Novel mechanism underlying fibrinogen biogenesis in the endoplasmic reticulum

内质网纤维蛋白原生物发生的新机制

• 批准号: 10681373
• 负责人: Shengyi Sun
• 金额: $ 5.76万
• 依托单位: WAYNE STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-15 至 2024-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10681373
• 关键词: Adult; Age; Age Months; Autophagocytosis; Biochemical; Biogenesis; Biological Assay; Blood coagulation; Coagulation Process; Data; Disease; Dominant-Negative Mutation; Endoplasmic Reticulum; Event; Exhibits; FGF21 gene; Fibrinogen; Growth; Hemorrhage; Hepatic; Hepatocyte; Homeostasis; Human; Imaging Techniques; Inclusion Bodies; Label; Liver; Missense Mutation; Molecular; Molecular Chaperones; Molecular Conformation; Mus; Pathogenesis; Pathogenicity; Pathologic; Patients; Proteins; Quality Control; Role; Testing; Therapeutic; Transmission Electron Microscopy; autosome; cell type; clinically relevant; disulfide bond; fibroblast growth factor 21; human disease; insight; liver injury; misfolded protein; mutant; novel; prevent; protein complex; protein misfolding; proteostasis; recruit; response; ubiquitin-protein ligase

A large number of diseases are now recognized as ‘conformational diseases’, caused by protein misfolding and subsequent aggregation. One example is hepatic fibrinogen storage disease (HFSD), where the underlying cause is the endoplasmic reticulum (ER) retention and aggregation of fibrinogen mutants, leading to liver damage, hypofibrinogenemia, and excessive bleeding. However, the molecular events underlying the biogenesis and quality control of, both wildtype and mutant fibrinogen, in the ER remain unknown. In the preliminary data of this application, we serendipitously found that the biogenesis of fibrinogen is regulated by the Sel1L-Hrd1 protein complex of the principal ER quality-control machinery, ER-associated degradation (ERAD). Sel1L-Hrd1 ERAD represents the most evolutionarily conserved branch of ERAD and targets misfolded ER proteins for cytosolic proteasomal degradation. Hepatocyte-specific Sel1L-deficient mice exhibit fibrinogen-containing inclusions in the ER of hepatocytes, hepatic damage and hypofibrinogenemia, resembling human patients with HFSD. Indeed, both wildtype and disease-causing mutants of fibrinogens are degraded by Sel1L-Hrd1 ERAD. These data point to a critical role of hepatocyte Sel1L-Hrd1 ERAD in fibrinogen biogenesis and live homeostasis. Hence, the overarching hypothesis of this application is that Sel1L-Hrd1 ERAD is a critical regulatory mechanism for fibrinogen biogenesis, coagulation and liver homeostasis by targeting misfolded, either wildtype or mutant, fibrinogen proteins for proteasomal degradation. This action of ERAD towards fibrinogen prevents the formation of toxic fibrinogen inclusions and aggregates in the liver. We will accomplish two Aims: (1) Demonstrate the significance and molecular mechanism of hepatic Sel1L-Hrd1 ERAD in coagulation and fibrinogen biogenesis; and (2) Delineate the pathological importance of Sel1L-Hrd1 ERAD in HFSD. Completion of these studies will not only delineate the significance and molecular mechanism underlying the ERAD function in early biogenesis of fibrinogen, but also have broader impact on the mechanism and therapeutical strategy for other conformational diseases associated with protein misfolding.

现在，大量疾病被认为是由蛋白质错误折叠和随后的聚集引起的“构象疾病”。一个例子是肝纤维蛋白原储存疾病（HFSD），其中的根本原因是纤维蛋白原突变体的内质网（ER）保留和聚集，导致肝损伤，低纤维蛋白原血症和多余的出血。但是，在ER中，生物发生和质量控制的分子事件仍然未知。在该应用程序的初步数据中，我们偶然发现纤维蛋白原的生物发生受主要ER质量控制机械的SEL1L-HRD1蛋白复合物调节，ER相关降解（ERAD）。 SEL1L-HRD1 ERAD代表了ERAD的最进化保守的分支，并且靶向错误折叠的ER蛋白用于胞质蛋白酶体降解。肝细胞特异性SEL1L缺陷小鼠在肝细胞，乙型肝炎损伤和低纤维蛋白原血症的ER中暴露了含纤维蛋白原的夹杂物，类似于HFSD的人类患者。实际上，SEL1L-HRD1 ERAD降解了纤维蛋白的野生型和引起疾病的突变体。这些数据表明，肝细胞SEL1L-HRD1 ERAD在纤维蛋白原生物发生和活体内平衡中的关键作用。因此，该应用的总体假设是SEL1L-HRD1 ERAD是通过靶向错误折叠（野生型或突变体），纤维蛋白蛋白的纤维蛋白原生物发生，凝结和肝稳态的关键调节机制，用于蛋白质组下降。 ERAD对纤维蛋白原的这种作用阻止了肝脏中有毒纤维蛋白原夹杂物和聚集体的形成。我们将实现两个目标：（1）证明肝素SEL1L-HRD1在凝结和纤维蛋白原生物发生中的显着性和分子机制； （2）描述了HFSD中SEL1L-HRD1 ERAD的病理重要性。这些研究的完成不仅会描述纤维蛋白原早期生物发生中剥离功能的重要性和分子机制，而且还对与蛋白质误后折扣相关的其他构型疾病的机制和治疗策略产生更大的影响。