Abstract 737: A Mutation in the Brugada Syndrome Gene Glycerol-3 Phosphate Dehydrogenase-1 Like Gene (GPD1-L) Disrupts Trafficking
Brugada syndrome is a life threatening autosomal dominant disorder characterized by ST segment elevation in the right precordial leads of the surface ECG. Mutations of the cardiac sodium (Na+) channel SCN5A cause ~20% of Brugada syndrome cases; most mutations decrease inward Na+ current, some by affecting SCN5A trafficking. Recently, we identified a novel Brugada syndrome gene (glycerol-3 phosphate dehydrogenase-1 like, GPD1-L) in a large family, with an A280V mutation present in all affected individuals but absent in 200 unaffected controls of mixed racial background. This mutation reduced Na+ current by 61% (p=0.01) without affecting channel gating when expressed in HEK cells stably or transiently expressing SCN5A. We therefore hypothesized that GPD1-L may either directly or indirectly modulate SCN5A trafficking. We engineered GPD1-L-GFP fusion constructs for sub-cellular localization by confocal microscopy. Wild type (WT) GPD1-L-GFP localized at the surface of COS-7 cells but A280V GPD1-L-GFP did not (Fig.1 A, B⇓). Direct staining of the HEK cells transfected with WT and A280V GPD1-L confirmed these results (Fig.1 C, D⇓). Co-immunoprecipitation of protein preparations from
GPD1-L transfected HEK cells stably expressing SCN5A and
mouse heart did not show direct interactions between GPD1-L and SCN5A.
However, surface membrane expression of SCN5A was decreased in HEK cells co-transfected with SCN5A and A280V GPD1-L as compared to WT GPD1-L (5.9% vs. 13%, p<0.02, n=7), despite no differences in total SCN5A expression. Thus, the A280V GPD1-L mutation affects membrane localization of GPD1-L and decreases surface expression of SCN5A, which leads to Brugada syndrome.