title: Cloning and functional analysis of goat glucose transporter 4.
abstract: OBJECTIVE
  Glucose transporter (GLUT) 4 is a major mediator of blood glucose levels and a key regulator of whole-body glucose homeostasis. This study aimed at evaluating the function of goat GLUT4 on glucose absorption and the effect of GLUT4 on lactose synthesis in goat mammary gland epithelial (GMGE) cells.
  
  
  METHODS
  Currently, the cDNA of GLUT4, a putative facilitative GLUT, was cloned from goat. To investigate the function of goat GLUT4, we constructed the eukaryotic expression vector pcDNA3.1-GLUT4 and used it to transfect GMGE cells, and then GLUT4 transfected GMGE (G4T-GMGE) cells were generated. The deduced GLUT4 sequence comprised 509 amino acids, what meant that a putative protein with a molecular weight of approximately 55 kDa would be produced. Both glucose uptake and lactose synthesis increased in the G4T-GMGE cells compared with the GMGE cells. At the transcriptional level, GLUT4 expression increased by nearly 55-fold in the G4T-GMGE cells, and the expression of amino acid transporters (SLC1A5, SLC3A2 and SLC7A5) enhanced as well; in contrast, GLUT1 expression decreased by more than 50 % in the G4T-GMGE cells.
  
  
  CONCLUSIONS
  These results suggest that goat GLUT4 functions in the transport of glucose and it may play a positive role in amino acid uptake in mammary glands.
authors.affiliation: Veterinary College, Nanjing Agricultural University, Weigang 1, Nanjing, 210095, Jiangsu, People's Republic of China.
authors.forename: Liqi
authors.initials: L
authors.lastname: Zhu
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Yu
authors.forename: Jian
authors.initials: J
authors.lastname: Lin
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.forename: Qian
authors.initials: Q
authors.lastname: Yang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D004847:Epithelial Cells / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D006041:Goats; D007328:Insulin / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000378:metabolism; D014162:Transfection
chemical_list: D051275:Glucose Transporter Type 4; D007328:Insulin; D005947:Glucose