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Mitochondrial uncoupling links lipid catabolism to Akt inhibition and resistance to tumorigenesis.

Nowinski SM, Solmonson A, Rundhaug JE, Rho O, Cho J, Lago CU, Riley CL, Lee S, Kohno S, Dao CK, Nikawa T, Bratton SB, Wright CW, Fischer SM, DiGiovanni J, Mills EM - Nat Commun (2015)

Bottom Line: Mechanistic studies reveal that uncoupling increases fatty acid oxidation and membrane phospholipid catabolism, and impairs recruitment of Akt to the plasma membrane.Overexpression of Akt overcomes metabolic regulation by UCP3, rescuing carcinogenesis.These findings demonstrate that mitochondrial uncoupling is an effective strategy to limit proliferation and tumorigenesis through inhibition of Akt, and illuminate a novel mechanism of crosstalk between mitochondrial metabolism and growth signalling.

View Article: PubMed Central - PubMed

Affiliation: Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Austin, Texas 78712, USA.

ABSTRACT
To support growth, tumour cells reprogramme their metabolism to simultaneously upregulate macromolecular biosynthesis while maintaining energy production. Uncoupling proteins (UCPs) oppose this phenotype by inducing futile mitochondrial respiration that is uncoupled from ATP synthesis, resulting in nutrient wasting. Here using a UCP3 transgene targeted to the basal epidermis, we show that forced mitochondrial uncoupling inhibits skin carcinogenesis by blocking Akt activation. Similarly, Akt activation is markedly inhibited in UCP3 overexpressing primary human keratinocytes. Mechanistic studies reveal that uncoupling increases fatty acid oxidation and membrane phospholipid catabolism, and impairs recruitment of Akt to the plasma membrane. Overexpression of Akt overcomes metabolic regulation by UCP3, rescuing carcinogenesis. These findings demonstrate that mitochondrial uncoupling is an effective strategy to limit proliferation and tumorigenesis through inhibition of Akt, and illuminate a novel mechanism of crosstalk between mitochondrial metabolism and growth signalling.

No MeSH data available.


Related in: MedlinePlus

Overexpression of Akt rescues proliferation in K5-UCP3 epidermis.(a) Immunoblot for Akt phosphorylation at Ser 473 in wild-type FVB, K5-UCP3, K5-Akt and bitransgenic K5-UCP3/K5-Akt epidermal lysates, 4 h following topical treatment with 2.5 μg TPA or acetone (vehicle control). Immunoblotting for β-Actin was used to confirm equal loading. (b) Immunohistochemistry for BrdU labelled cells in wild-type FVB/N, K5-UCP3, K5-Akt, and bitransgenic K5-UCP3/K5-Akt epidermis following topical treatment with single (1 × ) or multiple (4 × ) treatments with 2.5 μg TPA or acetone. Scale bars, 50 μ. (c) Quantification of BrdU labelled cells in the basal layer of the interfollicular epidermis (IFE). More than 100 cells from five randomly selected skin sections (total >500 cells) were counted from each of n=3 mice per genotype in each treatment group. Error bars represent means+/−s.e.m. (n=3 animals per group). *Indicates significantly different from acetone control, same genotype (**P<0.01, ***P<0.0001, one way analysis of variance (ANOVA) followed by Dunnett's post hoc analysis), † indicates significantly different from wild-type FVB/N, same treatment (††† P<0.0001, one way ANOVA followed by Dunnett's post hoc analysis).
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f5: Overexpression of Akt rescues proliferation in K5-UCP3 epidermis.(a) Immunoblot for Akt phosphorylation at Ser 473 in wild-type FVB, K5-UCP3, K5-Akt and bitransgenic K5-UCP3/K5-Akt epidermal lysates, 4 h following topical treatment with 2.5 μg TPA or acetone (vehicle control). Immunoblotting for β-Actin was used to confirm equal loading. (b) Immunohistochemistry for BrdU labelled cells in wild-type FVB/N, K5-UCP3, K5-Akt, and bitransgenic K5-UCP3/K5-Akt epidermis following topical treatment with single (1 × ) or multiple (4 × ) treatments with 2.5 μg TPA or acetone. Scale bars, 50 μ. (c) Quantification of BrdU labelled cells in the basal layer of the interfollicular epidermis (IFE). More than 100 cells from five randomly selected skin sections (total >500 cells) were counted from each of n=3 mice per genotype in each treatment group. Error bars represent means+/−s.e.m. (n=3 animals per group). *Indicates significantly different from acetone control, same genotype (**P<0.01, ***P<0.0001, one way analysis of variance (ANOVA) followed by Dunnett's post hoc analysis), † indicates significantly different from wild-type FVB/N, same treatment (††† P<0.0001, one way ANOVA followed by Dunnett's post hoc analysis).

Mentions: To establish the functional importance of UCP3-mediated changes in lipid homoeostasis and Akt activation in UCP3-induced resistance to tumour formation, we inter-bred K5-UCP3 animals with mice that over-express an epidermally targeted, wild-type Akt transgene (K5-Akt)33. Akt overexpression had no effect on epidermal respiration (Supplementary Fig. 7); however, as previously published, K5-Akt mice exhibited heightened Akt expression and activation compared with wild type controls. Bi-transgenic K5-UCP3/K5-Akt mice also displayed heightened Akt activation, indicating that Akt overexpression alone was capable of overcoming inhibition by UCP3 (Fig. 5a). In every treatment group, Akt overexpression also increased epidermal proliferation measured by BrdU incorporation, and rescued TPA-induced proliferation in K5-UCP3/K5-Akt animals (Fig. 5b,c).


Mitochondrial uncoupling links lipid catabolism to Akt inhibition and resistance to tumorigenesis.

Nowinski SM, Solmonson A, Rundhaug JE, Rho O, Cho J, Lago CU, Riley CL, Lee S, Kohno S, Dao CK, Nikawa T, Bratton SB, Wright CW, Fischer SM, DiGiovanni J, Mills EM - Nat Commun (2015)

Overexpression of Akt rescues proliferation in K5-UCP3 epidermis.(a) Immunoblot for Akt phosphorylation at Ser 473 in wild-type FVB, K5-UCP3, K5-Akt and bitransgenic K5-UCP3/K5-Akt epidermal lysates, 4 h following topical treatment with 2.5 μg TPA or acetone (vehicle control). Immunoblotting for β-Actin was used to confirm equal loading. (b) Immunohistochemistry for BrdU labelled cells in wild-type FVB/N, K5-UCP3, K5-Akt, and bitransgenic K5-UCP3/K5-Akt epidermis following topical treatment with single (1 × ) or multiple (4 × ) treatments with 2.5 μg TPA or acetone. Scale bars, 50 μ. (c) Quantification of BrdU labelled cells in the basal layer of the interfollicular epidermis (IFE). More than 100 cells from five randomly selected skin sections (total >500 cells) were counted from each of n=3 mice per genotype in each treatment group. Error bars represent means+/−s.e.m. (n=3 animals per group). *Indicates significantly different from acetone control, same genotype (**P<0.01, ***P<0.0001, one way analysis of variance (ANOVA) followed by Dunnett's post hoc analysis), † indicates significantly different from wild-type FVB/N, same treatment (††† P<0.0001, one way ANOVA followed by Dunnett's post hoc analysis).
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f5: Overexpression of Akt rescues proliferation in K5-UCP3 epidermis.(a) Immunoblot for Akt phosphorylation at Ser 473 in wild-type FVB, K5-UCP3, K5-Akt and bitransgenic K5-UCP3/K5-Akt epidermal lysates, 4 h following topical treatment with 2.5 μg TPA or acetone (vehicle control). Immunoblotting for β-Actin was used to confirm equal loading. (b) Immunohistochemistry for BrdU labelled cells in wild-type FVB/N, K5-UCP3, K5-Akt, and bitransgenic K5-UCP3/K5-Akt epidermis following topical treatment with single (1 × ) or multiple (4 × ) treatments with 2.5 μg TPA or acetone. Scale bars, 50 μ. (c) Quantification of BrdU labelled cells in the basal layer of the interfollicular epidermis (IFE). More than 100 cells from five randomly selected skin sections (total >500 cells) were counted from each of n=3 mice per genotype in each treatment group. Error bars represent means+/−s.e.m. (n=3 animals per group). *Indicates significantly different from acetone control, same genotype (**P<0.01, ***P<0.0001, one way analysis of variance (ANOVA) followed by Dunnett's post hoc analysis), † indicates significantly different from wild-type FVB/N, same treatment (††† P<0.0001, one way ANOVA followed by Dunnett's post hoc analysis).
Mentions: To establish the functional importance of UCP3-mediated changes in lipid homoeostasis and Akt activation in UCP3-induced resistance to tumour formation, we inter-bred K5-UCP3 animals with mice that over-express an epidermally targeted, wild-type Akt transgene (K5-Akt)33. Akt overexpression had no effect on epidermal respiration (Supplementary Fig. 7); however, as previously published, K5-Akt mice exhibited heightened Akt expression and activation compared with wild type controls. Bi-transgenic K5-UCP3/K5-Akt mice also displayed heightened Akt activation, indicating that Akt overexpression alone was capable of overcoming inhibition by UCP3 (Fig. 5a). In every treatment group, Akt overexpression also increased epidermal proliferation measured by BrdU incorporation, and rescued TPA-induced proliferation in K5-UCP3/K5-Akt animals (Fig. 5b,c).

Bottom Line: Mechanistic studies reveal that uncoupling increases fatty acid oxidation and membrane phospholipid catabolism, and impairs recruitment of Akt to the plasma membrane.Overexpression of Akt overcomes metabolic regulation by UCP3, rescuing carcinogenesis.These findings demonstrate that mitochondrial uncoupling is an effective strategy to limit proliferation and tumorigenesis through inhibition of Akt, and illuminate a novel mechanism of crosstalk between mitochondrial metabolism and growth signalling.

View Article: PubMed Central - PubMed

Affiliation: Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, Austin, Texas 78712, USA.

ABSTRACT
To support growth, tumour cells reprogramme their metabolism to simultaneously upregulate macromolecular biosynthesis while maintaining energy production. Uncoupling proteins (UCPs) oppose this phenotype by inducing futile mitochondrial respiration that is uncoupled from ATP synthesis, resulting in nutrient wasting. Here using a UCP3 transgene targeted to the basal epidermis, we show that forced mitochondrial uncoupling inhibits skin carcinogenesis by blocking Akt activation. Similarly, Akt activation is markedly inhibited in UCP3 overexpressing primary human keratinocytes. Mechanistic studies reveal that uncoupling increases fatty acid oxidation and membrane phospholipid catabolism, and impairs recruitment of Akt to the plasma membrane. Overexpression of Akt overcomes metabolic regulation by UCP3, rescuing carcinogenesis. These findings demonstrate that mitochondrial uncoupling is an effective strategy to limit proliferation and tumorigenesis through inhibition of Akt, and illuminate a novel mechanism of crosstalk between mitochondrial metabolism and growth signalling.

No MeSH data available.


Related in: MedlinePlus