Mechanisms for maintaining ER protein homeostasis in myelinating cells

维持髓鞘细胞内质网蛋白稳态的机制

• 批准号: 10115143
• 负责人: Wensheng Lin
• 金额: $ 33.69万
• 依托单位: UNIVERSITY OF MINNESOTA
• 依托单位国家: 美国
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-03-15 至 2023-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10115143
• 关键词: ATF6 gene; Adult; Attenuated; Biology; Cell membrane; Cells; Cessation of life; Complex; Data; Development; Endoplasmic Reticulum; Gene Expression; Goals; Homeostasis; Impairment; Knowledge; Mus; Myelin; Myelin Proteins; Myelin Sheath; Oligodendroglia; Phenotype; Process; Production; Proteins; Quality Control; Ribosomes; Role; Schwann Cells; Signal Pathway; Structure; Surface; Testing; Translations; Work; dysmyelination; endoplasmic reticulum stress; insight; mouse model; myelination; neuronal cell body; novel; overexpression; preservation; protein folding; protein function; proteostasis; response; young adult

Project Summary/Abstract: Myelinating cells, oligodendrocytes (OLs) in the CNS and Schwann cells (SCs) in the PNS, produce a vast amount of myelin sheath. Actively myelinating OLs and SCs must produce enormous amounts of myelin proteins to assemble myelin sheath during development. Mature OLs and SCs in adults need to produce a substantial amount of myelin proteins to maintain myelin structure homeostasis. Myelin proteins are synthesized, modified, and folded in the endoplasmic reticulum (ER). Maintaining ER protein homeostasis is essential and necessary for the function of myelinating cells. Currently available data indicate that actively myelinating OLs and SCs are more sensitive to disruption of ER protein homeostasis than mature OLs and SCs, due to the rate of myelin protein production. Nevertheless, the mechanisms by which myelinating cells maintain ER protein homeostasis remain unexplored. Misfolded/unfolded proteins in the ER are detected and degraded by a process known as ER-associated degradation (ERAD). In response to ER stress, activation of the unfolded protein response (UPR), which comprises three parallel signaling pathways PERK, IRE1, and ATF6α, restores ER protein homeostasis by facilitating protein folding, attenuating protein translation, and enhancing ERAD. Deletion of either PERK or ATF6α does not affect myelinating cells under normal conditions. Surprisingly, our preliminary results showed that double deletion of PERK and ATF6α in myelinating cells led to late-onset dysmyelination in the CNS of adult mice. Both PERK activation and ATF6α activation stimulates the expression of genes related to the Sel1L-Hrd1 complex, the best-characterized ERAD machinery. Intriguingly, our preliminary observation showed that Sel1L inactivation specifically in myelinating cells led to adult-onset dysmyelination in mice. Data indicate that overexpression of PLP, the most abundant myelin protein in the CNS and a substrate of ERAD, leads to soma retention of PLP in OLs, resulting in adult-onset dysmyelination in the CNS. Importantly, our preliminary data showed that both Sel1L inactivation and inactivation of PERK and ATF6α induced soma retention of PLP in OLs. Thus, in this proposal, we will test the hypothesis that the UPR is required for maintaining ER protein homeostasis and the viability and function of mature OLs in adults by regulating ERAD of PLP. In Aim 1, we will demonstrate that inactivation of PERK and ATF6α impairs the viability and function of mature OLs in adult mice. In Aim 2, we will demonstrate that Sel1L inactivation impairs the viability and function of mature OLs and SCs in adult mice. In Aim 3, we will determine if Sel1L inactivation compromises the viability and function of mature OLs through impairment of ERAD of PLP and subsequent soma retention of PLP. This work will uncover a mechanism responsible for maintaining ER protein homeostasis in mature OLs. The knowledge gained from these studies will advance our understanding of the biology of myelinating cells.

项目概要/摘要： CNS中的髓鞘形成细胞、少突胶质细胞（OL）和PNS中的许旺细胞（SC）产生大量的 髓鞘数量。活跃髓鞘形成的OL和SC必须产生大量的髓鞘 在发育过程中组装髓鞘的蛋白质。成年人中成熟的OL和SC需要产生一种 大量髓鞘蛋白质以维持髓鞘结构稳态。髓鞘蛋白质是 在内质网（ER）中合成、修饰和折叠。维持ER蛋白的稳态是 是髓鞘形成细胞功能所必需的。现有数据表明，积极 髓鞘化OL和SC比成熟OL对ER蛋白稳态的破坏更敏感， SC，由于髓鞘蛋白质产生的速率。然而，髓鞘形成细胞 维持内质网蛋白稳态仍是未知。检测ER中的错误折叠/未折叠蛋白， 被称为ER相关降解（ERAD）的过程降解。响应于ER应激， 未折叠蛋白反应（UPR），其包括三个平行的信号传导途径PERK、IRE 1和 ATF 6 α，通过促进蛋白质折叠，减弱蛋白质翻译， 增强ERAD。PERK或ATF 6 α的缺失在正常条件下不影响髓鞘形成细胞。 令人惊讶的是，我们的初步结果表明，髓鞘形成细胞中PERK和ATF 6 α的双缺失导致了 成年小鼠中枢神经系统迟发性髓鞘形成障碍。PERK激活和ATF 6 α激活均刺激 与Sel 1 L-Hrd 1复合物相关的基因的表达，Sel 1 L-Hrd 1复合物是最具特征的ERAD机制。 有趣的是，我们的初步观察表明，在髓鞘形成细胞中特异性的Sel 1 L失活导致了 小鼠的成年期髓鞘形成障碍。数据表明，PLP，最丰富的髓鞘， CNS中的蛋白质和ERAD的底物，导致索马在OL中保留PLP，导致成人发作 CNS中的髓鞘形成障碍。重要的是，我们的初步数据表明，Sel 1 L失活和 PERK和ATF 6 α失活诱导PLP在OLs中的索马滞留。因此，在本提案中，我们将测试 假设UPR是维持ER蛋白稳态和细胞活力和功能所必需的， 通过调节PLP的ERAD在成人中成熟OL。在目标1中，我们将证明PERK和 ATF 6 α损害成年小鼠成熟OL的活力和功能。在目标2中，我们将证明Sel 1 L 失活损害成年小鼠中成熟OL和SC的活力和功能。在目标3中，我们将确定 如果Sel 1 L失活通过损害PLP的ERAD而损害成熟OL的活力和功能， 以及随后的PLP的索马滞留。这项工作将揭示一种机制，负责维持ER 成熟OL中的蛋白质稳态。从这些研究中获得的知识将促进我们的理解 髓鞘细胞生物学的最新进展。