title: Molecular Effects of cTnC DCM Mutations on Calcium Sensitivity and Myofilament Activation-An Integrated Multiscale Modeling Study.
abstract: Mutations in cardiac troponin C (D75Y, E59D, and G159D), a key regulatory protein of myofilament contraction, have been associated with dilated cardiomyopathy (DCM). Despite reports of altered myofilament function in these mutants, the underlying molecular alterations caused by these mutations remain elusive. Here we investigate in silico the intramolecular mechanisms by which these mutations affect myofilament contraction. On the basis of the location of cardiac troponin C (cTnC) mutations, we tested the hypothesis that intramolecular effects can explain the altered myofilament calcium sensitivity of force development for D75Y and E59D cTnC, whereas altered cardiac troponin C-troponin I (cTnC-cTnI) interaction contributes to the reported contractile effects of the G159D mutation. We employed a multiscale approach combining molecular dynamics (MD) and Brownian dynamics (BD) simulations to estimate cTnC calcium association and hydrophobic patch opening. We then integrated these parameters into a Markov model of myofilament activation to compute the steady-state force-pCa relationship. The analysis showed that myofilament calcium sensitivity with D75Y and E59D can be explained by changes in calcium binding affinity of cTnC and the rate of hydrophobic patch opening, if a partial cTnC interhelical opening angle (110°) is sufficient for cTnI switch peptide association to cTnC. In contrast, interactions between cTnC and cTnI within the cardiac troponin complex must also be accounted for to explain contractile alterations due to G159D. In conclusion, this is the first multiscale in silico study to elucidate how direct molecular effects of genetic mutations in cTnC translate to altered myofilament contractile function.
authors.affiliation: Department of Bioengineering, University of California at San Diego , La Jolla, California 92093, United States.
authors.forename: Sukriti
authors.initials: S
authors.lastname: Dewan
authors.affiliation: Department of Bioengineering, University of California at San Diego , La Jolla, California 92093, United States.
authors.forename: Kimberly J
authors.initials: KJ
authors.lastname: McCabe
authors.affiliation: Department of Bioengineering, University of Washington , Seattle, Washington 98195, United States.|Center for Cardiovascular Biology, University of Washington , Seattle, Washington 98109, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Regnier
authors.affiliation: Department of Bioengineering, University of California at San Diego , La Jolla, California 92093, United States.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: McCulloch
authors.affiliation: Department of Chemistry & Biochemistry, Ohio State University , Columbus, Ohio 43210, United States.
authors.forename: Steffen
authors.initials: S
authors.lastname: Lindert
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D018360:Crystallography, X-Ray; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008390:Markov Chains; D056004:Molecular Dynamics Simulation; D009154:Mutation; D009200:Myocardial Contraction / Q000502:physiology; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D009210:Myofibrils / Q000378:metabolism*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017434:Protein Structure, Tertiary; D051381:Rats; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D019209:Troponin C / Q000235:genetics / Q000378:metabolism*; D019210:Troponin I / Q000235:genetics / Q000378:metabolism*
chemical_list: D019209:Troponin C; D019210:Troponin I; D002118:Calcium