Phosphorylation of SLP-76 by the ZAP-70 protein-tyrosine kinase is required for T-cell receptor function.
Two families of tyrosine kinases, the Src and Syk families, are required for T-cell receptor activation. While the Src kinases are responsible for phosphorylation of receptor-encoded signaling motifs and for up-regulation of ZAP-70 activity, the downstream substrates of ZAP-70 are unknown. Evidence is presented herein that the Src homology 2 (SH2) domain-containing leukocyte protein of 76 kDa (SLP-76) is a substrate of ZAP-70. Phosphorylation of SLP-76 is diminished in T cells that express a catalytically inactive ZAP-70. Moreover, SLP-76 is preferentially phosphorylated by ZAP-70 in vitro and in heterologous cellular systems. In T cells, overexpression of wild-type SLP-76 results in a hyperactive receptor, while expression of a SLP-76 molecule that is unable to be tyrosine-phosphorylated attenuates receptor function. In addition, the SH2 domain of SLP-76 is required for T-cell receptor function, although its role is independent of the ability of SLP-76 to undergo tyrosine phosphorylation. As SLP-76 interacts with both Grb2 and phospholipase C-gamma1, these data indicate that phosphorylation of SLP-76 by ZAP-70 provides an important functional link between the T-cell receptor and activation of ras and calcium pathways.
Bubeck Wardenburg
J
J
Center for Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Fu
C
C
Jackman
J K
JK
Flotow
H
H
Wilkinson
S E
SE
Williams
D H
DH
Johnson
R
R
Kong
G
G
Chan
A C
AC
Findell
P R
PR
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D004792:Enzyme Precursors / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics*; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D015398:Signal Transduction; D000072377:Syk Kinase; D013601:T-Lymphocytes / Q000502:physiology*; D051746:ZAP-70 Protein-Tyrosine Kinase; D018909:src Homology Domains
D048868:Adaptor Proteins, Signal Transducing; D004792:Enzyme Precursors; D007376:Interleukin-2; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D011948:Receptors, Antigen, T-Cell; C092947:SLP-76 signal Transducing adaptor proteins; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras); D002118:Calcium