CD72 Lyb-2(mouse), Ly-32.2, Ly-19.2
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
Type 2 glycoprotein
B Cell
Macrophage
T Cell
Dendritic Cell
B Lymphocyte
45 / 45

Expression
CD72 is expressed on all cells of the B cell lineage, on macrophages and some dendritic cells.  CD72 is expressed on all B lymphocytes from early progenitors through to mature cells but expression is downregulated during differentiation into plasma cells.  Anti-CD72 antibodies also label human tissue macrophages weakly.

Structure
MOLECULAR FAMILY NAME: Belongs to the C-type lectin family.

CD72 is a single-pass disulfide-linked homodimeric type-2 359 aa glycoprotein.  It contains an extracellular domain which contains a C-terminal domain followed by an α helical coiled coil that forms a 15 mm stalk and spacer between the lectin domain and glycosylation sites which are present within the stalk region, a transmembrane domain and cytoplasmic domains containing 2 ITIM motifs.  It is a member of a group of related cell surface molecules which induces the asialoglycoprotein receptors, CD23, and the Kupffer cell receptor. 

MOLECULAR MASS
Cell Type Unreduced Reduced
86 (major) kDa & 90 kDa 39 kDa & 43 (major) kDa

POST-TRANSCRIPTIONAL MODIFICATION

Alternative splicing yields a isoform displaying polymorphism.

POST-TRANSLATIONAL MODIFICATION: No information.


Ligands
LIGANDS AND MOLECULES ASSOCIATED WITH CD72

CD72 binds CD100.  Purified CD5 has been reported to bind CD72 on cells but this is controversial (see CD5).  Lectin-like activity has not been demonstrated. 

L. Biancone, M. A. Bowen, A. Lim, A. Aruffo, G. Andres, and I. Stamenkovic. Identification of a novel inducible cell-surface ligand of CD5 on activated lymphocytes. J.Exp.Med. 184 (3):811-819, 1996.

Function
CD72 is a putative ligand for CD100 and CD5.  When CD100 (Sem4D) engages CD72, B cells are more readily triggered through CD40.  B cell defects reduce proliferation and Ig production in CD100 deficient mice indicating the importance of CD72/CD100 interactions in lymphoid cell development.  CD100 appears to prevent negative regulation by CD72 as upon binding to CD72, dephosphorylation of ITIMs occurs and disassociation of SHP-1.  The protein phosphatase SHP-1 to associates with CD72 particularly after BCR ligation and it appears to be a substrate for SHP-1.  CD72 contains an ITAM motif which, when tyrosine phosphorylated, can bind SHP-1.  CD72 deficient mice have been fewer mature B cells and CD72-/-B cells display hyperproliferative responses to several B cell stimuli suggesting that CD72 may play a role in regulating signal threshold in B cells.  Also expression of CD72 can lead to downregulation of signaling through the BCR on B cells containing IgM or IgG.  These results suggest that disturbance of the function of CD72 as a regulator of signaling thresholds may lead to loss of mature B cells and in some cases, to autoimmune disease and may be involved in the control of B cell proliferation and differentiation.  Exposure of B cells to CD72 antibodies activates a variety of signaling pathways and can induce MHC Class II expression and B cell proliferation.  However, the significance of these observations is not clear.

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD72 IN INTACT ANIMAL

CD72 interaction with FcγR2B modifies susceptibility to SLE.


Comments
MOLECULAR INTERACTIONS-
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD72: No information

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD72: No information.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 971P21854
MouseA32331P21855J04170
Antibodies
3F3   View Reactivity
JA-117   View Reactivity

Revised June 25, 2008


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