title: PDGF receptor as a specific in vivo target for low M(r) phosphotyrosine protein phosphatase.
abstract: Low M(r) phosphotyrosine protein phosphatase (LMW-PTP) is a 18 kDa cytosolic enzyme widely distributed in eukaryotic cells. LMW-PTP catalyses the hydrolysis of phosphotyrosine residues and overexpression of the enzyme in normal and transformed cells inhibits cell proliferation. Site directed mutagenesis, together with crystallographic studies, have contributed to clarify the catalytic mechanism, which involves the active site signature sequence C12XXXXXR18, a main feature of all PTPase family members. In order to identify the LMW-PTP substrate/s we have expressed in NIH-3T3 cells a catalytically inert Cys12 to Ser phosphatase mutant which has preserved its capacity for substrate binding. Overexpression of the mutant phosphatase leads to enhanced cell proliferation and serum induced mitogenesis, indicating that the mutation results in the production of a dominant negative protein. Analysis of mutant LMW-PTP expressing cells has enabled us to demonstrate an association between LMW-PTP and platelet derived growth factor receptor that appears to be highly specific. Our data suggest a catalytic action of LMW-PTP on the phosphorylated platelet derived growth factor receptor.
authors.affiliation: Dipartimento di Scienze Biochimiche, Università di Firenze, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Chiarugi
authors.forename: P
authors.initials: P
authors.lastname: Cirri
authors.forename: G
authors.initials: G
authors.lastname: Raugei
authors.forename: G
authors.initials: G
authors.lastname: Camici
authors.forename: F
authors.initials: F
authors.lastname: Dolfi
authors.forename: A
authors.initials: A
authors.lastname: Berti
authors.forename: G
authors.initials: G
authors.lastname: Ramponi
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D004247:DNA / Q000096:biosynthesis; D004815:Epidermal Growth Factor / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D051379:Mice; D008970:Molecular Weight; D010641:Phenotype; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D017354:Point Mutation; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism*; D014162:Transfection
chemical_list: D007328:Insulin; D010982:Platelet-Derived Growth Factor; D004815:Epidermal Growth Factor; D004247:DNA; D017479:Receptors, Platelet-Derived Growth Factor; D017027:Protein Tyrosine Phosphatases