Hetero-trans-β-glucanase, an enzyme unique to Equisetum plants, functionalises cellulose

Cell walls are metabolically active components of plant cells. They contain diverse enzymes, including transglycanases (endotransglycosylases), enzymes that ‘cut and paste’ certain structural polysaccharide molecules and thus potentially remodel the wall during growth and development. Known transglycanase activities modify several cell‐wall polysaccharides (xyloglucan, mannans, mixed‐linkage β‐glucan and xylans); however, no transglycanases were known to act on cellulose, the principal polysaccharide of biomass. We now report the discovery and characterization of hetero‐trans‐β‐glucanase (HTG), a transglycanase that targets cellulose, in horsetails (Equisetum spp., an early‐diverging genus of monilophytes). HTG is also remarkable in predominantly catalysing hetero‐transglycosylation: its preferred donor substrates (cellulose or mixed‐linkage β‐glucan) differ qualitatively from its acceptor substrate (xyloglucan). HTG thus generates stable cellulose–xyloglucan and mixed‐linkage β‐glucan–xyloglucan covalent bonds, and may therefore strengthen ageing Equisetum tissues by inter‐linking different structural polysaccharides of the cell wall. 3D modelling suggests that only three key amino acid substitutions (Trp → Pro, Gly → Ser and Arg → Leu) are responsible for the evolution of HTG's unique specificity from the better‐known xyloglucan‐acting homo‐transglycanases (xyloglucan endotransglucosylase/hydrolases; XTH). Among land plants, HTG appears to be confined to Equisetum, but its target polysaccharides are widespread, potentially offering opportunities for enhancing crop mechanical properties, such as wind resistance. In addition, by linking cellulose to xyloglucan fragments previously tagged with compounds such as dyes or indicators, HTG may be useful biotechnologically for manufacturing stably functionalized celluloses, thereby potentially offering a commercially valuable ‘green’ technology for industrially manipulating biomass

Physiological Modification of the Contractile Force of Isolated Right Ventricular Papillary Muscles.

<p><b>(A) Frequency-dependent activation</b>; Isometric developed force values are expressed as a fraction of its corresponding value at the basal frequency of 4 Hz and presented as mean ± SEM, and (<b>B</b>) <b>β–adrenergic stimulation</b>; Isometric developed force values are expressed as a fraction of its corresponding value at the basal frequency of 4 Hz before isoproterenol addition and presented as mean ± SEM. Control; n = 12, Thyroxin (T4); n = 15, Dimethyl sulfoxide (DMSO); N = 10, Sorafenib; n = 9, Tadalafil_IP (intraperitoneal, 1 mg/kg); n = 10, Tadalafil_Or (oral, 4 mg/kg); n = 8, carboxymethylcellulose (CMC); n = 8, Macitentan_LD (Low dose: 30 mg/kg); n = 8, Macitentan_HD (High dose: 100 mg/kg); n = 7. Note: in the β–adrenergic stimulation curve (<b>B</b>), all isometric developed force values at which the muscles exhibited an arrhythmic behavior were excluded from the analysis. For example, the Macitentan_HD group has no representative point at isoproterenol concentration of 1 μM, because all muscles became arrhythmic at this concentration [i.e. 7 out of 7 (100%)]. (<b>C</b>) <b>Development of Arrhythmia</b>: % of arrhythmic muscles at different isoproterenol (Iso) concentrations. The absence of the representative bar of any group at any Iso concentration on the curve means the absence of arrhythmia at this concentration. *: indicates a significant change as revealed by one-way ANOVA followed by Dunnett Multiple Comparisons post-hoc test, comparing all groups to T4. +: indicates a significant change as revealed by two-way ANOVA.</p

The Effect of Sorafenib, Tadalafil and Macitentan Treatments on Thyroxin-Induced Hemodynamic Changes and Cardiac Abnormalities

<div><p>Multikinase inhibitors (e.g. Sorafenib), phosphodiesterase-5 inhibitors (e.g. Tadalafil), and endothelin-1 receptor blockers (e.g. Macitentan) exert influential protection in a variety of animal models of cardiomyopathy; however, their effects on thyroxin-induced cardiomyopathy have never been investigated. The goal of the present study was to assess the functional impact of these drugs on thyroxin-induced hemodynamic changes, cardiac hypertrophy and associated altered responses of the contractile myocardium both <i>in-vivo</i> at the whole heart level and <i>ex-vivo</i> at the cardiac tissue level. Control and thyroxin (500 μg/kg/day)-treated mice with or without 2-week treatments of sorafenib (10 mg/kg/day; I.P), tadalafil (1 mg/kg/day; I.P or 4 mg/kg/day; oral), macitentan (30 and 100 mg/kg/day; oral), and their vehicles were studied. Blood pressure, echocardiography and electrocardiogram were non-invasively evaluated, followed by <i>ex-vivo</i> assessments of isolated multicellular cardiac preparations. Thyroxin increased blood pressure, resulted in cardiac hypertrophy and left ventricular dysfunction <i>in-vivo</i>. Also, it caused contractile abnormalities in right ventricular papillary muscles <i>ex-vivo</i>. None of the drug treatments were able to significantly attenuate theses hemodynamic changes or cardiac abnormalities in thyroxin-treated mice. We show here for the first time that multikinase (raf1/b, VEGFR, PDGFR), phosphodiesterase-5, and endothelin-1 pathways have no major role in thyroxin-induced hemodynamic changes and cardiac abnormalities. In particular, our data show that the involvement of endothelin-1 pathway in thyroxine-induced cardiac hypertrophy/dysfunction seems to be model-dependent and should be carefully interpreted.</p></div

Contractile Profile of Isolated Right Ventricular Papillary Muscles.

<p>Contractile Profile of Isolated Right Ventricular Papillary Muscles.</p

Physiological Modification of the Contractile Force of Isolated Right Ventricular Papillary Muscles.

<p><b>(A) Frequency-dependent activation</b>; Isometric developed force values are expressed as a fraction of its corresponding value at the basal frequency of 4 Hz and presented as mean ± SEM, and (<b>B</b>) <b>β–adrenergic stimulation</b>; Isometric developed force values are expressed as a fraction of its corresponding value at the basal frequency of 4 Hz before isoproterenol addition and presented as mean ± SEM. Control; n = 12, Thyroxin (T4); n = 15, Dimethyl sulfoxide (DMSO); N = 10, Sorafenib; n = 9, Tadalafil_IP (intraperitoneal, 1 mg/kg); n = 10, Tadalafil_Or (oral, 4 mg/kg); n = 8, carboxymethylcellulose (CMC); n = 8, Macitentan_LD (Low dose: 30 mg/kg); n = 8, Macitentan_HD (High dose: 100 mg/kg); n = 7. Note: in the β–adrenergic stimulation curve (<b>B</b>), all isometric developed force values at which the muscles exhibited an arrhythmic behavior were excluded from the analysis. For example, the Macitentan_HD group has no representative point at isoproterenol concentration of 1 μM, because all muscles became arrhythmic at this concentration [i.e. 7 out of 7 (100%)]. (<b>C</b>) <b>Development of Arrhythmia</b>: % of arrhythmic muscles at different isoproterenol (Iso) concentrations. The absence of the representative bar of any group at any Iso concentration on the curve means the absence of arrhythmia at this concentration. *: indicates a significant change as revealed by one-way ANOVA followed by Dunnett Multiple Comparisons post-hoc test, comparing all groups to T4. +: indicates a significant change as revealed by two-way ANOVA.</p

Morphological Data.

<p>Morphological Data.</p

Electrocardiogram Analysis of Mice.

<p>Electrocardiogram Analysis of Mice.</p

Blood Pressure of Mice.

<p>Blood Pressure of Mice.</p