T cell activation induced by novel gain-of-function mutants of Syk and ZAP-70.
The Syk family tyrosine kinases play a crucial role in antigen receptor-mediated signal transduction, but their regulation and cellular targets remain incompletely defined. Following receptor engagement, phosphorylation of tyrosine residues within ZAP-70 and Syk is thought to control both kinase activity and recruitment of modulatory factors. We report here the characterization of novel mutants of ZAP-70 and Syk, in which conserved C-terminal tyrosine residues have been replaced by phenylalanines (ZAP YF-C, Syk YF-C). Both mutant kinases display a prominent gain-of-function phenotype in Jurkat T cells, as demonstrated by lymphokine promoter activation, tyrosine phosphorylation of potential targets in vivo, and elevated intracellular calcium mobilization. While the presence of p56-Lck was required for ZAP YF-C-induced signaling, Syk YF-C showed enhanced functional activity in Lck-deficient JCaM1 Jurkat cells. Our results implicate the C terminus of Syk family kinases as an important regulatory region modulating T cell activation.
Zeitlmann
L
L
Laboratorium für Molekulare Biologie, Genzentrum der Universität München, Feodor Lynen Strasse 25, D-81377 München, Germany.
Knorr
T
T
Knoll
M
M
Romeo
C
C
Sirim
P
P
Kolanus
W
W
D000595:Amino Acid Sequence; D002118:Calcium / Q000378:metabolism; D002384:Catalysis; D004792:Enzyme Precursors / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D000072377:Syk Kinase; D013601:T-Lymphocytes / Q000201:enzymology / Q000276:immunology*; D051746:ZAP-70 Protein-Tyrosine Kinase
D004792:Enzyme Precursors; D007376:Interleukin-2; D047908:Intracellular Signaling Peptides and Proteins; D011947:Receptors, Antigen, B-Cell; D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; D002118:Calcium