title: A vacuolar-H(+) -pyrophosphatase (TgVP1) is required for microneme secretion, host cell invasion, and extracellular survival of Toxoplasma gondii.
abstract: The vacuolar proton pyrophosphatase (H(+) -PPase) of Toxoplasma gondii (TgVP1), a membrane proton pump, localizes to acidocalcisomes and a novel lysosome-like compartment termed plant-like vacuole (PLV) or vacuolar compartment (VAC). We report the characterization of a T. gondii null mutant for the TgVP1 gene. Propagation of these mutants decreased significantly because of deficient attachment and invasion of host cells, which correlated with deficient microneme secretion. Processing of cathepsin L (CPL) in these mutants was deficient only when the parasites were incubated in the presence of low concentrations of the vacuolar H(+) -ATPase (V-H(+) -ATPase) inhibitor bafilomycin A1 , suggesting that either TgVP1 or the T. gondii V-H(+) -ATPase (TgVATPase) are sufficient to support CPL processing. The lack of TgVP1 did not affect processing of micronemal proteins, indicating that it does not contribute to proMIC maturations. The TgVP1 null mutants were more sensitive to extracellular conditions and were less virulent in mice. We demonstrate that T. gondii tachyzoites possess regulatory volume decrease capability during hypo-osmotic stress and this ability is impaired in TgVP1 null mutants implicating TgVP1 in osmoregulation. We hypothesize that osmoregulation is needed for host cell invasion and that TgVP1 plays a role during the normal lytic cycle of T. gondii.
authors: Center for Tropical and Emerging Global Diseases and Department of Cellular Biology, University of Georgia, GA, 30602-7400, USA; College of Veterinary Medicine, China Agricultural University, Beijing, 100193, China.
authors: Jing
authors: J
authors: Liu
authors: Douglas
authors: D
authors: Pace
authors: Zhicheng
authors: Z
authors: Dou
authors: Thayer P
authors: TP
authors: King
authors: Daniel
authors: D
authors: Guidot
authors: Zhu-Hong
authors: ZH
authors: Li
authors: Vern B
authors: VB
authors: Carruthers
authors: Silvia N J
authors: SN
authors: Moreno
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002470:Cell Survival; D004195:Disease Models, Animal; D004705:Endocytosis; D017353:Gene Deletion; D043564:Inorganic Pyrophosphatase / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D014122:Toxoplasma / Q000201:enzymology* / Q000378:metabolism / Q000502:physiology; D014124:Toxoplasmosis, Animal; D014617:Vacuoles / Q000201:enzymology* / Q000378:metabolism; D014774:Virulence
chemical_list: D015815:Cell Adhesion Molecules; D043564:Inorganic Pyrophosphatase