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APC Inhibits Ligand-Independent Wnt Signaling by the Clathrin Endocytic Pathway.
Saito-Diaz K, Benchabane H, Tiwari A, Tian A, Li B, Thompson JJ, Hyde AS, Sawyer LM, Jodoin JN, Santos E, Lee LA, Coffey RJ, Beauchamp RD, Williams CS, Kenworthy AK, Robbins DJ, Ahmed Y, Lee E
(2018) Dev Cell 44: 566-581.e8
MeSH Terms: Adenomatous Polyposis Coli Protein, Animals, Cells, Cultured, Clathrin, Drosophila melanogaster, Endocytosis, Female, Humans, Infant, Ligands, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Middle Aged, Wnt Proteins, Wnt Signaling Pathway, beta Catenin
Show Abstract · Added March 14, 2018
Adenomatous polyposis coli (APC) mutations cause Wnt pathway activation in human cancers. Current models for APC action emphasize its role in promoting β-catenin degradation downstream of Wnt receptors. Unexpectedly, we find that blocking Wnt receptor activity in APC-deficient cells inhibits Wnt signaling independently of Wnt ligand. We also show that inducible loss of APC is rapidly followed by Wnt receptor activation and increased β-catenin levels. In contrast, APC2 loss does not promote receptor activation. We show that APC exists in a complex with clathrin and that Wnt pathway activation in APC-deficient cells requires clathrin-mediated endocytosis. Finally, we demonstrate conservation of this mechanism in Drosophila intestinal stem cells. We propose a model in which APC and APC2 function to promote β-catenin degradation, and APC also acts as a molecular "gatekeeper" to block receptor activation via the clathrin pathway.
Copyright © 2018 Elsevier Inc. All rights reserved.
0 Communities
4 Members
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18 MeSH Terms
Formulation and characterization of poly(propylacrylic acid)/poly(lactic-co-glycolic acid) blend microparticles for pH-dependent membrane disruption and cytosolic delivery.
Fernando LP, Lewis JS, Evans BC, Duvall CL, Keselowsky BG
(2018) J Biomed Mater Res A 106: 1022-1033
MeSH Terms: Acrylic Resins, Animals, CHO Cells, Cell Death, Cell Membrane, Cricetinae, Cricetulus, Cytosol, Dendritic Cells, Endocytosis, Endosomes, Humans, Hydrogen-Ion Concentration, Mice, Inbred C57BL, Microspheres, Particle Size, Polylactic Acid-Polyglycolic Acid Copolymer, Proton Magnetic Resonance Spectroscopy
Show Abstract · Added March 14, 2018
Poly(lactic-co-glycolic acid) (PLGA) is widely used as a vehicle for delivery of pharmaceutically relevant payloads. PLGA is readily fabricated as a nano- or microparticle (MP) matrix to load both hydrophobic and hydrophilic small molecular drugs as well as biomacromolecules such as nucleic acids and proteins. However, targeting such payloads to the cell cytosol is often limited by MP entrapment and degradation within acidic endolysosomes. Poly(propylacrylic acid) (PPAA) is a polyelectrolyte polymer with the membrane disruptive capability triggered at low pH. PPAA has been previously formulated in various carrier configurations to enable cytosolic payload delivery, but requires sophisticated carrier design. Taking advantage of PPAA functionality, we have incorporated PPAA into PLGA MPs as a simple polymer mixture to enhance cytosolic delivery of PLGA-encapsulated payloads. Rhodamine loaded PLGA and PPAA/PLGA blend MPs were prepared by a modified nanoprecipitation method. Incorporation of PPAA into PLGA MPs had little to no effect on the size, shape, or loading efficiency, and evidenced no toxicity in Chinese hamster ovary epithelial cells. Notably, incorporation of PPAA into PLGA MPs enabled pH-dependent membrane disruption in a hemolysis assay, and a three-fold increased endosomal escape and cytosolic delivery in dendritic cells after 2 h of MP uptake. These results demonstrate that a simple PLGA/PPAA polymer blend is readily fabricated into composite MPs, enabling cytosolic delivery of an encapsulated payload. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1022-1033, 2018.
© 2017 Wiley Periodicals, Inc.
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1 Members
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18 MeSH Terms
Ubiquitin turnover and endocytic trafficking in yeast are regulated by Ser57 phosphorylation of ubiquitin.
Lee S, Tumolo JM, Ehlinger AC, Jernigan KK, Qualls-Histed SJ, Hsu PC, McDonald WH, Chazin WJ, MacGurn JA
(2017) Elife 6:
MeSH Terms: Endocytosis, Homeostasis, Phosphoprotein Phosphatases, Phosphorylation, Protein Processing, Post-Translational, Saccharomyces cerevisiae Proteins, Ubiquitin, Yeasts
Show Abstract · Added March 24, 2018
Despite its central role in protein degradation little is known about the molecular mechanisms that sense, maintain, and regulate steady state concentration of ubiquitin in the cell. Here, we describe a novel mechanism for regulation of ubiquitin homeostasis that is mediated by phosphorylation of ubiquitin at the Ser57 position. We find that loss of Ppz phosphatase activity leads to defects in ubiquitin homeostasis that are at least partially attributable to elevated levels of Ser57 phosphorylated ubiquitin. Phosphomimetic mutation at the Ser57 position of ubiquitin conferred increased rates of endocytic trafficking and ubiquitin turnover. These phenotypes are associated with bypass of recognition by endosome-localized deubiquitylases - including Doa4 which is critical for regulation of ubiquitin recycling. Thus, ubiquitin homeostasis is significantly impacted by the rate of ubiquitin flux through the endocytic pathway and by signaling pathways that converge on ubiquitin itself to determine whether it is recycled or degraded in the vacuole.
0 Communities
1 Members
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8 MeSH Terms
A disease-associated frameshift mutation in caveolin-1 disrupts caveolae formation and function through introduction of a de novo ER retention signal.
Copeland CA, Han B, Tiwari A, Austin ED, Loyd JE, West JD, Kenworthy AK
(2017) Mol Biol Cell 28: 3095-3111
MeSH Terms: Caveolae, Caveolin 1, Endocytosis, Endoplasmic Reticulum, Fibroblasts, Frameshift Mutation, Humans, Hypertension, Pulmonary, Mutation, Protein Transport
Show Abstract · Added April 2, 2019
Caveolin-1 (CAV1) is an essential component of caveolae and is implicated in numerous physiological processes. Recent studies have identified heterozygous mutations in the gene in patients with pulmonary arterial hypertension (PAH), but the mechanisms by which these mutations impact caveolae assembly and contribute to disease remain unclear. To address this question, we examined the consequences of a familial PAH-associated frameshift mutation in , P158PfsX22, on caveolae assembly and function. We show that C-terminus of the CAV1 P158 protein contains a functional ER-retention signal that inhibits ER exit and caveolae formation and accelerates CAV1 turnover in MEFs. Moreover, when coexpressed with wild-type (WT) CAV1 in MEFs, CAV1-P158 functions as a dominant negative by partially disrupting WT CAV1 trafficking. In patient skin fibroblasts, CAV1 and caveolar accessory protein levels are reduced, fewer caveolae are observed, and CAV1 complexes exhibit biochemical abnormalities. Patient fibroblasts also exhibit decreased resistance to a hypo-osmotic challenge, suggesting the function of caveolae as membrane reservoir is compromised. We conclude that the P158PfsX22 frameshift introduces a gain of function that gives rise to a dominant negative form of CAV1, defining a new mechanism by which disease-associated mutations in CAV1 impair caveolae assembly.
© 2017 Copeland, Han, et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).
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1 Members
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MeSH Terms
Autophagy-related protein Vps34 controls the homeostasis and function of antigen cross-presenting CD8α dendritic cells.
Parekh VV, Pabbisetty SK, Wu L, Sebzda E, Martinez J, Zhang J, Van Kaer L
(2017) Proc Natl Acad Sci U S A 114: E6371-E6380
MeSH Terms: Animals, Antigen Presentation, Autophagy, Autophagy-Related Proteins, CD8 Antigens, CD8-Positive T-Lymphocytes, Cells, Cultured, Class III Phosphatidylinositol 3-Kinases, Cross-Priming, Cytokines, Dendritic Cells, Endocytosis, Histocompatibility Antigens Class I, Melanoma, Experimental, Membrane Proteins, Mice, Mice, Knockout, Phagocytosis
Show Abstract · Added March 26, 2019
The class III PI3K Vacuolar protein sorting 34 (Vps34) plays a role in both canonical and noncanonical autophagy, key processes that control the presentation of antigens by dendritic cells (DCs) to naive T lymphocytes. We generated DC-specific -deficient mice to assess the contribution of Vps34 to DC functions. We found that DCs from these animals have a partially activated phenotype, spontaneously produce cytokines, and exhibit enhanced activity of the classic MHC class I and class II antigen-presentation pathways. Surprisingly, these animals displayed a defect in the homeostatic maintenance of splenic CD8α DCs and in the capacity of these cells to cross-present cell corpse-associated antigens to MHC class I-restricted T cells, a property that was associated with defective expression of the T-cell Ig mucin (TIM)-4 receptor. Importantly, mice deficient in the Vps34-associated protein Rubicon, which is critical for a noncanonical form of autophagy called "Light-chain 3 (LC3)-associated phagocytosis" (LAP), lacked such defects. Finally, consistent with their defect in the cross-presentation of apoptotic cells, DC-specific -deficient animals developed increased metastases in response to challenge with B16 melanoma cells. Collectively, our studies have revealed a critical role of Vps34 in the regulation of CD8α DC homeostasis and in the capacity of these cells to process and present antigens associated with apoptotic cells to MHC class I-restricted T cells. Our findings also have important implications for the development of small-molecule inhibitors of Vps34 for therapeutic purposes.
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MeSH Terms
In vivo histone H1 migration from necrotic to viable tissue.
Luhrs KA, Pink D, Schulte W, Zijlstra A, Lewis JD, Parseghian MH
(2017) Oncotarget 8: 16275-16292
MeSH Terms: Animals, CHO Cells, Cell Line, Tumor, Cell Survival, Cricetinae, Cricetulus, Endocytosis, Histones, Humans, Necrosis, Protein Transport
Show Abstract · Added April 6, 2017
Necrosis is induced by ischemic conditions within the core of many solid tumors. Using fluorescent fusion proteins, we provide in vivo evidence of histone trafficking among cancer cells in implanted tumors. In particular, the most abundant H1 isoform (H1.2) was found to be transported from necrotic tumor cells into surrounding viable cells where histones are selectively taken up by energy-dependent endocytosis. We propose that intercellular histone trafficking could function as a target for drug delivery. This concept was validated using an anti-histone antibody that was co-internalized with histones from dead cells into viable ones surrounding the necrotic regions of a tumor, where some of the most chemoresistant cells reside. These findings demonstrate that cellular translocation of conjugated drugs using anti-histone antibodies is a promising strategy for targeted drug delivery to chemoresistant tumors.
1 Communities
1 Members
0 Resources
11 MeSH Terms
Clostridium difficile Toxin A Undergoes Clathrin-Independent, PACSIN2-Dependent Endocytosis.
Chandrasekaran R, Kenworthy AK, Lacy DB
(2016) PLoS Pathog 12: e1006070
MeSH Terms: Adaptor Proteins, Signal Transducing, Animals, Bacterial Toxins, Blotting, Western, Caco-2 Cells, Clathrin, Clostridium Infections, Clostridium difficile, Endocytosis, Enterotoxins, Fluorescent Antibody Technique, Gene Knockdown Techniques, HEK293 Cells, Humans, Image Processing, Computer-Assisted, Mice, Microscopy, Confocal, Protein Transport, Reverse Transcriptase Polymerase Chain Reaction, Transfection, Virulence Factors
Show Abstract · Added April 26, 2017
Clostridium difficile infection affects a significant number of hospitalized patients in the United States. Two homologous exotoxins, TcdA and TcdB, are the major virulence factors in C. difficile pathogenesis. The toxins are glucosyltransferases that inactivate Rho family-GTPases to disrupt host cellular function and cause fluid secretion, inflammation, and cell death. Toxicity depends on receptor binding and subsequent endocytosis. TcdB has been shown to enter cells by clathrin-dependent endocytosis, but the mechanism of TcdA uptake is still unclear. Here, we utilize a combination of RNAi-based knockdown, pharmacological inhibition, and cell imaging approaches to investigate the endocytic mechanism(s) that contribute to TcdA uptake and subsequent cytopathic and cytotoxic effects. We show that TcdA uptake and cellular intoxication is dynamin-dependent but does not involve clathrin- or caveolae-mediated endocytosis. Confocal microscopy using fluorescently labeled TcdA shows significant colocalization of the toxin with PACSIN2-positive structures in cells during entry. Disruption of PACSIN2 function by RNAi-based knockdown approaches inhibits TcdA uptake and toxin-induced downstream effects in cells indicating that TcdA entry is PACSIN2-dependent. We conclude that TcdA and TcdB utilize distinct endocytic mechanisms to intoxicate host cells.
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1 Members
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21 MeSH Terms
LRRC8A channels support TNFα-induced superoxide production by Nox1 which is required for receptor endocytosis.
Choi H, Ettinger N, Rohrbough J, Dikalova A, Nguyen HN, Lamb FS
(2016) Free Radic Biol Med 101: 413-423
MeSH Terms: Cell Line, Cyclopentanes, Endocytosis, Gene Expression Regulation, HEK293 Cells, Humans, Indans, JNK Mitogen-Activated Protein Kinases, Membrane Proteins, Myocytes, Smooth Muscle, NADPH Oxidase 1, NF-kappa B, Phosphorylation, Protein Subunits, RNA, Small Interfering, Receptors, Tumor Necrosis Factor, Type I, Signal Transduction, Superoxide Dismutase, Superoxides, Tumor Necrosis Factor-alpha, Vascular Cell Adhesion Molecule-1
Show Abstract · Added March 26, 2019
Leucine Rich Repeat Containing 8A (LRRC8A) is a required component of volume-regulated anion channels (VRACs). In vascular smooth muscle cells, tumor necrosis factor-α (TNFα) activates VRAC via type 1 TNFα receptors (TNFR1), and this requires superoxide (O) production by NADPH oxidase 1 (Nox1). VRAC inhibitors suppress the inflammatory response to TNFα by an unknown mechanism. We hypothesized that LRRC8A directly supports Nox1 activity, providing a link between VRAC current and inflammatory signaling. VRAC inhibition by 4-(2-butyl-6,7-dichlor-2-cyclopentylindan-1-on-5-yl) oxobutyric acid (DCPIB) impaired NF-κB activation by TNFα. LRRC8A siRNA reduced the magnitude of VRAC and inhibited TNFα-induced NF-κB activation, iNOS and VCAM expression, and proliferation of VSMCs. Signaling steps disrupted by both siLRRC8A and DCPIB included; extracellular O production by Nox1, c-Jun N-terminal kinase (JNK) phosphorylation and endocytosis of TNFR1. Extracellular superoxide dismutase, but not catalase, selectively inhibited TNFR1 endocytosis and JNK phosphorylation. Thus, O is the critical extracellular oxidant for TNFR signal transduction. Reducing JNK expression (siJNK) increased extracellular O suggesting that JNK provides important negative feedback regulation to Nox1 at the plasma membrane. LRRC8A co-localized by immunostaining, and co-immunoprecipitated with, both Nox1 and its p22phox subunit. LRRC8A is a component of the Nox1 signaling complex. It is required for extracellular O production, which is in turn essential for TNFR1 endocytosis. These data are the first to provide a molecular mechanism for the potent anti-proliferative and anti-inflammatory effects of VRAC inhibition.
Copyright © 2016 Elsevier Inc. All rights reserved.
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1 Members
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MeSH Terms
C-terminal motif of human neuropeptide Y receptor determines internalization and arrestin recruitment.
Wanka L, Babilon S, Burkert K, Mörl K, Gurevich VV, Beck-Sickinger AG
(2017) Cell Signal 29: 233-239
MeSH Terms: Amino Acid Motifs, Amino Acid Sequence, Amino Acids, Animals, COS Cells, Cercopithecus aethiops, Endocytosis, HEK293 Cells, Humans, Mutant Proteins, Receptors, Neuropeptide Y, Reproducibility of Results, Sequence Alignment, Sequence Deletion, Structure-Activity Relationship, beta-Arrestin 2
Show Abstract · Added March 14, 2018
The human neuropeptide Y receptor is a rhodopsin-like G protein-coupled receptor (GPCR), which contributes to anorexigenic signals. Thus, this receptor is a highly interesting target for metabolic diseases. As GPCR internalization and trafficking affect receptor signaling and vice versa, we aimed to investigate the molecular mechanism of hYR desensitization and endocytosis. The role of distinct segments of the hYR carboxyl terminus was investigated by fluorescence microscopy, binding assays, inositol turnover experiments and bioluminescence resonance energy transfer assays to examine the internalization behavior of hYR and its interaction with arrestin-3. Based on results of C-terminal deletion mutants and substitution of single amino acids, the motif EESEHLPLSTVHTEVSKGS was identified, with glutamate, threonine and serine residues playing key roles, based on site-directed mutagenesis. Thus, we identified the internalization motif for the human neuropeptide Y receptor, which regulates arrestin-3 recruitment and receptor endocytosis.
Copyright © 2016 Elsevier Inc. All rights reserved.
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1 Members
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16 MeSH Terms
Electron Microscopy of Living Cells During in Situ Fluorescence Microscopy.
Liv N, van Oosten Slingeland DS, Baudoin JP, Kruit P, Piston DW, Hoogenboom JP
(2016) ACS Nano 10: 265-73
MeSH Terms: Animals, Bioreactors, Cell Line, Cells, Immobilized, Cercopithecus aethiops, Endocytosis, Fibroblasts, Microscopy, Electron, Scanning, Optical Imaging, Quantum Dots
Show Abstract · Added February 4, 2016
We present an approach toward dynamic nanoimaging: live fluorescence of cells encapsulated in a bionanoreactor is complemented with in situ scanning electron microscopy (SEM) on an integrated microscope. This allows us to take SEM snapshots on-demand, that is, at a specific location in time, at a desired region of interest, guided by the dynamic fluorescence imaging. We show that this approach enables direct visualization, with EM resolution, of the distribution of bioconjugated quantum dots on cellular extensions during uptake and internalization.
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10 MeSH Terms