Influence of proteasomal proteolysis on NO-synthase activity in isolated platelets
In experiments with isolated platelets it was shown, that application of proteasomal fraction ІІ (PF II) from rabbit’s reticulocytes changes the activity of endothelial nitric oxide synthase (eNOS). During incubation of sonicated platelets with PF II еNOS activity increased by 24.6% (p = 0.02). Methylated ubiquitin and clasto-lactacystin ?-lacton significantly eliminated this effect. So, it is not eNOS that is subsequent to proteasomal degradation, but a certain negative regulator of its activity. еNOS activity in platelets, treated with Н2О2(1 mМ), after incubation with PF II increased to a higer extent, and was 3.4 ± 0.36 UF/min х 106 cells (for 51.3% more, than in control), but Н2О2did not affect the activity of enzyme in platelets under analogous condition without addition of PF II. It was established, that еNOS activity decreases after 60 min of incubation with 10 mМ of clasto-lactacystin ?-lacton by 11.6%, and with 20 mМ – by 28.6% (p < 0.05). Data obtained witnesses about participation of ubiquitin-dependent proteasomal proteolysis in regulation of eNOS activity and possibility of the effect upon intensity of NO production due to acceleration of degradation of intracellular regulators of this enzyme’s activity.
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