title: Spermidine promotes adipogenesis of 3T3-L1 cells by preventing interaction of ANP32 with HuR and PP2A.
abstract: We have shown previously that the polyamine spermidine is indispensable for differentiation of 3T3-L1 preadipocytes. In the present study, we examined the mechanism of spermidine function by using the polyamine biosynthesis inhibitor α-difluoromethylornithine in combination with the metabolically stable polyamine analogues γ-methylspermidine or (R,R)-α,ω-bismethylspermine. At the early phase of differentiation, spermidine-depleted 3T3-L1 cells showed decreased translation of the transcription factor C/EBPβ (CCAAT/enhancer-binding protein β), decreased PP2A (protein phosphatase 2A) activity and increased cytoplasmic localization of the RNA-binding protein HuR (human antigen R). The amount of HuR bound to C/EBPβ mRNA was reduced, whereas the amount of bound CUGBP2, an inhibitor of C/EBPβ translation, was increased. ANP32 (acidic nuclear phosphoprotein 32) proteins, which are known PP2A inhibitors and HuR ligands, bound more PP2A and HuR in spermidine-depleted than in control cells, whereas immunodepletion of ANP32 proteins from the lysate of spermidine-depleted cells restored PP2A activity. Taken together, our data shows that spermidine promotes C/EBPβ translation in differentiating 3T3-L1 cells, and that this process is controlled by the interaction of ANP32 with HuR and PP2A.
authors.affiliation: A.I. Virtanen Institute, University of Eastern Finland, Yliopistonranta 1E, 70210 Kuopio, Finland. mervi.hyvonen@uef.fi
authors.forename: Mervi T
authors.initials: MT
authors.lastname: Hyvönen
authors.forename: Taina
authors.initials: T
authors.lastname: Koponen
authors.forename: Janne
authors.initials: J
authors.lastname: Weisell
authors.forename: Marko
authors.initials: M
authors.lastname: Pietilä
authors.forename: Alex R
authors.initials: AR
authors.lastname: Khomutov
authors.forename: Jouko
authors.initials: J
authors.lastname: Vepsäläinen
authors.forename: Leena
authors.initials: L
authors.lastname: Alhonen
authors.forename: Tuomo A
authors.initials: TA
authors.lastname: Keinänen
mesh_terms: D041721:3T3-L1 Cells; D050156:Adipogenesis / Q000187:drug effects* / Q000235:genetics; D000818:Animals; D051959:ELAV Proteins / Q000235:genetics / Q000378:metabolism*; D000518:Eflornithine / Q000494:pharmacology; D005260:Female; D008297:Male; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011073:Polyamines / Q000737:chemistry / Q000494:pharmacology; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013095:Spermidine / Q000494:pharmacology*
chemical_list: D051959:ELAV Proteins; D009687:Nuclear Proteins; D011073:Polyamines; D054648:Protein Phosphatase 2; D013095:Spermidine; D000518:Eflornithine