RUNX@ Subnuclear Targeting Integrates Signaling Pathways for Bone Formation

Runx2是一种支架蛋白，它与代表许多不同功能类别的蛋白质相互作用， 包括染色质重塑因子、细胞生长调控蛋白、成骨细胞分化 和骨基质的产生，以及那些转导发育信号通路的蛋白质 用于骨骼形成。我们已经确定Runx2招募到它的亚核区域与 核基质，信号通路的细胞内介质，既是正向调节，也是负向调节 骨形成，包括对BMP/转化生长因子(3)的反应的Smads，以及对 SRC信令。我们已经定义了Runx2蛋白中的特定点突变，它可以破坏这些关键的 Runx2和Smad以及Runx2与WW结构域蛋白的相互作用 影响靶基因上Runx2活性的因素数。这些点突变使我们能够解决 这些相互作用在小鼠敲入模型的核微环境中的体内意义。我们的 影响成骨细胞分化的miRNAs的发现引导我们解决microRNAs(MiRNA)如何实现这一点 靶向Runx2和Runx2辅助因子通过修饰形成的蛋白质来调节骨形成 在细胞核内运行2个共调节复合体。项目2现在将研究这些多重信令是如何 在成骨细胞分化过程中调控汇聚在Runx2上的通路以控制骨骼 队形。我们将1)鉴定完成所需的Runx2-Smad靶基因和调控复合体 BMP2成骨信号；2)表征影响BMP2成骨信号的生物学机制和信号通路 WW共调节蛋白与Runx2的组织以控制成骨；目的3)研究 靶向Runx2和共调节因子的miRNA候选者如何调控成骨。 临床意义：迫切需要开发治疗骨丢失的合成代谢疗法。 骨骼老化引起的骨质疏松症，或继发于代谢性骨骼疾病。我们的研究将 定义产生新骨的新靶点，以响应BMPs，将干细胞分化转向 成骨细胞谱系和鉴定骨形成的miRNA调节因子。其中的每一个都代表着潜力 促进成骨细胞分化和骨形成的治疗应用。例如，siRNA和 正在开发用于体内应用的miRNA技术。更安全的合成代谢疗法 可以开发激素疗法来刺激骨形成。

Runx2 is a scaffolding protein that interacts with proteins representing many different functional classes, including chromatin remodeling factors, proteins coupled to cell growth control, differentiation of osteoblasts and production of bone matrix, as well as those proteins that transduce developmental signaling pathways for bone formation. We have established that Runx2 recruits to its subnuclear domains associated with the nuclear matrix, intracellular mediators of signaling pathways that are both positive and negative regulators of bone formation, including Smads in response to BMP/TGF(3, and YAP, a WW domain protein in response to Src signaling. We have defined specific point mutations in the Runx2 protein that can disrupt these critical interactions between Runx2 and Smad and Runx2 with WW domain proteins, which include a growing number of factors that influence Runx2 activity on target genes. These point mutations allow us to address the in vivo significance of these interactions in nuclear microenvironments in mouse knock-in models. Our discovery of miRNAs that affect osteoblast differentiation leads us to address how micro-RNAs (miRNA) that target Runx2 and Runx2 co-factors regulate bone formation through modification of the proteins that form Runx2 coregulatory complexes in the nucleus. Project 2 will now pursue how these multiple signaling pathways which converge on Runx2 are regulated during osteoblast differentiation for the control of bone formation. We will 1) characterize Runx2-Smad target genes and regulatory complexes required to complete the BMP2 osteogenic signal; 2) characterize the biological mechanisms and signaling pathways influencing the organization of WW coregulatory proteins with Runx2 to control osteogenesis; and Aim 3) investigate how miRNA candidates that target Runx2 and coregulatory factors regulate osteogenesis. Clinical Relevance: There is a pressing need to develop anabolic therapies for treating bone loss in osteoporosis from the aging skeleton or induced secondary to a metabolic bone disorder. Our studies will define novel targets that produce new bone in response to BMPs, shift the stem cell differentiation towards the osteoblast lineage and identify miRNA regulators of bone formation. Each of these represents potential therapeutic applications to stimulate osteoblast differentiation and bone formation. For example, siRNA and miRNA technologies are being developed for in vivo application. Anabolic therapies that are safer than hormone treatments could be developed for stimulating bone formation.