Molecular characterization of a new member of the immunoglobulin superfamily that potentially functions in T-cell activation and development.

Differential hybridization cloning has been used to isolate a novel chicken thymic activation and developmental sequence (cTADS). The nucleotide sequence of the cTADS cDNA predicts an open reading frame of 439 amino acids. The inferred cTADS protein possesses a hydrophobic membrane-spanning domain and putative intracellular kinase activation domains. Its extracellular domain shares similarities with the immunoglobulin protein superfamily, featuring two conserved immunoglobulin folds that resemble C1 and C2 constant regions. The cTADS sequence shows similarity to a subfamily of proteins involved in cellular adhesion: chicken neural cell adhesion molecule and human opioid-binding adhesion molecule, and to proteins that have a biological role in intracellular signaling: mouse platelet-derived growth factor receptor and human fibroblast growth factor receptor. cTADS is differentially expressed in chicken thymic cells during embryonic development and during activation through the T-cell receptor. Sequence similarities and expression patterns suggest that cTADS could be involved in cell recognition and adhesion, and/or peptide ligand binding.