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

确定ER相关降解（ERAD）在神经内分泌细胞中的中心作用 总结 我的实验室对内质网内的蛋白质折叠和降解有着长期的兴趣 (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， vivo. ER相关降解（ERAD）是主要的蛋白质质量控制机制， 靶向ER中错误折叠的蛋白质用于胞质蛋白酶体降解。未能清除错误折叠的蛋白质 可能激活未折叠蛋白反应，或UPR。我们发现Sel 1 L-Hrd 1 ERAD 通过介导其周转来调节UPR传感器IRE 1a的激活（Sun等人，2015 Nat Cell Biol）。在两 最近的研究中，我们报道ERAD功能受损可能与代谢性疾病的发病机制直接相关， 疾病，因此具有显著的治疗潜力（Shi et al. 2017和Kim et al. 2018 J CIin Invest）。 具体来说，我们报道了AVP或POMC神经元中Sel 1 L缺乏的小鼠表现出糖尿病， 尿崩症和早发性肥胖。我们发现Sel 1 L-Hrd 1 ERAD控制着 两种激素原，proAVP和POMC，通过靶向蛋白酶体的错误折叠形式， 因此，本发明提供了一种用于抑制天然激素原降解的方法，从而防止大比例的天然激素原的聚集。我们现建议 为了验证Sel 1 L-Hrd 1 ERAD蛋白复合物在以下方面起关键作用的总体假设： 神经内分泌细胞通过直接募集错误折叠的激素原进行蛋白酶体降解， 协调其他ER质量控制机制的激活，如UPR和自噬，以确保 适当的激素原成熟和神经元内稳态。这种模式挑战了ER中的当前范式 通过将ERAD置于正常生理学和疾病发病机制中细胞功能的中心，使用 以POMC神经元为模型系统，我们将完成以下目的：（1）确定底层 ERAD-POMC相互作用的分子机制和治疗潜力;（2）证明 病理生理学的重要性和机制之间的串扰ERAD和自噬在 POMC神经元;（3）证明了POMC神经元的病理生理学重要性和机制。 ERAD和IRE 1 α在POMC神经元中的相互作用。这项研究将提供前所未有的见解， ERAD功能和神经内分泌细胞中的激素原生物学，这对人类具有直接的临床意义。 与激素原折叠和输出缺陷相关的疾病。 与人类健康的关系：所有神经肽都是作为前体蛋白质合成的， ER中的“激素原”;然而，它们在ER中成熟的分子机制仍然存在。 不太了解。本研究将建立ERAD在协调ER中的病理生理学意义 在激素原成熟过程中的内稳态，并探索靶向ERAD的治疗潜力， 治疗由于激素原成熟缺陷引起的疾病，如尿崩症、早发性 肥胖症和其他罕见疾病，如Prader-Willi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.