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Amoeba Proteus

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J Moraczewska – One of the best experts on this subject based on the ideXlab platform.

  • Characterisation of the Rac/PAK pathway in Amoeba Proteus.
    Protoplasma, 2005
    Co-Authors: W Kłopocka, J Moraczewska, M J Redowicz

    Abstract:

    Molecular mechanisms underlying the unique locomotion of the highly motile Amoeba Proteus still remain poorly understood. Recently, we have shown that blocking the endogenous Amoebal Rac-like protein(s) leads to distinct and irreversible changes in the appearance of these large migrating cells as well as to a significant inhibition of their locomotion. To elucidate the mechanism of the Rac pathway in Amoeba Proteus, we tested the effects of blocking the endogenous myosin I heavy chain kinase (MIHCK), one of the Rac effectors in AcanthAmoeba castellanii and Dictyostelium discoideum, with anti-MIHCK antibodies in migrating Amoebae, as well as the effect of inhibiting Rac and MIHCK on the actin polymerisation process. Antibodies against A. castellanii MIHCK detected an A. Proteus protein with a molecular mass (ca. 95 kDa) similar to the A. castellanii kinase. The cellular distribution of MIHCK in A. Proteus was very similar to those of Rac-like protein in Amoebae and MIHCK in A. castellanii. Amoebae microinjected with anti-MIHCK antibodies moved slower and protruded fewer wide pseudopodia (5-6) than the control cells (9-10), resembling to some extent the phenotype of cells microinjected with anti-Rac antibodies. The in vitro studies indicate that the A. Proteus Rac-like protein, but not the MIHCK isoform, is engaged in the regulation of the nucleation step of the actin polymerisation process. These observations suggest that MIHCK may be one of the effectors for Rac in these extremely large cells.

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  • characterisation of the rac pak pathway in Amoeba Proteus
    Protoplasma, 2005
    Co-Authors: Wanda Klopocka, J Moraczewska

    Abstract:

    Molecular mechanisms underlying the unique locomotion of the highly motile Amoeba Proteus still remain poorly understood. Recently, we have shown that blocking the endogenous Amoebal Rac-like protein(s) leads to distinct and irreversible changes in the appearance of these large migrating cells as well as to a significant inhibition of their locomotion. To elucidate the mechanism of the Rac pathway in Amoeba Proteus, we tested the effects of blocking the endogenous myosin I heavy chain kinase (MIHCK), one of the Rac effectors in AcanthAmoeba castellanii and Dictyostelium discoideum, with anti-MIHCK antibodies in migrating Amoebae, as well as the effect of inhibiting Rac and MIHCK on the actin polymerisation process. Antibodies against A. castellanii MIHCK detected an A. Proteus protein with a molecular mass (ca. 95 kDa) similar to the A. castellanii kinase. The cellular distribution of MIHCK in A. Proteus was very similar to those of Rac-like protein in Amoebae and MIHCK in A. castellanii. Amoebae microinjected with anti-MIHCK antibodies moved slower and protruded fewer wide pseudopodia (5–6) than the control cells (9–10), resembling to some extent the phenotype of cells microinjected with anti-Rac antibodies. The in vitro studies indicate that the A. Proteus Rac-like protein, but not the MIHCK isoform, is engaged in the regulation of the nucleation step of the actin polymerisation process. These observations suggest that MIHCK may be one of the effectors for Rac in these extremely large cells.

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Wanda Klopocka – One of the best experts on this subject based on the ideXlab platform.

  • characterisation of the rac pak pathway in Amoeba Proteus
    Protoplasma, 2005
    Co-Authors: Wanda Klopocka, J Moraczewska

    Abstract:

    Molecular mechanisms underlying the unique locomotion of the highly motile Amoeba Proteus still remain poorly understood. Recently, we have shown that blocking the endogenous Amoebal Rac-like protein(s) leads to distinct and irreversible changes in the appearance of these large migrating cells as well as to a significant inhibition of their locomotion. To elucidate the mechanism of the Rac pathway in Amoeba Proteus, we tested the effects of blocking the endogenous myosin I heavy chain kinase (MIHCK), one of the Rac effectors in AcanthAmoeba castellanii and Dictyostelium discoideum, with anti-MIHCK antibodies in migrating Amoebae, as well as the effect of inhibiting Rac and MIHCK on the actin polymerisation process. Antibodies against A. castellanii MIHCK detected an A. Proteus protein with a molecular mass (ca. 95 kDa) similar to the A. castellanii kinase. The cellular distribution of MIHCK in A. Proteus was very similar to those of Rac-like protein in Amoebae and MIHCK in A. castellanii. Amoebae microinjected with anti-MIHCK antibodies moved slower and protruded fewer wide pseudopodia (5–6) than the control cells (9–10), resembling to some extent the phenotype of cells microinjected with anti-Rac antibodies. The in vitro studies indicate that the A. Proteus Rac-like protein, but not the MIHCK isoform, is engaged in the regulation of the nucleation step of the actin polymerisation process. These observations suggest that MIHCK may be one of the effectors for Rac in these extremely large cells.

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M. Hanocq – One of the best experts on this subject based on the ideXlab platform.

  • Cytotoxicity of polyamines to Amoeba Proteus: Role of polyamine oxidase
    Cell Biology and Toxicology, 1996
    Co-Authors: E. Schenkel, J. G. Dubois, M. Helson-cambier, M. Hanocq

    Abstract:

    It has been shown that oxidation of polyamines by polyamine oxidases can produce toxic compounds (H_2O_2, aldehydes, ammonia) and that the polyamine oxidase-polyamine system is implicated, in vitro , in the death of several parasites. Using Amoeba Proteus as an in vitro model, we studied the cytotoxicity to these cells of spermine, spermidine, their acetyl derivatives, and their hypothetical precursors. Spermine and N ^1-acetylspermine were more toxic than emetine, an amoebicidal reference drug. Spermine presented a short-term toxicity, but a 48-h contact time was necessary for the high toxicity of spermidine. The uptake by Amoeba cells of the different polyamines tested was demonstrated. On the other hand, a high polyamine oxidase activity was identified in Amoeba Proteus crude extract. Spermine (theoretical 100%) and N ^1-acetylspermine (64%) were the best substrates at pH 9.5, while spermidine, its acetyl derivatives, and putrescine were very poorly oxidized by this enzyme (3–20%). Spermine oxidase activity was inhibited by phenylhydrazine (nil) and isoniazid (≈ 50%). Mepacrine did not inhibit the enzyme activity at pH 8. Neither monoamine nor diamine oxidase activity (≈ 10%) was found. It must be emphasized that spermine, the best enzyme substrate, is the most toxic polyamine. This finding suggests that knowledge of polyamine oxidase specificity can be used to modulate the cytotoxicity of polyamine derivatives. Amoeba Proteus was revealed as a simple model for investigation of the connection between cytotoxicity and enzyme activity.

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