title: Selective phosphorylation of PKA targets after β-adrenergic receptor stimulation impairs myofilament function in Mybpc3-targeted HCM mouse model.
abstract: OBJECTIVE
  Hypertrophic cardiomyopathy (HCM) has been associated with reduced β-adrenergic receptor (β-AR) signalling, leading downstream to a low protein kinase A (PKA)-mediated phosphorylation. It remained undefined whether all PKA targets will be affected similarly by diminished β-AR signalling in HCM. We aimed to investigate the role of β-AR signalling on regulating myofilament and calcium handling in an HCM mouse model harbouring a gene mutation (G > A transition on the last nucleotide of exon 6) in Mybpc3 encoding cardiac myosin-binding protein C.
  
  
  RESULTS
  Cardiomyocyte contractile properties and phosphorylation state were measured in left ventricular permeabilized and intact cardiomyocytes isolated from heterozygous (HET) or homozygous (KI) Mybpc3-targeted knock-in mice. Significantly higher myofilament Ca²⁺sensitivity and passive tension were detected in KI mice, which were normalized after PKA treatment. Loaded intact cardiomyocyte force-sarcomere length relation was impaired in both HET and KI mice, suggesting a reduced length-dependent activation. Unloaded cardiomyocyte function revealed an impaired myofilament contractile response to isoprenaline (ISO) in KI, whereas the calcium-handling response to ISO was maintained. This disparity was explained by an attenuated increase in cardiac troponin I (cTnI) phosphorylation in KI, whereas the increase in phospholamban (PLN) phosphorylation was maintained to wild-type values.
  
  
  CONCLUSIONS
  These data provide evidence that in the KI HCM mouse model, β-AR stimulation leads to preferential PKA phosphorylation of PLN over cTnI, resulting in an impaired inotropic and lusitropic response.
authors.affiliation: Department of Physiology, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center Amsterdam, Netherlands ICIN-Netherlands Heart Institute, Utrecht, The Netherlands a.najafi@vumc.nl.
authors.forename: Aref
authors.initials: A
authors.lastname: Najafi
authors.affiliation: Department of Physiology, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center Amsterdam, Netherlands.
authors.forename: Vasco
authors.initials: V
authors.lastname: Sequeira
authors.affiliation: Department of Physiology, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center Amsterdam, Netherlands.
authors.forename: Michiel
authors.initials: M
authors.lastname: Helmes
authors.affiliation: Department of Physiology, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center Amsterdam, Netherlands.
authors.forename: Ilse A E
authors.initials: IA
authors.lastname: Bollen
authors.affiliation: Department of Physiology, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center Amsterdam, Netherlands.
authors.forename: Max
authors.initials: M
authors.lastname: Goebel
authors.affiliation: Department of Physiology, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center Amsterdam, Netherlands.
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Regan
authors.affiliation: Institute of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany DZHK (German Centre for Cardiovascular Research), Partner Site Hamburg/Kiel/Lübeck, Germany.
authors.forename: Lucie
authors.initials: L
authors.lastname: Carrier
authors.affiliation: Department of Physiology, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center Amsterdam, Netherlands.
authors.forename: Diederik W D
authors.initials: DW
authors.lastname: Kuster
authors.affiliation: Department of Physiology, Institute for Cardiovascular Research (ICaR-VU), VU University Medical Center Amsterdam, Netherlands ICIN-Netherlands Heart Institute, Utrecht, The Netherlands.
authors.forename: Jolanda
authors.initials: J
authors.lastname: Van Der Velden
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002312:Cardiomyopathy, Hypertrophic / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D009200:Myocardial Contraction / Q000235:genetics* / Q000502:physiology; D009206:Myocardium / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D009210:Myofibrils / Q000378:metabolism; D010766:Phosphorylation; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D012518:Sarcomeres / Q000378:metabolism; D000099211:Phospholamban; D000099163:Myosin Binding Protein C
chemical_list: D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; D007545:Isoproterenol; D011943:Receptors, Adrenergic, beta; D000099211:Phospholamban; D000099163:Myosin Binding Protein C
keywords: Calcium handling; Contractility; Hypertrophic cardiomyopathy; β-adrenergic signalling