State Key Laboratory Breeding Base of Basic Science of Stomatology (Hubei-MOST) and Key Laboratory for Oral Biomedicine of Ministry of Education (KLOBM), School and Hospital of Stomatology, Wuhan University, Wuhan, 430079, China.
Department of Developmental Dentistry, University of Texas Health Science Center, San Antonio, Texas, 78229-3700, United States.
Sci Rep. 2016 Jul 19;6:29666. doi: 10.1038/srep29666.
Dentin sialophosphoprotein (DSPP) is a dentin extracellular matrix protein that is processed into dentin sialoprotein (DSP), dentin glycoprotein (DGP) and dentin phosphoprotein (DPP). DSP is mainly expressed in odontoblasts. We hypothesized that DSP interacts with cell surface receptors and subsequently activates intracellular signaling. Using DSP as bait for screening a protein library, we demonstrate that DSP acts as a ligand and binds to integrin β6. The 36 amino acid residues of DSP are sufficient to bind to integrin β6. This peptide promoted cell attachment, migration, differentiation and mineralization of dental mesenchymal cells. In addition, DSP (aa183-219) stimulated phosphorylation of ERK1/2 and P38 kinases. This activation was inhibited by an anti-integrin β6 antibody and siRNA. Furthermore, we demonstrate that this DSP fragment induces SMAD1/5/8 phosphorylation and nuclear translocation via ERK1/2 and P38 signaling. SMAD1/5/8 binds to SMAD binding elements (SBEs) in the DSPP gene promoter. SBE mutations result in a decrease in DSPP transcriptional activity. Endogenous DSPP expression was up-regulated by DSP (aa183-219) in dental mesenchymal cells. The data in the current study demonstrate for the first time that this DSP domain acts as a ligand in a RGD-independent manner and is involved in intracellular signaling via interacting with integrin β6. The DSP domain regulates DSPP expression and odontoblast homeostasis via a positive feedback loop.
牙本质涎磷蛋白 (DSPP) 是一种牙本质细胞外基质蛋白，可被加工为牙本质涎蛋白 (DSP)、牙本质糖蛋白 (DGP) 和牙本质磷蛋白 (DPP)。DSP 主要在成牙本质细胞中表达。我们假设 DSP 与细胞表面受体相互作用，随后激活细胞内信号转导。我们使用 DSP 作为诱饵筛选蛋白文库，证明 DSP 作为配体与整合素 β6 结合。DSP 的 36 个氨基酸残基足以与整合素 β6 结合。该肽促进牙间质细胞的黏附、迁移、分化和矿化。此外，DSP（aa183-219）刺激 ERK1/2 和 P38 激酶的磷酸化。这种激活被抗整合素 β6 抗体和 siRNA 抑制。此外，我们证明该 DSP 片段通过 ERK1/2 和 P38 信号通路诱导 SMAD1/5/8 的磷酸化和核转位。SMAD1/5/8 与 DSPP 基因启动子中的 SMAD 结合元件 (SBE) 结合。SBE 突变导致 DSPP 转录活性降低。内源性 DSPP 表达在牙间质细胞中被 DSP（aa183-219）上调。本研究首次证明，该 DSP 结构域以非 RGD 依赖的方式作为配体发挥作用，并通过与整合素 β6 相互作用参与细胞内信号转导。DSP 结构域通过正反馈环调节 DSPP 表达和成牙本质细胞稳态。
