CD179b IGLL1 (immunoglobulin λ-like polypeptide 1), IGO (Ig omega chain)
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Lineage Restricted Molecule
Polypeptide
B Cell
22 / 22

Expression
The cellular expression of CD179b is selectively expressed in the cytoplasma of pro-B and on the surface of early pre-B cells.  Low levels of CD179b 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 CD179b proteins are retained in the cytoplasm.  Surface expression of the CD179a/CD179b surrogate light chain on human pro-B cells is controversial.  In mice, 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 family.

CD179b is a 169 aa polypeptide.  It contains  a 50 aa-long  extracellular domain which contains a N-terminal region which shows no sequence homologies to any other proteins and the 119 aa-long C-terminal region shows homology to the J region, a b7-strand of the variable region, and the constant region of the l light chain a transmembrane domain and a cytoplasmic domain.  In the CD179a/CD179b surrogate light chain, the incomplete V domain of CD179a lacking the last β strand (β7) appears to be complemented by the extra β7 strand of CD179b, resulting in the formation of Ig light chain-like structure.  The CD/179a /CD179b surrogate light chain is  disulphide-linked to membrane bound IgM heavy chain associated with the signal transducing CD79a/CD79b heterodimer to form a B cell receptor-like structure, so-called pre-BCR and plays a critical role in early B cell differentiation. 

MOLECULAR MASS
Cell Type Unreduced Reduced
pro-B and pre-B cells 22 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 FOR CD179b AND MOLECULES ASSOCIATED WITH CD179b
Molecule Comment
CD179a CD179b associates with CD179a and Ig m heavy chain to form pre-BCR together with CD79a/CD79b heterodimer
CD79a CD179b associates with CD179a and Ig m heavy chain to form pre-BCR together with CD79a/CD79b heterodimer
CD79b CD179b associates with CD179a and Ig m heavy chain to form pre-BCR together with CD79a/CD79b heterodimer
Unknown 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 function of the CD179a/CD179b surrogate light chain in pro-B cells remains to be determined.  The preB cell receptor is found on the surface of proB and preB cells, where it is involved in transduction of signals for cellular proliferation, differentiation from the proB cell to the preB cell stage and allelic exclusion at the Ig heavy chain gene locus.  After limited proliferation, the cells fall into a resting state during which time rearrangements at the light chain locus are initiated.  The preB cell receptor is composed of a membrane-bound Ig μ heavy chain  in association with a heterodimeric surrogate light chain.  CD179b encodes one of the surrogate light chain subunits and is a member of the immunoglobulin gene superfamily but does not undergo rearrangement.  The 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 capacity of Ig m chain to associate with Ig light chain.

BIOCHEMICAL ACTIVITY

No enzymatic activity is known.

DISEASE RELEVANCE AND FUNCTION OF CD179b IN INTACT ANIMAL

Mutations in the CD179b gene have been shown to result in the impairment of B cell development and agammaglobulinemia in humans, an autosomal recessive disease in which few or no λ globulins or antibodies are made.  This impairment was also observed in knockout mice deficient for CD179b, but is less severe than in humans.



Comments
MOLECULAR INTERACTIONS -
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD179b: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD179b: No information.



Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 3543P15814
Antibodies

Revised June 25, 2008


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