Recombinant Human B-cell antigen receptor complex-associated protein alpha chain (CD79A）, partial (Active)

Function

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 and antigen presentation. Also required for BCR surface expression and for efficient differentiation of pro- and pre-B-cells. Stimulates SYK autophosphorylation and activation. Binds to BLNK, bringing BLNK into proximity with SYK and allowing SYK to phosphorylate BLNK. Also interacts with and increases activity of some Src-family tyrosine kinases. Represses BCR signaling during development of immature B-cells

Subcellular Location

Cell membrane (Single-pass type I membrane protein)

Disease Association

Agammaglobulinemia 3, autosomal recessive (AGM3) : A primary immunodeficiency characterized by profoundly low or absent serum antibodies and low or absent circulating B-cells due to an early block of B-cell development. Affected individuals develop severe infections in the first years of life. [The disease is caused by variants affecting the gene represented in this entry. Two different mutations, one at the splice donor site of intron 2 and the other at the splice acceptor site for exon 3, have been identified. Both mutations give rise to a truncated protein]

Tissue Specificity

B-cells

Subunit

Heterodimer of alpha and beta chains; disulfide-linked. 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 and two light chains (PubMed:35981043). Interacts through its phosphorylated ITAM domain with the SH2 domains of SYK which stimulates SYK autophosphorylation and activation. Also interacts, when phosphorylated on Tyr-210, with the SH2 domain of BLNK/SLP65, bringing BLNK into proximity with SYK and allowing SYK to phosphorylate BLNK which is necessary for trafficking of the BCR to late endosomes. Interacts with Src-family tyrosine kinases including FYN and LYN, increasing their activity (By similarity)

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• Hashimoto S. et al. Chromosomal localization, genomic structure, and allelic polymorphism of the human CD79 alpha (Ig-alpha/mb-1) gene. — Immunogenetics (1994)
• Ha H. et al. Structure, chromosomal localization, and methylation pattern of the human mb-1 gene. — J. Immunol. (1994)
• Hashimoto S. et al. Alternative splicing of CD79a (Ig-alpha/mb-1) and CD79b (Ig-beta/B29) RNA transcripts in human B cells. — Mol. Immunol. (1995)