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 degr...

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Bibliographic Details
Published in:Pflügers Archiv 2001-03, Vol.441 (6), p.807-815
Main Authors: Kockskämper, J, Sendhoff, K, Erlenkamp, S, Bordusa, F, Cerovsky, V, Glitsch, H G
Format: Article
Language:English
Subjects:
Animals
Cells
Chloride Channels - metabolism
Colforsin - pharmacology
Cyclic AMP-Dependent Protein Kinases - metabolism
Cystic fibrosis
Cystic Fibrosis Transmembrane Conductance Regulator - metabolism
Dose-Response Relationship, Drug
Guinea Pigs
Heart Ventricles - cytology
Heart Ventricles - metabolism
Kinases
Membrane Potentials - drug effects
Membrane Potentials - physiology
Membrane Proteins - metabolism
Muscle Fibers, Skeletal - cytology
Muscle Fibers, Skeletal - metabolism
Myocardium - cytology
Myocardium - metabolism
Patch-Clamp Techniques
Peptides
Proteins
Sodium-Potassium-Exchanging ATPase - metabolism
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Summary: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.
ISSN:0031-6768
1432-2013
DOI:10.1007/s004240000485