CD329 SIGLEC9 (sialic acid binding Ig-like lectin 9), CDw329
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
Type 1 glycoprotein
Monocyte
Granulocyte
NK Cell
T Cell
Neutrophil
Hepatocyte
Liver
Spleen
Bone Marrow
Leukocyte
Peripheral blood
Placenta
B Cell
50 / 50

Expression
CD329 is expressed on granulocytes, hepatocytes, subsets of NK, B and T cells and peripheral blood leukocytes but not on eosinophils.  Intermediate to high levels of expression on monocytes, neutrophils and a minor population of CD16+ and CD56- cells.  Weak expression is detected in 50% of B cells, NK cells and CD3+α/β T cells.  Expression is found in liver, bone marrow, placenta, spleen and at low levels in skeletal muscle, fetal brain, stomach, lung, thymus, prostate, mammary, adrenal gland, colon, trachea, cerebullum, testis, small intestine and spinal cordon.

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

CD329 is a single-pass type-1 446 aa lectin glycoprotein.  It contains a 17 aa signal sequence, 331 aa extracellular domain which contains 2 Ig-like C2-type domains and 1 N-terminal Ig-like V-type domain and has 8 potential N-linked glycosylation sites, a 21 aa transmembrane and 94 aa cytoplasmic domain which contains a classical immunoreceptor tyrosine-based inhibitory motif (ITIM) and a signaling lymphocytes activating molecule (SLAM)-like motif that  and shares an 80% identity with CD328 at the nucleotide level.  CD329 belongs to the Ig superfamily, which characteristically binds sialic acids to the cell surface. 

MOLECULAR MASS

POST-TRANSCRIPTIONAL MODIFICATION: No information.

POST-TRANSLATIONAL MODIFICATION

CD329 has 9 potential N-linked glycosylation sites.  CD329 contains a cytoplasmic motif that is referred to as the immunoreceptor tyrosine-based inhibitor motif (ITIM).  This motif is involved in modulation of cellular responses.  The phosphorylated ITIM can bind the SH2 domain of several SH2-containing phosphatases.

Ligands
LIGANDS AND MOLECULE ASSOCIATED WITH CD329

CD329 binds α2,3- and α2,6-linked sialic acids althought the underlying glycan influences the binding avidity.  Sialic α2,3-linked to Galβ1-4GlcNAc are better ligands than sialic acids α2,3-linked to Galβ1-3GalNAc.

Function
CD329 is a sialic acid dependent adhesion molecule belonging to a sialic acid binding Ig-like lectin family which is involved in the negative regulation of immune responses.  This putative adhesion molecule mediates the sialic-acid dependent binding to cells.  The sialic acid recognition may be masked by cis interactions with sialic acids on the same surface.  CD329 can negatively affect TCR signaling.  Ligand binding leads to recruitment of SHP-1 and subsequently reduced phosphorylation of Tyr319 on ZAP-70, which plays a role in the upregulation of gene transcription after TCR stimulation.  A recent study found that CD329 ligation can initiate both apoptotic and non-apoptotic death on the pro-inflammatory cytokine production.

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD329 IN INTACT ANIMAL: No information.

Comments
MOLECULAR INTERACTIONS-
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD329: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD329: No information.

ADDITIONAL INSIGHTS

For further information see Zhang, J. Q. et al (2000) J. Biol. Chme. 275: 22121-22126.




Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene27180Q9Y336
Antibodies

Revised June 25, 2008


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