Mechanisms of ER-Protein Quality Control in Podocytes

足细胞雌激素受体蛋白质质量控制的机制 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。SEL 1 L-HRD 1蛋白复合物 代表ERAD最保守的分支。我们最近发现，Sel 1 L缺乏的小鼠， 足细胞在约5周龄时发生蛋白尿，并过早死亡，平均寿命约为14周。 男性和女性（Yoshida等人，2021 J CIin Invest）。电镜分析显示足突 在Sel 1 L缺失的情况下消失和受损的裂隙隔膜。从机制上讲，我们发现SEL 1 L-HRD 1 足细胞中的ERAD在ER中新生nephrin的成熟中起关键作用，而不影响足细胞 细胞数量和存活率。在我们最近的工作中，我们的初步数据表明可能存在串扰， ERAD与足细胞中另一个关键降解途径自噬之间的协同作用。我们建议测试 SEL 1 L-HRD 1 ERAD蛋白复合物在足细胞中起关键作用的总体假设， 协调自噬的激活，这确保了细胞内稳态和过滤功能。该模型 通过将SEL 1 L-HRD 1 ERAD置于细胞生物学的中心， 在正常生理和疾病发病机制中的作用。使用各种鼠标模型，我们将完成 （1）证明SEL 1 L-HRD 1之间串扰的病理生理学重要性 （2）确定SEL 1 L-HRD 1 ERAD如何控制足细胞中的自噬活性。 （3）阐明ERAD和自噬在足细胞中的病理学意义和机制。 nephrin疾病突变体参与肾病综合征的发病机制。这项研究将提供前所未有的 深入了解足细胞中关键ER质量控制机制之间的串扰，并揭示了 靶向足细胞中ER稳态的治疗潜力。 与人类健康的相关性：足细胞和形成狭缝隔膜的缺陷， 涉及许多跨膜蛋白的结构，是肾病综合征的基础，影响儿童和成人， 所有年龄段虽然ER质量控制系统可能被整合以维持ER稳态， 质量控制系统之间的串扰还没有在体内进行研究。这项研究将建立 ERAD的病理生理学意义及其与足细胞自噬的相互作用 和疾病。

Mechanisms of ER Protein Quality Control in Podocytes 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. The SEL1L-HRD1 protein complex represents the most conserved branch of ERAD. We recently showed that mice with Sel1L deficiency in podocytes develop proteinuria at ~5 weeks of age and die prematurely with a median life span of ~14 weeks for both males and females (Yoshida et al. 2021 J CIin Invest). Electron microscopic analyses revealed foot process effacement and impaired slit diaphragm in the absence of Sel1L. Mechanistically, we showed that SEL1L-HRD1 ERAD in podocytes plays a critical role in the maturation of nascent nephrin in the ER, without affecting podocyte cell number and survival. In our recent work, our preliminary data suggested a possible crosstalk, or likely synergism, between ERAD and another key degradative pathway autophagy in podocytes. We propose to test the overarching hypothesis that the SEL1L-HRD1 ERAD protein complex plays a critical role in podocytes by coordinating the activation of autophagy, which ensures cellular homeostasis and filtration function. This model challenges/expands the current paradigm in ER biology by placing SEL1L-HRD1 ERAD at the center of cellular function in normal physiology and disease pathogenesis. Using various mouse models, we will accomplish the following Aims: (1) Demonstrate the pathophysiological importance of the crosstalk between SEL1L-HRD1 ERAD and autophagy in podocytes; (2) Determine how SEL1L-HRD1 ERAD controls autophagy activity in podocytes; and (3) Delineate the pathological importance and mechanism of ERAD and autophagy in the pathogenesis of nephrin disease mutants involved in nephrotic syndrome. This study will provide unprecedented insights into the crosstalk among key ER quality control machineries in podocytes, and shed new light on the therapeutic potential of targeting ER homeostasis in podocytes. RELEVANCE TO HUMAN HEALTH: Defects in podocytes and in the formation slit diaphragm, a specialized structure involving many transmembrane proteins, underlie nephrotic syndrome, affecting children and adults of all ages. While the ER quality control systems are presumably integrated to maintain ER homeostasis, the crosstalk between quality-control systems has not yet been investigated in vivo. This study will establish the pathophysiological significance of ERAD and the crosstalk between ERAD and autophagy in podocytes in health and diseases.