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Prydz K, Saraste J. The life cycle and enigmatic egress of coronaviruses. Mol Microbiol 2022; 117:1308-1316. [PMID: 35434857 PMCID: PMC9321882 DOI: 10.1111/mmi.14907] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 04/11/2022] [Accepted: 04/12/2022] [Indexed: 11/30/2022]
Abstract
There has been considerable recent interest in the life cycle of Severe Acute Respiratory Syndrome Coronavirus‐2 (SARS‐CoV‐2), the causative agent of the Covid‐19 pandemic. Practically every step in CoV replication—from cell attachment and uptake via genome replication and expression to virion assembly has been considered as a specific event that potentially could be targeted by existing or novel drugs. Interference with cellular egress of progeny viruses could also be adopted as a possible therapeutic strategy; however, the situation is complicated by the fact that there is no broad consensus on how CoVs find their way out of their host cells. The viral nucleocapsid, consisting of the genomic RNA complexed with nucleocapsid proteins obtains a membrane envelope during virus budding into the lumen of the intermediate compartment (IC) at the endoplasmic reticulum (ER)–Golgi interface. From here, several alternative routes for CoV extracellular release have been proposed. Strikingly, recent studies have shown that CoV infection leads to the disassembly of the Golgi ribbon and the mobilization of host cell compartments and protein machineries that are known to promote Golgi‐independent trafficking to the cell surface. Here, we discuss the life cycle of CoVs with a special focus on different possible pathways for virus egress.
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Affiliation(s)
- Kristian Prydz
- Department of Biosciences, University of Oslo, Norway and Department of Biomedicine and Molecular Imaging Center University of Bergen Norway
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Calcium levels in the Golgi complex regulate clustering and apical sorting of GPI-APs in polarized epithelial cells. Proc Natl Acad Sci U S A 2021; 118:2014709118. [PMID: 34389665 DOI: 10.1073/pnas.2014709118] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are lipid-associated luminal secretory cargoes selectively sorted to the apical surface of the epithelia where they reside and play diverse vital functions. Cholesterol-dependent clustering of GPI-APs in the Golgi is the key step driving their apical sorting and their further plasma membrane organization and activity; however, the specific machinery involved in this Golgi event is still poorly understood. In this study, we show that the formation of GPI-AP homoclusters (made of single GPI-AP species) in the Golgi relies directly on the levels of calcium within cisternae. We further demonstrate that the TGN calcium/manganese pump, SPCA1, which regulates the calcium concentration within the Golgi, and Cab45, a calcium-binding luminal Golgi resident protein, are essential for the formation of GPI-AP homoclusters in the Golgi and for their subsequent apical sorting. Down-regulation of SPCA1 or Cab45 in polarized epithelial cells impairs the oligomerization of GPI-APs in the Golgi complex and leads to their missorting to the basolateral surface. Overall, our data reveal an unexpected role for calcium in the mechanism of GPI-AP apical sorting in polarized epithelial cells and identify the molecular machinery involved in the clustering of GPI-APs in the Golgi.
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Sandora N, Putra MA, Busro PW, Ardiansyah, Muttaqin C, Makdinata W, Fitria NA, Kusuma TR. Preparation of Cell-Seeded Heart Patch In Vitro; Co-Culture of Adipose-Derived Mesenchymal Stem Cell and Cardiomyocytes in Amnion Bilayer Patch. Cardiovasc Eng Technol 2021; 13:193-206. [PMID: 34322787 DOI: 10.1007/s13239-021-00565-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 07/12/2021] [Indexed: 11/25/2022]
Abstract
INTRODUCTION Cardiovascular disease is the second killer across the globe, while coronary disease is the major cause. Cell therapy is one alternative to regenerate the infarcted heart wall. MATERIALS AND METHODS In this study, the cardiomyogenesis capacity of human adipose stem cells (hAdSC) and human cardiomyocytes (hCardio) cultured in a 3-D biological scaffold (decellularised amnion bilayer) for nine days in a static condition was investigated. The cardiomyogenesis capacity of hAdSC were identified using immunohistochemistry and RT-PCR. The population of the cells isolated from the heart tissue expressed cTnT-1 (13.38 ± 11.38%), cKit (7.85 ± 4.2%), ICAM (85.53 ± 8.69%), PECAM (61.63 ± 7.18%) and VCAM (35.9 ± 9.11%), while from the fat tissue expressed the mesenchymal phenotypes (CD73, CD90, CD105, but not CD45, CD34, CD11b, CD19 and HLA-DR). Two age groups of hAdSC donors were compared, the youngsters (30-40yo) and the elderly (60-70 yo). RESULTS The co-culture showed that after 5-day incubation, the seeded graft in the hAdSC-30 group had a tube-like appearance while the hAdSC-60 group demonstrated a disorganised pattern, despite of the MSC expressions of the hAdSC-60 were significantly higher. Initial co-culture showed no difference of ATP counts among all groups, however the hAdSC-30 group had the highest ATP count after 9 days culture (p = 0.004). After normalising to the normal myocardium, only the hAdSC-60 group expressed cTnT and MHC, very low, seen during the initial cultivation, but then disappeared. Meanwhile, the hAdSC-30 group expressed α-actinin, MHC and cTnT in the Day-5. The PPAR also was higher in the Day-5 compared to the Day-9 (p < 0.005). CONCLUSION Cardiomyogenesis capacity of hAdSC co-cultured with hCardio in a 3-D scaffold taken from the 30-40yo donor showed better morphology and viability than the 60-70yo group, but maintained less than 5 days in this system.
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Affiliation(s)
- Normalina Sandora
- Institute of Medical Education and Research Indonesia, Jakarta, 10430, Indonesia.
| | - Muhammad Arza Putra
- Department of Thoracic Surgery, RSCM, Faculty of Medicine, Universitas Indonesia, Jakarta, Indonesia
| | - Pribadi Wiranda Busro
- Department of Thoracic Surgery, RSCM, Faculty of Medicine, Universitas Indonesia, Jakarta, Indonesia
| | - Ardiansyah
- Department of Thoracic Surgery, RSCM, Faculty of Medicine, Universitas Indonesia, Jakarta, Indonesia
| | - Chaidar Muttaqin
- Department of Thoracic Surgery, RSCM, Faculty of Medicine, Universitas Indonesia, Jakarta, Indonesia
| | - William Makdinata
- Department of Thoracic Surgery, RSCM, Faculty of Medicine, Universitas Indonesia, Jakarta, Indonesia
| | - Nur Amalina Fitria
- Institute of Medical Education and Research Indonesia, Jakarta, 10430, Indonesia
| | - Tyas Rahmah Kusuma
- Institute of Medical Education and Research Indonesia, Jakarta, 10430, Indonesia
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Balmer EA, Faso C. The Road Less Traveled? Unconventional Protein Secretion at Parasite-Host Interfaces. Front Cell Dev Biol 2021; 9:662711. [PMID: 34109175 PMCID: PMC8182054 DOI: 10.3389/fcell.2021.662711] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 04/07/2021] [Indexed: 01/01/2023] Open
Abstract
Protein secretion in eukaryotic cells is a well-studied process, which has been known for decades and is dealt with by any standard cell biology textbook. However, over the past 20 years, several studies led to the realization that protein secretion as a process might not be as uniform among different cargos as once thought. While in classic canonical secretion proteins carry a signal sequence, the secretory or surface proteome of several organisms demonstrated a lack of such signals in several secreted proteins. Other proteins were found to indeed carry a leader sequence, but simply circumvent the Golgi apparatus, which in canonical secretion is generally responsible for the modification and sorting of secretory proteins after their passage through the endoplasmic reticulum (ER). These alternative mechanisms of protein translocation to, or across, the plasma membrane were collectively termed “unconventional protein secretion” (UPS). To date, many research groups have studied UPS in their respective model organism of choice, with surprising reports on the proportion of unconventionally secreted proteins and their crucial roles for the cell and survival of the organism. Involved in processes such as immune responses and cell proliferation, and including far more different cargo proteins in different organisms than anyone had expected, unconventional secretion does not seem so unconventional after all. Alongside mammalian cells, much work on this topic has been done on protist parasites, including genera Leishmania, Trypanosoma, Plasmodium, Trichomonas, Giardia, and Entamoeba. Studies on protein secretion have mainly focused on parasite-derived virulence factors as a main source of pathogenicity for hosts. Given their need to secrete a variety of substrates, which may not be compatible with canonical secretion pathways, the study of mechanisms for alternative secretion pathways is particularly interesting in protist parasites. In this review, we provide an overview on the current status of knowledge on UPS in parasitic protists preceded by a brief overview of UPS in the mammalian cell model with a focus on IL-1β and FGF-2 as paradigmatic UPS substrates.
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Affiliation(s)
- Erina A Balmer
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | - Carmen Faso
- Institute of Cell Biology, University of Bern, Bern, Switzerland
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Assembly and Cellular Exit of Coronaviruses: Hijacking an Unconventional Secretory Pathway from the Pre-Golgi Intermediate Compartment via the Golgi Ribbon to the Extracellular Space. Cells 2021; 10:cells10030503. [PMID: 33652973 PMCID: PMC7996754 DOI: 10.3390/cells10030503] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 02/18/2021] [Accepted: 02/18/2021] [Indexed: 12/20/2022] Open
Abstract
Coronaviruses (CoVs) assemble by budding into the lumen of the intermediate compartment (IC) at the endoplasmic reticulum (ER)-Golgi interface. However, why CoVs have chosen the IC as their intracellular site of assembly and how progeny viruses are delivered from this compartment to the extracellular space has remained unclear. Here we address these enigmatic late events of the CoV life cycle in light of recently described properties of the IC. Of particular interest are the emerging spatial and functional connections between IC elements and recycling endosomes (REs), defined by the GTPases Rab1 and Rab11, respectively. The establishment of IC-RE links at the cell periphery, around the centrosome and evidently also at the noncompact zones of the Golgi ribbon indicates that—besides traditional ER-Golgi communication—the IC also promotes a secretory process that bypasses the Golgi stacks, but involves its direct connection with the endocytic recycling system. The initial confinement of CoVs to the lumen of IC-derived large transport carriers and their preferential absence from Golgi stacks is consistent with the idea that they exit cells following such an unconventional route. In fact, CoVs may share this pathway with other intracellularly budding viruses, lipoproteins, procollagen, and/or protein aggregates experimentally introduced into the IC lumen.
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Saraste J, Prydz K. A New Look at the Functional Organization of the Golgi Ribbon. Front Cell Dev Biol 2019; 7:171. [PMID: 31497600 PMCID: PMC6713163 DOI: 10.3389/fcell.2019.00171] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2019] [Accepted: 08/07/2019] [Indexed: 12/14/2022] Open
Abstract
A characteristic feature of vertebrate cells is a Golgi ribbon consisting of multiple cisternal stacks connected into a single-copy organelle next to the centrosome. Despite numerous studies, the mechanisms that link the stacks together and the functional significance of ribbon formation remain poorly understood. Nevertheless, these questions are of considerable interest, since there is increasing evidence that Golgi fragmentation – the unlinking of the stacks in the ribbon – is intimately connected not only to normal physiological processes, such as cell division and migration, but also to pathological states, including neurodegeneration and cancer. Challenging a commonly held view that ribbon architecture involves the formation of homotypic tubular bridges between the Golgi stacks, we present an alternative model, based on direct interaction between the biosynthetic (pre-Golgi) and endocytic (post-Golgi) membrane networks and their connection with the centrosome. We propose that the central domains of these permanent pre- and post-Golgi networks function together in the biogenesis and maintenance of the more transient Golgi stacks, and thereby establish “linker compartments” that dynamically join the stacks together. This model provides insight into the reversible fragmentation of the Golgi ribbon that takes place in dividing and migrating cells and its regulation along a cell surface – Golgi – centrosome axis. Moreover, it helps to understand transport pathways that either traverse or bypass the Golgi stacks and the positioning of the Golgi apparatus in differentiated neuronal, epithelial, and muscle cells.
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Affiliation(s)
- Jaakko Saraste
- Department of Biomedicine and Molecular Imaging Center, University of Bergen, Bergen, Norway
| | - Kristian Prydz
- Department of Biosciences, University of Oslo, Oslo, Norway
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Baberg F, Geyh S, Waldera-Lupa D, Stefanski A, Zilkens C, Haas R, Schroeder T, Stühler K. Secretome analysis of human bone marrow derived mesenchymal stromal cells. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2019; 1867:434-441. [PMID: 30716505 DOI: 10.1016/j.bbapap.2019.01.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Revised: 01/24/2019] [Accepted: 01/29/2019] [Indexed: 12/16/2022]
Abstract
As an essential cellular component of the bone marrow (BM) microenvironment mesenchymal stromal cells (MSC) play a pivotal role for the physiological regulation of hematopoiesis, in particular through the secretion of cytokines and chemokines. Mass spectrometry (MS) facilitates the identification and quantification of a large amount of secreted proteins (secretome), but can be hampered by the false-positive identification of contaminating proteins released from dead cells or derived from cell medium. To reduce the likelihood of contaminations we applied an approach combining secretome and proteome analysis to characterize the physiological secretome of BM derived human MSC. Our analysis revealed a secretome consisting of 315 proteins. Pathway analyses of these proteins revealed a high abundance of proteins related to cell growth and/or maintenance, signal transduction and cell communication thereby representing key biological functions of BM derived MSC on protein level. Within the MSC secretome we identified several cytokines and growth factors such as VEGFC, TGF-β1, TGF-β2 and GDF6 which are known to be involved in the physiological regulation of hematopoiesis. By comparing the peptide patterns of secretomes and cell lysates 17 proteins were identified as candidates for proteolytic processing. Taken together, our combined MS work-flow reduced the likelihood of contaminations and enabled us to carve out a specific overview about the composition of the secretome from human BM derived MSC. This methodological approach and the specific secretome signature of BM derived MSC may serve as basis for future comparative analyses of the interplay of MSC and HSPC in patients with hematological malignancies.
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Affiliation(s)
- Falk Baberg
- Institute of Molecular Medicine, Heinrich-Heine-University, Düsseldorf, Germany
| | - Stefanie Geyh
- Department of Hematology, Oncology and Clinical Immunology, University of Düsseldorf, Medical Faculty, Düsseldorf, Germany
| | - Daniel Waldera-Lupa
- Institute of Molecular Medicine, Heinrich-Heine-University, Düsseldorf, Germany
| | - Anja Stefanski
- Molecular Proteomics Laboratory, Biomedical Research Center (BMFZ), Heinrich-Heine-University, Düsseldorf, Germany
| | - Christoph Zilkens
- Department of Orthopedic Surgery, University of Düsseldorf, Medical Faculty, Düsseldorf, Germany
| | - Rainer Haas
- Department of Hematology, Oncology and Clinical Immunology, University of Düsseldorf, Medical Faculty, Düsseldorf, Germany
| | - Thomas Schroeder
- Department of Hematology, Oncology and Clinical Immunology, University of Düsseldorf, Medical Faculty, Düsseldorf, Germany
| | - Kai Stühler
- Molecular Proteomics Laboratory, Biomedical Research Center (BMFZ), Heinrich-Heine-University, Düsseldorf, Germany.
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Zhao Z, Kesti T, Uğurlu H, Baur AS, Fagerlund R, Saksela K. Tyrosine phosphorylation directs TACE into extracellular vesicles via unconventional secretion. Traffic 2019; 20:202-212. [PMID: 30569492 DOI: 10.1111/tra.12630] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 12/17/2018] [Accepted: 12/18/2018] [Indexed: 02/06/2023]
Abstract
When studying how HIV-1 Nef can promote packaging of the proinflammatory transmembrane protease TACE (tumor necrosis factor-α converting enzyme) into extracellular vesicles (EVs) we have revealed a novel tyrosine kinase-regulated unconventional protein secretion (UPS) pathway for TACE. When TACE was expressed without its trafficking cofactor iRhom allosteric Hck activation by Nef triggered translocation of TACE into EVs. This process was insensitive to blocking of classical secretion by inhibiting endoplasmic reticulum (ER) to Golgi transport, and involved a distinct form of TACE devoid of normal glycosylation and incompletely processed for prodomain removal. Like most other examples of UPS this process was Golgi reassembly stacking protein (GRASP)-dependent but was not associated with ER stress. These data indicate that Hck-activated UPS provides an alternative pathway for TACE secretion that can bypass iRhom-dependent ER to Golgi transfer, and suggest that tyrosine phosphorylation might have a more general role in regulating UPS.
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Affiliation(s)
- Zhe Zhao
- Department of Virology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Tapio Kesti
- Department of Virology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Hasan Uğurlu
- Department of Virology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Andreas S Baur
- Department of Dermatology, Translational Research Center, University Hospital Erlangen, Erlangen, Germany
| | - Riku Fagerlund
- Department of Virology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Kalle Saksela
- Department of Virology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
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Saraste J, Marie M. Intermediate compartment (IC): from pre-Golgi vacuoles to a semi-autonomous membrane system. Histochem Cell Biol 2018; 150:407-430. [PMID: 30173361 PMCID: PMC6182704 DOI: 10.1007/s00418-018-1717-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/27/2018] [Indexed: 12/19/2022]
Abstract
Despite its discovery more than three decades ago and well-established role in protein sorting and trafficking in the early secretory pathway, the intermediate compartment (IC) has remained enigmatic. The prevailing view is that the IC evolved as a specialized organelle to mediate long-distance endoplasmic reticulum (ER)–Golgi communication in metazoan cells, but is lacking in other eukaryotes, such as plants and fungi. However, this distinction is difficult to reconcile with the high conservation of the core machineries that regulate early secretory trafficking from yeast to man. Also, it has remained unclear whether the pleiomorphic IC components—vacuoles, tubules and vesicles—represent transient transport carriers or building blocks of a permanent pre-Golgi organelle. Interestingly, recent studies have revealed that the IC maintains its compositional, structural and spatial properties throughout the cell cycle, supporting a model that combines the dynamic and stable aspects of the organelle. Moreover, the IC has been assigned novel functions, such as cell signaling, Golgi-independent trafficking and autophagy. The emerging permanent nature of the IC and its connections with the centrosome and the endocytic recycling system encourage reconsideration of its relationship with the Golgi ribbon, role in Golgi biogenesis and ubiquitous presence in eukaryotic cells.
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Affiliation(s)
- Jaakko Saraste
- Department of Biomedicine and Molecular Imaging Center (MIC), University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.
| | - Michaël Marie
- Department of Biomedicine and Molecular Imaging Center (MIC), University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway
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Grube L, Dellen R, Kruse F, Schwender H, Stühler K, Poschmann G. Mining the Secretome of C2C12 Muscle Cells: Data Dependent Experimental Approach To Analyze Protein Secretion Using Label-Free Quantification and Peptide Based Analysis. J Proteome Res 2018; 17:879-890. [DOI: 10.1021/acs.jproteome.7b00684] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Leonie Grube
- Molecular
Proteomics Laboratory, Biomedical Research Centre (BMFZ), Heinrich-Heine-University, Düsseldorf 40225, Germany
| | - Rafael Dellen
- Mathematical
Institute, Heinrich-Heine-University, Düsseldorf 40225, Germany
- Center for
Bioinformatics and Biostatistics, Biomedical Research Centre Heinrich-Heine-University, Düsseldorf 40225, Germany
| | - Fabian Kruse
- Molecular
Proteomics Laboratory, Biomedical Research Centre (BMFZ), Heinrich-Heine-University, Düsseldorf 40225, Germany
| | - Holger Schwender
- Mathematical
Institute, Heinrich-Heine-University, Düsseldorf 40225, Germany
- Center for
Bioinformatics and Biostatistics, Biomedical Research Centre Heinrich-Heine-University, Düsseldorf 40225, Germany
| | - Kai Stühler
- Molecular
Proteomics Laboratory, Biomedical Research Centre (BMFZ), Heinrich-Heine-University, Düsseldorf 40225, Germany
- Institute
for Molecular Medicine, University Hospital Düsseldorf, Düsseldorf 40225, Germany
| | - Gereon Poschmann
- Molecular
Proteomics Laboratory, Biomedical Research Centre (BMFZ), Heinrich-Heine-University, Düsseldorf 40225, Germany
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Jiang M, Wang Y, Tseng GN. Adult Ventricular Myocytes Segregate KCNQ1 and KCNE1 to Keep the IKs Amplitude in Check Until When Larger IKs Is Needed. Circ Arrhythm Electrophysiol 2017; 10:CIRCEP.117.005084. [PMID: 28611207 DOI: 10.1161/circep.117.005084] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Accepted: 05/15/2017] [Indexed: 11/16/2022]
Abstract
BACKGROUND KCNQ1 and KCNE1 assemble to form the slow delayed rectifier (IKs) channel critical for shortening ventricular action potentials during high β-adrenergic tone. However, too much IKs under basal conditions poses an arrhythmogenic risk. Our objective is to understand how adult ventricular myocytes regulate the IKs amplitudes under basal conditions and in response to stress. METHODS AND RESULTS We express fluorescently tagged KCNQ1 and KCNE1 in adult ventricular myocytes and follow their biogenesis and trafficking paths. We also study the distribution patterns of native KCNQ1 and KCNE1, and their relationship to IKs amplitudes, in chronically stressed ventricular myocytes, and use COS-7 cell expression to probe the underlying mechanism. We show that KCNQ1 and KCNE1 are both translated in the perinuclear region but traffic by different routes, independent of each other, to their separate subcellular locations. KCNQ1 mainly resides in the jSR (junctional sarcoplasmic reticulum), whereas KCNE1 resides on the cell surface. Under basal conditions, only a small portion of KCNQ1 reaches the cell surface to support the IKs function. However, in response to chronic stress, KCNQ1 traffics from jSR to the cell surface to boost the IKs amplitude in a process depending on Ca binding to CaM (calmodulin). CONCLUSIONS In adult ventricular myocytes, KCNE1 maintains a stable presence on the cell surface, whereas KCNQ1 is dynamic in its localization. KCNQ1 is largely in an intracellular reservoir under basal conditions but can traffic to the cell surface and boost the IKs amplitude in response to stress.
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Affiliation(s)
- Min Jiang
- From the Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond (M.J., Y.W., G.-N.T.); and Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (M.J.)
| | - Yuhong Wang
- From the Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond (M.J., Y.W., G.-N.T.); and Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (M.J.)
| | - Gea-Ny Tseng
- From the Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond (M.J., Y.W., G.-N.T.); and Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (M.J.).
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Basset A, Bouthemy P, Boulanger J, Waharte F, Salamero J, Kervrann C. An extended model of vesicle fusion at the plasma membrane to estimate protein lateral diffusion from TIRF microscopy images. BMC Bioinformatics 2017; 18:352. [PMID: 28738814 PMCID: PMC5525284 DOI: 10.1186/s12859-017-1765-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 07/14/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Characterizing membrane dynamics is a key issue to understand cell exchanges with the extra-cellular medium. Total internal reflection fluorescence microscopy (TIRFM) is well suited to focus on the late steps of exocytosis at the plasma membrane. However, it is still a challenging task to quantify (lateral) diffusion and estimate local dynamics of proteins. RESULTS A new model was introduced to represent the behavior of cargo transmembrane proteins during the vesicle fusion to the plasma membrane at the end of the exocytosis process. Two biophysical parameters, the diffusion coefficient and the release rate parameter, are automatically estimated from TIRFM image sequences, to account for both the lateral diffusion of molecules at the membrane and the continuous release of the proteins from the vesicle to the plasma membrane. Quantitative evaluation on 300 realistic computer-generated image sequences demonstrated the efficiency and accuracy of the method. The application of our method on 16 real TIRFM image sequences additionally revealed differences in the dynamic behavior of Transferrin Receptor (TfR) and Langerin proteins. CONCLUSION An automated method has been designed to simultaneously estimate the diffusion coefficient and the release rate for each individual vesicle fusion event at the plasma membrane in TIRFM image sequences. It can be exploited for further deciphering cell membrane dynamics.
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Affiliation(s)
- Antoine Basset
- Inria, Campus de Beaulieu, Rennes, 35042 France
- CNES, 18 avenue Edouard Belin, Toulouse, 31401 France
| | | | - Jérôme Boulanger
- Institut Curie, PSL Research University, CNRS UMR 144 and PICT-Cell and Tissue Imaging Facility, 12 rue Lhomond, Paris, 75005 France
- MRC Laboratory of Molecular Biology, University of Cambridge, Francis Crick Avenue, CBC Cambridge Biomedical Campus, Cambridge, CB2 0QH UK
| | - François Waharte
- Institut Curie, PSL Research University, CNRS UMR 144 and PICT-Cell and Tissue Imaging Facility, 12 rue Lhomond, Paris, 75005 France
| | - Jean Salamero
- Institut Curie, PSL Research University, CNRS UMR 144 and PICT-Cell and Tissue Imaging Facility, 12 rue Lhomond, Paris, 75005 France
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Heat Shock Protein HSP27 Secretion by Ovarian Cancer Cells Is Linked to Intracellular Expression Levels, Occurs Independently of the Endoplasmic Reticulum Pathway and HSP27's Phosphorylation Status, and Is Mediated by Exosome Liberation. DISEASE MARKERS 2017; 2017:1575374. [PMID: 28325957 PMCID: PMC5343262 DOI: 10.1155/2017/1575374] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 02/06/2017] [Accepted: 02/12/2017] [Indexed: 12/05/2022]
Abstract
The heat shock protein HSP27 has been correlated in ovarian cancer (OC) patients with aggressiveness and chemoresistance and, therefore, represents a promising potential biomarker for OC diagnosis, prognosis, and treatment response. Notably, secretion of soluble HSP27 has been described by a few cell types and may take place as well in OC cells. Therefore, we studied HSP27 secretion mechanisms under diverse cellular conditions in an OC cell model system. Secretion of HSP27 was characterized after overexpression of HSP27 by transfected plasmids and after heat shock. Intra- and extracellular HSP27 amounts were assessed by Western blotting and ELISA. Protein secretion was blocked by brefeldin A and the impact of the HSP27 phosphorylation status was analyzed overexpressing HSP27 phosphomutants. The present study demonstrated that HSP27 secretion by OVCAR-3 and SK-OV-3 cells depends on intracellular HSP27 concentrations. Moreover, HSP27 secretion is independent of the endoplasmic reticulum secretory pathway and HSP27 phosphorylation. Notably, analysis of OC cell-born exosomes not only confirmed the concentration-dependent correlation of HSP27 expression and secretion but also demonstrated a concentration-dependent incorporation of HSP27 protein into exosomes. Thus, secreted HSP27 may become more important as an extracellular factor which controls the tumor microenvironment and might be a noninvasive biomarker.
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Matlin KS, Caplan MJ. The secretory pathway at 50: a golden anniversary for some momentous grains of silver. Mol Biol Cell 2017; 28:229-232. [PMID: 28082520 PMCID: PMC5231891 DOI: 10.1091/mbc.e16-07-0508] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 11/17/2016] [Accepted: 11/22/2016] [Indexed: 11/30/2022] Open
Abstract
The secretory pathway along which newly synthesized secretory and membrane proteins traffic through the cell was revealed in two articles published 50 years ago. This discovery was the culmination of decades of effort to unite the power of biochemical and morphological methodologies in order to elucidate the dynamic nature of the cell's biosynthetic machinery. The secretory pathway remains a central paradigm of modern cell biology. Its elucidation 50 years ago inspired tremendous multidisciplinary and on-going efforts to understand the machinery that makes it run, the adaptations that permit it to serve the needs of specialized cell types, and the pathological consequences that arise when it is perturbed.
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Affiliation(s)
- Karl S Matlin
- Department of Surgery, University of Chicago, Chicago, IL 60637-1470
| | - Michael J Caplan
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06520-8026
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15
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Abstract
Cancer diagnosis and therapy is steadily improving. Still, diagnosis is frequently late and diagnosis and follow-up procedures mostly are time-consuming and expensive. Searching for tumor-derived exosomes (TEX) in body fluids may provide an alternative, minimally invasive, yet highly reliable diagnostic tool. Beyond this, there is strong evidence that TEX could become a potent therapeutics. Exosomes, small vesicles delivered by many cells of the organism, are found in all body fluids. Exosomes are characterized by lipid composition, common and donor cell specific proteins, mRNA, small non-coding RNA including miRNA and DNA. Particularly the protein and miRNA markers received much attention as they may allow for highly specific diagnosis and can provide hints toward tumor aggressiveness and progression, where exosome-based diagnosis and follow-up is greatly facilitated by the recovery of exosomes in body fluids, particularly the peripheral blood. Beyond this, exosomes are the most important intercellular communicators that modulate, instruct, and reprogram their surrounding as well as distant organs. In concern about TEX this includes message transfer from tumor cells toward the tumor stroma, the premetastatic niche, the hematopoietic system and, last but not least, the instruction of non-cancer stem cells by cancer-initiating cells (CIC). Taking this into account, it becomes obvious that "tailored" exosomes offer themselves as potent therapeutic delivery system. In brief, during the last 4-5 years there is an ever-increasing, overwhelming interest in exosome research. This boom appears fully justified provided the content of the exosomes becomes most thoroughly analyzed and their mode of intercellular interaction can be unraveled in detail as this knowledge will open new doors toward cancer diagnosis and therapy including immunotherapy and CIC reprogramming.
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Affiliation(s)
- Margot Zöller
- Tumor Cell Biology, University Hospital of Surgery, im Neuenheimer Feld 365, 69120, Heidelberg, Germany.
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16
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Staudt C, Gilis F, Boonen M, Jadot M. Molecular determinants that mediate the sorting of human ATG9A from the endoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1863:2299-310. [PMID: 27316455 DOI: 10.1016/j.bbamcr.2016.06.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 06/07/2016] [Accepted: 06/14/2016] [Indexed: 11/15/2022]
Abstract
ATG9A is a multispanning membrane protein required for autophagosome formation. Under basal conditions, neosynthesized ATG9A proteins travel to the Golgi apparatus and cycle between the trans-Golgi network and endosomes. In the present work, we searched for molecular determinants involved in the subcellular trafficking of human ATG9A in HeLa cells using sequential deletions and point mutations. Deletion of amino acids L(340) to L(354) resulted in the retention of ATG9A in the endoplasmic reticulum. In addition, we found that substitution of the L(711)YM(713) sequence (located in the C-terminal region of ATG9A) by alanine residues severely impaired its transport through the Golgi apparatus. This defect could be corrected by oligomerization of the mutant protein with co-transfected wild-type ATG9A, suggesting that ATG9A oligomerization may help its sorting through biosynthetic compartments. Lastly, the study of the consequences of the LYM/AAA mutation on the intracellular trafficking of ATG9A highlighted that some newly synthesized ATG9A can bypass the Golgi apparatus to reach the plasma membrane. Taken together, these findings provide new insights into the intracellular pathways followed by ATG9A to reach different subcellular compartments, and into the intramolecular determinants that drive the sorting of this protein.
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Affiliation(s)
- Catherine Staudt
- URPhyM-Laboratoire de Chimie Physiologique, Université de Namur, Belgium
| | - Florentine Gilis
- URPhyM-Laboratoire de Chimie Physiologique, Université de Namur, Belgium
| | - Marielle Boonen
- URPhyM-Laboratoire de Chimie Physiologique, Université de Namur, Belgium
| | - Michel Jadot
- URPhyM-Laboratoire de Chimie Physiologique, Université de Namur, Belgium.
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17
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Prydz K. Determinants of Glycosaminoglycan (GAG) Structure. Biomolecules 2015; 5:2003-22. [PMID: 26308067 PMCID: PMC4598785 DOI: 10.3390/biom5032003] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Revised: 08/17/2015] [Accepted: 08/18/2015] [Indexed: 01/05/2023] Open
Abstract
Proteoglycans (PGs) are glycosylated proteins of biological importance at cell surfaces, in the extracellular matrix, and in the circulation. PGs are produced and modified by glycosaminoglycan (GAG) chains in the secretory pathway of animal cells. The most common GAG attachment site is a serine residue followed by a glycine (-ser-gly-), from which a linker tetrasaccharide extends and may continue as a heparan sulfate, a heparin, a chondroitin sulfate, or a dermatan sulfate GAG chain. Which type of GAG chain becomes attached to the linker tetrasaccharide is influenced by the structure of the protein core, modifications occurring to the linker tetrasaccharide itself, and the biochemical environment of the Golgi apparatus, where GAG polymerization and modification by sulfation and epimerization take place. The same cell type may produce different GAG chains that vary, depending on the extent of epimerization and sulfation. However, it is not known to what extent these differences are caused by compartmental segregation of protein cores en route through the secretory pathway or by differential recruitment of modifying enzymes during synthesis of different PGs. The topic of this review is how different aspects of protein structure, cellular biochemistry, and compartmentalization may influence GAG synthesis.
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Affiliation(s)
- Kristian Prydz
- Department of Biosciences, University of Oslo, Box 1066, Blindern OSLO 0316, Norway.
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18
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Ertunc ME, Sikkeland J, Fenaroli F, Griffiths G, Daniels MP, Cao H, Saatcioglu F, Hotamisligil GS. Secretion of fatty acid binding protein aP2 from adipocytes through a nonclassical pathway in response to adipocyte lipase activity. J Lipid Res 2014; 56:423-34. [PMID: 25535287 DOI: 10.1194/jlr.m055798] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Adipocyte fatty acid binding protein 4, aP2, contributes to the pathogenesis of several common diseases including type 2 diabetes, atherosclerosis, fatty liver disease, asthma, and cancer. Although the biological functions of aP2 have classically been attributed to its intracellular action, recent studies demonstrated that aP2 acts as an adipokine to regulate systemic metabolism. However, the mechanism and regulation of aP2 secretion remain unknown. Here, we demonstrate a specific role for lipase activity in aP2 secretion from adipocytes in vitro and ex vivo. Our results show that chemical inhibition of lipase activity, genetic deficiency of adipose triglyceride lipase and, to a lesser extent, hormone-sensitive lipase blocked aP2 secretion from adipocytes. Increased lipolysis and lipid availability also contributed to aP2 release as determined in perilipin1-deficient adipose tissue explants ex vivo and upon treatment with lipids in vivo and in vitro. In addition, we identify a nonclassical route for aP2 secretion in exosome-like vesicles and show that aP2 is recruited to this pathway upon stimulation of lipolysis. Given the effect of circulating aP2 on glucose metabolism, these data support that targeting aP2 or the lipolysis-dependent secretory pathway may present novel mechanistic and translational opportunities in metabolic disease.
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Affiliation(s)
- Meric Erikci Ertunc
- Department of Genetics and Complex Diseases Harvard School of Public Health, Boston, MA Sabri Ülker Center, Harvard School of Public Health, Boston, MA
| | - Jørgen Sikkeland
- Department of Biosciences, National Institutes of Health, Bethesda, MD
| | - Federico Fenaroli
- Department of Biosciences, National Institutes of Health, Bethesda, MD
| | - Gareth Griffiths
- Department of Biosciences, National Institutes of Health, Bethesda, MD
| | - Mathew P Daniels
- University of Oslo, Oslo, Norway; and National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD
| | - Haiming Cao
- University of Oslo, Oslo, Norway; and National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD
| | - Fahri Saatcioglu
- Department of Biosciences, National Institutes of Health, Bethesda, MD
| | - Gökhan S Hotamisligil
- Department of Genetics and Complex Diseases Harvard School of Public Health, Boston, MA Sabri Ülker Center, Harvard School of Public Health, Boston, MA
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19
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Chutna O, Gonçalves S, Villar-Piqué A, Guerreiro P, Marijanovic Z, Mendes T, Ramalho J, Emmanouilidou E, Ventura S, Klucken J, Barral DC, Giorgini F, Vekrellis K, Outeiro TF. The small GTPase Rab11 co-localizes with α-synuclein in intracellular inclusions and modulates its aggregation, secretion and toxicity. Hum Mol Genet 2014; 23:6732-45. [PMID: 25092884 DOI: 10.1093/hmg/ddu391] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Alpha-synuclein (aSyn) misfolding and aggregation are pathological features common to several neurodegenerative diseases, including Parkinson's disease (PD). Mounting evidence suggests that aSyn can be secreted and transferred from cell to cell, participating in the propagation and spreading of pathological events. Rab11, a small GTPase, is an important regulator in both endocytic and secretory pathways. Here, we show that Rab11 is involved in regulating aSyn secretion. Rab11 knockdown or overexpression of either Rab11a wild-type (Rab11a WT) or Rab11a GDP-bound mutant (Rab11a S25N) increased secretion of aSyn. Furthermore, we demonstrate that Rab11 interacts with aSyn and is present in intracellular inclusions together with aSyn. Moreover, Rab11 reduces aSyn aggregation and toxicity. Our results suggest that Rab11 is involved in modulating the processes of aSyn secretion and aggregation, both of which are important mechanisms in the progression of aSyn pathology in PD and other synucleinopathies.
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Affiliation(s)
- Oldriska Chutna
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Lisbon, Portugal
| | - Susana Gonçalves
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Lisbon, Portugal
| | - Anna Villar-Piqué
- Department of Neurodegeneration and Restorative Research, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany
| | - Patrícia Guerreiro
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Lisbon, Portugal Department of Neurodegeneration and Restorative Research, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany
| | - Zrinka Marijanovic
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Lisbon, Portugal
| | - Tiago Mendes
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Lisbon, Portugal
| | - José Ramalho
- CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal
| | | | - Salvador Ventura
- Institut de Biotecnologia i Biomedicina Departament de Bioquimica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
| | - Jochen Klucken
- Department of Molecular Neurology, University Hospital, Erlangen, Germany
| | - Duarte C Barral
- CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Flaviano Giorgini
- Department of Genetics, University of Leicester, University Road, Leicester, UK and
| | - Kostas Vekrellis
- Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Tiago F Outeiro
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Lisbon, Portugal Department of Neurodegeneration and Restorative Research, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany Instituto de Fisiologia, Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal
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20
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Pranke IM, Sermet-Gaudelus I. Biosynthesis of cystic fibrosis transmembrane conductance regulator. Int J Biochem Cell Biol 2014; 52:26-38. [DOI: 10.1016/j.biocel.2014.03.020] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 03/19/2014] [Accepted: 03/20/2014] [Indexed: 01/19/2023]
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21
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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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22
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Malhotra V. Unconventional protein secretion: an evolving mechanism. EMBO J 2013; 32:1660-4. [PMID: 23665917 DOI: 10.1038/emboj.2013.104] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 04/12/2013] [Indexed: 11/09/2022] Open
Abstract
The process by which proteins are secreted without entering the classical endoplasmic reticulum (ER)-Golgi complex pathway, in eukaryotic cells, is conveniently called unconventional protein secretion. Recent studies on one such protein called Acb1 have revealed a number of components involved in its secretion. Interestingly, conditions that promote the secretion of Acb1 trigger the biogenesis of a new compartment called CUPS (Compartment for Unconventional Protein Secretion). CUPS form near the ER exit site but lack ER-specific proteins. Other proteins that share some of the features common with the secretion of Acb1 are interleukin-1β and tissue transglutaminase. Here I will review recent advances made in the field and propose a new model for unconventional protein secretion.
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23
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Cell-to-cell communication: current views and future perspectives. Cell Tissue Res 2013; 352:1-3. [DOI: 10.1007/s00441-013-1590-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2013] [Accepted: 02/12/2013] [Indexed: 12/28/2022]
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24
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Cohen S, Haimovich J, Hollander N. Distinct processing of the pre-B cell receptor and the B cell receptor. Mol Immunol 2012; 54:115-21. [PMID: 23267849 DOI: 10.1016/j.molimm.2012.11.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 11/04/2012] [Accepted: 11/13/2012] [Indexed: 02/03/2023]
Abstract
It has been recently demonstrated that while oligosaccharide moieties of μ heavy chains in the B-cell receptor (BCR) are of the complex type as expected, those of the pre-BCR on the surface of pre-B cells contain oligosaccharide moieties of the high-mannose type only. This is unique, because high-mannose glycans are generally restricted to the endoplasmic reticulum and not presented on the surface of mammalian cells. In the present study, we examined the processing of the unusually glycosylated μ heavy chains in pre-B cells. We demonstrate that the pre-BCR reaches the cell surface by a non-conventional brefeldin A-sensitive monensin-insensitive transport pathway. Although pre-BCR complexes consist of μ heavy chains with high-mannose oligosaccharide moieties, they are stably expressed in the plasma membrane and demonstrate turnover rates similar to those of the BCR. Thus, rapid internalization cannot account for their low surface expression, as previously postulated. Rather, we demonstrate that the low pre-BCR abundance in the plasma membrane results, at least in part, from insufficient production of surrogate light chains, which appears to be a limiting factor in pre-BCR expression.
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Affiliation(s)
- Sharon Cohen
- Department of Clinical Microbiology and Immunology, Sackler School of Medicine, Tel Aviv University, Tel Aviv 69978, Israel
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25
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Rabouille C, Malhotra V, Nickel W. Diversity in unconventional protein secretion. J Cell Sci 2012; 125:5251-5. [DOI: 10.1242/jcs.103630] [Citation(s) in RCA: 208] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Affiliation(s)
- Catherine Rabouille
- Hubrecht Institute for, Developmental Biology and Stem Cell Research, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands
| | - Vivek Malhotra
- Centre for Genomic Regulation, C/ Dr. Aiguader 88, 08003 Barcelona, Spain
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, 08010 Barcelona, Spain
| | - Walter Nickel
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
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