1
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Banerjee S, Minshall N, Webb H, Carrington M. How are Trypanosoma brucei receptors protected from host antibody-mediated attack? Bioessays 2024:e2400053. [PMID: 38713161 DOI: 10.1002/bies.202400053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 04/11/2024] [Accepted: 04/15/2024] [Indexed: 05/08/2024]
Abstract
Trypanosoma brucei is the causal agent of African Trypanosomiasis in humans and other animals. It maintains a long-term infection through an antigenic variation based population survival strategy. To proliferate in a mammal, T. brucei acquires iron and haem through the receptor mediated uptake of host transferrin and haptoglobin-hemoglobin respectively. The receptors are exposed to host antibodies but this does not lead to clearance of the infection. Here we discuss how the trypanosome avoids this fate in the context of recent findings on the structure and cell biology of the receptors.
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Affiliation(s)
- Sourav Banerjee
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Nicola Minshall
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Helena Webb
- Department of Biochemistry, University of Cambridge, Cambridge, UK
| | - Mark Carrington
- Department of Biochemistry, University of Cambridge, Cambridge, UK
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2
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Morrison LJ, Steketee PC, Tettey MD, Matthews KR. Pathogenicity and virulence of African trypanosomes: From laboratory models to clinically relevant hosts. Virulence 2023; 14:2150445. [PMID: 36419235 DOI: 10.1080/21505594.2022.2150445] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
African trypanosomes are vector-borne protozoa, which cause significant human and animal disease across sub-Saharan Africa, and animal disease across Asia and South America. In humans, infection is caused by variants of Trypanosoma brucei, and is characterized by varying rate of progression to neurological disease, caused by parasites exiting the vasculature and entering the brain. Animal disease is caused by multiple species of trypanosome, primarily T. congolense, T. vivax, and T. brucei. These trypanosomes also infect multiple species of mammalian host, and this complexity of trypanosome and host diversity is reflected in the spectrum of severity of disease in animal trypanosomiasis, ranging from hyperacute infections associated with mortality to long-term chronic infections, and is also a main reason why designing interventions for animal trypanosomiasis is so challenging. In this review, we will provide an overview of the current understanding of trypanosome determinants of infection progression and severity, covering laboratory models of disease, as well as human and livestock disease. We will also highlight gaps in knowledge and capabilities, which represent opportunities to both further our fundamental understanding of how trypanosomes cause disease, as well as facilitating the development of the novel interventions that are so badly needed to reduce the burden of disease caused by these important pathogens.
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Affiliation(s)
- Liam J Morrison
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK
| | - Pieter C Steketee
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK
| | - Mabel D Tettey
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Keith R Matthews
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
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3
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Ilboudo K, Hounyeme RE, Kabore J, Boulangé A, Gimonneau G, Salou E, Belem AGM, Lejon V, Compaoré CFA, Bucheton B, Koffi M, Solano P, Berthier D, Thevenon S, Jamonneau V. Experimental evidence that immune trypanolysis using the LiTat 1.3 and LiTat 1.5 variant antigen types is not specific to Trypanosoma brucei gambiense in pigs. Parasite 2022; 29:61. [PMID: 36562442 PMCID: PMC9879134 DOI: 10.1051/parasite/2022063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 12/04/2022] [Indexed: 12/24/2022] Open
Abstract
In the context of the human African trypanosomiasis elimination process, reliable and accurate diagnostic tools are crucial for exploring the role of a potential animal reservoir of Trypanosoma brucei gambiense. The immune trypanolysis test (TL) using the variant antigen types (VAT) LiTat 1.3 and LiTat 1.5, described as a specific serological method to detect people infected by T. b. gambiense, seems to be a promising tool. However, its specificity was recently questioned during field animal surveys. The present study evaluates the performance of TL during experimental T. b. brucei infection in pigs. Eight infected pigs and four uninfected pigs were followed up with blood and plasma collection. Blood was used for parasitological investigation. TL was performed on the plasma with the LiTat 1.3, LiTat 1.5 and LiTat 1.6 VATs. All control pigs remained negative to parasitological investigation and TL. Trypanosomes were detected in all the infected pigs and the first detection was between 10 and 14 days post infection (dpi). TL results showed that infected pigs developed antibodies against the three VATs. The first antibody detections by TL occurred between 14 and 21 dpi for antibodies directed against LiTat 1.6, 21 and 168 dpi for antibodies directed against LiTat 1.5 and 70, and 182 dpi for antibodies directed against LiTat 1.3. This study highlights for the first time that TL using LiTat 1.3 and LiTat 1.5 VATs is not specific to T. b. gambiense. Development of specific diagnostic tools for the detection of T. b. gambiense infections in animals, especially in pigs, is still needed.
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Affiliation(s)
- Kadidiata Ilboudo
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Unité de Recherche sur les Maladies à Vecteurs et Biodiversité, Centre International de Recherche-Développement sur l’Élevage en Zone Subhumide 01 BP 454 Bobo-Dioulasso 01 Burkina Faso
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Unité de Formation et de Recherche Sciences et Techniques, Université Nazi Boni 01 BP 1091 Bobo-Dioulasso Burkina-Faso
| | - Robert Eustache Hounyeme
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Unité de Recherche sur les Maladies à Vecteurs et Biodiversité, Centre International de Recherche-Développement sur l’Élevage en Zone Subhumide 01 BP 454 Bobo-Dioulasso 01 Burkina Faso
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Unité de Recherche « Trypanosomoses », Institut Pierre Richet 01 BP 1500 Bouaké Côte d’Ivoire
| | - Jacques Kabore
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Unité de Recherche sur les Maladies à Vecteurs et Biodiversité, Centre International de Recherche-Développement sur l’Élevage en Zone Subhumide 01 BP 454 Bobo-Dioulasso 01 Burkina Faso
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Unité de Formation et de Recherche Sciences et Techniques, Université Nazi Boni 01 BP 1091 Bobo-Dioulasso Burkina-Faso
| | - Alain Boulangé
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Unité de Recherche sur les Maladies à Vecteurs et Biodiversité, Centre International de Recherche-Développement sur l’Élevage en Zone Subhumide 01 BP 454 Bobo-Dioulasso 01 Burkina Faso
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Unité de Recherche « Trypanosomoses », Institut Pierre Richet 01 BP 1500 Bouaké Côte d’Ivoire
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Université de Montpellier, CIRAD, IRD, Intertryp F-34398 Montpellier France
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CIRAD, UMR INTERTRYP F-34398 Montpellier France
| | - Geoffrey Gimonneau
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Unité de Recherche sur les Maladies à Vecteurs et Biodiversité, Centre International de Recherche-Développement sur l’Élevage en Zone Subhumide 01 BP 454 Bobo-Dioulasso 01 Burkina Faso
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Université de Montpellier, CIRAD, IRD, Intertryp F-34398 Montpellier France
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Laboratoire National d’Élevage et de Recherches Vétérinaires, Service de Bio-Écologie et Pathologies Parasitaires BP 2057 Dakar – Hann Sénégal
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CIRAD, UMR INTERTRYP F-34398 Montpellier France
| | - Ernest Salou
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Unité de Recherche sur les Maladies à Vecteurs et Biodiversité, Centre International de Recherche-Développement sur l’Élevage en Zone Subhumide 01 BP 454 Bobo-Dioulasso 01 Burkina Faso
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Unité de Formation et de Recherche Sciences et Techniques, Université Nazi Boni 01 BP 1091 Bobo-Dioulasso Burkina-Faso
| | | | - Veerle Lejon
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Université de Montpellier, CIRAD, IRD, Intertryp F-34398 Montpellier France
| | - Charlie Franck Alfred Compaoré
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Unité de Recherche sur les Maladies à Vecteurs et Biodiversité, Centre International de Recherche-Développement sur l’Élevage en Zone Subhumide 01 BP 454 Bobo-Dioulasso 01 Burkina Faso
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Unité de Formation et de Recherche Sciences et Techniques, Université Nazi Boni 01 BP 1091 Bobo-Dioulasso Burkina-Faso
| | - Bruno Bucheton
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Université de Montpellier, CIRAD, IRD, Intertryp F-34398 Montpellier France
| | - Mathurin Koffi
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Laboratoire de Biodiversité et Gestion des Écosystèmes Tropicaux, Unité de Recherche en Génétique et Épidémiologie Moléculaire, UFR Environnement, Université Jean Lorougnon Guédé BP 150 Daloa Côte d’Ivoire
| | - Philippe Solano
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Université de Montpellier, CIRAD, IRD, Intertryp F-34398 Montpellier France
| | - David Berthier
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Université de Montpellier, CIRAD, IRD, Intertryp F-34398 Montpellier France
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CIRAD, UMR INTERTRYP F-34398 Montpellier France
| | - Sophie Thevenon
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Université de Montpellier, CIRAD, IRD, Intertryp F-34398 Montpellier France
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CIRAD, UMR INTERTRYP F-34398 Montpellier France
| | - Vincent Jamonneau
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Unité de Recherche « Trypanosomoses », Institut Pierre Richet 01 BP 1500 Bouaké Côte d’Ivoire
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Université de Montpellier, CIRAD, IRD, Intertryp F-34398 Montpellier France
,Corresponding author:
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4
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Pant J, Samanovic M, Nelson MT, Keceli MK, Verdi J, Beverley SM, Raper J. Interplay of Trypanosome Lytic Factor and innate immune cells in the resolution of cutaneous Leishmania infection. PLoS Pathog 2021; 17:e1008768. [PMID: 34559857 PMCID: PMC8494325 DOI: 10.1371/journal.ppat.1008768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 10/06/2021] [Accepted: 09/09/2021] [Indexed: 11/19/2022] Open
Abstract
Trypanosome Lytic Factor (TLF) is a primate-specific high-density lipoprotein (HDL) complex that, through the cation channel-forming protein apolipoprotein L-1 (APOL1), provides innate immunity to select kinetoplastid parasites. The immunoprotective effects of TLF have been extensively investigated in the context of its interaction with the extracellular protozoan Trypanosoma brucei brucei, to which it confers sterile immunity. We previously showed that TLF could act against an intracellular pathogen Leishmania, and here we dissected the role of TLF and its synergy with host-immune cells. Leishmania major is transmitted by Phlebotomine sand flies, which deposit the parasite intradermally into mammalian hosts, where neutrophils are the predominant phagocytes recruited to the site of infection. Once in the host, the parasites are phagocytosed and shed their surface glycoconjugates during differentiation to the mammalian-resident amastigote stage. Our data show that mice producing TLF have reduced parasite burdens when infected intradermally with metacyclic promastigotes of L. major, the infective, fly-transmitted stage. This TLF-mediated reduction in parasite burden was lost in neutrophil-depleted mice, suggesting that early recruitment of neutrophils is required for TLF-mediated killing of L. major. In vitro we find that only metacyclic promastigotes co-incubated with TLF in an acidic milieu were lysed. However, amastigotes were not killed by TLF at any pH. These findings correlated with binding experiments, revealing that labeled TLF binds specifically to the surface of metacyclic promastigotes, but not to amastigotes. Metacyclic promastigotes of L. major deficient in the synthesis of surface glycoconjugates LPG and/or PPG (lpg1- and lpg5A-/lpg5B- respectively) whose absence mimics the amastigote surface, were resistant to TLF-mediated lysis. We propose that TLF binds to the outer surface glycoconjugates of metacyclic promastigotes, whereupon it kills the parasite in the acidic phagosome of phagocytes. We hypothesize that resistance to TLF requires shedding of the surface glycoconjugates, which occurs several hours after phagocytosis by immune cells, creating a relatively short-lived but effective window for TLF to act against Leishmania. Leishmaniasis, the disease caused by parasites of the genus Leishmania, can be divided into cutaneous, muco-cutaneous and visceral leishmaniasis depending on the parasite species and the clinical outcome of the disease. Of the three, cutaneous leishmaniasis is the most common form, which is usually characterized by a localized lesion due to the infection of immune cells, primarily dermal and lymph node-resident macrophages. The time between infection and lesion appearance ranges from weeks to years, while some individuals never develop lesions. The length of this subclinical stage of leishmaniasis depends on a variety of factors: parasite virulence, infectious dose, and the host immune response. Therefore, it remains crucial to develop our understanding of each component of the host-parasite interface and assess the role that each component plays in the clinical outcome. Here, we analyze the interaction between L. major, a cutaneous strain, and the host innate immune factor Trypanosome Lytic Factor (TLF), a sub-class of circulating High-Density Lipoprotein (HDL). TLF provides sterile immunity to most extracellular African Trypanosomes by osmotically lysing the parasites. Lysis is driven by the primate specific protein apolipoprotein L-1 (APOL1), a cation channel-forming protein that is activated by a series of pH-dependent conformational changes. APOL1 inserts into cellular membranes at acidic pH and forms a closed ion channel that subsequently opens when re-exposed to neutral pH, resulting in ion flux. Using transgenic mice producing primate TLF, we show that both human and baboon TLFs ameliorate cutaneous Leishmania major infection and that this reduction in parasite burden correlates with: 1. infectious dose of metacyclic promastigotes 2. the concentration of circulating TLF in plasma and 3. early recruitment of neutrophils at the site of infection. Our results show that the acidification step is essential for TLF-mediated lysis of axenic metacyclic promastigotes of Leishmania in vitro. The susceptibility of metacyclic promastigotes to TLF-mediated lysis is governed by the surface glycoconjugates of Leishmania. We find that surface glycoconjugate-deficient Leishmania are resistant to TLF-mediated killing. Based on these data, we conclude that the shedding of surface glycoconjugates while transitioning from metacyclic promastigotes to amastigotes, results in parasite resistance to TLF-mediated lysis. Whether TLF is effective at killing metacyclic promastigotes of other experimentally tractable Leishmania sp., such as L. infantum and L. donovani, which have different surface glycoconjugate structures is yet to be tested. Our data raise the possibility that TLF may have lytic activity against a broader range of pathogens such as bacteria, viruses, fungi and parasites with surface glycoconjugates that transit through intracellular acidic compartments.
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Affiliation(s)
- Jyoti Pant
- Department of Biology, Hunter College, City University of New York, New York, New York, United States of America
- Molecular, Cellular and Developmental biology, The Graduate Center, City University of New York, New York, New York, United States of America
- * E-mail: (JP); (JR)
| | - Marie Samanovic
- Medical Parasitology, New York University Langone Medical Center, New York, New York, United States of America
| | - Maria T. Nelson
- Department of Biology, Hunter College, City University of New York, New York, New York, United States of America
| | - Mert K. Keceli
- Department of Biology, Hunter College, City University of New York, New York, New York, United States of America
| | - Joseph Verdi
- Department of Biology, Hunter College, City University of New York, New York, New York, United States of America
- Molecular, Cellular and Developmental biology, The Graduate Center, City University of New York, New York, New York, United States of America
| | - Stephen M. Beverley
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Jayne Raper
- Department of Biology, Hunter College, City University of New York, New York, New York, United States of America
- Molecular, Cellular and Developmental biology, The Graduate Center, City University of New York, New York, New York, United States of America
- * E-mail: (JP); (JR)
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5
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De Simone G, Pasquadibisceglie A, Polticelli F, di Masi A, Ascenzi P. Haptoglobin and the related haptoglobin protein: the N-terminus makes the difference. J Biomol Struct Dyn 2020; 40:2244-2253. [DOI: 10.1080/07391102.2020.1837675] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
| | | | - Fabio Polticelli
- Dipartimento di Scienze, Università Roma Tre, Roma, Italy
- Istituto Nazionale di Fisica Nucleare, Roma Tre Section, Roma, Italy
| | | | - Paolo Ascenzi
- Laboratorio Interdipartimentale di Microscopia Elettronica, Università Roma Tre, Roma, Italy
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6
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Giovinazzo JA, Thomson RP, Khalizova N, Zager PJ, Malani N, Rodriguez-Boulan E, Raper J, Schreiner R. Apolipoprotein L-1 renal risk variants form active channels at the plasma membrane driving cytotoxicity. eLife 2020; 9:51185. [PMID: 32427098 PMCID: PMC7292663 DOI: 10.7554/elife.51185] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 05/14/2020] [Indexed: 12/25/2022] Open
Abstract
Recently evolved alleles of Apolipoprotein L-1 (APOL1) provide increased protection against African trypanosome parasites while also significantly increasing the risk of developing kidney disease in humans. APOL1 protects against trypanosome infections by forming ion channels within the parasite, causing lysis. While the correlation to kidney disease is robust, there is little consensus concerning the underlying disease mechanism. We show in human cells that the APOL1 renal risk variants have a population of active channels at the plasma membrane, which results in an influx of both Na+ and Ca2+. We propose a model wherein APOL1 channel activity is the upstream event causing cell death, and that the activate-state, plasma membrane-localized channel represents the ideal drug target to combat APOL1-mediated kidney disease.
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Affiliation(s)
- Joseph A Giovinazzo
- Department of Biological Sciences, Hunter College at City University of New York, New York, United States
| | - Russell P Thomson
- Department of Biological Sciences, Hunter College at City University of New York, New York, United States
| | - Nailya Khalizova
- Department of Biological Sciences, Hunter College at City University of New York, New York, United States
| | - Patrick J Zager
- Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medicine, New York, United States
| | | | - Enrique Rodriguez-Boulan
- Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medicine, New York, United States
| | - Jayne Raper
- Department of Biological Sciences, Hunter College at City University of New York, New York, United States
| | - Ryan Schreiner
- Department of Ophthalmology, Margaret Dyson Vision Research Institute, Weill Cornell Medicine, New York, United States
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7
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Abstract
The association of variants in the APOL1 gene, which encodes apolipoprotein L1 (APOL1), with progressive nondiabetic kidney diseases in African Americans has prompted intense investigation into the function(s) of APOL1. APOL1 is an innate immune effector that protects human beings from infection by some trypanosomal parasites. We review the data characterizing APOL1 trypanolytic function, which has been a basis for studies of APOL1 function in mammalian cells. Subsequently, we discuss the studies that use animal models, mammalian cell culture models, and kidney biopsy tissue to discover the mechanisms of variant APOL1-associated kidney diseases.
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8
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Zanoni P, Velagapudi S, Yalcinkaya M, Rohrer L, von Eckardstein A. Endocytosis of lipoproteins. Atherosclerosis 2018; 275:273-295. [PMID: 29980055 DOI: 10.1016/j.atherosclerosis.2018.06.881] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 06/04/2018] [Accepted: 06/22/2018] [Indexed: 02/06/2023]
Abstract
During their metabolism, all lipoproteins undergo endocytosis, either to be degraded intracellularly, for example in hepatocytes or macrophages, or to be re-secreted, for example in the course of transcytosis by endothelial cells. Moreover, there are several examples of internalized lipoproteins sequestered intracellularly, possibly to exert intracellular functions, for example the cytolysis of trypanosoma. Endocytosis and the subsequent intracellular itinerary of lipoproteins hence are key areas for understanding the regulation of plasma lipid levels as well as the biological functions of lipoproteins. Indeed, the identification of the low-density lipoprotein (LDL)-receptor and the unraveling of its transcriptional regulation led to the elucidation of familial hypercholesterolemia as well as to the development of statins, the most successful therapeutics for lowering of cholesterol levels and risk of atherosclerotic cardiovascular diseases. Novel limiting factors of intracellular trafficking of LDL and the LDL receptor continue to be discovered and to provide drug targets such as PCSK9. Surprisingly, the receptors mediating endocytosis of high-density lipoproteins or lipoprotein(a) are still a matter of controversy or even new discovery. Finally, the receptors and mechanisms, which mediate the uptake of lipoproteins into non-degrading intracellular itineraries for re-secretion (transcytosis, retroendocytosis), storage, or execution of intracellular functions, are largely unknown.
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Affiliation(s)
- Paolo Zanoni
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Srividya Velagapudi
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Mustafa Yalcinkaya
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Lucia Rohrer
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Arnold von Eckardstein
- Institute for Clinical Chemistry, University and University Hospital Zurich, Zurich, Switzerland; Centre for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.
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9
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APOL1: The Balance Imposed by Infection, Selection, and Kidney Disease. Trends Mol Med 2018; 24:682-695. [PMID: 29886044 DOI: 10.1016/j.molmed.2018.05.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 05/07/2018] [Accepted: 05/14/2018] [Indexed: 02/07/2023]
Abstract
Chronic kidney disease (CKD) affects millions of people and constitutes a major health and financial burden worldwide. People of African descent are at an increased risk of developing kidney disease, which is mostly explained by two variants in the Apolipoprotein L1 (APOL1) gene that are found only in people of west African origin. It is hypothesized that these variants were genetically selected due to the protection they afford against African sleeping sickness, caused by the parasite Trypanosoma brucei. Targeting mutant APOL1 could have substantial therapeutic potential for treating kidney disease. In this review, we will describe the intriguing interplay between microbiology, genetics, and kidney disease as revealed in APOL1-associated kidney disease, discuss APOL1-induced cytotoxicity and its therapeutic implications.
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10
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The structure of serum resistance-associated protein and its implications for human African trypanosomiasis. Nat Microbiol 2018; 3:295-301. [PMID: 29358741 DOI: 10.1038/s41564-017-0085-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 11/27/2017] [Indexed: 11/08/2022]
Abstract
Only two trypanosome subspecies are able to cause human African trypanosomiasis. To establish an infection in human blood, they must overcome the innate immune system by resisting the toxic effects of trypanolytic factor 1 and trypanolytic factor 2 (refs. 1,2). These lipoprotein complexes contain an active, pore-forming component, apolipoprotein L1 (ApoL1), that causes trypanosome cell death 3 . One of the two human-infective subspecies, Trypanosoma brucei rhodesiense, differs from non-infective trypanosomes solely by the presence of the serum resistance-associated protein, which binds directly to ApoL1 and blocks its pore-forming capacity3-5. Since this interaction is the single critical event that renders T. b. rhodesiense human- infective, detailed structural information that allows identification of binding determinants is crucial to understand immune escape by the parasite. Here, we present the structure of serum resistance-associated protein and reveal the adaptations that occurred as it diverged from other trypanosome surface molecules to neutralize ApoL1. We also present our mapping of residues important for ApoL1 binding, giving molecular insight into this interaction at the heart of human sleeping sickness.
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11
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Currier RB, Cooper A, Burrell-Saward H, MacLeod A, Alsford S. Decoding the network of Trypanosoma brucei proteins that determines sensitivity to apolipoprotein-L1. PLoS Pathog 2018; 14:e1006855. [PMID: 29346416 PMCID: PMC5790291 DOI: 10.1371/journal.ppat.1006855] [Citation(s) in RCA: 17] [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: 09/12/2017] [Revised: 01/30/2018] [Accepted: 01/05/2018] [Indexed: 12/27/2022] Open
Abstract
In contrast to Trypanosoma brucei gambiense and T. b. rhodesiense (the causative agents of human African trypanosomiasis), T. b. brucei is lysed by apolipoprotein-L1 (apoL1)-containing human serum trypanolytic factors (TLF), rendering it non-infectious to humans. While the mechanisms of TLF1 uptake, apoL1 membrane integration, and T. b. gambiense and T. b. rhodesiense apoL1-resistance have been extensively characterised, our understanding of the range of factors that drive apoL1 action in T. b. brucei is limited. Selecting our bloodstream-form T. b. brucei RNAi library with recombinant apoL1 identified an array of factors that supports the trypanocidal action of apoL1, including six putative ubiquitin modifiers and several proteins putatively involved in membrane trafficking; we also identified the known apoL1 sensitivity determinants, TbKIFC1 and the V-ATPase. Most prominent amongst the novel apoL1 sensitivity determinants was a putative ubiquitin ligase. Intriguingly, while loss of this ubiquitin ligase reduces parasite sensitivity to apoL1, its loss enhances parasite sensitivity to TLF1-dominated normal human serum, indicating that free and TLF1-bound apoL1 have contrasting modes-of-action. Indeed, loss of the known human serum sensitivity determinants, p67 (lysosomal associated membrane protein) and the cathepsin-L regulator, 'inhibitor of cysteine peptidase', had no effect on sensitivity to free apoL1. Our findings highlight a complex network of proteins that influences apoL1 action, with implications for our understanding of the anti-trypanosomal action of human serum.
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Affiliation(s)
- Rachel B. Currier
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Anneli Cooper
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | | | - Annette MacLeod
- Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Sam Alsford
- London School of Hygiene and Tropical Medicine, London, United Kingdom
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12
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A co-evolutionary arms race: trypanosomes shaping the human genome, humans shaping the trypanosome genome. Parasitology 2017; 142 Suppl 1:S108-19. [PMID: 25656360 PMCID: PMC4413828 DOI: 10.1017/s0031182014000602] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Trypanosoma brucei is the causative agent of African sleeping sickness in humans and one of several pathogens that cause the related veterinary disease Nagana. A complex co-evolution has occurred between these parasites and primates that led to the emergence of trypanosome-specific defences and counter-measures. The first line of defence in humans and several other catarrhine primates is the trypanolytic protein apolipoprotein-L1 (APOL1) found within two serum protein complexes, trypanosome lytic factor 1 and 2 (TLF-1 and TLF-2). Two sub-species of T. brucei have evolved specific mechanisms to overcome this innate resistance, Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. In T. b. rhodesiense, the presence of the serum resistance associated (SRA) gene, a truncated variable surface glycoprotein (VSG), is sufficient to confer resistance to lysis. The resistance mechanism of T. b. gambiense is more complex, involving multiple components: reduction in binding affinity of a receptor for TLF, increased cysteine protease activity and the presence of the truncated VSG, T. b. gambiense-specific glycoprotein (TgsGP). In a striking example of co-evolution, evidence is emerging that primates are responding to challenge by T. b. gambiense and T. b. rhodesiense, with several populations of humans and primates displaying resistance to infection by these two sub-species.
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Gilden JK, Umaer K, Kruzel EK, Hecht O, Correa RO, Mansfield JM, Bangs JD. The role of the PI(3,5)P 2 kinase TbFab1 in endo/lysosomal trafficking in Trypanosoma brucei. Mol Biochem Parasitol 2017; 214:52-61. [PMID: 28356223 DOI: 10.1016/j.molbiopara.2017.03.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2017] [Revised: 03/22/2017] [Accepted: 03/23/2017] [Indexed: 12/01/2022]
Abstract
Protein trafficking through endo/lysosomal compartments is critically important to the biology of the protozoan parasite Trypanosoma brucei, but the routes material may take to the lysosome, as well as the molecular factors regulating those routes, remain incompletely understood. Phosphoinositides are signaling phospholipids that regulate many trafficking events by recruiting specific effector proteins to discrete membrane subdomains. In this study, we investigate the role of one phosphoinositide, PI(3,5)P2 in T. brucei. We find a low steady state level of PI(3,5)P2 in bloodstream form parasites comparable to that of other organisms. RNAi knockdown of the putative PI(3)P-5 kinase TbFab1 decreases the PI(3,5)P2 pool leading to rapid cell death. TbFab1 and PI(3,5)P2 both localize strongly to late endo/lysosomes. While most trafficking functions were intact in TbFab1 deficient cells, including both endocytic and biosynthetic trafficking to the lysosome, lysosomal turnover of an endogenous ubiquitinylated membrane protein, ISG65, was completely blocked suggesting that TbFab1 plays a role in the ESCRT-mediated late endosomal/multivesicular body degradative pathways. Knockdown of a second component of PI(3,5)P2 metabolism, the PI(3,5)P2 phosphatase TbFig4, also resulted in delayed turnover of ISG65. Together, these results demonstrate an essential role for PI(3,5)P2 in the turnover of ubiquitinylated membrane proteins and in trypanosome endomembrane biology.
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Affiliation(s)
- Julia K Gilden
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
| | - Khan Umaer
- Department of Microbiology Immunology, School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, USA.
| | - Emilia K Kruzel
- Department of Microbiology Immunology, School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, USA.
| | - Oliver Hecht
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
| | - Renan O Correa
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
| | - John M Mansfield
- Department of Bacteriology, University of Wisconsin-Madison, Madison, WI, USA.
| | - James D Bangs
- Department of Microbiology Immunology, School of Medicine and Biomedical Sciences, University at Buffalo (SUNY), Buffalo, NY, USA.
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Higgins MK, Lane-Serff H, MacGregor P, Carrington M. A Receptor's Tale: An Eon in the Life of a Trypanosome Receptor. PLoS Pathog 2017; 13:e1006055. [PMID: 28125726 PMCID: PMC5268388 DOI: 10.1371/journal.ppat.1006055] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
African trypanosomes have complex life cycles comprising at least ten developmental forms, variously adapted to different niches in their tsetse fly vector and their mammalian hosts. Unlike many other protozoan pathogens, they are always extracellular and have evolved intricate surface coats that allow them to obtain nutrients while also protecting them from the immune defenses of either insects or mammals. The acquisition of macromolecular nutrients requires receptors that function within the context of these surface coats. The best understood of these is the haptoglobin-hemoglobin receptor (HpHbR) of Trypanosoma brucei, which is used by the mammalian bloodstream form of the parasite, allowing heme acquisition. However, in some primates it also provides an uptake route for trypanolytic factor-1, a mediator of innate immunity against trypanosome infection. Recent studies have shown that during the evolution of African trypanosome species the receptor has diversified in function from a hemoglobin receptor predominantly expressed in the tsetse fly to a haptoglobin-hemoglobin receptor predominantly expressed in the mammalian bloodstream. Structural and functional studies of homologous receptors from different trypanosome species have allowed us to propose an evolutionary history for how one receptor has adapted to different roles in different trypanosome species. They also highlight the challenges that a receptor faces in operating on the complex trypanosome surface and show how these challenges can be met.
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Affiliation(s)
- Matthew K. Higgins
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Harriet Lane-Serff
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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Karathanasis SK, Freeman LA, Gordon SM, Remaley AT. The Changing Face of HDL and the Best Way to Measure It. Clin Chem 2016; 63:196-210. [PMID: 27879324 DOI: 10.1373/clinchem.2016.257725] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 10/26/2016] [Indexed: 01/08/2023]
Abstract
BACKGROUND HDL cholesterol (HDL-C) is a commonly used lipid biomarker for assessing cardiovascular health. While a central focus has been placed on the role of HDL in the reverse cholesterol transport (RCT) process, our appreciation for the other cardioprotective properties of HDL continues to expand with further investigation into the structure and function of HDL and its specific subfractions. The development of novel assays is empowering the research community to assess different aspects of HDL function, which at some point may evolve into new diagnostic tests. CONTENT This review discusses our current understanding of the formation and maturation of HDL particles via RCT, as well as the newly recognized roles of HDL outside RCT. The antioxidative, antiinflammatory, antiapoptotic, antithrombotic, antiinfective, and vasoprotective effects of HDL are all discussed, as are the related methodologies for assessing these different aspects of HDL function. We elaborate on the importance of protein and lipid composition of HDL in health and disease and highlight potential new diagnostic assays based on these parameters. SUMMARY Although multiple epidemiologic studies have confirmed that HDL-C is a strong negative risk marker for cardiovascular disease, several clinical and experimental studies have yielded inconsistent results on the direct role of HDL-C as an antiatherogenic factor. As of yet, our increased understanding of HDL biology has not been translated into successful new therapies, but will undoubtedly depend on the development of alternative ways for measuring HDL besides its cholesterol content.
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Affiliation(s)
| | - Lita A Freeman
- Lipoprotein Metabolism Section, Cardiovascular-Pulmonary Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD
| | - Scott M Gordon
- Lipoprotein Metabolism Section, Cardiovascular-Pulmonary Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD
| | - Alan T Remaley
- Lipoprotein Metabolism Section, Cardiovascular-Pulmonary Branch, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD.
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Cooper A, Capewell P, Clucas C, Veitch N, Weir W, Thomson R, Raper J, MacLeod A. A Primate APOL1 Variant That Kills Trypanosoma brucei gambiense. PLoS Negl Trop Dis 2016; 10:e0004903. [PMID: 27494254 PMCID: PMC4975595 DOI: 10.1371/journal.pntd.0004903] [Citation(s) in RCA: 22] [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: 05/08/2015] [Accepted: 07/14/2016] [Indexed: 01/19/2023] Open
Abstract
Humans are protected against infection from most African trypanosomes by lipoprotein complexes present in serum that contain the trypanolytic pore-forming protein, Apolipoprotein L1 (APOL1). The human-infective trypanosomes, Trypanosoma brucei rhodesiense in East Africa and T. b. gambiense in West Africa have separately evolved mechanisms that allow them to resist APOL1-mediated lysis and cause human African trypanosomiasis, or sleeping sickness, in man. Recently, APOL1 variants were identified from a subset of Old World monkeys, that are able to lyse East African T. b. rhodesiense, by virtue of C-terminal polymorphisms in the APOL1 protein that hinder that parasite’s resistance mechanism. Such variants have been proposed as candidates for developing therapeutic alternatives to the unsatisfactory anti-trypanosomal drugs currently in use. Here we demonstrate the in vitro lytic ability of serum and purified recombinant protein of an APOL1 ortholog from the West African Guinea baboon (Papio papio), which is able to lyse examples of all sub-species of T. brucei including T. b. gambiense group 1 parasites, the most common agent of human African trypanosomiasis. The identification of a variant of APOL1 with trypanolytic ability for both human-infective T. brucei sub-species could be a candidate for universal APOL1-based therapeutic strategies, targeted against all pathogenic African trypanosomes. African trypanosomes are protozoan parasites that affect both humans and animals in poor rural areas of sub-Saharan Africa, and are a major constraint on health and agricultural development. Disease control is principally dependent on the administration of drugs, which are old and largely unsatisfactory. Humans are naturally resistant to infection by most African trypanosomes species because of a lytic protein component in their blood, called APOL1. However, human-infective trypanosomes, T. b. rhodesiense in East Africa, and T. b. gambiense in West Africa, have evolved separate mechanisms to disarm this lytic protein and cause disease. Recently, variants of APOL1 were discovered in some primates that are able to kill the East African human disease-causing sub-species. These APOL1 variants form the basis of current attempts to create novel therapeutic interventions that can kill both animal and human-infective trypanosomes. In this study, we show that another variant of the same protein from a West African baboon species is able to kill, not only East African human-infective trypanosomes, but also the West African parasites, which causes the majority of human African trypanosomiasis cases. This new APOL1 variant could be a potential candidate for anti-trypanosomal therapies targeted at all pathogenic trypanosome species.
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Affiliation(s)
- Anneli Cooper
- Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Paul Capewell
- Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Caroline Clucas
- Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Nicola Veitch
- Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - William Weir
- Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Russell Thomson
- Department of Medical Parasitology, Langone School of Medicine, New York University, New York, New York, United States of America
| | - Jayne Raper
- Department of Medical Parasitology, Langone School of Medicine, New York University, New York, New York, United States of America
| | - Annette MacLeod
- Wellcome Trust Centre for Molecular Parasitology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- * E-mail:
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17
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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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18
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Vanwalleghem G, Fontaine F, Lecordier L, Tebabi P, Klewe K, Nolan DP, Yamaryo-Botté Y, Botté C, Kremer A, Burkard GS, Rassow J, Roditi I, Pérez-Morga D, Pays E. Coupling of lysosomal and mitochondrial membrane permeabilization in trypanolysis by APOL1. Nat Commun 2015; 6:8078. [PMID: 26307671 PMCID: PMC4560804 DOI: 10.1038/ncomms9078] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 07/15/2015] [Indexed: 12/21/2022] Open
Abstract
Humans resist infection by the African parasite Trypanosoma brucei owing to the trypanolytic activity of the serum apolipoprotein L1 (APOL1). Following uptake by endocytosis in the parasite, APOL1 forms pores in endolysosomal membranes and triggers lysosome swelling. Here we show that APOL1 induces both lysosomal and mitochondrial membrane permeabilization (LMP and MMP). Trypanolysis coincides with MMP and consecutive release of the mitochondrial TbEndoG endonuclease to the nucleus. APOL1 is associated with the kinesin TbKIFC1, of which both the motor and vesicular trafficking VHS domains are required for MMP, but not for LMP. The presence of APOL1 in the mitochondrion is accompanied by mitochondrial membrane fenestration, which can be mimicked by knockdown of a mitochondrial mitofusin-like protein (TbMFNL). The BH3-like peptide of APOL1 is required for LMP, MMP and trypanolysis. Thus, trypanolysis by APOL1 is linked to apoptosis-like MMP occurring together with TbKIFC1-mediated transport of APOL1 from endolysosomal membranes to the mitochondrion. The human serum protein apolipoprotein L1 (APOL1) is taken up by trypanosomes where it triggers cell death, forming pores in endolysosomal membranes. Vanwalleghem et al. show that APOL1 triggers both lysosomal and mitochondrial membrane permeabilization, and that the latter is responsible for trypanolysis.
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Affiliation(s)
- Gilles Vanwalleghem
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles (ULB), 12 rue des Prof Jeener et Brachet, B-6041 Gosselies, Belgium
| | - Frédéric Fontaine
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles (ULB), 12 rue des Prof Jeener et Brachet, B-6041 Gosselies, Belgium
| | - Laurence Lecordier
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles (ULB), 12 rue des Prof Jeener et Brachet, B-6041 Gosselies, Belgium
| | - Patricia Tebabi
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles (ULB), 12 rue des Prof Jeener et Brachet, B-6041 Gosselies, Belgium
| | - Kristoffer Klewe
- Institute of Biochemistry and Pathobiochemistry, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
| | - Derek P Nolan
- Molecular Parasitology Group, School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland
| | - Yoshiki Yamaryo-Botté
- Apicolipid Group, CNRS, Laboratoire Adaptation et Pathogénie des Microorganismes UMR5163/ Institut Albert Bonniot CRI Inserm/UJF U823, CNRS, Institut Jean Roget, 38700 La Tronche, France
| | - Cyrille Botté
- Apicolipid Group, CNRS, Laboratoire Adaptation et Pathogénie des Microorganismes UMR5163/ Institut Albert Bonniot CRI Inserm/UJF U823, CNRS, Institut Jean Roget, 38700 La Tronche, France
| | - Anneke Kremer
- IRC/VIB Bio Imaging Core, Gent, Technologiepark 927, B-9052 Gent, Belgium
| | | | - Joachim Rassow
- Institute of Biochemistry and Pathobiochemistry, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
| | - Isabel Roditi
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
| | - David Pérez-Morga
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles (ULB), 12 rue des Prof Jeener et Brachet, B-6041 Gosselies, Belgium.,Center for Microscopy and Molecular Imaging (CMMI), Université Libre de Bruxelles (ULB), 8 rue Adrienne Bolland, B-6041 Gosselies, Belgium
| | - Etienne Pays
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles (ULB), 12 rue des Prof Jeener et Brachet, B-6041 Gosselies, Belgium.,Walloon Excellence in Life sciences and Biotechnology (WELBIO), Wavre, Belgium
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19
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Lane-Serff H, MacGregor P, Lowe ED, Carrington M, Higgins MK. Structural basis for ligand and innate immunity factor uptake by the trypanosome haptoglobin-haemoglobin receptor. eLife 2014; 3:e05553. [PMID: 25497229 PMCID: PMC4383175 DOI: 10.7554/elife.05553] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 12/12/2014] [Indexed: 11/13/2022] Open
Abstract
The haptoglobin-haemoglobin receptor (HpHbR) of African trypanosomes allows acquisition of haem and provides an uptake route for trypanolytic factor-1, a mediator of innate immunity against trypanosome infection. In this study, we report the structure of Trypanosoma brucei HpHbR in complex with human haptoglobin-haemoglobin (HpHb), revealing an elongated ligand-binding site that extends along its membrane distal half. This contacts haptoglobin and the β-subunit of haemoglobin, showing how the receptor selectively binds HpHb over individual components. Lateral mobility of the glycosylphosphatidylinositol-anchored HpHbR, and a ∼50° kink in the receptor, allows two receptors to simultaneously bind one HpHb dimer. Indeed, trypanosomes take up dimeric HpHb at significantly lower concentrations than monomeric HpHb, due to increased ligand avidity that comes from bivalent binding. The structure therefore reveals the molecular basis for ligand and innate immunity factor uptake by trypanosomes and identifies adaptations that allow efficient ligand uptake in the context of the complex trypanosome cell surface.
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Affiliation(s)
- Harriet Lane-Serff
- Department of
Biochemistry, University of Oxford,
Oxford, United Kingdom
| | - Paula MacGregor
- Department of
Biochemistry, University of Cambridge,
Cambridge, United Kingdom
| | - Edward D Lowe
- Department of
Biochemistry, University of Oxford,
Oxford, United Kingdom
| | - Mark Carrington
- Department of
Biochemistry, University of Cambridge,
Cambridge, United Kingdom
| | - Matthew K Higgins
- Department of
Biochemistry, University of Oxford,
Oxford, United Kingdom
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20
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Abstract
African trypanosomes have been around for more than 100 million years, and have adapted to survival in a very wide host range. While various indigenous African mammalian host species display a tolerant phenotype towards this parasitic infection, and hence serve as perpetual reservoirs, many commercially important livestock species are highly disease susceptible. When considering humans, they too display a highly sensitive disease progression phenotype for infections with Trypanosoma brucei rhodesiense or Trypanosoma brucei gambiense, while being intrinsically resistant to infections with other trypanosome species. As extracellular trypanosomes proliferate and live freely in the bloodstream and lymphatics, they are constantly exposed to the immune system. Due to co-evolution, this environment however no longer poses a hostile threat, but has become the niche environment where trypanosomes thrive and obligatory await transmission through the bites of tsetse flies or other haematophagic vectors, ideally without causing severe side infection-associated pathology to their host. Hence, African trypanosomes have acquired various mechanisms to manipulate and control the host immune response, evading effective elimination. Despite the extensive research into trypanosomosis over the past 40 years, many aspects of the anti-parasite immune response remain to be solved and no vaccine is currently available. Here we review the recent work on the different escape mechanisms employed by African Trypanosomes to ensure infection chronicity and transmission potential.
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21
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Lecordier L, Uzureau P, Tebabi P, Pérez-Morga D, Nolan D, Schumann Burkard G, Roditi I, Pays E. Identification of Trypanosoma brucei components involved in trypanolysis by normal human serum. Mol Microbiol 2014; 94:625-36. [PMID: 25256834 DOI: 10.1111/mmi.12783] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/30/2014] [Indexed: 11/27/2022]
Abstract
Normal human serum (NHS) confers human resistance to infection by the parasite Trypanosoma brucei owing to the trypanolytic activity of apolipoprotein L1 (APOL1), present in two serum complexes termed Trypanolytic Factors (TLF-1 and -2). In order to identify parasite components involved in the intracellular trafficking and activity of TLFs, an inducible RNA interference (RNAi) genomic DNA library constructed in bloodstream form T. brucei was subjected to RNAi induction and selection for resistant parasites under NHS conditions favouring either TLF-1 or TLF-2 uptake. While TLF-1 conditions readily selected the haptoglobin-haemoglobin (HP-HB) surface receptor TbHpHbR as expected, given its known ability to bind TLF-1, under TLF-2 conditions no specific receptor for TLF-2 was identified. Instead, the screen allowed the identification of five distinct factors expected to be involved in the assembly of the vacuolar proton pump V-ATPase and consecutive endosomal acidification. These data confirm that lowering the pH during endocytosis is required for APOL1 toxic activity.
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Affiliation(s)
- Laurence Lecordier
- Laboratory of Molecular Parasitology, Institute of Molecular Biology and Medicine, Université Libre de Bruxelles, 12 rue des Professeurs Jeener et Brachet, B-6041, Gosselies, Belgium
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22
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Abstract
Trypanosoma brucei is a pathogenic unicellular eukaryote that infects humans and other mammals in sub-Saharan Africa. A central feature of trypanosome biology is the single flagellum of the parasite, which is an essential and multifunctional organelle that facilitates cell propulsion, controls cell morphogenesis and directs cytokinesis. Moreover, the flagellar membrane is a specialized subdomain of the cell surface that mediates attachment to host tissues and harbours multiple virulence factors. In this Review, we discuss the structure, assembly and function of the trypanosome flagellum, including canonical roles in cell motility as well as novel and emerging roles in cell morphogenesis and host-parasite interactions.
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Affiliation(s)
- Gerasimos Langousis
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California 90095, USA
| | - Kent L Hill
- 1] Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California 90095, USA. [2] Molecular Biology Institute, University of California, Los Angeles, California 90095, USA
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23
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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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Lin S, Morris MT, Ackroyd PC, Morris JC, Christensen KA. Peptide-targeted delivery of a pH sensor for quantitative measurements of intraglycosomal pH in live Trypanosoma brucei. Biochemistry 2013; 52:3629-37. [PMID: 23651061 DOI: 10.1021/bi400029m] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Studies of dynamic changes in organelles of protozoan parasite Trypanosoma brucei have been limited, in part because of the difficulty of targeting analytical probes to specific subcellular compartments. Here we demonstrate application of a ratiometric probe for pH quantification in T. brucei glycosomes. The probe consists of a peptide encoding the peroxisomal targeting sequence (F-PTS1, acetyl-CKGGAKL) coupled to fluorescein, which responds to pH. When incubated with living parasites, the probe is internalized within vesicular structures that colocalize with a glycosomal marker. Inhibition of uptake of F-PTS1 at 4 °C and pulse-chase colocalization with fluorescent dextran suggested that the probe is initially taken up by non-receptor-mediated endocytosis but is subsequently transported separately from dextran and localized within glycosomes, prior to the final fusion of labeled glycosomes and lysosomes as part of glycosomal turnover. Intraorganellar measurements and pH calibration with F-PTS1 in T. brucei glycosomes indicate that the resting glycosomal pH under physiological conditions is 7.4 ± 0.2. However, incubation in glucose-depleted buffer triggered mild acidification of the glycosome over a period of 20 min, with a final observed pH of 6.8 ± 0.3. This glycosomal acidification was reversed by reintroduction of glucose. Coupling of ratiometric fluorescent sensors and reporters to PTS peptides offers an invaluable tool for monitoring in situ glycosomal response(s) to changing environmental conditions and could be applied to additional kinetoplastid parasites.
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Affiliation(s)
- Sheng Lin
- Department of Chemistry and ‡Department of Genetics and Biochemistry, Clemson University , Clemson, South Carolina 29634, United States
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25
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DeJesus E, Kieft R, Albright B, Stephens NA, Hajduk SL. A single amino acid substitution in the group 1 Trypanosoma brucei gambiense haptoglobin-hemoglobin receptor abolishes TLF-1 binding. PLoS Pathog 2013; 9:e1003317. [PMID: 23637606 PMCID: PMC3630162 DOI: 10.1371/journal.ppat.1003317] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 03/05/2013] [Indexed: 11/19/2022] Open
Abstract
Critical to human innate immunity against African trypanosomes is a minor subclass of human high-density lipoproteins, termed Trypanosome Lytic Factor-1 (TLF-1). This primate-specific molecule binds to a haptoglobin-hemoglobin receptor (HpHbR) on the surface of susceptible trypanosomes, initiating a lytic pathway. Group 1 Trypanosoma brucei gambiense causes human African Trypanosomiasis (HAT), escaping TLF-1 killing due to reduced uptake. Previously, we found that group 1 T. b. gambiense HpHbR (TbgHpHbR) mRNA levels were greatly reduced and the gene contained substitutions within the open reading frame. Here we show that a single, highly conserved amino acid in the TbgHpHbR ablates high affinity TLF-1 binding and subsequent endocytosis, thus evading TLF-1 killing. In addition, we show that over-expression of TbgHpHbR failed to rescue TLF-1 susceptibility. These findings suggest that the single substitution present in the TbgHpHbR directly contributes to the reduced uptake and resistance to TLF-1 seen in these important human pathogens.
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Affiliation(s)
- E. DeJesus
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia
| | - R. Kieft
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia
| | - B. Albright
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia
| | - N. A. Stephens
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia
| | - S. L. Hajduk
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia
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26
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Higgins MK, Tkachenko O, Brown A, Reed J, Raper J, Carrington M. Structure of the trypanosome haptoglobin-hemoglobin receptor and implications for nutrient uptake and innate immunity. Proc Natl Acad Sci U S A 2013; 110:1905-10. [PMID: 23319650 PMCID: PMC3562850 DOI: 10.1073/pnas.1214943110] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
African trypanosomes are protected by a densely packed surface monolayer of variant surface glycoprotein (VSG). A haptoglobin-hemoglobin receptor (HpHbR) within this VSG coat mediates heme acquisition. HpHbR is also exploited by the human host to mediate endocytosis of trypanolytic factor (TLF)1 from serum, contributing to innate immunity. Here, the crystal structure of HpHbR from Trypanosoma congolense has been solved, revealing an elongated three α-helical bundle with a small membrane distal head. To understand the receptor in the context of the VSG layer, the dimensions of Trypanosoma brucei HpHbR and VSG have been determined by small-angle X-ray scattering, revealing the receptor to be more elongated than VSG. It is, therefore, likely that the receptor protrudes above the VSG layer and unlikely that the VSG coat can prevent immunoglobulin binding to the receptor. The HpHb-binding site has been mapped by single-residue mutagenesis and surface plasmon resonance. This site is located where it is readily accessible above the VSG layer. A single HbHpR polymorphism unique to human infective T. brucei gambiense has been shown to be sufficient to reduce binding of both HpHb and TLF1, modulating ligand affinity in a delicate balancing act that allows nutrient acquisition but avoids TLF1 uptake.
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MESH Headings
- Amino Acid Sequence
- Animals
- Binding Sites/genetics
- Endocytosis/immunology
- Host-Parasite Interactions/immunology
- Humans
- Immunity, Innate/immunology
- Models, Molecular
- Molecular Sequence Data
- Mutation
- Protein Binding
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Receptors, Cell Surface/chemistry
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/immunology
- Scattering, Small Angle
- Sequence Homology, Amino Acid
- Surface Plasmon Resonance
- Trypanosoma brucei brucei/genetics
- Trypanosoma brucei brucei/immunology
- Trypanosoma brucei brucei/physiology
- Trypanosoma brucei gambiense/genetics
- Trypanosoma brucei gambiense/immunology
- Trypanosoma brucei gambiense/physiology
- Trypanosoma congolense/genetics
- Trypanosoma congolense/immunology
- Trypanosoma congolense/physiology
- Trypanosomiasis, African/immunology
- Trypanosomiasis, African/parasitology
- Variant Surface Glycoproteins, Trypanosoma/chemistry
- Variant Surface Glycoproteins, Trypanosoma/genetics
- Variant Surface Glycoproteins, Trypanosoma/immunology
- X-Ray Diffraction
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Affiliation(s)
- Matthew K. Higgins
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Olga Tkachenko
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom; and
| | - Alan Brown
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom; and
| | - Jenny Reed
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom; and
| | - Jayne Raper
- Department of Biological Sciences, Hunter College, City University of New York, New York, NY 10065
| | - Mark Carrington
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom; and
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27
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Abstract
Complement-dependent destruction of invading micro-organisms is a crucial first-line defense against infection, yet both African and American trypanosomes are able to resist attack by complement. African trypanosomes resist non-specific complement attack by virtue of a thick glycoprotein surface coat, and the host range of certain African trypanosomes is believed to be defined by their susceptibility to a subclass of human high density lipoprotein (HDL) and/or a high molecular weight protein complex present in human serum. In the first part of this review, Stephen Tomlinson and Jayne Raper look at the properties and mechanisms of action of these trypanolytic factors on African trypanosomes, and discuss briefly the possible mechanisms whereby these human pathogens resist lysis by human serum. The mechanisms that enable the American trypanosome Trypanosoma cruzi to resist complement attack are reviewed in the second part of this article.
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Affiliation(s)
- S Tomlinson
- Department of Pathology, New York University Medical Center, New York, NY 10016, USA
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28
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Stephens NA, Kieft R, Macleod A, Hajduk SL. Trypanosome resistance to human innate immunity: targeting Achilles' heel. Trends Parasitol 2012; 28:539-45. [PMID: 23059119 DOI: 10.1016/j.pt.2012.09.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 09/14/2012] [Accepted: 09/15/2012] [Indexed: 10/27/2022]
Abstract
Trypanosome lytic factors (TLFs) are powerful, naturally occurring toxins in humans that provide sterile protection against infection by several African trypanosomes. These trypanocidal complexes predominantly enter the parasite by binding to the trypanosome haptoglobin/hemoglobin receptor (HpHbR), trafficking to the lysosome, causing membrane damage and, ultimately, cell lysis. Despite TLF-mediated immunity, the parasites that cause human African Trypanosomiasis (HAT), Trypanosoma brucei rhodesiense and Trypanosoma brucei gambiense, have developed independent mechanisms of resistance to TLF killing. In this review we describe the parasite defenses that allow trypanosome infections of humans and discuss how targeting these apparent strengths of the parasite may reveal their Achilles' heel, leading to new approaches in the treatment of HAT.
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Affiliation(s)
- Natalie A Stephens
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
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29
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Role of expression site switching in the development of resistance to human Trypanosome Lytic Factor-1 in Trypanosoma brucei brucei. Mol Biochem Parasitol 2011; 183:8-14. [PMID: 22226682 PMCID: PMC3343262 DOI: 10.1016/j.molbiopara.2011.12.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 12/16/2011] [Accepted: 12/19/2011] [Indexed: 12/21/2022]
Abstract
Human high-density lipoproteins (HDLs) play an important role in human innate immunity to infection by African trypanosomes with a minor subclass, Trypanosome Lytic Factor-1 (TLF-1), displaying highly selective cytotoxicity to the veterinary pathogen Trypanosoma brucei brucei but not against the human sleeping sickness pathogens Trypanosoma brucei gambiense or Trypanosoma brucei rhodesiense. T. b. rhodesiense has evolved the serum resistance associated protein (SRA) that binds and confers resistance to TLF-1 while T. b. gambiense lacks the gene for SRA indicating that these parasites have diverse mechanisms of resistance to TLF-1. Recently, we have shown that T. b. gambiense (group 1) resistance to TLF-1 correlated with the loss of the haptoglobin/hemoglobin receptor (HpHbR) expression, the protein responsible for high affinity binding and uptake of TLF-1. In the course of these studies we also examined TLF-1 resistant T. b. brucei cell lines, generated by long-term in vitro selection. We found that changes in TLF-1 susceptibility in T. b. brucei correlated with changes in variant surface glycoprotein (VSG) expression in addition to reduced TLF-1 binding and uptake. To determine whether the expressed VSG or expression site associated genes (ESAGs) contribute to TLF-1 resistance we prepared a TLF-1 resistant T. b. brucei with a selectable marker in a silent bloodstream expression site (BES). Drug treatment allowed rapid selection of trypanosomes that activated the tagged BES. These studies show that TLF-1 resistance in T. b. brucei is largely independent of the expressed VSG or ESAGs further supporting the central role of HpHbR expression in TLF-1 susceptibility in these cells.
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30
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Lumb JH, Leung KF, Dubois KN, Field MC. Rab28 function in trypanosomes: interactions with retromer and ESCRT pathways. J Cell Sci 2011; 124:3771-83. [PMID: 22100919 DOI: 10.1242/jcs.079178] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Early endosomal cargo is typically targeted to either a degradative or recycling pathway. Despite established functions for the retromer and ESCRT complexes at late endosomes/multivesicular bodies, the mechanisms integrating and coordinating these functions remain largely unknown. Rab family GTPases are key membrane trafficking organizers and could contribute. Here, in the unicellular organism Trypanosoma brucei, we demonstrate that Rab28 locates to the endosomal pathway and partially colocalizes with Vps23, an ESCRT I component. Rab28 is required for turnover of endocytosed proteins and for lysosomal delivery of protein cargo. Using RNA interference we find that in Rab28-depleted cells, protein levels of ESCRT I (Vps23/28) and retromer (Vps26) are also decreased, suggesting that Rab28 is an important regulator of these factors. We suggest that Rab28 coordinates the activity of retromer-dependent trafficking and ESCRT-mediated degradative pathways.
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Affiliation(s)
- Jennifer H Lumb
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
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31
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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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32
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Differences between Trypanosoma brucei gambiense groups 1 and 2 in their resistance to killing by trypanolytic factor 1. PLoS Negl Trop Dis 2011; 5:e1287. [PMID: 21909441 PMCID: PMC3167774 DOI: 10.1371/journal.pntd.0001287] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Accepted: 07/04/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The three sub-species of Trypanosoma brucei are important pathogens of sub-Saharan Africa. T. b. brucei is unable to infect humans due to sensitivity to trypanosome lytic factors (TLF) 1 and 2 found in human serum. T. b. rhodesiense and T. b. gambiense are able to resist lysis by TLF. There are two distinct sub-groups of T. b. gambiense that differ genetically and by human serum resistance phenotypes. Group 1 T. b. gambiense have an invariant phenotype whereas group 2 show variable resistance. Previous data indicated that group 1 T. b. gambiense are resistant to TLF-1 due in-part to reduced uptake of TLF-1 mediated by reduced expression of the TLF-1 receptor (the haptoglobin-hemoglobin receptor (HpHbR)) gene. Here we investigate if this is also true in group 2 parasites. METHODOLOGY Isogenic resistant and sensitive group 2 T. b. gambiense were derived and compared to other T. brucei parasites. Both resistant and sensitive lines express the HpHbR gene at similar levels and internalized fluorescently labeled TLF-1 similar fashion to T. b. brucei. Both resistant and sensitive group 2, as well as group 1 T. b. gambiense, internalize recombinant APOL1, but only sensitive group 2 parasites are lysed. CONCLUSIONS Our data indicate that, despite group 1 T. b. gambiense avoiding TLF-1, it is resistant to the main lytic component, APOL1. Similarly group 2 T. b. gambiense is innately resistant to APOL1, which could be based on the same mechanism. However, group 2 T. b. gambiense variably displays this phenotype and expression does not appear to correlate with a change in expression site or expression of HpHbR. Thus there are differences in the mechanism of human serum resistance between T. b. gambiense groups 1 and 2.
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33
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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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34
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Mechanism of Trypanosoma brucei gambiense (group 1) resistance to human trypanosome lytic factor. Proc Natl Acad Sci U S A 2010; 107:16137-41. [PMID: 20805508 DOI: 10.1073/pnas.1007074107] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Human innate immunity against most African trypanosomes, including Trypanosoma brucei brucei, is mediated by a minor subclass of toxic serum HDL, called trypanosome lytic factor-1 (TLF-1). This HDL contains two primate specific proteins, apolipoprotein L-1 and haptoglobin (Hp)-related protein, as well as apolipoprotein A-1. These assembled proteins provide a powerful defense against trypanosome infection. Trypanosoma brucei rhodesiense causes human African sleeping sickness because it has evolved an inhibitor of TLF-1, serum resistance-associated (SRA) protein. Trypanosoma brucei gambiense lacks the SRA gene, yet it infects humans. As transfection of T. b. gambiense (group 1) is not possible, we initially used in vitro-selected TLF-1-resistant T. b. brucei to examine SRA-independent mechanisms of TLF-1 resistance. Here we show that TLF-1 resistance in T. b. brucei is caused by reduced expression of the Hp/Hb receptor gene (TbbHpHbR). Importantly, T. b. gambiense (group 1) also showed a marked reduction in uptake of TLF-1 and a corresponding decrease in expression of T. b. gambiense Hp/Hb receptor (TbgHpHbR). Ectopic expression of TbbHpHbR in TLF-1-resistant T. b. brucei rescued TLF-1 uptake, demonstrating that decreased TbbHpHbR expression conferred TLF-1 resistance. Ectopic expression of TbgHpHbR in TLF-1-resistant T. b. brucei failed to rescue TLF-1 killing, suggesting that coding sequence changes altered Hp/Hb receptor binding affinity for TLF-1. We propose that the combination of coding sequence mutations and decreased expression of TbgHpHbR directly contribute to parasite evasion of human innate immunity and infectivity of group 1 T. b. gambiense.
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35
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Harrington JM, Widener J, Stephens N, Johnson T, Francia M, Capewell P, Macleod A, Hajduk SL. The plasma membrane of bloodstream-form African trypanosomes confers susceptibility and specificity to killing by hydrophobic peptides. J Biol Chem 2010; 285:28659-66. [PMID: 20615879 DOI: 10.1074/jbc.m110.151886] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Trypanosoma brucei is the causative agent of both a veterinary wasting disease and human African trypanosomiasis, or sleeping sickness. The cell membrane of the developmental stage found within the mammalian host, the bloodstream form (BSF), is highly dynamic, exhibiting rapid rates of endocytosis and lateral flow of glycosylphosphatidylinositol-anchored proteins. Here, we show that the cell membrane of these organisms is a target for killing by small hydrophobic peptides that increase the rigidity of lipid bilayers. Specifically, we have derived trypanocidal peptides that are based upon the hydrophobic N-terminal signal sequences of human apolipoproteins. These peptides selectively partitioned into the plasma membrane of BSF trypanosomes, resulting in an increase in the rigidity of the bilayer, dramatic changes in cell motility, and subsequent cell death. No killing of the developmental stage found within the insect midgut, the procyclic form, was observed. Additionally, the peptides exhibited no toxicity toward mammalian cell lines and did not induce hemolysis. Studies with model liposomes indicated that bilayer fluidity dictates the susceptibility of membranes to manipulation by hydrophobic peptides. We suggest that the composition of the BSF trypanosome cell membrane confers a high degree of fluidity and unique susceptibility to killing by hydrophobic peptides and is therefore a target for the development of trypanocidal drugs.
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Affiliation(s)
- John M Harrington
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, USA
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36
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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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37
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Inverso JA, Uphoff TS, Johnson SC, Paulnock DM, Mansfield JM. Biological variation among african trypanosomes: I. Clonal expression of virulence is not linked to the variant surface glycoprotein or the variant surface glycoprotein gene telomeric expression site. DNA Cell Biol 2010; 29:215-27. [PMID: 20307190 DOI: 10.1089/dna.2009.0991] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The potential association of variant surface glycoprotein (VSG) gene expression with clonal expression of virulence in African trypanosomes was addressed. Two populations of clonally related trypanosomes, which differ dramatically in virulence for the infected host, but display the same apparent VSG surface coat phenotype, were characterized with respect to the VSG genes expressed as well as the chromosome telomeric expression sites (ES) utilized for VSG gene transcription. The VSG gene sequences expressed by clones LouTat 1 and LouTat 1A of Trypanosoma brucei rhodesiense were identical, and gene expression in both clones occurred precisely by the same gene conversion events (duplication and transposition), which generated an expression-linked copy (ELC) of the VSG gene. The ELC was present on the same genomic restriction fragments in both populations and resided in the telomere of a 330-kb chromosome; a single basic copy of the LouTat 1/1A VSG gene, present in all variants of the LouTat 1 serodeme, was located at an internal site of a 1.5-Mb chromosome. Restriction endonuclease mapping of the ES telomere revealed that the VSG ELC of clones LouTat 1 and 1A resides in the same site. Therefore, these findings provide evidence that the VSG gene ES and, potentially, any cotranscribed ES-associated genes do not play a role in the clonal regulation of virulence because trypanosome clones LouTat 1 and 1A, which differ markedly in their virulence properties, both express identical VSG genes from the same chromosome telomeric ES.
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Affiliation(s)
- Jill A Inverso
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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38
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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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Immunobiology of African trypanosomes: need of alternative interventions. J Biomed Biotechnol 2010; 2010:389153. [PMID: 20182644 PMCID: PMC2826769 DOI: 10.1155/2010/389153] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Revised: 10/29/2009] [Accepted: 12/23/2009] [Indexed: 02/08/2023] Open
Abstract
Trypanosomiasis is one of the major parasitic diseases for which control is still far from reality. The vaccination approaches by using dominant surface proteins have not been successful, mainly due to antigenic variation of the parasite surface coat. On the other hand, the chemotherapeutic drugs in current use for the treatment of this disease are toxic and problems of resistance are increasing (see Kennedy (2004) and Legros et al. (2002)). Therefore, alternative approaches in both treatment and vaccination against trypanosomiasis are needed at this time. To be able to design and develop such alternatives, the biology of this parasite and the host response against the pathogen need to be studied. These two aspects of this disease with few examples of alternative approaches are discussed here.
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Membrane domains and flagellar pocket boundaries are influenced by the cytoskeleton in African trypanosomes. Proc Natl Acad Sci U S A 2009; 106:17425-30. [PMID: 19805090 DOI: 10.1073/pnas.0909289106] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
A key feature of immune evasion for African trypanosomes is the functional specialization of their surface membrane in an invagination known as the flagellar pocket (FP), the cell's sole site of endocytosis and exocytosis. The FP membrane is biochemically distinct yet continuous with those of the cell body and the flagellum. The structural features maintaining this individuality are not known, and we lack a clear understanding of how extracellular components gain access to the FP. Here, we have defined domains and boundaries on these surface membranes and identified their association with internal cytoskeletal features. The FP membrane appears largely homogeneous and uniformly involved in endocytosis. However, when endocytosis is blocked, receptor-mediated and fluid-phase endocytic markers accumulate specifically on membrane associated with four specialized microtubules in the FP region. These microtubules traverse a distinct boundary and associate with a channel that connects the FP lumen to the extracellular space, suggesting that the channel is the major transport route into the FP.
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41
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Pays E, Vanhollebeke B. Human innate immunity against African trypanosomes. Curr Opin Immunol 2009; 21:493-8. [PMID: 19559585 DOI: 10.1016/j.coi.2009.05.024] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Revised: 05/22/2009] [Accepted: 05/25/2009] [Indexed: 10/20/2022]
Abstract
Humans are naturally resistant to infection by the African trypanosome prototype Trypanosoma brucei brucei, and only two variant clones of this parasite can avoid this innate immunity and cause sleeping sickness. The resistance to T. brucei is due to serum complexes associating apolipoprotein A-1 (apoA1) with two primate-specific proteins, apolipoprotein L-1 (apoL1) and haptoglobin-related protein (Hpr). We discuss recent advances on the respective functions of apoL1 and Hpr in this system. ApoL1 was found to share structural and functional similarities with proteins of the apoptotic Bcl2 family, and to kill trypanosomes through anionic pore formation in the lysosomal membrane of the parasite. In association with hemoglobin (Hb), Hpr was found to promote the binding of the trypanolytic complexes to a haptoglobin (Hp)-Hb receptor of the trypanosome surface, hereby facilitating the internalization of apoL1. Hpr or apoL1 deficiency respectively leads to the reduction or abolishment of human protection against T. brucei.
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Affiliation(s)
- Etienne Pays
- Laboratory of Molecular Parasitology, IBMM, Université Libre de Bruxelles, 12, rue des Professeurs Jeener et Brachet, B-6041 Gosselies, Belgium
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42
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Harrington JM, Howell S, Hajduk SL. Membrane permeabilization by trypanosome lytic factor, a cytolytic human high density lipoprotein. J Biol Chem 2009; 284:13505-13512. [PMID: 19324878 DOI: 10.1074/jbc.m900151200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Trypanosome lytic factor (TLF) is a subclass of human high density lipoprotein (HDL) that mediates an innate immune killing of certain mammalian trypanosomes, most notably Trypanosoma brucei brucei, the causative agent of a wasting disease in cattle. Mechanistically, killing is initiated in the lysosome of the target trypanosome where the acidic pH facilitates a membrane-disrupting activity by TLF. Here we utilize a model liposome system to characterize the membrane binding and permeabilizing activity of TLF and its protein constituents, haptoglobin-related protein (Hpr), apolipoprotein L-1 (apoL-1), and apolipoprotein A-1 (apoA-1). We show that TLF efficiently binds and permeabilizes unilamellar liposomes at lysosomal pH, whereas non-lytic human HDL exhibits inefficient permeabilizing activity. Purified, delipidated Hpr and apoL-1 both efficiently permeabilize lipid bilayers at low pH. Trypanosome lytic factor, apoL-1, and apoA-1 exhibit specificity for anionic membranes, whereas Hpr permeabilizes both anionic and zwitterionic membranes. Analysis of the relative particle sizes of susceptible liposomes reveals distinctly different membrane-active behavior for native TLF and the delipidated protein components. We propose that lysosomal membrane damage in TLF-susceptible trypanosomes is initiated by the stable association of the TLF particle with the lysosomal membrane and that this is a property unique to this subclass of human HDL.
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Affiliation(s)
- John M Harrington
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
| | - Sawyer Howell
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602
| | - Stephen L Hajduk
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602.
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43
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Samanovic M, Molina-Portela MP, Chessler ADC, Burleigh BA, Raper J. Trypanosome lytic factor, an antimicrobial high-density lipoprotein, ameliorates Leishmania infection. PLoS Pathog 2009; 5:e1000276. [PMID: 19165337 PMCID: PMC2622765 DOI: 10.1371/journal.ppat.1000276] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Accepted: 12/17/2008] [Indexed: 11/19/2022] Open
Abstract
Innate immunity is the first line of defense against invading microorganisms. Trypanosome Lytic Factor (TLF) is a minor sub-fraction of human high-density lipoprotein that provides innate immunity by completely protecting humans from infection by most species of African trypanosomes, which belong to the Kinetoplastida order. Herein, we demonstrate the broader protective effects of human TLF, which inhibits intracellular infection by Leishmania, a kinetoplastid that replicates in phagolysosomes of macrophages. We show that TLF accumulates within the parasitophorous vacuole of macrophages in vitro and reduces the number of Leishmania metacyclic promastigotes, but not amastigotes. We do not detect any activation of the macrophages by TLF in the presence or absence of Leishmania, and therefore propose that TLF directly damages the parasite in the acidic parasitophorous vacuole. To investigate the physiological relevance of this observation, we have reconstituted lytic activity in vivo by generating mice that express the two main protein components of TLFs: human apolipoprotein L-I and haptoglobin-related protein. Both proteins are expressed in mice at levels equivalent to those found in humans and circulate within high-density lipoproteins. We find that TLF mice can ameliorate an infection with Leishmania by significantly reducing the pathogen burden. In contrast, TLF mice were not protected against infection by the kinetoplastid Trypanosoma cruzi, which infects many cell types and transiently passes through a phagolysosome. We conclude that TLF not only determines species specificity for African trypanosomes, but can also ameliorate an infection with Leishmania, while having no effect on T. cruzi. We propose that TLFs are a component of the innate immune system that can limit infections by their ability to selectively damage pathogens in phagolysosomes within the reticuloendothelial system. Innate immunity (present from birth) is the first line of defense against microorganisms and provides an initial barrier against disease. Here we show that a minor sub-fraction of human high-density lipoprotein (the good cholesterol), known as Trypanosome Lytic Factor (TLF), not only kills the parasite Trypanosoma brucei, but is also a more broadly acting antimicrobial component of the innate immune system in humans. As TLF is activated under acidic conditions, we evaluated the activity of TLF against the intracellular parasite Leishmania, which infects and grows within acidic compartments of macrophages, cells in our blood that normally destroy invading microorganisms. Here we show that TLF acts directly on Leishmania parasites, causing them to swell, thereby decreasing their infectivity. Furthermore, microscopy of macrophages infected with Leishmania reveal that TLF is taken up and delivered to the same compartment as Leishmania, concomitant with a reduction in the intracellular parasite number. Finally, we made mice that expressed the genes for human TLF; these mice reduced the pathogen burden and thereby controlled the Leishmania infection better than unmodified mice. In contrast, TLF mice were not protected from infection by Trypanosoma cruzi, a related parasite, which transiently passes through acidic compartments within cells.
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Affiliation(s)
- Marie Samanovic
- Medical Parasitology, New York University Langone Medical Center, New York, New York, United States of America
| | - Maria Pilar Molina-Portela
- Medical Parasitology, New York University Langone Medical Center, New York, New York, United States of America
| | - Anne-Danielle C. Chessler
- Immunology and Infectious Disease, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - Barbara A. Burleigh
- Immunology and Infectious Disease, Harvard School of Public Health, Boston, Massachusetts, United States of America
| | - Jayne Raper
- Medical Parasitology, New York University Langone Medical Center, New York, New York, United States of America
- * E-mail:
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44
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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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45
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Pays E, Vanhollebeke B. [The controversial story of the human trypanolytic factor]. Med Sci (Paris) 2008; 24:792-3. [PMID: 18950568 DOI: 10.1051/medsci/20082410792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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46
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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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47
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48
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Vanhollebeke B, De Muylder G, Nielsen MJ, Pays A, Tebabi P, Dieu M, Raes M, Moestrup SK, Pays E. A haptoglobin-hemoglobin receptor conveys innate immunity to Trypanosoma brucei in humans. Science 2008; 320:677-81. [PMID: 18451305 DOI: 10.1126/science.1156296] [Citation(s) in RCA: 186] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The protozoan parasite Trypanosoma brucei is lysed by apolipoprotein L-I, a component of human high-density lipoprotein (HDL) particles that are also characterized by the presence of haptoglobin-related protein. We report that this process is mediated by a parasite glycoprotein receptor, which binds the haptoglobin-hemoglobin complex with high affinity for the uptake and incorporation of heme into intracellular hemoproteins. In mice, this receptor was required for optimal parasite growth and the resistance of parasites to the oxidative burst by host macrophages. In humans, the trypanosome receptor also recognized the complex between hemoglobin and haptoglobin-related protein, which explains its ability to capture trypanolytic HDLs. Thus, in humans the presence of haptoglobin-related protein has diverted the function of the trypanosome haptoglobin-hemoglobin receptor to elicit innate host immunity against the parasite.
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Affiliation(s)
- Benoit Vanhollebeke
- Laboratory of Molecular Parasitology, Institute for Molecular Biology and Medicine, Université Libre de Bruxelles, 12 rue des Profs Jeener et Brachet, B6041 Gosselies, Belgium
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49
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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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50
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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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