pp60v-src phosphorylates and activates low molecular weight phosphotyrosine-protein phosphatase.
Low M(r) phosphotyrosine-protein phosphatase belongs to the non-receptor cytosolic phosphotyrosine-protein phosphatase subfamily. It has been demonstrated that this enzyme dephosphorylates receptor tyrosine kinases, namely the epidermal growth factor receptor in vitro and the platelet-derived growth factor receptor in vivo. Low M(r) phosphotyrosine-protein phosphatase is constitutively tyrosine-phosphorylated in NIH/3T3 cells transformed by pp60v-src. The same tyrosine kinase, previously immunoprecipitated, phosphorylates this enzyme in vitro as well. Phosphorylation is enhanced using phosphatase inhibitors and phenylarsine oxide-inactivated phosphatase, consistently with the existence of an auto-dephosphorylation process. Intermolecular dephosphorylation is demonstrated adding the active enzyme in a solution containing the inactivated and previously phosphorylated one. This tyrosine phosphorylation correlates with an increase in catalytic activity. Our results provide evidence of a physiological mechanism of low M(r) phosphotyrosine-protein phosphatase activity regulation.
Rigacci
S
S
Department of Biochemical Sciences, University of Firenze, Italy.
Degl'Innocenti
D
D
Bucciantini
M
M
Cirri
P
P
Berti
A
A
Ramponi
G
G
D016475:3T3 Cells; D000818:Animals; D002461:Cell Line, Transformed; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D015870:Gene Expression; D007700:Kinetics; D051379:Mice; D008970:Molecular Weight; D015688:Oncogene Protein pp60(v-src) / Q000302:isolation & purification / Q000378:metabolism*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000032:analysis; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D014162:Transfection
D011994:Recombinant Proteins; D019000:Phosphotyrosine; D015688:Oncogene Protein pp60(v-src); D017027:Protein Tyrosine Phosphatases