A novel mutation in SCN5A, delQKP 1507-1509, causing long QT syndrome: role of Q1507 residue in sodium channel inactivation

J Mol Cell Cardiol. 2003 Dec;35(12):1513-21. doi: 10.1016/j.yjmcc.2003.08.007.


Inherited long QT syndrome (LQTS) is caused by mutations in six genes including SCN5A, encoding the alpha-subunit of the human cardiac voltage-dependent sodium channel hNa(v)1.5. In LQT3, various mutations in SCN5A were identified, which produce a gain of channel function. The aim of this study was to screen SCN5A for mutations in a family with the LQT3 phenotype and to analyze the consequences of the mutation on the channel function. By polymerase chain reaction-denaturating high performance liquid chromatography-sequencing, we identified a novel deletion in SCN5A, delQKP 1507-1509, in the DIII-DIV linker of the sodium channel. The hNa(v)1.5/delQKP1507-1509, hNa(v)1.5/delQ1507 and hNa(v)1.5/Q1507A mutants were constructed in vitro, mutant channels were expressed in the tsA201 human cell line and studied using the whole-cell configuration of the patch clamp technique. A persistent inward sodium current of 1-1.5% of maximum currents measured at -30 mV in all mutant sodium channels was recorded, which was nearly completely blocked by the sodium-channel blockers tetrodotoxin and lidocaine. The deletion mutants resulted in a significant shift of steady-state activation to more depolarized voltages. The delQ1507 showed a small shift of steady-state inactivation towards more negative potentials, whereas no significant shifts were observed in both steady-state activation and inactivation in Q1507A compared to the wild-type Na(v)1.5 sodium channels. The novel SCN5A mutation, delQKP, induces a residual current as previously shown for other SCN5A mutations causing LQTS. DelQKP shares the deletion of Q1507 with the formerly known delKPQ 1505-1507. Our data suggest that Q1507 plays an important role in fast sodium channel inactivation.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Base Sequence
  • Cell Line
  • Child
  • Chromatography, High Pressure Liquid
  • DNA Mutational Analysis
  • Female
  • Genetic Testing
  • Heterozygote
  • Humans
  • Lidocaine / pharmacology
  • Long QT Syndrome / genetics*
  • Long QT Syndrome / physiopathology
  • Male
  • NAV1.5 Voltage-Gated Sodium Channel
  • Patch-Clamp Techniques
  • Pedigree
  • Polymerase Chain Reaction
  • Sequence Deletion*
  • Sodium Channel Blockers / pharmacology
  • Sodium Channels / drug effects
  • Sodium Channels / genetics*
  • Sodium Channels / metabolism*
  • Tetrodotoxin / pharmacology


  • NAV1.5 Voltage-Gated Sodium Channel
  • SCN5A protein, human
  • Sodium Channel Blockers
  • Sodium Channels
  • Tetrodotoxin
  • Lidocaine