Planctomycetes diversity associated with macroalgae

Planctomycetes associated with 12 macroalgae from the north coast of Portugal were isolated, using an improved method. A total of 138 isolates were found to comprise 10 operational taxonomic units (OTUs), with 65% of the strains being closely related to the species Rhodopirellula baltica. The other strains are probably new species or genera related to Rhodopirellula, Blastopirellula and Planctomyces. Some of the OTUs isolated are unique and have never been found before in previous studies. Catalyzed reporter deposition-FISH confirmed the presence of Planctomycetes on macroalgal surfaces. This study provides the first report of the cultured diversity of Planctomycetes on the epiphytic macroalgae community and presents clear evidence of their nutritional and intimate relationship.     

Modulation of poly-N-acetylglucosamine accumulation within mature Staphylococcus epidermidis biofilms grown in excess glucose

PNAG is a major component of Staphylococcus epidermidis biofilms involved in intercellular adhesion as well as in the interaction of the biofilm with components of the host immune response. Synthesis of PNAG has been found to be regulated by several environmental factors. In the present study, the effect of glucose metabolism-dependent culture medium acidification in PNAG accumulation was evaluated. Established S. epidermidis biofilms were allowed to grow in excess glucose with or without maintained pH conditions. PNAG accumulation in these biofilms was determined by flow cytometry and fluorescence microscopy using wheat germ agglutinin as a fluorescent probe. Biofilms grown in maintained pH conditions presented significantly higher amounts of this polymer as well as higher icaA expression than biofilms grown in acidic pH conditions. Moreover, PNAG accumulation in biofilms grown in non-maintained pH conditions occurred in association with cell death. Overall, we show that glucose metabolism by decreasing the culture pH affects biofilm physiology in respect to PNAG production and cell death. The reported in vitro modulation of PNAG accumulation within S. epidermidis biofilms further highlights the role of environment on determining the biofilm physiological state.     

P-cadherin role in normal breast development and cancer

P-cadherin is a cell-cell adhesion molecule, whose expression is highly associated with undifferentiated cells in normal adult epithelial tissues, as well as with poorly differentiated carcinomas. Its expression has been already reported in human embryonic stem cells and it is presumed to be a marker of stem or progenitor cells of some epithelial tissues. In normal breast, P-cadherin has an essential role during ductal mammary branching, being expressed by the monolayer of epithelial cap cells at the end buds. In mature mammary tissue, its expression is restricted to the myoepithelium; it has been postulated that it may also be present in early luminal progenitor cells. In breast cancer, P-cadherin is frequently overexpressed in high-grade tumours, being a well-established indicator of poor patient prognosis. It has been reported as an important inducer of cancer cell migration and invasion, with underlying molecular mechanisms involving the signalling mediated by its juxtamembrane domain, the secretion of matrix metalloproteases to the extracellular media, and the cleavage of a P-cadherin soluble form with pro-invasive activity. Intracellularly, this protein interferes with the endogenous cadherin/catenin complex, inducing p120-catenin delocalization to the cytoplasm, and the consequent activation of Rac1/Cdc42 and associated alterations in the actin cytoskeleton. Considering P-cadherin's role in cancer cell invasion and metastasis formation, a humanized monoclonal antibody was recently produced to antagonize P-cadherin-associated signalling pathways, which is currently under Phase I clinical trials. In this review, the most important findings about the role of P-cadherin in normal breast development and cancer will be illustrated and discussed, with emphasis on the most recent data.     

Sialylation regulates galectin-3/ligand interplay during mammary tumour progression--a case of targeted uncloaking

Galectin-3 is involved both in facilitating detachment of cells from primary tumour sites and favouring cancer cell adhesion and survival to anoikis in the blood stream. The mechanisms behind these apparently contradictory roles of the lectin have not yet been resolved. In order to investigate possible interplays between galectin-3 and its ligands underlying their role in the metastatic process, we examined mucin-1 (MUC1) and epidermal growth factor receptor (EGFR), well-known galectin-3 ligands, as well as galectin-3-binding site expression in a series of spontaneous canine malignant mammary tumours (CMMT) and a metastatic CMMT cell line. Despite the fact that CMMT cells expressed MUC1 and EGFR homogeneously over their plasma membrane, intravascular tumour cells, positive for galectin-3, expressed MUC1 and EGFR in a more focal membrane localization. Moreover, MUC1 overexpression in primary CMMT was present in parallel with down-regulation of galectin-3. Furthermore, in the CMT-U27 cell line, galectin-3 knock-down led to increased MUC1 expression, while MUC1 knock-down led to down-regulation of the lectin. Finally, removal of sialic acid from both CMMT and CMT-U27 xenograft samples exposed galectin-3-ligands throughout the tumour tissue, whereas these ligands were only present in galectin-3-positive invading cells in untreated samples. Interestingly indeed, we show that in vessel-invading cells, there is interaction between galectin-3 and the T antigen in vivo. We therefore hypothesized that loss of galectin-3 and sialylation-related masking of its ligands, in conjunction with their overexpression in specific tumour cell subpopulations, are crucial in regulating adhesive/de-adhesive events in the progression and invasive capacity of metastatic cells.     

The B-cell antigen receptor signals through a preformed transducer module of SLP65 and CIN85

Spleen tyrosine kinase Syk and its substrate SLP65 (also called BLNK) are proximal signal transducer elements of the B-cell antigen receptor (BCR). Yet, our understanding of signal initiation and processing is limited owing to the incomplete list of SLP65 interaction partners and our ignorance of their association kinetics. We have now determined and quantified the in vivo interactomes of SLP65 in resting and stimulated B cells by mass spectrometry. SLP65 orchestrated a complex signal network of about 30 proteins that was predominantly based on dynamic interactions. However, a stimulation-independent and constant association of SLP65 with the Cbl-interacting protein of 85 kDa (CIN85) was requisite for SLP65 phosphorylation and its inducible plasma membrane translocation. In the absence of a steady SLP65/CIN85 complex, BCR-induced Ca(2+) and NF-κB responses were abrogated. Finally, live cell imaging and co-immunoprecipitation experiments further confirmed that both SLP65 and CIN85 are key components of the BCR-associated primary transducer module required for the onset and progression phases of BCR signal transduction.     

CIGB-300, a synthetic peptide-based drug that targets the CK2 phosphoaceptor domain. Translational and clinical research

CK2 represents an oncology target scientifically validated. However, clinical research with inhibitors of the CK2-mediated phosphorylation event is still insufficient to recognize it as a clinically validated target. CIGB-300, an investigational peptide-based drug that targets the phosphoaceptor site, binds to a CK2 substrate array in vitro but mainly to B23/nucleophosmin in vivo. The CIGB-300 proapoptotic effect is preceded by its nucleolar localization, inhibition of the CK2-mediated phosphorylation on B23/nucleophosmin and nucleolar disassembly. Importantly, CIGB-300 shifted a protein array linked to apoptosis, ribosome biogenesis, cell proliferation, glycolisis, and cell motility in proteomic studies which helped to understand its mechanism of action. In the clinical ground, CIGB-300 has proved to be safe and well tolerated in a First-in-Human trial in women with cervical malignancies who also experienced signs of clinical benefit. In a second Phase 1 clinical trial in women with cervical cancer stage IB2/II, the MTD and DLT have been also identified in the clinical setting. Interestingly, in cervical tumors the B23/nucleophosmin protein levels were significantly reduced after CIGB-300 treatment at the nucleus compartment. In addition, expanded use of CIGB-300 in case studies has evidenced antitumor activity when administered as compassional option. Collectively, our data outline important clues on translational and clinical research from this novel peptide-based drug reinforcing its perspectives to treat cancer and paving the way to validate CK2 as a promising target in oncology.     

Genetic variability of the invasive cyanobacteria <Emphasis Type="Italic">Cylindrospermopsis raciborskii </Emphasis>from Bir M’cherga reservoir (Tunisia)

Cylindrospermopsis raciborskii is an invasive freshwater cyanobacteria of tropical origin, also found in temperate regions. Due to its known ability to produce potent toxins, such as cylindrospermopsin and the paralytic shellfish poisoning, this species is of major concern from a water quality perspective. This study presents a genetic characterization of four C. raciborskii strains isolated from the Bir M’cherga Tunisian reservoir. The toxicity assessment was investigated via molecular biology tools, which suggested that all the isolated strains were not producing cylindrospermopsin, saxitoxin, or microcystin. This result was further confirmed by HPLC and MALDI-TOF analyses. However, we report for the first time in C. raciborskii the presence of mcyA and mcyE, two segments of the microcystin synthetase mcy cluster. All the strains were identified taxonomically based on the 16S rRNA sequences, and their phylogenetic relationships were assessed using the rpoC1 region. Tunisian strains formed a distinct clade separated from the other African strains.     

Immunostimulatory activity of ConBr: a focus on splenocyte proliferation and proliferative cytokine secretion

Lectins constitute a class of glycoproteins, which are capable of selectively and reversibly binding to carbohydrates, distinguishing small structural differences in complex oligosaccharides. Studies have shown that the binding of lectins to cell-surface carbohydrates can lead to various effects such as cellular proliferation, histamine release and cytokine production. Canavalia brasiliensis lectin (ConBr) is a (D-mannose) D-glucose lectin. In this study, murine splenocytes were cultured to determine the effect of ConBr on cell proliferation, nitric oxide (NO) release and cytokine secretion. In addition, cellular viability assays were performed to evaluate any mitogenic activity induced by this lectin. ConBr significantly increased cell proliferation with minimal cell damage. This lectin was able to induce an increased production of cytokines such as IL-2, IL-6 and IFN-γ and a decreased production of IL- 10. The release of NO was also observed. The results of this study indicate that ConBr could potentially be used as an immunomodulator.     

Peptidomic analysis of the skin secretions of the frog <Emphasis Type="Italic">Pachymedusa dacnicolor</Emphasis>

High-resolution mass spectrometry-based peptidomics has been used to characterize several components in electro-stimulated skin secretions of the endemic Mexican frog Pachymedusa dacnicolor. Peptide mass screening performed in an Orbitrap-XL mass spectrometer showed that P. dacnicolor skin secretions possess 194 different components with molecular masses ranging mainly from 500 to 6,000 Da. Dozens of molecules were partially sequenced including two novel protease inhibitors. Additionally, one posttranslationally modified bradykinin and two novel dermaseptin-like antimicrobial peptides were fully sequenced. The novel peptide named here DMS-DA5 was fully characterized and showed potent antibacterial activity against various bacteria such as Escherichia coli, Bacillus subtilis, Salmonella enterica serovar typhimurium, and Pseudomonas aeruginosa with minimal inhibitory concentrations from 3.10 to 25.0 μM.     

The legacy of bacterial invasions on soil native communities

Soil microbial communities are often not resistant to the impact caused by microbial invasions, both in terms of structure and functionality, but it remains unclear whether these changes persist over time. Here, we used three strains of Escherichia coli O157:H7 (E. coli O157:H7), a species used for modelling bacterial invasions, to evaluate the resilience of the bacterial communities from four Chinese soils to invasion. The impact of E. coli O157:H7 strains on soil native communities was tracked for 120 days by analysing bacterial community composition as well as their metabolic potential. We showed that soil native communities were not resistant to invasion, as demonstrated by a decline in bacterial diversity and shifts in bacterial composition in all treatments. The resilience of native bacterial communities (diversity and composition) was inversely correlated with invader's persistence in soils (R² = 0.487, p < 0.001). Microbial invasions also impacted the functionality of the soil communities (niche breadth and community niche), the degree of resilience being dependent on soil or native community diversity. Collectively, our results indicate that bacteria invasions can potentially leave a footprint in the structure and functionality of soil communities, indicating the need of assessing the legacy of introducing exotic species in soil environments.