title: Requirement of PDZ domains for the stimulation of the epithelial Ca2+ channel TRPV5 by the NHE regulating factor NHERF2 and the serum and glucocorticoid inducible kinase SGK1.
abstract: Renal calcium reabsorption involves the epithelial calcium channel ECaC1 (TRPV5) which is tightly regulated by 1,25(OH)2D3. As shown recently, TRPV5 is activated by the serum and glucocorticoid inducible kinase SGK1, a kinase transcriptionally upregulated by 1,25(OH)2D3. This stimulatory effect is due to enhanced TRPV5 abundance in the plasma membrane and requires the presence of the scaffold protein NHERF2 (sodium hydrogen exchanger regulating factor 2). The present study aims to define the molecular requirements for the interaction of TRPV5 with SGK1 and NHERF2. Pull-down experiments and overlay assays revealed that the TRPV5 C-tail interacts in a Ca2+-independent manner with NHERF2. Deletion of the second but not of the first PDZ domain in NHERF2 abrogates the stimulating effect of SGK1/NHERF2 on TRPV5 protein abundance in the plasma membrane as quantified by chemiluminescence and electrophysiology. Thus, the second PDZ domain in NHERF2 is required for stabilization at or TRPV5 targeting to the plasma membrane. The experiments demonstrate the significance of SGK1 and NHERF2 as TRPV5 modulators which are likely to participate in the regulation of calcium homeostasis by 1,25(OH)2D3.
authors.affiliation: Dept. of Physiology I, University of Tübingen, Tübingen, Germany.
authors.forename: Monica
authors.initials: M
authors.lastname: Palmada
authors.forename: Susanne
authors.initials: S
authors.lastname: Poppendieck
authors.forename: Hamdy M
authors.initials: HM
authors.lastname: Embark
authors.forename: Stan F J
authors.initials: SF
authors.lastname: van de Graaf
authors.forename: Christoph
authors.initials: C
authors.lastname: Boehmer
authors.forename: René J M
authors.initials: RJ
authors.lastname: Bindels
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism*; D005938:Glucocorticoids / Q000378:metabolism; D006801:Humans; D017874:Immediate-Early Proteins; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D010750:Phosphoproteins; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011817:Rabbits; D044967:Serum / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers; D050916:TRPV Cation Channels; D014982:Xenopus laevis / Q000378:metabolism; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D002118:Calcium; D015220:Calcium Channels; D003598:Cytoskeletal Proteins; D005938:Glucocorticoids; D017874:Immediate-Early Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D017923:Sodium-Hydrogen Exchangers; D050916:TRPV Cation Channels; D000099184:Serum-Glucocorticoid Regulated Kinases; C492240:Trpv5 protein, mouse; C093376:sodium-hydrogen exchanger regulatory factor