Catalytically active TYK2 is essential for interferon-beta-mediated phosphorylation of STAT3 and interferon-alpha receptor-1 (IFNAR-1) but not for activation of phosphoinositol 3-kinase.
TYK2, a Janus kinase, plays both structural and catalytic roles in type I interferon (IFN) signaling. We recently reported (Rani, M. R. S., Gauzzi, C., Pellegrini, S., Fish, E., Wei, T., and Ransohoff, R. M. (1999) J. Biol. Chem. 274, 1891-1897) that catalytically active TYK2 was necessary for IFN-beta to induce the beta-R1 gene. We now report IFN-beta-mediated activation of STATs and other components in U1 (TYK2-null) cell lines that were complemented with kinase-negative (U1.KR930) or wild-type TYK2 (U1.wt). We found that IFN-beta induced phosphorylation on tyrosine of STAT3 in U1.wt cells but not in U1.KR930 cells, whereas STAT1 and STAT2 were activated in both cell lines. Additionally, IFN-beta-mediated phosphorylation of interferon-alpha receptor-1 (IFNAR-1) was defective in IFN-beta treated U1.KR930 cells, but evident in U1.wt cells. In U1A-derived cells, the p85/p110 phosphoinositol 3-kinase isoform was associated with IFNAR-1 but not STAT3, and the association was ligand-independent. Further, IFN-beta treatment stimulated IFNAR-1-associated phosphoinositol kinase activity equally in either U1.wt or U1.KR930 cells. Our results indicate that catalytically active TYK2 is required for IFN-beta-mediated tyrosine phosphorylation of STAT3 and IFNAR-1 in intact cells.
Rani
M R
MR
Department of Neurosciences, Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Leaman
D W
DW
Han
Y
Y
Leung
S
S
Croze
E
E
Fish
E N
EN
Wolfman
A
A
Ransohoff
R M
RM
D002384:Catalysis; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D016899:Interferon-beta / Q000378:metabolism*; D008565:Membrane Proteins; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D053633:Receptor, Interferon alpha-beta; D017471:Receptors, Interferon / Q000378:metabolism*; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D053634:TYK2 Kinase; D015534:Trans-Activators / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; C507964:IFNAR1 protein, human; D008565:Membrane Proteins; D011506:Proteins; D017471:Receptors, Interferon; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D053633:Receptor, Interferon alpha-beta; D016899:Interferon-beta; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D053634:TYK2 Kinase; C070139:TYK2 protein, human