Efficient T-cell receptor signaling requires a high-affinity interaction between the Gads C-SH3 domain and the SLP-76 RxxK motif.
The relationship between the binding affinity and specificity of modular interaction domains is potentially important in determining biological signaling responses. In signaling from the T-cell receptor (TCR), the Gads C-terminal SH3 domain binds a core RxxK sequence motif in the SLP-76 scaffold. We show that residues surrounding this motif are largely optimized for binding the Gads C-SH3 domain resulting in a high-affinity interaction (K(D)=8-20 nM) that is essential for efficient TCR signaling in Jurkat T cells, since Gads-mediated signaling declines with decreasing affinity. Furthermore, the SLP-76 RxxK motif has evolved a very high specificity for the Gads C-SH3 domain. However, TCR signaling in Jurkat cells is tolerant of potential SLP-76 crossreactivity, provided that very high-affinity binding to the Gads C-SH3 domain is maintained. These data provide a quantitative argument that the affinity of the Gads C-SH3 domain for SLP-76 is physiologically important and suggest that the integrity of TCR signaling in vivo is sustained both by strong selection of SLP-76 for the Gads C-SH3 domain and by a capacity to buffer intrinsic crossreactivity.
Seet
Bruce T
BT
Centre for Systems Biology, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada.
Berry
Donna M
DM
Maltzman
Jonathan S
JS
Shabason
Jacob
J
Raina
Monica
M
Koretzky
Gary A
GA
McGlade
C Jane
CJ
Pawson
Tony
T
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs / Q000235:genetics*; D002151:Calorimetry; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D019169:Jurkat Cells; D008156:Luciferases; D008958:Models, Molecular; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D017434:Protein Structure, Tertiary; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*; D020349:Surface Plasmon Resonance
D048868:Adaptor Proteins, Signal Transducing; C409587:GRAP2 protein, human; D010750:Phosphoproteins; D011948:Receptors, Antigen, T-Cell; C092947:SLP-76 signal Transducing adaptor proteins; D008156:Luciferases