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ATP Synthase c-Subunit Leak Causes Aberrant Cellular Metabolism in Fragile X Syndrome.

ABSTRACT: Loss of the gene (Fmr1) encoding Fragile X mental retardation protein (FMRP) causes increased mRNA translation and aberrant synaptic development. We find neurons of the Fmr1^-/y mouse have a mitochondrial inner membrane leak contributing to a "leak metabolism." In human Fragile X syndrome (FXS) fibroblasts and in Fmr1^-/y mouse neurons, closure of the ATP synthase leak channel by mild depletion of its c-subunit or pharmacological inhibition normalizes stimulus-induced and constitutive mRNA translation rate, decreases lactate and key glycolytic and tricarboxylic acid (TCA) cycle enzyme levels, and triggers synapse maturation. FMRP regulates leak closure in wild-type (WT), but not FX synapses, by stimulus-dependent ATP synthase β subunit translation; this increases the ratio of ATP synthase enzyme to its c-subunit, enhancing ATP production efficiency and synaptic growth. In contrast, in FXS, inability to close developmental c-subunit leak prevents stimulus-dependent synaptic maturation. Therefore, ATP synthase c-subunit leak closure encourages development and attenuates autistic behaviors.

SUBMITTER: Licznerski P

PROVIDER: S-EPMC7484101 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:New findingsWhat is the central question of this study? Humans with obesity have lower ATP synthesis in muscle along with lower content of the ?-subunit of the ATP synthase (?-F1-ATPase), the catalytic component of the ATP synthase. Does lower synthesis rate of ?-F1-ATPase in muscle contribute to these responses in humans with obesity? What is the main finding and its importance? Humans with obesity have a lower synthesis rate of ?-F1 -ATPase and ATP synthase specific activity in muscle. These findings indicate that reduced production of subunits forming the ATP synthase in muscle may contribute to impaired generation of ATP in obesity.AbstractThe content of the ?-subunit of the ATP synthase (?-F1 -ATPase), which forms the catalytic site of the enzyme ATP synthase, is reduced in muscle of obese humans, along with a reduced capacity for ATP synthesis. We studied 18 young (37 ± 8 years) subjects of which nine were lean (BMI = 23 ± 2 kg m-2 ) and nine were obese (BMI = 34 ± 3 kg m-2 ) to determine the fractional synthesis rate (FSR) and gene expression of ?-F1 -ATPase, as well as the specific activity of the ATP synthase. FSR of ?-F1 -ATPase was determined using a combination of isotope tracer infusion and muscle biopsies. Gene expression of ?-F1 -ATPase and specific activity of the ATP synthase were determined in the muscle biopsies. When compared to lean, obese subjects had lower muscle ?-F1 -ATPase FSR (0.10 ± 0.05 vs. 0.06 ± 0.03% h-1 ; P < 0.05) and protein expression (P < 0.05), but not mRNA expression (P > 0.05). Across subjects, abundance of ?-F1 -ATPase correlated with the FSR of ?-F1 -ATPase (P < 0.05). The specific activity of muscle ATP synthase was lower in obese compared to lean subjects (0.035 ± 0.004 vs. 0.042 ± 0.007 arbitrary units; P < 0.05), but this difference was not significant after the activity of the ATP synthase was adjusted to the ?-F1 -ATPase content (P > 0.05). Obesity impairs the synthesis of ?-F1 -ATPase in muscle at the translational level, reducing the content of ?-F1 -ATPase in parallel with reduced capacity for ATP generation via the ATP synthase complex.

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ATP Synthase c-Subunit Leak Causes Aberrant Cellular Metabolism in Fragile X Syndrome.

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