Regulation of the low molecular weight phosphotyrosine phosphatase by phosphorylation at tyrosines 131 and 132.
Activation of resting T lymphocytes is initiated by rapid but transient tyrosine phosphorylation of a number of cellular proteins. Several protein tyrosine kinases and protein tyrosine phosphatases are known to be important for this response. Here we report that normal T lymphocytes express the B isoform of low molecular weight protein tyrosine phosphatase B (LMPTP-B). The cDNA was cloned from Jurkat T cells, and an antiserum was raised against it. LMPTP immunoprecipitated from resting Jurkat T cells was found to be tyrosine phosphorylated. On stimulation of the cells through their T cell antigen receptor, the phosphotyrosine content of LMPTP-B declined rapidly. In co-transfected COS cells, Lck and Fyn caused phosphorylation of LMPTP, whereas Csk, Zap, and Jak2 did not. Most of the phosphate was located at Tyr-131, and some was also located at Tyr-132. Incubation of wild-type LMPTP with Lck and adenosine 5'-O-(thiotriphosphate) caused a 2-fold increase in the activity of LMPTP. Site-directed mutagenesis showed that Tyr-131 is important for the catalytic activity of LMPTP, and that thiophosphorylation of Tyr-131, and to a lesser degree Tyr-132, is responsible for the activation.
Tailor
P
P
Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA.
Gilman
J
J
Williams
S
S
Couture
C
C
Mustelin
T
T
D016475:3T3 Cells; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D003001:Cloning, Molecular; D004789:Enzyme Activation; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D019169:Jurkat Cells; D007700:Kinetics; D008213:Lymphocyte Activation; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051379:Mice; D008970:Molecular Weight; D016296:Mutagenesis; D009856:Oncogene Proteins, Viral / Q000378:metabolism; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000201:enzymology*; D014443:Tyrosine / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism
D007527:Isoenzymes; D009856:Oncogene Proteins, Viral; D014443:Tyrosine; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D019061:src-Family Kinases; D017027:Protein Tyrosine Phosphatases