Identification of a region in the human IRS2 promoter essential for stress induced transcription depending on SP1, NFI binding and ERK activation in HepG2 cells

Abstract

Recent studies have discovered changes in the insulin-/IGF1 signaling affecting glucose metabolism and the molecular pathogenesis of human hepatocellular cancer. Insulin/IGF1 receptor mediates its intracellular effects by recruitment of one out of the four different insulin receptor substrates (IRS). To investigate mechanisms of IRS2 expression, we analyzed transcriptional regulation of IRS2 in human HepG2 cells. We identified a region 688 bp upstream of the translation start codon responsible for w90% of basal human IRS2 promoter activity in HepG2 cells, and confirmed binding of specificity protein 1 (also called Sp1 transcription factor, SP1) and nuclear factor 1 (NFI) in this region. Mutation of both SP1 and NFI binding sites or inhibition of extracellular signal regulated kinase (ERK) suppressed IRS2 promoter activity almost completely, revealing a major role of MAP kinases (MAPK) for IRS2 transcription. Activating this cascade with oxidative stress increased IRS2 promoter activity and endogenous IRS2 expression substantially. IRS2 promoter activity rose even more after additional inhibition of p38MAPK indicating an inhibitory effect of p38MAPK on ERK mediated IRS2 transcription. Activation of the MAPK pathway using interleukin 1, beta (IL1B) increased IRS2 promoter activity similar to oxidative stress. In contrast IL1B decreases and inhibition of the MAPK pathway increases IRS1 promoter activity revealing opposed effects of IL1B and ERK on the expression of different IRS proteins. In conclusion we discovered a specific region (K688 to K611 bp) in the IRS2 promoter essential for basal promoter activity and oxidative stress induced transcription depending on ERK activation and SP1 and NFI binding in human hepatocytes.

Novel Insights into M3 Muscarinic Acetylcholine Receptor Physiology and Structure

“…The data that we obtained were consistent with the concept that activation of G q/11 signaling in pancreatic β-cells stimulates the PLCβ/PKC pathway (as expected), resulting in the activation of ERK1/2 which in turn stimulates the activity of the Irs2 promoter (also see Udelhoven et al, 2010). Additional studies with IRS2-deficient mice (Withers et al, 1998) demonstrated that the Rq-mediated beneficial effects on β-cell function required the presence of IRS2 (Jain et al, 2013).…”

The Maternally Expressed Gene Tssc3 Regulates the Expression of MASH2 Transcription Factor in Mouse Trophoblast Stem Cells through the AKT-Sp1 Signaling Pathway

“…In addition, the translocation induced by TSSC3 overexpression was inhibited by LY294002, a PI3K inhibitor. The association of Sp1 activation or translocation has been shown through the MAPK/ERK pathway (42). However, Sp1 translocation was suppressed by LY294002 in MCF7 cells as shown in a previous study (41) and by the present results (Fig.…”

Chronic activation of a designer Gq-coupled receptor improves β cell function

“…These data strongly support the concept that the stimulatory effect on β cell Irs2 expression following activation of a G q -coupled receptor requires stimulation of the PLCβ/PKC pathway, which ultimately leads to enhanced Irs2 promoter activity in an ERK1/2-dependent fashion ( Figure 7A). Interestingly, a recent study (34) demonstrated that ERK activation substantially enhances the activity of the Irs2 promoter by stimulating the binding of the SP1 and NFI transcription factors to a short promoter region.…”