Activation of a serine/threonine kinase signaling pathway by transforming growth factor type beta.
Transforming growth factor type beta (TGF-beta) is a multifunctional factor that regulates proliferation and differentiation of many cell types. TGF-beta mediates its effects by binding to and activating cell surface receptors that possess serine/threonine kinase activity. However, the intracellular signaling pathways through which TGF-beta receptors act remain largely unknown. Here we show that TGF-beta activates a 78-kDa protein (p78) serine/threonine kinase as evidenced by an in-gel kinase assay. Ligand-induced activation of the kinase was near-maximal 5 min after TGF-beta addition to the cells and occurred exclusively on serine and threonine residues. This kinase is distinct from TGF-beta receptor type II, as well as several cytoplasmic serine/threonine kinases of similar size, including protein kinase C, Raf, mitogen-activated protein kinase kinase kinase, and ribosomal S6 kinase. Indeed, these kinases can be separated almost completely from p78 kinase by immunoprecipitation with specific antibodies. Furthermore, using different cell lines, we demonstrate that p78 kinase is activated only in cells for which TGF-beta can act as a growth inhibitory factor. These data raise the interesting possibility that protein serine/threonine kinases contribute to the intracellular relay of biological signals originating from receptor serine/threonine kinases such as the TGF-beta receptors.
Atfi
A
A
McGill University, Department of Surgery, Montreal, Quebec, Canada.
Lepage
K
K
Allard
P
P
Chapdelaine
A
A
Chevalier
S
S
D016475:3T3 Cells; D000470:Alkaloids / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D004247:DNA / Q000096:biosynthesis; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000187:drug effects / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D019311:Staurosporine; D013552:Swine; D013936:Thymidine / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000470:Alkaloids; D004791:Enzyme Inhibitors; D047428:Protein Kinase Inhibitors; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D004247:DNA; D011494:Protein Kinases; D020794:Receptor Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D019311:Staurosporine; D013936:Thymidine