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Pathogenesis associated with a restrictive cardiomyopathy mutant in cardiac troponin T is due to reduced protein stability and greatly increased myofilament Ca2+ sensitivity.

Title: Pathogenesis associated with a restrictive cardiomyopathy mutant in cardiac troponin T is due to reduced protein stability and greatly increased myofilament Ca2+ sensitivity.
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Name(s): Parvatiyar, Michelle S, author
Pinto, Jose Renato, author
Type of Resource: text
Genre: Journal Article
Text
Date Issued: 2015-02-01
Physical Form: computer
online resource
Extent: 1 online resource
Language(s): English
Abstract/Description: Dilated and hypertrophic cardiomyopathy mutations in troponin can blunt effects of protein kinase A (PKA) phosphorylation of cardiac troponin I (cTnI), decreasing myofilament Ca2+-sensitivity; however this effect has never been tested for restrictive cardiomyopathy (RCM) mutants. This study explores whether an RCM cardiac troponin T mutant (cTnT-ΔE96) interferes with convergent PKA regulation and if TnT instability contributes to greatly enhanced Ca2+-sensitivity in skinned fibers. Force of contraction in skinned cardiac porcine fiber and spectroscopic studies were performed. A decrease of -0.26 and -0.25 pCa units in Ca2+-sensitivity of contraction after PKA incubation was observed for skinned fibers incorporated with WT or cTnT-ΔE96, respectively. To further assess whether cTnT-ΔE96 interferes solely with transmission of cTnI phosphorylation effects, skinned fibers were reconstituted with PKA pseudo-phosphorylated cTnI (cTnI-SS/DD.cTnC). Fibers displaced with cTnT-WT, reconstituted with cTnI-SS/DD.cTnC decreased Ca2+-sensitivity of force (pCa50=5.61) compared to control cTnI-WT.cTnC (pCa50=5.75), similarly affecting cTnT-ΔE96 (pCa50=6.03) compared to control \cTnI-WT.cTnC (pCa50=6.14). Fluorescence studies measuring cTnC(IAANS) Ca2+-affinity changes due to cTnT-ΔE96 indicated that higher complexity (thin filament) better recapitulates skinned fiber Ca2+ sensitive changes. Circular dichroism revealed reduced α-helicity and earlier thermal unfolding for cTnT-ΔE96 compared to WT. Although ineffective in decreasing myofilament Ca2+-sensitivity to normal levels, cTnT-ΔE96 does not interfere with PKA cTnI phosphorylation mediated effects; 2) cTnT-ΔE96 requires actin to increase cTnC Ca2+-affinity; and 3) deletion of E96 reduces cTnT stability, likely disrupting crucial thin filament interactions. The pathological effect of cTnT-ΔE96 is largely manifested by dramatic myofilament Ca2+-sensitization which still persists even after PKA phosphorylation mediated Ca2+-desensitization.
Identifier: FSU_pmch_25450489 (IID), 10.1016/j.bbagen.2014.09.029 (DOI), PMC4276470 (PMCID), 25450489 (RID), 25450489 (EID), S0304-4165(14)00366-3 (PII)
Keywords: Cardiac troponin T, Circular dichroism, Fluorescence, Restrictive cardiomyopathy, Skinned fiber, Troponin I phosphorylation
Grant Number: K99 HL103840, R00 HL103840, HL103840
Publication Note: This NIH-funded author manuscript originally appeared in PubMed Central at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4276470.
Subject(s): Animals
Calcium/metabolism
Cardiomyopathy, Dilated/genetics
Cardiomyopathy, Dilated/metabolism
Cardiomyopathy, Dilated/pathology
Cyclic AMP-Dependent Protein Kinases/genetics
Cyclic AMP-Dependent Protein Kinases/metabolism
Genetic Diseases, Inborn/genetics
Genetic Diseases, Inborn/metabolism
Genetic Diseases, Inborn/pathology
Humans
Mutation
Myocardium/metabolism
Myocardium/pathology
Myofibrils/genetics
Myofibrils/metabolism
Myofibrils/pathology
Phosphorylation/genetics
Protein Stability
Swine
Troponin T/genetics
Troponin T/metabolism
Persistent Link to This Record: http://purl.flvc.org/fsu/fd/FSU_pmch_25450489
Owner Institution: FSU
Is Part Of: Biochimica et biophysica acta.
0006-3002
Issue: iss. 2, vol. 1850

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Parvatiyar, M. S., & Pinto, J. R. (2015). Pathogenesis associated with a restrictive cardiomyopathy mutant in cardiac troponin T is due to reduced protein stability and greatly increased myofilament Ca2+ sensitivity. Biochimica Et Biophysica Acta. Retrieved from http://purl.flvc.org/fsu/fd/FSU_pmch_25450489