The roles of orphan nuclear receptors in the development and function of the immune system

Hormones and their receptors regulate cell growth,differentiation and apoptosis and also play important rolesin immune function.Recent studies on the subfamily of the orphan nuclear receptors known as retinoid-acidrelated orphan receptors (ROR) have shed important insights on the roles of this group of nuclear proteins inthe development and function of the immune system.RORα regulates inflammatory cytokine production inboth innate and adaptive immune system while RORγ regulates the normal development of T lymphocyterepertoire and secondary lymphoid organs.Cellular & Molecular Immunology.2004;1(6):401-407.     

Regulation of T helper 17 differentiation by orphan nuclear receptors: it's not just ROR gamma t anymore

T cells that produce IL-17 (T helper 17 cells) are implicated in autoimmune pathogenesis. In this issue of Immunity, Yang et al. (2008) report that the closely related orphan nuclear receptors ROR alpha and ROR gamma t work together to regulate T helper (Th)17 cell differentiation.     

The orphan nuclear receptor COUP-TFII is required for angiogenesis and heart development

The embryonic expression of COUP-TFII, an orphan nuclear receptor, suggests that it may participate in mesenchymal-epithelial interactions required for organogenesis. Targeted deletion of the COUP-TFII gene results in embryonic lethality with defects in angiogenesis and heart development. COUP-TFII mutants are defective in remodeling the primitive capillary plexus into large and small microcapillaries. In the COUP-TFII mutant heart, the atria and sinus venosus fail to develop past the primitive tube stage. Reciprocal interactions between the endothelium and the mesenchyme in the vascular system and heart are essential for normal development of these systems. In fact, the expression of Angiopoietin-1, a proangiogenic soluble factor thought to mediate the mesenchymal-endothelial interactions during heart development and vascular remodeling, is down-regulated in COUP-TFII mutants. This down-regulation suggests that COUP-TFII may be required for bidirectional signaling between the endothelial and mesenchymal compartments essential for proper angiogenesis and heart development.     

The quest for novel bioactive peptides utilizing orphan seven-transmembrane-domain receptors

Various sorts of bioactive molecules including hormones, neurotransmitters, and chemokines transmit signals into cells by binding to so-called seven-transmembrane-domain receptors (7TMRs). The recent progress in cDNA and genome DNA analyses has brought the discovery of numerous genes encoding ligand-unknown "orphan" 7TMRs. We have developed a strategy to identify the ligands of orphan 7TMRs by monitoring specific signal transductions induced in cells expressing orphan 7TMRs. Employing this method, we succeeded in identifying the natural ligands of the orphan 7TMRs, hGR3, and APJ. The ligand peptide identified for hGR3 was found to show a specific prolactin release promoting activity in rat anterior pituitary cells in in vitro culture and was therefore named "prolactin-releasing peptide." We named another novel bioactive peptide "apelin," for "APJ endogenous ligand." Although the biological functions of apelin are still under investigation, APJ reportedly acts as a coreceptor in the process of human immunodeficiency virus infection. We believe that the identification of orphan 7TMR ligands will provide clues to reveal the unknown regulatory mechanisms of various physiological phenomena and opportunities for novel drug discovery in the future. Received: 4 January 1999 / Accepted: 4 June 1999     

代谢性核受体及其与代谢综合征的关系

代谢性核受体是一组与代谢调节相关的配体激活核受体转录因子,主要包括脂质过氧化物体增殖物激活受体(PPARs)、肝X受体(LXRs)和法尼酯衍生物X受体(FXRs)3种。它们在胰岛素敏感性、脂肪生成、脂质代谢、能量代谢、血压调节、炎症、细胞生长和分化等过程中起着关键的调节作用,因而近年来倍受关注。越来越多的研究表明这3种核受体不仅与代谢综合征,包括胰岛素抵抗、糖耐量受损2、型糖尿病、肥胖、高脂血症、高血压和微白蛋白尿之间存在密切的关系,也在动脉粥样硬化的发生及发展中有重要的作用。本文就代谢性核受体的生物学活性和生理功能作一简述,并对其在代谢综合征发病机制中的作用进行重点讨论。     

HepG2细胞中RORγ相互作用蛋白的筛选及鉴定

目的筛选HepG2细胞中转录因子RORγ(the retinoid-related orphan nuclear receptor gamma)相互作用蛋白,并对这些蛋白进行初步鉴定,为阐述RORγ介导调节HepG2细胞中各种生理学进程提供理论依据。方法从HepG2细胞中克隆RORγ基因并连接入载体pCeMM CTAP(SG)中形成RORγ-CTAP(SG)融合基因,再将其亚克隆入含嘌呤霉素抗性基因的载体质粒中,构建pMSCVpuro RORγ-CTAP(SG)质粒;稳定转染HepG2细胞并对RORγ-CTAP(SG)融合基因的表达和定位进行检测后,进行大规模扩增培养;用TAP(串联亲和纯化)方法捕获RORγ相互作用蛋白,通过银染找出差异性蛋白条带,质谱鉴定得到候选RORγ相互作用蛋白;用免疫共沉淀方法对候选蛋白RORγ相互作用蛋白进行验证鉴定。结果成功构建了质粒pMSCVpuro RORγ-CTAP(SG)并得到稳定转染HepG2细胞株,同时RORγ-CTAP(SG)融合基因能定位表达于细胞核内;通过TAP方法获得了RORγ蛋白复合物,然后通过串联质谱分析和数据库搜索从银染差异性显著蛋白条带中找到7个候选RORγ相互作用蛋白;用RORγ蛋白进行免疫共沉淀,对纯化出的7个RORγ相互作用蛋白分别检测,证实了RIP140,HSP90和RORγ在HepG2中有相互作用关系。结论筛选并鉴定了HepG2细胞中蛋白RORγ的相互作用蛋白RIP140和HSP90,这些研究发现支持了RORγ是共调解蛋白依赖的转录因子且以复合物形式行使功能的假说。其中,HSP90可能扮演分子伴侣角色,而RIP140在HepG2细胞中则可能充当RORγ蛋白的转录调控伙伴蛋白,具体机制有待进一步研究。     

Hallucinogenic and neuroleptic drug interactions with potential neurotransmitter receptors in parasitic nematodes.

Receptors potentially involved in neurotransmitting have been characterised in the muscle tissue and in whole worms of the nematodes Ascaris suum and Onchocerca volvulus, respectively. Binding studies revealed a high affinity for LSD with apparent KD values of 94 nM for A. suum and 120 nM for O. volvulus, whereas those of the neuroleptics haloperidol, spiperone and mianserin were found to be in the micromolar range. A variety of neurotransmitter antagonists, known to bind with high affinities either to mammalian D1/2 or to 5-HT1/2 receptors, were tested for their ability to bind to the nematode receptor. Results from these displacement experiments using tritiated LSD, mianserin, spiperone and haloperidol show distinct specificities of the nematode receptors compared to known receptor classes of mammals. With respect to this novel specificity, the nematode receptors seem to be unique and clearly distinct from those of the hosts.