A mechanism for the suppression of interleukin-1-induced nuclear factor kappaB activation by protein phosphatase 2Ceta-2.
IL-1 (interleukin-1) is a pro-inflammatory cytokine that has a variety of effects during the process of inflammation. Stimulating cells with IL-1 initiates a signalling cascade that includes the activation of NF-kappaB (nuclear factor kappaB), and subsequently induces a variety of inflammatory genes. Although the molecular mechanism for the IL-1-induced activation of NF-kappaB has been well documented, much less is known about the mechanism by which protein phosphatases down-regulate this pathway. Here we show that mouse PP2Ceta-2 (protein serine/threonine phosphatase 2Ceta-2), a novel member of the protein serine/threonine phosphatase 2C family, inhibits the IL-1-NF-kappaB signalling pathway. Ectopic expression of PP2Ceta-2 in human embryonic kidney HEK293IL-1RI cells inhibited the IL-1-induced activation of NF-kappaB. TAK1 (transforming-growth-factor-beta-activated kinase 1) mediates the IL-1 signalling pathway to NF-kappaB, and we observed that the TAK1-induced activation of NF-kappaB was suppressed by PP2Ceta-2 expression. Expression of IKKbeta [IkappaB (inhibitory kappaB) kinase beta], which lies downstream of TAK1, activates NF-kappaB, and this activation was also readily reversed by PP2Ceta-2 co-expression. Additionally, PP2Ceta-2 knockdown with small interfering RNA further stimulated the IL-1-enhanced phosphorylation of IKKbeta and destabilization of IkappaBalpha in HeLa cells. PP2Ceta-2 knockdown also increased the IL-1-induced expression of IL-6 mRNA. Furthermore, IKKbeta was readily dephosphorylated by PP2Ceta-2 in vitro. These results suggest that PP2Ceta-2 inhibits the IL-1-NF-kappaB signalling pathway by selectively dephosphorylating IKKbeta.
Henmi
Takeaki
T
Department of Biochemistry, Institute of Development, Aging and Cancer, Tohoku University, Sendai, Japan.
Amano
Kazutaka
K
Nagaura
Yuko
Y
Matsumoto
Kunihiro
K
Echigo
Seishi
S
Tamura
Shinri
S
Kobayashi
Takayasu
T
D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D015536:Down-Regulation; D006367:HeLa Cells; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D007375:Interleukin-1 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism / Q000502:physiology; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D000071636:Protein Phosphatase 2C; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects
D007375:Interleukin-1; D015850:Interleukin-6; D007527:Isoenzymes; D016328:NF-kappa B; D034741:RNA, Small Interfering; D051550:I-kappa B Kinase; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C