External pore collapse as an inactivation mechanism for Kv4.3 K+ channels

J Membr Biol. 2002 Jul 1;188(1):73-86. doi: 10.1007/s00232-001-0173-3.


Kv4 channels are thought to lack a C-type inactivation mechanism (collapse of the external pore) and to inactivate as a result of a concerted action of cytoplasmic regions of the channel. To investigate whether Kv4 channels have outer pore conformational changes during the inactivation process, the inactivation properties of Kv4.3 were characterized in 0 mM and in 2 mM external K+ in whole-cell voltage-clamp experiments. Removal of external K+ increased the inactivation rates and favored cumulative inactivation by repetitive stimulation. The reduction in current amplitude during repetitive stimulation and the faster inactivation rates in 0 mM external K+ were not due to changes in the voltage dependence of channel opening or to internal K+ depletion. The extent of the collapse of the K+ conductance upon removal of external K+ was more pronounced in NMG+-than in Na+-containing solutions. The reduction in the current amplitude during cumulative inactivation by repetitive stimulation is not associated with kinetic changes, suggesting that it is due to a diminished number of functional channels with unchanged gating properties. These observations meet the criteria for a typical C-type inactivation, as removal of external K+ destabilizes the conducting state, leading to the collapse of the pore. A tentative model is presented, in which K+ bound to high-affinity K+-binding sites in the selectivity filter destabilizes an outer neighboring K+ modulatory site that is saturated at approximately 2 mM external K+. We conclude that Kv4 channels have a C-type inactivation mechanism and that previously reported alterations in the inactivation rates after N- and C- termini mutagenesis may arise from secondary changes in the electrostatic interactions between K+-binding sites in the selectivity filter and the neighboring K+-modulatory site, that would result in changes in its K+ occupancy.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Line
  • Delayed Rectifier Potassium Channels
  • Electric Conductivity
  • Humans
  • Ion Channel Gating / drug effects
  • Ion Channel Gating / physiology*
  • Kidney / embryology
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Models, Biological
  • Patch-Clamp Techniques
  • Potassium / metabolism*
  • Potassium / pharmacology
  • Potassium Channel Blockers / pharmacology
  • Potassium Channels / drug effects
  • Potassium Channels / physiology*
  • Potassium Channels, Voltage-Gated*
  • Shal Potassium Channels


  • Delayed Rectifier Potassium Channels
  • KCND3 protein, human
  • Potassium Channel Blockers
  • Potassium Channels
  • Potassium Channels, Voltage-Gated
  • Shal Potassium Channels
  • Potassium