Dataset Information

Regulation of titin-based cardiac stiffness by unfolded domain oxidation (UnDOx).

ABSTRACT: The relationship between oxidative stress and cardiac stiffness is thought to involve modifications to the giant muscle protein titin, which in turn can determine the progression of heart disease. In vitro studies have shown that S-glutathionylation and disulfide bonding of titin fragments could alter the elastic properties of titin; however, whether and where titin becomes oxidized in vivo is less certain. Here we demonstrate, using multiple models of oxidative stress in conjunction with mechanical loading, that immunoglobulin domains preferentially from the distal titin spring region become oxidized in vivo through the mechanism of unfolded domain oxidation (UnDOx). Via oxidation type-specific modification of titin, UnDOx modulates human cardiomyocyte passive force bidirectionally. UnDOx also enhances titin phosphorylation and, importantly, promotes nonconstitutive folding and aggregation of unfolded domains. We propose a mechanism whereby UnDOx enables the controlled homotypic interactions within the distal titin spring to stabilize this segment and regulate myocardial passive stiffness.

SUBMITTER: Loescher CM

PROVIDER: S-EPMC7533878 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Regulation of titin-based cardiac stiffness by unfolded domain oxidation (UnDOx).

Loescher Christine M CM Breitkreuz Martin M Li Yong Y Nickel Alexander A Unger Andreas A Dietl Alexander A Schmidt Andreas A Mohamed Belal A BA Kötter Sebastian S Schmitt Joachim P JP Krüger Marcus M Krüger Martina M Toischer Karl K Maack Christoph C Leichert Lars I LI Hamdani Nazha N Linke Wolfgang A WA

Proceedings of the National Academy of Sciences of the United States of America 20200914 39

The relationship between oxidative stress and cardiac stiffness is thought to involve modifications to the giant muscle protein titin, which in turn can determine the progression of heart disease. In vitro studies have shown that S-glutathionylation and disulfide bonding of titin fragments could alter the elastic properties of titin; however, whether and where titin becomes oxidized in vivo is less certain. Here we demonstrate, using multiple models of oxidative stress in conjunction with mechan ...[more]

PMID: 32929035

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Project description:The giant protein titin performs structure-preserving functions in the sarcomere and is important for the passive stiffness (Fpassive) of cardiomyocytes. Protein kinase D (PKD) enzymes play crucial roles in regulating myocardial contraction, hypertrophy, and remodeling. PKD phosphorylates myofilament proteins, but it is not known whether the giant protein titin is also a PKD substrate. Here, we aimed to determine whether PKD phosphorylates titin and thereby modulates cardiomyocyte Fpassive in normal and failing myocardium. The phosphorylation of titin was assessed in cardiomyocyte-specific PKD knock-out mice (cKO) and human hearts using immunoblotting with a phosphoserine/threonine and a phosphosite-specific titin antibody. PKD-dependent site-specific titin phosphorylation in vivo was quantified by mass spectrometry using stable isotope labeling by amino acids in cell culture (SILAC) of SILAC-labeled mouse heart protein lysates that were mixed with lysates isolated from hearts of either wild-type control (WT) or cKO mice. Fpassive of single permeabilized cardiomyocytes was recorded before and after PKD and HSP27 administration. All-titin phosphorylation was reduced in cKO compared to WT hearts. Multiple conserved PKD-dependent phosphosites were identified within the Z-disk, A-band and M-band regions of titin by quantitative mass spectrometry, and many PKD-dependent phosphosites detected in the elastic titin I-band region were significantly decreased in cKO. Analysis of titin site-specific phosphorylation showed unaltered or upregulated phosphorylation in cKO compared to matched WT hearts. Fpassive was elevated in cKO compared to WT cardiomyocytes and PKD administration lowered Fpassive of WT and cKO cardiomyocytes. Cardiomyocytes from hypertrophic cardiomyopathy (HCM) patients showed higher Fpassive compared to control hearts and significantly lower Fpassive after PKD treatment. In addition, we found higher phosphorylation at CaMKII-dependent titin sites in HCM compared to control hearts. Expression and phosphorylation of HSP27, a substrate of PKD, were elevated in HCM hearts, which was associated with increased PKD expression and phosphorylation. The relocalization of HSP27 in HCM away from the sarcomeric Z-disk and I-band suggested that HSP27 failed to exert its protective action on titin extensibility. This protection could, however, be restored by administration of HSP27, which significantly reduced Fpassive in HCM cardiomyocytes. These findings establish a previously unknown role for PKDin regulating diastolic passive properties of healthy and diseased hearts.

Dataset Information

Regulation of titin-based cardiac stiffness by unfolded domain oxidation (UnDOx).

Publications

Regulation of titin-based cardiac stiffness by unfolded domain oxidation (UnDOx).

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