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LITAF, A Novel Regulator of Cardiac Excitation
Author(s) -
MOSHAL KARNI S,
Roder Karim,
Werdich Andreas A,
Dural Nilufer Turan,
Kim Tae Yun,
Cooper Leroy L,
Lu Yi Chun,
Choi BumRak,
Terentyev Dmitry,
MacRae Calum,
Koren Gideon
Publication year - 2017
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.31.1_supplement.686.3
Subject(s) - ubiquitin ligase , hek 293 cells , ubiquitin , zebrafish , chemistry , gene knockdown , microbiology and biotechnology , ryanodine receptor , cancer research , calcium , biology , biochemistry , gene , organic chemistry
QT interval is a predictor of arrhythmia and sudden death. Genome‐wide association studies identified LITAF (lipopolysaccharide‐induced TNF factor) as one of the novel loci associated with a significant QT prolongation. Our goal is to investigate and understand the role of LITAF in regulating cardiac excitation. Methods Optical mapping was performed in zebrafish hearts and rabbit cardiomyocytes to determine the effect of LITAF on action potential duration (APD) and Ca 2+ transients. Effect of LITAF on cardiomyocyte Ca 2+ handling was determined by live cell confocal Ca 2+ imaging. To determine the effect of LITAF on cardiac L‐type calcium channel (LTCC) current (I Ca,L ), we use whole cell patch clamping. We use heterologous expression system to study the mechanism by which LITAF regulates expression of LTCC. Results We observed that LITAF loss‐of‐function in zebrafish increases the Ca 2+ transient amplitude. Overexpressed LITAF in rabbit cardiomyocytes (CM) downregulates LTCC, decreases Ca 2+ transients and calcium inward current through I Ca,L . In neonatal rabbit CM (NRbCM), overexpressed LITAF shortens APD, likely due to suppression of LTCC. The knockdown of LITAF in NRbCM prolongs the APD and causes an increase in spontaneous cytosolic Ca 2+ under isoproterenol. In HEK cells, overexpressed LITAF downregulates the total and surface pools of LTCC via increased Cava1c ubiquitination. A physical interaction between LITAF and the ubiquitin ligase NEDD4‐1 is required to increase Cava1c ubiquitination and its degradation in HEK cells. Conclusion We show that LITAF acts as molecular adaptor to link NEDD4‐1 ubiquitin ligases to the cardiac LTCC and control its membrane expression and function and thus cardiac excitation. Support or Funding Information NIH R01 Grant (4R01HL110791‐04) to GK