TMEM43 Mutation p.S358L Alters Intercalated Disc Protein Expression and Reduces Conduction Velocity in Arrhythmogenic Right Ventricular Cardiomyopathy

Abstract

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a myocardial disease characterized by fibro-fatty replacement of myocardium in the right ventricular free wall and frequently results in life-threatening ventricular arrhythmias and sudden cardiac death. A heterozygous missense mutation in the transmembrane protein 43 (TMEM43) gene, p.S358L, has been genetically identified to cause autosomal dominant ARVC type 5 in a founder population from the island of Newfoundland, Canada. Little is known about the function of the TMEM43 protein or how it leads to the pathogenesis of ARVC. We sought to determine the distribution of TMEM43 and the effect of the p.S358L mutation on the expression and distribution of various intercalated (IC) disc proteins as well as functional effects on IC disc gap junction dye transfer and conduction velocity in cell culture. Through Western blot analysis, transmission electron microscopy (TEM), immunofluorescence (IF), and electrophysiological analysis, our results showed that the stable expression of p.S358L mutation in the HL-1 cardiac cell line resulted in decreased Zonula Occludens (ZO-1) expression and the loss of ZO-1 localization to cell-cell junctions. Junctional Plakoglobin (JUP) and α-catenin proteins were redistributed to the cytoplasm with decreased localization to cell-cell junctions. Connexin-43 (Cx43) phosphorylation was altered, and there was reduced gap junction dye transfer and conduction velocity in mutant TMEM43-transfected cells. These observations suggest that expression of the p.S358L mutant of TMEM43 found in ARVC type 5 may affect localization of proteins involved in conduction, alter gap junction function and reduce conduction velocity in cardiac tissue.

Pathogenesis of Arrhythmogenic Cardiomyopathy

“…This finding has been confirmed in independent studies and has been seen in association with mutations in all of the desmosomal genes as well as in patients who fulfill diagnostic criteria for ACM but in whom no desmosomal mutation can be detected. 43, 44 Reduced plakoglobin signal at intercalated disks has also been reported in ACM patients from Newfoundland bearing the S358L mutation in TMEM43 45 and ACM patients from the Netherlands bearing the R14del mutation in PLN (but not in patients with the same PLN mutation but who present with a DCM phenotype). 31 Thus, reduced junctional signal for plakoglobin appears to track with the disease phenotype.…”

Genome wide association analysis in dilated cardiomyopathy reveals two new key players in systolic heart failure on chromosome 3p25.1 and 22q11.23

“…Moreover, XPC (p = 8.3 10 -15 ) and SLC6A6 (p = 6.9 10 -6 ) LV expressions were significantly increased in DCM patients compared to healthy donors ( Supplementary Table 7A) while LSM3 expression was significantly decreased (p = 7.6 10 -8 ). Functional candidate at this locus may include TMEM43, implied in arrhythmogenic right ventricular cardiomyopathy (ARVC) (39)(40)(41), and SLC6A6, for which a homozygous deletion affecting a splice site was found by whole-exome sequencing in a patient with idiopathic DCM (42).…”

Arrhythmogenic Right Ventricular Cardiomyopathy: From Pathophysiology to Diagnosis and Advances in Management

“…23 Murine cell studies have shown that the S358L missense mutation alters the localisation of intercalated disc proteins, changes gap junction function and reduces conduction velocity. 41 However, the mechanism by which this pathogenic variant causes ARVC is poorly understood at present.…”