Figure 6-12
The effect of co-receptors on signaling
For T-cells, either CD4 or CD8 is necessary for optimal signaling to occur through the TCR complex. With the proper co-receptor, only 10-100 identical MHC:peptide complexes on given cell are necessary to trigger a T-cell. Without the proper co-receptor, 10,000 are necessary.
Clustering brings the co-receptor associated Lck in close proximity to the ITAMs and other tyrosine targets within the TCR complex
ITAMs phophorylated by Lck, Fyn, others
Zap70 SH2 binds double phosphorylated ITAMs
Lck activates Zap70 kinase activity.
Zap70 phosphorylates LAT and SLP-76 adapters in rafts