Coordinate down-regulation of cartilage matrix gene expression in Bcl-2 deficient chondrocytes is associated with decreased SOX9 expression and decreased mRNA stability.
Aggrecans; Animals; C-Type; Cell Line; Chondrocytes/*physiology; Collagen Type II/genetics/metabolism; Dactinomycin; Down-Regulation; Extracellular Matrix Proteins/analysis/genetics/*metabolism; Gene Expression Regulation; Glycoproteins/analysis/genetics/*metabolism; High Mobility Group Proteins/genetics/*metabolism; Lectins; Matrilin Proteins; Messenger/analysis/biosynthesis; Polymerase Chain Reaction/methods; Proteoglycans/genetics/metabolism; Proto-Oncogene Proteins c-bcl-2/deficiency/genetics/*physiology; Rats; RNA; RNA Stability; Signal Transduction; SOX9 Transcription Factor; Transcription Factors/genetics/*metabolism; Transfection
The anti-apoptotic protein Bcl-2 has been shown to function in roles unrelated to apoptosis in a variety of cell types. We have previously reported that loss of Bcl-2 expression alters chondrocyte morphology and modulates aggrecan expression via an apoptosis-independent pathway. Here we show that Bcl-2 is required for chondrocytes to maintain expression of a variety of cartilage-specific matrix proteins. Using quantitative, real-time PCR, we demonstrate that Bcl-2-deficient chondrocytes coordinately down-regulate genes coding for hyaline cartilage matrix proteins including collagen II, collagen IX, aggrecan, and link protein. The decrease in steady-state level of these mRNA transcripts results, in part, from decreased mRNA stability in Bcl-2-deficient chondrocytes. Transcriptional regulation is also likely involved because chondrocytes with decreased Bcl-2 levels show decreased expression of SOX9, a transcription factor necessary for expressing the major cartilage matrix proteins. In contrast, chondrocytes constitutively expressing Bcl-2 have a stable phenotype when subjected to loss of serum factor signaling. These cells maintain high levels of SOX9, as well as the SOX9 targets collagen II and aggrecan. These results suggest that Bcl-2 is involved in a pathway important for maintaining a stable chondrocyte phenotype.
Kinkel Mary D; Horton Walter E Jr
Journal of cellular biochemistry
2003
2003-04
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1002/jcb.10442" target="_blank" rel="noreferrer noopener">10.1002/jcb.10442</a>
Farnesoid X Receptor Activation by Obeticholic Acid Elevates Liver Low-Density Lipoprotein Receptor Expression by mRNA Stabilization and Reduces Plasma Low-Density Lipoprotein Cholesterol in Mice.
human; LDL; LDLR protein; obeticholic acid; receptors; RNA stability; untranslated regions
Objective- The objective of this study was to determine whether and how activation of farnesoid X receptor (FXR) by obeticholic acid (OCA), a clinical FXR agonist, modulates liver low-density lipoprotein receptor (LDLR) expression under normolipidemic conditions. Approach and Results- Administration of OCA to chow-fed mice increased mRNA and protein levels of LDLR in the liver without affecting the sterol-regulatory element binding protein pathway. Profiling of known LDLR mRNA-binding proteins demonstrated that OCA treatment did not affect expressions of mRNA degradation factors hnRNPD (heterogeneous nuclear ribonucleoprotein D) or ZFP36L1 but increased the expression of Hu antigen R (HuR) an mRNA-stabilizing factor. Furthermore, inducing effects of OCA on LDLR and HuR expression were ablated in Fxr(-/-) mice. To confirm the post-transcriptional mechanism, we used transgenic mice (albumin-luciferase-untranslated region) that express a human LDLR mRNA 3' untranslated region luciferase reporter gene in the liver. OCA treatment led to significant rises in hepatic bioluminescence signals, Luc-untranslated region chimeric mRNA levels, and endogenous LDLR protein abundance, which were accompanied by elevations of hepatic HuR mRNA and protein levels in OCA-treated transgenic mice. In vitro studies conducted in human primary hepatocytes and HepG2 cells demonstrated that FXR activation by OCA and other agonists elicited the same inducing effect on LDLR expression as in the liver of normolipidemic mice. Furthermore, depletion of HuR in HepG2 cells by short interfering RNA transfection abolished the inducing effect of OCA on LDLR expression. Conclusions- Our study is the first to demonstrate that FXR activation increases LDLR expression in liver tissue by a post-transcriptional regulatory mechanism involving LDLR mRNA-stabilizing factor HuR.
Singh Amar Bahadur; Dong Bin; Kraemer Fredric B; Xu Yanyong; Zhang Yanqiao; Liu Jingwen
Arteriosclerosis, thrombosis, and vascular biology
2018
2018-10
Article information provided for research and reference use only. All rights are retained by the journal listed under publisher and/or the creator(s).
<a href="http://doi.org/10.1161/ATVBAHA.118.311122" target="_blank" rel="noreferrer noopener">10.1161/ATVBAHA.118.311122</a>