Department of Anatomy, Nihon University School of Dentistry, Tokyo, Japan.
Differentiation. 2012 Dec;84(5):392-9. doi: 10.1016/j.diff.2012.07.001. Epub 2012 Aug 17.
While the role of p75(NTR) signaling in the regulation of nerve-related cell growth and survival has been well documented, its actions in osteoblasts are poorly understood. In this study, we examined the effects of p75(NTR) on osteoblast proliferation and differentiation using the MC3T3-E1 pre-osteoblast cell line. Proliferation and osteogenic differentiation were significantly enhanced in p75(NTR)-overexpressing MC3T3-E1 cells (p75GFP-E1). In addition, expression of osteoblast-specific osteocalcin (OCN), bone sialoprotein (BSP), and osterix mRNA, ALP activity, and mineralization capacity were dramatically enhanced in p75GFP-E1 cells, compared to wild MC3T3-E1 cells (GFP-E1). To determine the binding partner of p75(NTR) in p75GFP-E1 cells during osteogenic differentiation, we examined the expression of trkA, trkB, and trkC that are known binding partners of p75(NTR), as well as NgR. Pharmacological inhibition of trk tyrosine kinase with the K252a inhibitor resulted in marked reduction in the level of ALPase under osteogenic conditions. The deletion of the GDI binding domain in the p75(NTR)-GFP construct had no effect on mineralization. Taken together, our studies demonstrated that p75(NTR) signaling through the trk tyrosine kinase pathway affects osteoblast functions by targeting osteoblast proliferation and differentiation.
虽然 p75（NTR）信号在调节神经相关细胞的生长和存活中的作用已得到充分证实，但它在成骨细胞中的作用知之甚少。在这项研究中，我们使用 MC3T3-E1 前成骨细胞系研究了 p75（NTR）对成骨细胞增殖和分化的影响。p75（NTR）过表达的 MC3T3-E1 细胞（p75GFP-E1）的增殖和成骨分化明显增强。此外，与野生型 MC3T3-E1 细胞（GFP-E1）相比，p75GFP-E1 细胞中骨钙素（OCN）、骨涎蛋白（BSP）和osterix mRNA 的表达、碱性磷酸酶（ALP）活性和矿化能力均显著增强。为了确定 p75（NTR）在成骨分化过程中与 p75GFP-E1 细胞结合的伴侣，我们研究了已知与 p75（NTR）结合的 trkA、trkB 和 trkC 以及 NgR 的表达。用 K252a 抑制剂抑制 trk 酪氨酸激酶可显著降低成骨条件下的 ALPase 水平。p75（NTR）-GFP 构建体中 GDI 结合域的缺失对矿化没有影响。总之，我们的研究表明，p75（NTR）信号通过 trk 酪氨酸激酶途径影响成骨细胞功能，靶向成骨细胞增殖和分化。
