The low Mr phosphotyrosine protein phosphatase behaves differently when phosphorylated at Tyr131 or Tyr132 by Src kinase.
The low molecular weight phosphotyrosine protein phosphatase (LMW-PTP) is phosphorylated by Src and Src-related kinases both in vitro and in vivo; in Jurkat cells, and in NIH-3T3 cells, it becomes tyrosine-phosphorylated upon stimulation by PDGF. In this study we show that pp60Src phosphorylates in vitro the enzyme at two tyrosine residues, Tyr131 and Tyr132, previously indicated as the main phosphorylation sites of the enzyme, whereas phosphorylation by the PDGF-R kinase is much less effective and not specific. The effects of LMW-PTP phosphorylation at each tyrosine residue were investigated by using Tyr131 and Tyr132 mutants. We found that the phosphorylation at either residue has differing effects on the enzyme behaviour: Tyr131 phosphorylation is followed by a strong (about 25-fold) increase of the enzyme specific activity, whereas phosphorylation at Tyr132 leads to Grb2 recruitment. These differing effects are discussed on the light of the enzyme structure.
Bucciantini
M
M
Department of Biochemical Sciences, University of Florence, Italy.
Chiarugi
P
P
Cirri
P
P
Taddei
L
L
Stefani
M
M
Raugei
G
G
Nordlund
P
P
Ramponi
G
G
D016475:3T3 Cells / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D051380:GRB2 Adaptor Protein; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008958:Models, Molecular; D008970:Molecular Weight; D009154:Mutation; D015688:Oncogene Protein pp60(v-src) / Q000276:immunology / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011487:Protein Conformation; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*; D019061:src-Family Kinases / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495949:Grb2 protein, mouse; D007527:Isoenzymes; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D014443:Tyrosine; D005982:Glutathione Transferase; D017479:Receptors, Platelet-Derived Growth Factor; D015688:Oncogene Protein pp60(v-src); D019061:src-Family Kinases; C490428:Acp1 protein, mouse; D017027:Protein Tyrosine Phosphatases