title: Downregulation of peptide transporters PEPT1 and PEPT2 by oxidative stress responsive kinase OSR1.
abstract: OBJECTIVE
  OSR1 (oxidative-stress-responsive kinase 1) participates in the regulation of renal tubular ion transport, cell volume and blood pressure. Whether OSR1 contributes to the regulation of organic solute transport remained; however, elusive. The present study thus explored the OSR1 sensitivity of the peptide transporters PEPT1 and PEPT2.
  
  
  METHODS
  cRNA encoding PEPT1 or PEPT2 were injected into Xenopus oocytes without or with additional injection of cRNA encoding wild-type OSR1, WNK1 insensitive inactive (T185A)OSR1, constitutively active (T185E)OSR1, and catalytically inactive (D164A)OSR1. Electrogenic peptide (glycine-glycine) transport was determined by dual electrode voltage clamp, the abundance of hemagglutinin-tagged PEPT2 (PEPT2-HA) by chemiluminescence.
  
  
  RESULTS
  In Xenopus oocytes injected with cRNA encoding PEPT1 or PEPT2, but not in oocytes injected with water, the dipeptide gly-gly (2 mM) generated an appreciable inward current (I(gly-gly)). Coexpression of OSR1 significantly decreased Igly-gly in both PEPT1 and PEPT2 expressing oocytes. The effect of OSR1 coexpression on Igly-gly in PEPT1 expressing oocytes was mimicked by coexpression of (T185E)OSR1, but not of (D164A)OSR1 or (T185A)OSR1. Kinetic analysis revealed that coexpression of OSR1 decreased maximal Igly-gly. OSR1 further decreased the PEPT2-HA protein abundance in the cell membrane.
  
  
  CONCLUSIONS
  OSR1 has the capacity to downregulate the peptide transporters PEPT1 and PEPT2 by decreasing the carrier protein abundance in the cell membrane.
authors.affiliation: Department of Physiology I, University of Tübingen, Tübingen, Germany.
authors.forename: Jamshed
authors.initials: J
authors.lastname: Warsi
authors.forename: Bernat
authors.initials: B
authors.lastname: Elvira
authors.forename: Rosi
authors.initials: R
authors.lastname: Bissinger
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: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D000074011:Peptide Transporter 1; D017346:Protein Serine-Threonine Kinases / Q000494:pharmacology*; D012313:RNA / Q000096:biosynthesis; D027981:Symporters / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D014981:Xenopus
chemical_list: D000074011:Peptide Transporter 1; C082186:SLC15A1 protein, human; D027981:Symporters; C093694:hydrogen-coupled oligopeptide transporter PepT2; D012313:RNA; C118135:OXSR1 protein, human; D017346:Protein Serine-Threonine Kinases