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MULTIVALENT PROTEIN GLYCOSYLATION: A DRIVING FORCE OF CANCER PROGRESSION AND ALZHEIMER’S DISEASE PATHOGENESIS

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Date Issued:
2022
Abstract/Description:
Glycosylation is a frequent and heterogeneous post-translational protein modification occurring in all domains of life. Aberrant cell-surface glycosylation is shown to mediate several processes involved in tumor cell proliferation, adhesion, and metastasis. Recent findings linked altered protein glycosylation to Alzheimer’s disease (AD) pathogenesis. One key obstacle in studying functional consequences of glycosylation has been the lack of structurally defined glycopeptide or protein model compounds for biochemical studies at the molecular level. For tumor progression, studies are crucial towards understanding the glycan-lectin recognition process tied to deciphering the information contained in glycan structures and for AD, foundational studies are necessary for understanding the role of O-glycosylation in protein processing and its fate toward the amyloid pathway. In chapter 1, a highly O-glycosylated transmembrane and cancer-associated mucin protein, MUC1, is used as a model for designing synthetic tools for exploring its role in metastasis via association with lectins and specificity of anti-MUC1 antibodies. This dissertation for the first time presents a MUC1-based positional scanning synthetic glycopeptide combinatorial library that varies in the number and location of tumor-associated Tn antigen. The importance of defined structural complexity for evaluating glycan density and glycosylation patterns for binding to Tn-specific plant lectins and anti-MUC1 (mouse) monoclonal antibodies was revealed using an enzyme-linked lectin assay (ELLA). Chapter 2 addressed the growing significance of peptide lectinomimics for recognizing tumor-specific glycans. Fluorescently labelled alanine scan analogues of odorranalectin (OL), a cyclic peptide that exhibits lectin like properties, were screened for binding BSA-conjugated monosaccharides using ELLA. Results revealed that Lys5, Phe7, Tyr9, Gly12, Leu14, and Thr17 were crucial for binding BSA-L-fucose, BSA-Dgalactose and BSA-N-acetyl-D-galactosamine. The thermodynamics of binding of the selected alanine analogues was evaluated by isothermal titration calorimetry. The thermodynamic profile of interactions with asialofetuin exhibits shift to an entropy-driven mechanism compared to fucoidan, which displayed an enthalpy-entropy compensation, typically associated with the carbohydrate-lectin recognition process. Chapter 3 focused on amyloid-precursor protein (APP) O-glycosylation and its role in AD pathogenesis. We synthesized native and Swedish-mutated (glyco)peptides with O-GalNAc moiety on Thr663 and/or Ser667 or Tyr681 to explore the role of glycosylation on conformation, secretase activity, and aggregation kinetics of Aβ40. Our results show that conformation is strongly dependent on external conditions such as buffer ions and solvent polarity as well as internal modifications of (glyco)peptides such as length, O-glycosylation, and Swedish mutation (Lys670Asn/Met671Leu). Furthermore, the level of β-secretase activity significantly increased for the glycopeptides containing the Swedish mutation compared to their nonglycosylated and native counterparts. Lastly, glycopeptides impacted the kinetics of Aβ40 aggregation by significantly increasing the lag phase and delaying aggregation onset, however, this effect was less pronounced for its Swedish-mutated counterparts.
Title: MULTIVALENT PROTEIN GLYCOSYLATION: A DRIVING FORCE OF CANCER PROGRESSION AND ALZHEIMER’S DISEASE PATHOGENESIS.
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Name(s): Singh, YashoNandini, author
Cudic, Maré, Thesis advisor
Florida Atlantic University, Degree grantor
Department of Chemistry and Biochemistry
Charles E. Schmidt College of Science
Type of Resource: text
Genre: Electronic Thesis Or Dissertation
Date Created: 2022
Date Issued: 2022
Publisher: Florida Atlantic University
Place of Publication: Boca Raton, Fla.
Physical Form: application/pdf
Extent: 268 p.
Language(s): English
Abstract/Description: Glycosylation is a frequent and heterogeneous post-translational protein modification occurring in all domains of life. Aberrant cell-surface glycosylation is shown to mediate several processes involved in tumor cell proliferation, adhesion, and metastasis. Recent findings linked altered protein glycosylation to Alzheimer’s disease (AD) pathogenesis. One key obstacle in studying functional consequences of glycosylation has been the lack of structurally defined glycopeptide or protein model compounds for biochemical studies at the molecular level. For tumor progression, studies are crucial towards understanding the glycan-lectin recognition process tied to deciphering the information contained in glycan structures and for AD, foundational studies are necessary for understanding the role of O-glycosylation in protein processing and its fate toward the amyloid pathway. In chapter 1, a highly O-glycosylated transmembrane and cancer-associated mucin protein, MUC1, is used as a model for designing synthetic tools for exploring its role in metastasis via association with lectins and specificity of anti-MUC1 antibodies. This dissertation for the first time presents a MUC1-based positional scanning synthetic glycopeptide combinatorial library that varies in the number and location of tumor-associated Tn antigen. The importance of defined structural complexity for evaluating glycan density and glycosylation patterns for binding to Tn-specific plant lectins and anti-MUC1 (mouse) monoclonal antibodies was revealed using an enzyme-linked lectin assay (ELLA). Chapter 2 addressed the growing significance of peptide lectinomimics for recognizing tumor-specific glycans. Fluorescently labelled alanine scan analogues of odorranalectin (OL), a cyclic peptide that exhibits lectin like properties, were screened for binding BSA-conjugated monosaccharides using ELLA. Results revealed that Lys5, Phe7, Tyr9, Gly12, Leu14, and Thr17 were crucial for binding BSA-L-fucose, BSA-Dgalactose and BSA-N-acetyl-D-galactosamine. The thermodynamics of binding of the selected alanine analogues was evaluated by isothermal titration calorimetry. The thermodynamic profile of interactions with asialofetuin exhibits shift to an entropy-driven mechanism compared to fucoidan, which displayed an enthalpy-entropy compensation, typically associated with the carbohydrate-lectin recognition process. Chapter 3 focused on amyloid-precursor protein (APP) O-glycosylation and its role in AD pathogenesis. We synthesized native and Swedish-mutated (glyco)peptides with O-GalNAc moiety on Thr663 and/or Ser667 or Tyr681 to explore the role of glycosylation on conformation, secretase activity, and aggregation kinetics of Aβ40. Our results show that conformation is strongly dependent on external conditions such as buffer ions and solvent polarity as well as internal modifications of (glyco)peptides such as length, O-glycosylation, and Swedish mutation (Lys670Asn/Met671Leu). Furthermore, the level of β-secretase activity significantly increased for the glycopeptides containing the Swedish mutation compared to their nonglycosylated and native counterparts. Lastly, glycopeptides impacted the kinetics of Aβ40 aggregation by significantly increasing the lag phase and delaying aggregation onset, however, this effect was less pronounced for its Swedish-mutated counterparts.
Identifier: FA00013949 (IID)
Degree granted: Dissertation (Ph.D.)--Florida Atlantic University, 2022.
Collection: FAU Electronic Theses and Dissertations Collection
Note(s): Includes bibliography.
Subject(s): Glycosylation
Alzheimer Disease
Lectins
Persistent Link to This Record: http://purl.flvc.org/fau/fd/FA00013949
Use and Reproduction: Copyright © is held by the author with permission granted to Florida Atlantic University to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
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Host Institution: FAU
Is Part of Series: Florida Atlantic University Digital Library Collections.