MiR-1306 Mediates the Feedback Regulation of the TGF-β/SMAD Signaling Pathway in Granulosa Cells.

Liu Yang,Qiuyu Cao,Qifa Li,Xing Du,Lu Liu,Zengxiang Pan

doi:10.3390/cells8040298

Abstract

Transforming growth factor-β receptor II (TGFBR2), the type II receptor of the TGF-β/SMA- and MAD-related protein (SMAD) signaling pathway, plays a crucial role in TGF-β signal transduction and is regulated by multiple factors. Nevertheless, the modulation of the non-coding RNA involved in the process of TGFBR2 expression in ovaries is not well studied. In our study, we isolated and characterized the 3′-untranslated region (UTR) of the porcine TGFBR2 gene and microRNA-1306 (miR-1306) was identified as the functional miRNA that targets TGFBR2 in porcine granulosa cells (GCs). Functional analysis showed that miR-1306 promotes apoptosis of GCs as well as attenuating the TGF-β/SMAD signaling pathway targeting and impairing TGFBR2 in GCs. Moreover, we identified the miR-1306 core promoter and found three potential SMAD4-binding elements (SBEs). Luciferase and chromatin immunoprecipitation (ChIP) assays revealed that the transcription factor SMAD4 directly binds to the miR-1306 core promoter and inhibits its transcriptional activity. Furthermore, the TGF-β/SMAD signaling pathway is modulated by SMAD4 positive feedback via inhibition of miR-1306 expression in GCs. Collectively, our findings provide evidence of an epigenetic mechanism that modulates as well as mediates the feedback regulation of the classical TGF-β/SMAD signaling pathway in GCs from porcine ovaries.

Highlights

The transforming growth factor beta (TGF-β)/SMA- and MAD-related protein (SMAD) signaling pathway plays a significant role in regulating numerous processes in the cell, including cellular proliferation [1], differentiation [2], and the cell cycle [3], as well as apoptosis [4], by introducing extracellular signal transduces into the cell nucleus
TGFBR2 is known to be the first receptor to be activated in the classical transforming growth factor-β (TGF-β)/SMAD signaling pathway and it mediates the effects of TGF-β ligands (TGF-β1) by forming a receptor–receptor complex pathway and it mediates the effects of TGF-β ligands (TGF-β1) by forming a receptor–receptor with TGFBR1, named ALK5
We demonstrated that miR-1306 has its own internal promoter that is independent of the host gene, and that SMAD4 serves as a negative regulatory factor and suppresses miR-1306 by directly binding to SMAD4-binding elements (SBEs) motif within this promoter region

Summary

Introduction

The transforming growth factor beta (TGF-β)/SMA- and MAD-related protein (SMAD) signaling pathway plays a significant role in regulating numerous processes in the cell, including cellular proliferation [1], differentiation [2], and the cell cycle [3], as well as apoptosis [4], by introducing extracellular signal transduces into the cell nucleus. Activation of the signal depends on the interaction between the ligand and TGFBR2 leading to the dimerization of TGFBR2 and TGFBR1. During this process, TGFBR1 is phosphorylated and activated by the kinase activity of TGFBR2. Activated TGFBR1 phosphorylates downstream molecules SMAD2 and SMAD3, subsequently leading to the formation of a trimeric complex with SMAD4. This complex translocates into the nucleus and modulates downstream gene transcription in response to extracellular signals [5]. Odontoblast-specific TGFBR2 conditional knockout in mice results in the loss of responsiveness to TGF-β along with inactivation of the TGF-β/SMAD pathway, causing impaired matrix formation and pulpal obliteration in odontoblasts [6]

Results

Discussion

Conclusion