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Long QT‐syndrome Associated Caveolin‐3 Mutations F97C and S141R Alter the Cardiac Transient Outward Kv Current and the L‐type Ca 2+ Currents
Author(s) -
Balijepalli Ravi,
Tyan Leonid,
Keefe Alexis,
Foell Jason D,
Kamp Timothy J
Publication year - 2016
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.30.1_supplement.lb605
Subject(s) - caveolae , myocyte , caveolin 3 , patch clamp , hek 293 cells , western blot , caveolin , transfection , electrophysiology , cardiac transient outward potassium current , long qt syndrome , medicine , ion channel , chemistry , microbiology and biotechnology , endocrinology , sodium channel , immunoprecipitation , cardiac action potential , biology , signal transduction , gene , sodium , qt interval , biochemistry , receptor , organic chemistry , repolarization
Caveolae are discrete microdomains in cardiomyocytes that localize many ion channels and signaling proteins. Mutations in the CAV3 gene, encoding caveolin‐3 (Cav‐3), a muscle specific scaffolding protein integral to caveolae in the cardiomyocytes, have been associated with a congenital Long QT syndrome (LQTS9). Previously we have shown that the LQTS associated Cav‐3 mutations, F97C and S141R; increase late sodium channel current in cardiomyocytes contributing to the prolonged action potential duration (APD), but co‐immunoprecipitation using lysates from mouse ventricular myocytes and western blot analysis revealed that Kv4.2, Kv4.3 and Ca v 1.2 channels also co‐IP with Cav‐3. Thus we evaluated whether disease the LQT associated mutations impacted heterologously expressed Kv4.2, Kv4.3, and Cav1.2 channels in HEK293 cells using whole cell patch clamp electrophysiology. Co‐expression of F97C (40.7 ± 5.9 pA/pF) or S141R (58.8 ± 7.7 pA/pF) significantly (p<0.001) reduced the peak I Kv4.2 densities compared to cells co‐expressing either Cav‐3 WT (80 ± 9.1 pA/pF) or pcDNA3.1 (88.6 ± 12.7 pA/pF). The co‐expression of F97C significantly reduced I Kv4.3 (213.8 ± 35 pA/pF) compared to Cav‐3 WT (336.7 ± 48.2 pA/pF). F97C also caused a reduction in the activation time constants of I kv4.2 and I kv4.3 , but did not impact the inactivation. Co‐expression of F97C and S141R significantly (p<0.05) slowed the recovery from inactivation of Kv4.2. On the other hand, co‐expression of S141R significantly increased the peak I Ca,L (‐14.8 ± 2.5 pA/pF, p<0.05) compared to Cav‐3 WT (−9.5 ± 2.4 pA/pF). Co‐expression of F97C (−7.6 ± 1.2 pA/pF) did not alter the peak I Ca,L density but significantly slowed the calcium dependent inactivation (CDI) of the I Ca,L . We conclude that the LQTS linked Cav‐3 mutations F97C and S141R, impart loss‐of‐function effects on I to but cause a gain‐of function effect on the I Ca,L and together these may contribute to the delay in ventricular repolarization and arrhythmogenesis in a setting of LQTS. Support or Funding Information R01 HL078878