Molecular cloning of Trypanosoma brucei CK2 catalytic subunits: the α isoform is nucleolar and phosphorylates the nucleolar protein Nopp44/46

Park, Jeong Hyun; Brekken, Deirdre L.; Randall, Amber C.; Parsons, Marilyn

doi:10.1016/s0166-6851(01)00407-8

Cited by 21 publications

(29 citation statements)

References 32 publications

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“…We found that, unlike protein kinases CK2, the GPEET kinase uses ATP but not GTP as phosphoryl donor, is not inhibited by low concentrations of heparin, and does not phosphorylate the typical CK2 substrate phosvitin (results not shown). In addition, although a recent report (63) demonstrated the presence of the gene for the protein kinase CK2 ␣ subunit in T. brucei, we can exclude its involvement in GPEET phosphorylation based on its nucleolar localization. Together, these results demonstrate that the enzyme responsible for GPEET phosphorylation in procyclic trypanosomes is not related to previously characterized ecto-protein kinases and represents a novel type of enzyme.…”

Section: Discussionmentioning

confidence: 64%

Coordinate Expression of GPEET Procyclin and Its Membrane-associated Kinase in Trypanosoma brucei Procyclic Forms

Schlaeppi

Malherbe

Bütikofer

2003

Journal of Biological Chemistry

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GPEET procyclin is a major glycosylphosphatidylinositol-anchored protein of procyclic (insect stage) trypanosomes in culture and is heavily phosphorylated in the GPEET pentapeptide repeat. The phosphorylation reaction is a late event and occurs during maturation and transport of GPEET or on the parasite surface by an ecto-protein kinase. Initial biochemical characterization of the GPEET kinase activity now shows that it depends on bivalent cations for maximal activity, is stimulated by sulfhydryl group reagents, and is specific for ATP as phosphoryl donor. No kinase activity is detected in bloodstream form trypanosomes in culture, whereas strong phosphorylation is observed in early procyclic forms. In addition, the GPEET kinase activity is absent from procyclic trypanosomes that have repressed GPEET synthesis but can be induced in these same stocks by conditions, which also induce GPEET expression. However, the presence of an active kinase does not depend on the presence of (functional) GPEET because it can be detected in parasites expressing a non-phosphorylatable GPEET mutant protein and in procyclin null mutant trypanosomes. Interestingly, the presence of the glycosylphosphatidylinositol lipid moiety seems necessary for GPEET to become phosphorylated. Together, the results demonstrate that GPEET and its kinase are expressed during the same life cycle stages and that factors that induce the expression of GPEET in vitro also induce the expression of the GPEET kinase.

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Section: Discussionmentioning

confidence: 64%

Coordinate Expression of GPEET Procyclin and Its Membrane-associated Kinase in Trypanosoma brucei Procyclic Forms

Schlaeppi

Malherbe

Bütikofer

2003

Journal of Biological Chemistry

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“…Consistently, tubulin has been reported to be the major phosphoprotein in another trypanosome, T. cruzi (Casas et al 2002), and likewise, T. cruzi tubulin has also been shown to be phosphorylated by a CK2-like activity (Casas et al 2002, Uzcanga et al 2003. In T. brucei, an evolutionarily more related parasite, two CK2 genes have been identified: CK2a1 and CK2a2 (Park et al 2002). Although, the protein encoded by CK2a1 was capable of associating with Nopp44/46, an abundant nucleolar phosphoprotein of T. brucei (Park et al 2002), no substrates for the kinase encoded by CK2a2 have been described yet.…”

Section: Discussionmentioning

confidence: 74%

“…In T. brucei, an evolutionarily more related parasite, two CK2 genes have been identified: CK2a1 and CK2a2 (Park et al 2002). Although, the protein encoded by CK2a1 was capable of associating with Nopp44/46, an abundant nucleolar phosphoprotein of T. brucei (Park et al 2002), no substrates for the kinase encoded by CK2a2 have been described yet. On the basis of the results shown here, it is plausible that T. brucei tubulin could also serve as a substrate for the CK2a2-encoded protein kinase.…”

Section: Discussionmentioning

confidence: 99%

“…Alternatively, 3) the presence of GTP might be linked to the phosphorylation of an intermediate "regulatory" element present in the parasite membranes, which would in turn be involved in the activation of the [γ-32 P] ATP-driven phosphorylation of tubulin by CK2. Interestingly, competition assays have revealed that, unlike most CK2s, the protein encoded by CK2a1 from T. brucei was capable of discriminating between ATP and GTP (Park et al 2002). These evidences imply that in comparison to mammalian CK2s, CK2s from salivarian trypanosomes have different affinities toward intracellular triphosphate nucleotides.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Identification of casein kinase 1, casein kinase 2, and cAMP-dependent protein kinase-like activities in Trypanosoma evansi

Galán-Caridad

Calabokis

Uzcanga

et al. 2004

Mem. Inst. Oswaldo Cruz

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“…Two catalytic subunits of CK2 were identified [23]. One of the subunits, CK2α (CK2A1, systematic name Tb09.211.4890) was previously characterized [24]. Unlike most other CK2s, the purified T. brucei CK2α subunit, as well as CK2α immunoprecipitated from the parasites, have only weak affinity for GTP.…”

Section: Introductionmentioning

confidence: 99%

Characterization of protein kinase CK2 from Trypanosoma brucei

Jensen

Kifer

Brekken

et al. 2007

Molecular and Biochemical Parasitology

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CK2 is a ubiquitous but enigmatic kinase. The difficulty in assigning a role to CK2 centers on the fact that, to date, no biologically relevant modulator of its function has been identified. One common theme revolves around a constellation of known substrates involved in growth control, compatible with its concentration in the nucleus and nucleolus. We had previously described the identification of two catalytic subunits of CK2 in Trypanosoma brucei and characterized one of them. Here we report the characterization of the second catalytic subunit, CK2α', and the identification and characterization of the regulatory subunit CK2β. All three subunits are primarily localized to the nucleolus in T. brucei. We also show that CK2β interacts with the nucleolar protein NOG1, adding to the interaction map which previously linked CK2α to the nucleolar protein NOPP44/46, which in turn associates with the rRNA binding protein p37. CK2 activity has four distinctive features: near equal affinity for GTP and ATP, heparin sensitivity, and stimulation by polyamines and polybasic peptides. Sequence comparison shows that the parasite orthologues have mutations in residues previously mapped as important in specifying affinity for GTP and stimulation by both polyamines and polybasic peptides. Studies of the enzymatic activity of the T. brucei CK2s show that both the affinity for GTP and stimulation by polyamines have been lost and only the features of heparin inhibition and stimulation by polybasic peptides are conserved.

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Molecular cloning of Trypanosoma brucei CK2 catalytic subunits: the α isoform is nucleolar and phosphorylates the nucleolar protein Nopp44/46

Cited by 21 publications

References 32 publications

Coordinate Expression of GPEET Procyclin and Its Membrane-associated Kinase in Trypanosoma brucei Procyclic Forms

Coordinate Expression of GPEET Procyclin and Its Membrane-associated Kinase in Trypanosoma brucei Procyclic Forms

Identification of casein kinase 1, casein kinase 2, and cAMP-dependent protein kinase-like activities in Trypanosoma evansi

Characterization of protein kinase CK2 from Trypanosoma brucei

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