The role of hypusine depletion in cytostasis induced by S-adenosyl-L-methionine decarboxylase inhibition: new evidence provided by 1-methylspermidine and 1,12-dimethylspermine.
The abilities of the natural polyamines, spermidine and spermine, and of the synthetic analogues, 1-methylspermidine and 1,12-dimethylspermine, to reverse the effects of the S-adenosyl-L-methionine decarboxylase inhibitor 5'-([(Z)-4-aminobut-2-enyl]methylamino)-5'-deoxyadenosine (AbeAdo) on L1210-cell growth were studied. L1210 cells were exposed to AbeAdo for 12 days to induce cytostasis and then exposed to spermidine, spermine, 1-methylspermidine or 1,12-dimethylspermine in the continued presence of AbeAdo. AbeAdo-induced cytostasis was overcome by the natural polyamines, spermidine and spermine. The cytostasis was also reversed by 1-methylspermidine. 1,12-Dimethylspermine had no effect on the AbeAdo-induced cytostasis of chronically treated cells, although it was active in permitting growth of cells treated with the ornithine decarboxylase inhibitor, alpha-difluoromethylornithine. The initial 12-day exposure to AbeAdo elevated intracellular putrescine levels, depleted intracellular spermidine and spermine, and resulted in the accumulation of unmodified eukaryotic translation initiation factor 5A (eIF-5A). Exposure of these cells to exogenous spermidine, which is the natural substrate for deoxyhypusine synthase, resulted in a decrease in the unmodified eIF-5A content. 1-Methylspermidine, which was found to be a substrate of deoxyhypusine synthase in vitro, also decreased the levels of unmodified eIF-5A in the AbeAdo-treated cells. Although spermine is not a substrate of deoxyhypusine synthase, spermine was converted into spermidine in the L1210 cells, and spermine addition to AbeAdo-treated cells resulted in the appearance of both intracellular spermine and spermidine and in the decrease in unmodified eIF-5A. Exogenous 1,12-dimethylspermine, which was not metabolized to spermine or to 1-methylspermidine and was not a substrate of deoxyhypusine synthase in vitro, did not decrease levels of unmodified eIF-5A. The finding that AbeAdo-induced cytostasis was only reversed by polyamines and polyamine analogues that result in the formation of hypusine or an analogue in eIF-5A is consistent with the hypothesis [Byers, Wiest, Wechter and Pegg (1993) Biochem. J. 290, 115-121] that AbeAdo-induced cytostasis is due to the depletion of the hypusine-containing form of eIF-5A, which is secondary to the depletion of spermidine by inhibition of S-adenosyl-L-methionine decarboxylase.
Byers
T L
TL
Department of Cell and Molecular Physiology, M.S. Hershey Medical Center, Hershey, PA 17033.
Lakanen
J R
JR
Coward
J K
JK
Pegg
A E
AE
D012437:Adenosylmethionine Decarboxylase / Q000037:antagonists & inhibitors*; D000818:Animals; D016466:CHO Cells; D002455:Cell Division / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D006224:Cricetinae; D003839:Deoxyadenosines / Q000494:pharmacology*; D000518:Eflornithine / Q000494:pharmacology; D007939:Leukemia L1210 / Q000473:pathology; D008239:Lysine / Q000031:analogs & derivatives* / Q000378:metabolism; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000378:metabolism; D016601:RNA-Binding Proteins; D013095:Spermidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013096:Spermine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured; D000097574:Eukaryotic Translation Initiation Factor 5A
D012437:Adenosylmethionine Decarboxylase; D003839:Deoxyadenosines; D000518:Eflornithine; D008239:Lysine; D000587:Oxidoreductases Acting on CH-NH Group Donors; D010448:Peptide Initiation Factors; D016601:RNA-Binding Proteins; D013095:Spermidine; D013096:Spermine; D000097574:Eukaryotic Translation Initiation Factor 5A; C073193:1-methylspermidine; C073195:1,12-dimethylspermine; C100028:hypusine; C065859:MDL 73811; C063507:deoxyhypusine synthase