scholarly journals Canonical Wnt signaling in megakaryocytes regulates proplatelet formation

Blood ◽  
2013 ◽  
Vol 121 (1) ◽  
pp. 188-196 ◽  
Author(s):  
Iain C. Macaulay ◽  
Jonathan N. Thon ◽  
Marloes R. Tijssen ◽  
Brian M. Steele ◽  
Bryan T. MacDonald ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Fetal Liver ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Wild Type ◽  
Density Lipoprotein Receptor ◽  
Proplatelet Formation ◽  
And Function ◽  
Canonical Wnt ◽  
Whole Genome Expression

Abstract Wnt signaling is involved in numerous aspects of vertebrate development and homeostasis, including the formation and function of blood cells. Here, we show that canonical and noncanonical Wnt signaling pathways are present and functional in megakaryocytes (MKs), with several Wnt effectors displaying MK-restricted expression. Using the CHRF288-11 cell line as a model for human MKs, the canonical Wnt3a signal was found to induce a time and dose-dependent increase in β-catenin expression. β-catenin accumulation was inhibited by the canonical antagonist dickkopf-1 (DKK1) and by the noncanonical agonist Wnt5a. Whole genome expression analysis demonstrated that Wnt3a and Wnt5a regulated distinct patterns of gene expression in MKs, and revealed a further interplay between canonical and noncanonical Wnt pathways. Fetal liver cells derived from low-density-lipoprotein receptor-related protein 6-deficient mice (LRP6−/−), generated dramatically reduced numbers of MKs in culture of lower ploidy (2N and 4N) than wild-type controls, implicating LRP6-dependent Wnt signaling in MK proliferation and maturation. Finally, in wild-type mature murine fetal liver-derived MKs, Wnt3a potently induced proplatelet formation, an effect that could be completely abrogated by DKK1. These data identify novel extrinsic regulators of proplatelet formation, and reveal a profound role for Wnt signaling in platelet production.

scholarly journals Exploring the mechanistic and temporal regulation of LRP6 endocytosis in canonical WNT signaling

2020 ◽  
Vol 133 (15) ◽  
pp. jcs243675 ◽  
Author(s):  
Fiete Haack ◽  
Kai Budde ◽  
Adelinde M. Uhrmacher
Keyword(s):  
Wnt Signaling ◽  
Temporal Dynamics ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Cell Types ◽  
Receptor Internalization ◽  
Canonical Wnt Signaling ◽  
Temporal Regulation ◽  
Density Lipoprotein Receptor ◽  
Canonical Wnt

ABSTRACTEndocytosis plays a pivotal regulatory role in canonical WNT signaling. Internalization of the low-density lipoprotein receptor-related protein 6 (LRP6) receptor complex can either promote or attenuate canonical WNT signaling, depending on the employed internalization pathway. Detailed analysis of the mechanism of LRP6 internalization and its temporal regulation is crucial for understanding the different cellular responses to WNT stimulation under varying conditions and in various cell types. Here, we elucidate the mechanisms involved in the internalization of LRP6 and re-evaluate existing, partly contradicting, theories on the regulation of LRP6 receptor internalization. We utilize a computational approach that aims at finding a set of mechanisms that accounts for the temporal dynamics of LRP6 receptor internalization upon WNT stimulation. Starting with a simple simulation model, we successively extend and probe the model's behavior based on quantitative measurements. The final model confirms that LRP6 internalization is clathrin independent in vertebrates, is not restricted to microdomains, and that signalosome formation delays LRP6 internalization within the microdomains. These findings partly revise the current understanding of LRP6 internalization in vertebrates.

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 Carvedilol Ameliorates Experimental Atherosclerosis by Regulating Cholesterol Efflux and Exosome Functions

2019 ◽  
Vol 20 (20) ◽  
pp. 5202 ◽  
Author(s):  
Chen ◽  
Tsui ◽  
Chuang ◽  
Chiang ◽  
Chen ◽  
...  
Keyword(s):  
Cholesterol Efflux ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Nuclear Factor Κb ◽  
Experimental Atherosclerosis ◽  
Atherosclerotic Cardiovascular Disease ◽  
Beneficial Effects ◽  
Abca1 Expression ◽  
Density Lipoprotein Receptor ◽  
And Function

Carvedilol (Cav), a nonselective β-blocker with α1 adrenoceptor blocking effect, has been used as a standard therapy for coronary artery disease. This study investigated the effects of Cav on exosome expression and function, ATP-binding cassette transporter A1 (ABCA1) expression, and cholesterol efflux that are relevant to the process of atherosclerosis. Human monocytic (THP-1) cell line and human hepatic (Huh-7) cells were treated with Cav, and cholesterol efflux was measured. Exosomes from cell culture medium or mice serum were isolated using glycan-coated recognition beads. Low-density lipoprotein receptor knockout (ldlr−/−) mice were fed with high-fat diet and treated with Cav. Cav accentuated cholesterol efflux and enhanced the expressions of ABCA1 protein and mRNA in both THP-1 and Huh-7 cells. In addition, Cav increased expression and function of exosomal ABCA1 in THP-1 macrophage exosomes. The mechanisms were associated with inhibition of nuclear factor-κB (NF-κB) and protein kinase B (Akt). In hypercholesterolemic ldlr−/− mice, Cav enhanced serum exosomal ABCA1 expression and suppressed atherosclerosis by inhibiting lipid deposition and macrophage accumulation. Cav halts atherosclerosis by enhancing cholesterol efflux and increasing ABCA1 expression in macrophages and in exosomes, possibly through NF-κB and Akt signaling, which provides mechanistic insights regarding the beneficial effects of Cav on atherosclerotic cardiovascular disease.

scholarly journals Clathrin and AP2 are required for PtdIns(4,5)P2-mediated formation of LRP6 signalosomes

2013 ◽  
Vol 200 (4) ◽  
pp. 419-428 ◽  
Author(s):  
Ingyu Kim ◽  
Weijun Pan ◽  
Sara A. Jones ◽  
Youxin Zhang ◽  
Xiaowei Zhuang ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Super Resolution ◽  
Adaptor Protein ◽  
Related Protein ◽  
Cell Surfaces ◽  
Wnt Proteins ◽  
Canonical Wnt ◽  
Wnt3a Stimulation

Canonical Wnt signaling is initiated by the binding of Wnt proteins to their receptors, low-density lipoprotein-related protein 5 and 6 (LRP5/6) and frizzled proteins, leading to phosphatidylinositol (4,5)bisphosphate (PtdIns(4,5)P2) production, signalosome formation, and LRP phosphorylation. However, the mechanism by which PtdIns(4,5)P2 regulates the signalosome formation remains unclear. Here we show that clathrin and adaptor protein 2 (AP2) were part of the LRP6 signalosomes. The presence of clathrin and AP2 in the LRP6 signalosomes depended on PtdIns(4,5)P2, and both clathrin and AP2 were required for the formation of LRP6 signalosomes. In addition, WNT3A-induced LRP6 signalosomes were primarily localized at cell surfaces, and WNT3A did not induce marked LRP6 internalization. However, rapid PtdIns(4,5)P2 hydrolysis induced artificially after WNT3A stimulation could lead to marked LRP6 internalization. Moreover, we observed WNT3A-induced LRP6 and clathrin clustering at cell surfaces using super-resolution fluorescence microscopy. Therefore, we conclude that PtdIns(4,5)P2 promotes the assembly of LRP6 signalosomes via the recruitment of AP2 and clathrin and that LRP6 internalization may not be a prerequisite for Wnt signaling to β-catenin stabilization.

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