Department of Diabetology & Endocrinology, Kanazawa Medical University, Uchinada, Japan.
Department of Hematology & Immunology, Kanazawa Medical University, Uchinada, Japan.
FEBS Open Bio. 2019 May;9(5):1029-1038. doi: 10.1002/2211-5463.12638. Epub 2019 Apr 22.
Endothelial-mesenchymal transition (EndMT) has emerged as an essential bioprocess responsible for the development of organ fibrosis. We have previously reported that fibroblast growth factor receptor 1 (FGFR1) is involved in the anti-EndMT effect of N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP). FGFR1 is expressed on the cell membrane and performs its biological function through interaction with co-receptors, including βklotho (KLB). However, it remains unknown whether KLB is involved in the anti-EndMT effects of AcSDKP. Here, we demonstrated that AcSDKP increased KLB expression in an FGFR1-dependent manner and that KLB deficiency induced AcSDKP-resistant EndMT via the induction of the mitogen-activated protein kinase (MAPK) pathway. In cultured endothelial cells, AcSDKP increased KLB protein level in an FGFR1-dependent manner through induction of the FGFR1-KLB complex. KLB suppression by small interfering RNA transfection did not affect FGFR1 levels and resulted in the induction of EndMT. In contrast to the EndMT observed under FGFR1 deficiency, the EndMT induced by KLB suppression was not accompanied by the induction of Smad3 phosphorylation; instead, KLB-deficient cells exhibited induced activation of the MAPK/extracellular signal-regulated kinase (ERK) kinase (MEK) and ERK pathways. Treatment with the specific MEK inhibitor U0126 diminished KLB deficiency-induced EndMT. Consistent with this finding, AcSDKP did not suppress either EndMT or MEK/ERK activation induced by KLB deficiency. Application of either FGF19 or FGF21 synergistically augmented the anti-EndMT effects of AcSDKP. Taken together, these results indicate that endogenous peptide AcSDKP exerts its activity through induction of the FGFR1-KLB complex in vascular endothelial cells.
内皮-间质转化（EndMT）已成为器官纤维化发展的重要生物学过程。我们之前的研究表明，成纤维细胞生长因子受体 1（FGFR1）参与了 N-乙酰丝氨酰-天冬氨酰-赖氨酰-脯氨酸（AcSDKP）的抗-EndMT 作用。FGFR1 表达在细胞膜上，并通过与共受体βklotho（KLB）等相互作用来发挥其生物学功能。然而，KLB 是否参与 AcSDKP 的抗-EndMT 作用尚不清楚。在这里，我们证明 AcSDKP 以 FGFR1 依赖的方式增加 KLB 的表达，并且 KLB 缺乏通过诱导丝裂原活化蛋白激酶（MAPK）通路诱导 AcSDKP 抵抗的 EndMT。在培养的内皮细胞中，AcSDKP 通过诱导 FGFR1-KLB 复合物以 FGFR1 依赖的方式增加 KLB 蛋白水平。通过小干扰 RNA 转染抑制 KLB 不影响 FGFR1 水平，并导致 EndMT 的诱导。与 FGFR1 缺乏引起的 EndMT 不同，KLB 抑制引起的 EndMT 不伴有 Smad3 磷酸化的诱导；相反，KLB 缺陷细胞表现出 MAPK/细胞外信号调节激酶（ERK）激酶（MEK）和 ERK 通路的诱导激活。用特异性 MEK 抑制剂 U0126 处理可减弱 KLB 缺乏诱导的 EndMT。与这一发现一致的是，AcSDKP 既不能抑制 KLB 缺乏诱导的 EndMT，也不能抑制 MEK/ERK 激活。应用 FGF19 或 FGF21 均可协同增强 AcSDKP 的抗-EndMT 作用。总之，这些结果表明，内源性肽 AcSDKP 通过诱导血管内皮细胞中的 FGFR1-KLB 复合物发挥其活性。
