Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10954103 | Journal of Molecular and Cellular Cardiology | 2010 | 9 Pages |
Abstract
Ca2+ desensitization of myofilaments is indicated as a primary mechanism for the pathogenesis of familial dilated cardiomyopathy (DCM) associated with the deletion of lysine 210 (ÎK210) in cardiac troponin T (cTnT). ÎK210 knock-in mice closely recapitulate the clinical phenotypes documented in patients with this mutation. Considerable evidence supports the proposition that phosphorylation of cardiac sarcomeric proteins is a key modulator of function and may exacerbate the effect of the deletion. In this study we investigate the impact of K210 deletion on phosphorylation propensity of sarcomeric proteins. Analysis of cardiac myofibrils isolated from ÎK210 hearts identified a decrease in phosphorylation of cTnI (46%), cTnT (30%) and MyBP-C (32%) compared with wild-type controls. Interestingly, immunoblot analyses with phospho-specific antibodies show augmented phosphorylation of cTnT-Thr203 (28%) and decreased phosphorylation of cTnI-Ser23/24 (41%) in mutant myocardium. In vitro kinase assays indicate that ÎK210 increases phosphorylation propensity of cTnT-Thr203 three-fold, without changing cTnI-Ser23/24 phosphorylation. Molecular modeling of cTnT-ÎK210 structure reveals changes in the electrostatic environment of cTnT helix (residues 203-224) that lead to a more basic environment around Thr203, which may explain the enhanced PKC-dependent phosphorylation. In addition, yeast two-hybrid assays indicate that cTnT-ÎK210 binds stronger to cTnI compared with cTnT-wt. Collectively, our observations suggest that cardiomyopathy-causing ÎK210 has far-reaching effects influencing cTnI-cTnT binding and posttranslational modifications of key sarcomeric proteins.
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Authors
Liliana Sfichi-Duke, Mary L. Garcia-Cazarin, C. Amelia Sumandea, Gail A. Sievert, C. William Balke, Dong-Yun Zhan, Sachio Morimoto, Marius P. Sumandea,