Ion selectivity filter regulates local anesthetic inhibition of G-protein-gated inwardly rectifying K+ channels

Biophys J. 2001 Feb;80(2):707-18. doi: 10.1016/S0006-3495(01)76050-X.


The weaver mutation (G156S) in G-protein-gated inwardly rectifying K+ (GIRK) channels alters ion selectivity and reveals sensitivity to inhibition by a charged local anesthetic, QX-314, applied extracellularly. In this paper, disrupting the ion selectivity in another GIRK channel, chimera I1G1(M), generates a GIRK channel that is also inhibited by extracellular local anesthetics. I1G1(M) is a chimera of IRK1 (G-protein-insensitive) and GIRK1 and contains the hydrophobic domains (M1-pore-loop-M2) of GIRK1 (G1(M)) with the N- and C-terminal domains of IRK1 (I1). The local anesthetic binding site in I1G1(M) is indistinguishable from that in GIRK2(wv) channels. Whereas chimera I1G1(M) loses K+ selectivity, although there are no mutations in the pore-loop complex, chimera I1G2(M), which contains the hydrophobic domain from GIRK2, exhibits normal K+ selectivity. Mutation of two amino acids that are unique in the pore-loop complex of GIRK1 (F137S and A143T) restores K+ selectivity and eliminates the inhibition by extracellular local anesthetics, suggesting that the pore-loop complex prevents QX-314 from reaching the intrapore site. Alanine mutations in the extracellular half of the M2 transmembrane domain alter QX-314 inhibition, indicating the M2 forms part of the intrapore binding site. Finally, the inhibition of G-protein-activated currents by intracellular QX-314 appears to be different from that observed in nonselective GIRK channels. The results suggest that inward rectifiers contain an intrapore-binding site for local anesthetic that is normally inaccessible from extracellular charged local anesthetics.

Publication types

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

MeSH terms

  • Anesthetics, Local / pharmacology*
  • Animals
  • Barium / pharmacology
  • Binding Sites
  • Biophysical Phenomena
  • Biophysics
  • Female
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • GTP-Binding Proteins / metabolism*
  • In Vitro Techniques
  • Ion Channel Gating / drug effects
  • Kinetics
  • Lidocaine / analogs & derivatives
  • Lidocaine / pharmacology
  • Mutation
  • Oocytes / metabolism
  • Potassium Channel Blockers*
  • Potassium Channels / chemistry
  • Potassium Channels / genetics
  • Potassium Channels / metabolism*
  • Potassium Channels, Inwardly Rectifying*
  • Recombinant Fusion Proteins / antagonists & inhibitors
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Xenopus


  • Anesthetics, Local
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • Potassium Channel Blockers
  • Potassium Channels
  • Potassium Channels, Inwardly Rectifying
  • Recombinant Fusion Proteins
  • QX-314
  • Barium
  • Lidocaine
  • GTP-Binding Proteins