Engagement of protein kinase C-theta in interferon signaling in T-cells.
Protein kinase C-theta (PKC-theta) plays important roles in the activation and survival of lymphocytes and is the predominant PKC isoform expressed in T-cells. Interferons regulate T-cell function and activation, but the precise signaling mechanisms by which they mediate such effects have not been elucidated. We determined whether PKC-theta is engaged in interferon (INF) signaling in T-cells. Both Type I (alpha, beta) and Type II (gamma) IFNs induced phosphorylation of PKC-theta in human T-cell lines and primary human T-lymphocytes. Such phosphorylation of PKC-theta resulted in activation of its kinase domain, suggesting that this kinase plays a functional role in interferon signaling. Consistent with this, inhibition of PKC-theta protein expression using small interfering RNAs (siRNA) abrogated IFN-alpha- and IFN-gamma-dependent gene transcription via GAS elements. Similarly, blocking of PKC-theta kinase activity by overexpression of a dominant-negative PKC-theta mutant also blocked GAS-driven transcription, further demonstrating a requirement for PKC-theta in IFN-dependent transcriptional activation. The effects of PKC-theta on IFN-dependent gene transcription were not mediated by regulation of the IFN-activated STAT pathway, as siRNA-mediated PKC-theta knockdown had no effects on STAT1 phosphorylation and binding of STAT1-containing complexes to SIE/GAS elements. On the other hand, siRNA-mediated PKC-theta inhibition blocked phosphorylation/activation of MKK4, suggesting that interferon-dependent PKC-theta activation regulates downstream engagement of MAP kinase pathways. Altogether, these findings demonstrate that PKC-theta is an interferon-inducible kinase and strongly suggest that it plays an important role in the generation of interferon-responses in T-cells.
Srivastava
Kishore K
KK
Robert H. Lurie Comprehensive Cancer Center and Division of Hematology-Oncology, Northwestern University Medical School and Lakeside Veterans Administration Medical Center, Chicago, Illinois 60611, USA.
Batra
Sandeep
S
Sassano
Antonella
A
Li
Yongzhong
Y
Majchrzak
Beata
B
Kiyokawa
Hiroaki
H
Altman
Amnon
A
Fish
Eleanor N
EN
Platanias
Leonidas C
LC
D002460:Cell Line; D045744:Cell Line, Tumor; D005799:Genes, Dominant; D006801:Humans; D007370:Interferon Type I / Q000378:metabolism; D007371:Interferon-gamma / Q000378:metabolism; D007372:Interferons / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D019169:Jurkat Cells; D008156:Luciferases / Q000378:metabolism; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009154:Mutation; D010766:Phosphorylation; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D007370:Interferon Type I; D007527:Isoenzymes; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D007371:Interferon-gamma; D007372:Interferons; D008156:Luciferases; C076233:PRKCQ protein, human; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta; D048670:MAP Kinase Kinase 4; C482559:MAP2K4 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases