Enhanced vulnerability to oxidative stress and induction of inflammatory gene expression in 3-phosphoglycerate dehydrogenase-deficient fibroblasts.

l-Serine (l-Ser) is a necessary precursor for the synthesis of proteins, lipids, glycine, cysteine, d-serine, and tetrahydrofolate metabolites. Low l-Ser availability activates stress responses and cell death; however, the underlying molecular mechanisms remain unclear. l-Ser is synthesized from 3-phosphoglycerate with 3-phosphoglycerate dehydrogenase (Phgdh) catalyzing the first reaction step. Here, we show that l-Ser depletion raises intracellular HO levels and enhances vulnerability to oxidative stress in Phgdh-deficient mouse embryonic fibroblasts. These changes were associated with reduced total glutathione levels. Moreover, levels of the inflammatory markers thioredoxin-interacting protein and prostaglandin-endoperoxide synthase 2 were upregulated under l-Ser-depleted conditions; this was suppressed by the addition of -acetyl-l-cysteine. Thus, intracellular l-Ser deficiency triggers an inflammatory response via increased oxidative stress, and l-Ser synthesis suppresses oxidative stress damage and inflammation when the external l-Ser supply is restricted.