CD318 CDCP1 (CUB domain-containing protein 1), SIMA135
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
Type 1 glycoprotein
Stem Cell
Epithelial Cell
Tumor Cell
Skeletal muscle
Colon
Keratinocyte
Bone Marrow
Carcinoma Cell
Breast
Hematopoietic Cell
140 / 140

Expression
CD318 is expressed on hematopoietic stem cell subsets, epithelial cells and in a number of human tumor cell lines as well as in  breast carcinoma but is over-expressed  in human lung and colorectal cancers.  High expression levels are in skeletal muscle and colon with lower levels in kidney, small intestine and placenta.  There is also expression in cells with phenotypes reminiscent of mesenchymal stem cells and neural cells.  CD318 is expressed by CD34+ CD133+ bone marrow cells and keratinocytes.

Structure
MOLECULAR FAMILY NAME

CD318 is a single-pass type-1 glycoprotein.  It contains 3 complement binding (CUB) extracellular domains which contains 9 glycosylation sites, a transmembrane domain and a cytoplasmic domain which has a short hexalysine stretch and 5 potential tyrosine phosphorylation sites.  The protein encoded by this gene is located on the cell surface and its shedding may lead to a soluble peptide.  CD318 is expressed as a 140 kDa (gp140) that is cleaved by trypsin to an 80 kDa form (gp80).  Plasmin also coverts gp140 to gp80.
 
MOLECULAR MASS

POST-TRANSCRIPTIONAL MODIFICATION

Alternative splicing yields 3 different isoforms.

POST-TRANSLATIONAL MODIFICATION

CD318 has 9 N-linked glycosylation sites.

Ligands
LIGANDS AND MOLECULE ASSOCIATED WITH CD318: No information.

Function
CD318 is a marker for hematopoietic progenitor cell subsets, in particular mesenchymal stem/protenitor cells and neural progenitor cells.  CD318 may be involved in cell adhesion, cell matrix associations or interactions with the extracellular matrix.  It may play a role in the regulation of anchorage versus migration versus differentiation via its phosphorylation.  MAb against CD318 was used to stimulate CD34+ bone marrow cells and this resulted in a two-fold increase in the formation of erythroid colony forming units (CFUs).

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD318 IN INTACT ANIMAL

CD318 may also be a novel marker for myeloid leukemia diagnosis and for immmature hematopoietic stem cell subsets.  It belongs to the tetraspanin web involved in tumor progression and metastasis.  CD318 is found to be overexpressed in colon and lung cancers.  Its expression level is correlated with the metastatic ability of carcinoma cells.  It is shown to be tyrosine phosphorylated in a cancer cell line.  CD318 may be a tumor-associated protein.   An in vitro model of wound activation demonstrated prolonged phosphorylation of the gp80 form of CD318 in foreskin keratinocytes.  Investigation is ongoing to determine if CD318-mediated signaling may play a role in wound repair of the epidermis.

Comments
MOLECULAR INTERACTIONS-
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD318: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD318: No information.

ADDITIONAL INSIGHTS

For further information see Buhring, H. J. et al (2004) Stem Cells 22: 334-343.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene64866Q9H5V8
Antibodies

Revised June 25, 2008


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