A comprehensive characterization of the T-cell antigen receptor complex composition by microcapillary liquid chromatography-tandem mass spectrometry

It has become apparent that many intracellular signaling processes involve the dynamic reorganization of cellular proteins into complex signaling asse mblies that have a specific subunit composition, function, and subcellular location. Since the elements of such assemblies interact physically, multip rotein signaling complexes can be isolated and analyzed. Recent technical a dvances in highly sensitive protein identification by electrospray-tandem m ass spectrometry have dramatically increased the sensitivity with which suc h analyses can be performed. The T-cell antigen receptor (TCR) is an oligom eric transmembrane protein complex that is essential to T-cell recognition and function. The extracellular protein domains are responsible for ligand binding while intracellular domains generate and transduce signals in respo nse to specific receptor-ligand interactions. We used microbore capillary c hromatography-tandem mass spectrometry to investigate the composition of th e TCR protein complex isolated from resting and activated cells of the muri ne T-cell line CD11.3. We identified all the previously known subunits of t he TCR/CD3 complex as well as proteins previously not known to associate wi th the TCR. The catalytic activities of some of these proteins could potent ially be used to interfere pharmacologically with TCR signaling.