Regulation of VLDL Transport and Secretion

VLDL 运输和分泌的调节

• 批准号: 10375546
• 负责人: Shadab A Siddiqi
• 金额: $ 33.53万
• 依托单位: UNIVERSITY OF CENTRAL FLORIDA
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-17 至 2024-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10375546
• 关键词: ADP-Ribosylation Factor 1; Affect; Atherosclerosis; Biochemical; Biogenesis; Blood; Cell membrane; Coat Protein Complex I; Complex; Data; Dyslipidemias; Endoplasmic Reticulum; Event; Fatty Acid-Binding Protein 1; Fatty Liver; Goals; Golgi Apparatus; Hepatic; Hepatocyte; Homeostasis; Hyperlipidemia; Intracellular Transport; Knockout Mice; Laboratories; Link; Lipids; Liver; Mediating; Membrane; Metabolic Diseases; Modeling; Molecular; Morphology; Peptides; Phosphorylation; Physiological Processes; Plasma; Process; Protein Isoforms; Protein Kinase; Protein Kinase C; Proteins; Proteomics; RBP4 gene; Regulation; Reporting; Role; SNAP receptor; Testing; Transmembrane Transport; Transport Process; Very low density lipoprotein; Vesicle; density; insight; knock-down; mutant; nano; novel; oxysterol binding protein; protein transport; therapeutic target; trafficking; trans-Golgi Network; vesicle transport; vesicle-associated membrane protein

Secretion of very-low-density lipoprotein (VLDL) from the liver is tightly controlled by its complex intracellular transport events. Aberrant VLDL secretion causes imbalance in lipid homeostasis which is associated with many metabolic diseases such as hyperlipidemia, hepatic steatosis etc. Biogenesis of VLDLs occurs in hepatic endoplasmic reticulum (ER); however, their maturation occurs in the Golgi. We have characterized the ER-to- Golgi VLDL transport process that is unique to the liver and have identified key regulators of this step; however, the transport of mature VLDL from the TGN to the PM for its secretion remains to be studied at the molecular level. In Aim 1, we extend our ongoing studies of determining the regulatory aspects of ER-to-Golgi transport. We have shown that SVIP is required for VTV biogenesis from the ER and VLDL secretion from hepatocytes. Our preliminary studies suggest that SVIP gets phosphorylated during VTV biogenesis; however, a specific protein kinase that phosphorylates SVIP is not known. We propose to identify the specific protein kinase that phosphorylates SVIP in Aim 1. Because phosphorylation of SVIP is specifically associated with VTV biogenesis and thus VLDL secretion, identification of a specific protein kinase will provide a novel selective target in controlling VLDL secretion. In Aim 2 and Aim 3, we propose to delineate the molecular machinery that regulates the post-TGN trafficking of mature VLDL. Our preliminary data suggest that mature VLDLs are transported from the TGN to the PM in distinct transport vesicles, the post-Golgi VLDL transport vesicle (PG-VTV), which are morphologically and biochemically different from other TGN-derived protein transport vesicles (PTV). Since the PG-VTV is distinct in its size, cargo, buoyant density and protein composition, we hypothesize that proteins, not previously considered important in the TGN-to-PM transport, mediate VLDL-selection and PG-VTV formation. These proteins are postulated to be important for cargo-selection, vesicle biogenesis and PG-VTV fusion with PM. In Aim 2, we propose to identify cargo-selecting protein that is required for effective packaging of mature VLDL in PG-VTV. We recently reported that L-FABP is required for normal VLDL secretion; however, the underlying mechanism is not known. In Aim 3, we will define the role of L-FABP and RBP4 in VLDL secretion from the liver. The proposed studies will shed new molecular insights into the poorly understood process of how mature VLDL is selected into the PG-VTV and is being transported to the PM for its eventual secretion in the blood and link these processes to identify potential targets in controlling VLDL secretion.

肝脏中非常低密度脂蛋白（VLDL）的分泌受其复杂的细胞内转运事件的紧密控制。异常的VLDL分泌会导致脂质稳态中的失衡，这与许多代谢性疾病（如高脂血症，肝脂肪变性等）有关。肝内质网（ER）发生VLDL的生物发生。但是，它们的成熟发生在高尔基体中。我们已经表征了肝脏独有的ER-GOLGI VLDL运输过程，并确定了此步骤的关键调节剂。然而，成熟的VLDL从TGN到PM的分泌尚待研究。在AIM 1中，我们扩展了我们正在进行的研究，以确定ER到高尔基运输的调节方面。我们已经表明，从肝细胞中的ER和VLDL分泌中，SVIP是VTV生物发生所必需的。我们的初步研究表明，在VTV生物发生过程中，SVIP磷酸化。但是，尚不清楚一种磷酸化SVIP的特定蛋白激酶。我们建议确定在AIM 1中磷酸化SVIP的特定蛋白激酶。因为SVIP的磷酸化与VTV生物发生特别相关，因此VLDL分泌，因此对特定蛋白激酶的鉴定将为控制VLDL分泌提供新的选择性靶标。在AIM 2和AIM 3中，我们建议描述调节成熟VLDL的TGN贩运后的分子机制。我们的初步数据表明，成熟的VLDL在不同的转运囊泡，Golgi VLDL转运囊泡（PG-VTV）中从TGN转移到PM，它们在形态和生化上与其他TGN衍生的蛋白质转运囊泡（PTV）在形态上和生化上不同。由于PG-VTV的大小，货物，浮力密度和蛋白质组成是不同的，因此我们假设蛋白质（以前在TGN-PM转运中都不重要，蛋白质在TGN-PM转运中不重要，介导VLDL选择和PG-VTV形成。这些蛋白质被认为对货物选择，囊泡生物发生和与PM的PG-VTV融合很重要。在AIM 2中，我们建议鉴定有效包装PG-VTV中成熟VLDL所需的货物选择蛋白。我们最近报道说，正常的VLDL分泌需要L-FABP。但是，基本机制尚不清楚。在AIM 3中，我们将定义L-FABP和RBP4在肝脏中VLDL分泌中的作用。拟议的研究将使人们对如何选择成熟的VLDL选择到PG-VTV的过程中，从而提供新的分子见解，并将其运输到PM中，以最终在血液中分泌，并将这些过程与控制VLDL分泌的潜在目标联系起来。