bims-mimbat 2022-10-02 papers

bims-mimbat

Biomed News

on Mitochondrial metabolism in brown adipose tissue

Issue of 2022–10–02
sixteen papers selected by
José Carlos de Lima-Júnior, University of California San Francisco

Generation of mega brown adipose tissue in adults by controlling brown adipocyte differentiation in vivo.
OPA1 Regulates Lipid Metabolism and Cold-Induced Browning of White Adipose Tissue in Mice.
A Window to the Potassium World. The Evidence of Potassium Energetics in the Mitochondria and Identity of the Mitochondrial ATP-Dependent K+ Channel.
MICU1 and MICU2 potentiation of Ca2+ uptake by the mitochondrial Ca2+ uniporter of Trypanosoma cruzi and its inhibition by Mg2.
Mitochondrial pyruvate supports lymphoma proliferation by fueling a glutamate pyruvate transaminase 2-dependent glutaminolysis pathway.
Differential requirements for mitochondrial electron transport chain components in the adult murine liver.
MYPT1-PP1β phosphatase negatively regulates both chromatin landscape and co-activator recruitment for beige adipogenesis.
Ca2+ channels couple spiking to mitochondrial metabolism in substantia nigra dopaminergic neurons.
On the role of ubiquinone in the proton translocation mechanism of respiratory complex I.
Evolved reductions in body temperature and the metabolic costs of thermoregulation in deer mice native to high altitude.
TFEB regulates sulfur amino acid and coenzyme A metabolism to support hepatic metabolic adaptation and redox homeostasis.
An LKB1-mitochondria axis controls TH17 effector function.
A reverse-selective ion exchange membrane for the selective transport of phosphates via an outer-sphere complexation-diffusion pathway.
Dissipation of the proton electrochemical gradient in chloroplasts promotes the oxidation of ATP synthase by thioredoxin-like proteins.
FO-F1 coupling and symmetry mismatch in ATP synthase resolved in every FO rotation step.
Tregs in visceral adipose tissue up-regulate circadian-clock expression to promote fitness and enforce a diurnal rhythm of lipolysis.

Proc Natl Acad Sci U S A. 2022 Oct 04. 119(40): e2203307119

Generation of mega brown adipose tissue in adults by controlling brown adipocyte differentiation in vivo.

Qiqiao Du, Jieyu Wu, Carina Fischer, Takahiro Seki, Xu Jing, Juan Gao, Xingkang He, Kayoko Hosaka, Le Tong, Akihiro Yasue, Masato Miyake, Mitsuaki Sobajima, Seiichi Oyadomari, Xiaoting Sun, Yunlong Yang, Qinjun Zhou, Minghua Ge, Wei Tao, Shuzhong Yao, Yihai Cao.

  Brown adipose tissue (BAT) is a highly specialized adipose tissue in its immobile location and size during the entire adulthood. In response to cold exposure and other β3-adrenoreceptor stimuli, BAT commits energy consumption by nonshivering thermogenesis (NST). However, the molecular machinery in controlling the BAT mass in adults is unknown. Here, we show our surprising findings that the BAT mass and functions can be manipulated in adult animals by controlling BAT adipocyte differentiation in vivo. Platelet-derived growth factor receptor α (PDGFα) expressed in BAT progenitor cells served a signaling function to avert adipose progenitor differentiation. Genetic and pharmacological loss-of-function of PDGFRα eliminated the differentiation barrier and permitted progenitor cell differentiation to mature and functional BAT adipocytes. Consequently, an enlarged BAT mass (megaBAT) was created by PDGFRα inhibition owing to increases of brown adipocyte numbers. Under cold exposure, a microRNA-485 (miR-485) was identified as a master suppressor of the PDGFRα signaling, and delivery of miR-485 also produced megaBAT in adult animals. Noticeably, megaBAT markedly improved global metabolism, insulin sensitivity, high-fat-diet (HFD)-induced obesity, and diabetes by enhancing NST. Together, our findings demonstrate that the adult BAT mass can be increased by blocking the previously unprecedented inhibitory signaling for BAT progenitor cell differentiation. Thus, blocking the PDGFRα for the generation of megaBAT provides an attractive strategy for treating obesity and type 2 diabetes mellitus (T2DM).

Keywords:  brown adipose tissue; metabolism; nonshivering thermogenesis; platelet-derived growth factor receptor α

DOI:  https://doi.org/10.1073/pnas.2203307119
Diabetes. 2022 Sep 28. pii: db220450. [Epub ahead of print]

OPA1 Regulates Lipid Metabolism and Cold-Induced Browning of White Adipose Tissue in Mice.

Renata O Pereira, Angela C Olvera, Alex Marti, Shi Fang, Jeffrey R White, Michael Westphal, Rana Hewezi, Salma T AshShareef, Luis Miguel Garcia Pena, Jivan Koneru, Matthew J Potthoff, E Dale Abel.

Mitochondria play a vital role in white adipose tissue homeostasis including adipogenesis, fatty acid synthesis, and lipolysis. We recently reported that the mitochondrial fusion protein optic atrophy 1 (OPA1) is required for induction of fatty acid oxidation and thermogenic activation in brown adipocytes. The present study investigated the role of OPA1 in white adipose tissue (WAT) function in vivo. We generated mice with constitutive or inducible knockout of OPA1 selectively in adipocytes. Studies were conducted under baseline conditions, at thermoneutrality, following high-fat feeding or during cold exposure. OPA1 deficiency reduced mitochondrial respiratory capacity in white adipocytes, impaired lipolytic signaling, repressed expression of de novo lipogenesis and triglyceride synthesis pathways and promoted adipose tissue senescence and inflammation. Reduced WAT mass was associated with hepatic triglycerides accumulation and glucose intolerance. Moreover, mice deficient for OPA1 in adipocytes had impaired adaptive thermogenesis, reduced cold-induced browning of sub-cutaneous WAT, and were completely resistant to diet-induced obesity. In conclusion, OPA1 expression and function in adipocytes is essential for adipose tissue expansion, lipid biosynthesis and fatty acid mobilization of WAT and brown adipocytes, and for thermogenic activation of brown and beige adipocytes.

DOI: https://doi.org/10.2337/db22-0450
Biochemistry (Mosc). 2022 Aug;87(8): 683-688

A Window to the Potassium World. The Evidence of Potassium Energetics in the Mitochondria and Identity of the Mitochondrial ATP-Dependent K+ Channel.

Dmitry B Zorov.

  The conclusions made in the three papers published in Function by Juhaszova et al. [Function, 3, 2022, zqab065, zqac001, zqac018], can be seen as a breakthrough in bioenergetics and mitochondrial medicine. For more than half a century, it has been believed that mitochondrial energetics is solely protonic and is based on the generation of electrochemical potential of hydrogen ions across the inner mitochondrial membrane upon oxidation of respiratory substrates, resulting in the generation of ATP via reverse transport of protons through the ATP synthase complex. Juhaszova et al. demonstrated that ATP synthase transfers not only protons, but also potassium ions, with the generation of ATP. This mechanism seems logical, given the fact that in eukaryotic cells, the concentration of potassium ions is several million times higher than the concentration of protons. The transport of K+ through the ATP synthase was enhanced by the activators of mitochondrial ATP-dependent K+ channel (mK/ATP), leading to the conclusion that ATP synthase is the material essence of mK/ATP. Beside ATP generation, the transport of osmotically active K+ to the mitochondrial matrix is accompanied by water entry to the matrix, leading to an increase in the matrix volume and activation of mitochondrial respiration with the corresponding increase in the ATP synthesis, which suggests an advantage of such transport for energy production. The driving force for K+ transport into the mitochondria is the membrane potential; an excess of K+ is exported from the matrix by the hypothetical K+/H+ exchangers. Inhibitory factor 1 (IF1) plays an important role in the activation of mK/ATP by increasing the chemo-mechanical efficiency of ATP synthase, which may be a positive factor in the protective anti-ischemic signaling.

Keywords:  ATP synthase; bioenergetics; ischemia; membrane potential; mitochondria; mitochondrial ATP-dependent potassium channel; potassium ions; protons; rotation; transport

DOI:  https://doi.org/10.1134/S0006297922080016
Cell Calcium. 2022 Sep 21. pii: S0143-4160(22)00127-0. [Epub ahead of print]107 102654

MICU1 and MICU2 potentiation of Ca2+ uptake by the mitochondrial Ca2+ uniporter of Trypanosoma cruzi and its inhibition by Mg2.

Mayara S Bertolini, Roberto Docampo.

  The mitochondrial Ca2+ uptake, which is important to regulate bioenergetics, cell death and cytoplasmic Ca2+ signaling, is mediated via the calcium uniporter complex (MCUC). In animal cells the MCUC is regulated by the mitochondrial calcium uptake 1 and 2 dimer (MICU1/MICU2), which has been proposed to act as gatekeeper preventing mitochondrial Ca2+ overload at low cytosolic Ca2+ levels. In contrast to animal cells, knockout of either MICU1 or MICU2 in Trypanosoma cruzi, the etiologic agent of Chagas disease, did not allow Ca2+ uptake at low extramitochondrial Ca2+ concentrations ([Ca2+]ext) and it was though that in the absence of one MICU the other would replace its role. However, previous attempts to knockout both genes were unsuccessful. Here, we designed a strategy to generate TcMICU1/TcMICU2 double knockout cell lines using CRISPR/Cas9 genome editing. Ablation of both genes was confirmed by PCR and Southern blot analyses. The absence of both proteins did not allow Ca2+ uptake at low [Ca2+]ext, significantly decreased the mitochondrial Ca2+ uptake at different [Ca2+]ext, without dissipation of the mitochondrial membrane potential, and increased the [Ca2+]ext set point needed for Ca2+ uptake, as we have seen with TcMICU1-KO and TcMICU2-KO cells. Mg2+ was found to be a negative regulator of MCUC-mediated mitochondrial Ca2+ uptake at different [Ca2+]ext. Occlusion of the MCUC pore by Mg2+ could partially explain the lack of mitochondrial Ca2+ uptake at low [Ca2+]ext in TcMICU1/TcMICU2-KO cells. In addition, TcMICU1/TcMICU2-KO epimastigotes had a lower growth rate, while infective trypomastigotes have a reduced capacity to invade host cells and to replicate within them as amastigotes.

Keywords:  CRISPR/Cas9; Gatekeeping; MICU; Magnesium; Mitochondrial calcium uniporter; Trypanosoma cruzi

DOI:  https://doi.org/10.1016/j.ceca.2022.102654
Sci Adv. 2022 Sep 30. 8(39): eabq0117

Mitochondrial pyruvate supports lymphoma proliferation by fueling a glutamate pyruvate transaminase 2-dependent glutaminolysis pathway.

Peng Wei, Alex J Bott, Ahmad A Cluntun, Jeffrey T Morgan, Corey N Cunningham, John C Schell, Yeyun Ouyang, Scott B Ficarro, Jarrod A Marto, Nika N Danial, Ralph J DeBerardinis, Jared Rutter.

The fate of pyruvate is a defining feature in many cell types. One major fate is mitochondrial entry via the mitochondrial pyruvate carrier (MPC). We found that diffuse large B cell lymphomas (DLBCLs) consume mitochondrial pyruvate via glutamate-pyruvate transaminase 2 to enable α-ketoglutarate production as part of glutaminolysis. This led us to discover that glutamine exceeds pyruvate as a carbon source for the tricarboxylic acid cycle in DLBCLs. As a result, MPC inhibition led to decreased glutaminolysis in DLBCLs, opposite to previous observations in other cell types. We also found that MPC inhibition or genetic depletion decreased DLBCL proliferation in an extracellular matrix (ECM)-like environment and xenografts, but not in a suspension environment. Moreover, the metabolic profile of DLBCL cells in ECM is markedly different from cells in a suspension environment. Thus, we conclude that the synergistic consumption and assimilation of glutamine and pyruvate enables DLBCL proliferation in an extracellular environment-dependent manner.

DOI: https://doi.org/10.1126/sciadv.abq0117
Elife. 2022 Sep 26. pii: e80919. [Epub ahead of print]11

Differential requirements for mitochondrial electron transport chain components in the adult murine liver.

Nicholas P Lesner, Xun Wang, Zhenkang Chen, Anderson Frank, Cameron Menezes, Sara House, Spencer D Shelton, Andrew Lemoff, David G McFadden, Janaka Wanaspura, Ralph J DeBerardinis, Prashant Mishra.

  Mitochondrial electron transport chain (ETC) dysfunction due to mutations in the nuclear or mitochondrial genome is a common cause of metabolic disease in humans and displays striking tissue specificity depending on the affected gene. The mechanisms underlying tissue specific phenotypes are not understood. Complex I (cI) is classically considered the entry point for electrons into the ETC, and in vitro experiments indicate that cI is required for basal respiration and maintenance of the NAD+/NADH ratio, an indicator of cellular redox status. This finding has largely not been tested in vivo. Here, we report that mitochondrial complex I is dispensable for homeostasis of the adult mouse liver; animals with hepatocyte-specific loss of cI function display no overt phenotypes or signs of liver damage, and maintain liver function, redox and oxygen status. Further analysis of cI-deficient livers did not reveal significant proteomic or metabolic changes, indicating little to no compensation is required in the setting of complex I loss. In contrast, complex IV (cIV) dysfunction in adult hepatocytes results in decreased liver function, impaired oxygen handling, steatosis, and liver damage, accompanied by significant metabolomic and proteomic perturbations. Our results support a model whereby complex I loss is tolerated in the mouse liver because hepatocytes use alternative electron donors to fuel the mitochondrial ETC.

Keywords:  cell biology; genetics; genomics; mouse

DOI:  https://doi.org/10.7554/eLife.80919
Nat Commun. 2022 Sep 29. 13(1): 5715

MYPT1-PP1β phosphatase negatively regulates both chromatin landscape and co-activator recruitment for beige adipogenesis.

Hiroki Takahashi, Ge Yang, Takeshi Yoneshiro, Yohei Abe, Ryo Ito, Chaoran Yang, Junna Nakazono, Mayumi Okamoto-Katsuyama, Aoi Uchida, Makoto Arai, Hitomi Jin, Hyunmi Choi, Myagmar Tumenjargal, Shiyu Xie, Ji Zhang, Hina Sagae, Yanan Zhao, Rei Yamaguchi, Yu Nomura, Yuichi Shimizu, Kaito Yamada, Satoshi Yasuda, Hiroshi Kimura, Toshiya Tanaka, Youichiro Wada, Tatsuhiko Kodama, Hiroyuki Aburatani, Min-Sheng Zhu, Takeshi Inagaki, Timothy F Osborne, Takeshi Kawamura, Yasushi Ishihama, Yoshihiro Matsumura, Juro Sakai.

Protein kinase A promotes beige adipogenesis downstream from β-adrenergic receptor signaling by phosphorylating proteins, including histone H3 lysine 9 (H3K9) demethylase JMJD1A. To ensure homeostasis, this process needs to be reversible however, this step is not well understood. We show that myosin phosphatase target subunit 1- protein phosphatase 1β (MYPT1-PP1β) phosphatase activity is inhibited via PKA-dependent phosphorylation, which increases phosphorylated JMJD1A and beige adipogenesis. Mechanistically, MYPT1-PP1β depletion results in JMJD1A-mediated H3K9 demethylation and activation of the Ucp1 enhancer/promoter regions. Interestingly, MYPT1-PP1β also dephosphorylates myosin light chain which regulates actomyosin tension-mediated activation of YAP/TAZ which directly stimulates Ucp1 gene expression. Pre-adipocyte specific Mypt1 deficiency increases cold tolerance with higher Ucp1 levels in subcutaneous white adipose tissues compared to control mice, confirming this regulatory mechanism in vivo. Thus, we have uncovered regulatory cross-talk involved in beige adipogenesis that coordinates epigenetic regulation with direct activation of the mechano-sensitive YAP/TAZ transcriptional co-activators.

DOI: https://doi.org/10.1038/s41467-022-33363-0
Sci Adv. 2022 Sep 30. 8(39): eabp8701

Ca2+ channels couple spiking to mitochondrial metabolism in substantia nigra dopaminergic neurons.

Enrico Zampese, David L Wokosin, Patricia Gonzalez-Rodriguez, Jaime N Guzman, Tatiana Tkatch, Jyothisri Kondapalli, William C Surmeier, Karis B D'Alessandro, Diego De Stefani, Rosario Rizzuto, Masamitsu Iino, Jeffery D Molkentin, Navdeep S Chandel, Paul T Schumacker, D James Surmeier.

How do neurons match generation of adenosine triphosphate by mitochondria to the bioenergetic demands of regenerative activity? Although the subject of speculation, this coupling is still poorly understood, particularly in neurons that are tonically active. To help fill this gap, pacemaking substantia nigra dopaminergic neurons were studied using a combination of optical, electrophysiological, and molecular approaches. In these neurons, spike-activated calcium (Ca2+) entry through Cav1 channels triggered Ca2+ release from the endoplasmic reticulum, which stimulated mitochondrial oxidative phosphorylation through two complementary Ca2+-dependent mechanisms: one mediated by the mitochondrial uniporter and another by the malate-aspartate shuttle. Disrupting either mechanism impaired the ability of dopaminergic neurons to sustain spike activity. While this feedforward control helps dopaminergic neurons meet the bioenergetic demands associated with sustained spiking, it is also responsible for their elevated oxidant stress and possibly to their decline with aging and disease.

DOI: https://doi.org/10.1126/sciadv.abp8701
FEBS Lett. 2022 Sep 30.

On the role of ubiquinone in the proton translocation mechanism of respiratory complex I.

Mårten Wikström, Amina Djurabekova, Vivek Sharma.

  Complex I converts oxidoreduction energy into a proton electrochemical gradient across the inner mitochondrial or bacterial cell membrane. This gradient is the primary source of energy for aerobic synthesis of ATP. Oxidation of reduced nicotinamide adenine dinucleotide (NADH) by ubiquinone (Q) yields NAD+ and ubiquinol (QH2 ), which is tightly coupled to translocation of four protons from the negatively to the positively charged side of the membrane. Electrons from NADH oxidation reach the iron-sulfur centre N2 positioned near the bottom of a tunnel that extends ca. 30Å from the membrane domain into the hydrophilic domain of the complex. The tunnel is occupied by ubiquinone, which can take a distal position near the N2 centre, or proximal positions closer to the membrane. Here, we review important structural, kinetic and thermodynamic properties of ubiquinone that define its role in complex I function. We suggest that this function exceeds that of a mere substrate or electron acceptor, and propose that ubiquinone may be the redox element of complex I coupling electron transfer to proton translocation.

Keywords:  energy conservation; mitochondria; oxidative phosphorylation; proton pumping

DOI:  https://doi.org/10.1002/1873-3468.14506
Proc Biol Sci. 2022 Sep 28. 289(1983): 20221553

Evolved reductions in body temperature and the metabolic costs of thermoregulation in deer mice native to high altitude.

Oliver H Wearing, Graham R Scott.

  The evolution of endothermy was instrumental to the diversification of birds and mammals, but the energetic demands of maintaining high body temperature could offset the advantages of endothermy in some environments. We hypothesized that reductions in body temperature help high-altitude natives overcome the metabolic challenges of cold and hypoxia in their native environment. Deer mice (Peromyscus maniculatus) from high-altitude and low-altitude populations were bred in captivity to the second generation and were acclimated as adults to warm normoxia or cold hypoxia. Subcutaneous temperature (Tsub, used as a proxy for body temperature) and cardiovascular function were then measured throughout the diel cycle using biotelemetry. Cold hypoxia increased metabolic demands, as reflected by increased food consumption and heart rate (associated with reduced vagal tone). These increased metabolic demands were offset by plastic reductions in Tsub (approx. 2°C) in response to cold hypoxia, and highlanders had lower Tsub (approx. 1°C) than lowlanders in both environmental treatments. Empirical and theoretical evidence suggested that these reductions could together reduce metabolic demands by approximately 10-30%. Therefore, plastic and evolved reductions in body temperature can help mammals overcome the metabolic challenges at high altitude and may be a valuable energy-saving strategy in some non-hibernating endotherms in extreme environments.

Keywords:  blood pressure; circadian rhythms; high-altitude acclimatization; high-altitude adaptation; metabolism; thermoregulation

DOI:  https://doi.org/10.1098/rspb.2022.1553
Nat Commun. 2022 Sep 28. 13(1): 5696

TFEB regulates sulfur amino acid and coenzyme A metabolism to support hepatic metabolic adaptation and redox homeostasis.

David Matye, Sumedha Gunewardena, Jianglei Chen, Huaiwen Wang, Yifeng Wang, Mohammad Nazmul Hasan, Lijie Gu, Yung Dai Clayton, Yanhong Du, Cheng Chen, Jacob E Friedman, Shelly C Lu, Wen-Xing Ding, Tiangang Li.

Fatty liver is a highly heterogenous condition driven by various pathogenic factors in addition to the severity of steatosis. Protein insufficiency has been causally linked to fatty liver with incompletely defined mechanisms. Here we report that fatty liver is a sulfur amino acid insufficient state that promotes metabolic inflexibility via limiting coenzyme A availability. We demonstrate that the nutrient-sensing transcriptional factor EB synergistically stimulates lysosome proteolysis and methionine adenosyltransferase to increase cysteine pool that drives the production of coenzyme A and glutathione, which support metabolic adaptation and antioxidant defense during increased lipid influx. Intriguingly, mice consuming an isocaloric protein-deficient Western diet exhibit selective hepatic cysteine, coenzyme A and glutathione deficiency and acylcarnitine accumulation, which are reversed by cystine supplementation without normalizing dietary protein intake. These findings support a pathogenic link of dysregulated sulfur amino acid metabolism to metabolic inflexibility that underlies both overnutrition and protein malnutrition-associated fatty liver development.

DOI: https://doi.org/10.1038/s41467-022-33465-9
Nature. 2022 Sep 28.

An LKB1-mitochondria axis controls TH17 effector function.

Francesc Baixauli, Klara Piletic, Daniel J Puleston, Matteo Villa, Cameron S Field, Lea J Flachsmann, Andrea Quintana, Nisha Rana, Joy Edwards-Hicks, Mai Matsushita, Michal A Stanczak, Katarzyna M Grzes, Agnieszka M Kabat, Mario Fabri, George Caputa, Beth Kelly, Mauro Corrado, Yaarub Musa, Katarzyna J Duda, Gerhard Mittler, David O'Sullivan, Hiromi Sesaki, Thomas Jenuwein, Joerg M Buescher, Edward J Pearce, David E Sanin, Erika L Pearce.

CD4+ T cell differentiation requires metabolic reprogramming to fulfil the bioenergetic demands of proliferation and effector function, and enforce specific transcriptional programmes1-3. Mitochondrial membrane dynamics sustains mitochondrial processes4, including respiration and tricarboxylic acid (TCA) cycle metabolism5, but whether mitochondrial membrane remodelling orchestrates CD4+ T cell differentiation remains unclear. Here we show that unlike other CD4+ T cell subsets, T helper 17 (TH17) cells have fused mitochondria with tight cristae. T cell-specific deletion of optic atrophy 1 (OPA1), which regulates inner mitochondrial membrane fusion and cristae morphology6, revealed that TH17 cells require OPA1 for its control of the TCA cycle, rather than respiration. OPA1 deletion amplifies glutamine oxidation, leading to impaired NADH/NAD+ balance and accumulation of TCA cycle metabolites and 2-hydroxyglutarate-a metabolite that influences the epigenetic landscape5,7. Our multi-omics approach revealed that the serine/threonine kinase liver-associated kinase B1 (LKB1) couples mitochondrial function to cytokine expression in TH17 cells by regulating TCA cycle metabolism and transcriptional remodelling. Mitochondrial membrane disruption activates LKB1, which restrains IL-17 expression. LKB1 deletion restores IL-17 expression in TH17 cells with disrupted mitochondrial membranes, rectifying aberrant TCA cycle glutamine flux, balancing NADH/NAD+ and preventing 2-hydroxyglutarate production from the promiscuous activity of the serine biosynthesis enzyme phosphoglycerate dehydrogenase (PHGDH). These findings identify OPA1 as a major determinant of TH17 cell function, and uncover LKB1 as a sensor linking mitochondrial cues to effector programmes in TH17 cells.

DOI: https://doi.org/10.1038/s41586-022-05264-1
Nat Nanotechnol. 2022 Sep 26.

A reverse-selective ion exchange membrane for the selective transport of phosphates via an outer-sphere complexation-diffusion pathway.

Arpita Iddya, Piotr Zarzycki, Ryan Kingsbury, Chia Miang Khor, Shengcun Ma, Jingbo Wang, Ian Wheeldon, Zhiyong Jason Ren, Eric M V Hoek, David Jassby.

Specific-ion selectivity is a highly desirable feature for the next generation of membranes. However, existing membranes rely on differences in charge, size and hydration energy, which limits their ability to target individual ion species. Here we demonstrate a nanocomposite ion-exchange membrane material that enables a reverse-selective transport mechanism that can selectively pass a single ion species. We demonstrate this transport mechanism with phosphate ions selectively transporting across negatively charged cation exchange membranes. Selective transport is enabled by the in situ growth of hydrous manganese oxide nanoparticles throughout a cation exchange membrane that provide a diffusion pathway via phosphate-specific, reversible outer-sphere interactions. On incorporating the hydrous manganese oxide nanoparticles, the membrane's phosphate flux increased by a factor of 27 over an unmodified cation exchange membrane, and the selectivity of phosphorous over sulfate, nitrate and chloride reaches 47, 100 and 20, respectively. By pairing ion-specific outer-sphere interactions between the target ions and appropriate nanoparticles, these nanocomposite ion-exchange materials can, in principle, achieve selective transport for a range of ions.

DOI: https://doi.org/10.1038/s41565-022-01209-x
J Biol Chem. 2022 Sep 26. pii: S0021-9258(22)00984-X. [Epub ahead of print] 102541

Dissipation of the proton electrochemical gradient in chloroplasts promotes the oxidation of ATP synthase by thioredoxin-like proteins.

Takatoshi Sekiguchi, Keisuke Yoshida, Ken-Ichi Wakabayashi, Toru Hisabori.

  Chloroplast FoF1-ATP synthase (CFoCF1) uses an electrochemical gradient of protons across the thylakoid membrane (ΔμH+) as an energy source in the ATP synthesis reaction. CFoCF1 activity is regulated by the redox state of a Cys pair on its central axis, i.e., the γ subunit (CF1-γ). When the ΔμH+ is formed by the photosynthetic electron transfer chain under light conditions, CF1-γ is reduced by thioredoxin (Trx), and the entire CFoCF1 enzyme is activated. The redox regulation of CFoCF1 is a key mechanism underlying the control of ATP synthesis under light conditions. In contrast, the oxidative deactivation process involving CFoCF1 has not been clarified. In the present study, we analyzed the oxidation of CF1-γ by two physiological oxidants in the chloroplast, namely the proteins Trx-like 2 and atypical Cys-His-rich Trx. Using the thylakoid membrane containing the reduced form of CFoCF1, we were able to assess the CF1-γ oxidation ability of these Trx-like proteins. Our kinetic analysis indicated that these proteins oxidized CF1-γ with a higher efficiency than that achieved by a chemical oxidant and typical chloroplast Trxs. Additionally, the CF1-γ oxidation rate due to Trx-like proteins and the affinity between them were changed markedly when ΔμH+ formation across the thylakoid membrane was manipulated artificially. Collectively, these results indicate that the formation status of the ΔμH+ controls the redox regulation of CFoCF1 to prevent energetic disadvantages in plants.

Keywords:  Chloroplast ATP synthase; oxidation; proton electrochemical gradient; redox regulation; thioredoxin

DOI:  https://doi.org/10.1016/j.jbc.2022.102541
Biophys J. 2022 Sep 28. pii: S0006-3495(22)00784-6. [Epub ahead of print]

FO-F1 coupling and symmetry mismatch in ATP synthase resolved in every FO rotation step.

Shintaroh Kubo, Toru Niina, Shoji Takada.

  FOF1 ATP synthase, a ubiquitous enzyme that synthesizes most ATP in living cells, is composed of two rotary motors, a membrane-embedded proton-driven FO motor, and a catalytic F1 motor. These motors share both central and peripheral stalks. Although both FO and F1 have pseudo-symmetric structures, their symmetries do not match. How symmetry mismatch is solved remains elusive because of the missing intermediate structures of the rotational steps. Here, for the case of Bacillus PS3 ATP synthases with 3- and 10-fold symmetries in F1 and FO, respectively, we uncovered the mechanical couplings between FO and F1 at every 36º-rotation step via molecular dynamics simulations and comparative studies of cryo-electron microscopy (EM) structures from three species. We found that the mismatch could be solved using several elements: (1) the F1 head partially rotates relative to the FO a-subunit via elastic distortion of the b-subunits, (2) the rotor is twisted, and (3) comparisons of cryo-EM structures further suggest that the c-ring rotary angles can deviate from the symmetric ones. In addition, the F1 motor may have non-canonical structures, relieving stronger frustration. Thus, we provide new insights for solving the symmetry mismatch problem.

Keywords:  F(O)F(1) ATP synthase; Molecular dynamics simulation; Molecular motor

DOI:  https://doi.org/10.1016/j.bpj.2022.09.034
Sci Immunol. 2022 Sep 30. 7(75): eabl7641

Tregs in visceral adipose tissue up-regulate circadian-clock expression to promote fitness and enforce a diurnal rhythm of lipolysis.

Tianli Xiao, P Kent Langston, Andrés R Muñoz-Rojas, Teshika Jayewickreme, Mitchell A Lazar, Christophe Benoist, Diane Mathis.

Regulatory T cells (Tregs) in nonlymphoid organs provide critical brakes on inflammation and regulate tissue homeostasis. Although so-called "tissue Tregs" are phenotypically and functionally diverse, serving to optimize their performance and survival, up-regulation of pathways related to circadian rhythms is a feature they share. Yet the diurnal regulation of Tregs and its consequences are controversial and poorly understood. Here, we profiled diurnal variations in visceral adipose tissue (VAT) and splenic Tregs in the presence and absence of core-clock genes. VAT, but not splenic, Tregs up-regulated their cell-intrinsic circadian program and exhibited diurnal variations in their activation and metabolic state. BMAL1 deficiency specifically in Tregs led to constitutive activation and poor oxidative metabolism in VAT, but not splenic, Tregs. Disruption of core-clock components resulted in loss of fitness: BMAL1-deficient VAT Tregs were preferentially lost during competitive transfers and in heterozygous TregBmal1Δ females. After 16 weeks of high-fat diet feeding, VAT inflammation was increased in mice harboring BMAL1-deficient Tregs, and the remaining cells lost the transcriptomic signature of bona fide VAT Tregs. Unexpectedly, VAT Tregs suppressed adipocyte lipolysis, and BMAL1 deficiency specifically in Tregs abrogated the characteristic diurnal variation in adipose tissue lipolysis, resulting in enhanced suppression of lipolysis throughout the day. These findings argue for the importance of the cell-intrinsic clock program in optimizing VAT Treg function and fitness.

DOI: https://doi.org/10.1126/sciimmunol.abl7641