Department of Biomedical Engineering, University of Rochester, Rochester, NY 14627, USA.
Department of Dermatology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA.
Cells. 2019 Oct 30;8(11):1351. doi: 10.3390/cells8111351.
Platelet-derived growth factor (PDGF) signaling is dysregulated in a wide variety of diseases, making PDGF an attractive therapeutic target. However, PDGF also affects numerous signaling cascades essential for tissue homeostasis, limiting the development of PDGF-based therapies that lack adverse side-effects. Recent studies showed that fibroblast-mediated assembly of extracellular matrix (ECM) fibronectin fibrils attenuates PDGF-induced intracellular calcium release by selectively inhibiting phosphoinositol 3-kinase (PI3K) activation while leaving other PDGF-mediated signaling cascades intact. In the present study, a series of recombinant fibronectin-derived fusion proteins were used to localize the sequences in fibronectin that are responsible for this inhibition. Results demonstrate that attenuation of PDGF-induced intracellular calcium release by the fibronectin matrix mimetic, FNIII1H,8-10 requires α5β1 integrin ligation, but is not dependent upon the matricryptic, heparin-binding site of FNIII1. Intact cell-binding fibronectin fragments were also unable to attenuate PDGF-induced intracellular calcium release. In contrast, a novel integrin-binding fragment that adopts an extended and aligned conformational state, inhibited both PI3K activation and intracellular calcium release in response to PDGF. Taken together, these studies provide evidence that attenuation of PDGF-induced intracellular calcium release by fibronectin is mediated by a novel conformation of the α5β1 integrin-binding, FNIII9-10 modules, that is expressed by fibrillar fibronectin.
血小板衍生生长因子（PDGF）信号在多种疾病中失调，使 PDGF 成为有吸引力的治疗靶点。然而，PDGF 也会影响许多对组织内稳态至关重要的信号级联反应，这限制了缺乏不良反应的基于 PDGF 的治疗方法的发展。最近的研究表明，成纤维细胞介导的细胞外基质（ECM）纤维连接蛋白纤维的组装通过选择性抑制磷酸肌醇 3-激酶（PI3K）激活来减轻 PDGF 诱导的细胞内钙释放，同时使其他 PDGF 介导的信号级联反应保持完整。在本研究中，使用一系列重组纤维连接蛋白衍生融合蛋白来定位纤维连接蛋白中负责这种抑制的序列。结果表明，纤维连接蛋白基质类似物 FNIII1H，8-10 对 PDGF 诱导的细胞内钙释放的抑制作用需要α5β1 整联蛋白的连接，但不依赖于纤维连接蛋白 FNIII1 的基质蛋白酶、肝素结合位点。完整的细胞结合纤维连接蛋白片段也不能抑制 PDGF 诱导的细胞内钙释放。相比之下，一种新型的整联蛋白结合片段采用延伸和对齐的构象状态，可抑制 PDGF 诱导的 PI3K 激活和细胞内钙释放。综上所述，这些研究提供的证据表明，纤维连接蛋白通过纤维连接蛋白 FNIII9-10 模块的新型构象来抑制 PDGF 诱导的细胞内钙释放，该构象由纤维状纤维连接蛋白表达。
