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Yamazaki Y, Kono K. Clathrin-mediated trafficking of phospholipid flippases is required for local plasma membrane/cell wall damage repair in budding yeast. Biochem Biophys Res Commun 2022; 606:156-162. [DOI: 10.1016/j.bbrc.2022.03.129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 03/09/2022] [Accepted: 03/23/2022] [Indexed: 11/02/2022]
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2
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Bairwa G, Caza M, Horianopoulos L, Hu G, Kronstad J. Role of clathrin-mediated endocytosis in the use of heme and hemoglobin by the fungal pathogen Cryptococcus neoformans. Cell Microbiol 2018; 21:e12961. [PMID: 30291809 DOI: 10.1111/cmi.12961] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 08/23/2018] [Accepted: 09/17/2018] [Indexed: 12/29/2022]
Abstract
Heme is a major source of iron for pathogens of humans, and its use is critical in determining the outcome of infection and disease. Cryptococcus neoformans is an encapsulated fungal pathogen that causes life-threatening infections in immunocompromised individuals. C. neoformans effectively uses heme as an iron source, but the underlying mechanisms are poorly defined. Non-iron metalloporphyrins (MPPs) are toxic analogues of heme and are thought to enter microbial cells via endogenous heme acquisition systems. We therefore carried out a mutant screen for susceptibility against manganese MPP (MnMPP) to identify new components for heme uptake in C. neoformans. We identified several genes involved in signalling, DNA repair, sugar metabolism, and trafficking that play important roles in susceptibility to MnMPP and in the use of heme as an iron source. We focused on investigating the role of clathrin-mediated endocytosis (CME) and found that several components of CME including Chc1, Las17, Rvs161, and Rvs167 are required for growth on heme and hemoglobin and for endocytosis and intracellular trafficking of these molecules. We show that the hemoglobin uptake process in C. neoformans involves clathrin heavy chain, Chc1, which appears to colocalise with hemoglobin-containing vesicles and to potentially assist in proper delivery of hemoglobin to the vacuole. Additionally, C. neoformans strains lacking Chc1, Las17, Rvs161, or Rvs167 were defective in the elaboration of several key virulence factors, and a las17 mutant was avirulent in a mouse model of cryptococcosis. Overall, this study unveils crucial functions of CME in the use of heme iron by C. neoformans and reveals a role for CME in fungal pathogenesis.
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Affiliation(s)
- Gaurav Bairwa
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | - Mélissa Caza
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | - Linda Horianopoulos
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada.,Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Guanggan Hu
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada
| | - James Kronstad
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, Canada.,Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
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Wang D, Li L, Wu G, Vasseur L, Yang G, Huang P. De novo transcriptome sequencing of Isaria cateniannulata and comparative analysis of gene expression in response to heat and cold stresses. PLoS One 2017; 12:e0186040. [PMID: 29023475 PMCID: PMC5638334 DOI: 10.1371/journal.pone.0186040] [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: 06/05/2017] [Accepted: 09/22/2017] [Indexed: 11/19/2022] Open
Abstract
Isaria cateniannulata is a very important and virulent entomopathogenic fungus that infects many insect pest species. Although I. cateniannulata is commonly exposed to extreme environmental temperature conditions, little is known about its molecular response mechanism to temperature stress. Here, we sequenced and de novo assembled the transcriptome of I. cateniannulata in response to high and low temperature stresses using Illumina RNA-Seq technology. Our assembly encompassed 17,514 unigenes (mean length = 1,197 bp), in which 11,445 unigenes (65.34%) showed significant similarities to known sequences in NCBI non-redundant protein sequences (Nr) database. Using digital gene expression analysis, 4,483 differentially expressed genes (DEGs) were identified after heat treatment, including 2,905 up-regulated genes and 1,578 down-regulated genes. Under cold stress, 1,927 DEGs were identified, including 1,245 up-regulated genes and 682 down-regulated genes. The expression patterns of 18 randomly selected candidate DEGs resulting from quantitative real-time PCR (qRT-PCR) were consistent with their transcriptome analysis results. Although DEGs were involved in many pathways, we focused on the genes that were involved in endocytosis: In heat stress, the pathway of clathrin-dependent endocytosis (CDE) was active; however at low temperature stresses, the pathway of clathrin-independent endocytosis (CIE) was active. Besides, four categories of DEGs acting as temperature sensors were observed, including cell-wall-major-components-metabolism-related (CWMCMR) genes, heat shock protein (Hsp) genes, intracellular-compatible-solutes-metabolism-related (ICSMR) genes and glutathione S-transferase (GST). These results enhance our understanding of the molecular mechanisms of I. cateniannulata in response to temperature stresses and provide a valuable resource for the future investigations.
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Affiliation(s)
- Dingfeng Wang
- Tea Research Institute, Fujian Academy of Agricultural Sciences, Fu’an, Fujian, China
| | - Liangde Li
- Tea Research Institute, Fujian Academy of Agricultural Sciences, Fu’an, Fujian, China
| | - Guangyuan Wu
- Tea Research Institute, Fujian Academy of Agricultural Sciences, Fu’an, Fujian, China
- * E-mail: (GYW); (GY)
| | - Liette Vasseur
- Key Laboratory of Integrated Pest Management for Fujian-Taiwan Crops, Ministry of Agriculture, Fuzhou, Fujian, China
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
- Department of Biological Sciences, Brock University, St Catharines, Ontario, Canada
| | - Guang Yang
- Key Laboratory of Integrated Pest Management for Fujian-Taiwan Crops, Ministry of Agriculture, Fuzhou, Fujian, China
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
- Key Laboratory of Green Control of Insect Pests (Fujian Agriculture and Forestry University), Fujian Province University, Fuzhou, Fujian, China
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
- * E-mail: (GYW); (GY)
| | - Pengrong Huang
- Key Laboratory of Integrated Pest Management for Fujian-Taiwan Crops, Ministry of Agriculture, Fuzhou, Fujian, China
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Institute of Applied Ecology, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
- Key Laboratory of Green Control of Insect Pests (Fujian Agriculture and Forestry University), Fujian Province University, Fuzhou, Fujian, China
- Fujian-Taiwan Joint Center for Ecological Control of Crop Pests, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
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4
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Kalb LC, Frederico YCA, Boehm C, Moreira CMDN, Soares MJ, Field MC. Conservation and divergence within the clathrin interactome of Trypanosoma cruzi. Sci Rep 2016; 6:31212. [PMID: 27502971 PMCID: PMC4977521 DOI: 10.1038/srep31212] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Accepted: 07/08/2016] [Indexed: 12/18/2022] Open
Abstract
Trypanosomatids are parasitic protozoa with a significant burden on human health. African and American trypanosomes are causative agents of Nagana and Chagas disease respectively, and speciated about 300 million years ago. These parasites have highly distinct life cycles, pathologies, transmission strategies and surface proteomes, being dominated by the variant surface glycoprotein (African) or mucins (American) respectively. In African trypanosomes clathrin-mediated trafficking is responsible for endocytosis and post-Golgi transport, with several mechanistic aspects distinct from higher organisms. Using clathrin light chain (TcCLC) and EpsinR (TcEpsinR) as affinity handles, we identified candidate clathrin-associated proteins (CAPs) in Trypanosoma cruzi; the cohort includes orthologs of many proteins known to mediate vesicle trafficking, but significantly not the AP-2 adaptor complex. Several trypanosome-specific proteins common with African trypanosomes, were also identified. Fluorescence microscopy revealed localisations for TcEpsinR, TcCLC and TcCHC at the posterior region of trypomastigote cells, coincident with the flagellar pocket and Golgi apparatus. These data provide the first systematic analysis of clathrin-mediated trafficking in T. cruzi, allowing comparison between protein cohorts and other trypanosomes and also suggest that clathrin trafficking in at least some life stages of T. cruzi may be AP-2-independent.
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Affiliation(s)
- Ligia Cristina Kalb
- Laboratory of Cell Biology, Instituto Carlos Chagas/Fiocruz-PR, Rua Prof. Algacyr Munhoz Mader 3775, Cidade Industrial, 81350-010 Curitiba, PR Brazil
- Laboratory of Molecular Biology of Trypanosomes, Instituto Carlos Chagas/Fiocruz-PR, Rua Prof. Algacyr Munhoz Mader 3775, Cidade Industrial, 81350-010 Curitiba, PR Brazil
| | - Yohana Camila A. Frederico
- Laboratory of Cell Biology, Instituto Carlos Chagas/Fiocruz-PR, Rua Prof. Algacyr Munhoz Mader 3775, Cidade Industrial, 81350-010 Curitiba, PR Brazil
| | - Cordula Boehm
- School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Claudia Maria do Nascimento Moreira
- Laboratory of Molecular Biology of Trypanosomes, Instituto Carlos Chagas/Fiocruz-PR, Rua Prof. Algacyr Munhoz Mader 3775, Cidade Industrial, 81350-010 Curitiba, PR Brazil
- School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Maurilio José Soares
- Laboratory of Cell Biology, Instituto Carlos Chagas/Fiocruz-PR, Rua Prof. Algacyr Munhoz Mader 3775, Cidade Industrial, 81350-010 Curitiba, PR Brazil
| | - Mark C. Field
- School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
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Zhang T, Sknepnek R, Bowick MJ, Schwarz JM. On the modeling of endocytosis in yeast. Biophys J 2015; 108:508-19. [PMID: 25650919 DOI: 10.1016/j.bpj.2014.11.3481] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 11/24/2014] [Accepted: 11/26/2014] [Indexed: 11/30/2022] Open
Abstract
The cell membrane deforms during endocytosis to surround extracellular material and draw it into the cell. Results of experiments on endocytosis in yeast show general agreement that 1) actin polymerizes into a network of filaments exerting active forces on the membrane to deform it, and 2) the large-scale membrane deformation is tubular in shape. In contrast, there are three competing proposals for precisely how the actin filament network organizes itself to drive the deformation. We use variational approaches and numerical simulations to address this competition by analyzing a meso-scale model of actin-mediated endocytosis in yeast. The meso-scale model breaks up the invagination process into three stages: 1) initiation, where clathrin interacts with the membrane via adaptor proteins; 2) elongation, where the membrane is then further deformed by polymerizing actin filaments; and 3) pinch-off. Our results suggest that the pinch-off mechanism may be assisted by a pearling-like instability. We rule out two of the three competing proposals for the organization of the actin filament network during the elongation stage. These two proposals could be important in the pinch-off stage, however, where additional actin polymerization helps break off the vesicle. Implications and comparisons with earlier modeling of endocytosis in yeast are discussed.
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Affiliation(s)
- Tao Zhang
- Department of Physics and Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York
| | - Rastko Sknepnek
- Department of Physics and Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York; Division of Physics, University of Dundee, Dundee, United Kingdom; Division of Computational Biology, University of Dundee, Dundee, United Kingdom
| | - M J Bowick
- Department of Physics and Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York
| | - J M Schwarz
- Department of Physics and Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York.
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6
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Abstract
Endocytosis, the process whereby the plasma membrane invaginates to form vesicles, is essential for bringing many substances into the cell and for membrane turnover. The mechanism driving clathrin-mediated endocytosis (CME) involves > 50 different protein components assembling at a single location on the plasma membrane in a temporally ordered and hierarchal pathway. These proteins perform precisely choreographed steps that promote receptor recognition and clustering, membrane remodeling, and force-generating actin-filament assembly and turnover to drive membrane invagination and vesicle scission. Many critical aspects of the CME mechanism are conserved from yeast to mammals and were first elucidated in yeast, demonstrating that it is a powerful system for studying endocytosis. In this review, we describe our current mechanistic understanding of each step in the process of yeast CME, and the essential roles played by actin polymerization at these sites, while providing a historical perspective of how the landscape has changed since the preceding version of the YeastBook was published 17 years ago (1997). Finally, we discuss the key unresolved issues and where future studies might be headed.
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Affiliation(s)
- Bruce L Goode
- Brandeis University, Department of Biology, Rosenstiel Center, Waltham, Massachusetts 02454
| | - Julian A Eskin
- Brandeis University, Department of Biology, Rosenstiel Center, Waltham, Massachusetts 02454
| | - Beverly Wendland
- The Johns Hopkins University, Department of Biology, Baltimore, Maryland 21218
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7
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Abstract
In clathrin-mediated membrane traffic, clathrin does not bind directly to cargo and instead binds to adaptors that mediate this function. For endocytosis, the main adaptor is the adaptor protein (AP)-2 complex, but it is uncertain how clathrin contacts AP-2. Here we tested in human cells the importance of the three binding sites that have been identified so far on the N-terminal domain (NTD) of clathrin. We find that mutation of each of the three sites on the NTD, alone or in combination, does not block clathrin/AP-2-mediated endocytosis in the same way as deletion of the NTD. We report here the fourth and final site on the NTD that is required for clathrin/AP-2-mediated endocytic function. Each of the four interaction sites can operate alone to mediate endocytosis. The observed functional redundancy between interaction sites on the NTD explains how productivity of clathrin-coated vesicle formation is ensured.
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Affiliation(s)
- Anna K. Willox
- The Physiological Laboratory, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
| | - Stephen J. Royle
- The Physiological Laboratory, University of Liverpool, Crown Street, Liverpool, L69 3BX, UK
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8
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Abstract
In recent years, cell biologists have uncovered a number of new functions for proteins that were previously thought to operate solely in membrane trafficking. These alternative roles, termed moonlighting functions, can occur at distinct intracellular sites or at different stages of the cell cycle. Here, I evaluate the evidence for mitotic moonlighting functions of proteins that have membrane trafficking roles during interphase. The aim is to identify key issues facing the field and to outline important questions for future work.
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Affiliation(s)
- Stephen J Royle
- Physiological Laboratory, University of Liverpool, Crown Street, Liverpool L69 3BX, UK.
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9
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Neumann-Staubitz P, Hall SL, Kuo J, Jackson AP. Characterization of a temperature-sensitive vertebrate clathrin heavy chain mutant as a tool to study clathrin-dependent events in vivo. PLoS One 2010; 5:e12017. [PMID: 20700507 PMCID: PMC2917355 DOI: 10.1371/journal.pone.0012017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2008] [Accepted: 07/15/2010] [Indexed: 01/27/2023] Open
Abstract
Clathrin and clathrin-dependent events are evolutionary conserved although it is believed that there are differences in the requirement for clathrin in yeast and higher vertebrates. Clathrin is a long-lived protein and thus, with clathrin knockdowns only long-term consequences of clathrin depletion can be studied. Here, we characterize the first vertebrate temperature-sensitive clathrin heavy chain mutant as a tool to investigate responses to rapid clathrin inactivation in higher eukaryotes. Although we created this mutant using a clathrin cryo-electron microscopy model and a yeast temperature-sensitive mutant as a guide, the resulting temperature-sensitive clathrin showed an altered phenotype compared to the corresponding yeast temperature-sensitive clathrin. First, it seemed to form stable triskelions at the non-permissive temperature although endocytosis was impaired under these conditions. Secondly, as a likely consequence of the stable triskelions at the non-permissive temperature, clathrin also localized correctly to its target membranes. Thirdly, we did not observe missorting of the lysosomal enzyme beta-glucuronidase which could indicate that the temperature-sensitive clathrin is still operating at the non-permissive temperature at the Golgi or, that, like in yeast, more than one TGN trafficking pathway exists. Fourthly, in contrast to yeast, actin does not appear to actively compensate in general endocytosis. Thus, there seem to be differences between vertebrates and yeast which can be studied in further detail with this newly created tool.
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Conibear E. Converging views of endocytosis in yeast and mammals. Curr Opin Cell Biol 2010; 22:513-8. [PMID: 20538447 DOI: 10.1016/j.ceb.2010.05.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Revised: 05/18/2010] [Accepted: 05/19/2010] [Indexed: 10/19/2022]
Abstract
Receptor-mediated endocytosis is important for the selective internalization of membrane proteins. In mammals, clathrin, adaptors, and dynamin play prominent roles in regulating cargo selection and vesicle formation. Endocytosis in yeast is generally conserved, but exhibits significant and perplexing differences in the relative importance of clathrin adaptors, dynamin-like proteins, and actin. Recent studies are now reconciling divergent views of endocytic processes in yeast and mammals. The discovery of cargo-specific functions for yeast homologs of mammalian clathrin adaptors has rapidly expanded the number of endocytic adaptors in yeast. Moreover, unifying models have been advanced to explain how dynamin, actin, and membrane-deforming proteins drive membrane scission. While differences remain, discoveries from each system will continue to inform the other.
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Affiliation(s)
- Elizabeth Conibear
- Centre for Molecular Medicine and Therapeutics, Child and Family Research Institute, Department of Medical Genetics, University of British Columbia, Vancouver, BC V5Z 4H4, Canada.
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11
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Angers CG, Merz AJ. HOPS interacts with Apl5 at the vacuole membrane and is required for consumption of AP-3 transport vesicles. Mol Biol Cell 2009; 20:4563-74. [PMID: 19741093 DOI: 10.1091/mbc.e09-04-0272] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Adaptor protein complexes (APs) are evolutionarily conserved heterotetramers that couple cargo selection to the formation of highly curved membranes during vesicle budding. In Saccharomyces cerevisiae, AP-3 mediates vesicle traffic from the late Golgi to the vacuolar lysosome. The HOPS subunit Vps41 is one of the few proteins reported to have a specific role in AP-3 traffic, yet its function remains undefined. We now show that although the AP-3 delta subunit, Apl5, binds Vps41 directly, this interaction occurs preferentially within the context of the HOPS docking complex. Fluorescence microscopy indicates that Vps41 and other HOPS subunits do not detectably colocalize with AP-3 at the late Golgi or on post-Golgi (Sec7-negative) vesicles. Vps41 and HOPS do, however, transiently colocalize with AP-3 vesicles when these vesicles dock at the vacuole membrane. In cells with mutations in HOPS subunits or the vacuole SNARE Vam3, AP-3 shifts from the cytosol to a membrane fraction. Fluorescence microscopy suggests that this fraction consists of post-Golgi AP-3 vesicles that have failed to dock or fuse at the vacuole membrane. We propose that AP-3 remains associated with budded vesicles, interacts with Vps41 and HOPS upon vesicle docking at the vacuole, and finally dissociates during docking or fusion.
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Affiliation(s)
- Cortney G Angers
- Department of Biochemistry, University of Washington, Seattle, WA 98195-3750, USA
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12
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Riechers SP, Stahl U, Lang C. Defects in intracellular trafficking and endocytic/vacuolar acidification determine the efficiency of endocytotic DNA uptake in yeast. J Cell Biochem 2009; 106:327-36. [PMID: 19115284 DOI: 10.1002/jcb.22009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The yeast Saccharomyces cerevisiae is a standard model system to study endocytosis. Here we describe the examination of a representative subset of deletion mutants to identify and locate steps in endocytic transport, endosomal/lysosomal acidification and in intracellular transport of hydrolases in non-viral transfection processes. When transport in late endocytosis is inhibited, transfection efficiency is significantly enhanced. Similarly, transfection efficiency is enhanced when the pH-value of the endosomal/vacuolar system is modified. Transfection efficiency is furthermore elevated when the N+/K+ transport in the endosomal system is disturbed. Finally, we observe enhanced transfection efficiency in mutants disturbed in the CVT/autophagy pathway and in hydrolase transport to the vacuole. In summary, non-viral transfection efficiency can be significantly increased by either (i) inhibiting the transport of endocytosed material before it enters the vacuole, or (ii) inducing a non-natural pH-value of the endosomal/vacuolar system, or (iii) slowing down degradative processes by inhibiting vacuolar hydrolases or the transport between Golgi and late endosome/vacuole.
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Affiliation(s)
- Sean-Patrick Riechers
- Department of Microbiology and Genetics, Institute for Biotechnology, Technische Universität Berlin, Gustav-Meyer-Allee 25, D-13355 Berlin, Germany
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Gustavsson M, Barmark G, Larsson J, Murén E, Ronne H. Functional genomics of monensin sensitivity in yeast: implications for post-Golgi traffic and vacuolar H+-ATPase function. Mol Genet Genomics 2008; 280:233-48. [PMID: 18612650 DOI: 10.1007/s00438-008-0359-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Accepted: 06/13/2008] [Indexed: 11/24/2022]
Abstract
We have screened a complete collection of yeast knockout mutants for sensitivity to monensin, an ionophore that interferes with intracellular transport. A total of 63 sensitive strains were found. Most of the strains were deleted for genes involved in post-Golgi traffic, with an emphasis on vacuolar biogenesis. A high correlation was thus seen with VPS and VAM genes, but there were also significant differences between the three sets of genes. A weaker correlation was seen with sensitivity to NaCl, in particular rate of growth effects. Interestingly, all 14 genes encoding subunits of the vacuolar H(+)-ATPase (V-ATPase) were absent in our screen, even though they appeared in the VPS or VAM screens. All monensin-sensitive mutants that could be tested interact synthetically with a deletion of the A subunit of the V-ATPase, Vma1. Synthetic lethality was limited to mutations affecting endocytosis or retrograde transport to Golgi. In addition, vma1 was epistatic over the monensin sensitivity of vacuolar transport mutants, but not endocytosis mutants. Deletions of the two isoforms of the V-ATPase a subunit, Vph1 and Stv1 had opposite effects on the monensin sensitivity of a ypt7 mutant. These findings are consistent with a model where monensin inhibits growth by interfering with the maintenance of an acidic pH in the late secretory pathway. The synthetic lethality of vma1 with mutations affecting retrograde transport to the Golgi further suggests that it is in the late Golgi that a low pH must be maintained.
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Affiliation(s)
- Marie Gustavsson
- Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden
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14
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Newpher TM, Lemmon SK. Clathrin is important for normal actin dynamics and progression of Sla2p-containing patches during endocytosis in yeast. Traffic 2007; 7:574-88. [PMID: 16643280 PMCID: PMC2975023 DOI: 10.1111/j.1600-0854.2006.00410.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Clathrin is a major vesicle coat protein involved in receptor-mediated endocytosis. In yeast and higher eukaryotes, clathrin is recruited to the plasma membrane during the early stage of endocytosis along with clathrin-associated adaptors. As coated pits undergo maturation, a burst of actin polymerization accompanies and helps drive vesicle internalization. Here, we investigate the dynamics of clathrin relative to the early endocytic patch protein Sla2p. We find that clathrin is recruited to the cortex prior to Sla2p. In the absence of clathrin, normal numbers of Sla2p patches form, but many do not internalize or are dramatically delayed in completion of endocytosis. Patches that do internalize receive Sla1p late, which is followed by Abp1, which appears near the end of Sla2p lifetime. In addition, clathrin mutants develop actin comet tails, suggesting an important function in actin patch organization/dynamics. Similar to its mammalian counterparts, the light chain (LC) subunit of yeast clathrin interacts directly with the coiled-coil domain of Sla2p. A mutant of Sla2p that no longer interacts with LC (sla2Delta376-573) results in delayed progression of endocytic patches and aberrant actin dynamics. These data demonstrate an important role for clathrin in organization and progression of early endocytic patches to the late stages of endocytosis.
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Affiliation(s)
- Thomas M. Newpher
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Sandra K. Lemmon
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH 44106, USA
- Department of Molecular and Cellular Pharmacology, University of Miami, Miami, FL 33101, USA
- Corresponding author: Sandra K. Lemmon,
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15
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Moseley JB, Goode BL. The yeast actin cytoskeleton: from cellular function to biochemical mechanism. Microbiol Mol Biol Rev 2006; 70:605-45. [PMID: 16959963 PMCID: PMC1594590 DOI: 10.1128/mmbr.00013-06] [Citation(s) in RCA: 287] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
All cells undergo rapid remodeling of their actin networks to regulate such critical processes as endocytosis, cytokinesis, cell polarity, and cell morphogenesis. These events are driven by the coordinated activities of a set of 20 to 30 highly conserved actin-associated proteins, in addition to many cell-specific actin-associated proteins and numerous upstream signaling molecules. The combined activities of these factors control with exquisite precision the spatial and temporal assembly of actin structures and ensure dynamic turnover of actin structures such that cells can rapidly alter their cytoskeletons in response to internal and external cues. One of the most exciting principles to emerge from the last decade of research on actin is that the assembly of architecturally diverse actin structures is governed by highly conserved machinery and mechanisms. With this realization, it has become apparent that pioneering efforts in budding yeast have contributed substantially to defining the universal mechanisms regulating actin dynamics in eukaryotes. In this review, we first describe the filamentous actin structures found in Saccharomyces cerevisiae (patches, cables, and rings) and their physiological functions, and then we discuss in detail the specific roles of actin-associated proteins and their biochemical mechanisms of action.
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Affiliation(s)
- James B Moseley
- Department of Biology and The Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02454, USA
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16
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Clark MG, Teply J, Haarer BK, Viggiano SC, Sept D, Amberg DC. A genetic dissection of Aip1p's interactions leads to a model for Aip1p-cofilin cooperative activities. Mol Biol Cell 2006; 17:1971-84. [PMID: 16421248 PMCID: PMC1415301 DOI: 10.1091/mbc.e05-10-0956] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Actin interacting protein 1 (Aip1p) and cofilin cooperate to disassemble actin filaments in vitro and are thought to promote rapid turnover of actin networks in vivo. The precise method by which Aip1p participates in these activities has not been defined, although severing and barbed-end capping of actin filaments have been proposed. To better describe the mechanisms and biological consequences of Aip1p activities, we undertook an extensive mutagenesis of AIP1 aimed at disrupting and mapping Aip1p interactions. Site-directed mutagenesis suggested that Aip1p has two actin binding sites, the primary actin binding site lies on the edge of its N-terminal beta-propeller and a secondary actin binding site lies in a comparable location on its C-terminal beta-propeller. Random mutagenesis followed by screening for separation of function mutants led to the identification of several mutants specifically defective for interacting with cofilin but still able to interact with actin. These mutants suggested that cofilin binds across the cleft between the two propeller domains, leaving the actin binding sites exposed and flanking the cofilin binding site. Biochemical, genetic, and cell biological analyses confirmed that the actin binding- and cofilin binding-specific mutants are functionally defective, whereas the genetic analyses further suggested a role for Aip1p in an early, internalization step of endocytosis. A complementary, unbiased molecular modeling approach was used to derive putative structures for the Aip1p-cofilin complex, the most stable of which is completely consistent with the mutagenesis data. We theorize that Aip1p-severing activity may involve simultaneous binding to two actin subunits with cofilin wedged between the two actin binding sites of the N- and C-terminal propeller domains.
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Affiliation(s)
- Michael G Clark
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
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17
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18
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Rappoport JZ, Benmerah A, Simon SM. Analysis of the AP-2 adaptor complex and cargo during clathrin-mediated endocytosis. Traffic 2005; 6:539-47. [PMID: 15941406 PMCID: PMC1360144 DOI: 10.1111/j.1600-0854.2005.00280.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Previously, we reported that the hetero-tetrameric adaptor complex AP-2 co-localizes with the static population of clathrin spots, whereas it is excluded from clathrin spots that disappear from the plasma membrane (forming clathrin-coated vesicles). More recently however, another group provided evidence that AP-2 markers could be observed coincident with disappearing clathrin spots. Thus, we tested several possible explanations for the apparent discrepancies in these two studies. We evaluated the potential contribution of nonred emission of clathrin-dsRed (used in both studies) in the simultaneous measurement of AP-2 and clathrin at various times. Additionally, we directly compared two different green fluorescent protein-tagged AP-2 constructs (similar to those used in the previous reports). These studies demonstrated that the duration of expression time greatly influences the subcellular localization of the AP-2 markers. Furthermore, we quantitatively evaluated the AP-2 fluorescence at the sites of numerous static and disappearing clathrin spots (at least 80 per group) and confirmed our initial observation that while AP-2 is present in nearly all static clathrin spots, it is excluded from the disappearing population of clathrin spots. Finally, in order to verify that clathrin spot disappearance represents clathrin-coated vesicle internalization, we simultaneously imaged clathrin and the cargo molecule transferrin at the cell surface.
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Affiliation(s)
- Joshua Z. Rappoport
- The Laboratory of Cellular Biophysics, The Rockefeller University, 1230 York Avenue, PO Box 304, New York, NY 10021, USA
| | - Alexandre Benmerah
- Department of Infectious Diseases, Institut Cochin (INSERM U567, CNRS UMR 8104, Université Paris 5), 27 rue du Faubourg St Jacques, Paris 75014, France
| | - Sanford M. Simon
- The Laboratory of Cellular Biophysics, The Rockefeller University, 1230 York Avenue, PO Box 304, New York, NY 10021, USA
- *Corresponding author: Sanford M. Simon,
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19
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Abstract
Clathrin-mediated endocytosis is the main path for receptor internalization in metazoans and is essential for controlling cell integrity and signaling. It is driven by a large array of protein and lipid interactions that have been deciphered mainly by biochemical and genetic means. To place these interactions into context, and ultimately build a fully operative model of endocytosis at the molecular level, it is necessary to know the kinetic details of the role of each protein in this process. In this review, we describe the recent efforts made, by using live cell imaging, to define clear steps in the formation of endocytic vesicles and to observe the recruitment of key proteins during membrane invagination, the scission of a newly formed vesicle, and its movement away from the plasma membrane.
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Affiliation(s)
- David Perrais
- Laboratoire de Physiologie Cellulaire de la Synapse, CNRS UMR 5091, Université Bordeaux 2, Institut François Magendie, 146 rue Léo Saignat, 33077 Bordeaux Cedex, France
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20
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Kaksonen M, Toret CP, Drubin DG. A modular design for the clathrin- and actin-mediated endocytosis machinery. Cell 2005; 123:305-20. [PMID: 16239147 DOI: 10.1016/j.cell.2005.09.024] [Citation(s) in RCA: 583] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 08/08/2005] [Accepted: 09/20/2005] [Indexed: 11/24/2022]
Abstract
Endocytosis depends on an extensive network of interacting proteins that execute a series of distinct subprocesses. Previously, we used live-cell imaging of six budding-yeast proteins to define a pathway for association of receptors, adaptors, and actin during endocytic internalization. Here, we analyzed the effects of 61 deletion mutants on the dynamics of this pathway, revealing functions for 15 proteins, and we analyzed the dynamics of 8 of these proteins. Our studies provide evidence for four protein modules that cooperate to drive coat formation, membrane invagination, actin-meshwork assembly, and vesicle scission during clathrin/actin-mediated endocytosis. We found that clathrin facilitates the initiation of endocytic-site assembly but is not needed for membrane invagination or vesicle formation. Finally, we present evidence that the actin-meshwork assembly that drives membrane invagination is nucleated proximally to the plasma membrane, opposite to the orientation observed for previously studied actin-assembly-driven motility processes.
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Affiliation(s)
- Marko Kaksonen
- Department of Molecular and Cell Biology, University of California, Berkeley, 94720, USA
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21
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Dupré S, Urban-Grimal D, Haguenauer-Tsapis R. Ubiquitin and endocytic internalization in yeast and animal cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1695:89-111. [PMID: 15571811 DOI: 10.1016/j.bbamcr.2004.09.024] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Endocytosis is involved in a wide variety of cellular processes, and the internalization step of endocytosis has been extensively studied in both lower and higher eukaryotic cells. Studies in mammalian cells have described several endocytic pathways, with the main emphasis on clathrin-dependent endocytosis. Genetic studies in yeast have underlined the critical role of actin and actin-binding proteins, lipid modification, and the ubiquitin conjugation system. The combined results of studies of endocytosis in higher and lower eukaryotic cells reveal an interesting interplay in the two systems, including a crucial role for ubiquitin-associated events. The ubiquitylation of yeast cell-surface proteins clearly acts as a signal triggering their internalization. Mammalian cells display variations on the common theme of ubiquitin-linked endocytosis, according to the cell-surface protein considered. Many plasma membrane channels, transporters and receptors undergo cell-surface ubiquitylation, required for the internalization or later endocytic steps of some cell-surface proteins, whereas for others, internalization involves interaction with the ubiquitin conjugation system or with ancillary proteins, which are themselves ubiquitylated. Epsins and Eps15 (or Eps15 homologs), are commonly involved in the process of endocytosis in all eukaryotes, their critical role in this process stemming from their capacity to bind ubiquitin, and to undergo ubiquitylation.
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Affiliation(s)
- S Dupré
- Institut Jacques Monod-CNRS Universités Paris VI and Paris VII, 2 place Jussieu 75005 Paris, France
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22
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Abstract
Endocytosis is characterized by movement and precisely controlled changes in membrane geometry during vesicle formation. Recent developments in live-cell imaging have enabled such movements to be monitored in vivo and correlated with the recruitment and dismissal of fluorescently labeled proteins. This experimental strategy has revealed the sequential recruitment of proteins that are involved in actin polymerization, and actin to single sites of endocytosis in both yeast and mammalian cells. Actin polymerization is correlated with the inward movements of endocytic organelles, which suggests that actin polymerization has a conserved role in this process. In this article, I will discuss three models for the role of actin polymerization in endocytosis.
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23
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Rodal AA, Kozubowski L, Goode BL, Drubin DG, Hartwig JH. Actin and septin ultrastructures at the budding yeast cell cortex. Mol Biol Cell 2004; 16:372-84. [PMID: 15525671 PMCID: PMC539180 DOI: 10.1091/mbc.e04-08-0734] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Budding yeast has been a powerful model organism for studies of the roles of actin in endocytosis and septins in cell division and in signaling. However, the depth of mechanistic understanding that can be obtained from such studies has been severely hindered by a lack of ultrastructural information about how actin and septins are organized at the cell cortex. To address this problem, we developed rapid-freeze and deep-etch techniques to image the yeast cell cortex in spheroplasted cells at high resolution. The cortical actin cytoskeleton assembles into conical or mound-like structures composed of short, cross-linked filaments. The Arp2/3 complex localizes near the apex of these structures, suggesting that actin patch assembly may be initiated from the apex. Mutants in cortical actin patch components with defined defects in endocytosis disrupted different stages of cortical actin patch assembly. Based on these results, we propose a model for actin function during endocytosis. In addition to actin structures, we found that septin-containing filaments assemble into two kinds of higher order structures at the cell cortex: rings and ordered gauzes. These images provide the first high-resolution views of septin organization in cells.
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Affiliation(s)
- Avital A Rodal
- Department of Biology, Rosenstiel Basic Medical Science Research Center, Brandeis University, Waltham, MA 02454, USA.
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24
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Abstract
Internalization of receptors, lipids, pathogens, and other cargo at the plasma membrane involves several different pathways and requires coordinated interactions between a variety of protein and lipid molecules. The actin cytoskeleton is an integral part of the cell cortex, and there is growing evidence that F-actin plays a direct role in these endocytic events. Genetic studies in yeast have firmly established a functional connection between actin and endocytosis. Identification of several proteins that may function at the interface between actin and the endocytic machinery has provided further evidence for this association in both yeast and mammalian cells. Several of these proteins are directly involved in regulating actin assembly and could thus harness forces produced during actin polymerization to facilitate specific steps in the endocytic process. Recent microscopy studies in mammalian cells provide powerful evidence that localized recruitment and polymerization of actin occurs at endocytic sites. In this review, we focus on progress made in elucidating the functions of the actin cytoskeleton in endocytosis.
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Affiliation(s)
- Asa E Y Engqvist-Goldstein
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202, USA
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25
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Membrane trafficking of yeast transporters: mechanisms and physiological control of downregulation. MOLECULAR MECHANISMS CONTROLLING TRANSMEMBRANE TRANSPORT 2004. [DOI: 10.1007/b97215] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
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26
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Baggett JJ, D'Aquino KE, Wendland B. The Sla2p Talin Domain Plays a Role in Endocytosis in Saccharomyces cerevisiae. Genetics 2003; 165:1661-74. [PMID: 14704157 PMCID: PMC1462899 DOI: 10.1093/genetics/165.4.1661] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Abstract
Clathrin-binding adaptors play critical roles for endocytosis in multicellular organisms, but their roles in budding yeast have remained unclear. To address this question, we created a quadruple mutant yeast strain lacking the genes encoding the candidate clathrin adaptors Yap1801p, Yap1802p, and Ent2p and containing a truncated version of Ent1p, Ent1ΔCBMp, missing its clathrin-binding motif. This strain was viable and competent for endocytosis, suggesting the existence of other redundant adaptor-like factors. To identify these factors, we mutagenized the quadruple clathrin adaptor mutant strain and selected cells that were viable in the presence of full-length Ent1p, but inviable with only Ent1ΔCBMp; these strains were named Rcb (requires clathrin binding). One mutant strain, rcb432, contained a mutation in SLA2 that resulted in lower levels of a truncated protein lacking the F-actin binding talin homology domain. Analyses of this sla2 mutant showed that the talin homology domain is required for endocytosis at elevated temperature, that SLA2 exhibits genetic interactions with both ENT1 and ENT2, and that the clathrin adaptors and Sla2p together regulate the actin cytoskeleton and revealed conditions under which Yap1801p and Yap1802p contribute to viability. Together, our data support the view that Sla2p is an adaptor that links actin to clathrin and endocytosis.
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Affiliation(s)
- Jennifer J Baggett
- Department of Biology, The Johns Hopkins University, Baltimore, Maryland 21218, USA
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27
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Horák J. The role of ubiquitin in down-regulation and intracellular sorting of membrane proteins: insights from yeast. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1614:139-55. [PMID: 12896807 DOI: 10.1016/s0005-2736(03)00195-0] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Ubiquitination is a versatile tool used by all eukaryotic organisms for controlling the stability, function, and intracellular localization of a wide variety of proteins. Two of the best characterized functions of protein ubiquitination are to mark proteins for degradation by cytosolic proteasome and to promote the internalization of certain plasma membrane proteins via the endocytotic pathway, followed by their degradation in the vacuole. Recent studies of membrane proteins both in yeast and mammalian cells suggest that the role of ubiquitin may extend beyond its function as an internalization signal in that it also may be required for modification of some component(s) of the endocytotic machinery, and for cargo protein sorting at the late endosome and the Golgi apparatus level. In this review, I will attempt to bring together what is currently known about the role of ubiquitination in controlling protein trafficking between the yeast plasma membrane, the trans-Golgi network, and the vacuole/lysosome.
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Affiliation(s)
- Jaroslav Horák
- Department of Membrane Transport, Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague, Czech Republic.
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28
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Affiliation(s)
- Gilbert Di Paolo
- Howard Hughes Medical Institute and Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
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29
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Abstract
Endocytic adaptor proteins select specific cargo for internalization by endocytosis through clathrin-coated pits or vesicles. Recent studies indicate that epsins might also be classified as adaptors.
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30
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Torralba S, Heath IB. Analysis of three separate probes suggests the absence of endocytosis in Neurospora crassa hyphae. Fungal Genet Biol 2002; 37:221-32. [PMID: 12431457 DOI: 10.1016/s1087-1845(02)00513-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Reports of the existence of endocytosis in filamentous fungi have been conflicting and inconclusive. For this reason, we have tested three independent markers in Neurospora crassa: the electron opaque marker lanthanum (La) and the fluorescent probes Lucifer yellow (LY) and FM4-64. Both La and LY were endocytosed by Saccharomyces cerevisiae cells, which were used as positive controls for endocytosis, but the probes did not accumulate in N. crassa hyphae. Only FM4-64 became internalized into N. crassa hyphae, but it induced abnormal changes in membrane systems and its internalization could be explained by mechanisms other than endocytosis. Together, our results suggest that endocytosis does not occur in N. crassa hyphae and question whether the styryl dyes do in fact reliably report normal endocytosis in filamentous fungi.
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Affiliation(s)
- Sara Torralba
- Department of Biology, York University, Toronto, Canada.
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31
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Morgan GW, Hall BS, Denny PW, Field MC, Carrington M. The endocytic apparatus of the kinetoplastida. Part II: machinery and components of the system. Trends Parasitol 2002; 18:540-6. [PMID: 12482539 DOI: 10.1016/s1471-4922(02)02392-9] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Endocytic systems within eukaryotic cells are a diverse set of intracellular transport pathways responsible for uptake, recycling, interaction with the exocytic system and degradation of molecules. Each of these pathways requires the interaction of distinct protein components that function in macromolecule sorting, control of transport rates and in membrane biogenesis. In the second of two articles on kinetoplastida endocytosis, the endocytic system in Trypanosoma brucei is considered as a model, and the molecules that control this system and the protein components of the endocytic pathway are discussed. We also consider novel mechanisms for sorting that have been proposed to operate in trypanosomes.
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Affiliation(s)
- Gareth W Morgan
- Wellcome Trust Laboratories for Molecular Parasitology, Dept of Biological Sciences, Imperial College of Science, Technology and Medicine, London, UK
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32
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Abstract
Endocytosis requires the coordinated interaction of a plethora of cytosolic and membrane proteins. In mammalian cells, clathrin plays a crucial role in this process as a scaffolding protein underlying the invaginating plasma membrane and surrounding the primary endocytic vesicle. Despite great similarities at the morphological level, the cargo of endocytic clathrin-coated vesicles in plant cells remains to be elucidated. Thus, the role of endocytosis in the plant cell is difficult to ascertain. This review will present important discoveries on putative endosomal compartments and on the functions of plasma membrane-derived plant clathrin-coated vesicles, but will also emphasize the striking similarities of the clathrin-, network- and vesicle fusion-machineries between plant and animal cells.
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Affiliation(s)
- Susanne E H Holstein
- Heidelberg Institute of Plant Sciences (HIP), Cell Biology, Im Neuenheimer Feld 230, D-69120 Heidelberg, Germany,
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33
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Henry KR, D'Hondt K, Chang J, Newpher T, Huang K, Hudson RT, Riezman H, Lemmon SK. Scd5p and clathrin function are important for cortical actin organization, endocytosis, and localization of sla2p in yeast. Mol Biol Cell 2002; 13:2607-25. [PMID: 12181333 PMCID: PMC117929 DOI: 10.1091/mbc.e02-01-0012] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
SCD5 was identified as a multicopy suppressor of clathrin HC-deficient yeast. SCD5 is essential, but an scd5-Delta338 mutant, expressing Scd5p with a C-terminal truncation of 338 amino acids, is temperature sensitive for growth. Further studies here demonstrate that scd5-Delta338 affects receptor-mediated and fluid-phase endocytosis and normal actin organization. The scd5-Delta338 mutant contains larger and depolarized cortical actin patches and a prevalence of G-actin bars. scd5-Delta338 also displays synthetic negative genetic interactions with mutations in several other proteins important for cortical actin organization and endocytosis. Moreover, Scd5p colocalizes with cortical actin. Analysis has revealed that clathrin-deficient yeast also have a major defect in cortical actin organization and accumulate G-actin. Overexpression of SCD5 partially suppresses the actin defect of clathrin mutants, whereas combining scd5-Delta338 with a clathrin mutation exacerbates the actin and endocytic phenotypes. Both Scd5p and yeast clathrin physically associate with Sla2p, a homologue of the mammalian huntingtin interacting protein HIP1 and the related HIP1R. Furthermore, Sla2p localization at the cell cortex is dependent on Scd5p and clathrin function. Therefore, Scd5p and clathrin are important for actin organization and endocytosis, and Sla2p may provide a critical link between clathrin and the actin cytoskeleton in yeast, similar to HIP1(R) in animal cells.
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Affiliation(s)
- Kenneth R Henry
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland Ohio 44106, USA
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34
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Zhang B, Zelhof AC. Amphiphysins: raising the BAR for synaptic vesicle recycling and membrane dynamics. Bin-Amphiphysin-Rvsp. Traffic 2002; 3:452-60. [PMID: 12047553 DOI: 10.1034/j.1600-0854.2002.30702.x] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Amphiphysins, members of the BAR (Bin-Amphiphysin-Rvsp) protein super family, have been postulated to play a key role in clathrin-mediated endocytosis of synaptic vesicles (SVs). This review focuses on recent genetic studies of the role of amphiphysins in SV recycling and membrane morphogenesis. In the mouse, brain-specific amphiphysin I and II regulate, but are not essential for, SV recycling. The role of this regulation appears important, as mice deficient in these proteins have seizures and are deficient in learning and memory. In the fruit fly Drosophila melanogaster, amphiphysin is found in muscles and is enriched at postsynaptic membranes of neuromuscular junctions (NMJs); however, it does not play a role in SV recycling. Rather, amphiphysin in fly muscles appears to regulate the organization and structure of the muscle T-tubule system and possibly the subsynaptic reticulum. Amphiphysin is also involved in membrane organization in both neurons and non-neuronal cells in Drosophila. These studies reveal pleiotropic functions for amphiphysins in clathrin-mediated endocytosis and the regulation of membrane dynamics, perhaps through the actin cytoskeleton.
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Affiliation(s)
- Bing Zhang
- Section of Neurobiology, University of Texas, Austin, TX 78712, USA.
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35
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Current awareness on yeast. Yeast 2002; 19:185-92. [PMID: 11788972 DOI: 10.1002/yea.820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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36
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Brodsky FM, Chen CY, Knuehl C, Towler MC, Wakeham DE. Biological basket weaving: formation and function of clathrin-coated vesicles. Annu Rev Cell Dev Biol 2002; 17:517-68. [PMID: 11687498 DOI: 10.1146/annurev.cellbio.17.1.517] [Citation(s) in RCA: 481] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
There has recently been considerable progress in understanding the regulation of clathrin-coated vesicle (CCV) formation and function. These advances are due to the determination of the structure of a number of CCV coat components at molecular resolution and the identification of novel regulatory proteins that control CCV formation in the cell. In addition, pathways of (a) phosphorylation, (b) receptor signaling, and (c) lipid modification that influence CCV formation, as well as the interaction between the cytoskeleton and CCV transport pathways are becoming better defined. It is evident that although clathrin coat assembly drives CCV formation, this fundamental reaction is modified by different regulatory proteins, depending on where CCVs are forming in the cell. This regulatory difference likely reflects the distinct biological roles of CCVs at the plasma membrane and trans-Golgi network, as well as the distinct properties of these membranes themselves. Tissue-specific functions of CCVs require even more-specialized regulation and defects in these pathways can now be correlated with human diseases.
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Affiliation(s)
- F M Brodsky
- Department of Biopharmaceutical Sciences, University of California, San Francisco, California, USA.
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