scholarly journals Wnt signaling activates MFSD2A to suppress vascular endothelial transcytosis and maintain blood-retinal barrier

2020 ◽  
Vol 6 (35) ◽  
pp. eaba7457
Author(s):  
Zhongxiao Wang ◽  
Chi-Hsiu Liu ◽  
Shuo Huang ◽  
Zhongjie Fu ◽  
Yohei Tomita ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Vision Loss ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Basic Function ◽  
Major Facilitator Superfamily ◽  
Dependent Manner ◽  
Omega 3 ◽  
Blood Retinal Barrier ◽  
Major Facilitator

Breakdown of the blood-retinal barrier (BRB) causes retinal edema and vision loss. We investigated the role of Wnt signaling in maintaining the BRB by limiting transcytosis. Mice lacking either the Wnt co-receptor low-density lipoprotein receptor–related protein 5 (Lrp5−/−) or the Wnt ligand Norrin (Ndpy/−) exhibit increased retinal vascular leakage and enhanced endothelial transcytosis. Wnt signaling directly controls the transcription of an endothelium-specific transcytosis inhibitor, major facilitator superfamily domain–containing protein 2a (MFSD2A), in a β-catenin–dependent manner. MFSD2A overexpression reverses Wnt deficiency–induced transcytosis in endothelial cells and in retinas. Moreover, Wnt signaling mediates MFSD2A-dependent vascular endothelium transcytosis through a caveolin-1 (CAV-1)–positive caveolae pathway. In addition, levels of omega-3 fatty acids are also decreased in Wnt signaling–deficient retinas, reflecting the basic function of MFSD2A as a lipid transporter. Our findings uncovered the Wnt/β-catenin/MFSD2A/CAV-1 axis as a key pathway governing endothelium transcytosis and inner BRB integrity.

scholarly journals eGFP-tagged Wnt-3a enables functional analysis of Wnt trafficking and signaling and kinetic assessment of Wnt binding to full-length Frizzled

2020 ◽  
Vol 295 (26) ◽  
pp. 8759-8774 ◽  
Author(s):  
Janine Wesslowski ◽  
Pawel Kozielewicz ◽  
Xianxian Wang ◽  
Haijun Cui ◽  
Hannes Schihada ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
3D Cell Culture ◽  
Binding Mode ◽  
Biologically Active ◽  
Live Cells ◽  
Dependent Manner ◽  
Biologically Relevant ◽  
Wnt Proteins

The Wingless/Int1 (Wnt) signaling system plays multiple, essential roles in embryonic development, tissue homeostasis, and human diseases. Although many of the underlying signaling mechanisms are becoming clearer, the binding mode, kinetics, and selectivity of 19 mammalian WNTs to their receptors of the class Frizzled (FZD1–10) remain obscure. Attempts to investigate Wnt-FZD interactions are hampered by the difficulties in working with Wnt proteins and their recalcitrance to epitope tagging. Here, we used a fluorescently tagged version of mouse Wnt-3a for studying Wnt-FZD interactions. We observed that the enhanced GFP (eGFP)-tagged Wnt-3a maintains properties akin to wild-type (WT) Wnt-3a in several biologically relevant contexts. The eGFP-tagged Wnt-3a was secreted in an evenness interrupted (EVI)/Wntless-dependent manner, activated Wnt/β-catenin signaling in 2D and 3D cell culture experiments, promoted axis duplication in Xenopus embryos, stimulated low-density lipoprotein receptor-related protein 6 (LRP6) phosphorylation in cells, and associated with exosomes. Further, we used conditioned medium containing eGFP-Wnt-3a to visualize its binding to FZD and to quantify Wnt-FZD interactions in real time in live cells, utilizing a recently established NanoBRET-based ligand binding assay. In summary, the development of a biologically active, fluorescent Wnt-3a reported here opens up the technical possibilities to unravel the intricate biology of Wnt signaling and Wnt-receptor selectivity.

Dynamic palmitoylation controls the microdomain localization of the DKK1 receptors CKAP4 and LRP6

2019 ◽  
Vol 12 (608) ◽  
pp. eaat9519 ◽  
Author(s):  
Ryota Sada ◽  
Hirokazu Kimura ◽  
Yuko Fukata ◽  
Masaki Fukata ◽  
Hideki Yamamoto ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Plasma Membrane ◽  
Wnt Signaling ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Dependent Manner ◽  
Promote Cell Proliferation ◽  
Akt Activation ◽  
Dependent Inhibition ◽  
Density Lipoprotein Receptor

Dickkopf1 (DKK1) was originally identified as an antagonist of Wnt signaling that binds to and induces the clathrin-mediated endocytosis of the Wnt coreceptors low-density lipoprotein receptor–related proteins 5 and 6 (LRP5/6). DKK1 also binds to cytoskeleton-associated protein 4 (CKAP4), which was originally identified as an endoplasmic reticulum (ER) protein but also functions at the plasma membrane as a receptor for various ligands. The DKK1-CKAP4 pathway is activated in several human cancers and promotes cell proliferation by activating signaling through the kinases PI3K and AKT. We found that both CKAP4 and LRP6 primarily localized to detergent-resistant membrane (DRM) fractions of the plasma membrane in a palmitoylation-dependent manner and that palmitoylation of CKAP4 was required for it to promote cell proliferation. DKK1 induced the depalmitoylation of both CKAP4 and LRP6 by acylprotein thioesterases (APTs), resulting in their translocation to the non-DRM fractions. Moreover, DKK1-dependent depalmitoylation of both receptors required activation of the PI3K-AKT pathway. DKK1 simultaneously bound CKAP4 and LRP6, resulting in the formation of a ternary complex. LRP5/6 knockdown decreased DKK1-dependent AKT activation and cancer cell proliferation through CKAP4, whereas CKAP4 knockdown did not affect DKK1-dependent inhibition of Wnt signaling through LRP5/6. These results indicate that the palmitoylation states of CKAP4 and LRP6 play important roles in their signaling and that LRP5/6 enhance DKK1-CKAP4 signaling.

scholarly journals Low-density lipoprotein receptor-related protein 1 (LRP1) is a novel receptor for apolipoprotein A4 (APOA4) in adipose tissue

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jie Qu ◽  
Sarah Fourman ◽  
Maureen Fitzgerald ◽  
Min Liu ◽  
Supna Nair ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Glucose Uptake ◽  
Molecular Mechanisms ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Lipoprotein Receptor ◽  
Dependent Manner ◽  
Related Protein ◽  
Density Lipoprotein Receptor ◽  
Lipoprotein Receptor Related Protein

AbstractApolipoprotein A4 (APOA4) is one of the most abundant and versatile apolipoproteins facilitating lipid transport and metabolism. APOA4 is synthesized in the small intestine, packaged onto chylomicrons, secreted into intestinal lymph and transported via circulation to several tissues, including adipose. Since its discovery nearly 4 decades ago, to date, only platelet integrin αIIbβ3 has been identified as APOA4 receptor in the plasma. Using co-immunoprecipitation coupled with mass spectrometry, we probed the APOA4 interactome in mouse gonadal fat tissue, where ApoA4 gene is not transcribed but APOA4 protein is abundant. We demonstrate that lipoprotein receptor-related protein 1 (LRP1) is the cognate receptor for APOA4 in adipose tissue. LRP1 colocalized with APOA4 in adipocytes; it interacted with APOA4 under fasting condition and their interaction was enhanced during lipid feeding concomitant with increased APOA4 levels in plasma. In 3T3-L1 mature adipocytes, APOA4 promoted glucose uptake both in absence and presence of insulin in a dose-dependent manner. Knockdown of LRP1 abrogated APOA4-induced glucose uptake as well as activation of phosphatidylinositol 3 kinase (PI3K)-mediated protein kinase B (AKT). Taken together, we identified LRP1 as a novel receptor for APOA4 in promoting glucose uptake. Considering both APOA4 and LRP1 are multifunctional players in lipid and glucose metabolism, our finding opens up a door to better understand the molecular mechanisms along APOA4-LRP1 axis, whose dysregulation leads to obesity, cardiovascular disease, and diabetes.

scholarly journals The neurorepellent, Slit2, prevents macrophage lipid loading by inhibiting CD36-dependent binding and internalization of oxidized low-density lipoprotein

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bushra Yusuf ◽  
Ilya Mukovozov ◽  
Sajedabanu Patel ◽  
Yi-Wei Huang ◽  
Guang Ying Liu ◽  
...  
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Super Resolution ◽  
Low Density ◽  
Dependent Manner ◽  
Oxidized Low Density Lipoprotein ◽  
Cortical Actin ◽  
Cytoskeletal Remodeling ◽  
Atherosclerotic Lesions ◽  
Modified Lipoproteins

AbstractAtherosclerosis is characterized by retention of modified lipoproteins, especially oxidized low density lipoprotein (oxLDL) within the sub-endothelial space of affected blood vessels. Recruited monocyte-derived and tissue-resident macrophages subsequently ingest oxLDL by binding and internalizing oxLDL via scavenger receptors, particularly CD36. The secreted neurorepellent, Slit2, acting through its transmembrane receptor, Roundabout-1 (Robo-1), was previously shown to inhibit recruitment of monocytes into nascent atherosclerotic lesions. The effects of Slit2 on oxLDL uptake by macrophages have not been explored. We report here that Slit2 inhibits uptake of oxLDL by human and murine macrophages, and the resulting formation of foam cells, in a Rac1-dependent and CD36-dependent manner. Exposure of macrophages to Slit2 prevented binding of oxLDL to the surface of cells. Using super-resolution microscopy, we observed that exposure of macrophages to Slit2 induced profound cytoskeletal remodeling with formation of a thick ring of cortical actin within which clusters of CD36 could not aggregate, thereby attenuating binding of oxLDL to the surface of cells. By inhibiting recruitment of monocytes into early atherosclerotic lesions, and the subsequent binding and internalization of oxLDL by macrophages, Slit2 could represent a potent new tool to combat individual steps that collectively result in progression of atherosclerosis.

scholarly journals Low-density-lipoprotein-receptor-related protein (LRP) interacts with a GTP-binding protein

1998 ◽  
Vol 336 (2) ◽  
pp. 381-386 ◽  
Author(s):  
Lothar GORETZKI ◽  
Barbara M. MUELLER
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Low Density ◽  
Lipoprotein Receptor ◽  
Dependent Manner ◽  
Related Protein ◽  
Gtp Binding ◽  
Density Lipoprotein Receptor ◽  
Dose Dependent ◽  
Lipoprotein Receptor Related Protein

The low-density-lipoprotein-receptor-related protein (LRP) binds and internalizes numerous ligands, including lipoproteins, proteinase–inhibitor complexes and others. We have shown previously that LRP-mediated ligand internalization is dependent on cAMP-dependent protein kinase (PKA) activity. Here, we investigated whether ligation of LRP increases the intracellular cAMP level and PKA activity via a stimulatory GTP-binding protein. Treatment of LRP-expressing cell lines with the LRP ligands lactoferrin or urokinase-type plasminogen activator caused a significant elevation in cAMP and stimulated PKA activity in a dose-dependent manner. Addition of the 39 kDa receptor-associated protein (RAP), an antagonist for ligand interactions with LRP, blocked the lactoferrin-induced increase in PKA activity, demonstrating a requirement for ligand binding to LRP. Incubation of cell membrane fractions with lactoferrin increased GTPase activity in a time- and dose-dependent manner, and treatment with LRP ligands suppressed cholera-toxin-mediated ADP-ribosylation of the Gsα subunit of a heterotrimeric G-protein. Affinity precipitation of LRP with RAP resulted in co-precipitation of two isoforms of Gsα from detergent extracts. We thus conclude that LRP is a signalling receptor that associates directly with a stimulatory heterotrimeric G-protein and activates a downstream PKA-dependent pathway.

scholarly journals Macrophage LRP1 Promotes Diet-Induced Hepatic Inflammation and Metabolic Dysfunction by Modulating Wnt Signaling

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Dianaly T. Au ◽  
Mary Migliorini ◽  
Dudley K. Strickland ◽  
Selen C. Muratoglu
Keyword(s):  
Insulin Resistance ◽  
Wnt Signaling ◽  
Cholesterol Metabolism ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Low Density ◽  
Lipoprotein Receptor ◽  
Hepatic Inflammation ◽  
Low Density Lipoprotein Receptor ◽  
Density Lipoprotein Receptor

Hepatic inflammation is associated with the development of insulin resistance, which can perpetuate the disease state and may increase the risk of metabolic syndrome and diabetes. Despite recent advances, mechanisms linking hepatic inflammation and insulin resistance are still unclear. The low-density lipoprotein receptor-related protein 1 (LRP1) is a large endocytic and signaling receptor that is highly expressed in macrophages, adipocytes, hepatocytes, and vascular smooth muscle cells. To investigate the potential role of macrophage LRP1 in hepatic inflammation and insulin resistance, we conducted experiments using macrophage-specific LRP1-deficient mice (macLRP1−/−) generated on a low-density lipoprotein receptor knockout (LDLR−/−) background and fed a Western diet. LDLR−/−; macLRP1−/− mice gained less body weight and had improved glucose tolerance compared to LDLR−/− mice. Livers from LDLR−/−; macLRP1−/− mice displayed lower levels of gene expression for several inflammatory cytokines, including Ccl3, Ccl4, Ccl8, Ccr1, Ccr2, Cxcl9, and Tnf, and reduced phosphorylation of GSK3α and p38 MAPK proteins. Furthermore, LRP1-deficient peritoneal macrophages displayed altered cholesterol metabolism. Finally, circulating levels of sFRP-5, a potent anti-inflammatory adipokine that functions as a decoy receptor for Wnt5a, were elevated in LDLR−/−; macLRP1−/− mice. Surface plasmon resonance experiments revealed that sFRP-5 is a novel high affinity ligand for LRP1, revealing that LRP1 regulates levels of this inhibitor of Wnt5a-mediated signaling. Collectively, our results suggest that LRP1 expression in macrophages promotes hepatic inflammation and the development of glucose intolerance and insulin resistance by modulating Wnt signaling.

scholarly journals Very-Low-Density Lipoprotein Receptor Fragment Shed from HeLa Cells Inhibits Human Rhinovirus Infection

1998 ◽  
Vol 72 (12) ◽  
pp. 10246-10250 ◽  
Author(s):  
Thomas C. Marlovits ◽  
Christina Abrahamsberg ◽  
Dieter Blaas
Keyword(s):  
Hela Cells ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Intercellular Adhesion Molecule ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Lipoprotein Receptor ◽  
Dependent Manner ◽  
Low Density Lipoprotein Receptor ◽  
Density Lipoprotein Receptor

ABSTRACT The large family of human rhinoviruses, the main causative agents of the common cold, is divided into the major and the minor group based on receptor specificity. Major group viruses attach to intercellular adhesion molecule 1 (ICAM-1), a member of the immunoglobulin superfamily, whereas minor group viruses use low-density lipoprotein receptors (LDLR) for cell entry. During early attempts aimed at isolating the minor group receptor, we discovered that a protein with virus binding activity was released from HeLa cells upon incubation with buffer at 37°C (F. Hofer, B. Berger, M. Gruenberger, H. Machat, R. Dernick, U. Tessmer, E. Kuechler, and D. Blaas, J. Gen. Virol. 73:627–632, 1992). In light of the recent discovery of several new members of the LDLR family, we reinvestigated the nature of this protein and present evidence for its being derived from the human very-low density lipoprotein receptor (VLDLR). A soluble VLDLR fragment encompassing the eight complement type repeats and representing the N-terminal part of the receptor was then expressed in the baculovirus system; both the shed protein and the recombinant soluble VLDLR bind minor group viruses and inhibit viral infection of HeLa cells in a concentration-dependent manner.

scholarly journals “A Comparative Study of Efficacy of Atorvastatin Alone and Atorvastatin with Omega-3 Fatty Acids Combination in Patients with Hyperlipidaemia Attending Tertiary Care Hospital”

2021 ◽  
pp. 482-490
Author(s):  
C. Srinivasa ◽  
K. La Kshminarayan ◽  
V. Srinivas ◽  
B. V. S. Chandrasekhar
Keyword(s):  
Fatty Acids ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Hdl Cholesterol ◽  
Low Density ◽  
Care Hospital ◽  
Omega 3 Fatty Acids ◽  
Omega 3 ◽  
Group A ◽  
Group B

Background: Current treatment with statins has become an integral part of vascular diseases but monotherapy has a significant residual event rate. Due to particularly one of the factor associated with atherogenic lipid phenotype that is characterized by a low high-density lipoprotein (HDL) cholesterol and increase in non-HDL cholesterol like Low-Density Lipoprotein (LDL). Omega-3 Fatty acids have demonstrated a preventiverole in primary and, particularly secondary cardiovascular diseases.  Hence this study was planned to compare the efficacy of Atorvastatin alone with Atorvastatin and Omega-3 fatty acids in treatment in hyperlipidaemia patients. Methods: The study was comparative, randomized, and prospective and open labeled conducted in MI patients. A total of 100 patients were selected based on inclusion and exclusion criteria. They were divided randomly into two Groups (Group–A and Group-B). Group-A was given Atorvastatin 10mg/day and Group-B was given Atorvastatin 10mg/day and Omega-3 fatty acids 600mg/day for 6 months. Follow up was done every month and efficacy was measured by assessing the lipoprotein levels in serum. Results: The results were compared before treatment and after 6 months treatment.The levels were significantly decreased Total Cholesterol (TC), LDL, Low-Density Lipoprotein (VLDL), Triglycerides (TG) and HDL levels were increased in Group–A and Group-B. When these results compared between two Groups the HDL levels were increased also it shown high significance (<0.001) but there were no significance changes in other cholesterol levels. Conclusion: The present study results showed that Atorvastatin and Omega-3 fatty acids treatment was more effective than Atorvastatin alone treatment in improving HDL-C levels from base line and it may have a additive effect in major coronary artery diseases.

Omega 3 Improves Both apoB100-containing Lipoprotein Turnover and their Sphingolipid Profile in Hypertriglyceridemia

2020 ◽  
Vol 105 (10) ◽  
pp. 3152-3164
Author(s):  
Véronique Ferchaud-Roucher ◽  
Yassine Zair ◽  
Audrey Aguesse ◽  
Michel Krempf ◽  
Khadija Ouguerram
Keyword(s):  
Low Density Lipoprotein ◽  
Lipoprotein Metabolism ◽  
Density Lipoprotein ◽  
Omega 3 ◽  
Pufa Supplementation ◽  
Multicompartmental Model ◽  
Neutral And Polar Lipids ◽  
Before And After ◽  
Positive Correlations ◽  
Vldl Triglyceride

Abstract Context Evidence for an association between sphingolipids and metabolic disorders is increasingly reported. Omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs) improve apolipoprotein B100 (apoB100)-containing lipoprotein metabolism, but their effects on the sphingolipid content in lipoproteins remain unknown. Objectives In subjects with hypertriglyceridemia, we analyzed the effect of n-3 LC-PUFAs on the turnover apoB100-containing lipoproteins and on their sphingolipid content and looked for the possible association between these lipid levels and apoB100-containing lipoprotein turnover parameters. Methods Six subjects underwent a kinetic study before and after n-3 supplementation for 2 months with 1 g of fish oil 3 times day containing 360 mg of eicosapentaenoic acid (EPA) and 240 mg of docosahexaenoic acid (DHA) in the form of triglycerides. We examined apoB100-containing lipoprotein turnover by primed perfusion labeled [5,5,5-2H3]-leucine and determined kinetic parameters using a multicompartmental model. We quantified sphingolipid species content in lipoproteins using mass spectrometry. Results Supplementation decreased very low-density lipoprotein (VLDL), triglyceride, and apoB100 concentrations. The VLDL neutral and polar lipids showed increased n-3 LC-PUFA and decreased n-6 LC-PUFA content. The conversion rate of VLDL1 to VLDL2 and of VLDL2 to LDL was increased. We measured a decrease in total apoB100 production and VLDL1 production. Supplementation reduced the total ceramide concentration in VLDL while the sphingomyelin content in LDL was increased. We found positive correlations between plasma palmitic acid and VLDL ceramide and between VLDL triglyceride and VLDL ceramide, and inverse correlations between VLDL n-3 LC-PUFA and VLDL production. Conclusion Based on these results, we hypothesize that the improvement in apoB100 metabolism during n-3 LC-PUFA supplementation is contributed to by changes in sphingolipids

scholarly journals Omega-3 Fatty Acids for the Management of Hypertriglyceridemia: A Science Advisory From the American Heart Association

Circulation ◽  
2019 ◽  
Vol 140 (12) ◽  
Author(s):  
Ann C. Skulas-Ray ◽  
Peter W.F. Wilson ◽  
William S. Harris ◽  
Eliot A. Brinton ◽  
Penny M. Kris-Etherton ◽  
...  
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Heart Association ◽  
The United States ◽  
Lipoprotein Cholesterol ◽  
Low Density ◽  
Omega 3 Fatty Acids ◽  
Omega 3 ◽  
Low Density Lipoprotein Cholesterol ◽  
Very High

Hypertriglyceridemia (triglycerides 200–499 mg/dL) is relatively common in the United States, whereas more severe triglyceride elevations (very high triglycerides, ≥500 mg/dL) are far less frequently observed. Both are becoming increasingly prevalent in the United States and elsewhere, likely driven in large part by growing rates of obesity and diabetes mellitus. In a 2002 American Heart Association scientific statement, the omega-3 fatty acids (n-3 FAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were recommended (at a dose of 2–4 g/d) for reducing triglycerides in patients with elevated triglycerides. Since 2002, prescription agents containing EPA+DHA or EPA alone have been approved by the US Food and Drug Administration for treating very high triglycerides; these agents are also widely used for hypertriglyceridemia. The purpose of this advisory is to summarize the lipid and lipoprotein effects resulting from pharmacological doses of n-3 FAs (>3 g/d total EPA+DHA) on the basis of new scientific data and availability of n-3 FA agents. In treatment of very high triglycerides with 4 g/d, EPA+DHA agents reduce triglycerides by ≥30% with concurrent increases in low-density lipoprotein cholesterol, whereas EPA-only did not raise low-density lipoprotein cholesterol in very high triglycerides. When used to treat hypertriglyceridemia, n-3 FAs with EPA+DHA or with EPA-only appear roughly comparable for triglyceride lowering and do not increase low-density lipoprotein cholesterol when used as monotherapy or in combination with a statin. In the largest trials of 4 g/d prescription n-3 FA, non–high-density lipoprotein cholesterol and apolipoprotein B were modestly decreased, indicating reductions in total atherogenic lipoproteins. The use of n-3 FA (4 g/d) for improving atherosclerotic cardiovascular disease risk in patients with hypertriglyceridemia is supported by a 25% reduction in major adverse cardiovascular events in REDUCE-IT (Reduction of Cardiovascular Events With EPA Intervention Trial), a randomized placebo-controlled trial of EPA-only in high-risk patients treated with a statin. The results of a trial of 4 g/d prescription EPA+DHA in hypertriglyceridemia are anticipated in 2020. We conclude that prescription n-3 FAs (EPA+DHA or EPA-only) at a dose of 4 g/d (>3 g/d total EPA+DHA) are an effective and safe option for reducing triglycerides as monotherapy or as an adjunct to other lipid-lowering agents.

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