[Show abstract][Hide abstract] ABSTRACT: A peroxisome proliferator-actived receptor (PPAR) response element (RE) in the promoter region of the adaptor-related protein complex 2, alpha 2 subunit (AP2α2) of mouse heart has been identified. The steroid hormone nuclear PPARs and the retinoid X receptors (RXRs) are important transcriptional factors that regulate gene expression, cell differentiation and lipid metabolism. They form homo- (RXR) and hetero- (PPAR-RXR) dimers that bind DNA at various REs. The AP2α2 gene is part of complex and process that transports lipids and proteins from the plasma membrane to the endosomal system. A PPAR activator (Wy14643) and DMSO (vehicle) was introduced into control and δ337T thyroid hormone receptor (TRβ1) transgenic mice. Heart tissue was extracted and AP2α2 gene expression was compared using Affymetrix expression arrays and qRT PCR among four groups [control, control with Wy14643, δ337T TRβ1 and δ337T TRβ1 with Wy14643]. The gene expression of AP2α2 in the Wy14643 control and transgenic mouse groups was significantly up regulated over the vehicle mouse groups in both the array (p < 0.01) and qRT PCR (p < 0.01) studies. Duplex oligo DNAs containing the PPAR/RXR motif (AGGTCA/TCCAGT) from the AP2α2 promoter were used in EMSA to verify binding of the PPAR and RXR receptors to their REs. pGL4.0 [Luc] constructs of the AP2α2 promoter with and without the PPAR/RXR motifs were co-transfected with mouse PPARα, β or γ1 into HepG2 cells and used in lucerifase assays to verify gene activation. In conclusion our study revealed that PPARα regulates the mouse cardiac AP2α2 gene in both the control and transgenic mouse.
Full-text · Article · Dec 2011 · The Protein Journal
[Show abstract][Hide abstract] ABSTRACT: The purpose of this study was to provide a better understanding of the regulatory role of the nuclear steroid receptor on the nuclear factor of kappa light polypeptide gene enhancer in B cells (NFkappaB) in mouse heart. NFkappaB regulates many nuclear genes and has been associated with many human cardiac diseases. NFkappaB's protein regulator gene, nuclear factor of kappa light polypeptide gene enhancer in B cells inhibitor alpha gene (IkappaBalpha), was found in this study to be regulated by peroxisome proliferator-activated receptors (PPARs). PPARs, retinoid X receptors (RXRs) and thyroid hormone receptors (THRs) are members of the nuclear receptor superfamily, which consists of a large number of transcription factors whose activities are regulated by their cognate ligands. These steroid hormone receptors are important regulators of gene expression and differentiation in the heart. These receptors form homo-(RXR, THR) and hetero-(PPAR-RXR, RXR-THR) dimers that bind DNA at various response elements (PPAR, RXR and THR) in the promoter regions of target genes. The PPAR/RXR response elements in the promoter of IkappaBalpha are described in this article. A known PPAR activator (Wy14643) and dimethylsulfoxide (vehicle) were introduced into control (FVB) and delta337T thyroid hormone receptor (TRbeta) transgenic mice. The delta337T TRbeta transgenic mouse has a resistance to the thyroid hormone (RTH) phenotype. Affymetrix 430_2 chip gene expression was examined for four study groups (control, control with Wy14643, delta337T TRbeta and delta337T TRbeta with Wy14643), consisting of seven mice each. IkappaBalpha mRNA expression in the Wy14643 control and in transgenic mice was upregulated significantly in microarray (P < 0.05) and quantitative RT-PCR (P < 0.01) analyses. The increase in mRNA level was also accompanied by an increase in IkappaBalpha protein in cells, as measured by Western blot analysis. Duplex oligo-DNAs containing the putative PPAR/RXR motif (AGGTCA/TCCAGT) from the IkappaBalpha promoter were used in gel shift assays to verify the binding of PPAR and RXR to their response elements. pGL4.0 [Luc] constructs of the IkappaBalpha promoter, with and without the PPAR/RXR motifs, were co-transfected with mouse PPAR alpha, beta and gamma(1) into HepG2 cells and used in luciferase assays to verify gene activation. In conclusion, our study revealed that PPAR regulates the mouse cardiac IkappaBalpha gene in both control and transgenic mouse heart. The implications of this finding are discussed in relation to possible changes in cardiac function.