title: A kinase-regulated mechanism controls CFTR channel gating by disrupting bivalent PDZ domain interactions.
abstract: Dynamic regulation of ion channels is critical for maintaining fluid balance in epithelial tissues. Cystic fibrosis, a genetic disease characterized by impaired fluid transport in epithelial tissues, is caused by dysfunctional cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel activity. Recent studies have shown that binding of PSD-95/Dlg/ZO-1 (PDZ) domain proteins to CFTR is important for retaining it at the apical membrane and for regulating its channel activity. Here, we describe a phosphorylation mechanism that regulates CFTR channel activity, which is mediated by PDZ domains. The Na+/H+ exchanger regulatory factor (NHERF) binds to CFTR and increases its open probability (Po). Protein kinase C disrupts the stimulatory effect of NHERF on CFTR channel Po. Phosphorylation by PKC of Ser-162 in the PDZ2 domain of NHERF is critical for this functional effect. Furthermore, a mutation in PDZ2 that mimics phosphorylation decreases CFTR binding and disrupts the ability of NHERF PDZ1-2 to stimulate CFTR channel Po. Our results identify a role for PKC and suggest that phosphorylation of NHERF PDZ2 domain may be an important mechanism for regulating CFTR channel activity.
authors.affiliation: Department of Physiology, University of Pennsylvania, Philadelphia, PA 19104-6085, USA.
authors.forename: Viswanathan
authors.initials: V
authors.lastname: Raghuram
authors.forename: Hayley
authors.initials: H
authors.lastname: Hormuth
authors.forename: J Kevin
authors.initials: JK
authors.lastname: Foskett
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry; D016466:CHO Cells; D006224:Cricetinae; D003432:Cross-Linking Reagents / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry* / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D000939:Epitopes; D006801:Humans; D007477:Ions / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000737:chemistry; D010766:Phosphorylation; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers
chemical_list: C505032:CFTR protein, human; D003432:Cross-Linking Reagents; D000939:Epitopes; D007477:Ions; D009419:Nerve Tissue Proteins; D017923:Sodium-Hydrogen Exchangers; C033652:postsynaptic density proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D001224:Aspartic Acid; D012694:Serine; D011493:Protein Kinase C