Dataset Information

Interleukin-1beta up-regulates RGS4 through the canonical IKK2/IkappaBalpha/NF-kappaB pathway in rabbit colonic smooth muscle.

ABSTRACT: Initial Ca2+-dependent contraction of the intestinal smooth muscle mediated by G(q)-coupled receptors is attenuated by RGS4 (regulator of G-protein signalling 4). Treatment of colonic muscle cells with IL-1beta (interleukin-1beta) inhibits acetylcholine-stimulated initial contraction through increasing the expression of RGS4. NF-kappaB (nuclear factor kappaB) signalling is the dominant pathway activated by IL-1beta. In the present study we show that RGS4 is a new target gene regulated by IL-1beta/NF-kappaB signalling. Exposure of cultured rabbit colonic muscle cells to IL-1beta induced a rapid increase in RGS4 mRNA expression, which was abolished by pretreatment with a transcription inhibitor, actinomycin D, implying a transcription-dependent mechanism. Existence of the canonical IKK2 [IkappaB (inhibitor of NF-kappaB) kinase 2]/IkappaBalpha pathway of NF-kappaB activation induced by IL-1beta in rabbit colonic muscle cells was validated with multiple approaches, including the induction of reporter luciferase activity and endogenous NF-kappaB-target gene expression, NF-kappaB-DNA binding activity, p65 nuclear translocation, IkappaBalpha degradation and the phosphorylation of IKK2 at Ser(177/181) and p65 at Ser(536). RGS4 up-regulation by IL-1beta was blocked by selective inhibitors of IKK2, IkappaBalpha or NF-kappaB activation, by effective siRNA (small interfering RNA) of IKK2, and in cells expressing either the kinase-inactive IKK2 mutant (K44A) or the phosphorylation-deficient IkappaBalpha mutant (S32A/S36A). An IKK2-specific inhibitor or effective siRNA prevented IL-1beta-induced inhibition of acetylcholine-stimulated PLC-beta (phopsholipase C-beta) activation. These results suggest that the canonical IKK2/IkappaBalpha pathway of NF-kappaB activation mediates the up-regulation of RGS4 expression in response to IL-1beta and contributes to the inhibitory effect of IL-1beta on acetylcholine-stimulated PLC-beta-dependent initial contraction in rabbit colonic smooth muscle.

SUBMITTER: Hu W

PROVIDER: S-EPMC3707494 | biostudies-literature | 2008 May

REPOSITORIES: biostudies-literature

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Interleukin-1beta up-regulates RGS4 through the canonical IKK2/IkappaBalpha/NF-kappaB pathway in rabbit colonic smooth muscle.

Hu Wenhui W Li Fang F Mahavadi Sunila S Murthy Karnam S KS

The Biochemical journal 20080501 1

Initial Ca2+-dependent contraction of the intestinal smooth muscle mediated by G(q)-coupled receptors is attenuated by RGS4 (regulator of G-protein signalling 4). Treatment of colonic muscle cells with IL-1beta (interleukin-1beta) inhibits acetylcholine-stimulated initial contraction through increasing the expression of RGS4. NF-kappaB (nuclear factor kappaB) signalling is the dominant pathway activated by IL-1beta. In the present study we show that RGS4 is a new target gene regulated by IL-1bet ...[more]

PMID: 18260825

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Project description:Initial Ca(2+)-dependent contraction of intestinal smooth muscle is inhibited upon IL-1beta treatment. The decrease in contraction reflects the upregulation of regulator of G protein signaling-4 (RGS4) via the canonical inhibitor of NF-kappaB kinase-2 (IKK2)/IkappaB-alpha/NF-kappaB pathway. Here, we show that the activation of various protein kinases, including ERK1/2, p38 MAPK, and phosphoinositide 3-kinase (PI3K), differentially modulates IL-1beta-induced upregulation of RGS4 in rabbit colonic muscle cells. IL-1beta treatment caused a transient phosphorylation of ERK1/2 and p38 MAPK. It also caused the phosphorylation of Akt and glycogen synthase kinase-3beta (GSK3beta), sequential downstream effectors of PI3K. Pretreatment with PD-98059 (an ERK inhibitor) and SB-203580 (a p38 MAPK inhibitor) significantly inhibited IL-1beta-induced RGS4 expression. In contrast, LY-294002 (a PI3K inhibitor) augmented, whereas GSK3beta inhibitors inhibited, IL-1beta-induced RGS4 expression. PD-98059 blocked IL-1beta-induced phosphorylation of IKK2, degradation of IkappaB-alpha, and phosphorylation and nuclear translocation of NF-kappaB subunit p65, whereas SB-203580 had a marginal effect, implying that the effect of ERK1/2 is exerted on the canonical IKK2/IkappaB-alpha/p65 pathway of NF-kappaB activation but that the effect of p38 MAPK may not predominantly involve NF-kappaB signaling. The increase in RGS4 expression enhanced by LY-294002 was accompanied by an increase in the phosphorylation of IKK2/IkappaB-alpha/p65 and blocked by pretreatment with inhibitors of IKK2 (IKK2-IV) and IkappaB-alpha (MG-132). Inhibition of GSK3beta abolished IL-1beta-induced phosphorylation of IKK2/p65. These findings suggest that ERK1/2 and p38 MAPK enhance IL-1beta-induced upregulation of RGS4; the effect of ERK1/2 reflects its ability to promote IKK2 phosphorylation and increase NF-kappaB activity. GSK3beta acts normally to augment the activation of the canonical NF-kappaB signaling. The PI3K/Akt/GSK3beta pathway attenuates IL-1beta-induced upregulation of RGS4 expression by inhibiting NF-kappaB activation.

Dataset Information

Interleukin-1beta up-regulates RGS4 through the canonical IKK2/IkappaBalpha/NF-kappaB pathway in rabbit colonic smooth muscle.

Publications

Interleukin-1beta up-regulates RGS4 through the canonical IKK2/IkappaBalpha/NF-kappaB pathway in rabbit colonic smooth muscle.

Similar Datasets

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