High resolution

Module 9: Figure TCR signalling

Molecular organization of a functional T cell receptor (TCR).

Details of the signalling complexes located within the immunological synapse (Module 9: Figure immunological synapse). Signalling begins when the α and β subunits of the T cell receptor (TCR) detect antigen (red dot) held in the jaws of the major histocompatibility complex II (MHCII) embedded in the surface of the antigen-presenting cell. The sequence begins with CD4 associating with MHCII, thereby bringing Lck into the complex to begin the phosphorylation cascade that also depends upon ζ-associated protein of 70 kDa (ZAP70). The phosphates on the scaffolding protein then draw in the signal transducers, such as phospholipase Cγ1 (PLCγ1), PtdIns 3-kinase (PI 3-K) and the Ras complex, to activate the various signalling pathways as described in more detail in the text. The activation of Ca2+ signalling by inositol 1,4,5-trisphosphate (InsP3) is described in Module 9: Figure T cell Ca2+ signalling.