Ankyrin-B: proteostasis and impact on cardiomyocyte behaviours in H9c2 cells




Chen, Lena

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Ankyrin-B (Ank-B) is a crucial scaffolding protein regulating expression and localization of contractile machinery in the cardiac muscle. Recent genetic investigations in the First Nations Community, the Gitxsan of Northern BC, identified a mutation in Ank-B (p.S646F c.1937 C>T) associated with a cardiac arrhythmia, Long QT Syndrome Type 4 (LQTS4). Distinct from other LQTS4 subtypes, individuals harbouring the p.S646F variant exhibit development deficits including cardiomyopathies and accessory electrical pathways. How p.S646F interferes with the development of the heart is unknown due to a fundamental lack of understanding regarding Ank-B proteostasis and its role in cardiac differentiation. Initial in silico analyses predicted the p.S646F mutant to be deleterious to the Ank-B protein. Using in vitro techniques, I determined p.S646F mutant reduced levels of Ank-B in H9c2 rat ventricular cardiomyoblasts. Furthermore, haploinsufficiency in mice was previously shown to result in developmental cardiac deficits. I, therefore, hypothesized that p.S646F interferes with Ank-B proteostasis, thereby affecting cardiomyocyte development. I showed that p.S646F destabilized Ank-B in cardiomyoblasts, due to increased degradation via the proteasome. Furthermore, overexpression of p.S646F Ank-B had a significant impact on cellular behaviour including reduced cell viability, and altered expression of cellular differentiation markers. Together these data address critical knowledge gaps with regards to Ank-B protein homeostasis and the role of Ank-B in cardiomyocyte viability and development. These findings inform the diagnosis and treatment of patients with the p.S646F variant, creating potential targeted pathways of intervention, and furthering our understanding of the role of the Ank-B in the development of the heart.



Ankyrin-B, Proteostasis, Development, Cardiomyocyte, Long QT