title: NHE3 inhibits PKA-dependent functional expression of CFTR by NHERF2 PDZ interactions.
abstract: It has been shown that when CFTR and NHE3 are co-expressed on the apical membrane of the A6-NHE3 cell monolayers, the two transporters interact via a shared regulatory complex composed of NHERF2, ezrin, and PKA. We observe here that co-expression of NHE3 reduced both PKA-dependent apical CFTR expression and its activation once in place by approximately 50%. To analyze the role of NHERF2 in this process, we transfected NHE3 expressing and non-expressing A6 monolayers with NHERF2 cDNA in which its binding domains had been deleted. When only CFTR is expressed on the apical membrane, deletion of any of the NHERF2 binding domains inhibited both PKA-dependent apical CFTR expression and its activation, while when NHE3 was co-expressed with CFTR PDZ2 deletion was without effect on CFTR sorting and activity. This suggests that when the PDZ2 domain is "sequestered" by interacting with NHE3 it can no longer participate in CFTR functional expression.
authors.affiliation: Department of General and Environmental Physiology, University of Bari, Via Amendola 165/A, 70126 Bari, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Favia
authors.forename: T
authors.initials: T
authors.lastname: Fanelli
authors.forename: A
authors.initials: A
authors.lastname: Bagorda
authors.forename: F
authors.initials: F
authors.lastname: Di Sole
authors.forename: S J
authors.initials: SJ
authors.lastname: Reshkin
authors.forename: P G
authors.initials: PG
authors.lastname: Suh
authors.forename: L
authors.initials: L
authors.lastname: Guerra
authors.forename: V
authors.initials: V
authors.lastname: Casavola
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D009154:Mutation; D009399:Nephrons / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D014162:Transfection; D014982:Xenopus laevis
chemical_list: D003598:Cytoskeletal Proteins; C000613387:Slc9a3 protein, rat; C498832:Slc9a3r2 protein, rat; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; D017868:Cyclic AMP-Dependent Protein Kinases