Biophysical Society Thematic Meeting | Canterbury 2023

Towards a More Perfect Union: Multi-Scale Models of Muscle and Their Experimental Validation

Poster Abstracts

20-POS Board 20 ASSESSING THE IMPACT OF HYPERTROPHIC CARDIOMYOPATHY ASSOCIATED MISSENSE VARIANTS ON ALPHA-ACTININ 2 STRUCTURE/FUNCTION Maya Noureddine 1 ; Fiyaz Mohammed 2 ; Katja Gehmlich 1 ; 1 University of Birmingham, Institute of Cardiovascular Sciences, Birmingham, United Kingdom 2 University of Birmingham, Institute of Immunology and Immunotherapy, Birmingham, United Kingdom Alpha-actinin 2 (ACTN2) is a key protein at the Z-disk of the sarcomere. It is critical for stabilizing the contractile muscle apparatus and organizing the thin actin filaments. ACTN2 encompasses several structural domains, including an N-terminal actin-binding domain, a flexible neck region, a central rod domain of spectrin repeats, and two C-terminal EF-hand motifs. The functionally relevant ACTN2 dimer predominantly assembles via the central rod domain. Stabilization of the ACTN2 dimer interface also involves key residues in the neck region and EF34-hand motif. Genetic missense variants in ACNT2 are associated with inherited cardiac conditions, cardiomyopathies. In particular, they can cause hypertrophic cardiomyopathy (HCM), a genetic disease characterized by sudden cardiac death, left ventricular hypertrophy and diastolic dysfunction, but disease mechanisms are only poorly understood. Therefore, defining the molecular mechanisms by which ACTN2 variants lead to HCM may help to develop targeted therapeutic approaches. Herein, we examine the impact of 20 HCM-causing variants, identified from the human gene mutation database, on the ACTN2 structure/function using various modelling software packages, including I-TASSER, Phyre2, and AlphaFold2. We demonstrate that HCM-linked variants are distributed across most ACTN2 structural modules, except for the neck region. Based on structural predictions, two variants are predicted to destabilize the dimer interface. In addition, we identified different variants which could adversely impact the structural integrity of specific ACTN2 domains. Finally, we assessed which of the HCM-associated variants could impact ACTN2 ligand binding to actin, PIP2, titin, and CamKII. Collectively, this study suggests diverse molecular mechanisms by which individual genetic variants could adversely impact ACNT2 structure/function, leading to cardiomyopathies. It formulates hypotheses to be tested by wet-lab experiments, and may thereby be the first step towards the development of novel therapeutic strategies.

85