1
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More KJ, Kaur H, Simpson AGB, Spiegel FW, Dacks JB. Contractile vacuoles: a rapidly expanding (and occasionally diminishing?) understanding. Eur J Protistol 2024; 94:126078. [PMID: 38688044 DOI: 10.1016/j.ejop.2024.126078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 03/18/2024] [Accepted: 03/20/2024] [Indexed: 05/02/2024]
Abstract
Osmoregulation is the homeostatic mechanism essential for the survival of organisms in hypoosmotic and hyperosmotic conditions. In freshwater or soil dwelling protists this is frequently achieved through the action of an osmoregulatory organelle, the contractile vacuole. This endomembrane organelle responds to the osmotic challenges and compensates by collecting and expelling the excess water to maintain the cellular osmolarity. As compared with other endomembrane organelles, this organelle is underappreciated and under-studied. Here we review the reported presence or absence of contractile vacuoles across eukaryotic diversity, as well as the observed variability in the structure, function, and molecular machinery of this organelle. Our findings highlight the challenges and opportunities for constructing cellular and evolutionary models for this intriguing organelle.
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Affiliation(s)
- Kiran J More
- Division of Infectious Diseases, Department of Medicine, and Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Harpreet Kaur
- Division of Infectious Diseases, Department of Medicine, and Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Alastair G B Simpson
- Centre for Comparative Genomics and Evolutionary Bioinformatics, Dalhousie University, Halifax, NS, Canada; Department of Biology, Dalhousie University, Halifax, NS, Canada
| | - Frederick W Spiegel
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Joel B Dacks
- Division of Infectious Diseases, Department of Medicine, and Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada; Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic; Centre for Life's Origins and Evolution, Department of Genetics, Evolution, & Environment, University College, London, United Kingdom.
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2
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Khan A, Mallick M, Ladke JS, Bhandari R. The ring rules the chain - inositol pyrophosphates and the regulation of inorganic polyphosphate. Biochem Soc Trans 2024; 52:567-580. [PMID: 38629621 DOI: 10.1042/bst20230256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2024] [Revised: 03/29/2024] [Accepted: 04/03/2024] [Indexed: 04/25/2024]
Abstract
The maintenance of phosphate homeostasis serves as a foundation for energy metabolism and signal transduction processes in all living organisms. Inositol pyrophosphates (PP-InsPs), composed of an inositol ring decorated with monophosphate and diphosphate moieties, and inorganic polyphosphate (polyP), chains of orthophosphate residues linked by phosphoanhydride bonds, are energy-rich biomolecules that play critical roles in phosphate homeostasis. There is a complex interplay between these two phosphate-rich molecules, and they share an interdependent relationship with cellular adenosine triphosphate (ATP) and inorganic phosphate (Pi). In eukaryotes, the enzymes involved in PP-InsP synthesis show some degree of conservation across species, whereas distinct enzymology exists for polyP synthesis among different organisms. In fact, the mechanism of polyP synthesis in metazoans, including mammals, is still unclear. Early studies on PP-InsP and polyP synthesis were conducted in the slime mould Dictyostelium discoideum, but it is in the budding yeast Saccharomyces cerevisiae that a clear understanding of the interplay between polyP, PP-InsPs, and Pi homeostasis has now been established. Recent research has shed more light on the influence of PP-InsPs on polyP in mammals, and the regulation of both these molecules by cellular ATP and Pi levels. In this review we will discuss the cross-talk between PP-InsPs, polyP, ATP, and Pi in the context of budding yeast, slime mould, and mammals. We will also highlight the similarities and differences in the relationship between these phosphate-rich biomolecules among this group of organisms.
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Affiliation(s)
- Azmi Khan
- Laboratory of Cell Signalling, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500039, India
| | - Manisha Mallick
- Laboratory of Cell Signalling, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500039, India
- Graduate Studies, Manipal Academy of Higher Education, Manipal, Karnataka 576104, India
| | - Jayashree S Ladke
- Laboratory of Cell Signalling, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500039, India
- Graduate Studies, Regional Centre for Biotechnology, Faridabad 121001, Haryana, India
| | - Rashna Bhandari
- Laboratory of Cell Signalling, Centre for DNA Fingerprinting and Diagnostics, Hyderabad 500039, India
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3
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Docampo R. Advances in the cellular biology, biochemistry, and molecular biology of acidocalcisomes. Microbiol Mol Biol Rev 2024; 88:e0004223. [PMID: 38099688 PMCID: PMC10966946 DOI: 10.1128/mmbr.00042-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2024] Open
Abstract
SUMMARYAcidocalcisomes are organelles conserved during evolution and closely related to the so-called volutin granules of bacteria and archaea, to the acidocalcisome-like vacuoles of yeasts, and to the lysosome-related organelles of animal species. All these organelles have in common their acidity and high content of polyphosphate and calcium. They are characterized by a variety of functions from storage of phosphorus and calcium to roles in Ca2+ signaling, osmoregulation, blood coagulation, and inflammation. They interact with other organelles through membrane contact sites or by fusion, and have several enzymes, pumps, transporters, and channels.
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Affiliation(s)
- Roberto Docampo
- Department of Cellular Biology, Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, USA
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4
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Cheng CY, Romero DP, Zoltner M, Yao MC, Turkewitz AP. Structure and dynamics of the contractile vacuole complex in Tetrahymena thermophila. J Cell Sci 2023; 136:jcs261511. [PMID: 37902010 PMCID: PMC10729820 DOI: 10.1242/jcs.261511] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Accepted: 10/23/2023] [Indexed: 10/31/2023] Open
Abstract
The contractile vacuole complex (CVC) is a dynamic and morphologically complex membrane organelle, comprising a large vesicle (bladder) linked with a tubular reticulum (spongiome). CVCs provide key osmoregulatory roles across diverse eukaryotic lineages, but probing the mechanisms underlying their structure and function is hampered by the limited tools available for in vivo analysis. In the experimentally tractable ciliate Tetrahymena thermophila, we describe four proteins that, as endogenously tagged constructs, localize specifically to distinct CVC zones. The DOPEY homolog Dop1p and the CORVET subunit Vps8Dp localize both to the bladder and spongiome but with different local distributions that are sensitive to osmotic perturbation, whereas the lipid scramblase Scr7p colocalizes with Vps8Dp. The H+-ATPase subunit Vma4 is spongiome specific. The live imaging permitted by these probes revealed dynamics at multiple scales including rapid exchange of CVC-localized and soluble protein pools versus lateral diffusion in the spongiome, spongiome extension and branching, and CVC formation during mitosis. Although the association with DOP1 and VPS8D implicate the CVC in endosomal trafficking, both the bladder and spongiome might be isolated from bulk endocytic input.
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Affiliation(s)
- Chao-Yin Cheng
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Daniel P. Romero
- Department of Pharmacology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Martin Zoltner
- Biotechnology Biomedicine Centre of the Academy of Sciences, České Budějovice, 370 05, Czech Republic
| | - Meng-Chao Yao
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan
| | - Aaron P. Turkewitz
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
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5
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Velle KB, Garner RM, Beckford TK, Weeda M, Liu C, Kennard AS, Edwards M, Fritz-Laylin LK. A conserved pressure-driven mechanism for regulating cytosolic osmolarity. Curr Biol 2023; 33:3325-3337.e5. [PMID: 37478864 PMCID: PMC10529079 DOI: 10.1016/j.cub.2023.06.061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 05/24/2023] [Accepted: 06/22/2023] [Indexed: 07/23/2023]
Abstract
Controlling intracellular osmolarity is essential to all cellular life. Cells that live in hypo-osmotic environments, such as freshwater, must constantly battle water influx to avoid swelling until they burst. Many eukaryotic cells use contractile vacuoles to collect excess water from the cytosol and pump it out of the cell. Although contractile vacuoles are essential to many species, including important pathogens, the mechanisms that control their dynamics remain unclear. To identify the basic principles governing contractile vacuole function, we investigate here the molecular mechanisms of two species with distinct vacuolar morphologies from different eukaryotic lineages: the discoban Naegleria gruberi and the amoebozoan slime mold Dictyostelium discoideum. Using quantitative cell biology, we find that although these species respond differently to osmotic challenges, they both use vacuolar-type proton pumps for filling contractile vacuoles and actin for osmoregulation, but not to power water expulsion. We also use analytical modeling to show that cytoplasmic pressure is sufficient to drive water out of contractile vacuoles in these species, similar to findings from the alveolate Paramecium multimicronucleatum. These analyses show that cytoplasmic pressure is sufficient to drive contractile vacuole emptying for a wide range of cellular pressures and vacuolar geometries. Because vacuolar-type proton-pump-dependent contractile vacuole filling and pressure-dependent emptying have now been validated in three eukaryotic lineages that diverged well over a billion years ago, we propose that this represents an ancient eukaryotic mechanism of osmoregulation.
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Affiliation(s)
- Katrina B Velle
- Department of Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Rikki M Garner
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Tatihana K Beckford
- Department of Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Makaela Weeda
- Department of Biology, Amherst College, Amherst, MA 01002, USA
| | - Chunzi Liu
- Department of Applied Mathematics, Harvard University, Cambridge, MA 02138, USA
| | - Andrew S Kennard
- Department of Biology, University of Massachusetts Amherst, Amherst, MA 01003, USA
| | - Marc Edwards
- Department of Biology, Amherst College, Amherst, MA 01002, USA
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6
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Down the membrane hole: Ion channels in protozoan parasites. PLoS Pathog 2022; 18:e1011004. [PMID: 36580479 PMCID: PMC9799330 DOI: 10.1371/journal.ppat.1011004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Parasitic diseases caused by protozoans are highly prevalent around the world, disproportionally affecting developing countries, where coinfection with other microorganisms is common. Control and treatment of parasitic infections are constrained by the lack of specific and effective drugs, plus the rapid emergence of resistance. Ion channels are main drug targets for numerous diseases, but their potential against protozoan parasites is still untapped. Ion channels are membrane proteins expressed in all types of cells, allowing for the flow of ions between compartments, and regulating cellular functions such as membrane potential, excitability, volume, signaling, and death. Channels and transporters reside at the interface between parasites and their hosts, controlling nutrient uptake, viability, replication, and infectivity. To understand how ion channels control protozoan parasites fate and to evaluate their suitability for therapeutics, we must deepen our knowledge of their structure, function, and modulation. However, methodological approaches commonly used in mammalian cells have proven difficult to apply in protozoans. This review focuses on ion channels described in protozoan parasites of clinical relevance, mainly apicomplexans and trypanosomatids, highlighting proteins for which molecular and functional evidence has been correlated with their physiological functions.
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7
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Abstract
Acidocalcisomes are electron-dense organelles rich in polyphosphate and inorganic and organic cations that are acidified by proton pumps, and possess several channels, pumps, and transporters. They are present in bacteria and eukaryotes and have been studied in greater detail in trypanosomatids. Biogenesis studies of trypanosomatid acidocalcisomes found that they share properties with lysosome-related organelles of animal cells. In addition to their described roles in autophagy, cation and phosphorus storage, osmoregulation, pH homeostasis, and pathogenesis, recent studies have defined the role of these organelles in phosphate utilization, calcium ion (Ca2+ ) signaling, and bioenergetics, and will be the main subject of this review.
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Affiliation(s)
- Roberto Docampo
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA
- Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
| | - Guozhong Huang
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA
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8
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Rijal R, Kirolos SA, Rahman RJ, Gomer RH. Dictyostelium discoideum cells retain nutrients when the cells are about to overgrow their food source. J Cell Sci 2022; 135:276454. [PMID: 36017702 PMCID: PMC9592050 DOI: 10.1242/jcs.260107] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 08/18/2022] [Indexed: 11/20/2022] Open
Abstract
Dictyostelium discoideum is a unicellular eukaryote that eats bacteria, and eventually outgrows the bacteria. D. discoideum cells accumulate extracellular polyphosphate (polyP), and the polyP concentration increases as the local cell density increases. At high cell densities, the correspondingly high extracellular polyP concentrations allow cells to sense that they are about to outgrow their food supply and starve, causing the D. discoideum cells to inhibit their proliferation. In this report, we show that high extracellular polyP inhibits exocytosis of undigested or partially digested nutrients. PolyP decreases plasma membrane recycling and apparent cell membrane fluidity, and this requires the G protein-coupled polyP receptor GrlD, the polyphosphate kinase Ppk1 and the inositol hexakisphosphate kinase I6kA. PolyP alters protein contents in detergent-insoluble crude cytoskeletons, but does not significantly affect random cell motility, cell speed or F-actin levels. Together, these data suggest that D. discoideum cells use polyP as a signal to sense their local cell density and reduce cell membrane fluidity and membrane recycling, perhaps as a mechanism to retain ingested food when the cells are about to starve. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Ramesh Rijal
- Department of Biology, Texas A&M University, College Station, TX 77843-3474, USA
| | - Sara A Kirolos
- Department of Biology, Texas A&M University, College Station, TX 77843-3474, USA
| | - Ryan J Rahman
- Department of Biology, Texas A&M University, College Station, TX 77843-3474, USA
| | - Richard H Gomer
- Department of Biology, Texas A&M University, College Station, TX 77843-3474, USA
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9
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Stasic AJ, Dykes EJ, Cordeiro CD, Vella SA, Fazli MS, Quinn S, Docampo R, Moreno SNJ. Ca 2+ entry at the plasma membrane and uptake by acidic stores is regulated by the activity of the V-H + -ATPase in Toxoplasma gondii. Mol Microbiol 2021; 115:1054-1068. [PMID: 33793004 DOI: 10.1111/mmi.14722] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 03/21/2021] [Accepted: 03/26/2021] [Indexed: 12/14/2022]
Abstract
Ca2+ is a universal intracellular signal that regulates many cellular functions. In Toxoplasma gondii, the controlled influx of extracellular and intracellular Ca2+ into the cytosol initiates a signaling cascade that promotes pathogenic processes like tissue destruction and dissemination. In this work, we studied the role of proton transport in cytosolic Ca2+ homeostasis and the initiation of Ca2+ signaling. We used a T. gondii mutant of the V-H+ -ATPase, a pump previously shown to transport protons to the extracellular medium, and to control intracellular pH and membrane potential and we show that proton gradients are important for maintaining resting cytosolic Ca2+ at physiological levels and for Ca2+ influx. Proton transport was also important for Ca2+ storage by acidic stores and, unexpectedly, the endoplasmic reticulum. Proton transport impacted the amount of polyphosphate (polyP), a phosphate polymer that binds Ca2+ and concentrates in acidocalcisomes. This was supported by the co-localization of the vacuolar transporter chaperone 4 (VTC4), the catalytic subunit of the VTC complex that synthesizes polyP, with the V-ATPase in acidocalcisomes. Our work shows that proton transport regulates plasma membrane Ca2+ transport and control acidocalcisome polyP and Ca2+ content, impacting Ca2+ signaling and downstream stimulation of motility and egress in T. gondii.
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Affiliation(s)
- Andrew J Stasic
- Center for Tropical and Emerging Global Diseases, University of Georgia, Georgia, GA, USA
| | - Eric J Dykes
- Center for Tropical and Emerging Global Diseases, University of Georgia, Georgia, GA, USA.,Department of Cellular Biology, University of Georgia, Athens, GA, USA
| | - Ciro D Cordeiro
- Center for Tropical and Emerging Global Diseases, University of Georgia, Georgia, GA, USA.,Department of Cellular Biology, University of Georgia, Athens, GA, USA
| | - Stephen A Vella
- Center for Tropical and Emerging Global Diseases, University of Georgia, Georgia, GA, USA
| | - Mojtaba S Fazli
- Department of Computer Sciences, University of Georgia, Athens, GA, USA
| | - Shannon Quinn
- Department of Cellular Biology, University of Georgia, Athens, GA, USA.,Department of Computer Sciences, University of Georgia, Athens, GA, USA
| | - Roberto Docampo
- Center for Tropical and Emerging Global Diseases, University of Georgia, Georgia, GA, USA.,Department of Cellular Biology, University of Georgia, Athens, GA, USA
| | - Silvia N J Moreno
- Center for Tropical and Emerging Global Diseases, University of Georgia, Georgia, GA, USA.,Department of Cellular Biology, University of Georgia, Athens, GA, USA
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10
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Gupta Y, Goicoechea S, Pearce CM, Mathur R, Romero JG, Kwofie SK, Weyenberg MC, Daravath B, Sharma N, Poonam, Akala HM, Kanzok SM, Durvasula R, Rathi B, Kempaiah P. The emerging paradigm of calcium homeostasis as a new therapeutic target for protozoan parasites. Med Res Rev 2021; 42:56-82. [PMID: 33851452 DOI: 10.1002/med.21804] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 10/10/2020] [Accepted: 03/31/2021] [Indexed: 12/13/2022]
Abstract
Calcium channels (CCs), a group of ubiquitously expressed membrane proteins, are involved in many pathophysiological processes of protozoan parasites. Our understanding of CCs in cell signaling, organelle function, cellular homeostasis, and cell cycle control has led to improved insights into their structure and functions. In this article, we discuss CCs characteristics of five major protozoan parasites Plasmodium, Leishmania, Toxoplasma, Trypanosoma, and Cryptosporidium. We provide a comprehensive review of current antiparasitic drugs and the potential of using CCs as new therapeutic targets. Interestingly, previous studies have demonstrated that human CC modulators can kill or sensitize parasites to antiparasitic drugs. Still, none of the parasite CCs, pumps, or transporters has been validated as drug targets. Information for this review draws from extensive data mining of genome sequences, chemical library screenings, and drug design studies. Parasitic resistance to currently approved therapeutics is a serious and emerging threat to both disease control and management efforts. In this article, we suggest that the disruption of calcium homeostasis may be an effective approach to develop new anti-parasite drug candidates and reduce parasite resistance.
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Affiliation(s)
- Yash Gupta
- Infectious Diseases, Mayo Clinic, Jacksonville, Florida, 32224, USA
| | - Steven Goicoechea
- Stritch School of Medicine, Loyola University Chicago, Chicago, Illinois, USA
| | - Catherine M Pearce
- Stritch School of Medicine, Loyola University Chicago, Chicago, Illinois, USA
| | - Raman Mathur
- Stritch School of Medicine, Loyola University Chicago, Chicago, Illinois, USA
| | - Jesus G Romero
- Stritch School of Medicine, Loyola University Chicago, Chicago, Illinois, USA
| | - Samuel K Kwofie
- Department of Biomedical Engineering, School of Engineering Sciences, College of Basic & Applied Sciences, West African Center for Cell Biology of Infectious Pathogens, Department of Biochemistry, Cell and Molecular Biology, College of Basic & Applied Sciences, University of Ghana, Accra, Ghana
| | - Matthew C Weyenberg
- Stritch School of Medicine, Loyola University Chicago, Chicago, Illinois, USA
| | - Bharathi Daravath
- Stritch School of Medicine, Loyola University Chicago, Chicago, Illinois, USA
| | - Neha Sharma
- Department of Chemistry, Hansraj College University Enclave, University of Delhi, Delhi, India
| | - Poonam
- Department of Chemistry, Miranda House University Enclave, University of Delhi, Delhi, India
| | | | - Stefan M Kanzok
- Department of Biology, Loyola University Chicago, Chicago, Illinois, USA
| | - Ravi Durvasula
- Infectious Diseases, Mayo Clinic, Jacksonville, Florida, 32224, USA
| | - Brijesh Rathi
- Department of Chemistry, Hansraj College University Enclave, University of Delhi, Delhi, India
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11
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Denoncourt A, Downey M. Model systems for studying polyphosphate biology: a focus on microorganisms. Curr Genet 2021; 67:331-346. [PMID: 33420907 DOI: 10.1007/s00294-020-01148-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 12/08/2020] [Accepted: 12/14/2020] [Indexed: 12/19/2022]
Abstract
Polyphosphates (polyP) are polymers of inorganic phosphates joined by high-energy bonds to form long chains. These chains are present in all forms of life but were once disregarded as 'molecular fossils'. PolyP has gained attention in recent years following new links to diverse biological roles ranging from energy storage to cell signaling. PolyP research in humans and other higher eukaryotes is limited by a lack of suitable tools and awaits the identification of enzymatic players that would enable more comprehensive studies. Therefore, many of the most important insights have come from single-cell model systems. Here, we review determinants of polyP metabolism, regulation, and function in major microbial systems, including bacteria, fungi, protozoa, and algae. We highlight key similarities and differences that may aid in our understanding of how polyP impacts cell physiology at a molecular level.
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Affiliation(s)
- Alix Denoncourt
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, K1H 8M5, Canada.,Ottawa Institute of Systems Biology, Ottawa, K1H 8M5, Canada
| | - Michael Downey
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, K1H 8M5, Canada. .,Ottawa Institute of Systems Biology, Ottawa, K1H 8M5, Canada.
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12
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Goodenough U, Heiss AA, Roth R, Rusch J, Lee JH. Acidocalcisomes: Ultrastructure, Biogenesis, and Distribution in Microbial Eukaryotes. Protist 2019; 170:287-313. [DOI: 10.1016/j.protis.2019.05.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 04/26/2019] [Accepted: 05/01/2019] [Indexed: 12/19/2022]
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13
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Venkatesh D, Zhang N, Zoltner M, del Pino RC, Field MC. Evolution of protein trafficking in kinetoplastid parasites: Complexity and pathogenesis. Traffic 2018; 19:803-812. [DOI: 10.1111/tra.12601] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 06/24/2018] [Accepted: 06/25/2018] [Indexed: 12/31/2022]
Affiliation(s)
| | - Ning Zhang
- School of Life Sciences; University of Dundee; Dundee UK
| | - Martin Zoltner
- School of Life Sciences; University of Dundee; Dundee UK
| | | | - Mark C. Field
- School of Life Sciences; University of Dundee; Dundee UK
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14
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Zaongo SD, Shaio MF, Ji DD. Effects of Culture Media On Naegleria fowleri Growth At Different Temperatures. J Parasitol 2018; 104:451-456. [PMID: 29869929 DOI: 10.1645/18-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Nelson medium and modified PYNFH medium were used for the axenic culture of the Naegleria fowleri clinical strain LDL to compare the effects of different temperatures on the organism's growth. In addition, Nelson medium supplemented with 1% peptone (N + pep) and modified PYNFH medium without peptone (PYNFH - pep), without yeast extract (PYNFH - yext), without folic acid (PYNFH - folac), and without yeast nucleic acid (PYNFH - yna) were used in order to compare the various effects of these medium components. In general, N. fowleri grew best at 37 C. The highest trophozoite densities per 10,000 μm2 were observed when N + pep and PYNFH - yext were used. At 25, 37, and 43 C, the growth density profile values were 50.5 ± 6.36 vs. 58 ± 1.41; 2,550 ± 494.97 vs. 2,100 ± 141.42; and 1,735 ± 21.21 vs. 1,800 ± 14.14, respectively. On the other hand, PYNFH - pep gave the lowest growth with its highest cell densities being 9 ± 1.41 at 25 C, 108 ± 7.07 at 37 C, and 169 ± 15.55 at 43 C. When the various medium components were compared, supplementation with peptone promoted parasite growth. Besides, yeast extract had an inhibitory effect and was able to swamp the growth promoting effect of peptone. Thus N + pep and PYNFH - yext are recommended as the best media for in vitro culture of N. fowleri.
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Affiliation(s)
- Silvere D Zaongo
- 1 International Health Program, National Yang-Ming University, No. 155, Sec. 2, Li-Nong St., Beitou District, Taipei (112), Taiwan
| | - Men-Fang Shaio
- 2 Department of Tropical Medicine, National Yang-Ming University, No. 155, Sec. 2, Li-Nong St., Beitou District, Taipei (112), Taiwan
| | - Dar-Der Ji
- 2 Department of Tropical Medicine, National Yang-Ming University, No. 155, Sec. 2, Li-Nong St., Beitou District, Taipei (112), Taiwan
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15
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Penen F, Isaure MP, Dobritzsch D, Bertalan I, Castillo-Michel H, Proux O, Gontier E, Le Coustumer P, Schaumlöffel D. Pools of cadmium in Chlamydomonas reinhardtii revealed by chemical imaging and XAS spectroscopy. Metallomics 2018; 9:910-923. [PMID: 28598481 DOI: 10.1039/c7mt00029d] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The green micro-alga Chlamydomonas reinhardtii is commonly used as a model to investigate metallic stress in photosynthetic organisms. The aim of this study was to explore processes implemented by three C. reinhardtii strains to cope with cadmium (Cd), and particularly to evidence Cd sequestration in the cell. For that, we used a combination of subcellular fractionation and chemical imaging (micro X-ray fluorescence (μXRF) and transmission electron microscopy (TEM/X-EDS)) to identify subcellular compartments of Cd accumulation, and X-ray absorption spectroscopy (XAS) to determine chemical Cd speciation. C. reinhardtii wild type strain 11/32b (wt), a newly design strain (pcs1) expressing a modified phytochelatin synthase in the chloroplast and a cell wall less strain CC400 (cw15) were exposed to 70 μM Cd. At this Cd concentration, cell vitality was not affected, however, the strains showed various strategies to cope with Cd stress. In wt, most of Cd was diffused in the whole cell, and complexed by thiol ligands, while the other part was associated with phosphate in vacuolar Ca polyphosphate granules. Thiol ligands increased with exposure time, confirming their important role in Cd stress. In pcs1, Cd was also present as vacuolar Ca polyphosphate granules, and diffused in the cell as Cd-thiol complexes. In addition, while it should be regarded with caution, a minor proportion of Cd complexed by carboxyl groups, was potentially provided by starch produced around the pyrenoid and in the chloroplast. Results suggested that pcs1 uses thiol compounds such as PC to a lesser extent for Cd sequestration than wt. In cw15, an excretion of Cd, Ca polyphosphate granules has to be considered. Finally, Cd was detected in the pyrenoid of all strains.
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Affiliation(s)
- F Penen
- Université de Pau et des Pays de l'Adour, CNRS, Institut des Sciences Analytiques et de Physico-Chimie pour l'Environnement et les Matériaux (IPREM), UMR 5254, Hélioparc, 2 avenue Pierre Angot, 64053 Pau, France.
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Abstract
Inorganic polyphosphate (polyP) accumulates in acidocalcisomes, acidic calcium stores that have been found from bacteria to human cells. Proton pumps, such as the vacuolar proton pyrophosphatase (V-H(+)-PPase or VP1), the vacuolar proton ATPase (V-H(+)-ATPase) or both, maintain their acidity. A vacuolar transporter chaperone (VTC) complex is involved in the synthesis and translocation of polyP to these organelles in several eukaryotes, such as yeast, trypanosomatids, Apicomplexan and algae. Studies in trypanosomatids have revealed the role of polyP and acidocalcisomes in osmoregulation and calcium signalling.
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Deciphering the relationship among phosphate dynamics, electron-dense body and lipid accumulation in the green alga Parachlorella kessleri. Sci Rep 2016; 6:25731. [PMID: 27180903 PMCID: PMC4867602 DOI: 10.1038/srep25731] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 04/18/2016] [Indexed: 01/08/2023] Open
Abstract
Phosphorus is an essential element for life on earth and is also important for modern agriculture, which is dependent on inorganic fertilizers from phosphate rock. Polyphosphate is a biological polymer of phosphate residues, which is accumulated in organisms during the biological wastewater treatment process to enhance biological phosphorus removal. Here, we investigated the relationship between polyphosphate accumulation and electron-dense bodies in the green alga Parachlorella kessleri. Under sulfur-depleted conditions, in which some symporter genes were upregulated, while others were downregulated, total phosphate accumulation increased in the early stage of culture compared to that under sulfur-replete conditions. The P signal was detected only in dense bodies by energy dispersive X-ray analysis. Transmission electron microscopy revealed marked ultrastructural variations in dense bodies with and without polyphosphate. Our findings suggest that the dense body is a site of polyphosphate accumulation, and P. kessleri has potential as a phosphate-accumulating organism.
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Lelandais G, Scheiber I, Paz-Yepes J, Lozano JC, Botebol H, Pilátová J, Žárský V, Léger T, Blaiseau PL, Bowler C, Bouget FY, Camadro JM, Sutak R, Lesuisse E. Ostreococcus tauri is a new model green alga for studying iron metabolism in eukaryotic phytoplankton. BMC Genomics 2016; 17:319. [PMID: 27142620 PMCID: PMC4855317 DOI: 10.1186/s12864-016-2666-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 04/26/2016] [Indexed: 11/17/2022] Open
Abstract
Background Low iron bioavailability is a common feature of ocean surface water and therefore micro-algae developed original strategies to optimize iron uptake and metabolism. The marine picoeukaryotic green alga Ostreococcus tauri is a very good model for studying physiological and genetic aspects of the adaptation of the green algal lineage to the marine environment: it has a very compact genome, is easy to culture in laboratory conditions, and can be genetically manipulated by efficient homologous recombination. In this study, we aimed at characterizing the mechanisms of iron assimilation in O. tauri by combining genetics and physiological tools. Specifically, we wanted to identify and functionally characterize groups of genes displaying tightly orchestrated temporal expression patterns following the exposure of cells to iron deprivation and day/night cycles, and to highlight unique features of iron metabolism in O. tauri, as compared to the freshwater model alga Chalamydomonas reinhardtii. Results We used RNA sequencing to investigated the transcriptional responses to iron limitation in O. tauri and found that most of the genes involved in iron uptake and metabolism in O. tauri are regulated by day/night cycles, regardless of iron status. O. tauri lacks the classical components of a reductive iron uptake system, and has no obvious iron regulon. Iron uptake appears to be copper-independent, but is regulated by zinc. Conversely, iron deprivation resulted in the transcriptional activation of numerous genes encoding zinc-containing regulation factors. Iron uptake is likely mediated by a ZIP-family protein (Ot-Irt1) and by a new Fea1-related protein (Ot-Fea1) containing duplicated Fea1 domains. The adaptation of cells to iron limitation involved an iron-sparing response tightly coordinated with diurnal cycles to optimize cell functions and synchronize these functions with the day/night redistribution of iron orchestrated by ferritin, and a stress response based on the induction of thioredoxin-like proteins, of peroxiredoxin and of tesmin-like methallothionein rather than ascorbate. We briefly surveyed the metabolic remodeling resulting from iron deprivation. Conclusions The mechanisms of iron uptake and utilization by O. tauri differ fundamentally from those described in C. reinhardtii. We propose this species as a new model for investigation of iron metabolism in marine microalgae. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2666-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Gaëlle Lelandais
- CNRS, Institut Jacques Monod, Université Paris Diderot-Paris 7, F-75013, Paris, France
| | - Ivo Scheiber
- Department of Parasitology, Faculty of Science, Charles University in Prague, 12844, Prague, Czech Republic
| | - Javier Paz-Yepes
- Ecole Normale Supérieure, PSL Research University, Institut de Biologie de l'Ecole Normale Supérieure (IBENS), CNRS UMR 8197, INSERM U1024, 46 rue d'Ulm, F-75005, Paris, France
| | - Jean-Claude Lozano
- Sorbonne Universités, University Pierre et Marie Curie, University of Paris VI, CNRS, Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, F-66650, Banyuls-sur-Mer, France
| | - Hugo Botebol
- Sorbonne Universités, University Pierre et Marie Curie, University of Paris VI, CNRS, Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, F-66650, Banyuls-sur-Mer, France
| | - Jana Pilátová
- Department of Parasitology, Faculty of Science, Charles University in Prague, 12844, Prague, Czech Republic
| | - Vojtěch Žárský
- Department of Parasitology, Faculty of Science, Charles University in Prague, 12844, Prague, Czech Republic
| | - Thibaut Léger
- CNRS, Institut Jacques Monod, Université Paris Diderot-Paris 7, F-75013, Paris, France
| | - Pierre-Louis Blaiseau
- Sorbonne Universités, University Pierre et Marie Curie, University of Paris VI, CNRS, Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, F-66650, Banyuls-sur-Mer, France
| | - Chris Bowler
- Ecole Normale Supérieure, PSL Research University, Institut de Biologie de l'Ecole Normale Supérieure (IBENS), CNRS UMR 8197, INSERM U1024, 46 rue d'Ulm, F-75005, Paris, France
| | - François-Yves Bouget
- Sorbonne Universités, University Pierre et Marie Curie, University of Paris VI, CNRS, Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, F-66650, Banyuls-sur-Mer, France
| | - Jean-Michel Camadro
- CNRS, Institut Jacques Monod, Université Paris Diderot-Paris 7, F-75013, Paris, France
| | - Robert Sutak
- Department of Parasitology, Faculty of Science, Charles University in Prague, 12844, Prague, Czech Republic.
| | - Emmanuel Lesuisse
- CNRS, Institut Jacques Monod, Université Paris Diderot-Paris 7, F-75013, Paris, France.
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Docampo R, Huang G. Acidocalcisomes of eukaryotes. Curr Opin Cell Biol 2016; 41:66-72. [PMID: 27125677 DOI: 10.1016/j.ceb.2016.04.007] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 03/30/2016] [Accepted: 04/07/2016] [Indexed: 01/01/2023]
Abstract
Acidocalcisomes are organelles rich in polyphosphate and cations and acidified by proton pumps. Although they have also been described in prokaryotes they have been better characterized in unicellular and multicellular eukaryotes. Eukaryotic acidocalcisomes belong to the group of lysosome-related organelles. They have a variety of functions, from the storage of cations and phosphorus to calcium signaling, autophagy, osmoregulation, blood coagulation, and inflammation. Acidocalcisomes of several unicellular eukaryotes possess a variety of transporters, channels and pumps implying a large energetic requirement for their maintenance and suggesting other important functions waiting to be discovered.
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Affiliation(s)
- Roberto Docampo
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA.
| | - Guozhong Huang
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, GA 30602, USA
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20
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Kizawa K, Aono T, Ohtomo R. PHO8 gene coding alkaline phosphatase of Saccharomyces cerevisiae is involved in polyphosphate metabolism. J GEN APPL MICROBIOL 2016; 62:297-302. [DOI: 10.2323/jgam.2016.05.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Keiko Kizawa
- Biotechnology Research Center, The University of Tokyo
| | | | - Ryo Ohtomo
- National Agriculture and Food Research Organization (NARO), Hokkaido Agricultural Research Center
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21
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Docampo R. The origin and evolution of the acidocalcisome and its interactions with other organelles. Mol Biochem Parasitol 2015; 209:3-9. [PMID: 26523947 DOI: 10.1016/j.molbiopara.2015.10.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 10/04/2015] [Accepted: 10/19/2015] [Indexed: 01/11/2023]
Abstract
Acidocalcisomes are acidic calcium stores that have been found from bacteria to human cells. They are rich in phosphorus compounds in the form of orthophosphate (Pi), pyrophosphate (PPi), and polyphosphate (polyP) and their acidity is maintained by proton pumps such as the vacuolar proton pyrophosphatase (V-H+-PPase, or VP1), the vacuolar proton ATPase (V-H+-ATPase), or both. Recent studies in trypanosomatids and in other species have revealed their role in phosphate metabolism, and cation and water homeostasis, as suggested by the presence of novel pumps, transporters, and channels. An important role in autophagy has also been described. The study of the biogenesis of acidocalcisomes as well as of the interactions of these lysosome-related organelles with other organelles have uncovered important roles in calcium signaling and osmoregulation. Significantly, despite conservation of acidocalcisomes across all of cellular life, there is evidence for intimate integration of these organelles with eukaryotic cellular functions, and which are directly relevant to parasites.
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Affiliation(s)
- Roberto Docampo
- Center for Tropical and Global Emerging Diseases and Department of Cellular Biology, University of Georgia, Athens 30602, USA; Departamento de Patología Clínica, Universidade Estadual de Campinas, São Paulo 13083-877, Brazil.
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22
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Niyogi S, Jimenez V, Girard-Dias W, de Souza W, Miranda K, Docampo R. Rab32 is essential for maintaining functional acidocalcisomes, and for growth and infectivity of Trypanosoma cruzi. J Cell Sci 2015; 128:2363-73. [PMID: 25964650 DOI: 10.1242/jcs.169466] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Accepted: 04/30/2015] [Indexed: 02/01/2023] Open
Abstract
The contractile vacuole complex (CVC) of Trypanosoma cruzi, the etiologic agent of Chagas disease, collects and expels excess water as a mechanism of regulatory volume decrease after hyposmotic stress; it also has a role in cell shrinking after hyperosmotic stress. Here, we report that, in addition to its role in osmoregulation, the CVC of T. cruzi has a role in the biogenesis of acidocalcisomes. Expression of dominant-negative mutants of the CVC-located small GTPase Rab32 (TcCLB.506289.80) results in lower numbers of less-electron-dense acidocalcisomes, lower content of polyphosphate, lower capacity for acidocalcisome acidification and Ca(2+) uptake that is driven by the vacuolar proton pyrophosphatase and the Ca(2+)-ATPase, respectively, as well as less-infective parasites, revealing the role of this organelle in parasite infectivity. By using fluorescence, electron microscopy and electron tomography analyses, we provide further evidence of the active contact of acidocalcisomes with the CVC, indicating an active exchange of proteins between the two organelles.
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Affiliation(s)
- Sayantanee Niyogi
- Department of Cellular Biology and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA
| | - Veronica Jimenez
- Department of Cellular Biology and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA
| | - Wendell Girard-Dias
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho and Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens - Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil
| | - Wanderley de Souza
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho and Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens - Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil Diretoria de Metrologia Aplicada a Ciências da Vida, Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMETRO), Xerém, Rio de Janeiro 25250-020, Brazil
| | - Kildare Miranda
- Laboratório de Ultraestrutura Celular Hertha Meyer, Instituto de Biofísica Carlos Chagas Filho and Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens - Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil Diretoria de Metrologia Aplicada a Ciências da Vida, Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMETRO), Xerém, Rio de Janeiro 25250-020, Brazil
| | - Roberto Docampo
- Department of Cellular Biology and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA
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Plattner H, Verkhratsky A. The ancient roots of calcium signalling evolutionary tree. Cell Calcium 2015; 57:123-32. [DOI: 10.1016/j.ceca.2014.12.004] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 12/05/2014] [Indexed: 12/26/2022]
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Huang G, Ulrich PN, Storey M, Johnson D, Tischer J, Tovar JA, Moreno SNJ, Orlando R, Docampo R. Proteomic analysis of the acidocalcisome, an organelle conserved from bacteria to human cells. PLoS Pathog 2014; 10:e1004555. [PMID: 25503798 PMCID: PMC4263762 DOI: 10.1371/journal.ppat.1004555] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 11/05/2014] [Indexed: 01/12/2023] Open
Abstract
Acidocalcisomes are acidic organelles present in a diverse range of organisms from bacteria to human cells. In this study acidocalcisomes were purified from the model organism Trypanosoma brucei, and their protein composition was determined by mass spectrometry. The results, along with those that we previously reported, show that acidocalcisomes are rich in pumps and transporters, involved in phosphate and cation homeostasis, and calcium signaling. We validated the acidocalcisome localization of seven new, putative, acidocalcisome proteins (phosphate transporter, vacuolar H+-ATPase subunits a and d, vacuolar iron transporter, zinc transporter, polyamine transporter, and acid phosphatase), confirmed the presence of six previously characterized acidocalcisome proteins, and validated the localization of five novel proteins to different subcellular compartments by expressing them fused to epitope tags in their endogenous loci or by immunofluorescence microscopy with specific antibodies. Knockdown of several newly identified acidocalcisome proteins by RNA interference (RNAi) revealed that they are essential for the survival of the parasites. These results provide a comprehensive insight into the unique composition of acidocalcisomes of T. brucei, an important eukaryotic pathogen, and direct evidence that acidocalcisomes are especially adapted for the accumulation of polyphosphate.
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Affiliation(s)
- Guozhong Huang
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Paul N Ulrich
- Department of Biology, Georgia State University, Atlanta, Georgia, United States of America
| | - Melissa Storey
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Darryl Johnson
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, United States of America
| | - Julie Tischer
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Javier A Tovar
- Department of Biology, Georgia State University, Atlanta, Georgia, United States of America
| | - Silvia N J Moreno
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
| | - Ron Orlando
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, United States of America
| | - Roberto Docampo
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, Athens, Georgia, United States of America
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25
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Raven JA, Doblin MA. Active water transport in unicellular algae: where, why, and how. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:6279-6292. [PMID: 25205578 DOI: 10.1093/jxb/eru360] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The occurrence of active water transport (net transport against a free energy gradient) in photosynthetic organisms has been debated for several decades. Here, active water transport is considered in terms of its roles, where it is found, and the mechanisms by which it could occur. First there is a brief consideration of the possibility of active water transport into plant xylem in the generation of root pressure and the refilling of embolized xylem elements, and from an unsaturated atmosphere into terrestrial organisms living in habitats with limited availability of liquid water. There is then a more detailed consideration of volume and osmotic regulation in wall-less freshwater unicells, and the possibility of generation of buoyancy in marine phytoplankton such as large-celled diatoms. Calculations show that active water transport is a plausible mechanism to assist cells in upwards vertical movements, requires less energy than synthesis of low-density organic solutes, and potentially on a par with excluding certain ions from the vacuole.
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Affiliation(s)
- John A Raven
- Division of Plant Sciences, University of Dundee at the James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK School of Plant Biology, University of Western Australia, M048, 35 Stirling Highway, Crawley, WA 6009, Australia
| | - Martina A Doblin
- Plant Functional Biology and Climate Change Cluster (C3), University of Technology Sydney, PO Box 123, NSW 2007, Australia
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26
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Colocation and role of polyphosphates and alkaline phosphatase in apatite biomineralization of elasmobranch tesserae. Acta Biomater 2014; 10:3899-910. [PMID: 24948547 DOI: 10.1016/j.actbio.2014.06.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2013] [Revised: 06/06/2014] [Accepted: 06/08/2014] [Indexed: 11/22/2022]
Abstract
Elasmobranchs (e.g. sharks and rays), like all fishes, grow continuously throughout life. Unlike other vertebrates, their skeletons are primarily cartilaginous, comprising a hyaline cartilage-like core, stiffened by a thin outer array of mineralized, abutting and interconnected tiles called tesserae. Tesserae bear active mineralization fronts at all margins and the tesseral layer is thin enough to section without decalcifying, making this a tractable but largely unexamined system for investigating controlled apatite mineralization, while also offering a potential analog for endochondral ossification. The chemical mechanism for tesserae mineralization has not been described, but has been previously attributed to spherical precursors, and alkaline phosphatase (ALP) activity. Here, we use a variety of techniques to elucidate the involvement of phosphorus-containing precursors in the formation of tesserae at their mineralization fronts. Using Raman spectroscopy, fluorescence microscopy and histological methods, we demonstrate that ALP activity is located with inorganic phosphate polymers (polyP) at the tessera-uncalcified cartilage interface, suggesting a potential mechanism for regulated mineralization: inorganic phosphate (Pi) can be cleaved from polyP by ALP, thus making Pi locally available for apatite biomineralization. The application of exogenous ALP to tissue cross-sections resulted in the disappearance of polyP and the appearance of Pi in uncalcified cartilage adjacent to mineralization fronts. We propose that elasmobranch skeletal cells control apatite biomineralization by biochemically controlling polyP and ALP production, placement and activity. Previous identification of polyP and ALP shown previously in mammalian calcifying cartilage supports the hypothesis that this mechanism may be a general regulating feature in the mineralization of vertebrate skeletons.
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Gomes FM, Ramos IB, Wendt C, Girard-Dias W, De Souza W, Machado EA, Miranda K. New insights into the in situ microscopic visualization and quantification of inorganic polyphosphate stores by 4',6-diamidino-2-phenylindole (DAPI)-staining. Eur J Histochem 2013; 57:e34. [PMID: 24441187 PMCID: PMC3896036 DOI: 10.4081/ejh.2013.e34] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 09/22/2013] [Accepted: 09/24/2013] [Indexed: 01/10/2023] Open
Abstract
Inorganic polyphosphate (PolyP) is a biological polymer that plays important roles in the cell physiology of both prokaryotic and eukaryotic organisms. Among the available methods for PolyP localization and quantification, a 4',6-diamidino-2-phenylindole(DAPI)-based assay has been used for visualization of PolyP-rich organelles. Due to differences in DAPI permeability to different compartments and/or PolyP retention after fixation, a general protocol for DAPI-PolyP staining has not yet been established. Here, we tested different protocols for DAPI-PolyP detection in a range of samples with different levels of DAPI permeability, including subcellular fractions, free-living cells and cryosections of fixed tissues. Subcellular fractions of PolyP-rich organelles yielded DAPI-PolyP fluorescence, although those with a complex external layer usually required longer incubation times, previous aldehyde fixation and/or detergent permeabilization. DAPI-PolyP was also detected in cryosections of OCT-embedded tissues analyzed by multi-photon microscopy. In addition, a semi-quantitative fluorimetric analysis of DAPI-stained fractions showed PolyP mobilization in a similar fashion to what has been demonstrated with the use of enzyme-based quantitative protocols. Taken together, our results support the use of DAPI for both PolyP visualization and quantification, although specific steps are suggested as a general guideline for DAPI-PolyP staining in biological samples with different degrees of DAPI and PolyP permeability.
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Affiliation(s)
- F M Gomes
- Universidade Federal do Rio de Janeiro.
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29
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Plattner H. Calcium regulation in the protozoan model, Paramecium tetraurelia. J Eukaryot Microbiol 2013; 61:95-114. [PMID: 24001309 DOI: 10.1111/jeu.12070] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 06/21/2013] [Accepted: 06/28/2013] [Indexed: 01/24/2023]
Abstract
Early in eukaryotic evolution, the cell has evolved a considerable inventory of proteins engaged in the regulation of intracellular Ca(2+) concentrations, not only to avoid toxic effects but beyond that to exploit the signaling capacity of Ca(2+) by small changes in local concentration. Among protozoa, the ciliate Paramecium may now be one of the best analyzed models. Ciliary activity and exo-/endocytosis are governed by Ca(2+) , the latter by Ca(2+) mobilization from alveolar sacs and a superimposed store-operated Ca(2+) -influx. Paramecium cells possess plasma membrane- and endoplasmic reticulum-resident Ca(2+) -ATPases/pumps (PMCA, SERCA), a variety of Ca(2+) influx channels, including mechanosensitive and voltage-dependent channels in the plasma membrane, furthermore a plethora of Ca(2+) -release channels (CRC) of the inositol 1,4,5-trisphosphate and ryanodine receptor type in different compartments, notably the contractile vacuole complex and the alveolar sacs, as well as in vesicles participating in vesicular trafficking. Additional types of CRC probably also occur but they have not been identified at a molecular level as yet, as is the equivalent of synaptotagmin as a Ca(2+) sensor for exocytosis. Among established targets and sensors of Ca(2+) in Paramecium are calmodulin, calcineurin, as well as Ca(2+) /calmodulin-dependent protein kinases, all with multiple functions. Thus, basic elements of Ca(2+) signaling are available for Paramecium.
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Affiliation(s)
- Helmut Plattner
- Department of Biology, University of Konstanz, P.O. Box 5544, 78457, Konstanz, Germany
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30
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Plattner H. The contractile vacuole complex of protists--new cues to function and biogenesis. Crit Rev Microbiol 2013; 41:218-27. [PMID: 23919298 DOI: 10.3109/1040841x.2013.821650] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The contractile vacuole complex (CVC) of freshwater protists sequesters the excess of water and ions (Ca(2+)) for exocytosis cycles at the pore. Sequestration is based on a chemiosmotic proton gradient produced by a V-type H(+)-ATPase. So far, many pieces of information available have not been combined to a comprehensive view on CVC biogenesis and function. One main function now appears as follows. Ca(2+)-release channels, type inositol 1,4,5-trisphosphate receptors (InsP3R), may serve for fine-tuning of local cytosolic Ca(2+) concentration and mediate numerous membrane-to-membrane interactions within the tubular spongiome meshwork. Such activity is suggested by the occurrence of organelle-specific soluble N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) and Ras-related in brain (Rab) proteins, which may regulate functional requirements. For tubulation, F-Bin-amphiphysin-Rvs (F-BAR) proteins are available. In addition, there is indirect evidence for the occurrence of H(+)/Ca(2+) exchangers (to sequester Ca(2+)) and mechanosensitive Ca(2+)-channels (for signaling the filling sate). The periodic activity of the CVC may be regulated by the mechanosensitive Ca(2+)-channels. Such channels are known to colocalize with and to be functionally supported by stomatins, which were recently detected in the CVC. A Kif18-related kinesin motor protein might control the length of radial arms. Two additional InsP3-related channels and several SNAREs are associated with the pore. De novo organelle biogenesis occurs under epigenetic control during mitotic activity and may involve the assembly of γ-tubulin, centrin, calmodulin and a never in mitosis A-type (NIMA) kinase - components also engaged in mitotic processes.
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Affiliation(s)
- Helmut Plattner
- Department of Biology, University of Konstanz , Konstanz , Germany
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New insights into roles of acidocalcisomes and contractile vacuole complex in osmoregulation in protists. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 305:69-113. [PMID: 23890380 DOI: 10.1016/b978-0-12-407695-2.00002-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
While free-living protists are usually subjected to hyposmotic environments, parasitic protists are also in contact with hyperosmotic habitats. Recent work in one of these parasites, Trypanosoma cruzi, has revealed that its contractile vacuole complex, which usually collects and expels excess water as a mechanism of regulatory volume decrease after hyposmotic stress, has also a role in cell shrinking when the cells are submitted to hyperosmotic stress. Trypanosomes also have an acidic calcium store rich in polyphosphate (polyP), named the acidocalcisome, which is involved in their response to osmotic stress. Here, we review newly emerging insights on the role of acidocalcisomes and the contractile vacuole complex in the cellular response to hyposmotic and hyperosmotic stresses. We also review the current state of knowledge on the composition of these organelles and their other roles in calcium homeostasis and protein trafficking.
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Plattner H, Sehring IM, Mohamed IK, Miranda K, De Souza W, Billington R, Genazzani A, Ladenburger EM. Calcium signaling in closely related protozoan groups (Alveolata): non-parasitic ciliates (Paramecium, Tetrahymena) vs. parasitic Apicomplexa (Plasmodium, Toxoplasma). Cell Calcium 2012; 51:351-82. [PMID: 22387010 DOI: 10.1016/j.ceca.2012.01.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 01/10/2012] [Accepted: 01/12/2012] [Indexed: 12/20/2022]
Abstract
The importance of Ca2+-signaling for many subcellular processes is well established in higher eukaryotes, whereas information about protozoa is restricted. Recent genome analyses have stimulated such work also with Alveolates, such as ciliates (Paramecium, Tetrahymena) and their pathogenic close relatives, the Apicomplexa (Plasmodium, Toxoplasma). Here we compare Ca2+ signaling in the two closely related groups. Acidic Ca2+ stores have been characterized in detail in Apicomplexa, but hardly in ciliates. Two-pore channels engaged in Ca2+-release from acidic stores in higher eukaryotes have not been stingently characterized in either group. Both groups are endowed with plasma membrane- and endoplasmic reticulum-type Ca2+-ATPases (PMCA, SERCA), respectively. Only recently was it possible to identify in Paramecium a number of homologs of ryanodine and inositol 1,3,4-trisphosphate receptors (RyR, IP3R) and to localize them to widely different organelles participating in vesicle trafficking. For Apicomplexa, physiological experiments suggest the presence of related channels although their identity remains elusive. In Paramecium, IP3Rs are constitutively active in the contractile vacuole complex; RyR-related channels in alveolar sacs are activated during exocytosis stimulation, whereas in the parasites the homologous structure (inner membrane complex) may no longer function as a Ca2+ store. Scrutinized comparison of the two closely related protozoan phyla may stimulate further work and elucidate adaptation to parasitic life. See also "Conclusions" section.
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Affiliation(s)
- H Plattner
- Department of Biology, University of Konstanz, P.O. Box 5560, 78457 Konstanz, Germany.
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von Bülow J, Müller-Lucks A, Kai L, Bernhard F, Beitz E. Functional characterization of a novel aquaporin from Dictyostelium discoideum amoebae implies a unique gating mechanism. J Biol Chem 2012; 287:7487-94. [PMID: 22262860 DOI: 10.1074/jbc.m111.329102] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The social amoeba Dictyostelium discoideum is a widely used model organism for studying basic functions of protozoan and metazoan cells, such as osmoregulation and cell motility. There is evidence from other species that cellular water channels, aquaporins (AQP), are central to both processes. Yet, data on D. discoideum AQPs is almost absent. Despite cloning of two putative D. discoideum AQPs, WacA, and AqpA, water permeability has not been shown. Further, WacA and AqpA are expressed at the late multicellular stage and in spores but not in amoebae. We cloned a novel AQP, AqpB, from amoeboidal D. discoideum cells. Wild-type AqpB was impermeable to water, glycerol, and urea when expressed in Xenopus laevis oocytes. Neither stepwise truncation of the N terminus nor selected point mutations activated the water channel. However, mutational truncation by 12 amino acids of an extraordinary long intracellular loop induced water permeability of AqpB, hinting at a novel gating mechanism. This AqpB mutant was inhibited by mercuric chloride, confirming the presence of a cysteine residue in the selectivity filter as predicted by our structure model. We detected AqpB by Western blot analysis in a glycosylated and a non-glycosylated form throughout all developmental stages. When expressed in D. discoideum amoebae, AqpB-GFP fusion constructs localized to vacuolar structures, to the plasma membrane, and to lamellipodia-like membrane protrusions. We conclude that the localization pattern in conjunction with channel gating may be indicative of AqpB functions in osmoregulation as well as cell motility of D. discoideum.
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Affiliation(s)
- Julia von Bülow
- Department of Medicinal and Pharmaceutical Chemistry, Christian-Albrechts-University of Kiel, 24118 Kiel, Germany
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Docampo R, Jimenez V, King-Keller S, Li ZH, Moreno SNJ. The role of acidocalcisomes in the stress response of Trypanosoma cruzi. ADVANCES IN PARASITOLOGY 2011; 75:307-24. [PMID: 21820562 DOI: 10.1016/b978-0-12-385863-4.00014-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Acidocalcisomes of Trypanosoma cruzi are acidic calcium-containing organelles rich in phosphorus in the form of pyrophosphate (PP(i)) and polyphosphate (poly P). Acidification of the organelles is driven by vacuolar proton pumps, one of which, the vacuolar-type proton pyrophosphatase, is absent in mammalian cells. A calcium ATPase is involved in calcium uptake, and an aquaporin is important for water transport. Enzymes involved in the synthesis and degradation of PPi and poly P are present within the organelle. Acidocalcisomes function as storage sites for cations and phosphorus, participate in PP(i) and poly P metabolism and volume regulation and are essential for virulence. A signalling pathway involving cyclic AMP generation is important for fusion of acidocalcisomes to the contractile vacuole complex, transference of aquaporin and volume regulation. This pathway is an excellent target for chemotherapy as shown by the effects of phosphodiesterase C inhibitors on parasite survival.
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Affiliation(s)
- Roberto Docampo
- Department of Cellular Biology and Center for Tropical and Global Emerging Diseases, University of Georgia, Athens, GA, USA
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Ramos I, Gomes F, Koeller CM, Saito K, Heise N, Masuda H, Docampo R, de Souza W, Machado EA, Miranda K. Acidocalcisomes as calcium- and polyphosphate-storage compartments during embryogenesis of the insect Rhodnius prolixus Stahl. PLoS One 2011; 6:e27276. [PMID: 22096545 PMCID: PMC3214050 DOI: 10.1371/journal.pone.0027276] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2011] [Accepted: 10/12/2011] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND The yolk of insect eggs is a cellular domain specialized in the storage of reserve components for embryo development. The reserve macromolecules are stored in different organelles and their interactions with the embryo cells are mostly unknown. Acidocalcisomes are lysosome-related organelles characterized by their acidic nature, high electron density and large content of polyphosphate bound to several cations. In this work, we report the presence of acidocalcisome-like organelles in eggs of the insect vector Rhodnius prolixus. METHODOLOGY/PRINCIPAL FINDINGS Characterization of the elemental composition of electron-dense vesicles by electron probe X-ray microanalysis revealed a composition similar to that previously described for acidocalcisomes. Following subcellular fractionation experiments, fractions enriched in acidocalcisomes were obtained and characterized. Immunofluorescence showed that polyphosphate polymers and the vacuolar proton translocating pyrophosphatase (V-H(+)-PPase, considered as a marker for acidocalcisomes) are found in the same vesicles and that these organelles are mainly localized in the egg cortex. Polyphosphate quantification showed that acidocalcisomes contain a significant amount of polyphosphate detected at day-0 eggs. Elemental analyses of the egg fractions showed that 24.5±0.65% of the egg calcium are also stored in such organelles. During embryogenesis, incubation of acidocalcisomes with acridine orange showed that these organelles are acidified at day-3 (coinciding with the period of yolk mobilization) and polyphosphate quantification showed that the levels of polyphosphate tend to decrease during early embryogenesis, being approximately 30% lower at day-3 compared to day-0 eggs. CONCLUSIONS We found that acidocalcisomes are present in the eggs and are the main storage compartments of polyphosphate and calcium in the egg yolk. As such components have been shown to be involved in a series of dynamic events that may control embryo growth, results reveal the potential involvement of a novel organelle in the storage and mobilization of inorganic elements to the embryo cells.
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Affiliation(s)
- Isabela Ramos
- Intituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Fabio Gomes
- Intituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Carolina M. Koeller
- Intituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Katsuharu Saito
- Faculty of Agriculture, Shinshu University, Minamiminowa, Nagano, Japan
| | - Norton Heise
- Intituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Hatisaburo Masuda
- Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Roberto Docampo
- Department of Cellular Biology, Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, United States of America
| | - Wanderley de Souza
- Intituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Diretoria de Programas, Instituto Nacional de Metrologia Normalização e Qualidade Industrial, Xerém, Brazil
| | - Ednildo A. Machado
- Intituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Diretoria de Programas, Instituto Nacional de Metrologia Normalização e Qualidade Industrial, Xerém, Brazil
| | - Kildare Miranda
- Intituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
- Diretoria de Programas, Instituto Nacional de Metrologia Normalização e Qualidade Industrial, Xerém, Brazil
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Abstract
Acidocalcisomes are acidic organelles containing calcium and a high concentration of phosphorus in the form of pyrophosphate (PP(i)) and polyphosphate (poly P). Organelles with these characteristics have been found from bacteria to human cells implying an early appearance and persistence over evolutionary time or their appearance by convergent evolution. Acidification of the organelles is driven by the presence of vacuolar proton pumps, one of which, the vacuolar proton pyrophosphatase, is absent in animals, where it is substituted by a vacuolar proton ATPase. A number of other pumps, antiporters, and channels have been described in acidocalcisomes of different species and are responsible for their internal content. Enzymes involved in the synthesis and degradation of PP(i) and poly P are present within the organelle. Acidocalcisomes function as storage sites for cations and phosphorus, and participate in PP(i) and poly P metabolism, calcium homeostasis, maintenance of intracellular pH, and osmoregulation. Experiments in which the acidocalcisome Ca(2+)-ATPase of different parasites were downregulated or eliminated, or acidocalcisome Ca(2+) was depleted revealed the importance of this store in Ca(2+) signaling needed for host invasion and virulence. Acidocalcisomes interact with other organelles in a number of organisms suggesting their association with the endosomal/lysosomal pathway, and are considered part of the lysosome-related group of organelles.
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Myre MA, Lumsden AL, Thompson MN, Wasco W, MacDonald ME, Gusella JF. Deficiency of huntingtin has pleiotropic effects in the social amoeba Dictyostelium discoideum. PLoS Genet 2011; 7:e1002052. [PMID: 21552328 PMCID: PMC3084204 DOI: 10.1371/journal.pgen.1002052] [Citation(s) in RCA: 41] [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: 11/23/2010] [Accepted: 03/02/2011] [Indexed: 11/24/2022] Open
Abstract
Huntingtin is a large HEAT repeat protein first identified in humans, where a polyglutamine tract expansion near the amino terminus causes a gain-of-function mechanism that leads to selective neuronal loss in Huntington's disease (HD). Genetic evidence in humans and knock-in mouse models suggests that this gain-of-function involves an increase or deregulation of some aspect of huntingtin's normal function(s), which remains poorly understood. As huntingtin shows evolutionary conservation, a powerful approach to discovering its normal biochemical role(s) is to study the effects caused by its deficiency in a model organism with a short life-cycle that comprises both cellular and multicellular developmental stages. To facilitate studies aimed at detailed knowledge of huntingtin's normal function(s), we generated a null mutant of hd, the HD ortholog in Dictyostelium discoideum. Dictyostelium cells lacking endogenous huntingtin were viable but during development did not exhibit the typical polarized morphology of Dictyostelium cells, streamed poorly to form aggregates by accretion rather than chemotaxis, showed disorganized F-actin staining, exhibited extreme sensitivity to hypoosmotic stress, and failed to form EDTA-resistant cell–cell contacts. Surprisingly, chemotactic streaming could be rescued in the presence of the bivalent cations Ca2+ or Mg2+ but not pulses of cAMP. Although hd− cells completed development, it was delayed and proceeded asynchronously, producing small fruiting bodies with round, defective spores that germinated spontaneously within a glassy sorus. When developed as chimeras with wild-type cells, hd− cells failed to populate the pre-spore region of the slug. In Dictyostelium, huntingtin deficiency is compatible with survival of the organism but renders cells sensitive to low osmolarity, which produces pleiotropic cell autonomous defects that affect cAMP signaling and as a consequence development. Thus, Dictyostelium provides a novel haploid organism model for genetic, cell biological, and biochemical studies to delineate the functions of the HD protein. Genetic evidence in humans and mouse models of Huntington's disease suggests that the disease mutation confers a deleterious gain-of-function on huntingtin that acts through the deregulation of some aspect of the protein's normal function(s). While huntingtin's function is poorly understood, its evolutionary conservation makes investigation of its physiological role in lower organisms an attractive route that has yet to be fully exploited. Therefore, we have used Dictyostelium discoideum to study the consequences of huntingtin (hd) deficiency. Developing Dictyostelium cells chemotax to form a multicellular slug that forms a fruiting body, comprising dormant spores encased above dead stalk cells. We found that hd− cells were hypersensitive to hypoosmotic stress. When starved, hd− cells aggregate by accretion, showed disorganized F-actin, and failed to form EDTA-resistant cell–cell contacts. Surprisingly, chemotactic signaling was rescued with Ca2+ or Mg2+ but not pulses of cAMP. Development of hd− mutants produced small fruiting bodies with round, defective spores, and when mixed with wild-type cells they didn't differentiate into spores. Our results are consistent with mammalian studies that show huntingtin is a multifunctional protein involved in many biochemical processes; and, importantly, they establish Dictyostelium as a valuable experimental organism for exploring in biochemical detail huntingtin's normal function(s).
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Affiliation(s)
- Michael A. Myre
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- * E-mail:
| | - Amanda L. Lumsden
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Morgan N. Thompson
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Wilma Wasco
- Genetics and Aging Research Unit, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Charlestown, Massachusetts, United States of America
| | - Marcy E. MacDonald
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - James F. Gusella
- Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston, Massachusetts, United States of America
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Ulrich PN, Jimenez V, Park M, Martins VP, Atwood J, Moles K, Collins D, Rohloff P, Tarleton R, Moreno SNJ, Orlando R, Docampo R. Identification of contractile vacuole proteins in Trypanosoma cruzi. PLoS One 2011; 6:e18013. [PMID: 21437209 PMCID: PMC3060929 DOI: 10.1371/journal.pone.0018013] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Accepted: 02/22/2011] [Indexed: 11/19/2022] Open
Abstract
Contractile vacuole complexes are critical components of cell volume regulation
and have been shown to have other functional roles in several free-living
protists. However, very little is known about the functions of the contractile
vacuole complex of the parasite Trypanosoma cruzi, the
etiologic agent of Chagas disease, other than a role in osmoregulation.
Identification of the protein composition of these organelles is important for
understanding their physiological roles. We applied a combined proteomic and
bioinfomatic approach to identify proteins localized to the contractile vacuole.
Proteomic analysis of a T. cruzi fraction enriched for
contractile vacuoles and analyzed by one-dimensional gel electrophoresis and
LC-MS/MS resulted in the addition of 109 newly detected proteins to the group of
expressed proteins of epimastigotes. We also identified different peptides that
map to at least 39 members of the dispersed gene family 1 (DGF-1) providing
evidence that many members of this family are simultaneously expressed in
epimastigotes. Of the proteins present in the fraction we selected several
homologues with known localizations in contractile vacuoles of other organisms
and others that we expected to be present in these vacuoles on the basis of
their potential roles. We determined the localization of each by expression as
GFP-fusion proteins or with specific antibodies. Six of these putative proteins
(Rab11, Rab32, AP180, ATPase subunit B, VAMP1, and phosphate transporter)
predominantly localized to the vacuole bladder. TcSNARE2.1, TcSNARE2.2, and
calmodulin localized to the spongiome. Calmodulin was also cytosolic. Our
results demonstrate the utility of combining subcellular fractionation,
proteomic analysis, and bioinformatic approaches for localization of organellar
proteins that are difficult to detect with whole cell methodologies. The CV
localization of the proteins investigated revealed potential novel roles of
these organelles in phosphate metabolism and provided information on the
potential participation of adaptor protein complexes in their biogenesis.
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Affiliation(s)
- Paul N. Ulrich
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Veronica Jimenez
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Miyoung Park
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Vicente P. Martins
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - James Atwood
- Complex Carbohydrate Research Center,
University of Georgia, Athens, Georgia, United States of America
| | - Kristen Moles
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Dalis Collins
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Peter Rohloff
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Rick Tarleton
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Silvia N. J. Moreno
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
| | - Ron Orlando
- Complex Carbohydrate Research Center,
University of Georgia, Athens, Georgia, United States of America
| | - Roberto Docampo
- Center for Tropical and Emerging Global
Diseases and Department of Cellular Biology, University of Georgia, Athens,
Georgia, United States of America
- * E-mail:
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Calcium- and polyphosphate-containing acidic granules of sea urchin eggs are similar to acidocalcisomes, but are not the targets for NAADP. Biochem J 2010; 429:485-95. [PMID: 20497125 PMCID: PMC2907711 DOI: 10.1042/bj20091956] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Acidocalcisomes are acidic calcium-storage compartments described from bacteria to humans and characterized by their high content in poly P (polyphosphate), a linear polymer of many tens to hundreds of Pi residues linked by high-energy phosphoanhydride bonds. In the present paper we report that millimolar levels of short-chain poly P (in terms of Pi residues) and inorganic PPi are present in sea urchin extracts as detected using 31P-NMR, enzymatic determinations and agarose gel electrophoresis. Poly P was localized to granules randomly distributed in the sea urchin eggs, as shown by labelling with the poly-P-binding domain of Escherichia coli exopolyphosphatase. These granules were enriched using iodixanol centrifugation and shown to be acidic and to contain poly P, as determined by Acridine Orange and DAPI (4',6'-diamidino-2-phenylindole) staining respectively. These granules also contained large amounts of calcium, sodium, magnesium, potassium and zinc, as detected by X-ray microanalysis, and bafilomycin A1-sensitive ATPase, pyrophosphatase and exopolyphosphatase activities, as well as Ca2+/H+ and Na+/H+ exchange activities, being therefore similar to acidocalcisomes described in other organisms. Calcium release from these granules induced by nigericin was associated with poly P hydrolysis. Although NAADP (nicotinic acid-adenine dinucleotide phosphate) released calcium from the granule fraction, this activity was not significantly enriched as compared with the NAADP-stimulated calcium release from homogenates and was not accompanied by poly P hydrolysis. GPN (glycyl-L-phenylalanine-naphthylamide) released calcium when added to sea urchin homogenates, but was unable to release calcium from acidocalcisome-enriched fractions, suggesting that these acidic stores are not the targets for NAADP.
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Docampo R, Ulrich P, Moreno SNJ. Evolution of acidocalcisomes and their role in polyphosphate storage and osmoregulation in eukaryotic microbes. Philos Trans R Soc Lond B Biol Sci 2010; 365:775-84. [PMID: 20124344 DOI: 10.1098/rstb.2009.0179] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Acidocalcisomes are acidic electron-dense organelles, rich in polyphosphate (poly P) complexed with calcium and other cations. While its matrix contains enzymes related to poly P metabolism, the membrane of the acidocalcisomes has a number of pumps (Ca(2+)-ATPase, V-H(+)-ATPase, H(+)-PPase), exchangers (Na(+)/H(+), Ca(2+)/H(+)), and at least one channel (aquaporin). Acidocalcisomes are present in both prokaryotes and eukaryotes and are an important storage of cations and phosphorus. They also play an important role in osmoregulation and interact with the contractile vacuole complex in a number of eukaryotic microbes. Acidocalcisomes resemble lysosome-related organelles (LRO) from mammalian cells in many of their properties. They share similar morphological characteristics, acidic properties, phosphorus contents and a system for targeting of their membrane proteins through adaptor complex-3 (AP-3). Storage of phosphate and cations may represent the ancestral physiological function of acidocalcisomes, with cation and pH homeostasis and osmoregulatory functions derived following the divergence of prokaryotes and eukaryotes.
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Affiliation(s)
- Roberto Docampo
- Department of Cellular Biology and Center for Tropical and Global Emerging Diseases, University of Georgia, Athens, GA 30602, USA.
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Abstract
Acidocalcisomes are acidic organelles with a high concentration of phosphorus present as pyrophosphate (PP(i)) and polyphosphate (poly P) complexed with calcium and other cations. The acidocalcisome membrane contains a number of pumps (Ca(2+)-ATPase, V-H(+)-ATPase, H(+)-PPase), exchangers (Na(+)/H(+), Ca(2+)/H(+)), and channels (aquaporins), while its matrix contains enzymes related to PP(i) and poly P metabolism. Acidocalcisomes have been observed in pathogenic, as well as non-pathogenic prokaryotes and eukaryotes, e.g. Chlamydomonas reinhardtii, and Dictyostelium discoideum. Some of the potential functions of the acidocalcisome are the storage of cations and phosphorus, the participation of phosphorus in PP(i) and poly P metabolism, calcium homeostasis, maintenance of intracellular pH homeostasis, and osmoregulation. In addition, acidocalcisomes resemble lysosome-related organelles (LRO) from mammalian cells in many of their properties. For example, we found that platelet dense granules, which are LROs, are very similar to acidocalcisomes. They share a similar size, acidic properties, and both contain PP(i), poly P, and calcium. Recent work that indicates that they also share the system for targeting of their membrane proteins through adaptor protein 3 reinforces this concept. The fact that acidocalcisomes interact with other organelles in parasitic protists, e.g. the contractile vacuole in Trypanosoma cruzi, and other vacuoles observed in Toxoplasma gondii, suggests that these cellular compartments may be associated with the endosomal/lysosomal pathway.
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Affiliation(s)
- Silvia N J Moreno
- Department of Cellular Biology and Center for Tropical and Global Emerging Diseases, University of Georgia, Athens, 30602, USA.
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Motta LS, Ramos IB, Gomes FM, de Souza W, Champagne DE, Santiago MF, Docampo R, Miranda K, Machado EA. Proton-pyrophosphatase and polyphosphate in acidocalcisome-like vesicles from oocytes and eggs of Periplaneta americana. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2009; 39:198-206. [PMID: 19111615 DOI: 10.1016/j.ibmb.2008.11.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 11/27/2008] [Accepted: 11/29/2008] [Indexed: 05/27/2023]
Abstract
Acidocalcisomes are acidic organelles containing large amounts of polyphosphate (poly P), a number of cations, and a variety of cation pumps in their limiting membrane. The vacuolar proton-pyrophosphatase (V-H(+)-PPase), a unique electrogenic proton-pump that couples pyrophosphate (PPi) hydrolysis to the active transport of protons across membranes, is commonly present in membranes of acidocalcisomes. In the course of insect oogenesis, a large amount of yolk protein is incorporated by the oocytes and stored in organelles called yolk granules (YGs). During embryogenesis, the content of these granules is degraded by acid hydrolases. These enzymes are activated by the acidification of the YG by a mechanism that is mediated by proton-pumps present in their membranes. In this work, we describe an H(+)-PPase activity in membrane fractions of oocytes and eggs of the domestic cockroach Periplaneta americana. The enzyme activity was optimum at pH around 7.0, and was dependent on Mg(2+) and inhibited by NaF, as well as by IDP and Ca(2+). Immunolocalization of the yolk preparation using antibodies against a conserved sequence of V-H(+)-PPases showed labeling of small vesicles, which also showed the presence of high concentrations of phosphorus, calcium and other elements, as revealed by electron probe X-ray microanalysis. In addition, poly P content was detected in ovaries and eggs and localized inside the yolk granules and the small vesicles. Altogether, our results provide evidence that numerous small vesicles of the eggs of P. americana present acidocalcisome-like characteristics. In addition, the possible role of these organelles during embryogenesis of this insect is discussed.
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Affiliation(s)
- Lucimar S Motta
- Laboratório de Entomologia Médica, Programa de Parasitologia e Biologia Celular, Instituto de Biofísica Carlos Chagas Filho, Brazil
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Acidic Ca2+ stores, excitability, and cell patterning in Dictyostelium discoideum. EUKARYOTIC CELL 2009; 8:696-702. [PMID: 19252125 DOI: 10.1128/ec.00360-08] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Rohloff P, Docampo R. A contractile vacuole complex is involved in osmoregulation in Trypanosoma cruzi. Exp Parasitol 2008; 118:17-24. [PMID: 17574552 PMCID: PMC2243178 DOI: 10.1016/j.exppara.2007.04.013] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2007] [Accepted: 04/25/2007] [Indexed: 10/23/2022]
Abstract
Acidocalcisomes are dense, acidic organelles with a high concentration of phosphorus present as pyrophosphate and polyphosphate complexed with calcium and other cations. Acidocalcisomes have been linked to the contractile vacuole complex in Chlamydomonas reinhardtii, Dictyostelium discoideum, and Trypanosoma cruzi. A microtubule- and cyclic AMP-mediated fusion of acidocalcisomes to the contractile vacuole complex in T. cruzi results in translocation of aquaporin and the resulting water movement which, in addition to swelling of acidocalcisomes, is responsible for the volume reversal not accounted for by efflux of osmolytes. Polyphosphate hydrolysis occurs during hyposmotic stress, probably increasing the osmotic pressure of the contractile vacuole and facilitating water movement.
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Affiliation(s)
- Peter Rohloff
- Department of Pathobiology and Medical Scholars Program, University of Illinos at Urbana-Champaign, Urbana, IL 61801
| | - Roberto Docampo
- Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, Paul D. Coverdell Center, University of Georgia, Athens, GA 30602
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Polyphosphate kinase 1, a conserved bacterial enzyme, in a eukaryote, Dictyostelium discoideum, with a role in cytokinesis. Proc Natl Acad Sci U S A 2007; 104:16486-91. [PMID: 17940044 DOI: 10.1073/pnas.0706847104] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Polyphosphate kinase 1 (PPK1), the principal enzyme responsible for reversible synthesis of polyphosphate (poly P) from the terminal phosphate of ATP, is highly conserved in bacteria and archaea. Dictyostelium discoideum, a social slime mold, is one of a few eukaryotes known to possess a PPK1 homolog (DdPPK1). Compared with PPK1 of Escherichia coli, DdPPK1 contains the conserved residues for ATP binding and autophosphorylation, but has an N-terminal extension of 370 aa, lacking homology with any known protein. Polyphosphate or ATP promote oligomerization of the enzyme in vitro. The DdPPK1 products are heterogeneous in chain length and shorter than those of E. coli. The unique DdPPK1 N-terminal domain was shown to be necessary for its enzymatic activity, cellular localization, and physiological functions. Mutants of DdPPK1, as previously reported, are defective in development, sporulation, and predation, and as shown here, in late stages of cytokinesis and cell division.
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46
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Malchow D, Lusche DF, De Lozanne A, Schlatterer C. A fast Ca2+-induced Ca2+-release mechanism in Dictyostelium discoideum. Cell Calcium 2007; 43:521-30. [PMID: 17854889 DOI: 10.1016/j.ceca.2007.08.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2007] [Revised: 07/16/2007] [Accepted: 08/09/2007] [Indexed: 11/17/2022]
Abstract
In vertebrate cells calcium-induced calcium release (CICR) is thought to be responsible for rapid cytosolic Ca(2+) elevations despite the occurrence of strong Ca(2+) buffering within the cytosol. In Dictyostelium, a CICR mechanism has not been reported. While analyzing Ca(2+) regulation in a vesicular fraction of Dictyostelium rich in Ca(2+)-flux activity, containing contractile vacuoles (CV) as the main component of acidic Ca(2+) stores and ER, we detected a rapid Ca(2+) change upon addition of Ca(2+) (CIC). CIC was three times larger in active stores accumulating Ca(2+) than before Ca(2+) uptake and in inactivated stores. Ca(2+) release was demonstrated with the calmodulin antagonist W7 that inhibits the V-type H(+)ATPase activity and Ca(2+) uptake of acidic Ca(2+) stores. W7 caused a rapid and large increase of extravesicular Ca(2+) ([Ca(2+)](e)), much faster and larger than thapsigargin (Tg), a Ca(2+)-uptake inhibitor of the ER. W7 treatment blocked CIC indicating that a large part of CIC is due to Ca(2+) release. The height of CIC depended on the filling state of the Ca(2+) stores. CIC was virtually unchanged in the iplA(-) strain that lacks a putative IP(3) or ryanodine receptor thought to be located at the endoplasmic reticulum. By contrast, CIC was reduced in two mutants, HGR8 and lvsA(-), that are impaired in acidic Ca(2+)-store function. Purified Ca(2+) stores enriched in CV still displayed CIC, indicating that CV are a source of Ca(2+)-induced Ca(2+) release. CIC-defective mutants were altered in their oscillatory properties. The irregularity of the HGR8 oscillation suggests that the principal oscillator is affected in this mutant.
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Affiliation(s)
- Dieter Malchow
- Department of Biology, University of Konstanz, P.O. Box 5560, D-78457 Konstanz, Germany.
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Ortiz-Gómez A, Jiménez C, Estévez AM, Carrero-Lérida J, Ruiz-Pérez LM, González-Pacanowska D. Farnesyl diphosphate synthase is a cytosolic enzyme in Leishmania major promastigotes and its overexpression confers resistance to risedronate. EUKARYOTIC CELL 2006; 5:1057-64. [PMID: 16835450 PMCID: PMC1489282 DOI: 10.1128/ec.00034-06] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Farnesyl diphosphate synthase is the most likely molecular target of aminobisphosphonates (e.g., risedronate), a set of compounds that have been shown to have antiprotozoal activity both in vitro and in vivo. This protein, together with other enzymes involved in isoprenoid biosynthesis, is an attractive drug target, yet little is known about the compartmentalization of the biosynthetic pathway. Here we show the intracellular localization of the enzyme in wild-type Leishmania major promastigote cells and in transfectants overexpressing farnesyl diphosphate synthase by using purified antibodies generated towards a homogenous recombinant Leishmania major farnesyl diphosphate synthase protein. Indirect immunofluorescence, together with immunoelectron microscopy, indicated that the enzyme is mainly located in the cytoplasm of both wild-type cells and transfectants. Digitonin titration experiments also confirmed this observation. Hence, while the initial step of isoprenoid biosynthesis catalyzed by 3-hydroxy-3-methylglutaryl-coenzyme A reductase is located in the mitochondrion, synthesis of farnesyl diphosphate by farnesyl diphosphate synthase is a cytosolic process. Leishmania major promastigote transfectants overexpressing farnesyl diphosphate synthase were highly resistant to risedronate, and the degree of resistance correlated with the increase in enzyme activity. Likewise, when resistance was induced by stepwise selection with the drug, the resulting resistant promastigotes exhibited increased levels of farnesyl diphosphate synthase. The overproduction of protein under different conditions of exposure to risedronate further supports the hypothesis that this enzyme is the main target of aminobisphosphonates in Leishmania cells.
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Affiliation(s)
- Aurora Ortiz-Gómez
- Instituto de Parasitología y Biomedicina López-Neyra, Consejo Superior de Investigaciones Científicas, Avda. del Conocimiento s/n, Parque Tecnológico Ciencias de la Salud, 18100 Armilla, Granada, Spain
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Rohloff P, Docampo R. Ammonium production during hypo-osmotic stress leads to alkalinization of acidocalcisomes and cytosolic acidification in Trypanosoma cruzi. Mol Biochem Parasitol 2006; 150:249-55. [PMID: 17005261 DOI: 10.1016/j.molbiopara.2006.08.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Revised: 08/17/2006] [Accepted: 08/21/2006] [Indexed: 11/17/2022]
Abstract
Osmotic swelling of Trypanosoma cruzi epimastigotes resulted in alkalinization of acidocalcisomes, as revealed by changes in acridine orange fluorescence of intact cells. Concomitant with these changes, intracellular ammonium levels increased while extracellular ammonium levels decreased significantly. Hypo-osmotic stress also resulted in cytosolic acidification. The observed changes in intracellular pH (pH(i)) were independent of extracellular calcium, and other ions concentration. Taken together, these results are consistent with a stimulation of ammonium production upon hypo-osmotic stress and its accumulation in acidocalcisomes resulting in their alkalinization, which might be responsible for polyphosphate hydrolysis and osmotic changes in the organelles.
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Affiliation(s)
- Peter Rohloff
- Department of Pathobiology and Medical Scholars Program, University of Illinos at Urbana-Champaign, Urbana, IL, USA
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Veiga N, Torres J, Domínguez S, Mederos A, Irvine RF, Díaz A, Kremer C. The behaviour of myo-inositol hexakisphosphate in the presence of magnesium(II) and calcium(II): protein-free soluble InsP6 is limited to 49 microM under cytosolic/nuclear conditions. J Inorg Biochem 2006; 100:1800-10. [PMID: 16920196 PMCID: PMC1874250 DOI: 10.1016/j.jinorgbio.2006.06.016] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Revised: 06/21/2006] [Accepted: 06/25/2006] [Indexed: 11/30/2022]
Abstract
Progress in the biology of myo-inositol hexakisphosphate (InsP(6)) has been delayed by the lack of a quantitative description of its multiple interactions with divalent cations. Our recent initial description of these [J. Torres, S. Dominguez, M.F. Cerda, G. Obal, A. Mederos, R.F. Irvine, A. Diaz, C. Kremer, J. Inorg. Biochem. 99 (2005) 828-840] predicted that under cytosolic/nuclear conditions, protein-free soluble InsP(6) occurs as Mg(5)(H(2)L), a neutral complex that exists thanks to a significant, but undefined, window of solubility displayed by solid Mg(5)(H(2)L).22H(2)O (L is fully deprotonated InsP(6)). Here we complete the description of the InsP(6)-Mg(2+)-Ca(2+) system, defining the solubilities of the Mg(2+) and Ca(2+) (Ca(5)(H(2)L).16H(2)O) solids in terms of K(s0)=[M(2+)](5)[H(2)L(10-)], with pK(s0)=32.93 for M=Mg and pK(s0)=39.3 for M=Ca. The concentration of soluble Mg(5)(H(2)L) at 37 degrees C and I=0.15M NaClO(4) is limited to 49muM, yet InsP(6) in mammalian cells may reach 100muM. Any cytosolic/nuclear InsP(6) in excess of 49muM must be protein- or membrane-bound, or as solid Mg(5)(H(2)L).22H(2)O, and any extracellular InsP(6) (e.g. in plasma) is surely protein-bound.
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Affiliation(s)
- Nicolás Veiga
- Cátedra de Química Inorgánica, Departamento Estrella Campos, Facultad de Química, Universidad de la República, Montevideo, Uruguay
| | - Julia Torres
- Cátedra de Química Inorgánica, Departamento Estrella Campos, Facultad de Química, Universidad de la República, Montevideo, Uruguay
| | - Sixto Domínguez
- Departamento de Química Inorgánica, Universidad de La Laguna, Tenerife, Canary Islands, Spain
| | - Alfredo Mederos
- Departamento de Química Inorgánica, Universidad de La Laguna, Tenerife, Canary Islands, Spain
| | - Robin F. Irvine
- Department of Pharmacology, University of Cambridge, Cambridge, UK
| | - Alvaro Díaz
- Cátedra de Inmunología, Facultad de Química/Ciencias, Universidad de la República, Montevideo, Uruguay
- Corresponding authors. Fax: +598 2 4874320 (A. Díaz), +598 2 9241906 (C. Kremer).
| | - Carlos Kremer
- Cátedra de Química Inorgánica, Departamento Estrella Campos, Facultad de Química, Universidad de la República, Montevideo, Uruguay
- Corresponding authors. Fax: +598 2 4874320 (A. Díaz), +598 2 9241906 (C. Kremer).
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50
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Malchow D, Lusche DF, Schlatterer C, De Lozanne A, Müller-Taubenberger A. The contractile vacuole in Ca2+-regulation in Dictyostelium: its essential function for cAMP-induced Ca2+-influx. BMC DEVELOPMENTAL BIOLOGY 2006; 6:31. [PMID: 16787542 PMCID: PMC1513554 DOI: 10.1186/1471-213x-6-31] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Accepted: 06/20/2006] [Indexed: 11/10/2022]
Abstract
BACKGROUND cAMP-induced Ca2+-influx in Dictyostelium is controlled by at least two non-mitochondrial Ca2+-stores: acidic stores and the endoplasmic reticulum (ER). The acidic stores may comprise the contractile vacuole network (CV), the endosomal compartment and acidocalcisomes. Here the role of CV in respect to function as a potential Ca2+-store was investigated. RESULTS Dajumin-GFP labeled contractile vacuoles were purified 7-fold by anti-GFP-antibodies in a magnetic field. The purified CV were shown for the first time to accumulate and release Ca2+. Release of Ca2+ was elicited by arachidonic acid or the calmodulin antagonist W7, the latter due to inhibition of the pump. The characteristics of Ca2+-transport and Ca2+-release of CV were compared to similarly purified vesicles of the ER labeled by calnexin-GFP. Since the CV proved to be a highly efficient Ca2+-compartment we wanted to know whether or not it takes part in cAMP-induced Ca2+-influx. We made use of the LvsA--mutant expected to display reduced Ca2+-transport due to loss of calmodulin. We found a severe reduction of cAMP-induced Ca2+-influx into whole cells. CONCLUSION The contractile vacuoles in Dictyostelium represent a highly efficient acidic Ca2+-store that is required for cAMP-induced Ca2+-influx.
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Affiliation(s)
- Dieter Malchow
- Department of Biology, University of Konstanz, D-78457 Konstanz, Germany
| | - Daniel F Lusche
- Department of Biology, University of Konstanz, D-78457 Konstanz, Germany
- WM Keck Research Facility, Department of Biological Sciences 014 BBE Iowa City, IA 52242, USA
| | | | - Arturo De Lozanne
- Section of Molecular Cell Developmental Biology, University of Texas at Austin, Austin, Tex 78712, USA
| | - Annette Müller-Taubenberger
- MaxPlanckInstitute for Biochemistry, D-82152 Martinsried, Germany
- Institute for Cell Biology (ABI), Ludwig Maximilians University München, D-80336 München, Germany
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