In-depth profiling of mannose-terminating glycoproteins in cancer, innate immunity and pathogenic infections
Creators: name: Chatterjee, Sayantani
Publisher: name: Macquarie University
Year: 2024
Subjects: classificationCode: 399999
subject: Other education not elsewhere classified

description: Protein <em>N</em>-glycosylation, the addition of complex carbohydrates (glycans) to polypeptides via sequon-located asparagine residues, is a common post-translational modification important for many (patho)physiological processes. Recent literature suggests that the mannose-terminating <em>N</em>-glycans spanning the poorly studied paucimannosidic (Man1-3GlcNAc2Fuc0-1, M1(F)-M3(F)) and the more conventional oligomannosidic (Man5-9GlcNAc2, M5-M9) types are involved in key glycoimmunological processes. Thus, the focus of this thesis was to explore mannose-terminating glycoproteins in (patho)physiological conditions of particular relevance to human health and disease including in cancer, innate immunity and bloodstream infections using quantitative glycomics. 
To set the scene, <strong>Chapter 1 </strong>concisely introduces biological and technological concepts used in the thesis. This opening chapter also features two comprehensive review papers in which I have surveyed the literature to improve our knowledge of mannose-terminating <em>N</em>-glycans in human glycobiology <strong>(Publication 1) </strong>and specifically in human neutrophils <strong>(Publication 2)</strong>. The introductory chapter is followed by three experimental data chapters and a concluding chapter. 
Firstly, the link between mannose-terminating <em>N</em>-glycans and cancer was explored by interrogating a large collection of <em>N</em>-glycome datasets generated from diverse human cancer cell lines and tissues (<strong>Chapter 2</strong>). Paucimannosidic (particularly M2F-M3F) (<strong>Publication 3</strong>) and oligomannosidic (particularly M7-M9) (<strong>Publication 4</strong>) <em>N</em>-glycans were found to be prominent features of most cancer cell lines and consistently enriched in tumour tissues. Thus, previously unknown associations between mannose-terminating <em>N</em>-glycoproteins and cancer were established, advancing our understanding of the underpinning disease mechanisms and opening avenues for new cancer markers. 
Next, the mannose-terminating <em>N</em>-glycans were investigated in the context of neutrophils that form an important component of the tumour micro-environment and our innate immune system (<strong>Chapter 3</strong>). The dynamic neutrophil glycoproteome remains largely unexplored. To this end, I contributed to a study that quantitatively mapped the <em>N</em>-glycan fine structures across the neutrophil granules (<strong>Publication 5</strong>). In short, oligomannosidic <em>N</em>-glycans were found to be enriched on the neutrophil cell surface while PMGs were enriched in the azurophilic granules. These finding prompted a detailed structure-function-biosynthesis follow-up study of myeloperoxidase, a key antimicrobial neutrophil glycoprotein (<strong>Publication 6</strong>). Excitingly, this study found that site-specific mannosylated <em>N</em>-glycans modulate the enzyme activity of myeloperoxidase. Collectively, these efforts have generated new fundamental insight into neutrophil glycobiology. 
Finally, the mannose-terminating <em>N</em>-glycans were studied in bloodstream infections (bacteraemia) (<strong>Chapter 4</strong>). I performed quantitative <em>N</em>-glycomics of sera from bacteremic patients infected with four different pathogens (<em>Escherichia coli</em>, <em>Staphylococcus aureus</em>, <em>Pseudomonas aeruginosa </em>and <em>Streptococcus viridans</em>) and healthy donors (<strong>Publication 7</strong>). The bacteremic sera displayed surprisingly weak neutrophil-derived glyco-features (paucimannosylation) possibly due to rapid removal from blood and/or a limited release of mannose-terminating <em>N</em>-glycans from activated neutrophils. Excitingly, other features of the serum glycomics data instead accurately stratified healthy donors from bacteremic patients thus opening avenues for the development of new markers for bacteraemia. 
In conclusion (<strong>Chapter 5</strong>), this thesis has investigated mannose-terminating <em>N</em>-glycans in diverse pathophysiological conditions using quantitative glycomics. These efforts have produced novel data and findings that contribute to our understanding of the dynamic expression and biological roles of mannose-terminating glycoproteins in cancer, innate immunity and pathogenic infections.