title: Calcineurin and Sorting-Related Receptor with A-Type Repeats Interact to Regulate the Renal Na⁺-K⁺-2Cl⁻ Cotransporter.
abstract: The furosemide-sensitive Na(+)-K(+)-2Cl(-)-cotransporter (NKCC2) is crucial for NaCl reabsorption in kidney thick ascending limb (TAL) and drives the urine concentrating mechanism. NKCC2 activity is modulated by N-terminal phosphorylation and dephosphorylation. Serine-threonine kinases that activate NKCC2 have been identified, but less is known about phosphatases that deactivate NKCC2. Inhibition of calcineurin phosphatase has been shown to stimulate transport in the TAL and the distal convoluted tubule. Here, we identified NKCC2 as a target of the calcineurin Aβ isoform. Short-term cyclosporine administration in mice augmented the abundance of phospho-NKCC2, and treatment of isolated TAL with cyclosporine increased the chloride affinity and transport activity of NKCC2. Because sorting-related receptor with A-type repeats (SORLA) may affect NKCC2 phosphoregulation, we used SORLA-knockout mice to test whether SORLA is involved in calcineurin-dependent modulation of NKCC2. SORLA-deficient mice showed more calcineurin Aβ in the apical region of TAL cells and less NKCC2 phosphorylation and activity compared with littermate controls. In contrast, overexpression of SORLA in cultured cells reduced the abundance of endogenous calcineurin Aβ. Cyclosporine administration rapidly normalized the abundance of phospho-NKCC2 in SORLA-deficient mice, and a functional interaction between calcineurin Aβ and SORLA was further corroborated by binding assays in rat kidney extracts. In summary, we have shown that calcineurin Aβ and SORLA are key components in the phosphoregulation of NKCC2. These results may have clinical implications for immunosuppressive therapy using calcineurin inhibitors.
authors.affiliation: Department of Anatomy, Charité-Universitätsmedizin Berlin, Berlin, Germany;
authors.forename: Aljona
authors.initials: A
authors.lastname: Borschewski
authors.affiliation: Institute of Physiology, Kiel University, Kiel, Germany;
authors.forename: Nina
authors.initials: N
authors.lastname: Himmerkus
authors.affiliation: Department of Anatomy, Charité-Universitätsmedizin Berlin, Berlin, Germany;
authors.forename: Christin
authors.initials: C
authors.lastname: Boldt
authors.affiliation: Department of Anatomy, Charité-Universitätsmedizin Berlin, Berlin, Germany;
authors.forename: Katharina I
authors.initials: KI
authors.lastname: Blankenstein
authors.affiliation: Division of Nephrology and Hypertension, Oregon Health & Science University and VA Medical Center, Portland, Oregon;
authors.forename: James A
authors.initials: JA
authors.lastname: McCormick
authors.affiliation: Division of Nephrology and Hypertension, Oregon Health & Science University and VA Medical Center, Portland, Oregon;
authors.forename: Rebecca
authors.initials: R
authors.lastname: Lazelle
authors.affiliation: Max Delbrueck Center for Molecular Medicine, Berlin, Germany; and.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Willnow
authors.affiliation: Medizinische Klinik IV, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Vera
authors.initials: V
authors.lastname: Jankowski
authors.affiliation: Institute of Physiology, Kiel University, Kiel, Germany;
authors.forename: Allein
authors.initials: A
authors.lastname: Plain
authors.affiliation: Institute of Physiology, Kiel University, Kiel, Germany;
authors.forename: Markus
authors.initials: M
authors.lastname: Bleich
authors.affiliation: Division of Nephrology and Hypertension, Oregon Health & Science University and VA Medical Center, Portland, Oregon;
authors.forename: David H
authors.initials: DH
authors.lastname: Ellison
authors.affiliation: Department of Anatomy, Charité-Universitätsmedizin Berlin, Berlin, Germany; kerim.mutig@charite.de sebastian.bachmann@charite.de.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Bachmann
authors.affiliation: Department of Anatomy, Charité-Universitätsmedizin Berlin, Berlin, Germany; kerim.mutig@charite.de sebastian.bachmann@charite.de.
authors.forename: Kerim
authors.initials: K
authors.lastname: Mutig
mesh_terms: D000818:Animals; D019703:Calcineurin / Q000502:physiology*; D007668:Kidney / Q000378:metabolism*; D008297:Male; D026901:Membrane Transport Proteins / Q000502:physiology*; D051379:Mice; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D011973:Receptors, LDL / Q000502:physiology*; D028021:Sodium-Potassium-Chloride Symporters / Q000502:physiology*
chemical_list: D026901:Membrane Transport Proteins; D011973:Receptors, LDL; D028021:Sodium-Potassium-Chloride Symporters; C491168:Sorl1 protein, mouse; D019703:Calcineurin; C525674:PPP3CB protein, human
keywords: cell signaling; cyclosporine; epithelial sodium transport