Oral Presentation HUPO 2019 - 18th Human Proteome Organization World Congress

Comparative glycoproteomic analyses of cerebrospinal fluids reveal novel molecular players in Alzheimer’s disease (#178)

Lingjun Li 1 , Xiaofang Zhong 1 , Zhengwei Chen 1 , Qinying Yu 1 , Cynthia Carlsson 1 , Ozioma Okonkwo 1
  1. University of Wisconsin - Madison - Madison, WI, Madison, WISCONSIN, United States

Alzheimer’s disease (AD) is the most common form of dementia in the elderly population.  While several peptide and protein biomarkers in cerebrospinal fluid (CSF) have been used for AD diagnosis, an unequivocal diagnosis in the early phases of AD is still lacking. Furthermore, the discovery and establishment of reliable biomarkers capable of monitoring progression and degree of cognitive impairment as well as potential efficacy of therapy remains a major challenge. To address this challenge, we are developing multiplexed isobaric and isotopic tagging strategies to discover, identify and evaluate candidate biomarkers of AD in CSFs obtained from asymptomatic cognitively-healthy middle-aged adults, older cognitively-normal adults, and patients with mild cognitive impairment (MCI) and AD.  In the current study, we developed global glycoproteomics approach that combines enhanced N-glycopeptide sequential enrichment by hydrophilic interaction chromatography (HILIC) and boronic acid enrichment with electron transfer and higher-energy collision dissociation (EThcD) for large-scale intact glycopeptide analysis.  In total, 3596 intact N-glycopeptides from 676 N-glycosites and 358 N-glycoproteins were identified in CSF.  To our knowledge, this was the largest site-specific N-glycoproteome dataset reported for CSF so far.  As accumulating evidence suggests that aberrant glycosylation is implicated in AD pathogenesis, we perform large-scale comparative glycoproteomic analysis of CSF samples from control and AD patients, revealing distinct glycosylation patterns and dynamic changes of certain glycoforms. 1519 intact N-glycopeptides mapping to 178 glycosites on 107 glycoproteins were quantified via the 12-plex DiLeu (N,N-dimethyl leucine) tagging strategy. 19 N-glycopeptides were dysregulated in the progression of AD. Moreover, our data revealed that 25 aberrant N-glycopeptides in MCI were modified into 54 different glycoforms at the same site of a given protein in AD, termed as disease stage-specific N-glycopeptides. Collectively, our approach enables the elucidation of glycoprotein microheterogeneity and correlation of subtle changes in glycan structural repertoire to disease progression of AD.