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|Human Cell lysate that Human Siglec-2 / CD22 transfected / overexpressed for Western blot (WB) positive control. The whole cell lysate is provided in 1X Sample Buffer (1X modified RIPA buffer+1X SDS loading buffer).|
|A DNA sequence encoding the human CD22 isoform-beta (P20273-1) extracellular domain (Met 1-Arg 687) was fused with a polyhistidine tag at the C-terminus.|
|The recombinant human CD22 consists of 679 amino acids and predictes a molecular mass of 76.6 kDa. In SDS-PAGE under reducing conditions, the apparent molecular mass of rhCD22 is approximately 120-130 kDa due to glycosylation.|
|Cell lysate was prepared by homogenization in ice-cold modified RIPA Lysis Buffer with cocktail of protease inhibitors (Sigma). Cell debris was removed by centrifugation. Protein concentration was determined by Bradford assay (Bio-Rad protein assay, Microplate Standard assay). The cell lysate was boiled for 5 min in 1 x SDS loading buffer (50 mM Tris-HCl pH 6.8, 12.5% glycerol, 1% sodium dodecylsulfate, 0.01% bromophenol blue) containing 5% b-mercaptoethanol, and lyophilized.|
|Modified RIPA Lysis Buffer: 50 mM Tris-HCl pH 7.4, 150 mM NaCl, 1mM EDTA, 1% Triton X-100, 0.1% SDS, 1% Sodium deoxycholate, 1mM PMSF.|
|12.5% SDS-PAGE Stained with Coomassie Blue after protein purification.|
|Samples are stable for up to twelve months from date of receipt.|
|1. Centrifuge the tube for a few seconds and ensure the pellet at the bottom of the tube. 2. Re-dissolve the pellet using 200μL pure water and boil for 2-5 min. 3. Store the lyophilized cell lysate at 4℃. After re-dissolution, recommend to aliquot it into smaller quantities and store at -80℃.|
|1 X Sample Buffer (1 X modified RIPA buffer+1 X SDS loading buffer).|
|Store at 4℃. After re-dissolution, aliquot and store at -80℃.|
|Western blot (WB): Use at an assay dependent dilution.|
Other Applications: Not tested.
Optimal dilutions/concentrations should be determined by the end user.
CD22 is a member of the immunoglobulin superfamily, SIGLEC family of lectins. It is first expressed in the cytoplasm of pro-B and pre-B cells, and on the surface as B cells mature to become IgD+. CD22 serves as an adhesion receptor for sialic acid-bearing ligands expressed on erythrocytes and all leukocyte classes. In addition to its potential role as a mediator of intercellular interactions, signal transduction through CD22 can activate B cells and modulate antigen receptor signaling in vitro. The phenotype of CD22-deficient mice suggests that CD22 is primarily involved in the generation of mature B cells within the bone marrow, blood, and marginal zones of lymphoid tissues. CD22 recruits the tyrosine phosphatase Src homology 2 domain-containing phosphatase 1 (SHP-1) to immunoreceptor tyrosine-based inhibitory motifs (ITIMs) and inhibits B-cell receptor (BCR)-induced Ca2+ signaling on normal B cells. CD22 interacts specifically with ligands carrying alpha2-6-linked sialic acids. As an inhibitory coreceptor of the B-cell receptor (BCR), CD22 plays a critical role in establishing signalling thresholds for B-cell activation. Like other coreceptors, the ability of CD22 to modulate B-cell signalling is critically dependent upon its proximity to the BCR, and this in turn is governed by the binding of its extracellular domain to alpha2,6-linked sialic acid ligands. However, genetic studies in mice reveal that some CD22 functions are regulated by ligand binding, whereas other functions are ligand-independent and may only require expression of an intact CD22 cytoplasmic domain at the B-cell surface. CD19 regulates CD22 phosphorylation by augmenting Lyn kinase activity, while CD22 inhibits CD19 phosphorylation via SHP-1.