The biological and structural characterization of Mycobacterium tuberculosis UvrA provides novel insights into its mechanism of action

Mycobacterium tuberculosis is an extremely well adapted intracellular human pathogen that is exposed to multiple DNA damaging chemical assaults originating from the host defence mechanisms. As a consequence, this bacterium is thought to possess highly efficient DNA repair machineries, the nucleotide excision repair (NER) system amongst these. Although NER is of central importance to DNA repair in M. tuberculosis, our understanding of the processes in this species is limited. The conserved UvrABC endonuclease represents the multi-enzymatic core in bacterial NER, where the UvrA ATPase provides the DNA lesion-sensing function. The herein reported genetic analysis demonstrates that M. tuberculosis UvrA is important for the repair of nitrosative and oxidative DNA damage. Moreover, our biochemical and structural characterization of recombinant M. tuberculosis UvrA contributes new insights into its mechanism of action. In particular, the structural investigation reveals an unprecedented conformation of the UvrB-binding domain that we propose to be of functional relevance. Taken together, our data suggest UvrA as a potential target for the development of novel anti-tubercular agents and provide a biochemical framework for the identification of small-molecule inhibitors interfering with the NER activity in M. tuberculosis.     

EBV lytic-phase protein BGLF5 contributes to TLR9 downregulation during productive infection

Viruses use a wide range of strategies to modulate the host immune response. The human gammaherpesvirus EBV, causative agent of infectious mononucleosis and several malignant tumors, encodes proteins that subvert immune responses, notably those mediated by T cells. Less is known about EBV interference with innate immunity, more specifically at the level of TLR-mediated pathogen recognition. The viral dsDNA sensor TLR9 is expressed on B cells, a natural target of EBV infection. Here, we show that EBV particles trigger innate immune signaling pathways through TLR9. Furthermore, using an in vitro system for productive EBV infection, it has now been possible to compare the expression of TLRs by EBV(-) and EBV(+) human B cells during the latent and lytic phases of infection. Several TLRs were found to be differentially expressed either in latently EBV-infected cells or after induction of the lytic cycle. In particular, TLR9 expression was profoundly decreased at both the RNA and protein levels during productive EBV infection. We identified the EBV lytic-phase protein BGLF5 as a protein that contributes to downregulating TLR9 levels through RNA degradation. Reducing the levels of a pattern-recognition receptor capable of sensing the presence of EBV provides a mechanism by which the virus could obstruct host innate antiviral responses.     

Growth impairment after TBI of leukemia survivors children: a model- based investigation

Background

Children receiving Total Body Irradiation (TBI) in preparation for Hematopoietic Stem Cell Transplantation (HSCT) are at risk for Growth Hormone Deficiency (GHD), which sometimes severely compromises their Final Height (FH). To better represent the impact of such therapies on growth we apply a mathematical model, which accounts both for the gompertzian-like growth trend and the hormone-related ‘spurts’, and evaluate how the parameter values estimated on the children undergoing TBI differ from those of the matched normal population.

Methods

25 patients long-term childhood lymphoblastic and myeloid acute leukaemia survivors followed at Pediatric Onco-Hematology, Stem Cell Transplantation and Cellular Therapy Division, Regina Margherita Children’s Hospital (Turin, Italy) were retrospectively analysed for assessing the influence of TBI on their longitudinal growth and for validating a new method to estimate the GH therapy effects. Six were treated with GH therapy after a GHD diagnosis.

Results

We show that when TBI was performed before puberty overall growth and pubertal duration were significantly impaired, but such growth limitations were completely reverted in the small sample (6 over 25) of children who underwent GH replacement therapies.

Conclusion

Since in principle the model could account for any additional growth ‘spurt’ induced by therapy, it may become a useful ‘simulation’ tool for paediatricians for comparing the predicted therapy effectiveness depending on its timing and dosage.

     

PDCD10 Gene Mutations in Multiple Cerebral Cavernous Malformations

Cerebral cavernous malformations (CCMs) are vascular abnormalities that may cause seizures, intracerebral haemorrhages, and focal neurological deficits. Familial form shows an autosomal dominant pattern of inheritance with incomplete penetrance and variable clinical expression. Three genes have been identified causing familial CCM: KRIT1/CCM1, MGC4607/CCM2, and PDCD10/CCM3. Aim of this study is to report additional PDCD10/CCM3 families poorly described so far which account for 10-15% of hereditary cerebral cavernous malformations. Our group investigated 87 consecutive Italian affected individuals (i.e. positive Magnetic Resonance Imaging) with multiple/familial CCM through direct sequencing and Multiplex Ligation-Dependent Probe Amplification (MLPA) analysis. We identified mutations in over 97.7% of cases, and PDCD10/CCM3 accounts for 13.1%. PDCD10/CCM3 molecular screening revealed four already known mutations and four novel ones. The mutated patients show an earlier onset of clinical manifestations as compared to CCM1/CCM2 mutated patients. The study of further families carrying mutations in PDCD10/CCM3 may help define a possible correlation between genotype and phenotype; an accurate clinical follow up of the subjects would help define more precisely whether mutations in PDCD10/CCM3 lead to a characteristic phenotype.     

The C2238/αANP Variant Is a Negative Modulator of Both Viability and Function of Coronary Artery Smooth Muscle Cells

Background

Abnormalities of vascular smooth muscle cells (VSMCs) contribute to development of vascular disease. Atrial natriuretic peptide (ANP) exerts important effects on VSMCs. A common ANP molecular variant (T2238C/αANP) has recently emerged as a novel vascular risk factor.

Objectives

We aimed at identifying effects of CC2238/αANP on viability, migration and motility in coronary artery SMCs, and the underlying signaling pathways.

Methods and Results

Cells were exposed to either TT2238/αANP or CC2238/αANP. At the end of treatment, cell viability, migration and motility were evaluated, along with changes in oxidative stress pathway (ROS levels, NADPH and eNOS expression), on Akt phosphorylation and miR21 expression levels. CC2238/αANP reduced cell vitality, increased apoptosis and necrosis, increased oxidative stress levels, suppressed miR21 expression along with consistent changes of its molecular targets (PDCD4, PTEN, Bcl2) and of phosphorylated Akt levels. As a result of increased oxidative stress, CC2238/αANP markedly stimulated cell migration and increased cell contraction. NPR-C gene silencing with specific siRNAs restored cell viability, miR21 expression, and reduced oxidative stress induced by CC2238/αANP. The cAMP/PKA/CREB pathway, driven by NPR-C activation, significantly contributed to both miR21 and phosphoAkt reduction upon CC2238/αANP. miR21 overexpression by mimic-hsa-miR21 rescued the cellular damage dependent on CC2238/αANP.

Conclusions

CC2238/αANP negatively modulates viability through NPR-C/cAMP/PKA/CREB/miR21 signaling pathway, and it augments oxidative stress leading to increased migratory and vasoconstrictor effects in coronary artery SMCs. These novel findings further support a damaging role of this common αANP variant on vessel wall and its potential contribution to acute coronary events.     

Casein Kinase 2 dependent phosphorylation of eIF4B regulates BACE1 expression in Alzheimer’s disease

Alzheimer’s disease (AD) is the most common age-related neurodegenerative disorder. Increased Aβ production plays a fundamental role in the pathogenesis of the disease and BACE1, the protease that triggers the amyloidogenic processing of APP, is a key protein and a pharmacological target in AD. Changes in neuronal activity have been linked to BACE1 expression and Aβ generation, but the underlying mechanisms are still unclear. We provide clear evidence for the role of Casein Kinase 2 in the control of activity-driven BACE1 expression in cultured primary neurons, organotypic brain slices, and murine AD models. More specifically, we demonstrate that neuronal activity promotes Casein Kinase 2 dependent phosphorylation of the translation initiation factor eIF4B and this, in turn, controls BACE1 expression and APP processing. Finally, we show that eIF4B expression and phosphorylation are increased in the brain of APPPS1 and APP-KI mice, as well as in AD patients. Overall, we provide a definition of a mechanism linking brain activity with amyloid production and deposition, opening new perspectives from the therapeutic standpoint.Subject terms: Kinases, Alzheimer''s disease, Neuronal physiology, Pathogenesis     

Leap-dynamics: efficient sampling of conformational space of proteins and peptides in solution

A molecular simulation scheme, called Leap-dynamics, that provides efficient sampling of protein conformational space in solution is presented. The scheme is a combined approach using a fast sampling method, imposing conformational 'leaps' to force the system over energy barriers, and molecular dynamics (MD) for refinement. The presence of solvent is approximated by a potential of mean force depending on the solvent accessible surface area. The method has been successfully applied to N-acetyl-L-alanine-N-methylamide (alanine dipeptide), sampling experimentally observed conformations inaccessible to MD alone under the chosen conditions. The method predicts correctly the increased partial flexibility of the mutant Y35G compared to native bovine pancreatic trypsin inhibitor. In particular, the improvement over MD consists of the detection of conformational flexibility that corresponds closely to slow motions identified by nuclear magnetic resonance techniques.     

Control of fertility and fecundity of sheep by means of hormonal manipulation

The results of four experiments are presented in summary form. The data are considered in relationship to the improvement of the fecundity and fertility of the Australian ewe breeding flock. In the first, three commonly used methods of oestrous synchronization were examined and showed differences that are attributed to the different patterns of hormonal changes associated with the methods demonstrated. The second experiment looked at the use of active immunization against testosterone and concluded that this method can improve fecundity but not fertility. The third experiment, a group of five trials, studied the use of progestagen sponges and PMSG in anoestrous ewes as a means of inducing normal fertility. The extensive data produced in this experiment allowed the relationships between ovulation rate and fertility and between fertility and prolificacy (fecundity) to be examined. Fertility appeared greatest when the mean flock ovulation rate was about 2.5. At this ovulation rate prolificacy was also improved and a high proportion of twins were produced. We concluded that high fertility and low prolificacy (i.e. of 1.00) are an unlikely combination. In the final experiment the effect of post-mating hormonal supplementation on fertility was examined and a number of earlier reports were confirmed by showing that fertility can be improved with supplementary progesterone between days 10 and 25 post-mating. The effect appears to be modified by hormonal and nutritional factors.     

Heat stress and seasonal effects on reproduction in the dairy cow--a review

In dairy cows inseminated during the hot months of the year, there is a decrease in fertility. Different factors contribute to this situation; the most important are a consequence of increased temperature and humidity that result in a decreased expression of overt estrus and a reduction in appetite and dry matter intake. Heat stress reduces the degree of dominance of the selected follicle and this can be seen as reduced steroidogenic capacity of its theca and granulosa cells and a fall in blood estradiol concentrations. Plasma progesterone levels can be increased or decreased depending on whether the heat stress is acute or chronic, and on the metabolic state of the animal. These endocrine changes reduce follicular activity and alter the ovulatory mechanism, leading to a decrease in oocyte and embryo quality. The uterine environment is also modified, reducing the likelihood of embryo implantation. Appetite and dry matter intake are both reduced by heat stress thus prolonging the postpartum period of negative energy balance and increasing the calving-conception interval, particularly in high producing dairy cows. The utilization of cooling systems may have a beneficial effect on fertility but dairy cows cooled in this way are still unable to match the fertility achieved in winter. Recent studies suggest that the use of gonadotropins to induce follicular development and ovulation can decrease the severity of seasonal postpartum infertility in dairy cows.