miR-148a is a downstream effector of X-box-binding protein 1 that silences Wnt10b during adipogenesis of 3T3-L1 cells

Abstract

Wnt10b, an endogenous inhibitor of adipogenesis, maintains preadipocytes in an undifferentiated state by suppressing adipogenic transcription factors. We have previously demonstrated that Wnt10b transcription during adipogenesis is negatively regulated by X-box-binding protein 1 (XBP1), an important transcription factor of the unfolded protein response. In this report, we demonstrate that XBP1s can directly induce the transcription of microRNA-148a, which in turn mediates the silencing of Wnt10b mRNA during adipogenic differentiation of 3T3-L1 cells. Stability of Wnt10b mRNA was found to be significantly increased by knockdown of XBP1s. Using computational algorithms, a set of microRNAs was predicted to bind Wnt10b mRNA, of which microRNA-148a was selected as a potential target for XBP1s. Our results revealed that microRNA-148a could bind to the 3′UTR of Wnt10b mRNA. Its ectopic expression significantly suppressed both Wnt10b expression and β-catenin activity. When we altered the expression of XBP1 in 3T3-L1 cells, microRNA-148a levels changed accordingly. A potential XBP1 response element was found in the promoter region of microRNA-148a, and XBP1s directly bound to this response element as shown by point mutation analysis and chromatin immunoprecipitation assay. In addition, a microRNA-148a mimic significantly restored adipogenic potential in XBP1-deficient 3T3-L1 cells. These findings provide the first evidence that XBP1s can regulate Wnt10b by a post-transcriptional mechanism through directly inducing microRNA-148a.

Constitutive UPRERactivation sustains tumor cell differentiation

“…As hypothesized, we observed an upregulation of XBP1s compared to untreated cells, a downregulation of miR148a and the subsequent upregulation of SOX2 ( Figure 6H). Hence, the expression of reprogramming TFs including SOX2 is downregulated by miR148a, clarifying a relationship previously documented in the literature (20), and miR148a is directly induced by XBP1s (19). Therefore we delineate a novel IRE1-dependent signaling cascade that maintains GBM cell differentiation.…”

“…Interestingly, miR148a was identified previously as a transcriptional target of XBP1s using chromatin immunoprecipitation (19) and SOX2 mRNA presents miR148a binding sites ( Figures S6A-D). To further document the IRE1-dependent control of miR148a expression, we first showed that miR148a levels were decreased in IRE1 signaling deficient cells when compared to parental cells ( Figure 6D).…”

“…SOX2) (Figures 4, 5). Our focus on miR148a was motivated by the demonstration that this miRNA was identified as i) as a transcriptional target of XBP1s (19) and ii) a potential binder of SOX2 mRNA ( Figure S6). Interestingly miR148a promotes plasma cell differentiation by targeting germinal center TFs MITF and BACH2 (21), which thus could also occur under the control of XBP1s, a major player in this process (22).…”

The IRE1α-XBP1s pathway promotes insulin-stimulated glucose uptake in adipocytes by increasing PPARγ activity

“…Most of the knowledge regarding the role of XBP1s in insulin sensitivity comes from in vitro studies of adipogenesis. In this context, we have also previously identified a set of pro-adipogenic mechanisms by which XBP1s stimulates PPARγ2 expression directly and indirectly by regulating Wnt10b and miR-148a, respectively 8 – 10 . Findings from a relatively thorough in vitro investigation suggest that XBP1s plays a pro-adipogenic role.…”

Exosomes of pasteurized milk: potential pathogens of Western diseases

“…Ectopic expression of miR-148a accelerated differentiation and partially rescued Wnt1-mediated inhibition of adipogenesis, whereas knockdown of miR-148a inhibited adipogenesis [121,122]. In addition, miR-148a has been shown to silence Wnt10b, a further endogenous inhibitor of adipogenesis during 3T3-L1 cell differentiation [123]. A further study demonstrated that increased expression of miR-148a via suppression of DNMT1 enhanced adipocyte differentiation [124].…”