-
Cellular and Molecular Gastroenterology... 2024
Topics: Glycosylation; Lipid Metabolism; Liver; Humans; Animals; Sugars
PubMed: 38583483
DOI: 10.1016/j.jcmgh.2024.03.010 -
The Biochemical Journal Sep 2022Eukaryotic protein glycosylation is mediated by glycosyl- and oligosaccharyl-transferases. Here, we describe how African trypanosomes exhibit both evolutionary...
Eukaryotic protein glycosylation is mediated by glycosyl- and oligosaccharyl-transferases. Here, we describe how African trypanosomes exhibit both evolutionary conservation and significant divergence compared with other eukaryotes in how they synthesise their glycoproteins. The kinetoplastid parasites have conserved components of the dolichol-cycle and oligosaccharyltransferases (OSTs) of protein N-glycosylation, and of glycosylphosphatidylinositol (GPI) anchor biosynthesis and transfer to protein. However, some components are missing, and they process and decorate their N-glycans and GPI anchors in unique ways. To do so, they appear to have evolved a distinct and functionally flexible glycosyltransferases (GT) family, the GT67 family, from an ancestral eukaryotic β3GT gene. The expansion and/or loss of GT67 genes appears to be dependent on parasite biology. Some appear to correlate with the obligate passage of parasites through an insect vector, suggesting they were acquired through GT67 gene expansion to assist insect vector (tsetse fly) colonisation. Others appear to have been lost in species that subsequently adopted contaminative transmission. We also highlight the recent discovery of a novel and essential GT11 family of kinetoplastid parasite fucosyltransferases that are uniquely localised to the mitochondria of Trypanosoma brucei and Leishmania major. The origins of these kinetoplastid FUT1 genes, and additional putative mitochondrial GT genes, are discussed.
Topics: Glycosylation; Glycosylphosphatidylinositols; Glycosyltransferases; Trypanosoma; Trypanosoma brucei brucei
PubMed: 36066312
DOI: 10.1042/BCJ20210778 -
Topics in Current Chemistry 2015Glycoproteins are an important class of naturally occurring biomolecules which play a pivotal role in many biological processes. They are biosynthesized as complex... (Review)
Review
Glycoproteins are an important class of naturally occurring biomolecules which play a pivotal role in many biological processes. They are biosynthesized as complex mixtures of glycoforms through post-translational protein glycosylation. This fact, together with the challenges associated with producing them in homogeneous form, has hampered detailed structure-function studies of glycoproteins as well as their full exploitation as potential therapeutic agents. By contrast, chemical synthesis offers the unique opportunity to gain access to homogeneous glycoprotein samples for rigorous biological evaluation. Herein, we review recent methods for the assembly of complex glycopeptides and glycoproteins and present several examples from our laboratory towards the total chemical synthesis of clinically relevant glycosylated proteins that have enabled synthetic access to full-length homogeneous glycoproteins.
Topics: Glycoproteins; Glycosylation; Molecular Structure; Protein Engineering
PubMed: 25805144
DOI: 10.1007/128_2014_622 -
Journal of Molecular Biology Aug 2016Glycosylation is a ubiquitous modification that occurs on proteins and lipids in all living cells. Consistent with their high complexity, glycans play crucial biological... (Review)
Review
Glycosylation is a ubiquitous modification that occurs on proteins and lipids in all living cells. Consistent with their high complexity, glycans play crucial biological roles in protein quality control and recognition events. Asparagine-linked protein N-glycosylation, the most complex glycosylation, initiates in the endoplasmic reticulum and matures in the Golgi apparatus. This process not only requires an accurate distribution of processing machineries, such as glycosyltransferases, glycosidases, and nucleotide sugar transporters, but also needs an efficient and well-organized factory that is responsible for the fidelity and quality control of sugar chain processing. In addition, accurate glycosylation must occur in coordination with protein trafficking and sorting. These activities are carried out by the Golgi apparatus, a membrane organelle in the center of the secretory pathway. To accomplish these tasks, the Golgi has developed into a unique stacked structure of closely aligned, flattened cisternae in which Golgi enzymes reside; in mammalian cells, dozens of Golgi stacks are often laterally linked into a ribbon-like structure. Here, we review our current knowledge of how the Golgi structure is formed and why its formation is required for accurate glycosylation, with the focus on how the Golgi stacking factors GRASP55 and GRASP65 generate the Golgi structure and how the conserved oligomeric Golgi complex maintains Golgi enzymes in different Golgi subcompartments by retrograde protein trafficking.
Topics: Animals; Biological Transport; Endoplasmic Reticulum; Glycosylation; Golgi Apparatus; Humans; Membrane Proteins; Protein Transport
PubMed: 26956395
DOI: 10.1016/j.jmb.2016.02.030 -
Proteomics Aug 2022Glycosylation of viral proteins is required for the progeny formation and infectivity of virtually all viruses. It is increasingly clear that distinct glycans also play... (Review)
Review
Glycosylation of viral proteins is required for the progeny formation and infectivity of virtually all viruses. It is increasingly clear that distinct glycans also play pivotal roles in the virus's ability to shield and evade the host's immune system. Recently, there has been a great advancement in structural identification and quantitation of viral glycosylation, especially spike proteins. Given the ongoing pandemic and the high demand for structure analysis of SARS-CoV-2 densely glycosylated spike protein, mass spectrometry methodologies have been employed to accurately determine glycosylation patterns. There are still many challenges in the determination of site-specific glycosylation of SARS-CoV-2 viral spike protein. This is compounded by some conflicting results regarding glycan site occupancy and glycan structural characterization. These are probably due to differences in the expression systems, form of expressed spike glycoprotein, MS methodologies, and analysis software. In this review, we recap the glycosylation of spike protein and compare among various studies. Also, we describe the most recent advancements in glycosylation analysis in greater detail and we explain some misinterpretation of previously observed data in recent publications. Our study provides a comprehensive view of the spike protein glycosylation and highlights the importance of consistent glycosylation determination.
Topics: COVID-19; Glycosylation; Humans; Mass Spectrometry; Polysaccharides; SARS-CoV-2; Spike Glycoprotein, Coronavirus
PubMed: 35700310
DOI: 10.1002/pmic.202100322 -
Cells Aug 2020The protein glycosylation is a post-translational modification of crucial importance for its involvement in molecular recognition, protein trafficking, regulation, and... (Review)
Review
The protein glycosylation is a post-translational modification of crucial importance for its involvement in molecular recognition, protein trafficking, regulation, and inflammation. Indeed, abnormalities in protein glycosylation are correlated with several disease states such as cancer, inflammatory diseases, and congenial disorders. The understanding of cellular mechanisms through the elucidation of glycan composition encourages researchers to find analytical solutions for their detection. Actually, the multiplicity and diversity of glycan structures bond to the proteins, the variations in polarity of the individual saccharide residues, and the poor ionization efficiencies make their detection much trickier than other kinds of biopolymers. An overview of the most prominent techniques based on mass spectrometry (MS) for protein glycosylation (glycoproteomics) studies is here presented. The tricks and pre-treatments of samples are discussed as a crucial step prodromal to the MS analysis to improve the glycan ionization efficiency. Therefore, the different instrumental MS mode is also explored for the qualitative and quantitative analysis of glycopeptides and the glycans structural composition, thus contributing to the elucidation of biological mechanisms.
Topics: Glycosylation; Humans; Mass Spectrometry; Protein Processing, Post-Translational; Proteomics
PubMed: 32872358
DOI: 10.3390/cells9091986 -
Molecular & Cellular Proteomics : MCP 2021Mass spectrometry-based glycoproteomics has gone through some incredible developments over the last few years. Technological advances in glycopeptide enrichment,... (Review)
Review
Mass spectrometry-based glycoproteomics has gone through some incredible developments over the last few years. Technological advances in glycopeptide enrichment, fragmentation methods, and data analysis workflows have enabled the transition of glycoproteomics from a niche application, mainly focused on the characterization of isolated glycoproteins, to a mature technology capable of profiling thousands of intact glycopeptides at once. In addition to numerous biological discoveries catalyzed by the technology, we are also observing an increase in studies focusing on global protein glycosylation and the relationship between multiple glycosylation sites on the same protein. It has become apparent that just describing protein glycosylation in terms of micro- and macro-heterogeneity, respectively, the variation and occupancy of glycans at a given site, is not sufficient to describe the observed interactions between sites. In this perspective we propose a new term, meta-heterogeneity, to describe a higher level of glycan regulation: the variation in glycosylation across multiple sites of a given protein. We provide literature examples of extensive meta-heterogeneity on relevant proteins such as antibodies, erythropoietin, myeloperoxidase, and a number of serum and plasma proteins. Furthermore, we postulate on the possible biological reasons and causes behind the intriguing meta-heterogeneity observed in glycoproteins.
Topics: Animals; Glycoproteins; Glycosylation; Humans; Software
PubMed: 33561609
DOI: 10.1074/mcp.R120.002093 -
Molecular Biology Reports Aug 2022N-linked protein glycosylation is an essential co-and posttranslational protein modification that occurs in all three domains of life; the assembly of N-glycans follows... (Review)
Review
N-linked protein glycosylation is an essential co-and posttranslational protein modification that occurs in all three domains of life; the assembly of N-glycans follows a complex sequence of events spanning the (Endoplasmic Reticulum) ER and the Golgi apparatus. It has a significant impact on both physicochemical properties and biological functions. It plays a significant role in protein folding and quality control, glycoprotein interaction, signal transduction, viral attachment, and immune response to infection. Glycoengineering of protein employed for improving protein properties and plays a vital role in the production of recombinant glycoproteins and struggles to humanize recombinant therapeutic proteins. It considers an alternative platform for biopharmaceuticals production. Many immune proteins and antibodies are glycosylated. Pathogen's glycoproteins play vital roles during the infection cycle and their expression of specific oligosaccharides via the N-glycosylation pathway to evade detection by the host immune system. This review focuses on the aspects of N-glycosylation processing, glycoengineering approaches, their role in viral attachment, and immune responses to infection.
Topics: Endoplasmic Reticulum; Glycoproteins; Glycosylation; Golgi Apparatus; Humans; Polysaccharides; Recombinant Proteins; Virus Diseases
PubMed: 35364718
DOI: 10.1007/s11033-022-07359-4 -
Cellular and Molecular Life Sciences :... Jul 2015Asparagine (N)-linked protein glycosylation, which takes place in the eukaryotic endoplasmic reticulum (ER), is important for protein folding, quality control and the... (Review)
Review
Asparagine (N)-linked protein glycosylation, which takes place in the eukaryotic endoplasmic reticulum (ER), is important for protein folding, quality control and the intracellular trafficking of secretory and membrane proteins. It is known that, during N-glycosylation, considerable amounts of lipid-linked oligosaccharides (LLOs), the glycan donor substrates for N-glycosylation, are hydrolyzed to form free N-glycans (FNGs) by unidentified mechanisms. FNGs are also generated in the cytosol by the enzymatic deglycosylation of misfolded glycoproteins during ER-associated degradation. FNGs derived from LLOs and misfolded glycoproteins are eventually merged into one pool in the cytosol and the various glycan structures are processed to a near homogenous glycoform. This article summarizes the current state of our knowledge concerning the formation and catabolism of FNGs.
Topics: Asparagine; Biosynthetic Pathways; Endoplasmic Reticulum; Glycosylation; Hydrolysis; Lipopolysaccharides; Models, Biological; Polysaccharides; Protein Folding
PubMed: 25772500
DOI: 10.1007/s00018-015-1881-7 -
Biotechnology Advances 2024A key aspect of successful viral vaccine design is the elicitation of neutralizing antibodies targeting viral attachment and fusion glycoproteins that embellish viral... (Review)
Review
A key aspect of successful viral vaccine design is the elicitation of neutralizing antibodies targeting viral attachment and fusion glycoproteins that embellish viral particles. This observation has catalyzed the development of numerous viral glycoprotein mimetics as vaccines. Glycans can dominate the surface of viral glycoproteins and as such, the viral glycome can influence the antigenicity and immunogenicity of a candidate vaccine. In one extreme, glycans can form an integral part of epitopes targeted by neutralizing antibodies and are therefore considered to be an important feature of key immunogens within an immunization regimen. In the other extreme, the existence of peptide and bacterially expressed protein vaccines shows that viral glycosylation can be dispensable in some cases. However, native-like glycosylation can indicate native-like protein folding and the presence of conformational epitopes. Furthermore, going beyond native glycan mimicry, in either occupancy of glycosylation sites or the glycan processing state, may offer opportunities for enhancing the immunogenicity and associated protection elicited by an immunogen. Here, we review key determinants of viral glycosylation and how recombinant immunogens can recapitulate these signatures across a range of enveloped viruses, including HIV-1, Ebola virus, SARS-CoV-2, Influenza and Lassa virus. The emerging understanding of immunogen glycosylation and its control will help guide the development of future vaccines in both recombinant protein- and nucleic acid-based vaccine technologies.
Topics: Glycosylation; Glycoproteins; Antibodies, Neutralizing; Epitopes; Vaccines; Polysaccharides
PubMed: 37972669
DOI: 10.1016/j.biotechadv.2023.108283