bims-mimbat 2024-06-09 papers

bims-mimbat

Biomed News

on Mitochondrial metabolism in brown adipose tissue

Issue of 2024–06–09
twelve papers selected by
José Carlos de Lima-Júnior, Washington University

Two-stage evolution of mammalian adipose tissue thermogenesis.
Functional diversity among cardiolipin binding sites on the mitochondrial ADP/ATP carrier.
Cardiolipin clustering promotes mitochondrial membrane dynamics.
Liver mitochondrial coupling efficiency and its relationship to oxidative capacity and adenine nucleotide translocase content: A comparative study among crocodiles, birds and mammals.
Mitochondrial lipidomes are tissue specific - low cholesterol contents relate to UCP1 activity.
Expanding the π-system of fatty acid-anion transporter conjugates modulates their mechanism of proton transport and mitochondrial uncoupling activity.
The evolution of thermogenesis in mammals.
Chloroplast envelope K+/H+ antiporters are involved in cytosol pH regulation.
Structure and mechanism of the K+/H+ exchanger KefC.
Flies on the rise: acclimation effect on mitochondrial oxidation capacity at normal and high temperatures in Drosophila melanogaster.
Quantitative Assessment of Morphological Changes in Lipid Droplets and Lipid-Mito Interactions with Aging in Brown Adipose.
ADH1B, the adipocyte-enriched alcohol dehydrogenase, plays an essential, cell-autonomous role in human adipogenesis.

Science. 2024 Jun 07. 384(6700): 1111-1117

Two-stage evolution of mammalian adipose tissue thermogenesis.

Susanne Keipert, Michael J Gaudry, Maria Kutschke, Michaela Keuper, Margeoux A S Dela Rosa, Yiming Cheng, José M Monroy Kuhn, Rutger Laterveer, Camila A Cotrim, Peter Giere, Fabiana Perocchi, Regina Feederle, Paul G Crichton, Dominik Lutter, Martin Jastroch.

Brown adipose tissue (BAT) is a heater organ that expresses thermogenic uncoupling protein 1 (UCP1) to maintain high body temperatures during cold stress. BAT thermogenesis is considered an overarching mammalian trait, but its evolutionary origin is unknown. We show that adipose tissue of marsupials, which diverged from eutherian mammals ~150 million years ago, expresses a nonthermogenic UCP1 variant governed by a partial transcriptomic BAT signature similar to that found in eutherian beige adipose tissue. We found that the reconstructed UCP1 sequence of the common eutherian ancestor displayed typical thermogenic activity, whereas therian ancestor UCP1 is nonthermogenic. Thus, mammalian adipose tissue thermogenesis may have evolved in two distinct stages, with a prethermogenic stage in the common therian ancestor linking UCP1 expression to adipose tissue and thermal stress. We propose that in a second stage, UCP1 acquired its thermogenic function specifically in eutherians, such that the onset of mammalian BAT thermogenesis occurred only after the divergence from marsupials.

DOI: https://doi.org/10.1126/science.adg1947
EMBO J. 2024 Jun 05.

Functional diversity among cardiolipin binding sites on the mitochondrial ADP/ATP carrier.

Nanami Senoo, Dinesh K Chinthapalli, Matthew G Baile, Vinaya K Golla, Bodhisattwa Saha, Abraham O Oluwole, Oluwaseun B Ogunbona, James A Saba, Teona Munteanu, Yllka Valdez, Kevin Whited, Macie S Sheridan, Dror Chorev, Nathan N Alder, Eric R May, Carol V Robinson, Steven M Claypool.

  Lipid-protein interactions play a multitude of essential roles in membrane homeostasis. Mitochondrial membranes have a unique lipid-protein environment that ensures bioenergetic efficiency. Cardiolipin (CL), the signature mitochondrial lipid, plays multiple roles in promoting oxidative phosphorylation (OXPHOS). In the inner mitochondrial membrane, the ADP/ATP carrier (AAC in yeast; adenine nucleotide translocator, ANT in mammals) exchanges ADP and ATP, enabling OXPHOS. AAC/ANT contains three tightly bound CLs, and these interactions are evolutionarily conserved. Here, we investigated the role of these buried CLs in AAC/ANT using a combination of biochemical approaches, native mass spectrometry, and molecular dynamics simulations. We introduced negatively charged mutations into each CL-binding site of yeast Aac2 and established experimentally that the mutations disrupted the CL interactions. While all mutations destabilized Aac2 tertiary structure, transport activity was impaired in a binding site-specific manner. Additionally, we determined that a disease-associated missense mutation in one CL-binding site in human ANT1 compromised its structure and transport activity, resulting in OXPHOS defects. Our findings highlight the conserved significance of CL in AAC/ANT structure and function, directly tied to specific lipid-protein interactions.

Keywords:  Cardiolipin; Lipid–Protein Interaction; Membrane Transport; Mitochondria; Oxidative Phosphorylation

DOI:  https://doi.org/10.1038/s44318-024-00132-2
bioRxiv. 2024 May 23. pii: 2024.05.21.595226. [Epub ahead of print]

Cardiolipin clustering promotes mitochondrial membrane dynamics.

Kelly E Zuccaro, Luciano A Abriata, Fernando Teixeira Pinto Meireles, Frank R Moss, Adam Frost, Matteo Dal Peraro, Halil Aydin.

Cardiolipin (CL) is a mitochondria-specific phospholipid that forms heterotypic interactions with membrane-shaping proteins and regulates the dynamic remodeling and function of mitochondria. However, the precise mechanisms through which CL influences mitochondrial morphology are not well understood. In this study, employing molecular dynamics (MD) simulations, we observed CL localize near the membrane-binding sites of the mitochondrial fusion protein Optic Atrophy 1 (OPA1). To validate these findings experimentally, we developed a bromine-labeled CL probe to enhance cryoEM contrast and characterize the structure of OPA1 assemblies bound to the CL-brominated lipid bilayers. Our images provide direct evidence of interactions between CL and two conserved motifs within the paddle domain (PD) of OPA1, which control membrane-shaping mechanisms. We further observed a decrease in membrane remodeling activity for OPA1 in lipid compositions with increasing concentrations of monolyso-cardiolipin (MLCL). Suggesting that the partial replacement of CL by MLCL accumulation, as observed in Barth syndrome-associated mutations of the tafazzin phospholipid transacylase, compromises the stability of protein-membrane interactions. Our analyses provide insights into how biological membranes regulate the mechanisms governing mitochondrial homeostasis.
Teaser: This study reveals how CL modulates the activity of OPA1 and how MLCL impacts its ability to govern mitochondrial function.

DOI: https://doi.org/10.1101/2024.05.21.595226
Mitochondrion. 2024 Jun 04. pii: S1567-7249(24)00067-9. [Epub ahead of print] 101909

Liver mitochondrial coupling efficiency and its relationship to oxidative capacity and adenine nucleotide translocase content: A comparative study among crocodiles, birds and mammals.

Damien Roussel, Nathan Roussel, Yann Voituron, Benjamin Rey.

  The primary objective of this study was to assess whether adenine nucleotide translocase (ANT) content could be associated with phylogenetic disparities in mitochondrial coupling efficiency, within liver mitochondria obtained from rats, crocodiles, and ducklings. Our measurements included mitochondrial membrane conductance, ANT content, and oxidative phosphorylation fluxes at various steady-state rates. We observed significant variations in liver mitochondrial coupling efficiency across the three species. These variations correlated with interspecific differences in mitochondrial oxidative capacity and, to a lesser extent, the ANT content of liver mitochondria. These findings expand upon previous research by highlighting the pivotal role of oxidative capacity and ANT in modulating mitochondrial efficiency on an interspecific scale.

Keywords:  Adenine nucleotide translocase (ANT); Archosaurs; Liver; Oxidative phosphorylation; Proton leak

DOI:  https://doi.org/10.1016/j.mito.2024.101909
Life Sci Alliance. 2024 Aug;pii: e202402828. [Epub ahead of print]7(8):

Mitochondrial lipidomes are tissue specific - low cholesterol contents relate to UCP1 activity.

Sarah Brunner, Marcus Höring, Gerhard Liebisch, Sabine Schweizer, Josef Scheiber, Piero Giansanti, Maria Hidrobo, Sven Hermeling, Josef Oeckl, Natalia Prudente de Mello, Fabiana Perocchi, Claudine Seeliger, Akim Strohmeyer, Martin Klingenspor, Johannes Plagge, Bernhard Küster, Ralph Burkhardt, Klaus-Peter Janssen, Josef Ecker.

Lipid composition is conserved within sub-cellular compartments to maintain cell function. Lipidomic analyses of liver, muscle, white and brown adipose tissue (BAT) mitochondria revealed substantial differences in their glycerophospholipid (GPL) and free cholesterol (FC) contents. The GPL to FC ratio was 50-fold higher in brown than white adipose tissue mitochondria. Their purity was verified by comparison of proteomes with ER and mitochondria-associated membranes. A lipid signature containing PC and FC, calculated from the lipidomic profiles, allowed differentiation of mitochondria from BAT of mice housed at different temperatures. Elevating FC in BAT mitochondria prevented uncoupling protein (UCP) 1 function, whereas increasing GPL boosted it. Similarly, STARD3 overexpression facilitating mitochondrial FC import inhibited UCP1 function in primary brown adipocytes, whereas a knockdown promoted it. We conclude that the mitochondrial GPL/FC ratio is key for BAT function and propose that targeting it might be a promising strategy to promote UCP1 activity.

DOI: https://doi.org/10.26508/lsa.202402828
Chemistry. 2024 Jun 05. e202400931

Expanding the π-system of fatty acid-anion transporter conjugates modulates their mechanism of proton transport and mitochondrial uncoupling activity.

Edward York, Daniel A McNaughton, David S Gertner, Philip A Gale, Michael Murray, Tristan Rawling.

  Mitochondrial uncoupling by small molecule protonophores is a promising strategy for developing novel anticancer agents. Recently, aryl urea substituted fatty acids (aryl ureas) were identified as a new class of protonophoric anticancer agents. To mediate proton transport these molecules self-assemble into membrane-permeable anionic dimers in which intermolecular hydrogen bonds between the carboxylate and aryl-urea anion receptor delocalise the negative charge across the aromatic π-system. In this work, we extend the aromatic π-system by introducing a second phenyl substituent to the aryl urea scaffold and compare the proton transport mechanisms and mitochondrial uncoupling actions of these compounds to their monoaryl analogues. It was found that incorporation of meta-linked phenyl substituents into the aryl urea scaffold enhanced proton transport in vesicles and demonstrated superior capacity to depolarise mitochondria, inhibit ATP production and reduce the viability of MDA-MB-231 breast cancer cells. In contrast, diphenyl ureas linked through a 1,4-distribution across the phenyl ring displayed diminished proton transport activity, despite both diphenyl urea isomers possessing similar binding affinities for carboxylates. Mechanistic studies suggest that inclusion of a second aryl ring changes the proton transport mechanism, presumably due to steric factors that impose higher energy penalties for dimer formation.

Keywords:  Anticancer; anion transporter; mitochondrial uncoupling; proton transport

DOI:  https://doi.org/10.1002/chem.202400931
Science. 2024 Jun 07. 384(6700): 1065-1066

The evolution of thermogenesis in mammals.

Katharine R Grabek, Ryan J Sprenger.

Comparative genomics elucidates the steps enabling heat production in fat tissue.

DOI: https://doi.org/10.1126/science.adp8782
Physiol Plant. 2024 May-Jun;176(3):176(3): e14376

Chloroplast envelope K+/H+ antiporters are involved in cytosol pH regulation.

María Pilar Rodríguez-Rosales, Lourdes Rubio, Jesper Torbol Pedersen, María Nieves Aranda-Sicilia, José Antonio Fernández, Kees Venema.

Variations in light intensity induce cytosol pH changes in photosynthetic tissues, providing a possible signal to adjust a variety of biochemical, physiological and developmental processes to the energy status of the cells. It was shown that these pH changes are partially due to the transport of protons in or out of the thylakoid lumen. However, the ion transporters in the chloroplast that transmit these pH changes to the cytosol are not known. KEA1 and KEA2 are K+/H+ antiporters in the chloroplast inner envelope that adjust stromal pH in light-to-dark transitions. We previously determined that stromal pH is higher in kea1kea2 mutant cells. In this study, we now show that KEA1 and KEA2 are required to attenuate cytosol pH variations upon sudden light intensity changes in leaf mesophyll cells, showing they are important components of the light-modulated pH signalling module. The kea1kea2 mutant mesophyll cells also have a considerably less negative membrane potential. Membrane potential is dependent on the activity of the plasma membrane proton ATPase and is regulated by secondary ion transporters, mainly potassium channels in the plasma membrane. We did not find significant differences in the activity of the plasma membrane proton pump but found a strongly increased membrane permeability to protons, especially potassium, of the double mutant plasma membranes. Our results indicate that chloroplast envelope K+/H+ antiporters not only affect chloroplast pH but also have a strong impact on cellular ion homeostasis and energization of the plasma membrane.

DOI: https://doi.org/10.1111/ppl.14376
Nat Commun. 2024 Jun 04. 15(1): 4751

Structure and mechanism of the K+/H+ exchanger KefC.

Ashutosh Gulati, Surabhi Kokane, Annemarie Perez-Boerema, Claudia Alleva, Pascal F Meier, Rei Matsuoka, David Drew.

Intracellular potassium (K+) homeostasis is fundamental to cell viability. In addition to channels, K+ levels are maintained by various ion transporters. One major family is the proton-driven K+ efflux transporters, which in gram-negative bacteria is important for detoxification and in plants is critical for efficient photosynthesis and growth. Despite their importance, the structure and molecular basis for K+-selectivity is poorly understood. Here, we report ~3.1 Å resolution cryo-EM structures of the Escherichia coli glutathione (GSH)-gated K+ efflux transporter KefC in complex with AMP, AMP/GSH and an ion-binding variant. KefC forms a homodimer similar to the inward-facing conformation of Na+/H+ antiporter NapA. By structural assignment of a coordinated K+ ion, MD simulations, and SSM-based electrophysiology, we demonstrate how ion-binding in KefC is adapted for binding a dehydrated K+ ion. KefC harbors C-terminal regulator of K+ conductance (RCK) domains, as present in some bacterial K+-ion channels. The domain-swapped helices in the RCK domains bind AMP and GSH and they inhibit transport by directly interacting with the ion-transporter module. Taken together, we propose that KefC is activated by detachment of the RCK domains and that ion selectivity exploits the biophysical properties likewise adapted by K+-ion-channels.

DOI: https://doi.org/10.1038/s41467-024-49082-7
J Exp Biol. 2024 Jun 06. pii: jeb.247706. [Epub ahead of print]

Flies on the rise: acclimation effect on mitochondrial oxidation capacity at normal and high temperatures in Drosophila melanogaster.

Arianne Blanchard, Mélanie Aminot, Nathalie Gould, Adèle Léger, Nicolas Pichaud.

  Increased average temperatures and extreme thermal events (such as heatwaves) brought forth by climate change impose important constraints on aerobic metabolism. Notably, mitochondrial metabolism, which is affected by both long- and short-term temperature changes, has been put forward as an important determinant for thermal tolerance of organisms. This study examines the influence of phenotypic plasticity on metabolic and physiological parameters in Drosophila and the link between mitochondrial functions and their upper thermal limits. We showed that Drosophila acclimated to 15 °C have a 0.65 °C lower critical thermal maximum (CTmax) compared to those acclimated to 24 °C. Drosophila acclimated to 15 °C exhibited a higher proportion of shorter saturated and monounsaturated fatty acids, concomitant with lower proportions of polyunsaturated fatty acids. No mitochondrial quantitative changes (fractional area and number) were detected between acclimation groups, but changes of mitochondrial oxidation capacities were observed. Specifically, in both 15 °C- and 24 °C-acclimated groups, complex I-induced respiration was increased when measured between 15 and 24 °C, but drastically declined when measured at 40 °C. When succinate and glycerol-3-phosphate were added, this decrease was however compensated in flies acclimated to 24 °C, suggesting an important impact of acclimation on mitochondrial functions related to thermal tolerance. Our study reveals that the use of oxidative substrates at high temperatures is influenced by acclimation temperature and strongly related to upper thermal tolerance as a difference of 0.65 °C in CTmax translates into important mitochondrial changes.

Keywords:  Acclimation; CTmax; Fatty acids; Insects; Mitochondrial density.; Mitochondrial oxygen consumption; Oxidative substrates

DOI:  https://doi.org/10.1242/jeb.247706
bioRxiv. 2024 May 21. pii: 2023.09.23.559135. [Epub ahead of print]

Quantitative Assessment of Morphological Changes in Lipid Droplets and Lipid-Mito Interactions with Aging in Brown Adipose.

Amber Crabtree, Kit Neikirk, Julia Pinette, Aaron Whiteside, Bryanna Shao, Jessica McKenzie, Zer Vue, Larry Vang, Han Le, Mert Dermici, Taseer Ahmad, Trinity Celeste Owens, Ashton Oliver, Faben Zeleke, Heather K Beasley, Edgar Garza Lopez, Estevão Scudese, Taylor Rodman, Kinuthia Kabugi, Alice Koh, Suzanne Navarro, Jacob Lam, Ben Kirk, Margaret Mungai, Mariya Sweetwyne, Ho-Jin Koh, Elma Zaganjor, Steven M Damo, Jennifer A Gaddy, Annet Kirabo, Sandra A Murray, Anthonya Cooper, Clintoria Williams, Melanie R McReynolds, Andrea G Marshall, Antentor Hinton.

The physical characteristics of brown adipose tissue (BAT) are defined by the presence of multilocular lipid droplets (LD) within the brown adipocytes and a high abundance of iron-containing mitochondria, which give it its characteristic color. Normal mitochondrial function is, in part, regulated by organelle-to-organelle contacts. Particularly, the contact sites that mediate mitochondria-LD interactions are thought to have various physiological roles, such as the synthesis and metabolism of lipids. Aging is associated with mitochondrial dysfunction, and previous studies show that there are changes in mitochondrial structure and proteins that modulate organelle contact sites. However, how mitochondria-LD interactions change with aging has yet to be fully clarified. Therefore, we sought to define age-related changes in LD morphology and mitochondria-lipid interactions in BAT. We examined the three-dimensional morphology of mitochondria and LDs in young (3-month) and aged (2-year) murine BAT using serial block face-scanning electron microscopy and the Amira program for segmentation, analysis, and quantification. Analysis showed reductions in LD volume, area, and perimeter in aged samples compared to young samples. Additionally, we observed changes in LD appearance and type in aged samples compared to young samples. Notably, we found differences in mitochondrial interactions with LDs, which could implicate that these contacts may be important for energetics in aging. Upon further investigation, we also found changes in mitochondrial and cristae structure for mitochondria interacting with LD lipids. Overall, these data define the nature of LD morphology and organelle-organelle contacts during aging and provide insight into LD contact site changes that interconnect biogerontology and mitochondrial functionality, metabolism, and bioactivity in aged BAT.
Abstract Figure:

DOI: https://doi.org/10.1101/2023.09.23.559135
Proc Natl Acad Sci U S A. 2024 Jun 11. 121(24): e2319301121

ADH1B, the adipocyte-enriched alcohol dehydrogenase, plays an essential, cell-autonomous role in human adipogenesis.

Qatar Genome Project

  Alcohol dehydrogenase 1B (ADH1B) is a primate-specific enzyme which, uniquely among the ADH class 1 family, is highly expressed both in adipose tissue and liver. Its expression in adipose tissue is reduced in obesity and increased by insulin stimulation. Interference with ADH1B expression has also been reported to impair adipocyte function. To better understand the role of ADH1B in adipocytes, we used CRISPR/Cas9 to delete ADH1B in human adipose stem cells (ASC). Cells lacking ADH1B failed to differentiate into mature adipocytes manifested by minimal triglyceride accumulation and a marked reduction in expression of established adipocyte markers. As ADH1B is capable of converting retinol to retinoic acid (RA), we conducted rescue experiments. Incubation of ADH1B-deficient preadipocytes with 9-cis-RA, but not with all-transretinol, significantly rescued their ability to accumulate lipids and express markers of adipocyte differentiation. A homozygous missense variant in ADH1B (p.Arg313Cys) was found in a patient with congenital lipodystrophy of unknown cause. This variant significantly impaired the protein's dimerization, enzymatic activity, and its ability to rescue differentiation in ADH1B-deficient ASC. The allele frequency of this variant in the Middle Eastern population suggests that it is unlikely to be a fully penetrant cause of severe lipodystrophy. In conclusion, ADH1B appears to play an unexpected, crucial and cell-autonomous role in human adipocyte differentiation by serving as a necessary source of endogenous retinoic acid.

Keywords:  9-cis retinoic acid; ADH1B; adipocyte differentiation; alcohol dehydrogenase 1B; human adipose stem cells

DOI:  https://doi.org/10.1073/pnas.2319301121