CD79a MB1, Igα, Ly-54
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Lineage Restricted Molecule
Type 1 glycoprotein
B Lymphocyte
B Cell
Plasma
32 / 32
33 / 33

Expression
CD79α expression is restricted on B lymphocytes, first appearing on the surface at the pre-B cell stage and remaining through all stages of B cell differentiation prior to plasma cells.  Expression is present on early B cell maturation with marginal zone and follicular mantle B cells having stronger expression than germinal center.  The surrogate l chain and a truncated Dm heavy chain are expressed on pre-B cells. 

Structure
MOLECULAR FAMILY NAME:  Belongs to the immunoglobulin supergene family.

CD79α is a single-pass type-1 226 aa glycoprotein.  It contains an 109 aa extracellular domain which contains 1 Ig-like C2-type domain and 6 potential N-glycosylation sites, a 22 aa transmembrane domain and a 61 aa cytoplasmic domain containing an ITIM motif.  CD79α exists at the surface as a disulfide-linked heterodimer with CD79β non-covalently associated with membrane Ig.  It is proposed that each BCR complex contains 2 heterodimers of CD79α and CD79β.  All classes of heavy chains can associate with the CD79 heterodimer.  The cys residue found in the Ser-Cys-Gly-Thr sequence present in both CD79α and β is considered to be the site where the disulfide bond occurs.
 
MOLECULAR MASS
Cell Type Unreduced Reduced
32-33 kDa

POST-TRANSCRIPTIONAL MODIFICATION

Alternative splicing yields 2 transcript different isoforms.

POST-TRANSLATIONAL MODIFICATION

CD79α is phosphorylated on tyrosine upon B cell activation.

Ligands
LIGANDS AND MOLECULES ASSOCIATED WITH CD79α

Membrane Ig binds antigen.  Different pairs of  BCR-associated proteins (BAP) molecules have been identified which specifically associate with IgM or IgD.  As with CD3/TCR, phosphorylated ITAM motifs of CD79α bind to SH2 domains of B cell intracellular signaling molecules.



Function
CD79α and CD79β create a heterodimer that is disulfide linked and noncovalently binds to Ig to form BCR.  The heterodimer via BCR has been shown to function synergistically to induce apoptosis.  The heterodimer is necessary to escort the receptor complex to the cell membrane.  When mIgM binds binds antigen, the heterodimer transduces the signal and promotes endocytosis of bound antigen for intracellular degradation and presentation to T helper cells.  Antigen binding leads to internalization and presentation of antigen to T cells via MHC molecules, or can signal the B cell directly, in the case of multivalent antigens which crosslink several mIg molecules.  CD79α transmits signals into the cytoplasm upon antigen-binding to surface Igs.  CD79α binds Igs (CD5/CD19/CD22/CD179β).  Crosslinking of BCR leads to the activation of B cells.  This is dependent on CD79α for signal transduction.  Transmembrane signaling through surface Ig leads to the rapid activation of a phospholipase C and tyrosine kinases. 

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD79α IN INTACT ANIMAL

CD79α is useful in differential diagnosis of B cell neoplasms from T cell or myeloid neoplasms and is a useful marker of precursor B acute lymphoblastic leukemia (pre-B-ALL).

Comments
MOLECULAR INTERACTIONS-
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD79α: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD79α: No information.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 973P11912
MouseA43540P11911X13450
Antibodies
HM47   View Reactivity

Revised June 25, 2008


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