Translational Control in Cartilage Biology. - Resubmission - 1

描述(申请人提供)：本提案的重点是软骨生物学中的翻译控制。软骨细胞是负责骨骼和软骨组织生长和维持的主要细胞。软骨细胞稳态失调会导致多种肌肉骨骼疾病，包括骨关节炎(OA)。虽然许多研究都集中在调控软骨细胞增殖和分化的转录机制上，但翻译调控在这些过程中的作用从未得到解决。它是 众所周知，软骨细胞的增殖和分化受到许多信号分子的调控，其中一个核心作用是成纤维细胞生长因子(FGFs)。虽然在大多数细胞类型中，FGFs诱导增殖并保护细胞免受凋亡，但增殖的软骨细胞对FGFs的反应是不同的，反应是生长抑制。根据我们的初步数据，在经成纤维细胞生长因子处理的软骨细胞中，蛋白质合成显著减少，这种反应与许多其他系统中生长因子对蛋白质合成的刺激相反。此外，我们还能够检测到成纤维细胞生长因子诱导的真核细胞起始因子4E结合蛋白(4E-BP)的激活，这是一种已知的帽依赖翻译抑制物。4E-BP在人关节软骨细胞中也有活性，但在骨性关节炎软骨中活性显著降低，表明在这种病理状态下，翻译机构的调节被解除。本研究旨在探讨成纤维细胞生长因子下调增殖期软骨细胞蛋白质合成和调控软骨细胞分化过程中蛋白质合成的机制。在这项应用的第一部分，我们将研究成纤维细胞生长因子对增殖软骨细胞蛋白质合成的抑制作用。我们将确定导致这种不同反应的机制。我们提案的第二部分旨在确定在蛋白质合成普遍抑制下主动翻译的特定mRNA池。我们将使用核糖体图谱来识别这些mRNA。该提案的最后部分将旨在确定与正常人类软骨相比，导致骨关节炎软骨中翻译机制激活的机制。该项目将为促进骨性关节炎和其他肌肉骨骼疾病的新的特定靶点提供基础。

DESCRIPTION (provided by applicant): This proposal is focused on translation control in cartilage biology. Chondrocytes are the primary cells responsible for the growth and maintenance of bones and cartilage tissue. Deregulation of chondrocyte homeostasis gives rise to a variety of musculoskeletal disorders, including osteoarthritis (OA). While many studies have focused on transcriptional mechanisms involved in regulation of chondrocytes proliferation and differentiation, the role of translation control in these processes has never been addressed. It is well established, that chondrocytes proliferation and differentiation are regulated by a number of signaling molecules and one of the central roles in these processes belongs to Fibroblast Growth Factors (FGFs). While in most cell types FGFs induce proliferation and protect from apoptosis, proliferating chondrocytes are distinct in their response to FGF, responding with growth inhibition. According to our preliminary data, protein synthesis is dramatically decreased in FGF-treated chondrocytes, a response that is opposite to well established stimulation of protein synthesis by growth factors in many other systems. Moreover, we were able to detect FGF-induced activation of eukaryotic Initiation Factor 4E Binding Protein (4E-BP) which is a known inhibitor of cap-dependent translation. While 4E-BP was also active in human articular chondrocytes, its activity was significantly lower in OA cartilage, indicating deregulation of translational apparatus under this pathological condition. This proposal aims to investigate the mechanism that mediates FGF-induced downregulation of protein synthesis in proliferating chondrocytes and regulation of protein synthesis during differentiation of chondrocytes. In the first part of this application we will investigate FGF-induced inhibition of protein synthesis in proliferative chondrocytes. We will determine the mechanism leading to this diverse response. The second part of our proposal will aim to identify specific pools of mRNAs that are actively translated under general repression of protein synthesis. We will employ ribosomal profiling to identify these mRNAs. The last part of the proposal will aim to determine the mechanism leading to activation of translation machinery in OA cartilage when compared to normal human cartilage. This project will provide basis for facilitating new specific targets in OA and other musculoskeletal disorders.