1
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Yu Y, Chen D, Farmer SM, Xu S, Rios B, Solbach A, Ye X, Ye L, Zhang S. Endolysosomal trafficking controls yolk granule biogenesis in vitellogenic Drosophila oocytes. PLoS Genet 2024; 20:e1011152. [PMID: 38315726 PMCID: PMC10898735 DOI: 10.1371/journal.pgen.1011152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2023] [Revised: 02/27/2024] [Accepted: 01/22/2024] [Indexed: 02/07/2024] Open
Abstract
Endocytosis and endolysosomal trafficking are essential for almost all aspects of physiological functions of eukaryotic cells. As our understanding on these membrane trafficking events are mostly from studies in yeast and cultured mammalian cells, one challenge is to systematically evaluate the findings from these cell-based studies in multicellular organisms under physiological settings. One potentially valuable in vivo system to address this challenge is the vitellogenic oocyte in Drosophila, which undergoes extensive endocytosis by Yolkless (Yl), a low-density lipoprotein receptor (LDLR), to uptake extracellular lipoproteins into oocytes and package them into a specialized lysosome, the yolk granule, for storage and usage during later development. However, by now there is still a lack of sufficient understanding on the molecular and cellular processes that control yolk granule biogenesis. Here, by creating genome-tagging lines for Yl receptor and analyzing its distribution in vitellogenic oocytes, we observed a close association of different endosomal structures with distinct phosphoinositides and actin cytoskeleton dynamics. We further showed that Rab5 and Rab11, but surprisingly not Rab4 and Rab7, are essential for yolk granules biogenesis. Instead, we uncovered evidence for a potential role of Rab7 in actin regulation and observed a notable overlap of Rab4 and Rab7, two Rab GTPases that have long been proposed to have distinct spatial distribution and functional roles during endolysosomal trafficking. Through a small-scale RNA interference (RNAi) screen on a set of reported Rab5 effectors, we showed that yolk granule biogenesis largely follows the canonical endolysosomal trafficking and maturation processes. Further, the data suggest that the RAVE/V-ATPase complexes function upstream of or in parallel with Rab7, and are involved in earlier stages of endosomal trafficking events. Together, our study provides s novel insights into endolysosomal pathways and establishes vitellogenic oocyte in Drosophila as an excellent in vivo model for dissecting the highly complex membrane trafficking events in metazoan.
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Affiliation(s)
- Yue Yu
- The Brown Foundation Institute of Molecular Medicine, McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
- Program in Neuroscience, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences (MD Anderson UTHealth GSBS), Houston, Texas, United States of America
| | - Dongsheng Chen
- The Brown Foundation Institute of Molecular Medicine, McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
- The College of Life Sciences, Anhui Normal University, #1 Beijing East Road, Wuhu, Anhui, People’s Republic of China
| | - Stephen M. Farmer
- The Brown Foundation Institute of Molecular Medicine, McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
- Program in Neuroscience, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences (MD Anderson UTHealth GSBS), Houston, Texas, United States of America
- Program in Biochemistry and Cell Biology, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences (MD Anderson UTHealth GSBS), Houston, Texas, United States of America
| | - Shiyu Xu
- The Brown Foundation Institute of Molecular Medicine, McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
| | - Beatriz Rios
- The Brown Foundation Institute of Molecular Medicine, McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
- Program in Neuroscience, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences (MD Anderson UTHealth GSBS), Houston, Texas, United States of America
| | - Amanda Solbach
- The Brown Foundation Institute of Molecular Medicine, McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
- Program in Neuroscience, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences (MD Anderson UTHealth GSBS), Houston, Texas, United States of America
- Programs in Genetics and Epigenetics, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences (MD Anderson UTHealth GSBS), Houston, Texas, United States of America
| | - Xin Ye
- The Brown Foundation Institute of Molecular Medicine, McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
| | - Lili Ye
- The Brown Foundation Institute of Molecular Medicine, McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
| | - Sheng Zhang
- The Brown Foundation Institute of Molecular Medicine, McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
- Program in Neuroscience, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences (MD Anderson UTHealth GSBS), Houston, Texas, United States of America
- Programs in Genetics and Epigenetics, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences (MD Anderson UTHealth GSBS), Houston, Texas, United States of America
- Department of Neurobiology and Anatomy, McGovern Medical School at the University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
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2
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Takatsuka H, Higaki T, Ito M. At the Nexus between Cytoskeleton and Vacuole: How Plant Cytoskeletons Govern the Dynamics of Large Vacuoles. Int J Mol Sci 2023; 24:ijms24044143. [PMID: 36835552 PMCID: PMC9967756 DOI: 10.3390/ijms24044143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 02/15/2023] [Accepted: 02/16/2023] [Indexed: 02/22/2023] Open
Abstract
Large vacuoles are a predominant cell organelle throughout the plant body. They maximally account for over 90% of cell volume and generate turgor pressure that acts as a driving force of cell growth, which is essential for plant development. The plant vacuole also acts as a reservoir for sequestering waste products and apoptotic enzymes, thereby enabling plants to rapidly respond to fluctuating environments. Vacuoles undergo dynamic transformation through repeated enlargement, fusion, fragmentation, invagination, and constriction, eventually resulting in the typical 3-dimensional complex structure in each cell type. Previous studies have indicated that such dynamic transformations of plant vacuoles are governed by the plant cytoskeletons, which consist of F-actin and microtubules. However, the molecular mechanism of cytoskeleton-mediated vacuolar modifications remains largely unclear. Here we first review the behavior of cytoskeletons and vacuoles during plant development and in response to environmental stresses, and then introduce candidates that potentially play pivotal roles in the vacuole-cytoskeleton nexus. Finally, we discuss factors hampering the advances in this research field and their possible solutions using the currently available cutting-edge technologies.
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Affiliation(s)
- Hirotomo Takatsuka
- School of Biological Science and Technology, College of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
- Correspondence:
| | - Takumi Higaki
- Faculty of Advanced Science and Technology, Kumamoto University, Kurokami, Chuo-ku, Kumamoto 860-8555, Japan
- International Research Organization for Advanced Science and Technology, Kumamoto University, Kurokami, Chuo-ku, Kumamoto 860-8555, Japan
| | - Masaki Ito
- School of Biological Science and Technology, College of Science and Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
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3
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Laundon D, Chrismas N, Bird K, Thomas S, Mock T, Cunliffe M. A cellular and molecular atlas reveals the basis of chytrid development. eLife 2022; 11:73933. [PMID: 35227375 PMCID: PMC8887899 DOI: 10.7554/elife.73933] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 02/01/2022] [Indexed: 12/26/2022] Open
Abstract
The chytrids (phylum Chytridiomycota) are a major fungal lineage of ecological and evolutionary importance. Despite their importance, many fundamental aspects of chytrid developmental and cell biology remain poorly understood. To address these knowledge gaps, we combined quantitative volume electron microscopy and comparative transcriptome profiling to create an 'atlas' of the cellular and molecular basis of the chytrid life cycle, using the model chytrid Rhizoclosmatium globosum. From our developmental atlas, we describe the transition from the transcriptionally inactive free-swimming zoospore to the more biologically complex germling, and show that lipid processing is multifaceted and dynamic throughout the life cycle. We demonstrate that the chytrid apophysis is a compartmentalised site of high intracellular trafficking, linking the feeding/attaching rhizoids to the reproductive zoosporangium, and constituting division of labour in the chytrid cell plan. We provide evidence that during zoosporogenesis, zoospores display amoeboid morphologies and exhibit endocytotic cargo transport from the interstitial maternal cytoplasm. Taken together, our results reveal insights into chytrid developmental biology and provide a basis for future investigations into non-dikaryan fungal cell biology.
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Affiliation(s)
- Davis Laundon
- Marine Biological Association, The Laboratory, Citadel Hill, Plymouth, United Kingdom.,School of Environmental Sciences, University of East Anglia, Norwich, United Kingdom
| | - Nathan Chrismas
- Marine Biological Association, The Laboratory, Citadel Hill, Plymouth, United Kingdom
| | - Kimberley Bird
- Marine Biological Association, The Laboratory, Citadel Hill, Plymouth, United Kingdom
| | - Seth Thomas
- Marine Biological Association, The Laboratory, Citadel Hill, Plymouth, United Kingdom
| | - Thomas Mock
- School of Environmental Sciences, University of East Anglia, Norwich, United Kingdom
| | - Michael Cunliffe
- Marine Biological Association, The Laboratory, Citadel Hill, Plymouth, United Kingdom.,School of Biological and Marine Sciences, University of Plymouth, Plymouth, United Kingdom
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4
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Miner GE, Sullivan KD, Zhang C, Rivera-Kohr D, Guo A, Hurst LR, Ellis EC, Starr ML, Jones BC, Fratti RA. Phosphatidylinositol 3,5-bisphosphate regulates Ca 2+ transport during yeast vacuolar fusion through the Ca 2+ ATPase Pmc1. Traffic 2021; 21:503-517. [PMID: 32388897 DOI: 10.1111/tra.12736] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 05/04/2020] [Accepted: 05/06/2020] [Indexed: 01/02/2023]
Abstract
The transport of Ca2+ across membranes precedes the fusion and fission of various lipid bilayers. Yeast vacuoles under hyperosmotic stress become fragmented through fission events that requires the release of Ca2+ stores through the TRP channel Yvc1. This requires the phosphorylation of phosphatidylinositol-3-phosphate (PI3P) by the PI3P-5-kinase Fab1 to produce transient PI(3,5)P2 pools. Ca2+ is also released during vacuole fusion upon trans-SNARE complex assembly, however, its role remains unclear. The effect of PI(3,5)P2 on Ca2+ flux during fusion was independent of Yvc1. Here, we show that while low levels of PI(3,5)P2 were required for Ca2+ uptake into the vacuole, increased concentrations abolished Ca2+ efflux. This was as shown by the addition of exogenous dioctanoyl PI(3,5)P2 or increased endogenous production of by the hyperactive fab1T2250A mutant. In contrast, the lack of PI(3,5)P2 on vacuoles from the kinase dead fab1EEE mutant showed delayed and decreased Ca2+ uptake. The effects of PI(3,5)P2 were linked to the Ca2+ pump Pmc1, as its deletion rendered vacuoles resistant to the effects of excess PI(3,5)P2 . Experiments with Verapamil inhibited Ca2+ uptake when added at the start of the assay, while adding it after Ca2+ had been taken up resulted in the rapid expulsion of Ca2+ . Vacuoles lacking both Pmc1 and the H+ /Ca2+ exchanger Vcx1 lacked the ability to take up Ca2+ and instead expelled it upon the addition of ATP. Together these data suggest that a balance of efflux and uptake compete during the fusion pathway and that the levels of PI(3,5)P2 can modulate which path predominates.
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Affiliation(s)
- Gregory E Miner
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Katherine D Sullivan
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Chi Zhang
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - David Rivera-Kohr
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Annie Guo
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Logan R Hurst
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Ez C Ellis
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Matthew L Starr
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Brandon C Jones
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Rutilio A Fratti
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.,Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
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5
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SNAREs, tethers and SM proteins: how to overcome the final barriers to membrane fusion? Biochem J 2020; 477:243-258. [PMID: 31951000 DOI: 10.1042/bcj20190050] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 12/04/2019] [Accepted: 12/16/2019] [Indexed: 12/18/2022]
Abstract
Physiological membrane vesicles are built to separate reaction spaces in a stable manner, even when they accidentally collide or are kept in apposition by spatial constraints in the cell. This requires a natural resistance to fusion and mixing of their content, which originates from substantial energetic barriers to membrane fusion [1]. To facilitate intracellular membrane fusion reactions in a controlled manner, proteinaceous fusion machineries have evolved. An important open question is whether protein fusion machineries actively pull the fusion reaction over the present free energy barriers, or whether they rather catalyze fusion by lowering those barriers. At first sight, fusion proteins such as SNARE complexes and viral fusion proteins appear to act as nano-machines, which mechanically transduce force to the membranes and thereby overcome the free energy barriers [2,3]. Whether fusion proteins additionally alter the free energy landscape of the fusion reaction via catalytic roles is less obvious. This is a question that we shall discuss in this review, with particular focus on the influence of the eukaryotic SNARE-dependent fusion machinery on the final step of the reaction, the formation and expansion of the fusion pore.
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6
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Ahmadpour D, Babazadeh R, Nystrom T. Hitchhiking on vesicles: a way to harness age-related proteopathies? FEBS J 2020; 287:5068-5079. [PMID: 32336030 DOI: 10.1111/febs.15345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/06/2020] [Accepted: 04/23/2020] [Indexed: 12/27/2022]
Abstract
Central to proteopathies and leading to most age-related neurodegenerative disorders is a failure in protein quality control (PQC). To harness the toxicity of misfolded and damaged disease proteins, such proteins are either refolded, degraded by temporal PQC, or sequestered by spatial PQC into specific, organelle-associated, compartments within the cell. Here, we discuss the impact of vesicle trafficking pathways in general, and syntaxin 5 in particular, as key players in spatial PQC directing misfolded proteins to the surface of vacuole and mitochondria, which facilitates their clearance and detoxification. Since boosting vesicle trafficking genetically can positively impact on spatial PQC and make cells less sensitive to misfolded disease proteins, we speculate that regulators of such trafficking might serve as therapeutic targets for age-related neurological disorders.
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Affiliation(s)
- Doryaneh Ahmadpour
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health-AgeCap, University of Gothenburg, Sweden.,Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, Sahlgrenska Academy at the University of Gothenburg, Sweden
| | - Roja Babazadeh
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health-AgeCap, University of Gothenburg, Sweden.,Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Thomas Nystrom
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health-AgeCap, University of Gothenburg, Sweden
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7
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Zhang H, Xiao Y, Deng X, Feng H, Li Z, Zhang L, Chen H. OsVPE3 Mediates GA-induced Programmed Cell Death in Rice Aleurone Layers via Interacting with Actin Microfilaments. RICE (NEW YORK, N.Y.) 2020; 13:22. [PMID: 32232682 PMCID: PMC7105518 DOI: 10.1186/s12284-020-00376-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 02/21/2020] [Indexed: 06/10/2023]
Abstract
BACKGROUND Vacuolar processing enzymes (VPEs) have been identified as the enzymes that regulate vacuole-mediated programmed cell death (PCD) in plants. The mechanism that VPE regulates the PCD in rice aleurone layers remains unknown. RESULTS The aleurone layers treated with distilled water exerted caspase-1 and VPE activity, both of which were inhibited by the caspase-1 specific inhibitor Ac-YVAD-CMK but not by the caspase-3 specific inhibitor Ac-DEVD-CHO. However, the caspase-1 and caspase-3 inhibitors weakened the activity of caspase-3. Combined with the effects of endogenous gibberellin (GA) on the induction of OsVPEs, we suggest that the OsVPE3 in the aleurone layers, which exhibits caspase-1-like activity, is a key molecule in GA-induced PCD via regulating the protease with caspase-3-like activity. Many studies have confirmed that vacuolar fusion is an important feature of vacuole-mediated PCD in plants. In this experiment, the process of vacuole fusion was accompanied by changes in the structure of actin filaments (AFs), specifically, their depolymerization and polymerization. The process of vacuolar fusion was accelerated or delayed by the promotion or inhibition of the depolymerization of AFs, respectively. Here, the inhibition of OsVPE3 blocked the depolymerization of AFs and delayed the fusion of vacuoles, indicating that OsVPE3 can regulate the fusion of vacuoles in rice aleurone layers via mediating AFs. Furthermore, the depolymerization of AFs contributed to the up-regulation of OsVPE3 gene expression and VPE activity, resulting in accelerated PCD in rice aleurone layers. However, the inhibitor of VPE reversed the effects of AF depolymerization on the activity of VPE, then postponing the process of PCD, implying that AF can involve in GA-induced PCD of rice aleurone layers by mediating OsVPE3. CONCLUSIONS Together, activation of OsVPE3 and depolymerization of AFs shortened the process of vacuolation and PCD in rice aleurone layers, and OsVPE3 interacted with AFs during regulation.
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Affiliation(s)
- Heting Zhang
- Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou, 570228, China
| | - Yu Xiao
- Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou, 570228, China
| | - Xiaojiang Deng
- Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou, 570228, China
| | - Hongyu Feng
- Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou, 570228, China
| | - Zhe Li
- Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou, 570228, China
| | - Lulu Zhang
- Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou, 570228, China
| | - Huiping Chen
- Key Laboratory of Tropical Biological Resources of Ministry of Education, Hainan University, Haikou, 570228, China.
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8
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Kaiser S, Eisa A, Kleine-Vehn J, Scheuring D. NET4 Modulates the Compactness of Vacuoles in Arabidopsis thaliana. Int J Mol Sci 2019; 20:ijms20194752. [PMID: 31557830 PMCID: PMC6801981 DOI: 10.3390/ijms20194752] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 09/20/2019] [Accepted: 09/23/2019] [Indexed: 11/29/2022] Open
Abstract
The dimension of the plants largest organelle—the vacuole—plays a major role in defining cellular elongation rates. The morphology of the vacuole is controlled by the actin cytoskeleton, but molecular players remain largely unknown. Recently, the Networked (NET) family of membrane-associated, actin-binding proteins has been identified. Here, we show that NET4A localizes to highly constricted regions of the vacuolar membrane and contributes to vacuolar morphology. Using genetic interference, we found that deregulation of NET4 abundance increases vacuolar occupancy, and that overexpression of NET4 abundance decreases vacuolar occupancy. Our data reveal that NET4A induces more compact vacuoles, correlating with reduced cellular and organ growth in Arabidopsis thaliana.
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Affiliation(s)
- Sabrina Kaiser
- Plant Pathology, University of Kaiserslautern, 67663 Kaiserslautern, Germany.
| | - Ahmed Eisa
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Applied Life Sciences (BOKU), 1190 Vienna, Austria.
- Current address: Plant Biochemistry and Physiology, Ludwig-Maximilians-University Munich, 80539 Munich, Germany.
| | - Jürgen Kleine-Vehn
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Applied Life Sciences (BOKU), 1190 Vienna, Austria.
| | - David Scheuring
- Plant Pathology, University of Kaiserslautern, 67663 Kaiserslautern, Germany.
- Department of Applied Genetics and Cell Biology, University of Natural Resources and Applied Life Sciences (BOKU), 1190 Vienna, Austria.
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9
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10
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Leng Y, Ye G, Zeng D. Genetic Dissection of Leaf Senescence in Rice. Int J Mol Sci 2017; 18:E2686. [PMID: 29232920 PMCID: PMC5751288 DOI: 10.3390/ijms18122686] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2017] [Revised: 11/28/2017] [Accepted: 12/01/2017] [Indexed: 12/04/2022] Open
Abstract
Leaf senescence, the final stage of leaf development, is a complex and highly regulated process that involves a series of coordinated actions at the cellular, tissue, organ, and organism levels under the control of a highly regulated genetic program. In the last decade, the use of mutants with different levels of leaf senescence phenotypes has led to the cloning and functional characterizations of a few genes, which has greatly improved the understanding of genetic mechanisms underlying leaf senescence. In this review, we summarize the recent achievements in the genetic mechanisms in rice leaf senescence.
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Affiliation(s)
- Yujia Leng
- State Key Lab for Rice Biology, China National Rice Research Institute, Hangzhou 310006, China.
- CAAS-IRRI Joint Laboratory for Genomics-assisted Germplasm Enhancement, Agricultural Genomics Institute in Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China.
| | - Guoyou Ye
- CAAS-IRRI Joint Laboratory for Genomics-assisted Germplasm Enhancement, Agricultural Genomics Institute in Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518120, China.
| | - Dali Zeng
- State Key Lab for Rice Biology, China National Rice Research Institute, Hangzhou 310006, China.
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11
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Asymmetric Inheritance of Aggregated Proteins and Age Reset in Yeast Are Regulated by Vac17-Dependent Vacuolar Functions. Cell Rep 2017; 16:826-38. [PMID: 27373154 PMCID: PMC4963537 DOI: 10.1016/j.celrep.2016.06.016] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 01/29/2016] [Accepted: 05/31/2016] [Indexed: 11/24/2022] Open
Abstract
Age can be reset during mitosis in both yeast and stem cells to generate a young daughter cell from an aged and deteriorated one. This phenomenon requires asymmetry-generating genes (AGGs) that govern the asymmetrical inheritance of aggregated proteins. Using a genome-wide imaging screen to identify AGGs in Saccharomyces cerevisiae, we discovered a previously unknown role for endocytosis, vacuole fusion, and the myosin-dependent adaptor protein Vac17 in asymmetrical inheritance of misfolded proteins. Overproduction of Vac17 increases deposition of aggregates into cytoprotective vacuole-associated sites, counteracts age-related breakdown of endocytosis and vacuole integrity, and extends replicative lifespan. The link between damage asymmetry and vesicle trafficking can be explained by a direct interaction between aggregates and vesicles. We also show that the protein disaggregase Hsp104 interacts physically with endocytic vesicle-associated proteins, such as the dynamin-like protein, Vps1, which was also shown to be required for Vac17-dependent sequestration of protein aggregates. These data demonstrate that two physiognomies of aging-reduced endocytosis and protein aggregation-are interconnected and regulated by Vac17.
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12
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Chaillot J, Tebbji F, García C, Wurtele H, Pelletier R, Sellam A. pH-Dependant Antifungal Activity of Valproic Acid against the Human Fungal Pathogen Candida albicans. Front Microbiol 2017; 8:1956. [PMID: 29062309 PMCID: PMC5640775 DOI: 10.3389/fmicb.2017.01956] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Accepted: 09/22/2017] [Indexed: 11/20/2022] Open
Abstract
Current antifungal drugs suffer from limitations including toxicity, the emergence of resistance and decreased efficacy at low pH that are typical of human vaginal surfaces. Here, we have shown that the antipsychotic drug valproic acid (VPA) exhibited a strong antifungal activity against both sensitive and resistant Candida albicans in pH condition similar to that encountered in vagina. VPA exerted a strong anti-biofilm activity and attenuated damage of vaginal epithelial cells caused by C. albicans. We also showed that VPA synergizes with the allylamine antifungal, Terbinafine. We undertook a chemogenetic screen to delineate biological processes that underlies VPA-sensitivity in C. albicans and found that vacuole-related genes were required to tolerate VPA. Confocal fluorescence live-cell imaging revealed that VPA alters vacuole integrity and support a model where alteration of vacuoles contributes to the antifungal activity. Taken together, this study suggests that VPA could be used as an effective antifungal against vulvovaginal candidiasis.
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Affiliation(s)
- Julien Chaillot
- Infectious Diseases Research Centre-CRI, Research Center of the CHU de Québec, Université Laval, Quebec, QC, Canada
| | - Faiza Tebbji
- Infectious Diseases Research Centre-CRI, Research Center of the CHU de Québec, Université Laval, Quebec, QC, Canada
| | - Carlos García
- Infectious Diseases Research Centre-CRI, Research Center of the CHU de Québec, Université Laval, Quebec, QC, Canada
| | - Hugo Wurtele
- Maisonneuve-Rosemont Hospital Research Center, Montreal, QC, Canada.,Department of Medicine, Université de Montréal, Montreal, QC, Canada
| | - René Pelletier
- Medical Microbiology and Infectious Diseases, Research Center of the CHU de Québec, Quebec, QC, Canada
| | - Adnane Sellam
- Infectious Diseases Research Centre-CRI, Research Center of the CHU de Québec, Université Laval, Quebec, QC, Canada.,Department of Microbiology, Infectious Disease and Immunology, Faculty of Medicine, University Laval, Quebec, QC, Canada
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13
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Gottschling DE, Nyström T. The Upsides and Downsides of Organelle Interconnectivity. Cell 2017; 169:24-34. [PMID: 28340346 DOI: 10.1016/j.cell.2017.02.030] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 02/13/2017] [Accepted: 02/21/2017] [Indexed: 12/31/2022]
Abstract
Interconnectivity and feedback control are hallmarks of biological systems. This includes communication between organelles, which allows them to function and adapt to changing cellular environments. While the specific mechanisms for all communications remain opaque, unraveling the wiring of organelle networks is critical to understand how biological systems are built and why they might collapse, as occurs in aging. A comprehensive understanding of all the routes involved in inter-organelle communication is still lacking, but important themes are beginning to emerge, primarily in budding yeast. These routes are reviewed here in the context of sub-system proteostasis and complex adaptive systems theory.
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Affiliation(s)
| | - Thomas Nyström
- Institute for Biomedicine, Sahlgrenska Academy, University of Gothenburg, 405 30 Gothenburg, Sweden.
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14
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Tsuji T, Fujimoto M, Tatematsu T, Cheng J, Orii M, Takatori S, Fujimoto T. Niemann-Pick type C proteins promote microautophagy by expanding raft-like membrane domains in the yeast vacuole. eLife 2017; 6:e25960. [PMID: 28590904 PMCID: PMC5462540 DOI: 10.7554/elife.25960] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Accepted: 05/16/2017] [Indexed: 11/13/2022] Open
Abstract
Niemann-Pick type C is a storage disease caused by dysfunction of NPC proteins, which transport cholesterol from the lumen of lysosomes to the limiting membrane of that compartment. Using freeze fracture electron microscopy, we show here that the yeast NPC orthologs, Ncr1p and Npc2p, are essential for formation and expansion of raft-like domains in the vacuolar (lysosome) membrane, both in stationary phase and in acute nitrogen starvation. Moreover, the expanded raft-like domains engulf lipid droplets by a microautophagic mechanism. We also found that the multivesicular body pathway plays a crucial role in microautophagy in acute nitrogen starvation by delivering sterol to the vacuole. These data show that NPC proteins promote microautophagy in stationary phase and under nitrogen starvation conditions, likely by increasing sterol in the limiting membrane of the vacuole.
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Affiliation(s)
- Takuma Tsuji
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Megumi Fujimoto
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Tsuyako Tatematsu
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Jinglei Cheng
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Minami Orii
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Sho Takatori
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Toyoshi Fujimoto
- Department of Molecular Cell Biology and Anatomy, Nagoya University Graduate School of Medicine, Nagoya, Japan
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15
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Hill SM, Hanzén S, Nyström T. Restricted access: spatial sequestration of damaged proteins during stress and aging. EMBO Rep 2017; 18:377-391. [PMID: 28193623 PMCID: PMC5331209 DOI: 10.15252/embr.201643458] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Revised: 12/19/2016] [Accepted: 01/24/2017] [Indexed: 01/08/2023] Open
Abstract
The accumulation of damaged and aggregated proteins is a hallmark of aging and increased proteotoxic stress. To limit the toxicity of damaged and aggregated proteins and to ensure that the damage is not inherited by succeeding cell generations, a system of spatial quality control operates to sequester damaged/aggregated proteins into inclusions at specific protective sites. Such spatial sequestration and asymmetric segregation of damaged proteins have emerged as key processes required for cellular rejuvenation. In this review, we summarize findings on the nature of the different quality control sites identified in yeast, on genetic determinants required for spatial quality control, and on how aggregates are recognized depending on the stress generating them. We also briefly compare the yeast system to spatial quality control in other organisms. The data accumulated demonstrate that spatial quality control involves factors beyond the canonical quality control factors, such as chaperones and proteases, and opens up new venues in approaching how proteotoxicity might be mitigated, or delayed, upon aging.
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Affiliation(s)
- Sandra Malmgren Hill
- Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden
| | - Sarah Hanzén
- Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden
| | - Thomas Nyström
- Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden
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16
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The relationship between vacuolation and initiation of PCD in rice (Oryza sativa) aleurone cells. Sci Rep 2017; 7:41245. [PMID: 28117452 PMCID: PMC5259747 DOI: 10.1038/srep41245] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 12/19/2016] [Indexed: 02/05/2023] Open
Abstract
Vacuole fusion is a necessary process for the establishment of a large central vacuole, which is the central location of various hydrolytic enzymes and other factors involved in death at the beginning of plant programmed cell death (PCD). In our report, the fusion of vacuoles has been presented in two ways: i) small vacuoles coalesce to form larger vacuoles through membrane fusion, and ii) larger vacuoles combine with small vacuoles when small vacuoles embed into larger vacuoles. Regardless of how fusion occurs, a large central vacuole is formed in rice (Oryza sativa) aleurone cells. Along with the development of vacuolation, the rupture of the large central vacuole leads to the loss of the intact plasma membrane and the degradation of the nucleus, resulting in cell death. Stabilizing or disrupting the structure of actin filaments (AFs) inhibits or promotes the fusion of vacuoles, which delays or induces PCD. In addition, the inhibitors of the vacuolar processing enzyme (VPE) and cathepsin B (CathB) block the occurrence of the large central vacuole and delay the progression of PCD in rice aleurone layers. Overall, our findings provide further evidence for the rupture of the large central vacuole triggering the PCD in aleruone layers.
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17
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Ho R, Stroupe C. The HOPS/Class C Vps Complex Tethers High-Curvature Membranes via a Direct Protein-Membrane Interaction. Traffic 2016; 17:1078-90. [PMID: 27307091 DOI: 10.1111/tra.12421] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 06/13/2016] [Accepted: 06/13/2016] [Indexed: 01/13/2023]
Abstract
Membrane tethering is a physical association of two membranes before their fusion. Many membrane tethering factors have been identified, but the interactions that mediate inter-membrane associations remain largely a matter of conjecture. Previously, we reported that the homotypic fusion and protein sorting/Class C vacuolar protein sorting (HOPS/Class C Vps) complex, which has two binding sites for the yeast vacuolar Rab GTPase Ypt7p, can tether two low-curvature liposomes when both membranes bear Ypt7p. Here, we show that HOPS tethers highly curved liposomes to Ypt7p-bearing low-curvature liposomes even when the high-curvature liposomes are protein-free. Phosphorylation of the curvature-sensing amphipathic lipid-packing sensor (ALPS) motif from the Vps41p HOPS subunit abrogates tethering of high-curvature liposomes. A HOPS complex without its Vps39p subunit, which contains one of the Ypt7p binding sites in HOPS, lacks tethering activity, though it binds high-curvature liposomes and Ypt7p-bearing low-curvature liposomes. Thus, HOPS tethers highly curved membranes via a direct protein-membrane interaction. Such high-curvature membranes are found at the sites of vacuole tethering and fusion. There, vacuole membranes bend sharply, generating large areas of vacuole-vacuole contact. We propose that HOPS localizes via the Vps41p ALPS motif to these high-curvature regions. There, HOPS binds via Vps39p to Ypt7p in an apposed vacuole membrane.
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Affiliation(s)
- Ruoya Ho
- Department of Molecular Physiology and Biological Physics and Center for Membrane Biology, University of Virginia School of Medicine, Charlottesville, VA, USA
| | - Christopher Stroupe
- Department of Molecular Physiology and Biological Physics and Center for Membrane Biology, University of Virginia School of Medicine, Charlottesville, VA, USA.
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18
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Rao Y, Yang Y, Xu J, Li X, Leng Y, Dai L, Huang L, Shao G, Ren D, Hu J, Guo L, Pan J, Zeng D. EARLY SENESCENCE1 Encodes a SCAR-LIKE PROTEIN2 That Affects Water Loss in Rice. PLANT PHYSIOLOGY 2015; 169:1225-39. [PMID: 26243619 PMCID: PMC4587469 DOI: 10.1104/pp.15.00991] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 08/01/2015] [Indexed: 05/21/2023]
Abstract
The global problem of drought threatens agricultural production and constrains the development of sustainable agricultural practices. In plants, excessive water loss causes drought stress and induces early senescence. In this study, we isolated a rice (Oryza sativa) mutant, designated as early senescence1 (es1), which exhibits early leaf senescence. The es1-1 leaves undergo water loss at the seedling stage (as reflected by whitening of the leaf margin and wilting) and display early senescence at the three-leaf stage. We used map-based cloning to identify ES1, which encodes a SCAR-LIKE PROTEIN2, a component of the suppressor of cAMP receptor/Wiskott-Aldrich syndrome protein family verprolin-homologous complex involved in actin polymerization and function. The es1-1 mutants exhibited significantly higher stomatal density. This resulted in excessive water loss and accelerated water flow in es1-1, also enhancing the water absorption capacity of the roots and the water transport capacity of the stems as well as promoting the in vivo enrichment of metal ions cotransported with water. The expression of ES1 is higher in the leaves and leaf sheaths than in other tissues, consistent with its role in controlling water loss from leaves. GREEN FLUORESCENT PROTEIN-ES1 fusion proteins were ubiquitously distributed in the cytoplasm of plant cells. Collectively, our data suggest that ES1 is important for regulating water loss in rice.
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Affiliation(s)
- Yuchun Rao
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
| | - Yaolong Yang
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
| | - Jie Xu
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
| | - Xiaojing Li
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
| | - Yujia Leng
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
| | - Liping Dai
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
| | - Lichao Huang
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
| | - Guosheng Shao
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
| | - Deyong Ren
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
| | - Jiang Hu
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
| | - Longbiao Guo
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
| | - Jianwei Pan
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
| | - Dali Zeng
- State Key Laboratory of Rice Biology, China National Rice Research Institute, Hangzhou 310006, China (Y.R., Y.Y., J.X., Y.L., L.D., L.H., G.S., D.R., J.H., L.G., D.Z.);College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua 321004, China (Y.R., X.L., J.P.); andKey Laboratory of Crop Physiology, Ecology, and Genetic Breeding, Ministry of Education, Jiangxi Agricultural University, Nanchang 330045, China (Y.Y., J.X.)
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19
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Gavrin A, Jansen V, Ivanov S, Bisseling T, Fedorova E. ARP2/3-Mediated Actin Nucleation Associated With Symbiosome Membrane Is Essential for the Development of Symbiosomes in Infected Cells of Medicago truncatula Root Nodules. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:605-14. [PMID: 25608180 DOI: 10.1094/mpmi-12-14-0402-r] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The nitrogen-fixing rhizobia in the symbiotic infected cells of root nodules are kept in membrane compartments derived from the host cell plasma membrane, forming what are known as symbiosomes. These are maintained as individual units, with mature symbiosomes having a specific radial position in the host cell cytoplasm. The mechanisms that adapt the host cell architecture to accommodate intracellular bacteria are not clear. The intracellular organization of any cell depends heavily on the actin cytoskeleton. Dynamic rearrangement of the actin cytoskeleton is crucial for cytoplasm organization and intracellular trafficking of vesicles and organelles. A key component of the actin cytoskeleton rearrangement is the ARP2/3 complex, which nucleates new actin filaments and forms branched actin networks. To clarify the role of the ARP2/3 complex in the development of infected cells and symbiosomes, we analyzed the pattern of actin microfilaments and the functional role of ARP3 in Medicago truncatula root nodules. In infected cells, ARP3 protein and actin were spatially associated with maturing symbiosomes. Partial ARP3 silencing causes defects in symbiosome development; in particular, ARP3 silencing disrupts the final differentiation steps in functional maturation into nitrogen-fixing units.
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Affiliation(s)
- Aleksandr Gavrin
- Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, 6708PB, Wageningen, The Netherlands
| | - Veerle Jansen
- Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, 6708PB, Wageningen, The Netherlands
| | - Sergey Ivanov
- Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, 6708PB, Wageningen, The Netherlands
| | - Ton Bisseling
- Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, 6708PB, Wageningen, The Netherlands
| | - Elena Fedorova
- Laboratory of Molecular Biology, Wageningen University, Droevendaalsesteeg 1, 6708PB, Wageningen, The Netherlands
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20
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Shaham S. Glial development and function in the nervous system of Caenorhabditis elegans. Cold Spring Harb Perspect Biol 2015; 7:a020578. [PMID: 25573712 DOI: 10.1101/cshperspect.a020578] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The nematode, Caenorhabditis elegans, has served as a fruitful setting for understanding conserved biological processes. The past decade has seen the rise of this model organism as an important tool for uncovering the mysteries of the glial cell, which partners with neurons to generate a functioning nervous system in all animals. C. elegans affords unparalleled single-cell resolution in vivo in examining glia-neuron interactions, and similarities between C. elegans and vertebrate glia suggest that lessons learned from this nematode are likely to have general implications. Here, I summarize what has been gleaned over the past decade since C. elegans glia research became a concerted area of focus. Studies have revealed that glia are essential elements of a functioning C. elegans nervous system and play key roles in its development. Importantly, glial influence on neuronal function appears to be dynamic. Key questions for the field to address in the near- and long-term have emerged, and these are discussed within.
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Affiliation(s)
- Shai Shaham
- Laboratory of Developmental Genetics, The Rockefeller University, New York, New York 10065
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21
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Bodman JAR, Yang Y, Logan MR, Eitzen G. Yeast translation elongation factor-1A binds vacuole-localized Rho1p to facilitate membrane integrity through F-actin remodeling. J Biol Chem 2015; 290:4705-4716. [PMID: 25561732 DOI: 10.1074/jbc.m114.630764] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rho GTPases are molecular switches that modulate a variety of cellular processes, most notably those involving actin dynamics. We have previously shown that yeast vacuolar membrane fusion requires re-organization of actin filaments mediated by two Rho GTPases, Rho1p and Cdc42p. Cdc42p initiates actin polymerization to facilitate membrane tethering; Rho1p has a role in the late stages of vacuolar fusion, but its mode of action is unknown. Here, we identified eEF1A as a vacuolar Rho1p-interacting protein. eEF1A (encoded by the TEF1 and TEF2 genes in yeast) is an aminoacyl-tRNA transferase needed during protein translation. eEF1A also has a second function that is independent of translation; it binds and organizes actin filaments into ordered cable structures. Here, we report that eEF1A interacts with Rho1p via a C-terminal subdomain. This interaction occurs predominantly when both proteins are in the GDP-bound state. Therefore, eEF1A is an atypical downstream effector of Rho1p. eEF1A does not promote vacuolar fusion; however, overexpression of the Rho1p-interacting subdomain affects vacuolar morphology. Vacuoles were destabilized and prone to leakage when treated with the eEF1A inhibitor narciclasine. We propose a model whereby eEF1A binds to Rho1p-GDP on the vacuolar membrane; it is released upon Rho1p activation and then bundles actin filaments to stabilize fused vacuoles. Therefore, the Rho1p-eEF1A complex acts to spatially localize a pool of eEF1A to vacuoles where it can readily organize F-actin.
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Affiliation(s)
- James A R Bodman
- From the Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Yang Yang
- From the Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Michael R Logan
- From the Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Gary Eitzen
- From the Department of Cell Biology, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
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22
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Zhang C, Hicks GR, Raikhel NV. Plant vacuole morphology and vacuolar trafficking. FRONTIERS IN PLANT SCIENCE 2014; 5:476. [PMID: 25309565 PMCID: PMC4173805 DOI: 10.3389/fpls.2014.00476] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Accepted: 08/29/2014] [Indexed: 05/23/2023]
Abstract
Plant vacuoles are essential organelles for plant growth and development, and have multiple functions. Vacuoles are highly dynamic and pleiomorphic, and their size varies depending on the cell type and growth conditions. Vacuoles compartmentalize different cellular components such as proteins, sugars, ions and other secondary metabolites and play critical roles in plants response to different biotic/abiotic signaling pathways. In this review, we will summarize the patterns of changes in vacuole morphology in certain cell types, our understanding of the mechanisms of plant vacuole biogenesis, and the role of SNAREs and Rab GTPases in vacuolar trafficking.
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Affiliation(s)
- Chunhua Zhang
- *Correspondence: Chunhua Zhang, Center for Plant Cell Biology and Department of Botany and Plant Sciences, University of California at Riverside, 900 University Avenue, Riverside, CA 92521, USA e-mail:
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23
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Sasser TL, Fratti RA. Class C ABC transporters and Saccharomyces cerevisiae vacuole fusion. CELLULAR LOGISTICS 2014; 4:e943588. [PMID: 25610719 DOI: 10.4161/21592780.2014.943588] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 06/18/2014] [Indexed: 01/05/2023]
Abstract
Membrane fusion is carried out by core machinery that is conserved throughout eukaryotes. This is comprised of Rab GTPases and their effectors, and SNARE proteins, which together are sufficient to drive the fusion of reconstituted proteoliposomes. However, an outer layer of factors that are specific to individual trafficking pathways in vivo regulates the spatial and temporal occurrence of fusion. The homotypic fusion of Saccharomyces cerevisiae vacuolar lysosomes utilizes a growing set of factors to regulate the fusion machinery that include members of the ATP binding cassette (ABC) transporter family. Yeast vacuoles have five class C ABC transporters that are known to transport a variety of toxins into the vacuole lumen as part of detoxifying the cell. We have found that ABCC transporters can also regulate vacuole fusion through novel mechanisms. For instance Ybt1 serves as negative regulator of fusion through its effects on vacuolar Ca2+ homeostasis. Additional studies showed that Ycf1 acts as a positive regulator by affecting the efficient recruitment of the SNARE Vam7. Finally, we discuss the potential interface between the translocation of lipids across the membrane bilayer, also known as lipid flipping, and the efficiency of fusion.
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Key Words
- ABC, ATP binding cassette
- Bpt1
- Ca2+ homeostasis
- DAG, diacylglycerol
- HOPS, homotypic fusion and vacuole protein sorting complex
- MDR, multidrug resistance
- MSD, membrane spanning domain
- NBD, nucleotide binding domain
- Nft1
- PA, phosphatidic acid
- PC, phosphatidylcholine
- PE, phosphatidylethanolamine
- PI(3, 5)P2, phosphatidylinositol 3, 5-bisphosphate
- PI, phosphatidylinositol
- PI3P
- PI3P, phosphatidylinositol 3-phosphate
- PS, phosphatidylserine
- PX, phox homology
- SNARE
- SNARE, soluble N-ethylmaleimide-sensitive factor attachment protein receptors
- Vam7
- Vmr1
- Ybt1
- Ycf1
- lipid flipping
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Affiliation(s)
- Terry L Sasser
- Department of Biochemistry; University of Illinois at Urbana-Champaign ; Urbana, IL USA
| | - Rutilio A Fratti
- Department of Biochemistry; University of Illinois at Urbana-Champaign ; Urbana, IL USA
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Croisé P, Estay-Ahumada C, Gasman S, Ory S. Rho GTPases, phosphoinositides, and actin: a tripartite framework for efficient vesicular trafficking. Small GTPases 2014; 5:e29469. [PMID: 24914539 DOI: 10.4161/sgtp.29469] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Rho GTPases are well known regulators of the actin cytoskeleton that act by binding and activating actin nucleators. They are therefore involved in many actin-based processes, including cell migration, cell polarity, and membrane trafficking. With the identification of phosphoinositide kinases and phosphatases as potential binding partners or effectors, Rho GTPases also appear to participate in the regulation of phosphoinositide metabolism. Since both actin dynamics and phosphoinositide turnover affect the efficiency and the fidelity of vesicle transport between cell compartments, Rho GTPases have emerged as critical players in membrane trafficking. Rho GTPase activity, actin remodeling, and phosphoinositide metabolism need to be coordinated in both space and time to ensure the progression of vesicles along membrane trafficking pathways. Although most molecular pathways are still unclear, in this review, we will highlight recent advances made in our understanding of how Rho-dependent signaling pathways organize actin dynamics and phosphoinositides and how phosphoinositides potentially provide negative feedback to Rho GTPases during endocytosis, exocytosis and membrane exchange between intracellular compartments.
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Affiliation(s)
- Pauline Croisé
- CNRS UPR 3212; Institut des Neurosciences Cellulaires et Intégratives; Université de Strasbourg; Strasbourg, France
| | - Catherine Estay-Ahumada
- CNRS UPR 3212; Institut des Neurosciences Cellulaires et Intégratives; Université de Strasbourg; Strasbourg, France
| | - Stéphane Gasman
- CNRS UPR 3212; Institut des Neurosciences Cellulaires et Intégratives; Université de Strasbourg; Strasbourg, France
| | - Stéphane Ory
- CNRS UPR 3212; Institut des Neurosciences Cellulaires et Intégratives; Université de Strasbourg; Strasbourg, France
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Zheng J, Han SW, Rodriguez-Welsh MF, Rojas-Pierce M. Homotypic vacuole fusion requires VTI11 and is regulated by phosphoinositides. MOLECULAR PLANT 2014; 7:1026-1040. [PMID: 24569132 DOI: 10.1093/mp/ssu019] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Most plant cells contain a large central vacuole that is essential to maintain cellular turgor. We report a new mutant allele of VTI11 that implicates the SNARE protein VTI11 in homotypic fusion of protein storage and lytic vacuoles. Fusion of the multiple vacuoles present in vti11 mutants could be induced by treatment with Wortmannin and LY294002, which are inhibitors of Phosphatidylinositol 3-Kinase (PI3K). We provide evidence that Phosphatidylinositol 3-Phosphate (PtdIns(3)P) regulates vacuole fusion in vti11 mutants, and that fusion of these vacuoles requires intact microtubules and actin filaments. Finally, we show that Wortmannin also induced the fusion of guard cell vacuoles in fava beans, where vacuoles are naturally fragmented after ABA-induced stomata closure. These results suggest a ubiquitous role of phosphoinositides in vacuole fusion, both during the development of the large central vacuole and during the dynamic vacuole remodeling that occurs as part of stomata movements.
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Affiliation(s)
- Jiameng Zheng
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA
| | - Sang Won Han
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA
| | | | - Marcela Rojas-Pierce
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA.
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26
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Oikonomou G, Shaham S. On the morphogenesis of glial compartments in the sensory organs of Caenorhabditis elegans. WORM 2013; 1:51-5. [PMID: 24058823 PMCID: PMC3670172 DOI: 10.4161/worm.19343] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Glial cells surround neuronal endings and isolate them within specialized compartments. This architecture is found at synapses in the central nervous system, as well as at receptive endings of sensory neurons. Recent studies are beginning to uncover the contributions of glial compartments to the functions of the ensheathed neurons. However, the cellular and molecular processes that guide compartment morphogenesis remain unknown. The main sensory organ of Caenorhabditis elegans, the amphid, provides an experimentally tractable setting in which to address the mechanisms underlying glial compartment formation. Amphid development is stereotyped and amphid structure is easily assayed. We recently uncovered a molecular tug of war that regulates the size of the amphid sensory compartment. The Nemo-like kinase LIT-1 interacts with the glial cytoskeleton to promote compartment growth, a process that also involves components of the retromer complex, while the Patched-related transmembrane protein DAF-6 keeps this expansion in check. Here we discuss how regulation of secretion by the cytoskeleton could guide the sculpting of glial compartments.
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Affiliation(s)
- Grigorios Oikonomou
- Laboratory of Developmental Genetics; The Rockefeller University; New York, NY USA
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The MAP kinase Slt2 is involved in vacuolar function and actin remodeling in Saccharomyces cerevisiae mutants affected by endogenous oxidative stress. Appl Environ Microbiol 2013; 79:6459-71. [PMID: 23956390 DOI: 10.1128/aem.01692-13] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Oxidative stress causes transient actin cytoskeleton depolarization and also provokes vacuole fragmentation in wild-type cells. Under conditions of oxidative stress induced by hydrogen peroxide, the Slt2 protein is required to repolarize the actin cytoskeleton and to promote vacuole fusion. In this study, we show that grx3 grx4 and grx5 mutants are cellular models of endogenous oxidative stress. This stress is the result of alterations in iron homeostasis that lead to impairment of vacuolar function and also to disorganization of the actin cytoskeleton. Slt2 overexpression suppresses defects in vacuolar function and actin cytoskeleton organization in the grx3 grx4 mutant. Slt2 exerts this effect independently of the intracellular levels of reactive oxygen species (ROS) and of iron homeostasis. The deletion of SLT2 in the grx3 grx4 mutant results in synthetic lethality related to vacuolar function with substantial vacuole fragmentation. The observation that both Vps4 and Vps73 (two proteins related to vacuole sorting) suppress vacuole fragmentation and actin depolarization in the grx3 grx4 slt2 triple mutant strengthens the hypothesis that Slt2 plays a role in vacuole homeostasis related to actin dynamics. Here we show that in sod1, grx5, and grx3 grx4 slt2 mutants, all of which are affected by chronic oxidative stress, the overexpression of Slt2 favors vacuole fusion through a mechanism dependent on an active actin cytoskeleton.
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Abbineni PS, Hibbert JE, Coorssen JR. Critical role of cortical vesicles in dissecting regulated exocytosis: overview of insights into fundamental molecular mechanisms. THE BIOLOGICAL BULLETIN 2013; 224:200-217. [PMID: 23995744 DOI: 10.1086/bblv224n3p200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Regulated exocytosis is one of the defining features of eukaryotic cells, underlying many conserved and essential functions. Definitively assigning specific roles to proteins and lipids in this fundamental mechanism is most effectively accomplished using a model system in which distinct stages of exocytosis can be effectively separated. Here we discuss the establishment of sea urchin cortical vesicle fusion as a model to study regulated exocytosis-a system in which the docked, release-ready, and late Ca(2+)-triggered steps of exocytosis are isolated and can be quantitatively assessed using the rigorous coupling of functional and molecular assays. We provide an overview of the insights this has provided into conserved molecular mechanisms and how these have led to and integrate with findings from other regulated exocytotic cells.
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Affiliation(s)
- Prabhodh S Abbineni
- Department of Molecular Physiology, School of Medicine, University of Western Sydney, NSW, Australia
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29
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Sasser TL, Lawrence G, Karunakaran S, Brown C, Fratti RA. The yeast ATP-binding cassette (ABC) transporter Ycf1p enhances the recruitment of the soluble SNARE Vam7p to vacuoles for efficient membrane fusion. J Biol Chem 2013; 288:18300-10. [PMID: 23658021 DOI: 10.1074/jbc.m112.441089] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The Saccharomyces cerevisiae vacuole contains five ATP-binding cassette class C (ABCC) transporters, including Ycf1p, a family member that was originally characterized as a Cd(2+) transporter. Ycf1p has also been found to physically interact with a wide array of proteins, including factors that regulate vacuole homeostasis. In this study, we examined the role of Ycf1p and other ABCC transporters in the regulation of vacuole homotypic fusion. We found that deletion of YCF1 attenuated in vitro vacuole fusion by up to 40% relative to wild-type vacuoles. Plasmid-expressed wild-type Ycf1p rescued the deletion phenotype; however, Ycf1p containing a mutation of the conserved Lys-669 to Met in the Walker A box of the first nucleotide-binding domain (Ycf1p(K669M)) was unable to complement the fusion defect of ycf1Δ vacuoles. This indicates that the ATPase activity of Ycf1p is required for its function in regulating fusion. In addition, we found that deleting YCF1 caused a striking decrease in vacuolar levels of the soluble SNARE Vam7p, whereas total cellular levels were not altered. The attenuated fusion of ycf1Δ vacuoles was rescued by the addition of recombinant Vam7p to in vitro experiments. Thus, Ycf1p contributes in the recruitment of Vam7p to the vacuole for efficient membrane fusion.
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Affiliation(s)
- Terry L Sasser
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Rodrigues J, Silva RD, Noronha H, Pedras A, Gerós H, Côrte-Real M. Flow cytometry as a novel tool for structural and functional characterization of isolated yeast vacuoles. Microbiology (Reading) 2013; 159:848-856. [DOI: 10.1099/mic.0.062570-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Affiliation(s)
- Jorge Rodrigues
- Departamento de Biologia, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- Centro de Biologia Molecular e Ambiental (CBMA), Departamento de Biologia, Campus de Gualtar, 4710-057 Braga, Portugal
| | - Rui D. Silva
- Departamento de Biologia, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- Centro de Biologia Molecular e Ambiental (CBMA), Departamento de Biologia, Campus de Gualtar, 4710-057 Braga, Portugal
| | - Henrique Noronha
- Centro de Investigação e de Tecnologias Agro-Ambientais e Biológicas (CITAB), Quinta de Prados, 5001-801 Vila Real, Portugal
- Departamento de Biologia, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - Andreia Pedras
- Departamento de Biologia, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- Centro de Biologia Molecular e Ambiental (CBMA), Departamento de Biologia, Campus de Gualtar, 4710-057 Braga, Portugal
| | - Hernâni Gerós
- Centro de Investigação e de Tecnologias Agro-Ambientais e Biológicas (CITAB), Quinta de Prados, 5001-801 Vila Real, Portugal
- Departamento de Biologia, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - Manuela Côrte-Real
- Departamento de Biologia, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal
- Centro de Biologia Molecular e Ambiental (CBMA), Departamento de Biologia, Campus de Gualtar, 4710-057 Braga, Portugal
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Solinger JA, Spang A. Tethering complexes in the endocytic pathway: CORVET and HOPS. FEBS J 2013; 280:2743-57. [PMID: 23351085 DOI: 10.1111/febs.12151] [Citation(s) in RCA: 138] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Revised: 01/10/2013] [Accepted: 01/23/2013] [Indexed: 12/21/2022]
Abstract
Endocytosis describes the processes by which proteins, peptides and solutes, and also pathogens, enter the cell. Endocytosed material progresses to endosomes. Genetic studies in yeast, worms, flies and mammals have identified a set of universally conserved proteins that are essential for early-to-late endosome transition and lysosome biogenesis, and for endolysosomal trafficking pathways, including autophagy. The two Vps-C complexes CORVET (class C core vacuole/endosome tethering) and HOPS (homotypic fusion and vacuole protein sorting) perform diverse biochemical functions in endocytosis: they tether membranes, interact with Rab GTPases, activate and proof-read SNARE assembly to drive membrane fusion, and possibly attach endosomes to the cytoskeleton. In addition, several of the CORVET and HOPS subunits have diversified in metazoans, and probably form additional specialized complexes to accomodate the higher complexity of trafficking pathways in these cells. Recent studies offer new insights into the complex relationships between CORVET and HOPS complexes and other factors of the endolysosomal pathway. Interactions with V-ATPase, the ESCRT machinery, phosphoinositides, the cytoskeleton and the Rab switch suggest an intricate cooperative network for endosome maturation. Accumulating evidence supports the view that endosomal tethering complexes implement a regulatory logic that governs endomembrane identity and dynamics.
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Li LJ, Ren F, Gao XQ, Wei PC, Wang XC. The reorganization of actin filaments is required for vacuolar fusion of guard cells during stomatal opening in Arabidopsis. PLANT, CELL & ENVIRONMENT 2013; 36:484-97. [PMID: 22891733 DOI: 10.1111/j.1365-3040.2012.02592.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The reorganization of actin filaments (AFs) and vacuoles in guard cells is involved in the regulation of stomatal movement. However, it remains unclear whether there is any interaction between the reorganization of AFs and vacuolar changes during stomatal movement. Here, we report the relationship between the reorganization of AFs and vacuolar fusion revealed in pharmacological experiments, and characterizing stomatal opening in actin-related protein 2 (arp2) and arp3 mutants. Our results show that cytochalasin-D-induced depolymerization or phalloidin-induced stabilization of AFs leads to an increase in small unfused vacuoles during stomatal opening in wild-type (WT) Arabidopsis plants. Light-induced stomatal opening is retarded and vacuolar fusion in guard cells is impaired in the mutants, in which the reorganization and the dynamic parameters of AFs are aberrant compared with those of the WT. In WT, AFs tightly surround the small separated vacuoles, forming a ring that encircles the boundary membranes of vacuoles partly fused during stomatal opening. In contrast, in the mutants, most AFs and actin patches accumulate abnormally around the nuclei of the guard cells, which probably further impair vacuolar fusion and retard stomatal opening. Our results suggest that the reorganization of AFs regulates vacuolar fusion in guard cells during stomatal opening.
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Affiliation(s)
- Li-Juan Li
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
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33
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Zhang C, Mallery EL, Szymanski DB. ARP2/3 localization in Arabidopsis leaf pavement cells: a diversity of intracellular pools and cytoskeletal interactions. FRONTIERS IN PLANT SCIENCE 2013; 4:238. [PMID: 23874346 PMCID: PMC3709099 DOI: 10.3389/fpls.2013.00238] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Accepted: 06/16/2013] [Indexed: 05/03/2023]
Abstract
In plant cells the actin cytoskeleton adopts many configurations, but is best understood as an unstable, interconnected track that rearranges to define the patterns of long distance transport of organelles during growth. Actin filaments do not form spontaneously; instead filament nucleators, such as the evolutionarily conserved actin-related protein (ARP) 2/3 complex, can efficiently generate new actin filament networks when in a fully activated state. A growing number of genetic experiments have shown that ARP2/3 is necessary for morphogenesis in processes that range from tip growth during root nodule formation to the diffuse polarized growth of leaf trichomes and pavement cells. Although progress has been rapid in the identification of proteins that function in series to positively regulate ARP2/3, less has been learned about the actual function of ARP2/3 in cells. In this paper, we analyze the localization of ARP2/3 in Arabidopsis leaf pavement cells. We detect a pool of ARP2/3 in the nucleus, and also find that ARP2/3 is efficiently and specifically clustered on multiple organelle surfaces and associates with both the actin filament and microtubule cytoskeletons. Our mutant analyses and ARP2/3 and actin double labeling experiments indicate that the clustering of ARP2/3 on organelle surfaces and an association with actin bundles does not necessarily reflect an active pool of ARP2/3, and instead most of the complex appears to exist as a latent organelle-associated pool.
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Affiliation(s)
- Chunhua Zhang
- Department of Agronomy, Purdue UniversityWest Lafayette, IN, USA
| | | | - Daniel B. Szymanski
- Department of Agronomy, Purdue UniversityWest Lafayette, IN, USA
- Department of Biology, Purdue UniversityWest Lafayette, IN, USA
- *Correspondence: Daniel B. Szymanski, Department of Agronomy, Purdue University, Lily Hall of Life Sciences, 915 West State Street, West Lafayette, IN 47907-2054, USA e-mail:
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34
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35
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Abstract
Cdc42 is a key factor in the control of cell polarity and morphogenesis. Fission yeast Cdc42 regulates formin activation and actin cable assembly. Cdc42 is also required for exocyst function, contributing to polarized secretion. Additionally, Cdc42 participates in membrane trafficking, endosome recycling, and vacuole formation. We show here how Cdc42 is required for the correct transport/recycling to the plasma membrane of the glucan synthases Bgs1 and Bgs4, responsible of cell wall biosynthesis and polarized growth at the cell tips.
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Affiliation(s)
- Miguel Estravis
- CSIC; Departamento de Microbiología y Genética; Instituto de Biología Funcional y Genómica; Universidad de Salamanca; Edificio Departamental; Salamanca, Spain
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36
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Karunakaran S, Sasser T, Rajalekshmi S, Fratti RA. SNAREs, HOPS and regulatory lipids control the dynamics of vacuolar actin during homotypic fusion in S. cerevisiae. J Cell Sci 2012; 125:1683-92. [PMID: 22357954 DOI: 10.1242/jcs.091900] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Homotypic vacuole fusion requires SNAREs, the Rab Ypt7p, the tethering complex HOPS, regulatory lipids and actin. In Saccharomyces cerevisiae, actin functions at two stages of vacuole fusion. Pre-existing actin filaments are depolymerized to allow docking and assembly of the vertex ring (a microdomain enriched in proteins and lipids that mediate fusion). Actin is then polymerized late in the pathway to aid fusion. Here, we report that the fusion machinery regulates the accumulation of actin at the vertex ring. Using Cy3-labeled yeast actin to track its dynamics, we found that its vertex enrichment was abolished when actin monomers were stabilized by latrunculin-B, independent of the extent of incorporation. By contrast, stabilization of filamentous actin with jasplakinolide markedly augmented actin vertex enrichment. Importantly, agents that inhibit SNAREs, Ypt7p and HOPS inhibited the vertex enrichment of actin, demonstrating that the cytoskeleton and the fusion machinery are interdependently regulated. Actin mobilization was also inhibited by ligating ergosterol and PtdIns(3)P, whereas the ligation or modification of PtdIns(4,5)P(2) augmented the vertex enrichment of actin. The proteins and lipids that regulated actin mobilization to the vertex did not affect the total incorporation of Cy3-actin, indicating that actin mobilization and polymerization activities can be dissociated during membrane fusion.
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Affiliation(s)
- Surya Karunakaran
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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37
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Regulation of vacuolar H+-ATPase activity by the Cdc42 effector Ste20 in Saccharomyces cerevisiae. EUKARYOTIC CELL 2012; 11:442-51. [PMID: 22327006 DOI: 10.1128/ec.05286-11] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the budding yeast Saccharomyces cerevisiae, the Cdc42 effector Ste20 plays a crucial role in the regulation of filamentous growth, a response to nutrient limitation. Using the split-ubiquitin technique, we found that Ste20 forms a complex with Vma13, an important regulatory subunit of vacuolar H(+)-ATPase (V-ATPase). This protein-protein interaction was confirmed by a pulldown assay and coimmunoprecipitation. We also demonstrate that Ste20 associates with vacuolar membranes and that Ste20 stimulates V-ATPase activity in isolated vacuolar membranes. This activation requires Ste20 kinase activity and does not depend on increased assembly of the V1 and V0 sectors of the V-ATPase, which is a major regulatory mechanism. Furthermore, loss of V-ATPase activity leads to a strong increase in invasive growth, possibly because these cells fail to store and mobilize nutrients efficiently in the vacuole in the absence of the vacuolar proton gradient. In contrast to the wild type, which grows in rather small, isolated colonies on solid medium during filamentation, hyperinvasive vma mutants form much bigger aggregates in which a large number of cells are tightly clustered together. Genetic data suggest that Ste20 and the protein kinase A catalytic subunit Tpk2 are both activated in the vma13Δ strain. We propose that during filamentous growth, Ste20 stimulates V-ATPase activity. This would sustain nutrient mobilization from vacuolar stores, which is beneficial for filamentous growth.
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38
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Kallay LM, Brett CL, Tukaye DN, Wemmer MA, Chyou A, Odorizzi G, Rao R. Endosomal Na+ (K+)/H+ exchanger Nhx1/Vps44 functions independently and downstream of multivesicular body formation. J Biol Chem 2011; 286:44067-44077. [PMID: 21998311 DOI: 10.1074/jbc.m111.282319] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The multivesicular body (MVB) is an endosomal intermediate containing intralumenal vesicles destined for membrane protein degradation in the lysosome. In Saccharomyces cerevisiae, the MVB pathway is composed of 17 evolutionarily conserved ESCRT (endosomal sorting complex required for transport) genes grouped by their vacuole protein sorting Class E mutant phenotypes. Only one integral membrane protein, the endosomal Na+ (K+)/H+ exchanger Nhx1/Vps44, has been assigned to this class, but its role in the MVB pathway has not been directly tested. Herein, we first evaluated the link between Nhx1 and the ESCRT proteins and then used an unbiased phenomics approach to probe the cellular role of Nhx1. Select ESCRT mutants (vps36Δ, vps20Δ, snf7Δ, and bro1Δ) with defects in cargo packaging and intralumenal vesicle formation shared multiple growth phenotypes with nhx1Δ. However, analysis of cellular trafficking and ultrastructural examination by electron microscopy revealed that nhx1Δ cells retain the ability to sort cargo into intralumenal vesicles. In addition, we excluded a role for Nhx1 in Snf7/Bro1-mediated cargo deubiquitylation and Rim101 response to pH stress. Genetic epistasis experiments provided evidence that NHX1 and ESCRT genes function in parallel. A genome-wide screen for single gene deletion mutants that phenocopy nhx1Δ yielded a limited gene set enriched for endosome fusion function, including Rab signaling and actin cytoskeleton reorganization. In light of these findings and the absence of the so-called Class E compartment in nhx1Δ, we eliminated a requirement for Nhx1 in MVB formation and suggest an alternative post-ESCRT role in endosomal membrane fusion.
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Affiliation(s)
- Laura M Kallay
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Christopher L Brett
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205; Department of Biology, Concordia University, Montréal, Quebec H3G 1M8, Canada
| | - Deepali N Tukaye
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Megan A Wemmer
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309
| | - Anthony Chyou
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Greg Odorizzi
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309
| | - Rajini Rao
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
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Abstract
Being deeply connected to signalling, cell dynamics, growth, regulation, and defence, endocytic processes are linked to almost all aspects of cell life and disease. In this review, we focus on endosomes in the classical endocytic pathway, and on the programme of changes that lead to the formation and maturation of late endosomes/multivesicular bodies. The maturation programme entails a dramatic transformation of these dynamic organelles disconnecting them functionally and spatially from early endosomes and preparing them for their unidirectional role as a feeder pathway to lysosomes.
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40
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Oikonomou G, Perens EA, Lu Y, Watanabe S, Jorgensen EM, Shaham S. Opposing activities of LIT-1/NLK and DAF-6/patched-related direct sensory compartment morphogenesis in C. elegans. PLoS Biol 2011; 9:e1001121. [PMID: 21857800 PMCID: PMC3153439 DOI: 10.1371/journal.pbio.1001121] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Accepted: 06/28/2011] [Indexed: 12/23/2022] Open
Abstract
Glial cells surround neuronal endings to create enclosed compartments required for neuronal function. This architecture is seen at excitatory synapses and at sensory neuron receptive endings. Despite the prevalence and importance of these compartments, how they form is not known. We used the main sensory organ of C. elegans, the amphid, to investigate this issue. daf-6/Patched-related is a glia-expressed gene previously implicated in amphid sensory compartment morphogenesis. By comparing time series of electron-microscopy (EM) reconstructions of wild-type and daf-6 mutant embryos, we show that daf-6 acts to restrict compartment size. From a genetic screen, we found that mutations in the gene lit-1/Nemo-like kinase (NLK) suppress daf-6. EM and genetic studies demonstrate that lit-1 acts within glia, in counterbalance to daf-6, to promote sensory compartment expansion. Although LIT-1 has been shown to regulate Wnt signaling, our genetic studies demonstrate a novel, Wnt-independent role for LIT-1 in sensory compartment size control. The LIT-1 activator MOM-4/TAK1 is also important for compartment morphogenesis and both proteins line the glial sensory compartment. LIT-1 compartment localization is important for its function and requires neuronal signals. Furthermore, the conserved LIT-1 C-terminus is necessary and sufficient for this localization. Two-hybrid and co-immunoprecipitation studies demonstrate that the LIT-1 C-terminus binds both actin and the Wiskott-Aldrich syndrome protein (WASP), an actin regulator. We use fluorescence light microscopy and fluorescence EM methodology to show that actin is highly enriched around the amphid sensory compartment. Finally, our genetic studies demonstrate that WASP is important for compartment expansion and functions in the same pathway as LIT-1. The studies presented here uncover a novel, Wnt-independent role for the conserved Nemo-like kinase LIT-1 in controlling cell morphogenesis in conjunction with the actin cytoskeleton. Our results suggest that the opposing daf-6 and lit-1 glial pathways act together to control sensory compartment size. The nervous system of most animals consists of two related cell types, neurons and glia. A striking property of glia is their ability to ensheath neuronal cells, which can help increase the efficiency of synaptic communication between neurons. Sensory neuron receptive endings in the periphery, as well as excitatory synapses in the central nervous system, often lie within specialized compartments formed by glial processes. Despite the prevalence of these compartments, and their importance for neuronal function and signal transmission, little is known about how they form. We have used the amphid, the main sensory organ of the worm Caenorhabditis elegans, to investigate glial sensory compartment morphogenesis. We demonstrate that the glia-expressed gene daf-6/Patched-related acts to restrict the size of the sensory compartment, while the Nemo-like kinase lit-1 acts within glia in the opposite direction, to promote sensory compartment expansion. We show that LIT-1 localizes to the sensory compartment through a highly conserved domain. This domain can interact both with actin, which outlines the compartment, and with the regulator of actin polymerization WASP, which acts in the same pathway as lit-1. We postulate that Nemo-like kinases could have broader roles as regulators of cellular morphogenesis, in addition to their traditional role in regulating the Wnt signaling pathway.
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Affiliation(s)
- Grigorios Oikonomou
- Laboratory of Developmental Genetics, The Rockefeller University, New York, New York, United States of America
| | - Elliot A. Perens
- Laboratory of Developmental Genetics, The Rockefeller University, New York, New York, United States of America
| | - Yun Lu
- Laboratory of Developmental Genetics, The Rockefeller University, New York, New York, United States of America
| | - Shigeki Watanabe
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
| | - Erik M. Jorgensen
- Howard Hughes Medical Institute, Department of Biology, University of Utah, Salt Lake City, Utah, United States of America
| | - Shai Shaham
- Laboratory of Developmental Genetics, The Rockefeller University, New York, New York, United States of America
- * E-mail:
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41
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Manogaran AL, Hong JY, Hufana J, Tyedmers J, Lindquist S, Liebman SW. Prion formation and polyglutamine aggregation are controlled by two classes of genes. PLoS Genet 2011; 7:e1001386. [PMID: 21625618 PMCID: PMC3098188 DOI: 10.1371/journal.pgen.1001386] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Accepted: 04/14/2011] [Indexed: 11/20/2022] Open
Abstract
Prions are self-perpetuating aggregated proteins that are not limited to mammalian systems but also exist in lower eukaryotes including yeast. While much work has focused around chaperones involved in prion maintenance, including Hsp104, little is known about factors involved in the appearance of prions. De novo appearance of the [PSI+] prion, which is the aggregated form of the Sup35 protein, is dramatically enhanced by transient overexpression of SUP35 in the presence of the prion form of the Rnq1 protein, [PIN+]. When fused to GFP and overexpressed in [ps−] [PIN+] cells, Sup35 forms fluorescent rings, and cells with these rings bud off [PSI+] daughters. We investigated the effects of over 400 gene deletions on this de novo induction of [PSI+]. Two classes of gene deletions were identified. Class I deletions (bug1Δ, bem1Δ, arf1Δ, and hog1Δ) reduced the efficiency of [PSI+] induction, but formed rings normally. Class II deletions (las17Δ, vps5Δ, and sac6Δ) inhibited both [PSI+] induction and ring formation. Furthermore, class II deletions reduced, while class I deletions enhanced, toxicity associated with the expanded glutamine repeats of the huntingtin protein exon 1 that causes Huntington's disease. This suggests that prion formation and polyglutamine aggregation involve a multi-phase process that can be inhibited at different steps. Certain proteins that exist in functional unaggregated conformers can also form self-perpetuating infectious aggregates called prions. Here we investigate factors involved in the initial switch to the prion form. De novo appearance of the [PSI+] prion, which is the aggregated form of the Sup35 protein, is dramatically enhanced by overexpression of the SUP35 gene in the presence of the prion form of the Rnq1 protein, [PIN+]. When tagged with green fluorescent protein and transiently overexpressed in [psi−] [PIN+] cells, Sup35 forms fluorescent rings, and cells with these rings give rise to daughter cells that are [PSI+]. Here, we investigate factors required for this induction of [PSI+]. Analyses of over 400 gene deletions revealed two classes that reduce [PSI+] induction: one class forms fluorescent rings normally, and the other does not. Interestingly, the former class enhanced, while the latter class reduced, toxicity associated with the expanded polyglutamine repeats of the huntingtin protein exon 1 that causes Huntington's disease. These results suggest that prion formation and polyglutamine aggregation involve a multi-phase process that can be inhibited at different steps.
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Affiliation(s)
- Anita L. Manogaran
- Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, Illinois, United States of America
- Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin, United States of America
| | - Joo Y. Hong
- Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Joan Hufana
- Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, Illinois, United States of America
| | - Jens Tyedmers
- Zentrum fuer Molekulare Biologie Heidelberg, DKFZ-ZMBH-Alliance, Universitaet Heidelberg, Heidelberg, Germany
- Whitehead Institute for Biomedical Research and Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Susan Lindquist
- Whitehead Institute for Biomedical Research and Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Susan W. Liebman
- Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, Illinois, United States of America
- * E-mail:
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42
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Abstract
RhoGDIs (Rho GDP-dissociation inhibitors) are the natural inhibitors of Rho GTPases. They interfere with Rho protein function by either blocking upstream activation or association with downstream signalling molecules. RhoGDIs can also extract membrane-bound Rho GTPases to form soluble cytosolic complexes. We have shown previously that purified yeast RhoGDI Rdi1p, can inhibit vacuole membrane fusion in vitro. In the present paper we functionally dissect Rdi1p to discover its mode of regulating membrane fusion. Overexpression of Rdi1p in vivo profoundly affected cell morphology including increased actin patches in mother cells indicative of polarity defects, delayed ALP (alkaline phosphatase) sorting and the presence of highly fragmented vacuoles indicative of membrane fusion defects. These defects were not caused by the loss of typical transport and fusion proteins, but rather were linked to the reduction of membrane localization and activation of Cdc42p and Rho1p. Subcellular fractionation showed that Rdi1p is predominantly a cytosolic monomer, free of bound Rho GTPases. Overexpression of endogenous Rdi1p, or the addition of exogenous Rdi1p, generated stable cytosolic complexes. Rdi1p structure-function analysis showed that membrane association via the C-terminal β-sheet domain was required for the functional inhibition of membrane fusion. Furthermore, Rdi1p inhibited membrane fusion through the binding of Rho GTPases independent from its extraction activity.
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43
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Huang AX, She XP. Actin microfilaments and vacuoles are downstream targets of H 2O 2 signalling pathways in hyperosmotic stress-induced stomatal closure. FUNCTIONAL PLANT BIOLOGY : FPB 2011; 38:303-313. [PMID: 32480886 DOI: 10.1071/fp10079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Accepted: 02/08/2011] [Indexed: 06/11/2023]
Abstract
Changes in osmotic pressure can induce stomatal closure to reduce transpirational water loss from plants. In the present work, we investigated the mechanism underlying the perception and transduction of extracellular changes in osmotic pressure in Vicia faba L. guard cells. Using an epidermal strip bioassay and laser-scanning confocal microscopy, we provide evidence that hyperosmotic stress treatment led to stomatal closure and the rapid promotion of hydrogen peroxide (H2O2) production in V. faba guard cells. The effects were largely reduced by H2O2 scavengers ASA, CAT, NADPH oxidase inhibitor DPI and cell wall peroxidase inhibitor SHAM. These results indicate that hyperosmotic stress induces stomatal closure by promoting H2O2 production. Cytochalasin B (CB), latrunculin B (Lat B) and jasplakinolide (JK) inhibited stomatal closure induced by hyperosmotic stress but didn't prevent the increase of endogenous H2O2 levels, suggesting that microfilaments reorganisation participates in stomatal closure induced by hyperosmotic stress, and may act downstream of H2O2 signalling processes. In addition, we observed splitting of big vacuoles into many small vacuoles in response to hyperosmotic stress and H2O2 treatment, and CB inhibited these changes of vacuoles; stomatal closure was also inhibited. Taken together these results indicate that the stomatal closure in response to hyperosmotic stress may initiate H2O2 generation, and that reorganisation of microfilaments and the changing of vacuoles occurs downstream of H2O2 signalling processes.
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Affiliation(s)
- Ai-Xia Huang
- Key Laboratory of Medicinal Plant Resource and Natural Pharmaceutical Chemistry of Ministry of Education, College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China
| | - Xiao-Ping She
- College of Life Sciences, Shaanxi Normal University, Xi'an 710062, China
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44
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Rho GTPases and exocytosis: what are the molecular links? Semin Cell Dev Biol 2010; 22:27-32. [PMID: 21145407 DOI: 10.1016/j.semcdb.2010.12.002] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2010] [Revised: 12/01/2010] [Accepted: 12/01/2010] [Indexed: 02/08/2023]
Abstract
Delivery of proteins or lipids to the plasma membrane or into the extracellular space occurs through exocytosis, a process that requires tethering, docking, priming and fusion of vesicles, as well as F-actin rearrangements in response to specific extracellular cues. GTPases of the Rho family have been implicated as important regulators of exocytosis, but how Rho proteins control this process is an open question. In this review, we focus on molecular connections that drive Rho-dependent exocytosis in polarized and regulated exocytosis. Specifically, we present data showing that Rho proteins interaction with the exocyst complex and IQGAP mediates polarized exocytosis, whereas interaction with actin-binding proteins like N-WASP mediates regulated exocytosis.
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45
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Wickner W. Membrane fusion: five lipids, four SNAREs, three chaperones, two nucleotides, and a Rab, all dancing in a ring on yeast vacuoles. Annu Rev Cell Dev Biol 2010; 26:115-36. [PMID: 20521906 DOI: 10.1146/annurev-cellbio-100109-104131] [Citation(s) in RCA: 217] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Although fusion mechanisms are highly conserved in evolution and among organelles of the exocytic and endocytic pathways, yeast vacuole homotypic fusion offers unique technical advantages: excellent genetics, clear organelle cytology, in vitro colorimetric fusion assays, and reconstitution of fusion from all-pure components, including a Rab GTPase, HOPS (homotypic fusion and vacuole protein sorting complex), four SNAREs [soluble N-ethylmaleimide-sensitive factor (NSF) attachment receptors] that snare (bind) each other, SNARE-complex disassembly chaperones, and vacuolar lipids. Vacuole fusion studies offer paradigms of the interdependence of lipids and fusion proteins to assemble a fusion microdomain, distinct lipid functions, SNARE complex proofreading through the synergy between HOPS and the SNARE disassembly chaperones, and the role of each fusion protein in promoting radical bilayer restructuring for fusion without lysis.
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Affiliation(s)
- William Wickner
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755-3844, USA.
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46
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Qiu QS, Fratti RA. The Na+/H+ exchanger Nhx1p regulates the initiation of Saccharomyces cerevisiae vacuole fusion. J Cell Sci 2010; 123:3266-75. [DOI: 10.1242/jcs.067637] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Nhx1p is a Na+(K+)/H+ antiporter localized at the vacuolar membrane of the yeast Saccharomyces cerevisiae. Nhx1p regulates the acidification of cytosol and vacuole lumen, and is involved in membrane traffic from late endosomes to the vacuole. Deletion of the gene leads to aberrant vacuolar morphology and defective vacuolar protein sorting. These phenotypes are hallmarks of malfunctioning vacuole homeostasis and indicate that membrane fusion is probably altered. Here, we investigated the role of Nhx1p in the regulation of homotypic vacuole fusion. Vacuoles isolated from nhx1Δ yeast showed attenuated fusion. Assays configured to differentiate between the first round of fusion and ongoing rounds showed that nhx1Δ vacuoles were only defective in the first round of fusion, suggesting that Nhx1p regulates an early step in the pathway. Although fusion was impaired on nhx1Δ vacuoles, SNARE complex formation was indistinguishable from wild-type vacuoles. Fusion could be rescued by adding the soluble SNARE Vam7p. However, Vam7p only activated the first round of nhx1Δ vacuole fusion. Once fusion was initiated, nhx1Δ vacuoles appeared behave in a wild-type manner. Complementation studies showed that ion transport function was required for Nhx1p-mediated support of fusion. In addition, the weak base chloroquine restored nhx1Δ fusion to wild-type levels. Together, these data indicate that Nhx1p regulates the initiation of fusion by controlling vacuole lumen pH.
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Affiliation(s)
- Quan-Sheng Qiu
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- School of Life Sciences, Lanzhou University, Lanzhou City, Tianshui Road 222, 730000, China
| | - Rutilio A. Fratti
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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Woronowicz K, Dilks JR, Rozenvayn N, Dowal L, Blair PS, Peters CG, Woronowicz L, Flaumenhaft R. The platelet actin cytoskeleton associates with SNAREs and participates in alpha-granule secretion. Biochemistry 2010; 49:4533-42. [PMID: 20429610 DOI: 10.1021/bi100541t] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Following platelet activation, platelets undergo a dramatic shape change mediated by the actin cytoskeleton and accompanied by secretion of granule contents. While the actin cytoskeleton is thought to influence platelet granule secretion, the mechanism for this putative regulation is not known. We found that disruption of the actin cytoskeleton by latrunculin A inhibited alpha-granule secretion induced by several different platelet agonists without significantly affecting activation-induced platelet aggregation. In a cell-free secretory system, platelet cytosol was required for alpha-granule secretion. Inhibition of actin polymerization prevented alpha-granule secretion in this system, and purified platelet actin could substitute for platelet cytosol to support alpha-granule secretion. To determine whether SNAREs physically associate with the actin cytoskeleton, we isolated the Triton X-100 insoluble actin cytoskeleton from platelets. VAMP-8 and syntaxin-2 associated only with actin cytoskeletons of activated platelets. Syntaxin-4 and SNAP-23 associated with cytoskeletons isolated from either resting or activated platelets. When syntaxin-4 and SNAP-23 were tested for actin binding in a purified protein system, only syntaxin-4 associated directly with polymerized platelet actin. These data show that the platelet cytoskeleton interacts with select SNAREs and that actin polymerization facilitates alpha-granule release.
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Affiliation(s)
- Kamil Woronowicz
- Division of Hemostasis and Thrombosis, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA
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48
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Lam JKW, Armes SP, Stolnik S. The involvement of microtubules and actin filaments in the intracellular transport of non-viral gene delivery system. J Drug Target 2010; 19:56-66. [DOI: 10.3109/10611861003733938] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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49
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Cdc42p and Rho1p are sequentially activated and mechanistically linked to vacuole membrane fusion. Biochem Biophys Res Commun 2010; 394:64-9. [DOI: 10.1016/j.bbrc.2010.02.102] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2010] [Accepted: 02/09/2010] [Indexed: 11/22/2022]
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50
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Lee JY, Koga H, Kawaguchi Y, Tang W, Wong E, Gao YS, Pandey UB, Kaushik S, Tresse E, Lu J, Taylor JP, Cuervo AM, Yao TP. HDAC6 controls autophagosome maturation essential for ubiquitin-selective quality-control autophagy. EMBO J 2010; 29:969-80. [PMID: 20075865 DOI: 10.1038/emboj.2009.405] [Citation(s) in RCA: 579] [Impact Index Per Article: 41.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Accepted: 12/16/2009] [Indexed: 11/09/2022] Open
Abstract
Autophagy is primarily considered a non-selective degradation process induced by starvation. Nutrient-independent basal autophagy, in contrast, imposes intracellular QC by selective disposal of aberrant protein aggregates and damaged organelles, a process critical for suppressing neurodegenerative diseases. The molecular mechanism that distinguishes these two fundamental autophagic responses, however, remains mysterious. Here, we identify the ubiquitin-binding deacetylase, histone deacetylase-6 (HDAC6), as a central component of basal autophagy that targets protein aggregates and damaged mitochondria. Surprisingly, HDAC6 is not required for autophagy activation; rather, it controls the fusion of autophagosomes to lysosomes. HDAC6 promotes autophagy by recruiting a cortactin-dependent, actin-remodelling machinery, which in turn assembles an F-actin network that stimulates autophagosome-lysosome fusion and substrate degradation. Indeed, HDAC6 deficiency leads to autophagosome maturation failure, protein aggregate build-up, and neurodegeneration. Remarkably, HDAC6 and F-actin assembly are completely dispensable for starvation-induced autophagy, uncovering the fundamental difference of these autophagic modes. Our study identifies HDAC6 and the actin cytoskeleton as critical components that define QC autophagy and uncovers a novel regulation of autophagy at the level of autophagosome-lysosome fusion.
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Affiliation(s)
- Joo-Yong Lee
- Department of Pharmacology and Cancer Biology, Duke University, Durham, NC 27710, USA
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