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New Strategy Developed Benefiting Early Diagnosis of Alzheimer’s Diseases

August 06, 2021      Author:

Alzheimer’s disease (AD), the most common neurodegenerative disease, is characterized by the main feature of the abnormal generation and accumulation of amyloid β-protein (Aβ) in patients’ brain tissue. Amyloid protein precursor (APP) formed by Aβ is a highly glycosylated glycoprotein. Glycosylation of protein plays a key role in regulating the processing of APP and the production of Aβ. Accurate determination of glycosylation modification information of APP is of great significance for understanding the role of APP protein in the occurrence of AD and the development of early diagnosis methods.

Recently, Zhang Yan’s and Yan Wei’s research team from Shanghai Centre of Systems Biomedicine, SJTU jointly developed a targeted MS combined multi-fragment strategy (TMMF) based on MS multi-fragmentation.

The method accurately depicts the O-glycosites and O-glycan structures on APP. It provides insights for understanding the molecular function of APP and the pathogenesis of AD from the level of glycosylation modification of protein, discovering AD therapeutic targets and developing early diagnosis strategies of AD. The research result was published in BBA-General Subjects under the title “Comprehensive analysis of o-glycosylation of amyloid precursor protein (APP) using targeted and multi-fragmentation MS strategy”.

Shi Jingjing, a postgraduate student in Zhang Yan’s research team, and Ku Xin, an associate researcher of Yan Wei’s research team, are the co-first authors of this paper. Prof. Zhang Yan and Prof. Yan Wei are the co-corresponding authors of this paper. This research is supported by the National Natural Science Foundation of China, Shanghai Science and Technology Commission, etc.

 

Author: Zhang Yan, Wang Huayao

Source: Shanghai Centre of Systems Biomedicine, SJTU

Translated by Zhou Rong

 

 

ABSTRACT:

Background

The aberrant proteolytic processing of amyloid precursor protein (APP) into amyloid β peptide (Aβ) in brain is a critical step in the pathogenesis of Alzheimer's disease (AD). As an O-glycosylated protein, O-glycosylation of APP is considered to be related to Aβ generation. Therefore, comprehensive analysis of APP O-glycosylation is important for understanding its functions.

Methods

We developed a Targeted MS approach with Multi-Fragmentation techniques (TMMF strategy), and successfully characterized O-glycosylation profiling of APP695 expressed in HEK-293 T cells. We calculated relative abundance of glycopeptides with various O-glycosites and O-glycans, and further investigated the alteration of APP O-glycosylation upon TNF-α treatment.

Results

A total of 14 O-glycosites were identified on three glycopeptides of APP, and at least four O-glycans including GalNAc (Tn antigen), core 1, and mono/di-sialylated core 1 glycans were determinant at the residues of Thr576 and Thr577. We found a dense cluster of truncated O-glycans on the region nearby beginning of E2 domain and high abundance of sialylated O-glycans on the region close to β-cleavage site. Moreover, we also observed that TNF-α could upregulate the expression of APP and the truncated O-glycans on APP in HEK-293 T cell.

Conclusion

Our study established an intact O-glycopeptide MS analysis strategy for APP O-glycopeptide identification with enhanced fragmentation efficiency and detection sensitivity. These results provide a comprehensive O-glycosylation map of APP expressed in HEK-293 T cell.

General significance

The accurate O-glycosites and O-glycan structures on APP may lead to a better understanding of the roles O-glycosylation plays in the processing and functions of APP.