Cofilin-2 Phosphorylation and Sequestration in Myocardial Aggregates

• Published in: Journal of the American College of Cardiology 2015-03, Vol.65 (12), p.1199-1214
• Main Authors: Subramanian, Khaushik, BS, Gianni, Davide, PhD, Balla, Cristina, MD, PhD, Assenza, Gabriele Egidy, MD, Joshi, Mugdha, BS, Semigran, Marc J., MD, Macgillivray, Thomas E., MD, Van Eyk, Jennifer E., PhD, Agnetti, Giulio, PhD, Paolocci, Nazareno, MD, PhD, Bamburg, James R., PhD, Agrawal, Pankaj B., MD, del Monte, Federica, MD, PhD
• Format: Article
• Language: English
• Subjects: adenovirus; Cardiology; Cardiomyocytes; Cardiomyopathy; Cardiovascular; Heart; heart failure; Internal Medicine; nemaline; Pathogenesis; Phosphorylation; Proteins; Rodents
• ISSN: 0735-1097; 1558-3597
• DOI: 10.1016/j.jacc.2015.01.031

Abstract Background Recently, tangles and plaque-like aggregates have been identified in certain cases of dilated cardiomyopathy (DCM), traditionally labeled idiopathic (iDCM), where there is no specific diagnostic test or targeted therapy. This suggests a potential underlying cause for some of the iDCM cases. Objectives This study sought to identify the make-up of myocardial aggregates to understand the molecular mechanisms of these cases of DCM; this strategy has been central to understanding Alzheimer’s disease. Methods Aggregates were extracted from human iDCM samples with high congophilic reactivity (an indication of plaque presence), and the findings were validated in a larger cohort of samples. We tested the expression, distribution, and activity of cofilin in human tissue and generated a cardiac-specific knockout mouse model to investigate the functional impact of the human findings. We also modeled cofilin inactivity in vitro by using pharmacological and genetic gain- and loss-of-function approaches. Results Aggregates in human myocardium were enriched for cofilin-2, an actin-depolymerizing protein known to participate in neurodegenerative diseases and nemaline myopathy. Cofilin-2 was predominantly phosphorylated, rendering it inactive. Cardiac-specific haploinsufficiency of cofilin-2 in mice recapitulated the human disease’s morphological, functional, and structural phenotype. Pharmacological stimulation of cofilin-2 phosphorylation and genetic overexpression of the phosphomimetic protein promoted the accumulation of “stress-like” fibers and severely impaired cardiomyocyte contractility. Conclusions Our study provides the first biochemical characterization of prefibrillar myocardial aggregates in humans and the first report to link cofilin-2 to cardiomyopathy. The findings suggest a common pathogenetic mechanism connecting certain iDCMs and other chronic degenerative diseases, laying the groundwork for new therapeutic strategies.