Expression of inducible 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase/PFKFB3 isoforms in adipocytes and their potential role in glycolytic regulation.
6-Phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase) catalyzes the synthesis and degradation of fructose 2,6-bisphosphate (F2,6BP), which is a powerful activator of 6-phosphofructo-1-kinase, the rate-limiting enzyme of glycolysis. Four genes encode PFK-2/FBPase (PFKFB1-4), and an inducible isoform (iPFK-2/PFKFB3) has been found to mediate F2,6BP production in proliferating cells. We have investigated the role of iPFK-2/PFKFB3 and related isoforms in the regulation of glycolysis in adipocytes. Human visceral fat cells express PFKFB3 mRNA, and three alternatively spliced isoforms of iPFK-2/PFKFB3 are expressed in the epididymal fat pad of the mouse. Forced expression of the iPFK-2/PFKFB3 in COS-7 cells resulted in increased glucose uptake and cellular F2,6BP content. Prolonged insulin treatment of 3T3-L1 adipocytes led to reduced PFKFB3 mRNA expression, and epididymal fat pads from db/db mice also showed decreased expression of PFKFB3 mRNA. Finally, anti-phospho-iPFK-2(Ser461) Western blotting revealed strong reactivity in insulin-treated 3T3-L1 adipocyte, suggesting that insulin induces the phosphorylation of PFKFB3 protein. These data expand the role of these structurally unique iPFK-2/PFKFB3 isoforms in the metabolic regulation of adipocytes.
Atsumi
Toshiya
T
Department of Medicine II, Graduate School of Medicine, Hokkaido University, Kita 15, Nishi 7, Kita-ku, Sapporo 060-8638, Japan. tatsumi@med.hokudai.ac.jp
Nishio
Taro
T
Niwa
Hirokatsu
H
Takeuchi
Jun
J
Bando
Hidenori
H
Shimizu
Chikara
C
Yoshioka
Narihito
N
Bucala
Richard
R
Koike
Takao
T
D016475:3T3 Cells; D017667:Adipocytes / Q000201:enzymology*; D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence; D005091:Exons; D006019:Glycolysis / Q000502:physiology*; D006706:Homeostasis; D006801:Humans; D007328:Insulin / Q000502:physiology; D007527:Isoenzymes / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D025481:Phosphofructokinase-2 / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D007328:Insulin; D007527:Isoenzymes; D012333:RNA, Messenger; C107345:PFKFB3 protein, human; D025481:Phosphofructokinase-2