title: SPAK and OSR1 dependent down-regulation of murine renal outer medullary K channel ROMK1.
abstract: OBJECTIVE
  The kinases SPAK (SPS1-related proline/alanine-rich kinase) and OSR1 (oxidative stress-responsive kinase 1) participate in the regulation of the NaCl cotransporter NCC and the Na+, K+, 2Cl- cotransporter NKCC2. The kinases are regulated by WNK (with-no-K[Lys]) kinases. Mutations of genes encoding WNK kinases underly Gordon's syndrome, a monogenic disease leading to hypertension and hyperkalemia. WNK kinases further regulate the renal outer medullary K+ channel ROMK1. The present study explored, whether SPAK and/or OSR1 have similarly the potential to modify the activity of ROMK1.
  
  
  METHODS
  ROMK1 was expressed in Xenopus oocytes with or without additional expression of wild-type SPAK, constitutively active (T233E)SPAK, catalytically inactive (D212A)SPAK, wild-type OSR1, constitutively active (T185E)OSR1 and catalytically inactive (D164A)OSR1. Channel activity was determined utilizing dual electrode voltage clamp and ROMK1 protein abundance in the cell membrane utilizing chemiluminescence of ROMK1 containing an extracellular hemagglutinin epitope (ROMK1-HA).
  
  
  RESULTS
  ROMK1 activity and ROMK1-HA protein abundance were significantly down-regulated by wild-type SPAK and (T233E)SPAK, but not by (D212A)SPAK. Similarly, ROMK1 activity and ROMK1-HA protein abundance were significantly down-regulated by wild-type OSR1 and (T185E)OSR1, but not by (D164A)OSR1.
  
  
  CONCLUSIONS
  ROMK1 protein abundance and activity are down-regulated by SPAK and OSR1.
authors.affiliation: Department of Physiology I, University of Tübingen, Tübingen, Germany.
authors.forename: Bernat
authors.initials: B
authors.lastname: Elvira
authors.forename: Carlos
authors.initials: C
authors.lastname: Munoz
authors.forename: Jose
authors.initials: J
authors.lastname: Borras
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.forename: Jamshed
authors.initials: J
authors.lastname: Warsi
authors.forename: Sumant Singh
authors.initials: SS
authors.lastname: Ajay
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Shumilina
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000818:Animals; D007679:Kidney Medulla / Q000378:metabolism*; D051379:Mice; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics* / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: C510693:Kcnj1 protein, mouse; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; C486407:Stk39 protein, mouse; C534421:OXSR1 protein, mouse; D017346:Protein Serine-Threonine Kinases