DC-SIGN and SRCL bind glycans of carcinoembryonic antigen (CEA) and CEA-related cell adhesion molecule 1 (CEACAM1): recombinant human glycan-binding receptors as analytical tools

Members of the family of carcinoembryonic antigen (CEA)-related cell adhesion molecules (CEACAMs) belonging to the immunoglobulin (Ig) superfamily are expressed in a variety of normal and malignant human tissues. As components of the cell membrane, these glycoproteins can make contact with adjacent cells. CEACAM1 and CEACAM5 (CEA) express Lewisx (Lex) structures. As shown by mass spectrometry in conjunction with enzymatic digestion, CEACAM1 contains at least seven Lex residues. Fucosyltransferase IX is the main fucosyltransferase responsible for attachment of terminal fucose, the key feature of the Lex structure, to CEA and CEACAM1. The Lex residues of both, CEACAM1 and CEA, interact with the human Lex-binding glycan receptors DC-SIGN and SRCL. Since subpopulations of human macrophages express DC-SIGN or SRCL, Lex-carrying CEACAMs may modulate the immune response in normal tissues such as the human placenta or in malignant tumours, for example in colorectal, pancreatic or lung carcinomas.