The Role of Phosphatidylinositides in Lipid Metabolism

磷脂酰肌醇在脂质代谢中的作用

基本信息

批准号：
10065516
负责人：
Marisa Wong Medina
金额：
$ 42.04万
依托单位：
UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-05-12 至 2022-11-30
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10065516
关键词：
American Animal Model Animals Autophagocytosis Autophagosome Back Binding Blood Cardiometabolic Disease Cell membrane Cell model Cell surface Cells Cholesterol Defect Development Early Endosome Endosomes Enzymes Eukaryotic Cell Family Fatty acid glycerol esters Female Four Core Genotypes Goals Gonadal Hormones Heart Diseases HepG2 Hepatic Hepatocyte Hormone use Impairment In Vitro Integral Membrane Protein Investigation Knock-out Knockout Mice Lead Lipids Lipoproteins Liver Low Density Lipoprotein Receptor Low-Density Lipoproteins Lysosomes Metabolic Diseases Metabolism Modeling Molecular Mus Nonesterified Fatty Acids Oculocerebrorenal Syndrome Pathway interactions Phenotype Phosphatidylinositols Phosphoric Monoester Hydrolases Plasma Play Ploidies Process Recycling Regulation Risk Factors Role Sex Chromosomes Stains Testing Triglycerides Vesicle cardiometabolic risk cardiovascular disorder prevention disorder risk fatty acid oxidation inhibitor/antagonist inositol-1,4,5-trisphosphate 5-phosphatase knock-down lipid biosynthesis lipid metabolism male mouse model non-alcoholic fatty liver disease novel therapeutics overexpression receptor receptor recycling sex therapeutic target trafficking uptake

项目摘要

SUMMARY As key directors of intracellular trafficking, phosphotidylinsotides (PIs) are a family of low abundance lipids that impact almost every process within the eukaryotic cell. The low-density lipoprotein receptor (LDLR), a major determinant of blood LDL levels, is the most efficacious therapeutic target for the prevention of cardiovascular disease. Upon LDL binding, LDLR at the cell surface is internalized, where it releases the bound LDL and then recycles back to the cell surface or is directed to the lysosome for degradation. Recently, we found that knock- down of transmembrane protein 55B (TMEM55B), a phosphatidylinositol (4,5) bisphosphate [PI(4,5)P] phosphatase, stimulated decay of LDLR protein in cells and raised plasma LDLC in mice. Since PI(4,5)P is involved in lysosome formation, we hypothesize that PI(4,5)P phosphatases (such as TMEM55B) may alter LDLC by regulating LDLR intracellular trafficking. We also found that reduction of PI(4,5)P phosphatases caused severely impaired secretion of triglycerides into plasma. Notably, this occurred without the accumulation of liver fat, and interestingly, was observed only in male mice, with no effect in females. The lack of hepatic fat accumulation may be attributed to a number of different mechanisms including increased lipophagy (a process of selective autophagy in which lipid droplets are targeted for lysosomal decay). PI(4,5)P is an important regulator of lysosome reformation after autophagosome fusion, and we found that TMEM55B knock-down increased lysosomes. These findings suggest that PI(4,5)P phosphatases may modulate hepatic TG secretion and storage through a lysosome-dependent mechanism. Thus, the overall objective of this proposal is to evaluate the role of PI(4,5)P in LDLR recycling and TG secretion. In Aim 1 we will i) Test if PI(4,5)P metabolizing enzymes impact plasma LDL in the absence of LDLR using genetically modified mouse models; ii) Evaluate the effect of modifying PI(4,5)P on Ldlr intracellular levels and localization in mouse hepatocytes; iii) Test if expression of enzymatically inactive Tmem55b rescues the phenotypes observed in the Tmem55b knockout mouse; and iv) Evaluate if PI(4,5)P phosphatase regulation of LDLR recycling is dependent on known regulators of LDLR decay. In Aim 2 we will i) Compare TG secretion in whole body versus liver-specific Tmem55b knockout male mice to confirm that the defect is a hepatic mechanism; ii) Test if lack of hepatic fat accumulation, as would be expected to result from impaired TG secretion, in hepatocytes from Tmem55b knockout mice is due to changes in fatty acid oxidation, synthesis, or uptake, or TG synthesis; iii) Determine PI(4,5)P phosphatases depend on lysosome and/or autophagosomes to impair TG secretion; and iv) Evaluate if the sex-specific effect of PI(4,5)P modulation of TG secretion is due to the sex chromosome complement (XX vs. XY) and/or gonadal hormones. Investigation of the role of PI(4,5)P in lipid and lipoprotein metabolism may lead to the development of new therapeutic options for reducing cardiometabolic disease risk.

概括作为细胞内贩运的关键主管，磷酸丁基固定剂（PI）是一个低丰度脂质的家族，影响真核细胞中的几乎每个过程。低密度脂蛋白受体（LDLR），主要血液LDL水平的决定因素是预防心血管的最有效的治疗靶点疾病。 LDL结合后，在细胞表面的LDLR被内在化，在此释放结合的LDL，然后回收回到细胞表面或针对溶酶体降解。最近，我们发现敲门跨膜蛋白55b（TMEM55B）的下降，一种磷脂酰肌醇（4,5）双磷酸[PI（4,5）P] 磷酸酶，刺激细胞中LDLR蛋白的衰减，并在小鼠中升高的血浆LDLC。因为Pi（4,5）p是参与溶酶体形成，我们假设PI（4,5）P磷酸酶（例如TMEM55B）可能会改变 LDLC通过调节LDLR细胞内贩运。我们还发现PI（4,5）P磷酸酶的降低引起将甘油三酸酯分泌到血浆中严重受损。值得注意的是，这是没有肝脏积累的情况脂肪和有趣的是仅在雄性小鼠中观察到，对女性没有影响。缺乏肝脂肪积累可能归因于多种不同的机制，包括增加脂肪（一个过程）选择性自噬的脂质液滴靶向溶酶体衰减）。 PI（4,5）P是重要的调节器自噬体融合后的溶酶体改革，我们发现TMEM55B敲低增加溶酶体。这些发现表明PI（4,5）P磷酸酶可能调节肝TG分泌和储存通过溶酶体依赖性机制。因此，该提案的总体目的是评估 LDLR回收和TG分泌中的Pi（4,5）p。在AIM 1中，我们将测试PI（4,5）P代谢酶的影响是否血浆LDL在没有基因修饰的小鼠模型的情况下没有LDLR的情况下； ii）评估修改的效果 LDLR细胞内水平和小鼠肝细胞中的定位pi（4,5）p； iii）测试酶的表达是否非活性TMEM55B营救了TMEM55B敲除小鼠中观察到的表型；和iv）评估是否 LDLR回收的PI（4,5）P磷酸酶调节取决于已知的LDLR衰变调节剂。在目标2中我们将比较全身与肝脏特异性TMEM55B敲除雄性小鼠的TG分泌以确认缺陷是一种肝机制； ii）测试如果缺乏肝脂肪的积累，预计会导致在TG分泌受损的情况下，在TMEM55B敲除小鼠的肝细胞中是由于脂肪酸的变化而引起的氧化，合成或摄取或TG合成； iii）确定PI（4,5）P磷酸酶取决于溶酶体和/或自噬体可损害TG分泌； iv）评估PI（4,5）P调制的性别特异性效应是否是否 TG分泌的是性染色体补体（XX与XY）和/或性腺激素。调查 PI（4,5）P在脂质和脂蛋白代谢中的作用可能导致新的治疗选择的发展用于降低心脏代谢疾病风险。