Membrin/GOSR2 is a novel NaV1.5-interacting protein modulating cardiac conduction

Abstract

Abstract Background Genome-wide association studies have associated a locus spanning GOSR2 with QRS- and QT-interval. GOSR2 encodes Membrin, a protein located at the cis-Golgi, which plays a role in protein trafficking. Altered trafficking of the cardiac sodium channel (NaV1.5), encoded by SCN5A, has been shown to reduce cardiac conduction. Purpose To explore the modulatory role of Membrin on cardiac conduction and sodium channel availability. Methods and results Tandem Affinity Purification in H10 cells (derived from neonatal rat cardiomyocytes) overexpressing the NaV1.5 C-terminus identified Membrin as a putative interactor of NaV1.5. We subsequently confirmed the interaction between NaV1.5 and Membrin by means of a co-immunoprecipitation assay in HEK293A cells that overexpress NaV1.5 and Membrin. To investigate whether Membrin affects cardiac conduction we recorded optical action potentials from the left ventricle (LV) of Langendorff-perfused hearts from Gosr2+/− mice and wild type (WT) littermate controls. Conduction velocity was measured at steady state pacing (cycle length 120ms) and at the minimal possible cycle length (S2min), during S1S2 pacing. Longitudinal conduction velocity was increased in Gosr2+/− mice compared to WT at steady state- (76.44 vs. 67.00 cm/s) as well as at S2min (62.00 vs. 51.86 cm/s, p=0.039, n=10 and 9, resp.). Single cell patch-clamp studies revealed a shortened action potential duration at 90% repolarization at all pacing frequencies (390 vs 342 V/s at 2Hz, p=0.036) in isolated mid-LV cardiomyocytes of Gosr2+/− mice compared to WT. In addition, the maximal upstroke velocity was increased in Gosr2+/− mid-LV cardiomyocytes at frequencies of 6Hz and higher (390 vs 342 V/s at 6Hz, p=0.044). Conclusion Our findings identify Membrin as a novel interacting protein of NaV1.5 and a modulator of cardiac conduction. We propose that Membrin acts through ion channel trafficking or by modulating the posttranslational maturation of ion channels. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Leducq foundation