Fig. 5.

Exogenous PE partially rescues colony formation under starvation in H23 cells expressing PEPCK-M shRNA. (A) H23 cells stably expressing Ctrl-sh or PEPCK-M shRNA (PEPCK-M-sh1 and PEPCK-M-sh2) were plated for colony formation and treated with different glucose and serum concentrations for 7 d followed by recovery in normal growth medium. The number of seeded cells per well was adjusted to avoid coalescence of colonies. (B) A starvation period of 72 h in serum-free medium containing 0.2 mM glucose was followed by 2-wk recovery in normal growth medium. Scans of cell culture plates are shown at Right. (A and B) Groups were compared using one-way ANOVA with Dunnett post hoc analysis versus Ctrl-sh. (C) Partial rescue by exogenous DOPE (PE 36:2) added during starvation. Group comparisons were made using two-sided, unpaired Student’s t tests. (A–C) Data are mean ± SEM from four independent experiments. *P < 0.05, **P < 0.01, ***P < 0.001; n.s., nonsignificant. (D) Proposed model for the synthesis of the GPL backbone from glyceroneogenesis via PEPCK-M as an alternative pathway under starvation.