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Charge at the local anesthetic binding site modulates steady state inactivation of voltage gated Na channels
Author(s) -
McNulty Megan M,
Edgerton Gabrielle B,
Fozzard Harry A,
Hanck Dorothy A
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a1158-d
Subject(s) - gating , chemistry , biophysics , depolarization , gene isoform , membrane potential , binding site , patch clamp , mutagenesis , stereochemistry , biochemistry , receptor , mutation , biology , gene
Local anesthetics inhibit pain by binding to the inner pore of voltage‐gated Na channels and blocking permeation. Mutagenesis identified a Phe in the pore‐lining S6 of DIV in multiple isoforms as the most important contributor to use‐dependent block, and we have recently studied this position in the cardiac isoform (Na V 1.5, 1759). As for other isoforms, replacing Phe1759 with either positively charged Lys or Arg, negatively charged Asp or Glu, or neutral Cys reduced use‐dependent block 15–40‐fold. Charge substitutions at 1759 also altered the electrostatic environment of the inner pore resulting in significant effects on Na permeation. Here we examined whether charge at 1759 also exerts effects on channel gating. With the exception of Glu, which depolarized activation ~10 mV, minimal effects on activation were observed. All charged substitutions, however, altered closed‐state inactivation (at 1s). Arg and Lys (positive substitutes), hyperpolarized inactivation 6 and 10 mV, whereas Glu and Asp (negative substitutes), exerted the opposite effect, depolarizing inactivation 8 and 25 mV. Gating current studies have previously suggested a unique role of the DIV voltage sensor in channel inactivation. Therefore, these data suggest that this DIV Phe may be associated with structures involved in channel inactivation. R01HL065661 (HF, DH), T32HL072742 (MM), T32GM07839 and Pritzker Fellow (GE).