Cytokine-induced phosphorylation of pp100 in FDC-ER cells is at tyrosine residues.
Using FDC-P1 cells stably transfected with a murine erythropoietin receptor cDNA as a model, we recently have shown that erythropoietin (EPO), IL-3 and GM-CSF each induce the rapid phosphorylation of a common cytosolic target, i.e., a M(r) 100,000 phosphoprotein "pp100". Presently, we demonstrate that cytokine-induced phosphorylation of pp100 is primarily at tyrosine residues. This is shown by Western blotting with the anti-phosphotyrosine antibody PY20, and by the resistance of [32P]-pp100 to hydroxide-mediated hydrolysis of phosphates. These data, together with the recent observation by Linnekin et al. that pp100/p97 apparently associates directly with EPO receptors, suggest that pp100 may comprise an immediate common component in the signal transduction pathways of EPO, IL-3, GM-CSF and possibly other type I/II cytokine receptors. Additional analyses suggest that pp100 is distinct from a previously described M(r) 100,000 cytosolic target which is tyrosine phosphorylated in hematopoietic cells upon activation of T-cell receptors.
D000818:Animals; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D051379:Mice; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D017467:Receptors, Erythropoietin / Q000235:genetics / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives / Q000302:isolation & purification / Q000378:metabolism*
D016207:Cytokines; D010750:Phosphoproteins; D011948:Receptors, Antigen, T-Cell; D017467:Receptors, Erythropoietin; D019000:Phosphotyrosine; D014443:Tyrosine