Biology subjects

Bouillaud, F.

Publications and source records attributed to Bouillaud, F..

6 recordsLinked to original sources

bioRxiv2024

Mitochondrial maintenance is involved in the exceptional longevity of reproductive queens of the eusocial ant Lasius niger

Most social insects are characterized by a wide disparity in life-history traits between individuals of the same species. Sterile workers live for months or years while queens may live for decades. Theories of ageing emphasise the importance of metabolism and oxidative stress in explaining longevity, with mitochondrial bioenergetics standing at the crossroads of energy and reactive oxygen species production. Studying mitochondrial functioning therefore takes on its full relevance in determining the nature of the mechanisms that explain the contrasting longevities between insect social castes. We addressed this question in an eusocial species, the black garden ant Lasius niger. We found that caste differences in mitochondrial bioenergetics and oxidative balance only partially match with predictions of the oxidative stress theory of ageing. Long-lived queens were characterized by a lower metabolic rate, lower mitochondrial density yet not necessarily lower levels of mitochondrial oxidative damages. Despite this, queens did not show reduced ATP content; rather, they even possessed a higher energy load in their mitochondria. Converging clues suggested better mitochondrial maintenance in queen ants, with enhanced dynamics of mitochondrial fission and fusion and a more marked expression of mitochondrial enzymes of the Krebs cycle. Overall, our data paves the way for studying deeper into how the rate of ATP production per mitochondria is related to the investment in mitochondrial and somatic cellular maintenance, and whether it has specifically been selected as a key mechanism in defining the still unexplained paradoxical longevity of the queen reproductive caste.

physiology↗

bioRxiv2023

Utilization of a Clark electrode device as a respirometer for small insects: a convincing test on ants allowing to detect discontinuous respiration

Respirometry provides a direct measure of an organisms respiration, which is a significant component of its metabolic rate. Amongst ants, variations in lifespan between different social castes (such as workers and queens) can be substantial, varying according to the species. As metabolic rate is higher in short-living species, we aimed to establish how metabolic rate and longevity may have coevolved within ants casts. As a first methodological step, we validate here the use of a Clark electrode initially design for measuring mitochondrial respiration control pathways, for flow-through oxygen consumption in ant, by comparison with stop flow oxygen consumption and carbon dioxide production utilizing the indirect calorimetry methodology. The global aim is to provide a reliable methodology to conduct accurate comparisons of metabolic rates within and among ant species. As expected, using Clarck electrode entails high time resolution and revealed that queens and workers exhibited discontinuous respiration, with episodes of apnea up to 20 minutes.

physiology↗

bioRxiv2022

Molecular determinants of inhibition of UCP1-mediated respiratory uncoupling

Brown adipose tissue expresses uncoupling protein 1 (UCP1), a mitochondrial transporter that uncouples respiration from ATP synthesis and dissipates energy as heat, making it a target for treating obesity and related metabolic disorders. Here, we combine molecular dynamics simulations with mitochondrial respiration assays to investigate how purine nucleotides inhibit respiration uncoupling by UCP1. Simulations predict that GDP binds UCP1 in the common substrate binding site in an upright orientation, where the base moiety interacts with a pair of charged residues (R92/E191) that are specifically conserved in the subfamily of UCPs. E191, among others, interacts with purine but not pyrimidine bases, suggesting a rationale for nucleotide specificity in UCP1 inhibition. We also identify a triplet of uncharged residues involved in hydrophobic contacts with GDP. Site-directed mutagenesis of either I187 or W281 to alanine increases lauric acid-induced uncoupling activity of UCP1 and partially suppresses inhibition of UCP1 activity by GDP in yeast spheroplasts. The triple mutant (F88, I187, W281) to alanine is overactivated by lauric acid even in a high concentration of purine nucleotides. Variants at these positions may help increase energy expenditure in a cellular and therapeutic context.

biophysics↗

bioRxiv2022

Antiviral effect of thiazolides relies on mitochondrial mild uncoupling

BackgroundViruses are dependent on cellular energy metabolism for their replication, the drug Nitazoxanide (Alinia) was shown to interfere with both. An effect of Alinia on cellular energy metabolism is the uncoupling of mitochondrial oxidative phosphorylation (OXPHOS). Our hypothesis was that uncoupling grounds the antiviral properties of Alinia. MethodsAlinia or an unrelated uncoupler were applied to a viral releasing cell line to obtain the same increasing levels of uncoupling hence identical interference with OXPHOS. FindingsDecrease in infectious viral particles release reflected the intensity of interference irrespective of the nature of the drug and was significant with modest deviation ([≤]25%) from normal. InterpretationsA mild interference on cellular energy metabolism impacts significantly on viral replication cycle. This would explain Alinias antiviral properties in vitro moreover antiviral action of Alinia is supported by clinical trials. PerspectivesAltogether this indicates that moderate interference with mitochondrial bioenergetics should be considered as a ground for a therapeutic effect. In addition, Alinia would constitute example for a safe therapeutical use of an uncoupler, which deserves consideration for a wider range of applications.

biochemistry↗

bioRxiv2020

Structural models of mitochondrial uncoupling proteins obtained in DPC micelles are not physiologically relevant for their uncoupling activity.

Uncoupling protein 1 (UCP1) is found in the inner mitochondrial membrane of brown adipocyte. In the presence of long-chain fatty acids (LCFA), UCP1 increases the proton conductance, which, in turn, increases fatty acid oxidation and energy release as heat. Several atomic models of UCP1 and UCP2 have been obtained by NMR in dodecylphosphocholine (DPC), a detergent known to inactivate UCP1. Based on NMR titration experiment on UCP1 with LCFA, it has been proposed that K56 and K269 are crucial for LCFA binding and UCP1 activation. Given the numerous controversies on the use of DPC for structure-function analyses of membrane proteins, we revisited those UCP1 mutants in a more physiological context by expressing them in the mitochondria of S. cerevisiae. Mitochondrial respiration, assayed on permeabilized spheroplasts, enables the determination of UCP1 activation and inhibition. The K56S, K269S and K56S/K269S mutants did not display any default in activation, which shows that the NMR experiments in DPC detergent are not relevant to understand UCP1 function.

biochemistry↗

bioRxiv2020

USP9X deubiquitinase couples the pluripotency network and cell metabolism to regulate ESC differentiation potential

Embryonic stem cells (ESC) have the unique ability to differentiate into all three germ cell layers. ESC transition through different states of pluripotency in response to growth factor signals and environmental cues before becoming terminally differentiated. Here, we demonstrated, by a multi-omic strategy, that the deubiquitinase USP9X regulates the developmental potential of ESC, and their transition from a naive to a more developmentally advance, or primed, state of pluripotency. We show that USP9X facilitates developmental gene expression and induces modifications of the mitochondrial bioenergetics, including decreased routing of pyruvate towards its oxidation and reduced respiration. In addition, USP9X binds to the pluripotency factor ESRRB, regulates its abundance and the transcriptional levels of a subset of its target genes. Finally, under permissive culture conditions, depletion of Usp9X accelerates cell differentiation in all cell lineages. We thus identified a new regulator of naive pluripotency and show that USP9X couples ESRRB pluripotency transcriptional network and cellular metabolism, both of which are important for ESC fate and pluripotency.

cell biology↗