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Milne SM, Edeen PT, Fay DS. TAT-1, a phosphatidylserine flippase, affects molting and regulates membrane trafficking in the epidermis of C. elegans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.09.15.613099. [PMID: 39314363 PMCID: PMC11419146 DOI: 10.1101/2024.09.15.613099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/25/2024]
Abstract
Membrane trafficking is a conserved process required for the movement and distribution of proteins and other macromolecules within cells. The Caenorhabditis elegans NIMA-related kinases NEKL-2 (human NEK8/9) and NEKL-3 (human NEK6/7) are conserved regulators of membrane trafficking and are required for the completion of molting. We used a genetic approach to identify reduction-of-function mutations in tat-1 that suppress nekl -associated molting defects. tat-1 encodes the C. elegans ortholog of mammalian ATP8A1/2, a phosphatidylserine (PS) flippase that promotes the asymmetric distribution of PS to the cytosolic leaflet of lipid membrane bilayers. CHAT-1 (human CDC50), a conserved chaperone, was required for the correct localization of TAT-1, and chat-1 inhibition strongly suppressed nekl defects. Using a PS sensor, we found that TAT-1 was required for the normal localization of PS at apical endosomes and that loss of TAT-1 led to aberrant endosomal morphologies. Consistent with this, TAT-1 localized to early endosomes and to recycling endosomes marked with RME-1, the C. elegans ortholog of the human EPS15 homology (EH) domain-containing protein, EHD1. TAT-1, PS biosynthesis, and the PS-binding protein RFIP-2 (human RAB11-FIP2) were all required for the normal localization of RME-1 to apical endosomes. Consistent with these proteins functioning together, inhibition of RFIP-2 or RME-1 led to the partial suppression of nekl molting defects, as did the inhibition of PS biosynthesis. Using the auxin-inducible degron system, we found that depletion of NEKL-2 or NEKL-3 led to defects in RME-1 localization and that a reduction in TAT-1 function partially restored RME-1 localization in NEKL-3-depleted cells. ARTICLE SUMMARY Endocytosis is an essential process required for the movement of proteins and lipids within cells. NEKL-2 and NEKL-3, two evolutionarily conserved proteins in the nematode Caenorhabditis elegans , are important regulators of endocytosis. In the current study, the authors describe a new functional link between the NEKLs and several proteins with known roles in endocytosis including TAT-1, a conserved enzyme that moves lipids between the bilayers of cellular membranes. As previous work implicated NEKLs in developmental defects and cancer, the present study can provide new insights into how the misregulation of endocytosis affects human health and disease.
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Ruturaj, Mishra M, Saha S, Maji S, Rodriguez-Boulan E, Schreiner R, Gupta A. Regulation of the apico-basolateral trafficking polarity of the homologous copper-ATPases ATP7A and ATP7B. J Cell Sci 2024; 137:jcs261258. [PMID: 38032054 PMCID: PMC10729821 DOI: 10.1242/jcs.261258] [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: 04/19/2023] [Accepted: 10/05/2023] [Indexed: 12/01/2023] Open
Abstract
The homologous P-type copper-ATPases (Cu-ATPases) ATP7A and ATP7B are the key regulators of copper homeostasis in mammalian cells. In polarized epithelia, upon copper treatment, ATP7A and ATP7B traffic from the trans-Golgi network (TGN) to basolateral and apical membranes, respectively. We characterized the sorting pathways of Cu-ATPases between TGN and the plasma membrane and identified the machinery involved. ATP7A and ATP7B reside on distinct domains of TGN in limiting copper conditions, and in high copper, ATP7A traffics to basolateral membrane, whereas ATP7B traverses common recycling, apical sorting and apical recycling endosomes en route to apical membrane. Mass spectrometry identified regulatory partners of ATP7A and ATP7B that include the adaptor protein-1 complex. Upon knocking out pan-AP-1, sorting of both Cu-ATPases is disrupted. ATP7A loses its trafficking polarity and localizes on both apical and basolateral surfaces in high copper. By contrast, ATP7B loses TGN retention but retained its trafficking polarity to the apical domain, which became copper independent. Using isoform-specific knockouts, we found that the AP-1A complex provides directionality and TGN retention for both Cu-ATPases, whereas the AP-1B complex governs copper-independent trafficking of ATP7B solely. Trafficking phenotypes of Wilson disease-causing ATP7B mutants that disrupts putative ATP7B-AP1 interaction further substantiates the role of AP-1 in apical sorting of ATP7B.
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Affiliation(s)
- Ruturaj
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
| | - Monalisa Mishra
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
| | - Soumyendu Saha
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
| | - Saptarshi Maji
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
| | - Enrique Rodriguez-Boulan
- Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medicine, New York, NY 10021, USA
| | - Ryan Schreiner
- Division of Regenerative Medicine, Department of Medicine, Weill Cornell Medicine, New York, NY 10021, USA
| | - Arnab Gupta
- Department of Biological Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal 741246, India
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3
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Tutanov OS, Glass SE, Coffey RJ. Emerging connections between GPI-anchored proteins and their extracellular carriers in colorectal cancer. EXTRACELLULAR VESICLES AND CIRCULATING NUCLEIC ACIDS 2023; 4:195-217. [PMID: 37840781 PMCID: PMC10569057 DOI: 10.20517/evcna.2023.17] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2023]
Abstract
Although extracellular vesicles (EVs) were discovered over 40 years ago, there has been a resurgence of interest in secreted vesicles and their attendant cargo as novel modes of intracellular communication. In addition to vesicles, two amembranous nanoparticles, exomeres and supermeres, have been isolated and characterized recently. In this rapidly expanding field, it has been challenging to assign cargo and specific functions to a particular carrier. Refinement of isolation methods, well-controlled studies, and guidelines detailed by Minimal Information for Studies of Extracellular Vesicles (MISEV) are being employed to "bring order to chaos." In this review, we will briefly summarize three types of extracellular carriers - small EVs (sEVs), exomeres, and supermeres - in the context of colorectal cancer (CRC). We found that a number of GPI-anchored proteins (GPI-APs) are overexpressed in CRC, are enriched in exosomes (a distinct subset of sEVs), and can be detected in exomeres and supermeres. This affords the opportunity to elaborate on GPI-AP biogenesis, modifications, and trafficking using DPEP1, a GPI-AP upregulated in CRC, as a prime example. We have cataloged the GPI-anchored proteins secreted in CRC and will highlight features of select CRC-associated GPI-anchored proteins we have detected. Finally, we will discuss the remaining challenges and future opportunities in studying these secreted GPI-APs in CRC.
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Affiliation(s)
- Oleg S. Tutanov
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
| | - Sarah E. Glass
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee 37232, USA
| | - Robert J. Coffey
- Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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4
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Sandoval L, Labarca M, Retamal C, Sánchez P, Larraín J, González A. Sonic hedgehog is basolaterally sorted from the TGN and transcytosed to the apical domain involving Dispatched-1 at Rab11-ARE. Front Cell Dev Biol 2022; 10:833175. [PMID: 36568977 PMCID: PMC9768590 DOI: 10.3389/fcell.2022.833175] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Accepted: 11/04/2022] [Indexed: 12/12/2022] Open
Abstract
Hedgehog proteins (Hhs) secretion from apical and/or basolateral domains occurs in different epithelial cells impacting development and tissue homeostasis. Palmitoylation and cholesteroylation attach Hhs to membranes, and Dispatched-1 (Disp-1) promotes their release. How these lipidated proteins are handled by the complex secretory and endocytic pathways of polarized epithelial cells remains unknown. We show that polarized Madin-Darby canine kidney cells address newly synthesized sonic hedgehog (Shh) from the TGN to the basolateral cell surface and then to the apical domain through a transcytosis pathway that includes Rab11-apical recycling endosomes (Rab11-ARE). Both palmitoylation and cholesteroylation contribute to this sorting behavior, otherwise Shh lacking these lipid modifications is secreted unpolarized. Disp-1 mediates first basolateral secretion from the TGN and then transcytosis from Rab11-ARE. At the steady state, Shh predominates apically and can be basolaterally transcytosed. This Shh trafficking provides several steps for regulation and variation in different epithelia, subordinating the apical to the basolateral secretion.
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Affiliation(s)
- Lisette Sandoval
- Centro de Biología Celular y Biomedicina (CEBICEM), Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago, Chile
| | - Mariana Labarca
- Centro de Biología Celular y Biomedicina (CEBICEM), Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago, Chile,Centro Ciencia y Vida, Fundación Ciencia para la Vida, Santiago, Chile
| | - Claudio Retamal
- Centro de Biología Celular y Biomedicina (CEBICEM), Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago, Chile,Centro Ciencia y Vida, Fundación Ciencia para la Vida, Santiago, Chile
| | - Paula Sánchez
- Centro de Envejecimiento y Regeneración (CARE), Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Juan Larraín
- Centro de Envejecimiento y Regeneración (CARE), Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Alfonso González
- Centro de Biología Celular y Biomedicina (CEBICEM), Facultad de Medicina y Ciencia, Universidad San Sebastián, Santiago, Chile,Centro Ciencia y Vida, Fundación Ciencia para la Vida, Santiago, Chile,Centro de Envejecimiento y Regeneración (CARE), Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile,*Correspondence: Alfonso González,
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5
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Gao H, Wang B, Chen R, Jin Z, Ren L, Yang J, Wang W, Zheng N, Lin R. Effects of hydrogen peroxide on endothelial function in three-dimensional hydrogel vascular model and regulation mechanism of polar protein Par3. Biomed Mater 2022; 17. [PMID: 35901804 DOI: 10.1088/1748-605x/ac8538] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 07/28/2022] [Indexed: 11/11/2022]
Abstract
Three-dimensional (3D) cell cultures better reflect the function of endothelial cells (ECs) than two-dimensional (2D) cultures. In recent years, studies have found that ECs cultured in a 3D luminal structure can mimic the biological characteristics and phenotypes of vascular ECs, thus making it more suitable for endothelial dysfunction research. In this study, we used a 3D model and 2D tissue culture polystyrene (TCP) to investigate the effects of cell polarity on hydrogen peroxide (H2O2)-induced endothelial dysfunction and its related mechanisms. We observed the cell morphology, oxidative stress, and barrier and endothelial function of human umbilical vein endothelial cells (HUVECs) in 3D and 2D cultures. We then used Illumina to detect the differentially expressed genes in the 3D-cultured HUVEC with and without H2O2 stimulation, using ClusterProfiler for Gene Ontology (GO) function enrichment analysis and Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathway enrichment analysis of differentially expressed genes. Finally, we explored the role and mechanism of polar protein partitioning defective protein 3 (Par3) in the regulation of ECs. ECs were inoculated into the 3D hydrogel channel; after stimulation with H2O2, the morphology of HUVECs changed, the boundary was blurred, the expression of intercellular junction proteins decreased, and the barrier function of the EC layer was damaged. 3D culture increased the oxidative stress response of cells stimulated by H2O2 compared to 2D TCPs. The polarity-related protein Par3 and cell division control protein 42 (CDC42) were screened using bioinformatics analysis, and western blotting was used to verify the results. Par3 knockdown significantly suppressed claudin1 (CLDN1) and vascular endothelial cadherin (VE-cadherin). These results suggest that the polar protein Par3 can protect H2O2-induced vascular ECs from damage by regulating CLDN1 and VE-cadherin.
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Affiliation(s)
- Hongqian Gao
- Xi'an Jiaotong University, Department of Pharmacology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an 710061,Shaanxi, P. R. China, Xi'an, Shaanxi, 710061, CHINA
| | - Bo Wang
- Xi'an Jiaotong University, Department of Pharmacology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an 710061,Shaanxi, P. R. China, Xi'an, Shaanxi, 710061, CHINA
| | - Ruomeng Chen
- Mechanical and electrical engineering department, Tangshan university, Mechanical and electrical engineering department, Tangshan university, Tang Shan 063000, Hebei, P. R. China, Tangshan, 063000, CHINA
| | - Zhen Jin
- Department of Pharmacology, Xi'an Jiaotong University Health Science Center, Department of Pharmacology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an 710061,Shaanxi, P. R. China, Xi'an, 710061, CHINA
| | - Lingxuan Ren
- Department of Pharmacology, Xi'an Jiaotong University Health Science Center, Department of Pharmacology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an 710061,Shaanxi, P. R. China, Xi'an, 710061, CHINA
| | - Jianjun Yang
- Department of Pharmacology, Xi'an Jiaotong University Health Science Center, Department of Pharmacology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an 710061,Shaanxi, P. R. China, Xi'an, 710061, CHINA
| | - Weirong Wang
- Xi'an Jiaotong University, Department of Medical Laboratory Animal Science, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, China, Xi'an, Shaanxi, 710061, CHINA
| | - Nanbo Zheng
- Department of Pharmacology, Xi'an Jiaotong University School of Basic Medical Sciences, Department of Pharmacology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an 710061,Shaanxi, P. R. China, Xi'an, Shaanxi, 710061, CHINA
| | - Rong Lin
- Department of Pharmacology, Xi'an Jiaotong University Health Science Center, Department of Pharmacology, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an 710061,Shaanxi, P. R. China, Xi'an, 710061, CHINA
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6
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Bosma EK, Darwesh S, Zheng JY, van Noorden CJF, Schlingemann RO, Klaassen I. Quantitative Assessment of the Apical and Basolateral Membrane Expression of VEGFR2 and NRP2 in VEGF-A-stimulated Cultured Human Umbilical Vein Endothelial Cells. J Histochem Cytochem 2022; 70:557-569. [PMID: 35876388 PMCID: PMC9393510 DOI: 10.1369/00221554221115767] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Endothelial cells (ECs) form a precisely regulated polarized monolayer in capillary walls. Vascular endothelial growth factor-A (VEGF-A) induces endothelial hyperpermeability, and VEGF-A applied to the basolateral side, but not the apical side, has been shown to be a strong barrier disruptor in blood-retinal barrier ECs. We show here that VEGF-A presented to the basolateral side of human umbilical vein ECs (HUVECs) induces higher permeability than apical stimulation, which is similar to results obtained with bovine retinal ECs. We investigated with immunocytochemistry and confocal imaging the distribution of VEGF receptor-2 (VEGFR2) and neuropilin-2 (NRP2) in perinuclear apical and basolateral membrane domains. Orthogonal z-sections of cultured HUVECs were obtained, and the fluorescence intensity at the apical and basolateral membrane compartments was measured. We found that VEGFR2 and NRP2 are evenly distributed throughout perinuclear apical and basolateral membrane compartments in unstimulated HUVECs grown on Transwell inserts, whereas basolateral VEGF-A stimulation induces a shift toward basolateral VEGFR2 and NRP2 localization. When HUVECs were grown on coverslips, the distribution of VEGFR2 and NRP2 across the perinuclear apical and basolateral membrane domains was different. Our findings demonstrate that HUVECs dynamically regulate VEGFR2 and NRP2 localization on membrane microdomains, depending on growth conditions and the polarity of VEGF-A stimulation.
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Affiliation(s)
- Esmeralda K Bosma
- Ocular Angiogenesis Group, Department of Ophthalmology, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands.,Amsterdam Cardiovascular Sciences, Microcirculation, Amsterdam, The Netherlands.,Amsterdam Neuroscience, Cellular & Molecular Mechanisms, Amsterdam, The Netherlands
| | - Shahan Darwesh
- Ocular Angiogenesis Group, Department of Ophthalmology, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands.,Amsterdam Cardiovascular Sciences, Microcirculation, Amsterdam, The Netherlands.,Amsterdam Neuroscience, Cellular & Molecular Mechanisms, Amsterdam, The Netherlands
| | - Jia Y Zheng
- Ocular Angiogenesis Group, Department of Ophthalmology, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands.,Amsterdam Cardiovascular Sciences, Microcirculation, Amsterdam, The Netherlands.,Amsterdam Neuroscience, Cellular & Molecular Mechanisms, Amsterdam, The Netherlands
| | - Cornelis J F van Noorden
- Ocular Angiogenesis Group, Department of Ophthalmology, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands.,Department of Genetic Toxicology and Cancer Biology, National Institute of Biology, Ljubljana, Slovenia
| | - Reinier O Schlingemann
- Ocular Angiogenesis Group, Department of Ophthalmology, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands.,Amsterdam Cardiovascular Sciences, Microcirculation, Amsterdam, The Netherlands.,Amsterdam Neuroscience, Cellular & Molecular Mechanisms, Amsterdam, The Netherlands.,Department of Ophthalmology, Fondation Asile des Aveugles, Jules-Gonin Eye Hospital, University of Lausanne, Lausanne, Switzerland
| | - Ingeborg Klaassen
- Ocular Angiogenesis Group, Department of Ophthalmology, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands.,Amsterdam Cardiovascular Sciences, Microcirculation, Amsterdam, The Netherlands.,Amsterdam Neuroscience, Cellular & Molecular Mechanisms, Amsterdam, The Netherlands
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7
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Zhao Y, Gan L, Ren L, Lin Y, Ma C, Lin X. Factors influencing the blood-brain barrier permeability. Brain Res 2022; 1788:147937. [PMID: 35568085 DOI: 10.1016/j.brainres.2022.147937] [Citation(s) in RCA: 49] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 04/28/2022] [Accepted: 05/03/2022] [Indexed: 12/14/2022]
Abstract
The blood-brain barrier (BBB) is a dynamic structure that protects the brain from harmful blood-borne, endogenous and exogenous substances and maintains the homeostatic microenvironment. All constituent cell types play indispensable roles in the BBB's integrity, and other structural BBB components, such as tight junction proteins, adherens junctions, and junctional proteins, can control the barrier permeability. Regarding the need to exchange nutrients and toxic materials, solute carriers, ATP-binding case families, and ion transporter, as well as transcytosis regulate the influx and efflux transport, while the difference in localisation and expression can contribute to functional differences in transport properties. Numerous chemical mediators and other factors such as non-physicochemical factors have been identified to alter BBB permeability by mediating the structural components and barrier function, because of the close relationship with inflammation. In this review, we highlight recently gained mechanistic insights into the maintenance and disruption of the BBB. A better understanding of the factors influencing BBB permeability could contribute to supporting promising potential therapeutic targets for protecting the BBB and the delivery of central nervous system drugs via BBB permeability interventions under pathological conditions.
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Affiliation(s)
- Yibin Zhao
- The Third Clinical Medical College, Zhejiang Chinese Medical University, Hangzhou, China; Department of Neurobiology and Acupuncture Research, Zhejiang Chinese Medical University, Hangzhou, China
| | - Lin Gan
- The Third Clinical Medical College, Zhejiang Chinese Medical University, Hangzhou, China; Department of Neurobiology and Acupuncture Research, Zhejiang Chinese Medical University, Hangzhou, China
| | - Li Ren
- The Third Clinical Medical College, Zhejiang Chinese Medical University, Hangzhou, China; Department of Neurobiology and Acupuncture Research, Zhejiang Chinese Medical University, Hangzhou, China
| | - Yubo Lin
- The Third Clinical Medical College, Zhejiang Chinese Medical University, Hangzhou, China; Department of Neurobiology and Acupuncture Research, Zhejiang Chinese Medical University, Hangzhou, China
| | - Congcong Ma
- The Third Clinical Medical College, Zhejiang Chinese Medical University, Hangzhou, China; Department of Neurobiology and Acupuncture Research, Zhejiang Chinese Medical University, Hangzhou, China
| | - Xianming Lin
- The Third Clinical Medical College, Zhejiang Chinese Medical University, Hangzhou, China; Department of Neurobiology and Acupuncture Research, Zhejiang Chinese Medical University, Hangzhou, China.
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8
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Levic DS, Bagnat M. Self-organization of apical membrane protein sorting in epithelial cells. FEBS J 2022; 289:659-670. [PMID: 33864720 PMCID: PMC8522177 DOI: 10.1111/febs.15882] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 03/25/2021] [Accepted: 04/14/2021] [Indexed: 02/03/2023]
Abstract
Polarized epithelial cells are characterized by the asymmetric distribution of proteins between apical and basolateral domains of the plasma membrane. This asymmetry is highly conserved and is fundamental to epithelial cell physiology, development, and homeostasis. How proteins are segregated for apical or basolateral delivery, a process known as sorting, has been the subject of considerable investigation for decades. Despite these efforts, the rules guiding apical sorting are poorly understood and remain controversial. Here, we consider mechanisms of apical membrane protein sorting and argue that they are largely driven by self-organization and biophysical principles. The preponderance of data to date is consistent with the idea that apical sorting is not ruled by a dedicated protein-based sorting machinery and relies instead on the concerted effects of oligomerization, phase separation of lipids and proteins in membranes, and pH-dependent glycan interactions.
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Affiliation(s)
- Daniel S. Levic
- Department of Cell Biology, Duke University, Durham, NC 27710, USA
| | - Michel Bagnat
- Department of Cell Biology, Duke University, Durham, NC 27710, USA
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9
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Redhai S, Boutros M. The Role of Organelles in Intestinal Function, Physiology, and Disease. Trends Cell Biol 2021; 31:485-499. [PMID: 33551307 DOI: 10.1016/j.tcb.2021.01.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 01/04/2021] [Accepted: 01/11/2021] [Indexed: 02/06/2023]
Abstract
The intestine maintains homeostasis by coordinating internal biological processes to adjust to fluctuating external conditions. The intestinal epithelium is continuously renewed and comprises multiple cell types, including absorptive cells, secretory cells, and resident stem cells. An important feature of this organ is its ability to coordinate many processes including cell proliferation, differentiation, regeneration, damage/stress response, immune activity, feeding behavior, and age-related changes by using conserved signaling pathways. However, the subcellular spatial organization of these signaling events and the organelles involved has only recently been studied in detail. Here we discuss how organelles of intestinal cells serve to initiate, mediate, and terminate signals, that are vital for homeostasis.
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Affiliation(s)
- Siamak Redhai
- German Cancer Research Center (DKFZ), Division Signaling and Functional Genomics, and Heidelberg University, BioQuant and Medical Faculty Mannheim, D-69120 Heidelberg, Germany.
| | - Michael Boutros
- German Cancer Research Center (DKFZ), Division Signaling and Functional Genomics, and Heidelberg University, BioQuant and Medical Faculty Mannheim, D-69120 Heidelberg, Germany.
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10
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Rozés-Salvador V, González-Billault C, Conde C. The Recycling Endosome in Nerve Cell Development: One Rab to Rule Them All? Front Cell Dev Biol 2020; 8:603794. [PMID: 33425908 PMCID: PMC7793921 DOI: 10.3389/fcell.2020.603794] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 11/11/2020] [Indexed: 12/13/2022] Open
Abstract
Endocytic recycling is an intracellular process that returns internalized molecules back to the plasma membrane and plays crucial roles not only in the reuse of receptor molecules but also in the remodeling of the different components of this membrane. This process is required for a diversity of cellular events, including neuronal morphology acquisition and functional regulation, among others. The recycling endosome (RE) is a key vesicular component involved in endocytic recycling. Recycling back to the cell surface may occur with the participation of several different Rab proteins, which are master regulators of membrane/protein trafficking in nerve cells. The RE consists of a network of interconnected and functionally distinct tubular subdomains that originate from sorting endosomes and transport their cargoes along microtubule tracks, by fast or slow recycling pathways. Different populations of REs, particularly those formed by Rab11, Rab35, and Arf6, are associated with a myriad of signaling proteins. In this review, we discuss the cumulative evidence suggesting the existence of heterogeneous domains of REs, controlling different aspects of neurogenesis, with a particular focus on the commonalities and singularities of these REs and their contribution to nerve development and differentiation in several animal models.
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Affiliation(s)
- Victoria Rozés-Salvador
- Instituto de Investigación Médica Mercedes y Martín Ferreyra INIMEC-CONICET-UNC, Córdoba, Argentina.,Instituto de Ciencias Básicas, Universidad Nacional de Villa María, Córdoba, Argentina
| | - Christian González-Billault
- Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile.,Department of Neurosciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Geroscience Center for Brain Health and Metabolism, Santiago, Chile.,The Buck Institute for Research on Aging, Novato, CA, United States
| | - Cecilia Conde
- Instituto de Investigación Médica Mercedes y Martín Ferreyra INIMEC-CONICET-UNC, Córdoba, Argentina
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11
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Toth AE, Holst MR, Nielsen MS. Vesicular Transport Machinery in Brain Endothelial Cells: What We Know and What We Do not. Curr Pharm Des 2020; 26:1405-1416. [PMID: 32048959 DOI: 10.2174/1381612826666200212113421] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 12/03/2019] [Indexed: 12/20/2022]
Abstract
The vesicular transport machinery regulates numerous essential functions in cells such as cell polarity, signaling pathways, and the transport of receptors and their cargoes. From a pharmaceutical perspective, vesicular transport offers avenues to facilitate the uptake of therapeutic agents into cells and across cellular barriers. In order to improve receptor-mediated transcytosis of biologics across the blood-brain barrier and into the diseased brain, a detailed understanding of intracellular transport mechanisms is essential. The vesicular transport machinery is a highly complex network and involves an array of protein complexes, cytosolic adaptor proteins, and the subcellular structures of the endo-lysosomal system. The endo-lysosomal system includes several types of vesicular entities such as early, late, and recycling endosomes, exosomes, ectosomes, retromer-coated vesicles, lysosomes, trans-endothelial channels, and tubules. While extensive research has been done on the trafficking system in many cell types, little is known about vesicular trafficking in brain endothelial cells. Consequently, assumptions on the transport system in endothelial cells are based on findings in polarised epithelial cells, although recent studies have highlighted differences in the endothelial system. This review highlights aspects of the vesicular trafficking machinery in brain endothelial cells, including recent findings, limitations, and opportunities for further studies.
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Affiliation(s)
- Andrea E Toth
- Department of Biomedicine, Faculty of Health, Aarhus University, Høegh-Guldberg Gade 10, 8000 Aarhus C, Denmark
| | - Mikkel R Holst
- Department of Biomedicine, Faculty of Health, Aarhus University, Høegh-Guldberg Gade 10, 8000 Aarhus C, Denmark
| | - Morten S Nielsen
- Department of Biomedicine, Faculty of Health, Aarhus University, Høegh-Guldberg Gade 10, 8000 Aarhus C, Denmark
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12
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Redpath GMI, Betzler VM, Rossatti P, Rossy J. Membrane Heterogeneity Controls Cellular Endocytic Trafficking. Front Cell Dev Biol 2020; 8:757. [PMID: 32850860 PMCID: PMC7419583 DOI: 10.3389/fcell.2020.00757] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 07/20/2020] [Indexed: 12/21/2022] Open
Abstract
Endocytic trafficking relies on highly localized events in cell membranes. Endocytosis involves the gathering of protein (cargo/receptor) at distinct plasma membrane locations defined by specific lipid and protein compositions. Simultaneously, the molecular machinery that drives invagination and eventually scission of the endocytic vesicle assembles at the very same place on the inner leaflet of the membrane. It is membrane heterogeneity - the existence of specific lipid and protein domains in localized regions of membranes - that creates the distinct molecular identity required for an endocytic event to occur precisely when and where it is required rather than at some random location within the plasma membrane. Accumulating evidence leads us to believe that the trafficking fate of internalized proteins is sealed following endocytosis, as this distinct membrane identity is preserved through the endocytic pathway, upon fusion of endocytic vesicles with early and sorting endosomes. In fact, just like at the plasma membrane, multiple domains coexist at the surface of these endosomes, regulating local membrane tubulation, fission and sorting to recycling pathways or to the trans-Golgi network via late endosomes. From here, membrane heterogeneity ensures that fusion events between intracellular vesicles and larger compartments are spatially regulated to promote the transport of cargoes to their intracellular destination.
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Affiliation(s)
- Gregory M I Redpath
- Department of Biochemistry, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand.,The ANZAC Research Institute, Concord Repatriation General Hospital, Concord, NSW, Australia
| | - Verena M Betzler
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland.,Biotechnology Institute Thurgau (BITg) at the University of Konstanz, Kreuzlingen, Switzerland
| | - Pascal Rossatti
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland.,Biotechnology Institute Thurgau (BITg) at the University of Konstanz, Kreuzlingen, Switzerland
| | - Jérémie Rossy
- Biotechnology Institute Thurgau (BITg) at the University of Konstanz, Kreuzlingen, Switzerland.,Department of Biology, University of Konstanz, Konstanz, Germany
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13
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Sasaki K, Yoshida H. Golgi stress response and organelle zones. FEBS Lett 2019; 593:2330-2340. [PMID: 31344260 DOI: 10.1002/1873-3468.13554] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 07/21/2019] [Accepted: 07/22/2019] [Indexed: 12/29/2022]
Abstract
Organelles have been studied traditionally as single units, but a novel concept is now emerging: each organelle has distinct functional zones that regulate specific functions. The Golgi apparatus seems to have various zones, including zones for: glycosylphosphatidylinositol-anchored proteins; proteoglycan, mucin and lipid glycosylation; transport of cholesterol and ceramides; protein degradation (Golgi membrane-associated degradation); and signalling for apoptosis. The capacity for these specific functions and the size of the corresponding zones appear to be tightly regulated by the Golgi stress response to accommodate cellular demands. For instance, the proteoglycan and mucin zones seem to be separately augmented during the differentiation of chondrocytes and goblet cells, respectively. The mammalian Golgi stress response consists of several response pathways. The TFE3 pathway regulates the general function of the Golgi, such as structural maintenance, N-glycosylation and vesicular transport, whereas the proteoglycan pathway increases the expression of glycosylation enzymes for proteoglycans. The CREB3 and HSP47 pathways regulate pro- and anti-apoptotic functions, respectively. These observations indicate that the Golgi is a dynamic organelle, the capacity of which is upregulated according to cellular needs.
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Affiliation(s)
- Kanae Sasaki
- Department of Molecular Biochemistry, Graduate School of Life Science, University of Hyogo, Japan
| | - Hiderou Yoshida
- Department of Molecular Biochemistry, Graduate School of Life Science, University of Hyogo, Japan
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14
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Pulgar VM. Transcytosis to Cross the Blood Brain Barrier, New Advancements and Challenges. Front Neurosci 2019; 12:1019. [PMID: 30686985 PMCID: PMC6337067 DOI: 10.3389/fnins.2018.01019] [Citation(s) in RCA: 249] [Impact Index Per Article: 49.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 12/18/2018] [Indexed: 01/21/2023] Open
Abstract
The blood brain barrier (BBB) presents a formidable challenge to the delivery of drugs into the brain. Several strategies aim to overcome this obstacle and promote efficient and specific crossing through BBB of therapeutically relevant agents. One of those strategies uses the physiological process of receptor-mediated transcytosis (RMT) to transport cargo through the brain endothelial cells toward brain parenchyma. Recent developments in our understanding of intracellular trafficking and receptor binding as well as in protein engineering and nanotechnology have potentiated the opportunities for treatment of CNS diseases using RMT. In this mini-review, the current understanding of BBB structure is discussed, and recent findings exemplifying critical advances in RMT-mediated brain drug delivery are briefly presented.
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Affiliation(s)
- Victor M Pulgar
- Department of Pharmaceutical Sciences, Campbell University, Buies Creek, NC, United States.,Department of Obstetrics and Gynecology, Wake Forest School of Medicine, Winston-Salem, NC, United States
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15
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Close WL, Glassbrook JE, Gurczynski SJ, Pellett PE. Infection-Induced Changes Within the Endocytic Recycling Compartment Suggest a Roadmap of Human Cytomegalovirus Egress. Front Microbiol 2018; 9:1888. [PMID: 30186245 PMCID: PMC6113367 DOI: 10.3389/fmicb.2018.01888] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Accepted: 07/27/2018] [Indexed: 12/22/2022] Open
Abstract
Human cytomegalovirus (HCMV) is an important pathogen in developing fetuses, neonates, and individuals with compromised immune systems. Gaps in our understanding of the mechanisms required for virion assembly stand in the way of development of antivirals targeting late stages of viral replication. During infection, HCMV causes a dramatic reorganization of the host endosecretory system, leading to the formation of the cytoplasmic virion assembly complex (cVAC), the site of virion assembly. As part of cVAC biogenesis, the composition and behavior of endosecretory organelles change. To gain more comprehensive understanding of the impact HCMV infection has on components of the cellular endocytic recycling compartment (ERC), we used previously published transcriptional and proteomic datasets to predict changes in the directionality of ERC trafficking. We identified infection-associated changes in gene expression that suggest shifts in the balance between endocytic and exocytic recycling pathways, leading to formation of a secretory trap within the cVAC. Conversely, there was a corresponding shift favoring outbound secretory vesicle trafficking, indicating a potential role in virion egress. These observations are consistent with previous studies describing sequestration of signaling molecules, such as IL-6, and the synaptic vesicle-like properties of mature HCMV virions. Our analysis enabled development of a refined model incorporating old and new information related to the behavior of the ERC during HCMV replication. While limited by the paucity of integrated systems-level data, the model provides an informed basis for development of experimentally testable hypotheses related to mechanisms involved in HCMV virion maturation and egress. Information from such experiments will provide a robust roadmap for rational development of novel antivirals for HCMV and related viruses.
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Affiliation(s)
- William L. Close
- Department of Microbiology, Immunology and Biochemistry, Wayne State University School of Medicine, Detroit, MI, United States
| | - James E. Glassbrook
- Department of Microbiology, Immunology and Biochemistry, Wayne State University School of Medicine, Detroit, MI, United States
| | - Stephen J. Gurczynski
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, United States
| | - Philip E. Pellett
- Department of Microbiology, Immunology and Biochemistry, Wayne State University School of Medicine, Detroit, MI, United States
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16
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Toth AE, Siupka P, P Augustine TJ, Venø ST, Thomsen LB, Moos T, Lohi HT, Madsen P, Lykke-Hartmann K, Nielsen MS. The Endo-Lysosomal System of Brain Endothelial Cells Is Influenced by Astrocytes In Vitro. Mol Neurobiol 2018; 55:8522-8537. [PMID: 29560581 DOI: 10.1007/s12035-018-0988-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Accepted: 03/05/2018] [Indexed: 12/28/2022]
Abstract
Receptor- and adsorptive-mediated transport through brain endothelial cells (BEC) of the blood-brain barrier (BBB) involves a complex array of subcellular vesicular structures, the endo-lysosomal system. It consists of several types of vesicles, such as early, recycling, and late endosomes, retromer-positive structures, and lysosomes. Since this system is important for receptor-mediated transcytosis of drugs across brain capillaries, our aim was to characterise the endo-lysosomal system in BEC with emphasis on their interactions with astrocytes. We used primary porcine BEC in monoculture and in co-culture with primary rat astrocytes. The presence of astrocytes changed the intraendothelial vesicular network and significantly impacted vesicular number, morphology, and distribution. Additionally, gene set enrichment analysis revealed that 60 genes associated with vesicular trafficking showed altered expression in co-cultured BEC. Cytosolic proteins involved in subcellular trafficking were investigated to mark transport routes, such as RAB25 for transcytosis. Strikingly, the adaptor protein called AP1-μ1B, important for basolateral sorting in epithelial cells, was not expressed in BEC. Altogether, our data pin-point unique features of BEC trafficking network, essentially mapping the endo-lysosomal system of in vitro BBB models. Consequently, our findings constitute a valuable basis for planning the optimal route across the BBB when advancing drug delivery to the brain.
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Affiliation(s)
- Andrea E Toth
- Department of Biomedicine, Faculty of Health, Aarhus University, Ole Worms Allé 3, 8000, Aarhus, Denmark.,Lundbeck Foundation, Research Initiative on Brain Barriers and Drug Delivery, Scherfigsvej 7, 2100, Copenhagen, Denmark
| | - Piotr Siupka
- Department of Biomedicine, Faculty of Health, Aarhus University, Ole Worms Allé 3, 8000, Aarhus, Denmark.,Lundbeck Foundation, Research Initiative on Brain Barriers and Drug Delivery, Scherfigsvej 7, 2100, Copenhagen, Denmark
| | - Thomas J P Augustine
- Research Program for Molecular Neurology, Helsinki University, Haartmaninkatu 8, 00290, Helsinki, Finland
| | - Susanne T Venø
- Department of Biomedicine, Faculty of Health, Aarhus University, Ole Worms Allé 3, 8000, Aarhus, Denmark.,Lundbeck Foundation, Research Initiative on Brain Barriers and Drug Delivery, Scherfigsvej 7, 2100, Copenhagen, Denmark
| | - Louiza B Thomsen
- Lundbeck Foundation, Research Initiative on Brain Barriers and Drug Delivery, Scherfigsvej 7, 2100, Copenhagen, Denmark.,Laboratory of Neurobiology, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 3, 9220, Aalborg, Denmark
| | - Torben Moos
- Lundbeck Foundation, Research Initiative on Brain Barriers and Drug Delivery, Scherfigsvej 7, 2100, Copenhagen, Denmark.,Laboratory of Neurobiology, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 3, 9220, Aalborg, Denmark
| | - Hannes T Lohi
- Research Program for Molecular Neurology, Helsinki University, Haartmaninkatu 8, 00290, Helsinki, Finland
| | - Peder Madsen
- Department of Biomedicine, Faculty of Health, Aarhus University, Ole Worms Allé 3, 8000, Aarhus, Denmark
| | - Karin Lykke-Hartmann
- Department of Biomedicine, Faculty of Health, Aarhus University, Ole Worms Allé 3, 8000, Aarhus, Denmark.,Department of Clinical Genetics, Aarhus University Hospital, Brendstrupgårdsvej 21, 8200, Aarhus, Denmark.,Department of Clinical Medicine, Faculty of Health, Aarhus University, Bartholins Alle 6, 8000, Aarhus, Denmark
| | - Morten S Nielsen
- Department of Biomedicine, Faculty of Health, Aarhus University, Ole Worms Allé 3, 8000, Aarhus, Denmark. .,Lundbeck Foundation, Research Initiative on Brain Barriers and Drug Delivery, Scherfigsvej 7, 2100, Copenhagen, Denmark.
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17
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Brandán YR, Guaytima EDV, Favale NO, Pescio LG, Sterin-Speziale NB, Márquez MG. The inhibition of sphingomyelin synthase 1 activity induces collecting duct cells to lose their epithelial phenotype. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2017; 1865:309-322. [PMID: 29128370 DOI: 10.1016/j.bbamcr.2017.11.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 10/30/2017] [Accepted: 11/07/2017] [Indexed: 12/20/2022]
Abstract
Epithelial tissue requires that cells attach to each other and to the extracellular matrix by the assembly of adherens junctions (AJ) and focal adhesions (FA) respectively. We have previously shown that, in renal papillary collecting duct (CD) cells, both AJ and FA are located in sphingomyelin (SM)-enriched plasma membrane microdomains. In the present work, we investigated the involvement of SM metabolism in the preservation of the epithelial cell phenotype and tissue organization. To this end, primary cultures of renal papillary CD cells were performed. Cultured cells preserved the fully differentiated epithelial phenotype as reflected by the presence of primary cilia. Cells were then incubated for 24h with increasing concentrations of D609, a SM synthase (SMS) inhibitor. Knock-down experiments silencing SMS 1 and 2 were also performed. By combining biochemical and immunofluorescence studies, we found experimental evidences suggesting that, in CD cells, SMS 1 activity is essential for the preservation of cell-cell adhesion structures and therefore for the maintenance of CD tissue/tubular organization. The inhibition of SMS 1 activity induced CD cells to lose their epithelial phenotype and to undergo an epithelial-mesenchymal transition (EMT) process.
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Affiliation(s)
- Yamila Romina Brandán
- Instituto de Investigaciones en Ciencias de la Salud Humana (IICSHUM), Universidad Nacional de La Rioja, Av. Luis Vernet 1000, 5300 La Rioja, Argentina
| | - Edith Del Valle Guaytima
- Instituto de Investigaciones en Ciencias de la Salud Humana (IICSHUM), Universidad Nacional de La Rioja, Av. Luis Vernet 1000, 5300 La Rioja, Argentina
| | - Nicolás Octavio Favale
- Instituto de Química y Físico-Química Biológica (IQUIFIB) -CONICET, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina; Cátedra de Biología Celular, Departamento de Ciencias Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina
| | - Lucila Gisele Pescio
- Instituto de Química y Físico-Química Biológica (IQUIFIB) -CONICET, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina; Cátedra de Biología Celular, Departamento de Ciencias Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina
| | - Norma B Sterin-Speziale
- Instituto de Química y Físico-Química Biológica (IQUIFIB) -CONICET, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina.
| | - María Gabriela Márquez
- Instituto de Investigaciones en Ciencias de la Salud Humana (IICSHUM), Universidad Nacional de La Rioja, Av. Luis Vernet 1000, 5300 La Rioja, Argentina.
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18
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Garcia-Castillo MD, Chinnapen DJF, Lencer WI. Membrane Transport across Polarized Epithelia. Cold Spring Harb Perspect Biol 2017; 9:cshperspect.a027912. [PMID: 28213463 DOI: 10.1101/cshperspect.a027912] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Polarized epithelial cells line diverse surfaces throughout the body forming selective barriers between the external environment and the internal milieu. To cross these epithelial barriers, large solutes and other cargoes must undergo transcytosis, an endocytic pathway unique to polarized cell types, and significant for the development of cell polarity, uptake of viral and bacterial pathogens, transepithelial signaling, and immunoglobulin transport. Here, we review recent advances in our knowledge of the transcytotic pathway for proteins and lipids. We also discuss briefly the promise of harnessing the molecules that undergo transcytosis as vehicles for clinical applications in drug delivery.
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Affiliation(s)
| | - Daniel J-F Chinnapen
- Division of Gastroenterology, Boston Children's Hospital, Boston, Massachusetts 02155.,Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02155.,Department of Pediatrics, Harvard Digestive Diseases Center, Boston, Massachusetts 02155
| | - Wayne I Lencer
- Division of Gastroenterology, Boston Children's Hospital, Boston, Massachusetts 02155.,Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02155.,Department of Pediatrics, Harvard Digestive Diseases Center, Boston, Massachusetts 02155
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19
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Treyer A, Pujato M, Pechuan X, Müsch A. Iterative sorting of apical and basolateral cargo in Madin-Darby canine kidney cells. Mol Biol Cell 2016; 27:2259-71. [PMID: 27226480 PMCID: PMC4945143 DOI: 10.1091/mbc.e16-02-0096] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 05/19/2016] [Indexed: 01/21/2023] Open
Abstract
A novel assay quantitatively distinguishes different cargo pairs by their degree of colocalization at the TGN and the evolution of colocalization during their TGN-to-surface transport. Apical NTRp75 and basolateral VSVG in MDCK cells undergo continuous sorting between TGN exit and surface arrival. For several decades, the trans-Golgi network (TGN) was considered the most distal stop and hence the ultimate protein-sorting station for distinct apical and basolateral transport carriers that reach their respective surface domains in the direct trafficking pathway. However, recent reports of apical and basolateral cargoes traversing post-Golgi compartments accessible to endocytic ligands before their arrival at the cell surface and the post-TGN breakup of large pleomorphic membrane fragments that exit the Golgi region toward the surface raised the possibility that compartments distal to the TGN mediate or contribute to biosynthetic sorting. Here we describe the development of a novel assay that quantitatively distinguishes different cargo pairs by their degree of colocalization at the TGN and by the evolution of colocalization during their TGN-to-surface transport. Keys to the high resolution of our approach are 1) conversion of perinuclear organelle clustering into a two-dimensional microsomal spread and 2) identification of TGN and post-TGN cargo without the need for a TGN marker that universally cosegregates with all cargo. Using our assay, we provide the first evidence that apical NTRp75 and basolateral VSVG in Madin–Darby canine kidney cells still undergo progressive sorting after they exit the TGN toward the cell surface.
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Affiliation(s)
- Aleksandr Treyer
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Mario Pujato
- Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, NY 10461 Center for Autoimmune Genomics and Etiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229
| | - Ximo Pechuan
- Department of Systems and Computational Biology, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Anne Müsch
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY 10461
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20
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Avaritt BR, Swaan PW. Internalization and Subcellular Trafficking of Poly-l-lysine Dendrimers Are Impacted by the Site of Fluorophore Conjugation. Mol Pharm 2015; 12:1961-9. [DOI: 10.1021/mp500765e] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Brittany R. Avaritt
- Department
of Pharmaceutical
Sciences, Center for Nanobiotechnology, University of Maryland, Baltimore, 20 Penn Street, Baltimore, Maryland 21201, United States
| | - Peter W. Swaan
- Department
of Pharmaceutical
Sciences, Center for Nanobiotechnology, University of Maryland, Baltimore, 20 Penn Street, Baltimore, Maryland 21201, United States
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21
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Barrile R, Kasendra M, Rossi-Paccani S, Merola M, Pizza M, Baldari C, Soriani M, Aricò B. Neisseria meningitidis subverts the polarized organization and intracellular trafficking of host cells to cross the epithelial barrier. Cell Microbiol 2015; 17:1365-75. [PMID: 25801707 DOI: 10.1111/cmi.12439] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Revised: 03/13/2015] [Accepted: 03/14/2015] [Indexed: 12/19/2022]
Abstract
Translocation of the nasopharyngeal barrier by Neisseria meningitidis occurs via an intracellular microtubule-dependent pathway and represents a crucial step in its pathogenesis. Despite this fact, the interaction of invasive meningococci with host subcellular compartments and the resulting impact on their organization and function have not been investigated. The influence of serogroup B strain MC58 on host cell polarity and intracellular trafficking system was assessed by confocal microscopy visualization of different plasma membrane-associated components (such as E-cadherin, ZO-1 and transferrin receptor) and evaluation of the transferrin uptake and recycling in infected Calu-3 monolayers. Additionally, the association of N. meningitidis with different endosomal compartments was evaluated through the concomitant staining of bacteria and markers specific for Rab11, Rab22a, Rab25 and Rab3 followed by confocal microscopy imaging. Subversion of the host cell architecture and intracellular trafficking system, denoted by mis-targeting of cell plasma membrane components and perturbations of transferrin transport, was shown to occur in response to N. meningitidis infection. Notably, the appearance of all of these events seems to positively correlate with the efficiency of N. meningitidis to cross the epithelial barrier. Our data reveal for the first time that N. meningitidis is able to modulate the host cell architecture and function, which might serve as a strategy of this pathogen for overcoming the nasopharyngeal barrier without affecting the monolayer integrity.
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Affiliation(s)
- Riccardo Barrile
- Department of Microbial Molecular Biology, Novartis Vaccines and Diagnostics (a GSK company), Siena, Italy.,Biomimetic Microsystems platform, Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, MA, 02115, USA
| | - Magdalena Kasendra
- Department of Microbial Molecular Biology, Novartis Vaccines and Diagnostics (a GSK company), Siena, Italy
| | - Silvia Rossi-Paccani
- Department of Microbial Molecular Biology, Novartis Vaccines and Diagnostics (a GSK company), Siena, Italy
| | - Marcello Merola
- Department of Microbial Molecular Biology, Novartis Vaccines and Diagnostics (a GSK company), Siena, Italy.,Department of Biology, University of Naples 'Federico II', Napoli, Italy
| | - Mariagrazia Pizza
- Department of Microbial Molecular Biology, Novartis Vaccines and Diagnostics (a GSK company), Siena, Italy
| | - Cosima Baldari
- Department of Life Sciences, University of Siena, Siena, Italy
| | - Marco Soriani
- Department of Microbial Molecular Biology, Novartis Vaccines and Diagnostics (a GSK company), Siena, Italy
| | - Beatrice Aricò
- Department of Microbial Molecular Biology, Novartis Vaccines and Diagnostics (a GSK company), Siena, Italy
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22
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Favale NO, Santacreu BJ, Pescio LG, Marquez MG, Sterin-Speziale NB. Sphingomyelin metabolism is involved in the differentiation of MDCK cells induced by environmental hypertonicity. J Lipid Res 2015; 56:786-800. [PMID: 25670801 DOI: 10.1194/jlr.m050781] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Sphingolipids (SLs) are relevant lipid components of eukaryotic cells. Besides regulating various cellular processes, SLs provide the structural framework for plasma membrane organization. Particularly, SM is associated with detergent-resistant microdomains. We have previously shown that the adherens junction (AJ) complex, the relevant cell-cell adhesion structure involved in cell differentiation and tissue organization, is located in an SM-rich membrane lipid domain. We have also demonstrated that under hypertonic conditions, Madin-Darby canine kidney (MDCK) cells acquire a differentiated phenotype with changes in SL metabolism. For these reasons, we decided to evaluate whether SM metabolism is involved in the acquisition of the differentiated phenotype of MDCK cells. We found that SM synthesis mediated by SM synthase 1 is involved in hypertonicity-induced formation of mature AJs, necessary for correct epithelial cell differentiation. Inhibition of SM synthesis impaired the acquisition of mature AJs, evoking a disintegration-like process reflected by the dissipation of E-cadherin and β- and α-catenins from the AJ complex. As a consequence, MDCK cells did not develop the hypertonicity-induced differentiated epithelial cell phenotype.
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Affiliation(s)
- Nicolás Octavio Favale
- Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina IQUIFIB-LANAIS-PROEM-CONICET, Ciudad Autónoma de Buenos Aires, Argentina
| | - Bruno Jaime Santacreu
- Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina IQUIFIB-LANAIS-PROEM-CONICET, Ciudad Autónoma de Buenos Aires, Argentina
| | - Lucila Gisele Pescio
- Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina IQUIFIB-LANAIS-PROEM-CONICET, Ciudad Autónoma de Buenos Aires, Argentina
| | - Maria Gabriela Marquez
- IQUIFIB-LANAIS-PROEM-CONICET, Ciudad Autónoma de Buenos Aires, Argentina Instituto de Investigaciones en Ciencias de la Salud Humana (IICSHUM), Universidad Nacional de La Rioja , La Rioja, Argentina
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23
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Eaton S, Martin-Belmonte F. Cargo sorting in the endocytic pathway: a key regulator of cell polarity and tissue dynamics. Cold Spring Harb Perspect Biol 2014; 6:a016899. [PMID: 25125399 DOI: 10.1101/cshperspect.a016899] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The establishment and maintenance of polarized plasma membrane domains is essential for cellular function and proper development of organisms. Epithelial cells polarize along two fundamental axes, the apicobasal and the planar, both depending on finely regulated protein trafficking mechanisms. Newly synthesized proteins destined for either surface domain are processed along the biosynthetic pathway and segregated into distinct subsets of transport carriers emanating from the trans-Golgi network or endosomes. This exocytic trafficking has been identified as essential for proper epithelial polarization. Accumulating evidence now reveals that endocytosis and endocytic recycling play an equally important role in epithelial polarization and the appropriate localization of key polarity proteins. Here, we review recent work in metazoan systems illuminating the connections between endocytosis, postendocytic trafficking, and cell polarity, both apicobasal and planar, in the formation of differentiated epithelial cells, and how these processes regulate tissue dynamics.
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Affiliation(s)
- Suzanne Eaton
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Fernando Martin-Belmonte
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas (CSIC), Madrid 28049, Spain
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24
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Stoops EH, Caplan MJ. Trafficking to the apical and basolateral membranes in polarized epithelial cells. J Am Soc Nephrol 2014; 25:1375-86. [PMID: 24652803 DOI: 10.1681/asn.2013080883] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Renal epithelial cells must maintain distinct protein compositions in their apical and basolateral membranes in order to perform their transport functions. The creation of these polarized protein distributions depends on sorting signals that designate the trafficking route and site of ultimate functional residence for each protein. Segregation of newly synthesized apical and basolateral proteins into distinct carrier vesicles can occur at the trans-Golgi network, recycling endosomes, or a growing assortment of stations along the cellular trafficking pathway. The nature of the specific sorting signal and the mechanism through which it is interpreted can influence the route a protein takes through the cell. Cell type-specific variations in the targeting motifs of a protein, as are evident for Na,K-ATPase, demonstrate a remarkable capacity to adapt sorting pathways to different developmental states or physiologic requirements. This review summarizes our current understanding of apical and basolateral trafficking routes in polarized epithelial cells.
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Affiliation(s)
- Emily H Stoops
- Departments of Cellular & Molecular Physiology and Cell Biology, Yale University School of Medicine, New Haven, Connecticut
| | - Michael J Caplan
- Departments of Cellular & Molecular Physiology and Cell Biology, Yale University School of Medicine, New Haven, Connecticut
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25
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Preston JE, Joan Abbott N, Begley DJ. Transcytosis of Macromolecules at the Blood–Brain Barrier. PHARMACOLOGY OF THE BLOOD BRAIN BARRIER: TARGETING CNS DISORDERS 2014; 71:147-63. [DOI: 10.1016/bs.apha.2014.06.001] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Using replication defective viruses to analyze membrane trafficking in polarized epithelial cells. Methods Cell Biol 2013. [PMID: 24295304 DOI: 10.1016/b978-0-12-417164-0.00008-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Epithelial cells in culture, especially once they are polarized, are extremely hard to manipulate by transient transfection methods. The use of replication defective adenoviruses for gene expression or replication defective retroviruses or lentiviruses to express shRNA for gene knockdown provides efficient tools to manipulate gene expression patterns even in hard-to-transfect cell lines. One of the advantages of using defective adenoviruses for gene expression is that once the virus has been generated, it can easily be applied to a wide variety of cells. In addition, replication defective retro- and lentiviruses are used to stably deplete proteins from cell lines, which subsequently may be used for analyzing the polarized surface delivery of receptors that may be expressed using defective adenoviruses. The latter approach is especially useful if the expressed shRNA also encodes GFP for easy assessment of shRNA-expressing cells. Thus the use of defective viruses in epithelial cell research is convenient. This makes a detailed infection protocol a research tool that would be valuable to many laboratories. Here we describe in detail how cells are infected with defective retro- or lentiviruses and subsequently selected for stable gene knockdown. We then describe how these cells may be used for infection with defective adenoviruses and the subsequent analyses.
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Abstract
Hepatocytes, like other epithelia, are situated at the interface between the organism's exterior and the underlying internal milieu and organize the vectorial exchange of macromolecules between these two spaces. To mediate this function, epithelial cells, including hepatocytes, are polarized with distinct luminal domains that are separated by tight junctions from lateral domains engaged in cell-cell adhesion and from basal domains that interact with the underlying extracellular matrix. Despite these universal principles, hepatocytes distinguish themselves from other nonstriated epithelia by their multipolar organization. Each hepatocyte participates in multiple, narrow lumina, the bile canaliculi, and has multiple basal surfaces that face the endothelial lining. Hepatocytes also differ in the mechanism of luminal protein trafficking from other epithelia studied. They lack polarized protein secretion to the luminal domain and target single-spanning and glycosylphosphatidylinositol-anchored bile canalicular membrane proteins via transcytosis from the basolateral domain. We compare this unique hepatic polarity phenotype with that of the more common columnar epithelial organization and review our current knowledge of the signaling mechanisms and the organization of polarized protein trafficking that govern the establishment and maintenance of hepatic polarity. The serine/threonine kinase LKB1, which is activated by the bile acid taurocholate and, in turn, activates adenosine monophosphate kinase-related kinases including AMPK1/2 and Par1 paralogues has emerged as a key determinant of hepatic polarity. We propose that the absence of a hepatocyte basal lamina and differences in cell-cell adhesion signaling that determine the positioning of tight junctions are two crucial determinants for the distinct hepatic and columnar polarity phenotypes.
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Affiliation(s)
- Aleksandr Treyer
- Albert Einstein College of Medicine, Department of Developmental and Molecular Biology, Bronx, New York, USA
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Zhang H, Kim A, Abraham N, Khan LA, Göbel V. Vesicular sorting controls the polarity of expanding membranes in the C. elegans intestine. WORM 2013; 2:e23702. [PMID: 24058862 PMCID: PMC3670463 DOI: 10.4161/worm.23702] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2013] [Accepted: 01/16/2013] [Indexed: 11/19/2022]
Abstract
Biological tubes consist of polarized epithelial cells with apical membranes building the central lumen and basolateral membranes contacting adjacent cells or the extracellular matrix. Cellular polarity requires distinct inputs from outside the cell, e.g., the matrix, inside the cell, e.g., vesicular trafficking and the plasma membrane and its junctions.1 Many highly conserved polarity cues have been identified, but their integration during the complex process of polarized tissue and organ morphogenesis is not well understood. It is assumed that plasma-membrane-associated polarity determinants, such as the partitioning-defective (PAR) complex, define plasma membrane domain identities, whereas vesicular trafficking delivers membrane components to these domains, but lacks the ability to define them. In vitro studies on lumenal membrane biogenesis in mammalian cell lines now indicate that trafficking could contribute to defining membrane domains by targeting the polarity determinants, e.g., the PARs, themselves.2 This possibility suggests a mechanism for PARs’ asymmetric distribution on membranes and places vesicle-associated polarity cues upstream of membrane-associated polarity determinants. In such an upstream position, trafficking might even direct multiple membrane components, not only polarity determinants, an original concept of polarized plasma membrane biogenesis3,4that was largely abandoned due to the failure to identify a molecularly defined intrinsic vesicular sorting mechanism. Our two recent studies on C. elegans intestinal tubulogenesis reveal that glycosphingolipids (GSLs) and the well-recognized vesicle components clathrin and its AP-1 adaptor are required for targeting multiple apical molecules, including polarity regulators, to the expanding apical/lumenal membrane.5,6 These findings support GSLs’ long-proposed role in in vivo polarized epithelial membrane biogenesis and development and identify a novel function in apical polarity for classical post-Golgi vesicle components. They are also compatible with a vesicle-intrinsic sorting mechanism during membrane biogenesis and suggest a model for how vesicles could acquire apical directionality during the assembly of the functionally critical polarized lumenal surfaces of epithelial tubes.
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Affiliation(s)
- Hongjie Zhang
- Department of Pediatrics; Massachusetts General Hospital; Harvard Medical School; Boston, MA USA
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Matsudaira T, Uchida Y, Tanabe K, Kon S, Watanabe T, Taguchi T, Arai H. SMAP2 regulates retrograde transport from recycling endosomes to the Golgi. PLoS One 2013; 8:e69145. [PMID: 23861959 PMCID: PMC3704519 DOI: 10.1371/journal.pone.0069145] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 06/03/2013] [Indexed: 02/04/2023] Open
Abstract
Retrograde transport is where proteins and lipids are transported back from the plasma membrane (PM) and endosomes to the Golgi, and crucial for a diverse range of cellular functions. Recycling endosomes (REs) serve as a sorting station for the retrograde transport and we recently identified evection-2, an RE protein with a pleckstrin homology (PH) domain, as an essential factor of this pathway. How evection-2 regulates retrograde transport from REs to the Golgi is not well understood. Here, we report that evection-2 binds to SMAP2, an Arf GTPase-activating protein. Endogenous SMAP2 localized mostly in REs and to a lesser extent, the trans-Golgi network (TGN). SMAP2 binds evection-2, and the RE localization of SMAP2 was abolished in cells depleted of evection-2. Knockdown of SMAP2, like that of evection-2, impaired the retrograde transport of cholera toxin B subunit (CTxB) from REs. These findings suggest that evection-2 recruits SMAP2 to REs, thereby regulating the retrograde transport of CTxB from REs to the Golgi.
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Affiliation(s)
- Tatsuyuki Matsudaira
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
| | - Yasunori Uchida
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
| | - Kenji Tanabe
- Medical Research Institute, Tokyo Women’s Medical University, Tokyo, Japan
| | - Shunsuke Kon
- Department of Molecular Immunology, Institute of Development, Aging and Cancer, Tohoku University, Sendai-shi, Miyagi, Japan
| | - Toshio Watanabe
- Department of Biological Science, Graduate School of Humanities and Sciences, Nara Women’s University, Nara-shi, Nara, Japan
| | - Tomohiko Taguchi
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
- Pathological Cell Biology Laboratory, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
- * E-mail: (TT) (HA)
| | - Hiroyuki Arai
- Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
- Pathological Cell Biology Laboratory, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
- * E-mail: (TT) (HA)
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Yin X, Murphy SJ, Wilkes MC, Ji Y, Leof EB. Retromer maintains basolateral distribution of the type II TGF-β receptor via the recycling endosome. Mol Biol Cell 2013; 24:2285-98. [PMID: 23720763 PMCID: PMC3708733 DOI: 10.1091/mbc.e13-02-0093] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
After basolateral (BL) cell surface delivery, retromer promotes type II TGF-β receptor exit and recycling to the BL plasma membrane. In the absence of retromer, however, type II receptors aberrantly sort and are mislocalized such that both BL and apical expression is observed independent of the Rab11-positive apical recycling endosome. Transforming growth factor β (TGF-β) is critical for the development and maintenance of epithelial structures. Because receptor localization and trafficking affect the cellular and organismal response to TGF-β, the present study was designed to address how such homeostatic control is regulated. To that end, we identify a new role for the mammalian retromer complex in maintaining basolateral plasma membrane expression of the type II TGF-β receptor (TβRII). Retromer and TβRII associate in the presence or absence of TGF-β ligand. After retromer knockdown, although TβRII internalization and trafficking to a Rab5-positive compartment occur as in wild-type cells, receptor recycling is inhibited. This results in TβRII mislocalization from the basolateral to both the basolateral and apical plasma membranes independent of Golgi transit and the Rab11-positive apical recycling endosome. The data support a model in which, after initial basolateral TβRII delivery, steady-state polarized TβRII expression is maintained by retromer/TβRII binding and delivery to the common recycling endosome.
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Affiliation(s)
- Xueqian Yin
- Thoracic Disease Research Unit, Departments of Biochemistry/Molecular Biology and Medicine, Mayo Clinic Cancer Center, Rochester, MN 55905, USA
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Abstract
Epithelial cells have an apical-basolateral axis of polarity, which is required for epithelial functions including barrier formation, vectorial ion transport and sensory perception. Here we review what is known about the sorting signals, machineries and pathways that maintain this asymmetry, and how polarity proteins interface with membrane-trafficking pathways to generate membrane domains de novo. It is becoming apparent that membrane traffic does not simply reinforce polarity, but is critical for the generation of cortical epithelial cell asymmetry.
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The role of secretory and endocytic pathways in the maintenance of cell polarity. Essays Biochem 2012; 53:29-39. [PMID: 22928506 DOI: 10.1042/bse0530029] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Epithelial cells line virtually every organ cavity in the body and are important for vectorial transport through epithelial monolayers such as nutrient uptake or waste product excretion. Central to these tasks is the establishment of epithelial cell polarity. During organ development, epithelial cells set up two biochemically distinct plasma membrane domains, the apical and the basolateral domain. Targeting of correct constituents to each of these regions is essential for maintaining epithelial cell polarity. Newly synthesized transmembrane proteins destined for the basolateral or apical membrane domain are sorted into separate transport carriers either at the TGN (trans-Golgi network) or in perinuclear REs (recycling endosomes). After initial delivery, transmembrane proteins, such as nutrient receptors, frequently undergo multiple rounds of endocytosis followed by re-sorting in REs. Recent work in epithelial cells highlights the REs as a potent sorting station with different subdomains representing individual targeting zones that facilitate the correct surface delivery of transmembrane proteins.
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Stanley AC, Lieu ZZ, Wall AA, Venturato J, Khromykh T, Hamilton NA, Gleeson PA, Stow JL. Recycling endosome-dependent and -independent mechanisms for IL-10 secretion in LPS-activated macrophages. J Leukoc Biol 2012; 92:1227-39. [PMID: 23012430 DOI: 10.1189/jlb.0412191] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
IL-10 is a key anti-inflammatory cytokine secreted by activated macrophages as a feedback control mechanism to prevent excessive inflammatory responses. Here, we define multiple intracellular trafficking pathways involved in the secretion of newly synthesized IL-10 from macrophages following TLR4 activation with LPS, and show how this relates to the previously defined trafficking pathways for IL-6 and TNF in macrophages simultaneously producing these proinflammatory cytokines. IL-10 exits the Golgi in multiple tubular carriers, including those dependent on p230GRIP. Some of the IL-10 is then delivered to recycling endosomes, where cytokine sorting may occur prior to its release. Another portion of the IL-10 is delivered to the cell surface in distinct vesicles colabeled for apoE. Thus, we show at least two post-Golgi pathways via which IL-10 is trafficked, ensuring its secretion from activated macrophages under different physiological conditions.
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Affiliation(s)
- A C Stanley
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
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35
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Sun L, Liu O, Desai J, Karbassi F, Sylvain MA, Shi A, Zhou Z, Rocheleau CE, Grant BD. CED-10/Rac1 regulates endocytic recycling through the RAB-5 GAP TBC-2. PLoS Genet 2012; 8:e1002785. [PMID: 22807685 PMCID: PMC3395619 DOI: 10.1371/journal.pgen.1002785] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 05/10/2012] [Indexed: 12/03/2022] Open
Abstract
Rac1 is a founding member of the Rho-GTPase family and a key regulator of membrane remodeling. In the context of apoptotic cell corpse engulfment, CED-10/Rac1 acts with its bipartite guanine nucleotide exchange factor, CED-5/Dock180-CED-12/ELMO, in an evolutionarily conserved pathway to promote phagocytosis. Here we show that in the context of the Caenorhabditis elegans intestinal epithelium CED-10/Rac1, CED-5/Dock180, and CED-12/ELMO promote basolateral recycling. Furthermore, we show that CED-10 binds to the RAB-5 GTPase activating protein TBC-2, that CED-10 contributes to recruitment of TBC-2 to endosomes, and that recycling cargo is trapped in recycling endosomes in ced-12, ced-10, and tbc-2 mutants. Expression of GTPase defective RAB-5(Q78L) also traps recycling cargo. Our results indicate that down-regulation of early endosome regulator RAB-5/Rab5 by a CED-5, CED-12, CED-10, TBC-2 cascade is an important step in the transport of cargo through the basolateral recycling endosome for delivery to the plasma membrane.
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Affiliation(s)
- Lin Sun
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey, United States of America
| | - Ou Liu
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey, United States of America
| | - Jigar Desai
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey, United States of America
| | - Farhad Karbassi
- Division of Endocrinology and Metabolism, Department of Medicine, McGill University and McGill University Health Centre Research Institute, Montreal, Quebec, Canada
| | - Marc-André Sylvain
- Division of Endocrinology and Metabolism, Department of Medicine, McGill University and McGill University Health Centre Research Institute, Montreal, Quebec, Canada
| | - Anbing Shi
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey, United States of America
| | - Zheng Zhou
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Christian E. Rocheleau
- Division of Endocrinology and Metabolism, Department of Medicine, McGill University and McGill University Health Centre Research Institute, Montreal, Quebec, Canada
| | - Barth D. Grant
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey, United States of America
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36
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McKenzie JE, Raisley B, Zhou X, Naslavsky N, Taguchi T, Caplan S, Sheff D. Retromer guides STxB and CD8-M6PR from early to recycling endosomes, EHD1 guides STxB from recycling endosome to Golgi. Traffic 2012; 13:1140-59. [PMID: 22540229 DOI: 10.1111/j.1600-0854.2012.01374.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 04/25/2012] [Accepted: 04/27/2012] [Indexed: 12/23/2022]
Abstract
Retrograde trafficking transports proteins, lipids and toxins from the plasma membrane to the Golgi and endoplasmic reticulum (ER). To reach the Golgi, these cargos must transit the endosomal system, consisting of early endosomes (EE), recycling endosomes, late endosomes and lysosomes. All cargos pass through EE, but may take different routes to the Golgi. Retromer-dependent cargos bypass the late endosomes to reach the Golgi. We compared how two very different retromer-dependent cargos negotiate the endosomal sorting system. Shiga toxin B, bound to the external layer of the plasma membrane, and chimeric CD8-mannose-6-phosphate receptor (CI-M6PR), which is anchored via a transmembrane domain. Both appear to pass through the recycling endosome. Ablation of the recycling endosome diverted both of these cargos to an aberrant compartment and prevented them from reaching the Golgi. Once in the recycling endosome, Shiga toxin required EHD1 to traffic to the TGN, while the CI-M6PR was not significantly dependent on EHD1. Knockdown of retromer components left cargo in the EE, suggesting that it is required for retrograde exit from this compartment. This work establishes the recycling endosome as a required step in retrograde traffic of at least these two retromer-dependent cargos. Along this pathway, retromer is associated with EE to recycling endosome traffic, while EHD1 is associated with recycling endosome to TGN traffic of STxB.
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Affiliation(s)
- Jenna E McKenzie
- Howard Hughes Medical Research Institute, Department of Molecular and Cellular Biology, University of California, Berkley, Berkley, CA 94720, USA
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37
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Abstract
Endocytosis and endosomal trafficking play a multitude of roles in cellular function beyond regulating entry of essential nutrients. In this review, we discuss the cell biological principles of endosomal trafficking, the neuronal adaptations to endosomal organization, and the role of endosomal trafficking in neural development. In particular, we consider how cell fate decisions, polarity, migration, and axon outgrowth and guidance are influenced by five endosomal tricks: dynamic modulation of receptor levels by endocytosis and recycling, cargo-specific responses via cargo-specific endocytic regulators, cell-type-specific endocytic regulation, ligand-specific endocytic regulation, and endosomal regulation of ligand processing and trafficking.
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Affiliation(s)
- Chan Choo Yap
- Department of Neuroscience, University of Virginia, 409 Lane Road, Charlottesville, VA 22908, USA
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38
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39
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Mattila PE, Youker RT, Mo D, Bruns JR, Cresawn KO, Hughey RP, Ihrke G, Weisz OA. Multiple biosynthetic trafficking routes for apically secreted proteins in MDCK cells. Traffic 2011; 13:433-42. [PMID: 22118573 DOI: 10.1111/j.1600-0854.2011.01315.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 11/21/2011] [Accepted: 11/21/2011] [Indexed: 11/30/2022]
Abstract
Many newly synthesized membrane proteins traverse endocytic intermediates en route to the surface in polarized epithelial cells; however, the biosynthetic itinerary of secreted proteins has not been elucidated. We monitored the trafficking route of two secreted proteins with different apical sorting signals: the N-glycan-dependent cargo glycosylated growth hormone (gGH) and Ensol, a soluble version of endolyn whose apical sorting is independent of N-glycans. Both proteins were observed to colocalize in part with apical recycling endosome (ARE) markers. Cargo that lacks an apical targeting signal and is secreted in a nonpolarized manner did not localize to the ARE. Expression of a dominant-negative mutant of myosin Vb, which disrupts ARE export of glycan-dependent membrane proteins, selectively inhibited apical release of gGH but not Ensol. Fluorescence recovery after photobleaching (FRAP) measurements revealed that gGH in the ARE was less mobile than Ensol, consistent with tethering to a sorting receptor. However, knockdown of galectin-3 or galectin-4, lectins implicated in apical sorting, had no effect on the rate or polarity of gGH secretion. Together, our results suggest that apically secreted cargoes selectively access the ARE and are exported via differentially regulated pathways.
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Affiliation(s)
- Polly E Mattila
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA, USA
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40
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Lasiecka ZM, Winckler B. Mechanisms of polarized membrane trafficking in neurons -- focusing in on endosomes. Mol Cell Neurosci 2011; 48:278-87. [PMID: 21762782 DOI: 10.1016/j.mcn.2011.06.013] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 06/21/2011] [Accepted: 06/25/2011] [Indexed: 12/13/2022] Open
Abstract
Neurons are polarized cells that have a complex and unique morphology: long processes (axons and dendrites) extending far from the cell body. In addition, the somatodendritic and axonal domains are further divided into specific subdomains, such as synapses (pre- and postsynaptic specializations), proximal and distal dendrites, axon initial segments, nodes of Ranvier, and axon growth cones. The striking asymmetry and complexity of neuronal cells are necessary for their function in receiving, processing and transferring electrical signals, with each domain playing a precise function in these processes. In order to establish and maintain distinct neuronal domains, mechanisms must exist for protein delivery to specific neuronal compartments, such that each compartment has the correct functional molecular composition. How polarized membrane domains are established and maintained is a long-standing question. Transmembrane proteins, such as receptors and adhesion molecules, can be transported to their proper membrane domains by several pathways. The biosynthetic secretory system delivers newly synthesized transmembrane proteins from the ER via the Golgi and trans-Golgi-network (TGN) to the plasma membrane. In addition, the endosomal system is critically involved in many instances in ensuring proper (re)targeting of membrane components because it can internalize and degrade mislocalized proteins, or recycle proteins from one domain to another. The endosomal system is thus crucial for establishing and maintaining neuronal polarity. In this review, we focus mainly on the intracellular compartments that serve as sorting stations for polarized transport, with particular emphasis on the emerging roles of endosomes.
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Affiliation(s)
- Zofia M Lasiecka
- Department of Neuroscience, University of Virginia Medical School, 409 Lane Rd. Extension, MR4-6116, Charlottesville, VA 22908, USA
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41
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Recycling endosomes in apical plasma membrane domain formation and epithelial cell polarity. Trends Cell Biol 2010; 20:618-26. [PMID: 20833047 DOI: 10.1016/j.tcb.2010.08.004] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Revised: 08/05/2010] [Accepted: 08/06/2010] [Indexed: 01/24/2023]
Abstract
Recycling endosomes have taken central stage in the intracellular sorting and polarized trafficking of apical and basolateral plasma membrane components. Molecular players in the underlying mechanisms are now emerging, including small GTPases, class V myosins and adaptor proteins. In particular, defects in the expression or function of these recycling endosome-associated and endosome-regulating proteins have been implicated in cell surface polarity defects and diseases, including microvillus inclusion disease, arthrogryposis-renal dysfunction-cholestasis syndrome, and virus susceptibility. Key findings are that recycling endosomes recruit and deliver core polarity proteins to lateral cell surfaces and initiate the biogenesis of apical plasma membrane domains and epithelial cell polarity. Here, we review recent data that implicate recycling endosomes in the establishment and maintenance of epithelial cell polarity.
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Abstract
Wiring of the brain relies initially on the correct outgrowth of axons to reach the appropriate target area for innervation. A large number of guidance receptors present in the plasma membrane of axonal growth cones and elsewhere on the neuron read and execute directional cues present in the extracellular environment of the navigating growth cone. The exact timing, levels, and localization of expression of the guidance receptors in the plasma membrane therefore determine the outcome of guidance decisions. Many guidance receptors are localized in exquisitely precise spatial and temporal patterns. The cellular mechanisms ensuring these localization patterns include spatially accurate sorting after synthesis in the secretory pathway, retrieval of inappropriately expressed receptors by endocytosis followed by degradation or recycling, and restriction of diffusion. This article will discuss the machinery and regulation underlying the restricted distribution of membrane receptors, focusing on the currently best-studied example, the L1 cell adhesion molecule. In addition to the long-range mechanisms ensuring appropriate localization, the same mechanisms can act locally to adjust levels and localization of receptors. These local mechanisms are regulated by ligand binding and subsequent activation of local signaling cascades. It is likely that the localization of all guidance receptors is regulated by a combination of sorting, retrieval, recycling and retention, similar to the ones we discuss here for L1.
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Affiliation(s)
- Bettina Winckler
- University of Virginia, Department of Neuroscience, Charlottesville, Virgina 22908, USA
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43
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Woodcroft BJ, Hammond L, Stow JL, Hamilton NA. Automated organelle-based colocalization in whole-cell imaging. Cytometry A 2009; 75:941-50. [DOI: 10.1002/cyto.a.20786] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Gonzalez A, Rodriguez-Boulan E. Clathrin and AP1B: key roles in basolateral trafficking through trans-endosomal routes. FEBS Lett 2009; 583:3784-95. [PMID: 19854182 DOI: 10.1016/j.febslet.2009.10.050] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Revised: 10/15/2009] [Accepted: 10/20/2009] [Indexed: 12/12/2022]
Abstract
Research following introduction of the MDCK model system to study epithelial polarity (1978) led to an initial paradigm that posited independent roles of the trans Golgi network (TGN) and recycling endosomes (RE) in the generation of, respectively, biosynthetic and recycling routes of plasma membrane (PM) proteins to apical and basolateral PM domains. This model dominated the field for 20 years. However, studies over the past decade and the discovery of the involvement of clathrin and clathrin adaptors in protein trafficking to the basolateral PM has led to a new paradigm. TGN and RE are now believed to cooperate closely in both biosynthetic and recycling trafficking routes. Here, we critically review these recent advances and the questions that remain unanswered.
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Affiliation(s)
- Alfonso Gonzalez
- Departamento de Inmunología Clínica y Reumatología, Facultad de Medicina, Centro de Regulación Celular y Patología and Centro de Envejecimiento y Regeneración, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, 6510260 Santiago, Chile.
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45
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Grant BD, Donaldson JG. Pathways and mechanisms of endocytic recycling. Nat Rev Mol Cell Biol 2009; 10:597-608. [PMID: 19696797 DOI: 10.1038/nrm2755] [Citation(s) in RCA: 1063] [Impact Index Per Article: 70.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Endocytic recycling is coordinated with endocytic uptake to control the composition of the plasma membrane. Although much of our understanding of endocytic recycling has come from studies on the transferrin receptor, a protein internalized through clathrin-dependent endocytosis, increased interest in clathrin-independent endocytosis has led to the discovery of new endocytic recycling systems. Recent insights into the regulatory mechanisms that control endocytic recycling have focused on recycling through tubular carriers and the return to the cell surface of cargoes that enter cells through clathrin-independent mechanisms. Recent work emphasizes the importance of regulated recycling in processes as diverse as cytokinesis, cell adhesion, morphogenesis, cell fusion, learning and memory.
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Affiliation(s)
- Barth D Grant
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, USA.
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46
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Veldhuis NA, Valova VA, Gaeth AP, Palstra N, Hannan KM, Michell BJ, Kelly LE, Jennings I, Kemp BE, Pearson RB, Robinson PJ, Camakaris J. Phosphorylation regulates copper-responsive trafficking of the Menkes copper transporting P-type ATPase. Int J Biochem Cell Biol 2009; 41:2403-12. [PMID: 19576997 DOI: 10.1016/j.biocel.2009.06.008] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2009] [Revised: 06/24/2009] [Accepted: 06/25/2009] [Indexed: 12/25/2022]
Abstract
The Menkes copper-translocating P-type ATPase (ATP7A) is a critical copper transport protein functioning in systemic copper absorption and supply of copper to cuproenzymes in the secretory pathway. Mutations in ATP7A can lead to the usually lethal Menkes disease. ATP7A function is regulated by copper-responsive trafficking between the trans-Golgi Network and the plasma membrane. We have previously reported basal and copper-responsive kinase phosphorylation of ATP7A but the specific phosphorylation sites had not been identified. As copper stimulates both trafficking and phosphorylation of ATP7A we aimed to identify all the specific phosphosites and to determine whether trafficking and phosphorylation are linked. We identified twenty in vivo phosphorylation sites in the human ATP7A and eight in hamster, all clustered within the N- and C-terminal cytosolic domains. Eight sites were copper-responsive and hence candidates for regulating copper-responsive trafficking or catalytic activity. Mutagenesis of the copper-responsive phosphorylation site Serine-1469 resulted in mislocalization of ATP7A in the presence of added copper in both polarized (Madin Darby canine kidney) and non-polarized (Chinese Hamster Ovary) cells, strongly suggesting that phosphorylation of specific serine residues is required for copper-responsive ATP7A trafficking to the plasma membrane. A constitutively phosphorylated site, Serine-1432, when mutated to alanine also resulted in mislocalization in the presence of added copper in polarized Madin Darby kidney cells. These studies demonstrate that phosphorylation of specific serine residues in ATP7A regulates its sub-cellular localization and hence function and will facilitate identification of the kinases and signaling pathways involved in regulating this pivotal copper transporter.
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Affiliation(s)
- Nicholas A Veldhuis
- Genetics Department, The University of Melbourne, Melbourne, Victoria, Australia
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47
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Tzaban S, Massol RH, Yen E, Hamman W, Frank SR, Lapierre LA, Hansen SH, Goldenring JR, Blumberg RS, Lencer WI. The recycling and transcytotic pathways for IgG transport by FcRn are distinct and display an inherent polarity. ACTA ACUST UNITED AC 2009; 185:673-84. [PMID: 19451275 PMCID: PMC2711563 DOI: 10.1083/jcb.200809122] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The Fc receptor FcRn traffics immunoglobulin G (IgG) in both directions across polarized epithelial cells that line mucosal surfaces, contributing to host defense. We show that FcRn traffics IgG from either apical or basolateral membranes into the recycling endosome (RE), after which the actin motor myosin Vb and the GTPase Rab25 regulate a sorting step that specifies transcytosis without affecting recycling. Another regulatory component of the RE, Rab11a, is dispensable for transcytosis, but regulates recycling to the basolateral membrane only. None of these proteins affect FcRn trafficking away from lysosomes. Thus, FcRn transcytotic and recycling sorting steps are distinct. These results are consistent with a single structurally and functionally heterogeneous RE compartment that traffics FcRn to both cell surfaces while discriminating between recycling and transcytosis pathways polarized in their direction of transport.
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Affiliation(s)
- Salit Tzaban
- Children's Hospital, Gastroenterology Division, Harvard Digestive Diseases Center, Harvard Medical School, Boston, MA 02115, USA
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48
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Fölsch H, Mattila PE, Weisz OA. Taking the scenic route: biosynthetic traffic to the plasma membrane in polarized epithelial cells. Traffic 2009; 10:972-81. [PMID: 19453969 DOI: 10.1111/j.1600-0854.2009.00927.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The maintenance of epithelial cell function requires the establishment and continuous renewal of differentiated apical and basolateral plasma membrane domains with distinct lipid and protein compositions. Newly synthesized proteins destined for either surface domain are processed along the biosynthetic pathway and segregated into distinct subsets of transport carriers emanating from the trans-Golgi network. Recent studies have illuminated additional complexities in the subsequent delivery of these proteins to the cell surface. In particular, multiple routes to the apical and basolateral cell surfaces have been uncovered, and many of these involve indirect passage through endocytic compartments. This review summarizes our current understanding of these routes and discusses open issues that remain to be clarified.
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Affiliation(s)
- Heike Fölsch
- Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208, USA.
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49
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Ward ES, Ober RJ. Chapter 4: Multitasking by exploitation of intracellular transport functions the many faces of FcRn. Adv Immunol 2009; 103:77-115. [PMID: 19755184 DOI: 10.1016/s0065-2776(09)03004-1] [Citation(s) in RCA: 127] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The MHC Class I-related receptor, FcRn, transports antibodies of the immunoglobulin G (IgG) class within and across a diverse array of different cell types. Through this transport, FcRn serves multiple roles throughout adult life that extend well beyond its earlier defined function of transcytosing IgGs from mother to offspring. These roles include the maintenance of IgG levels and the delivery of antigen in the form of immune complexes to degradative compartments within cells. Recent studies have led to significant advances in knowledge of the intracellular trafficking of FcRn and (engineered) IgGs at both the molecular and cellular levels. The engineering of FcRn-IgG (or Fc) interactions to generate antibodies of increased longevity represents an area of active interest, particularly in the light of the expanding use of antibodies in therapy. The strict pH dependence of FcRn-IgG interactions, with binding at pH 6 that becomes essentially undetectable as near neutral pH is approached, is essential for efficient transport. The requirement for retention of low affinity at near neutral pH increases the complexity of engineering antibodies for increased half-life. Conversely, engineered IgGs that have gained significant binding for FcRn at this pH can be potent inhibitors of FcRn that lower endogenous IgG levels and have multiple potential uses as therapeutics. In addition, molecular studies of FcRn-IgG interactions indicate that mice have limitations as preclinical models for FcRn function, primarily due to cross-species differences in FcRn-binding specificity.
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Affiliation(s)
- E Sally Ward
- Department of Immunology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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50
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Nejsum LN, Nelson WJ. Epithelial cell surface polarity: the early steps. FRONT BIOSCI-LANDMRK 2009; 14:1088-98. [PMID: 19273117 DOI: 10.2741/3295] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Establishment and maintenance of epithelial cell surface polarity is of vital importance for the correct function of transporting epithelia. To maintain normal cell function, the distribution of apical and basal-lateral proteins is highly regulated and defects in expression levels or plasma membrane targeting can have severe consequences. It has been shown recently that initiation of cell-surface polarity occurs immediately upon cell-cell contact, and requires components of the lateral targeting patch, the Exocyst and the lateral SNARE complex to specify delivery of basolateral proteins to the site of cell-cell adhesion. The Exocyst and SNARE complex are present in the cytoplasm in single epithelial cells before adhesion. Upon initial cell-cell adhesion, E-cadherin accumulates at the forming contact between cells. Shortly hereafter, components of the lateral targeting patch, the Exocyst and the lateral SNARE complex, co-localize with E-cadherin at the forming contact, where they function in specifying the delivery of basal-lateral.
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Affiliation(s)
- Lene N Nejsum
- Departments of Biology, and Molecular and Cellular Physiology, The James H. Clark Center, Bio-X Program, Stanford University, 318 Campus Drive E200, Stanford, CA 94305-5430, USA.
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