CD179a VPREB1 (V pre-β lymphocyte gene 1), IGVPB ( Ig iota chain)
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Lineage Restricted Molecule
Polypeptide
B Cell
16 / 16
18 / 18

Expression
CD179a is selectively expressed in association with CD179b to form a surrogate light chain on pro-B and early pre-B cells.  Low levels of CD179a can be detected on the cell surface of early pre-B cells as a component of pre-B cell receptor (pre-BCR).  The vast majority of CD179a is retained in the cytoplasm.  Surface expression of the CD179a/CD179b surrogate light chain on human pro-B cells is controversial.  In mice, the surrogate light is detected on the surface of pro-B cells in association with a 130 kDa unknown protein.



Structure
MOLECULAR FAMILY NAME:  Belongs to the immunoglobulin gene superfamily.

CD179a is a 126 aa polypeptide.  It contains a 19 aa extracellular domain which contains an Ig V-domain-like structure, but it lacks the last b strand (b7) of a typical V-domain and a carboxyl terminal end that shows no sequence homologies to any other protein, a transmembrane and cytoplasmic domain.  CD179a associates non-covalently with CD179b, (l5 or l -like), carrying an Ig C domain-like structure to form a surrogate Ig light chain-like structure, which is called the surrogate light chain or pseudo light chain.  In this complex, the incomplete V domain of CD179a appears to be complemented by the extra β7 strand of CD179b carrying a C domain resulting in the formation of Ig light chain-like structure.  The CD179a/CD179b surrogate light chain is disulphide-linked to the membrane bound IgM heavy chain in association with a signal transducing CD79a/CD79b heterodimer to form the pre-B-cell receptor-like structure, so-called pre-BCR
    
MOLECULAR MASS
Cell Type Unreduced Reduced
Human pre-B cells 16-18 kDa
Mouse pre-B cells 16 kDa

POST-TRANSCRIPTIONAL MODIFICATION: No information.

POST-TRANSLATIONAL MODIFICATION: No information.


Ligands
The ligand of pre-BCR remains to be determined and might not exist.

LIGANDS AND MOLECULES ASSOCIATED WITH CD179a
Molecule Comment
CD179b CD179a associates with CD179b and Ig m heavy chain to form pre-BCR together with CD79a/CD79b heterodimer
Ig m heavy chain CD179a associates with CD179b and Ig m heavy chain to form pre-BCR together with CD79a/CD79b heterodimer
Unknown 130 kDa glycoprotein A 130 kDa glycoprotein was reported both in human and mice, which associates with CD179a/CD179b surrogate light chain on the surface of pro-B cell lines


Function
The  functional role of the CD179a/CD179b surrogate light chain expressed in pro-B cells remains to be determined.  CD179a is a marker of pro-B and early pre-B cells.  The surrogate light chain is a component of the pre-B cell receptor that plays a critical role in early B cell differentiation.  The pre-BCR complex containing CD179a transduces signaling for proliferation and differentiation.  Cellular proliferation and differentiation from proB cell to preB cell stage results in 2 to 5 divisions of pre-B cells.  At the end of this proliferate expansion, pre-B cells fall into a resting state, during which time rearraqngements at the light chain locus are initiated.  PreBCR complex transduces signals for allelic exclusion at the IgM heavy chain gene locus.  PreBCR promotes Ig light chain gene rearrangements.  Thus, pre-BCR functions as a checkpoint in early B cell development to monitor the production of Ig m heavy chain through a functional rearrangement of Ig heavy chain gene as well as the potency of Ig m heavy chain to associate with Ig light chain.

BIOCHEMICAL ACTIVITY

No enzymatic activity is known.

DISEASE RELEVANCE AND FUNCTION OF CD179a IN INTACT ANIMAL

To date, no CD179a-related human disease or pathology has been reported.  However, deficiency of other components of the pre-BCR such as CD179b, Ig m heavy chain and CD79a has been shown to result in severe impairment of B cell development and agammaglobulinemia in humans.  Only a partial block in B cell development was observed in Vpre-B1-knockout mice, since Vpre-B2, highly homologous to Vpre-B1, is expressed in mice in contrast to humans.


Comments
MOLECULAR INTERACTIONS -
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD179a: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD179a: No information.



Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 7441P12018
Antibodies

Revised June 25, 2008


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