title: The Volume Activated Potassium Channel KCNK5 is Up-Regulated in Activated Human T Cells, but Volume Regulation is Impaired.
abstract: OBJECTIVE
  The potential role of the two-pore domain potassium channel KCNK5 (also known as TASK-2 and K(2P)5.1) in activated T cell physiology has only recently been described. So far KCNK5 has been described to be up-regulated in T cells in multiple sclerosis patients and to be implicated in the volume regulatory mechanism regulatory volume decrease (RVD) in T cells.
  
  
  METHODS
  We investigated the time-dependent expression pattern of KCNK5 in CD3/CD28 activated human T cells using qPCR and Western blotting and its role in RVD using a Coulter Counter.
  
  
  RESULTS
  KCNK5 is highly up-regulated in CD3/CD28 activated T cells both at mRNA (after 24 h) and protein level (72 and 144 h), but despite this up-regulation the RVD response is inhibited. Furthermore, the swelling-activated Cl- permeability in activated T cells is strongly decreased, and the RVD inhibition is predominantly due to the decreased Cl- permeability.
  
  
  CONCLUSIONS
  The up-regulated KCNK5 in activated human T cells does not play a volume regulatory role, due to decreased Cl- permeability. We speculate that the KCNK5 up-regulation might play a role in hyperpolarization of the cell membrane leading to increased Ca2+ influx and proliferation of T cells.
authors.affiliation: Section for Cell and Developmental Biology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Signe S
authors.initials: SS
authors.lastname: Kirkegaard
authors.forename: Pernille Dyhl
authors.initials: PD
authors.lastname: Strøm
authors.forename: Steen
authors.initials: S
authors.lastname: Gammeltoft
authors.forename: Anker Jon
authors.initials: AJ
authors.lastname: Hansen
authors.forename: Else K
authors.initials: EK
authors.lastname: Hoffmann
mesh_terms: D018106:CD28 Antigens / Q000378:metabolism; D017252:CD3 Complex / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D048429:Cell Size / Q000187:drug effects; D002713:Chlorine / Q000378:metabolism; D006801:Humans; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000235:genetics; D008213:Lymphocyte Activation; D024683:Potassium Channels, Tandem Pore Domain / Q000235:genetics* / Q000378:metabolism*; D013601:T-Lymphocytes / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D018106:CD28 Antigens; D017252:CD3 Complex; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C410295:KCNK5 protein, human; C496923:KCNN4 protein, human; D024683:Potassium Channels, Tandem Pore Domain; D002713:Chlorine; D002118:Calcium