title: Use Dependent Attenuation of Rat HCN1-Mediated Ih in Intact HEK293 Cells.
abstract: OBJECTIVE
  Cationic currents (Ih) through the fast activating and relatively cAMP insensitive subtype of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, HCN1, are limited by cytosolic factors in mammalian cells. This cytosolic HCN1 break is boosted by changes in membrane voltage that are not characterized on a biophysical level, yet.
  
  
  METHODS
  We overexpressed rat (r)HCN1 in human embryonic kidney cells (HEK293) and recorded pharmacologically isolated Ih in cell-attached or whole-cell mode of the patch-clamp technique.
  
  
  RESULTS
  Recurring activation of rHCN1 reduced and slowed Ih in intact HEK293 cells (cell-attached mode). On the contrary, sustained disruption of the intracellular content (whole-cell mode) ceased activity dependence and partially enables voltage dependent hysteresis. The activity induced Ih attenuation in intact cells was independent of the main external cation, depended on the number of previous forced activations and was - at least in part - due to a shift in the voltage dependence of activation towards hyperpolarization as estimated by an adapted tail current analysis. Intracellular elevation of cAMP could not reverse the changes in Ih.
  
  
  CONCLUSIONS
  Reduction of rHCN1 mediated Ih is use dependent and may involve the coupling of voltage sensor and pore.
authors.forename: Lennart
authors.initials: L
authors.lastname: Barthel
authors.forename: Olivia
authors.initials: O
authors.lastname: Reetz
authors.forename: Ulf
authors.initials: U
authors.lastname: Strauss
mesh_terms: D000818:Animals; D002412:Cations / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D057809:HEK293 Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / Q000235:genetics / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D002412:Cations; C578667:Hcn1 protein, rat; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D015221:Potassium Channels; D011994:Recombinant Proteins; D012964:Sodium; D000242:Cyclic AMP