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1.
Curr Biol ; 2020 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-33035485

RESUMO

Several plant proteins are preferentially localized to one end of a cell, allowing a polarity to be assigned to the cell. These cell polarity proteins often exhibit coordinated patterns between neighboring cells, termed tissue cell polarity. Tissue cell polarity is widespread in plants and can influence how cells grow, divide, and differentiate [1-5]. However, it is unclear whether cell polarity is established through cell-intrinsic or -extrinsic mechanisms and how polarity is coupled to growth. To address these issues, we analyzed the behavior of a tissue cell polarity protein BASL (BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE) in the simplifying context of cultured cell filaments and in protoplasts before and during regeneration. We show that BASL is polarly localized when ectopically expressed in tobacco BY-2 cell cultures. Ectopic BASL is found preferentially at the developing tips of cell filaments, likely marking a polarized molecular address. Polarity can shift during the cell cycle and is resistant to treatment with microtubule, actin or auxin transport inhibitors. BASL also exhibits polar localization in spherical protoplasts, in contrast to other polarity proteins so far tested. BASL polarity within protoplasts is dynamic and resistant to auxin transport inhibitors. As protoplasts regenerate, polarity remains dynamic in isotropically growing cells but becomes fixed in anisotropic cells and aligns with the axis of cell growth. Our findings suggest that plant cells have an intrinsic ability to polarize and that environmental or developmental cues may act by biasing the direction of this polarity and thus the orientation of anisotropic growth.

2.
Sci Rep ; 10(1): 15284, 2020 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-32943714

RESUMO

Acute myocardial ischaemia and reperfusion (I-R) are major causes of ventricular arrhythmias in patients with a history of coronary artery disease. Ursodeoxycholic acid (UDCA) has previously been shown to be antiarrhythmic in fetal hearts. This study was performed to investigate if UDCA protects against ischaemia-induced and reperfusion-induced arrhythmias in the adult myocardium, and compares the effect of acute (perfusion only) versus prolonged (2 weeks pre-treatment plus perfusion) UDCA administration. Langendorff-perfused adult Sprague-Dawley rat hearts were subjected to acute regional ischaemia by ligation of the left anterior descending artery (10 min), followed by reperfusion (2 min), and arrhythmia incidence quantified. Prolonged UDCA administration reduced the incidence of acute ischaemia-induced arrhythmias (p = 0.028), with a reduction in number of ventricular ectopic beats during the ischaemic phase compared with acute treatment (10 ± 3 vs 58 ± 15, p = 0.036). No antiarrhythmic effect was observed in the acute UDCA administration group. Neither acute nor prolonged UDCA treatment altered the incidence of reperfusion arrhythmias. The antiarrhythmic effect of UDCA may be partially mediated by an increase in cardiac wavelength, due to the attenuation of conduction velocity slowing (p = 0.03), and the preservation of Connexin43 phosphorylation during acute ischaemia (p = 0.0027). The potential antiarrhythmic effects of prolonged UDCA administration merit further investigation.

3.
Front Cell Dev Biol ; 8: 695, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32850816

RESUMO

Mediastinal lymphadenopathy and auto-antibodies are clinical phenomena during ischemic heart failure pointing to an autoimmune response against the heart. T and B cells have been convincingly demonstrated to be activated after myocardial infarction, a prerequisite for the generation of mature auto-antibodies. Yet, little is known about the immunoglobulin isotype repertoire thus pathological potential of anti-heart auto-antibodies during heart failure. We obtained human myocardial tissue from ischemic heart failure patients and induced experimental MI in rats. We found that anti-heart autoimmunity persists during heart failure. Rat mediastinal lymph nodes are enlarged and contain active secondary follicles with mature isotype-switched IgG2a B cells. Mature IgG2a auto-antibodies specific for cardiac antigens are present in rat heart failure serum, and IgG and complement C3 deposits are evident in heart failure tissue of both rats and human patients. Previously established myocardial inflammation, and the herein provided proof of B cell maturation in lymph nodes and myocardial deposition of mature auto-antibodies, provide all the hallmark signs of an established autoimmune response in chronic heart failure.

4.
Nanoscale ; 12(30): 16315-16329, 2020 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-32720664

RESUMO

Mechanical properties of single myocytes contribute to the whole heart performance, but the measurement of mechanics in living cells at high resolution with minimal force interaction remains challenging. Angiotensin II (AngII) is a peptide hormone that regulates a number of physiological functions, including heart performance. It has also been shown to contribute to cell mechanics by inducing cell stiffening. Using non-contact high-resolution Scanning Ion Conductance Microscopy (SICM), we determine simultaneously cell topography and membrane transverse Young's modulus (YM) by a constant pressure application through a nanopipette. While applying pressure, the vertical position is recorded and a deformation map is generated from which YM can be calculated and corrected for the uneven geometry. High resolution of this method also allows studying specific membrane subdomains, such as Z-grooves and crests. We found that short-term AngII treatment reduces the transversal YM in isolated adult rat cardiomyocytes acting via an AT1 receptor. Blocking either a TGF-ß1 receptor or Rho kinase abolishes this effect. Analysis of the cytoskeleton showed that AngII depletes microtubules by decreasing long-lived detyrosinated and acetylated microtubule populations. Interestingly, in the failing cardiomyocytes, which are stiffer than controls, the short-term AngII treatment also reduces the YM, thus normalizing the mechanical state of cells. This suggests that the short-term softening effect of AngII on cardiac cells is opposite to the well-characterized long-term hypertrophic effect. In conclusion, we generate a precise nanoscale indication map of location-specific transverse cortical YM within the cell and this can substantially advance our understanding of cellular mechanics in a physiological environment, for example in isolated cardiac myocytes.

5.
Cardiovasc Res ; 2020 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-32402067

RESUMO

AIMS: Conflicting data exist supporting differing mechanisms for sustaining ventricular fibrillation (VF), ranging from disorganised multiple-wavelet activation to organised rotational activities (RAs). Abnormal gap junction (GJ) coupling and fibrosis are important in initiation and maintenance of VF. We investigated whether differing ventricular fibrosis patterns and the degree of GJ coupling affected the underlying VF mechanism. METHODS AND RESULTS: Optical mapping of 65 Langendorff-perfused rat hearts was performed to study VF mechanisms in control hearts with acute GJ modulation, and separately in three differing chronic ventricular fibrosis models; compact (CF), diffuse (DiF) and patchy (PF). VF dynamics were quantified with phase mapping and frequency dominance index (FDI) analysis, a power ratio of the highest amplitude dominant frequency in the cardiac frequency spectrum.Enhanced GJ coupling with rotigaptide (n = 10) progressively organised fibrillation in a concentration-dependent manner; increasing FDI (0nM: 0.53±0.04, 80nM: 0.78±0.03, p < 0.001), increasing RA sustained VF time (0nM:44±6%, 80nM: 94±2%, p < 0.001) and stabilised RAs (maximum rotations for a RA; 0nM:5.4±0.5, 80nM: 48.2±12.3, p < 0.001). GJ uncoupling with carbenoxolone progressively disorganised VF; the FDI decreased (0µM: 0.60±0.05, 50µM: 0.17±0.03, p < 0.001) and RA-sustained VF time decreased (0µM: 61±9%, 50µM: 3±2%, p < 0.001).In CF, VF activity was disorganised and the RA-sustained VF time was the lowest (CF: 27±7% versus PF: 75±5%, p < 0.001). Global fibrillatory organisation measured by FDI was highest in PF (PF: 0.67±0.05 versus CF: 0.33±0.03, p < 0.001). PF harboured the longest duration and most spatially stable RAs (patchy: 1411±266ms versus compact: 354±38ms, p < 0.001). DiF (n = 11) exhibited an intermediately organised VF pattern, sustained by a combination of multiple-wavelets and short-lived RAs. CONCLUSION: The degree of GJ coupling and pattern of fibrosis influences the mechanism sustaining VF. There is a continuous spectrum of organisation in VF, ranging between globally organised fibrillation sustained by stable RAs and disorganised, possibly multiple-wavelet driven fibrillation with no RAs. TRANSLATIONAL PERSPECTIVE: Multiple competing mechanisms have been proposed for sustaining VF. We reframed conflicting mechanisms reported in sustaining fibrillation and defined them as part of a continuum of varying global organisation, with some sustained by stable rotationalactivities. The underlying cardiac electroarchitecture, namely gap junction coupling and fibrosis, were important determinants of the VF mechanism. Characterising the VF mechanism and its relationship to the cardiac electroarchitecture may facilitate a patient-tailored treatment approach towards VF prevention in VF survivors. Organised fibrillation sustained by stable rotational activities could be considered for targeted ablation. Disorganised fibrillation dynamics may be better suited for conventional pharmacotherapy.

7.
Elife ; 92020 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-32228862

RESUMO

Cardiomyocyte ß3-adrenoceptors (ß3-ARs) coupled to soluble guanylyl cyclase (sGC)-dependent production of the second messenger 3',5'-cyclic guanosine monophosphate (cGMP) have been shown to protect from heart failure. However, the exact localization of these receptors to fine membrane structures and subcellular compartmentation of ß3-AR/cGMP signals underpinning this protection in health and disease remain elusive. Here, we used a Förster Resonance Energy Transfer (FRET)-based cGMP biosensor combined with scanning ion conductance microscopy (SICM) to show that functional ß3-ARs are mostly confined to the T-tubules of healthy rat cardiomyocytes. Heart failure, induced via myocardial infarction, causes a decrease of the cGMP levels generated by these receptors and a change of subcellular cGMP compartmentation. Furthermore, attenuated cGMP signals led to impaired phosphodiesterase two dependent negative cGMP-to-cAMP cross-talk. In conclusion, topographic and functional reorganization of the ß3-AR/cGMP signalosome happens in heart failure and should be considered when designing new therapies acting via this receptor.

8.
Front Cardiovasc Med ; 6: 34, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31001543

RESUMO

Background: Dissimilar ventricular rhythms refer to the occurrence of different ventricular tachyarrhythmias in the right and left ventricles or different rates of the same tachyarrhythmia in the two ventricles. Objective: We investigated the inducibility of dissimilar ventricular rhythms, their underlying mechanisms, and the impact of anti-arrhythmic drugs (lidocaine and amiodarone) on their occurrence. Methods: Ventricular tachyarrhythmias were induced with burst pacing in 28 Langendorff-perfused Sprague Dawley rat hearts (14 control, 8 lidocaine, 6 amiodarone) and bipolar electrograms recorded from the right and left ventricles. Fourteen (6 control, 4 lidocaine, 4 amiodarone) further hearts underwent optical mapping of transmembrane voltage to study interventricular electrophysiological differences and mechanisms of dissimilar rhythms. Results: In control hearts, dissimilar ventricular rhythms developed in 8/14 hearts (57%). In lidocaine treated hearts, there was a lower cycle length threshold for developing dissimilar rhythms, with 8/8 (100%) hearts developing dissimilar rhythms in comparison to 0/6 in the amiodarone group. Dissimilar ventricular tachycardia (VT) rates occurred at longer cycle lengths with lidocaine vs. control (57.1 ± 7.9 vs. 36.6 ± 8.4 ms, p < 0.001). The ratio of LV:RV VT rate was greater in the lidocaine group than control (1.91 ± 0.30 vs. 1.76 ± 0.36, p < 0.001). The gradient of the action potential duration (APD) restitution curve was shallower in the RV compared with LV (Control - LV: 0.12 ± 0.03 vs RV: 0.002 ± 0.03, p = 0.015), leading to LV-to-RV conduction block during VT. Conclusion: Interventricular differences in APD restitution properties likely contribute to the occurrence of dissimilar rhythms. Sodium channel blockade with lidocaine increases the likelihood of dissimilar ventricular rhythms.

9.
Curr Biol ; 28(16): 2638-2646.e4, 2018 08 20.
Artigo em Inglês | MEDLINE | ID: mdl-30100337

RESUMO

Tissue-wide polarity fields, in which cell polarity is coordinated across the tissue, have been described for planar organs such as the Drosophila wing and are considered important for coordinating growth and differentiation [1]. In planar plant organs, such as leaves, polarity fields have been identified for subgroups of cells, such as stomatal lineages [2], trichomes [3, 4], serrations [5], or early developmental stages [6]. Here, we show that ectopic induction of the stomatal protein BASL (BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE) reveals a tissue-wide epidermal polarity field in leaves throughout development. Ectopic GFP-BASL is typically localized toward the proximal end of cells and to one lobe of mature pavement cells, revealing a polarity field that aligns with the proximodistal axis of the leaf (base to tip). The polarity field is largely parallel to the midline of the leaf but diverges in more lateral positions, particularly at later stages in development, suggesting it may be deformed during growth. The polarity field is observed in the speechless mutant, showing that it is independent of stomatal lineages, and is observed in isotropic cells, showing that cell shape anisotropy is not required for orienting polarity. Ectopic BASL forms convergence and divergence points at serrations, mirroring epidermal PIN polarity patterns, suggesting a common underlying polarity mechanism. Thus, we show that similar to the situation in animals, planar plant organs have a tissue-wide cell polarity field, and this may provide a general cellular mechanism for guiding growth and differentiation.


Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/fisiologia , Proteínas de Ciclo Celular/genética , Polaridade Celular , Expressão Ectópica do Gene , Folhas de Planta/crescimento & desenvolvimento , Arabidopsis/genética , Arabidopsis/crescimento & desenvolvimento , Proteínas de Arabidopsis/metabolismo , Proteínas de Ciclo Celular/metabolismo , Diferenciação Celular , Folhas de Planta/fisiologia
10.
Adv Funct Mater ; 28(21): 1800618, 2018 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-29875619

RESUMO

An auxetic conductive cardiac patch (AuxCP) for the treatment of myocardial infarction (MI) is introduced. The auxetic design gives the patch a negative Poisson's ratio, providing it with the ability to conform to the demanding mechanics of the heart. The conductivity allows the patch to interface with electroresponsive tissues such as the heart. Excimer laser microablation is used to micropattern a re-entrant honeycomb (bow-tie) design into a chitosan-polyaniline composite. It is shown that the bow-tie design can produce patches with a wide range in mechanical strength and anisotropy, which can be tuned to match native heart tissue. Further, the auxetic patches are conductive and cytocompatible with murine neonatal cardiomyocytes in vitro. Ex vivo studies demonstrate that the auxetic patches have no detrimental effect on the electrophysiology of both healthy and MI rat hearts and conform better to native heart movements than unpatterned patches of the same material. Finally, the AuxCP applied in a rat MI model results in no detrimental effect on cardiac function and negligible fibrotic response after two weeks in vivo. This approach represents a versatile and robust platform for cardiac biomaterial design and could therefore lead to a promising treatment for MI.

11.
Stem Cell Reports ; 9(5): 1415-1422, 2017 11 14.
Artigo em Inglês | MEDLINE | ID: mdl-28988988

RESUMO

Tissue engineering offers an exciting possibility for cardiac repair post myocardial infarction. We assessed the effects of combined polyethylene glycol hydrogel (PEG), human induced pluripotent stem cell-derived cardiomyocyte (iPSC-CM), and erythropoietin (EPO) therapy in a rat model of myocardial infarction. PEG with/out iPSC-CMs and EPO; iPSC-CMs in saline; or saline alone was injected into infarcted hearts shortly after infarction. Injection of almost any combination of the therapeutics limited acute elevations in chamber volumes. After 10 weeks, attenuation of ventricular remodeling was identified in all groups that received PEG injections, while ejection fractions were significantly increased in the gel-EPO, cell, and gel-cell-EPO groups. In all treatment groups, infarct thickness was increased and regions of muscle were identified within the scar. However, no grafted cells were detected. Hence, iPSC-CM-encapsulating bioactive hydrogel therapy can improve cardiac function post myocardial infarction and increase infarct thickness and muscle content despite a lack of sustained donor-cell engraftment.


Assuntos
Células-Tronco Pluripotentes Induzidas/transplante , Infarto do Miocárdio/terapia , Transplante de Células-Tronco/métodos , Animais , Células Cultivadas , Eritropoetina/administração & dosagem , Eritropoetina/uso terapêutico , Humanos , Hidrogéis/química , Células-Tronco Pluripotentes Induzidas/citologia , Injeções Intralesionais , Masculino , Miócitos Cardíacos/citologia , Polietilenoglicóis/química , Ratos , Ratos Nus
12.
Cardiovasc Res ; 113(7): 770-782, 2017 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-28505272

RESUMO

Aims: Cardiomyocyte ß2-adrenergic receptor (ß2AR) cyclic adenosine monophosphate (cAMP) signalling is regulated by the receptors' subcellular location within transverse tubules (T-tubules), via interaction with structural and regulatory proteins, which form a signalosome. In chronic heart failure (HF), ß2ARs redistribute from T-tubules to the cell surface, which disrupts functional signalosomes and leads to diffuse cAMP signalling. However, the functional consequences of structural changes upon ß2AR-cAMP signalling during progression from hypertrophy to advanced HF are unknown. Methods and results: Rat left ventricular myocytes were isolated at 4-, 8-, and 16-week post-myocardial infarction (MI), ß2ARs were stimulated either via whole-cell perfusion or locally through the nanopipette of the scanning ion conductance microscope. cAMP release was measured via a Förster Resonance Energy Transfer-based sensor Epac2-camps. Confocal imaging of di-8-ANNEPS-stained cells and immunoblotting were used to determine structural alterations. At 4-week post-MI, T-tubule regularity, density and junctophilin-2 (JPH2) expression were significantly decreased. The amplitude of local ß2AR-mediated cAMP in T-tubules was reduced and cAMP diffused throughout the cytosol instead of being locally confined. This was accompanied by partial caveolin-3 (Cav-3) dissociation from the membrane. At 8-week post-MI, the ß2AR-mediated cAMP response was observed at the T-tubules and the sarcolemma (crest). Finally, at 16-week post-MI, the whole cell ß2AR-mediated cAMP signal was depressed due to adenylate cyclase dysfunction, while overall Cav-3 levels were significantly increased and a substantial portion of Cav-3 dissociated into the cytosol. Overexpression of JPH2 in failing cells in vitro or AAV9.SERCA2a gene therapy in vivo did not improve ß2AR-mediated signal compartmentation or reduce cAMP diffusion. Conclusion: Although changes in T-tubule structure and ß2AR-mediated cAMP signalling are significant even at 4-week post-MI, progression to the HF phenotype is not linear. At 8-week post-MI the loss of ß2AR-mediated cAMP is temporarily reversed. Complete disorganization of ß2AR-mediated cAMP signalling due to changes in functional receptor localization and cellular structure occurs at 16-week post-MI.


Assuntos
AMP Cíclico/metabolismo , Insuficiência Cardíaca/metabolismo , Miócitos Cardíacos/metabolismo , Receptores Adrenérgicos beta 2/metabolismo , Sarcolema/metabolismo , Sistemas do Segundo Mensageiro , Remodelação Ventricular , Adenilil Ciclases/metabolismo , Animais , Técnicas Biossensoriais , Caveolina 3/metabolismo , Células Cultivadas , Difusão , Modelos Animais de Doenças , Progressão da Doença , Terapia Genética/métodos , Fatores de Troca do Nucleotídeo Guanina/genética , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Insuficiência Cardíaca/etiologia , Insuficiência Cardíaca/fisiopatologia , Insuficiência Cardíaca/terapia , Masculino , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Microscopia Eletroquímica de Varredura/métodos , Infarto do Miocárdio/complicações , Miócitos Cardíacos/patologia , Transporte Proteico , Ratos Sprague-Dawley , Sarcolema/patologia , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/genética , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/metabolismo , Fatores de Tempo , Transfecção
13.
Circ Res ; 119(8): 944-55, 2016 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-27572487

RESUMO

RATIONALE: Disruption in subcellular targeting of Ca(2+) signaling complexes secondary to changes in cardiac myocyte structure may contribute to the pathophysiology of a variety of cardiac diseases, including heart failure (HF) and certain arrhythmias. OBJECTIVE: To explore microdomain-targeted remodeling of ventricular L-type Ca(2+) channels (LTCCs) in HF. METHODS AND RESULTS: Super-resolution scanning patch-clamp, confocal and fluorescence microscopy were used to explore the distribution of single LTCCs in different membrane microdomains of nonfailing and failing human and rat ventricular myocytes. Disruption of membrane structure in both species led to the redistribution of functional LTCCs from their canonical location in transversal tubules (T-tubules) to the non-native crest of the sarcolemma, where their open probability was dramatically increased (0.034±0.011 versus 0.154±0.027, P<0.001). High open probability was linked to enhance calcium-calmodulin kinase II-mediated phosphorylation in non-native microdomains and resulted in an elevated ICa,L window current, which contributed to the development of early afterdepolarizations. A novel model of LTCC function in HF was developed; after its validation with experimental data, the model was used to ascertain how HF-induced T-tubule loss led to altered LTCC function and early afterdepolarizations. The HF myocyte model was then implemented in a 3-dimensional left ventricle model, demonstrating that such early afterdepolarizations can propagate and initiate reentrant arrhythmias. CONCLUSIONS: Microdomain-targeted remodeling of LTCC properties is an important event in pathways that may contribute to ventricular arrhythmogenesis in the settings of HF-associated remodeling. This extends beyond the classical concept of electric remodeling in HF and adds a new dimension to cardiovascular disease.


Assuntos
Arritmias Cardíacas/fisiopatologia , Canais de Cálcio Tipo L/fisiologia , Insuficiência Cardíaca/fisiopatologia , Microdomínios da Membrana/fisiologia , Miócitos Cardíacos/fisiologia , Adulto , Idoso , Animais , Arritmias Cardíacas/epidemiologia , Arritmias Cardíacas/etiologia , Células Cultivadas , Feminino , Insuficiência Cardíaca/epidemiologia , Insuficiência Cardíaca/etiologia , Humanos , Masculino , Pessoa de Meia-Idade , Ratos , Ratos Sprague-Dawley
14.
Sci Adv ; 2(11): e1601007, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28138526

RESUMO

Electrically active constructs can have a beneficial effect on electroresponsive tissues, such as the brain, heart, and nervous system. Conducting polymers (CPs) are being considered as components of these constructs because of their intrinsic electroactive and flexible nature. However, their clinical application has been largely hampered by their short operational time due to a decrease in their electronic properties. We show that, by immobilizing the dopant in the conductive scaffold, we can prevent its electric deterioration. We grew polyaniline (PANI) doped with phytic acid on the surface of a chitosan film. The strong chelation between phytic acid and chitosan led to a conductive patch with retained electroactivity, low surface resistivity (35.85 ± 9.40 kilohms per square), and oxidized form after 2 weeks of incubation in physiological medium. Ex vivo experiments revealed that the conductive nature of the patch has an immediate effect on the electrophysiology of the heart. Preliminary in vivo experiments showed that the conductive patch does not induce proarrhythmogenic activities in the heart. Our findings set the foundation for the design of electronically stable CP-based scaffolds. This provides a robust conductive system that could be used at the interface with electroresponsive tissue to better understand the interaction and effect of these materials on the electrophysiology of these tissues.


Assuntos
Compostos de Anilina , Quitosana , Membranas Artificiais , Miocárdio , Ácido Fítico , Compostos de Anilina/química , Compostos de Anilina/farmacologia , Animais , Quitosana/química , Quitosana/farmacologia , Condutividade Elétrica , Ácido Fítico/química , Ácido Fítico/farmacologia , Ratos
15.
Science ; 350(6267): 1521-4, 2015 Dec 18.
Artigo em Inglês | MEDLINE | ID: mdl-26680197

RESUMO

In terrestrial ecosystems, plants take up phosphate predominantly via association with arbuscular mycorrhizal fungi (AMF). We identified loss of responsiveness to AMF in the rice (Oryza sativa) mutant hebiba, reflected by the absence of physical contact and of characteristic transcriptional responses to fungal signals. Among the 26 genes deleted in hebiba, DWARF 14 LIKE is, the one responsible for loss of symbiosis . It encodes an alpha/beta-fold hydrolase, that is a component of an intracellular receptor complex involved in the detection of the smoke compound karrikin. Our finding reveals an unexpected plant recognition strategy for AMF and a previously unknown signaling link between symbiosis and plant development.


Assuntos
Furanos/metabolismo , Hidrolases/metabolismo , Micorrizas/fisiologia , Oryza/enzimologia , Oryza/microbiologia , Proteínas de Plantas/metabolismo , Piranos/metabolismo , Simbiose/fisiologia , Hidrolases/genética , Oryza/genética , Fosfatos/metabolismo , Proteínas de Plantas/genética , Simbiose/genética , Transcrição Genética
16.
Circ Cardiovasc Genet ; 8(5): 643-52, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26175529

RESUMO

BACKGROUND: Mutations in sarcomeric and cytoskeletal proteins are a major cause of hereditary cardiomyopathies, but our knowledge remains incomplete as to how the genetic defects execute their effects. METHODS AND RESULTS: We used cysteine and glycine-rich protein 3, a known cardiomyopathy gene, in a yeast 2-hybrid screen and identified zinc-finger and BTB domain-containing protein 17 (ZBTB17) as a novel interacting partner. ZBTB17 is a transcription factor that contains the peak association signal (rs10927875) at the replicated 1p36 cardiomyopathy locus. ZBTB17 expression protected cardiac myocytes from apoptosis in vitro and in a mouse model with cardiac myocyte-specific deletion of Zbtb17, which develops cardiomyopathy and fibrosis after biomechanical stress. ZBTB17 also regulated cardiac myocyte hypertrophy in vitro and in vivo in a calcineurin-dependent manner. CONCLUSIONS: We revealed new functions for ZBTB17 in the heart, a transcription factor that may play a role as a novel cardiomyopathy gene.


Assuntos
Cardiomiopatias/genética , Insuficiência Cardíaca/genética , Proteínas Nucleares/genética , Animais , Proteínas de Ligação a DNA , Coração/fisiologia , Humanos , Fatores de Transcrição Kruppel-Like/genética , Fatores de Transcrição Kruppel-Like/fisiologia , Proteínas com Domínio LIM/genética , Proteínas com Domínio LIM/metabolismo , Camundongos , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Proteínas Nucleares/fisiologia , Proteínas Inibidoras de STAT Ativados/genética , Proteínas Inibidoras de STAT Ativados/fisiologia , Ratos , Estresse Fisiológico , Técnicas de Cultura de Tecidos , Ubiquitina-Proteína Ligases
17.
Pflugers Arch ; 466(6): 1093-9, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24531746

RESUMO

Mechanosensation and mechanotransduction are fundamental aspects of biology, but the link between physical stimuli and biological responses remains not well understood. The perception of mechanical stimuli, their conversion into biochemical signals, and the transmission of these signals are particularly important for dynamic organs such as the heart. Various concepts have been introduced to explain mechanosensation at the molecular level, including effects on signalosomes, tensegrity, or direct activation (or inactivation) of enzymes. Striated muscles, including cardiac myocytes, differ from other cells in that they contain sarcomeres which are essential for the generation of forces and which play additional roles in mechanosensation. The majority of cardiomyopathy causing candidate genes encode structural proteins among which titin probably is the most important one. Due to its elastic elements, titin is a length sensor and also plays a role as a tension sensor (i.e., stress sensation). The recent discovery of titin mutations being a major cause of dilated cardiomyopathy (DCM) also underpins the importance of mechanosensation and mechanotransduction in the pathogenesis of heart failure. Here, we focus on sarcomere-related mechanisms, discuss recent findings, and provide a link to cardiomyopathy and associated heart failure.


Assuntos
Insuficiência Cardíaca/metabolismo , Mecanotransdução Celular , Sarcômeros/metabolismo , Animais , Insuficiência Cardíaca/fisiopatologia , Humanos , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Sarcômeros/fisiologia
18.
Circulation ; 126(6): 697-706, 2012 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-22732314

RESUMO

BACKGROUND: Takotsubo cardiomyopathy is an acute heart failure syndrome characterized by myocardial hypocontractility from the mid left ventricle to the apex. It is precipitated by extreme stress and can be triggered by intravenous catecholamine administration, particularly epinephrine. Despite its grave presentation, Takotsubo cardiomyopathy is rapidly reversible, with generally good prognosis. We hypothesized that this represents switching of epinephrine signaling through the pleiotropic ß(2)-adrenergic receptor (ß(2)AR) from canonical stimulatory G-protein-activated cardiostimulant to inhibitory G-protein-activated cardiodepressant pathways. METHODS AND RESULTS: We describe an in vivo rat model in which a high intravenous epinephrine, but not norepinephrine, bolus produces the characteristic reversible apical depression of myocardial contraction coupled with basal hypercontractility. The effect is prevented via G(i) inactivation by pertussis toxin pretreatment. ß(2)AR number and functional responses were greater in isolated apical cardiomyocytes than in basal cardiomyocytes, which confirmed the higher apical sensitivity and response to circulating epinephrine. In vitro studies demonstrated high-dose epinephrine can induce direct cardiomyocyte cardiodepression and cardioprotection in a ß(2)AR-Gi-dependent manner. Preventing epinephrine-G(i) effects increased mortality in the Takotsubo model, whereas ß-blockers that activate ß(2)AR-G(i) exacerbated the epinephrine-dependent negative inotropic effects without further deaths. In contrast, levosimendan rescued the acute cardiac dysfunction without increased mortality. CONCLUSIONS: We suggest that biased agonism of epinephrine for ß(2)AR-G(s) at low concentrations and for G(i) at high concentrations underpins the acute apical cardiodepression observed in Takotsubo cardiomyopathy, with an apical-basal gradient in ß(2)ARs explaining the differential regional responses. We suggest this epinephrine-specific ß(2)AR-G(i) signaling may have evolved as a cardioprotective strategy to limit catecholamine-induced myocardial toxicity during acute stress.


Assuntos
Modelos Animais de Doenças , Epinefrina/sangue , Subunidades alfa Gi-Go de Proteínas de Ligação ao GTP/fisiologia , Receptores Adrenérgicos beta 2/fisiologia , Cardiomiopatia de Takotsubo/sangue , Animais , Antiarrítmicos/administração & dosagem , Antiarrítmicos/sangue , Células Cultivadas , Epinefrina/administração & dosagem , Subunidades alfa Gi-Go de Proteínas de Ligação ao GTP/agonistas , Subunidades alfa Gi-Go de Proteínas de Ligação ao GTP/sangue , Humanos , Masculino , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/fisiologia , Ratos , Ratos Sprague-Dawley , Transdução de Sinais/efeitos dos fármacos , Transdução de Sinais/fisiologia
19.
J Biol Chem ; 287(31): 25696-705, 2012 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-22692210

RESUMO

The contractile performance of the heart is linked to the energy that is available to it. Yet, the heart needs to respond quickly to changing demands. During diastole, the heart fills with blood and the heart chambers expand. Upon activation, contraction of cardiac muscle expels blood into the circulation. Early in systole, parts of the left ventricle are being stretched by incoming blood, before contraction causes shrinking of the ventricle. We explore here the effect of stretch of contracting permeabilized cardiac trabeculae of the rat on the rate of inorganic phosphate (P(i)) release resulting from ATP hydrolysis, using a fluorescent sensor for P(i) with millisecond time resolution. Stretch immediately reduces the rate of P(i) release, an effect observed both at full calcium activation (32 µmol/liter of Ca(2+)), and at a physiological activation level of 1 µmol/liter of Ca(2+). The results suggest that stretch redistributes the actomyosin cross-bridges toward their P(i)-containing state. The redistribution means that a greater fraction of cross-bridges will be poised to rapidly produce a force-generating transition and movement, compared with cross-bridges that have not been subjected to stretch. At the same time stretch modifies the P(i) balance in the cytoplasm, which may act as a cytoplasmic signal for energy turnover.


Assuntos
Cálcio/fisiologia , Contração Miocárdica , Miocárdio/metabolismo , Fosfatos/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Fenômenos Biomecânicos , Cálcio/farmacologia , Feminino , Técnicas In Vitro , Contração Isométrica , Cinética , Miocárdio/enzimologia , Miosinas/metabolismo , Ratos , Ratos Sprague-Dawley , Sarcômeros/metabolismo , Sarcômeros/fisiologia , Estresse Fisiológico
20.
J Mol Cell Cardiol ; 49(3): 380-9, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20600154

RESUMO

We have investigated a transgenic mouse model of inherited dilated cardiomyopathy that stably expresses the ACTC E361G mutation at around 50% of total actin in the heart. F-actin isolated from ACTC E361G mouse hearts was incorporated into thin filaments with native human tropomyosin and troponin and compared with NTG mouse actin by in vitro motility assay. There was no significant difference in sliding speed, fraction of filaments motile or Ca(2+)-sensitivity (ratio EC(50) E361G/NTG=0.95+/-0.08). The Ca(2+)-sensitivity of force in skinned trabeculae from ACTC E361G mice was slightly higher than NTG (EC(50) E361G/NTG=0.78+/-0.04). The molecular phenotype was revealed when troponin was dephosphorylated; Ca(2+)-sensitivity of E361G-containing thin filaments was now lower than NTG (EC(50) E361G(dPTn)/NTG(dPTn)=2.15+/-0.09). We demonstrated that this was due to uncoupling of Ca(2+)-sensitivity from troponin I phosphorylation by comparing Ca(2+)-sensitivity of phosphorylated and dephosphorylated thin filaments. For NTG actin-containing thin filaments EC(50) native/dPTn=3.0+/-0.3 but for E361G-containing thin filaments EC(50) native/dPTn=1.04+/-0.07.We studied contractility in isolated myocytes and found no significant differences under basal conditions. We measured cardiac performance by cine-MRI, echocardiography and with a conductance catheter over a period of 4 to 18 months and found minimal systematic differences between NTG and ACTC E361G mice under basal conditions. However, the increase in septal thickening, ejection fraction, heart rate and cardiac output following dobutamine treatment was significantly less in ACTC E361G mice compared with NTG. We propose that the ACTC E361G mutation uncouples myofilament Ca(2+)-sensitivity from Troponin I phosphorylation and blunts the response to adrenergic stimulation, leading to a reduced cardiac reserve with consequent contractile dysfunction under stress, leading to dilated cardiomyopathy.


Assuntos
Actinas/fisiologia , Cardiomiopatia Dilatada/metabolismo , Cardiomiopatia Dilatada/patologia , Modelos Animais de Doenças , Coração/fisiopatologia , Animais , Cardiomiopatia Dilatada/genética , Humanos , Camundongos , Camundongos Transgênicos , Mutação/genética , Fenótipo , Tropomiosina/metabolismo , Troponina/metabolismo
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