Altered gating and local anesthetic block mediated by residues in the I-S6 and II-S6 transmembrane segments of voltage-dependent Na+ channels

Andrei Kondratiev, Gordon F. Tomaselli

Research output: Contribution to journalArticle

Abstract

The cytoplasmic side of the voltage-dependent Na+ channel pore is putatively formed by the S6 segments of domains I to IV. The role of amino acid residues of I-S6 and II-S6 in channel gating and local anesthetic (LA) block was investigated using the cysteine scanning mutagenesis of the rat skeletal muscle Na+ channel (Nav1.4). G428C uniquely reduced sensitivity to rested state or first-pulse block by lidocaine without alterations in the voltage dependence or kinetics of gating that would otherwise account for the increase in the IC50 for block. Mutations in I-S6 (N434C and 1436C) and in II-S6 (L785C and V787C) increased sensitivity to first-pulse block by lidocaine. Enhanced inactivation accounted for the increased sensitivity of N434C to lidocaine and hastening of inactivation of 1436C in the absence of drug could account for higher affinity first-pulse block. Mutations in I-S6 (1424C, 1425C, and F430C) and in II-S6 (1782C and V786C) reduced the use-dependent lidocaine block. The reduction in use-dependent block of F430C was consistent with alterations in inactivation gating; the other mutants did not exhibit gating changes that could explain the reduced sensitivity to lidocaine. Therefore, several amino acids (1424, 1425, G428, 1782, and V786), in addition to those previously identified (Yarov-Yarovoy et al., 2002), alter the sensitivity of Nav1.4 to lidocaine, independent of mutation-induced changes in gating. The magnitude of the change in the IC50 values, the isoform, and LA dependence of the changes in affinity suggest that the determinants of binding in I-S6 and II-S6 are subsidiary to those in IV-S6.

Original languageEnglish (US)
Pages (from-to)741-752
Number of pages12
JournalMolecular Pharmacology
Volume64
Issue number3
DOIs
StatePublished - Sep 1 2003

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S 6
Local Anesthetics
Lidocaine
Mutation
Inhibitory Concentration 50
Amino Acids
Mutagenesis
Cysteine
Protein Isoforms
Skeletal Muscle

ASJC Scopus subject areas

  • Pharmacology

Cite this

Altered gating and local anesthetic block mediated by residues in the I-S6 and II-S6 transmembrane segments of voltage-dependent Na+ channels. / Kondratiev, Andrei; Tomaselli, Gordon F.

In: Molecular Pharmacology, Vol. 64, No. 3, 01.09.2003, p. 741-752.

Research output: Contribution to journalArticle

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