title: Role of hypusinated eukaryotic translation initiation factor 5A in polyamine depletion-induced cytostasis.
abstract: We have earlier shown that alpha-methylated spermidine and spermine analogues rescue cells from polyamine depletion-induced growth inhibition and maintain pancreatic integrity under severe polyamine deprivation. However, because alpha-methylspermidine can serve as a precursor of hypusine, an integral part of functional eukaryotic translation initiation factor 5A required for cell proliferation, and because alpha, omega-bismethylspermine can be converted to methylspermidine, it is not entirely clear whether the restoration of cell growth is actually attributable to hypusine formed from these polyamine analogues. Here, we have used optically active isomers of methylated spermidine and spermine and show that polyamine depletion-induced acute cytostasis in cultured cells could be reversed by all the isomers of the methylpolyamines irrespective of whether they served or not as precursors of hypusine. In transgenic rats with activated polyamine catabolism, all the isomers similarly restored liver regeneration and reduced plasma alpha-amylase activity associated with induced pancreatitis. Under the above experimental conditions, the (S, S)- but not the (R, R)-isomer of bismethylspermine was converted to methylspermidine apparently through the action of spermine oxidase strongly preferring the (S, S)-isomer. Of the analogues, however, only (S)-methylspermidine sustained cell growth during prolonged (more than 1 week) inhibition of polyamine biosynthesis. It was also the only isomer efficiently converted to hypusine, indicating that deoxyhypusine synthase likewise possesses hidden stereospecificity. Taken together, the results show that growth inhibition in response to polyamine depletion involves two phases, an acute and a late hypusine-dependent phase.
authors: A. I. Virtanen Institute for Molecular Sciences, University of Kuopio, PO Box 1627, FI-70211 Kuopio, Finland.
authors: Mervi T
authors: MT
authors: Hyvönen
authors: Tuomo A
authors: TA
authors: Keinänen
authors: Marc
authors: M
authors: Cerrada-Gimenez
authors: Riitta
authors: R
authors: Sinervirta
authors: Nikolay
authors: N
authors: Grigorenko
authors: Alex R
authors: AR
authors: Khomutov
authors: Jouko
authors: J
authors: Vepsäläinen
authors: Leena
authors: L
authors: Alhonen
authors: Juhani
authors: J
authors: Jänne
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D049109:Cell Proliferation; D000518:Eflornithine / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D008239:Lysine / Q000031:analogs & derivatives* / Q000737:chemistry; D008954:Models, Biological; D010195:Pancreatitis / Q000378:metabolism; D010448:Peptide Initiation Factors / Q000235:genetics* / Q000502:physiology*; D011073:Polyamines / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000502:physiology*; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry; D013095:Spermidine / Q000031:analogs & derivatives / Q000737:chemistry; D013237:Stereoisomerism; D000516:alpha-Amylases / Q000378:metabolism; D000097574:Eukaryotic Translation Initiation Factor 5A
chemical_list: D000518:Eflornithine; D008239:Lysine; D010448:Peptide Initiation Factors; D011073:Polyamines; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D013095:Spermidine; D000516:alpha-Amylases; D000097574:Eukaryotic Translation Initiation Factor 5A; C073193:1-methylspermidine; C100028:hypusine