title: Cyclophilin B interacts with sodium-potassium ATPase and is required for pump activity in proximal tubule cells of the kidney.
abstract: Cyclophilins (Cyps), the intracellular receptors for Cyclosporine A (CsA), are responsible for peptidyl-prolyl cis-trans isomerisation and for chaperoning several membrane proteins. Those functions are inhibited upon CsA binding. Albeit its great benefits as immunosuppressant, the use of CsA has been limited by undesirable nephrotoxic effects, including sodium retention, hypertension, hyperkalemia, interstial fibrosis and progressive renal failure in transplant recipients. In this report, we focused on the identification of novel CypB-interacting proteins to understand the role of CypB in kidney function and, in turn, to gain further insight into the molecular mechanisms of CsA-induced toxicity. By means of yeast two-hybrid screens with human kidney cDNA, we discovered a novel interaction between CypB and the membrane Na/K-ATPase β1 subunit protein (Na/K-β1) that was confirmed by pull-down, co-immunoprecipitation and confocal microscopy, in proximal tubule-derived HK-2 cells. The Na/K-ATPase pump, a key plasma membrane transporter, is responsible for maintenance of electrical Na+ and K+ gradients across the membrane. We showed that CypB silencing produced similar effects on Na/K-ATPase activity than CsA treatment in HK-2 cells. It was also observed an enrichment of both alpha and beta subunits in the ER, what suggested a possible failure on the maturation and routing of the pump from this compartment towards the plasma membrane. These data indicate that CypB through its interaction with Na/K-β1 might regulate maturation and trafficking of the pump through the secretory pathway, offering new insights into the relationship between cyclophilins and the nephrotoxic effects of CsA.
authors.affiliation: Fisiopatología Renal, Centre d'Investigacions en Bioquímica i Biologia Molecular, Institut de Recerca Vall d'Hebron, Hospital Universitari Vall d'Hebron, Barcelona, Spain.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Suñé
authors.forename: Eduard
authors.initials: E
authors.lastname: Sarró
authors.forename: Marta
authors.initials: M
authors.lastname: Puigmulé
authors.forename: Joan
authors.initials: J
authors.lastname: López-Hellín
authors.forename: Madeleine
authors.initials: M
authors.lastname: Zufferey
authors.forename: Thomas
authors.initials: T
authors.lastname: Pertel
authors.forename: Jeremy
authors.initials: J
authors.lastname: Luban
authors.forename: Anna
authors.initials: A
authors.lastname: Meseguer
mesh_terms: D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002461:Cell Line, Transformed; D002522:Chlorocebus aethiops; D021983:Cyclophilins / Q000235:genetics / Q000378:metabolism*; D016572:Cyclosporine / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000254:Sodium-Potassium-Exchanging ATPase / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: C503551:ATP1B1 protein, human; D004791:Enzyme Inhibitors; D021122:Protein Subunits; C081786:cyclophilin B; D016572:Cyclosporine; D021983:Cyclophilins; D000254:Sodium-Potassium-Exchanging ATPase