Prolactin receptor triggering. Evidence for rapid tyrosine kinase activation.
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.
Rui
H
H
H. Lee Moffitt Cancer Institute and Research Center, University of South Florida, Tampa 33612.
Djeu
J Y
JY
Evans
G A
GA
Kelly
P A
PA
Farrar
W L
WL
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
D008565:Membrane Proteins; D010750:Phosphoproteins; D010761:Phosphorus Radioisotopes; D011981:Receptors, Prolactin; D019000:Phosphotyrosine; D014443:Tyrosine; D000255:Adenosine Triphosphate; D011388:Prolactin; D011505:Protein-Tyrosine Kinases