| Research Abstract |
6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase (PFK-2/F2, 6BPase) is the enzyme responsible for the synthesis and degradation of fructose-2, 6-bisphosphate (F2, 6BP). F2, 6BP in turn is a powerful allosteric activator of 6-phosphofructo-1-kinase (PFK-1), which is the rate-limiting enzyme for glycolysis. At least 4 genes encode PFK-2/FBPase (PFKFB1-4), and an inducible PFK-2 (iPFK-2), encoded by PFKFB3, has been discovered to mediate F2, 6BP production in adipocytes suggesting the potential role of iPFK-2 in triglyceride synthesis. In this study, we investigated the role of iPFK-2/PFKFB3 in skeletal muscle.
The PFKFB3 gene generates multiple isoforms by the alternative splicing of 7 exon (A-G). We analyzed the splicing variants present in mouse skeletal muscle, and observed the expression of the three variants, PFKFB3-ACG, ACDG, and AG, with PFKFB3-ACDG being the dominantly expressed form. To investigate the effect of LPS, which is a stimulant of glycolysis in muscle, on the expression of PFKFB3 mRNA, eight-wk old BALB/c mice were injected intraperitoneally with LPS and three hours later the muscle was removed and the expression of PFKFB3 mRNA analyzed by real-time RT-PCR. A significant induction of PFKFB3 mRNA was observed after LPS treatment, and the expression pattern of splicing variants in LPS treated mice was different from that of control mice. HEK293 cells stably transfected with plasmids encoding the different splice variants of PFKFB3 (PFKFB3-ACCT, PFKFB3-ACDG or PFKFB3-AG) showed a marked elevation in intracellular F2, 6BP content.
These data are consistent with a role for the overproduction of F2, 6BP in the induction of metabolic alteration. Moreover, the in vivo data suggest that the stimulation of iPFK-2 in skeletal muscle may be a potential target for the treatment of diabetes
|
