title: Hypercontractile mutant of ventricular myosin essential light chain leads to disruption of sarcomeric structure and function and results in restrictive cardiomyopathy in mice.
abstract: OBJECTIVE
  The E143K (Glu → Lys) mutation in the myosin essential light chain has been associated with restrictive cardiomyopathy (RCM) in humans, but the mechanisms that underlie the development of defective cardiac function are unknown. Using transgenic E143K-RCM mice, we sought to determine the molecular and cellular triggers of E143K-induced heart remodelling.
  
  
  RESULTS
  The E143K-induced abnormalities in cardiac function and morphology observed by echocardiography and invasive haemodynamics were paralleled by augmented active and passive tension measured in skinned papillary muscle fibres compared with wild-type (WT)-generated force. In vitro, E143K-myosin had increased duty ratio and binding affinity to actin compared with WT-myosin, increased actin-activated ATPase activity and slower rates of ATP-dependent dissociation of the acto-myosin complex, indicating an E143K-induced myosin hypercontractility. E143K was also observed to reduce the level of myosin regulatory light chain phosphorylation while that of troponin-I remained unchanged. Small-angle X-ray diffraction data showed a decrease in the filament lattice spacing (d1,0) with no changes in the equatorial reflections intensity ratios (I1,1/I1,0) in E143K vs. WT skinned papillary muscles. The hearts of mutant-mice demonstrated ultrastructural defects and fibrosis that progressively worsened in senescent animals and these changes were hypothesized to contribute to diastolic disturbance and to mild systolic dysfunction. Gene expression profiles of E143K-hearts supported the histopathology results and showed an upregulation of stress-response and collagen genes. Finally, proteomic analysis evidenced RCM-dependent metabolic adaptations and higher energy demands in E143K vs. WT hearts.
  
  
  CONCLUSIONS
  As a result of the E143K-induced myosin hypercontractility, the hearts of RCM mice model exhibited cardiac dysfunction, stiff ventricles and physiological, morphologic, and metabolic remodelling consistent with the development of RCM. Future efforts should be directed toward normalization of myosin motor function and the use of myosin-specific therapeutics to avert the hypercontractile state of E143K-myosin and prevent pathological cardiac remodelling.
authors.affiliation: Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Chen-Ching
authors.initials: CC
authors.lastname: Yuan
authors.affiliation: Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Kazmierczak
authors.affiliation: Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Jingsheng
authors.initials: J
authors.lastname: Liang
authors.affiliation: Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Rosemeire
authors.initials: R
authors.lastname: Kanashiro-Takeuchi
authors.affiliation: Illinois Institute of Technology, Chicago, IL 60616, USA.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Irving
authors.affiliation: Department of Neurobiology, Physiology and Behavior, University of California, Davis, CA 95616, USA.
authors.forename: Aldrin V
authors.initials: AV
authors.lastname: Gomes
authors.affiliation: Department of Biochemistry and Molecular Biology, Mayo Clinic Rochester, Rochester, MN 55905, USA.
authors.forename: Yihua
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Biochemistry and Molecular Biology, Mayo Clinic Rochester, Rochester, MN 55905, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Burghardt
authors.affiliation: Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
authors.forename: Danuta
authors.initials: D
authors.lastname: Szczesna-Cordary
mesh_terms: D000199:Actins / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002313:Cardiomyopathy, Restrictive / Q000235:genetics* / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D003094:Collagen / Q000378:metabolism; D004195:Disease Models, Animal; D004734:Energy Metabolism; D005260:Female; D005355:Fibrosis; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008822:Mice, Transgenic; D009154:Mutation; D009200:Myocardial Contraction / Q000235:genetics*; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D018994:Myosin Light Chains / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation; D012518:Sarcomeres / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D016277:Ventricular Function, Left / Q000235:genetics*; D024723:Ventricular Myosins / Q000235:genetics* / Q000378:metabolism; D020257:Ventricular Remodeling / Q000235:genetics*
chemical_list: D000199:Actins; D018994:Myosin Light Chains; D000255:Adenosine Triphosphate; D003094:Collagen; D024723:Ventricular Myosins
keywords: Cardiac myosin essential light chain; Diastolic and systolic dysfunction; Hypercontractility; Myosin step size; Proteomics