p21ras induced differentiation-related gene expression in fetal brown adipocyte primary cells and cell lines.
Transfection of primary rat fetal brown adipocytes with constructs of SV40 large T antigen, alone and together with lys12-mutated H-ras gene, gave permanent cell lines showing an immortalized or transformed phenotype, respectively, all of them selected by the expression of the uncoupling protein (UCP), a tissue-specific marker. Primary brown adipocytes and immortalized cell lines respond to insulin-like growth factor I (IGF-I) by increasing their lipid content and the mRNA expression of both the adipogenic marker fatty acid synthase (FAS) and the thermogenic marker UCP. IGF-I-induced differentiation-related gene expression at 24 h in both primary and immortalized brown adipocytes was mediated by an increase in p21ras.GTP active protein content. Transformed cell lines overexpressing exogenous p21ras (mainly in its ras.GTP active form) constitutively showed a higher lipid content and a higher FAS and UCP mRNA expression compared to primary and immortalized cells. These transformed cells were IGF-I independent with respect to their studied differentiation-related parameters. Additionally, transient transfection of primary brown adipocytes with the transforming ras gene induced UCP and FAS mRNA expression as well as cotransactivated UCP-chloramphenicol acetyltransferase fusion gene. Moreover, IGF-I transactivation of UCP promoter was partially precluded by cotransfection with the dominant-negative ras gene. Our results strongly suggest that IGF-I/p21ras induces adipogenic- and thermogenic-related gene expression in brown adipocytes.
Lorenzo
M
M
Departamento de Bioquímica y Biología Molecular, Facultad de Farmacia, Universidad Complutense, Madrid, Spain.
Valverde
A M
AM
Teruel
T
T
Alvarez
A
A
Benito
M
M
D017667:Adipocytes / Q000737:chemistry / Q000166:cytology* / Q000378:metabolism*; D002001:Adipose Tissue, Brown / Q000196:embryology; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics; D015415:Biomarkers; D003994:Bucladesine / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics; D002454:Cell Differentiation; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D064429:Fatty Acid Synthases / Q000235:genetics; D005786:Gene Expression Regulation / Q000502:physiology*; D005799:Genes, Dominant / Q000235:genetics; D011905:Genes, ras / Q000235:genetics; D006160:Guanosine Triphosphate / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D007473:Ion Channels; D008055:Lipids / Q000032:analysis; D008565:Membrane Proteins / Q000235:genetics; D024101:Mitochondrial Proteins; D009154:Mutation; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics* / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D017451:Receptors, Somatomedin / Q000235:genetics; D013539:Simian virus 40 / Q000276:immunology; D000071256:Uncoupling Protein 1
D000952:Antigens, Polyomavirus Transforming; D015415:Biomarkers; D002352:Carrier Proteins; D007473:Ion Channels; D008055:Lipids; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; D017451:Receptors, Somatomedin; D000071256:Uncoupling Protein 1; D003994:Bucladesine; D007334:Insulin-Like Growth Factor I; D006160:Guanosine Triphosphate; D064429:Fatty Acid Synthases; D016283:Proto-Oncogene Proteins p21(ras)