title: Negative regulation of the creatine transporter SLC6A8 by SPAK and OSR1.
abstract: OBJECTIVE
  Transport regulation involves several kinases including SPAK (SPS1-related proline/alanine-rich kinase) and OSR1 (oxidative stress-responsive kinase 1), which are under control of WNK (with-no-K[Lys]) kinases. The present study explored whether SPAK and/or OSR1 participate in the regulation of the creatine transporter CreaT (SLC6A8), which accomplishes Na+ coupled cellular uptake of creatine in several tissues including kidney, intestine, heart, skeletal muscle and brain.
  
  
  METHODS
  cRNA encoding SLC6A8 was injected into Xenopus laevis oocytes with or without additional injection of cRNA encoding wild-type SPAK, constitutively active (T233E)SPAK, WNK insensitive (T233A)SPAK, catalytically inactive (D212A)SPAK, wild-type OSR1, constitutively active (T185E)OSR1, WNK insensitive (T185A)OSR1 and catalytically inactive (D164A)OSR1. Transporter activity was determined from creatine (1 mM) induced current utilizing dual electrode voltage clamp.
  
  
  RESULTS
  Coexpression of wild-type SPAK and of (T233E)SPAK, but not of (T233A)SPAK or of (D212A)SPAK was followed by a significant decrease of creatine induced current in SLC6A8 expressing oocytes. Coexpression of SPAK significantly decreased maximal transport rate. Coexpression of wild-type OSR1, (T185E)OSR1 and (T185A)OSR1 but not of (D164A)OSR1 significantly negatively regulated SLC6A8 activity. OSR1 again decreased significantly maximal transport rate.
  
  
  CONCLUSIONS
  Both, SPAK and OSR1, are negative regulators of the creatine transporter SLC6A8.
authors.affiliation: Department of Physiology I, University of Tübingen, Tübingen, Germany.
authors.forename: Myriam
authors.initials: M
authors.lastname: Fezai
authors.forename: Bernat
authors.initials: B
authors.lastname: Elvira
authors.forename: Jose
authors.initials: J
authors.lastname: Borras
authors.forename: Mossadok
authors.initials: M
authors.lastname: Ben-Attia
authors.forename: Zohreh
authors.initials: Z
authors.lastname: Hoseinzadeh
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000818:Animals; D003401:Creatine / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D050480:Plasma Membrane Neurotransmitter Transport Proteins / Q000096:biosynthesis* / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D014018:Tissue Distribution; D014982:Xenopus laevis
chemical_list: D009419:Nerve Tissue Proteins; D050480:Plasma Membrane Neurotransmitter Transport Proteins; C094770:SLC6A8 protein, human; C118135:OXSR1 protein, human; D017346:Protein Serine-Threonine Kinases; C486409:STK39 protein, human; D003401:Creatine