College of Animal Science and Technology, Nanjing Agricultural University, Nanjing, China.
J Cell Physiol. 2020 Mar;235(3):2260-2272. doi: 10.1002/jcp.29134. Epub 2019 Sep 6.
Both TGF-β/SMAD4 signaling pathway and HAS2-HA system have been shown to control granulosa cell (GC) state in mammalian ovary. However, the regulatory relationship between TGF-β/SMAD4 signaling pathway and HA system in GCs is not well known. Here, we report that the TGF-β/SMAD4 signaling pathway activates the HAS2-HA system by binding directly to the HAS2 promoter, ultimately controlling the GC state via the CD44-Caspase3 axis. SMAD4-induced HAS2 expression, HAS2-driven HA secretion, and HAS2-mediated GC state (proliferation and apoptosis) by interacting directly with the promoter region of the HAS2 gene. The CD44-Caspase3 axis, located downstream of the HAS2-HA system, was also activated by SMAD4 and the TGF-β/SMAD4 signaling pathway. However, there was no feedback regulation of the TGF-β/SMAD4 signaling pathway by the HAS2-HA system in GCs. In addition, we found that miRNA-26b attenuated HAS2 expression via SMAD4-dependent and -independent mechanisms. Our findings provide compelling evidence that HAS2 is a direct transcriptional target of SMAD4. They also reveal a novel mechanism by which the TGF-β/SMAD4 signaling pathway controls the GC state and alters the structural components of GCs in porcine ovaries.
TGF-β/SMAD4 信号通路和 HAS2-HA 系统都被证明可以控制哺乳动物卵巢中的颗粒细胞（GC）状态。然而，TGF-β/SMAD4 信号通路和 HAS2-HA 系统在 GCs 中的调节关系尚不清楚。在这里，我们报告 TGF-β/SMAD4 信号通路通过直接结合 HAS2 启动子激活 HAS2-HA 系统，最终通过 CD44-Caspase3 轴控制 GC 状态。SMAD4 诱导 HAS2 表达，HAS2 驱动的 HA 分泌，以及 HAS2 通过与 HAS2 基因启动子区域直接相互作用介导的 GC 状态（增殖和凋亡）。HAS2-HA 系统下游的 CD44-Caspase3 轴也被 SMAD4 和 TGF-β/SMAD4 信号通路激活。然而，在 GCs 中，HAS2-HA 系统对 TGF-β/SMAD4 信号通路没有反馈调节。此外，我们发现 miRNA-26b 通过 SMAD4 依赖和非依赖的机制减弱 HAS2 的表达。我们的研究结果提供了令人信服的证据表明 HAS2 是 SMAD4 的直接转录靶标。它们还揭示了 TGF-β/SMAD4 信号通路控制 GC 状态并改变猪卵巢中 GC 结构成分的新机制。
