CD300a CMRF35H,  CMRF35H9, IRC1, IRC2, IRP60
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
Type 1 glycoprotein
Granulocyte
Monocyte
Neutrophil
NK Cell
B Cell
T Cell
Dendritic Cell
Mast Cell
60 / 60

Expression
CD300a is expressed by subsets of T cells, B cells, monocytes, mast cells, granulocytes, NK cells, neutrophils and dendritic cells.  Expression is also on 25% of circulating T cells and 15% of circulating B cells.  The CD300a antigen (CMRF35A) was identified by reactivity with a monoclonal antibody.

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

CD300a is a single-pass type-1 282 aa transmembrane glycoprotein.  It contains a 17 aa signal sequence, an 163 aa extracellular domain which contains 1 Ig-like V-type domain which is closely related to the 1st, 3rd and 4th IgSF domains of the poly-Ig receptor on epithelial cells, 2 N-linked glycosylation sites, a 45 aa membrane proximal domain which contains several serine and threonine residues that are potential O-linked glycosylation sites and a proline-rich relatively rigid hinge domain, a 21 aa transmembrane domain and a 98 aa cytoplasmic domain containing 3 potential immunoreceptor tyrosine-based inhibitory motifs (ITIMs) and a di-leucine motif which is associated with endocytosis.  The Ig-like domain is related to the Ig-binding domains of the Fc receptor for polymeric IgA and IgM.  The Pro- and Ser-rich sequence in the extracellular domain forms the hinge-like region with links to the V-set domain to a transmembrane sequence containing a charged residue glutamine.  The presence of this charged residue suggests that the CD300a antigen may associate with other molecules in the membrane.   Tyrosine phosphorlation of ITIMs leads to interaction with protein tyrosine phosphatases SHP-1 and SHP-2.
 
MOLECULAR MASS

POST-TRANSCRIPTIONAL MODIFICATION

Alternative splicing yields 3 different isoforms.

POST-TRANSLATIONAL MODIFICATION

CD300a has 2 potential N-linked glycosylation sites and is phosphorylated on tyrosine.

Ligands
LIGANDS AND MOLECULE ASSOCIATED WITH CD300a: No information.

Function
Mitogenic stimulation of peripheral blood lymphocytes reduces both mRNA levels and cell surface expression of the CD300a antigen.  The function of CD300a is under investigation but it is postulated to be an inhibitory receptor which may contribute to the down-regulation of cytolytic activity in natural killer cells.  MAb cross linking to CD300a has recently been shown to suppress effects of IL-5, GM-CSF and eotaxin on peripheral blood eosinophils in vitro.  The cytoplasmic tail of CD300a contains motifs similiar to ITIM motifs found in some leukocyte surface receptors.  Their expression in hemopoietic cells suggests that they may play a role in the regulation of leukocyte function.

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD300a IN INTACT ANIMAL: No information.

Comments
MOLECULAR INTERACTIONS-
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD300a: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD300a: No information.

ADDITIONAL INSIGHTS

For further information see Green, B. J. et al (1998) Int. Immunol. 10: 891-899.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene11314Q9UGN4
Antibodies

Revised June 25, 2008


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