[CEACAM1--a less well-known member of the family of carcinoembryonic antigens].

CEACAM1 (carcinoembryonic antigen-related cell adhesion molecule 1) is a transmembrane glycoprotein belonging to the carcinoembryonic antigen (CEA) family and immunoglobulin superfamily. It is localized mainly in the apical domains of polarized epithelia, leukocytes and endothelia. With respect to this wide tissue distribution the research is focused on the study of its biological functions. Structural and functional analyses show that the extracellular domain of CEACAM1 participates in homotypic and heterotypic adhesion, whereas the cytoplasmic domain takes part in cell growth inhibition and signal transduction. Whereas CEA is highly expressed in adenocarcinomas, CEACAM1 expression is down regulated in many tumors and its tumor-supressive function was confirmed. CEACAM1 also takes part in insulin metabolism, acts as a promotor of cholesterol crystallization and serves as a binding receptor for certain bacterial strains in humans as well as hepatitis virus in mice.