Regulation of xenobiotic receptors PXR and CAR: implications in drug disposition

 描述(由申请人提供)：我们研究了人类孕烷X受体(HPXR)和构成雄烷受体(HCAR)的调节及其在药物处置中的作用。HPXR和HCAR都是核受体：1)受许多结构不同的化学物质调节，直接通过受体结合或间接通过信号串扰调节；2)转录调节药物代谢酶和转运蛋白，以控制异种生物的处置和内生平衡；3)不仅与药物效应有关，而且与人类疾病的发展有关，如糖尿病和癌症；4)与维甲酸X受体形成异二聚体，与其靶基因的启动子结合，这可能是受体独有的或重叠的；5)受共激活因子和辅助抑制因子的影响；以及6)类似或相互作用 与各种调控伙伴不同，包括化学品、DNA元素、蛋白质和microRNAs。在我们对hPXR和HCAR的调控和功能的整体理解中，仍然存在几个关键的差距。首先，hPXR和HCAR不仅调节药物代谢，而且还与其他信号分子相互作用，调节或被它们调节。尽管正在取得进展，但我们缺乏关于hPXR和HCAR与其监管机构的互动，以及这些互动的监管和监管的完整图景。其次，需要系统的努力来开发化学工具来详细剖析hPXR和Hcar的调控。我们的两个长期目标是全面研究hPXR和HCAR的调控及其对药物处置和人类疾病的影响，并开发化学工具来阐明hPXR和HCAR的调控及其在预防药物毒性和提高生物利用度方面的潜在应用。我们通过发现调节hPXR和HCAR的机制，包括蛋白质-蛋白质相互作用、翻译后修饰和转录后调节(MicroRNAs)，以及开发新的hPXR拮抗剂SPA70、HCAR反向激动剂CINPA1及其类似物，朝着这些目标迈进。在资助期间，我们将面对三个挑战：(1)通过研究SPA70在多大程度上防止药物毒性和CINPA1降低耐药性并确定潜在的机制，说明hPXR和HCAR如何调节药物毒性和耐药性。(2)通过获得hPXR与拮抗剂(SPA70)和hCAR与反向激动剂(CINPA1)的共晶结构并进行结构-功能分析，明确了hPXR拮抗剂和HCAR反向激动剂作用的基本机制。(3)更好地理解hPXR和Hcar蛋白-蛋白质相互作用网络和相互调节效应，首先研究遗传毒性和外源反应通路之间的信号串扰如何减少遗传毒性应激的影响。综上所述，我们的发现不仅将使我们更广泛地理解hPXR和HCAR的调节以及它们如何控制人体对外源生物S和内生生物的反应，而且还将为进一步研究它们广泛的细胞功能提供新的hPXR和HCAR调节剂，并为预防药物毒性和提高药物的生物利用度提供治疗指导。

 DESCRIPTION (provided by applicant): We study regulation of the human pregnane X receptor (hPXR) and constitutive androstane receptor (hCAR) and their roles in drug disposition. Both hPXR and hCAR: 1) are nuclear receptors modulated by many structurally diverse chemicals, either directly via receptor binding or indirectly via signaling cross-talk; 2) transcriptionally regulate drug metabolizing enzymes and transporters to control xenobiotic disposition and endobiotic homeostasis; 3) are implicated not only in drug effects but also in the development of human diseases, such as diabetes and cancer; 4)form heterodimers with retinoid X receptor to bind the promoters of their target genes, which may be unique to a receptor or overlap; 5) are affected by coactivators and corepressors; and 6) interact similarly or differently with various regulatory partners, including chemicals, DNA elements, proteins, and microRNAs. Several key gaps remain in our overall understanding of hPXR and hCAR regulation and function. First, hPXR and hCAR not only regulate drug metabolism but also interact with other signaling molecules, regulating or being regulated by them. Despite ongoing progress, we lack a complete picture of hPXR and hCAR interactions with their regulators, and of the regulation by and regulation of these interactions. Second, a systematic effort is needed to develop chemical tools to dissect hPXR and hCAR regulation in detail. Our two long-term goals are to comprehensively examine the regulation of hPXR and hCAR and its implications for drug disposition and human diseases, and to develop chemical tools to elucidate hPXR and hCAR regulation and its potential application for preventing drug toxicity and improving bioavailability. We have advanced toward these goals by discovering mechanisms that regulate hPXR and hCAR, including protein-protein interactions, post-translational modification and post-transcriptional regulation (microRNAs), and by developing the novel hPXR antagonist SPA70, the hCAR inverse agonist CINPA1, and their analogs. We will meet 3 challenges during the funding period: (1) Illustrate how hPXR and hCAR regulate drug toxicity and resistance by examining to what extent SPA70 prevents drug toxicity and CINPA1 reduces drug resistance and determining the underlying mechanisms. (2) Define the fundamental mechanism responsible for the action of hPXR antagonists and hCAR inverse agonists by obtaining the co-crystal structures of hPXR with antagonist (SPA70) and hCAR with inverse agonist (CINPA1) and carrying out structural-functional analysis. (3) Better understand hPXR and hCAR protein-protein interaction networks and reciprocal regulatory effects, starting by examining how signaling cross-talk between genotoxic- and xenobiotic-responsive pathways reduces the effect of genotoxic stress. Together, our findings will provide not only a broader comprehension of the regulation of hPXR and hCAR and how they control the human body's response to xenobiotic s and endobiotics, but also novel modulators of hPXR and hCAR for further interrogating their broad cellular function, and as leads for therapies to prevent drug toxicity and improve drug bioavailability.