title: Regulation of the voltage gated K channel Kv1.3 by recombinant human klotho protein.
abstract: OBJECTIVE
  Klotho, a protein mainly produced in the kidney and released into circulating blood, contributes to the negative regulation of 1,25(OH)2D3 formation and is thus a powerful regulator of mineral metabolism. As β-glucuronidase, alpha Klotho protein further regulates the stability of several carriers and channels in the plasma membrane and thus regulates channel and transporter activity. Accordingly, alpha Klotho protein participates in the regulation of diverse functions seemingly unrelated to mineral metabolism including lymphocyte function. The present study explored the impact of alpha Klotho protein on the voltage gated K+ channel Kv1.3.
  
  
  METHODS
  cRNA encoding Kv1.3 (KCNA3) was injected into Xenopus oocytes and depolarization induced outward current in Kv1.3 expressing Xenopus oocytes determined utilizing dual electrode voltage clamp. Experiments were performed without or with prior treatment with recombinant human Klotho protein (50 ng/ml, 24 hours) in the absence or presence of a β-glucuronidase inhibitor D-saccharic acid-1,4-lactone (DSAL, 10 µM). Moreover, the voltage gated K+ current was determined in Jcam lymphoma cells by whole cell patch clamp following 24 hours incubation without or with recombinant human Klotho protein (50 ng/ml, 24 hours). Kv1.3 protein abundance in Jcam cells was determined utilising fluorescent antibodies in flow cytometry.
  
  
  RESULTS
  In Kv1.3 expressing Xenopus oocytes the Kv1.3 currents and the protein abundance of Kv1.3 were both significantly enhanced after treatment with recombinant human Klotho protein (50 ng/ml, 24 hours), an effect reversed by presence of DSAL. Moreover, treatment with recombinant human Klotho protein increased Kv currents and Kv1.3 protein abundance in Jcam cells.
  
  
  CONCLUSIONS
  Alpha Klotho protein enhances Kv1.3 channel abundance and Kv1.3 currents in the plasma membrane, an effect depending on its β-glucuronidase activity.
authors.affiliation: Department of Physiology, University of Tübingen, Tübingen, Germany.
authors.forename: Ahmad
authors.initials: A
authors.lastname: Almilaji
authors.forename: Sabina
authors.initials: S
authors.lastname: Honisch
authors.forename: Guilai
authors.initials: G
authors.lastname: Liu
authors.forename: Bernat
authors.initials: B
authors.lastname: Elvira
authors.forename: Sumant Singh
authors.initials: SS
authors.lastname: Ajay
authors.forename: Zohreh
authors.initials: Z
authors.lastname: Hosseinzadeh
authors.forename: Musaab
authors.initials: M
authors.lastname: Ahmed
authors.forename: Carlos
authors.initials: C
authors.lastname: Munoz
authors.forename: Mentor
authors.initials: M
authors.lastname: Sopjani
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D005937:Glucaric Acid / Q000494:pharmacology; D005966:Glucuronidase / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006801:Humans; D000090265:Klotho Proteins; D051664:Kv1.3 Potassium Channel / Q000096:biosynthesis / Q000187:drug effects*; D007783:Lactones / Q000494:pharmacology; D009865:Oocytes; D018408:Patch-Clamp Techniques; D011994:Recombinant Proteins / Q000494:pharmacology; D014981:Xenopus
chemical_list: C571832:D-Glucaric acid, 1,4-lactone; C496973:KCNA3 protein, human; D051664:Kv1.3 Potassium Channel; D007783:Lactones; D011994:Recombinant Proteins; D005966:Glucuronidase; D000090265:Klotho Proteins; D005937:Glucaric Acid