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.
|Co-inhibitory immune checkpoint pathways||Co-stimulatory immune checkpoint pathways|
|PD1 & PD-L1 immune checkpoint pathway||CD40 & CD40L immune checkpoint pathway|
|CTLA-4 & CD80 (CD86) immune checkpoint pathway||OX40 & OX40L immune checkpoint pathway|
|B7-H3 / CD276 immune checkpoint pathway||HVEM & LIGHT immune checkpoint pathway|
|B7-H4 / B7S1 / B7x immune checkpoint pathway||CD28 & CD80 (CD86) immune checkpoint pathway|
|HVEM & BTLA immune checkpoint pathway||GITR & GITR Ligand immune checkpoint pathway|
|HVEM & CD160 immune checkpoint pathway||CD27 & CD70 immune checkpoint pathway|
|LAG3 / CD223 / Lymphocyte activation gene 3 immune checkpoint pathway||4-1BB & 4-1BBL immune checkpoint pathway|
|Galectin-9 & TIM-3 immune checkpoint pathway||ICOS & ICOS Ligand immune checkpoint pathway|
|Indoleamine 2,3-dioxygenase/IDO immune checkpoint pathway||CD266 & CD155 immune checkpoint pathway|
|VISTA / B7-H5 / GI24 immune checkpoint pathway|
|SIRP alpha & CD47 immune checkpoint pathway|
|2B4 & CD48 immune checkpoint pathway|
|TIGIT & CD155 immune checkpoint pathway|