title: The calmodulin antagonist W-7 inhibits the epithelial Na+/H+ exchanger via modulating membrane surface potential.
abstract: NHE3 is regulated via alterations in membrane surface charge. This is achieved through altered binding of cationic regions in the cytosolic-terminus of the exchanger with the inner leaflet of the plasma membrane. Calmodulin antagonists, including W-7, regulate surface potential and inhibit NHE3 activity. Utilizing fluorescent protein conjugated membrane probes we show that binding of cationic, but not hydrophobic peptides, to the plasma membrane is prevented by W-7. An interaction between cationic regions in the regulatory, cytosolic domain of NHE3 to anionic phospholipids in either reconstituted liposomes or the plasma membrane in cell culture is similarly prevented by W-7, at a concentration that inhibits the exchanger. We propose therefore that W-7 inhibits NHE3 activity, at least in part, by altering the association of cationic segments within the carboxy-terminus of the exchanger with anionic phospholipids in the plasma membrane.
authors.affiliation: Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada.
authors.forename: Valentin
authors.initials: V
authors.lastname: Jaumouillé
authors.forename: Devishree
authors.initials: D
authors.lastname: Krishnan
authors.forename: R Todd
authors.initials: RT
authors.lastname: Alexander
mesh_terms: D000818:Animals; D002147:Calmodulin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects*; D009893:Opossums; D010743:Phospholipids / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013449:Sulfonamides / Q000494:pharmacology*
chemical_list: D002147:Calmodulin; D004791:Enzyme Inhibitors; D010743:Phospholipids; D017923:Sodium-Hydrogen Exchangers; D013449:Sulfonamides; C017967:W 7