New Aminoacyl-tRNA Synthetase-like Protein in Insecta with an Essential Mitochondrial Function

Aminoacyl-tRNA synthetases (ARS) are modular enzymes that aminoacylate transfer RNAs (tRNA) for their use by the ribosome during protein synthesis. ARS are essential and universal components of the genetic code that were almost completely established before the appearance of the last common ancestor of all living species. This long evolutionary history explains the growing number of functions being discovered for ARS, and for ARS homologues, beyond their canonical role in gene translation. Here we present a previously uncharacterized paralogue of seryl-tRNA synthetase named SLIMP (seryl-tRNA synthetase-like insect mitochondrial protein). SLIMP is the result of a duplication of a mitochondrial seryl-tRNA synthetase (SRS) gene that took place in early metazoans and was fixed in Insecta. Here we show that SLIMP is localized in the mitochondria, where it carries out an essential function that is unrelated to the aminoacylation of tRNA. The knockdown of SLIMP by RNA interference (RNAi) causes a decrease in respiration capacity and an increase in mitochondrial mass in the form of aberrant mitochondria.     

Macroinvertebrate succession during leaf litter breakdown in a perennial karstic river in Western Brazil

Leaf litter is a major basal resource to stream ecosystems, but few studies addressed their role in karst systems, mainly in intermittent springs and lakes. Patterns of resource use in perennial rivers are poorly known, although the input of leaf litter strongly influences macroinvertebrate assemblage structure. In this study, we evaluated the structure of macroinvertebrate assemblages along the decomposition of leaf litter in a tropical karst river, using leaf litter cages made of coarse nylon mesh (25 mm) to allow colonization by macroinvertebrates. The experiment was followed weekly for 10 weeks. The assemblages were dominated by snails (90.5% of total fauna), hyalellid amphipods, and larval chironomid midges, with highest abundances in the intermediate stages of the experiment, resulting in a gradient in assemblage structure. The large abundance of snails, which are common in other karst systems, suggest that this group may have an important role in decomposer food webs, facilitating or directly contributing to leaf breakdown. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Micropropagation of ‘Durondeau’ pear in modified-gelled medium

Summary The influence of partial substitution of agar by galactomannans (GMs) in culture media was studied in pear (Pyrus communis L. cv. ‘Durondeau’) micropropagation. GMs. extracted from seeds of Cassia fastuosa (cassia) or Cyamopsis tetragonolobus (guar gum, a commercial GM), were mixed in equal proportions with agar to a final concentration of 0.3% (w/v) for each type of gelling agent. The production of multiple shoots and the formation of roots from shoots were compared with the control solidified with agar alone at a concentration of 0.6% (w/v). In the media solidified with the mixtures of agar/guar and agar/cassia GMs, an, increase of 32 and 17%, respectively, was obtained in the number of regenerated shoots. The modified media promoted a higher number of roots and increased the rooting percentage. A maximum of 91% rooting was obtained in the medium solidified with the agar/cassia GM and containing 9.80 μM indole-3-butyric acid. Less callus formation at the base of the shoot was also observed on this medium. The improved in vitro performance of shoot formation and rooting, combined with a significantly lower cost, suggests a potential use of agar/GM gels in plant tissue culture.     

Preservation of Alpha-3 Neuronal Nicotinic Acetylcholine Receptor Expression in Sympathetic Ganglia After Brain Death

The goal of this study was to evaluate if the immunohistochemical expression of alpha-3 neuronal nicotinic acetylcholine receptor subunit in sympathetic ganglia remains stable after brain death, determining the possible use of sympathetic thoracic ganglia from subjects after brain death as study group. The third left sympathetic ganglion was resected from patients divided in two groups: BD—organ donors after brain death and CON—patients submitted to sympathectomy for hyperhidrosis (control group). Immunohistochemical staining for alpha-3 neuronal nicotinic acetylcholine receptor subunit was performed; strong and weak expression areas were quantified in both groups. The BD group showed strong alpha-3 neuronal nicotinic acetylcholine receptor expression in 6.55% of the total area, whereas the CON group showed strong expression in 5.91% (p = 0.78). Weak expression was found in 6.47% of brain-dead subjects and in 7.23% of control subjects (p = 0.31). Brain death did not affect the results of the immunohistochemical analysis of sympathetic ganglia, and its use as study group is feasible.     

Oxidative Stress Parameters in Urine from Patients with Disorders of Propionate Metabolism: a Beneficial Effect of l-Carnitine Supplementation

Propionic (PA) and methylmalonic (MMA) acidurias are inherited disorders caused by deficiency of propionyl-CoA carboxylase and methylmalonyl-CoA mutase, respectively. Affected patients present acute metabolic crises in the neonatal period and long-term neurological deficits. Treatments of these diseases include a protein restricted diet and l-carnitine supplementation. l-Carnitine is widely used in the therapy of these diseases to prevent secondary l-carnitine deficiency and promote detoxification, and several recent in vitro and in vivo studies have reported antioxidant and antiperoxidative effects of this compound. In this study, we evaluated the oxidative stress parameters, isoprostane and di-tyrosine levels, and the antioxidant capacity, in urine from patients with PA and MMA at the diagnosis, and during treatment with l-carnitine and protein-restricted diet. We verified a significant increase of isoprostanes and di-tyrosine, as well as a significant reduction of the antioxidant capacity in urine from these patients at diagnosis, as compared to controls. Furthermore, treated patients presented a marked reduction of isoprostanes and di-tyrosine levels in relation to untreated patients. In addition, patients with higher levels of protein and lipid oxidative damage, determined by di-tyrosine and isoprostanes levels, also presented lower urinary concentrations of total and free l-carnitine. In conclusion, the present results indicate that treatment with low protein diet and l-carnitine significantly reduces urinary biomarkers of protein and lipid oxidative damage in patients with disorders of propionate metabolism and that l-carnitine supplementation may be specially involved in this protection.     

A role for tRNA modifications in genome structure and codon usage

Transfer RNA (tRNA) gene content is a differentiating feature of genomes that contributes to the efficiency of the translational apparatus, but the principles shaping tRNA gene copy number and codon composition are poorly understood. Here, we report that the emergence of two specific tRNA modifications shaped the structure and composition of all extant genomes. Through the analysis of more than 500 genomes, we identify two kingdom-specific tRNA modifications as major contributors that separated archaeal, bacterial, and eukaryal genomes in terms of their tRNA gene composition. We show that, contrary to prior observations, genomic codon usage and tRNA gene frequencies correlate in all kingdoms if these two modifications are taken into account and that presence or absence of these modifications explains patterns of gene expression observed in previous studies. Finally, we experimentally demonstrate that human gene expression levels correlate well with genomic codon composition if these identified modifications are considered.     

Protein kinase C (PKC)ζ-mediated Gαq stimulation of ERK5 protein pathway in cardiomyocytes and cardiac fibroblasts

Gq-coupled G protein-coupled receptors (GPCRs) mediate the actions of a variety of messengers that are key regulators of cardiovascular function. Enhanced Gα(q)-mediated signaling plays an important role in cardiac hypertrophy and in the transition to heart failure. We have recently described that Gα(q) acts as an adaptor protein that facilitates PKCζ-mediated activation of ERK5 in epithelial cells. Because the ERK5 cascade is known to be involved in cardiac hypertrophy, we have investigated the potential relevance of this pathway in cardiovascular Gq-dependent signaling using both cultured cardiac cell types and chronic administration of angiotensin II in mice. We find that PKCζ is required for the activation of the ERK5 pathway by Gq-coupled GPCR in neonatal and adult murine cardiomyocyte cultures and in cardiac fibroblasts. Stimulation of ERK5 by angiotensin II is blocked upon pharmacological inhibition or siRNA-mediated silencing of PKCζ in primary cultures of cardiac cells and in neonatal cardiomyocytes isolated from PKCζ-deficient mice. Moreover, upon chronic challenge with angiotensin II, these mice fail to promote the changes in the ERK5 pathway, in gene expression patterns, and in hypertrophic markers observed in wild-type animals. Taken together, our results show that PKCζ is essential for Gq-dependent ERK5 activation in cardiomyocytes and cardiac fibroblasts and indicate a key cardiac physiological role for the Gα(q)/PKCζ/ERK5 signaling axis.     

Activation of c-Jun N-terminal kinase (JNK) during mitosis in retinal progenitor cells

Most studies of c-Jun N-terminal Kinase (JNK) activation in retinal tissue were done in the context of neurodegeneration. In this study, we investigated the behavior of JNK during mitosis of progenitor cells in the retina of newborn rats. Retinal explants from newborn rats were kept in vitro for 3 hours and under distinct treatments. Sections of retinal explants or freshly fixed retinal tissue were used to detect JNK phosphorylation by immunohistochemistry, and were examined through both fluorescence and confocal microscopy. Mitotic cells were identified by chromatin morphology, histone-H3 phosphorylation, and location in the retinal tissue. The subcellular localization of proteins was analyzed by double staining with both a DNA marker and an antibody to each protein. Phosphorylation of JNK was also examined by western blot. The results showed that in the retina of newborn rats (P1), JNK is phosphorylated during mitosis of progenitor cells, mainly during the early stages of mitosis. JNK1 and/or JNK2 were preferentially phosphorylated in mitotic cells. Inhibition of JNK induced cell cycle arrest, specifically in mitosis. Treatment with the JNK inhibitor decreased the number of cells in anaphase, but did not alter the number of cells in either prophase/prometaphase or metaphase. Moreover, cells with aberrant chromatin morphology were found after treatment with the JNK inhibitor. The data show, for the first time, that JNK is activated in mitotic progenitor cells of developing retinal tissue, suggesting a new role of JNK in the control of progenitor cell proliferation in the retina.     

In vitro evaluation of co-exposure of arsenium and an organic nanomaterial (fullerene, C₆₀) in zebrafish hepatocytes

Taking into account the concept of the "Trojan Horse", where contaminants may have its entry into specific organs potentiated by its association with nanomaterials, the aim of this study was to analyze the joint toxic effects induced by an organic nanomaterial, fullerene (C(60)) with the metalloid arsenic (As(III)). Hepatocytes of zebrafish Danio rerio were exposed to As(III) (2.5 or 100 μM), C(60) or As+C(60) for 4h, not altering cells viability. Intracellular reactive oxygen species concentration was reduced in cells exposed only to the C(60) (1mg/L) and in the treatment of 100 μM As(III)+C(60). Co-exposure with C(60) abolished the peak of the antioxidant glutathione (GSH) registered in cells exposed to the lowest As(III) concentration (2.5 μM). A similar result was observed in terms of lipid damage (TBARS). Total antioxidant capacity was significantly higher at both As(III) concentrations co-exposed to C(60) when compared with the control group. Activity of glutathione-S-transferase omega, a limiting enzyme in the methylation pathway of As(III), was reduced in the 100 μM As(III)+C(60) treatment. Cells co-exposed to C(60) had a significantly higher accumulation of As(III), showing a "Trojan Horse" effect which did not result in higher cell toxicity. Instead, co-exposure of As(III) with C(60) showed to reduce cellular injury.