Recombinant Human B-lymphocyte antigen CD19 (CD19), partial Protein

Function

Functions as a coreceptor for the B-cell antigen receptor complex (BCR) on B-lymphocytes (PubMed:29523808). Decreases the threshold for activation of downstream signaling pathways and for triggering B-cell responses to antigens (PubMed:1373518, PubMed:16672701, PubMed:2463100). Activates signaling pathways that lead to the activation of phosphatidylinositol 3-kinase and the mobilization of intracellular Ca(2+) stores (PubMed:12387743, PubMed:16672701, PubMed:9317126, PubMed:9382888). Is not required for early steps during B cell differentiation in the blood marrow (PubMed:9317126). Required for normal differentiation of B-1 cells (By similarity). Required for normal B cell differentiation and proliferation in response to antigen challenges (PubMed:1373518, PubMed:2463100). Required for normal levels of serum immunoglobulins, and for production of high-affinity antibodies in response to antigen challenge (PubMed:12387743, PubMed:16672701, PubMed:9317126)

Subcellular Location

Cell membrane (Single-pass type I membrane protein); Membrane raft (Single-pass type I membrane protein)

Disease Association

Immunodeficiency, common variable, 3 (CVID3) : A primary immunodeficiency characterized by antibody deficiency, hypogammaglobulinemia, recurrent bacterial infections and an inability to mount an antibody response to antigen. The defect results from a failure of B-cell differentiation and impaired secretion of immunoglobulins; the numbers of circulating B-cells is usually in the normal range, but can be low. [The disease is caused by variants affecting the gene represented in this entry]

Tissue Specificity

Detected on marginal zone and germinal center B cells in lymph nodes (PubMed:2463100). Detected on blood B cells (at protein level) (PubMed:16672701, PubMed:2463100)

Subunit

Interacts with CR2/CD21 (PubMed:1702139). Part of a complex composed of CD19, CR2/CD21, CD81 and IFITM1/CD225 in the membrane of mature B-cells (PubMed:1383329). Interacts directly with CD81 (via the second extracellular domain); this interaction is initiated early during biosynthesis in the ER/pre-Golgi compartments and is essential for trafficking and compartmentalization of CD19 receptor on the cell surface of activated B cells (PubMed:16449649). Interacts with VAV (PubMed:10706702). Interacts with GRB2 and SOS when phosphorylated on Tyr-348 and/or Tyr-378. Interacts with PLCG2 when phosphorylated on Tyr-409 (PubMed:10706702). Interacts with LYN (PubMed:7687428). Interacts (when tyrosine phosphorylated) with the regulatory p85 subunit of phosphatidylinositol 3-kinase (PIK3R1 or PIK3R2) (PubMed:7684160). Interacts with GRB2 (PubMed:29523808)

• Stamenkovic I. et al. CD19, the earliest differentiation antigen of the B cell lineage, bears three extracellular immunoglobulin-like domains and an Epstein-Barr virus-related cytoplasmic tail. — J. Exp. Med. (1988)
• Tedder T.F. et al. Isolation of cDNAs encoding the CD19 antigen of human and mouse B lymphocytes. A new member of the immunoglobulin superfamily. — J. Immunol. (1989)
• Kozmik Z. et al. The promoter of the CD19 gene is a target for the B-cell-specific transcription factor BSAP. — Mol. Cell. Biol. (1992)
• Zhou L.J. et al. Structure of the genes encoding the CD19 antigen of human and mouse B lymphocytes. — Immunogenetics (1992)
• Kuroki K. et al. Polymorphisms of human CD19 gene: possible association with susceptibility to systemic lupus erythematosus in Japanese. — Genes Immun. (2002)
• Ota T. et al. Complete sequencing and characterization of 21,243 full-length human cDNAs. — Nat. Genet. (2004)
• Livingston R.J. et al. PubMed: CI-JGR3DF5COMGD (OCT-)
• Martin J. et al. The sequence and analysis of duplication-rich human chromosome 16. — Nature (2004)