title: Role of C/EBPβ-LAP and C/EBPβ-LIP in early adipogenic differentiation of human white adipose-derived progenitors and at later stages in immature adipocytes.
abstract: We investigated the role of the major isoforms of CCAAT enhancer binding protein β (C/EBPβ), C/EBPβ-LAP and C/EBPβ-LIP, in adipogenesis of human white adipose-derived stromal/progenitor cells (ASC). C/EBPβ gene expression was transiently induced early in adipogenesis. At later stages, in immature adipocytes, the C/EBPβ mRNA and protein levels declined. The C/EBPβ-LIP protein steady-state level decreased considerably stronger than the C/EBPβ-LAP level and the C/EBPβ-LIP half-life was significantly shorter than the C/EBPβ-LAP half-life. The turn-over of both C/EBPβ-isoforms was regulated by ubiquitin/proteasome-dependent degradation. These data suggest that the protein stability of the C/EBPβ-isoforms is differentially regulated in the course of adipogenesis and in immature adipocytes. Constitutive overexpression of C/EBPβ-LIP had antiadipogenic activity in human ASC. C/EBPβ-LAP, which promotes adipogenesis in mouse 3T3-L1 preadipocytes by directly activating expression of the adipogenic keyregulator PPARγ2, induced the expression of PPARγ2 and of the adipocyte differentiation gene product FABP4 in confluent ASC in the absence of adipogenic hormones. At later stages after hormone cocktail-induced adipogenesis, in immature adipocytes, constitutive overexpression of C/EBPβ-LAP led to reduced expression of PPARγ2 and FABP4, C/EBPα expression was downregulated and the expression of the adipocyte differentiation gene products adiponectin and leptin was impaired. These findings suggest that constitutive overexpression of C/EBPβ-LAP induces adipogenesis in human ASC and negatively regulates the expression of adipogenic regulators and certain adipocyte differentiation gene products in immature adipocytes. We conclude the regulation of both C/EBPβ gene expression and C/EBPβ-LIP and C/EBPβ-LAP protein turn-over plays an important role for the expression of adipogenic regulators and/or adipocyte differentiation genes in early adipogenic differentiation of human ASC and at later stages in human immature adipocytes.
authors: Department of Cell Metabolism and Differentiation Research, Institute for Biomedical Aging Research of the University of Innsbruck, Rennweg 10, Innsbruck, Austria. stefanlechner1@gmx.at
authors: Stefan
authors: S
authors: Lechner
authors: Maria C
authors: MC
authors: Mitterberger
authors: Monika
authors: M
authors: Mattesich
authors: Werner
authors: W
authors: Zwerschke
mesh_terms: D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D050156:Adipogenesis; D052242:Adiponectin / Q000378:metabolism; D052436:Adipose Tissue, White / Q000166:cytology* / Q000378:metabolism; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D050556:Fatty Acid-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D020738:Leptin / Q000378:metabolism; D047495:PPAR gamma / Q000235:genetics / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism; D017154:Stromal Cells / Q000166:cytology / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D052242:Adiponectin; D022782:CCAAT-Enhancer-Binding Protein-beta; C545012:CEBPB protein, human; C493410:FABP4 protein, human; D050556:Fatty Acid-Binding Proteins; D020738:Leptin; D047495:PPAR gamma; D020033:Protein Isoforms; D012333:RNA, Messenger