Glycobiology最新文献

Aberrant O-glycosylation of mucin-type glycopeptide 1 (MUC1) is implicated in cancerous cellular processes involving the manipulation of immune response to favour tumour growth and metastasis. There is an unmet need for systems glycobiology models to probe the relationship between MUC1 O-glycosylation and immune cells within the tumour microenvironment. We expand on the sparsely understood MUC1 and immune cell interactions by building a complete systems model that combines the glycosylation network in the tumour cell with downstream biological networks. An ordinary differential equations-based model of the effect of aberrant glycosylation on immune modulation in breast cancer was constructed. The model comprises three interdependent component models that are MUC1-type O-glycosylation in the tumour cell, chemokine secretion in macrophages, and signal transduction in the tumour cells. A comparative CytoCopasi algorithm was developed to sequentially perturb the networks by an aberrant O-glycosylation. Comparative simulations revealed that upregulation of tumour-associated MUC1 sialyl-T antigen in Luminal A breast cancer stimulated the upregulation of the chemokine CXCL5 in tumour-associated macrophages. Consequently, increased CXCL5 binding by the tumour cell led to a positive feedback loop through overactive signal transduction and autocrine CXCL5 production. Finally, perturbing the glycosylation network with the sialyltransferase inhibitor Soyasaponin-I abrogated the cancerous upregulations in the downstream networks.

Photorhabdus laumondii is a well-known bacterium with a complex life cycle involving mutualism with nematodes of the genus Heterorhabditis and pathogenicity towards insect hosts. It provides an excellent model for studying the diverse roles of lectins, saccharide-binding proteins, in both symbiosis and pathogenicity. This study focuses on the seven-bladed β-propeller lectins of P. laumondii (PLLs), examining their biochemical properties (structure and saccharide specificity) and biological functions (gene expression, interactions with the nematode symbiont, and the host immune system response). Structural analyses revealed diverse oligomeric states among PLLs and a unique organisation of binding sites not described outside the PLL lectin family. Lectins exhibited high specificity for fucosylated and O-methylated saccharides with a significant avidity effect for multivalent ligands. Gene expression analysis across bacterial growth phases revealed that PLLs are predominantly expressed during the exponential phase. Interaction studies with the host immune system demonstrated that PLL5 uniquely induced melanisation in Galleria mellonella hemolymph. Furthermore, PLL2, PLL3, and PLL5 interfered with reactive oxygen species production in human blood cells, indicating their potential role in modulating host immune responses. Biofilm formation assays and binding studies with nematode life stages showed no significant involvement of PLLs in nematode colonization. Our findings highlight the primary role of PLLs in Photorhabdus pathogenicity rather than in symbiosis and offer valuable insight into the fascinating dynamics within the Photorhabdus-nematode-insect triparted system.

Over 50% of human proteins are estimated to be glycosylated, making glycosylation one of the most common post-translational modifications (PTMs) of proteins. A glycoinformatics resource such as the GlyGen knowledgebase, consisting of experimentally verified sequence-specific glycosylation sites, is critical for advancing research in glycobiology. Unfortunately, most experimental studies report glycosylation sites in free text format in scientific literature, mentioning gene names and amino acid positions without providing protein sequence identifiers, making it difficult to mine reported sites that can be mapped onto specific protein sequences. We have developed GlycoSiteMiner, which is an automated literature mining-based pipeline that extracts experimentally verified protein sequence-specific glycosylation sites from PubMed abstracts. The pipeline employs ML/AI algorithms to filter out incorrectly identified sites and has been applied to 33 million PubMed abstracts, identifying 1118 new sequence-specific glycosylation sites that were not previously present in the GlyGen resource.

Dystroglycan (DG) binds to extracellular matrix via its O-glycans, which are sequentially modified in a specific order by DG-specific enzymes: POMGNT2, B3GalNT2, and POMK in the endoplasmic reticulum (ER), followed by FKTN, FKRP, TMEM5, B4GAT1 and LARGE1 in the Golgi apparatus. However, there have been no comprehensive and systematic studies on the major localization of these enzymes. Here, we expressed fluorescent fusion proteins of DG-specific modifying enzymes under the control of short CMV promoter and observed their primary localization using the latest microscopy along with localization markers: mEGFP-KDEL for the ER, GM130 and GRASP55 for the cis-/medial-Golgi, and TGN46 and GCC1 for the trans-Golgi network. As a result, POMGNT2 and B3GalNT2 were localized to the ER as expected, but POMK was localized predominantly to the cis-/medial-Golgi showing co-localization with GRASP55. FKTN, FKRP and TMEM5 were partially co-localized with both cis-/medial- and trans-Golgi network markers. Though B4GAT1 did not co-localize with GM130 or TGN46, it co-localized with GCC1 another trans-Golgi network marker, indicating Golgi subcompartmentalization. LARGE1, the final glycosyltransferase involved in the modification of DG's O-glycan, was localized in the cis-/medial-Golgi, but did not overlap with trans-Golgi network markers. An EndoH sensitivity assay demonstrated that DG-specific enzymes interacting with DG were localized in the early secretory pathway. Our results reveal that POMK and B4GAT1 function at locations distinct from their major localization and support the conclusion that the modification of matriglycan on DG is completed at the cis-/medial-Golgi.

Human lectins are critical carbohydrate-binding proteins that recognize diverse glycoconjugates from microorganisms and can play a key role in host-microbe interactions. Despite their importance in immune recognition and microbe binding, the specific glycan ligands and functions of many human lectins remain poorly understood. Using previous proof-of-concept studies on selected lectins as the foundation for this work, we present ten additional glycan analysis probes (GAPs) from a diverse set of human soluble lectins, offering robust tools to investigate glycan-mediated interactions. We describe a protein engineering platform that enables scalable production of GAPs that maintain native-like conformations and oligomerization states, equipped with functional reporter tags for targeted glycan profiling. We demonstrate that the soluble GAP reagents can be used in various applications, including glycan array analysis, mucin-binding assays, tissue staining, and microbe binding in complex populations. These capabilities make GAPs valuable for dissecting interactions relevant to understanding host responses to microbes. The tools can also be used to probe differential microbial and mammalian glycan interactions, which are crucial for understanding the interactions of lectins in a physiological environment where both glycan types exist. GAPs have potential as diagnostic and prognostic tools for detecting glycan alterations in chronic diseases, microbial dysbiosis, and immune-related conditions.

Galectins are a family of β-galactosides-binding protein, crucial regulators of host-virus interactions. They achieve this by recognizing specific glycan patterns on viral surfaces or mediating interactions with intracellular viral or host proteins, subsequently influencing the critical phases of the viral life cycle, such as attachment, replication, immune evasion, and reactivation. Furthermore, galectins modulate host immune responses, shaping the progression and outcomes of viral infections. This review comprehensively examines the roles of both endogenous and exogenous galectins in viral infections, noting that only a few galectins, including Galectin-1, -3, -4, -7, -8, and -9, Have been identified as key players in viral infection. Notably, Galectin-1, -3, and -9 play diverse functions in both DNA and RNA viral infection. Emerging evidence highlights the potential of Galectin-4 and -8 as intracellular sensors and modulators of viral pathogenesis. Endogenous galectins, produced by host cells, act through both glycan-dependent and glycan-independent mechanisms, influencing viral processes and immune responses. Exogenous galectins, which are secreted by other cells or administered as recombinant proteins, can either enhance or counteract the actions of endogenous galectins. The functions of galectins are virus-specific and context-dependent, serving as either promoters or inhibitors of viral replication and reactivation. Dysregulation of galectin expression is often linked to disease progression, highlighting their potential as diagnostic and prognostic biomarkers, as well as therapeutic targets. The important and varied roles that galectins play in viral infections are highlighted in this review, which also provides fresh insights into host-pathogen interactions and the development of antiviral tactics.

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