The hypertrophic cardiomyopathy-associated A331P actin variant enhances basal contractile activity and elicits resting muscle dysfunction
Matthew H. Doran,
Michael J. Rynkiewicz,
Evan Despond,
Meera C. Viswanathan,
Aditi Madan,
Kripa Chitre,
Axel J. Fenwick,
Duncan Sousa,
William Lehman,
John F. Dawson,
Anthony Cammarato
Affiliations
Matthew H. Doran
Department of Pharmacology, Physiology & Biophysics, Boston University Chobanian & Avedisian School of Medicine, 72 E. Concord St, Boston, MA 02118, USA
Michael J. Rynkiewicz
Department of Pharmacology, Physiology & Biophysics, Boston University Chobanian & Avedisian School of Medicine, 72 E. Concord St, Boston, MA 02118, USA
Evan Despond
Department Molecular and Cellular Biology, University of Guelph, 50 Stone Road E, Guelph, ON N1G 2W1, Canada
Meera C. Viswanathan
Department of Medicine, Division of Cardiology, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205, USA
Aditi Madan
Department of Medicine, Division of Cardiology, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205, USA
Kripa Chitre
Department of Medicine, Division of Cardiology, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205, USA
Axel J. Fenwick
Department of Medicine, Division of Cardiology, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205, USA
Duncan Sousa
Department of Biophysics, Johns Hopkins University, 725 N. Wolfe Street, Baltimore, MD 21205, USA
William Lehman
Department of Pharmacology, Physiology & Biophysics, Boston University Chobanian & Avedisian School of Medicine, 72 E. Concord St, Boston, MA 02118, USA
John F. Dawson
Department Molecular and Cellular Biology, University of Guelph, 50 Stone Road E, Guelph, ON N1G 2W1, Canada; Corresponding author
Anthony Cammarato
Department of Medicine, Division of Cardiology, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205, USA; Department of Physiology, Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA; Corresponding author
Summary: Previous studies aimed at defining the mechanistic basis of hypertrophic cardiomyopathy caused by A331P cardiac actin have reported conflicting results. The mutation is located along an actin surface strand, proximal to residues that interact with tropomyosin. These F-actin-tropomyosin associations are vital for proper contractile inhibition. To help resolve disease pathogenesis, we implemented a multidisciplinary approach. Transgenic Drosophila, expressing A331P actin, displayed skeletal muscle hypercontraction and elevated basal myocardial activity. A331P thin filaments, reconstituted using recombinant human cardiac actin, exhibited higher in vitro myosin-based sliding speeds, exclusively at low Ca2+ concentrations. Cryo-EM-based reconstructions revealed no detectable A331P-related structural perturbations in F-actin. In silico, however, the P331-containing actin surface strand was less mobile and established diminished van der Waal’s attractive forces with tropomyosin, which correlated with greater variability in inhibitory tropomyosin positioning. Such mutation-induced effects potentially elevate resting contractile activity among our models and may stimulate pathology in patients.
