title: Purinergic inhibition of the epithelial Na+ transport via hydrolysis of PIP2.
abstract: Stimulation of purinergic receptors inhibits amiloride-sensitive Na+ transport in epithelial tissues by an unknown mechanism. Because previous studies excluded the role of intracellular Ca2+ or protein kinase C, we examined whether purinergic regulation of Na+ absorption occurs via hydrolysis of phospholipid such as phosphatidylinositol-bisphosphates (PIP2). Inhibition of amiloride-sensitive short-circuit currents (Isc-Amil) by adenine 5'-triphosphate (ATP) in native tracheal epithelia and M1 collecting duct cells was suppressed by binding neomycin to PIP2, and recovery from ATP inhibition was abolished by blocking phosphatidylinositol-4-kinase or diacylglycerol kinase. Stimulation by ATP depleted PIP2 from apical membranes, and PIP2 co-immunoprecipitated the beta subunit of ENaC. ENaC was inhibited by ATP stimulation of P2Y2 receptors in Xenopus oocytes. Mutations in the PIP2 binding domain of betaENaC but not gammaENaC reduced ENaC currents without affecting surface expression. Collectively, these data supply evidence for a novel and physiologically relevant regulation of ENaC in epithelial tissues. Although surface expression is controlled by its C terminus, N-terminal binding of betaENaC to PIP2 determines channel activity.
authors.affiliation: Institut für Physiologie, Universität Regensburg, Universitätsstrasse 31, Regensburg, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Kunzelmann
authors.forename: T
authors.initials: T
authors.lastname: Bachhuber
authors.forename: R
authors.initials: R
authors.lastname: Regeer
authors.forename: D
authors.initials: D
authors.lastname: Markovich
authors.forename: J
authors.initials: J
authors.lastname: Sun
authors.forename: R
authors.initials: R
authors.lastname: Schreiber
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000737:chemistry / Q000378:metabolism; D053503:Epithelial Sodium Channels; D006868:Hydrolysis; D007685:Kidney Tubules, Collecting / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D051379:Mice; D009865:Oocytes / Q000737:chemistry / Q000378:metabolism; D018408:Patch-Clamp Techniques / Q000379:methods; D010455:Peptides / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011983:Receptors, Purinergic / Q000378:metabolism; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D026941:Sodium Channel Blockers / Q000494:pharmacology*; D015222:Sodium Channels / Q000096:biosynthesis / Q000378:metabolism*; D014132:Trachea / Q000737:chemistry / Q000378:metabolism; D014981:Xenopus
chemical_list: D053503:Epithelial Sodium Channels; C546386:P2ry2 protein, mouse; D010455:Peptides; D019269:Phosphatidylinositol 4,5-Diphosphate; D011983:Receptors, Purinergic; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D000255:Adenosine Triphosphate