Adhesion? Sticking & Signalling E. Yvonne Jones Erice 2006

T cell – target cell interactions, a particular form of cell-cell communication with specificity contributed by pMHC – TCR binding. Result: T cell receptor (TCR) signalling and formation of an ‘Immunological Synapse’.

Immunodominant HLA-A2 tumour epitope NY-ESO : SLLMWITQC SLLMWITQV stimulates faster polarisation of lytic granules to the immunological synapse Chen & Stewart-Jones et al (2005) J. Exp. Med But, all pMHCs are not equal…

Structure of the immunodominant  V17-  V10s2 T cell receptor with HLA A2/influenza matrix epitope …..as used by >one billion humans! and all TCRs are not equal… Stewart-Jones et al (2003) Nature Immunol

Vβ17 Flu Matrix T Cells- The Most Abundant T cell Clonotype on the Planet An estimated 3 billion people have HLA-A2 All have had Influenza Flu matrix responses dominate the immune reaction to infection Vβ17 clonotype constitutes > 80% of that response 0.5 kg of this receptor circulating in the world Stacking the receptors end-to-end would stretch more than halfway to Neptune (2.6 billion km) Guillaume Stewart-Jones, Jeffrey Ishizuka & John Bell, unpublished calculation

Why is a  V17-  V10s2 TCR so good at recognising HLA A2/influenza matrix epitope?

Kuby, 4 th edition

T cell receptors (TCRs) Gene segments Combinations Vα50 Jα x 10 3 alpha chains Vβ20 Jβ13 Dβ2 520 beta chains Any alpha with any beta chain1.3 x 10 6 The potential TCR repertoire is further increased by the addition of N region nucleotides. The recombination process is not precise. the exact points of splicing between V, D and J regions can vary over several nucleotides extra nucleotides, called N regions, can also be inserted at these joints. The number of TCRs that we make is ~2.5 x 10 7

Flu matrix peptide presented by HLA-A2 provides few sidechains for TCR recognition The challenge

TCR positioned to insert CRD3  between peptide and alpha 2 helix The answer

Why is a  V17-  V10s2 TCR so good at recognising HLA A2/influenza matrix epitope? Its because of a distinctive CDR3  motif and combination of residues unique to  V17-  V10s2 CDR1 and CDR2 loops that allow the CDR3  to be positioned optimally to sample a unique feature of the pMHC surface Stewart-Jones et al (2003) Nature Immunol. 4,

sTCR mutants made and tested Jeffrey Ishizuka & Guillaume Stewart-Jones

Vβ17 CDR2 Offers a Unique Sequence and Energetic Landscape

So we are still on target with our hypothesis for why a  V17-  V10s2 TCR is so good at recognising HLA A2/influenza matrix epitope. But why is this TCR-pMHC immunodominant over all other TCR-pMHC interactions involving influenza virus epitopes presented by the MHC class I molecule HLA A2?

T cell – target cell interactions, a particular form of cell-cell communication with specificity contributed by pMHC – TCR binding. Result: T cell receptor (TCR) signalling and formation of an ‘Immunological Synapse’.

Receptor protein tyrosine phosphatases: classification

A B C D RPTP  expression on axonal growth cones (A and B, Ledig et al., 1999) and at the endothelial cell junctions (C and D, Bianchi et al., 1999). RPTP  is a cell-adhesion molecule involved in neural development (axon growth) and angiogenesis. S S RPTP 

Crystal structure of the MAM-Ig unit Aricescu & Hon (2006) EMBO J RPTP  S S N C for dimers need MIg-FNIII RPTP  S S N C S S MAM-Ig RPTP  S S N C and for adhesion need MIg-2xFNIII so… * structure function? NO

MIg structure plus biophysical and functional data generated several possible models for RPTP  adhesive interactions * * monomer pH-dependent dimer (trans) trans/trans zipper trans/cis zipper Zipper model, consistent with the extended planarity of the plasma membrane observed at intercellular contact sites and with the multiple interactions observed between RPTP  ectodomains I recommend you go and see Radu Aricescu’s poster in the Thursday afternoon session (also Christian Siebold’s poster on cell guidance signalling…)

Christian Siebold Radu Aricescu Weixian Lu (Jeffrey Ishizuka) & Guillaume Stewart-Jones In collaboration with: John Bell, Vincenzo Cerundolo, Andrew McMichael & Anton van der Merwe