Abstract：
OBJECTIVE: Bone morphogenetic protein-9 (BMP9) is critical for bone morphogenetic protein receptor type-2 (BMPR2) signalling in pulmonary vascular endothelial cells. Furthermore, human genetics studies support the central role of disrupted BMPR2 mediated BMP9 signalling in vascular endothelial cells in the initiation of pulmonary arterial hypertension (PAH). In addition, loss-of-function mutations in BMP9 have been identified in PAH patients. BMP9 is considered to play an important role in vascular homeostasis and quiescence.
RESULTS: We identified a novel BMP9 target as the class-3 semaphorin, SEMA3G. Although originally identified as playing a role in neuronal development, class-3 semaphorins may have important roles in endothelial function. Here we show that BMP9 transcriptional regulation of SEMA3G occurs via ALK1 and the canonical Smad pathway, requiring both Smad1 and Smad5. Knockdown studies demonstrated redundancy between type-2 receptors in that BMPR2 and ACTR2A were compensatory. Increased SEMA3G expression by BMP9 was found to be regulated by the transcription factor, SOX17. Moreover, we observed that SEMA3G regulates VEGF signalling by inhibiting VEGFR2 phosphorylation and that VEGF, in contrast to BMP9, negatively regulated SEMA3G transcription. Functional endothelial cell assays of VEGF-mediated migration and network formation revealed that BMP9 inhibition of VEGF was abrogated by SEMA3G knockdown. Conversely, treatment with recombinant SEMA3G partially mimicked the inhibitory action of BMP9 in these assays.
CONCLUSIONS: This study provides further evidence for the anti-angiogenic role of BMP9 in microvascular endothelial cells and these functions are mediated at least in part via SOX17 and SEMA3G induction.
RESULTS: We identified a novel BMP9 target as the class-3 semaphorin, SEMA3G. Although originally identified as playing a role in neuronal development, class-3 semaphorins may have important roles in endothelial function. Here we show that BMP9 transcriptional regulation of SEMA3G occurs via ALK1 and the canonical Smad pathway, requiring both Smad1 and Smad5. Knockdown studies demonstrated redundancy between type-2 receptors in that BMPR2 and ACTR2A were compensatory. Increased SEMA3G expression by BMP9 was found to be regulated by the transcription factor, SOX17. Moreover, we observed that SEMA3G regulates VEGF signalling by inhibiting VEGFR2 phosphorylation and that VEGF, in contrast to BMP9, negatively regulated SEMA3G transcription. Functional endothelial cell assays of VEGF-mediated migration and network formation revealed that BMP9 inhibition of VEGF was abrogated by SEMA3G knockdown. Conversely, treatment with recombinant SEMA3G partially mimicked the inhibitory action of BMP9 in these assays.
CONCLUSIONS: This study provides further evidence for the anti-angiogenic role of BMP9 in microvascular endothelial cells and these functions are mediated at least in part via SOX17 and SEMA3G induction.
摘要：
目的：骨形态发生蛋白-9（BMP9）对于肺血管内皮细胞中的骨形态发生蛋白受体2（BMPR2）信号传导至关重要。此外，人类遗传学研究支持血管内皮细胞中BMPR2介导的BMP9信号传导被破坏在肺动脉高压(PAH)的启动中的重要作用.此外,已在PAH患者中鉴定出BMP9功能缺失突变。BMP9被认为在血管稳态和静止中起重要作用。
结果：我们确定了一种新的BMP9靶标，即3类信号蛋白，SEMA3G。尽管最初被认为在神经元发育中起作用，3类信号蛋白可能在内皮功能中起重要作用。在这里，我们显示SEMA3G的BMP9转录调控通过ALK1和规范的Smad途径发生，需要Smad1和Smad5。敲除研究表明，2型受体之间存在冗余，因为BMPR2和ACTR2A是代偿性的。发现BMP9增加的SEMA3G表达受转录因子调节，SOX17.此外，我们观察到SEMA3G通过抑制VEGFR2磷酸化来调节VEGF信号,与BMP9相反，负调节SEMA3G转录。VEGF介导的迁移和网络形成的功能性内皮细胞测定显示,通过SEMA3G敲低消除了BMP9对VEGF的抑制。相反，用重组SEMA3G处理在这些测定中部分模拟了BMP9的抑制作用。
结论：这项研究为BMP9在微血管内皮细胞中的抗血管生成作用提供了进一步的证据，这些功能至少部分是通过SOX17和SEMA3G诱导介导的。
结果：我们确定了一种新的BMP9靶标，即3类信号蛋白，SEMA3G。尽管最初被认为在神经元发育中起作用，3类信号蛋白可能在内皮功能中起重要作用。在这里，我们显示SEMA3G的BMP9转录调控通过ALK1和规范的Smad途径发生，需要Smad1和Smad5。敲除研究表明，2型受体之间存在冗余，因为BMPR2和ACTR2A是代偿性的。发现BMP9增加的SEMA3G表达受转录因子调节，SOX17.此外，我们观察到SEMA3G通过抑制VEGFR2磷酸化来调节VEGF信号,与BMP9相反，负调节SEMA3G转录。VEGF介导的迁移和网络形成的功能性内皮细胞测定显示,通过SEMA3G敲低消除了BMP9对VEGF的抑制。相反，用重组SEMA3G处理在这些测定中部分模拟了BMP9的抑制作用。
结论：这项研究为BMP9在微血管内皮细胞中的抗血管生成作用提供了进一步的证据，这些功能至少部分是通过SOX17和SEMA3G诱导介导的。
