Role of PDZK1 in lipid metabolism and atherosclerosis

连接蛋白、锚定蛋白和支架蛋白在信号转导中起着重要作用。在许多 在某些情况下，信号蛋白之间的相互作用是由结合到 特定的蛋白质结构域，如src同源(SH)、pTyr结合(PTB)或PDZ结构域。这些相互作用 负责确定受体和转运蛋白的位置、功能和活性 其他。几年前，我们分离出一种新的蛋白质，我们将其命名为PDZK1。PDZK1包含四个PDZ 蛋白质相互作用结构域，并与许多膜的羧基末端部分相互作用 相关蛋白包括高密度脂蛋白、清道夫受体SR-BI和几种离子 渠道，其中之一涉及多药耐药。因此，PDZK1很可能在 生物过程多种多样，如脂代谢和心血管疾病，离子通道组织和 多药耐药。 我们产生了一只PDZK1基因敲除小鼠，其特征是血浆胆固醇水平升高 并显著降低SR-BI在肝脏中的表达，导致胆固醇反向转运受损。 PDZK1加入ARH(常染色体隐性遗传性高胆固醇血症中缺陷基因的产物)是什么 可能是一个不断壮大的细胞质接头蛋白家族，它们控制着细胞的组织特异性活动 表面受体。 最近，我们使用转基因小鼠模型确定，在转基因小鼠模型中，截断形式的 PDZK1在PDZK1 KO小鼠肝脏中过表达，提示PDZK1的四个PDZ结构域都是必需的 对于正常SR-BI的表达、定位和功能，尽管PDZ2的单个结构域的确切作用 尤其是PDZ4，仍然未知。我们已经确定SR-BI能够与另一个站点交互 在PDZK1内，除了已知的与PDZ1的相互作用外。此外，我们还解决了晶体结构问题 PDZK1的第一结构域及其与SR-BI的相互作用。我们还确定了PDZK1是 提示PDZK1可能是心血管疾病治疗的一个有吸引力的靶点。 我们现在的目标是研究PDZK1/SR-BI蛋白质簇的分子组织。我们会 定义PDZK1的第二和第四个PDZ结构域(PDZ2和PDZ4)的功能，并确定其 结合伴侣，通过X射线结晶学确定PDZK1的完整结构，得到三个 并了解PDZK1如何与其结合伙伴相互作用。我们会 使用转基因小鼠模型关联在体外获得的结果，其中改变(突变/截断) PDZK1转基因将在PDZK1 KO小鼠的肝脏中表达。这样的研究可能会提供必要的 促进胆固醇反向转运的新疗法的开发背景 动脉粥样硬化病变和心肌梗死的形成。

Adaptor, anchoring and scaffolding proteins play an important role in signal transduction. In many situations, the interaction between signaling proteins is mediated by small amino acid sequences binding to specific protein domains, such as src homology (SH), pTyr-binding (PTB) or PDZ domains. These interactions are responsible for determining location, function and activity of receptor and transporter proteins among others. A few years ago, we isolated a novel protein that we named PDZK1. PDZK1 contains four PDZ protein-interaction domains and interacts with the carboxy-terminal portion of a number of membrane associated proteins including the high density lipoprotein (HDL) scavenger receptor SR-BI and several ion channels, one of them involved in multidrug resistance. As a result, PDZK1 is likely to play an important role in biological processes as diverse as lipid metabolism and cardiovascular disease, ion channel organization and multidrug resistance. We generated a PDZK1 knockout mouse which is characterized by increased plasma cholesterol levels and markedly reduced expression of SR-BI in the liver, resulting in impaired "reverse cholesterol transport". PDZK1 joins ARH (the product of the defective gene in autosomal recessive hypercholesterolemia) in what is likely to be a growing family of cytoplasmic adaptor proteins that control the tissue specific activity of cell surface receptors. More recently, we have determined, using a transgenic mouse model in which truncated forms of PDZK1 were overexpressed in the liver of PDZK1 KO mice, that all four PDZ domains of PDZK1 are necessary for normal SR-BI expression, localization and function, although the precise role of individual domains, PDZ2 and PDZ4 in particular, remains unknown. We have determined that SR-BI is able to interact with another site within PDZK1, in addition to the known interaction with PDZ1. In addition, we have solved the crystal structure of the first domain of PDZK1 and its interaction with SR-BI. We have also determined that PDZK1 is atheroprotective, suggesting that PDZK1 may be an attractive target for therapies in cardiovascular diseases. Our objectives are now to study the molecular organization of the PDZK1/SR-BI protein cluster. We will define the functions of the second and fourth PDZ domains (PDZ2 and PDZ4) of PDZK1 and identify their binding partners, define the complete structure of PDZK1 by X-ray crystallography to obtain a three dimensional structure of the molecule and understand how PDZK1 interacts with its binding partners. We will correlate the results obtained in vitro using a transgenic mouse model, where altered (mutated/truncated) PDZK1 transgenes will be expressed in the liver of PDZK1 KO mice. Such studies may provide the necessary background for the development of new therapies promoting reverse cholesterol transport to prevent the formation of atherosclerotic lesions and myocardial infarction.