title: The Apoptotic Role of Metacaspase in Toxoplasma gondii.
abstract: Toxoplasma gondii is a major opportunistic pathogen that spreads in a range of animal species and human beings. Quite a few characterizations of apoptosis have been identified in T. gondii treated with apoptosis inducers, but the molecular mechanisms of the pathway are not clearly understood. Metacaspases are caspase-like cysteine proteases that can be found in plants, fungi, and protozoa in which caspases are absent. Metacaspases are multifunctional proteases involved in apoptosis-like cell death, insoluble protein aggregate clearance, and cell proliferation. To investigate whether T. gondii metacaspase (TgMCA) is involved in the apoptosis of the parasites, we generated TgMCA mutant strains. Western blot analysis indicated that the autoproteolytic processing of TgMCA was the same as that for metacaspases of some other species. Indirect immunofluorescence assay (IFA) showed that TgMCA was dispersed throughout the cytoplasm and relocated to the nucleus when the parasites were exposed to the extracellular environment, which indicated the execution of its function in the nucleus. The number of apoptosis parasites was significantly diminished in the TgMCA knockout strain and increased in the TgMCA overexpression strain after treatment with extracellular buffer, as determined by the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. The lack of TgMCA did not affect the parasite propagation in vitro and virulence in vivo, suggesting that it is probably redundant in parasite propagation. But overexpression of TgMCA reduced the intracellular parasites growth in vitro. The TgMCA knockout strain showed more viability in extracellular buffer compared to the parental and overexpression lines. In this study, we demonstrated that TgMCA contributes to the apoptosis of T. gondii.
authors.affiliation: Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Protozoa Laboratory, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Muzi
authors.initials: M
authors.lastname: Li
authors.affiliation: Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Protozoa Laboratory, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.affiliation: Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Protozoa Laboratory, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.affiliation: Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Protozoa Laboratory, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Pan
authors.initials: P
authors.lastname: Hao
authors.affiliation: Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Protozoa Laboratory, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Ma
authors.affiliation: Key Laboratory of Animal Epidemiology and Zoonosis, Ministry of Agriculture, National Animal Protozoa Laboratory, College of Veterinary Medicine, China Agricultural University Beijing, China.
authors.forename: Qun
authors.initials: Q
authors.lastname: Liu
keywords: T. gondii; apoptosis; knockout; metacaspase; programmed cell death
references.citation: Front Cell Infect Microbiol. 2012 Jul 10;2:95
references.pmid: 22919685
references.citation: Parasit Vectors. 2011 Mar 25;4:44
references.pmid: 21439063
references.citation: Cell Death Differ. 2012 Aug;19(8):1358-69
references.pmid: 22402587
references.citation: Eukaryot Cell. 2007 Oct;6(10):1745-57
references.pmid: 17715367
references.citation: Mol Microbiol. 2011 Jan;79(1):222-39
references.pmid: 21166905
references.citation: Nat Cell Biol. 2009 Nov;11(11):1347-54
references.pmid: 19820703
references.citation: PLoS One. 2014 Nov 04;9(11):e111993
references.pmid: 25369210
references.citation: Trends Parasitol. 2007 Aug;23(8):376-83
references.pmid: 17588817
references.citation: J Biol Chem. 2012 Aug 24;287(35):29251-9
references.pmid: 22761449
references.citation: Apoptosis. 2013 Jun;18(6):664-80
references.pmid: 23468121
references.citation: Parasite Immunol. 2013 Mar-Apr;35(3-4):109-19
references.pmid: 23163958
references.citation: Parasit Vectors. 2011 Feb 28;4:26
references.pmid: 21356053
references.citation: Nat Rev Microbiol. 2013 Jan;11(1):58-66
references.pmid: 23202528
references.citation: Proc Natl Acad Sci U S A. 2010 Jul 27;107(30):13348-53
references.pmid: 20624963
references.citation: Cell Death Differ. 2011 Aug;18(8):1279-88
references.pmid: 21597462
references.citation: Proc Natl Acad Sci U S A. 2012 May 8;109(19):7469-74
references.pmid: 22529389
references.citation: Mol Cell. 2000 Oct;6(4):961-7
references.pmid: 11090634
references.citation: Science. 2014 Jun 20;344(6190):1389-92
references.pmid: 24855027
references.citation: Cell Death Differ. 2010 Mar;17(3):377-8
references.pmid: 20154701
references.citation: Curr Biol. 2004 May 4;14(9):R339-40
references.pmid: 15120084
references.citation: PLoS Pathog. 2011 Dec;7(12):e1002320
references.pmid: 22174671
references.citation: J Cell Sci. 2006 Mar 15;119(Pt 6):1105-17
references.pmid: 16507595
references.citation: MBio. 2014 May 13;5(3):e01114-14
references.pmid: 24825012
references.citation: Proc Natl Acad Sci U S A. 2006 Sep 12;103(37):13837-42
references.pmid: 16945916
references.citation: Mol Biochem Parasitol. 2006 Jan;145(1):18-28
references.pmid: 16213036
references.citation: Toxicol Pathol. 2007 Jun;35(4):495-516
references.pmid: 17562483
references.citation: Parasit Vectors. 2010 Nov 09;3:104
references.pmid: 21062457
references.citation: Cell Death Dis. 2013 Feb 14;4:e490
references.pmid: 23412383
references.citation: Annu Rev Biochem. 2011;80:1055-87
references.pmid: 21456965
references.citation: PLoS One. 2011;6(11):e27867
references.pmid: 22140476
references.citation: FEBS Lett. 2013 Aug 19;587(16):2517-22
references.pmid: 23850889
references.citation: J Infect Dis. 2007 Jun 15;195(12):1852-9
references.pmid: 17492602
references.citation: Science. 2010 Dec 3;330(6009):1393-7
references.pmid: 21097903
references.citation: Mol Cell. 2002 Apr;9(4):911-7
references.pmid: 11983181