Diminished tyrosine protein kinase activity in T cells unresponsive to TCR stimulation.
Tyrosine phosphorylation is thought to be one of the earliest steps in antigenic activation of T cells. Three nonreceptor tyrosine kinases, p56lck, p60fyn, and ZAP-70, are known to be involved in T cell receptor (TCR) signaling, albeit their functional roles appear to be different. Whereas p60fyn and ZAP-70 are functionally associated with the T cell antigen receptor, p56lck is essential for TCR signaling without being directly coupled to the TCR. We have studied a mutant variant of the Jurkat T cell line (J32-3.2), in which basal activities of p56lck and p60fyn are 2- to 2.5-fold reduced relative to those in its parental line (J32) while basal activity of ZAP-70 remains unchanged, and compared responses of J32-3.2 and J32 to TCR stimulation. We have demonstrated that tyrosine phosphorylation following CD3 cross-linking in J32-3.2 cells was extremely short-lived and thus insufficient for the induction of subsequent physiological responses. This was at least partially due to the diminished tyrosine kinase activity in these cells. A decrease in the activity of src-related kinases was caused primarily by their lower expression, whereas expression of ZAP-70 was unchanged but its response to CD3 cross-linking was diminished, correlating with the deficient tyrosine phosphorylation of the CD3 zeta-chain, recently observed in J32-3.2. These data are consistent with the idea that src-related kinases phosphorylate the zeta-chain, which in turn recruits ZAP-70 required to sustain the signal.
Tsygankov
A Y
AY
Department of Molecular Biology, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, NJ 08543-4000.
Kim
H W
HW
Pratt
J C
JC
Spana
C
C
Class
K
K
Gaulton
G N
GN
Kamoun
M
M
Bolen
J B
JB
D017252:CD3 Complex / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D007295:Inositol Phosphates / Q000378:metabolism; D007376:Interleukin-2 / Q000378:metabolism; D015688:Oncogene Protein pp60(v-src) / Q000032:analysis / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000187:drug effects / Q000502:physiology*; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology* / Q000201:enzymology* / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
D017252:CD3 Complex; D007295:Inositol Phosphates; D007376:Interleukin-2; D010716:Phosphatidylinositols; D011948:Receptors, Antigen, T-Cell; D015375:Receptors, Interleukin-2; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D015688:Oncogene Protein pp60(v-src); D002118:Calcium