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1.
Sci Rep ; 10(1): 18784, 2020 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-33139771

RESUMO

Nanoindentation technology with high spatial resolution and force sensitivity is widely used to measure the mechanical properties of hard biomaterials and tissues. However, its reliability to analyze soft biomaterials and organs has not been tested. Here, we evaluated the utility of nanoindentation to measure the passive mechanical properties of soft biological specimen. Kidney, liver, spleen and uterus samples were harvested from C57BL/6 N mice. We assessed test-retest repeatability in biological specimen and hydrogel controls using Bland-Altman diagrams, intraclass correlation coefficients (ICCs) and the within-subject coefficients of variation (COVs). The results were calculated using Hertzian, JKR and Oliver & Pharr models. Similar to hydrogels, Bland-Altman plots of all biological specimen showed good reliability in stiffness test and retest examinations. In gels, ICCs were larger than 0.8 and COVs were smaller than 15% in all three models. In kidney, liver, spleen and uterus, ICCs were consistently larger than 0.8 only in the Hertzian model but not in the JKR and Oliver & Pharr models. Similarly, COVs were consistently smaller than 15% in kidney, liver, spleen and uterus only in the Hertzian model but not in the other models. We conclude that nanoindentation technology is feasible in detecting the stiffness of kidney, liver, spleen and uterus. The Hertzian model is the preferred method to provide reliable results on ex vivo organ stiffness of the biological specimen under study.

2.
Cell Rep ; 32(10): 108117, 2020 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-32905764

RESUMO

Recent advances in induced pluripotent stem cell (iPSC) technology and directed differentiation of iPSCs into cardiomyocytes (iPSC-CMs) make it possible to model genetic heart disease in vitro. We apply CRISPR/Cas9 genome editing technology to introduce three RBM20 mutations in iPSCs and differentiate them into iPSC-CMs to establish an in vitro model of RBM20 mutant dilated cardiomyopathy (DCM). In iPSC-CMs harboring a known causal RBM20 variant, the splicing of RBM20 target genes, calcium handling, and contractility are impaired consistent with the disease manifestation in patients. A variant (Pro633Leu) identified by exome sequencing of patient genomes displays the same disease phenotypes, thus establishing this variant as disease causing. We find that all-trans retinoic acid upregulates RBM20 expression and reverts the splicing, calcium handling, and contractility defects in iPSC-CMs with different causal RBM20 mutations. These results suggest that pharmacological upregulation of RBM20 expression is a promising therapeutic strategy for DCM patients with a heterozygous mutation in RBM20.

3.
Nat Commun ; 11(1): 3133, 2020 06 19.
Artigo em Inglês | MEDLINE | ID: mdl-32561764

RESUMO

Proximity proteomics has greatly advanced the analysis of native protein complexes and subcellular structures in culture, but has not been amenable to study development and disease in vivo. Here, we have generated a knock-in mouse with the biotin ligase (BioID) inserted at titin's Z-disc region to identify protein networks that connect the sarcomere to signal transduction and metabolism. Our census of the sarcomeric proteome from neonatal to adult heart and quadriceps reveals how perinatal signaling, protein homeostasis and the shift to adult energy metabolism shape the properties of striated muscle cells. Mapping biotinylation sites to sarcomere structures refines our understanding of myofilament dynamics and supports the hypothesis that myosin filaments penetrate Z-discs to dampen contraction. Extending this proof of concept study to BioID fusion proteins generated with Crispr/CAS9 in animal models recapitulating human pathology will facilitate the future analysis of molecular machines and signaling hubs in physiological, pharmacological, and disease context.


Assuntos
Carbono-Nitrogênio Ligases/genética , Proteínas de Escherichia coli/genética , Proteínas Quinases/metabolismo , Proteoma/metabolismo , Proteômica/métodos , Proteínas Repressoras/genética , Sarcômeros/metabolismo , Animais , Animais Recém-Nascidos , Biotinilação/genética , Feminino , Técnicas de Introdução de Genes , Masculino , Redes e Vias Metabólicas , Camundongos Transgênicos , Modelos Animais , Miocárdio/citologia , Miocárdio/metabolismo , Estudo de Prova de Conceito , Mapas de Interação de Proteínas/fisiologia , Proteínas Quinases/genética , Proteostase/fisiologia , Músculo Quadríceps/citologia , Músculo Quadríceps/metabolismo , Sarcômeros/genética , Transdução de Sinais/fisiologia , Relação Estrutura-Atividade
4.
Am J Physiol Cell Physiol ; 318(1): C163-C173, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31747312

RESUMO

Fluorescence recovery after photobleaching (FRAP) has been useful in delineating cardiac myofilament biology, and innovations in fluorophore chemistry have expanded the array of microscopic assays used. However, one assumption in FRAP is the irreversible photobleaching of fluorescent proteins after laser excitation. Here we demonstrate reversible photobleaching regarding the photoconvertible fluorescent protein mEos3.2. We used CRISPR/Cas9 genome editing in human induced pluripotent stem cells (hiPSCs) to knock-in mEos3.2 into the COOH terminus of titin to visualize sarcomeric titin incorporation and turnover. Upon cardiac induction, the titin-mEos3.2 fusion protein is expressed and integrated in the sarcomeres of hiPSC-derived cardiomyocytes (CMs). STORM imaging shows M-band clustered regions of bound titin-mEos3.2 with few soluble titin-mEos3.2 molecules. FRAP revealed a baseline titin-mEos3.2 fluorescence recovery of 68% and half-life of ~1.2 h, suggesting a rapid exchange of sarcomeric titin with soluble titin. However, paraformaldehyde-fixed and permeabilized titin-mEos3.2 hiPSC-CMs surprisingly revealed a 55% fluorescence recovery. Whole cell FRAP analysis in paraformaldehyde-fixed, cycloheximide-treated, and untreated titin-mEos3.2 hiPSC-CMs displayed no significant differences in fluorescence recovery. FRAP in fixed HEK 293T expressing cytosolic mEos3.2 demonstrates a 58% fluorescence recovery. These data suggest that titin-mEos3.2 is subject to reversible photobleaching following FRAP. Using a mouse titin-eGFP model, we demonstrate that no reversible photobleaching occurs. Our results reveal that reversible photobleaching accounts for the majority of titin recovery in the titin-mEos3.2 hiPSC-CM model and should warrant as a caution in the extrapolation of reliable FRAP data from specific fluorescent proteins in long-term cell imaging.


Assuntos
Diferenciação Celular , Conectina/metabolismo , Recuperação de Fluorescência Após Fotodegradação , Células-Tronco Pluripotentes Induzidas/metabolismo , Microscopia de Fluorescência , Microscopia de Vídeo , Miócitos Cardíacos/metabolismo , Sarcômeros/metabolismo , Adulto , Linhagem Celular , Conectina/genética , Humanos , Cinética , Proteínas Luminescentes/metabolismo , Masculino , Proteínas Recombinantes de Fusão/metabolismo , Reprodutibilidade dos Testes , Sarcômeros/genética
5.
Proc Natl Acad Sci U S A ; 116(50): 25126-25136, 2019 12 10.
Artigo em Inglês | MEDLINE | ID: mdl-31757849

RESUMO

Cardiac protein homeostasis, sarcomere assembly, and integration of titin as the sarcomeric backbone are tightly regulated to facilitate adaptation and repair. Very little is known on how the >3-MDa titin protein is synthesized, moved, inserted into sarcomeres, detached, and degraded. Here, we generated a bifluorescently labeled knockin mouse to simultaneously visualize both ends of the molecule and follow titin's life cycle in vivo. We find titin mRNA, protein synthesis and degradation compartmentalized toward the Z-disk in adult, but not embryonic cardiomyocytes. Originating at the Z-disk, titin contributes to a soluble protein pool (>15% of total titin) before it is integrated into the sarcomere lattice. Titin integration, disintegration, and reintegration are stochastic and do not proceed sequentially from Z-disk to M-band, as suggested previously. Exchange between soluble and integrated titin depends on titin protein composition and differs between individual cardiomyocytes. Thus, titin dynamics facilitate embryonic vs. adult sarcomere remodeling with implications for cardiac development and disease.


Assuntos
Miócitos Cardíacos/metabolismo , Proteínas Quinases , Proteostase/fisiologia , Animais , Camundongos , Camundongos Transgênicos , Microscopia , Proteínas Quinases/genética , Proteínas Quinases/metabolismo , Sarcômeros/metabolismo , Análise de Célula Única
6.
Sci Rep ; 9(1): 6768, 2019 05 01.
Artigo em Inglês | MEDLINE | ID: mdl-31043663

RESUMO

The Coxsackievirus and adenovirus receptor (CAR) is essential for normal electrical conductance in the heart, but its role in the postnatal brain is largely unknown. Using brain specific CAR knockout mice (KO), we discovered an unexpected role of CAR in neuronal communication. This includes increased basic synaptic transmission at hippocampal Schaffer collaterals, resistance to fatigue, and enhanced long-term potentiation. Spontaneous neurotransmitter release and speed of endocytosis are increased in KOs, accompanied by increased expression of the exocytosis associated calcium sensor synaptotagmin 2. Using proximity proteomics and binding studies, we link CAR to the exocytosis machinery as it associates with syntenin and synaptobrevin/VAMP2 at the synapse. Increased synaptic function does not cause adverse effects in KO mice, as behavior and learning are unaffected. Thus, unlike the connexin-dependent suppression of atrioventricular conduction in the cardiac knockout, communication in the CAR deficient brain is improved, suggesting a role for CAR in presynaptic processes.

7.
Eur Heart J ; 40(40): 3318-3332, 2019 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-31004144

RESUMO

AIMS: Heart failure with preserved ejection fraction (HFpEF) and pathological cardiac aging share a complex pathophysiology, including extracellular matrix remodelling (EMR). Protease-activated receptor 2 (PAR2) deficiency is associated with EMR. The roles of PAR1 and PAR2 have not been studied in HFpEF, age-dependent cardiac fibrosis, or diastolic dysfunction (DD). METHODS AND RESULTS: Evaluation of endomyocardial biopsies from patients with HFpEF (n = 14) revealed that a reduced cardiac PAR2 expression was associated with aggravated DD and increased myocardial fibrosis (r = -0.7336, P = 0.0028). In line, 1-year-old PAR2-knockout (PAR2ko) mice suffered from DD with preserved systolic function, associated with an increased age-dependent α-smooth muscle actin expression, collagen deposition (1.7-fold increase, P = 0.0003), lysyl oxidase activity, collagen cross-linking (2.2-fold increase, P = 0.0008), endothelial activation, and inflammation. In the absence of PAR2, the receptor-regulating protein caveolin-1 was down-regulated, contributing to an augmented profibrotic PAR1 and transforming growth factor beta (TGF-ß)-dependent signalling. This enhanced TGF-ß/PAR1 signalling caused N-proteinase (ADAMTS3) and C-proteinase (BMP1)-related increased collagen I production from cardiac fibroblasts (CFs). PAR2 overexpression in PAR2ko CFs reversed these effects. The treatment with the PAR1 antagonist, vorapaxar, reduced cardiac fibrosis by 44% (P = 0.03) and reduced inflammation in a metabolic disease model (apolipoprotein E-ko mice). Patients with HFpEF with upstream PAR inhibition via FXa inhibitors (n = 40) also exhibited reduced circulating markers of fibrosis and DD compared with patients treated with vitamin K antagonists (n = 20). CONCLUSIONS: Protease-activated receptor 2 is an important regulator of profibrotic PAR1 and TGF-ß signalling in the heart. Modulation of the FXa/FIIa-PAR1/PAR2/TGF-ß-axis might be a promising therapeutic approach to reduce HFpEF.

8.
Circulation ; 139(15): 1813-1827, 2019 04 09.
Artigo em Inglês | MEDLINE | ID: mdl-30700140

RESUMO

BACKGROUND: Titin is a giant elastic protein that spans the half-sarcomere from Z-disk to M-band. It acts as a molecular spring and mechanosensor and has been linked to striated muscle disease. The pathways that govern titin-dependent cardiac growth and contribute to disease are diverse and difficult to dissect. METHODS: To study titin deficiency versus dysfunction, the authors generated and compared striated muscle specific knockouts (KOs) with progressive postnatal loss of the complete titin protein by removing exon 2 (E2-KO) or an M-band truncation that eliminates proper sarcomeric integration, but retains all other functional domains (M-band exon 1/2 [M1/2]-KO). The authors evaluated cardiac function, cardiomyocyte mechanics, and the molecular basis of the phenotype. RESULTS: Skeletal muscle atrophy with reduced strength, severe sarcomere disassembly, and lethality from 2 weeks of age were shared between the models. Cardiac phenotypes differed considerably: loss of titin leads to dilated cardiomyopathy with combined systolic and diastolic dysfunction-the absence of M-band titin to cardiac atrophy and preserved function. The elastic properties of M1/2-KO cardiomyocytes are maintained, while passive stiffness is reduced in the E2-KO. In both KOs, we find an increased stress response and increased expression of proteins linked to titin-based mechanotransduction (CryAB, ANKRD1, muscle LIM protein, FHLs, p42, Camk2d, p62, and Nbr1). Among them, FHL2 and the M-band signaling proteins p62 and Nbr1 are exclusively upregulated in the E2-KO, suggesting a role in the differential pathology of titin truncation versus deficiency of the full-length protein. The differential stress response is consistent with truncated titin contributing to the mechanical properties in M1/2-KOs, while low titin levels in E2-KOs lead to reduced titin-based stiffness and increased strain on the remaining titin molecules. CONCLUSIONS: Progressive depletion of titin leads to sarcomere disassembly and atrophy in striated muscle. In the complete knockout, remaining titin molecules experience increased strain, resulting in mechanically induced trophic signaling and eventually dilated cardiomyopathy. The truncated titin in M1/2-KO helps maintain the passive properties and thus reduces mechanically induced signaling. Together, these findings contribute to the molecular understanding of why titin mutations differentially affect cardiac growth and have implications for genotype-phenotype relations that support a personalized medicine approach to the diverse titinopathies.


Assuntos
Cardiomiopatia Dilatada/metabolismo , Mecanotransdução Celular , Miócitos Cardíacos/metabolismo , Proteínas Quinases/deficiência , Sarcômeros/metabolismo , Disfunção Ventricular Esquerda/metabolismo , Disfunção Ventricular Direita/metabolismo , Animais , Cardiomiopatia Dilatada/genética , Cardiomiopatia Dilatada/patologia , Cardiomiopatia Dilatada/fisiopatologia , Deleção de Genes , Masculino , Camundongos Knockout , Músculo Esquelético/metabolismo , Músculo Esquelético/patologia , Atrofia Muscular/genética , Atrofia Muscular/metabolismo , Atrofia Muscular/patologia , Miócitos Cardíacos/patologia , Fenótipo , Proteínas Quinases/genética , Sarcômeros/patologia , Disfunção Ventricular Esquerda/genética , Disfunção Ventricular Esquerda/patologia , Disfunção Ventricular Esquerda/fisiopatologia , Disfunção Ventricular Direita/genética , Disfunção Ventricular Direita/patologia , Disfunção Ventricular Direita/fisiopatologia , Função Ventricular Esquerda , Função Ventricular Direita
9.
Hum Mol Genet ; 28(24): 4043-4052, 2019 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-29893868

RESUMO

Mutations in the lamin A/C gene (LMNA) cause an autosomal dominant inherited form of dilated cardiomyopathy associated with cardiac conduction disease (hereafter referred to as LMNA cardiomyopathy). Compared with other forms of dilated cardiomyopathy, mutations in LMNA are responsible for a more aggressive clinical course owing to a high rate of malignant ventricular arrhythmias. Gap junctions are intercellular channels that allow direct communication between neighboring cells, which are involved in electrical impulse propagation and coordinated contraction of the heart. For gap junctions to properly control electrical synchronization in the heart, connexin-based hemichannels must be correctly targeted to intercalated discs, Cx43 being the major connexin in the working myocytes. We here showed an altered distribution of Cx43 in a mouse model of LMNA cardiomyopathy. However, little is known on the molecular mechanisms of Cx43 remodeling in pathological context. We now show that microtubule cytoskeleton alteration and decreased acetylation of α-tubulin lead to remodeling of Cx43 in LMNA cardiomyopathy, which alters the correct communication between cardiomyocytes, ultimately leading to electrical conduction disturbances. Preventing or reversing this process could offer a strategy to repair damaged heart. Stabilization of microtubule cytoskeleton using Paclitaxel improved intraventricular conduction defects. These results indicate that microtubule cytoskeleton contributes to the pathogenesis of LMNA cardiomyopathy and that drugs stabilizing the microtubule may be beneficial for patients.

10.
J Gen Physiol ; 151(1): 42-52, 2019 01 07.
Artigo em Inglês | MEDLINE | ID: mdl-30567709

RESUMO

Heart failure with preserved ejection fraction (HFpEF) is a complex syndrome characterized by a preserved ejection fraction but increased diastolic stiffness and abnormalities of filling. Although the prevalence of HFpEF is high and continues to rise, no effective therapies exist; however, the diabetic drug metformin has been associated with improved diastolic function in diabetic patients. Here we determine the therapeutic potential of metformin for improving diastolic function in a mouse model with HFpEF-like symptoms. We combine transverse aortic constriction (TAC) surgery with deoxycorticosterone acetate (DOCA) supplementation to obtain a mouse model with increased diastolic stiffness and exercise intolerance. Echocardiography and pressure-volume analysis reveal that providing metformin to TAC/DOCA mice improves diastolic function in the left ventricular (LV) chamber. Muscle mechanics show that metformin lowers passive stiffness of the LV wall muscle. Concomitant with this improvement in diastolic function, metformin-treated TAC/DOCA mice also demonstrate preserved exercise capacity. No metformin effects are seen in sham operated mice. Extraction experiments on skinned ventricular muscle strips show that the metformin-induced reduction of passive stiffness in TAC/DOCA mice is due to an increase in titin compliance. Using phospho-site-specific antibodies, we assay the phosphorylation of titin's PEVK and N2B spring elements. Metformin-treated mice have unaltered PEVK phosphorylation but increased phosphorylation of PKA sites in the N2B element, a change which has previously been shown to lower titin's stiffness. Consistent with this result, experiments with a mouse model deficient in the N2B element reveal that the beneficial effect of metformin on LV chamber and muscle stiffness requires the presence of the N2B element. We conclude that metformin offers therapeutic benefit during HFpEF by lowering titin-based passive stiffness.


Assuntos
Diástole/efeitos dos fármacos , Insuficiência Cardíaca/tratamento farmacológico , Metformina/farmacologia , Proteínas Quinases/metabolismo , Animais , Acetato de Desoxicorticosterona/farmacologia , Modelos Animais de Doenças , Insuficiência Cardíaca/metabolismo , Ventrículos do Coração/efeitos dos fármacos , Ventrículos do Coração/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Miocárdio/metabolismo , Fosforilação/efeitos dos fármacos , Volume Sistólico/efeitos dos fármacos
11.
PLoS One ; 13(6): e0198492, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29889873

RESUMO

Diastolic dysfunction is increasingly prevalent in our ageing society and an important contributor to heart failure. The giant protein titin could serve as a therapeutic target, as its elastic properties are a main determinant of cardiac filling in diastole. This study aimed to develop a high throughput pharmacological screen to identify small molecules that affect titin isoform expression through differential inclusion of exons encoding the elastic PEVK domains. We used a dual luciferase splice reporter assay that builds on the titin splice factor RBM20 to screen ~34,000 small molecules and identified several compounds that inhibit the exclusion of PEVK exons. These compounds belong to the class of cardenolides and affect RBM20 dependent titin exon exclusion but did not affect RBFOX1 mediated splicing of FMNL3. We provide evidence that cardenolides do not bind to the RNA interacting domain of RBM20, but reduce RBM20 protein levels and alter transcription of select splicing factors that interact with RBM20. Cardenolides affect titin isoform expression. Understanding their mode of action and harnessing the splice effects through chemical modifications that suppress the effects on ion homeostasis and more selectively affect cardiac splicing has the potential to improve cardiac filling and thus help patients with diastolic heart failure, for which currently no targeted therapy exists.


Assuntos
Cardenolídeos/farmacologia , Conectina/genética , Descoberta de Drogas , Genes Reporter , Processamento de RNA/efeitos dos fármacos , Cardenolídeos/química , Cardenolídeos/metabolismo , Conectina/antagonistas & inibidores , Conectina/metabolismo , Digitoxina/química , Digitoxina/metabolismo , Digitoxina/farmacologia , Células HEK293 , Ensaios de Triagem em Larga Escala/métodos , Humanos , Isoformas de Proteínas/antagonistas & inibidores , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Transcrição Genética/efeitos dos fármacos
12.
Nucleic Acids Res ; 46(10): 5227-5238, 2018 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-29518215

RESUMO

RNA-binding motif protein 20 (RBM20) is a cardiac splice regulator that adapts cardiac filling via its diverse substrates-including the sarcomeric protein titin. The molecular basis and regulation of RBM20-dependent exon exclusion are largely unknown. In tissue culture experiments, we show that the combination of RNA recognition motif (RRM) and C-terminus is necessary and sufficient for RBM20 activity, indicating an important function of the ZnF2 domain in splicing repression. Using splice reporter and in vitro binding assays targeting titin exons 241-243, we identified a minimal genomic segment that is necessary for RBM20-mediated splicing repression of the alternative exon. Here, RBM20 binds the cluster containing most RBM20 binding motifs through its RRM domain and represses the upstream and downstream introns. For subsequent exon exclusion, specific regions upstream, downstream and within the alternative exon 242 are required. Regulation of exon exclusion involves PTB4 as a novel titin splice regulator, which counteracts RBM20 repressor activity in HEK293 cells. Together, these mechanistic insights into the regulation and action of RBM20 and PTB4 provide a basis for the future development of RBM20 modulators that adapt titin elasticity in cardiac disease.


Assuntos
Conectina/genética , Éxons , Ribonucleoproteínas Nucleares Heterogêneas/metabolismo , Proteína de Ligação a Regiões Ricas em Polipirimidinas/metabolismo , Proteínas de Ligação a RNA/metabolismo , Processamento Alternativo , Sítios de Ligação , Conectina/metabolismo , Células HEK293 , Ribonucleoproteínas Nucleares Heterogêneas/genética , Humanos , Íntrons , Proteína de Ligação a Regiões Ricas em Polipirimidinas/genética , Proteínas de Ligação a RNA/genética , Globinas beta/genética
13.
RNA Biol ; 15(3): 359-368, 2018 03 04.
Artigo em Inglês | MEDLINE | ID: mdl-29028411

RESUMO

PAR-CLIP (photoactivatable ribonucleoside-enhanced crosslinking and immunoprecipitation) facilitates the identification and mapping of protein/RNA interactions. So far, it has been limited to select cell-lines as it requires efficient 4SU uptake. To increase transcriptome complexity and thus identify additional RNA-protein interaction sites we fused HEK 293 T-Rex cells (HEK293-Y) that express the RNA binding protein YBX1 with PC12 cells expressing eGFP (PC12-eGFP). The resulting hybrids enable PAR-CLIP on a neuronally expanded transcriptome (Fusion-CLIP) and serve as a proof of principle. The fusion cells express both parental marker genes YBX1 and eGFP and the expanded transcriptome contains human and rat transcripts. PAR-CLIP of fused cells versus the parental HEK293-Y identified 768 novel RNA targets of YBX1. We were able to trace the origin of the majority of the short PAR-CLIP reads as they differentially mapped to the human and rat genome. Furthermore, Fusion-CLIP expanded the CAUC RNA binding motif of YBX1 to UCUUUNNCAUC. The fusion of HEK293-Y and PC12-eGFP cells resulted in cells with a diverse genome expressing human and rat transcripts that enabled the identification of novel YBX1 substrates. The technique allows the expansion of the HEK 293 transcriptome and makes PAR-CLIP available to fusion cells of diverse origin.


Assuntos
Fusão Celular/métodos , Proteínas de Fluorescência Verde/química , Proteínas de Fluorescência Verde/metabolismo , RNA Mensageiro/metabolismo , Proteína 1 de Ligação a Y-Box/química , Proteína 1 de Ligação a Y-Box/metabolismo , Motivos de Aminoácidos , Animais , Sítios de Ligação , Reagentes para Ligações Cruzadas , Perfilação da Expressão Gênica/métodos , Células HEK293 , Humanos , Imunoprecipitação , Células PC12 , Ligação Proteica , Ratos
14.
Eur Heart J ; 38(46): 3449-3460, 2017 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-29029073

RESUMO

Aims: In this study, we aimed to clinically and genetically characterize LVNC patients and investigate the prevalence of variants in known and novel LVNC disease genes. Introduction: Left ventricular non-compaction cardiomyopathy (LVNC) is an increasingly recognized cause of heart failure, arrhythmia, thromboembolism, and sudden cardiac death. We sought here to dissect its genetic causes, phenotypic presentation and outcome. Methods and results: In our registry with follow-up of in the median 61 months, we analysed 95 LVNC patients (68 unrelated index patients and 27 affected relatives; definite familial LVNC = 23.5%) by cardiac phenotyping, molecular biomarkers and exome sequencing. Cardiovascular events were significantly more frequent in LVNC patients compared with an age-matched group of patients with non-ischaemic dilated cardiomyopathy (hazard ratio = 2.481, P = 0.002). Stringent genetic classification according to ACMG guidelines revealed that TTN, LMNA, and MYBPC3 are the most prevalent disease genes (13 patients are carrying a pathogenic truncating TTN variant, odds ratio = 40.7, Confidence interval = 21.6-76.6, P < 0.0001, percent spliced in 76-100%). We also identified novel candidate genes for LVNC. For RBM20, we were able to perform detailed familial, molecular and functional studies. We show that the novel variant p.R634L in the RS domain of RBM20 co-segregates with LVNC, leading to titin mis-splicing as revealed by RNA sequencing of heart tissue in mutation carriers, protein analysis, and functional splice-reporter assays. Conclusion: Our data demonstrate that the clinical course of symptomatic LVNC can be severe. The identified pathogenic variants and distribution of disease genes-a titin-related pathomechanism is found in every fourth patient-should be considered in genetic counselling of patients. Pathogenic variants in the nuclear proteins Lamin A/C and RBM20 were associated with worse outcome.


Assuntos
Hipertrofia Ventricular Esquerda/genética , Mutação/genética , Adulto , Arritmias Cardíacas/genética , Cardiomiopatia Dilatada/genética , Conectina/genética , Morte Súbita Cardíaca/etiologia , Feminino , Predisposição Genética para Doença/genética , Humanos , Lamina Tipo A/genética , Masculino , Linhagem , Proteínas de Ligação a RNA/genética
15.
Science ; 356(6335): 307-311, 2017 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-28428423

RESUMO

The African naked mole-rat's (Heterocephalus glaber) social and subterranean lifestyle generates a hypoxic niche. Under experimental conditions, naked mole-rats tolerate hours of extreme hypoxia and survive 18 minutes of total oxygen deprivation (anoxia) without apparent injury. During anoxia, the naked mole-rat switches to anaerobic metabolism fueled by fructose, which is actively accumulated and metabolized to lactate in the brain. Global expression of the GLUT5 fructose transporter and high levels of ketohexokinase were identified as molecular signatures of fructose metabolism. Fructose-driven glycolytic respiration in naked mole-rat tissues avoids feedback inhibition of glycolysis via phosphofructokinase, supporting viability. The metabolic rewiring of glycolysis can circumvent the normally lethal effects of oxygen deprivation, a mechanism that could be harnessed to minimize hypoxic damage in human disease.


Assuntos
Adaptação Fisiológica , Anaerobiose , Encéfalo/fisiologia , Frutose/metabolismo , Glicólise , Ratos-Toupeira/metabolismo , Oxigênio/metabolismo , Animais , Encéfalo/metabolismo , Frutoquinases/metabolismo , Transportador de Glucose Tipo 5/metabolismo , Ácido Láctico/metabolismo , Camundongos , Miocárdio/metabolismo , Sacarose/metabolismo
16.
J Mol Med (Berl) ; 94(12): 1349-1358, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27889803

RESUMO

Impaired diastolic filling is a main contributor to heart failure with preserved ejection fraction (HFpEF), a syndrome with increasing prevalence and no treatment. Both collagen and the giant sarcomeric protein titin determine diastolic function. Since titin's elastic properties can be adjusted physiologically, we evaluated titin-based stiffness as a therapeutic target. We adjusted RBM20-dependent cardiac isoform expression in the titin N2B knockout mouse with increased ventricular stiffness. A ~50 % reduction of RBM20 activity does not only maintain cardiac filling in diastole but also ameliorates cardiac atrophy and thus improves cardiac function in the N2B-deficient heart. Reduced RBM20 activity partially normalized gene expression related to muscle development and fatty acid metabolism. The adaptation of cardiac growth was related to hypertrophy signaling via four-and-a-half lim-domain proteins (FHLs) that translate mechanical input into hypertrophy signals. We provide a novel link between cardiac isoform expression and trophic signaling via FHLs and suggest cardiac splicing as a therapeutic target in diastolic dysfunction. KEY MESSAGE: Increasing the length of titin isoforms improves ventricular filling in heart disease. FHL proteins are regulated via RBM20 and adapt cardiac growth. RBM20 is a therapeutic target in diastolic dysfunction.


Assuntos
Cardiomegalia/metabolismo , Insuficiência Cardíaca/metabolismo , Ventrículos do Coração/metabolismo , Proteínas Quinases/genética , Proteínas de Ligação a RNA/genética , Animais , Cardiomegalia/genética , Cardiomegalia/patologia , Colágeno/genética , Colágeno/metabolismo , Diástole/fisiologia , Regulação da Expressão Gênica , Insuficiência Cardíaca/genética , Insuficiência Cardíaca/patologia , Ventrículos do Coração/patologia , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas com Domínio LIM/genética , Proteínas com Domínio LIM/metabolismo , Masculino , Camundongos , Camundongos Knockout , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Miocárdio/metabolismo , Miocárdio/patologia , Proteínas Quinases/deficiência , Proteínas de Ligação a RNA/metabolismo , Transdução de Sinais , Volume Sistólico/fisiologia
17.
J Clin Invest ; 126(10): 3999-4015, 2016 10 03.
Artigo em Inglês | MEDLINE | ID: mdl-27643434

RESUMO

The canonical atrial myocyte (AM) is characterized by sparse transverse tubule (TT) invaginations and slow intracellular Ca2+ propagation but exhibits rapid contractile activation that is susceptible to loss of function during hypertrophic remodeling. Here, we have identified a membrane structure and Ca2+-signaling complex that may enhance the speed of atrial contraction independently of phospholamban regulation. This axial couplon was observed in human and mouse atria and is composed of voluminous axial tubules (ATs) with extensive junctions to the sarcoplasmic reticulum (SR) that include ryanodine receptor 2 (RyR2) clusters. In mouse AM, AT structures triggered Ca2+ release from the SR approximately 2 times faster at the AM center than at the surface. Rapid Ca2+ release correlated with colocalization of highly phosphorylated RyR2 clusters at AT-SR junctions and earlier, more rapid shortening of central sarcomeres. In contrast, mice expressing phosphorylation-incompetent RyR2 displayed depressed AM sarcomere shortening and reduced in vivo atrial contractile function. Moreover, left atrial hypertrophy led to AT proliferation, with a marked increase in the highly phosphorylated RyR2-pS2808 cluster fraction, thereby maintaining cytosolic Ca2+ signaling despite decreases in RyR2 cluster density and RyR2 protein expression. AT couplon "super-hubs" thus underlie faster excitation-contraction coupling in health as well as hypertrophic compensatory adaptation and represent a structural and metabolic mechanism that may contribute to contractile dysfunction and arrhythmias.


Assuntos
Sinalização do Cálcio , Átrios do Coração/citologia , Miócitos Cardíacos/fisiologia , Agonistas Adrenérgicos beta/farmacologia , Animais , Cálcio/metabolismo , Células Cultivadas , Humanos , Junções Intercelulares/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Microtúbulos/metabolismo , Contração Miocárdica , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/ultraestrutura , Fosforilação , Processamento de Proteína Pós-Traducional , Transporte Proteico , Canal de Liberação de Cálcio do Receptor de Rianodina
18.
PLoS One ; 10(6): e0129424, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26076477

RESUMO

The coxsackie- and adenovirus receptor (CXADR) is a member of the immunoglobulin protein superfamily, present in various epithelial cells including glomerular epithelial cells. Beside its known function as a virus receptor, it also constitutes an integral part of cell-junctions. Previous studies in the zebrafish pronephros postulated a potential role of CXADR for the terminal differentiation of glomerular podocytes and correct patterning of the elaborated foot process architecture. However, due to early embryonic lethality of constitutive Cxadr knockout mice, mammalian data on kidney epithelial cells have been lacking. Interestingly, Cxadr is robustly expressed during podocyte development and in adulthood in response to glomerular injury. We therefore used a conditional transgenic approach to elucidate the function of Cxadr for podocyte development and stress response. Surprisingly, we could not discern a developmental phenotype in podocyte specific Cxadr knock-out mice. In addition, despite a significant up regulation of CXADR during toxic, genetic and immunologic podocyte injury, we could not detect any impact of Cxadr on these injury models. Thus these data indicate that in contrast to lower vertebrate models, mammalian podocytes have acquired molecular programs to compensate for the loss of Cxadr.


Assuntos
Proteína de Membrana Semelhante a Receptor de Coxsackie e Adenovirus/genética , Proteína de Membrana Semelhante a Receptor de Coxsackie e Adenovirus/metabolismo , Deleção de Genes , Podócitos/metabolismo , Estresse Fisiológico , Animais , Expressão Gênica , Técnicas de Inativação de Genes , Rim/embriologia , Rim/metabolismo , Glomérulos Renais/citologia , Glomérulos Renais/embriologia , Glomérulos Renais/metabolismo , Glomérulos Renais/ultraestrutura , Camundongos , Camundongos Knockout
19.
Sci Transl Med ; 7(270): 270ra6, 2015 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-25589632

RESUMO

The recent discovery of heterozygous human mutations that truncate full-length titin (TTN, an abundant structural, sensory, and signaling filament in muscle) as a common cause of end-stage dilated cardiomyopathy (DCM) promises new prospects for improving heart failure management. However, realization of this opportunity has been hindered by the burden of TTN-truncating variants (TTNtv) in the general population and uncertainty about their consequences in health or disease. To elucidate the effects of TTNtv, we coupled TTN gene sequencing with cardiac phenotyping in 5267 individuals across the spectrum of cardiac physiology and integrated these data with RNA and protein analyses of human heart tissues. We report diversity of TTN isoform expression in the heart, define the relative inclusion of TTN exons in different isoforms (using the TTN transcript annotations available at http://cardiodb.org/titin), and demonstrate that these data, coupled with the position of the TTNtv, provide a robust strategy to discriminate pathogenic from benign TTNtv. We show that TTNtv is the most common genetic cause of DCM in ambulant patients in the community, identify clinically important manifestations of TTNtv-positive DCM, and define the penetrance and outcomes of TTNtv in the general population. By integrating genetic, transcriptome, and protein analyses, we provide evidence for a length-dependent mechanism of disease. These data inform diagnostic criteria and management strategies for TTNtv-positive DCM patients and for TTNtv that are identified as incidental findings.


Assuntos
Alelos , Conectina/genética , Coração/fisiologia , Mutação , Transcrição Genética , Adolescente , Adulto , Idoso , Cardiomiopatia Dilatada/genética , Cardiomiopatia Dilatada/patologia , Estudos de Coortes , Conectina/fisiologia , Éxons , Variação Genética , Voluntários Saudáveis , Insuficiência Cardíaca/genética , Insuficiência Cardíaca/terapia , Humanos , Imunoglobulinas/metabolismo , Pessoa de Meia-Idade , Isoformas de Proteínas/genética , Isoformas de Proteínas/fisiologia , Adulto Jovem
20.
J Biol Chem ; 290(4): 2419-30, 2015 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-25488665

RESUMO

Src homology and collagen A (ShcA) is an adaptor protein that binds to tyrosine kinase receptors. Its germ line deletion is embryonic lethal with abnormal cardiovascular system formation, and its role in cardiovascular development is unknown. To investigate its functional role in cardiovascular development in mice, ShcA was deleted in cardiomyocytes and vascular smooth muscle cells by crossing ShcA flox mice with SM22a-Cre transgenic mice. Conditional mutant mice developed signs of severe dilated cardiomyopathy, myocardial infarctions, and premature death. No evidence of a vascular contribution to the phenotype was observed. Histological analysis of the heart revealed aberrant sarcomeric Z-disk and M-band structures, and misalignments of T-tubules with Z-disks. We find that not only the ErbB3/Neuregulin signaling pathway but also the baroreceptor reflex response, which have been functionally associated, are altered in the mutant mice. We further demonstrate that ShcA interacts with Caveolin-1 and the costameric protein plasma membrane Ca(2+)/calmodulin-dependent ATPase (PMCA), and that its deletion leads to abnormal dystrophin signaling. Collectively, these results demonstrate that ShcA interacts with crucial proteins and pathways that link Z-disk and costamere.


Assuntos
Costâmeros/metabolismo , Coração/embriologia , Miócitos Cardíacos/metabolismo , Miócitos de Músculo Liso/metabolismo , Proteínas Adaptadoras da Sinalização Shc/metabolismo , Alelos , Animais , Aorta Torácica/metabolismo , Pressão Sanguínea , Sobrevivência Celular , Distrofina/metabolismo , Ecocardiografia , Deleção de Genes , Regulação da Expressão Gênica no Desenvolvimento , Imagem por Ressonância Magnética , Camundongos , Camundongos Transgênicos , Microscopia Confocal , Fenótipo , ATPases Transportadoras de Cálcio da Membrana Plasmática/metabolismo , RNA Interferente Pequeno/metabolismo , Ratos , Receptor ErbB-3/metabolismo , Proteínas Adaptadoras da Sinalização Shc/genética , Proteína 1 de Transformação que Contém Domínio 2 de Homologia de Src
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