"Tissue" transglutaminase contributes to the formation of disulphide bridges in proteins of mitochondrial respiratory complexes

In this study we provide the first in vivo evidences showing that, under physiological conditions, "tissue" transglutaminase (TG2) might acts as a protein disulphide isomerase (PDI) and through this activity contributes to the correct assembly of the respiratory chain complexes. Mice lacking TG2 exhibit mitochondrial energy production impairment, evidenced by decreased ATP levels after physical challenge. This defect is phenotypically reflected in a dramatic decrease of motor behaviour of the animals. We propose that the molecular mechanism, underlying such a phenotype, resides in a defective disulphide bonds formation in ATP synthase (complex V), NADH-ubiquinone oxidoreductase (complex I), succinate-ubiquinone oxidoreductase (complex II) and cytochrome c oxidase (complex IV). In addition, TG2-PDI might control the respiratory chain by modulating the formation of the prohibitin complexes. These data elucidate a new pathway that directly links the TG2-PDI enzymatic activity with the regulation of mitochondrial respiratory chain function.     

Effetti del trattamento In Vivo con auxlna di internodi di pisello sulla fosforilazione ossidativa dei mitocondri In Vitro

Abstract

EFFECT OF TREATMENT WITH IAA OF PEA INTERNODE SECTIONS ON THE OXIDATIVE PHOSPHORYLATION OF THEIR MITOCHONDRIA. — It was previously shown that auxin treatment raises the level of ATP in pea stem sections, under the conditions where the hormone stimulates growth (MARRé AND FORTI). It is also known that under the same conditions auxin stimulates oxygen uptake (MARRé, FORTI e ARRIGONI; MARRÉ and FORTI), and that the auxin induced respiration is most probably mediated by cytochrome oxidase (MARRÉ, FORTI and GAUR).

However, auxin has no effect when added to isolated mitochondria. In this paper, the effect of auxin treatment of the tissue on the activity of mitochondria isolated after the hormone treatment has been studied. It has been found that oxidative phosphorylation of mitochondria from the auxin treated pea stem sections is 13% higher than that of controi sections. The auxin effect is significant at 96% probabilities. There is no effect of the hormone on the P/O ratio.     

Selective Vulnerability of Spinal and Cortical Motor Neuron Subpopulations in delta7 SMA Mice

Loss of the survival motor neuron gene (SMN1) is responsible for spinal muscular atrophy (SMA), the most common inherited cause of infant mortality. Even though the SMA phenotype is traditionally considered as related to spinal motor neuron loss, it remains debated whether the specific targeting of motor neurons could represent the best therapeutic option for the disease. We here investigated, using stereological quantification methods, the spinal cord and cerebral motor cortex of ∆7 SMA mice during development, to verify extent and selectivity of motor neuron loss. We found progressive post-natal loss of spinal motor neurons, already at pre-symptomatic stages, and a higher vulnerability of motor neurons innervating proximal and axial muscles. Larger motor neurons decreased in the course of disease, either for selective loss or specific developmental impairment. We also found a selective reduction of layer V pyramidal neurons associated with layer V gliosis in the cerebral motor cortex. Our data indicate that in the ∆7 SMA model SMN loss is critical for the spinal cord, particularly for specific motor neuron pools. Neuronal loss, however, is not selective for lower motor neurons. These data further suggest that SMA pathogenesis is likely more complex than previously anticipated. The better knowledge of SMA models might be instrumental in shaping better therapeutic options for affected patients.     

On the identity of dnaP and dnaF genes of Bacillus subtilis

Summary The dnaP strains of Bacillus subtilis are altered in the initiation of DNA replication at high temperature (Riva et al., 1975). Fine mapping of the gene shows that it is located very close to the dnaF gene, described by Karamata and Gross (1970) and mapped by Love et al. (1976) in the polC region. The phenotype of both mutants is indistinguishable: the DNA synthesis stops at non permissive temperature after synthesizing an amount of DNA equivalent to the completion of the rounds of replication already initiated; at permissive temperature they are abnormally sensitive to MMS and are reduced in the ability to be transformed. Both mutants are to be considered as belonging to the dnaF locus.The dnaF gene is very close to the polC gene, which specifies the DNA polymerase III of B. subtilis. The DNA polymerase III of the dnaF mutants is not temperature sensitive in vitro, however, the level of this enzyme is lower by a factor of 4 or 5 in the dnaF mutants, at the permissive temperature. Following shift of dnaF cultures to the non permissive temperature, the level of DNA polymerase III activity specifically decreases further by a factor of at least 10 in the mutant, whereas the DNA polymerase I level is unaffected.The possible roles of the dnaF gene in the control of the cellular level of the DNA polymerase III, and the possibility of a regulatory role of DNA polymerase III in the initiation of DNA replication in bacteria are discussed.Abbreviations and symbols HPUra 6-(p-hydroxyphenylazo)-uracil; mic, minimum inhibitory concentration - MMS methyl-methanesufonate - Pol I Pol II and Pol III: DNA polymerase I, II and III respectively - PCMB parachloro-mercuri-benzoate     

EBEC 2012—An energetic time in Freiburg

The seventeenth European Bioenergetics Conference (EBEC) took place in September 2012 at the Albert‐Ludwigs‐University in Freiburg, Germany, and was hosted by Thorsten Friedrich. The conference is a biannual event that brings together researchers from across the globe to discuss progress in this diverse and challenging field.     

Enantioselective Preparation,Conformational Analysis and Absolute Configuration of Highly Substituted Aziridines

The first example of organocatalytic aziridination reaction of α‐substituted‐α,β‐unsaturated ketones is presented. The reaction was found to be highly enantio‐ and diastereoselective, yielding N‐tosylated aziridines. Low‐temperature nuclear magnetic resonance (NMR) spectra allowed for the determination of the N‐inversion barrier, that was found to be quite lower with respect to unsubstituted aziridines. A thorough conformational analysis supported by low‐temperature NMR data allowed for the determination of the absolute configuration of the main stereoisomer by means of time‐dependent Density Functional Theory simulation of the electronic circular dichroism spectra. Chirality 27:875–887, 2015. © 2015 Wiley Periodicals, Inc.     

Skeletal muscle apoptotic signaling predicts thigh muscle volume and gait speed in community-dwelling older persons: an exploratory study

Background

Preclinical studies strongly suggest that accelerated apoptosis in skeletal myocytes may be involved in the pathogenesis of sarcopenia. However, evidence in humans is sparse. In the present study, we investigated whether apoptotic signaling in the skeletal muscle was associated with indices of muscle mass and function in older persons.

Methodology/Principal Findings

Community-dwelling older adults were categorized into high-functioning (HF) or low-functioning (LF) groups according to their short physical performance battery (SPPB) summary score. Participants underwent an isokinetic knee extensor strength test and 3-dimensional magnetic resonance imaging of the thigh. Vastus lateralis muscle samples were obtained by percutaneous needle biopsy and assayed for the expression of a set of apoptotic signaling proteins. Age, sex, number of comorbid conditions and medications as well as knee extensor strength were not different between groups. HF participants displayed greater thigh muscle volume compared with LF persons. Multivariate partial least squares (PLS) regressions showed significant correlations between caspase-dependent apoptotic signaling proteins and the muscular percentage of thigh volume (R² = 0.78; Q² = 0.61) as well as gait speed (R² = 0.81; Q² = 0.56). Significant variables in the PLS model of percent muscle volume were active caspase-8, cleaved caspase-3, cytosolic cytochrome c and mitochondrial Bak. The regression model of gait speed was mainly described by cleaved caspase-3 and mitochondrial Bax and Bak. PLS predictive apoptotic variables did not differ between functional groups. No correlation was determined between apoptotic signaling proteins and muscle strength or quality (strength per unit volume).

Conclusions/Significance

Data from this exploratory study show for the first time that apoptotic signaling is correlated with indices of muscle mass and function in a cohort of community-dwelling older persons. Future larger-scale studies are needed to corroborate these preliminary findings and determine if down-regulation of apoptotic signaling in skeletal myocytes will provide improvements in the muscle mass and functional status of older persons.     

Perturbation of cytochrome P450, generation of oxidative stress and induction of DNA damage in Cyprinus carpio exposed in situ to potable surface water

Epidemiological evidence suggests a link between consumption of chlorinated drinking water and various cancers. Chlorination of water rich in organic chemicals produces carcinogenic organochlorine by-products (OBPs) such as trihalomethanes and haloacetic acids. Since the discovery of the first OBP in the 1970s, there have been several investigations designed to determine the biological effects of single chemicals or small artificial OBP combinations. However, there is still insufficient information regarding the general biological response to these compounds, and further studies are still needed to evaluate their potential genotoxic effects. In the current study, we evaluated the effect of three drinking water disinfectants on the activity of cytochrome P450 (CYP)-linked metabolizing enzymes and on the generation of oxidative stress in the livers of male and female Cyprinus carpio fish (carp). The fish were exposed in situ for up 20 days to surface water obtained from the Trasmene lake in Italy. The water was treated with 1-2 mg/L of either sodium hypochlorite (NaClO) or chlorine dioxide (ClO2) as traditional disinfectants or with a relatively new disinfectant product, peracetic acid (PAA). Micronucleus (MN) frequencies in circulating erythrocytes from the fish were also analysed as a biomarker of genotoxic effect. In the CYP-linked enzyme assays, a significant induction (up to a 57-fold increase in the deethylation of ethoxyresorufin with PAA treatment) and a notable inactivation (up to almost a 90% loss in hydroxylation of p-nitrophenol with all disinfectants, and of testosterone 2beta-hydroxylation with NaClO) was observed in subcellular liver preparations from exposed fish. Using the electron paramagnetic resonance (EPR) spectroscopy radical-probe technique, we also observed that CYP-modulation was associated with the production of reactive oxygen species (ROS). In addition, we found a significant increase in MN frequency in circulating erythrocytes after 10 days of exposure of fish to water treated with ClO2, while a non-significant six-fold increase in MN frequency was observed with NaClO, but not with PAA. Our data suggest that the use of ClO2 and NaClO to disinfect drinking water could generate harmful OBP mixtures that are able to perturb CYP-mediated reactions, generate oxidative stress and induce genetic damage. These data may provide a mechanistic explanation for epidemiological studies linking consumption of chlorinated drinking water to increased risk of urinary, gastrointestinal and bladder cancers.     

Does tumor growth follow a "universal law"?

A general model for the ontogenetic growth of living organisms has been recently proposed. Here we investigate the extension of this model to the growth of solid malignant tumors. A variety of in vitro and in vivo data are analysed and compared with the prediction of a "universal" law, relating properly rescaled tumor masses and tumor growth times. The results support the notion that tumor growth follows such a universal law. Several important implications of this finding are discussed, including its relevance for tumor metastasis and recurrence, cell turnover rates, angiogenesis and invasion.