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AMPK maintains energy homeostasis and survival in cancer cells via regulating p38/PGC-1 α -mediated mitochondrial biogenesis

View Article: PubMed Central - PubMed

ABSTRACT

Cancer cells exhibit unique metabolic response and adaptation to the fluctuating microenvironment, yet molecular and biochemical events imprinting this phenomenon are unclear. Here, we show that metabolic homeostasis and adaptation to metabolic stress in cancer cells are primarily achieved by an integrated response exerted by the activation of AMPK. We provide evidence that AMPK-p38-PGC-1α axis, by regulating energy homeostasis, maintains survival in cancer cells under glucose-limiting conditions. Functioning as a molecular switch, AMPK promotes glycolysis by activating PFK2, and facilitates mitochondrial metabolism of non-glucose carbon sources thereby maintaining cellular ATP level. Interestingly, we noted that AMPK can promote oxidative metabolism via increasing mitochondrial biogenesis and OXPHOS capacity via regulating expression of PGC-1α through p38MAPK activation. Taken together, our study signifies the fundamental role of AMPK in controlling cellular bioenergetics and mitochondrial biogenesis in cancer cells.

No MeSH data available.


Related in: MedlinePlus

AMPK promotes glycolysis by activating PFK2. (a) H1299 cells were grown in DMEM without glucose and glutamine, and supplemented with 1 mM, 5 mM and 25 mM glucose. Cells were simultaneously treated with 0.5 mM AICAR and/or 10 μM compound C for 24 h. Fresh medium (DMEM containing 25 mM glucose and 10% FBS) was added after 24 h and further grown for indicated time points. Time-dependent glucose utilization in H1299 cells under basal (i), AICAR treated (ii) or in the presence of compound C plus AICAR (iii). (b) Representative photographs of culture medium from H1299 cells grown under above-mentioned conditions for 24 h. (c, d) lactate secretion (c) and glucose utilization (d) in H1299 cells grown under the conditions used in a. (e) Immunoblots showing phosphorylated and basal levels PFK2 in H1299 (EV and DN) cells grown under indicated conditions for 24 h. (f) PFK activity in H1299 (EV and DN) cells grown under indicated conditions for 24 h. (g) Relative glucose utilization in H1299-EV and H1299-DN cells treated with or without AICAR for 36 h. Values are represented as mean±S.D. *P<0.05, **P<0.01 and ***P<0.001 denote significant differences between the groups.
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fig5: AMPK promotes glycolysis by activating PFK2. (a) H1299 cells were grown in DMEM without glucose and glutamine, and supplemented with 1 mM, 5 mM and 25 mM glucose. Cells were simultaneously treated with 0.5 mM AICAR and/or 10 μM compound C for 24 h. Fresh medium (DMEM containing 25 mM glucose and 10% FBS) was added after 24 h and further grown for indicated time points. Time-dependent glucose utilization in H1299 cells under basal (i), AICAR treated (ii) or in the presence of compound C plus AICAR (iii). (b) Representative photographs of culture medium from H1299 cells grown under above-mentioned conditions for 24 h. (c, d) lactate secretion (c) and glucose utilization (d) in H1299 cells grown under the conditions used in a. (e) Immunoblots showing phosphorylated and basal levels PFK2 in H1299 (EV and DN) cells grown under indicated conditions for 24 h. (f) PFK activity in H1299 (EV and DN) cells grown under indicated conditions for 24 h. (g) Relative glucose utilization in H1299-EV and H1299-DN cells treated with or without AICAR for 36 h. Values are represented as mean±S.D. *P<0.05, **P<0.01 and ***P<0.001 denote significant differences between the groups.

Mentions: AMPK is known to induce glycolysis by directly phosphorylating 6-phosphofructo-2-kinase (PFK2) in muscles, which by activating PFK, enhances glycolytic rate.28,29 To explore role of AMPK in metabolic homeostasis, we cultured H1299 cells in the presence of varying concentrations of glucose with or without AICAR and compound C, and after 24 h, medium was replenished with fresh medium containing 25 mM glucose. We noticed that cells grown in no or less glucose exhibited increased glucose utilization in a time-dependent manner upon replenishing glucose (Figure 5a-i). AICAR treatment further enhanced glucose utilization which was reduced by compound C under these conditions (Figures 5a-ii and a-iii). Lactate secretion (Figures 5b and c) was proportionally associated with utilization of glucose under these conditions (Figure 5d). Increased phosphorylation of PFK2 with concomitant increased activity of rate-limiting enzyme PFK was detected in H1299-EV cells grown in glucose-limiting conditions and/or treated with AICAR (Figures 5e and f). However, no change in the phosphorylated level of PFK2 and PFK activity was observed in H1299-DN cells under identical conditions (Figures 5e and f). A significant decrease in the glucose utilization was observed in H1299-DN cells treated or untreated with AICAR as compared with H1299-EV cells (Figure 5g). Our results suggest that AMPK mediates metabolic and energy homeostasis in cancer cell under glucose-limiting conditions by promoting both glycolytic as well as mitochondrial metabolism.


AMPK maintains energy homeostasis and survival in cancer cells via regulating p38/PGC-1 α -mediated mitochondrial biogenesis
AMPK promotes glycolysis by activating PFK2. (a) H1299 cells were grown in DMEM without glucose and glutamine, and supplemented with 1 mM, 5 mM and 25 mM glucose. Cells were simultaneously treated with 0.5 mM AICAR and/or 10 μM compound C for 24 h. Fresh medium (DMEM containing 25 mM glucose and 10% FBS) was added after 24 h and further grown for indicated time points. Time-dependent glucose utilization in H1299 cells under basal (i), AICAR treated (ii) or in the presence of compound C plus AICAR (iii). (b) Representative photographs of culture medium from H1299 cells grown under above-mentioned conditions for 24 h. (c, d) lactate secretion (c) and glucose utilization (d) in H1299 cells grown under the conditions used in a. (e) Immunoblots showing phosphorylated and basal levels PFK2 in H1299 (EV and DN) cells grown under indicated conditions for 24 h. (f) PFK activity in H1299 (EV and DN) cells grown under indicated conditions for 24 h. (g) Relative glucose utilization in H1299-EV and H1299-DN cells treated with or without AICAR for 36 h. Values are represented as mean±S.D. *P<0.05, **P<0.01 and ***P<0.001 denote significant differences between the groups.
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fig5: AMPK promotes glycolysis by activating PFK2. (a) H1299 cells were grown in DMEM without glucose and glutamine, and supplemented with 1 mM, 5 mM and 25 mM glucose. Cells were simultaneously treated with 0.5 mM AICAR and/or 10 μM compound C for 24 h. Fresh medium (DMEM containing 25 mM glucose and 10% FBS) was added after 24 h and further grown for indicated time points. Time-dependent glucose utilization in H1299 cells under basal (i), AICAR treated (ii) or in the presence of compound C plus AICAR (iii). (b) Representative photographs of culture medium from H1299 cells grown under above-mentioned conditions for 24 h. (c, d) lactate secretion (c) and glucose utilization (d) in H1299 cells grown under the conditions used in a. (e) Immunoblots showing phosphorylated and basal levels PFK2 in H1299 (EV and DN) cells grown under indicated conditions for 24 h. (f) PFK activity in H1299 (EV and DN) cells grown under indicated conditions for 24 h. (g) Relative glucose utilization in H1299-EV and H1299-DN cells treated with or without AICAR for 36 h. Values are represented as mean±S.D. *P<0.05, **P<0.01 and ***P<0.001 denote significant differences between the groups.
Mentions: AMPK is known to induce glycolysis by directly phosphorylating 6-phosphofructo-2-kinase (PFK2) in muscles, which by activating PFK, enhances glycolytic rate.28,29 To explore role of AMPK in metabolic homeostasis, we cultured H1299 cells in the presence of varying concentrations of glucose with or without AICAR and compound C, and after 24 h, medium was replenished with fresh medium containing 25 mM glucose. We noticed that cells grown in no or less glucose exhibited increased glucose utilization in a time-dependent manner upon replenishing glucose (Figure 5a-i). AICAR treatment further enhanced glucose utilization which was reduced by compound C under these conditions (Figures 5a-ii and a-iii). Lactate secretion (Figures 5b and c) was proportionally associated with utilization of glucose under these conditions (Figure 5d). Increased phosphorylation of PFK2 with concomitant increased activity of rate-limiting enzyme PFK was detected in H1299-EV cells grown in glucose-limiting conditions and/or treated with AICAR (Figures 5e and f). However, no change in the phosphorylated level of PFK2 and PFK activity was observed in H1299-DN cells under identical conditions (Figures 5e and f). A significant decrease in the glucose utilization was observed in H1299-DN cells treated or untreated with AICAR as compared with H1299-EV cells (Figure 5g). Our results suggest that AMPK mediates metabolic and energy homeostasis in cancer cell under glucose-limiting conditions by promoting both glycolytic as well as mitochondrial metabolism.

View Article: PubMed Central - PubMed

ABSTRACT

Cancer cells exhibit unique metabolic response and adaptation to the fluctuating microenvironment, yet molecular and biochemical events imprinting this phenomenon are unclear. Here, we show that metabolic homeostasis and adaptation to metabolic stress in cancer cells are primarily achieved by an integrated response exerted by the activation of AMPK. We provide evidence that AMPK-p38-PGC-1&alpha; axis, by regulating energy homeostasis, maintains survival in cancer cells under glucose-limiting conditions. Functioning as a molecular switch, AMPK promotes glycolysis by activating PFK2, and facilitates mitochondrial metabolism of non-glucose carbon sources thereby maintaining cellular ATP level. Interestingly, we noted that AMPK can promote oxidative metabolism via increasing mitochondrial biogenesis and OXPHOS capacity via regulating expression of PGC-1&alpha; through p38MAPK activation. Taken together, our study signifies the fundamental role of AMPK in controlling cellular bioenergetics and mitochondrial biogenesis in cancer cells.

No MeSH data available.


Related in: MedlinePlus