Defining the Central Role of ER-Associated Degradation (ERAD) in Neuroendocrine Cells

内质网相关降解(ERAD)在神经内分泌细胞中的中枢作用 摘要 我的实验室长期以来一直对内质网中的蛋白质折叠和降解感兴趣。 (Er)通过定义哺乳动物内质网质量控制机制的生理和病理重要性 活着。内质网相关降解(ERAD)是蛋白质质量控制的主要机制 针对内质网中错误折叠的蛋白质进行胞浆蛋白酶体降解。未能清除错误折叠的蛋白质 在内质网中可能激活了未折叠的蛋白质反应，即UPR。我们发现Sel1L-Hrd1 ERAD 通过调节UPR传感器IRE1a的周转来调节其激活(Sun等人)。2015 NAT Cell Biol)。分成两份 最近的研究表明，ERAD功能受损可能与代谢性心脏病的发病机制直接相关 疾病，从而具有巨大的治疗潜力(Shiet al.2017和Kim等人。2018 J Ciin Invest)。 具体地说，我们报告了AVP或POMC神经元中Sel1L缺乏的小鼠出现糖尿病 尿崩症和早发性肥胖症。我们发现Sel1L-Hrd1 ERAD控制着细胞的成熟 内质网中的两种前激素，proAVP和POMC，通过靶向蛋白酶体的错误折叠形式 降解，从而防止很大比例的本土前激素聚集。我们现在提议 为了检验Sel1L-Hrd1 ERAD蛋白复合体在 通过直接招募错误折叠的前激素用于蛋白酶体降解的神经内分泌细胞 协调启动其他ER质量控制机制，如普遍定期审议和自噬，以确保 适当的激素前体成熟和神经元动态平衡。该模型挑战了ER中当前的范式 在正常生理和疾病发病机制中，ERAD处于细胞功能的中心。vbl.使用 POMC神经元作为模型系统，我们将实现以下目标：(1)确定潜在的 ERAD-POMC相互作用的分子机制和治疗潜力；(2)证明 ERAD和自噬之间串扰的病理生理学意义和机制 以及(3)证实了POMC神经元的病理生理学意义和机制。 前角运动神经元中ERAD和IRE1α之间的串扰。这项研究将提供前所未有的洞察力 神经内分泌细胞的ERAD功能和激素原生物学对人类有直接的临床意义 与激素前体折叠和输出缺陷有关的疾病。 与人类健康相关：所有神经肽都是作为前体蛋白合成的，称为 内质网中的“前激素”；然而，它们在内质网中成熟的分子机制仍然存在。 人们对此知之甚少。本研究将确立ERAD在协调ER中的病理生理学意义 前激素成熟过程中的动态平衡和探讨靶向ERAD的治疗潜力 治疗可归因于激素原成熟缺陷的疾病，如早发性尿崩症 肥胖，以及其他罕见的疾病，如普拉德-威利综合征。

Defining the Central Role of ER-Associated Degradation (ERAD) in Neuroendocrine Cells SUMMARY My laboratory has a long-standing interest in protein folding and degradation within the endoplasmic reticulum (ER) by defining the physiological and pathological importance of mammalian ER quality-control machineries in vivo. ER-associated degradation (ERAD) is the principal protein quality-control mechanism responsible for targeting misfolded proteins in the ER for cytosolic proteasomal degradation. Failure to clear misfolded proteins in the ER presumably activates the unfolded protein response, or UPR. We showed that Sel1L-Hrd1 ERAD modulates the activation of UPR sensor IRE1a by mediating its turnover (Sun et al. 2015 Nat Cell Biol). In two recent studies, we reported that impaired ERAD function may be directly linked to the pathogenesis of metabolic diseases, thereby holding significant therapeutic potential (Shi et al. 2017 and Kim et al. 2018 J CIin Invest). Specifically, we reported that mice with Sel1L deficiency in either AVP or POMC neurons exhibit diabetes insipidus and early-onset obesity, respectively. We showed that Sel1L-Hrd1 ERAD controls the maturation of two prohormones, proAVP and POMC, within the ER by targeting the misfolded forms for proteasomal degradation, thereby preventing the aggregation of a large proportion of native prohormones. We now propose to test the overarching hypothesis that the Sel1L-Hrd1 ERAD protein complex plays a critical role in neuroendocrine cells by directly recruiting misfolded prohormones for proteasomal degradation and by coordinating the activation of other ER quality-control machineries, such as UPR and autophagy, to ensure proper prohormone maturation and neuronal homeostasis. This model challenges the current paradigm in ER biology by placing ERAD at the center of cellular function in normal physiology and disease pathogenesis. Using POMC neurons as a model system, we will accomplish the following Aims: (1) determine the underlying molecular mechanisms and therapeutic potential of ERAD-POMC interactions; (2) demonstrate the pathophysiological importance and mechanisms underlying the crosstalk between ERAD and autophagy in POMC neurons; and (3) demonstrate the pathophysiological importance and mechanisms underlying the crosstalk between ERAD and IRE1α in POMC neurons. This study will provide unprecedented insights into ERAD function and prohormone biology in neuroendocrine cells, which has direct clinical implications for human diseases that are associated with defects of prohormone folding and export. RELEVANCE TO HUMAN HEALTH: All neuropeptides are synthesized as precursor proteins known as “prohormones” in the ER; however, molecular mechanisms underlying their maturation within the ER remain poorly understood. This study will establish the pathophysiological significance of ERAD in coordinating ER homeostasis during prohormone maturation and explore the therapeutic potential of targeting ERAD in the treatment of diseases attributed to defects in prohormone maturation, such as diabetes insipidus, early-onset obesity, and other rare diseases such as Prader-Willi Syndrome.