Functional Analysis of a Unique Troponin C Mutation, GLY159ASP, that Causes Familial Dilated Cardiomyopathy, Studied in Explanted Heart Muscle
| Autor: | Steven B. Marston, Andrew E. Messer, Douglas G. Ward, Anita C. Hoskins, Jonathan C. Kentish, Clare E. Gallon, Michael Burch, Emma C. Dyer, Adam Jacques, Juan Pablo Kaski |
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| Jazyk: | angličtina |
| Rok vydání: | 2009 |
| Předmět: |
Cardiomyopathy
Dilated medicine.medical_specialty Genotype Glycine Cardiomyopathy Tropomyosin Troponin C Troponin T Internal medicine Troponin I medicine Humans Myocyte Myocytes Cardiac Phosphorylation Cytoskeleton Actin Aspartic Acid biology Skeletal muscle musculoskeletal system medicine.disease Myocardial Contraction Troponin Actins Recombinant Proteins Phenotype Endocrinology medicine.anatomical_structure Child Preschool Mutation biology.protein Calcium Cardiology and Cardiovascular Medicine Protein Processing Post-Translational |
| Zdroj: | U101 |
| Popis: | Background— Familial dilated cardiomyopathy can be caused by mutations in the proteins of the muscle thin filament. In vitro, these mutations decrease Ca 2+ sensitivity and cross-bridge turnover rate, but the mutations have not been investigated in human tissue. We studied the Ca 2+ -regulatory properties of myocytes and troponin extracted from the explanted heart of a patient with inherited dilated cardiomyopathy due to the cTnC G159D mutation. Methods and Results— Mass spectroscopy showed that the mutant cTnC was expressed approximately equimolar with wild-type cTnC. Contraction was compared in skinned ventricular myocytes from the cTnC G159D patient and nonfailing donor heart. Maximal Ca 2+ -activated force was similar in cTnC G159D and donor myocytes, but the Ca 2+ sensitivity of cTnC G159D myocytes was higher (EC 50 G159D/donor=0.60). Thin filaments reconstituted with skeletal muscle actin and human cardiac tropomyosin and troponin were studied by in vitro motility assay. Thin filaments containing the mutation had a higher Ca 2+ sensitivity (EC 50 G159D/donor=0.55�0.13), whereas the maximally activated sliding speed was unaltered. In addition, the cTnC G159D mutation blunted the change in Ca 2+ sensitivity when TnI was dephosphorylated. With wild-type troponin, Ca 2+ sensitivity was increased (EC 50 P/unP=4.7�1.9) but not with cTnC G159D troponin (EC 50 P/unP=1.2�0.1). Conclusions— We propose that uncoupling of the relationship between phosphorylation and Ca 2+ sensitivity could be the cause of the dilated cardiomyopathy phenotype. The differences between these data and previous in vitro results show that native phosphorylation of troponin I and troponin T and other posttranslational modifications of sarcomeric proteins strongly influence the functional effects of a mutation. |
| Databáze: | OpenAIRE |
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