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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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2
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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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3
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Asady B, Dick CF, Ehrenman K, Sahu T, Romano JD, Coppens I. A single Na+-Pi cotransporter in Toxoplasma plays key roles in phosphate import and control of parasite osmoregulation. PLoS Pathog 2021; 16:e1009067. [PMID: 33383579 PMCID: PMC7817038 DOI: 10.1371/journal.ppat.1009067] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 01/20/2021] [Accepted: 10/14/2020] [Indexed: 11/22/2022] Open
Abstract
Inorganic ions such as phosphate, are essential nutrients required for a broad spectrum of cellular functions and regulation. During infection, pathogens must obtain inorganic phosphate (Pi) from the host. Despite the essentiality of phosphate for all forms of life, how the intracellular parasite Toxoplasma gondii acquires Pi from the host cell is still unknown. In this study, we demonstrated that Toxoplasma actively internalizes exogenous Pi by exploiting a gradient of Na+ ions to drive Pi uptake across the plasma membrane. The Na+-dependent phosphate transport mechanism is electrogenic and functionally coupled to a cipargarmin sensitive Na+-H+-ATPase. Toxoplasma expresses one transmembrane Pi transporter harboring PHO4 binding domains that typify the PiT Family. This transporter named TgPiT, localizes to the plasma membrane, the inward buds of the endosomal organelles termed VAC, and many cytoplasmic vesicles. Upon Pi limitation in the medium, TgPiT is more abundant at the plasma membrane. We genetically ablated the PiT gene, and ΔTgPiT parasites are impaired in importing Pi and synthesizing polyphosphates. Interestingly, ΔTgPiT parasites accumulate 4-times more acidocalcisomes, storage organelles for phosphate molecules, as compared to parental parasites. In addition, these mutants have a reduced cell volume, enlarged VAC organelles, defects in calcium storage and a slightly alkaline pH. Overall, these mutants exhibit severe growth defects and have reduced acute virulence in mice. In survival mode, ΔTgPiT parasites upregulate several genes, including those encoding enzymes that cleave or transfer phosphate groups from phosphometabolites, transporters and ions exchangers localized to VAC or acidocalcisomes. Taken together, these findings point to a critical role of TgPiT for Pi supply for Toxoplasma and also for protection against osmotic stresses. Inorganic phosphate (Pi) is indispensable for the biosynthesis of key cellular components, and is involved in many metabolic and signaling pathways. Transport across the plasma membrane is the first step in the utilization of Pi. The import mechanism of Pi by the intracellular parasite Toxoplasma is unknown. We characterized a transmembrane, high-affinity Na+-Pi cotransporter, named TgPiT, expressed by the parasite at the plasma membrane for Pi uptake. Interestingly, TgPiT is also localized to inward buds of the endosomal VAC organelles and some cytoplasmic vesicles. Loss of TgPiT results in a severe reduction in Pi internalization and polyphosphate levels, but stimulation of the biogenesis of phosphate-enriched acidocalcisomes. ΔTgPiT parasites have a shrunken cell body, enlarged VAC organelles, poor release of stored calcium and a mildly alkaline pH, suggesting a role for TgPiT in the maintenance of overall ionic homeostasis. ΔTgPiT parasites are poorly infectious in vitro and in mice. The mutant appears to partially cope with the absence of TgPiT by up-regulating genes coding for ion transporters and enzymes catalyzing phosphate group transfer. Our data highlight a scenario in which the role of TgPiT in Pi and Na+ transport is functionally coupled with osmoregulation activities central to sustain Toxoplasma survival.
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Affiliation(s)
- Beejan Asady
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore Maryland, United States of America
| | - Claudia F. Dick
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore Maryland, United States of America
| | - Karen Ehrenman
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore Maryland, United States of America
| | - Tejram Sahu
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore Maryland, United States of America
| | - Julia D. Romano
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore Maryland, United States of America
| | - Isabelle Coppens
- Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore Maryland, United States of America
- * E-mail:
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Kohl K, Zangger H, Rossi M, Isorce N, Lye LF, Owens KL, Beverley SM, Mayer A, Fasel N. Importance of polyphosphate in the Leishmania life cycle. MICROBIAL CELL 2018; 5:371-384. [PMID: 30175107 PMCID: PMC6116282 DOI: 10.15698/mic2018.08.642] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Protozoan parasites contain negatively charged polymers of a few up to several hundreds of phosphate residues. In other organisms, these poly-phosphate (polyP) chains serve as an energy source and phosphate reservoir, and have been implicated in adaptation to stress and virulence of pathogenic organisms. In this study, we confirmed first that the polyP polymerase vacuolar transporter chaperone 4 (VTC4) is responsible for polyP synthesis in Leishmania parasites. During Leishmaniain vitro culture, polyP is accumulated in logarithmic growth phase and subsequently consumed once stationary phase is reached. However, polyP is not essential since VTC4-deficient (vtc4-) Leishmania proliferated normally in culture and differentiated into infective metacyclic parasites and into intracellular and axenic amastigotes. In in vivo mouse infections, L. majorVTC4 knockout showed a delay in lesion formation but ultimately gave rise to strong pathology, although we were unable to restore virulence by complementation to confirm this phenotype. Knockdown of VTC4 did not alter the course of L. guyanensis infections in mice, suggesting that polyP was not required for infection, or that very low levels of it suffice for lesion development. At higher temperatures, Leishmania promastigotes highly consumed polyP, and both knockdown or deletion of VTC4 diminished parasite survival. Thus, although polyP was not essential in the life cycle of the parasite, our data suggests a role for polyP in increasing parasite survival at higher temperatures, a situation faced by the parasite when transmitted to humans.
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Affiliation(s)
- Kid Kohl
- Department of Biochemistry, University of Lausanne, Epalinges, Switzerland
| | - Haroun Zangger
- Department of Biochemistry, University of Lausanne, Epalinges, Switzerland
| | - Matteo Rossi
- Department of Biochemistry, University of Lausanne, Epalinges, Switzerland
| | - Nathalie Isorce
- Department of Biochemistry, University of Lausanne, Epalinges, Switzerland
| | - Lon-Fye Lye
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Katherine L Owens
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Stephen M Beverley
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Andreas Mayer
- Department of Biochemistry, University of Lausanne, Epalinges, Switzerland
| | - Nicolas Fasel
- Department of Biochemistry, University of Lausanne, Epalinges, Switzerland
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Varas M, Valdivieso C, Mauriaca C, Ortíz-Severín J, Paradela A, Poblete-Castro I, Cabrera R, Chávez FP. Multi-level evaluation of Escherichia coli polyphosphate related mutants using global transcriptomic, proteomic and phenomic analyses. Biochim Biophys Acta Gen Subj 2017; 1861:871-883. [PMID: 28069396 DOI: 10.1016/j.bbagen.2017.01.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 12/26/2016] [Accepted: 01/05/2017] [Indexed: 12/20/2022]
Abstract
BACKGROUND Polyphosphate (polyP) is a linear biopolymer found in all living cells. In bacteria, mutants lacking polyphosphate kinase 1 (PPK1), the enzyme responsible for synthesis of most polyP, have many structural and functional defects. However, little is known about the causes of these pleiotropic alterations. The link between ppk1 deletion and those numerous phenotypes observed can be the result of complex molecular interactions that can be elucidated via a systems biology approach. METHODS By integrating different omics levels (transcriptome, proteome and phenome), we described the functioning of various metabolic pathways among Escherichia coli polyphosphate mutant strains (Δppk1, Δppx, and ΔpolyP). Bioinformatic analyses reveal the complex metabolic and regulatory bases of the phenotypes unique to polyP mutants. RESULTS Our results suggest that during polyP deficiency (Δppk1 mutant), metabolic pathways needed for energy supply are up-regulated, including fermentation, aerobic and anaerobic respiration. Transcriptomic and q-proteomic contrasting changes between Δppk1 and Δppx mutant strains were observed in those central metabolic pathways and confirmed by using Phenotypic microarrays. In addition, our results suggest a regulatory connection between polyP, second messenger metabolism, alternative Sigma/Anti-Sigma factors and type-II toxin-antitoxin (TA) systems. CONCLUSIONS We suggest a broader role for polyP via regulation of ATP-dependent proteolysis of type II toxin-antitoxin system and alternative Sigma/Anti-Sigma factors, that could explain the multiple structural and functional deficiencies described due to alteration of polyP metabolism. GENERAL SIGNIFICANCE Understanding the interplay of polyP in bacterial metabolism using a systems biology approach can help to improve design of novel antimicrobials toward pathogens.
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Affiliation(s)
- Macarena Varas
- Systems Microbiology Laboratory, Department of Biology, Faculty of Science, University of Chile, Chile.
| | - Camilo Valdivieso
- Systems Microbiology Laboratory, Department of Biology, Faculty of Science, University of Chile, Chile; Department of Ecology, Faculty of Science, University of Chile, Chile.
| | - Cecilia Mauriaca
- Systems Microbiology Laboratory, Department of Biology, Faculty of Science, University of Chile, Chile.
| | - Javiera Ortíz-Severín
- Systems Microbiology Laboratory, Department of Biology, Faculty of Science, University of Chile, Chile.
| | | | - Ignacio Poblete-Castro
- Facultad de Ciencias Biológicas, Center for Bioinformatics and Integrative Biology, Biosystems Engineering Laboratory, Universidad Andrés Bello, Chile.
| | - Ricardo Cabrera
- Department of Biology, Faculty of Sciences, University of Chile, Chile.
| | - Francisco P Chávez
- Systems Microbiology Laboratory, Department of Biology, Faculty of Science, University of Chile, Chile.
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6
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Milligan-Myhre K, Wilson SK, Knoll LJ. Developmental change in translation initiation alters the localization of a common microbial protein necessary for Toxoplasma chronic infection. Mol Microbiol 2016; 102:1086-1098. [PMID: 27671212 PMCID: PMC5161674 DOI: 10.1111/mmi.13538] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/22/2016] [Indexed: 11/28/2022]
Abstract
The Toxoplasma gondii cyst stage is resistant to drug therapy. To identify potential targets for new therapeutics, we screened insertional mutants of T. gondii for a reduced ability to form cysts in the brains of mice. In one of these mutants, named 38C3, the mutagenesis plasmid inserted into the mRNA of a protein that is highly conserved in microbes but is not present in humans. The mutation in 38C3 causes reduced brain cyst production during chronic infection, but does not affect acute virulence, so the disrupted gene and protein are called T. gondii Brain Colonization Protein 1 (TgBCP1). TgBCP1 has three potential in frame start codons that produce 51, 33 or 25 kDa proteins. In rapidly replicating tachyzoites, translation initiates at the third methionine, producing the 25 kDa form that is conserved in many bacteria and protozoans. Brain cysts exclusively express the 51 kDa form of TgBCP1, which is secreted from the parasites and localizes to the cyst wall. Only expression of the long form of TgBCP1 restored cyst formation in the 38C3 mutant. TgBCP1 is essential for cyst formation and is the first example of a developmental regulation in translation initiation site preference for a T. gondii protein.
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Affiliation(s)
| | - Sarah K. Wilson
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706
| | - Laura J. Knoll
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, WI 53706
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7
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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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8
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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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9
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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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10
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Toxoplasma gondii upregulates interleukin-12 to prevent Plasmodium berghei-induced experimental cerebral malaria. Infect Immun 2014; 82:1343-53. [PMID: 24396042 DOI: 10.1128/iai.01259-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
A chronic infection with the parasite Toxoplasma gondii has previously been shown to protect mice against subsequent viral, bacterial, or protozoal infections. Here we have shown that a chronic T. gondii infection can prevent Plasmodium berghei ANKA-induced experimental cerebral malaria (ECM) in C57BL/6 mice. Treatment with soluble T. gondii antigens (STAg) reduced parasite sequestration and T cell infiltration in the brains of P. berghei-infected mice. Administration of STAg also preserved blood-brain barrier function, reduced ECM symptoms, and significantly decreased mortality. STAg treatment 24 h post-P. berghei infection led to a rapid increase in serum levels of interleukin 12 (IL-12) and gamma interferon (IFN-γ). By 5 days after P. berghei infection, STAg-treated mice had reduced IFN-γ levels compared to those of mock-treated mice, suggesting that reductions in IFN-γ at the time of ECM onset protected against lethality. Using IL-10- and IL-12βR-deficient mice, we found that STAg-induced protection from ECM is IL-10 independent but IL-12 dependent. Treatment of P. berghei-infected mice with recombinant IL-12 significantly decreased parasitemia and mortality. These data suggest that IL-12, either induced by STAg or injected as a recombinant protein, mediates protection from ECM-associated pathology potentially through early induction of IFN-γ and reduction in parasitemia. These results highlight the importance of early IL-12 induction in protection against ECM.
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Ulrich PN, Lander N, Kurup SP, Reiss L, Brewer J, Soares Medeiros LC, Miranda K, Docampo R. The acidocalcisome vacuolar transporter chaperone 4 catalyzes the synthesis of polyphosphate in insect-stages of Trypanosoma brucei and T. cruzi. J Eukaryot Microbiol 2014; 61:155-65. [PMID: 24386955 DOI: 10.1111/jeu.12093] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 11/06/2013] [Accepted: 11/06/2013] [Indexed: 11/27/2022]
Abstract
Polyphosphate is a polymer of inorganic phosphate found in both prokaryotes and eukaryotes. Polyphosphate typically accumulates in acidic, calcium-rich organelles known as acidocalcisomes, and recent research demonstrated that vacuolar transporter chaperone 4 catalyzes its synthesis in yeast. The human pathogens Trypanosoma brucei and T. cruzi possess vacuolar transporter chaperone 4 homologs. We demonstrate that T. cruzi vacuolar transporter chaperone 4 localizes to acidocalcisomes of epimastigotes by immunofluorescence and immuno-electron microscopy and that the recombinant catalytic region of the T. cruzi enzyme is a polyphosphate kinase. RNA interference of the T. brucei enzyme in procyclic form parasites reduced short chain polyphosphate levels and resulted in accumulation of pyrophosphate. These results suggest that this trypanosome enzyme is an important component of a polyphosphate synthase complex that utilizes ATP to synthesize and translocate polyphosphate to acidocalcisomes in insect stages of these parasites.
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Affiliation(s)
- Paul N Ulrich
- Department of Cellular Biology, Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, 30602, USA; Department of Biology, Georgia State University, Atlanta, GA, 30303, USA
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Gerasimaitė R, Sharma S, Desfougères Y, Schmidt A, Mayer A. Coupled synthesis and translocation restrains polyphosphate to acidocalcisome-like vacuoles and prevents its toxicity. J Cell Sci 2014; 127:5093-104. [DOI: 10.1242/jcs.159772] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Eukaryotes contain inorganic polyphosphate (polyP) and acidocalcisomes, which sequester polyP and store amino acids and divalent cations. Why polyP is sequestered in dedicated organelles has been unknown. We show that polyP produced in the cytosol of yeast becomes toxic. Reconstitution of polyP translocation with purified vacuoles, the acidocalcisomes of yeast, showed that cytosolic polyP cannot be imported whereas polyP produced by the VTC complex, an endogenous vacuolar polyP polymerase, is efficiently imported and does not interfere with growth. PolyP synthesis and import require an electrochemical gradient, probably as a driving force for polyP translocation. VTC exposes its catalytic domain to the cytosol and carries nine vacuolar transmembrane domains. Mutations in the VTC transmembrane regions, which likely constitute the translocation channel, block not only polyP translocation but also synthesis. Since they are far from the cytosolic catalytic domain of VTC, this suggests that the VTC complex obligatorily couples synthesis of polyP to its import in order to avoid toxic intermediates in the cytosol. Sequestration of otherwise toxic polyP may be one reason for the existence of acidocalcisomes in eukaryotes.
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Affiliation(s)
- Silvia N J Moreno
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, Georgia, USA.
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14
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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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15
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Phosphate homeostasis in the yeast Saccharomyces cerevisiae, the key role of the SPX domain-containing proteins. FEBS Lett 2012; 586:289-95. [PMID: 22285489 DOI: 10.1016/j.febslet.2012.01.036] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 01/11/2012] [Accepted: 01/16/2012] [Indexed: 12/27/2022]
Abstract
In the yeast Saccharomyces cerevisiae, a working model for nutrient homeostasis in eukaryotes, inorganic phosphate (Pi) homeostasis is regulated by the PHO pathway, a set of phosphate starvation induced genes, acting to optimize Pi uptake and utilization. Among these, a subset of proteins containing the SPX domain has been shown to be key regulators of Pi homeostasis. In this review, we summarize the recent progresses in elucidating the mechanisms controlling Pi homeostasis in yeast, focusing on the key roles of the SPX domain-containing proteins in these processes, as well as describing the future challenges and opportunities in this fast-moving field.
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Achbergerová L, Nahálka J. Polyphosphate--an ancient energy source and active metabolic regulator. Microb Cell Fact 2011; 10:63. [PMID: 21816086 PMCID: PMC3163519 DOI: 10.1186/1475-2859-10-63] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Accepted: 08/04/2011] [Indexed: 11/23/2022] Open
Abstract
There are a several molecules on Earth that effectively store energy within their covalent bonds, and one of these energy-rich molecules is polyphosphate. In microbial cells, polyphosphate granules are synthesised for both energy and phosphate storage and are degraded to produce nucleotide triphosphate or phosphate. Energy released from these energetic carriers is used by the cell for production of all vital molecules such as amino acids, nucleobases, sugars and lipids. Polyphosphate chains directly regulate some processes in the cell and are used as phosphate donors in gene regulation. These two processes, energetic metabolism and regulation, are orchestrated by polyphosphate kinases. Polyphosphate kinases (PPKs) can currently be categorized into three groups (PPK1, PPK2 and PPK3) according their functionality; they can also be divided into three groups according their homology (EcPPK1, PaPPK2 and ScVTC). This review discusses historical information, similarities and differences, biochemical characteristics, roles in stress response regulation and possible applications in the biotechnology industry of these enzymes. At the end of the review, a hypothesis is discussed in view of synthetic biology applications that states polyphosphate and calcium-rich organelles have endosymbiotic origins from ancient protocells that metabolized polyphosphate.
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Affiliation(s)
- Lucia Achbergerová
- Slovak Academy of Sciences, Institute of Chemistry, Centre for Glycomics, Dúbravská cesta 9, Bratislava, Slovakia
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Milligan-Myhre KC, Rooney PJ, Knoll LJ. Examination of a virulence mutant uncovers the ribosome biogenesis regulatory protein of Toxoplasma gondii. J Parasitol 2011; 97:1173-7. [PMID: 21736491 DOI: 10.1645/ge-2741.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Several insertional mutants identified in a screen for Toxoplasma gondii that were defective in establishing a chronic infection had a common site of plasmid insertion. This insertion site was determined to be 43 bp upstream of the transcription initiation site of a gene whose predicted product has homology to ribosome biogenesis regulatory protein Rrs1p, an essential protein required for ribosome biogenesis in Saccharomyces cerevisiae. Northern blot analysis of this locus, termed TgRRS1 , showed that in the C3 mutant, the full-length transcript is down-regulated and at least 1 new smaller transcript is present. Restoration of the intact predicted promoter and locus to TgRRS1 insertional mutant strain C3 did not restore brain cyst formation to the levels of the parent strain. Epitope-tagged TgRRS1 was found to localize to the parasite nucleolus, in an area corresponding to the granular component region. TgRRS1 can serve as a marker for the sub-nucleolar granular component region of T. gondii.
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