Proximity labeling of cis-ligands of CD22/Siglec-2 reveals stepwise α2,6 sialic acid-dependent and -independent interactions

• Published in: Biochemical and biophysical research communications 2018-01, Vol.495 (1), p.854-859
• Main Authors: Alborzian Deh Sheikh, Amin, Akatsu, Chizuru, Imamura, Akihiro, Abdu-Allah, Hajjaj H.M., Takematsu, Hiromu, Ando, Hiromune, Ishida, Hideharu, Tsubata, Takeshi
• Format: Article
• Language: English
• Subjects: 60 APPLIED LIFE SCIENCES; BIOTIN; CD22; Cis-ligands; LECTINS; LYMPHOCYTES; MICE; Proximity labeling; RECEPTORS; SIALIC ACID; Sialic acids; WEAK INTERACTIONS
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2017.11.086

Lectins expressed on the cell surface are often bound and regulated by the membrane molecules containing the glycan ligands on the same cell (cis-ligands). However, molecular nature and function of cis-ligands are generally poorly understood partly because of weak interaction between lectins and glycan ligands. Cis-ligands are most extensively studied in CD22 (also known as Siglec-2), an inhibitory B lymphocyte receptor specifically recognizing α2,6 sialic acids. CD22, CD45 and IgM are suggested to be ligands of CD22. Here we labeled molecules in the proximity of CD22 in situ on B cell surface using biotin-tyramide. Molecules including CD22, CD45 and IgM were labeled in wild-type but not ST6GalI−/- B cells that lack α2,6 sialic acids, indicating that these molecules associate with CD22 by lectin-glycan interaction, and are therefore cis-ligands. In ST6GalI−/- B cells, these cis-ligands are located in a slightly more distance from CD22. Thus, the lectin-glycan interaction recruits cis-ligands already located in the relative proximity of CD22 through non-lectin-glycan interaction to the close proximity. Moreover, cis-ligands are labeled in Cmah−/- B cells that lack Neu5Gc preferred by mouse CD22 as efficiently as in wild-type B cells, indicating that very low affinity lectin-glycan interaction is sufficient for recruiting cis-ligands, and can be detected by proximity labeling. Thus, proximity labeling with tyramide appears to be a useful method to identify cis-ligands and to analyze their interaction with the lectins. •Cis-ligands of CD22 are efficiently labeled by proximity labeling with tyramide.•Cis-ligands in relative proximity of CD22 in the absence of lectin-glycan interaction.•Lectin-glycan interaction further recruits cis-ligands to the close proximity of CD22.•Very low affinity interaction is sufficient for recruitment of cis-ligands to CD22.