Regulation of ClC-2 chloride channels in T84 cells by TGF-alpha.
The almost ubiquitously expressed ClC-2 chloride channel is activated by hyperpolarization and osmotic cell swelling. Osmotic swelling also activates a different class of outwardly rectifying chloride channels, and several reports point to a link between protein tyrosine phosphorylation and activation of these channels. This study examines the possibility that transforming growth factor-alpha (TGF-alpha) modulates ClC-2 activity in human colonic epithelial (T84) cells. TGF-alpha (0.17 nM) irreversibly inhibited ClC-2 current in nystatin-perforated whole cell patch-clamp experiments, whereas a superimposed reversible activation of the current was observed at 8.3 nM TGF-alpha. Both effects required activation of the intrinsic epidermal growth factor receptor (EGFR) tyrosine kinase activity, of phosphoinositide 3-kinase, and of protein kinase C. With microspectrofluorimetry of the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, TGF-alpha was shown to reversibly alkalinize T84 cells at 8.3 nM but not at 0.17 nM, suggesting that 8.3 nM TGF-alpha-induced alkalinization activates ClC-2 current. This study indicates that ClC-2 channels are targets for EGFR signaling in epithelial cells.
Bali
M
M
Institut National de la Santé et de la Recherche Médicale U. 467, Faculté de Médecine Necker, 156, rue de Vaugirard, 75730 Paris Cedex 15, France.
Lipecka
J
J
Edelman
A
A
Fritsch
J
J
D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D018118:Chloride Channels / Q000378:metabolism*; D002867:Chromones / Q000494:pharmacology; D003106:Colon / Q000166:cytology; D003600:Cytosol / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000166:cytology / Q000201:enzymology*; D009025:Morpholines / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011522:Protons; D015398:Signal Transduction / Q000502:physiology; D012964:Sodium / Q000494:pharmacology; D019789:Tetraethylammonium / Q000494:pharmacology; D016211:Transforming Growth Factor alpha / Q000494:pharmacology*; D014443:Tyrosine / Q000378:metabolism
D018118:Chloride Channels; D002867:Chromones; D004791:Enzyme Inhibitors; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D011522:Protons; D012964:Sodium; D019789:Tetraethylammonium; D016211:Transforming Growth Factor alpha; D014443:Tyrosine; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one