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Inhibition of Nicotinamide Phosphoribosyltransferase (NAMPT), an Enzyme Essential
for NAD+ Biosynthesis, Leads to Altered Carbohydrate Metabolism in Cancer Cells
#MMPMID25944913
Tan B
; Dong S
; Shepard RL
; Kays L
; Roth KD
; Geeganage S
; Kuo MS
; Zhao G
J Biol Chem
2015[Jun]; 290
(25
): 15812-15824
PMID25944913
show ga
Nicotinamide phosphoribosyltransferase (NAMPT) has been extensively studied due
to its essential role in NAD(+) biosynthesis in cancer cells and the prospect of
developing novel therapeutics. To understand how NAMPT regulates cellular
metabolism, we have shown that the treatment with FK866, a specific NAMPT
inhibitor, leads to attenuation of glycolysis by blocking the glyceraldehyde
3-phosphate dehydrogenase step (Tan, B., Young, D. A., Lu, Z. H., Wang, T.,
Meier, T. I., Shepard, R. L., Roth, K., Zhai, Y., Huss, K., Kuo, M. S., Gillig,
J., Parthasarathy, S., Burkholder, T. P., Smith, M. C., Geeganage, S., and Zhao,
G. (2013) Pharmacological inhibition of nicotinamide phosphoribosyltransferase
(NAMPT), an enzyme essential for NAD(+) biosynthesis, in human cancer cells:
metabolic basis and potential clinical implications. J. Biol. Chem. 288,
3500-3511). Due to technical limitations, we failed to separate isotopomers of
phosphorylated sugars. In this study, we developed an enabling LC-MS methodology.
Using this, we confirmed the previous findings and also showed that NAMPT
inhibition led to accumulation of fructose 1-phosphate and sedoheptulose
1-phosphate but not glucose 6-phosphate, fructose 6-phosphate, and sedoheptulose
7-phosphate as previously thought. To investigate the metabolic basis of the
metabolite formation, we carried out biochemical and cellular studies and
established the following. First, glucose-labeling studies indicated that
fructose 1-phosphate was derived from dihydroxyacetone phosphate and
glyceraldehyde, and sedoheptulose 1-phosphate was derived from dihydroxyacetone
phosphate and erythrose via an aldolase reaction. Second, biochemical studies
showed that aldolase indeed catalyzed these reactions. Third, glyceraldehyde- and
erythrose-labeling studies showed increased incorporation of corresponding labels
into fructose 1-phosphate and sedoheptulose 1-phosphate in FK866-treated cells.
Fourth, NAMPT inhibition led to increased glyceraldehyde and erythrose levels in
the cell. Finally, glucose-labeling studies showed accumulated fructose
1,6-bisphosphate in FK866-treated cells mainly derived from dihydroxyacetone
phosphate and glyceraldehyde 3-phosphate. Taken together, this study shows that
NAMPT inhibition leads to attenuation of glycolysis, resulting in further
perturbation of carbohydrate metabolism in cancer cells. The potential clinical
implications of these findings are also discussed.
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