title: SPAK Sensitive Regulation of the Epithelial Na Channel ENaC.
abstract: OBJECTIVE
  The WNK-dependent STE20/SPS1-related proline/alanine-rich kinase SPAK participates in the regulation of NaCl and Na(+),K(+),2Cl(-) cotransport and thus renal salt excretion. The present study explored whether SPAK has similarly the potential to regulate the epithelial Na(+) channel (ENaC).
  
  
  METHODS
  ENaC was expressed in Xenopus oocytes with or without additional expression of wild type SPAK, constitutively active (T233E)SPAK, WNK insensitive (T233A)SPAK or catalytically inactive (D212A)SPAK, and ENaC activity estimated from amiloride (50 µM) sensitive current (Iamil) in dual electrode voltage clamp experiments. Moreover, Ussing chamber was employed to determine Iamil in colonic tissue from wild type mice (spak(wt/wt)) and from gene targeted mice carrying WNK insensitive SPAK (spak(tg/tg)).
  
  
  RESULTS
  Iamil was observed in ENaC-expressing oocytes, but not in water-injected oocytes. In ENaC expressing oocytes Iamil was significantly increased following coexpression of wild-type SPAK and (T233E)SPAK, but not following coexpression of (T233A)SPAK or (D212A)SPAK. Colonic Iamil was significantly higher in spak(wt/wt) than in spak(tg/tg) mice.
  
  
  CONCLUSIONS
  SPAK has the potential to up-regulate ENaC.
authors.affiliation: Department of Physiology, University of Tuebingen, Tuebingen, Germany.
authors.forename: Musaab
authors.initials: M
authors.lastname: Ahmed
authors.forename: Madhuri S
authors.initials: MS
authors.lastname: Salker
authors.forename: Bernat
authors.initials: B
authors.lastname: Elvira
authors.forename: Anja T
authors.initials: AT
authors.lastname: Umbach
authors.forename: Hajar
authors.initials: H
authors.lastname: Fakhri
authors.forename: Amal M
authors.initials: AM
authors.lastname: Saeed
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Shumilina
authors.forename: Zohreh
authors.initials: Z
authors.lastname: Hosseinzadeh
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000450:Aldosterone / Q000097:blood; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D003106:Colon / Q000378:metabolism; D004232:Diuretics / Q000494:pharmacology; D056827:Endosomal Sorting Complexes Required for Transport / Q000378:metabolism; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000502:physiology*; D005260:Female; D051379:Mice; D015778:Minor Histocompatibility Antigens; D000075702:Nedd4 Ubiquitin Protein Ligases; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology*; D012965:Sodium Chloride / Q000378:metabolism / Q000652:urine; D064466:Solute Carrier Family 12, Member 1 / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D015854:Up-Regulation / Q000502:physiology; D000076204:WNK Lysine-Deficient Protein Kinase 1; D014982:Xenopus laevis
chemical_list: D004232:Diuretics; D056827:Endosomal Sorting Complexes Required for Transport; D053503:Epithelial Sodium Channels; D015778:Minor Histocompatibility Antigens; C578715:Slc12a1 protein, mouse; D064466:Solute Carrier Family 12, Member 1; D012965:Sodium Chloride; D000450:Aldosterone; D000584:Amiloride; D000075702:Nedd4 Ubiquitin Protein Ligases; D044767:Ubiquitin-Protein Ligases; C486407:Stk39 protein, mouse; D017346:Protein Serine-Threonine Kinases; D000076204:WNK Lysine-Deficient Protein Kinase 1; C498744:Wnk1 protein, mouse