Tyrosine kinase-independent extracellular action of genistein on the CFTR Cl- channel in guinea pig ventricular myocytes and CFTR-transfected mouse fibroblasts.
The effects of genistein, a protein tyrosine kinase inhibitor, on the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel were studied in guinea pig ventricular myocytes and in NIH3T3 mouse fibroblasts stably transfected with CFTR cDNA by the whole-cell patch-clamp technique. Genistein did not activate whole-cell Cl- currents when applied to the intracellular (pipette) solution. In contrast, when applied to the extracellular solution, genistein alone promptly activated the Cl- current in a fully reversible manner. Also, extracellular genistein reversibly potentiated the forskolin-activated Cl- current. However, both basal and forskolin-activated Cl- currents were not affected by other protein tyrosine kinase inhibitors, including herbimycin A, lavendustin A, tyrphostin 21, tyrphostin 47, and tyrphostin 51. A nonspecific inhibitor of protein phosphatases, orthovanadate, had no effect on the genistein-induced activation of CFTR. Pretreatment with a protein kinase inhibitor, either H-89 or H-7, or with an adenylate cyclase inhibitor, SQ 22536, also had no effect on the genistein-induced response. Thus, it is concluded that genistein alone activates CFTR by a protein tyrosine kinase-independent and protein phosphatase-independent mechanism from the extracellular side, but not from the intracellular side.
Zhou
S S
SS
Department of Cellular and Molecular Physiology, National Institute for Physiological Sciences, Okazaki, 444-8585, Japan.
Hazama
A
A
Okada
Y
Y
D016475:3T3 Cells; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D019833:Genistein / Q000008:administration & dosage / Q000494:pharmacology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D051379:Mice; D009206:Myocardium / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D011493:Protein Kinase C / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D014162:Transfection
D004791:Enzyme Inhibitors; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D017027:Protein Tyrosine Phosphatases