Haslea silbo, a novel cosmopolitan species of blue diatoms

Specimens of a new species of blue diatoms from the genus Haslea Simonsen were discovered in geographically distant sampling sites, first in the Canary Archipelago, then North Carolina, Gulf of Naples, the Croatian South Adriatic Sea, and Turkish coast of the Eastern Mediterranean Sea. An exhaustive characterization of these specimens, using a combined morphological and genomic approach led to the conclusion that they belong to a single new to science cosmopolitan species, Haslea silbo sp. nov. A preliminary characterization of its blue pigment shows similarities to marennine produced by Haslea ostrearia, as evidenced by UV–visible spectrophotometry and Raman spectrome-try. Life cycle stages including auxosporulation were also observed, providing data on the cardinal points of this species. For the two most geographically distant populations (North Carolina and East Mediterranean), complete mitochondrial and plastid genomes were sequenced. The mitogenomes of both strains share a rare atp6 pseudogene, but the number, nature, and positions of the group II introns inside its cox1 gene differ between the two populations. There are also two pairs of genes fused in single ORFs. The plastid genomes are characterized by large regions of recombination with plasmid DNA, which are in both cases located between the ycf35 and psbA genes, but whose content differs between the strains. The two sequenced strains hosts three plasmids coding for putative serine recombinase protein whose sequences are compared, and four out of six of these plasmids were highly conserved

Substitution of Pichia pastoris-derived recombinant proteins with mannose containing O- and N-linked glycans decreases specificity of diagnostic tests

Background: Recombinant proteins from Pichia pastoris need to be fully evaluated before used as diagnostic tools. Objective: The objective of this study was to investigate whether glycosylation by P. pastoris interferes with the specificity of diagnostic tests. Methods: An autoantigen involved in Wegener's disease ( protease 3) and 2 major inhalant allergens from grass pollen (Dac g 5) and house dust mite (Der p 1) were produced as recombinant molecules in P. pastoris. O-linked glycans on Dac g 5 were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The immune reactivity of the recombinant proteins was compared to that of their natural counterparts by ELISA and a radio-allergosorbent test (RAST) as well as by ELISA and RAST inhibition. Results: In contrast to the non-glycosylated natural allergen, recombinant Dac g 5 was shown to carry at least 2 small mannose-containing O-glycans. We showed that both these O-glycans and the N-linked glycans on recombinant protease 3 and recombinant Der p 1 were recognized in ELISA by IgG antibodies in sera of healthy individuals. These IgG responses were closely correlated. The natural autoantigen and allergens were not recognized by IgG antibodies from healthy subjects. The carbohydrate nature of the epitopes recognized by IgG on the recombinant proteins was confirmed by inhibition studies with mannose and yeast mannan. IgE recognition of yeast glycans was observed in 2 out of 9 positive sera from patients with allergic bronchopulmonary aspergillosis. Conclusion: Production of recombinant molecules in yeast (or moulds) can introduce IgG-binding glycans that negatively affect the specificity of diagnostic tests. Copyright (C) 2004 S. Karger AG, Base

The atypical chemokine receptor 3 interacts with Connexin 43 inhibiting astrocytic gap junctional intercellular communication

International audienceThe atypical chemokine receptor 3 (ACKR3) plays a pivotal role in directing the migration of various cellular populations and its over-expression in tumors promotes cell proliferation and invasiveness. The intracellular signaling pathways transducing ACKR3-dependent effects remain poorly characterized, an issue we addressed by identifying the interactome of ACKR3. Here, we report that recombinant ACKR3 expressed in HEK293T cells recruits the gap junction protein Connexin 43 (Cx43). Cx43 and ACKR3 are co-expressed in mouse brain astrocytes and human glioblastoma cells and form a complex in embryonic mouse brain. Functional in vitro studies show enhanced ACKR3 interaction with Cx43 upon ACKR3 agonist stimulation. Furthermore, ACKR3 activation promotes β-arrestin2- and dynamin-dependent Cx43 internalization to inhibit gap junctional intercellular communication in primary astrocytes. These results demonstrate a functional link between ACKR3 and gap junctions that might be of pathophysiological relevance

Arsenic response of three altiplanic Exiguobacterium strains with different tolerance levels against the metalloid species : a proteomics study

International audienceExiguobacterium is a polyextremophile bacterial genus with a physiology that allows it to develop in different adverse environments. The Salar de Huasco is one of these environments due to its altitude, atmospheric pressure, solar radiation, temperature variations, pH, salinity, and the presence of toxic compounds such as arsenic. However, the physiological and/or molecular mechanisms that enable them to prosper in these environments have not yet been described. Our research group has isolated several strains of Exiguobacterium genus from different sites of Salar de Huasco, which show diferent resistance levels to As(III) and As(V). In this work, we compare the protein expression patterns of the three strains in response to arsenic by a proteomic approach; strains were grown in absence of the metalloid and in presence of As(III) and As(V) sublethal concentrations and the protein separation was carried out in 2D electrophoresis gels (2D-GE). In total, 999 spots were detected, between 77 and 173 of which showed significant changes for As(III) among the three strains, and between 90 and 143 for As(V) respectively compared to the corresponding control condition. Twenty-eight of those were identified by mass spectrometry (MS). Among these identified proteins, the ArsA (ATPase from the As(III) efflux pump) was found to be up-regulated in response to both arsenic conditions in the three strains, as well as the Co-enzyme A disulfide reductase (Cdr) in the two more resistant strains. Interestingly, in this genus the gene that codifies for Cdr is found within the genic context of the ars operon. We suggest that this protein could be restoring antioxidants molecules, necessary for the As(V) reduction. Additionally, among the proteins that change their expression against As, we found several with functions relevant to stress response, e.g. Hpf, LuxS, GLpX, GlnE and Fur. This study allowed us to shed light into the physiology necessary for these bacteria to be able to tolerate the toxicity and stress generated by the presence of arsenic in their niche

gamma-secretase inhibition promotes cell death, Noxa upregulation and sensitization to BH3 mimetic ABT-737 in human breast cancer cells.

International audienceABSTRACT: INTRODUCTION: Inappropriate Notch signalling, downstream of -secretase activity, is understood to have tumor-promoting function and to be associated with poor outcome in cancer, of the breast in particular. The molecular basis of anti-tumoral effects of its inhibitors, remain however poorly characterized. Moreover, the effects of their combination with the pro-apoptototic pharmacological inhibitor of Bcl2/BclxL, ABT-737, have never been evaluated. In this study, we thus specifically addressed the biological consequences of targeting -secretase and Bcl2/BclxL, alone or simultaneously, in breast cancer cell lines as well as in a novel human breast cancer ex vivo assay. METHODS: Using in vitro 2D or 3D cultures of breast cancer cells plus a novel preclinical short term ex vivo assay that correctly maintains human mammary tissue integrity and preserves tumor microenvironment, we tested the effects of the pharmalogical -secretase inhibitor GSIXII used as a single agent or in combination with ABT-737. RESULTS: We show herein that the -secretase inhibitor GSIXII, efficiently induces apoptosis in breast cancer cell lines by a process that relies on the induction of Noxa, a pro-apoptotic Bcl2-homology 3 domain (BH3)-only protein of the Bcl-2 family that functions as an inhibitor of anti-apoptotic Mcl1. GSIXII also targets mammary cancer stem-like cells since it dramatically prevents in vitro mammosphere formation. Moreover, combining GSIXII treatment with ABT-737, a BH3-mimetic inhibitor of additional anti-apoptotic proteins such as Bcl-2 and Bcl-xL leads to both synergistic apoptotic response in breast cancer cells and to an inhibitory effect on mammosphere formation. These effects are also found when a Notch transcriptional inhibitor, SAHM1, is used. Finally, we evaluated individual human tumor responses to -secretase inhibition alone or in combination with ABT-737 in ex vivo assays. Analysis of a series of 30 consecutive tumors indicated that a majority of tumors are sensitive to apoptosis induction by GSIXII and that association of GSIXII with ABT-737 leads to an enhanced induction of apoptosis in tumor cells. CONCLUSIONS: We thus provide evidence that -secretase, and downstream Notch signalling, are relevant targets in breast cancer. GSIXII, used as single agent or in combination with clinically relevant BH3-mimetics, is a promising innovative pro-apoptotic strategy to treat mammary tumors