Regulation of elongation factor-2 kinase by pH.
Elongation factor-2 kinase (eEF-2K) is a Ca(2+)/calmodulin-dependent protein kinase that phosphorylates and inactivates eEF-2 and that can regulate the rate of protein synthesis at the elongation stage. Here we report that a slight decrease in pH, within the range observed in vivo, leads to a dramatic activation of eEF-2K. The activity of eEF-2K in mouse liver extracts, as well as the activity of purified recombinant human eEF-2K, is low at pH 7.2-7.4 and is increased by severalfold when the pH drops to 6.6-6.8. eEF-2K requires calmodulin for activity at neutral as well as acidic pH. Kinetic studies demonstrate that the pH does not affect the K(M) for ATP or eEF-2 and activation of eEF-2K at acidic pH is due to an increase in V(max). To analyze the potential role of eEF-2K in regulating protein synthesis by pH, we constructed a mouse fibroblast cell line that expresses eEF-2K in a tetracycline-regulated manner. Overexpression of eEF-2K led to a decreased rate of protein synthesis at acidic pH, but not at neutral pH. Our results suggest that pH-dependent activation of eEF-2K may play a role in the global inhibition of protein synthesis during tissue acidosis, which accompanies such processes as hypoxia and ischemia.
Dorovkov
Maxim V
MV
Department of Pharmacology, University of Medicine and Dentistry of New Jersey--Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, New Jersey 08854, USA.
Pavur
Karen S
KS
Petrov
Alexey N
AN
Ryazanov
Alexey G
AG
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D002147:Calmodulin / Q000502:physiology; D004023:Dictyostelium; D054736:Elongation Factor 2 Kinase; D004789:Enzyme Activation / Q000235:genetics / Q000502:physiology; D005347:Fibroblasts / Q000201:enzymology / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000201:enzymology / Q000502:physiology*; D007700:Kinetics; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D020652:Peptide Elongation Factor 2 / Q000378:metabolism; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000378:metabolism; D010766:Phosphorylation; D014176:Protein Biosynthesis; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection
D002147:Calmodulin; D020652:Peptide Elongation Factor 2; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C517689:EEF2K protein, human; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C517690:Eef2k protein, mouse; D054736:Elongation Factor 2 Kinase