptide inhibitor of PKA in the pipette solution (PKI, 20 microM) blocked forskolin's effect on Ip. However, regardless of the time allowed for cell dialysis, there still was a marked, transient activation of I(CFTR), which could be prevented by: (1) a short pre-activation of I(CFTR) with forskolin or (2) the additional inclusion in the pipette solution of a synthetic peptide (Ht31 peptide, 60 microM) that interferes with PKA binding to its anchoring proteins. Thus, there is a tight functional coupling between PKA and CFTR Cl- channels in guinea-pig ventricular myocytes. The coupling is probably due to the close physical proximity of channels and kinases mediated by PKA anchoring proteins. Na+-K+ pumps, on the other hand, though also regulated by PKA, appear to be loosely coupled to the kinases.
Kockskämper
J
J
Loyola University Chicago, Stritch School of Medicine, Department of Physiology, Maywood, IL 60153, USA. jkocksk@luc.edu
Sendhoff
K
K
Erlenkamp
S
S
Bordusa
F
F
Cerovsky
V
V
Glitsch
H G
HG
D000818:Animals; D018118:Chloride Channels / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D018118:Chloride Channels; D008565:Membrane Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D017868:Cyclic AMP-Dependent Protein Kinases; D000254:Sodium-Potassium-Exchanging ATPase