The importance of side branches of glycosylphosphatidylinositol anchors: a molecular dynamics perspective.

Many proteins are anchored to the cell surface of eukaryotes using a unique family of glycolipids called glycosylphosphatidylinositol (GPI) anchors. These glycolipids also exist without a covalently bound protein, in particular on the cell surfaces of protozoan parasites where they are densely populated. GPIs and GPI-anchored proteins participate in multiple cellular processes such as signal transduction, cell adhesion, protein trafficking and pathogenesis of Malaria, Toxoplasmosis, Trypanosomiasis and prion diseases, among others.

Synthetic phosphoethanolamine-modified oligosaccharides reveal the importance of glycan length and substitution in biofilm-inspired assemblies.

Bacterial biofilm matrices are nanocomposites of proteins and polysaccharides with remarkable mechanical properties. Efforts understanding and tuning the protein component have been extensive, whereas the polysaccharide part remained mostly overlooked. The discovery of phosphoethanolamine (pEtN) modified cellulose in E.

Genome-wide CRISPR screen reveals CLPTM1L as a lipid scramblase required for efficient glycosylphosphatidylinositol biosynthesis.

SignificanceScramblases translocate lipids across the lipid bilayer without consumption of ATP, thereby regulating lipid distributions in cellular membranes. Cytosol-to-lumen translocation across the endoplasmic reticulum (ER) membrane is a common process among lipid glycoconjugates involved in posttranslational protein modifications in eukaryotes. These translocations are thought to be mediated by specific ER-resident scramblases, but the identity of these proteins and the underlying molecular mechanisms have been elusive.

Rescue of Glycosylphosphatidylinositol-Anchored Protein Biosynthesis Using Synthetic Glycosylphosphatidylinositol Oligosaccharides.

The attachment of proteins to the cell membrane using a glycosylphosphatidylinositol (GPI) anchor is a ubiquitous process in eukaryotic cells. Deficiencies in the biosynthesis of GPIs and the concomitant production of GPI-anchored proteins lead to a series of rare and complicated disorders associated with inherited GPI deficiencies (IGDs) in humans. Currently, there is no treatment for patients suffering from IGDs.

Zwitterionic Character and Lipid Composition Determine the Behaviour of Glycosylphosphatidylinositol Fragments in Monolayers.

Glycosylphosphatidylinositols (GPIs) are complex glycolipids found in free form or anchoring proteins to the outer leaflet of the cell membrane in eukaryotes. GPIs have been associated with the formation of lipid rafts and protein sorting on membranes. The presence of a conserved glycan core with cell-specific modifications together with lipid remodelling during biosynthesis suggest that the properties of the glycolipids are being fine-tuned.

Advances in the Chemical Synthesis of Carbohydrates and Glycoconjugates.

Carbohydrates are functional and structural biomolecules with structures ranging from monosaccharides to polysaccharides. They are naturally found as pure glycans or attached to lipids and proteins forming glycoconjugates. The biosynthesis of carbohydrates is not genetically controlled.

Structural base for the transfer of GPI-anchored glycoproteins into fungal cell walls.

The correct distribution and trafficking of proteins are essential for all organisms. Eukaryotes evolved a sophisticated trafficking system which allows proteins to reach their destination within highly compartmentalized cells. One eukaryotic hallmark is the attachment of a glycosylphosphatidylinositol (GPI) anchor to C-terminal ω-peptides, which are used as a zip code to guide a subset of membrane-anchored proteins through the secretory pathway to the plasma membrane.

Protein-observed 19F NMR of LecA from Pseudomonas aeruginosa.

The carbohydrate-binding protein LecA (PA-IL) from Pseudomonas aeruginosa plays an important role in the formation of biofilms in chronic infections. Development of inhibitors to disrupt LecA-mediated biofilms is desired but it is limited to carbohydrate-based ligands. Moreover, discovery of drug-like ligands for LecA is challenging because of its weak affinities.

Phosphoglycan-sensitized platform for specific detection of anti-glycan IgG and IgM antibodies in serum.

Glycosylphosphatidylinositol anchored proteins (GPI-APs) are natural conjugates in the plasma membrane of eukaryotic cells that result from the attachment of a glycolipid to the C-terminus of many proteins. GPI-APs play a crucial role in cell signaling and adhesion and have implications in health and diseases. GPI-APs and GPIs without protein (free GPIs) are found in abundance on the surface of the protozoan parasite Toxoplasma gondii.

A Glycan Array-Based Assay for the Identification and Characterization of Plant Glycosyltransferases.

Growing plants with modified cell wall compositions is a promising strategy to improve resistance to pathogens, increase biomass digestibility, and tune other important properties. In order to alter biomass architecture, a detailed knowledge of cell wall structure and biosynthesis is a prerequisite. We report here a glycan array-based assay for the high-throughput identification and characterization of plant cell wall biosynthetic glycosyltransferases (GTs).

Semisynthesis of Functional Glycosylphosphatidylinositol-Anchored Proteins.

Glypiation is a common posttranslational modification of eukaryotic proteins involving the attachment of a glycosylphosphatidylinositol (GPI) glycolipid. GPIs contain a conserved phosphoglycan that is modified in a cell- and tissue-specific manner. GPI complexity suggests roles in biological processes and effects on the attached protein, but the difficulties to get homogeneous material have hindered studies.

Corrigendum: Mucins and Pathogenic Mucin-Like Molecules Are Immunomodulators During Infection and Targets for Diagnostics and Vaccines.

[This corrects the article DOI: 10.3389/fchem.2019.

Mucins and Pathogenic Mucin-Like Molecules Are Immunomodulators During Infection and Targets for Diagnostics and Vaccines.

Mucins and mucin-like molecules are highly O-glycosylated proteins present on the cell surface of mammals and other organisms. These glycoproteins are highly diverse in the apoprotein and glycan cores and play a central role in many biological processes and diseases. Mucins are the most abundant macromolecules in mucus and are responsible for its biochemical and biophysical properties.

Glycan size and attachment site location affect electron transfer dissociation (ETD) fragmentation and automated glycopeptide identification.

We established a small synthetic N-glycopeptide library to systematically evaluate the effect of glycosylation site location and glycan size on the efficiency of electron transfer dissociation (ETD) fragmentation and subsequent automated identification. The glycopeptides within this library differed in glycosylation site position and glycan size ranging from the pentasaccharide N-glycan core to fully sialylated, biantennary N-glycans. Factors such as glycan size, glycosylation site position within a glycopeptide and individual precursor m/z all significantly impacted the number and quality of assignable glycopeptide backbone fragments.

Immunological Evaluation of Synthetic Glycosylphosphatidylinositol Glycoconjugates as Vaccine Candidates against Malaria.

Glycosylphosphatidylinositols (GPIs) are complex glycolipids present on the surfaces of parasites that may act as toxins during the progression of malaria. GPIs can activate the immune system during infection and induce the formation of anti-GPI antibodies that neutralize their activity. Therefore, an antitoxic vaccine based on GPI glycoconjugates may prevent malaria pathogenesis.

Detection of Anti- Antibodies in Human Sera Using Synthetic Glycosylphosphatidylinositol Glycans on a Bead-Based Multiplex Assay.

Toxoplasmosis, while often an asymptomatic parasitic disease in healthy individuals, can cause severe complications in immunocompromised persons and during pregnancy. The most common method to diagnose infections is the serological determination of antibodies directed against parasite protein antigens. Here we report the use of a bead-based multiplex assay containing a synthetic phosphoglycan portion of the glycosylphosphatidylinositol (GPI) for the detection of GPI-specific antibodies in human sera.

γδ-T cells promote IFN-γ-dependent pathogenesis upon liver-stage infection.

Cerebral malaria (CM) is a major cause of death due to infection. Both parasite and host factors contribute to the onset of CM, but the precise cellular and molecular mechanisms that contribute to its pathogenesis remain poorly characterized. Unlike conventional αβ-T cells, previous studies on murine γδ-T cells failed to identify a nonredundant role for this T cell subset in experimental cerebral malaria (ECM).

Structural determinants of coiled coil mechanics.

The natural abundance of coiled coil (CC) motifs in the cytoskeleton and the extracellular matrix suggests that CCs play a crucial role in the bidirectional mechanobiochemical signaling between cells and the matrix. Their functional importance and structural simplicity has allowed the development of numerous applications, such as protein-origami structures, drug delivery systems and biomaterials. With the goal of establishing CCs as nanomechanical building blocks, we investigated the importance of helix propensity and hydrophobic core packing on the mechanical stability of 4-heptad CC heterodimers.

Synthesis of Galactosylated Glycosylphosphatidylinositol Derivatives from Trypanosoma brucei.

Trypanosoma brucei uses variant surface glycoproteins (VSGs) to evade the host immune system and ensure parasitic longevity in animals and humans. VSGs are attached to the cell membrane by complex glycosylphosphatidylinositol anchors (GPI). Distinguishing structural feature of VSG GPIs are multiple α- and β-galactosides attached to the conserved GPI core structure.

(19)F NMR-Guided Design of Glycomimetic Langerin Ligands.

C-type lectin receptors (CLRs) play a pivotal role in pathogen defense and immune homeostasis. Langerin, a CLR predominantly expressed on Langerhans cells, represents a potential target receptor for the development of anti-infectives or immunomodulatory therapies. As mammalian carbohydrate binding sites typically display high solvent exposure and hydrophilicity, the recognition of natural monosaccharide ligands is characterized by low affinities.

The Art of Destruction: Optimizing Collision Energies in Quadrupole-Time of Flight (Q-TOF) Instruments for Glycopeptide-Based Glycoproteomics.

In-depth site-specific investigations of protein glycosylation are the basis for understanding the biological function of glycoproteins. Mass spectrometry-based N- and O-glycopeptide analyses enable determination of the glycosylation site, site occupancy, as well as glycan varieties present on a particular site. However, the depth of information is highly dependent on the applied analytical tools, including glycopeptide fragmentation regimes and automated data analysis.

ECBS & ICBS 2015 Joint Meeting: Bringing Chemistry to Life.

The European Chemical Biology Society (ECBS) and the International Chemical Biology Society (ICBS) recently organized a joint meeting in Berlin. This meeting had more than 250 participants. Four keynote lectures were given by Timothy Mitchison, David Tirrell, Carolyn Bertozzi and Jason Chin; in addition there were 13 invited speakers, 20 selected oral talks and 30 talks selected from 90 posters.

Investigation of the protective properties of glycosylphosphatidylinositol-based vaccine candidates in a Toxoplasma gondii mouse challenge model.

Vaccination against the ubiquitous parasite Toxoplasma gondii would provide the most efficient prevention against toxoplasmosis-related congenital, brain and eye diseases in humans. We investigated the immune response elicited by pathogen-specific glycosylphosphatidylinositol (GPI) glycoconjugates using carbohydrate microarrays in a BALB/c mouse model. We further examined the protective properties of the glycoconjugates in a lethal challenge model using the virulent T.

Defining the Interaction of Human Soluble Lectin ZG16p and Mycobacterial Phosphatidylinositol Mannosides.

ZG16p is a soluble mammalian lectin that interacts with mannose and heparan sulfate. Here we describe detailed analysis of the interaction of human ZG16p with mycobacterial phosphatidylinositol mannosides (PIMs) by glycan microarray and NMR. Pathogen-related glycan microarray analysis identified phosphatidylinositol mono- and di-mannosides (PIM1 and PIM2) as novel ligand candidates of ZG16p.