title: Constitutively unmasked CD22 on B cells of ST6Gal I knockout mice: novel sialoside probe for murine CD22.
abstract: The interaction of CD22 with glycoprotein ligands bearing the Siaalpha2,6Gal-R sequence is believed to modulate its function as a regulator of B cell signaling. Although a commercial sialoside-polyacrylamide (PAA) probe, NeuAc- alpha2,6Gal-PAA, has facilitated studies on ligand binding by human CD22, murine CD22 binds instead with high affinity to NeuGcalpha2,6Gal-R. A multivalent probe with this sequence was constructed to facilitate investigations of ligand binding in CD22 function using genetically defined murine models. The probe is based on the sialoside-PAA platform, which is then biotinylated for easy detection. A series of sialoside probes were constructed with two different length linker arms between the sialoside and the backbone and three different sialoside to PAA molar ratios. The NeuGcalpha2,6Gal-PAA probe is specific for CD22: it binds to sialidase-treated B cells of wild-type mice but not B cells of CD22-null mice. Additionally, because the probe only binds to sialidase-treated wild-type cells, it confirms that CD22 is constitutively "masked" on most B cells from wild-type mice by binding to ligands in cis. In contrast, the probe bound equally well to native or sialidase-treated B cells from the immunocompromised ligand-deficient ST6Gal I knockout mice, demonstrating that CD22 is constitutively "unmasked" in these cells.
authors.affiliation: Department of Molecular Biology, The Scripps Research Institute, 10550 N. Torrey Pines Rd., MEM-L71, La Jolla, CA 92075, USA.
authors.forename: Brian E
authors.initials: BE
authors.lastname: Collins
authors.forename: Ola
authors.initials: O
authors.lastname: Blixt
authors.forename: Nicolai V
authors.initials: NV
authors.lastname: Bovin
authors.forename: Claus-Peter
authors.initials: CP
authors.lastname: Danzer
authors.forename: Daniel
authors.initials: D
authors.lastname: Chui
authors.forename: Jamey D
authors.initials: JD
authors.lastname: Marth
authors.forename: Lars
authors.initials: L
authors.lastname: Nitschke
authors.forename: James C
authors.initials: JC
authors.lastname: Paulson
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000276:immunology*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D015815:Cell Adhesion Molecules; D037102:Lectins / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D015335:Molecular Probes; D051918:Sialic Acid Binding Ig-like Lectin 2; D012799:Sialyltransferases / Q000235:genetics / Q000502:physiology*; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase
chemical_list: D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; C497868:Cd22 protein, mouse; D015815:Cell Adhesion Molecules; D037102:Lectins; D015335:Molecular Probes; D051918:Sialic Acid Binding Ig-like Lectin 2; D012799:Sialyltransferases; D000094802:beta-D-Galactoside alpha 2-6-Sialyltransferase