title: KCNK5 is functionally down-regulated upon long-term hypotonicity in Ehrlich ascites tumor cells.
abstract: OBJECTIVE
  Regulatory volume decrease (RVD) in response to acute cell swelling is well described and KCNK5 (also known as TASK-2 or K2P5.1) has been shown to be the volume sensitive K(+) channel in Ehrlich cells. Very little is, on the other hand, known about the effects of long-term hypotonicity on expression and function of KCNK5, thus we have investigated the effect of long-term hypotonicity (24h - 48h) on KCNK5 in Ehrlich cells on the mRNA, protein and physiological levels.
  
  
  METHODS
  Physiological effects of long-term hypotonicity were measured using patch-clamp and Coulter counter techniques. Expression patterns of KCNK5 on mRNA and protein levels were established using real-time qPCR and western blotting respectively.
  
  
  RESULTS
  The maximum swelling-activated current through KCNK5 was significantly decreased upon 48h of hypotonicity and likewise the RVD response was significantly impaired after both 24 and 48h of hypotonic stimulation. No significant differences in the KCNK5 mRNA expression patterns between control and stimulated cells were observed, but a significant decrease in the KCNK5 protein level 48h after stimulation was found.
  
  
  CONCLUSIONS
  The data suggest that the strong physiological impairment of KCNK5 in Ehrlich cells after long-term hypotonic stimulation is predominantly due to down-regulation of the KCNK5 protein synthesis.
authors.affiliation: Section of Cell and Developmental Biology, Institute of Biology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Signe Skyum
authors.initials: SS
authors.lastname: Kirkegaard
authors.forename: Tune
authors.initials: T
authors.lastname: Wulff
authors.forename: Steen
authors.initials: S
authors.lastname: Gammeltoft
authors.forename: Else Kay
authors.initials: EK
authors.lastname: Hoffmann
mesh_terms: D000818:Animals; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism* / Q000473:pathology; D048429:Cell Size; D015536:Down-Regulation; D005786:Gene Expression Regulation; D051379:Mice; D009997:Osmotic Pressure / Q000502:physiology*; D018408:Patch-Clamp Techniques; D024683:Potassium Channels, Tandem Pore Domain / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: C498739:Kcnk5 protein, mouse; D024683:Potassium Channels, Tandem Pore Domain