1
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Cabana VC, Sénécal AM, Bouchard AY, Kourrich S, Cappadocia L, Lussier MP. AP-1 contributes to endosomal targeting of the ubiquitin ligase RNF13 via a secondary and novel non-canonical binding motif. J Cell Sci 2024; 137:jcs262035. [PMID: 39206621 DOI: 10.1242/jcs.262035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 08/20/2024] [Indexed: 09/04/2024] Open
Abstract
Cellular trafficking between organelles is typically assured by short motifs that contact carrier proteins to transport them to their destination. The ubiquitin E3 ligase RING finger protein 13 (RNF13), a regulator of proliferation, apoptosis and protein trafficking, localizes to endolysosomal compartments through the binding of a dileucine motif to clathrin adaptor protein complex AP-3. Mutations within this motif reduce the ability of RNF13 to interact with AP-3. Here, our study shows the discovery of a glutamine-based motif that resembles a tyrosine-based motif within the C-terminal region of RNF13 that binds to the clathrin adaptor protein complex AP-1, notably without a functional interaction with AP-3. Using biochemical, molecular and cellular approaches in HeLa cells, our study demonstrates that a RNF13 dileucine variant uses an AP-1-dependent pathway to be exported from the Golgi towards the endosomal compartment. Overall, this study provides mechanistic insights into the alternate route used by this variant of the dileucine sorting motif of RNF13.
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Affiliation(s)
- Valérie C Cabana
- Département de Chimie, Université du Québec à Montréal, 2101, rue Jeanne-Mance, Montréal, QC H2X 2J6, Canada
- Centre d'Excellence en Recherche sur les Maladies Orphelines - Fondation Courtois (CERMO-FC), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
- Regroupement québécois de recherche sur la fonction, l'ingénierie et les applications des protéines (PROTEO), Montréal, QC H3C 3P8, Canada
| | - Audrey M Sénécal
- Département de Chimie, Université du Québec à Montréal, 2101, rue Jeanne-Mance, Montréal, QC H2X 2J6, Canada
- Centre d'Excellence en Recherche sur les Maladies Orphelines - Fondation Courtois (CERMO-FC), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
- Regroupement québécois de recherche sur la fonction, l'ingénierie et les applications des protéines (PROTEO), Montréal, QC H3C 3P8, Canada
| | - Antoine Y Bouchard
- Département de Chimie, Université du Québec à Montréal, 2101, rue Jeanne-Mance, Montréal, QC H2X 2J6, Canada
- Centre d'Excellence en Recherche sur les Maladies Orphelines - Fondation Courtois (CERMO-FC), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
- Regroupement québécois de recherche sur la fonction, l'ingénierie et les applications des protéines (PROTEO), Montréal, QC H3C 3P8, Canada
| | - Saïd Kourrich
- Centre d'Excellence en Recherche sur les Maladies Orphelines - Fondation Courtois (CERMO-FC), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
- Département des Sciences Biologiques, Université du Québec à Montréal, 141 avenue du Président-Kennedy, Montréal, QC H2X 3X8, Canada
- Center for Studies in Behavioral Neurobiology, Concordia University, Montreal, QC H4B 1R6, Canada
| | - Laurent Cappadocia
- Département de Chimie, Université du Québec à Montréal, 2101, rue Jeanne-Mance, Montréal, QC H2X 2J6, Canada
- Centre d'Excellence en Recherche sur les Maladies Orphelines - Fondation Courtois (CERMO-FC), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
- Regroupement québécois de recherche sur la fonction, l'ingénierie et les applications des protéines (PROTEO), Montréal, QC H3C 3P8, Canada
| | - Marc P Lussier
- Département de Chimie, Université du Québec à Montréal, 2101, rue Jeanne-Mance, Montréal, QC H2X 2J6, Canada
- Centre d'Excellence en Recherche sur les Maladies Orphelines - Fondation Courtois (CERMO-FC), Université du Québec à Montréal, Montréal, QC H2X 3Y7, Canada
- Regroupement québécois de recherche sur la fonction, l'ingénierie et les applications des protéines (PROTEO), Montréal, QC H3C 3P8, Canada
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2
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Ai Y, Guo C, Garcia-Contreras M, Sánchez B. LS, Saftics A, Shodubi O, Raghunandan S, Xu J, Tsai SJ, Dong Y, Li R, Jovanovic-Talisman T, Gould SJ. Endocytosis blocks the vesicular secretion of exosome marker proteins. SCIENCE ADVANCES 2024; 10:eadi9156. [PMID: 38718108 PMCID: PMC11078179 DOI: 10.1126/sciadv.adi9156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 04/04/2024] [Indexed: 05/12/2024]
Abstract
Exosomes are secreted vesicles of ~30 to 150 nm diameter that play important roles in human health and disease. To better understand how cells release these vesicles, we examined the biogenesis of the most highly enriched human exosome marker proteins, the exosomal tetraspanins CD81, CD9, and CD63. We show here that endocytosis inhibits their vesicular secretion and, in the case of CD9 and CD81, triggers their destruction. Furthermore, we show that syntenin, a previously described exosome biogenesis factor, drives the vesicular secretion of CD63 by blocking CD63 endocytosis and that other endocytosis inhibitors also induce the plasma membrane accumulation and vesicular secretion of CD63. Finally, we show that CD63 is an expression-dependent inhibitor of endocytosis that triggers the vesicular secretion of lysosomal proteins and the clathrin adaptor AP-2 mu2. These results suggest that the vesicular secretion of exosome marker proteins in exosome-sized vesicles occurs primarily by an endocytosis-independent pathway.
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Affiliation(s)
- Yiwei Ai
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Chenxu Guo
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Marta Garcia-Contreras
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Laura S. Sánchez B.
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Andras Saftics
- Department of Cancer Biology and Molecular Medicine, Beckman Research Institute, City of Hope, Duarte, CA 91010, USA
| | - Oluwapelumi Shodubi
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Shankar Raghunandan
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Junhao Xu
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Shang Jui Tsai
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Yi Dong
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Rong Li
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Mechanobiology Institute and Department of Biological Sciences, National University of Singapore, Singapore 117558, Singapore
| | - Tijana Jovanovic-Talisman
- Department of Cancer Biology and Molecular Medicine, Beckman Research Institute, City of Hope, Duarte, CA 91010, USA
| | - Stephen J. Gould
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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3
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Guo C, Sachithanandham J, Zhong W, Craney M, Villano J, Pekosz A, Gould SJ. Antigen-display exosomes provide adjuvant-free protection against SARS-CoV-2 disease at nanogram levels of spike protein. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.04.574272. [PMID: 38328234 PMCID: PMC10849639 DOI: 10.1101/2024.01.04.574272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
As the only bionormal nanovesicle, exosomes have high potential as a nanovesicle for delivering vaccines and therapeutics. We show here that the loading of type-1 membrane proteins into the exosome membrane is induced by exosome membrane anchor domains, EMADs, that maximize protein delivery to the plasma membrane, minimize protein sorting to other compartments, and direct proteins into exosome membranes. Using SARS-CoV-2 spike as an example and EMAD13 as our most effective exosome membrane anchor, we show that cells expressing a spike-EMAD13 fusion protein produced exosomes that carry dense arrays of spike trimers on 50% of all exosomes. Moreover, we find that immunization with spike-EMAD13 exosomes induced strong neutralizing antibody responses and protected hamsters against SARS-CoV-2 disease at doses of just 0.5-5 ng of spike protein, without adjuvant, demonstrating that antigen-display exosomes are particularly immunogenic, with important implications for both structural and expression-dependent vaccines.
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Affiliation(s)
- Chenxu Guo
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Jaiprasath Sachithanandham
- Department of Microbiology and Immunology, The Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205
| | - William Zhong
- Department of Microbiology and Immunology, The Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205
| | - Morgan Craney
- Department of Molecular and Comparative Pathobiology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Jason Villano
- Department of Molecular and Comparative Pathobiology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Andrew Pekosz
- Department of Microbiology and Immunology, The Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD 21205
| | - Stephen J Gould
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
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4
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Ai Y, Guo C, Garcia-Contreras M, Sanchez LS, Saftics A, Shodubi O, Raghunandan S, Xu J, Tsai SJ, Dong Y, Li R, Jovanovic-Talisman T, Gould S. Syntenin and CD63 Promote Exosome Biogenesis from the Plasma Membrane by Blocking Cargo Endocytosis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.26.542409. [PMID: 37292617 PMCID: PMC10245948 DOI: 10.1101/2023.05.26.542409] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Exosomes are small extracellular vesicles important in health and disease. Syntenin is thought to drive the biogenesis of CD63 exosomes by recruiting Alix and the ESCRT machinery to endosomes, initiating an endosome-mediated pathway of exosome biogenesis. Contrary to this model, we show here that syntenin drives the biogenesis of CD63 exosomes by blocking CD63 endocytosis, thereby allowing CD63 to accumulate at the plasma membrane, the primary site of exosome biogenesis. Consistent with these results, we find that inhibitors of endocytosis induce the exosomal secretion of CD63, that endocytosis inhibits the vesicular secretion of exosome cargo proteins, and that high-level expression of CD63 itself also inhibits endocytosis. These and other results indicate that exosomes bud primarily from the plasma membrane, that endocytosis inhibits their loading into exosomes, that syntenin and CD63 are expression-dependent regulators of exosome biogenesis, and that syntenin drives the biogenesis of CD63 exosomes even in Alix knockout cells.
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5
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DeGroot ACM, Gollapudi S, Zhao C, LaMonica MF, Stachowiak JC. Weakly Internalized Receptors Use Coated Vesicle Heterogeneity to Evade Competition during Endocytosis. Biochemistry 2021; 60:2195-2205. [PMID: 34170686 PMCID: PMC8483609 DOI: 10.1021/acs.biochem.1c00268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The uptake of receptors by clathrin-mediated endocytosis underlies signaling, nutrient import, and recycling of transmembrane proteins and lipids. In the complex, crowded environment of the plasma membrane, receptors are internalized when they bind to components of the clathrin coat, such as the major adaptor protein, AP2. Receptors with higher affinity for AP2 are known to be more strongly internalized compared to receptors with lower affinity. However, it remains unclear how receptors with different affinities compete for space within crowded endocytic structures. To address this question, we constructed receptors with varying affinities for AP2 and allowed them to compete against one another during internalization. As expected, the internalization of a receptor with high affinity for AP2 was reduced when it was coexpressed with a competing receptor of similar affinity. However, receptors of low affinity for AP2 were surprisingly difficult to displace from endocytic structures, even when expressed alongside receptors with much higher affinity. To understand how these low-affinity receptors are protected from competition, we looked at AP2 heterogeneity across clathrin-coated structures. When we examined structures with lower-than-average AP2 content, we found that they were relatively enriched in cargo of low affinity for AP2 and depleted of cargo with high affinity. These findings suggest that the heterogeneity of adaptor protein content across the population of endocytic structures enables the internalization of diverse receptors. Given the critical role that internalization plays in signaling, this effect may help to prevent strongly internalized receptors from interfering with the cell's ability to process signals from weakly internalized receptors.
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Affiliation(s)
| | - Sadhana Gollapudi
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Chi Zhao
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Megan F. LaMonica
- Department of Biomedical Engineering, The University of Texas at Austin
| | - Jeanne C. Stachowiak
- Department of Biomedical Engineering, The University of Texas at Austin
- Institute for Cellular and Molecular Biology, The University of Texas at Austin
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6
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DeGroot ACM, Zhao C, LaMonica MF, Hayden CC, Stachowiak JC. Molecular thermodynamics of receptor competition for endocytic uptake. SOFT MATTER 2019; 15:7448-7461. [PMID: 31502617 PMCID: PMC6918483 DOI: 10.1039/c9sm00876d] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Endocytic uptake of receptors from the cell surface plays an important role in diverse processes from cell signaling to nutrient internalization. Understanding the mechanisms by which endocytic structures select receptors for internalization is of fundamental importance to our understanding of cellular physiology. Binding of receptors to the endocytic protein machinery is known to facilitate receptor loading into endocytic structures. However, many receptor species use the same small set of biochemical motifs to interact with the endocytic machinery, suggesting that receptors may compete for a limited number of binding sites within endocytic structures. Previous studies have shown that such competition can substantially modify receptor uptake. However, a predictive biophysical understanding of this phenomenon is currently lacking. Toward addressing this gap, here we employ quantitative imaging and statistical thermodynamics to measure and predict the competition between two distinct receptor species that are internalized simultaneously from the cell surface. Our studies demonstrate that when receptors compete for the same interactions with the endocytic machinery, their uptake is fundamentally coupled. Importantly, we find that these trends can be quantitatively predicted by a simple thermodynamic analysis. These results suggest that multiple receptor species reach an equilibrium partitioning between endocytic structures and the surrounding plasma membrane as the receptors compete for occupancy within dynamic endocytic structures. More broadly, this work provides a quantitative framework for predicting the impact of competition on receptor uptake, an effect which has the potential to physically couple signaling pathways that impact diverse aspects of cellular physiology.
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Affiliation(s)
- Andre C M DeGroot
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712, USA.
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7
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Weinberg ZY, Puthenveedu MA. Regulation of G protein-coupled receptor signaling by plasma membrane organization and endocytosis. Traffic 2019; 20:121-129. [PMID: 30536564 PMCID: PMC6415975 DOI: 10.1111/tra.12628] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 11/27/2018] [Accepted: 12/05/2018] [Indexed: 12/11/2022]
Abstract
The trafficking of G protein coupled-receptors (GPCRs) is one of the most exciting areas in cell biology because of recent advances demonstrating that GPCR signaling is spatially encoded. GPCRs, acting in a diverse array of physiological systems, can have differential signaling consequences depending on their subcellular localization. At the plasma membrane, GPCR organization could fine-tune the initial stages of receptor signaling by determining the magnitude of signaling and the type of effectors to which receptors can couple. This organization is mediated by the lipid composition of the plasma membrane, receptor-receptor interactions, and receptor interactions with intracellular scaffolding proteins. GPCR organization is subsequently changed by ligand binding and the regulated endocytosis of these receptors. Activated GPCRs can modulate the dynamics of their own endocytosis through changing clathrin-coated pit dynamics, and through the scaffolding adaptor protein β-arrestin. This endocytic regulation has signaling consequences, predominantly through modulation of the MAPK cascade. This review explores what is known about receptor sorting at the plasma membrane, protein partners that control receptor endocytosis, and the ways in which receptor sorting at the plasma membrane regulates downstream trafficking and signaling.
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Affiliation(s)
- Zara Y Weinberg
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, Michigan
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8
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Wang B, Zhang J, Song F, Tian M, Shi B, Jiang H, Xu W, Wang H, Zhou M, Pan X, Gu J, Yang S, Jiang L, Li Z. EGFR regulates iron homeostasis to promote cancer growth through redistribution of transferrin receptor 1. Cancer Lett 2016; 381:331-40. [DOI: 10.1016/j.canlet.2016.08.006] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 06/30/2016] [Accepted: 08/05/2016] [Indexed: 12/21/2022]
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9
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Ockenga W, Tikkanen R. Revisiting the endocytosis of the m2 muscarinic acetylcholine receptor. MEMBRANES 2015; 5:197-213. [PMID: 25985102 PMCID: PMC4496640 DOI: 10.3390/membranes5020197] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Accepted: 05/05/2015] [Indexed: 11/16/2022]
Abstract
The agonist-induced endocytosis of the muscarinic acetylcholine receptor M2 is different from that of the other members of the muscarinic receptor family. The uptake of the M2 receptor involves the adapter proteins of the β-arrestin family and the small GTPase ADP-ribosylation factor 6. However, it has remained inconclusive if M2 endocytosis is dependent on clathrin or the large GTPase dynamin. We here show by means of knocking down the clathrin heavy chain that M2 uptake upon agonist stimulation requires clathrin. The expression of various dominant-negative dynamin-2 mutants and the use of chemical inhibitors of dynamin function revealed that dynamin expression and membrane localization as such appear to be necessary for M2 endocytosis, whereas dynamin GTPase activity is not required for this process. Based on the data from the present and from previous studies, we propose that M2 endocytosis takes place by means of an atypical clathrin-mediated pathway that may involve a specific subset of clathrin-coated pits/vesicles.
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Affiliation(s)
- Wymke Ockenga
- Institute of Biochemistry, Medical Faculty, University of Giessen, Friedrichstrasse 24, D-35392 Giessen, Germany.
| | - Ritva Tikkanen
- Institute of Biochemistry, Medical Faculty, University of Giessen, Friedrichstrasse 24, D-35392 Giessen, Germany.
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10
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Abstract
Endocytosis is an essential process of eukaryotic cells that facilitates numerous cellular and organismal functions. The formation of vesicles from the plasma membrane serves the internalization of ligands and receptors and leads to their degradation or recycling. A number of distinct mechanisms have been described over the years, several of which are only partially characterized in terms of mechanism and function. These are often referred to as novel endocytic pathways. The pathways differ in their mode of uptake and in their intracellular destination. Here, an overview of the set of cellular proteins that facilitate the different pathways is provided. Further, the approaches to distinguish between the pathways by different modes of perturbation are critically discussed, emphasizing the use of genetic tools such as dominant negative mutant proteins.
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Affiliation(s)
- Lena Kühling
- Emmy Noether Group: Virus Endocytosis, Institutes of Molecular Virology and Medical Biochemistry, ZMBE, Westphalian Wilhelms University of Münster, Von-Esmarch-Str. 56, Münster, 48149, Germany
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11
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Puri C, Renna M, Bento C, Moreau K, Rubinsztein D. Diverse autophagosome membrane sources coalesce in recycling endosomes. Cell 2013; 154:1285-99. [PMID: 24034251 PMCID: PMC3791395 DOI: 10.1016/j.cell.2013.08.044] [Citation(s) in RCA: 321] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Revised: 06/28/2013] [Accepted: 08/23/2013] [Indexed: 01/28/2023]
Abstract
Autophagic protein degradation is mediated by autophagosomes that fuse with lysosomes, where their contents are degraded. The membrane origins of autophagosomes may involve multiple sources. However, it is unclear if and where distinct membrane sources fuse during autophagosome biogenesis. Vesicles containing mATG9, the only transmembrane autophagy protein, are seen in many sites, and fusions with other autophagic compartments have not been visualized in mammalian cells. We observed that mATG9 traffics from the plasma membrane to recycling endosomes in carriers that appear to be routed differently from ATG16L1-containing vesicles, another source of autophagosome membrane. mATG9- and ATG16L1-containing vesicles traffic to recycling endosomes, where VAMP3-dependent heterotypic fusions occur. These fusions correlate with autophagosome formation, and both processes are enhanced by perturbing membrane egress from recycling endosomes. Starvation, a primordial autophagy activator, reduces membrane recycling from recycling endosomes and enhances mATG9-ATG16L1 vesicle fusion. Thus, this mechanism may fine-tune physiological autophagic responses. mATG9 traffics from the plasma membrane to recycling endosomes mATG9 vesicles fuse with ATG16L1 vesicles in recycling endosomes VAMP3, Rab11, myosin Vb, and starvation regulate mATG9-ATG16L1 vesicle fusion mATG9-ATG16L1 vesicle fusions regulate autophagosome formation
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Affiliation(s)
- Claudia Puri
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK
| | - Maurizio Renna
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK
| | - Carla F. Bento
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK
| | - Kevin Moreau
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK
| | - David C. Rubinsztein
- Department of Medical Genetics, Cambridge Institute for Medical Research, University of Cambridge, Hills Road, Cambridge CB2 0XY, UK
- Corresponding author
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12
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Traub LM, Bonifacino JS. Cargo recognition in clathrin-mediated endocytosis. Cold Spring Harb Perspect Biol 2013; 5:a016790. [PMID: 24186068 DOI: 10.1101/cshperspect.a016790] [Citation(s) in RCA: 223] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The endosomal system is expansive and complex, characterized by swift morphological transitions, dynamic remodeling of membrane constituents, and intracellular positioning changes. To properly navigate this ever-altering membrane labyrinth, transmembrane protein cargoes typically require specific sorting signals that are decoded by components of protein coats. The best-characterized sorting process within the endosomal system is the rapid internalization of select transmembrane proteins within clathrin-coated vesicles. Endocytic signals consist of linear motifs, conformational determinants, or covalent modifications in the cytosolic domains of transmembrane cargo. These signals are interpreted by a diverse set of clathrin-associated sorting proteins (CLASPs) that translocate from the cytosol to the inner face of the plasma membrane. Signal recognition by CLASPs is highly cooperative, involving additional interactions with phospholipids, Arf GTPases, other CLASPs, and clathrin, and is regulated by large conformational changes and covalent modifications. Related sorting events occur at other endosomal sorting stations.
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Affiliation(s)
- Linton M Traub
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
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13
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Jha A, Watkins SC, Traub LM. The apoptotic engulfment protein Ced-6 participates in clathrin-mediated yolk uptake in Drosophila egg chambers. Mol Biol Cell 2012; 23:1742-64. [PMID: 22398720 PMCID: PMC3338440 DOI: 10.1091/mbc.e11-11-0939] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
During oogenesis in Drosophila, the phagocytic engulfment protein Ced-6 recognizes the atypical endocytic sorting signal within the vitellogenin receptor Yolkless. Because Ced-6 displays all of the features of an authentic clathrin adaptor, an unrecognized clathrin dependence for Ced-6/Gulp operation during phagocytosis is possible. Clathrin-mediated endocytosis and phagocytosis are both selective surface internalization processes but have little known mechanistic similarity or interdependence. Here we show that the phosphotyrosine-binding (PTB) domain protein Ced-6, a well-established phagocytosis component that operates as a transducer of so-called “eat-me” signals during engulfment of apoptotic cells and microorganisms, is expressed in the female Drosophila germline and that Ced-6 expression correlates with ovarian follicle development. Ced-6 exhibits all the known biochemical properties of a clathrin-associated sorting protein, yet ced-6–null flies are semifertile despite massive accumulation of soluble yolk precursors in the hemolymph. This is because redundant sorting signals within the cytosolic domain of the Drosophila vitellogenin receptor Yolkless, a low density lipoprotein receptor superfamily member, occur; a functional atypical dileucine signal binds to the endocytic AP-2 clathrin adaptor directly. Nonetheless, the Ced-6 PTB domain specifically recognizes the noncanonical Yolkless FXNPXA sorting sequence and in HeLa cells promotes the rapid, clathrin-dependent uptake of a Yolkless chimera lacking the distal dileucine signal. Ced-6 thus operates in vivo as a clathrin adaptor. Because the human Ced-6 orthologue GULP similarly binds to clathrin machinery, localizes to cell surface clathrin-coated structures, and is enriched in placental clathrin-coated vesicles, new possibilities for Ced-6/Gulp operation during phagocytosis must be considered.
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Affiliation(s)
- Anupma Jha
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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14
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McMahon HT, Boucrot E. Molecular mechanism and physiological functions of clathrin-mediated endocytosis. Nat Rev Mol Cell Biol 2011; 12:517-33. [PMID: 21779028 DOI: 10.1038/nrm3151] [Citation(s) in RCA: 1550] [Impact Index Per Article: 119.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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15
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Liu AP, Aguet F, Danuser G, Schmid SL. Local clustering of transferrin receptors promotes clathrin-coated pit initiation. ACTA ACUST UNITED AC 2011; 191:1381-93. [PMID: 21187331 PMCID: PMC3010081 DOI: 10.1083/jcb.201008117] [Citation(s) in RCA: 161] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The relationship between cargo accumulation and clathrin-coated pit initiation and maturation is examined by direct visualization of receptor-engaged clathrin-coated pits. Clathrin-mediated endocytosis (CME) is the major pathway for concentrative uptake of receptors and receptor–ligand complexes (cargo). Although constitutively internalized cargos are known to accumulate into maturing clathrin-coated pits (CCPs), whether and how cargo recruitment affects the initiation and maturation of CCPs is not fully understood. Previous studies have addressed these issues by analyzing the global effects of receptor overexpression on CME or CCP dynamics. Here, we exploit a refined approach using expression of a biotinylated transferrin receptor (bTfnR) and controlling its local clustering using mono- or multivalent streptavidin. We show that local clustering of bTfnR increased CCP initiation. By tracking cargo loading in individual CCPs, we found that bTfnR clustering preceded clathrin assembly and confirmed that bTfnR-containing CCPs mature more efficiently than bTfnR-free CCPs. Although neither the clustering nor the related changes in cargo loading altered the rate of CCP maturation, bTfnR-containing CCPs exhibited significantly longer lifetimes than other CCPs within the same cell. Together these results demonstrate that cargo composition is a key source of the differential dynamics of CCPs.
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Affiliation(s)
- Allen P Liu
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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16
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Expression and functional validation of new p38α transcriptional targets in tumorigenesis. Biochem J 2011; 434:549-58. [DOI: 10.1042/bj20101410] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
p38α MAPK (mitogen-activated protein kinase) plays an important tumour suppressor role, which is mediated by both its negative effect on cell proliferation and its pro-apoptotic activity. Surprisingly, most tumour suppressor mechanisms co-ordinated by p38α have been reported to occur at the post-translational level. This contrasts with the important role of p38α in the regulation of transcription and the profound changes in gene expression that normally occur during tumorigenesis. We have analysed whole-genome expression profiles of Ras-transformed wild-type and p38α-deficient cells and have identified 202 genes that are potentially regulated by p38α in transformed cells. Expression analysis has confirmed the regulation of these genes by p38α in tumours, and functional validation has identified several of them as probable mediators of the tumour suppressor effect of p38α on Ras-induced transformation. Interestingly, approx. 10% of the genes that are negatively regulated by p38α in transformed cells contribute to EGF (epidermal growth factor) receptor signalling. Our results suggest that inhibition of EGF receptor signalling by transcriptional targets of p38α is an important function of this signalling pathway in the context of tumour suppression.
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17
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Welling PA, Weisz OA. Sorting it out in endosomes: an emerging concept in renal epithelial cell transport regulation. Physiology (Bethesda) 2011; 25:280-92. [PMID: 20940433 DOI: 10.1152/physiol.00022.2010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Ion and water transport by the kidney is continually adjusted in response to physiological cues. Selective endocytosis and endosomal trafficking of ion transporters are increasingly appreciated as mechanisms to acutely modulate renal function. Here, we discuss emerging paradigms in this new area of investigation.
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Affiliation(s)
- Paul A Welling
- Department of Physiology, University of Maryland School of Medicine, Baltimore, MD, USA
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18
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Mettlen M, Loerke D, Yarar D, Danuser G, Schmid SL. Cargo- and adaptor-specific mechanisms regulate clathrin-mediated endocytosis. ACTA ACUST UNITED AC 2010; 188:919-33. [PMID: 20231386 PMCID: PMC2845073 DOI: 10.1083/jcb.200908078] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Clathrin-coated pit size and dynamic behavior varies with low density lipoprotein receptor (LDLR) expression levels in a manner dependent on the LDLR-specific adaptors, Dab2 and ARH. Clathrin-mediated endocytosis of surface receptors and their bound ligands (i.e., cargo) is highly regulated, including by the cargo itself. One of the possible sources of the observed heterogeneous dynamics of clathrin-coated pits (CCPs) might be the different cargo content. Consistent with this, we show that CCP size and dynamic behavior varies with low density lipoprotein receptor (LDLR) expression levels in a manner dependent on the LDLR-specific adaptors, Dab2 and ARH. In Dab2-mCherry–expressing cells, varying LDLR expression leads to a progressive increase in CCP size and to the appearance of nonterminal endocytic events. In LDLR and ARH-mCherry–expressing cells in addition to an increase in CCP size, turnover of abortive CCPs increases, and the rate of CCP maturation decreases. Altogether, our results underscore the highly dynamic and cargo-responsive nature of CCP assembly and suggest that the observed heterogeneity is, in part, related to compositional differences (e.g., cargo and adaptors) between CCPs.
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Affiliation(s)
- Marcel Mettlen
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
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19
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Pedersen GA, Chakraborty S, Steinhauser AL, Traub LM, Madsen M. AMN directs endocytosis of the intrinsic factor-vitamin B(12) receptor cubam by engaging ARH or Dab2. Traffic 2010; 11:706-20. [PMID: 20088845 DOI: 10.1111/j.1600-0854.2010.01042.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Cubam is a multi-ligand receptor involved in dietary uptake of intrinsic factor-vitamin B(12) in the small intestine and reabsorption of various low-molecular-weight proteins (such as albumin, transferrin, apolipoprotein A-I and vitamin D-binding protein) in the kidney. Cubam is composed of two proteins: cubilin and amnionless. Cubilin harbors ligand binding capabilities, while amnionless provides membrane anchorage and potential endocytic capacity via two FXNPXF signals within the cytosolic domain. These signals are similar to the FXNPXY signals found in members of the low-density lipoprotein receptor superfamily, which associate with clathrin-associated sorting proteins, including Disabled-2 (Dab2) and autosomal recessive hypercholesterolemia (ARH), during endocytosis. We therefore investigated the functionality of each amnionless FXNPXF signal and their respective interaction with sorting proteins. By sequential mutation and expression of a panel of amnionless mutants combined with yeast two-hybrid analyses, we demonstrate that the signals are functionally redundant and both are able to mediate endocytosis of cubam through interaction with Dab2 and ARH.
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Affiliation(s)
- Gitte Albinus Pedersen
- Department of Medical Biochemistry, University of Aarhus, Ole Worms Allé, Bldg. 1170-1171, Aarhus C, Denmark
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20
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Tickets to ride: selecting cargo for clathrin-regulated internalization. Nat Rev Mol Cell Biol 2009; 10:583-96. [PMID: 19696796 DOI: 10.1038/nrm2751] [Citation(s) in RCA: 416] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Clathrin-mediated endocytosis oversees the constitutive packaging of selected membrane cargoes into transport vesicles that fuse with early endosomes. The process is responsive to activation of signalling receptors and ion channels, promptly clearing post-translationally tagged forms of cargo off the plasma membrane. To accommodate the diverse array of transmembrane proteins that are variably gathered into forming vesicles, a dedicated sorting machinery cooperates to ensure that non-competitive uptake from the cell surface occurs within minutes. Recent structural and functional data reveal remarkable plasticity in how disparate sorting signals are recognized by cargo-selective clathrin adaptors, such as AP-2. Cargo loading also seems to govern whether coats ultimately bud or dismantle abortively at the cell surface.
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21
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Chen J, Wang J, Meyers KR, Enns CA. Transferrin-directed internalization and cycling of transferrin receptor 2. Traffic 2009; 10:1488-501. [PMID: 19682329 DOI: 10.1111/j.1600-0854.2009.00961.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Transferrin receptor 2 (TfR2) is a homologue of transferrin receptor 1 (TfR1) but has distinct functions from TfR1 in iron homeostasis. In keeping with its proposed role in iron sensing, previous studies showed that TfR2 has a short half-life and that holo-Tf stabilizes TfR2 by redirecting it from a degradative pathway to a recycling pathway. In this study, we characterized how the endocytosis, recycling and degradation of TfR2 relates to its function and differs from TfR1. TfR2 endocytosis was adaptor protein-2 (AP-2) dependent. Flow cytometry analysis showed that TfR1 and TfR2 utilized the same endocytic pathway only in the presence of holo-Tf, indicating that holo-Tf alters the interaction of TfR2 with the endocytic machinery. Unlike TfR1, phosphofurin acidic cluster sorting protein 1 (PACS-1) binds to the cytoplasmic domain of TfR2 and data suggest that PACS-1 is involved in the TfR2 recycling. Depletion of TSG101 by siRNA or expression of a dominant negative Vps4 inhibited TfR2 degradation, indicating that TfR2 degradation occurs through a multivesicular body (MVB) pathway. TfR2 degradation is not mediated through ubiquitination on the single lysine (K31) in the cytoplasmic domain or on the amino terminal residue. No ubiquitination of TfR2 by HA-ubiquitin was detected, indicating a lack of direct TfR2 ubiquitination involvement in its degradation.
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Affiliation(s)
- Juxing Chen
- Department of Cell and Developmental Biology L215, Oregon Health & Science University, Portland, OR 97239, USA
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22
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Internalization of swine vesicular disease virus into cultured cells: a comparative study with foot-and-mouth disease virus. J Virol 2009; 83:4216-26. [PMID: 19225001 DOI: 10.1128/jvi.02436-08] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We performed a comparative analysis of the internalization mechanisms used by three viruses causing important vesicular diseases in animals. Swine vesicular disease virus (SVDV) internalization was inhibited by treatments that affected clathrin-mediated endocytosis and required traffic through an endosomal compartment. SVDV particles were found in clathrin-coated pits by electron microscopy and colocalized with markers of early endosomes by confocal microscopy. SVDV infectivity was significantly inhibited by drugs that raised endosomal pH. When compared to foot-and-mouth disease virus (FMDV), which uses clathrin-mediated endocytosis, the early step of SVDV was dependent on the integrity of microtubules. SVDV-productive endocytosis was more sensitive to plasma membrane cholesterol extraction than that of FMDV, and differential cell signaling requirements for virus infection were also found. Vesicular stomatitis virus, a model virus internalized by clathrin-mediated endocytosis, was included as a control of drug treatments. These results suggest that different clathrin-mediated routes are responsible for the internalization of these viruses.
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23
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Hammond JW, Griffin K, Jih GT, Stuckey J, Verhey KJ. Co-operative Versus Independent Transport of Different Cargoes by Kinesin-1. Traffic 2008; 9:725-41. [DOI: 10.1111/j.1600-0854.2008.00722.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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24
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Traub LM, Lukacs GL. Decoding ubiquitin sorting signals for clathrin-dependent endocytosis by CLASPs. J Cell Sci 2007; 120:543-53. [PMID: 17287393 DOI: 10.1242/jcs.03385] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Cargo selectivity is a hallmark of clathrin-mediated endocytosis. A wide range of structurally unrelated internalization signals specify the preferential clustering of transmembrane cargo into clathrin coats forming on the plasma membrane. Intriguingly, the classical endocytic adaptor AP-2 appears to recognize only a subset of these endocytic sorting signals. New data now reveal the molecular basis for recognition of other internalization signals, including post-translationally appended ubiquitin, by clathrin-coat-associated sorting proteins (CLASPs). Curiously, structurally related ubiquitin-recognition modules are shared by select CLASPs and the 26S proteasome, and recent work indicates that both display similar requirements for ubiquitin binding. During endocytosis, these modules engage oligoubiquitylated cargo in the form of polyubiquitin chains and/or multiple single ubiquitin molecules appended to different acceptor lysines. Functional separation between clathrin-mediated endocytosis and proteasome-dependent proteolysis is probably ensured by temporally regulated, local assembly of ubiquitin-tagged membrane cargo at sorting stations on the cell surface, shielding ubiquitin sorting signals from the proteasome. Thus, an expanded repertoire of CLASPs couples the process of clathrin-coat assembly with high-fidelity incorporation of assorted, cargo-specific sorting signals.
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Affiliation(s)
- Linton M Traub
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, PA 15261, USA, and Program in Cell and Lung Biology, Hospital for Sick Children Research Institute, Toronto, Ontario, Canada.
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25
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Abstract
The heptahelical G protein-coupled receptor (GPCR) family includes approximately 900 members and is the largest family of signaling receptors encoded in the mammalian genome. G protein-coupled receptors elicit cellular responses to diverse extracellular stimuli at the plasma membrane and some internalized receptors continue to signal from intracellular compartments. In addition to rapid desensitization, receptor trafficking is critical for regulation of the temporal and spatial aspects of GPCR signaling. Indeed, GPCR internalization functions to control signal termination and propagation as well as receptor resensitization. Our knowledge of the mechanisms that regulate mammalian GPCR endocytosis is based predominantly on arrestin regulation of receptors through a clathrin- and dynamin-dependent pathway. However, multiple clathrin adaptors, which recognize distinct endocytic signals, are now known to function in clathrin-mediated endocytosis of diverse cargo. Given the vast number and diversity of GPCRs, the complexity of clathrin-mediated endocytosis and the discovery of multiple clathrin adaptors, a single universal mechanism controlling endocytosis of all mammalian GPCRs is unlikely. Indeed, several recent studies now suggest that endocytosis of different GPCRs is regulated by distinct mechanisms and clathrin adaptors. In this review, we discuss the diverse mechanisms that regulate clathrin-dependent GPCR endocytosis.
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Affiliation(s)
- Breann L Wolfe
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, 1106 Mary Ellen Jones Building, CB#7365, Chapel Hill, NC 27599-7563, USA
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26
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Walker F, Zhang HH, Burgess AW. Identification of a novel EGF-sensitive cell cycle checkpoint. Exp Cell Res 2007; 313:511-26. [PMID: 17157295 DOI: 10.1016/j.yexcr.2006.10.026] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2006] [Revised: 10/27/2006] [Accepted: 10/27/2006] [Indexed: 12/21/2022]
Abstract
The site of action of growth factors on mammalian cell cycle has been assigned to the boundary between the G1 and S phases. We show here that Epidermal Growth Factor (EGF) is also required for mitosis. BaF/3 cells expressing the EGFR (BaF/wtEGFR) synthesize DNA in response to EGF, but arrest in S-phase. We have generated a cell line (BaF/ERX) with defective downregulation of the EGFR and sustained activation of EGFR signalling pathways: these cells undergo mitosis in an EGF-dependent manner. The transit of BaF/ERX cells through G2/M strictly requires activation of EGFR and is abolished by AG1478. This phenotype is mimicked by co-expression of ErbB2 in BaF/wtEGFR cells, and abolished by inhibition of the EGFR kinase, suggesting that sustained signalling of the EGFR, through impaired downregulation of the EGFR or heterodimerization, is required for completion of the cycle. We have confirmed the role of EGFR signalling in the G2/M phase of the cell cycle using a human tumor cell line which overexpresses the EGFR and is dependent on EGFR signalling for growth. These findings unmask an EGF-sensitive checkpoint, helping to understand the link between sustained EGFR signalling, proliferation and the acquisition of a radioresistant phenotype in cancer cells.
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Affiliation(s)
- Francesca Walker
- Ludwig Institute for Cancer Research, P.O Royal Melbourne Hospital, Parkville, Victoria 3050, Australia.
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27
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Johnson MB, Chen J, Murchison N, Green FA, Enns CA. Transferrin receptor 2: evidence for ligand-induced stabilization and redirection to a recycling pathway. Mol Biol Cell 2006; 18:743-54. [PMID: 17182845 PMCID: PMC1805103 DOI: 10.1091/mbc.e06-09-0798] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Transferrin receptor 2 (TfR2) is a homologue of transferrin receptor 1 (TfR1), the protein that delivers iron to cells through receptor-mediated endocytosis of diferric transferrin (Fe(2)Tf). TfR2 also binds Fe(2)Tf, but it seems to function primarily in the regulation of systemic iron homeostasis. In contrast to TfR1, the trafficking of TfR2 within the cell has not been extensively characterized. Previously, we showed that Fe(2)Tf increases TfR2 stability, suggesting that trafficking of TfR2 may be regulated by interaction with its ligand. In the present study, therefore, we sought to identify the mode of TfR2 degradation, to characterize TfR2 trafficking, and to determine how Fe(2)Tf stabilizes TfR2. Stabilization of TfR2 by bafilomycin implies that TfR2 traffics to the lysosome for degradation. Confocal microscopy reveals that treatment of cells with Fe(2)Tf increases the fraction of TfR2 localizing to recycling endosomes and decreases the fraction of TfR2 localizing to late endosomes. Mutational analysis of TfR2 shows that the mutation G679A, which blocks TfR2 binding to Fe(2)Tf, increases the rate of receptor turnover and prevents stabilization by Fe(2)Tf, indicating a direct role of Fe(2)Tf in TfR2 stabilization. The mutation Y23A in the cytoplasmic domain of TfR2 inhibits its internalization and degradation, implicating YQRV as an endocytic motif.
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Affiliation(s)
| | - Juxing Chen
- Cell and Developmental Biology, Oregon Health & Science University, Portland, OR 97239
| | - Nicholas Murchison
- Cell and Developmental Biology, Oregon Health & Science University, Portland, OR 97239
| | - Frank A. Green
- Cell and Developmental Biology, Oregon Health & Science University, Portland, OR 97239
| | - Caroline A. Enns
- Cell and Developmental Biology, Oregon Health & Science University, Portland, OR 97239
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28
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Ortiz-Zapater E, Soriano-Ortega E, Marcote MJ, Ortiz-Masiá D, Aniento F. Trafficking of the human transferrin receptor in plant cells: effects of tyrphostin A23 and brefeldin A. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2006; 48:757-70. [PMID: 17059402 DOI: 10.1111/j.1365-313x.2006.02909.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Plant cells possess much of the molecular machinery necessary for receptor-mediated endocytosis (RME), but this process still awaits detailed characterization. In order to identify a reliable and well-characterized marker to investigate RME in plant cells, we have expressed the human transferrin receptor (hTfR) in Arabidopsis protoplasts. We have found that hTfR is mainly found in endosomal (Ara7- and FM4-64-positive) compartments, but also at the plasma membrane, where it mediates binding and internalization of its natural ligand transferrin (Tfn). Cell surface expression of hTfR increases upon treatment with tyrphostin A23, which inhibits the interaction between the YTRF endocytosis signal in the hTfR cytosolic tail and the mu2-subunit of the AP2 complex. Indeed, tyrphostin A23 inhibits Tfn internalization and redistributes most of hTfR to the plasma membrane, suggesting that the endocytosis signal of hTfR is functional in Arabidopsis protoplasts. Co-immunoprecipitation experiments show that hTfR is able to interact with a mu-adaptin subunit from Arabidopsis cytosol, a process that is blocked by tyrphostin A23. In contrast, treatment with brefeldin A, which inhibits recycling from endosomes back to the plasma membrane in plant cells, leads to the accumulation of Tfn and hTfR in larger patches inside the cell, reminiscent of BFA compartments. Therefore, hTfR has the same trafficking properties in Arabidopsis protoplasts as in animal cells, and cycles between the plasma membrane and endosomal compartments. The specific inhibition of Tfn/hTfR internalization and recycling by tyrphostin A23 and BFA, respectively, thus provide valuable molecular tools to characterize RME and the recycling pathway in plant cells.
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Affiliation(s)
- Elena Ortiz-Zapater
- Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad de Valencia, Avda Vicente Andrés Estellés s/n, 46100-Burjassot (Valencia), Spain
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29
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Abstract
Clathrin-mediated endocytosis is a major route for diverse cargo to enter the cellular endocytic pathway. New findings by Puthenveedu and von Zastrow (2006) suggest that certain cargo proteins, such as G protein coupled receptors that bind to PDZ domains, regulate their own targeting to a subset of clathrin-coated pits. Thus, cargo proteins may cause functional specialization of vesicle trafficking within the early endocytic pathway.
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Affiliation(s)
- Volker Haucke
- Institute of Chemistry and Biochemistry, Laboratory of Membrane Biochemistry, Freie Universität Berlin, Takustrasse 6, 14195 Berlin, Germany.
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30
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Puthenveedu MA, von Zastrow M. Cargo Regulates Clathrin-Coated Pit Dynamics. Cell 2006; 127:113-24. [PMID: 17018281 DOI: 10.1016/j.cell.2006.08.035] [Citation(s) in RCA: 207] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2006] [Revised: 06/02/2006] [Accepted: 08/01/2006] [Indexed: 11/15/2022]
Abstract
Clathrin-coated pits (CCPs) are generally considered a uniform population of endocytic machines containing mixed constitutive and regulated membrane cargo. Contrary to this view, we show that regulated endocytosis of G protein-coupled receptors (GPCRs) occurs preferentially through a subset of CCPs. Significantly, GPCR-containing CCPs are also functionally distinct, as their surface residence time is regulated locally by GPCR cargo via PDZ-dependent linkage to the actin cytoskeleton. Such cargo-regulated CCPs show delayed recruitment of dynamin and can undergo an abortive event in which clathrin coats separate from the plasma membrane without concomitant receptor endocytosis. Segregation of cargo into CCP subsets, combined with cargo-dependent control of CCP dynamics, suggests a simple kinetic mechanism to generate functional specialization early in the endocytic pathway and reduce competition between diverse endocytic cargo.
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Affiliation(s)
- Manojkumar A Puthenveedu
- Department of Psychiatry, University of California at San Francisco, 600 16th Street, San Francisco, CA 94158, USA
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31
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Maurer ME, Cooper JA. The adaptor protein Dab2 sorts LDL receptors into coated pits independently of AP-2 and ARH. J Cell Sci 2006; 119:4235-46. [PMID: 16984970 DOI: 10.1242/jcs.03217] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clathrin-mediated endocytosis requires cargo-specific adaptor proteins that recognize specific receptors and recruit them into coated pits. ARH [also called low-density lipoprotein receptor (LDLR) adaptor protein] serves as an adaptor for LDLR endocytosis in liver. However, ARH is dispensable for LDL uptake by some other cell types. Here, we show that the adaptor Dab2 plays a major role in LDLR internalization in HeLa cells and fibroblasts. Dab2 mediates internalization of LDLRs but not transferrin receptors independently of ARH and the classic clathrin adaptor AP-2. If Dab2 is absent, ARH can mediate LDLR endocytosis, but its action requires AP-2. Furthermore, the rate of LDLR endocytosis is decreased when Dab2 is absent and Dab2, but not ARH, catalyzes the efficient clustering of LDLR into coated pits. Dab2 activity requires its binding to clathrin, LDLR and phospholipids. Dab2 is also involved in moving LDLRs off filopodia. We suggest that Dab2 is a cargo-specific endocytic adaptor protein, stably associating with phospholipids and clathrin to sort LDLR to nascent-coated pits, whereas ARH might accelerate later steps in LDLR endocytosis in cooperation with AP-2.
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Affiliation(s)
- Meghan E Maurer
- Molecular and Cellular Biology Program, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, Seattle, WA 98109, USA
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32
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Abstract
Recent work shows that specific adaptor interactions may sort receptors into distinct cohorts of clathrin-coated vesicles. These different vesicle populations deliver cargo to sorting endosomes of differing motilities and maturation rates, thereby determining the probability of receptor recycling and the duration of endosomal signaling.
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Affiliation(s)
- Michael J Clague
- Physiological Laboratory, University of Liverpool, Crown Street, Liverpool L69 3BX, UK.
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33
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Keyel PA, Mishra SK, Roth R, Heuser JE, Watkins SC, Traub LM. A single common portal for clathrin-mediated endocytosis of distinct cargo governed by cargo-selective adaptors. Mol Biol Cell 2006; 17:4300-17. [PMID: 16870701 PMCID: PMC1635374 DOI: 10.1091/mbc.e06-05-0421] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Sorting of transmembrane cargo into clathrin-coated vesicles requires endocytic adaptors, yet RNA interference (RNAi)-mediated gene silencing of the AP-2 adaptor complex only disrupts internalization of a subset of clathrin-dependent cargo. This suggests alternate clathrin-associated sorting proteins participate in cargo capture at the cell surface, and a provocative recent proposal is that discrete endocytic cargo are sorted into compositionally and functionally distinct clathrin coats. We show here that the FXNPXY-type internalization signal within cytosolic domain of the LDL receptor is recognized redundantly by two phosphotyrosine-binding domain proteins, Dab2 and ARH; diminishing both proteins by RNAi leads to conspicuous LDL receptor accumulation at the cell surface. AP-2-dependent uptake of transferrin ensues relatively normally in the absence of Dab2 and ARH, clearly revealing delegation of sorting operations at the bud site. AP-2, Dab2, ARH, transferrin, and LDL receptors are all present within the vast majority of clathrin structures at the surface, challenging the general existence of specialized clathrin coats for segregated internalization of constitutively internalized cargo. However, Dab2 expression is exceptionally low in hepatocytes, likely accounting for the pathological hypercholesterolemia that accompanies ARH loss.
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Affiliation(s)
- Peter A. Keyel
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
| | - Sanjay K. Mishra
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
| | - Robyn Roth
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - John E. Heuser
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Simon C. Watkins
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
| | - Linton M. Traub
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
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34
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Johannessen LE, Pedersen NM, Pedersen KW, Madshus IH, Stang E. Activation of the epidermal growth factor (EGF) receptor induces formation of EGF receptor- and Grb2-containing clathrin-coated pits. Mol Cell Biol 2006; 26:389-401. [PMID: 16382132 PMCID: PMC1346888 DOI: 10.1128/mcb.26.2.389-401.2006] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
In HeLa cells depleted of adaptor protein 2 complex (AP2) by small interfering RNA (siRNA) to the mu2 or alpha subunit or by transient overexpression of an AP2 sequestering mutant of Eps15, endocytosis of the transferrin receptor (TfR) was strongly inhibited. However, epidermal growth factor (EGF)-induced endocytosis of the EGF receptor (EGFR) was inhibited only in cells where the alpha subunit had been knocked down. By immunoelectron microscopy, we found that in AP2-depleted cells, the number of clathrin-coated pits was strongly reduced. When such cells were incubated with EGF, new coated pits were formed. These contained EGF, EGFR, clathrin, and Grb2 but not the TfR. The induced coated pits contained the alpha subunit, but labeling density was reduced compared to control cells. Induction of clathrin-coated pits required EGFR kinase activity. Overexpression of Grb2 with inactivating point mutations in N- or C-terminal SH3 domains or in both SH3 domains inhibited EGF-induced formation of coated pits efficiently, even though Grb2 SH3 mutations did not block activation of mitogen-activated protein kinase (MAPK) or phosphatidylinositol 3-kinase (PI3K). Our data demonstrate that EGFR-induced signaling and Grb2 are essential for formation of clathrin-coated pits accommodating the EGFR, while activation of MAPK and PI3K is not required.
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Affiliation(s)
- Lene E Johannessen
- Institute of Pathology, The University of Oslo, Rikshospitalet, N-0027 Oslo, Norway
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35
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Tosoni D, Puri C, Confalonieri S, Salcini AE, De Camilli P, Tacchetti C, Di Fiore PP. TTP specifically regulates the internalization of the transferrin receptor. Cell 2006; 123:875-88. [PMID: 16325581 DOI: 10.1016/j.cell.2005.10.021] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2005] [Revised: 08/10/2005] [Accepted: 10/13/2005] [Indexed: 10/25/2022]
Abstract
Different plasma membrane receptors are internalized through saturable/noncompetitive pathways, suggesting cargo-specific regulation. Here, we report that TTP (SH3BP4), a SH3-containing protein, specifically regulates the internalization of the transferrin receptor (TfR). TTP interacts with endocytic proteins, including clathrin, dynamin, and the TfR, and localizes selectively to TfR-containing coated-pits (CCP) and -vesicles (CCV). Overexpression of TTP specifically inhibits TfR internalization, and causes the formation of morphologically aberrant CCP, which are probably fission impaired. This effect is mediated by the SH3 of TTP, which can bind to dynamin, and it is rescued by overexpression of dynamin. Functional ablation of TTP causes a reduction in TfR internalization, and reduced cargo loading and size of TfR-CCV. Tyrosine phosphorylation of either TTP or dynamin prevents their interaction, pointing to a possible mechanism of exclusion of TTP from some CCP. Thus, TTP might represent one of the long sought for molecules that allow cargo-specific control of clathrin endocytosis.
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Affiliation(s)
- Daniela Tosoni
- IFOM, Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milan, Italy
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36
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Ayala P, Wilbur JS, Wetzler LM, Tainer JA, Snyder A, So M. The pilus and porin of Neisseria gonorrhoeae cooperatively induce Ca2+ transients in infected epithelial cells. Cell Microbiol 2005; 7:1736-48. [PMID: 16309460 DOI: 10.1111/j.1462-5822.2005.00586.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Purified pili and porin from Neisseria quickly mobilize calcium (Ca(2+)) stores in monocytes and epithelial cells, ultimately influencing host cell viability as well as bacterial intracellular survival. Here, we examined the Ca(2+) transients induced in human epithelial cells during infection by live, piliated N. gonorrhoeae. Porin induced an influx of Ca(2+) from the extracellular medium less than 60 s post infection. The porin-induced transient is followed by a pilus-induced release of Ca(2+) from intracellular stores. The timing of these events is similar to that observed using purified proteins. Interestingly, the porin-induced Ca(2+) flux is required for the pilus-induced transient, indicating that the pilus-induced Ca(2+) release is, itself, Ca(2+) dependent. Several lines of evidence indicate that porin is present on pili. Moreover, pilus retraction strongly influences the porin- and pilus-induced Ca(2+) fluxes. These and other results strongly suggest that the pilus and porin cooperate to modulate calcium signalling in epithelial cells, and propose a model to explain how N. gonorrhoeae triggers Ca(2+) transients in the initial stages of pilus-mediated attachment.
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Affiliation(s)
- Patricia Ayala
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR 97239, USA.
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37
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Palmer CL, Lim W, Hastie PG, Toward M, Korolchuk VI, Burbidge SA, Banting G, Collingridge GL, Isaac JT, Henley JM. Hippocalcin functions as a calcium sensor in hippocampal LTD. Neuron 2005; 47:487-94. [PMID: 16102532 PMCID: PMC1563146 DOI: 10.1016/j.neuron.2005.06.014] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2004] [Revised: 04/11/2005] [Accepted: 06/10/2005] [Indexed: 11/30/2022]
Abstract
It is not fully understood how NMDAR-dependent LTD causes Ca(2+)-dependent endocytosis of AMPARs. Here we show that the neuronal Ca(2+) sensor hippocalcin binds the beta2-adaptin subunit of the AP2 adaptor complex and that along with GluR2 these coimmunoprecipitate in a Ca(2+)-sensitive manner. Infusion of a truncated mutant of hippocalcin (HIP(2-72)) that lacks the Ca(2+) binding domains prevents synaptically evoked LTD but has no effect on LTP. These data indicate that the AP2-hippocalcin complex acts as a Ca(2+) sensor that couples NMDAR-dependent activation to regulated endocytosis of AMPARs during LTD.
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Affiliation(s)
- Claire L. Palmer
- MRC Centre for Synaptic PlasticityDepartment of AnatomySchool of Medical SciencesUniversity of BristolBristol, BS8 1 TDUnited Kingdom
| | - Wonil Lim
- MRC Centre for Synaptic PlasticityDepartment of AnatomySchool of Medical SciencesUniversity of BristolBristol, BS8 1 TDUnited Kingdom
| | - Peter G.R. Hastie
- MRC Centre for Synaptic PlasticityDepartment of AnatomySchool of Medical SciencesUniversity of BristolBristol, BS8 1 TDUnited Kingdom
| | - Marie Toward
- MRC Centre for Synaptic PlasticityDepartment of AnatomySchool of Medical SciencesUniversity of BristolBristol, BS8 1 TDUnited Kingdom
| | - Viktor I. Korolchuk
- Department of BiochemistrySchool of Medical SciencesUniversity of BristolBristol, BS8 1 TDUnited Kingdom
| | - Stephen A. Burbidge
- Neurology Centre of Excellence for Drug Discovery GlaxoSmithKlineNew Frontiers Science Park, Third AvenueHarlow, Essex, CM19 5AWUnited Kingdom
| | - George Banting
- Department of BiochemistrySchool of Medical SciencesUniversity of BristolBristol, BS8 1 TDUnited Kingdom
| | - Graham L. Collingridge
- MRC Centre for Synaptic PlasticityDepartment of AnatomySchool of Medical SciencesUniversity of BristolBristol, BS8 1 TDUnited Kingdom
| | - John. T.R. Isaac
- MRC Centre for Synaptic PlasticityDepartment of AnatomySchool of Medical SciencesUniversity of BristolBristol, BS8 1 TDUnited Kingdom
- National Institute of Neurological Disorders and StrokeNational Institutes of Health35 Convent DriveBethesda, Maryland 20892
| | - Jeremy M. Henley
- MRC Centre for Synaptic PlasticityDepartment of AnatomySchool of Medical SciencesUniversity of BristolBristol, BS8 1 TDUnited Kingdom
- Correspondence:
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38
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Weise F, Thilo L, Engstler M, Wiese M, Benzel I, Kühn C, Bühring HJ, Overath P. Binding affinity and capacity of putative adaptor-mediated sorting of a Type I membrane protein in Leishmania mexicana. Mol Biochem Parasitol 2005; 142:203-11. [PMID: 15890416 DOI: 10.1016/j.molbiopara.2005.04.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2005] [Revised: 03/28/2005] [Accepted: 04/11/2005] [Indexed: 10/25/2022]
Abstract
The membrane-bound acid phosphatase (MBAP), a Type I membrane protein predominantly associated with endosomal/lysosomal structures of Leishmania mexicana promastigotes, contains motifs in its cytosolic COOH-terminal tail (-MEVWRRYMKFKNKQSEAIIV-COOH) akin to tyrosine- and di-leucine-based sorting signals in multicellular organisms. Here, we first show that the COOH-terminal residues IIV of MBAP, but not the Y-residue, are required for endosomal targeting, suggesting specific binding to an adaptor complex at the cell surface. We then determine whether specific binding can be saturated by analysing the efficiency of endosomal targeting for increasing numbers of MBAP molecules per cell. The ratio of the steady-state abundance of wild-type MBAP on the cell surface to MBAP on endosomes increases until the distribution is no longer different from that observed for a mutant MBAP which lacks the IIV-motif or for a glycosylphosphatidylinositol-anchored form, both of which are distributed according to bulk membrane flow. A quantitative analysis of these in vivo results indicates specific binding to a putative adaptor complex with an affinity of about 10-4M to 50,000 sorting sites on the cell surface.
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Affiliation(s)
- Frank Weise
- Max-Planck-Institut für Biologie, Abteilung Membranbiochemie, D-72076 Tübingen, Germany
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Traub LM. Common principles in clathrin-mediated sorting at the Golgi and the plasma membrane. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1744:415-37. [PMID: 15922462 DOI: 10.1016/j.bbamcr.2005.04.005] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2005] [Revised: 04/17/2005] [Accepted: 04/19/2005] [Indexed: 12/12/2022]
Abstract
Clathrin-mediated vesicular trafficking events underpin the vectorial transfer of macromolecules between several eukaryotic membrane-bound compartments. Classical models for coat operation, focused principally on interactions between clathrin, the heterotetrameric adaptor complexes, and cargo molecules, fail to account for the full complexity of the coat assembly and sorting process. New data reveal that targeting of clathrin adaptor complexes is generally supported by phosphoinositides, that cargo recognition by heterotetrameric adaptors depends on phosphorylation-driven conformational alterations, and that dedicated clathrin-associated sorting proteins (CLASPs) exist to promote the selective trafficking of specific categories of cargo. A host of accessory factors also participate in coat polymerization events, and the independently folded appendage domains that project off the heterotetrameric adaptor core function as recruitment platforms that appear to oversee assembly operations. It is also now clear that focal polymerization of branched actin microfilaments contributes to clathrin-coated vesicle assembly and movement at both plasma membrane and Golgi sites. This improved appreciation of the complex mechanisms governing clathrin-dependent sorting events reveals several common principles of clathrin operation at the Golgi and the plasma membrane.
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Affiliation(s)
- Linton M Traub
- Department of Cell Biology and Physiology University of Pittsburgh School of Medicine 3500 Terrace Street, S325BST Pittsburgh, PA 15206, USA.
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40
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Bonnah RA, Hoelter J, Steeghs L, Enns CA, So M, Muckenthaler MU. Lipooligosaccharide-independent alteration of cellular homeostasis in Neisseria meningitidis-infected epithelial cells. Cell Microbiol 2005; 7:869-85. [PMID: 15888088 DOI: 10.1111/j.1462-5822.2005.00519.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Neisseria meningitidis (MC) is an important cause of meningitis and septic shock. Primary loose attachment of MC to host epithelial cells is mediated by type IV pili. Lipooligosaccharide (LOS), opacity (Opa) proteins and glycolipid adhesins facilitate subsequent tight attachment. MC infection causes numerous changes in host epithelial cell homeostasis. These include cortical plaque formation, increased expression of proinflammatory cytokines and alterations in host iron homeostasis. Using both biochemical and genetic approaches, we examined the role of LOS in mediating these events. We first examined specific cellular iron homeostasis changes that occur following addition of purified MC LOS to epithelial cells. Using an MC mutant that completely lacks LOS (MC lps tbp), we examined pili-mediated attachment and cortical plaque formation in human endocervical epithelial cells (A431). We also tested whether the lack of LOS alters cellular homeostasis, including changes in the levels of host stress response factors and proinflammatory cytokines. MC lps tbp elicited the formation of cortical plaques in A431 cells. However, the plaques were less pronounced than those formed by the MC parent. Surprisingly, the proinflammatory cytokine TNF(alpha) was upregulated during infection in MC lps tbp-infected cells. Furthermore, alterations in iron homeostasis, including lower transferrin receptor 1 (TfR-1) levels, altered TfR-1 trafficking, an 'iron-starvation' gene expression profile and low iron regulatory protein (IRP) binding activity are independent of LOS. Our results demonstrate that LOS is partially involved in both the attachment to host cells and formation of cortical plaques. However, TNFalpha induction and changes in iron homeostasis observed in MC-infected epithelial cells are independent of LOS.
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41
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Mishra SK, Keyel PA, Edeling MA, Dupin AL, Owen DJ, Traub LM. Functional dissection of an AP-2 beta2 appendage-binding sequence within the autosomal recessive hypercholesterolemia protein. J Biol Chem 2005; 280:19270-80. [PMID: 15728179 DOI: 10.1074/jbc.m501029200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The autosomal recessive hypercholesterolemia (ARH) protein plays a critical role in regulating plasma low density lipoprotein (LDL) levels. Inherited defects in ARH lead to a hypercholesterolemia that closely phenocopies that caused by a defective LDL receptor. The elevated serum LDL-cholesterol levels typical of ARH patients and the pronounced accumulation of the LDL receptor at the cell surface of hepatocytes in ARH-null mice argue that ARH operates by promoting the internalization of the LDL receptor within clathrin-coated vesicles. ARH contains an amino-terminal phosphotyrosine-binding domain that associates physically with the LDL receptor internalization sequence and with phosphoinositides. The carboxyl-terminal half of ARH contains a clathrin-binding sequence and a separate AP-2 adaptor binding region providing a plausible mechanism for how ARH can act as an endocytic adaptor or CLASP (clathrin-associated sorting protein) to couple LDL receptors with the clathrin machinery. Because the interaction with AP-2 is highly selective for the independently folded appendage domain of the beta2 subunit, we have characterized the ARH beta2 appendage-binding sequence in detail. Unlike the known alpha appendage-binding motifs, ARH requires an extensive sequence tract to bind the beta appendage with comparably high affinity. A minimal 16-residue sequence functions autonomously and depends upon ARH residues Asp253, Phe259, Leu262, and Arg266. We suggested that biased beta subunit engagement by ARH and the only other beta2 appendage selective adaptor, beta-arrestin, promotes efficient incorporation of this mechanistically distinct subset of CLASPs into clathrin-coated buds.
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MESH Headings
- Adaptor Proteins, Signal Transducing/chemistry
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/physiology
- Alanine/chemistry
- Amino Acid Motifs
- Amino Acid Sequence
- Animals
- Arginine/chemistry
- Arrestins/metabolism
- Calorimetry
- Carbocyanines/pharmacology
- Cholesterol, LDL/blood
- Clathrin/metabolism
- Cytosol/metabolism
- DNA/metabolism
- DNA-Binding Proteins/chemistry
- DNA-Binding Proteins/physiology
- Endocytosis
- Fluorescent Dyes/pharmacology
- Genes, Recessive
- Glutathione Transferase/metabolism
- Green Fluorescent Proteins/chemistry
- Green Fluorescent Proteins/metabolism
- Humans
- Hypercholesterolemia/genetics
- Kinetics
- Lipoproteins, LDL/metabolism
- Mice
- Microtubule-Associated Proteins/metabolism
- Models, Molecular
- Molecular Sequence Data
- Mutagenesis
- Peptides/chemistry
- Protein Binding
- Protein Conformation
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Receptors, LDL
- Sequence Homology, Amino Acid
- Transcription Factor AP-2
- Transcription Factors/chemistry
- Transcription Factors/physiology
- Two-Hybrid System Techniques
- beta-Arrestins
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Affiliation(s)
- Sanjay K Mishra
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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42
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Abstract
Transmembrane proteins destined to endosomes are selectively accumulated in clathrin-coated pits at the plasma membrane and rapidly internalized in clathrin-coated vesicles. The recognition of specific sequence motifs in transmembrane cargo by coated-pit proteins confers specificity on the endocytic process. Interaction of membrane cargo with the clathrin adaptor protein complex AP-2 is the major mechanism of cargo sorting into coated pits in mammalian cells. Recent studies have revealed a variety of alternative mechanisms of cargo recruitment involving additional adaptor proteins. These alternative mechanisms appear to be particularly important during clathrin-mediated endocytosis of signaling receptors.
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Affiliation(s)
- Alexander Sorkin
- Department of Pharmacology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
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43
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Swiatecka-Urban A, Boyd C, Coutermarsh B, Karlson KH, Barnaby R, Aschenbrenner L, Langford GM, Hasson T, Stanton BA. Myosin VI regulates endocytosis of the cystic fibrosis transmembrane conductance regulator. J Biol Chem 2004; 279:38025-31. [PMID: 15247260 DOI: 10.1074/jbc.m403141200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a cyclic AMP-regulated Cl(-) channel expressed in the apical plasma membrane in fluid-transporting epithelia. Although CFTR is rapidly endocytosed from the apical membrane of polarized epithelial cells and efficiently recycled back to the plasma membrane, little is known about the molecular mechanisms regulating CFTR endocytosis and endocytic recycling. Myosin VI, an actin-dependent, minus-end directed mechanoenzyme, has been implicated in clathrin-mediated endocytosis in epithelial cells. The goal of this study was to determine whether myosin VI regulates CFTR endocytosis. Endogenous, apical membrane CFTR in polarized human airway epithelial cells (Calu-3) formed a complex with myosin VI, the myosin VI adaptor protein Disabled 2 (Dab2), and clathrin. The tail domain of myosin VI, a dominant-negative recombinant fragment, displaced endogenous myosin VI from interacting with Dab2 and CFTR and increased the expression of CFTR in the plasma membrane by reducing CFTR endocytosis. However, the myosin VI tail fragment had no effect on the recycling of endocytosed CFTR or on fluid-phase endocytosis. CFTR endocytosis was decreased by cytochalasin D, an actin-filament depolymerizing agent. Taken together, these data indicate that myosin VI and Dab2 facilitate CFTR endocytosis by a mechanism that requires actin filaments.
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44
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Du L, Post SR. Macrophage colony-stimulating factor differentially regulates low density lipoprotein and transferrin receptors. J Lipid Res 2004; 45:1733-40. [PMID: 15210846 DOI: 10.1194/jlr.m400140-jlr200] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Endocytosis mediated by both LDL receptors (LDLRs) and transferrin receptors (TfRs) occurs in clathrin-coated pits and requires specific tyrosine-based internalization sequences located in the cytoplasmic domain of these receptors. Internalization of these receptors is mediated by endocytic proteins that interact with the internalization domains. We previously showed that macrophage colony-stimulating factor (M-CSF) rapidly increases LDLR-dependent uptake and metabolism of LDL. To study the mechanism by which M-CSF regulates LDL uptake, we compared the effect of M-CSF on the internalization of LDL and transferrin (Tf). Our results show that M-CSF substantially increased the rate of LDLR internalization without increasing LDLR localization on the cell surface. In contrast, M-CSF treatment of macrophages rapidly increased the localization of TfR to the cell surface but did not alter the relative rate of Tf internalization. Moreover, M-CSF regulated TfR and LDLR via the activation of distinct signaling pathways. Recruitment of TfR to the cell surface was attenuated by phosphatidylinositol 3-kinase inhibitors, whereas stimulated LDL uptake was inhibited by the serine/threonine phosphatase inhibitor okadaic acid. Taken together, our results indicate that M-CSF differentially regulates receptors that undergo endocytosis and that increased LDL uptake results from a selective increase in the rate of LDLR internalization.
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Affiliation(s)
- Liqin Du
- Graduate Program in Nutritional Sciences, University of Kentucky, Lexington, KY 40536-0298, USA
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45
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Abstract
Sorting of transmembrane proteins to endosomes and lysosomes is mediated by signals present within the cytosolic domains of the proteins. Most signals consist of short, linear sequences of amino acid residues. Some signals are referred to as tyrosine-based sorting signals and conform to the NPXY or YXXO consensus motifs. Other signals known as dileucine-based signals fit [DE]XXXL[LI] or DXXLL consensus motifs. All of these signals are recognized by components of protein coats peripherally associated with the cytosolic face of membranes. YXXO and [DE]XXXL[LI] signals are recognized with characteristic fine specificity by the adaptor protein (AP) complexes AP-1, AP-2, AP-3, and AP-4, whereas DXXLL signals are recognized by another family of adaptors known as GGAs. Several proteins, including clathrin, AP-2, and Dab2, have been proposed to function as recognition proteins for NPXY signals. YXXO and DXXLL signals bind in an extended conformation to the mu2 subunit of AP-2 and the VHS domain of the GGAs, respectively. Phosphorylation events regulate signal recognition. In addition to peptide motifs, ubiquitination of cytosolic lysine residues also serves as a signal for sorting at various stages of the endosomal-lysosomal system. Conjugated ubiquitin is recognized by UIM, UBA, or UBC domains present within many components of the internalization and lysosomal targeting machinery. This complex array of signals and recognition proteins ensures the dynamic but accurate distribution of transmembrane proteins to different compartments of the endosomal-lysosomal system.
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Affiliation(s)
- Juan S Bonifacino
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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46
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Abstract
The AP-2 adaptor complex is widely viewed as a linchpin molecule in clathrin-mediated endocytosis, simultaneously binding both clathrin and receptors. This dual interaction couples cargo capture with clathrin coat assembly, but it has now been discovered that the association with cargo is tightly regulated. Remarkably, AP-2 is not obligatory for all clathrin-mediated uptake, and several alternate adaptors appear to perform similar sorting and assembly functions at the clathrin bud site.
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Affiliation(s)
- Linton M Traub
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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47
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Lee JK, Bussey KJ, Gwadry FG, Reinhold W, Riddick G, Pelletier SL, Nishizuka S, Szakacs G, Annereau JP, Shankavaram U, Lababidi S, Smith LH, Gottesman MM, Weinstein JN. Comparing cDNA and oligonucleotide array data: concordance of gene expression across platforms for the NCI-60 cancer cells. Genome Biol 2003; 4:R82. [PMID: 14659019 PMCID: PMC329421 DOI: 10.1186/gb-2003-4-12-r82] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2003] [Revised: 07/14/2003] [Accepted: 10/27/2003] [Indexed: 11/17/2022] Open
Abstract
Microarray gene-expression profiles are generally validated one gene at a time by real-time RT-PCR. A different approach is described, based on simultaneous mutual validation of large numbers of genes using two different expression-profiling platforms. Microarray gene-expression profiles are generally validated one gene at a time by real-time RT-PCR. We describe here a different approach based on simultaneous mutual validation of large numbers of genes using two different expression-profiling platforms. The result described here for the NCI-60 cancer cell lines is a consensus set of genes that give similar profiles on spotted cDNA arrays and Affymetrix oligonucleotide chips. Global concordance is parameterized by a 'correlation of correlations' coefficient.
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Affiliation(s)
- Jae K Lee
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-8322, USA
- Current address: Department of Health Evaluation Sciences, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Kimberly J Bussey
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-8322, USA
| | - Fuad G Gwadry
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-8322, USA
| | - William Reinhold
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-8322, USA
| | - Gregory Riddick
- Current address: Department of Health Evaluation Sciences, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Sandra L Pelletier
- Current address: Department of Health Evaluation Sciences, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Satoshi Nishizuka
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-8322, USA
| | - Gergely Szakacs
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-8322, USA
| | - Jean-Phillipe Annereau
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-8322, USA
| | - Uma Shankavaram
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-8322, USA
| | - Samir Lababidi
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-8322, USA
| | - Lawrence H Smith
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-8322, USA
| | - Michael M Gottesman
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-8322, USA
| | - John N Weinstein
- Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-8322, USA
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48
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Zhou Y, Zhang J, King ML. Xenopus autosomal recessive hypercholesterolemia protein couples lipoprotein receptors with the AP-2 complex in oocytes and embryos and is required for vitellogenesis. J Biol Chem 2003; 278:44584-92. [PMID: 12944396 DOI: 10.1074/jbc.m308870200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
ARH is required for normal endocytosis of the low density lipoprotein (LDL) receptor in liver and mutations within this gene cause autosomal recessive hypercholesterolemia in humans. xARH is a localized maternal RNA in Xenopus with an unknown function in oogenesis and embryogenesis. Like ARH, xARH contains a highly conserved phosphotyrosine binding domain and a clathrin box. To address the function of xARH, we examined its expression pattern in development and used pull-down experiments to assess interactions between xARH, lipoprotein receptors and proteins in embryo extracts. xARH was detected concentrated at the cell periphery as well as in the perinuclear region of oocytes and embryos. In pull-down experiments, the xARH phosphotyrosine binding domain interacted with the LDL and vitellogenin receptors found in Xenopus oocytes and embryos. Mutations within the receptor internalization signal specifically abolished this interaction. The xARH C-terminal region pulled-down several proteins from embryo extracts including alpha- and beta-adaptins, subunits of the AP-2 endocytic complex. Mutations within either of the two Dvarphi(F/W) motifs found in xARH abolished binding to alpha- and beta-adaptins. Expression of a dominant negative mutant of xARH missing the clathrin box and one functional Dvarphi(F/W) motif severely inhibited endocytosis of vitellogenin in cultured oocytes. The data indicate that xARH acts as an adaptor protein linking LDL and vitellogenin receptors directly with the AP-2 complex. In oocytes, we propose that xARH mediates the uptake of lipoproteins from the blood for storage in endosomes and later use in the embryo. Our findings point to an evolutionarily conserved function for ARH in lipoprotein uptake.
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Affiliation(s)
- Yi Zhou
- Department of Cell Biology and Anatomy, University of Miami School of Medicine, Miami, Florida 33136, USA
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Soutar AK, Naoumova RP, Traub LM. Genetics, clinical phenotype, and molecular cell biology of autosomal recessive hypercholesterolemia. Arterioscler Thromb Vasc Biol 2003; 23:1963-70. [PMID: 12958046 DOI: 10.1161/01.atv.0000094410.66558.9a] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The recent characterization of a rare genetic defect causing autosomal recessive hypercholesterolemia (ARH) has provided new insights into the underlying mechanism of clathrin-mediated internalization of the LDL receptor. Mutations in ARH on chromosome 1p35-36.1 prevent normal internalization of the LDL receptor by cultured lymphocytes and monocyte-derived macrophages but not by skin fibroblasts. In affected cells, LDL receptor protein accumulates at the cell surface; this also occurs in the livers of recombinant mice lacking ARH, thereby providing an explanation for the failure of clearance of LDL from the plasma in subjects lacking ARH. The approximately 50 known affected individuals are mostly of Sardinian or Middle Eastern origin. The clinical phenotype of ARH is similar to that of classic homozygous familial hypercholesterolemia caused by defects in the LDL receptor gene, but it is more variable, generally less severe, and more responsive to lipid-lowering therapy. Structural features of the ARH protein and its capacity to interact simultaneously with the internalization sequence of the LDL receptor, plasma membrane phospholipids, and the clathrin endocytic machinery suggest how ARH can play a pivotal role in gathering the LDL receptor into forming endocytic carrier vesicles.
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Affiliation(s)
- Anne K Soutar
- MRC Clinical Sciences Centre, Hammersmith Hospital, Faculty of Medicine, Imperial College, London, UK.
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Abstract
We have used RNA interference to knock down the AP-2 mu2 subunit and clathrin heavy chain to undetectable levels in HeLaM cells. Clathrin-coated pits associated with the plasma membrane were still present in the AP-2-depleted cells, but they were 12-fold less abundant than in control cells. No clathrin-coated pits or vesicles could be detected in the clathrin-depleted cells, and post-Golgi membrane compartments were swollen. Receptor-mediated endocytosis of transferrin was severely inhibited in both clathrin- and AP-2-depleted cells. Endocytosis of EGF, and of an LDL receptor chimera, were also inhibited in the clathrin-depleted cells; however, both were internalized as efficiently in the AP-2-depleted cells as in control cells. These results indicate that AP-2 is not essential for clathrin-coated vesicle formation at the plasma membrane, but that it is one of several endocytic adaptors required for the uptake of certain cargo proteins including the transferrin receptor. Uptake of the EGF and LDL receptors may be facilitated by alternative adaptors.
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Affiliation(s)
- Alison Motley
- University of Cambridge, Department of Clinical Biochemistry, Cambridge Institute for Medical Research, Cambridge CB2 2XY, UK
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