bims-mimbat 2023-01-22 papers

bims-mimbat

Biomed News

on Mitochondrial metabolism in brown adipose tissue

Issue of 2023–01–22
fourteen papers selected by
José Carlos de Lima-Júnior, Washington University

CoQ Regulates Brown Adipose Tissue Respiration and Uncoupling Protein 1 Expression.
Repeated short excursions from thermoneutrality suffice to restructure brown adipose tissue.
SON-light activation of glucose regulation.
Linoleic Acid-Enriched Diet Increases Mitochondrial Tetralinoleoyl Cardiolipin, OXPHOS Protein Levels, and Uncoupling in Interscapular Brown Adipose Tissue during Diet-Induced Weight Gain.
Mitochondria regulate intracellular coenzyme Q transport and ferroptotic resistance via STARD7.
Rats lacking Ucp1 present a novel translational tool for the investigation of thermogenic adaptation during cold challenge.
Anmyungambi Decoction Ameliorates Obesity through Activation of Non-Shivering Thermogenesis in Brown and White Adipose Tissues.
Goldilocks calcium concentrations and the regulation of oxidative phosphorylation: too much, too little, or just right.
Light modulates glucose metabolism by a retina-hypothalamus-brown adipose tissue axis.
BMI-adjusted adipose tissue volumes exhibit depot-specific and divergent associations with cardiometabolic diseases.
Discovery and validation of new Hv1 proton channel inhibitors with onco-therapeutic potential.
Linoleate-Enrichment of Mitochondrial Cardiolipin Molecular Species Is Developmentally Regulated and a Determinant of Metabolic Phenotype.
Energetics and evolution of anaerobic microbial eukaryotes.
ION CHANNEL THERMODYNAMICS STUDIED WITH TEMPERATURE JUMPS MEASURED AT THE CELL MEMBRANE.

Antioxidants (Basel). 2022 Dec 22. pii: 14. [Epub ahead of print]12(1):

CoQ Regulates Brown Adipose Tissue Respiration and Uncoupling Protein 1 Expression.

Ching-Fang Chang, Amanda L Gunawan, Irene Liparulo, Peter-James H Zushin, Ambre M Bertholet, Yuriy Kirichok, Andreas Stahl.

  Coenzyme Q (CoQ, aka ubiquinone) is a key component of the mitochondrial electron transport chain (ETC) and membrane-incorporated antioxidant. CoQ10 deficiencies encompass a heterogeneous spectrum of clinical phenotypes and can be caused by hereditary mutations in the biosynthesis pathway or result from pharmacological interventions such as HMG-CoA Reductase inhibitors, and statins, which are widely used to treat hypercholesterolemia and prevent cardiovascular disease. How CoQ deficiency affects individual tissues and cell types, particularly mitochondrial-rich ones such as brown adipose tissue (BAT), has remained poorly understood. Here we show that pharmacological and genetic models of BAT CoQ deficiency show altered respiration that can only in part be explained by classical roles of CoQ in the respiration chain. Instead, we found that CoQ strongly impacts brown and beige adipocyte respiration via the regulation of uncoupling protein 1 (UCP1) expression. CoQ deficiency in BAT robustly decreases UCP1 protein levels and uncoupled respiration unexpectedly, resulting in increased inner mitochondrial membrane potential and decreased ADP/ATP ratios. Suppressed UCP1 expression was also observed in a BAT-specific in vivo model of CoQ deficiency and resulted in enhanced cold sensitivity. These findings demonstrate an as yet unappreciated role of CoQ in the transcriptional regulation of key thermogenic genes and functions.

Keywords:  Coenzyme Q; brown adipose tissue; mitochondrial function; thermogenesis

DOI:  https://doi.org/10.3390/antiox12010014
Biochimie. 2023 Jan 16. pii: S0300-9084(23)00006-8. [Epub ahead of print]

Repeated short excursions from thermoneutrality suffice to restructure brown adipose tissue.

Victoria S Davies, Erik Lindsund, Natasa Petrovic, Barbara Cannon, Jan Nedergaard.

Given the presence of brown adipose tissue in adult humans, an important issue is whether human brown adipose tissue is recruitable. Cold exposure is the canonical recruitment treatment; however, in experimental animals (mice), recruitment of brown adipose tissue is normally induced by placing the mice in constant cold, a procedure not feasible in humans. For possible translational applications, we have therefore investigated whether shorter daily excursions from thermoneutrality would suffice to qualitatively and quantitatively induce recruitment in mice. Mice, housed at thermoneutrality (30 °C) to mimic human conditions, were transferred every day for 4 weeks to cool conditions (18 °C), for 0, 15, 30, 120 and 420 min (or placed constantly in 18 °C). On the examination day, the mice were not exposed to cold. Very short daily exposures (≤30 minutes) were sufficient to induce structural changes in the form of higher protein density in brown adipose tissue, changes that may affect the identification of the tissue in e.g. computer tomography and other scan studies. To estimate thermogenic capacity, UCP1 protein levels were followed. No UCP1 protein was detectable in inguinal white adipose tissue. In the interscapular brown adipose tissue, a remarkable two-phase reaction was seen. Very short daily exposures (≤30 minutes) were sufficient to induce a significant increase in total UCP1 levels. For attainment of full cold acclimation, the mice had, however, to remain exposed to the cold. The studies indicate that marked alterations in brown adipose tissue composition can be induced in mammals through relatively modest stimulation events.

DOI: https://doi.org/10.1016/j.biochi.2023.01.006
Cell. 2023 Jan 19. pii: S0092-8674(22)01588-4. [Epub ahead of print]186(2): 238-240

SON-light activation of glucose regulation.

Gisela Geoghegan, Judith Simcox.

Body temperature maintenance is an important regulator of glucose homeostasis. In this issue of Cell, Meng et al. discover a regulatory axis in which light activation of photoreceptive retinal ganglia stimulates the supraoptic nucleus (SON) to inhibit brown adipose tissue (BAT) thermogenesis and impair glucose homeostasis. This could explain the impact of constant light exposure on metabolism.

DOI: https://doi.org/10.1016/j.cell.2022.12.045
Biology (Basel). 2022 Dec 21. pii: 9. [Epub ahead of print]12(1):

Linoleic Acid-Enriched Diet Increases Mitochondrial Tetralinoleoyl Cardiolipin, OXPHOS Protein Levels, and Uncoupling in Interscapular Brown Adipose Tissue during Diet-Induced Weight Gain.

Deena B Snoke, Connor A Mahler, Austin Angelotti, Rachel M Cole, Genevieve C Sparagna, Kedryn K Baskin, Martha A Belury.

  Cardiolipin (CL) is a phospholipid unique to the inner mitochondrial membrane that supports respiratory chain structure and function and is demonstrated to be influenced by types of dietary fats. However, the influence of dietary fat on CL species and how this best supports mitochondrial function in brown adipose tissue (BAT), which exhibits an alternative method of energy utilization through the uncoupling of the mitochondrial proton gradient to generate heat, is not well understood. Therefore, the aim of our study was to evaluate metabolic parameters, interscapular BAT CL quantity, species, and mitochondrial function in mice consuming isocaloric moderate-fat diets with either lard (LD; similar fatty acid profile to western dietary patterns) or safflower oil high in linoleic acid (SO), shown to be metabolically favorable in large clinical meta-analyses. Mice fed the SO diet exhibited decreased adiposity, improved insulin sensitivity, and enrichment of LA-containing CL species in BAT CL. Furthermore, mice fed the SO diet exhibit higher levels of OXPHOS complex proteins and increased oxygen consumption in BAT. Our findings demonstrate that dietary consumption of LA-rich oil improves metabolic parameters, increases LA-containing CL species, and improves BAT function when compared to the consumption of lard in mice during diet-induced weight gain.

Keywords:  brown adipose tissue; cardiolipin; dietary fat; high fat diet; insulin sensitivity; linoleic acid; metabolic syndrome; obesity

DOI:  https://doi.org/10.3390/biology12010009
Nat Cell Biol. 2023 Jan 19.

Mitochondria regulate intracellular coenzyme Q transport and ferroptotic resistance via STARD7.

Soni Deshwal, Mashun Onishi, Takashi Tatsuta, Tim Bartsch, Eileen Cors, Katharina Ried, Kathrin Lemke, Hendrik Nolte, Patrick Giavalisco, Thomas Langer.

Coenzyme Q (or ubiquinone) is a redox-active lipid that serves as universal electron carrier in the mitochondrial respiratory chain and antioxidant in the plasma membrane limiting lipid peroxidation and ferroptosis. Mechanisms allowing cellular coenzyme Q distribution after synthesis within mitochondria are not understood. Here we identify the cytosolic lipid transfer protein STARD7 as a critical factor of intracellular coenzyme Q transport and suppressor of ferroptosis. Dual localization of STARD7 to the intermembrane space of mitochondria and the cytosol upon cleavage by the rhomboid protease PARL ensures the synthesis of coenzyme Q in mitochondria and its transport to the plasma membrane. While mitochondrial STARD7 preserves coenzyme Q synthesis, oxidative phosphorylation function and cristae morphogenesis, cytosolic STARD7 is required for the transport of coenzyme Q to the plasma membrane and protects against ferroptosis. A coenzyme Q variant competes with phosphatidylcholine for binding to purified STARD7 in vitro. Overexpression of cytosolic STARD7 increases ferroptotic resistance of the cells, but limits coenzyme Q abundance in mitochondria and respiratory cell growth. Our findings thus demonstrate the need to coordinate coenzyme Q synthesis and cellular distribution by PARL-mediated STARD7 processing and identify PARL and STARD7 as promising targets to interfere with ferroptosis.

DOI: https://doi.org/10.1038/s41556-022-01071-y
Acta Physiol (Oxf). 2023 Jan 17. e13935

Rats lacking Ucp1 present a novel translational tool for the investigation of thermogenic adaptation during cold challenge.

Jaycob D Warfel, Carrie M Elks, David S Bayless, Bolormaa Vandanmagsar, Allison C Stone, Samuel E Velasquez, Paola Olivares-Nazar, Robert C Noland, Sujoy Ghosh, Jinying Zhang, Randall L Mynatt.

   AIM: Valuable studies have tested the role of Ucp1 on body temperature maintenance in mice, and we sought to create a Ucp1 knockout in rats (Ucp1-/- ) to provide insight into thermogenic mechanisms in larger mammals.
METHODS: We used CRISPR/Cas9 technology to create Ucp1-/- rats. Body weight and adiposity was measured, and rats were subjected to indirect calorimetry. Rats were either exposed to room temperature, 4o C for 24 hours, or 4o C for 14 days. Analysis of Brown and White Adipose tissue and skeletal muscle was conducted via histology, western blot comparison of oxidative phosphorylation proteins, and qPCR to compare mitochondrial DNA levels and mRNA expression profiles. RNA-seq was performed in skeletal muscle.
RESULTS: Ucp1-/- rats withstood 4o C for 14 days, but core temperature steadily declined. All rats lost body weight after 14 days at 4o C, but controls increased food intake more robustly than Ucp1-/- rats. Brown adipose tissue shows signs of decreased activity in Ucp1-/- rats, while mitochondrial lipid metabolism markers in white adipose tissue and skeletal muscle were increased. Ucp1-/- rats display more visible shivering and energy expenditure than controls at 4o C. Skeletal muscle transcriptomics showed more differences between genotypes at 23o C than at 4o C.
CONCLUSION: Room temperature presents sufficient cold stress to rats lacking Ucp1 to activate compensatory thermogenic mechanisms in skeletal muscle, which are only activated in control rats following exposure to 4o C. These results provide novel insight into thermogenic responses to Ucp1-deficiency; and highlight Ucp1-/- rats as an attractive translational model for the study of thermogenesis.

Keywords:  Ucp1; brown adipose tissue; non-shivering thermogenesis; thermogenesis

DOI:  https://doi.org/10.1111/apha.13935
Antioxidants (Basel). 2022 Dec 26. pii: 49. [Epub ahead of print]12(1):

Anmyungambi Decoction Ameliorates Obesity through Activation of Non-Shivering Thermogenesis in Brown and White Adipose Tissues.

Woo Yong Park, Gahee Song, Mina Boo, Hyo In Kim, Ja Yeon Park, Se Jin Jung, Minji Choi, Beomsu Kim, Young Doo Kim, Myung-Ho Kim, Kwan-Il Kim, Hyun Jeong Kwak, Jungtae Leem, Jae-Young Um, Jinbong Park.

  Obesity is a burden to global health. Non-shivering thermogenesis of brown adipose tissue (BAT) and white adipose tissue (WAT) is a novel strategy for obesity treatment. Anmyungambi (AMGB) decoction is a multi-herb decoction with clinical anti-obesity effects. Here, we show the effects of AMGB decoction using high-fat diet (HFD)-fed C57BL6/J mice. All four versions of AMGB decoction (100 mg/kg/day, oral gavage for 28 days) suppressed body weight gain and obesity-related blood parameters in the HFD-fed obese mice. They also inhibited adipogenesis and induced lipolysis in inguinal WAT (iWAT). Especially, the AMGB-4 with 2:1:3:3 composition was the most effective; thus, further studies were performed with the AMGB-4 decoction. The AMGB-4 decoction displayed a dose-dependent body weight gain suppression. Serum triglyceride, total cholesterol, and blood glucose decreased as well. In epididymal WAT, iWAT, and BAT, the AMGB-4 decoction increased lipolysis markers. Additionally, the AMGB-4 decoction-fed mice showed an increased non-shivering thermogenic program in BAT and iWAT. Excessive reactive oxygen species (ROS) and suppressed antioxidative factors induced by the HFD feeding were also altered to normal levels by the AMGB-4 decoction treatment. Overall, our study supports the clinical use of AMGB decoction for obesity treatment by studying its mechanisms. AMGB decoction alleviates obesity through the activation of the lipolysis-thermogenesis program and the elimination of pathological ROS in thermogenic adipose tissues.

Keywords:  AMP-activated protein kinase; Anmyungambi decoction; beige adipocytes; brown adipose tissue; lipolysis; non-shivering thermogenesis; obesity; reactive oxygen species

DOI:  https://doi.org/10.3390/antiox12010049
J Biol Chem. 2023 Jan 12. pii: S0021-9258(23)00036-4. [Epub ahead of print] 102904

Goldilocks calcium concentrations and the regulation of oxidative phosphorylation: too much, too little, or just right.

Eloisa A Vilas-Boas, João Victor Cabral-Costa, Vitor M Ramos, Camille C Caldeira da Silva, Alicia J Kowaltowski.

  Calcium (Ca2+) is a key regulator in diverse intracellular signaling pathways, and has long been implicated in metabolic control and mitochondrial function. Mitochondria can actively take up large amounts of Ca2+, thereby acting as important intracellular Ca2+ buffers and affecting cytosolic Ca2+ transients. Excessive mitochondrial matrix Ca2+ is known to be deleterious due to opening of the mitochondrial permeability transition pore (mPTP) and consequent membrane potential dissipation, leading to mitochondrial swelling, rupture, and cell death. Moderate Ca2+ within the organelle, on the other hand, can directly or indirectly activate mitochondrial matrix enzymes, possibly impacting on ATP production. Here, we aimed to determine in a quantitative manner if extra or intramitochondrial Ca2+ modulate oxidative phosphorylation in mouse liver mitochondria and intact hepatocyte cell lines. To do so, we monitored the effects of more modest versus supra-physiological increases in cytosolic and mitochondrial Ca2+ on oxygen consumption rates. Isolated mitochondria present increased respiratory control ratios (a measure of oxidative phosphorylation efficiency) when incubated with low (2.4 ± 0.6 μM) and medium (22.0 ± 2.4 μM) Ca2+ concentrations in the presence of complex I-linked substrates pyruvate plus malate and α-ketoglutarate, respectively, but not complex II-linked succinate. In intact cells, both low and high cytosolic Ca2+ led to decreased respiratory rates, while ideal rates were present under physiological conditions. High Ca2+ decreased mitochondrial respiration in a substrate-dependent manner, mediated by mPTP. Overall, our results uncover a Goldilocks effect of Ca2+ on liver mitochondria, with specific "just right" concentrations that activate oxidative phosphorylation.

Keywords:  calcium transport; electron transfer chain; metabolic flux; mitochondria; oxidative phosphorylation

DOI:  https://doi.org/10.1016/j.jbc.2023.102904
Cell. 2023 Jan 19. pii: S0092-8674(22)01537-9. [Epub ahead of print]186(2): 398-412.e17

Light modulates glucose metabolism by a retina-hypothalamus-brown adipose tissue axis.

Jian-Jun Meng, Jia-Wei Shen, Guang Li, Chang-Jie Ouyang, Jia-Xi Hu, Zi-Shuo Li, Hang Zhao, Yi-Ming Shi, Mei Zhang, Rong Liu, Ju-Tao Chen, Yu-Qian Ma, Huan Zhao, Tian Xue.

  Public health studies indicate that artificial light is a high-risk factor for metabolic disorders. However, the neural mechanism underlying metabolic modulation by light remains elusive. Here, we found that light can acutely decrease glucose tolerance (GT) in mice by activation of intrinsically photosensitive retinal ganglion cells (ipRGCs) innervating the hypothalamic supraoptic nucleus (SON). Vasopressin neurons in the SON project to the paraventricular nucleus, then to the GABAergic neurons in the solitary tract nucleus, and eventually to brown adipose tissue (BAT). Light activation of this neural circuit directly blocks adaptive thermogenesis in BAT, thereby decreasing GT. In humans, light also modulates GT at the temperature where BAT is active. Thus, our work unveils a retina-SON-BAT axis that mediates the effect of light on glucose metabolism, which may explain the connection between artificial light and metabolic dysregulation, suggesting a potential prevention and treatment strategy for managing glucose metabolic disorders.

Keywords:  brain circuit; brown adipose tissue; glucose metabolism; ipRGCs; light; supraoptic nucleus

DOI:  https://doi.org/10.1016/j.cell.2022.12.024
Nat Commun. 2023 Jan 17. 14(1): 266

BMI-adjusted adipose tissue volumes exhibit depot-specific and divergent associations with cardiometabolic diseases.

Saaket Agrawal, Marcus D R Klarqvist, Nathaniel Diamant, Takara L Stanley, Patrick T Ellinor, Nehal N Mehta, Anthony Philippakis, Kenney Ng, Melina Claussnitzer, Steven K Grinspoon, Puneet Batra, Amit V Khera.

For any given body mass index (BMI), individuals vary substantially in fat distribution, and this variation may have important implications for cardiometabolic risk. Here, we study disease associations with BMI-independent variation in visceral (VAT), abdominal subcutaneous (ASAT), and gluteofemoral (GFAT) fat depots in 40,032 individuals of the UK Biobank with body MRI. We apply deep learning models based on two-dimensional body MRI projections to enable near-perfect estimation of fat depot volumes (R2 in heldout dataset = 0.978-0.991 for VAT, ASAT, and GFAT). Next, we derive BMI-adjusted metrics for each fat depot (e.g. VAT adjusted for BMI, VATadjBMI) to quantify local adiposity burden. VATadjBMI is associated with increased risk of type 2 diabetes and coronary artery disease, ASATadjBMI is largely neutral, and GFATadjBMI is associated with reduced risk. These results - describing three metabolically distinct fat depots at scale - clarify the cardiometabolic impact of BMI-independent differences in body fat distribution.

DOI: https://doi.org/10.1038/s41467-022-35704-5
Biochim Biophys Acta Mol Cell Res. 2023 Jan 12. pii: S0167-4889(22)00207-5. [Epub ahead of print]1870(3): 119415

Discovery and validation of new Hv1 proton channel inhibitors with onco-therapeutic potential.

Antoun El Chemaly, Vincent Jaquet, Yves Cambet, Aurélie Caillon, Ophélie Cherpin, Alexia Balafa, Karl-Heinz Krause, Nicolas Demaurex.

  The voltage-gated hydrogen channel Hv1 encoded in humans by the HVCN1 gene is a highly selective proton channel that allows large fluxes of protons across biological membranes. Hv1 form functional dimers of four transmembrane spanning proteins resembling the voltage sensing domain of potassium channels. Each subunit is highly selective for protons and is controlled by changes in the transmembrane voltage and pH gradient. Hv1 is most expressed in phagocytic cells where it sustains NADPH oxidase-dependent bactericidal function and was reported to facilitate antibody production by B cells and to promote the maturation and motility of spermatocytes. Hv1 contributes to neuroinflammation following brain damage and favors cancer progression possibly by extruding protons generated during aerobic glycolysis of cancer cells. Lack of specific Hv1 inhibitors has hampered translation of this knowledge to treat immune, fertility, or malignancy diseases. In this study, we show that the genetic deletion of Hv1 delays tumor development in a mouse model of granulocytic sarcoma and report the discovery and characterization of two novel bioavailable inhibitors of Hv1 channels that we validate by orthogonal assays and electrophysiological recordings.

Keywords:  Cancer; Ion channels; Oxidases; Pharmacology; Screening; pH homeostasis

DOI:  https://doi.org/10.1016/j.bbamcr.2022.119415
Biology (Basel). 2022 Dec 24. pii: 32. [Epub ahead of print]12(1):

Linoleate-Enrichment of Mitochondrial Cardiolipin Molecular Species Is Developmentally Regulated and a Determinant of Metabolic Phenotype.

Genevieve C Sparagna, Raleigh L Jonscher, Sydney R Shuff, Elisabeth K Phillips, Cortney E Wilson, Kathleen C Woulfe, Anastacia M Garcia, Brian L Stauffer, Kathryn C Chatfield.

  Cardiolipin (CL), the major mitochondrial phospholipid, regulates the activity of many mitochondrial membrane proteins. CL composition is shifted in heart failure with decreases in linoleate and increases in oleate side chains, but whether cardiolipin composition directly regulates metabolism is unknown. This study defines cardiolipin composition in rat heart and liver at three distinct ages to determine the influence of CL composition on beta-oxidation (ß-OX). CL species, expression of ß-OX and glycolytic genes, and carnitine palmitoyltransferase (CPT) activity were characterized in heart and liver from neonatal, juvenile, and adult rats. Ventricular myocytes were cultured from neonatal, juvenile, and adult rats and cardiolipin composition and CPT activity were measured. Cardiolipin composition in neonatal rat ventricular cardiomyocytes (NRVMs) was experimentally altered and mitochondrial respiration was assessed. Linoleate-enrichment of CL was observed in rat heart, but not liver, with increasing age. ß-OX genes and CPT activity were generally higher in adult heart and glycolytic genes lower, as a function of age, in contrast to liver. Palmitate oxidation increased in NRVMs when CL was enriched with linoleate. Our results indicate (1) CL is developmentally regulated, (2) linoleate-enrichment is associated with increased ß-OX and a more oxidative mitochondrial phenotype, and (3) experimentally induced linoleate-enriched CL in ventricular myocytes promotes a shift from pyruvate metabolism to fatty acid ß-OX.

Keywords:  beta-oxidation; cardiolipin; fatty acid; heart; linoleic acid; liver; metabolism; mitochondria; rat

DOI:  https://doi.org/10.3390/biology12010032
Nat Microbiol. 2023 Jan 16.

Energetics and evolution of anaerobic microbial eukaryotes.

Sergio A Muñoz-Gómez.

Mitochondria and aerobic respiration have been suggested to be required for the evolution of eukaryotic cell complexity. Aerobic respiration is several times more energetically efficient than fermentation. Moreover, aerobic respiration occurs at internalized mitochondrial membranes that are not constrained by a sublinear scaling with cell volume. However, diverse and complex anaerobic eukaryotes (for example, free-living and parasitic unicellular, and even small multicellular, eukaryotes) that exclusively rely on fermentation for energy generation have evolved repeatedly from aerobic ancestors. How do fermenting eukaryotes maintain their cell volumes and complexity while relying on such a low energy-yielding process? Here I propose that reduced rates of ATP generation in fermenting versus respiring eukaryotes are compensated for by longer cell cycles that satisfy lifetime energy demands. A literature survey and growth efficiency calculations show that fermenting eukaryotes divide approximately four to six times slower than aerobically respiring counterparts with similar cell volumes. Although ecological advantages such as competition avoidance offset lower growth rates and yields in the short term, fermenting eukaryotes inevitably have fewer physiological and ecological possibilities, which ultimately constrain their long-term evolutionary trajectories.

DOI: https://doi.org/10.1038/s41564-022-01299-2
Biophys J. 2023 Jan 17. pii: S0006-3495(23)00031-0. [Epub ahead of print]

ION CHANNEL THERMODYNAMICS STUDIED WITH TEMPERATURE JUMPS MEASURED AT THE CELL MEMBRANE.

Carlos A Z Bassetto, Bernardo I Pinto, Ramon Latorre, Francisco Bezanilla.

Perturbing the temperature of a system modifies its energy landscape thus providing a ubiquitous tool to understand biological processes. Here, we developed a framework to generate sudden temperature jumps (Tjumps) and sustained temperature steps (Tsteps) to study the temperature dependence of membrane proteins under voltage-clamp, while measuring the membrane temperature. Utilizing the melanin under the Xenopus laevis oocytes membrane as a photothermal transducer, we achieved short Tjumps up to 10 ºC in less than 1.5 ms and constant Tsteps for durations up to 150 ms. We followed the temperature at the membrane with submillisecond time resolution by measuring the time-course of membrane capacitance, which is linearly related to temperature. We applied Tjumps in Kir 1.1b, which reveals a highly temperature-sensitive blockage relief and characterized the effects of Tsteps on the temperature-sensitive channels TRPM8 and TRPV1. These newly developed approaches provide a general tool to study membrane proteins thermodynamics.

DOI: https://doi.org/10.1016/j.bpj.2023.01.015