Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
Morinaga Institute of Biological Science, Yokohama 236-0003, Japan.
Int J Mol Sci. 2019 Mar 27;20(7):1541. doi: 10.3390/ijms20071541.
Both adiponectin and secreted protein, acidic and rich in cysteine (SPARC) inhibit platelet-derived growth factor-BB (PDGF-BB)-induced and basic fibroblast growth factor (FGF2)-induced angiogenic activities through direct and indirect interactions. Although SPARC enhances nerve growth factor (NGF)-dependent neurogenesis, the physical interaction of NGFβ with adiponectin and SPARC remains obscure. Therefore, we first examined their intermolecular interaction by surface plasmon resonance method. NGFβ bound to immobilized SPARC with the binding constant of 59.4 nM, comparable with that of PDGF-BB (24.5 nM) but far less than that of FGF2 (14.4 µM). NGFβ bound to immobilized full length adiponectin with the binding constant of 103 nM, slightly higher than those of PDGF-BB (24.3 nM) and FGF2 (80.2 nM), respectively. Treatment of PC12 cells with SPARC did not cause mitogen-activated protein kinase (MAPK) activation and neurite outgrowth. However, simultaneous addition of SPARC with NGFβ enhanced NGFβ-induced MAPK phosphorylation and neurite outgrowth. Treatment of the cells with adiponectin increased AMP-activated protein kinase (AMPK) phosphorylation but failed to induce neurite outgrowth. Simultaneous treatment with NGFβ and adiponectin significantly reduced cell size and the number of cells with neurite, even after silencing the adiponectin receptors by their siRNA. These results indicate that NGFβ directly interacts with adiponectin and SPARC, whereas these interactions oppositely regulate NGFβ functions.
脂联素和富含半胱氨酸的酸性分泌蛋白（SPARC）均可通过直接和间接相互作用抑制血小板衍生生长因子-BB（PDGF-BB）和碱性成纤维细胞生长因子（FGF2）诱导的血管生成活性。虽然 SPARC 增强了神经生长因子（NGF）依赖性神经发生，但 NGFβ 与脂联素和 SPARC 的物理相互作用仍不清楚。因此，我们首先通过表面等离子体共振法检查了它们的分子间相互作用。NGFβ与固定化 SPARC 的结合常数为 59.4 nM，与 PDGF-BB（24.5 nM）相当，但远低于 FGF2（14.4 µM）。NGFβ与固定化全长脂联素的结合常数为 103 nM，略高于 PDGF-BB（24.3 nM）和 FGF2（80.2 nM）。用 SPARC 处理 PC12 细胞不会引起丝裂原活化蛋白激酶（MAPK）激活和轴突生长。然而，同时添加 SPARC 和 NGFβ 增强了 NGFβ 诱导的 MAPK 磷酸化和轴突生长。用脂联素处理细胞会增加 AMP 激活的蛋白激酶（AMPK）磷酸化，但不能诱导轴突生长。同时用 NGFβ 和脂联素处理会显著减小细胞大小和具有轴突的细胞数量，即使在用其 siRNA 沉默脂联素受体后也是如此。这些结果表明，NGFβ 与脂联素和 SPARC 直接相互作用，而这些相互作用则相反调节 NGFβ 的功能。
