Culture and Assay of Large-Scale Mixed-Stage Caenorhabditis elegans Populations.

Caenorhabditis elegans (C. elegans) has been and remains a valuable model organism to study developmental biology, aging, neurobiology, and genetics. The large body of work on C. elegans makes it an ideal candidate to integrate into large-population, whole-animal studies to dissect the complex biological components and their relationships with another organism. In order to use C. elegans in collaborative -omics research, a method is needed to generate large populations of animals where a single sample can be split and assayed across diverse platforms for comparative analyses. Here, a method to culture and collect an abundant mixed-stage C. elegans population on a large-scale culture plate (LSCP) and subsequent phenotypic data is presented. This pipeline yields sufficient numbers of animals to collect phenotypic and population data, along with any data needed for -omics experiments (i.e., genomics, transcriptomics, proteomics, and metabolomics). In addition, the LSCP method requires minimal manipulation to the animals themselves, less user preparation time, provides tight environmental control, and ensures that handling of each sample is consistent throughout the study for overall reproducibility. Lastly, methods to document population size and population distribution of C. elegans life stages in a given LSCP are presented.

Elevated levels of glycosylphosphatidylinositol (GPI) anchored proteins in plasma from human cancers detected by C. septicum alpha toxin.

The glycosylphosphatidylinositol (GPI) anchor is a glycan and lipid posttranslational modification added to proteins in the endoplasmic reticulum. Certain enzymes within the GPI biosynthetic pathway, particularly the subunits of the GPI transamidase, are elevated in various human cancers. Specific GPI anchored proteins, such as carcinoembryonic antigen and mesothelin, have been described as potential biomarkers for certain cancers; however, the overall levels of GPI anchored proteins present in plasma from cases of human cancers have not been evaluated. We have developed the use of a bacterial toxin known as alpha toxin from Clostridium septicum to detect GPI anchored proteins in vitro. In this study, we use alpha toxin to detect GPI anchored proteins present in plasma from cases of several types of human cancers. Our data indicate that human cancers with previously documented elevations of GPI transamidase subunits show increased alpha toxin binding to plasma from patients with these cancers, indicating increased levels of GPI anchored proteins. Furthermore, our results reveal very low levels of alpha toxin binding to plasma from patients with no malignant disease indicating few GPI anchored proteins are present. These data suggest that GPI anchored proteins present in plasma from these cancers represent biomarkers with potential use for cancer detection.

Mannose receptor (MR) engagement by mesothelin GPI anchor polarizes tumor-associated macrophages and is blocked by anti-MR human recombinant antibody.

Tumor-infiltrating macrophages respond to microenvironmental signals by developing a tumor-associated phenotype characterized by high expression of mannose receptor (MR, CD206). Antibody cross-linking of CD206 triggers anergy in dendritic cells and CD206 engagement by tumoral mucins activates an immune suppressive phenotype in tumor-associated macrophages (TAMs). Many tumor antigens are heavily glycosylated, such as tumoral mucins, and/or attached to tumor cells by mannose residue-containing glycolipids (GPI anchors), as for example mesothelin and the family of carcinoembryonic antigen (CEA). However, the binding to mannose receptor of soluble tumor antigen GPI anchors via mannose residues has not been systematically studied. To address this question, we analyzed the binding of tumor-released mesothelin to ascites-infiltrating macrophages from ovarian cancer patients. We also modeled functional interactions between macrophages and soluble mesothelin using an in vitro system of co-culture in transwells of healthy donor macrophages with human ovarian cancer cell lines. We found that soluble mesothelin bound to human macrophages and that the binding depended on the presence of GPI anchor and of mannose receptor. We next challenged the system with antibodies directed against the mannose receptor domain 4 (CDR4-MR). We isolated three novel anti-CDR4-MR human recombinant antibodies (scFv) using a yeast-display library of human scFv. Anti-CDR4-MR scFv #G11 could block mesothelin binding to macrophages and prevent tumor-induced phenotype polarization of CD206(low) macrophages towards TAMs. Our findings indicate that tumor-released mesothelin is linked to GPI anchor, engages macrophage mannose receptor, and contributes to macrophage polarization towards TAMs. We propose that compounds able to block tumor antigen GPI anchor/CD206 interactions, such as our novel anti-CRD4-MR scFv, could prevent tumor-induced TAM polarization and have therapeutic potential against ovarian cancer, through polarization control of tumor-infiltrating innate immune cells.

Synthetic, structural, and biosynthetic studies of an unusual phospho-glycopeptide derived from α-dystroglycan.

Aberrant glycosylation of α-dystroglycan (α-DG) results in loss of interactions with the extracellular matrix and is central to the pathogenesis of several disorders. To examine protein glycosylation of α-DG, a facile synthetic approach has been developed for the preparation of unusual phosphorylated O-mannosyl glycopeptides derived from α-DG by a strategy in which properly protected phospho-mannosides are coupled with a Fmoc protected threonine derivative, followed by the use of the resulting derivatives in automated solid-phase glycopeptide synthesis using hyper-acid-sensitive Sieber amide resin. Synthetic efforts also provided a reduced phospho-trisaccharide, and the NMR data of this derivative confirmed the proper structural assignment of the unusual phospho-glycan structure. The glycopeptides made it possible to explore factors that regulate the elaboration of critical glycans. It was established that a glycopeptide having a 6-phospho-O-mannosyl residue is not an acceptor for action by the enzyme POMGnT1, which attaches ß(1,2)-GlcNAc to O-mannosyl moietes, whereas the unphosphorylated derivate was readily extended by the enzyme. This finding implies a specific sequence of events in determining the structural fate of the O-glycan. It has also been found that the activity of POMGnT1 is dependent on the location of the acceptor site in the context of the underlying polypeptide/glycopeptide sequence. Conformational analysis by NMR has shown that the O-mannosyl modification does not exert major conformational effect on the peptide backbone. It is, however, proposed that these residues, introduced at the early stages of glycoprotein glycosylation, have an ability to regulate the loci of subsequent O-GalNAc additions, which do exert conformational effects. The studies show that through access to discrete glycopeptide structures, it is possible to reveal complex regulation of O-glycan processing on α-DG that has significant implications both for its normal post-translational maturation, and the mechanisms of the pathologies associated with hypoglycosylated α-DG.