TY - JOUR
T1 - The SH3 Domain of Itk/Emt Binds to Proline-Rich Sequences in the Cytoplasmic Domain of the T Cell Costimulatory Receptor CD28
AU - Marengère, Luc E.M.
AU - Okkenhaug, Klaus
AU - Clavreul, Anne
AU - Couez, Dominique
AU - Gibson, Spencer
AU - Mills, Gordon B.
AU - Mak, Tak W.
AU - Rottapel, Robert
PY - 1997/10/1
Y1 - 1997/10/1
N2 - Engagement of the transmembrane receptor CD28 potentiates T cell survival, proliferation, and activation. The biochemical basis by which CD28 controls these outcomes is unclear, although early events following cross-linking of the receptor are characterized by tyrosine phosphorylation of CD28 and other cellular substrates. We demonstrate that following CD28 ligation, a CD28-associated tyrosine kinase activity is increased in parallel to activation of the T cell-specific tyrosine kinase Itk (Itk/Emt), while Lck and Fyn kinase activities are not increased. We show that Itk forms an inducible complex with CD28, mediated by the SH3 domain of Itk and the diproline motifs of CD28. Site-directed mutagenesis of the N-terminal diproline motif of CD28 abrogates the association of CD28 with the SH3 domain of Itk, while mutations within the C-terminal diproline motif have little effect. Peptides corresponding to the N-terminal diproline motif were more efficient at abrogating the interaction between CD28 and the SH3 domain of Itk, than peptides corresponding to the C-terminal diproline motif. In addition, peptides corresponding to the N-terminal diproline motif of CD28 activated the tyrosine kinase activity of Itk to levels similar to those observed following Ab-mediated cross-linking of CD28. Together, our data show that the SH3 domain of Itk binds to a proline-rich motif within the cytoplasmic tail of CD28, and define a mechanism by which CD28 couples to and activates a downstream tyrosine kinase.
AB - Engagement of the transmembrane receptor CD28 potentiates T cell survival, proliferation, and activation. The biochemical basis by which CD28 controls these outcomes is unclear, although early events following cross-linking of the receptor are characterized by tyrosine phosphorylation of CD28 and other cellular substrates. We demonstrate that following CD28 ligation, a CD28-associated tyrosine kinase activity is increased in parallel to activation of the T cell-specific tyrosine kinase Itk (Itk/Emt), while Lck and Fyn kinase activities are not increased. We show that Itk forms an inducible complex with CD28, mediated by the SH3 domain of Itk and the diproline motifs of CD28. Site-directed mutagenesis of the N-terminal diproline motif of CD28 abrogates the association of CD28 with the SH3 domain of Itk, while mutations within the C-terminal diproline motif have little effect. Peptides corresponding to the N-terminal diproline motif were more efficient at abrogating the interaction between CD28 and the SH3 domain of Itk, than peptides corresponding to the C-terminal diproline motif. In addition, peptides corresponding to the N-terminal diproline motif of CD28 activated the tyrosine kinase activity of Itk to levels similar to those observed following Ab-mediated cross-linking of CD28. Together, our data show that the SH3 domain of Itk binds to a proline-rich motif within the cytoplasmic tail of CD28, and define a mechanism by which CD28 couples to and activates a downstream tyrosine kinase.
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M3 - Article
C2 - 9317120
AN - SCOPUS:0031255110
SN - 0022-1767
VL - 159
SP - 3220
EP - 3229
JO - Journal of Immunology
JF - Journal of Immunology
IS - 7
ER -