The spatial distribution of thin filament activation influences force development and myosin activity in computational models of muscle contraction

Diastolic dysfunction is general to all idiopathic dilated (IDCM) and hypertrophic cardiomyopathy (HCM) patients. Relaxation deficits may result from increased actin–myosin formation during diastole due to altered tropomyosin position, which blocks myosin binding to actin in the absence of Ca2+. We investigated whether ADP-stimulated force development (without Ca2+) can be used to reveal changes in actin–myosin blockade in human cardiomyopathy cardiomyocytes. Cardiac samples from HCM patients, harboring thick-filament (MYH7mut, MYBPC3mut) and thin-filament (TNNT2mut, TNNI3mut) mutations, and IDCM were compared with sarcomere mutation-negative HCM (HCMsmn) and nonfailing donors. Myofilament ADP sensitivity was higher in IDCM and HCM compared with donors, whereas it was lower for MYBPC3. Increased ADP sensitivity in IDCM, HCMsmn, and MYH7mut was caused by low phosphorylation of myofilament proteins, as it was normalized to donors by protein kinase A (PKA) treatment. Troponin exchange experiments in a TNNT2mut sample corrected the abnormal actin–myosin blockade. In MYBPC3trunc samples, ADP sensitivity highly correlated with cardiac myosin-binding protein-C (cMyBP-C) protein level. Incubation of cardiomyocytes with cMyBP-C antibody against the actin-binding N-terminal region reduced ADP sensitivity, indicative of cMyBP-C’s role in actin–myosin regulation. In the presence of Ca2+, ADP increased myofilament force development and sarcomere stiffness. Enhanced sarcomere stiffness in sarcomere mutation-positive HCM samples was irrespective of the phosphorylation background. In conclusion, ADP-stimulated contraction can be used as a tool to study how protein phosphorylation and mutant proteins alter accessibility of myosin binding on actin. In the presence of Ca2+, pathologic [ADP] and low PKA-phosphorylation, high actin–myosin formation could contribute to the impaired myocardial relaxation observed in cardiomyopathies.

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1P252 Structure Analysis of the Thin Filament Including Troponin by X-ray Diffraction(8. Muscle contraction and muscle protein,Poster Session,Abstract,Meeting Program of EABS & BSJ 2006)

Seibutsu Butsuri ◽

10.2142/biophys.46.s209_4 ◽

2006 ◽

Vol 46 (supplement2) ◽

pp. S209

Author(s):

Tatsuhito Matsuo ◽

Yutaka Ueno ◽

Yasunori Takezawa ◽

Katsuzo Wakabayashi

Keyword(s):

Muscle Contraction ◽

Structure Analysis ◽

Thin Filament ◽

Poster Session ◽

Muscle Protein ◽

X Ray Diffraction ◽

X Ray ◽

Meeting Program

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Contributions of Ca 2+ -Independent Thin Filament Activation to Cardiac Muscle Function

Biophysical Journal ◽

10.1016/j.bpj.2015.09.028 ◽

2015 ◽

Vol 109 (10) ◽

pp. 2101-2112 ◽

Cited By ~ 17

Author(s):

Yasser Aboelkassem ◽

Jordan A. Bonilla ◽

Kimberly J. McCabe ◽

Stuart G. Campbell

Keyword(s):

Cardiac Muscle ◽

Muscle Function ◽

Thin Filament ◽

Filament Activation

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Cardiac Thin Filament Activation Modulation by Stretch

Biophysical Journal ◽

10.1016/j.bpj.2012.11.2507 ◽

2013 ◽

Vol 104 (2) ◽

pp. 453a

Author(s):

Younss Ait Mou ◽

Pieter P. de Tombe

Keyword(s):

Thin Filament ◽

Filament Activation

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Abl activation regulates the dissociation of CAS from cytoskeletal vimentin by modulating CAS phosphorylation in smooth muscle

AJP Cell Physiology ◽

10.1152/ajpcell.00095.2010 ◽

2010 ◽

Vol 299 (3) ◽

pp. C630-C637 ◽

Cited By ~ 21

Author(s):

Li Jia ◽

Dale D. Tang

Keyword(s):

Smooth Muscle ◽

Muscle Contraction ◽

Actin Polymerization ◽

Spatial Location ◽

Smooth Muscle Contraction ◽

Nonreceptor Tyrosine Kinase ◽

Force Development ◽

Muscle Inhibition ◽

A Cell ◽

Contractile Activation

Abl is a nonreceptor tyrosine kinase that is required for smooth muscle contraction. However, the mechanism by which Abl regulates smooth muscle contraction is not completely understood. In the present study, Abl underwent phosphorylation at Tyr412 (an index of Abl activation) in smooth muscle in response to contractile activation. Treatment with a cell-permeable decoy peptide, but not the control peptide, attenuated Abl phosphorylation during contractile stimulation. Treatment with the decoy peptide did not affect the association of Abl with the cytoskeletal protein vinculin and the spatial location of vinculin in smooth muscle. Inhibition of Abl phosphorylation by the decoy peptide attenuated the agonist-induced phosphorylation of Crk-associated substrate (CAS), an adapter protein participating in the signaling processes that regulate force development in smooth muscle. Additionally, previous studies have shown that contractile stimulation triggers the dissociation of CAS from the vimentin network, which is important for cytoskeletal signaling and contraction in smooth muscle. In this report, the decrease in the amount of CAS in cytoskeletal vimentin in response to contractile activation was reversed by the Abl inhibition with the decoy peptide. Moreover, force development and the enhancement of F-actin-to-G-actin ratios (an indication of actin polymerization) upon contractile activation were also attenuated by the Abl inhibition. However, myosin phosphorylation induced by contractile activation was not affected by the inhibition of Abl. These results suggest that Abl regulates the dissociation of CAS from the vimentin network, actin polymerization, and contraction by modulating CAS phosphorylation in smooth muscle.

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