Chemoecological study of the invasive alga Caulerpa taxifolia var. distichophylla from the Sicilian coast

Aquatic Ecology - Marine invasive species and their bioactive metabolites have become critical ecological issues in the Mediterranean Sea. In particular, the highly invasive green algae Caulerpa...     

Polarization-dependent selective transport to the apical membrane by KIF5B in MDCK cells

Microtubule-based vesicular transport is well documented in epithelial cells, but the specific motors involved and their regulation during polarization are largely unknown. We demonstrate that KIF5B mediates post-Golgi transport of an apical protein in epithelial cells, but only after polarity has developed. Time-lapse imaging of EB1-GFP in polarized MDCK cells showed microtubule plus ends growing toward the apical membrane, implying that plus end-directed N-kinesins might be used to transport apical proteins. Indeed, time-lapse microscopy revealed that expression of a KIF5B dominant negative or microinjection of function-blocking KIF5 antibodies inhibited selectively post-Golgi transport of the apical marker, p75-GFP, after polarization of MDCK cells. Expression of other KIF dominant negatives did not alter p75-GFP trafficking. Immunoprecipitation experiments demonstrated an interaction between KIF5B and p75-GFP in polarized, but not in subconfluent, MDCK cells. Our results demonstrate that apical protein transport depends on selective microtubule motors and that epithelial cells switch kinesins for post-Golgi transport during acquisition of polarity.     

Statistics for proteomics: experimental design and 2-DE differential analysis

Proteomics relies on the separation of complex protein mixtures using bidimensional electrophoresis. This approach is largely used to detect the expression variations of proteins prepared from two or more samples. Recently, attention was drawn on the reliability of the results published in literature. Among the critical points identified were experimental design, differential analysis and the problem of missing data, all problems where statistics can be of help. Using examples and terms understandable by biologists, we describe how a collaboration between biologists and statisticians can improve reliability of results and confidence in conclusions.     

The size of the plasmacytoid dendritic cell compartment is a multigenic trait dominated by a locus on mouse chromosome 7

Plasmacytoid dendritic cells (pDC) compose one of the many distinct dendritic cell subsets. The primary function of pDC is to potently produce type 1 IFNs upon stimulation, which is highly relevant in antiviral responses. Consequently, the ability to manipulate the size of the pDC compartment in vivo may increase the capacity to clear viral infections. In an attempt to identify genetic loci affecting the size of the pDC compartment, defined by both the proportion and absolute number of pDC, we undertook an unbiased genetic approach. Linkage analysis using inbred mouse strains identified a locus on chromosome 7 (Pdcc1) significantly linked to both the proportion and the absolute number of pDC in the spleen. Moreover, loci on either chromosome 11 (Pdcc2) or 9 (Pdcc3) modified the effect of Pdcc1 on chromosome 7 for the proportion and absolute number of pDC, respectively. Further analysis using mice congenic for chromosome 7 confirmed Pdcc1, demonstrating that variation within this genetic interval can regulate the size of the pDC compartment. Finally, mixed bone marrow chimera experiments showed that both the proportion and the absolute number of pDC are regulated by cell-intrinsic hematopoietic factors. Our findings highlight the multigenic regulation of the size of the pDC compartment and will facilitate the identification of genes linked to this trait.     

Synthesis and biological characterisation of sirtuin inhibitors based on the tenovins

The tenovins are small molecule inhibitors of the NAD(+)-dependent family of protein deacetylases known as the sirtuins. There remains considerable interest in inhibitors of this enzyme family due to possible applications in both cancer and neurodegenerative disease therapy. Through the synthesis of novel tenovin analogues, further insights into the structural requirements for activity against the sirtuins in vitro are provided. In addition, the activity of one of the analogues in cells led to an improved understanding of the function of SirT1 in cells.     

Claudin-2 promotes breast cancer liver metastasis by facilitating tumor cell interactions with hepatocytes

We previously identified claudin-2 as a functional mediator of breast cancer liver metastasis. We now confirm that claudin-2 levels are elevated in liver metastases, but not in skin metastases, compared to levels in their matched primary tumors in patients with breast cancer. Moreover, claudin-2 is specifically expressed in liver-metastatic breast cancer cells compared to populations derived from bone or lung metastases. The increased liver tropism exhibited by claudin-2-expressing breast cancer cells requires claudin-2-mediated interactions between breast cancer cells and primary hepatocytes. Furthermore, the reduction of the claudin-2 expression level, either in cancer cells or in primary hepatocytes, diminishes these heterotypic cell-cell interactions. Finally, we demonstrate that the first claudin-2 extracellular loop is essential for mediating tumor cell-hepatocyte interactions and the ability of breast cancer cells to form liver metastases in vivo. Thus, during breast cancer liver metastasis, claudin-2 shifts from acting within tight-junctional complexes to functioning as an adhesion molecule between breast cancer cells and hepatocytes.     

Novel lactoferrampin antimicrobial peptides derived from human lactoferrin

Human lactoferrampin is a novel antimicrobial peptide found in the cationic N-terminal lobe of the iron-binding human lactoferrin protein. The amino acid sequence that directly corresponds to the previously characterized bovine lactoferrin-derived lactoferrampin peptide is inactive on its own (WNLLRQAQEKFGKDKSP, residues 269-285). However, by increasing the net positive charge near the C-terminal end of human lactoferrampin, a significant increase in its antibacterial and Candidacidal activity was obtained. Conversely, the addition of an N-terminal helix cap (sequence DAI) did not have any appreciable effect on the antibacterial or antifungal activity of human lactoferrampin peptides, even though it markedly influenced that of bovine lactoferrampin. The solution structure of five human lactoferrampin variants was determined in SDS micelles and all of the structures display a well-defined amphipathic N-terminal helix and a flexible cationic C-terminus. Differential scanning calorimetry studies indicate that this peptide is capable of inserting into the hydrophobic core of a membrane, while fluorescence spectroscopy results suggest that a hydrophobic patch encompassing the single Trp and Phe residues as well as Leu, Ile and Ala side chains mediates the interaction between the peptide and the hydrophobic core of a phospholipid bilayer.