Comparative analysis of sialic acid α2–3/6 galactose glycan-binding proteins in human saliva and serum

Abstract

It has been discovered that SAα2–6 Gal glycans prevailingly distribute in human upper respiratory tract while a few SAα2–3 Gal glycans distribute in human lower respiratory tract. In this study, we aimed to separate and identify SAα2–3/6 Gal glycan-binding proteins (GBPs) in human saliva and serum, since that these GBPs may possess anti-influenza A virus (anti-IAVs) protective effects by binding to receptor glycoconjugates earlier than virus hemagglutinin (HA). By using SAα2–3/6 Gal glycan-magnetic particles complexes, a total of 116 GBPs (33 SAα2–3 Gal GBPs, S3GBPs; 22 SAα2–6 Gal GBPs, S6GBPs; and 61 SAα2–3/6 Gal GBPs, SGBPs) in saliva and 144 GBPs (29 S3GBPs, 27 S6GBPs and 88 SGBPs) in serum were identified. Through emPAI analysis, for 61 saliva SGBPs, 16.39% showed higher extracting amount by SAα2–3 Gal, and 57.38% showed higher extracting amount by SAα2–6 Gal; for 88 serum SGBPs, only 2.27% showed higher extracting amount by SAα2–3 Gal, and up to 89.77% showed higher extracting amount by SAα2–6 Gal. A computational docking approach verified the docking between cystatin/apolipoprotein A-I and SAα2–3/6 Gal. Our study may supply useful information to help understand the nature protective role of saliva, and the anti-IAVs double effects of proteins that simultaneously play sialoglycoprotein and SAα2–3/6 Gal GBP roles.