Glucose Starvation-Induced Rapid Death of Nrf1α-Deficient, but Not Nrf2-Deficient, Hepatoma Cells Results from Its Fatal Defects in the Redox Metabolism Reprogramming

Figure 4

Deterioration of altered glucose metabolism and energy demands by glucose deprivation of Nrf1α^-/- cells. (a) A schematic diagram to give a concise explanation of glycosis, gluconeogenesis, and pentose phosphate pathways (PPP). The key rate-limiting enzymes are indicated, apart from TCA (citric acid cycle). In some words, phospho- is represented by a single P letter. (b) Distinct ATP levels of WT, Nrf1α^-/-, and Nrf2^-/- cells were determined after glucose deprivation for 0-12 h. (c–l) Altered mRNA expression levels of key metabolic genes: (i) (c) GLUT1 (glucose transporter 1), (d) HK1 (hexokinase 1), (e) HK2, (f) PFKL (phosphofructokinase liver type), and (g) LDHA (lactate dehydrogenase A) involved in the glycolysis pathway; (ii) (h) G6PD (glucose-6-phosphate dehydrogenase) and (i) PGD (phosphogluconate dehydrogenase) as rate-limiting enzymes in the PPP; (iii) (j) PC (pyruvate carboxylase), (k) PCK2 (phosphoenolpyruvate carboxykinase 2), and (l) FBP1 (fructose bisphosphatase 1) responsible for the gluconeogenesis pathway, were analyzed by RT-qPCR analysis of WT, Nrf1α^-/-, and Nrf2^-/- cells that had been starved, or not starved, in the glucose-free media for 0-12 h. Then, the asterisk “” only represents a significant change in WT, Nrf1α^-/-, and Nrf2^-/- cell lines in the glucose-free culture for 0 h (), while the letters A, B, and C represent significant changes in the same cell line without glucose cultured for 0, 6, and 12 h (). (m) Phospho-AMPK^Thr172/AMPK ratios were calculated by the intensity of their immunoblots in Nrf1/2^+/+, Nrf1α^-/-, and Nrf2^-/- cells. (n–p) Changes in protein abundances of GLUT1, HK1, HK2, G6PD, PCK1, PCK2, AMPK, and its phospho-AMPK^Thr172 were determined by Western blotting of Nrf1/2^+/+ (n), Nrf1α^-/- (o), and Nrf2^-/- (p) cells, after having been glucose-starved, or not, for 0-12 h.