Biology subjects

Chien, Y.-C.

Publications and source records attributed to Chien, Y.-C..

4 recordsLinked to original sources

bioRxiv2026

Siglec-7 and -15 recognize repeated clustered sulfo-sialo O-glycan motifs on select O-glycoproteins

Siglecs are key immunoreceptors in immune homeostasis and cancer immunosuppression. Diverse endogenous and exogenous sialoglycan ligands induce Siglec-mediated immunoregulation, but the nature of endogenous Siglec ligands and how seemingly ubiquitous sialoglycans achieve selectivity is unclear. Here, we employed a HEK293 cell-based array and glycoprotein reporters designed from human mucins and mucin-like proteins with O-glycans in natural clusters and repeat motifs to dissect specificities of Siglec-7 and -15. We first used precomplexed Siglec-Fc chimera to demonstrate that CHST1-mediated 6-O-sulfation markedly enhanced binding to select O-glycoproteins, namely MAdCAM1, CD43, and PSGL-1. Probing binding properties of Siglec-7 expressed exogenously on CHO cells or endogenously on human monocytes by reverse assays employing fluorophore-tagged O-glycoprotein reporters revealed specific binding to the sulfo-sialyl core1 O-glycoform of the same O-glycoproteins. Our study indicates that Siglec-7 on immune cells employs multivalent interactions with repeated motifs of clustered sulfo-sialyl O-glycans to drive selectivity in ligand interactions and Siglec-induced immunosuppression.

molecular biology↗

bioRxiv2025

H3N2 influenza virus tropism shifts to glycan receptors on tracheal ciliated cells

Human H3N2 influenza viruses, introduced during the 1968 pandemic, have evolved to recognize human-type sialic acid-containing receptors (Neu5Ac2-6Gal) extended with at least three LacNAc (Gal{beta}1-4GlcNAc) repeats. To investigate this restriction in the context of virus attachment to the airway epithelium, we comprehensively analyzed the glycome of human nasal and tracheal epithelial cells. Using a synthetic N-glycan library that reflects the structural diversity of the human airway glycome, we found that only bi-antennary N-glycans with extended human-type receptors on at least one branch serve as receptors for the recent H3 hemagglutinins (HAs). Such receptors are found on tracheal epithelium but are deficient in nasal epithelium. Immunofluorescence analysis on human trachea reveals that recent H3 HAs preferentially attach to ciliated cells, consistent with single-cell RNA sequencing analysis indicating that these cells express glycosyltransferases that produce extended glycan chains. These findings suggest that H3N2 viruses have developed a tropism for tracheal ciliated cells. (146 words)

microbiology↗

bioRxiv2021

Structure-activity relationships of B.1.617 and other SARS-CoV-2 spike variants

The surge of COVID-19 infection cases is spurred by emerging SARS-CoV-2 variants such as B.1.617. Here we report 38 cryo-EM structures, corresponding to the spike protein of the Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2) and Kappa (B.1.617.1) variants in different functional states with and without its receptor, ACE2. Mutations on the N-terminal domain not only alter the conformation of the highly antigenic supersite of the Delta variant, but also remodel the glycan shield by deleting or adding N-glycans of the Delta and Gamma variants, respectively. Substantially enhanced ACE2 binding was observed for all variants, whose mutations on the receptor binding domain modulate the electrostatics of the binding interfaces. Despite their abilities to escape host immunity, all variants can be potently neutralized by three unique antibodies.

biophysics↗

bioRxiv2021

Distinct shifts in site-specific glycosylation pattern of SARS-CoV-2 spike proteins associated with arising mutations in the D614G and Alpha variants

Extensive glycosylation of the spike protein of SARS-CoV-2 virus not only shields the major part of it from host immune responses, but glycans at specific sites also act on its conformation dynamics and contribute to efficient host receptor binding, and hence infectivity. As variants of concern arise during the course of the COVID-19 pandemic, it is unclear if mutations accumulated within the spike protein would affect its site-specific glycosylation pattern. The Alpha variant derived from the D614G lineage is distinguished from others by having deletion mutations located right within an immunogenic supersite of the spike N-terminal domain that make it refractory to most neutralizing antibodies directed against this domain. Despite maintaining an overall similar structural conformation, our mass spectrometry-based site-specific glycosylation analyses of similarly produced spike proteins with and without the D614G and Alpha variant mutations reveal a significant shift in the processing state of N-glycans on one specific N-terminal domain site. Its conversion to a higher proportion of complex type structures is indicative of altered spatial accessibility attributable to mutations specific to the Alpha variant that may impact its transmissibility. This and other more subtle changes in glycosylation features detected at other sites provide crucial missing information otherwise not apparent in the available cryogenic electron microscopy-derived structures of the spike protein variants.

biochemistry↗