CEACAM1 / CD66a is a single-pass type-1 glycoprotein which belongs within the Ig gene superfamily. It contains a 34 amino acid (aa) leader sequence, an extracellular domain which contains a N-terminal IgV-like domain and three of IgC2-like domains (382 aa), a transmembrane domain (43 aa), a cytoplasmic domain (67 aa) and two of the potential tyrosine phosphorylation sites. CEACAM1 / CD66a is heavily N-glycosylated with more than 60% of the mass contributed by N-linked glycans.
CEACAM1 / CD66a isoforms with transmembrane domain are mostly cell-membrane anchored, whereas those without transmembrane domain are secreted. They are mostly expressed in cells of epithelial and endothelial, lymphoid and myeloid cells.
CEACAM1 / CD66a is capable of homophilic with CEACAM1 / CD66a or heterophilic adhesion with CEA and CEACAM6. Isoforms of CEACAM1 / CD66a with a long cytoplasmic domain generally transmit inhibitory signals, whereas isoforms with a short cytoplasmic domain indicate a regulated interaction with the cytoskeleton. CEACAM1 / CD66a has been implicated in various types of intercellular-adhesion and intracellular-signaling of cell survival, differentiation and growth in both normal and cancer cells.
Daniel Sanghoon Shin et al. The evolution of checkpoint blockade as a cancer therapy: what's here, what's next? Current Opinion in Immunology, 2015; 33: 23-35.