CD66e CEACAM5 (carcinembryonic antigen-related cell adhesion molecule), CEA, meconium antigen 100
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
GPI anchor
Epithelial Cell
100 / 100
200 / 200

Expression
CD66e is expressed on epithelial cells but CD66e carcinoembryonic antigen (CEA) has not been detected on hematopoietic cells.


Structure
MOLECULAR FAMILY NAME: Belongs to the carcinoembryonic antigen gene family.

CD66e is a single-pass GPI-anchored glycoprotein.  It contains a 34 aa leader peptide, a 642 aa extracellular domain which contains 6 Ig-like C2-type domains and 1 Ig-like V-type domain and is GPI-anchored to the membrane.  CD66 molecules, like the CD2 family, lack the canonical inter-b-sheet disulfide, followed by a variable number of C2-set Ig-like domains.  The CEA gene family belongs within the Ig gene superfamily.

MOLECULAR MASS
Cell Type Unreduced Reduced Comment
Epithelial cells 180-200 kDa

POST-TRANSCRIPTIONAL MODIFICATION

CD66e is GPI-anchored but with no splice variants.

POST-TRANSLATIONAL MODIFICATION

CD66e is heavily and variably N-glycosylated with 29 N-glycosylation sites.

Ligands
CD66 molecules can mediate cell-cell adhesion by homotypic interactions and/or by heterotypic interactions with other CD66 molecules. CD66e exhibits both heterotypic and homotypic interactions whereas CD66b binds only heterotypically to CD66e.  The binding sites for these interactions lie within their N-terminal V-set IgSF domains. Carbohydrate structures on CD66c mediate binding to E. coli type 1 fimbriae and may be important in presenting sLe x-related ligands to the endothelial cell adhesion molecule CD66e.

LIGANDS AND MOLECULES ASSOCIATED WITH CD66e
Molecule Comment
CD66a Binds the protein core of CD66e not the carbohydrate
CD66c Binds the protein core of CD66e not the carbohydrate
CD66e Binds the protein core of CD66e not the carbohydrate
Unknown molecule on bacteria Binds the carbohydrate on CD66e not the protein core




Function
CD66e is capable of homophilic and heterophilic adhesion to protein cores of CD66a and CD66c.  The ability of CD66 molecules to mediate cell-cell adhesion and their rapid upregulation following activation suggests that they may contribute to the interactions of activated granulocytes with each other or with the endothelia or epithelia.  However, direct functional evidence for such a role is lacking.  Crosslinking of CD66 molecules with antibodies can stimulate integrin-mediated neutrophil adhesion to endothelial cells, suggesting a possible signaling role.

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD66e IN INTACT ANIMAL

CD66e is a receptor for N. gonorrhorae influencing tissue interactions and cellular responses.  CD66e is a receptor for Opa proteins of pathogenic Neisseria (as also CD66a, CD66c and CD66d).  Inhibition of CD66e increases apoptotic rate of colon cancer cells and inhibits metastatic tumor growth.  Serum CEA is used as a clinical marker of tumor burden.  CD66e may be a potential target for tumor imaging and drug targeting.  CD66e is a receptor for Afa/Dr adhesions of diffusely adhering E. coli, which upon binding leads to activation of signal transduction pathways that result in proinflammatory responses and structural and functional damage to the brush border and junctions of intestinal epithelial cells.

Comments
The CEA family in humans and other mammals.
The human CEA molecules are a family of closely related, IgSF domain-containing glycoproteins encoded by a dense cluster of at least 18 genes within ~1.2 Mb with a 65%-75% sequence identity.  Based on sequence similarity and gene proximity this family can be divided into 2 subgroups, with a 80%-95% sequence identity within each subgroup. The CEA subgroup,  >7 genes, encodes predominantly cell surface molecules, whereas the pregnancy-specific glycoprotein (PSG) subgroup,  >11 genes, encodes secreted molecules.  CEA and PSG subgroups have also been identified in the mouse and the rat.  However, molecules within the subgroups show greater intraspecies,  >80%, than interspecies,  ~60% identity, making it impossible to identify species orthologues.  Indeed orthologues may not exist since sequence analysis suggests that there has been independent and parallel evolution of the CEA and PSG subgroups following the divergence of rodents and humans.

MOLECULAR INTERACTIONS -
PROTEINS AND DNA ELEMENTS WHICH REGULATE CD66e
Molecule Comment
Upstream stimulatory factor (USF)
Sp1
Sp1-like factor

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD66e: No information.

ADDITIONAL INSIGHTS

CD66e is capable of both homophilic and heterophilic adhesion, and may play a role in the process of metastasis of cancer cells.  CD66e is found in serum and is used clinically as a marker of tumor burden and a potential target of tumor imaging and drug targeting.  CD66e is removed by Kupfer cells in the liver via a specific receptor.  Interaction of CD66e with Kupfer cells stimulates release of various cytokines that may alter tumor cell growth in the liver.

Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 1048P06731
Antibodies

Revised June 25, 2008


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