Fig. 2.

PEPCK-M is essential for Ser/Gly synthesis. a, b ¹³C enrichment of serine and glycine in HeLa cells exposed to 2 mM [U-¹³C]glutamine for 4 h in the DMEM media containing 10% dFCS and 0 mM glucose. Incorporation of ¹³C was analyzed using GC-MS. Statistical significance compared with shCtrl was determined by unpaired two-tailed Student’s t test. c Quantitative real-time PCR analysis of PCK2 mRNA expression levels in shCtrl HeLa cells grown in 0 mM glucose MEM media with or without 0.4 mM serine and 0.4 mM glycine (Ser/Gly) for 6 or 12 h. Values were normalized to time 0 h. Two-way ANOVA with Sidak multiple comparison post-test analysis indicate significance of Ser/Gly effect (*). d Cell viability was measured in HeLa cells using an MTT assay after 72 h of growth in 0 mM glucose MEM media with or without 0.4 mM serine and 0.4 mM glycine (Ser/Gly). The sensitivity of each cell line to the addition of serine and glycine is shown as fold change with respect to the viability in the presence of +Ser/Gly. Two-way ANOVA with Sidak multiple comparison post-test analysis indicate significance vs + Ser/Gly (*)