CD79A; B-cell antigen receptor complex-associated protein alpha chain; Ig-alpha; MB-1 membrane glycoprotein; surface IgM-associated protein; membrane-bound immunoglobulin-associated protein (CD79A, IGA, MB1)
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Function
- component of B-cell antigen receptor
- required in cooperation with CD79B for initiation of the signal transduction cascade activated by binding of antigen to the B-cell antigen receptor complex (BCR) which leads to internalization of the complex, trafficking to late endosomes & antigen presentation
- also required for BCR surface expression & for efficient differentiation of pro- & pre-B-cells
- stimulates SYK autophosphorylation & activation
- binds to BLNK, bringing BLNK into proximity with SYK & allowing SYK to phosphorylate BLNK
- also interacts with & increases activity of some Src-family tyrosine kinases
- represses BCR signaling during development of immature B cells phosphorylated on Tyr, Ser & Thr upon B-cell activation
- phosphorylation of Tyr by Src-family kinases is an early & essential feature of the BCR signaling cascade the phosphorylated Tyr serve as docking sites for SH2-domain containing kinases, leading to their activation which in turn leads to phosphorylation of downstream targets
- phosphorylation of Ser & Thr may prevent subsequent Tyr phosphorylation
- part of the B-cell antigen receptor complex where the alpha/beta chain heterodimer is non-covalently associated with an antigen-specific membrane-bound surface immunoglobulin of two heavy chains & two light chains
- interacts through its phosphorylated ITAM domain with the SH2 domains of SYK which stimulates SYK autophosphorylation & activation
- also interacts, when phosphorylated on Tyr-210, with the SH2 domain of BLNK/SLP65, bringing BLNK into proximity with SYK & allowing SYK to phosphorylate BLNK which is necessary for trafficking of the BCR to late endosomes
- interacts with Src-family tyrosine kinases including FYN & LYN, increasing their activity (putative)
Structure
- heterodimer of alpha & beta chains, disulfide-linked
- contains 1 Ig-like C2-type domain (immunoglobulin-like)
- contains 1 ITAM domain
Compartment
- cell membrane; single-pass type I membrane protein
- following antigen binding, B-cell receptor translocates from detergent-soluble regions of the cell membrane to lipid rafts although signal transduction through the complex can also occur outside lipid rafts (putative)
Alternative splicing
at least 2 isoforms
Expression
- B-cells
- early B cell differentiation
- plasma cells
- acute lymphoblastic leukemia
- B cell lymphoma
- lymphocyte-predominant Hodgkin's lymphoma
Pathology
- defects in CD79A are a cause of non-Bruton type agammaglobulinemia
- somatic hypermutation of gene seen in
More general terms
Component of
References
- ↑ UniProt http://www.uniprot.org/uniprot/P11912.html
- ↑ Entrez Gene http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=973
- ↑ http://www.pathologyoutlines.com/cdmarkers.html 20 May 2003
- ↑ CD79Abase; Note: CD79A mutation db http://bioinf.uta.fi/CD79Abase/