Mutant caveolin-3 induces persistent late sodium current and is associated with long-QT syndrome

Circulation. 2006 Nov 14;114(20):2104-12. doi: 10.1161/CIRCULATIONAHA.106.635268. Epub 2006 Oct 23.

Abstract

Background: Congenital long-QT syndrome (LQTS) is a primary arrhythmogenic syndrome stemming from perturbed cardiac repolarization. LQTS, which affects approximately 1 in 3000 persons, is 1 of the most common causes of autopsy-negative sudden death in the young. Since the sentinel discovery of cardiac channel gene mutations in LQTS in 1995, hundreds of mutations in 8 LQTS susceptibility genes have been identified. All 8 LQTS genotypes represent primary cardiac channel defects (ie, ion channelopathy) except LQT4, which is a functional channelopathy because of mutations in ankyrin-B. Approximately 25% of LQTS remains unexplained pathogenetically. We have pursued a "final common pathway" hypothesis to elicit novel LQTS-susceptibility genes. With the recent observation that the LQT3-associated, SCN5A-encoded cardiac sodium channel localizes in caveolae, which are known membrane microdomains whose major component in the striated muscle is caveolin-3, we hypothesized that mutations in caveolin-3 may represent a novel pathogenetic mechanism for LQTS.

Methods and results: Using polymerase chain reaction, denaturing high-performance liquid chromatography, and direct DNA sequencing, we performed open reading frame/splice site mutational analysis on CAV3 in 905 unrelated patients referred for LQTS genetic testing. CAV3 mutations were engineered by site-directed mutagenesis and the molecular phenotype determined by transient heterologous expression into cell lines that stably express the cardiac sodium channel hNa(v)1.5. We identified 4 novel mutations in CAV3-encoded caveolin-3 that were absent in >1000 control alleles. Electrophysiological analysis of sodium current in HEK293 cells stably expressing hNa(v)1.5 and transiently transfected with wild-type and mutant caveolin-3 demonstrated that mutant caveolin-3 results in a 2- to 3-fold increase in late sodium current compared with wild-type caveolin-3. Our observations are similar to the increased late sodium current associated with LQT3-associated SCN5A mutations.

Conclusions: The present study reports the first CAV3 mutations in subjects with LQTS, and we provide functional data demonstrating a gain-of-function increase in late sodium current.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Caveolin 3 / genetics*
  • Cell Line
  • DNA Mutational Analysis
  • Electric Conductivity
  • Electrocardiography
  • Electrophysiology
  • Female
  • Humans
  • Immunoprecipitation
  • Long QT Syndrome / diagnosis
  • Long QT Syndrome / genetics
  • Long QT Syndrome / metabolism
  • Long QT Syndrome / physiopathology*
  • Male
  • Molecular Sequence Data
  • Muscle Proteins / metabolism
  • Mutation*
  • Myocardium / metabolism
  • NAV1.5 Voltage-Gated Sodium Channel
  • Sodium Channels / metabolism*
  • Time Factors
  • Transfection

Substances

  • Caveolin 3
  • Muscle Proteins
  • NAV1.5 Voltage-Gated Sodium Channel
  • SCN5A protein, human
  • Sodium Channels