Beta2-adrenergic receptor regulate Toll-like receptor 4-induced late-phase NF-kappaB activation.
Stimulation of Toll-like receptor 4 (TLR4) by lipopolysaccharide (LPS) triggers myeloid differentiation factor 88 (MyD88)-dependent early-phase NF-kappaB activation and Toll/IL-1 receptor domain-containing adaptor-inducing IFN-beta (TRIF)-dependent late-phase NF-kappaB activation. In a previous study, we have shown that beta(2)-adrenergic receptor (beta(2)AR) functions as a negative regulator of NF-kappaB activation through beta-arrestin 2 in the macrophage cell line RAW264 and that down-regulation of beta(2)AR expression in response to LPS is essential for NF-kappaB activation and expression of its target gene, inducible nitric oxide synthase (NOS II). Here, we demonstrate that beta(2)AR plays an important role in TRIF-dependent late-phase NF-kappaB activation. LPS-stimulated down-regulation was induced in MyD88-knockdown cells, but not in TRIF-knockdown cells, suggesting that beta(2)AR expression was down-regulated by the TRIF-dependent pathway. On the other hand, depletion of beta(2)AR or beta-arrestin 2 expression by siRNA decreased cytoplasmic IkappaB alpha and abrogated late-phase IkappaB alpha degradation and NF-kappaB activation in response to LPS. Inducible nitric oxide synthase (NOS II) expression was increased continuously during 24 h of LPS stimulation in control cells, but decreased in beta(2)AR or beta-arrestin 2-knockdown cells after 6 h of LPS stimulation. These findings suggest that beta(2)AR functions not only as a negative regulator of NF-kappaB activation, but also as a stabilizing factor of the NF-kappaB/IkappaB alpha complex through cytoplasmic beta-arrestin 2, and that TRIF-dependent down-regulation of beta(2)AR expression increases the level of cytoplasmic NF-kappaB/IkappaB alpha complex free from beta-arrestin 2, leading to continuous late-phase NF-kappaB activation.
Kizaki
Takako
T
Department of Molecular Predictive Medicine and Sport Science, Kyorin University, School of Medicine, Mitaka 181-8611, Japan. kizaki@kyorin-u.ac.jp
Shirato
Ken
K
Sakurai
Takuya
T
Ogasawara
Jun-etsu
JE
Oh-ishi
Shuji
S
Matsuoka
Takeshi
T
Izawa
Tetsuya
T
Imaizumi
Kazuhiko
K
Haga
Shukoh
S
Ohno
Hideki
H
D033942:Adaptor Proteins, Vesicular Transport / Q000276:immunology / Q000378:metabolism; D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002460:Cell Line; D015536:Down-Regulation; D055785:Gene Knockdown Techniques; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics; D016328:NF-kappa B / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000276:immunology / Q000502:physiology*; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000276:immunology / Q000502:physiology*; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins
D033942:Adaptor Proteins, Vesicular Transport; D019390:Arrestins; D008070:Lipopolysaccharides; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D052247:Nitric Oxide Synthase Type II; D018343:Receptors, Adrenergic, beta-2; D051197:Toll-Like Receptor 4; D000071560:beta-Arrestin 2; D000071557:beta-Arrestins; C000605258:Arrb2 protein, mouse; C476286:Ticam1 protein, mouse; C493487:Tlr4 protein, mouse