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This Article Full Text Full Text (PDF) All Versions of this Article: 288/6/H2666    most recent 00521.2004v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Chen, T. Articles by Sheets, M. F. Search for Related Content PubMed PubMed Citation Articles by Chen, T. Articles by Sheets, M. F.

Reduced voltage dependence of inactivation in the SCN5A sodium channel mutation delF1617

The Nora Eccles Harrison Cardiovascular Research and Training Institute and Department of Internal Medicine, University of Utah, Salt Lake City, Utah

Submitted 3 June 2004 ; accepted in final form 12 January 2005

Deletion of a phenylalanine at position 1617 (delF1617) in the extracellular linker between segments S3 and S4 in domain IV of the human heart Na⁺ channel (hH1a) has been tentatively associated with long QT syndrome type 3 (LQT3). In a mammalian cell expression system, we compared whole cell, gating, and single-channel currents of delF1617 with those of wild-type hH1a. The half points of the peak activation-voltage curve for the two channels were similar, as were the deactivation time constants at hyperpolarized test potentials. However, delF1617 demonstrated a significant negative shift of –7 mV in the half point of the voltage-dependent Na⁺ channel availability curve compared with wild type. In addition, both the time course of decay of Na⁺ current (I_Na) and two-pulse development of inactivation of delF1617 were faster at negative test potentials, whereas they tended to be slower at positive potentials compared with wild type. Mean channel open times for delF1617 were shorter at potentials <0 mV, whereas they were longer at potentials >0 mV compared with wild type. Using anthopleurin-A, a site-3 toxin that inhibits movement of segment S4 in domain IV (S4-DIV), we found that gating charge contributed by the S4-DIV in delF1617 was reduced 37% compared with wild type. We conclude that deletion of a single amino acid in the S3-S4 linker of domain IV alters the voltage dependence of fast inactivation via a reduction in the gating charge contributed by S4-DIV and can cause either a gain or loss of I_Na, depending on membrane potential.

gating charge; single channel; voltage sensor; S3-S4 linker; domain IV

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