|CD32||FcγRII2A, 2B & 2C (Fcγ receptor type II), CDw32, gp40|
|Molecule Type||Antigen Expression||Molecular Weight|
Min / Max
|Non-lineage Restricted Molecule|
Type 1 glycoprotein
|40 / 40|
|CD32A gene is expressed on a range of leukocytes including monocytes, macrophages, Langerhans cells, granulocytes, B cells, myeloid cells, dendritic cells and platelets, as well as on endothelial cells of the placenta. There is a low expression on T-cell subset. The CD32B gene is present on B lymphocytes, monocytes and macrophages but not on NK cells. The CD32C gene is expressed on NK cells.|
|MOLECULAR FAMILY NAME: Belongs to the immunoglobulin gene family.|
CD32 is a single-pass type-1 glycoprotein. There are 3 genes, CD32A, CD32B and CD32C. A 281 aa CD32A contains a 34 aa leader sequence, an extracellular domain which contains 2 Ig-like C2-type domains and 1 N-glycosylation site, a transmembrane domain and a intracellular cytoplasmic domain containing an ITAM motif. A 291 aa CD32B contains a 42 aa signal sequence, an extracellular domain which contains 2 Ig-like C2-type domains and 1 N-glycosylation site, a transmembrane domain and an 19 aa cytoplasmic domain containing an ITIM motif. CD32C is a hybrid between A and B gene. CD32C has
a transmembrane domain and has a high homology with the extracellular domain of CD32B, and with the cytoplasmic domain of CD32A having an ITAM motif.
Alternative splicing yields 9 different isoforms from 3 genes, 2A, 2B and 2C. 2A has 2 isoforms, 2B has 3 isoforms and 2C has 4 isoforms. One of the 2A isoforms lacks a transmembrane domain. One of the 2B isoforms has a 19 aa insert in the cytoplasmic domains and another isoform lacks the L2 exon in the extracellular domain. Two of the 2C isoforms lack the ITAM motif and the third isoform is a soluble form.
POST-TRANSLATIONAL MODIFICATION: No information.
|LIGANDS AND MOLECULES ASSOCIATED WITH CD32|
CD32 is a low affinity Fcg receptor and only binds polymeric or aggregated IgG. The isotype preference for CD32 is IgG3 >IgG1 >IgG2 = IGg4. The A isoform has been shown to associate with CD11b/CD18 but not CD11c/CD18. The cytoplasmic portion of the B1 isoform associates with the tyrosine phosphatase SHP-1 and the inositol-5'-phosphatase SHIP via a phosphorylated IxYxxL motif.
|CD32 molecules have a low affinity for monomeric IgG but bind immune complexes efficiently. CD32 regulates B cell function and is a major player in the immune complex-induced tissue damage and seems to have a major inhibitory role preventing the development of autoimmune disease. Occupation of CD32 can trigger IgG-mediated phagocytosis and an oxidative burst in neutrophils and monocytes, possibly in coordination with the ligation of other receptors such as CD26 and CD11b/CD18 and presents on platelets can trigger aggregation and granule release. ITAM-bearing isoforms mediate activation and ITIM-bearing isoforms mediate downregulate responses. CD32A is a potent inducer of phagocytosis and degranulation. Heterotypic CD32A and CD32B genes trigger synergistic responses and may be important for regulation and inductions of select leukocyte function. |
CD32A is the only receptor that interacts with IgG2 and is problably involved in the clearing of the clearing of encapsulated bacteria. The CD32B gene mediates feedback inhibition of B cell responses and inhibition of antibody uptake and presentation to T cells. It has demonstrated to regulate inflammatory responses. The CD32C gene is expressed on NK cells but varies between individuals due to polymorphisms. The function of CD32C has yet to be determined, but in vitro studies show that triggering with antigen-antibody complexes results in cell activation and triggering of antibody-dependent cellular cytotoxicity.
BIOCHEMICAL ACTIVITY: No information.
DISEASE RELEVANCE AND FUNCTION OF CD32 IN INTACT ANIMAL
Mutations in CD32B play a role in follicular lymphoma and may play a role in tumor progression. It interacts with the measles virus N protein which is released in the blood following lysis of measles infected cells thereby blocking inflammatory immune response. It is also thought to play a role in the pathogenesis of human systemic lupus erythematosis (SLE). 2A is thought to play a role in lupus nephritis and cystic fibrosis.
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD32: No information.
SUBSTRATES: No information.
ENZYMES WHICH MODIFY CD32: No information.
In humans, the CD32 genes are intercalated with those of CD16 in a complex locus.
Database accession numbers
Revised June 25, 2008