AMP-activated protein kinase activity during metabolic rate depression in the hypoxic goldfish, Carassius auratus.
Cell survival during hypoxia exposure requires a metabolic reorganization to decrease ATP demands to match the reduced capacity for ATP production. We investigated whether AMP-activated protein kinase (AMPK) activity responds to 12 h exposure to severe hypoxia ( approximately 0.3 mg O2 l(-1)) in the anoxia-tolerant goldfish (Carassius auratus). Hypoxia exposure in goldfish was characterized by a strong activation of creatine phosphate hydrolysis and glycolysis in liver and muscle. AMPK activity increased by approximately 5.5-fold in goldfish liver within 0.5 h hypoxia exposure and this increase in activity was temporally associated with an 11-fold increase in [AMP(free)]/[ATP]. No changes in total AMPK protein amount were observed, suggesting that the changes in AMPK activity are due to post-translational phosphorylation of the protein. Hypoxia exposure had no effect on the expression of two identified AMPK alpha-subunit isoforms and caused an approximately 50% decrease in the mRNA levels of AMPK beta-subunit isoform. Changes in AMPK activity in the liver were associated with an increase in percentage phosphorylation of a well-characterized target of AMPK, eukaryotic elongation factor-2 (eEF2), and decreases in protein synthesis rates measured in liver cell-free extracts. No activation of AMPK was observed in muscle, brain, heart or gill during the 12 h hypoxia exposure suggesting a tissue-specific regulation of AMPK possibly related to a lack of change in cellular [AMP(free)]/[ATP] as observed in muscle.
Jibb
Lindsay A
LA
Department of Zoology, The University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4.
Richards
Jeffrey G
JG
D055372:AMP-Activated Protein Kinases / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D015687:Cell Hypoxia; D004789:Enzyme Activation; D029941:Fish Proteins / Q000378:metabolism* / Q000502:physiology; D006054:Goldfish / Q000378:metabolism*; D006868:Hydrolysis; D008099:Liver / Q000166:cytology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D020652:Peptide Elongation Factor 2 / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis; D020033:Protein Isoforms / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D021122:Protein Subunits / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism
D029941:Fish Proteins; D020652:Peptide Elongation Factor 2; D020033:Protein Isoforms; D021122:Protein Subunits; D012333:RNA, Messenger; D010725:Phosphocreatine; D055372:AMP-Activated Protein Kinases; D010100:Oxygen