Identification and characterization of an interleukin-3 receptor-associated 110-kDa serine/threonine kinase.
We recently reported that interleukin-3 (IL-3) stimulation of the murine IL-3-responsive cell line, B6SUtA1, results in the rapid phosphorylation of the beta subunit of the IL-3 receptor (IL-3R), not only on tyrosine residues but on serine/threonine (Ser/Thr) residues as well. Since this occurred even at 4 degrees C, it suggested that a Ser/Thr-specific kinase might be closely associated with the IL-3R. To test this possibility, IL-3R complexes were isolated with anti-IL-3R (alpha IL-3R) antibodies, and in vitro phosphorylation studies were undertaken. These revealed the presence of a 110-kDa protein that was heavily phosphorylated in vitro on serine and threonine residues and that bound selectively to gamma-ATP-Sepharose beads. Moreover, this protein, which was not the 110-kDa subunit of phosphatidylinositol 3-kinase, was tyrosine phosphorylated in response to IL-3 and was specifically labeled in vitro with azido-[32P]ATP. These data, together with in vitro kinase inhibitor studies, suggest that an as yet uncharacterized H7- and staurosporine-sensitive 110-kDa Ser/Thr kinase may be constitutively associated with the IL-3R and activated following IL-3 stimulation. A comparison of IL-3R and erythropoietin receptor complexes suggests that this 110-kDa protein may be preferentially associated with the IL-3R.
Liu
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Terry Fox Laboratory, British Columbia Cancer Research Centre, Vancouver, Canada.
Cutler
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Krystal
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D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D066298:In Vitro Techniques; D007377:Interleukin-3 / Q000494:pharmacology*; D007546:Isoquinolines / Q000494:pharmacology; D051379:Mice; D008970:Molecular Weight; D010766:Phosphorylation; D019000:Phosphotyrosine; D010879:Piperazines / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D017467:Receptors, Erythropoietin / Q000378:metabolism; D016185:Receptors, Interleukin-3 / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction; D019311:Staurosporine; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D000470:Alkaloids; D007377:Interleukin-3; D007546:Isoquinolines; D010879:Piperazines; D017467:Receptors, Erythropoietin; D016185:Receptors, Interleukin-3; D019000:Phosphotyrosine; D014443:Tyrosine; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D017346:Protein Serine-Threonine Kinases; D019311:Staurosporine