title: Myosin regulatory light chain (RLC) phosphorylation change as a modulator of cardiac muscle contraction in disease.
abstract: Understanding how cardiac myosin regulatory light chain (RLC) phosphorylation alters cardiac muscle mechanics is important because it is often altered in cardiac disease. The effect this protein phosphorylation has on muscle mechanics during a physiological range of shortening velocities, during which the heart generates power and performs work, has not been addressed. We have expressed and phosphorylated recombinant Rattus norvegicus left ventricular RLC. In vitro we have phosphorylated these recombinant species with cardiac myosin light chain kinase and zipper-interacting protein kinase. We compare rat permeabilized cardiac trabeculae, which have undergone exchange with differently phosphorylated RLC species. We were able to enrich trabecular RLC phosphorylation by 40% compared with controls and, in a separate series, lower RLC phosphorylation to 60% of control values. Compared with the trabeculae with a low level of RLC phosphorylation, RLC phosphorylation enrichment increased isometric force by more than 3-fold and peak power output by more than 7-fold and approximately doubled both maximum shortening speed and the shortening velocity that generated peak power. We augmented these measurements by observing increased RLC phosphorylation of human and rat HF samples from endocardial left ventricular homogenate. These results demonstrate the importance of increased RLC phosphorylation in the up-regulation of myocardial performance and suggest that reduced RLC phosphorylation is a key aspect of impaired contractile function in the diseased myocardium.
authors.affiliation: Molecular Medicine Section, National Heart and Lung Institute, Imperial College London, London SW7 2AZ, UK.
authors.forename: Christopher
authors.initials: C
authors.lastname: Toepfer
authors.forename: Valentina
authors.initials: V
authors.lastname: Caorsi
authors.forename: Thomas
authors.initials: T
authors.lastname: Kampourakis
authors.forename: Markus B
authors.initials: MB
authors.lastname: Sikkel
authors.forename: Timothy G
authors.initials: TG
authors.lastname: West
authors.forename: Man-Ching
authors.initials: MC
authors.lastname: Leung
authors.forename: Sara A
authors.initials: SA
authors.lastname: Al-Saud
authors.forename: Kenneth T
authors.initials: KT
authors.lastname: MacLeod
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Lyon
authors.forename: Steven B
authors.initials: SB
authors.lastname: Marston
authors.forename: James R
authors.initials: JR
authors.lastname: Sellers
authors.forename: Michael A
authors.initials: MA
authors.lastname: Ferenczi
mesh_terms: D000818:Animals; D006333:Heart Failure / Q000378:metabolism; D006352:Heart Ventricles / Q000473:pathology; D006801:Humans; D008297:Male; D009200:Myocardial Contraction; D009203:Myocardial Infarction / Q000378:metabolism* / Q000503:physiopathology; D009210:Myofibrils / Q000378:metabolism; D018994:Myosin Light Chains / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley; D034421:Sus scrofa
chemical_list: D018994:Myosin Light Chains
keywords: Cardiac Muscle; Muscle; Myosin; Phosphorylation; Physiology