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Xu ZS, Li FJ, Hide G, Lun ZR, Lai DH. Vacuolar ATPase depletion contributes to dysregulation of endocytosis in bloodstream forms of Trypanosoma brucei. Parasit Vectors 2020; 13:214. [PMID: 32334612 PMCID: PMC7183646 DOI: 10.1186/s13071-020-04068-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Accepted: 04/09/2020] [Indexed: 12/04/2022] Open
Abstract
Background Vacuolar H+-ATPase (V-ATPase) is a highly conserved protein complex which hydrolyzes ATP and pumps protons to acidify vacuolar vesicles. Beyond its role in pH maintenance, the involvement of V-ATPase in endocytosis is well documented in mammals and plants but is less clear in Trypanosoma brucei. Methods In this study, the subcellular localization of V-ATPase subunit B (TbVAB) of T. brucei was assessed via in situ N-terminal YFP-tagging and immunofluorescence assays. Transgenic bloodstream forms (BSF) of T. brucei were generated which comprised either a V-ATPase subunit B (TbVAB) conditional knockout or a V-ATPase subunit A (TbVAA) knockdown. Acridine orange and BCECF-AM were employed to assess the roles of V-ATPase in the pH regulation of BSF T. brucei. The endocytic activities of three markers were also characterized by flow cytometry analyses. Furthermore, trypanosomes were counted from trypanolysis treatment groups (either containing 1% or 5% NHS) and endocytosed trypanosome lytic factor (TLF) was also analyzed by an immunoblotting assay. Results TbVAB was found to localize to acidocalcisomes, lysosomes and probably also to endosomes of BSF of T. brucei and was demonstrated to be essential for cell growth. TbVAB depletion neutralized acidic organelles at 24 hours post-tetracycline depletion (hpd), meanwhile the steady state intracellular pH increased from 7.016 ± 0.013 to 7.422 ± 0.058. Trypanosomes with TbVAB depletion at 24 hpd were found to take up more transferrin (2.068 ± 0.277 fold) but less tomato lectin (49.31 ± 22.57%) by endocytosis, while no significant change was detected in dextran uptake. Similar endocytic dysregulated phenotypes were also observed in TbVAA knockdown cells. In addition, TbVAB depleted trypanosomes showed a low uptake of TLF and exhibited less sensitive to lysis in both 1% and 5% NHS treatments. Conclusions TbVAB is a key component of V-ATPase and was found to play a key function in endocytosis as well as exhibiting different effects in a receptor/cargo dependent manner in BSF of T. brucei. Besides vacuolar alkalinization, the dysregulation of endocytosis in TbVAB depleted T. brucei is considered to contribute to the reduced sensitivity to lysis by normal human serum.![]()
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Affiliation(s)
- Zhi-Shen Xu
- Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, and Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Sun Yat-Sen University, Guangzhou, 510275, The People's Republic of China
| | - Feng-Jun Li
- Department of Biological Sciences, National University of Singapore, Singapore, 11754, Singapore
| | - Geoff Hide
- Biomedical Research Centre and Ecosystems and Environment Research Centre, School of Science, Engineering and Environment, University of Salford, Salford, M5 4WT, UK
| | - Zhao-Rong Lun
- Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, and Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Sun Yat-Sen University, Guangzhou, 510275, The People's Republic of China. .,Biomedical Research Centre and Ecosystems and Environment Research Centre, School of Science, Engineering and Environment, University of Salford, Salford, M5 4WT, UK.
| | - De-Hua Lai
- Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, and Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Sun Yat-Sen University, Guangzhou, 510275, The People's Republic of China.
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Fontaine F, Lecordier L, Vanwalleghem G, Uzureau P, Van Reet N, Fontaine M, Tebabi P, Vanhollebeke B, Büscher P, Pérez-Morga D, Pays E. APOLs with low pH dependence can kill all African trypanosomes. Nat Microbiol 2017; 2:1500-1506. [PMID: 28924146 PMCID: PMC5660622 DOI: 10.1038/s41564-017-0034-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 08/24/2017] [Indexed: 02/02/2023]
Abstract
The primate-specific serum protein apolipoprotein L1 (APOL1) is the only secreted member of a family of cell death promoting proteins 1-4 . APOL1 kills the bloodstream parasite Trypanosoma brucei brucei, but not the human sleeping sickness agents T.b. rhodesiense and T.b. gambiense 3 . We considered the possibility that intracellular members of the APOL1 family, against which extracellular trypanosomes could not have evolved resistance, could kill pathogenic T. brucei subspecies. Here we show that recombinant APOL3 (rAPOL3) kills all African trypanosomes, including T.b. rhodesiense, T.b. gambiense and the animal pathogens Trypanosoma evansi, Trypanosoma congolense and Trypanosoma vivax. However, rAPOL3 did not kill more distant trypanosomes such as Trypanosoma theileri or Trypanosoma cruzi. This trypanolytic potential was partially shared by rAPOL1 from Papio papio (rPpAPOL1). The differential killing ability of rAPOL3 and rAPOL1 was associated with a distinct dependence on acidic pH for activity. Due both to its instability and toxicity when injected into mice, rAPOL3 cannot be used for the treatment of infection, but an experimental rPpAPOL1 mutant inspired by APOL3 exhibited enhanced trypanolytic activity in vitro and the ability to completely inhibit T.b. gambiense infection in mice. We conclude that pH dependence influences the trypanolytic potential of rAPOLs.
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Affiliation(s)
- Frédéric Fontaine
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des Profs Jeener et Brachet, B-6041, Gosselies, Belgium
| | - Laurence Lecordier
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des Profs Jeener et Brachet, B-6041, Gosselies, Belgium
| | - Gilles Vanwalleghem
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des Profs Jeener et Brachet, B-6041, Gosselies, Belgium.,School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, 4072, Australia
| | - Pierrick Uzureau
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des Profs Jeener et Brachet, B-6041, Gosselies, Belgium.,Laboratoire de Médecine Expérimentale (ULB222), Hôpital André Vésale, Université Libre de Bruxelles, 706, route de Gozée, B-6110, Montigny le Tilleul, Belgium
| | - Nick Van Reet
- Unit of Parasite Diagnostics, Institute of Tropical Medicine, 155, Nationalestraat, B-2000, Antwerpen, Belgium
| | - Martina Fontaine
- Laboratory of Immunobiology, IBMM, Université Libre de Bruxelles, 12, rue des Profs Jeener et Brachet, B-6041, Gosselies, Belgium
| | - Patricia Tebabi
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des Profs Jeener et Brachet, B-6041, Gosselies, Belgium
| | - Benoit Vanhollebeke
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des Profs Jeener et Brachet, B-6041, Gosselies, Belgium
| | - Philippe Büscher
- Unit of Parasite Diagnostics, Institute of Tropical Medicine, 155, Nationalestraat, B-2000, Antwerpen, Belgium
| | - David Pérez-Morga
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des Profs Jeener et Brachet, B-6041, Gosselies, Belgium.,Center for Microscopy and Molecular Imaging (CMMI), Université Libre de Bruxelles, 12, rue des Profs Jeener et Brachet, B-6041, Gosselies, Belgium
| | - Etienne Pays
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des Profs Jeener et Brachet, B-6041, Gosselies, Belgium.
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Greene AS, Hajduk SL. Trypanosome Lytic Factor-1 Initiates Oxidation-stimulated Osmotic Lysis of Trypanosoma brucei brucei. J Biol Chem 2016; 291:3063-75. [PMID: 26645690 PMCID: PMC4742767 DOI: 10.1074/jbc.m115.680371] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Revised: 11/12/2015] [Indexed: 01/18/2023] Open
Abstract
Human innate immunity against the veterinary pathogen Trypanosoma brucei brucei is conferred by trypanosome lytic factors (TLFs), against which human-infective T. brucei gambiense and T. brucei rhodesiense have evolved resistance. TLF-1 is a subclass of high density lipoprotein particles defined by two primate-specific apolipoproteins: the ion channel-forming toxin ApoL1 (apolipoprotein L1) and the hemoglobin (Hb) scavenger Hpr (haptoglobin-related protein). The role of oxidative stress in the TLF-1 lytic mechanism has been controversial. Here we show that oxidative processes are involved in TLF-1 killing of T. brucei brucei. The lipophilic antioxidant N,N'-diphenyl-p-phenylenediamine protected TLF-1-treated T. brucei brucei from lysis. Conversely, lysis of TLF-1-treated T. brucei brucei was increased by the addition of peroxides or thiol-conjugating agents. Previously, the Hpr-Hb complex was postulated to be a source of free radicals during TLF-1 lysis. However, we found that the iron-containing heme of the Hpr-Hb complex was not involved in TLF-1 lysis. Furthermore, neither high concentrations of transferrin nor knock-out of cytosolic lipid peroxidases prevented TLF-1 lysis. Instead, purified ApoL1 was sufficient to induce lysis, and ApoL1 lysis was inhibited by the antioxidant DPPD. Swelling of TLF-1-treated T. brucei brucei was reminiscent of swelling under hypotonic stress. Moreover, TLF-1-treated T. brucei brucei became rapidly susceptible to hypotonic lysis. T. brucei brucei cells exposed to peroxides or thiol-binding agents were also sensitized to hypotonic lysis in the absence of TLF-1. We postulate that ApoL1 initiates osmotic stress at the plasma membrane, which sensitizes T. brucei brucei to oxidation-stimulated osmotic lysis.
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Affiliation(s)
- Amy Styer Greene
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
| | - Stephen L Hajduk
- From the Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
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Human trypanolytic factor APOL1 forms pH-gated cation-selective channels in planar lipid bilayers: relevance to trypanosome lysis. Proc Natl Acad Sci U S A 2015; 112:2894-9. [PMID: 25730870 DOI: 10.1073/pnas.1421953112] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Apolipoprotein L-1 (APOL1), the trypanolytic factor of human serum, can lyse several African trypanosome species including Trypanosoma brucei brucei, but not the human-infective pathogens T. brucei rhodesiense and T. brucei gambiense, which are resistant to lysis by human serum. Lysis follows the uptake of APOL1 into acidic endosomes and is apparently caused by colloid-osmotic swelling due to an increased ion permeability of the plasma membrane. Here we demonstrate that nanogram quantities of full-length recombinant APOL1 induce ideally cation-selective macroscopic conductances in planar lipid bilayers. The conductances were highly sensitive to pH: their induction required acidic pH (pH 5.3), but their magnitude could be increased 3,000-fold upon alkalinization of the milieu (pK(a) = 7.1). We show that this phenomenon can be attributed to the association of APOL1 with the bilayer at acidic pH, followed by the opening of APOL1-induced cation-selective channels upon pH neutralization. Furthermore, the conductance increase at neutral pH (but not membrane association at acidic pH) was prevented by the interaction of APOL1 with the serum resistance-associated protein, which is produced by T. brucei rhodesiense and prevents trypanosome lysis by APOL1. These data are consistent with a model of lysis that involves endocytic recycling of APOL1 and the formation of cation-selective channels, at neutral pH, in the parasite plasma membrane.
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Alsford S, Currier RB, Guerra-Assunção JA, Clark TG, Horn D. Cathepsin-L can resist lysis by human serum in Trypanosoma brucei brucei. PLoS Pathog 2014; 10:e1004130. [PMID: 24830321 PMCID: PMC4022737 DOI: 10.1371/journal.ppat.1004130] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 04/02/2014] [Indexed: 11/18/2022] Open
Abstract
Closely related African trypanosomes cause lethal diseases but display distinct host ranges. Specifically, Trypanosoma brucei brucei causes nagana in livestock but fails to infect humans, while Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense cause sleeping sickness in humans. T. b. brucei fails to infect humans because it is sensitive to innate immune complexes found in normal human serum known as trypanolytic factor (TLF) 1 and 2; the lytic component is apolipoprotein-L1 in both TLFs. TLF resistance mechanisms of T. b. gambiense and T. b. rhodesiense are now known to arise through either gain or loss-of-function, but our understanding of factors that render T. b. brucei susceptible to lysis by human serum remains incomplete. We conducted a genome-scale RNA interference (RNAi) library screen for reduced sensitivity to human serum. Among only four high-confidence ‘hits’ were all three genes previously shown to sensitize T. b. brucei to human serum, the haptoglobin-haemoglobin receptor (HpHbR), inhibitor of cysteine peptidase (ICP) and the lysosomal protein, p67, thereby demonstrating the pivotal roles these factors play. The fourth gene identified encodes a predicted protein with eleven trans-membrane domains. Using chemical and genetic approaches, we show that ICP sensitizes T. b. brucei to human serum by modulating the essential cathepsin, CATL, a lysosomal cysteine peptidase. A second cathepsin, CATB, likely to be dispensable for growth in in vitro culture, has little or no impact on human-serum sensitivity. Our findings reveal major and novel determinants of human-serum sensitivity in T. b. brucei. They also shed light on the lysosomal protein-protein interactions that render T. b. brucei exquisitely sensitive to lytic factors in human serum, and indicate that CATL, an important potential drug target, has the capacity to resist these factors. The interplay among host innate immunity and resistance mechanisms in African trypanosomes has a major impact on the host range of these tsetse-fly transmitted parasites, defining their ability to cause disease in humans. A genome-scale RNAi screen identified a highly restricted set of four genes that sensitise trypanosomes to human serum: those encoding the haptoglobin-haemoglobin receptor, a predicted trans-membrane channel, a lysosomal membrane-protein and the cysteine peptidase inhibitor. An analysis of the cysteine peptidases revealed cathepsin-L as the protease regulated by the inhibitor – and with the capacity to render the parasite resistant to lysis by human serum. These findings emphasise the importance of parasite factors for the delivery and stability of host toxins. They also shed light on the control of proteolysis by parasites and potential unanticipated consequences of therapies that target the parasite proteases.
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Affiliation(s)
- Sam Alsford
- London School of Hygiene & Tropical Medicine, London, United Kingdom
- * E-mail:
| | - Rachel B. Currier
- London School of Hygiene & Tropical Medicine, London, United Kingdom
| | | | - Taane G. Clark
- London School of Hygiene & Tropical Medicine, London, United Kingdom
| | - David Horn
- Division of Biological Chemistry & Drug Discovery, College of Life Sciences, University of Dundee, Dundee, United Kingdom
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Silverman JS, Schwartz KJ, Hajduk SL, Bangs JD. Late endosomal Rab7 regulates lysosomal trafficking of endocytic but not biosynthetic cargo in Trypanosoma brucei. Mol Microbiol 2011; 82:664-78. [PMID: 21923766 DOI: 10.1111/j.1365-2958.2011.07842.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
We present the first functional analysis of the small GTPase, TbRab7, in Trypanosoma brucei. TbRab7 defines discrete late endosomes closely juxtaposed to the terminal p67(+) lysosome. RNAi indicates that TbRab7 is essential in bloodstream trypanosomes. Initial rates of endocytosis were unaffected, but lysosomal delivery of cargo, including tomato lectin (TL) and trypanolytic factor (TLF) were blocked. These accumulate in a dispersed internal compartment of elevated pH, likely derived from the late endosome. Surface binding of TL but not TLF was reduced, suggesting that cellular distribution of flagellar pocket receptors is differentially regulated by TbRab7. TLF activity was reduced approximately threefold confirming that lysosomal delivery is critical for trypanotoxicity. Unexpectedly, delivery of endogenous proteins, p67 and TbCatL, were unaffected indicating that TbRab7 does not regulate biosynthetic lysosomal trafficking. Thus, unlike mammalian cells and yeast, lysosomal trafficking of endocytosed and endogenous proteins occur via different routes and/or are regulated differentially. TbRab7 silencing had no effect on a cryptic default pathway to the lysosome, suggesting that the default lysosomal reporters p67ΔTM, p67ΔCD and VSGΔGPI do not utilize the endocytic pathway as previously proposed. Surprisingly, conditional knockout indicates that TbRab7 may be non-essential in procyclic insect form trypanosomes.
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Affiliation(s)
- Jason S Silverman
- Department of Medical Microbiology and Immunology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
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Endosomal localization of the serum resistance-associated protein in African trypanosomes confers human infectivity. EUKARYOTIC CELL 2011; 10:1023-33. [PMID: 21705681 DOI: 10.1128/ec.05112-11] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Trypanosoma brucei rhodesiense is the causative agent of human African sleeping sickness. While the closely related subspecies T. brucei brucei is highly susceptible to lysis by a subclass of human high-density lipoproteins (HDL) called trypanosome lytic factor (TLF), T. brucei rhodesiense is resistant and therefore able to establish acute and fatal infections in humans. This resistance is due to expression of the serum resistance-associated (SRA) gene, a member of the variant surface glycoprotein (VSG) gene family. Although much has been done to establish the role of SRA in human serum resistance, the specific molecular mechanism of SRA-mediated resistance remains a mystery. Thus, we report the trafficking and steady-state localization of SRA in order to provide more insight into the mechanism of SRA-mediated resistance. We show that SRA traffics to the flagellar pocket of bloodstream-form T. brucei organisms, where it localizes transiently before being endocytosed to its steady-state localization in endosomes, and we demonstrate that the critical point of colocalization between SRA and TLF occurs intracellularly.
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Wheeler RJ. The trypanolytic factor-mechanism, impacts and applications. Trends Parasitol 2010; 26:457-64. [PMID: 20646962 DOI: 10.1016/j.pt.2010.05.005] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Revised: 05/19/2010] [Accepted: 05/20/2010] [Indexed: 11/25/2022]
Abstract
The Trypanosoma brucei subspecies T. brucei brucei is non-human infective due to susceptibility to lysis by trypanolytic factor (TLF) in human serum. Reviewed here are the advances which have revealed apolipoprotein L1 (ApoL1), found in high density lipoprotein, as the lysis-inducing component of TLF, the means of uptake via haptoglobin-related protein receptor and the mechanism of resistance in T. b. rhodesiense via its serum resistance-associated (SRA) protein. The first practical steps to application of these discoveries are now in progress; transgenic animals expressing either baboon or minimally truncated human ApoL1 show resistance to both T. b. brucei and T. b. rhodesiense. This has major implications for treatment and prevention of human and animal African trypanosomiasis.
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Affiliation(s)
- Richard J Wheeler
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, UK.
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Vanhollebeke B, Pays E. The trypanolytic factor of human serum: many ways to enter the parasite, a single way to kill. Mol Microbiol 2010; 76:806-14. [PMID: 20398209 DOI: 10.1111/j.1365-2958.2010.07156.x] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Humans have developed a particular innate immunity system against African trypanosomes, and only two Trypanosoma brucei clones (T. b. gambiense, T. b. rhodesiense) can resist this defence and cause sleeping sickness. The main players of this immunity are the primate-specific apolipoprotein L-I (apoL1) and haptoglobin-related protein (Hpr). These proteins are both associated with two serum complexes, a minor subfraction of HDLs and an IgM/apolipoprotein A-I (apoA1) complex, respectively, termed trypanosome lytic factor (TLF) 1 and TLF2. Although the two complexes appear to lyse trypanosomes by the same mechanism, they enter the parasite through various modes of uptake. In case of TLF1 one uptake process was characterized. When released in the circulation, haemoglobin (Hb) binds to Hpr, hence to TLF1. In turn the TLF1-Hpr-Hb complex binds to the trypanosome haptoglobin (Hp)-Hb receptor, whose original function is to ensure haem uptake for optimal growth of the parasite. This binding triggers efficient uptake of TLF1 and subsequent trypanosome lysis. While Hpr is involved as TLF ligand, the lytic activity is due to apoL1, a Bcl-2-like pore-forming protein. We discuss the in vivo relevance of this uptake pathway in the context of other potentially redundant delivery routes.
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Affiliation(s)
- Benoit Vanhollebeke
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des Professeurs Jeener et Brachet, B-6041 Gosselies, Belgium
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Thomson R, Samanovic M, Raper J. Activity of trypanosome lytic factor: a novel component of innate immunity. Future Microbiol 2009; 4:789-96. [PMID: 19722834 DOI: 10.2217/fmb.09.57] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Trypanosome lytic factors (TLFs) are high-density lipoproteins and components of primate innate immunity. TLFs are characterized by their ability to kill extracellular protozoon parasites of the genus Trypanosoma. Two subspecies of Trypanosoma brucei have evolved resistance to TLFs and can consequently infect humans, resulting in the disease African sleeping sickness. The unique protein components of TLFs are a hemoglobin-binding protein, haptoglobin-related protein and a pore-forming protein, apoL-I. The recent advances in our understanding of the roles that these proteins play in the mechanism of TLF-mediated lysis are highlighted in this article. In light of recent data, which demonstrate that TLFs can ameliorate infection by the intracellular pathogen Leishmania, we also discuss the broader function of TLFs as components of innate immunity.
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Affiliation(s)
- Russell Thomson
- Medical Parasitology, New York University Langone Medical Center, 341 East 25th Street, New York, NY 10010, USA.
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Field MC, Lumb JH, Adung'a VO, Jones NG, Engstler M. Chapter 1 Macromolecular Trafficking and Immune Evasion in African Trypanosomes. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 278:1-67. [DOI: 10.1016/s1937-6448(09)78001-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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All Trypanosoma cruzi developmental forms present lysosome-related organelles. Histochem Cell Biol 2008; 130:1187-98. [PMID: 18696100 DOI: 10.1007/s00418-008-0486-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/27/2008] [Indexed: 01/07/2023]
Abstract
Trypanosoma cruzi epimastigote forms concentrate their major protease, cruzipain, in the same compartment where these parasites store macromolecules obtained from medium and for this ability these organelles were named as reservosomes. Intracellular digestion occurs mainly inside reservosomes and seems to be modulated by cruzipain and its natural inhibitor chagasin that also concentrates in reservosomes. T. cruzi mammalian forms, trypomastigotes and amastigotes, are unable to capture macromolecules by endocytosis, but also express cruzipain and chagasin, whose role in infectivity has been described. In this paper, we demonstrate that trypomastigotes and amastigotes also concentrate cruzipain, chagasin as well as serine carboxypeptidase in hydrolase-rich compartments of acidic nature. The presence of P-type proton ATPase indicates that this compartment is acidified by the same enzyme as epimastigote endocytic compartments. Electron microscopy analyzes showed that these organelles are placed at the posterior region of the parasite body, are single membrane bound and possess an electron-dense matrix with electronlucent inclusions. Three-dimensional reconstruction showed that these compartments have different size and shape in trypomastigotes and amastigotes. Based on these evidences, we suggest that all T. cruzi developmental stages present lysosome-related organelles that in epimastigotes have the additional and unique ability of storing cargo.
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Molina-Portela MP, Samanovic M, Raper J. Distinct roles of apolipoprotein components within the trypanosome lytic factor complex revealed in a novel transgenic mouse model. ACTA ACUST UNITED AC 2008; 205:1721-8. [PMID: 18606856 PMCID: PMC2525602 DOI: 10.1084/jem.20071463] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Humans express a unique subset of high-density lipoproteins (HDLs) called trypanosome lytic factors (TLFs) that kill many Trypanosoma parasite species. The proteins apolipoprotein (apo) A-I, apoL-I, and haptoglobin-related protein, which are involved in TLF structure and function, were expressed through the introduction of transgenes in mice to explore their physiological roles in vivo. Transgenic expression of human apolipoprotein L-I alone conferred trypanolytic activity in vivo. Coexpression of human apolipoprotein A-I and haptoglobin-related protein (Hpr) had an effect on the integration of apolipoprotein L-I into HDL, and both proteins were required to increase the specific activity of TLF, which was measurable in vitro. Unexpectedly, truncated apolipoprotein L-I devoid of the serum resistance gene interacting domain, which was previously shown to kill human infective trypanosomes, was not trypanolytic in transgenic mice despite being coexpressed with human apolipoprotein A-I and Hpr and incorporated into HDLs. We conclude that all three human apolipoproteins act cooperatively to achieve maximal killing capacity and that truncated apolipoprotein L-I does not function in transgenic animals.
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Affiliation(s)
- Maria Pilar Molina-Portela
- Department of Medical Parasitology, New York University Langone Medical Center/School of Medicine, New York, NY 10010, USA
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Peck RF, Shiflett AM, Schwartz KJ, McCann A, Hajduk SL, Bangs JD. The LAMP-like protein p67 plays an essential role in the lysosome of African trypanosomes. Mol Microbiol 2008; 68:933-46. [PMID: 18430083 DOI: 10.1111/j.1365-2958.2008.06195.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
RNAi knockdown was employed to study the function of p67, a lysosome-associated membrane protein (LAMP)-like type I transmembrane lysosomal glycoprotein in African trypanosomes. Conditional induction of p67 dsRNA resulted in specific approximately 90% reductions in de novo p67 synthesis in both mammalian bloodstream and procyclic insect-stage parasites. Bloodstream cell growth was severely retarded with extensive death after > 24 h of induction. Biosynthetic trafficking of residual p67, and of the soluble lysosomal protease trypanopain, were unimpaired. Endocytosis of tomato lectin, a surrogate receptor-mediated cargo, was only mildly impaired (approximately 20%), but proper lysosomal targeting was unaffected. p67 ablation had dramatic effects on lysosomal morphology with gross enlargement (four- to fivefold) and internal membrane profiles reminiscent of autophagic vacuoles. Ablation of p67 expression rendered bloodstream trypanosomes refractory to lysis by human trypanolytic factor (TLF), a lysosomally activated host innate immune mediator. Similar effects on lysosomal morphology and TLF sensitivity were also obtained by two pharmacological agents that neutralize lysosomal pH--chloroquine and bafilomycin A1. Surprisingly, however, lysosomal pH was not affected in ablated cells suggesting that other physiological alterations must account for increased resistance to TLF. These results indicate p67 plays an essential role in maintenance of normal lysosomal structure and physiology in bloodstream-stage African trypanosomes.
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Affiliation(s)
- Ronald F Peck
- Department of Medical Microbiology & Immunology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706, USA
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15
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Widener J, Nielsen MJ, Shiflett A, Moestrup SK, Hajduk S. Hemoglobin is a co-factor of human trypanosome lytic factor. PLoS Pathog 2007; 3:1250-61. [PMID: 17845074 PMCID: PMC1971115 DOI: 10.1371/journal.ppat.0030129] [Citation(s) in RCA: 46] [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: 02/22/2007] [Accepted: 07/18/2007] [Indexed: 11/18/2022] Open
Abstract
Trypanosome lytic factor (TLF) is a high-density lipoprotein (HDL) subclass providing innate protection to humans against infection by the protozoan parasite Trypanosoma brucei brucei. Two primate-specific plasma proteins, haptoglobin-related protein (Hpr) and apolipoprotein L-1 (ApoL-1), have been proposed to kill T. b. brucei both singularly or when co-assembled into the same HDL. To better understand the mechanism of T. b. brucei killing by TLF, the protein composition of TLF was investigated using a gentle immunoaffinity purification technique that avoids the loss of weakly associated proteins. HDL particles recovered by immunoaffinity absorption, with either anti-Hpr or anti-ApoL-1, were identical in protein composition and specific activity for T. b. brucei killing. Here, we show that TLF-bound Hpr strongly binds Hb and that addition of Hb stimulates TLF killing of T. b. brucei by increasing the affinity of TLF for its receptor, and by inducing Fenton chemistry within the trypanosome lysosome. These findings suggest that TLF in uninfected humans may be inactive against T. b. brucei prior to initiation of infection. We propose that infection of humans by T. b. brucei causes hemolysis that triggers the activation of TLF by the formation of Hpr-Hb complexes, leading to enhanced binding, trypanolytic activity, and clearance of parasites.
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Affiliation(s)
- Justin Widener
- Program in Pathobiology, Brown University, Providence, Rhode Island, United States of America
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | | | - April Shiflett
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
| | | | - Stephen Hajduk
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, United States of America
- * To whom correspondence should be addressed. E-mail:
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16
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Vanhollebeke B, Nielsen MJ, Watanabe Y, Truc P, Vanhamme L, Nakajima K, Moestrup SK, Pays E. Distinct roles of haptoglobin-related protein and apolipoprotein L-I in trypanolysis by human serum. Proc Natl Acad Sci U S A 2007; 104:4118-23. [PMID: 17360487 PMCID: PMC1820718 DOI: 10.1073/pnas.0609902104] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2006] [Indexed: 11/18/2022] Open
Abstract
Apolipoprotein L-I (apoL-I) is a human high-density lipoprotein (HDL) component able to kill Trypanosoma brucei brucei by forming anion-selective pores in the lysosomal membrane of the parasite. Another HDL component, haptoglobin-related protein (Hpr), has been suggested as an additional toxin required for full trypanolytic activity of normal human serum. We recently reported the case of a human lacking apoL-I (apoL-I(-/-)HS) as the result of frameshift mutations in both apoL-I alleles. Here, we show that this serum, devoid of any trypanolytic activity, exhibits normal concentrations of HDL-bound Hpr. Conversely, the serum of individuals with normal HDL-bound apoL-I but who lack Hpr and haptoglobin [Hp(r)(-/-)HS] as the result of gene deletion (anhaptoglobinemia) exhibited phenotypically normal but delayed trypanolytic activity. The trypanolytic properties of Hp(r)(-/-)HS were mimicked by free recombinant apoL-I, whereas recombinant Hpr did not affect trypanosomes. The lysis delay observed with either Hp(r)(-/-)HS or recombinant apoL-I could entirely be attributed to a defect in the uptake of the lytic components. Thus, apoL-I is responsible for the trypanolytic activity of normal human serum, whereas Hpr allows fast uptake of the carrier HDL particles, presumably through their binding to an Hp/Hpr surface receptor of the parasite.
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Affiliation(s)
- Benoit Vanhollebeke
- *Laboratory of Molecular Parasitology, Institut de Biologie et de Médecine Moléculaires, Université Libre de Bruxelles, 12, Rue des Profs Jeener et Brachet, B6041 Gosselies, Belgium
| | - Marianne J. Nielsen
- Department of Medical Biochemistry, University of Aarhus, DK-8000 Aarhus, Denmark
| | | | - Philippe Truc
- Institut de Recherche pour le Développement, Unité de Recherche 117 Trypanosomoses Africaines, Instituto de Combate e Controlo das Tripanosossomiases, CP 2657 Luanda, Angola; and
| | - Luc Vanhamme
- *Laboratory of Molecular Parasitology, Institut de Biologie et de Médecine Moléculaires, Université Libre de Bruxelles, 12, Rue des Profs Jeener et Brachet, B6041 Gosselies, Belgium
| | | | - Soren K. Moestrup
- Department of Medical Biochemistry, University of Aarhus, DK-8000 Aarhus, Denmark
| | - Etienne Pays
- *Laboratory of Molecular Parasitology, Institut de Biologie et de Médecine Moléculaires, Université Libre de Bruxelles, 12, Rue des Profs Jeener et Brachet, B6041 Gosselies, Belgium
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17
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Faulkner SD, Oli MW, Kieft R, Cotlin L, Widener J, Shiflett A, Cipriano MJ, Pacocha SE, Birkeland SR, Hajduk SL, McArthur AG. In vitro generation of human high-density-lipoprotein-resistant Trypanosoma brucei brucei. EUKARYOTIC CELL 2007; 5:1276-86. [PMID: 16896212 PMCID: PMC1539141 DOI: 10.1128/ec.00116-06] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The host range of African trypanosomes is influenced by innate protective molecules in the blood of primates. A subfraction of human high-density lipoprotein (HDL) containing apolipoprotein A-I, apolipoprotein L-I, and haptoglobin-related protein is toxic to Trypanosoma brucei brucei but not the human sleeping sickness parasite Trypanosoma brucei rhodesiense. It is thought that T. b. rhodesiense evolved from a T. b. brucei-like ancestor and expresses a defense protein that ablates the antitrypanosomal activity of human HDL. To directly investigate this possibility, we developed an in vitro selection to generate human HDL-resistant T. b. brucei. Here we show that conversion of T. b. brucei from human HDL sensitive to resistant correlates with changes in the expression of the variant surface glycoprotein (VSG) and abolished uptake of the cytotoxic human HDLs. Complete transcriptome analysis of the HDL-susceptible and -resistant trypanosomes confirmed that VSG switching had occurred but failed to reveal the expression of other genes specifically associated with human HDL resistance, including the serum resistance-associated gene (SRA) of T. b. rhodesiense. In addition, we found that while the original active expression site was still utilized, expression of three expression site-associated genes (ESAG) was altered in the HDL-resistant trypanosomes. These findings demonstrate that resistance to human HDLs can be acquired by T. b. brucei.
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Affiliation(s)
- Sara D Faulkner
- Josephine Bay Paul Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA
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18
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Shiflett AM, Faulkner SD, Cotlin LF, Widener J, Stephens N, Hajduk SL. African Trypanosomes: Intracellular Trafficking of Host Defense Molecules. J Eukaryot Microbiol 2007; 54:18-21. [PMID: 17300512 DOI: 10.1111/j.1550-7408.2006.00228.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Trypanosoma brucei brucei is the causative agent of Nagana in cattle and can infect a wide range of mammals but is unable to infect humans because it is susceptible to the innate cytotoxic activity of normal human serum. A minor subfraction of human high-density lipoprotein (HDL), containing apolipoprotein A-I (APOA1), apolipoprotein L-I (APOL1) and haptoglobin-related protein (HPR) provides this innate protection against T. b. brucei infection. Both HPR and APOL1 are cytotoxic to T. b. brucei but their specific activities for killing increase several hundred-fold when assembled in the same HDL. This HDL is called trypanosome lytic factor (TLF) and kills T. b. brucei following receptor binding, endocytosis, and lysosomal localization. Trypanosome lytic factor is activated in the acidic lysosome and facilitates lysosomal membrane disruption. Lysosomal localization is necessary for T. b. brucei killing by TLF. Trypanosoma brucei rhodesiense, which is indistinguishable from T. b. brucei, is resistant to TLF killing and causes human African sleeping sickness. Human infectivity by T. b. rhodesiense correlates with the evolution of a human serum resistance associated protein (SRA) that is able to ablate TLF killing. When T. b. brucei is transfected with the SRA gene it becomes highly resistant to TLF and human serum. In the SRA transfected cells, intracellular trafficking of TLF is altered and TLF mainly localizes to a subset of SRA containing cytoplasmic vesicles but not to the lysosome. These findings indicate that the cellular distribution of TLF is influenced by SRA expression and may directly determine susceptibility.
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Affiliation(s)
- April M Shiflett
- Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA
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19
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Jensby Nielsen M, Bo Nielsen L, Moestrup SK. High-density lipoprotein and innate immunity. ACTA ACUST UNITED AC 2006. [DOI: 10.2217/17460875.1.6.729] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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20
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Pays E, Vanhollebeke B, Vanhamme L, Paturiaux-Hanocq F, Nolan DP, Pérez-Morga D. The trypanolytic factor of human serum. Nat Rev Microbiol 2006; 4:477-86. [PMID: 16710327 DOI: 10.1038/nrmicro1428] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
African trypanosomes (the prototype of which is Trypanosoma brucei brucei) are protozoan parasites that infect a wide range of mammals. Human blood, unlike the blood of other mammals, has efficient trypanolytic activity, and this needs to be counteracted by these parasites. Resistance to this activity has arisen in two subspecies of Trypanosoma brucei - Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense - allowing these parasites to infect humans, and this results in sleeping sickness in East Africa and West Africa, respectively. Study of the mechanism by which T. b. rhodesiense escapes lysis by human serum led to the identification of an ionic-pore-forming apolipoprotein - known as apolipoprotein L1 - that is associated with high-density-lipoprotein particles in human blood. In this Opinion article, we argue that apolipoprotein L1 is the factor that is responsible for the trypanolytic activity of human serum.
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Affiliation(s)
- Etienne Pays
- Laboratory of Molecular Parasitology, Institute of Molecular Biology and Medicine (IBMM), Université Libre de Bruxelles, 12 rue des Professeurs Jeener et Brachet, B-6041 Gosselies, Belgium.
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21
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Oli MW, Cotlin LF, Shiflett AM, Hajduk SL. Serum resistance-associated protein blocks lysosomal targeting of trypanosome lytic factor in Trypanosoma brucei. EUKARYOTIC CELL 2006; 5:132-9. [PMID: 16400175 PMCID: PMC1360256 DOI: 10.1128/ec.5.1.132-139.2006] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Trypanosoma brucei brucei is the causative agent of nagana in cattle and can infect a wide range of mammals but is unable to infect humans because it is susceptible to the innate cytotoxic activity of normal human serum. A minor subfraction of human high-density lipoprotein (HDL) containing apolipoprotein A-I (apoA-I), apolipoprotein L-I (apoL-I), and haptoglobin-related protein (Hpr) provides this innate protection against T. b. brucei infection. This HDL subfraction, called trypanosome lytic factor (TLF), kills T. b. brucei following receptor binding, endocytosis, and lysosomal localization. Trypanosoma brucei rhodesiense, which is morphologically and physiologically indistinguishable from T. b. brucei, is resistant to TLF-mediated killing and causes human African sleeping sickness. Human infectivity by T. b. rhodesiense correlates with the evolution of a resistance-associated protein (SRA) that is able to ablate TLF killing. To examine the mechanism of TLF resistance, we transfected T. b. brucei with an epitope-tagged SRA gene. Transfected T. b. brucei expressed SRA mRNA at levels comparable to those in T. b. rhodesiense and was highly resistant to TLF. In the SRA-transfected cells, intracellular trafficking of TLF was altered, with TLF being mainly localized to a subset of SRA-containing cytoplasmic vesicles but not to the lysosome. These results indicate that the cellular distribution of TLF is influenced by SRA expression and may directly determine the organism's susceptibility to TLF.
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Affiliation(s)
- Monika W Oli
- Global Infectious Disease Program, Josephine Bay Paul Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, Massachusetts 02543, USA
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22
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Shiflett AM, Bishop JR, Pahwa A, Hajduk SL. Human High Density Lipoproteins Are Platforms for the Assembly of Multi-component Innate Immune Complexes. J Biol Chem 2005; 280:32578-85. [PMID: 16046400 DOI: 10.1074/jbc.m503510200] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human innate immunity to non-pathogenic species of African trypanosomes is provided by human high density lipoprotein (HDL) particles. Here we show that native human HDLs containing haptoglobin-related protein (Hpr), apolipoprotein L-I (apoL-I) and apolipoprotein A-I (apoA-I) are the principle antimicrobial molecules providing protection from trypanosome infection. Other HDL subclasses containing either apoA-I and apoL-I or apoA-I and Hpr have reduced trypanolytic activity, whereas HDL subclasses lacking apoL-I and Hpr are non-toxic to trypanosomes. Highly purified, lipid-free Hpr and apoL-I were both toxic to Trypanosoma brucei brucei but with specific activities at least 500-fold less than those of native HDLs, suggesting that association of these apolipoproteins within the HDL particle was necessary for optimal cytotoxicity. These studies show that HDLs can serve as platforms for the assembly of multiple synergistic proteins and that these assemblies may play a critical role in the evolution of primate-specific innate immunity to trypanosome infection.
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Affiliation(s)
- April M Shiflett
- Josephine Bay Paul Center, Global Infectious Disease Program, Marine Biological Laboratory, Woods Hole, Massachussetts 02543, USA
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23
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Pérez-Morga D, Vanhollebeke B, Paturiaux-Hanocq F, Nolan DP, Lins L, Homblé F, Vanhamme L, Tebabi P, Pays A, Poelvoorde P, Jacquet A, Brasseur R, Pays E. Apolipoprotein L-I promotes trypanosome lysis by forming pores in lysosomal membranes. Science 2005; 309:469-72. [PMID: 16020735 DOI: 10.1126/science.1114566] [Citation(s) in RCA: 243] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Apolipoprotein L-I is the trypanolytic factor of human serum. Here we show that this protein contains a membrane pore-forming domain functionally similar to that of bacterial colicins, flanked by a membrane-addressing domain. In lipid bilayer membranes, apolipoprotein L-I formed anion channels. In Trypanosoma brucei, apolipoprotein L-I was targeted to the lysosomal membrane and triggered depolarization of this membrane, continuous influx of chloride, and subsequent osmotic swelling of the lysosome until the trypanosome lysed.
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MESH Headings
- 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid/pharmacology
- Amino Acid Sequence
- Animals
- Anions/metabolism
- Apolipoprotein L1
- Apolipoproteins/chemistry
- Apolipoproteins/genetics
- Apolipoproteins/metabolism
- Apolipoproteins/pharmacology
- Cells, Immobilized
- Chlorides/metabolism
- Colicins/chemistry
- Colicins/pharmacology
- Escherichia coli/drug effects
- Escherichia coli/growth & development
- Humans
- Intracellular Membranes/drug effects
- Intracellular Membranes/metabolism
- Intracellular Membranes/ultrastructure
- Ion Channels/metabolism
- Lipid Bilayers/chemistry
- Lipoproteins, HDL/chemistry
- Lipoproteins, HDL/genetics
- Lipoproteins, HDL/metabolism
- Lipoproteins, HDL/pharmacology
- Lysosomes/drug effects
- Lysosomes/metabolism
- Lysosomes/ultrastructure
- Models, Molecular
- Molecular Sequence Data
- Mutation
- Permeability
- Protein Conformation
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Recombinant Proteins/metabolism
- Trypanosoma brucei brucei/drug effects
- Trypanosoma brucei brucei/metabolism
- Trypanosoma brucei brucei/ultrastructure
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Affiliation(s)
- David Pérez-Morga
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des Profs Jeener et Brachet, B6041 Gosselies, Belgium
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24
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Vanhamme L, Pays E. The trypanosome lytic factor of human serum and the molecular basis of sleeping sickness. Int J Parasitol 2004; 34:887-98. [PMID: 15217727 DOI: 10.1016/j.ijpara.2004.04.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2004] [Revised: 04/20/2004] [Accepted: 04/20/2004] [Indexed: 02/08/2023]
Abstract
Trypanosoma brucei brucei infects a wide range of mammals but is unable to infect humans because this subspecies is lysed by normal human serum (NHS). The trypanosome lytic factor is associated with High Density Lipoproteins (HDLs). Several HDL-associated components have been proposed as candidate lytic factors, and contradictory hypotheses concerning the mechanism of lysis have been suggested. Elucidation of the process by which Trypanosoma brucei rhodesiense resists lysis and causes human sleeping sickness has indicated that the HDL-bound apolipoprotein L-I (apoL-I) could be the long-sought after lytic component of NHS. This research also allowed the identification of a specific diagnostic DNA probe for T. b. rhodesiense, and may lead to the development of novel anti-trypanosome strategies for use in the field.
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Affiliation(s)
- Luc Vanhamme
- Department of Molecular Biology, Laboratory of Molecular Parasitology, IBMM, University of Brussels, 12, rue des Professeurs Jeener et Brachet, B6041 Gosselies, Belgium
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25
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Vanhamme L, Paturiaux-Hanocq F, Poelvoorde P, Nolan DP, Lins L, Van Den Abbeele J, Pays A, Tebabi P, Van Xong H, Jacquet A, Moguilevsky N, Dieu M, Kane JP, De Baetselier P, Brasseur R, Pays E. Apolipoprotein L-I is the trypanosome lytic factor of human serum. Nature 2003; 422:83-7. [PMID: 12621437 DOI: 10.1038/nature01461] [Citation(s) in RCA: 351] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2002] [Accepted: 02/03/2003] [Indexed: 01/27/2023]
Abstract
Human sleeping sickness in east Africa is caused by the parasite Trypanosoma brucei rhodesiense. The basis of this pathology is the resistance of these parasites to lysis by normal human serum (NHS). Resistance to NHS is conferred by a gene that encodes a truncated form of the variant surface glycoprotein termed serum resistance associated protein (SRA). We show that SRA is a lysosomal protein, and that the amino-terminal alpha-helix of SRA is responsible for resistance to NHS. This domain interacts strongly with a carboxy-terminal alpha-helix of the human-specific serum protein apolipoprotein L-I (apoL-I). Depleting NHS of apoL-I, by incubation with SRA or anti-apoL-I, led to the complete loss of trypanolytic activity. Addition of native or recombinant apoL-I either to apoL-I-depleted NHS or to fetal calf serum induced lysis of NHS-sensitive, but not NHS-resistant, trypanosomes. Confocal microscopy demonstrated that apoL-I is taken up through the endocytic pathway into the lysosome. We propose that apoL-I is the trypanosome lytic factor of NHS, and that SRA confers resistance to lysis by interaction with apoL-I in the lysosome.
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Affiliation(s)
- Luc Vanhamme
- Laboratory of Molecular Parasitology, IBMM, University of Brussels, 12, rue des Profs Jeener et Brachet, B6041 Gosselies, Belgium
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26
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Campillo N, Carrington M. The origin of the serum resistance associated (SRA) gene and a model of the structure of the SRA polypeptide from Trypanosoma brucei rhodesiense. Mol Biochem Parasitol 2003; 127:79-84. [PMID: 12615339 DOI: 10.1016/s0166-6851(02)00306-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Nuria Campillo
- Department of Biochemistry, 80 Tennis Court Road, Cambridge CB2 1GA, UK
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27
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Green HP, Del Pilar Molina Portela M, St Jean EN, Lugli EB, Raper J. Evidence for a Trypanosoma brucei lipoprotein scavenger receptor. J Biol Chem 2003; 278:422-7. [PMID: 12401813 DOI: 10.1074/jbc.m207215200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
African trypanosomes are lipid auxotrophs that live in the bloodstream of their human and animal hosts. Trypanosomes require lipoproteins in addition to other serum components in order to multiply under axenic culture conditions. Delipidation of the lipoproteins abrogates their capacity to support trypanosome growth. Both major classes of serum lipoproteins, LDL and HDL, are primary sources of lipids, delivering cholesterol esters, cholesterol, and phospholipids to trypanosomes. We show evidence for the existence of a trypanosome lipoprotein scavenger receptor, which facilitates the endocytosis of both native and modified lipoproteins, including HDL and LDL. This lipoprotein scavenger receptor also exhibits selective lipid uptake, whereby the uptake of the lipid components of the lipoprotein exceeds that of the protein components. Trypanosome lytic factor (TLF1), an unusual HDL found in human serum that protects from infection by lysing Trypanosoma brucei brucei, is also bound and endocytosed by this lipoprotein scavenger receptor. HDL and LDL compete for the binding and uptake of TLF1 and thereby attenuate the trypanosome lysis mediated by TLF1. We also show that a mammalian scavenger receptor facilitates lipid uptake from TLF1 in a manner similar to the trypanosome scavenger receptor. Based on these results we propose that HDL, LDL, and TLF1 are all bound and taken up by a lipoprotein scavenger receptor, which may constitute the parasite's major pathway mediating the uptake of essential lipids.
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Affiliation(s)
- Heather P Green
- Department of Medical and Molecular Parasitology, New York University School of Medicine, New York, New York 10010, USA
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28
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Morgan GW, Hall BS, Denny PW, Carrington M, Field MC. The kinetoplastida endocytic apparatus. Part I: a dynamic system for nutrition and evasion of host defences. Trends Parasitol 2002; 18:491-6. [PMID: 12473365 DOI: 10.1016/s1471-4922(02)02391-7] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The endocytic system of kinetoplastid parasites is a highly polarized membrane network focused on the flagellar pocket localized at one end of the cell. When first characterized, the endosomal network was envisioned as a simple system for uptake of extracellular material by fluid-phase or receptor-mediated mechanisms. Subsequently, it has become clear that the kinetoplastid endosomal system has an active and vital role in avoiding the host immune system and virulence, as well as providing the basic functions to fulfil cellular nutritional requirements. In two reviews, recent advances in the definition and comprehension of kinetoplastida endocytosis are discussed and, in Trypanosoma brucei in particular as the more developed experimental system. In Part 1, the endocytic system is considered in context of the surface molecules and their potential roles in virulence.
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Affiliation(s)
- Gareth W Morgan
- Wellcome Trust Laboratories for Molecular Parasitology, Dept of Biological Sciences, Imperial College of Science, Technology and Medicine, Exhibition Road, London, UK
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29
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Alexander DL, Schwartz KJ, Balber AE, Bangs JD. Developmentally regulated trafficking of the lysosomal membrane protein p67 in Trypanosoma brucei. J Cell Sci 2002; 115:3253-63. [PMID: 12140257 DOI: 10.1242/jcs.115.16.3253] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
p67 is a lysosomal type I membrane glycoprotein of Trypanosoma brucei. In procyclic stage cells p67 trafficks to the lysosome without modification, but in the bloodstream stage Golgi processing adds poly-N-acetyllactosamine to N-glycans. In both stages proteolytic fragmentation occurs in the lysosome, but turnover is approximately nine times faster in bloodstream cells. Trafficking of wildtype p67 and mutants missing the cytoplasmic (p67ΔCD) or cytoplasmic/transmembrane domains (p67ΔTM) was monitored by pulse-chase,surface biotinylation and immunofluorescence. Overexpressed wildtype p67 trafficks normally in procyclics, but some leaks to the cell surface suggesting that the targeting machinery is saturable. p67ΔCD and p67ΔTM are delivered to the cell surface and secreted, respectively. The membrane/cytoplasmic domains function correctly in procyclic cells when fused to GFP indicating that these domains are sufficient for stage-specific lysosomal targeting. In contrast, p67 wildtype and deletion reporters are overwhelmingly targeted to the lysosome and degraded in bloodstream cells. These findings suggest that either redundant developmentally regulated targeting signals/machinery are operative in this stage or that the increased endocytic activity of bloodstream cells prevents export of the deletion reporters.
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Affiliation(s)
- David L Alexander
- The Department of Medical Microbiology and Immunology, University of Wisconsin-Madison Medical School, Madison, WI 53706, USA
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30
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McConville MJ, Mullin KA, Ilgoutz SC, Teasdale RD. Secretory pathway of trypanosomatid parasites. Microbiol Mol Biol Rev 2002; 66:122-54; table of contents. [PMID: 11875130 PMCID: PMC120783 DOI: 10.1128/mmbr.66.1.122-154.2002] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The Trypanosomatidae comprise a large group of parasitic protozoa, some of which cause important diseases in humans. These include Trypanosoma brucei (the causative agent of African sleeping sickness and nagana in cattle), Trypanosoma cruzi (the causative agent of Chagas' disease in Central and South America), and Leishmania spp. (the causative agent of visceral and [muco]cutaneous leishmaniasis throughout the tropics and subtropics). The cell surfaces of these parasites are covered in complex protein- or carbohydrate-rich coats that are required for parasite survival and infectivity in their respective insect vectors and mammalian hosts. These molecules are assembled in the secretory pathway. Recent advances in the genetic manipulation of these parasites as well as progress with the parasite genome projects has greatly advanced our understanding of processes that underlie secretory transport in trypanosomatids. This article provides an overview of the organization of the trypanosomatid secretory pathway and connections that exist with endocytic organelles and multiple lytic and storage vacuoles. A number of the molecular components that are required for vesicular transport have been identified, as have some of the sorting signals that direct proteins to the cell surface or organelles in the endosome-vacuole system. Finally, the subcellular organization of the major glycosylation pathways in these parasites is reviewed. Studies on these highly divergent eukaryotes provide important insights into the molecular processes underlying secretory transport that arose very early in eukaryotic evolution. They also reveal unusual or novel aspects of secretory transport and protein glycosylation that may be exploited in developing new antiparasite drugs.
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Affiliation(s)
- Malcolm J McConville
- Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria 3010, Australia.
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Bishop JR, Shimamura M, Hajduk SL. Insight into the mechanism of trypanosome lytic factor-1 killing of Trypanosoma brucei brucei. Mol Biochem Parasitol 2001; 118:33-40. [PMID: 11704271 DOI: 10.1016/s0166-6851(01)00361-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
It has been known for almost a century that normal human serum can lyse the extracellular blood parasite Trypanosoma brucei brucei. This process is a result of a non-immune killing factor in human sera known as trypanosome lytic factor (TLF). In this work, we demonstrate that killing of T. b. brucei by trypanosome lytic factor-1 (TLF-1) in vitro is inhibited by the lipophyllic iron chelator, LI, the lipophyllic antioxidant DPPD, and the protease inhibitors antipain and E64. Thus TLF-1 killing likely requires iron, oxidants, and serine and cysteine proteases. Furthermore, we demonstrate that TLF-1 mediated lysis causes measurable peroxidation in T. brucei lipids via a reaction that is inhibited by DPPD, weak bases, and human haptoglobin. We hypothesize that TLF-1 lysis requires intracellular factors within the trypanosome including high intracellular H2O2 and high polyenoic lipid concentrations, lysosomal acidification and proteases, and intracellular iron sources. The data presented supports the hypothesis that the combination of these factors with TLF-1 inside the lysosome results in lysosomal membrane breakdown, release of the lysosomal contents, and subsequent autodigestion of the cell.
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Affiliation(s)
- J R Bishop
- Department of Biochemistry and Molecular Genetics, Schools of Medicine and Dentistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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