Unstructured Hydrophilic Sequences in Prokaryotic Proteomes Correlate with Dehydration Tolerance and Host Association

Water loss or desiccation is among the most life-threatening stresses. It leads to DNA double-strand breakage, protein aggregation, cell shrinkage, and low water activity precluding all biological functions. Yet, in all kingdoms of life, rare organisms are resistant to desiccation through prevention or reversibility of such damage. Here, we explore possible hallmarks of prokaryotic desiccation tolerance in their proteomes. The content of unstructured, low complexity (LC) regions was analyzed in a total of 460 bacterial and archaeal proteomes.It appears that species endowed with proteomes abundant in unstructured hydrophilic LC regions are desiccation-tolerant or sporulating bacteria, halophilic archaea and bacteria, or host-associated species. In the desiccation- and radiation-resistant bacterium Deinococcus radiodurans, most proteins that contain large hydrophilic LC regions have unassigned function, but those with known function are mostly involved in diverse cellular recovery processes. Such LC regions are typically absent in orthologous proteins in desiccation-sensitive species. D. radiodurans encodes also special LC proteins, akin to those associated with desiccation resistance of plant seeds and some plants and animals. Therefore, we postulate that large unstructured hydrophilic LC regions and proteins provide for cellular resistance to dehydration and we discuss mechanisms of their protective activity.     

Cell-associated hemolysis activity in the clinical strain of <Emphasis Type="Italic">Pseudomonas fluorescens MFN1032</Emphasis>

Background  

MFN1032 is a clinical Pseudomonas fluorescens strain able to grow at 37°C. MFN1032 cells induce necrosis and apoptosis in rat glial cells at this temperature. This strain displays secretion-mediated hemolytic activity involving phospholipase C and cyclolipopeptides. Under laboratory conditions, this activity is not expressed at 37°C. This activity is tightly regulated and is subject to phase variation.     

Global regulation of gene expression in response to cysteine availability in <Emphasis Type="Italic">Clostridium perfringens</Emphasis>

Background  

Cysteine has a crucial role in cellular physiology and its synthesis is tightly controlled due to its reactivity. However, little is known about the sulfur metabolism and its regulation in clostridia compared with other firmicutes. In Clostridium perfringens, the two-component system, VirR/VirS, controls the expression of the ubiG operon involved in methionine to cysteine conversion in addition to the expression of several toxin genes. The existence of links between the C. perfringens virulence regulon and sulfur metabolism prompted us to analyze this metabolism in more detail.     

Relationship between angiogenesis and inflammation in experimental arthritis

Background. Angiogenesis is involved in rheumatoid arthritis (RA) leading to leucocyte recruitment and inflammation in the synovium. Furthermore, synovial inflammation itself further potentiates endothelial proliferation and angiogenesis. In this study, we aimed at evaluating the reciprocical relationship between synovial inflammation and angiogenesis in a RA model, namely collagen-induced arthritis (CIA). Methods. CIA was induced by immunization of DBA/1 mice with collagen type II in adjuvant. Endothelial cells were detected using a GSL-1 lectin-specific immunohistochemical staining on knee joint sections. Angiogenesis, clinical scores and histological signs of arthritis were evaluated from the induction of CIA until the end of the experiment. Angiogenesis was quantified by counting both the isolated endothelial cells and vessels stained on each section. To evaluate the effect of increased angiogenesis on CIA, VEGF gene transfer was performed using an adeno-associated virus encoding VEGF (AAV-VEGF), by intra-muscular or intra-articular injection in mice with CIA. Results. We showed an increase in synovial angiogenesis from day 6 to day 55 after CIA induction, and, moreover, joint vascularization and clinical scores of arthritis were correlated (p < 0.0001, r = 0.61). Vascularization and histological scores were also correlated (p = 0.0006, r = 0.51). Systemic VEGF overexpression in mice with CIA was followed by an aggravation of arthritis as compared to AAV-lacZ control group (p < 0.0001). In contrast, there was no difference in clinical scores between control mice and mice injected within the knee with AAV-VEGF, even if joint vascularization was higher in this group than in all other groups (p = 0,05 versus non-injected group). Intra-articular AAV-VEGF injections induced more severe signs of histological inflammation and bone destruction than AAV-Lac Z or no injection. Conclusion. Angiogenesis and joint inflammation evolve in parallel during collagen-induced arthritis. Furthermore, this work shows that exogenous VEGF can aggravate CIA. It is direct evidence that the increase in joint vascularization leads to an exacerbation of arthritis. Taken together, these results emphasize the role of angiogenesis in inflammatory arthritis. It also suggests an early involvement of angiogenesis in joint inflammation.     

First Identification of Novel NDM Carbapenemase,NDM-7, in Escherichia coli in France

Background

The NDM-1 carbapenemase has been identified in 2008 in Enterobacteriaceae. Since then, several reports have emphasized its rapid dissemination throughout the world. The spread of NDM carbapenemases involve several bla _NDM gene variants associated with various plasmids among several Gram negative species.

Methodology

A multidrug-resistant E. coli isolate recovered from urine of a patient who had travelled to Burma has been characterized genetically and biochemically.

Principal Findings

E. coli COU was resistant to all antibiotics tested except amikacin, tigecycline, fosfomycin, and chloramphenicol. Analysis of the antibiotic resistance traits identified a metallo-ß-lactamase, a novel NDM variant, NDM-7. It differs from NDM-4 by a single amino acid substitution sharing an identical extended spectrum profile towards carbapenems. The bla _NDM-7 gene was located on an untypeable conjugative plasmid and associated with a close genetic background similar to those described among the bla _NDM-1 genes. The isolate also harbours bla _CTXM-15 and bla _OXA-1 genes and belonged to ST167.

Significance

This study highlights that spread of NDM producers correspond to spread of multiple bla _NDM genes and clones and therefore will be difficult to control.     

Mouse Hepatic Oval Cells Require Met-Dependent PI3K to Impair TGF-β-Induced Oxidative Stress and Apoptosis

We have previously shown that oval cells harboring a genetically inactivated Met tyrosine kinase (Met^−/− oval cells) are more sensitive to TGF-β-induced apoptosis than cells expressing a functional Met (Met^flx/flx), demonstrating that the HGF/Met axis plays a pivotal role in oval cell survival. Here, we have examined the mechanism behind this effect and have found that TGF-β induced a mitochondria-dependent apoptotic cell death in Met^flx/flx and Met^−/− oval cells, associated with a marked increase in levels of the BH3-only proteins Bim and Bmf. Bmf plays a key role during TGF-β-mediated apoptosis since knocking down of BMF significantly diminished the apoptotic response in Met^−/− oval cells. TGF-β also induced oxidative stress accompanied by NADPH oxidase 4 (Nox4) mRNA up-regulation and decreased protein levels of antioxidant enzymes. Antioxidants inhibit both TGF-β-induced caspase 3 activity and Bmf up-regulation, revealing an oxidative stress-dependent Bmf regulation by TGF-β. Notably, oxidative stress-related events were strongly amplified in Met^−/− oval cells, emphasizing the critical role of Met in promoting survival. Pharmacological inhibition of PI3K did impair HGF-driven protection from TGF-β-induced apoptosis and increased sensitivity of Met^flx/flx oval cells to TGF-ß by enhancing oxidative stress, reaching apoptotic indices similar to those obtained in Met^−/− oval cells. Interestingly, both PI3K inhibition and/or knockdown itself resulted in caspase-3 activation and loss of viability in Met^flx/flx oval cells, whereas no effect was observed in Met^−/− oval cells. Altogether, results presented here provide solid evidences that both paracrine and autocrine HGF/Met signaling requires PI3K to promote mouse hepatic oval cell survival against TGF-β-induced oxidative stress and apoptosis.     

The many routes of Golgi-dependent trafficking

The Golgi apparatus lies at the center of intracellular trafficking, controlling secretory and retrograde routes. Its role is essential both to ensure housekeeping cellular functions and to sustain highly differentiated ones. While Golgi dynamics and function have been studied by many groups for several decades now, and intensely for more than 40 years, the mechanisms of Golgi-dependent secretion, how anterograde and retrograde intra-Golgi transports are controlled, as well as the regulation of the Golgi stacked structure and function are some of the many questions that are still open. We will review here the main characteristics of intra-Golgi trafficking discuss the different models that were built to explain the diversity of intra-Golgi routes and its dynamics and propose an integrative model.     

Role of insert-1 of myosin VI in modulating nucleotide affinity

Myosin VI is unique in its directionality among myosin superfamily members and also displays a slow and strain-dependent rate of ATP binding that allows for gating between its heads. In this study we demonstrate that leucine 310 is positioned by a class VI-specific insert, insert-1, so as to account for the selective hindrance of ATP versus ADP binding. Mutation of leucine 310 to glycine removes all influence of insert-1 on ATP binding. Furthermore, by analyzing myosin VI structures with either leucine 310 substituted to a glycine or complete removal of insert-1, we conclude that nucleotides may initially bind to myosin by their purine rings before docking their phosphate moieties. Otherwise, insert-1 could not exert a differential influence on ATP versus ADP binding.     

Effects of Different Tissue Microenvironments on Gene Expression in Breast Cancer Cells

In metastasis, circulating tumor cells penetrate the walls of blood vessels and enter the metastatic target tissue, thereby becoming exposed to novel and relatively unsupportive microenvironments. In the new microenvironments, the tumor cells often remain in a dormant state indefinitely and must adapt before they are able to successfully colonize the tissue. Very little is known about this adaptive process. We studied temporal changes in gene expression when breast cancer cells adapt to survive and grow on brain, bone marrow, and lung tissue maintained in an in vivo culture system, as models of the metastatic colonization of these tissues. We observed the transient activation of genes typically associated with homeostasis and stress during the initial stages of adaptation, followed by the activation of genes that mediate more advanced functions, such as elaboration of cell morphology and cell division, as the cells adapted to thrive in the host tissue microenvironment. We also observed the temporary induction of genes characteristic of the host tissue, which was particularly evident when tumor cells were grown on brain tissue. These early transient gene expression events suggest potential points of therapeutic intervention that are not evident in data from well-established tumors.