A novel ryanodine receptor in the hormonal regulation of hepatic metabolism

肝脏代谢激素调节中的新型兰尼定受体

• 批准号: 8058627
• 负责人: ANDREW P THOMAS
• 金额: $ 19.31万
• 依托单位: UNIV OF MED/DENT OF NJ-NJ MEDICAL SCHOOL
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-15 至 2013-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8058627
• 关键词: Biochemical; Brain; Caffeine; Calcium Signaling; Catecholamines; Cells; Chinese Hamster Ovary Cell; Cholestasis; Complex; Cyclic ADP-Ribose; Disease; Dose; Endocrine; Epithelium; Feedback; Frequencies; Gastrointestinal tract structure; Gene Expression; Generations; Genes; Health; Hepatic; Hepatitis; Hepatocyte; Hormonal; Hormones; ITPR1 gene; Inositol; Investigation; Length; Liver; Mediating; Metabolism; Molecular Structure; Muscle; Pancreas; Pancreatitis; Pathway interactions; Pattern; Physiological; Play; Process; Property; Protein Isoforms; Proteins; Public Health; Rattus; Regulation; Role; RyR1; Ryanodine; Ryanodine Receptor Calcium Release Channel; Ryanodine Receptors; Second Messenger Systems; Secretory Cell; Series; Signal Pathway; Signal Transduction; Signaling Protein; Site; Tissues; Vasopressins; Work; cell preparation; hormone regulation; improved; inhibitor/antagonist; innovation; liver function; new therapeutic target; novel; public health relevance; receptor; response; second messenger

DESCRIPTION (provided by applicant): The effects of hormones such as catecholamines and vasopressin on hepatic metabolism and secretion are mediated by alterations in the concentration of cytosolic free Ca2+ ([Ca2+]c), largely as a result of Ca2+ mobilization from intracellular stores by the second messenger inositol 1,4,5-trisphosphate (IP3). The [Ca2+]c signals elicited by these hormones are organized in the form of [Ca2+]c oscillations and waves, whose frequency is controlled by hormone dose. Frequency-modulated [Ca2+]c oscillations may serve a number of regulatory functions, including improved fidelity, sensitivity and targeted regulation of specific processes. While the role of IP3-receptors in this pathway is well established, it has recently become evident that other Ca2+ release and Ca2+-feedback components contribute to extend the temporal and spatial range of [Ca2+]c oscillations. One way in which this might be achieved is through interplay between IP3R and the other major class of intracellular Ca2+ release channels, the ryanodine receptors (RyRs). RyRs are typically activated by Ca2+ through a Ca2+-induced Ca2+ release (CICR) mechanism, but they can also be activated by another second messenger, cyclic-ADPribose (cADPR). Although the RyRs have been well-characterized in excitable tissues (primarily muscle and brain), relatively little is known about the identity and properties of RyRs in nonexcitable cells. We have recently identified and cloned a unique RyR isoform from rat hepatocytes (RyR1b), which is derived from the RyR1 gene, but with an alternative start site that gives rise to a protein of only 40% the size of full length muscle RyRs. We hypothesize that RyR1b has distinct functional properties that underlie its contribution to [Ca2+]c signaling in hepatocytes and other nonexcitable secretory cells, where it may be the principal RyR isoform. Specifically, we propose that RyR1b plays a key role in enhancing and sustaining ER Ca2+ release initiated by IP3R activation. We will examine the potential role of RyR1b in two specific aims: In Aim 1 we will carry out heterologous expression studies to investigate the function and regulatory properties of RyR1b, including regulation by [Ca2+]c, cADPR and its interactions with IP3 and the IP3R. In Aim 2 we will investigate the subcellular distribution and regulation of RyR1b in primary hepatocytes, and determine how it contributes to the temporal and spatial pattern of [Ca2+]c signaling during hormonal stimulation of these cells. RyR1b appears to be a major new addition to the superfamily of intracellular Ca2+ release channels, with distinct properties. It may have specific functions that are tuned to the signaling requirements of nonexcitable secretory epithelia and endocrine cells. Thus, the proposed work is innovative and has the potential for high impact, with significant biomedical health relevance. PUBLIC HEALTH RELEVANCE: The proposed work will investigate the role and regulation of a newly discovered calcium signaling protein (RyR1b) that appears to play a role in mediating the effects of hormones on liver function. It is also postulated to participate in signaling in other tissues, including the pancreas and cells of the digestive tract. Since derangements of signaling in these tissues are frequently associated with disease states (eg. hepatitis, cholestasis, pancreatitis), characterization of the properties of RyR1b has significant potential public health impact. Its unique molecular structure may yield a novel therapeutic target.

描述（由申请人提供）：儿茶酚胺和加压素等激素对肝脏代谢和分泌的影响是通过胞质游离 Ca2+ ([Ca2+]c) 浓度的变化介导的，这主要是由于第二信使肌醇 1,4,5-三磷酸 (IP3) 从细胞内储存的 Ca2+ 动员的结果。这些激素引发的 [Ca2+]c 信号以 [Ca2+]c 振荡和波的形式组织，其频率由激素剂量控制。调频 [Ca2+]c 振荡可发挥多种调节功能，包括提高特定过程的保真度、灵敏度和针对性调节。虽然 IP3 受体在此途径中的作用已得到充分证实，但最近发现其他 Ca2+ 释放和 Ca2+ 反馈成分有助于扩展 [Ca2+]c 振荡的时间和空间范围。实现这一目标的一种方法是通过 IP3R 与另一类主要的细胞内 Ca2+ 释放通道——兰尼碱受体 (RyRs) 之间的相互作用。 RyR 通常通过 Ca2+ 诱导的 Ca2+ 释放 (CICR) 机制被 Ca2+ 激活，但它们也可以被另一种第二信使环 ADP 核糖 (cADPR) 激活。尽管 RyR 在可兴奋组织（主要是肌肉和大脑）中已得到很好的表征，但人们对非兴奋细胞中 RyR 的身份和特性知之甚少。我们最近从大鼠肝细胞中鉴定并克隆了一种独特的 RyR 亚型 (RyR1b)，它源自 RyR1 基因，但具有替代起始位点，产生的蛋白质仅为全长肌肉 RyR 大小的 40%。我们假设 RyR1b 具有独特的功能特性，这些特性是其对肝细胞和其他非兴奋性分泌细胞中 [Ca2+]c 信号传导的贡献的基础，它可能是主要的 RyR 同工型。具体来说，我们认为 RyR1b 在增强和维持 IP3R 激活引发的 ER Ca2+ 释放中发挥关键作用。我们将研究 RyR1b 在两个具体目标中的潜在作用：在目标 1 中，我们将进行异源表达研究，以研究 RyR1b 的功能和调节特性，包括 [Ca2+]c、cADPR 的调节及其与 IP3 和 IP3R 的相互作用。在目标 2 中，我们将研究原代肝细胞中 RyR1b 的亚细胞分布和调节，并确定它在这些细胞的激素刺激过程中如何影响 [Ca2+]c 信号传导的时间和空间模式。 RyR1b 似乎是细胞内 Ca2+ 释放通道超家族的一个重要新成员，具有独特的特性。它可能具有适应非兴奋性分泌上皮细胞和内分泌细胞的信号传导需求的特定功能。因此，拟议的工作具有创新性，具有产生巨大影响的潜力，具有显着的生物医学健康相关性。 公共健康相关性：拟议的工作将研究新发现的钙信号蛋白（RyR1b）的作用和调节，该蛋白似乎在介导激素对肝功能的影响中发挥作用。它还被认为参与其他组织的信号传导，包括胰腺和消化道细胞。由于这些组织中信号传导的紊乱通常与疾病状态（例如肝炎、胆汁淤积、胰腺炎）相关，因此 RyR1b 特性的表征具有重大的潜在公共健康影响。其独特的分子结构可能会产生新的治疗靶点。