A Theileria parva type 1 protein phosphatase activity
Laboratoire de Signalisation Immuno-Parasitaire, URA CNRS 1960, Département d'Immunologie, Institut Pasteur, 25 rue du Dr Roux, 75015 Paris, France Molecular and Biochemical Parasitology
(Impact Factor: 1.79).
10/2000; 110(1):161-166. DOI: 10.1016/S0166-6851(00)00266-8
The protozoan parasite Theileria (spp. parva and annulata) infects bovine leukocytes and provokes a leukaemia-like disease in vivo. In this study, we have detected a type 1 serine/threonine phosphatase activity with phosphorylase a as a substrate, in protein extracts of parasites purified from infected B lymphocytes. In contrast to this type 1 activity, dose response experiments with okadaic acid (OA), a well characterised inhibitor of type 1 and 2A protein phosphatases, indicated that type 2A is the predominant activity detected in host B cells. Furthermore, consistent with polycation-specific activation of the type 2A phosphatase, protamine failed to activate the parasite-associated phosphorylase a phosphatase activity. Moreover, inhibition of phosphorylase a dephosphorylation by phospho-DARPP-32, a specific type 1 inhibitor, clearly demonstrated that a type 1 phosphatase is specifically associated with the parasite, while the type 2A is predominantly expressed in the host lymphocyte. Since an antibody against bovine catalytic protein phosphatase 1 (PP1) subunit only recognised the PP1 in B cells, but not in parasite extracts, we conclude that in parasites the PP1 activity is of parasitic origin. Intriguingly, since type 1 OA-sensitive phosphatase activity has been recently described in Plasmodium falciparum, we can conclude that these medically important parasites produce their one PP1.
Available from: Ray Pierce
- "Among the phosphatases, PP1 has been identified in P. falciparum (PfPP1c) and it accounts for the major phosphatase activity in total parasite extracts [1,17,18]. The use of potent inhibitors of phosphatases showed that P. falciparum predominantly expressed PP1-like activity which appears to control parasite growth and seems to be involved in the release of infectious merozoites [19,20]. "
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ABSTRACT: It is clear that the coordinated and reciprocal actions of kinases and phosphatases are fundamental in the regulation of development and growth of the malaria parasite. Protein Phosphatase type 1 is a key enzyme playing diverse and essential roles in cell survival. Its dephosphorylation activity/specificity is governed by the interaction of its catalytic subunit (PP1c) with regulatory proteins. Among these, inhibitor-2 (I2) is one of the most evolutionarily ancient PP1 regulators. In vivo studies in various organisms revealed a defect in chromosome segregation and cell cycle progression when the function of I2 is blocked.
In this report, we present evidence that Plasmodium falciparum, the causative agent of the most deadly form of malaria, expresses a structural homolog of mammalian I2, named PfI2. Biochemical, in vitro and in vivo studies revealed that PfI2 binds PP1 and inhibits its activity. We further showed that the motifs 12KTISW16 and 102HYNE105 are critical for PfI2 inhibitory activity. Functional studies using the Xenopus oocyte model revealed that PfI2 is able to overcome the G2/M cell cycle checkpoint by inducing germinal vesicle breakdown. Genetic manipulations in P. falciparum suggest an essential role of PfI2 as no viable mutants with a disrupted PfI2 gene were detectable. Additionally, peptides derived from PfI2 and competing with RVxF binding sites in PP1 exhibit anti-plasmodial activity against blood stage parasites in vitro.
Taken together, our data suggest that the PfI2 protein could play a role in the regulation of the P. falciparum cell cycle through its PfPP1 phosphatase regulatory activity. Structure-activity studies of this regulator led to the identification of peptides with anti-plasmodial activity against blood stage parasites in vitro suggesting that PP1c-regulator interactions could be a novel means to control malaria.
BMC Biology 07/2013; 11(1):80. DOI:10.1186/1741-7007-11-80 · 7.98 Impact Factor
Available from: JUAN LUIS CASTILLO
- "The presence of PP1 and its isoforms has been demonstrated in a broad range of protozoan parasites (Erondu and Donelson, 1991; Cayla et al., 2000; Orr et al., 2000; Kumar et al., 2002; Kutuzov and Andreeva, 2008). However, to our knowledge the enzyme had not yet been identified in T. vaginalis prior to this study. "
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ABSTRACT: In this work, evidence for a critical role of Trichomonas vaginalis protein phosphatase 1 gamma (TvPP1γ) in proliferation and attachment of the parasite to the mammalian cell is provided. Firstly, proliferation and attachment of T. vaginalis parasites to HeLa cells was blocked by calyculin A (CA), a potent PP1 inhibitor. Secondly, it was demonstrated that the enzyme activity of native and recombinant TvPP1γ proteins was inhibited by CA. Thirdly, reverse genetic studies confirmed that antisense oligonucleotides targeted to PP1γ but not PP1α or β inhibited proliferation and attachment of trichomonads CA-treated parasites underwent cytoskeletal modifications, including a lack of axostyle typical labelling, suggesting that cytoskeletal phosphorylation could be regulated by a CA-sensitive phosphatase where the role of PP1γ could not be ruled out. Analysis of subcellular distribution of TvPP1γ by cell fractionation and electron microscopy demonstrated the association between TvPP1γ and the cytoskeleton. The expression of adhesins, AP120 and AP65, at the cell surface was also inhibited by CA. The concomitant inhibition of expression of adhesins and changes in the cytoskeleton in CA-treated parasites suggest a specific role for PP1γ -dependent dephosphorylation in the early stages of the host-parasite interaction. Molecular modelling of TvPP1γ showed the conservation of residues critical for maintaining proper folding into the gross structure common to PP1 proteins. Taken together, these results suggest that TvPP1γ could be considered a potential novel drug target for treatment of trichomoniasis.
International journal for parasitology 06/2012; 42(8):715-27. DOI:10.1016/j.ijpara.2012.03.012 · 3.87 Impact Factor
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ABSTRACT: Host cell invasion by Toxoplasma gondii tachyzoites relies on many coordinated processes. The tachyzoite participates in invasion by providing an actomyosin-dependent force driving it into the nascent parasitophorous vacuole as well as by releasing molecules which contribute to the vacuole membrane. Exposure to type 1/2A protein phosphatase inhibitors, okadaic acid (OA) or tautomycin significantly impairs tachyzoite invasiveness. Furthermore, the tachyzoite extract contains a biochemically active type 1, but not a type 2A, serine-threonine protein phosphatase, which is immunologically related to eukaryotic phosphatase type 1 catalytic subunit. When tachyzoite extracts are incubated with a monoclonal antibody reactive to human type 1 catalytic subunit, other T. gondii molecules are coprecipitated among which one competes with the inhibitory toxin OA. Finally, in vitro phosphate labelling assays indicate that the biochemically characterized PP1 activity controls the phosphorylation of several proteins. Taken together, these data strongly suggest that the type 1 phosphatase activity detected in invasive tachyzoites is implicated in the control of the host cell invasion process.
Microbes and Infection 04/2002; 4(3):271-8. DOI:10.1016/S1286-4579(02)01538-1 · 2.86 Impact Factor
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