scholarly journals Rab8-dependent Recycling Promotes Endosomal Cholesterol Removal in Normal and Sphingolipidosis Cells

2007 ◽  
Vol 18 (1) ◽  
pp. 47-56 ◽  
Author(s):  
Matts D. Linder ◽  
Riikka-Liisa Uronen ◽  
Maarit Hölttä-Vuori ◽  
Peter van der Sluijs ◽  
Johan Peränen ◽  
...  
Keyword(s):  
Cholesterol Efflux ◽  
Ldl Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Receptor Activation ◽  
Cholesterol Esterification ◽  
Rab Gtpase ◽  
Cell Periphery ◽  
Regulatory Machinery ◽  
Niemann Pick

The mechanisms by which low-density lipoprotein (LDL)-cholesterol exits the endocytic circuits are not well understood. The process is defective in Niemann–Pick type C (NPC) disease in which cholesterol and sphingolipids accumulate in late endosomal compartments. This is accompanied by defective cholesterol esterification in the endoplasmic reticulum and impaired ATP-binding cassette transporter A1 (ABCA1)-dependent cholesterol efflux. We show here that overexpression of the recycling/exocytic Rab GTPase Rab8 rescued the late endosomal cholesterol deposition and sphingolipid mistrafficking in NPC fibroblasts. Rab8 redistributed cholesterol from late endosomes to the cell periphery and stimulated cholesterol efflux to the ABCA1-ligand apolipoprotein A-I (apoA-I) without increasing cholesterol esterification. Depletion of Rab8 from wild-type fibroblasts resulted in cholesterol deposition within late endosomal compartments. This cholesterol accumulation was accompanied by impaired clearance of LDL-cholesterol from endocytic circuits to apoA-I and could not be bypassed by liver X receptor activation. Our findings establish Rab8 as a key component of the regulatory machinery that leads to ABCA1-dependent removal of cholesterol from endocytic circuits.

scholarly journals Interplay between Asters/GRAMD1s and phosphatidylserine in intermembrane transport of LDL cholesterol

2022 ◽  
Vol 119 (2) ◽  
pp. e2120411119
Author(s):  
Michael N. Trinh ◽  
Michael S. Brown ◽  
Joachim Seemann ◽  
Gonçalo Vale ◽  
Jeffrey G. McDonald ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Ldl Cholesterol ◽  
Chinese Hamster Ovary Cells ◽  
Low Density Lipoprotein ◽  
Chinese Hamster ◽  
Density Lipoprotein ◽  
Cholesterol Esterification ◽  
Gene Encoding ◽  
Ovary Cells ◽  
Genes Encoding

Low-density lipoprotein (LDL) delivers cholesterol to mammalian cells through receptor-mediated endocytosis. The LDL cholesterol is liberated in lysosomes and transported to the plasma membrane (PM) and from there to the endoplasmic reticulum (ER). Excess ER cholesterol is esterified with a fatty acid for storage as cholesteryl esters. Recently, we showed that PM-to-ER transport of LDL cholesterol requires phosphatidylserine (PS). Others showed that PM-to-ER transport of cholesterol derived from other sources requires Asters (also called GRAMD1s), a family of three ER proteins that bridge between the ER and PM by binding to PS. Here, we use a cholesterol esterification assay and other measures of ER cholesterol delivery to demonstrate that Asters participate in PM-to-ER transport of LDL cholesterol in Chinese hamster ovary cells. Knockout of the gene encoding PTDSS1, the major PS-synthesizing enzyme, lowered LDL-stimulated cholesterol esterification by 85%, whereas knockout of all three Aster genes lowered esterification by 65%. The reduction was even greater (94%) when the genes encoding PTDSS1 and the three Asters were knocked out simultaneously. We conclude that Asters participate in LDL cholesterol delivery from PM to ER, and their action depends in large part, but not exclusively, on PS. The data also indicate that PS participates in another delivery pathway, so far undefined, that is independent of Asters.

scholarly journals The intracellular transport of low density lipoprotein-derived cholesterol is defective in Niemann-Pick type C fibroblasts.

1989 ◽  
Vol 108 (5) ◽  
pp. 1625-1636 ◽  
Author(s):  
L Liscum ◽  
R M Ruggiero ◽  
J R Faust
Keyword(s):  
Plasma Membrane ◽  
Intracellular Transport ◽  
Ldl Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Cholesterol Transport ◽  
Low Density ◽  
Unesterified Cholesterol ◽  
Type C ◽  
Niemann Pick

Niemann-Pick disease type C (NPC) is characterized by substantial intracellular accumulation of unesterified cholesterol. The accumulation of unesterified cholesterol in NPC fibroblasts cultured with low density lipoprotein (LDL) appears to result from the inability of LDL to stimulate cholesterol esterification in addition to impaired LDL-mediated downregulation of LDL receptor activity and cellular cholesterol synthesis. Although a defect in cholesterol transport in NPC cells has been inferred from previous studies, no experiments have been reported that measure the intracellular movement of LDL-cholesterol specifically. We have used four approaches to assess intracellular cholesterol transport in normal and NPC cells and have determined the following: (a) mevinolin-inhibited NPC cells are defective in using LDL-cholesterol for growth. However, exogenously added mevalonate restores cell growth equally in normal and NPC cells; (b) the transport of LDL-derived [3H]cholesterol to the plasma membrane is slower in NPC cells, while the rate of appearance of [3H]acetate-derived, endogenously synthesized [3H]cholesterol at the plasma membrane is the same for normal and NPC cells; (c) in NPC cells, LDL-derived [3H]cholesterol accumulates in lysosomes to higher levels than normal, resulting in defective movement to other cell membranes; and (d) incubation of cells with LDL causes an increase in cholesterol content of NPC lysosomes that is threefold greater than that observed in normal lysosomes. Our results indicate that a cholesterol transport defect exists in NPC that is specific for LDL-derived cholesterol.

scholarly journals Adenovirus RIDα uncovers a novel pathway requiring ORP1L for lipid droplet formation independent of NPC1

2013 ◽  
Vol 24 (21) ◽  
pp. 3309-3325 ◽  
Author(s):  
Nicholas L. Cianciola ◽  
Diane J. Greene ◽  
Richard E. Morton ◽  
Cathleen R. Carlin
Keyword(s):  
Ldl Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Loss Of Function ◽  
Major Pathway ◽  
Alternative Pathways ◽  
Oxysterol Binding Protein ◽  
Niemann Pick Disease ◽  
Niemann Pick ◽  
Cholesterol Storage

Niemann–Pick disease type C (NPC) is caused by mutations in NPC1 or NPC2, which coordinate egress of low-density-lipoprotein (LDL)-cholesterol from late endosomes. We previously reported that the adenovirus-encoded protein RIDα rescues the cholesterol storage phenotype in NPC1-mutant fibroblasts. We show here that RIDα reconstitutes deficient endosome-to-endoplasmic reticulum (ER) transport, allowing excess LDL-cholesterol to be esterified by acyl-CoA:cholesterol acyltransferase and stored in lipid droplets (LDs) in NPC1-deficient cells. Furthermore, the RIDα pathway is regulated by the oxysterol-binding protein ORP1L. Studies have classified ORP1L as a sterol sensor involved in LE positioning downstream of GTP-Rab7. Our data, however, suggest that ORP1L may play a role in transport of LDL-cholesterol to a specific ER pool designated for LD formation. In contrast to NPC1, which is dispensable, the RIDα/ORP1L-dependent route requires functional NPC2. Although NPC1/NPC2 constitutes the major pathway, therapies that amplify minor egress routes for LDL-cholesterol could significantly improve clinical management of patients with loss-of-function NPC1 mutations. The molecular identity of putative alternative pathways, however, is poorly characterized. We propose RIDα as a model system for understanding physiological egress routes that use ORP1L to activate ER feedback responses involved in LD formation.

scholarly journals Selective Aster inhibitors distinguish vesicular and nonvesicular sterol transport mechanisms

2020 ◽  
Vol 118 (2) ◽  
pp. e2024149118
Author(s):  
Xu Xiao ◽  
Youngjae Kim ◽  
Beatriz Romartinez-Alonso ◽  
Kristupas Sirvydis ◽  
Daniel S. Ory ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Ldl Cholesterol ◽  
Regulatory Element ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Transport Mechanisms ◽  
Sterol Transport ◽  
Niemann Pick ◽  
Small Molecule Modulators

The Aster proteins (encoded by the Gramd1a-c genes) contain a ligand-binding fold structurally similar to a START domain and mediate nonvesicular plasma membrane (PM) to endoplasmic reticulum (ER) cholesterol transport. In an effort to develop small molecule modulators of Asters, we identified 20α-hydroxycholesterol (HC) and U18666A as lead compounds. Unfortunately, both 20α-HC and U18666A target other sterol homeostatic proteins, limiting their utility. 20α-HC inhibits sterol regulatory element-binding protein 2 (SREBP2) processing, and U18666A is an inhibitor of the vesicular trafficking protein Niemann–Pick C1 (NPC1). To develop potent and selective Aster inhibitors, we synthesized a series of compounds by modifying 20α-HC and U18666A. Among these, AI (Aster inhibitor)-1l, which has a longer side chain than 20α-HC, selectively bound to Aster-C. The crystal structure of Aster-C in complex with AI-1l suggests that sequence and flexibility differences in the loop that gates the binding cavity may account for the ligand specificity for Aster C. We further identified the U18666A analog AI-3d as a potent inhibitor of all three Aster proteins. AI-3d blocks the ability of Asters to bind and transfer cholesterol in vitro and in cells. Importantly, AI-3d also inhibits the movement of low-density lipoprotein (LDL) cholesterol to the ER, although AI-3d does not block NPC1. This finding positions the nonvesicular Aster pathway downstream of NPC1-dependent vesicular transport in the movement of LDL cholesterol to the ER. Selective Aster inhibitors represent useful chemical tools to distinguish vesicular and nonvesicular sterol transport mechanisms in mammalian cells.

Moving beyond the “LDL hypothesis”

VASA ◽  
2015 ◽  
Vol 44 (5) ◽  
pp. 333-340 ◽  
Author(s):  
Christian Werner ◽  
Ulrich Laufs
Keyword(s):  
Ldl Cholesterol ◽  
Causal Relation ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Clinical Trial Data ◽  
Randomised Clinical Trial ◽  
Trial Data ◽  
Low Density Lipoprotein Cholesterol ◽  
Genetic Studies ◽  
Statin Drug

Abstract. Summary: The term “LDL hypothesis” is frequently used to describe the association of low-density lipoprotein cholesterol (LDL-cholesterol, LDL-C) and cardiovascular (CV) events. Recent data from genetic studies prove a causal relation between serum LDL-C and CV events. These data are in agreement with mechanistic molecular studies and epidemiology. New randomised clinical trial data show that LDL-C lowering with statins and a non-statin drug, ezetimibe, reduces CV events. We therefore believe that the “LDL-hypothesis” has been proven; the term appears to be outdated and should be replaced by “LDL causality”.

Platelet Aggregation and Plasma Lipoproteins in Alcoholics During Alcohol Withdrawal

1986 ◽  
Vol 55 (02) ◽  
pp. 173-177 ◽  
Author(s):  
K Desai ◽  
J S Owen ◽  
D T Wilson ◽  
R A Hutton
Keyword(s):  
Platelet Aggregation ◽  
Alcohol Withdrawal ◽  
Ldl Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Hdl Cholesterol ◽  
Plasma Lipoprotein ◽  
Cholesterol Concentration ◽  
Arachidonic Acid Content ◽  
Low Density

SummaryPlatelet aggregation, platelet lipid composition and plasma lipoprotein concentrations were measured each week in a group of seventeen alcoholics, without overt liver disease, for one month, following acute, total alcohol withdrawal. The platelets were initially hypoaggregable but, within 1-2 weeks of cessation of drinking, they became hyperaggregable and then gradually returned towards normal values. Hyperaggregability could not be explained by increases in either the cholesterol or the arachidonic acid content of the platelets. Plasma very-low-density lipoprotein cholesterol levels remained high throughout the study, but the initially raised levels of high-density lipoprotein (HDL) cholesterol fell by 26%. Low-density lipoprotein (LDL) cholesterol concentration rose by 10% after two weeks of withdrawal but then returned to about the starting level. The resulting changes in the plasma LDL-cholesterol: HDL-cholesterol ratio, which had increased by more than 50% after two weeks of abstinence, essentially paralleled the time course of enhanced platelet reactivity in all but four of the alcoholics. These findings suggest that alterations in plasma lipoprotein concentrations during acute alcohol withdrawal may be a contributory factor to the haemostatic disorders present in such patients.

Risk factors for cardiovascular diseases and development of prehypertension

2018 ◽  
pp. 37-43
Author(s):  
В.В. Шерстнев ◽  
М.А. Грудень ◽  
В.П. Карлина ◽  
В.М. Рыжов ◽  
А.В. Кузнецова ◽  
...  
Keyword(s):  
Risk Factors ◽  
Blood Pressure ◽  
Cardiovascular Disease ◽  
Ldl Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Hdl Cholesterol ◽  
Serum Levels ◽  
Left Ventricular ◽  
Optimal Blood Pressure

Цель - исследование взаимосвязи факторов риска сердечно-сосудистых заболеваний и развития предгипертонии. Методика. Проведен сравнительный и корреляционный анализы показателей модифицируемых и немодифицируемых факторов риска сердечно-сосудистых заболеваний у обследованных лиц в возрасте 30-60 лет с «оптимальным» артериальным давлением, (n = 63, АД <120/80 мм рт.ст.) и лиц с предгипертонией (n = 52, АД = 120-139/80-89 мм рт.ст.). Результаты. Показано, что лица с предгипертонией по сравнению с группой лиц, имеющих «оптимальное» артериальное давление характеризуются статистически значимо повышенным содержанием холестерина и холестерина липопротеидов низкой плотности, интеллектуальным характером трудовой деятельности, а также значимыми сочетаниями факторов риска: повышенный уровень холестерина липопротеидов низкой плотности с интеллектуальным характером трудовой деятельности; повышенное содержание креатинина с уровнем триглициридов; наследственная отягощенность по заболеваниям почек и интеллектуальным характером трудовой деятельности; наследственная отягощенность по сахарному диабету и гипертрофия левого желудочка сердца. У лиц с предгипертонией документированы перестройки структуры взаимосвязи (количество, направленность и сила корреляций) между показателями факторов риска в сравнении с лицами, имеющими «оптимальное» артериальное давление. Заключение. Выявленные особенности взаимосвязей факторов риска сердечно-сосудистых заболеваний при предгипертонии рассматриваются как проявление начальной стадии дизрегуляционной патологии и нарушения регуляции физиологических систем поддержания оптимального уровня артериального давления. The aim of the study was to investigate the relationship between risk factors for cardiovascular disease and development of prehypertension. Methods. Comparative and correlation analyses of modifiable and non-modifiable risk factors for cardiovascular disease were performed in subjects aged 30-60 with «optimal» blood pressure (n = 63, BP <120/80 mm Hg) and prehypertension (n = 52, BP = 120-139 / 80-89 mm Hg). Results. The group with prehypertension compared with the «optimal» blood pressure group had significantly increased serum levels of low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol, sedentary/intellectual type of occupation, and significant combinations of risk factors. The risk factor combinations included an increased level of LDL cholesterol and a sedentary/intellectual occupation; increased serum levels of creatinine and triglycerides; hereditary burden of kidney disease and a sedentary/intellectual occupation; hereditary burden of diabetes mellitus and cardiac left ventricular hypotrophy. In subjects with prehypertension compared to subjects with «optimal» blood pressure, changes in correlations (correlation number, direction, and strength) between parameters of risk factors were documented. Conclusion. The features of interrelationships between risk factors for cardiovascular disease observed in prehypertension are considered a manifestation of early dysregulation pathology and disordered regulation of physiological systems, which maintain optimal blood pressure.

scholarly journals Effects of Weight Gain after 20 Years of Age and Incidence of Hyper-Low-Density Lipoprotein Cholesterolemia: The Iki Epidemiological Study of Atherosclerosis and Chronic Kidney Disease (ISSA-CKD)

2021 ◽  
Vol 10 (14) ◽  
pp. 3098
Author(s):  
Shota Okutsu ◽  
Yoshifumi Kato ◽  
Shunsuke Funakoshi ◽  
Toshiki Maeda ◽  
Chikara Yoshimura ◽  
...  
Keyword(s):  
Weight Gain ◽  
General Population ◽  
Ldl Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Population Based ◽  
Lipid Lowering ◽  
Low Density ◽  
Obesity Hypertension ◽  
Old Men

The aim of this study was to investigate the effects of long-term weight gain from the age of 20 on incidence of hyper-low-density-lipoprotein (LDL) cholesterolemia in the general population of Japanese people. Methods: We conducted a population-based retrospective cohort study using annual health checkup data for residents of Iki City, Nagasaki Prefecture, Japan. A total of 3179 adult (≥30 years old) men and women without hyper-LDL cholesterolemia at baseline, who underwent two or more health checkups were included in the analysis. Information on weight gain (≥10 kg) after 20 years of age was obtained using questionnaire. The outcome of this study was development of hyper-LDL cholesterolemia defined as LDL-cholesterol level ≥3.62 mmol/L and/or initiation of lipid-lowering medications. Results: During a mean follow-up period of 4.53 years, 665 of the 3179 participants developed hyper-LDL cholesterolemia (46.5/1000 person-years). The incidence of hyper-LDL cholesterolemia was higher in participants with a weight gain of ≥10 kg (55.3/1000 person-years) than among those with a weight gain of <10 kg (41.8/1000 person-years). This association remained statistically significant even after adjustment for age, sex, smoking, daily drinking, exercise, obesity, hypertension, and diabetes (multivariable hazard ratio 1.31, 95% confidence interval 1.08–1.58, p = 0.006). Conclusion: A weight gain of ≥10 after 20 years of age affected the development of hyper-LDL cholesterol regardless of age, sex, and obesity in a general population of Japanese.

scholarly journals Particles and corrected particles of LDL and non-HDL are stronger predicters of coronary lesion in postmenopausal women

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Chuang Li ◽  
Jingxun Chen ◽  
Siyue Wei ◽  
Mei Zhang ◽  
Yushun Chu ◽  
...  
Keyword(s):  
Risk Factors ◽  
Postmenopausal Women ◽  
Apolipoprotein B ◽  
Operating Characteristic ◽  
Ldl Cholesterol ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Hdl Cholesterol ◽  
Spearman Correlation ◽  
Coronary Lesion

Abstract Background The optimum lipid indexes, predicting the coronary lesion in postmenopausal women are not clear. Objective To evaluate the optimum lipid predicter for coronary lesion in routine and advanced lipid tests. Method 300 postmenopausal women were enrolled and assigned into coronary heart disease (CHD) Group (242), and non-CHD Group (58). Routine and advanced lipid indexes were measured with standard laboratory test and nuclear magnetic resonance (NMR) spectroscopy. The correlation and predictivities for CHD of routine and advanced lipid indexes were performed with Logistic regression, Spearman correlation analysis and receiver operating characteristic (ROC). Results Age (hazard ratio (HR) 2.58, 95% confidence interval (CI) 1.08–5.86, P = 0.03), apolipoprotein B (ApoB) (HR 1.35, 95% CI 1.15–1.59, P < 0.001), corrected particles of low-density lipoprotein (LDL-p-corr) (HR 1.05, 95% CI 1.03–1.06, P < 0.001) and corrected particles of non-high-density lipoprotein (non-HDL-p-corr) (HR 1.02, 95% CI 1.01–1.03, P < 0.001) were the risk factors of CHD. LDL cholesterol (LDL-C), LDL-p, LDL-p-corr, HDL cholesterol (HDL-C), non-HDL cholesterol (non-HDL-C), non-HDL-p and non-HDL-p-corr were in linear correlation with Gensini score. Advanced lipid indexes LDL-p (area under curve (AUC) = 0.750, P = 0.02), LDL-p-corr (AUC = 0.759, P = 0.02), non-HDL-p (AUC = 0.693, P = 0.03) and non-HDL-p-corr (AUC = 0.699, P = 0.03) were more predictive for CHD than the routine ones (LDL-C and non-HDL-C). Conclusion In postmenopausal women, age, ApoB, LDL-p-corr and non-HDL-p-corr were risk factors of CHD. Compared with traditional lipid items, LDL-p, LDL-p-corr, non-HDL-p and non-HDL-p-corr may be better lipid indexes for CHD in postmenopausal women.

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