title: Prolactin receptor triggering. Evidence for rapid tyrosine kinase activation.
abstract: The mechanism of action of prolactin (PRL) has remained obscure despite the unveiling of the primary structure of PRL receptors. The present study demonstrates rapid PRL receptor-mediated tyrosine phosphorylation of at least three cellular proteins, designated p120, p97, and p40, in a rat T-lymphoma (Nb2-11C) as revealed by antiphosphotyrosine immunoblotting. One of the phosphotyrosyl proteins, p120, co-purified with activated PRL receptor complexes obtained using either anti-ligand or anti-receptor antibodies. Furthermore, in vitro incubation of affinity-purified PRL receptor complexes from PRL-stimulated cells with ATP in the presence of a tyrosine phosphatase inhibitor, resulted in a 10-15-fold increase in the phosphotyrosine content of p120, as revealed by antiphosphotyrosine immunoblotting. Parallel experiments utilizing [gamma-32P]ATP confirmed a rapid and time-dependent incorporation of phosphate into p120 in the same affinity-purified PRL receptor complexes. These data provide strong evidence for the involvement of a tyrosine kinase in PRL signal transduction and suggest the presence of a tyrosine kinase within the activated PRL receptor complex.
authors.affiliation: H. Lee Moffitt Cancer Institute and Research Center, University of South Florida, Tampa 33612.
authors.forename: H
authors.initials: H
authors.lastname: Rui
authors.forename: J Y
authors.initials: JY
authors.lastname: Djeu
authors.forename: G A
authors.initials: GA
authors.lastname: Evans
authors.forename: P A
authors.initials: PA
authors.lastname: Kelly
authors.forename: W L
authors.initials: WL
authors.lastname: Farrar
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001345:Autoradiography; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D006801:Humans; D015151:Immunoblotting; D007700:Kinetics; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism; D008970:Molecular Weight; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D019000:Phosphotyrosine; D011388:Prolactin / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011981:Receptors, Prolactin / Q000302:isolation & purification / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
chemical_list: D008565:Membrane Proteins; D010750:Phosphoproteins; D010761:Phosphorus Radioisotopes; D011981:Receptors, Prolactin; D019000:Phosphotyrosine; D014443:Tyrosine; D000255:Adenosine Triphosphate; D011388:Prolactin; D011505:Protein-Tyrosine Kinases