Quantitative flux analysis reveals folate-dependent NADPH production. (Nature. 2014 Jun 12;510(7504):298-302.)

報告日期: 2015/11/17
報告時間: 3:10/4:00
報告學生: 杜洪齊
講評老師: 張文粲
附件下載: 下載[1522-1443055086-1.pdf] 

Quantitative flux analysis reveals folate-dependent

NADPH production

Nature. 2014;510(7504):298-302

Jing Fan, Jiangbin Ye, Jurre J. Kamphorst, Tomer Shlomi, Craig B. Thompson & Joshua D. Rabinowitz

Student: Hung-Chi Tu                         Time:2015/11/17 15:10-16:00

Commentator: Dr. Wen-Tsan Chang              Place: Room 602

Abstract

NADPH, the reduced form of nicotinamide adenine dinucleotide phosphate (NADP+), is produced mainly from glucose through the oxidative pentose phosphate pathway (oxPPP). NADPH production is involved in redox defence and reductive biosynthesis including lipogenesis and nucleotide synthesis1. However, other pathways contributing to NADPH production and their relative contribution remain to be unravel. By liquid chromatography–mass spectrometry (LC-MS), metabolites collected from cells cultured with 2H-labelled or 13C and 14C isotope-labelled substrates were analyzed to calculate the pathway’s fractional contribution to total cytosolic NADPH production. Agree with previous reports, oxPPP was found to be a major pathway of NADPH production with 30 to 50% fractional contribution to total cytosolic NADPH production. Intriguingly, folate-mediated one-carbon metabolism was predicted to be another major NADPH production pathway bygenome-scale human metabolic model2. Consist with the prediction, the fractional contribution of folate-dependent NADPH production was confirmed to be comparable to oxPPP through this LC-MS analysis. Knockdown of methylene tetrahydrofolate dehydrogenase (MTHFD), a key enzyme mediates the folate-dependent NADPH production, resulted in decreased NADPH/NADP+ ratio, GSH/GSSG ratio and cell growth rates and increased sensitivity to oxidative stress, suggesting the essential role of folate metabolism in producing NADPH to facilitate redox defence. In conclusion, this study identified that in addition to oxPPP, folate-mediated one-carbon metabolism is also a major NADPH production pathway with comparable NADPH-producing ability. Furthermore, it highlights the importance of folate metabolism in redox defence through NADPH production in addition to nucleotide synthesis.

References

1. Ying W.NAD+/NADH and NADP+/NADPH in cellular functions and cell death: regulation and biological consequences.Antioxid Redox Signal. 2008;10(2):179-206.

2. Duarte NC et al. Global reconstruction of the human metabolic network based on genomic and bibliomic data.Proc Natl Acad Sci U S A. 2007;104(6):1777-82.