Regulation of a human chloride channel. a paradigm for integrating input from calcium, type ii calmodulin-dependent protein kinase, and inositol 3,4,5,6-tetrakisphosphate.
We have studied the regulation of Ca(2+)-dependent chloride (Cl(Ca)) channels in a human pancreatoma epithelial cell line (CFPAC-1), which does not express functional cAMP-dependent cystic fibrosis transmembrane conductance regulator chloride channels. In cell-free patches from these cells, physiological Ca(2+) concentrations activated a single class of 1-picosiemens Cl(-)-selective channels. The same channels were also stimulated by a purified type II calmodulin-dependent protein kinase (CaMKII), and in cell-attached patches by purinergic agonists. In whole-cell recordings, both Ca(2+)- and CaMKII-dependent mechanisms contributed to chloride channel stimulation by Ca(2+), but the CaMKII-dependent pathway was selectively inhibited by inositol 3,4,5,6-tetrakisphosphate (Ins(3,4,5,6)P(4)). This inhibitory effect of Ins(3,4,5,6)P(4) on Cl(Ca) channel stimulation by CaMKII was reduced by raising [Ca(2+)] and prevented by inhibition of protein phosphatase activity with 100 nm okadaic acid. These data provide a new context for understanding the physiological relevance of Ins(3,4,5,6)P(4) in the longer term regulation of Ca(2+)-dependent Cl(-) fluxes in epithelial cells.
Ho
M W
MW
Inositide Signaling and Membrane Signaling Groups, Laboratory of Signal Transduction, NIEHS, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA. ho1@niehs.nih.gov
Kaetzel
M A
MA
Armstrong
D L
DL
Shears
S B
SB
D002118:Calcium / Q000378:metabolism*; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D018118:Chloride Channels / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004847:Epithelial Cells / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism*; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D008954:Models, Biological; D019319:Okadaic Acid / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms; D014407:Tumor Cells, Cultured; D015854:Up-Regulation; D014544:Uridine Triphosphate / Q000378:metabolism
D018118:Chloride Channels; D007295:Inositol Phosphates; D007476:Ionophores; D020033:Protein Isoforms; C081652:inositol-3,4,5,6-tetrakisphosphate; D019319:Okadaic Acid; D000242:Cyclic AMP; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium; D014544:Uridine Triphosphate