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