The Role of Sortilin in the Regulation of Apolipoprotein B Secretion from the liver and heart

项目摘要 包括冠状动脉疾病（CAD）和2型糖尿病（T2 D）在内的心脏代谢疾病是主要的 所有社会的死亡和发病原因。这些和其他代谢性疾病具有共同的病因学 损伤，包括血脂异常，富含甘油三酯的脂蛋白（TRL）的病理性升高和低密度脂蛋白（LDL） 脂蛋白胆固醇（LDL-C），治疗这些风险因素已被证明可以减少疾病负担， 进展虽然他汀类药物有效降低LDL-C，但许多人对其不良反应不耐受， 这些药物可能不能解决由其他致动脉粥样硬化脂蛋白引起的残余血管风险 TRL，包括极低密度脂蛋白（VLDL）。VLDL是合成LDL的前体， 从肝脏分泌，为外周组织提供甘油三酯，因此是一种未充分开发的潜力 减少TRL介导的血脂异常的途径是抑制肝脏VLDL分泌。VLDL的调节 分泌是复杂的并且不完全了解。载脂蛋白B（apoB）是一种重要的蛋白质组分， VLDL在肝细胞中通过多种调节途径在严格的转录后控制下合成， 并从肝细胞分泌到循环中，以甘油三酯的形式提供营养， 外周组织随着apoB成熟， 分泌的VLDL颗粒，特别是在内质网后区室中，知之甚少。一种新型 由血浆脂质性状的全基因组关联研究（GWAS）产生的基因是SORT 1基因， 编码分拣蛋白，一种普遍表达的多配体分拣受体。我们的实验室以前建立 SORT 1作为与血浆胆固醇和CAD相关的基因组位点的致病基因， 表明分拣蛋白负调节VLDL-apoB分泌。然而，详细的分子 分拣蛋白调节apoB代谢和VLDL分泌的潜在机制仍不清楚。的 对分拣蛋白如何调节脂蛋白代谢和心脏代谢风险的精确理解， 重要的治疗意义。因此，本研究金提案的目标是充分阐明 肝脏和心脏中分拣蛋白对VLDL-apoB代谢的机制和协调。具体来说，博士。 Conlon将研究肝分拣蛋白调节ER后apoB降解命运的假设 并输出以对抗脂质过载和分泌应激，分拣蛋白的功能是协调细胞内 apoB代谢对到达高尔基体的apoB颗粒的数量和质量以及 ER后分泌前蛋白水解（PERPP）活性。为了验证这一假设，Sort 1肝特异性基因敲除小鼠 并且将在存在各种应激源的情况下使用体外肝细胞模型。此外，她将 探索apoB分泌如何保护心肌细胞免受脂毒性，以及分拣蛋白在调节脂毒性中的作用。 心脏apoB分泌。该提案还旨在对康伦博士进行新技术培训并提供指导 使她能够过渡到一个独立的调查员与职业生涯的学术。

PROJECT SUMMARY Cardiometabolic diseases including coronary artery disease (CAD) and type 2 diabetes (T2D) are major causes of death and morbidity in all societies. These and other metabolic diseases have common etiological insults, including dyslipidemia, the pathological elevation of triglyceride-rich lipoproteins (TRLs) and low-density lipoprotein cholesterol (LDL-C), and treating these risk factors has been shown to reduce disease burden and progression. While statins effectively lower LDL-C, many people are intolerant to their adverse effects and these drugs may not address the residual vascular risk conferred by other proatherogenic lipoproteins such as TRLs, including very low density lipoproteins (VLDLs). VLDLs are precursors to LDL that are synthesized and secreted from the liver to provide triglycerides to peripheral tissues, and thus one underexplored potential avenue for reducing TRL-mediated dyslipidemia is to curb hepatic VLDL secretion. The regulation of VLDL secretion is complex and incompletely understood. Apolipoprotein B (apoB), the key protein component of VLDL, is synthesized in the hepatocyte under tight post-transcriptional control by multiple regulatory pathways, and secreted from the hepatocyte into the circulation to provide nutrition in the form of triglycerides to peripheral tissues. The precise coordination of the pathways governing the fate of apoB as matures into secreted VLDL particles, especially in post-endoplasmic reticulum compartments, is poorly known. A novel gene arising from genome-wide association studies (GWAS) for plasma lipid traits is the SORT1 gene, encoding sortilin, a ubiquitously expressed multi-ligand sorting receptor. Our laboratory previously established SORT1 as the causal gene at the genomic locus associated with plasma cholesterol and CAD and demonstrated that sortilin negatively regulates VLDL-apoB secretion. However, the detailed molecular mechanisms underlying sortilin’s regulation of apoB metabolism and VLDL secretion remain unknown. The precise understanding of how sortilin regulates lipoprotein metabolism and cardiometabolic risk may have important therapeutic implications. The goal of this fellowship proposal is thus to fully elucidate the mechanisms and coordination of VLDL-apoB metabolism by sortilin in the liver and the heart. Specifically, Dr. Conlon will investigate the hypothesis that hepatic sortilin regulates the post-ER fate of apoB for degradation and export to combat lipid overload and secretory stress and that sortilin functions to coordinate intracellular apoB metabolism in response to the number and quality of apoB particles that reach the Golgi and the level of post-ER pre-secretory proteolysis (PERPP) activity. To test this hypothesis, Sort1 liver specific knockout mice and in vitro hepatocyte models will be utilized in the presence of various stressors. Additionally, she will explore how apoB secretion might protect cardiomyocytes from lipotoxicity and the role of sortilin in regulating cardiac apoB secretion. This proposal also aims train Dr. Conlon in new techniques and provide mentoring to allow her to transition into an independent investigator with a career in academics.