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Lo CH, O’Connor LM, Loi GWZ, Saipuljumri EN, Indajang J, Lopes KM, Shirihai OS, Grinstaff MW, Zeng J. Acidic Nanoparticles Restore Lysosomal Acidification and Rescue Metabolic Dysfunction in Pancreatic β-Cells under Lipotoxic Conditions. ACS NANO 2024; 18:15452-15467. [PMID: 38830624 PMCID: PMC11192035 DOI: 10.1021/acsnano.3c09206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2023] [Revised: 05/09/2024] [Accepted: 05/16/2024] [Indexed: 06/05/2024]
Abstract
Type 2 diabetes (T2D), a prevalent metabolic disorder lacking effective treatments, is associated with lysosomal acidification dysfunction, as well as autophagic and mitochondrial impairments. Here, we report a series of biodegradable poly(butylene tetrafluorosuccinate-co-succinate) polyesters, comprising a 1,4-butanediol linker and varying ratios of tetrafluorosuccinic acid (TFSA) and succinic acid as components, to engineer lysosome-acidifying nanoparticles (NPs). The synthesized NPs are spherical with diameters of ≈100 nm and have low polydispersity and good stability. Notably, TFSA NPs, which are composed entirely of TFSA, exhibit the strongest degradation capability and superior acidifying properties. We further reveal significant downregulation of lysosomal vacuolar (H+)-ATPase subunits, which are responsible for maintaining lysosomal acidification, in human T2D pancreatic islets, INS-1 β-cells under chronic lipotoxic conditions, and pancreatic tissues of high-fat-diet (HFD) mice. Treatment with TFSA NPs restores lysosomal acidification, autophagic function, and mitochondrial activity, thereby improving the pancreatic function in INS-1 cells and HFD mice with lipid overload. Importantly, the administration of TFSA NPs to HFD mice reduces insulin resistance and improves glucose clearance. These findings highlight the therapeutic potential of lysosome-acidifying TFSA NPs for T2D.
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Affiliation(s)
- Chih Hung Lo
- Lee
Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232, Singapore
| | - Lance M. O’Connor
- College
of Biological Sciences, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Gavin Wen Zhao Loi
- Lee
Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232, Singapore
| | | | - Jonathan Indajang
- Meinig
School of Biomedical Engineering, Cornell
University, Ithaca, New York 14853, United States
| | - Kaitlynn M. Lopes
- Department
of Chemistry, Boston University, Boston, Massachusetts 02215, United States
| | - Orian S. Shirihai
- Division
of Endocrinology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California 90045, United States
- Department
of Molecular and Medical Pharmacology, University
of California, Los Angeles, Los
Angeles, California 90095, United States
| | - Mark W. Grinstaff
- Department
of Chemistry, Boston University, Boston, Massachusetts 02215, United States
- Department
of Biomedical Engineering, Boston University, Boston, Massachusetts 02215, United States
| | - Jialiu Zeng
- Lee
Kong Chian School of Medicine, Nanyang Technological University, Singapore 308232, Singapore
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2
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Aji G, Jiang S, Obulkasim H, Lu Z, Wang W, Xia P. Sphingosine kinase 2 regulates insulin receptor trafficking in hepatocytes. Exp Biol Med (Maywood) 2023; 248:44-51. [PMID: 36408724 PMCID: PMC9989153 DOI: 10.1177/15353702221131886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Disturbed insulin receptor (InsR) trafficking is associated with impaired insulin signaling and the development of diabetes. Sphingosine kinase (SphK), including SphK1 and SphK2, is a key enzyme of sphingolipid metabolism, which has been implicated in the regulation of membrane trafficking. More recently, we have reported that SphK2 is a key regulator of hepatic insulin signaling and glucose homeostasis. However, the role of SphK in InsR trafficking is still undefined. Huh7 cells were treated with specific SphK1 and SphK2 inhibitors or SphK1- and SphK2-specific small interfering RNA (siRNA) in the presence or absence of insulin. Flow cytometry and immunofluorescence assays were carried out to investigate the role of SphK in InsR trafficking. InsR endocytosis, recycling, and insulin signaling were analyzed. Inhibition of SphK2, but not SphK1, by either specific pharmaceutic inhibitors or siRNA, significantly suppressed InsR endocytosis and recycling following insulin stimulation. Consequently, the insulin-stimulated Akt activation was significantly attenuated by SphK2 inhibition in hepatocytes. Moreover, the effect of SphK2 on InsR trafficking was mediated via the clathrin-dependent mechanism. Thus, our results show that SphK2 is able to regulate InsR trafficking. These findings suggest that SphK2 may impinge on hepatic insulin signaling by regulating InsR trafficking, providing further mechanistic evidence that SphK2 could serve as a potential intervention target against insulin resistance and T2D (type 2 diabetes).
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Affiliation(s)
- Gulibositan Aji
- State Key Laboratory of Pathogenesis, Prevention and Treatment of High Incidence Diseases in Central Asia, Department of Endocrinology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830000, China.,Department of Endocrinology and Metabolism, Zhongshan Hospital and Fudan Institute for Metabolic Diseases, Fudan University, Shanghai 200032, China
| | - Sheng Jiang
- State Key Laboratory of Pathogenesis, Prevention and Treatment of High Incidence Diseases in Central Asia, Department of Endocrinology, The First Affiliated Hospital of Xinjiang Medical University, Urumqi 830000, China
| | - Halmurat Obulkasim
- Department of General Surgery, Traditional Chinese Medicine Hospital Affiliated to Xinjiang Medical University, Urumqi 830000, China
| | - Zhiqiang Lu
- Department of Endocrinology and Metabolism, Zhongshan Hospital and Fudan Institute for Metabolic Diseases, Fudan University, Shanghai 200032, China
| | - Wei Wang
- Department of Endocrinology and Metabolism, Zhongshan Hospital and Fudan Institute for Metabolic Diseases, Fudan University, Shanghai 200032, China
| | - Pu Xia
- Department of Endocrinology and Metabolism, Zhongshan Hospital and Fudan Institute for Metabolic Diseases, Fudan University, Shanghai 200032, China
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3
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Sidibe DK, Kulkarni VV, Dong A, Herr JB, Vogel MC, Stempel MH, Maday S. Brain-derived neurotrophic factor stimulates the retrograde pathway for axonal autophagy. J Biol Chem 2022; 298:102673. [PMID: 36336077 PMCID: PMC9768381 DOI: 10.1016/j.jbc.2022.102673] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 10/27/2022] [Accepted: 11/01/2022] [Indexed: 11/06/2022] Open
Abstract
Autophagy is a lysosomal degradation pathway important for neuronal development, function, and survival. How autophagy in axons is regulated by neurotrophins to impact neuronal viability and function is poorly understood. Here, we use live-cell imaging in primary neurons to investigate the regulation of axonal autophagy by the neurotrophin brain-derived neurotrophic factor (BDNF) and elucidate whether autophagosomes carry BDNF-mediated signaling information. We find that BDNF induces autophagic flux in primary neurons by stimulating the retrograde pathway for autophagy in axons. We observed an increase in autophagosome density and retrograde flux in axons, and a corresponding increase in autophagosome density in the soma. However, we find little evidence of autophagosomes comigrating with BDNF. In contrast, BDNF effectively engages its cognate receptor TrkB to undergo retrograde transport in the axon. These compartments, however, are distinct from LC3-positive autophagic organelles in the axon. Together, we find that BDNF stimulates autophagy in the axon, but retrograde autophagosomes do not appear to carry BDNF cargo. Thus, autophagosomes likely do not play a major role in relaying neurotrophic signaling information across the axon in the form of active BDNF/TrkB complexes. Rather, BDNF likely stimulates autophagy as a consequence of BDNF-induced processes that require canonical roles for autophagy in degradation.
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Affiliation(s)
| | | | | | | | | | | | - Sandra Maday
- Department of Neuroscience, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, Pennsylvania, USA.
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4
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Liu J, Qi Y, Chao J, Sathuvalli P, Y Lee L, Li S. CREG1 promotes lysosomal biogenesis and function. Autophagy 2021; 17:4249-4265. [PMID: 33966596 PMCID: PMC8726608 DOI: 10.1080/15548627.2021.1909997] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
CREG1 is a small glycoprotein which has been proposed as a transcription repressor, a secretory ligand, a lysosomal, or a mitochondrial protein. This is largely because of lack of antibodies for immunolocalization validated through gain- and loss-of-function studies. In the present study, we demonstrate, using antibodies validated for immunofluorescence microscopy, that CREG1 is mainly localized to the endosomal-lysosomal compartment. Gain- and loss-of-function analyses reveal an important role for CREG1 in both macropinocytosis and clathrin-dependent endocytosis. CREG1 also promotes acidification of the endosomal-lysosomal compartment and increases lysosomal biogenesis. Functionally, overexpression of CREG1 enhances macroautophagy/autophagy and lysosome-mediated degradation, whereas knockdown or knockout of CREG1 has opposite effects. The function of CREG1 in lysosomal biogenesis is likely attributable to enhanced endocytic trafficking. Our results demonstrate that CREG1 is an endosomal-lysosomal protein implicated in endocytic trafficking and lysosomal biogenesis.Abbreviations: AIFM1/AIF: apoptosis inducing factor mitochondria associated 1; AO: acridine orange; ATP6V1H: ATPase H+ transporting V1 subunit H; CALR: calreticulin; CREG: cellular repressor of E1A stimulated genes; CTSC: cathepsin C; CTSD: cathepsin D; EBAG9/RCAS1: estrogen receptor binding site associated antigen 9; EIPA: 5-(N-ethyl-N-isopropyl)amiloride; ER: endoplasmic reticulum; GFP: green fluorescent protein; HEXA: hexosaminidase subunit alpha; IGF2R: insulin like growth factor 2 receptor; LAMP1: lysosomal associated membrane protein 1; M6PR: mannose-6-phosphate receptor, cation dependent; MAPK1/ERK2: mitogen-activated protein kinase 1; MTORC1: mechanistic target of rapamycin kinase complex 1; PDIA2: protein disulfide isomerase family A member 2; SQSTM1/p62: sequestosome 1; TF: transferrin; TFEB: transcription factor EB.
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Affiliation(s)
- Jie Liu
- Department of Surgery, Rutgers University-Robert Wood Johnson Medical School, New Brunswick, NJ, USA
| | - Yanmei Qi
- Department of Surgery, Rutgers University-Robert Wood Johnson Medical School, New Brunswick, NJ, USA
| | - Joshua Chao
- Department of Surgery, Rutgers University-Robert Wood Johnson Medical School, New Brunswick, NJ, USA
| | - Pranav Sathuvalli
- Department of Surgery, Rutgers University-Robert Wood Johnson Medical School, New Brunswick, NJ, USA
| | - Leonard Y Lee
- Department of Surgery, Rutgers University-Robert Wood Johnson Medical School, New Brunswick, NJ, USA
| | - Shaohua Li
- Department of Surgery, Rutgers University-Robert Wood Johnson Medical School, New Brunswick, NJ, USA
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5
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Boutchueng-Djidjou M, Belleau P, Bilodeau N, Fortier S, Bourassa S, Droit A, Elowe S, Faure RL. A type 2 diabetes disease module with a high collective influence for Cdk2 and PTPLAD1 is localized in endosomes. PLoS One 2018; 13:e0205180. [PMID: 30300385 PMCID: PMC6177195 DOI: 10.1371/journal.pone.0205180] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 09/20/2018] [Indexed: 01/19/2023] Open
Abstract
Despite the identification of many susceptibility genes our knowledge of the underlying mechanisms responsible for complex disease remains limited. Here, we identified a type 2 diabetes disease module in endosomes, and validate it for functional relevance on selected nodes. Using hepatic Golgi/endosomes fractions, we established a proteome of insulin receptor-containing endosomes that allowed the study of physical protein interaction networks on a type 2 diabetes background. The resulting collated network is formed by 313 nodes and 1147 edges with a topology organized around a few major hubs with Cdk2 displaying the highest collective influence. Overall, 88% of the nodes are associated with the type 2 diabetes genetic risk, including 101 new candidates. The Type 2 diabetes module is enriched with cytoskeleton and luminal acidification–dependent processes that are shared with secretion-related mechanisms. We identified new signaling pathways driven by Cdk2 and PTPLAD1 whose expression affects the association of the insulin receptor with TUBA, TUBB, the actin component ACTB and the endosomal sorting markers Rab5c and Rab11a. Therefore, the interactome of internalized insulin receptors reveals the presence of a type 2 diabetes disease module enriched in new layers of feedback loops required for insulin signaling, clearance and islet biology.
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Affiliation(s)
- Martial Boutchueng-Djidjou
- Départment of Pediatrics, Faculty of Medicine, Université Laval, Centre de Recherche du CHU de Québec, Québec city, Canada
| | - Pascal Belleau
- Plateforme Protéomique de l’Est du Québec, Université Laval. Université Laval, Québec, QC, Canada
| | - Nicolas Bilodeau
- Départment of Pediatrics, Faculty of Medicine, Université Laval, Centre de Recherche du CHU de Québec, Québec city, Canada
| | - Suzanne Fortier
- Départment of Pediatrics, Faculty of Medicine, Université Laval, Centre de Recherche du CHU de Québec, Québec city, Canada
| | - Sylvie Bourassa
- Plateforme Protéomique de l’Est du Québec, Université Laval. Université Laval, Québec, QC, Canada
| | - Arnaud Droit
- Plateforme Protéomique de l’Est du Québec, Université Laval. Université Laval, Québec, QC, Canada
| | - Sabine Elowe
- Départment of Pediatrics, Faculty of Medicine, Université Laval, Centre de Recherche du CHU de Québec, Québec city, Canada
| | - Robert L. Faure
- Départment of Pediatrics, Faculty of Medicine, Université Laval, Centre de Recherche du CHU de Québec, Québec city, Canada
- * E-mail:
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6
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Desbuquois B, Authier F. [Involvement of the endosomal compartment in cellular insulin signaling]. Biol Aujourdhui 2014; 208:137-150. [PMID: 25190573 DOI: 10.1051/jbio/2014016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Indexed: 06/03/2023]
Abstract
The insulin receptor and insulin signaling proteins downstream the receptor reside in different subcellular compartments and undergo redistribution within the cell upon insulin activation. Endocytosis of the insulin-receptor complex, by mediating ligand degradation and receptor dephosphorylation, is generally viewed as a mechanism which attenuates or arrests insulin signal transduction. However, several observations suggest that insulin receptor endocytosis and/or recruitement of insulin signaling proteins to endosomes are also involved in a positive regulation of insulin signaling: (1) upon internalization, the insulin receptor remains transiently phosphorylated and activated; (2) in insulin-stimulated cells or tissues, signaling proteins of the PI3K/Akt and Ras/Raf/Mek/Erk pathways are recruited to endosomes or other intracellular compartments, in which they undergo phosphorylation and/or activation; and (3) depletion or overexpression of proteins involved in the regulation of membrane trafficking and endocytosis interfere with insulin signaling. These observations support a spatial and temporal regulation of insulin signal transduction and reinforce the concept that, as for other membrane signaling receptors, endocytosis and signaling are functionally linked.
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Affiliation(s)
- Bernard Desbuquois
- Inserm U1016 et CNRS UMR 8104, Institut Cochin, et Université Paris Descartes, 24 rue du Faubourg Saint Jacques, 75014 Paris, France
| | - François Authier
- Service Information Scientifique et Technique (IST) de l'Inserm, Délégation Régionale Inserm Paris V, 2 rue d'Alésia, 75014 Paris, France
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7
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Xu Y, Parmar A, Roux E, Balbis A, Dumas V, Chevalier S, Posner BI. Epidermal growth factor-induced vacuolar (H+)-atpase assembly: a role in signaling via mTORC1 activation. J Biol Chem 2012; 287:26409-22. [PMID: 22689575 DOI: 10.1074/jbc.m112.352229] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Using proteomics and immunofluorescence, we demonstrated epidermal growth factor (EGF) induced recruitment of extrinsic V(1) subunits of the vacuolar (H(+))-ATPase (V-ATPase) to rat liver endosomes. This was accompanied by reduced vacuolar pH. Bafilomycin, an inhibitor of V-ATPase, inhibited EGF-stimulated DNA synthesis and mammalian target of rapamycin complex 1 (mTORC1) activation as indicated by a decrease in eukaryotic initiation factor 4E-binding 1 (4E-BP1) phosphorylation and p70 ribosomal S6 protein kinase (p70S6K) phosphorylation and kinase activity. There was no corresponding inhibition of EGF-induced Akt and extracellular signal-regulated kinase (Erk) activation. Chloroquine, a neutralizer of vacuolar pH, mimicked bafilomycin effects. Bafilomycin did not inhibit the association of mTORC1 with Raptor nor did it affect AMP-activated protein kinase activity. Rather, the intracellular concentrations of essential but not non-essential amino acids were decreased by bafilomycin in EGF-treated primary rat hepatocytes. Cycloheximide, a translation elongation inhibitor known to augment intracellular amino acid levels, prevented the effect of bafilomycin on amino acids levels and completely reversed its inhibition of EGF-induced mTORC1 activation. In vivo administration of EGF stimulated the recruitment of Ras homologue enriched in brain (Rheb) but not mammalian target of rapamycin (mTOR) to endosomes and lysosomes. This was inhibited by chloroquine treatment. Our results suggest a role for vacuolar acidification in EGF signaling to mTORC1.
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Affiliation(s)
- Yanqing Xu
- Polypeptide Hormone Laboratory, Faculty of Medicine, McGill University, Montreal, Quebec H3A 2B2, Canada
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8
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Fedjaev M, Parmar A, Xu Y, Vyetrogon K, Difalco MR, Ashmarina M, Nifant'ev I, Posner BI, Pshezhetsky AV. Global analysis of protein phosphorylation networks in insulin signaling by sequential enrichment of phosphoproteins and phosphopeptides. MOLECULAR BIOSYSTEMS 2012; 8:1461-71. [PMID: 22362066 DOI: 10.1039/c2mb05440j] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Although the important role of protein phosphorylation in insulin signaling networks is well recognized, its analysis in vivo has not been pursued in a systematic fashion through proteome-wide studies. Here we undertake a global analysis of insulin-induced changes in the rat liver cytoplasmic and endosomal phosphoproteome by sequential enrichment of phosphoproteins and phosphopeptides. After subcellular fractionation proteins were denatured and loaded onto iminodiacetic acid-modified Sepharose with immobilized Al³⁺ ions (IMAC-Al resin). Retained phosphoproteins were eluted with 50 mM phosphate and proteolytically digested. The digest was then loaded onto an IMAC-Al resin and phosphopeptides were eluted with 50 mM phosphate, and resolved by 2-dimensional liquid chromatography, which combined offline weak anion exchange and online reverse phase separations. The peptides were identified by tandem mass spectrometry, which also detected the phosphorylation sites. Non-phosphorylated peptides found in the flow-through of the IMAC-Al columns were also analyzed providing complementary information for protein identification. In this study we enriched phosphopeptides to ~85% purity and identified 1456 phosphopeptides from 604 liver phosphoproteins. Eighty-nine phosphosites including 45 novel ones in 83 proteins involved in vesicular transport, metabolism, cell motility and structure, gene expression and various signaling pathways were changed in response to insulin treatment. Together these findings could provide potential new markers for evaluating insulin action and resistance in obesity and diabetes.
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Affiliation(s)
- Michael Fedjaev
- Department of Medical Genetics, CHU Sainte-Justine, University of Montreal, Montreal, Quebec H3T 1C5, Canada
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9
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Kulkarni MV, Tettamanzi MC, Murphy JW, Keeler C, Myszka DG, Chayen NE, Lolis EJ, Hodsdon ME. Two independent histidines, one in human prolactin and one in its receptor, are critical for pH-dependent receptor recognition and activation. J Biol Chem 2010; 285:38524-33. [PMID: 20889499 DOI: 10.1074/jbc.m110.172072] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human prolactin (hPRL), a member of the family of hematopoietic cytokines, functions as both an endocrine hormone and autocrine/paracrine growth factor. We have previously demonstrated that recognition of the hPRL·receptor depends strongly on solution acidity over the physiologic range from pH 6 to pH 8. The hPRL·receptor binding interface contains four histidines whose protonation is hypothesized to regulate pH-dependent receptor recognition. Here, we systematically dissect its molecular origin by characterizing the consequences of His to Ala mutations on pH-dependent receptor binding kinetics, site-specific histidine protonation, and high resolution structures of the intermolecular interface. Thermodynamic modeling of the pH dependence to receptor binding affinity reveals large changes in site-specific protonation constants for a majority of interface histidines upon complexation. Removal of individual His imidazoles reduces these perturbations in protonation constants, which is most likely explained by the introduction of solvent-filled, buried cavities in the crystallographic structures without inducing significant conformational rearrangements.
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Affiliation(s)
- Mandar V Kulkarni
- Department of Laboratory Medicine, Yale School of Medicine, New Haven, Connecticut 06520, USA
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10
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Hettiarachchi KD, Zimmet PZ, Danial NN, Myers MA. Transplacental exposure to the vacuolar-ATPase inhibitor bafilomycin disrupts survival signaling in β cells and delays neonatal remodeling of the endocrine pancreas. ACTA ACUST UNITED AC 2008; 60:295-306. [DOI: 10.1016/j.etp.2008.02.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2007] [Accepted: 02/15/2008] [Indexed: 12/31/2022]
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11
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Quinlan CL, Costa ADT, Costa CL, Pierre SV, Dos Santos P, Garlid KD. Conditioning the heart induces formation of signalosomes that interact with mitochondria to open mitoKATP channels. Am J Physiol Heart Circ Physiol 2008; 295:H953-H961. [PMID: 18621853 DOI: 10.1152/ajpheart.00520.2008] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Perfusion of the heart with bradykinin triggers cellular signaling events that ultimately cause opening of mitochondrial ATP-sensitive K+ (mitoKATP) channels, increased H2O2 production, inhibition of the mitochondrial permeability transition (MPT), and cardioprotection. We hypothesized that the interaction of bradykinin with its receptor induces the assembly of a caveolar signaling platform (signalosome) that contains the enzymes of the signaling pathway and that migrates to mitochondria to induce mitoKATP channel opening. We developed a novel method for isolating and purifying signalosomes from Langendorff-perfused rat hearts treated with bradykinin. Fractions containing the signalosomes were found to open mitoKATP channels in mitochondria isolated from untreated hearts via the activation of mitochondrial PKC-epsilon. mitoKATP channel opening required signalosome-dependent phosphorylation of an outer membrane protein. Immunodetection analysis revealed the presence of the bradykinin B2 receptor only in the fraction isolated from bradykinin-treated hearts. Immunodetection and immunogold labeling of caveolin-3, as well as sensitivity to cholesterol depletion and resistance to Triton X-100, attested to the caveolar nature of the signalosomes. Ischemic preconditioning, ischemic postconditioning, and perfusion with ouabain also led to active signalosome fractions that opened mitoKATP channels in mitochondria from untreated hearts. These results provide initial support for a novel mechanism for signal transmission from a plasma membrane receptor to mitoKATP channels.
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Affiliation(s)
- Casey L Quinlan
- Department of Biology, Portland State University, PO Box 751, Portland, OR 97201-0751, USA
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12
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Choi YO, Park JH, Song YS, Lee W, Moriyama Y, Choe H, Leem CH, Jang YJ. Involvement of vesicular H+-ATPase in insulin-stimulated glucose transport in 3T3-F442A adipocytes. Endocr J 2007; 54:733-43. [PMID: 17827791 DOI: 10.1507/endocrj.k07-090] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In secretory cells, osmotic swelling of secretory granules is proposed to be an intermediate step in exocytic fusion of the granules with the plasma membrane. For osmotic swelling of the granule, a H (+) gradient generated by vacuolar-type H (+) -ATPase (V-ATPase) may be a driving force for accumulation of K (+) via its exchange with H (+) , concurrent with accumulation of Cl (-) and H(2)O. Here, we investigated whether a similar chemiosmotic mechanism is involved in the insulin-stimulated recruitment of GLUT4 to the plasma membrane in 3T3-F442A adipocytes. Incubating cells in a hypo-osmotic medium significantly increased 2-deoxy glucose (2-DG) uptake and the plasma membrane GLUT4 content (possibly via induction of osmotic swelling of GLUT4-containing vesicles (G4V)) and also potentiated the insulin-stimulated 2-DG uptake. Promotion of the G4V membrane ionic permeability using nigericin, an electroneutral K (+) /H (+) exchange ionophore, increased 2-DG uptake and the plasma membrane GLUT4 content. However, co-treatment with nigericin and insulin did not show an additive effect. Bafilomycin A(1), a diagnostically specific inhibitor of V-ATPase, inhibited insulin- and nigericin-stimulated 2-DG uptake. Immunoadsorption plus immunoblotting demonstrated that GLUT4 and V-ATPase co-localize in the same intracellular membranes. Together, these results indicate that V-ATPases in the G4V membrane may play an important role in the insulin-stimulated exocytic fusion of G4V with the plasma membrane via its participation in osmotic swelling of the vesicle.
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Affiliation(s)
- Young Ok Choi
- Department of Physiology, University of Ulsan College of Medicine, Seoul, Korea
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13
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Bertacca A, Ciccarone A, Cecchetti P, Vianello B, Laurenza I, Del Prato S, Benzi L. High insulin levels impair intracellular receptor trafficking in human cultured myoblasts. Diabetes Res Clin Pract 2007; 78:316-23. [PMID: 17644209 DOI: 10.1016/j.diabres.2007.06.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2007] [Accepted: 06/02/2007] [Indexed: 01/18/2023]
Abstract
Chronic hyperinsulinemia is both a marker and a cause for insulin resistance. This study analyzes the effect of long-term exposure to high insulin levels on insulin-insulin receptor metabolism in human myoblasts. Cells were grown in the presence of low (107 pM, SkMC-L) or high (1430 pM, SkMC-H) insulin concentrations. Insulin receptor (IR) phosphorylation, IR internalization, dissociation and recycling, as well as insulin degradation have been investigated. Basal IR phosphorylation was higher in SkMC-H than in SkMC-L (P<0.01) but after acute insulin stimulation (10nM insulin for 10 min), IR phosphorylation increased (P<0.01) in SkMC-L, but not in SkMC-H. Chronic hyperinsulinism significantly decreased insulin-IR complex internalization (P<0.01). Nevertheless the t(1/2) value of receptor internalization was similar in both cells. Intracellular dissociation of insulin-IR complex was slightly but significantly lower in SkMC-H than in SkMC-L. Finally, SkMC-H showed a complete, but significantly delayed recycling of IR to plasma membrane (t(1/2)=20 min versus SkMC-L t(1/2)=7 min). The time course of intracellular degradation measured by HPLC, showed whenever studied, significantly (P<0.01) higher levels of intracellular intact insulin in cells exposed to high insulin concentrations. Nevertheless, the patterns of insulin degradation were over-imposable between SkMC-H and SkMC-L. In summary, continuous exposure of cultured myoblasts to high insulin levels induces subtle derangements of intracellular receptor trafficking and insulin degradation. These alterations may contribute to the insulin resistance of hyperinsulinemic states such as obesity and Type 2 Diabetes.
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Affiliation(s)
- Anna Bertacca
- Department of Endocrinology and Metabolism, School of Medicine, University of Pisa, Ospedale Cisanello, Via Paradisa, 2, 56124 Pisa, Italy.
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Beitia Ortiz de Zarate I, Cantero-Aguilar L, Longo M, Berlioz-Torrent C, Rozenberg F. Contribution of endocytic motifs in the cytoplasmic tail of herpes simplex virus type 1 glycoprotein B to virus replication and cell-cell fusion. J Virol 2007; 81:13889-903. [PMID: 17913800 PMCID: PMC2168835 DOI: 10.1128/jvi.01231-07] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The use of endocytic pathways by viral glycoproteins is thought to play various functions during viral infection. We previously showed in transfection assays that herpes simplex virus type 1 (HSV-1) glycoprotein B (gB) is transported from the cell surface back to the trans-Golgi network (TGN) and that two motifs of gB cytoplasmic tail, YTQV and LL, function distinctly in this process. To investigate the role of each of these gB trafficking signals in HSV-1 infection, we constructed recombinant viruses in which each motif was rendered nonfunctional by alanine mutagenesis. In infected cells, wild-type gB was internalized from the cell surface and concentrated in the TGN. Disruption of YTQV abolished internalization of gB during infection, whereas disruption of LL induced accumulation of internalized gB in early recycling endosomes and impaired its return to the TGN. The growth of both recombinants was moderately diminished. Moreover, the fusion phenotype of cells infected with the gB recombinants differed from that of cells infected with the wild-type virus. Cells infected with the YTQV-mutated virus displayed reduced cell-cell fusion, whereas giant syncytia were observed in cells infected with the LL-mutated virus. Furthermore, blocking gB internalization or impairing gB recycling to the cell surface, using drugs or a transdominant negative form of Rab11, significantly reduced cell-cell fusion. These results favor a role for endocytosis in virus replication and suggest that gB intracellular trafficking is involved in the regulation of cell-cell fusion.
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15
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El Hage T, Merlen C, Fabrega S, Authier F. Role of receptor-mediated endocytosis, endosomal acidification and cathepsin D in cholera toxin cytotoxicity. FEBS J 2007; 274:2614-29. [PMID: 17451437 DOI: 10.1111/j.1742-4658.2007.05797.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Using the in situ liver model system, we have recently shown that, after cholera toxin binding to hepatic cells, cholera toxin accumulates in a low-density endosomal compartment, and then undergoes endosomal proteolysis by the aspartic acid protease cathepsin-D [Merlen C, Fayol-Messaoudi D, Fabrega S, El Hage T, Servin A, Authier F (2005) FEBS J272, 4385-4397]. Here, we have used a subcellular fractionation approach to address the in vivo compartmentalization and cytotoxic action of cholera toxin in rat liver parenchyma. Following administration of a saturating dose of cholera toxin to rats, rapid endocytosis of both cholera toxin subunits was observed, coincident with massive internalization of both the 45 kDa and 47 kDa Gsalpha proteins. These events coincided with the endosomal recruitment of ADP-ribosylation factor proteins, especially ADP-ribosylation factor-6, with a time course identical to that of toxin and the A subunit of the stimulatory G protein (Gsalpha) translocation. After an initial lag phase of 30 min, these constituents were linked to NAD-dependent ADP-ribosylation of endogenous Gsalpha, with maximum accumulation observed at 30-60 min postinjection. Assessment of the subsequent postendosomal fate of internalized Gsalpha revealed sustained endolysosomal transfer of the two Gsalpha isoforms. Concomitantly, cholera toxin increased in vivo endosome acidification rates driven by the ATP-dependent H(+)-ATPase pump and in vitro vacuolar acidification in hepatoma HepG2 cells. The vacuolar H(+)-ATPase inhibitor bafilomycin and the cathepsin D inhibitor pepstatin A partially inhibited, both in vivo and in vitro, the cAMP response to cholera toxin. This cathepsin D-dependent action of cholera toxin under the control of endosomal acidity was confirmed using cellular systems in which modification of the expression levels of cathepsin D, either by transfection of the cathepsin D gene or small interfering RNA, was followed by parallel changes in the cytotoxic response to cholera toxin. Thus, in hepatic cells, a unique endocytic pathway was revealed following cholera toxin administration, with regulation specificity most probably occurring at the locus of the endosome and implicating endosomal proteases, such as cathepsin D, as well as organelle acidification.
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Affiliation(s)
- Tatiana El Hage
- INSERM, U756; and Université Paris-Sud, Faculté de Pharmacie, Châtenay, Malabry, France
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16
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George A, Leahy H, Zhou J, Morin PJ. The vacuolar-ATPase inhibitor bafilomycin and mutant VPS35 inhibit canonical Wnt signaling. Neurobiol Dis 2007; 26:125-33. [PMID: 17239604 DOI: 10.1016/j.nbd.2006.12.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Revised: 11/10/2006] [Accepted: 12/06/2006] [Indexed: 12/26/2022] Open
Abstract
Endosomal acidification and transport are essential functions in signal transduction. Recent data suggest that Wnt signaling requires intact endosomal transport machinery but the effects of endosomal acidification on Wnt signal transduction have not been evaluated. Here we report that bafilomycin, a specific inhibitor of the vacuolar proton ATPase that blocks endosomal acidification, inhibits canonical Wnt signal transduction initiated by Wnt ligand and partially inhibits signaling initiated by disheveled. Bafilomycin does not affect Tcf promoter activation by beta-catenin. These data indicate that endosomal acidification is necessary for Wnt signaling. To identify interactions between endosomal transport proteins and Wnt receptors, we performed a GST fusion protein pulldown experiment and identified a possible indirect interaction between the LRP6 intracellular domain and vacuolar protein sorting protein 35 (VPS35). We show that an N-terminal deletion mutant of VPS35 reduces canonical Wnt signaling in HEK-293 cells expressing exogenous Wnt-1. These data suggest that endosomal V-type ATPase activity and retromer trafficking proteins are functionally important in Wnt signal transduction.
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Affiliation(s)
- Ana George
- Geriatric Research, Education, and Clinical Center, Edith Nourse Rogers Memorial Veteran's Administration Hospital, Bedford, MA 01730-1114, USA
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17
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Hettiarachchi KD, Zimmet PZ, Myers MA. The plecomacrolide vacuolar-ATPase inhibitor bafilomycin, alters insulin signaling in MIN6 beta-cells. Cell Biol Toxicol 2007; 22:169-81. [PMID: 16555000 DOI: 10.1007/s10565-006-0054-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Accepted: 01/05/2006] [Indexed: 12/31/2022]
Abstract
Inhibition of endosomal acidification disturbs insulin signaling in both liver and adipose cells. In this study we used MIN6 beta cells to determine whether bafilomycin, a potent inhibitor of the proton-translocating vacuolar ATPase, disrupts insulin signaling in islet beta cells. Pretreatment of MIN6 cells with varying concentrations of bafilomycin according to a time course revealed concentration and time-dependent changes in phosphorylation of insulin receptor signaling components. Increased phosphorylation of insulin receptor (IR), IRS2 and Akt was prolonged at low bafilomycin concentrations (10 and 50 nmol/L), whereas at high concentrations (100 and 200 nmol/L) phosphorylation rapidly returned to basal levels or below. Akt activation was demonstrated by transient increases in phosphorylation of BAD, cytoplasmic retention of FoxO1 and increased preproinsulin mRNA. Bcl2 expression was also transiently increased but reduced after 30 min exposure to bafilomycin, and this coincided with reduced cell viability. Thus, in beta cells inhibition of endosomal acidification by low concentrations of bafilomycin transiently increases insulin signaling, whereas high concentrations promote cell death. Bafilomycin and other agents that interfere with insulin signaling may contribute to diabetes development through disturbing homeostatic control of beta cell growth.
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Affiliation(s)
- K D Hettiarachchi
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
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18
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Fedjaev M, Trudel S, Tjon-A-Pan N, Parmar A, Posner BI, Levy E, Nifant'ev I, Pshezhetsky AV. Quantitative analysis of a proteome by N-terminal stable-isotope labelling of tryptic peptides. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2007; 21:2671-9. [PMID: 17659651 DOI: 10.1002/rcm.3128] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Covalent modification of peptides and proteins with compounds containing stable isotopes (isotope tagging) has become an essential tool to detect dynamic changes in the proteome following external or internal influence; however, using terminal amino groups for global isotope labelling of tryptic peptides is challenged by the similar reactivity of the amino groups of lysine residues. We describe a new quantitative method based on selective tagging of the terminal amino groups of tryptic peptides with pentafluorophenyl esters containing stable isotopes. The labelled peptides were resolved by two-dimensional nanoflow liquid chromatography on weak anion-exchange and reversed-phase columns and then identified and quantified by tandem mass spectrometry. The method was applied to compare the proteomes of plasma membranes from proliferating and differentiated human colorectal adenocarcinoma (Caco-2) cells and endosomes purified from the livers of rats stimulated with insulin and epidermal growth factor. The comparison of the results obtained by isotope tagging and biochemical assays demonstrate that global isotope tagging with pentafluorophenyl esters allows accurate quantification of complex protein samples.
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Affiliation(s)
- Michael Fedjaev
- Sainte-Justine Hospital Research Center, University of Montreal, 3175 Côte Ste-Catherine Road, Montreal (Quebec), H3T 1C5, Canada
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19
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Hori SS, Kurland IJ, DiStefano JJ. Role of endosomal trafficking dynamics on the regulation of hepatic insulin receptor activity: models for Fao cells. Ann Biomed Eng 2006; 34:879-92. [PMID: 16708271 DOI: 10.1007/s10439-005-9065-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Accepted: 11/07/2005] [Indexed: 02/06/2023]
Abstract
Evidence indicates that endosomal insulin receptor (IR) trafficking plays a role in regulating insulin signal transduction. To evaluate its importance, we developed a series of biokinetic models for quantifying activated surface and endosomal IR dynamics from published experimental data. Starting with a published two-compartment Fao hepatoma model, a four-pool model was formulated that depicts IR autophosphorylation after receptor binding, IR endosomal internalization/trafficking, insulin dissociation from and dephosphorylation of internalized IR, and recycling of unliganded, dephosphorylated IR to the plasma membrane. Quantification required three additional data sets, two measured, but unmodeled by the same group. A five-pool model created to include endosomal trafficking of the nonphosphorylated insulin-IR complex was fitted using the same data sets, augmented with another published data set. Creation of a six-pool model added the physiologically relevant dissociation of insulin ligand from the activated endosomal IR. More importantly, all three models, validated against additional data not used in model fitting, predict that, mechanistically, internalization of activated IR is a rate-limiting step, at least under the receptor saturating conditions of the fitting data. This rate includes the transit time to a site where insulin dissociation from and/or dephosphorylation of the IR occurs by docking with protein-tyrosine phosphatases (PTPases), or where a sufficient conformational change occurs in the IR, perhaps due to insulin-IR dissociation, where associated PTPases may complete IR dephosphorylation. Our new models indicate that key events in endosomal IR trafficking have significance in mediating IR activity, possibly serving to regulate insulin signal transduction.
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Affiliation(s)
- Sharon S Hori
- Biocybernetics Laboratory, Department of Computer Science, University of California, Los Angeles, CA 90095-1596, USA.
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20
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Bohnert S, Schiavo G. Tetanus Toxin Is Transported in a Novel Neuronal Compartment Characterized by a Specialized pH Regulation. J Biol Chem 2005; 280:42336-44. [PMID: 16236708 DOI: 10.1074/jbc.m506750200] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Tetanus toxin binds specifically to motor neurons at the neuromuscular junction. There, it is internalized into vesicular carriers undergoing fast retrograde transport to the spinal cord. Despite the importance of this axonal transport pathway in health and disease, its molecular and biophysical characterization is presently lacking. We sought to fill this gap by determining the pH regulation of this compartment in living motor neurons using a chimera of the tetanus toxin binding fragment (TeNT HC) and a pH-sensitive variant of the green fluorescent protein (ratiometric pHluorin). We have demonstrated that moving retrograde carriers display a narrow range of neutral pH values, which is kept constant during transport. Stationary TeNT HC-positive organelles instead exhibit a wide spectrum of pH values, ranging from acidic to neutral. This distinct pH regulation is due to a differential targeting of the vacuolar (H+) ATPase, which is not present on moving TeNT HC compartments. Accordingly, inhibition of the vacuolar (H+) ATPase under conditions that completely abolish the intracellular accumulation of acidotrophic dyes does not affect axonal retrograde transport of TeNT HC. However, a functional vacuolar (H+) ATPase is required for early steps of TeNT HC trafficking following endocytosis, and it is localized to axonal vesicles containing TeNT HC. Altogether, these findings indicate that the vacuolar (H+ ATPase plays a specific role in early sorting events directing TeNT HC to axonal carriers but not in their subsequent progression along the retrograde transport route, which escapes acidification and targeting to degradative organelles.
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Affiliation(s)
- Stephanie Bohnert
- Molecular NeuroPathobiology Laboratory, Cancer Research UK, London Research Institute, Lincoln's Inn Fields Laboratories, 44 Lincoln's Inn Fields, London WC2A 3PX, United Kingdom
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Disbrow GL, Hanover JA, Schlegel R. Endoplasmic reticulum-localized human papillomavirus type 16 E5 protein alters endosomal pH but not trans-Golgi pH. J Virol 2005; 79:5839-46. [PMID: 15827198 PMCID: PMC1082759 DOI: 10.1128/jvi.79.9.5839-5846.2005] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The human papillomavirus type 16 (HPV-16) E5 protein is a small, hydrophobic polypeptide that is expressed in virus-infected keratinocytes and alters receptor signaling pathways, apoptotic responses, and endosomal pH. Despite its ability to inhibit endosomal acidification, the HPV-16 E5 protein is found predominantly in the endoplasmic reticulum (ER), suggesting that its effect may be indirect and perhaps global. To determine whether E5 alters the pHs of additional intracellular compartments, we transduced human keratinocytes with a codon-optimized E5 vector and then quantified endosomal and trans-Golgi pHs using sensitive, compartment-specific, ratiometric pHluorin constructs. E5 protein increased endosomal pH from 5.9 to 6.9 but did not affect the normal trans-Golgi pH of 6.3. Confirming the lack of alteration in trans-Golgi pH, we observed no alterations in the acidification-dependent processing of the proH3 protein. C-terminal deletions of E5, which retained normal expression and localization in the ER, were defective for endosomal alkalization. Thus, E5 does not uniformly alkalinize intracellular compartments, and its C-terminal 10 amino acids appear to mediate interactions with critical ER targets that modulate proton pump function and/or localization.
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Affiliation(s)
- Gary L Disbrow
- Department of Pathology, Georgetown University Medical School, Basic Science Building, Room 113, 3900 Reservoir Rd., NW, Washington, DC 20057, USA
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