title: Dual Regulatory Role of Polyamines in Adipogenesis.
abstract: Adipogenesis is a complex process, accompanied by a chain of interdependent events. Disruption of key events in this cascade may interfere with the correct formation of adipose tissue. Polyamines were demonstrated necessary for adipogenesis; however, the underlying mechanism by which they act has not been established. Here, we examined the effect of polyamine depletion on the differentiation of 3T3-L1 preadipocytes. Our results demonstrate that polyamines are required early in the adipogenic process. Polyamine depletion inhibited the second division of the mitotic clonal expansion (MCE), and inhibited the expression of PPARγ and C/EBPα, the master regulators of adipogenesis. However, it did not affect the expression of their transcriptional activator, C/EBPβ. Additionally, polyamine depletion resulted in elevation of mRNA and protein levels of the stress-induced C/EBP homologous protein (CHOP), whose dominant negative function is known to inhibit C/EBPβ DNA binding activity. Conditional knockdown of CHOP in polyamine-depleted preadipocytes restored PPARγ and C/EBPα expression, but failed to recover MCE and differentiation. Thus, our results suggest that the need for MCE in the adipogenic process is independent from the requirement for PPARγ and C/EBPα expression. We conclude that de novo synthesis of polyamines during adipogenesis is required for down-regulation of CHOP to allow C/EBPβ activation, and for promoting MCE.
authors.affiliation: Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 7610001, Israel.
authors.forename: Shirley
authors.initials: S
authors.lastname: Brenner
authors.affiliation: Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 7610001, Israel.
authors.forename: Zippi
authors.initials: Z
authors.lastname: Bercovich
authors.affiliation: Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 7610001, Israel.
authors.forename: Yulia
authors.initials: Y
authors.lastname: Feiler
authors.affiliation: Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 7610001, Israel.
authors.forename: Rom
authors.initials: R
authors.lastname: Keshet
authors.affiliation: Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 7610001, Israel. Electronic address: chaim.kahana@weizmann.ac.il.
authors.forename: Chaim
authors.initials: C
authors.lastname: Kahana
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism; D050156:Adipogenesis / Q000235:genetics / Q000502:physiology*; D000818:Animals; D015317:Biogenic Polyamines / Q000378:metabolism*; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D002454:Cell Differentiation; D055785:Gene Knockdown Techniques; D051379:Mice; D008938:Mitosis; D008954:Models, Biological; D009955:Ornithine Decarboxylase / Q000378:metabolism; D047495:PPAR gamma / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013095:Spermidine / Q000378:metabolism; D051742:Transcription Factor CHOP / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
chemical_list: D015317:Biogenic Polyamines; D022782:CCAAT-Enhancer-Binding Protein-beta; D022762:CCAAT-Enhancer-Binding Proteins; C530718:CEBPA protein, mouse; C545013:Cebpb protein, mouse; C497250:Ddit3 protein, mouse; D047495:PPAR gamma; D012333:RNA, Messenger; D051742:Transcription Factor CHOP; D009955:Ornithine Decarboxylase; D013095:Spermidine
keywords: CCAAT-enhancer-binding protein (C/EBP); CHOP; DFMO; Ornithine decarboxylase; adipocyte; adipogenesis; cell differentiation; polyamine