Elucidating KChIP effects on Kv4.3 inactivation and recovery kinetics with a minimal KChIP2 isoform

J Physiol. 2002 Nov 15;545(1):5-11. doi: 10.1113/jphysiol.2002.031856.

Abstract

Kv channel interacting proteins (KChIPs) are Ca(2+)-binding proteins with four EF-hands. KChIPs modulate Kv4 channel gating by slowing inactivation kinetics and accelerating recovery kinetics. Thus, KChIPs are believed to be important regulators of Kv4 channels underlying transient outward K(+) currents in many excitable cell types. We have cloned a structurally minimal KChIP2 isoform (KChIP2d) from ferret heart. KChIP2d corresponds to the final 70 C-terminal amino acids of other KChIPs and has only one EF-hand. We demonstrate that KChIP2d is a functional KChIP that both accelerates recovery and slows inactivation kinetics of Kv4.3, indicating that the minimal C-terminus can maintain KChIP regulatory properties. We utilize KChIP2d to further demonstrate that: (i) the EF-hand modulates effects on Kv4.3 inactivation but not recovery; (ii) Ca(2+)-dependent effects on Kv4.3 inactivation are mediated through a mechanism reflected in the slow time constant of inactivation; and (iii) a short stretch of amino acids exclusive of the EF-hand partially mediates Ca(2+)-independent effects on recovery. Our results demonstrate that distinct regions of a KChIP molecule are involved in modulating inactivation and recovery. The potential ability of KChIP EF-hands to sense intracellular Ca(2+) levels and transduce these changes to alterations in Kv4 channel inactivation kinetics may serve as a mechanism allowing intracellular Ca(2+) transients to modulate repolarization. KChIP2d is a valuable tool for elucidating structural domains of KChIPs involved in Kv4 channel regulation.

Publication types

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

MeSH terms

  • Amino Acid Sequence / genetics
  • Animals
  • Calcium / physiology
  • Calcium-Binding Proteins / genetics
  • Calcium-Binding Proteins / physiology*
  • Cloning, Molecular
  • Electrophysiology
  • Female
  • Ferrets
  • Humans
  • Kinetics
  • Kv Channel-Interacting Proteins
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Mutation / physiology
  • Myocardium / metabolism
  • Nerve Tissue Proteins / genetics
  • Neuronal Calcium-Sensor Proteins
  • Neuropeptides
  • Oocytes
  • Potassium Channels / physiology*
  • Potassium Channels, Voltage-Gated*
  • Protein Isoforms / physiology
  • Shal Potassium Channels
  • Xenopus Proteins*
  • Xenopus laevis

Substances

  • Calcium-Binding Proteins
  • KCND3 protein, human
  • KCNIP2 protein, human
  • Kv Channel-Interacting Proteins
  • Nerve Tissue Proteins
  • Neuronal Calcium-Sensor Proteins
  • Neuropeptides
  • Potassium Channels
  • Potassium Channels, Voltage-Gated
  • Protein Isoforms
  • Shal Potassium Channels
  • Xenopus Proteins
  • frequenin calcium sensor proteins
  • Calcium