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Uboldi AD, Wilde ML, McRae EA, Stewart RJ, Dagley LF, Yang L, Katris NJ, Hapuarachchi SV, Coffey MJ, Lehane AM, Botte CY, Waller RF, Webb AI, McConville MJ, Tonkin CJ. Protein kinase A negatively regulates Ca2+ signalling in Toxoplasma gondii. PLoS Biol 2018; 16:e2005642. [PMID: 30208022 PMCID: PMC6152992 DOI: 10.1371/journal.pbio.2005642] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 09/24/2018] [Accepted: 08/20/2018] [Indexed: 11/18/2022] Open
Abstract
The phylum Apicomplexa comprises a group of obligate intracellular parasites that alternate between intracellular replicating stages and actively motile extracellular forms that move through tissue. Parasite cytosolic Ca2+ signalling activates motility, but how this is switched off after invasion is complete to allow for replication to begin is not understood. Here, we show that the cyclic adenosine monophosphate (cAMP)-dependent protein kinase A catalytic subunit 1 (PKAc1) of Toxoplasma is responsible for suppression of Ca2+ signalling upon host cell invasion. We demonstrate that PKAc1 is sequestered to the parasite periphery by dual acylation of PKA regulatory subunit 1 (PKAr1). Upon genetic depletion of PKAc1 we show that newly invaded parasites exit host cells shortly thereafter, in a perforin-like protein 1 (PLP-1)-dependent fashion. Furthermore, we demonstrate that loss of PKAc1 prevents rapid down-regulation of cytosolic [Ca2+] levels shortly after invasion. We also provide evidence that loss of PKAc1 sensitises parasites to cyclic GMP (cGMP)-induced Ca2+ signalling, thus demonstrating a functional link between cAMP and these other signalling modalities. Together, this work provides a new paradigm in understanding how Toxoplasma and related apicomplexan parasites regulate infectivity. Central to pathogenesis and infectivity of Toxoplasma and related parasites is their ability to move through tissue, invade host cells, and establish a replicative niche. Ca2+-dependent signalling pathways are important for activating motility, host cell invasion, and egress, yet how this signalling is turned off after invasion is unclear. Here, we show that a cAMP-dependent protein kinase A (PKA) is essential for rapid suppression of Ca2+ signalling upon completion of host cell invasion. Parasites lacking this kinase rapidly invoke an egress program to re-exit host cells, thus preventing the establishment of a stable infection. This finding therefore highlights the first factor required for Toxoplasma (and any related apicomplexan parasite) to switch from invasive to the replicative forms.
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Affiliation(s)
- Alessandro D. Uboldi
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Mary-Louise Wilde
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Emi A. McRae
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Rebecca J. Stewart
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Laura F. Dagley
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Luning Yang
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Australia
- School of Medicine, Tsinghua University, Beijing, China
| | - Nicholas J. Katris
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
- Institute of Advanced Biosciences, CNRS UMR5309, INSERM U1209, Université Grenoble Alpes, Grenoble, France
| | | | - Michael J. Coffey
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Adele M. Lehane
- Research School of Biology, The Australian National University, A.C.T., Australia
| | - Cyrille Y. Botte
- Institute of Advanced Biosciences, CNRS UMR5309, INSERM U1209, Université Grenoble Alpes, Grenoble, France
| | - Ross F. Waller
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Andrew I. Webb
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Australia
| | - Malcolm J. McConville
- Department of Biochemistry and Molecular Biology, Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Australia
| | - Christopher J. Tonkin
- The Walter and Eliza Hall Institute of Medical Research, Parkville, Australia
- Department of Medical Biology, The University of Melbourne, Parkville, Australia
- * E-mail:
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Rajendran E, Hapuarachchi SV, Miller CM, Fairweather SJ, Cai Y, Smith NC, Cockburn IA, Bröer S, Kirk K, van Dooren GG. Cationic amino acid transporters play key roles in the survival and transmission of apicomplexan parasites. Nat Commun 2017; 8:14455. [PMID: 28205520 PMCID: PMC5316894 DOI: 10.1038/ncomms14455] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 12/30/2016] [Indexed: 11/09/2022] Open
Abstract
Apicomplexans are obligate intracellular parasites that scavenge essential nutrients from their hosts via transporter proteins on their plasma membrane. The identities of the transporters that mediate amino acid uptake into apicomplexans are unknown. Here we demonstrate that members of an apicomplexan-specific protein family-the Novel Putative Transporters (NPTs)-play key roles in the uptake of cationic amino acids. We show that an NPT from Toxoplasma gondii (TgNPT1) is a selective arginine transporter that is essential for parasite survival and virulence. We also demonstrate that a homologue of TgNPT1 from the malaria parasite Plasmodium berghei (PbNPT1), shown previously to be essential for the sexual gametocyte stage of the parasite, is a cationic amino acid transporter. This reveals a role for cationic amino acid scavenging in gametocyte biology. Our study demonstrates a critical role for amino acid transporters in the survival, virulence and life cycle progression of these parasites.
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Affiliation(s)
- Esther Rajendran
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Sanduni V Hapuarachchi
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Catherine M Miller
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Smithfield, Queensland 4878, Australia
| | - Stephen J Fairweather
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Yeping Cai
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Nicholas C Smith
- Queensland Tropical Health Alliance Research Laboratory, Australian Institute of Tropical Health and Medicine, James Cook University, Smithfield, Queensland 4878, Australia
| | - Ian A Cockburn
- John Curtin School of Medical Research, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Stefan Bröer
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Kiaran Kirk
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
| | - Giel G van Dooren
- Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia
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Hapuarachchi SV, Cobbold SA, Shafik SH, Dennis ASM, McConville MJ, Martin RE, Kirk K, Lehane AM. The Malaria Parasite's Lactate Transporter PfFNT Is the Target of Antiplasmodial Compounds Identified in Whole Cell Phenotypic Screens. PLoS Pathog 2017; 13:e1006180. [PMID: 28178359 PMCID: PMC5298231 DOI: 10.1371/journal.ppat.1006180] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Accepted: 01/11/2017] [Indexed: 11/19/2022] Open
Abstract
In this study the ‘Malaria Box’ chemical library comprising 400 compounds with antiplasmodial activity was screened for compounds that perturb the internal pH of the malaria parasite, Plasmodium falciparum. Fifteen compounds induced an acidification of the parasite cytosol. Two of these did so by inhibiting the parasite’s formate nitrite transporter (PfFNT), which mediates the H+-coupled efflux from the parasite of lactate generated by glycolysis. Both compounds were shown to inhibit lactate transport across the parasite plasma membrane, and the transport of lactate by PfFNT expressed in Xenopus laevis oocytes. PfFNT inhibition caused accumulation of lactate in parasitised erythrocytes, and swelling of both the parasite and parasitised erythrocyte. Long-term exposure of parasites to one of the inhibitors gave rise to resistant parasites with a mutant form of PfFNT that showed reduced inhibitor sensitivity. This study provides the first evidence that PfFNT is a druggable antimalarial target. The emergence and spread of Plasmodium falciparum strains resistant to leading antimalarial drugs has intensified the need to discover and develop drugs that kill the parasite via new mechanisms. Here we screened compounds that are known to inhibit P. falciparum growth for their effects on the pH inside the parasite. We identified fifteen compounds that decrease the pH inside the parasite, and determined the mechanism by which two of these, MMV007839 and MMV000972, disrupt pH and kill the parasite. The two compounds were found to inhibit the P. falciparum formate nitrite transporter (PfFNT), a transport protein that is located on the parasite surface and that serves to remove the waste product lactic acid from the parasite. The compounds inhibited both the H+-coupled transport of lactate across the parasite plasma membrane and the transport of lactate by PfFNT expressed in Xenopus oocytes. In addition to disrupting pH, PfFNT inhibition led to a build-up of lactate in the parasite-infected red blood cell and the swelling of both the parasite and the infected red blood cell. Exposing parasites to MMV007839 over a prolonged time period gave rise to resistant parasites with a mutant form of PfFNT that was less sensitive to the compound. This study validates PfFNT as a novel antimalarial drug target.
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Affiliation(s)
| | - Simon A Cobbold
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, VIC, Australia
| | - Sarah H Shafik
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Adelaide S M Dennis
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Malcolm J McConville
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, VIC, Australia
| | - Rowena E Martin
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Kiaran Kirk
- Research School of Biology, Australian National University, Canberra, ACT, Australia
| | - Adele M Lehane
- Research School of Biology, Australian National University, Canberra, ACT, Australia
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