A case for protein-level and site-level specificity in glycoproteomic studies of disease

Abstract

Abnormal glycosylation of proteins is known to be either resultant or causative of a variety of diseases. This makes glycoproteins appealing targets as potential biomarkers and focal points of molecular studies on the development and progression of human ailment. To date, a majority of efforts in disease glycoproteomics have tended to center on either determining the concentration of a given glycoprotein, or on profiling the total population of glycans released from a mixture of glycoproteins. While these approaches have demonstrated some diagnostic potential, they are inherently insensitive to the fine molecular detail which distinguishes unique and possibly disease relevant glycoforms of specific proteins. As a consequence, such analyses can be of limited sensitivity, specificity, and accuracy because they do not comprehensively consider the glycosylation status of any particular glycoprotein, or of any particular glycosylation site. Therefore, significant opportunities exist to improve glycoproteomic inquiry into disease by engaging in these studies at the level of individual glycoproteins and their exact loci of glycosylation. In this concise review, the rationale for glycoprotein and glycosylation site specificity is developed in the context of human disease glycoproteomics with an emphasis on N-glycosylation. Recent examples highlighting disease-related perturbations in glycosylation will be presented, including those involving alterations in the overall glycosylation of a specific protein, alterations in the occupancy of a given glycosylation site, and alterations in the compositional heterogeneity of glycans occurring at a given glycosylation site. Each will be discussed with particular emphasis on how protein-specific and site-specific approaches can contribute to improved discrimination between glycoproteomes and glycoproteins associated with healthy and unhealthy states.

Precursor ion survival energies of protonated N-glycopeptides and their weak dependencies on high mannose N-glycan composition in collision-induced dissociation

“…1–4 Consequently, the glycosylation status of proteins has garnered significant attention from the standpoint of human health and disease. 5–7 In this context, anomalous modes of protein glycosylation may be predictive or indicative of a given disease state, as well documented in many forms of cancer. 8–10 Alternatively, defects of protein glycosylation may serve to trigger a given disease state, such as in the various congenital disorders of glycosylation.…”

Multiple Reaction Monitoring for the Quantitation of Serum Protein Glycosylation Profiles: Application to Ovarian Cancer

“…Protein glycosylation is a common post-translational modification, and differential protein glycosylation has been identified as a characteristic of many common diseases. , Hence, there is active interest in the development and application of analytical techniques aimed to monitor protein glycosylation. Glycan analysis at the site- and protein-specific level remains difficult, because identification of both the peptide moiety and the glycan is necessary . This is even more prominent for analyses in a high-throughput manner, which are often necessary in biomedical research involving large numbers of patient samples.…”

“…Glycan analysis at the site-and protein-specific level remains difficult, because identification of both the peptide moiety and the glycan is necessary. 3 This is even more prominent for analyses in a high-throughput manner, which are often necessary in biomedical research involving large numbers of patient samples. Common analytical strategies involve either release of the glycans directly from all proteins in the tissue (e.g., refs 4,5 ) or glycan-or glycopeptide analysis of individual proteins purified from biological samples (e.g., refs 6,7 ).…”

Linkage Memory in Underivatized Protonated Carbohydrates

“…glycopeptides), which are typically analyzed as protonated ions, tandem MS is incapable of providing full information on the branching pattern, linkage information, or stereochemistry of the glycan 11 . Understanding glycobiology at the highest level of detail, including site-specific localization of all glycan structural isomers within glycoproteins 12 , will necessitate a thorough understanding of the properties of carbohydrate fragment ions.…”