title: Mechanisms regulating GLUT4 transcription in skeletal muscle cells are highly conserved across vertebrates.
abstract: The glucose transporter 4 (GLUT4) plays a key role in glucose uptake in insulin target tissues. This transporter has been extensively studied in many species in terms of its function, expression and cellular traffic and complex mechanisms are involved in its regulation at many different levels. However, studies investigating the transcription of the GLUT4 gene and its regulation are scarce. In this study, we have identified the GLUT4 gene in a teleost fish, the Fugu (Takifugu rubripes), and have cloned and characterized a functional promoter of this gene for the first time in a non-mammalian vertebrate. In silico analysis of the Fugu GLUT4 promoter identified potential binding sites for transcription factors such as SP1, C/EBP, MEF2, KLF, SREBP-1c and GC-boxes, as well as a CpG island, but failed to identify a TATA box. In vitro analysis revealed three transcription start sites, with the main residing 307 bp upstream of the ATG codon. Deletion analysis determined that the core promoter was located between nucleotides -132/+94. By transfecting a variety of 5´deletion constructs into L6 muscle cells we have determined that Fugu GLUT4 promoter transcription is regulated by insulin, PG-J2, a PPARγ agonist, and electrical pulse stimulation. Furthermore, our results suggest the implication of motifs such as PPARγ/RXR and HIF-1α in the regulation of Fugu GLUT4 promoter activity by PPARγ and contractile activity, respectively. These data suggest that the characteristics and regulation of the GLUT4 promoter have been remarkably conserved during the evolution from fish to mammals, further evidencing the important role of GLUT4 in metabolic regulation in vertebrates.
authors.affiliation: Departament de Fisiologia i Immunologia, Facultat de Biologia, Universitat de Barcelona and Institut de Biomedicina de la Universitat de Barcelona (IBUB), Barcelona, Spain.
authors.forename: Rubén
authors.initials: R
authors.lastname: Marín-Juez
authors.forename: Mónica
authors.initials: M
authors.lastname: Diaz
authors.forename: Jordi
authors.initials: J
authors.lastname: Morata
authors.forename: Josep V
authors.initials: JV
authors.lastname: Planas
mesh_terms: D024506:5' Flanking Region; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D002460:Cell Line; D003001:Cloning, Molecular; D019295:Computational Biology / Q000379:methods; D017124:Conserved Sequence; D004558:Electric Stimulation; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000187:drug effects; D017930:Genes, Reporter; D051275:Glucose Transporter Type 4 / Q000235:genetics* / Q000378:metabolism; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D008969:Molecular Sequence Data; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D047495:PPAR gamma / Q000378:metabolism; D011401:Promoter Regions, Genetic; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid; D017422:Sequence Analysis, DNA; D023741:Takifugu; D024363:Transcription Initiation Site; D014158:Transcription, Genetic
chemical_list: D051275:Glucose Transporter Type 4; D007328:Insulin; D047495:PPAR gamma