Involvement of protein kinase C during activation of the mitogen-activated protein kinase cascade by leukemia inhibitory factor. Evidence for participation of multiple signaling pathways.
We show here that treatment of 3T3-L1 cells with leukemia inhibitory factor (LIF) stimulates the activation of mitogen-activated protein kinase kinase (MAPKK), mitogen-activated protein kinase (MAPK), and S6 protein kinase (S6K) activities both in a time- and dose-dependent manner. A single peak of MAPKK activity, four peaks of activity against the S6 synthetic peptide, RRLSSLRA (S6 peptide), and three distinct peaks toward myelin basic protein (MBP) were observed after Mono-Q chromatography of LIF-stimulated cell extracts. Two of the MBP kinase activities correlated with the stimulation of extracellular signal-regulated kinases 1 and 2. Interestingly, down-regulation of protein kinase C (PKC) by chronic treatment of 3T3-L1 cells with phorbol ester was found to attenuate, but not block, the LIF-mediated stimulation of MAPKK, MAPK, and S6K activities in 3T3-L1 cells. Treatment of 3T3-L1 cells with epidermal growth factor increased MAPKK, MAPK, and S6K activities to a similar extent as LIF, but this activation was not attenuated by down-regulation of PKC. Our results suggest that the full activation of the MAPK cascade by LIF may require inputs from multiple signaling pathways, one of which is dependent upon the presence of functional PKC.
Schiemann
W P
WP
Department of Pharmacology, University of Washington, Seattle 98195.
Nathanson
N M
NM
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002852:Chromatography, Ion Exchange; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D006131:Growth Inhibitors / Q000494:pharmacology*; D015850:Interleukin-6; D007700:Kinetics; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines / Q000494:pharmacology*; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases; D008969:Molecular Sequence Data; D004676:Myelin Basic Protein / Q000302:isolation & purification / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D019893:Ribosomal Protein S6 Kinases; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D006131:Growth Inhibitors; D015850:Interleukin-6; D053605:Leukemia Inhibitory Factor; C507838:Lif protein, mouse; D008222:Lymphokines; D004676:Myelin Basic Protein; D010703:Phorbol Esters; D010750:Phosphoproteins; C008876:phorbol-12,13-didecanoate; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D019893:Ribosomal Protein S6 Kinases; D011493:Protein Kinase C; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D013755:Tetradecanoylphorbol Acetate