Phosphorylation of eukaryotic elongation factor 2 in differentiating and proliferating HL-60 cells.
Ca(2+)-and calmodulin-dependent protein kinase III (CaM PKIII) phosphorylates eukaryotic elongation factor 2 (eEF-2) in HL-60 cells. Dephosphorylation of the factor in these cells is catalyzed by phosphoprotein phosphatase 2A alone. Differentiation of the HL-60 cells by all-trans retinoic acid resulted in a reduced growth rate and a marked decrease in the intracellular concentration of eEF-2. During differentiation the activity of the eEF-2 kinase is gradually reduced and reaches 10% of that found in undifferentiated cells 5 days after the onset of differentiation. The capacity to dephosphorylate phospho-eEF-2 remained unaltered in the growth-arrested cells. Differentiation without reduced proliferation was induced in the HL-60 cells by interferon-gamma. Under these conditions, differentiation had no effect on the cellular content of eEF-2 or the ability to dephosphorylate phospho-eEF-2. However, the differentiated cells showed a dramatic decrease in the specific activity of the eEF-2 kinase. The results show that the cellular content of eEF-2 varies with the rate of proliferation and that the activity of the eEF-2 kinase is high in undifferentiated proliferating cells and decreases upon differentiation even under conditions of an unaltered growth rate.
Nilsson
A
A
Department of Zoological Cell Biology, Arrhenius Laboratories E5, Stockholm University, Sweden.
Nygård
O
O
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002454:Cell Differentiation; D002455:Cell Division; D002460:Cell Line; D054736:Elongation Factor 2 Kinase; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011817:Rabbits; D051381:Rats; D014407:Tumor Cells, Cultured
D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors; D010750:Phosphoproteins; D007371:Interferon-gamma; C517689:EEF2K protein, human; C517691:Eef2k protein, rat; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D054736:Elongation Factor 2 Kinase