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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: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:Background: The phospholamban (PLN) p.Arg14del mutation belongs to the established causes of dilated cardiomyopathy, with the molecular disease mechanisms incompletely understood. We used human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes, CRISPR/Cas9 gene editing and patient heart samples to investigate the molecular pathomechanisms of PLN p.Arg14del cardiomyopathy. Methods and results: Patient dermal fibroblasts carrying the PLN p.Arg14del mutation were reprogrammed into hiPSC, isogenic controls were established by CRISPR/Cas9. Cells were differentiated into cardiomyocytes and characterized in 2D and 3D-engineered heart tissue (EHT) format. Mutant cardiomyocytes revealed significantly prolonged Ca2+ transient decay time, Ca2+-load dependent irregular beating pattern and lower peak force compared to isogenic controls. While this data support the reported super-inhibitory effect of PLN p.Arg14del on the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase, an unchanged SR Ca2+ content argued against disturbed SR Ca2+ cycling as the sole cause of contractile dysfunction. Label-free proteomic analysis of p.Arg14del EHTs revealed less endoplasmic reticulum (ER), ribosomal and mitochondrial proteins. Electron microscopy showed dilation of the rough ER, large lipid droplets in close association with mitochondria and reduced mitochondrial number. Follow-up experiments confirmed impairment of the rough ER/mitochondria compartment and enhanced oxidative stress in PLN p.Arg14del. Relevance for human disease was demonstrated by immunohistochemistry of human heart samples. PLN p.Arg14del end-stage heart failure samples revealed perinuclear aggregates positive for ER marker proteins and oxidative stress in comparison to ischemic heart failure - and non-failing donor heart samples. Surprisingly, transduction of PLN p.Arg14del EHTs with the Ca2+ binding protein GCaMP6f reversed the contractile, molecular and morphological disease phenotype. Conclusion: This study identified impairment of the rough ER/mitochondria compartment without SR dysfunction as a novel disease mechanism underlying PLN p.Arg14del cardiomyopathy. The pathology was improved by Ca2+-scavenging, suggesting impaired local Ca2+ cycling as an important disease culprit.

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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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