CITED2 and Mechanical Loads

描述(申请人提供)：软骨退化，类风湿性关节炎和骨性关节炎的标志，与组织的机械使用状态密切相关。机械过度使用可导致软骨破坏，不使用可加重软骨破坏；然而，生理相关水平的机械负荷可以保护关节组织免受退化。然而，调节生理负荷的保护效应和不适当的机械使用的损害效应的细胞机制仍不清楚。我们最近发现了一种新的转录调控因子CITED2(CBP/p300-反式激活因子与富含ED的Tail 2)，它由生理水平的机械负荷诱导软骨细胞和其他细胞，其表达与与软骨降解有关的基质金属蛋白酶(MMPs)的产生呈负相关。因此，我们假设CITED2是介导机械负荷对软骨降解影响的调节通路的关键元件。这些研究针对这一信号通路有三个特定的目的：(1)确定机械负荷(间歇静水压力)下软骨细胞中CITED2表达的变化与MMPs调控之间的关系；(2)确定CITED2调控基质金属蛋白酶基因表达的分子机制；(3)确定机械负荷调节CITED2表达的具体机制。在这些研究中，我们将通过实验改变参与这一信号通路的分子组件的表达或活性，并监测由此导致的适当靶基因(CITED2，MMPs)表达的变化。我们还将通过体外和体内结合试验来表征这些调控途径的分子成员之间的相互作用。最后，我们将测试机械负荷对基质金属蛋白酶表达的影响是否可以用一种生物调节器来模拟，这种生物调节器已经被发现针对这种新的分子开关机制的特定分子成分。因此，这些研究的结果将为抗击关节退行性疾病的治疗方法确定新的靶点，并将提高我们对正常结缔组织更新和病理性退化背后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.