Letter abstract
Nature Chemical Biology 1, 93 - 97 (2005)
Published online: 12 June 2005 | doi:10.1038/nchembio713
Homomultimeric complexes of CD22 in B cells revealed by protein-glycan cross-linking
Shoufa Han1,2, Brian E Collins1,2, Per Bengtson1 & James C Paulson1
CD22 is a negative regulator of B-cell receptor signaling, an activity mediated by recruitment of SH2 domain–containing phosphatase 1 through a phosphorylated immunoreceptor tyrosine inhibitory motif in its cytoplasmic domain1. As in other members of the sialic acid–binding immunoglobulin-like lectin, or siglec, family, the extracellular N-terminal immunoglobulin domain of CD22 binds to glycan ligands containing sialic acid, which are highly expressed on B-cell glycoproteins2. B-cell glycoproteins bind to CD22 in cis and 'mask' the ligand-binding domain3, modulating its activity as a regulator of B-cell signaling4, 5, 6. To assess cell-surface cis ligand interactions, we developed a new method for in situ photoaffinity cross-linking of glycan ligands to CD22. Notably, CD45, surfaceIgM (sIgM) and other glycoproteins that bind to CD22 in vitro7, 8 do not appear to be important cis ligands of CD22 in situ. Instead, CD22 seems to recognize glycans of neighboring CD22 molecules as cis ligands, forming homomultimeric complexes.
- Departments of Molecular Biology and Molecular and Experimental Medicine, The Scripps Research Institute, 10550 North Torrey Pines Road, MEM-L71, La Jolla, California 92037, USA.
- Both authors contributed equally to this work.
Correspondence to: James C Paulson1 e-mail: jpaulson@scripps.edu
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