Abstract
Foxo1 plays an important role in the integration of hormone-activated signaling pathways with the complex transcriptional cascade that promotes preadipocyte differentiation of clonal cell lines from rodents. We isolated the full-length cDNA of porcine FoxO1 gene using RACE, confirmed by visual Northern blotting. The deduced amino acids indicated 94% and 90% identities with the corresponding human and mice aa. Analysis of the aa sequence, showed that it included a Forkhead domain (aa 167-247), a transmembrane structure domain (aa 90-113), a LXXLL motif (aa 469-473), and 51 Ser, 8 Thr, and 4 Tyr phosphorylation sites, indicating a potential important role for FoxO1 transcriptional activity in vivo. Using the IMpRH panel, we mapped FoxO1 gene to chromosome 11p13. Our data provide basic molecular information useful for the further investigation on the function of FoxO1 gene. Time-course analysis of FoxO1 expressions indicated that levels of mRNA and protein gradually increased from day 0 to 3, and it reached almost maximal level at day 3, then decreased from day 5 to 7 in porcine primary preadipocyte differentiation. After induction by IGF-1, GPDH activity and accumulation of lipid increased, however, expressions of FoxO1 mRNA and protein were inhibited in a dose dependent manner. These results suggest that FoxO1 takes part in porcine preadipocyte differentiation and expressions of FoxO1 were regulated by IGF-1.
Highlights
Foxo1 is a member of the evolutionarily conserved forkhead box O (Foxo) subfamily of forkhead transcription factors (Kaestner et al, 2000; Birkenkamp et al, 2003), which are thought to be important in mediating effects of insulin and growth factors on glucose homeostasis and processes such as cell differentiation (Nakae et al, 2003), glucose metabolism (Nakae et al, 2002; Daitoku et al, 2003), cell-cycle regulation (Stahl et al, 2002), apoptosis (Dijkers et al, 2002), and oxidative stress resistance (Kops et al, 2002)
Foxo1 is expressed in tissues involved in energy metabolism such as liver, muscle, and adipose tissue, where its function is inhibited by insulin and insulin-like growth factor I (Farmer et al, 2003)
The full-length cDNA of FoxO1 was cloned from pig and verified by virtual Northern blots
Summary
Foxo is a member of the evolutionarily conserved Foxo subfamily of forkhead transcription factors (Kaestner et al, 2000; Birkenkamp et al, 2003), which are thought to be important in mediating effects of insulin and growth factors on glucose homeostasis and processes such as cell differentiation (Nakae et al, 2003), glucose metabolism (Nakae et al, 2002; Daitoku et al, 2003), cell-cycle regulation (Stahl et al, 2002), apoptosis (Dijkers et al, 2002), and oxidative stress resistance (Kops et al, 2002). In vitro adipogenesis requires a sequence of events, including growth arrest of proliferating preadipocytes, coordinated reentry into the cell cycle with limited clonal expansion, and growth arrest associated with terminal differentiation. These processes are accompanied by characteristic changes in gene expression. Foxo plays an important role in coupling insulin signaling to preadipocyte differentiation (Nakae et al, 2003)
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