Abstract 363: The Glycerol-3-Phosphate Dehydrogenase 1-Like (GPD1-L) Brugada Syndrome Gene Modulates Na+ Current in Myocytes
Introduction: Brugada Syndrome is a rare, autosomal dominant condition leading to arrhythmias and sudden death. Recently, we identified a mutation (A280V) in GPD1-L in a large Brugada syndrome family. In HEK-293 cells, A280V disrupted trafficking of both GPD1-L and the cardiac Na+ channel (SCN5A) to the cell membrane and led to an ∼50% decrease in Na+ current (INa). Here, we tested the hypothesis that A280V would alter membrane trafficking and reduce INa in cardiac myocytes.
Methods: To assess GPD1-L trafficking, ventricular myocytes isolated from 1-day-old rats were transfected with either wild type (WT) or A280V GPD1-L-GFP (Green Fluorescence Protein) fusion protein and imaged by confocal light microscopy; membrane fluorescence was quantitated. For electrophysiology, myocytes were co-infected with adeno-associated virus (AAV9) containing either WT or A280V GPD1-L and AAV6 containing GFP driven by a troponin promoter. INa was recorded 48 hours later by whole-cell voltage clamp.
Results: Membrane fluorescence was decreased by 65% in myocytes transfected with A280V (n=7) vs. WT GPD1-L-GFP (n=9, p<0.01; Fig. 1A⇓). Peak INa was decreased by up to 47% in myocytes infected with A280V vs. WT GPD1-L (at 0 mV, −266 to −142 pA/pF, p =0.03; Fig. 1B⇓).
Conclusion: The A280V mutation alters GPD1-L membrane trafficking and decreases INa in cardiac myocytes, similar to its effect in HEK-293 cells. These results support the hypothesis that GPD1-L mutations cause Brugada syndrome by modulating Na+ channel trafficking in the heart.