Amiloride analogs induce the phosphorylation of elongation factor-2 in vascular endothelial cells.
5-(N-Ethyl-N-isopropyl)amiloride (EIPA), a potent inhibitor of Na+/H+ antiport, reduced [35S]methionine incorporation in proteins and induced the phosphorylation of a Mr 95,000 protein in bovine aortic endothelial cells. This protein was previously shown to become phosphorylated in response to ATP, bradykinin, and A23187 (1) and was identified as elongation factor-2 (2). The action of EIPA was independent of changes in cytosolic pH, because it was neither mimicked by sodium acetate nor inhibited by ammonium chloride, and it was reproduced by 2',4'-dimethylbenzamil, an analog of amiloride that is inactive on the Na+/H+ antiport. Furthermore, EIPA enhanced the Ca2(+)-dependent phosphorylation of a similar Mr 95,000 protein in a cell-free system, rabbit reticulocyte lysate, where an inhibitory effect of amiloride on protein synthesis has already been described (3). Because phosphorylation decreases the activity of elongation factor-2, our observation might explain why amiloride analogs inhibit protein synthesis.
Demolle
D
D
Institute of Interdisciplinary Research, School of Medicine, Université Libre de Bruxelles, Belgium.
Lecomte
M
M
Boutherin-Falson
O
O
Cragoe
E J
EJ
Nairn
A C
AC
Boeynaems
J M
JM
D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D008970:Molecular Weight; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors / Q000378:metabolism*; D010766:Phosphorylation; D012156:Reticulocytes / Q000187:drug effects / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000378:metabolism
D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors; D012261:Ribonucleoproteins; D000584:Amiloride; D008715:Methionine; C039614:ethylisopropylamiloride