title: Perturbed length-dependent activation in human hypertrophic cardiomyopathy with missense sarcomeric gene mutations.
abstract: BACKGROUND
  High-myofilament Ca(2+) sensitivity has been proposed as a trigger of disease pathogenesis in familial hypertrophic cardiomyopathy (HCM) on the basis of in vitro and transgenic mice studies. However, myofilament Ca(2+) sensitivity depends on protein phosphorylation and muscle length, and at present, data in humans are scarce.
  
  
  OBJECTIVE
  To investigate whether high myofilament Ca(2+) sensitivity and perturbed length-dependent activation are characteristics for human HCM with mutations in thick and thin filament proteins.
  
  
  RESULTS
  Cardiac samples from patients with HCM harboring mutations in genes encoding thick (MYH7, MYBPC3) and thin (TNNT2, TNNI3, TPM1) filament proteins were compared with sarcomere mutation-negative HCM and nonfailing donors. Cardiomyocyte force measurements showed higher myofilament Ca(2+) sensitivity in all HCM samples and low phosphorylation of protein kinase A (PKA) targets compared with donors. After exogenous PKA treatment, myofilament Ca(2+) sensitivity was similar (MYBPC3mut, TPM1mut, sarcomere mutation-negative HCM), higher (MYH7mut, TNNT2mut), or even significantly lower (TNNI3mut) compared with donors. Length-dependent activation was significantly smaller in all HCM than in donor samples. PKA treatment increased phosphorylation of PKA-targets in HCM myocardium and normalized length-dependent activation to donor values in sarcomere mutation-negative HCM and HCM with truncating MYBPC3 mutations but not in HCM with missense mutations. Replacement of mutant by wild-type troponin in TNNT2mut and TNNI3mut corrected length-dependent activation to donor values.
  
  
  CONCLUSIONS
  High-myofilament Ca(2+) sensitivity is a common characteristic of human HCM and partly reflects hypophosphorylation of PKA targets compared with donors. Length-dependent sarcomere activation is perturbed by missense mutations, possibly via posttranslational modifications other than PKA hypophosphorylation or altered protein-protein interactions, and represents a common pathomechanism in HCM.
authors.affiliation: Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, the Netherlands. v.sequeiraoliveira@vumc.nl
authors.forename: Vasco
authors.initials: V
authors.lastname: Sequeira
authors.forename: Paul J M
authors.initials: PJ
authors.lastname: Wijnker
authors.forename: Louise L A M
authors.initials: LL
authors.lastname: Nijenkamp
authors.forename: Diederik W D
authors.initials: DW
authors.lastname: Kuster
authors.forename: Aref
authors.initials: A
authors.lastname: Najafi
authors.forename: E Rosalie
authors.initials: ER
authors.lastname: Witjas-Paalberends
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Regan
authors.forename: Nicky
authors.initials: N
authors.lastname: Boontje
authors.forename: Folkert J
authors.initials: FJ
authors.lastname: Ten Cate
authors.forename: Tjeerd
authors.initials: T
authors.lastname: Germans
authors.forename: Lucie
authors.initials: L
authors.lastname: Carrier
authors.forename: Sakthivel
authors.initials: S
authors.lastname: Sadayappan
authors.forename: Marjon A
authors.initials: MA
authors.lastname: van Slegtenhorst
authors.forename: Ruud
authors.initials: R
authors.lastname: Zaremba
authors.forename: D Brian
authors.initials: DB
authors.lastname: Foster
authors.forename: Anne M
authors.initials: AM
authors.lastname: Murphy
authors.forename: Corrado
authors.initials: C
authors.lastname: Poggesi
authors.forename: Cris
authors.initials: C
authors.lastname: Dos Remedios
authors.forename: Ger J M
authors.initials: GJ
authors.lastname: Stienen
authors.forename: Carolyn Y
authors.initials: CY
authors.lastname: Ho
authors.forename: Michelle
authors.initials: M
authors.lastname: Michels
authors.forename: Jolanda
authors.initials: J
authors.lastname: van der Velden
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D002118:Calcium / Q000378:metabolism; D024722:Cardiac Myosins / Q000235:genetics; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics* / Q000473:pathology* / Q000503:physiopathology; D002352:Carrier Proteins / Q000235:genetics; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D020930:MAP Kinase Kinase Kinases / Q000235:genetics; D008297:Male; D051379:Mice; D008875:Middle Aged; D020125:Mutation, Missense; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D009210:Myofibrils / Q000473:pathology* / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000235:genetics; D010766:Phosphorylation / Q000502:physiology; D017346:Protein Serine-Threonine Kinases; D012518:Sarcomeres / Q000473:pathology* / Q000502:physiology*; D014335:Tropomyosin / Q000235:genetics; D020107:Troponin T / Q000235:genetics; D055815:Young Adult; D000099163:Myosin Binding Protein C
chemical_list: D002118:Calcium; D024722:Cardiac Myosins; D002352:Carrier Proteins; D017868:Cyclic AMP-Dependent Protein Kinases; D020930:MAP Kinase Kinase Kinases; D018995:Myosin Heavy Chains; D017346:Protein Serine-Threonine Kinases; D014335:Tropomyosin; D020107:Troponin T; D000099163:Myosin Binding Protein C; C501641:MYH7 protein, human; C545568:TNNT2 protein, human; C490775:TPM1 protein, human; C481078:TNNI3K protein, human
keywords: calcium; cardiomyopathy; contractility; hypertrophy; myocardium