CITED2 and Mechanical Loads

描述（由申请人提供）：软骨退化，类风湿关节炎和骨关节炎的标志，与组织的机械使用状态密切相关。软骨损伤可由机械过度使用引起，并因不使用而加剧；然而，生理上相关水平的机械负荷可以保护关节组织免受降解。然而，介导生理负荷的保护作用和不适当的机械使用的破坏作用的细胞机制仍不清楚。我们最近发现了一种新的转录调节因子CITED2 （CBP/p300与ed富尾2相互作用的反激活因子），它在软骨细胞和其他细胞中通过生理相关水平的机械负荷诱导，其表达与涉及软骨降解的基质金属蛋白酶（MMPs）的产生呈负相关。因此，我们假设CITED2是介导机械载荷对软骨降解影响的调节途径的关键因素。拟议的研究有三个具体目的，旨在表征这一信号通路：(1)确定CITED2表达变化与软骨细胞中响应机械负荷（间歇性静水压力）的MMPs调节之间的关系；(2)确定CITED2调控MMP基因表达的分子机制；(3)确定机械载荷调控CITED2表达的具体机制。在这些研究中，我们将通过实验修饰参与该信号通路的分子组分的表达或活性，并监测相应靶基因（CITED2, MMPs）表达的变化。我们还将通过体外和体内结合分析表征这些调节途径分子成员之间的相互作用。最后，我们将测试机械负载对MMP表达的影响是否可以使用一种生物调节剂来模拟，这种调节剂已经被发现针对这种新型分子开关机制的特定分子成分。因此，这些研究的结果将确定治疗关节退行性疾病的新靶点，并将提高我们对正常结缔组织更新和病理降解的基本生物学过程的理解。

DESCRIPTION (provided by applicant): Cartilage degradation, the hallmark of rheumatoid arthritis and osteoarthritis, is closely linked to the tissue's state of mechanical usage. Cartilage breakdown can be induced by mechanical overuse and exacerbated by disuse; however, mechanical loading at physiologically relevant levels can protect joint tissues from degradation. Yet the cellular mechanisms that mediate both the protective effects of physiological loading and the damaging effects of inappropriate mechanical usage remain unclear. We recently identified a novel transcriptional regulator CITED2 (CBP/p300-lnteracting Transactivator with ED-rich tail 2) that is induced in chondrocytes and other cells by physiologically relevant levels of mechanical loading, and whose expression is inversely correlated with the production of matrix metalloproteinases (MMPs) implicated in cartilage degradation. We therefore hypothesize that CITED2 is a key element of the regulatory pathway that mediates the effects of mechanical loading on cartilage degradation. The proposed studies have three specific aims directed at characterizing this signaling pathway: (1) to determine the relationship between changes in CITED2 expression and the regulation of MMPs in chondrocytes responding to mechanical loading (intermittent hydrostatic pressure); (2) to identify molecular mechanisms by which CITED2 regulates the expression of MMP genes; and (3) to identify specific mechanisms by which mechanical loading regulates the expression of CITED2. In these studies we will experimentally modify the expression or activity of molecular components participating in this signaling pathway and monitor resulting changes in the expression of the appropriate target genes (CITED2, MMPs). We will also characterize interactions between molecular members of these regulatory pathways by in vitro and in vivo binding assays. Finally we will test whether the effects of mechanical loading on MMP expression can be mimicked using a biological regulator that has been found to target a specific molecular component of this novel molecular switching mechanism. The results of these studies will thus identify novel targets for therapeutic approaches to combat joint degenerative diseases, and will improve our understanding of the fundamental biological processes underlying both normal connective tissue turnover and pathologic degradation.