title: Constitutively active signal transducer and activator of transcription 5 can replace the requirement for growth hormone in adipogenesis of 3T3-F442A preadipocytes.
abstract: Although it is the best characterized in vitro model of GH action, the mechanisms used by GH to induce differentiation of murine 3T3-F442A preadipocytes remain unclear. Here we have examined the role of three transcriptional regulators in adipogenesis. These regulators are either rapidly induced in response to GH [Stra13, signal transducer and activator of transcription (Stat)3] or of central importance to GH signaling (Stat5). Retroviral transfection of 3T3-F442A preadipocytes was used to increase expression of Stra13, Stat3, and Stat5a. Only Stat5a transfection increased the expression of adipogenic markers peroxisome proliferator-activated receptor gamma, CCAAT enhancer binding protein (C/EBP)alpha, and adipose protein 2/fatty acid-binding protein in response to GH, as determined by quantitative RT-PCR. Transfection with constitutively active Stat3 and Stat5a revealed that constitutively active Stat5a but not Stat3 was able to replace the GH requirement for adipogenesis. Constitutively active Stat5a but not Stat3 was able to increase the formation of lipid droplets and expression of alpha-glycerol phosphate dehydrogenase toward levels seen in mature adipocytes. Constitutively active Stat5a was also able to increase the expression of transcripts for C/EBPalpha to similar levels as GH, and of C/EBPbeta, peroxisome proliferator-activated receptor gamma, and adipose protein 2/fatty acid-binding protein transcripts to a lesser extent. An in vivo role for GH in murine adipogenesis is supported by significantly decreased epididymal fat depot size in young GH receptor-deleted mice, before manifestation of the lipolytic actions of GH. We conclude that Stat5 is a critical factor in GH-induced, and potentially prolactin-induced, murine adipogenesis.
authors.affiliation: School of Biomedical Sciences and the Institute for Molecular Bioscience, The University of Queensland, Queensland 4072 Brisbane, Australia.
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Shang
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Waters
mesh_terms: D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001369:Axons / Q000502:physiology; D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D013006:Growth Hormone / Q000494:pharmacology / Q000502:physiology*; D007700:Kinetics; D051379:Mice; D018345:Mice, Knockout; D008894:Milk Proteins; D011388:Prolactin / Q000494:pharmacology; D011986:Receptors, Somatotropin / Q000172:deficiency / Q000235:genetics / Q000502:physiology; D012190:Retroviridae / Q000235:genetics; D050799:STAT5 Transcription Factor; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D008894:Milk Proteins; D011986:Receptors, Somatotropin; D050799:STAT5 Transcription Factor; C494093:Stat5a protein, mouse; D015534:Trans-Activators; D011388:Prolactin; D013006:Growth Hormone