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. 2017 Aug 3;548(7665):112-116.
doi: 10.1038/nature23275. Epub 2017 Jul 19.

Fructose-1,6-bisphosphate and aldolase mediate glucose sensing by AMPK

Affiliations

Fructose-1,6-bisphosphate and aldolase mediate glucose sensing by AMPK

Chen-Song Zhang et al. Nature. .

Abstract

The major energy source for most cells is glucose, from which ATP is generated via glycolysis and/or oxidative metabolism. Glucose deprivation activates AMP-activated protein kinase (AMPK), but it is unclear whether this activation occurs solely via changes in AMP or ADP, the classical activators of AMPK. Here, we describe an AMP/ADP-independent mechanism that triggers AMPK activation by sensing the absence of fructose-1,6-bisphosphate (FBP), with AMPK being progressively activated as extracellular glucose and intracellular FBP decrease. When unoccupied by FBP, aldolases promote the formation of a lysosomal complex containing at least v-ATPase, ragulator, axin, liver kinase B1 (LKB1) and AMPK, which has previously been shown to be required for AMPK activation. Knockdown of aldolases activates AMPK even in cells with abundant glucose, whereas the catalysis-defective D34S aldolase mutant, which still binds FBP, blocks AMPK activation. Cell-free reconstitution assays show that addition of FBP disrupts the association of axin and LKB1 with v-ATPase and ragulator. Importantly, in some cell types AMP/ATP and ADP/ATP ratios remain unchanged during acute glucose starvation, and intact AMP-binding sites on AMPK are not required for AMPK activation. These results establish that aldolase, as well as being a glycolytic enzyme, is a sensor of glucose availability that regulates AMPK.

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Conflict of interest statement

The authors declare no competing financial interests.

Figures

Extended Data Figure 1
Extended Data Figure 1. Glucose deprivation activates AMPK via an AMP/ADP independent mechanism.
a, Phosphorylation of AMPK (pT172) and ACC (pACC) analyzed by immunoblotting from the experiment shown in Fig. 1a; the upper panel shows quantification of the pT172:AMPKα ratios (mean ± SD, n = 2). b-c, Glucose deprivation rapidly activates AMPK without altering cellular AMP:ATP or ADP:ATP ratios in HEK293T cells. Cells were grown in full medium (25 mM glucose, 4 mM alanyl-glutamine, 1 mM pyruvate, 10% serum) and then switched to medium without glucose, with other components unchanged, for 15 min or 2 h. AMPK activation was monitored by immunoblotting for p-AMPKα and p-ACC (a), and intracellular AMP:ATP/ADP:ATP ratios determined by CE:MS (b, results are mean ± SD, n = 3). d, Adenine nucleotide ratios are unaltered in mouse liver after starvation. Mice were fed ad libitum or fasted for 16 h, freeze-clamped liver samples prepared, and AMP:ATP/ADP:ATP ratios measured by CE-MS. Results are mean ± SD, n = 6; ns, not significant by Student’s t-test. e, Decrease in plasma glucose concentrations induced by fasting mice for 16 h. Mice from the same experiment shown in Fig. 1d were either fed ad libitum or were deprived of food for 16 h and plasma glucose determined. Circles are individual data points and horizontal lines are means ± SD, n = 6; P value computed by Student’s t test. f, Extracts were prepared from livers of mice treated as in d (6 mice per group) and analysed by Western blotting using the indicated antibodies. g, Western blots from the same experiment shown in Fig. 1c. Although shown as separate panels, the blots with each antibody were from the same gel scanned at the same time, and are therefore directly comparable. h, quantification of blots in g. Results are mean ± SD, n = 2. i, ADP:ATP ratios determined by LC:MS, from the same experiments shown in Fig. 1c and d. j, Time course of effects of starving MEFs for glucose only, or glucose and glutamine, in the presence of serum. The experiment was as in Fig. 1c except that the medium contained 10% fetal calf serum throughout. k, l, ADP:ATP ratios determined by LC:MS, from the experiments shown in Figs. 1e-h. All experiments were performed at least twice.
Extended Data Figure 2
Extended Data Figure 2. Glucose deprivation activates AMPK by a mechanism distinct from energy stress.
a, b, d, AXIN-/- (a), LAMTOR1-/- (b) and CaMKK2 knockdown (d) MEFs were incubated with DMEM containing indicated concentrations of glucose for 2 h. The levels of p-AMPKα and p-ACC in the cell lysates were analyzed by immunoblotting. c, AMP:ATP and ADP:ATP ratios in AXIN-/- and LAMTOR1-/- MEFs, generated as in Fig. 2a, b. e, Validation of monoclonal anti-β2 antibody for use in immunofluorescence microscopy. Parental wild type HEK293 cells, or β2 KO cells, were stained with DAPI (blue, nuclei) and anti-β2 antibody (green). Representative merged images are shown, obtained using identical intensity settings. f, Glucose starvation causes translocation of AMPKβ2 to the lysosome in HEK-293 cells that is dependent on N-myristoylation. The experiment was performed in β2 KO cells as in Fig. 1c, except that the lysosomal marker LAMP1 (tagged with RFP) was co-expressed with the WT or AMPK-β2 mutants. Upper panels show merged images stained blue [4',6-diamidino-2-phenylindole (DAPI), nuclei], red (LAMP1, lysosomes) and green (AMPK-β2, detected using antibody validated in Extended Data Fig. 2e), in cells incubated with or without glucose for 20 min. Lower small panels are magnifications of the areas indicated by dashed boxes in the upper panels, showing (L to R) red and green channels and merged images. g, Experiment identical to that shown in Fig. 2c, but expressing AMPK-β1, either WT, G2A or S108A mutants, in β1 KO cells. Results are mean ± SD, n = 4. All experiments were performed at least twice.
Extended Data Figure 3
Extended Data Figure 3. Glycolytic intermediate(s) is responsible for repression of AMPK in the presence of glucose.
All intact cell experiments in this Figure were performed in the presence of 10% serum. a, Summary of glycolysis pathway and pathways branching off it. PPP, pentose phosphate pathway; SSP, serine synthesis pathway; HP, hexosamine pathway. b, c, Knockdown of G6PD (glucose-6-phosphate dehydrogenase) (b) or PHGDH (phosphoglycerate dehydrogenase) (c) has no effect on AMPK activation. HEK293T cells were infected with lentivirus expressing siRNA against G6PD (b) or PHGDH (c), or siRNA against GFP as a control; the cells were then incubated in the DMEM medium with (25 mM) or without glucose for 2 h, followed by analysis of p-AMPKα and p-ACC levels. d, The hexosamine pathway is not involved in AMPK regulation under glucose deprivation. MEFs were incubated for 2 h in the DMEM medium containing GlcNAc (N-acetylglucosamine), an supplement of hexosamine pathway which cannot be converted back to glucose, at indicated concentrations and 25 mM or 0 mM glucose. Cells were then subjected to immunoblotting. Experiments in b and c were performed twice, and that in d 3 times.
Extended Data Figure 4
Extended Data Figure 4. Absence of fructose-1,6-bisphosphate (FBP) defines a starvation signal for AMPK activation.
All intact cell experiments in this Figure were performed in the presence of 10% serum. a, FBP dissociates AXIN/LKB1 from LAMTOR1 in vitro. The same experiment identical to that in Fig. 3b was performed except that the bacterially expressed His-tagged AXIN was used in lieu of AXIN-containing cytosol, incubating with light organelles purified from MEFs glucose-starved for 2 h. b, FBP modulates the interaction between AMPK and LKB1. Cytosol from unstarved MEFs was mixed with light organelles purified from 2-h-glucose-starved ALDO-TKD MEFs or WT MEFs, followed by addition of 200 μM FBP. The mixtures were then dissolved and LKB1 was immunoprecipitated. c, Concentrations of FBP in mouse liver after starvation for 16 h. FBP levels from mouse livers were determined by CE-MS. The amounts of FBP were estimated according to the standard curve generated by plotting the peak-area ratios of unlabeled:13C-labelled FBP (derived from [U-13C]FBP used as internal standard) against the concentrations of unlabeled FBP. The results were obtained by dividing its amount by the estimated volume of liver, and the concentrations of free-state FBP were then estimated as described previously. Values are presented as mean ± SEM, n = 5 for each condition, P = 9.627 × 10-5 (Student’s t-test). d, e, Intracellular FBP levels were measured by CE-MS in MEFs after incubation in medium containing different concentrations of glucose (d), or in glucose-free DMEM for the indicated time periods (e). Values are presented as mean ± SD, n = 3 for each treatment; *P = 0.0187, FBP levels in cells incubated in 10 mM glucose were compared to those in cells incubated with medium containing 5 mM glucose; †P = 0.0102, cells incubated with medium containing 5 mM to 3 mM glucose; P = 0.831, cells incubated with medium containing 25 mM to 10 mM glucose; P = 0.00577, comparison of incubation in glucose-free medium for 0 min to 15 min (ANOVA). f, Plasma glucose concentrations (left panel) and intracellular FBP levels (right panel) in mouse liver. FBP were determined by CE-MS analysis. Results are mean ± SD, n = 6 for each condition; P value by Student’s t-test. g, h, Linear correlation between extracellular glucose concentrations and intracellular FBP levels. FBP levels in MEFs, measured at 2 h of incubation in medium containing various concentrations of glucose as shown in d, and in the starved mouse liver shown in f, were plotted against their corresponding glucose concentrations in the culture medium (g) and plasma (h), respectively. i, FBP levels in SLO-permeabilized MEFs. Levels of FBP in regularly cultured SLO-permeabilized MEFs (left panel), or glucose-starved SLO-permeabilized MEFs treated with exogenous FBP (right panel), were determined by CE-MS analysis. Results are mean ± SD, n = 3 for each condition; P value by Student’s t-test (left panel) and ANOVA (right panel). Experiments shown in left and right panels were performed simultaneously and shared a single control (SLO-permeabilized MEFs incubated in medium containing 25 mM glucose). j-l, Addition of exogenous FBP to permeabilized MEFs blocks glucose starvation-induced AMPK activation. Various glycolytic intermediates (200 μM) as indicated were individually added to the 2-h-glucose-starved WT (j), PFK1-KD (k) or TPI-KD (l) MEFs pre-incubated with SLO for 5 min. After incubating for another 15 min, cells were lysed and were analyzed by immunoblotting. Experiments in this figure were performed twice.
Extended Data Figure 5
Extended Data Figure 5. Modulation of FBP controls AMPK activation.
All intact cell experiments in this Figure were performed in the presence of 10% serum. a, Knockdown of PFK1 activates AMPK in unstarved cells. HEK293T cells were infected with lentivirus expressing PFKP, PFKL and PFKM siRNA, or GFP siRNA as a control, and were incubated in the DMEM medium with or without glucose for 2 h, followed by analysis of p-AMPKα and p-ACC levels. b, c, Effects of overexpression of FBP1 and PFKP on AMPK activation. HEK293T cells were infected with lentivirus expressing FBP1 (b) or PFKP (c), and were then incubated in the DMEM medium with indicated glucose concentrations for 2 h, followed by analysis of p-AMPKα and p-ACC levels. d, Knockdown of GAPDH has no effect on AMPK activation. MEFs were infected with lentivirus expressing GAPDH siRNA, or GFP siRNA as a control, and were glucose-starved for 2 h, followed by analysis of p-AMPKα and p-ACC levels. Experiments in this figure were performed twice.
Extended Data Figure 6
Extended Data Figure 6. Knockdown of aldolase renders AMPK activation constitutive.
All intact cell experiments in this Figure were performed in the presence of 10% serum. a, Schematic diagram showing the strategy for knocking down the three aldolases (isozymes ALDOA-C) in MEFs. In detail, MEFs carrying doxycycline-inducible expression of ALDOA-C were cultured in medium containing doxycycline (Dox, 100 ng/ml), and were infected with lentivirus expressing siRNA against ALDOA, ALDOB and ALDOC sequentially, or GFP siRNA as a control, followed by incubation in doxycycline-free medium for another 12 h. For Fig. 4a and 4b, #1 siRNAs targeting each enzyme were used. b, Validation of the efficiency and specificity of siRNAs targeting ALDOA-C in MEFs. Cell lysates from MEFs expressing siRNAs against ALDOA, ALDOB, ALDOC or GFP as a control (minus) were immunoblotted as indicated. c, Validation of aldolase-knockdown efficiency by measuring the activity of aldolase in ALDO-TKD cells. Aldolase activities in cell lysates prepared from ALDO-TKD and WT MEFs were measured. Results are mean ± SD, n = 3; P value by ANOVA. d, Knockdown of the three aldolase isozymes renders AMPK activation constitutive. In an experiment identical to Fig. 4a for knocking down the aldolases, the #2 siRNAs targeting each isozyme were used. e, Pyruvate kinase (PK) is not involved in regulation of AMPK. HEK293T cells were infected with lentivirus expressing PKM and PKLR siRNA, or GFP siRNA as a control; the cells were then incubated in the DMEM medium with or without glucose for 2 h, followed by analysis of p-AMPKα and p-ACC levels. f, Knockdown of aldolase does not alter the energy status in MEFs. AMP:ATP/ADP:ATP ratios in WT and ALTO-TKD MEFs were measured by CE-MS. Results are mean ± SD, n = 3; N.S., not significant by Student’s t-test. g-i, Aldolase regulates AMPK through the lysosomal pathway. Aldolases in LKB1-/- (g), LAMTOR1-/- (h) and CaMKK2-/- (i) MEFs were knocked down following the procedures described in a, and were incubated with DMEM medium with 25 mM glucose. The levels of p-AMPKα and p-ACC in the cell lysates were analyzed by immunoblotting. j, Triple knockdown of aldolases promotes the formation of Ragulator-AXIN/LKB1-AMPK complex. Endogenous LAMTOR1 in regularly cultured or glucose-starved ALDO-TKD MEFs were immunoprecipitated, followed by immunoblotting. k, Knockdown of aldolase enhances the interaction between AMPK and LKB1. Experiment identical to that shown in j, but the endogenous LKB1 was immunoprecipitated. l, FBP fails to dissociate AXIN/LKB1 from LAMTOR1 on light organelles purified from starved ALDO-TKD MEFs. Cytosol from unstarved MEFs was mixed with light organelles purified from 2-h-glucose-starved ALDO-TKD MEFs or WT MEFs as a control, and 200 μM FBP was then added to the mixture. The mixtures were then solubilized and LAMTOR1 was immunoprecipitated. m, Addition of exogenous FBP fails to block glucose starvation-induced AMPK activation in permeabilized ALDO-TKD MEFs. FBP (200 μM) was added to the 2-h-glucose-starved ALDO-TKD MEFs or WT MEFs that had been pre-incubated with SLO for 5 min. After incubating for another 15 min, cells were subjected to immunoblotting. n, FBP is the unique intermediate that modulates aldolase for sensing the availability of glucose. FBP, fructose-2,6-bisphosphate (F26P), and fructose-1-phosphate (F1P) at 200 μM were individually added to light organelles purified from 2-h-glucose-starved MEFs. The mixtures were then solubilized and LAMTOR1 was immunoprecipitated, followed by immunoblotting to determine co-precipitated proteins. Experiments in b, e, g-l were performed 3 times, and that in c, d, f, m and n twice.
Extended Data Figure 7
Extended Data Figure 7. AXIN is constitutively localized to lysosomes in aldolase-deficient MEFs and HEK293T cells.
All intact cell experiments in this Figure were performed in the presence of 10% serum. a, b, Immunofluorescent staining in WT and ALDO-TKD MEFs (a) and HEK293T cells (b) was performed. Rat anti-LAMP2 antibody and goat anti-AXIN antibody were used for staining MEFs (a), and mouse anti-LAMP1 antibody and goat anti-AXIN antibody for HEK293T cells (b). The antibodies had been validated previously. c, d, Mander’s overlap coefficients of a and b were graphed in c and d, respectively, as mean ± SD, n = 61 (siGFP, unstarved), 54 (siGFP, GS), 60 (siALDOA-C, unstarved), 58 (siALDOA-C, GS) (c) and n = 57 (siGFP, unstarved), 48 (siGFP, GS), 52 (siALDOA-C, unstarved), 51 (siALDOA-C, GS) (d) for each group; P value by ANOVA. N.S., not significant. The experiment was performed twice.
Extended Data Figure 8
Extended Data Figure 8. Effects of aldolase mutants on AMPK activation.
All intact cell experiments in this Figure were performed in the presence of 10% serum. a, ALDOA-D34S mutant increases intracellular FBP levels under glucose starvation. HEK293T cells stably expressing ALDOA or its D34S mutant were incubated in DMEM with or without glucose for 2 h, followed by measuring FBP levels. Results are mean ± SD, n = 3; P value by ANOVA. N.S., not significant. b, D34S mutant of ALDOA that still binds FBP in glucose-free medium exhibits reduced AMPK activation. ALDO-TKD MEFs stably expressing ALDOA-D34S, or wild type ALDOA as control, were incubated in DMEM medium with or without glucose for 2 h, followed by immunoblotting. c, ALDOA-D34S blunts the formation of Ragulator-AXIN/LKB1-AMPK complex. HEK293T cells stably expressing ALDOA and ALDOA-D34S were lysed and the endogenous LAMTOR1 was immunoprecipitated, followed by immunoblotting. d, Adenovirus-mediated expression of the D34S mutant in mouse liver blocks AMPK activation after starvation. Adenovirus expressing ALDOA-D34S, or WT ALDOA as control, was injected into the tail veins of 6-week-old mice. Five days later, mice were fasted for 16 h. Phosphorylation of AMPKα and ACC were then determined by immunoblotting. e, K230A mutant of aldolase promotes the formation of Ragulator-AXIN/LKB1-AMPK complex. Endogenous LAMTOR1 in unstarved or glucose-starved WT MEFs and ALDOA-K230A MEFs were immunoprecipitated, followed by immunoblotting. f, FBP fails to dissociate AXIN/LKB1 from LAMTOR1 on light organelles purified from starved ALDOA-K230A MEFs. Cytosol from unstarved MEFs was mixed with light organelles purified from 2-h-glucose-starved ALDOA-K230A MEFs or WT MEFs as a control, and 200 μM FBP was then added to each mixture. The mixtures were then dissolved and LAMTOR1 was immunoprecipitated, followed by immunoblotting. g, Addition of exogenous FBP fails to block glucose starvation-induced AMPK activation in permeabilized ALDO-K230A expressed, TKD-MEFs (ALDOA-K230A MEFs). FBP (200 μM) was added to the 2-h-glucose-starved ALDOA-K230A MEFs or WT MEFs that had been pre-incubated with SLO for 5 min. After incubating for another 15 min, cells were subjected to immunoblotting. Experiments in c and f were performed 3 times, and that in a, b, d, e and g twice.
Extended Data Figure 9
Extended Data Figure 9. FBP is predominantly derived from glucose.
All intact cell experiments in this Figure were performed in the presence of 10% serum. a, Isotopomeric distribution of metabolites derived from D-[U-13C]glucose. 13C atoms are marked as filled circles. Note that FBP can be converted from various substrates besides glucose, but the conversion of glucose to F6P and then to FBP (grey-shaded area) is the only way that yields completely M+6 labelled FBP. b, c, MEFs (b) or HEK293T cells (c) were incubated in DMEM medium without glucose for 4 h. The medium was then added with 25 mM D-[U-13C]glucose. After 15 min or 4 h of incubation, the labeled FBP levels in cells were measured by CE-MS. The results shown that FBP produced after re-addition of glucose to the MEFs was almost entirely M+6 labelled. The experiment was performed twice.
Extended Data Figure 10
Extended Data Figure 10. Aldolase interacts with the v-ATPase-Ragulator complex.
a, A simplified model depicting that aldolase is a sensor of glucose availability that directly links glucose shortage to activation of AMPK. b, HEK293T cells were lysed and the endogenous aldolase was immunoprecipitated, followed by immunoblotting. The experiment was performed twice.
Figure 1
Figure 1. Glucose deprivation activates AMPK via an AMP/ADP independent mechanism.
a, MEFs were grown in full medium and then switched to medium containing reduced concentrations of glucose for 4 h, or full medium with 300 μM berberine (Ber) for 1 h, and AMPK activity in immunoprecipitates was measured (mean ± SD, n = 3; asterisks show significant differences from 25 mM glucose). b, MEFs were incubated as in (a) and intracellular AMP:ATP/ADP:ATP ratios determined by LC:MS. Results are mean ± SD, n = 3; asterisks show significant differences from control with 25 mM glucose. c, MEFs were grown in full medium and then incubated overnight in the same medium but with 5 mM glucose. At time zero, medium was removed and replaced with the same medium (+Glc+Gln), medium lacking glucose only (-Glc+Gln), or medium lacking glucose and glutamine (-Glc-Gln), all without serum. AMPK was isolated by immunoprecipitation (IP) and kinase activity determined. Results are mean ± SD, n = 4; asterisks show significant differences from control (+Glc+Gln); daggers (†) show significant differences between -Glc+Gln and -Glc-Gln samples at the same time point. d, AMP:ATP ratios in an experiment as in c. Results are mean ± SD (n = 3); statistical significance as in c. e, g, as c, but using HEK293 cells expressing wild type (WT) FLAG-tagged AMPK-γ2 (e) or an AMP/ADP-insensitive R531G (RG) mutant (g). Results are mean ± SD, n = 4; statistical significance as in c. f, h, as d, but using HEK293 cells expressing WT or RG mutant. Results are mean ± SD, n = 3; statistical significance as in c. All experiments were performed at least twice.
Figure 2
Figure 2. Glucose starvation activates AMPK by a lysosomal mechanism different from energy stress.
a-b, Rapid effect of glucose removal on AMPK, but not the delayed effect of removal of glucose and glutamine, is dependent on AXIN and LAMTOR1. Experiments were performed in MEFs without serum as in Fig. 1c, except that cells carried homozygous floxed alleles of the AXIN (AXINF/F) (a) or LAMTOR1 (LAMTOR1F/F) (b) genes. Prior to the experiment (36 h), MEFs were pre-treated with adenoviral vector expressing either Cre recombinase or empty vector. Samples were taken for AMPK assay; results in the top panels are mean ± SD, n = 4. The lower panels show western blotting of cell lysates using the indicated antibodies. c, Endogenous AMPKβ2 was knocked out in HEK293 cells by CRISPR-Cas9, and WT β2, or G2A or S108A mutants, were re-expressed by transient transfection. Cells were then treated by removing glucose, or glucose plus glutamine, for 20 min as in a, or with 5 µM 991 or 300 µM berberine for 1 h, all without serum. AMPKβ2 complexes were immunoprecipitated and AMPK activity determined. Results are mean ± SD, n = 4; asterisks or exact P values indicate means significantly different from controls (left-hand columns) of the same genotype. d, Glucose starvation causes translocation of AMPKβ2 to the lysosome in HEK-293 cells that is dependent on N-myristoylation. The data are derived from the experiment shown in Extended Data Fig. 2f. Pearson correlations between red (lysosomes) and green (AMPK-β2) stain across the cytoplasm were determined; results are for 7-9 cells under each condition, with horizontal bars representing mean ± SD. e, MEFs expressing WT LKB1 or a C433S knock-in were incubated ± glucose and/or glutamine for 20 min, or with DMSO, A769662 (300 µM) or berberine (300 µM) for 1 h, all without serum. Endogenous AMPK was immunoprecipitated and assayed (top) or lysates were analysed by Western blotting using the indicated antibodies (bottom). Results in the top panel are mean ± SD, n = 4; asterisks or exact P values show results significantly different from controls in full medium (removal of glucose and/or glutamine) or DMSO controls (A769662 and berberine). All experiments were performed at least twice.
Figure 3
Figure 3. Absence of fructose-1,6-bisphosphate (FBP) defines a starvation signal for AMPK activation.
All intact cell experiments in this Figure were performed in the presence of 10% serum. a, HEK293T cells were infected with lentivirus expressing indicated siRNAs; the cells were then starved for glucose for 2 h, followed by analysis of p-AMPKα and p-ACC levels. b, Cytosol from unstarved MEFs was mixed with light organelles purified from glucose-starved MEFs. Various glycolytic intermediates (200 μM) as indicated were individually added to the mixture. The mixtures were then dissolved and LAMTOR1 was immunoprecipitated. c, FBP at physiologically relevant concentrations completely dissociates AXIN/LKB1 from LAMTOR1. d, FBP (10 μM) was added to the 2-h-glucose-starved MEFs pre-incubated with streptolysin O (SLO) for 5 min. After incubating for another 15 min, cells were lysed and were analyzed by immunoblotting. Experiments in a, b and d were performed 3 times, and the experiments in c twice.
Figure 4
Figure 4. Aldolase is the receptor for FBP physically linking glucose deprivation to AMPK activation.
All intact cell experiments in this Figure were performed in the presence of 10% serum. a, b, ALDO-TKD MEFs were generated from WT MEFs (a) or AXIN-/- MEFs (b) following the procedures depicted in Extended Data Fig. 6a. The cells were then incubated in the DMEM medium with or without glucose for 2 h, followed by analysis of p-AMPKα and p-ACC levels. c, d, Activation of AMPK in HEK293T cells stably expressing ALDOA-D34S (c), or in ALDO-TKD MEFs stably expressing ALDOA-K230A (d) were analyzed as in a. The experiment in a was performed 4 times, that in b and d twice, and that in c 3 times.

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