AMP-activated protein kinase activity during metabolic rate depression in the hypoxic goldfish, Carassius auratus.

Abstract

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.

• Authors: Lindsay A Jibb, Jeffrey G Richards
• Journal: The Journal of experimental biology (J Exp Biol) Vol. 211 Issue Pt 19 Pg. 3111-22 (Oct 2008) ISSN: 0022-0949 [Print] England
• PMID: 18805810 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Fish Proteins
• Peptide Elongation Factor 2
• Protein Isoforms
• Protein Subunits
• RNA, Messenger
• Phosphocreatine
• AMP-Activated Protein Kinases
• Oxygen

Topics

• AMP-Activated Protein Kinases (metabolism, physiology)
• Animals
• Cell Hypoxia
• Enzyme Activation
• Fish Proteins (metabolism, physiology)
• Goldfish (metabolism)
• Hydrolysis
• Liver (cytology, metabolism)
• Muscle, Skeletal (cytology, metabolism)
• Oxygen (metabolism)
• Peptide Elongation Factor 2 (metabolism)
• Phosphocreatine (metabolism)
• Phosphorylation
• Protein Biosynthesis
• Protein Isoforms (metabolism)
• Protein Processing, Post-Translational
• Protein Subunits (metabolism)
• RNA, Messenger (metabolism)