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- Garberg, Per, et al.
(författare)
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Binding of tellurium to hepatocellular selenoproteins during incubationwith inorganic tellurite : consequences for the activity ofselenium-dependent glutathione peroxidase
- 1999
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Ingår i: International Journal of Biochemistry and Cell Biology. - 1357-2725 .- 1878-5875. ; 31:2, s. 291-301
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Tidskriftsartikel (refereegranskat)abstract
- The metallic group XVIa elements selenium and tellurium possess remarkably similar chemical properties. However, unlike selenium, tellurium is not an essential micronutrient and, indeed, induces both acute and chronic toxicity in a variety of species. Despite this, very little is known of the molecular mechanisms of toxicity of tellurium, particularly with respect to potential chemical interactions with selenium-containing components in the cell. In this work we describe a novel interaction of inorganic tellurite with hepatocellular selenoproteins, particularly with selenium-dependent glutathione peroxidase. The accumulation of (121Te)-tellurite into cultured primary rat liver hepatocytes was shown to be much more rapid than that of (75Se)-selenite on a molar basis. Neither the uptake of (121Te)-tellurite nor of (75Se)-selenite was affected by a large molar excess of the unlabelled counterpart, respectively. Interestingly, separation of the hepatocellular proteins on continuous pH denaturing gels demonstrated clear binding of radiolabelled tellurium to a number of protein bands, including one at 23 and one at 58 kDa, which corresponded to proteins readily labelled in cells treated with (75Se)-selenite. The binding of (121Te) to these proteins was insensitive to reduction with mercaptoethanol and not affected by pre-treatment of the cells with cycloheximide. When purified selenium-dependent glutathione peroxidase was treated directly with (121Te)-tellurite, the protein became labelled in an analogous manner to that achieved in intact cells. This was not affected by coincubation of the enzyme with (121Te)-tellurite and one or both of its substrates. Additionally, incubation of the peroxidase with tellurite effectively inhibited its ability to catalyse glutathione-dependent reduction of hydrogen peroxide. These data suggest that inorganic tellurite delivers tellurium to the intracellular milieu in a form capable of binding to some intracellular selenoproteins and at least in the case of glutathione peroxidase, cause inhibition of catalytic activity. The nature of the binding seems not to be due to the insertion of tellurocysteine into the protein and the insensitivity to reductive cleavage with mercaptoethanol seems to preclude the formation of stable telluro-selenides in the proteins. These data may offer alternative explanations for the established toxicity of tellurium via disruption of selenoprotein function, particularly by the induction of intracellular oxidative stress by the inhibition of Se-dependent glutathione peroxidase.
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- Ruge, Toralph, et al.
(författare)
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Nutritional regulation of lipoprotein lipase in mice
- 2004
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Ingår i: International Journal of Biochemistry and Cell Biology. - 1357-2725 .- 1878-5875. ; 36:2, s. 320-329
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Tidskriftsartikel (refereegranskat)abstract
- Tissue-specific regulation of lipoprotein lipase (LPL) has been extensively studied in rats. The mouse is now the most used animal in lipoprotein research, and we have therefore explored the regulation of LPL in this species. In C57 black mice, fed ad libitum adipose tissue LPL activity changed about three-fold with the time of day, indicating a circadian rhythm. The highest activity was at midnight and the lowest activity was at noon. Withdrawal of food did not markedly accelerate the drop of activity that occurred from midnight until noon, but prevented the return of activity that occurred during the evening and early night. When food was returned to mice that had been fasted for 24h, adipose tissue LPL activity rose rapidly and returned to the fed level in 2h. LPL mass in adipose tissue changed less than LPL activity, indicating that regulation is mainly post-translational as previously demonstrated for rats. When transcription was blocked in fasted mice, adipose tissue LPL activity increased, as previously observed in rats. LPL activity in heart was highest early in the light period at 9:00h and lowest at 21:00h. The change was, however, only about 30%. Heparin-releasable LPL activity in heart was 1.8-fold higher in mice fasted for 6h compared to fed controls. We conclude that LPL activity responds to the nutritional state in the same direction and by the same mechanisms in mice as in rats, but the magnitude of the changes are less in mice.
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- Andersson, Linda, 1973, et al.
(författare)
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Deficiency in perilipin 5 reduces mitochondrial function and membrane depolarization in mouse hearts.
- 2017
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Ingår i: The international journal of biochemistry & cell biology. - : Elsevier BV. - 1878-5875 .- 1357-2725. ; 91:Pt A, s. 9-13
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Tidskriftsartikel (refereegranskat)abstract
- Myocardial triglycerides stored in lipid droplets are important in regulating the intracellular delivery of fatty acids for energy generation in mitochondria, for membrane biosynthesis, and as agonists for intracellular signaling. Previously, we showed that deficiency in the lipid droplet protein perilipin 5 (Plin5) markedly reduces triglyceride storage in cardiomyocytes and increases the flux of fatty acids into phospholipids. Here, we investigated whether Plin5 deficiency in cardiomyocytes alters mitochondrial function. We found that Plin5 deficiency reduced mitochondrial oxidative capacity. Furthermore, in mitochondria from Plin5((-/)(-)) hearts, the fatty acyl composition of phospholipids in mitochondrial membranes was altered and mitochondrial membrane depolarization was markedly compromised. These findings suggest that mitochondria isolated from hearts deficient in Plin5, have specific functional defects.
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