Upregulation of RGS4 expression by IL-1{beta} in colonic smooth muscle is enhanced by ERK1/2 and p38 MAPK and inhibited by the PI3K/Akt/GSK3{beta} pathway

• Published in: American Journal of Physiology: Cell Physiology 2009-06, Vol.296 (6), p.C1310
• Main Authors: Hu, Wenhui, Li, Fang, Mahavadi, Sunila, Murthy, Karnam S
• Format: Article
• Language: English
• Subjects: Cells; Gene expression; Glycoproteins; Kinases; Rabbits; Signal transduction
• ISSN: 0363-6143; 1522-1563
• DOI: 10.1152/ajpcell.00573.2008

1 Department of Physiology and Biophysics, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, Virginia; and 2 Department of Neuroscience, Temple University School of Medicine, Philadelphia, Pennsylvania Submitted 7 November 2008 ; accepted in final form 9 April 2009 Initial Ca 2+ -dependent contraction of intestinal smooth muscle is inhibited upon IL-1β treatment. The decrease in contraction reflects the upregulation of regulator of G protein signaling-4 (RGS4) via the canonical inhibitor of NF- B kinase-2 (IKK2)/I B- /NF- B pathway. Here, we show that the activation of various protein kinases, including ERK1/2, p38 MAPK, and phosphoinositide 3-kinase (PI3K), differentially modulates IL-1β-induced upregulation of RGS4 in rabbit colonic muscle cells. IL-1β treatment caused a transient phosphorylation of ERK1/2 and p38 MAPK. It also caused the phosphorylation of Akt and glycogen synthase kinase-3β (GSK3β), sequential downstream effectors of PI3K. Pretreatment with PD-98059 (an ERK inhibitor) and SB-203580 (a p38 MAPK inhibitor) significantly inhibited IL-1β-induced RGS4 expression. In contrast, LY-294002 (a PI3K inhibitor) augmented, whereas GSK3β inhibitors inhibited, IL-1β-induced RGS4 expression. PD-98059 blocked IL-1β-induced phosphorylation of IKK2, degradation of I B- , and phosphorylation and nuclear translocation of NF- B subunit p65, whereas SB-203580 had a marginal effect, implying that the effect of ERK1/2 is exerted on the canonical IKK2/I B- /p65 pathway of NF- B activation but that the effect of p38 MAPK may not predominantly involve NF- B signaling. The increase in RGS4 expression enhanced by LY-294002 was accompanied by an increase in the phosphorylation of IKK2/I B- /p65 and blocked by pretreatment with inhibitors of IKK2 (IKK2-IV) and I B- (MG-132). Inhibition of GSK3β abolished IL-1β-induced phosphorylation of IKK2/p65. These findings suggest that ERK1/2 and p38 MAPK enhance IL-1β-induced upregulation of RGS4; the effect of ERK1/2 reflects its ability to promote IKK2 phosphorylation and increase NF- B activity. GSK3β acts normally to augment the activation of the canonical NF- B signaling. The PI3K/Akt/GSK3β pathway attenuates IL-1β-induced upregulation of RGS4 expression by inhibiting NF- B activation. smooth muscle cells; rabbit; short interfering RNA; nuclear factor- B; signal transduction; regulator of G protein signaling; interleukin-1β; extracellular signal-regulated kinase 1/2; mitogen-activated protein