A peroxisome proliferator-response element in the murine mc2-r promoter regulates its transcriptional activation during differentiation of 3T3-L1 adipocytes.
Adrenocorticotropic hormone can stimulate lipolysis and suppress leptin expression in murine adipocytes. These effects are mediated via the melanocortin 2 receptor (MC2-R), which is expressed when 3T3-L1 cells are induced to undergo adipogenesis. In this study, we have characterized the mc2-r promoter in the murine adipocyte, one of the few extra-adrenal sites of expression and a cell type that lacks steroidogenic factor 1 (SF-1), a transcription factor that is required for mc2-r expression in adrenal cells. Transcriptional regulation of the mc2-r in the absence of SF-1 was investigated by 5' deletion analysis of the murine mc2-r promoter in both undifferentiated and differentiated 3T3-L1 cells. The results revealed the presence of a 59-base pair regulatory region within the promoter containing an adipocyte-specific enhancer. The ability of this region to confer enhanced activity in the adipocyte was mapped to a peroxisome proliferator-response element (PPRE)-like sequence that bound to peroxisome proliferator-activated receptor gamma (PPARgamma) and its heterodimeric partner retinoid X receptor alpha (RXRalpha) in adipocyte nuclear extracts. Co-transfection of PPARgamma2/RXRalpha with the pMC2-R(-112/+105)GL3 reporter resulted in transcriptional activation in preadipocytes, and this response required an intact PPRE. Mutation of the PPRE to prevent PPARgamma/RXRalpha binding resulted in a complete abrogation of the pMC2-R(-112/+105)GL3 reporter activity in day 3 differentiated 3T3-L1 cells, demonstrating a key role played by this site in regulating MC2-R expression in the murine adipocyte. These data highlight a novel mechanism for mc2-r transcription, which may have significance in both adrenal and extra-adrenal sites of expression.
Noon
Luke A
LA
Molecular Endocrinology Center, William Harvey Research Institute, Bart's and the London, Queen Mary University of London, London, EC1A 7BE, United Kingdom.
Clark
Adrian J L
AJ
King
Peter J
PJ
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000502:physiology*; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D051379:Mice; D011401:Promoter Regions, Genetic / Q000235:genetics; D044103:Receptor, Melanocortin, Type 2 / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology*; D054339:Steroidogenic Factor 1; D014157:Transcription Factors / Q000502:physiology*; D015533:Transcriptional Activation / Q000502:physiology
D044103:Receptor, Melanocortin, Type 2; D018160:Receptors, Cytoplasmic and Nuclear; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; C515058:steroidogenic factor 1, mouse