In Euglena gracilis, a Heat-Shock Protein Related to hsc73 Is Constitutive and Stress Inducible

To determine the onset of the Cd2+-hyperaccumulating phenotype in Euglena gracilis, induced by Hg2+ pretreatment (Avilés et al. in Arch Microbiol 180:1-10, 2003), the changes in cellular growth, Cd2+ uptake, and intracellular contents of sulfide, cysteine, gamma-glutamylcysteine, glutathione and phytochelatins during the progress of the culture were analyzed. In cells exposed to 0.2 mM CdCl2, the Cd2+-hyperaccumulating phenotype was apparent only after 48 h of culture, as indicated by the significant increase in cell growth and higher internal contents of sulfide and thiol-compounds, along with a higher gamma-glutamylcysteine synthetase activity. However, the stiochiometry of thiol-compounds/Cd2+ accumulated was similar for both control and Hg2+-pretreated cells. Moreover, the value for this ratio was 2.1 or lower after 48-h culture, which does not suffice to fully inactivate Cd2+. It is concluded that, although the glutathione and phytochelatin synthesis pathway is involved in the development of the Cd2+-hyperaccumulating phenotype in E. gracilis, apparently other pathways and sub-cellular mechanisms are also involved. These may be an increase in other Cd2+ chelating molecules such as di- and tricarboxylic acids, phosphate and polyphosphates, as well as Cd2+ compartmentation into organelles.

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Time-course development of the Cd2+ hyper-accumulating phenotype in Euglena gracilis

Avilés

Torres-Márquez

Mendoza‐Cózatl

et al. 2005

Arch Microbiol

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P-glycoprotein-like protein contributes to cadmium resistance in Euglena gracilis

Einicker‐Lamas

Morales

Miranda

et al. 2003

Journal of Comparative Physiology B: Biochemical, Systemic, and

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Selective pressures from polluted environments have led to the development of resistance systems in aquatic organisms. Using different techniques, this study examined a cadmium defense mechanism of the freshwater unicellular protozoa Euglena gracilis, and found it to be an efflux pump similar to the multidrug resistance P-glycoprotein. Cd(2+)-treated E. gracilis were able to extrude Rhodamine 123 at 21 degrees C, but not at 4 degrees C. Furthermore, verapamil, a P-glycoprotein modulator, partially blocked the efflux process (at 21 degrees C), and enhanced the Cd(2+) toxic effects on these cells. Western immunoblots of cell lysates, using the anti-P-glycoprotein antibody JSB-1, revealed a 120-KDa protein, which was expressed, in high amounts on Cd(2+)-exposed cells (74% above the control values). Moreover, cells treated with JSB-1 became more sensitive to the harmful effects of cadmium, showing a decreased survival rate. Taken together, these results suggest that a MDR phenotype has evolved in Euglena as one of the mechanisms for cadmium detoxification.

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A new homolog of FocA transporters identified in cadmium-resistant Euglena gracilis

Deloménie

Foti

Floch

et al. 2007

Biochemical and Biophysical Research Communications

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In Euglena gracilis, a Heat-Shock Protein Related to hsc73 Is Constitutive and Stress Inducible

Cited by 5 publications

References 25 publications

Time-course development of the Cd2+ hyper-accumulating phenotype in Euglena gracilis

Time-course development of the Cd2+ hyper-accumulating phenotype in Euglena gracilis

P-glycoprotein-like protein contributes to cadmium resistance in Euglena gracilis

A new homolog of FocA transporters identified in cadmium-resistant Euglena gracilis

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