Hypertrophic cardiomyopathy mutations increase myofilament Ca 2+ buffering, alter intracellular Ca 2+ handling, and stimulate Ca 2+ -dependent signaling.

Autor: Robinson P; From the Cardiovascular Medicine Division, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, United Kingdom paulr@well.ox.ac.uk., Liu X; From the Cardiovascular Medicine Division, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, United Kingdom., Sparrow A; From the Cardiovascular Medicine Division, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, United Kingdom., Patel S; From the Cardiovascular Medicine Division, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, United Kingdom., Zhang YH; From the Cardiovascular Medicine Division, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, United Kingdom., Casadei B; From the Cardiovascular Medicine Division, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, United Kingdom., Watkins H; From the Cardiovascular Medicine Division, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, United Kingdom., Redwood C; From the Cardiovascular Medicine Division, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 9DU, United Kingdom.
Jazyk: angličtina
Zdroj: The Journal of biological chemistry [J Biol Chem] 2018 Jul 06; Vol. 293 (27), pp. 10487-10499. Date of Electronic Publication: 2018 May 14.
DOI: 10.1074/jbc.RA118.002081
Abstrakt: Mutations in thin filament regulatory proteins that cause hypertrophic cardiomyopathy (HCM) increase myofilament Ca 2+ sensitivity. Mouse models exhibit increased Ca 2+ buffering and arrhythmias, and we hypothesized that these changes are primary effects of the mutations (independent of compensatory changes) and that increased Ca 2+ buffering and altered Ca 2+ handling contribute to HCM pathogenesis via activation of Ca 2+ -dependent signaling. Here, we determined the primary effects of HCM mutations on intracellular Ca 2+ handling and Ca 2+ -dependent signaling in a model system possessing Ca 2+ -handling mechanisms and contractile protein isoforms closely mirroring the human environment in the absence of potentially confounding remodeling. Using adenovirus, we expressed HCM-causing variants of human troponin-T, troponin-I, and α-tropomyosin (R92Q, R145G, and D175N, respectively) in isolated guinea pig left ventricular cardiomyocytes. After 48 h, each variant had localized to the I-band and comprised ∼50% of the total protein. HCM mutations significantly lowered the K d of Ca 2+ binding, resulting in higher Ca 2+ buffering of mutant cardiomyocytes. We observed increased diastolic [Ca 2+ ] and slowed Ca 2+ reuptake, coupled with a significant decrease in basal sarcomere length and slowed relaxation. HCM mutant cells had higher sodium/calcium exchanger activity, sarcoplasmic reticulum Ca 2+ load, and sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2) activity driven by Ca 2+ /calmodulin-dependent protein kinase II (CaMKII) phosphorylation of phospholamban. The ryanodine receptor (RyR) leak/load relationship was also increased, driven by CaMKII-mediated RyR phosphorylation. Altered Ca 2+ homeostasis also increased signaling via both calcineurin/NFAT and extracellular signal-regulated kinase pathways. Altered myofilament Ca 2+ buffering is the primary initiator of signaling cascades, indicating that directly targeting myofilament Ca 2+ sensitivity provides an attractive therapeutic approach in HCM.
(© 2018 Robinson et al.)
Databáze: MEDLINE
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