Characterization of ATP-dependent proteolysis in embryos of the brine shrimp, Artemia franciscana

Under anoxia, embryos of Artemia franciscana enter a state of quiescence. During this time protein synthesis is depressed, and continued degradation of proteins could jeopardize the ability to recover from quiescence upon return to favorable conditions. In this study, we developed an assay for monit...

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Bibliographic Details
Published in:Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology Biochemical, systemic, and environmental physiology, 2000-03, Vol.170 (2), p.125-133
Main Authors: van Breukelen, F, Hand, S C
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - metabolism
Animals
Artemia - embryology
Artemia - metabolism
Artemia franciscana
Cyclic AMP-Dependent Protein Kinases - metabolism
Endopeptidases - metabolism
Hydrogen-Ion Concentration
Hydrolysis
Hypoxia - metabolism
Kinetics
Protein Kinase C - metabolism
Proteins - metabolism
Ubiquitins - metabolism
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Summary:Under anoxia, embryos of Artemia franciscana enter a state of quiescence. During this time protein synthesis is depressed, and continued degradation of proteins could jeopardize the ability to recover from quiescence upon return to favorable conditions. In this study, we developed an assay for monitoring ATP/ ubiquitin-dependent proteolysis in order to establish the presence of this degradation mechanism in A. franciscana embryos, and to describe some characteristics that may regulate its function during anoxia-induced quiescence. For lysates experimentally depleted of adenylates, supplementation with ATP and ubiquitin stimulated protein degradation rates by 92 +/- 17% (mean +/- SE) compared to control rates. The stimulation by ATP was maximal at concentrations > or =11 micromol x l(-1). In the presence of ATP and ubiquitin, ubiquitin-conjugated proteins were produced by lysates during the course of the 4-h assays, as detected by Western blotting. Acute acidification of lysates to values approximating the intracellular pH observed under anoxia completely inhibited ATP/ubiquitin-dependent proteolysis. Depressed degradation was also observed under conditions where net ATP hydrolysis occurred. These results suggest that ATP/ubiquitin-dependent proteolysis is markedly inhibited under cellular conditions promoted by anoxia. Inhibition of proteolysis during quiescence may be one critical factor that increases macromolecular stability, which may ultimately govern the duration of embryo survival under anoxia.
ISSN:0174-1578
1432-136X
DOI:10.1007/s003600050267