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Dysferlin facilitates tubular membrane proliferation promoting hypertrophic remodeling of the heart under pressure overload - Sham vs TAC mouse hearts

ABSTRACT: BACKGROUND: Cardiac hypertrophy compensates for increased biomechanical stress of the heart induced by prevalent cardiovascular pathologies, but can result in cardiac failure if left untreated. We hypothesized that the tail-anchored protein Dysferlin with multiple Ca2+-binding C2-domains is critical for the integrity of the transverse-axial tubule (TAT) network inside cardiomyocytes, and contributes to the proliferation of TAT endomembranes during pressure overload-induced cardiac hypertrophy. OBJECTIVE: To reveal the impact of the membrane fusion and repair protein Dysferlin on TAT network stabilization and proliferation necessary for the hypertrophic growth of cardiomyocytes. METHODS AND RESULTS: Super-resolution light and electron microscopy of mouse cardiomyocytes identified a specific localization of Dysferlin in a vesicular compartment in nanometric proximity to contact sites of the TAT network with the sarcoplasmic reticulum (SR), a.k.a. junctional complexes for Ca2+-induced Ca2+ release. Mass spectrometry was used to characterize the cardiac Dysferlin interactome, thereby identifying a novel protein interaction with the membrane-tethering SR protein Juncophilin-2, a known interactor of L-type Ca2+ channels and Ryanodine Receptor Ca2+ release channels in junctional complexes. While the Dysferlin knockout caused a mild progressive phenotype of dilated cardiomyopathy in the mouse heart, global proteome analysis revealed changes preceding systolic failure. Following transverse aortic constriction (TAC), Dysferlin protein expression was significantly increased in hypertrophied wild-type myocardium, while Dysferlin knockout animals presented markedly reduced left-ventricular hypertrophy. Live-cell membrane imaging demonstrated a profound reorganization of the TAT network in wild-type left-ventricular myocytes post-TAC with robust proliferation of axial tubules, which critically depended on the increased expression of Dysferlin within newly-emerging tubule components. CONCLUSIONS: Dysferlin represents a new molecular target in cardiac disease that protects the integrity of tubule-SR junctional complexes for regulated excitation-contraction coupling, and controls TAT network reorganization and tubular membrane proliferation in cardiomyocyte hypertrophy induced by pressure-overload.

INSTRUMENT(S): TripleTOF 5600

ORGANISM(S): Mus Musculus (mouse)

TISSUE(S): Heart

DISEASE(S): Cardiovascular System Disease

SUBMITTER: Christof Lenz

LAB HEAD: Christof Lenz

PROVIDER: PXD053037 | Pride | 2024-07-15

REPOSITORIES: Pride

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			Action	DRS
	D_Kownatzki_290119_010519_DIA_A_16.wiff	Wiff
	D_Kownatzki_290119_010519_DIA_A_16.wiff.scan	Wiff
	D_Kownatzki_290119_010519_DIA_A_17.wiff	Wiff
	D_Kownatzki_290119_010519_DIA_A_17.wiff.scan	Wiff
	D_Kownatzki_290119_010519_DIA_A_18.wiff	Wiff

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Project description:BACKGROUND: Cardiac hypertrophy compensates for increased biomechanical stress of the heart induced by prevalent cardiovascular pathologies, but can result in cardiac failure if left untreated. We hypothesized that the tail-anchored protein Dysferlin with multiple Ca2+-binding C2-domains is critical for the integrity of the transverse-axial tubule (TAT) network inside cardiomyocytes, and contributes to the proliferation of TAT endomembranes during pressure overload-induced cardiac hypertrophy. OBJECTIVE: To reveal the impact of the membrane fusion and repair protein Dysferlin on TAT network stabilization and proliferation necessary for the hypertrophic growth of cardiomyocytes. METHODS AND RESULTS: Super-resolution light and electron microscopy of mouse cardiomyocytes identified a specific localization of Dysferlin in a vesicular compartment in nanometric proximity to contact sites of the TAT network with the sarcoplasmic reticulum (SR), a.k.a. junctional complexes for Ca2+-induced Ca2+ release. Mass spectrometry was used to characterize the cardiac Dysferlin interactome, thereby identifying a novel protein interaction with the membrane-tethering SR protein Juncophilin-2, a known interactor of L-type Ca2+ channels and Ryanodine Receptor Ca2+ release channels in junctional complexes. While the Dysferlin knockout caused a mild progressive phenotype of dilated cardiomyopathy in the mouse heart, global proteome analysis revealed changes preceding systolic failure. Following transverse aortic constriction (TAC), Dysferlin protein expression was significantly increased in hypertrophied wild-type myocardium, while Dysferlin knockout animals presented markedly reduced left-ventricular hypertrophy. Live-cell membrane imaging demonstrated a profound reorganization of the TAT network in wild-type left-ventricular myocytes post-TAC with robust proliferation of axial tubules, which critically depended on the increased expression of Dysferlin within newly-emerging tubule components. CONCLUSIONS: Dysferlin represents a new molecular target in cardiac disease that protects the integrity of tubule-SR junctional complexes for regulated excitation-contraction coupling, and controls TAT network reorganization and tubular membrane proliferation in cardiomyocyte hypertrophy induced by pressure-overload.

Project description:Intracellular calcium (Ca2+) overload is known to play a critical role in the development of cardiac dysfunction. Despite the remarkable improvement in managing the progression of heart disease, developing effective therapies for heart failure (HF) remains a challenge. A better understanding of molecular mechanisms that maintain proper Ca2+ levels and contractility in the injured heart could be of therapeutic value. Here, we report that the transcription factor Zinc finger E-box-binding homeobox2 (ZEB2) is induced by Hypoxia-inducible factor 1-alpha (HIF1a) in hypoxic cardiomyocytes and regulates a network of genes involved in Ca2+-handling and contractility during ischemic heart disease. Gain- and loss-of-function studies in genetic mouse models revealed ZEB2 in cardiomyocytes to be necessary and sufficient to protect the heart against ischemia-induced diastolic dysfunction and structural remodeling. Moreover, RNA sequencing (RNA-seq) of ZEB2-overexpressing (Zeb2 cTg) hearts post-injury implicated ZEB2 in regulating numerous Ca2+-handling and contractility-related genes. Mechanistically, ZEB2 overexpression increased the phosphorylation of phospholamban (PLN) at both serine-16 and threonine-17, implying enhanced activity of sarcoplasmic reticulum Ca2+-ATPase (SERCA2a), thereby augmenting SR Ca2+ uptake and contractility. Furthermore, we observed a decrease in the activity of Ca2+-dependent calcineurin/NFAT signaling in Zeb2 cTg hearts, which is the main driver of pathological cardiac remodeling. On a post-transcriptional level, we showed that ZEB2 expression can be regulated by the cardiomyocyte-specific microRNA-208a (miR-208a). Blocking the function of miR-208a with antimiR-208a increased ZEB2 expression in the heart and effectively protected from the development of pathological cardiac hypertrophy. Together, we present ZEB2 as a central regulator of contractility and Ca2+-handling components in the mammalian heart. Further mechanistic understanding of the role of ZEB2 in regulating Ca2+ homeostasis in cardiomyocytes is an essential step towards the development of improved therapies for HF.

Project description:Cardiac sarcoplasmic reticulum (SR) plays a central role in cellular Ca homeostasis, as does endoplasmic reticulum (ER) in the nonmuscle cell. The importance of SR Ca-handling function has led to detailed understanding of Ca-release and re-uptake protein complexes, but relatively little information regarding other known ER functions. We isolated cardiac membranes based upon their ability to efficiently accumulate Ca by the SR,ER-ATPase (SERCA-positive membranes), a process known to produce two characteristic SR membrane fractions: those enriched in known junctional SR markers, and those enriched in proteins originating from classic ER subdomains. Using standard proteomic techniques, we determined the SR proteins in three membrane preparations: 1) the highest-density SERCA-positive microsomes (HighSR); 2) the slightly less dense SERCA-positive microsomes that are constrained by a ryanodine-dependent leak (MedSR); and the original crude cardiac microsomes. Only a third of all crude microsomal proteins in heart were enriched in SERCA-positive membranes at least two fold. This protocol completely excluded known contractile, mitochondrial, sarcolemmal, and other major microsomal proteins, producing a far cleaner preparation of SR. Each SERCA-positive protein was distributed between HighSR and MedSR membrane vesicles in accordance with relative densities of SERCA2a versus ryanodine receptor. The distributions reinforced past findings on the distributions for several of the major known proteins. When combined with values for relative abundance, and enrichment over crude membranes, our protocol conveniently and effectively exposed multiple domains of the cardiac ER/SR. Most of the highly enriched and abundant cardiac SR/ER proteins represent proteins that have received little research attention. The data generate a useful quantitative analysis of intracellular membrane structure and function within cardiomyocytes, and may provide a reliable way of gauging broader changes in cardiac SR.

Project description:Cardiac hypertrophy is an important and independent risk factor for the development of cardiac myopathy that may lead to heart failure. Cardiac hypertrophy manifests as an enlargement of the individual cardiomyocytes, which impairs the function of the heart. The only way to cure end-stage cardiac myopathy is by heart transplantation, a possibility limited due to lack of donor hearts. Therefore, early diagnosis of cardiac hypertrophy is needed in order to be able to initiate interventions that may prevent further progression of the disease. The mechanisms underlying the development of cardiac hypertrophy are yet not well understood. To increase the knowledge about mechanisms and regulatory pathways involved in the progression of cardiac hypertrophy, we have developed a human induced pluripotent stem cell (hiPSC)-based in vitro model of cardiac hypertrophy and performed extensive characterization of the model using multi-omics analyses. In a series of experiments, hiPSC-derived cardiomyocytes were stimulated with Endothelin-1 for 8, 24, 48 and 72 hours and their transcriptome and secreted proteome were analyzed thoroughly. The transcriptomic data show many enriched canonical pathways related to cardiac hypertrophy already at the earliest time point, e.g., cardiac hypertrophy signaling, actin cytoskeleton signaling and PI3K/AKT signaling. Cluster analysis of the differentially expressed genes showed that there are numerous clusters of genes that are dysregulated over the time period of 8 to 72h. An integrated transcriptome-secretome analysis enabled the identification of multimodal biomarkers of high relevance for monitoring early cardiac hypertrophy progression. Taken together, the results from this study demonstrate that our in vitro model displays a hypertrophic response on transcriptomic- and secreted proteomic level. The results also provide novel insight into the underlying mechanisms of cardiac hypertrophy and novel putative early cardiac hypertrophy biomarkers have been identified that will be further validated to assess their clinical relevance.

Project description:VEGF family members are important regulators of vascular functions. Promoting VEGFA signalling in aged mice has been shown to delay various aging phenotypes and extend the survival of aged mice. Although there is profound knowledge on functions of VEGFA, VEGFB has not been investigated in the context of cardiac aging. Our RNA data of aged mouse hearts revealed significant downregulation of Vegfb in the heart, specifically in endothelial cells and cardiomyocytes, while VEGFB expression was reduced in endothelial cells, fibroblasts and cardiomyocytes in aged human hearts. By contrast, VEGFB expression was exclusively reduced in cardiomyocytes of patients with cardiac hypertrophy. Hence, we investigated whether Vegfb gene therapy can revert age-dependent cardiac pathologies. We overexpressed Vegfb186, the soluble VEGFB isoform, via AAV9 vector transduction into 18-month-old C57Bl/6J male mice. AAV9-Vegfb treatment prevented progression age-related diastolic dysfunction and decreased cardiac fibrosis. We further found a rescue of aging-related left ventricular denervation in the hearts of AVV9-Vegfb treated old mice which was associated with an increase in heart rate variability. However, heart to body weight ratio and cardiomyocyte hypertrophy were increased in the AAV9-Vegfb treated mouse hearts, without alteration of cardiac systolic or diastolic function. Histological and transcriptomic analyses revealed that VEGFB186 induces compensatory cardiac hypertrophy which was accompanied by a rescued length-width-ratio, reduced fibrosis and the absence of cardiac inflammation. Cardiac single-nuclei RNA sequencing further suggested that AAV9-Vegfb treatment affects cardiac hypertrophy putatively via STAT3 which was validated in vitro. In conclusion, our data reveals that Vegfb overexpression partially reverses pathological alterations in the aging heart. Despite the overall improvement of the age-related cardiac phenotype, the AAV9-Vegfb-mediated induced cardiac hypertrophy which might reflect protective hypertrophy.

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Dysferlin facilitates tubular membrane proliferation promoting hypertrophic remodeling of the heart under pressure overload - Sham vs TAC mouse hearts

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