1
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DeCoursey TE. Transcendent Aspects of Proton Channels. Annu Rev Physiol 2024; 86:357-377. [PMID: 37931166 PMCID: PMC10938948 DOI: 10.1146/annurev-physiol-042222-023242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
A handful of biological proton-selective ion channels exist. Some open at positive or negative membrane potentials, others open at low or high pH, and some are light activated. This review focuses on common features that result from the unique properties of protons. Proton conduction through water or proteins differs qualitatively from that of all other ions. Extraordinary proton selectivity is needed to ensure that protons permeate and other ions do not. Proton selectivity arises from a proton pathway comprising a hydrogen-bonded chain that typically includes at least one titratable amino acid side chain. The enormously diverse functions of proton channels in disparate regions of the phylogenetic tree can be summarized by considering the chemical and electrical consequences of proton flux across membranes. This review discusses examples of cells in which proton efflux serves to increase pHi, decrease pHo, control the membrane potential, generate action potentials, or compensate transmembrane movement of electrical charge.
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Affiliation(s)
- Thomas E DeCoursey
- Department of Physiology & Biophysics, Rush University, Chicago, Illinois, USA;
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2
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Fung CW, Chau KY, Tong DCS, Knox C, Tam SST, Tan SY, Loi DSC, Leung Z, Xu Y, Lan Y, Qian PY, Chan KYK, Wu AR. Parentage influence on gene expression under acidification revealed through single-embryo sequencing. Mol Ecol 2023; 32:6796-6808. [PMID: 37888909 DOI: 10.1111/mec.17148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Revised: 09/06/2023] [Accepted: 09/18/2023] [Indexed: 10/28/2023]
Abstract
The dissolution of anthropogenic carbon dioxide (CO2 ) in seawater has altered its carbonate chemistry in the process of ocean acidification (OA). OA affects the viability of marine species. In particular, calcifying organisms and their early planktonic larval stages are considered vulnerable. These organisms often utilize energy reserves for metabolism rather than growth and calcification as supported by bulk RNA-sequencing (RNA-seq) experiments. Yet, transcriptomic profiling of a bulk sample reflects the average gene expression of the population, neglecting the variations between individuals, which forms the basis for natural selection. Here, we used single-embryo RNA-seq on larval sea urchin Heliocidaris crassispina, which is a commercially and ecologically valuable species in East Asia, to document gene expression changes to OA at an individual and family level. Three paternal half-sibs groups were fertilized and exposed to 3 pH conditions (ambient pH 8.0, 7.7 and 7.4) for 12 h prior to sequencing and oxygen consumption assay. The resulting transcriptomic profile of all embryos can be distinguished into four clusters, with differences in gene expressions that govern biomineralization, cell differentiation and patterning, as well as metabolism. While these responses were influenced by pH conditions, the male identities also had an effect. Specifically, a regression model and goodness of fit tests indicated a significant interaction between sire and pH on the probability of embryo membership in different clusters of gene expression. The single-embryo RNA-seq approach is promising in climate stressor research because not only does it highlight potential impacts before phenotypic changes were observed, but it also highlights variations between individuals and lineages, thus enabling a better determination of evolutionary potential.
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Affiliation(s)
- Cheuk Wang Fung
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Kin Yung Chau
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Daniel Chun Sang Tong
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Claire Knox
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Sindy Sing Ting Tam
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Sin Yen Tan
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Danson Shek Chun Loi
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Ziuwin Leung
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Ying Xu
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Yi Lan
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
- Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Pei-Yuan Qian
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
- Department of Ocean Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
| | - Kit Yu Karen Chan
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
- Biology Department, Swarthmore College, Swarthmore, Pennsylvania, USA
| | - Angela Ruohao Wu
- Division of Life Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
- Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Hong Kong SAR, China
- Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, China
- Center for Aging Science, The Hong Kong University of Science and Technology, Hong Kong SAR, China
- State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong SAR, China
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3
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Tu YH, Liu N, Xiao C, Gavrilova O, Reitman ML. Loss of Otopetrin 1 affects thermoregulation during fasting in mice. PLoS One 2023; 18:e0292610. [PMID: 37812612 PMCID: PMC10561838 DOI: 10.1371/journal.pone.0292610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 09/09/2023] [Indexed: 10/11/2023] Open
Abstract
OBJECTIVE Otopetrin 1 (OTOP1) is a proton channel that is highly expressed in brown adipose tissue. We examined the physiology of Otop1-/- mice, which lack functional OTOP1. METHODS Mice were studied by indirect calorimetry and telemetric ambulatory body temperature monitoring. Mitochondrial function was measured as oxygen consumption and extracellular acidification. RESULTS Otop1-/- mice had similar body temperatures as control mice at baseline and in response to cold and hot ambient temperatures. However, in response to fasting the Otop1-/- mice exhibited an exaggerated hypothermia and hypometabolism. Similarly, in ex vivo tests of Otop1-/- brown adipose tissue mitochondrial function, there was no change in baseline oxygen consumption, but the oxygen consumption was reduced after maximal uncoupling with FCCP and increased upon stimulation with the β3-adrenergic agonist CL316243. Mast cells also express Otop1, and Otop1-/- mice had intact, possibly greater hypothermia in response to mast cell activation by the adenosine A3 receptor agonist MRS5698. No increase in insulin resistance was observed in the Otop1-/- mice. CONCLUSIONS Loss of OTOP1 does not change basal function of brown adipose tissue but affects stimulated responses.
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Affiliation(s)
- Yu-Hsiang Tu
- Diabetes, Endocrinology and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States of America
| | - Naili Liu
- Mouse Metabolism Core, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States of America
| | - Cuiying Xiao
- Diabetes, Endocrinology and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States of America
| | - Oksana Gavrilova
- Mouse Metabolism Core, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States of America
| | - Marc L. Reitman
- Diabetes, Endocrinology and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States of America
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4
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Liang Z, Wilson CE, Teng B, Kinnamon SC, Liman ER. The proton channel OTOP1 is a sensor for the taste of ammonium chloride. Nat Commun 2023; 14:6194. [PMID: 37798269 PMCID: PMC10556057 DOI: 10.1038/s41467-023-41637-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Accepted: 09/12/2023] [Indexed: 10/07/2023] Open
Abstract
Ammonium (NH4+), a breakdown product of amino acids that can be toxic at high levels, is detected by taste systems of organisms ranging from C. elegans to humans and has been used for decades in vertebrate taste research. Here we report that OTOP1, a proton-selective ion channel expressed in sour (Type III) taste receptor cells (TRCs), functions as sensor for ammonium chloride (NH4Cl). Extracellular NH4Cl evoked large dose-dependent inward currents in HEK-293 cells expressing murine OTOP1 (mOTOP1), human OTOP1 and other species variants of OTOP1, that correlated with its ability to alkalinize the cell cytosol. Mutation of a conserved intracellular arginine residue (R292) in the mOTOP1 tm 6-tm 7 linker specifically decreased responses to NH4Cl relative to acid stimuli. Taste responses to NH4Cl measured from isolated Type III TRCs, or gustatory nerves were strongly attenuated or eliminated in an Otop1-/- mouse strain. Behavioral aversion of mice to NH4Cl, reduced in Skn-1a-/- mice lacking Type II TRCs, was entirely abolished in a double knockout with Otop1. These data together reveal an unexpected role for the proton channel OTOP1 in mediating a major component of the taste of NH4Cl and a previously undescribed channel activation mechanism.
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Affiliation(s)
- Ziyu Liang
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
- Program in Neuroscience, University of Southern California, Los Angeles, CA, 90089, USA
| | - Courtney E Wilson
- Department of Otolaryngology, University of Colorado Medical School, 12700 E 19(th) Avenue, MS 8606, Aurora, CO, 80045, USA
| | - Bochuan Teng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA
- Program in Neuroscience, University of Southern California, Los Angeles, CA, 90089, USA
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Sue C Kinnamon
- Department of Otolaryngology, University of Colorado Medical School, 12700 E 19(th) Avenue, MS 8606, Aurora, CO, 80045, USA
| | - Emily R Liman
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, CA, 90089, USA.
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5
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Hildebrand J, Chang WW, Hu MY, Stumpp M. Characterization of digestive proteases in the gut of a basal deuterostome. J Exp Biol 2023; 226:jeb245789. [PMID: 37470128 DOI: 10.1242/jeb.245789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 07/12/2023] [Indexed: 07/21/2023]
Abstract
Digestive systems are complex organs that allow organisms to absorb energy from their environment to fuel vital processes such as growth, development and the maintenance of homeostasis. A comprehensive understanding of digestive physiology is therefore essential to fully understand the energetics of an organism. The digestion of proteins is of particular importance because most heterotrophic organisms are not able to synthesize all essential amino acids. While Echinoderms are basal deuterostomes that share a large genetic similarity with vertebrates, their digestion physiology remains largely unexplored. Using a genetic approach, this work demonstrated that several protease genes including an enteropeptidase, aminopeptidase, carboxypeptidase and trypsin involved in mammalian digestive networks are also found in sea urchin larvae. Through characterization including perturbation experiments with different food treatments and pharmacological inhibition of proteases using specific inhibitors, as well as transcriptomic analysis, we conclude that the trypsin-2 gene codes for a crucial enzyme for protein digestion in Strongylocentrotus purpuratus. Measurements of in vivo digestion rates in the transparent sea urchin larva were not altered by pharmacological inhibition of trypsin (using soybean trypsin inhibitor) or serine proteases (aprotinin), suggesting that proteases are not critically involved in the initial step of microalgal breakdown. This work provides new insights into the digestive physiology of a basal deuterostome and allows comparisons from the molecular to the functional level in the digestive systems of vertebrates and mammals. This knowledge will contribute to a better understanding for conserved digestive mechanisms that evolved in close interaction with their biotic and abiotic environment.
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Affiliation(s)
- Jasper Hildebrand
- Zoological Institute, Christian-Albrechts University of Kiel, 24118 Kiel, Germany
| | - William W Chang
- Institute of Physiology, Christian-Albrechts University of Kiel, 24118 Kiel, Germany
| | - Marian Y Hu
- Institute of Physiology, Christian-Albrechts University of Kiel, 24118 Kiel, Germany
| | - Meike Stumpp
- Zoological Institute, Christian-Albrechts University of Kiel, 24118 Kiel, Germany
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6
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Tresguerres M, Kwan GT, Weinrauch A. Evolving views of ionic, osmotic and acid-base regulation in aquatic animals. J Exp Biol 2023; 226:jeb245747. [PMID: 37522267 DOI: 10.1242/jeb.245747] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/01/2023]
Abstract
The regulation of ionic, osmotic and acid-base (IOAB) conditions in biological fluids is among the most fundamental functions in all organisms; being surrounded by water uniquely shapes the IOAB regulatory strategies of water-breathing animals. Throughout its centennial history, Journal of Experimental Biology has established itself as a premier venue for publication of comparative, environmental and evolutionary studies on IOAB regulation. This Review provides a synopsis of IOAB regulation in aquatic animals, some of the most significant research milestones in the field, and evolving views about the underlying cellular mechanisms and their evolutionary implications. It also identifies promising areas for future research and proposes ideas for enhancing the impact of aquatic IOAB research.
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Affiliation(s)
- Martin Tresguerres
- Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92037, USA
| | - Garfield T Kwan
- Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, Davis, CA 95616, USA
| | - Alyssa Weinrauch
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB R3T 2M5, Canada
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7
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Dubicka Z, Bojanowski MJ, Bijma J, Bickmeyer U. Mg-rich amorphous to Mg-low crystalline CaCO 3 pathway in foraminifera. Heliyon 2023; 9:e18331. [PMID: 37519760 PMCID: PMC10375801 DOI: 10.1016/j.heliyon.2023.e18331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 07/13/2023] [Accepted: 07/13/2023] [Indexed: 08/01/2023] Open
Abstract
Calcium carbonate minerals produced by marine organisms play a central role in the global carbon cycle and carbonate sedimentation, which influence the climate by regulating atmospheric CO2 levels. Foraminifera are important marine single-celled organisms that have produced calcite shells for over 300 million years. Here, we present new observations promoting our understanding for foraminiferal biocalcification by studying Amphistegina lessonii. We integrated in vivo confocal autofluorescence and dye fluorescence imaging with elemental analysis of the cell supporting the concept that the calcite shells of foraminifera are produced via deposition of intracellularly formed Mg-rich amorphous calcium carbonate (Mg-ACC) particles that transform into a stable mineral phase. This process is likely accompanied by the activity of endosymbiotic microalgae and seawater-derived endocytic vesicles that provide calcification substrates such as DIC, Ca2+, and Mg2+. The final transformation of semi-liquid amorphous nanoparticles into a crystalline shell was associated with Mg2+ liberation.
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Affiliation(s)
- Zofia Dubicka
- Ecological Chemistry, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, 27-570, Germany
- University of Warsaw, Warsaw, 02-089, Poland
| | | | - Jelle Bijma
- Marine Biogeosciences, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, 27-570, Germany
| | - Ulf Bickmeyer
- Ecological Chemistry, Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, 27-570, Germany
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8
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Teng B, Kaplan J, Liang Z, Chyung KS, Goldschen-Ohm MP, Liman ER. Zinc activation of OTOP proton channels identifies structural elements of the gating apparatus. eLife 2023; 12:85317. [PMID: 37053086 PMCID: PMC10101688 DOI: 10.7554/elife.85317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Accepted: 03/27/2023] [Indexed: 04/14/2023] Open
Abstract
Otopetrin proteins (OTOPs) form proton-selective ion channels that are expressed in diverse cell types where they mediate detection of acids or regulation of pH. In vertebrates there are three family members: OTOP1 is required for formation of otoconia in the vestibular system and it forms the receptor for sour taste, while the functions of OTOP2 and OTOP3 are not yet known. Importantly, the gating mechanisms of any of the OTOP channels are not well understood. Here, we show that zinc (Zn2+), as well as other transition metals including copper (Cu2+), potently activates murine OTOP3 (mOTOP3). Zn2+ pre-exposure increases the magnitude of mOTOP3 currents to a subsequent acid stimulus by as much as 10-fold. In contrast, mOTOP2 currents are insensitive to activation by Zn2+. Swapping the extracellular tm 11-12 linker between mOTOP3 and mOTOP2 was sufficient to eliminate Zn2+ activation of mOTOP3 and confer Zn2+ activation on mOTOP2. Mutation to alanine of H531 and E535 within the tm 11-12 linker and H234 and E238 within the 5-6 linker reduced or eliminated activation of mOTOP3 by Zn2+, indicating that these residues likely contribute to the Zn2+ activating site. Kinetic modeling of the data is consistent with Zn2+ stabilizing the opn2+en state of the channel, competing with H+ for activation of the channels. These results establish the tm 11-12 and tm 5-6 linkers as part of the gating apparatus of OTOP channels and a target for drug discovery. Zn2+ is an essential micronutrient and its activation of OTOP channels will undoubtedly have important physiological sequelae.
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Affiliation(s)
- Bochuan Teng
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, United States
- Program in Neuroscience, University of Southern California, Los Angeles, United States
| | - Joshua Kaplan
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, United States
- Program in Neuroscience, University of Southern California, Los Angeles, United States
| | - Ziyu Liang
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, United States
- Program in Neuroscience, University of Southern California, Los Angeles, United States
| | - Kevin Saejin Chyung
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | | | - Emily Ruth Liman
- Section of Neurobiology, Department of Biological Sciences, University of Southern California, Los Angeles, United States
- Program in Neuroscience, University of Southern California, Los Angeles, United States
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9
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Chang WW, Thies AB, Tresguerres M, Hu MY. Soluble adenylyl cyclase coordinates intracellular pH homeostasis and biomineralization in calcifying cells of a marine animal. Am J Physiol Cell Physiol 2023; 324:C777-C786. [PMID: 36779665 DOI: 10.1152/ajpcell.00524.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023]
Abstract
Biomineralizing cells concentrate dissolved inorganic carbon (DIC) and remove protons from the site of mineral precipitation. However, the molecular regulatory mechanisms that orchestrate pH homeostasis and biomineralization of calcifying cells are poorly understood. Here, we report that the acid-base sensing enzyme soluble adenylyl cyclase (sAC) coordinates intracellular pH (pHi) regulation in the calcifying primary mesenchyme cells (PMCs) of sea urchin larvae. Single-cell transcriptomics, in situ hybridization, and immunocytochemistry elucidated the spatiotemporal expression of sAC during skeletogenesis. Live pHi imaging of PMCs revealed that the downregulation of sAC activity with two structurally unrelated small molecules inhibited pHi regulation of PMCs, an effect that was rescued by the addition of cell-permeable cAMP. Pharmacological sAC inhibition also significantly reduced normal spicule growth and spicule regeneration, establishing a link between PMC pHi regulation and biomineralization. Finally, increased expression of sAC mRNA was detected during skeleton remineralization and exposure to CO2-induced acidification. These findings suggest that transcriptional regulation of sAC is required to promote remineralization and to compensate for acidic stress. This work highlights the central role of sAC in coordinating acid-base regulation and biomineralization in calcifying cells of a marine animal.
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Affiliation(s)
| | - Angus B Thies
- Scripps Institution of Oceanography, University of California San Diego, California, United States
| | - Martin Tresguerres
- Scripps Institution of Oceanography, University of California San Diego, California, United States
| | - Marian Y Hu
- Institute of Physiology, Christian-Albrechts-Universität zu Kiel, Kiel, Germany
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10
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Li S, Al-Sheikh U, Chen Y, Kang L. Nematode homologs of the sour taste receptor Otopetrin1 are evolutionarily conserved acid-sensitive proton channels. Front Cell Dev Biol 2023; 11:1133890. [PMID: 36776560 PMCID: PMC9909269 DOI: 10.3389/fcell.2023.1133890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 01/16/2023] [Indexed: 01/27/2023] Open
Abstract
Numerous taste receptors and related molecules have been identified in vertebrates and invertebrates. Otopetrin1 has recently been identified as mammalian sour taste receptor which is essential for acid sensation. However, whether other Otopetrin proteins are involved in PH-sensing remains unknown. In C. elegans, there are eight otopetrin homologous genes but their expression patterns and functions have not been reported so far. Through heterologous expression in HEK293T cells, we found that ceOTOP1a can be activated by acid in NMDG+ solution without conventional cations, which generated inward currents and can be blocked by zinc ions. Moreover, we found that Otopetrin channels are widely expressed in numerous tissues, especially in sensory neurons in the nematode. These results suggest that the biophysical characteristics of the Otopetrin channels in nematodes are generally conserved. However, a series of single gene mutations of otopetrins, which were constructed by CRISPR-Cas9 method, did not affect either calcium responses in ASH polymodal sensory neurons to acid stimulation or acid avoidance behaviors, suggesting that Otopetrin channels might have diverse functions among species. This study reveals that nematode Otopetrins are evolutionarily conserved acid-sensitive proton channels, and provides a framework for further revealing the function and mechanisms of Otopetrin channels in both invertebrates and vertebrates.
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Affiliation(s)
- Shitian Li
- Department of Neurobiology and Department of Neurosurgery of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China,Liangzhu Laboratory, MOE Frontier Science Center for Brain Science and Brain-machine Integration, State Key Laboratory of Brain-machine Intelligence, Zhejiang University, Hangzhou, China,NHC and CAMS Key Laboratory of Medical Neurobiology, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Umar Al-Sheikh
- Department of Neurobiology and Department of Neurosurgery of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China,Liangzhu Laboratory, MOE Frontier Science Center for Brain Science and Brain-machine Integration, State Key Laboratory of Brain-machine Intelligence, Zhejiang University, Hangzhou, China,NHC and CAMS Key Laboratory of Medical Neurobiology, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Yili Chen
- Department of Neurobiology and Department of Neurosurgery of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China,*Correspondence: Yili Chen, ; Lijun Kang,
| | - Lijun Kang
- Department of Neurobiology and Department of Neurosurgery of the Fourth Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China,Liangzhu Laboratory, MOE Frontier Science Center for Brain Science and Brain-machine Integration, State Key Laboratory of Brain-machine Intelligence, Zhejiang University, Hangzhou, China,NHC and CAMS Key Laboratory of Medical Neurobiology, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China,*Correspondence: Yili Chen, ; Lijun Kang,
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11
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Tian L, Zhang H, Yang S, Luo A, Kamau PM, Hu J, Luo L, Lai R. Vertebrate OTOP1 is also an alkali-activated channel. Nat Commun 2023; 14:26. [PMID: 36596786 PMCID: PMC9810603 DOI: 10.1038/s41467-022-35754-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 12/23/2022] [Indexed: 01/04/2023] Open
Abstract
Although alkaline sensation is critical for survival, alkali-activated receptors are yet to be identified in vertebrates. Here, we showed that the OTOP1 channel can be directly activated by extracellular alkali. Notably, OTOP1 biphasically mediated proton influx and efflux with extracellular acid and base stimulation, respectively. Mutations of K221 and R554 at the S5-S6 and S11-S12 linkers significantly reduced alkali affinity without affecting acid activation, suggesting that different domains are responsible for acid- and alkali-activation of OTOP1. The selectivity for H+ was significantly higher in OTOP1 activated by alkali than that by acid, further suggesting that the two activations might be independent gating processes. Given that the alkali-activation of OTOP1 and the required key residues were conserved in the six representative vertebrates, we cautiously propose that OTOP1 participates in alkaline sensation in vertebrates. Thus, our study identified OTOP1 as an alkali-activated channel.
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Affiliation(s)
- Lifeng Tian
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province/National & Local Joint Engineering Center of Natural Bioactive Peptides, Kunming Institute of Zoology, Chinese Academy of Sciences, 650223, Kunming, Yunnan, China.,National Resource Center for Non-Human Primates, Kunming Primate Research Center/National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, 650107, Kunming, Yunnan, China.,University of Chinese Academy of Sciences, 100049, Beijing, China.,School of Molecular Medicine, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, 310024, Hangzhou, China.,The cancer Hospital of the University of Chinese Academy of Sciences, Institute of Basic Medicine and Cancer (IBMC), Chinese Academy of Sciences, 310022, Hangzhou, China
| | - Hao Zhang
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province/National & Local Joint Engineering Center of Natural Bioactive Peptides, Kunming Institute of Zoology, Chinese Academy of Sciences, 650223, Kunming, Yunnan, China.,National Resource Center for Non-Human Primates, Kunming Primate Research Center/National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, 650107, Kunming, Yunnan, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Shilong Yang
- College of Wildlife and Protected Area, Northeast Forestry University, 150040, Harbin, China
| | - Anna Luo
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province/National & Local Joint Engineering Center of Natural Bioactive Peptides, Kunming Institute of Zoology, Chinese Academy of Sciences, 650223, Kunming, Yunnan, China.,National Resource Center for Non-Human Primates, Kunming Primate Research Center/National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, 650107, Kunming, Yunnan, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Peter Muiruri Kamau
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province/National & Local Joint Engineering Center of Natural Bioactive Peptides, Kunming Institute of Zoology, Chinese Academy of Sciences, 650223, Kunming, Yunnan, China.,National Resource Center for Non-Human Primates, Kunming Primate Research Center/National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, 650107, Kunming, Yunnan, China.,University of Chinese Academy of Sciences, 100049, Beijing, China.,Sino-African Joint Research Center, Kunming Institute of Zoology, Chinese Academy of Sciences, 650223, Kunming, Yunnan, China
| | - Jingmei Hu
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province/National & Local Joint Engineering Center of Natural Bioactive Peptides, Kunming Institute of Zoology, Chinese Academy of Sciences, 650223, Kunming, Yunnan, China.,National Resource Center for Non-Human Primates, Kunming Primate Research Center/National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, 650107, Kunming, Yunnan, China.,University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Lei Luo
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province/National & Local Joint Engineering Center of Natural Bioactive Peptides, Kunming Institute of Zoology, Chinese Academy of Sciences, 650223, Kunming, Yunnan, China. .,National Resource Center for Non-Human Primates, Kunming Primate Research Center/National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, 650107, Kunming, Yunnan, China.
| | - Ren Lai
- Key Laboratory of Animal Models and Human Disease Mechanisms of the Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province/National & Local Joint Engineering Center of Natural Bioactive Peptides, Kunming Institute of Zoology, Chinese Academy of Sciences, 650223, Kunming, Yunnan, China. .,National Resource Center for Non-Human Primates, Kunming Primate Research Center/National Research Facility for Phenotypic & Genetic Analysis of Model Animals (Primate Facility), Kunming Institute of Zoology, Chinese Academy of Sciences, 650107, Kunming, Yunnan, China. .,School of Molecular Medicine, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, 310024, Hangzhou, China. .,Sino-African Joint Research Center, Kunming Institute of Zoology, Chinese Academy of Sciences, 650223, Kunming, Yunnan, China.
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12
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Extracellular carbonic anhydrase activity promotes a carbon concentration mechanism in metazoan calcifying cells. Proc Natl Acad Sci U S A 2022; 119:e2203904119. [PMID: 36161891 DOI: 10.1073/pnas.2203904119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many calcifying organisms utilize metabolic CO2 to generate CaCO3 minerals to harden their shells and skeletons. Carbonic anhydrases are evolutionary ancient enzymes that have been proposed to play a key role in the calcification process, with the underlying mechanisms being little understood. Here, we used the calcifying primary mesenchyme cells (PMCs) of sea urchin larva to study the role of cytosolic (iCAs) and extracellular carbonic anhydrases (eCAs) in the cellular carbon concentration mechanism (CCM). Molecular analyses identified iCAs and eCAs in PMCs and highlight the prominent expression of a glycosylphosphatidylinositol-anchored membrane-bound CA (Cara7). Intracellular pH recordings in combination with CO2 pulse experiments demonstrated iCA activity in PMCs. iCA activity measurements, together with pharmacological approaches, revealed an opposing contribution of iCAs and eCAs on the CCM. H+-selective electrodes were used to demonstrate eCA-catalyzed CO2 hydration rates at the cell surface. Knockdown of Cara7 reduced extracellular CO2 hydration rates accompanied by impaired formation of specific skeletal segments. Finally, reduced pHi regulatory capacities during inhibition and knockdown of Cara7 underscore a role of this eCA in cellular HCO3- uptake. This work reveals the function of CAs in the cellular CCM of a marine calcifying animal. Extracellular hydration of metabolic CO2 by Cara7 coupled to HCO3- uptake mechanisms mitigates the loss of carbon and reduces the cellular proton load during the mineralization process. The findings of this work provide insights into the cellular mechanisms of an ancient biological process that is capable of utilizing CO2 to generate a versatile construction material.
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13
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Ettensohn CA, Guerrero-Santoro J, Khor JM. Lessons from a transcription factor: Alx1 provides insights into gene regulatory networks, cellular reprogramming, and cell type evolution. Curr Top Dev Biol 2022; 146:113-148. [PMID: 35152981 DOI: 10.1016/bs.ctdb.2021.10.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The skeleton-forming cells of sea urchins and other echinoderms have been studied by developmental biologists as models of cell specification and morphogenesis for many decades. The gene regulatory network (GRN) deployed in the embryonic skeletogenic cells of euechinoid sea urchins is one of the best understood in any developing animal. Recent comparative studies have leveraged the information contained in this GRN, bringing renewed attention to the diverse patterns of skeletogenesis within the phylum and the evolutionary basis for this diversity. The homeodomain-containing transcription factor, Alx1, was originally shown to be a core component of the skeletogenic GRN of the sea urchin embryo. Alx1 has since been found to be key regulator of skeletal cell identity throughout the phylum. As such, Alx1 is currently serving as a lens through which multiple developmental processes are being investigated. These include not only GRN organization and evolution, but also cell reprogramming, cell type evolution, and the gene regulatory control of morphogenesis. This review summarizes our current state of knowledge concerning Alx1 and highlights the insights it is yielding into these important developmental and evolutionary processes.
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Affiliation(s)
- Charles A Ettensohn
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, United States.
| | | | - Jian Ming Khor
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, United States
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14
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Teng B, Kaplan JP, Liang Z, Krieger Z, Tu YH, Burendei B, Ward AB, Liman ER. Structural motifs for subtype-specific pH-sensitive gating of vertebrate otopetrin proton channels. eLife 2022; 11:77946. [PMID: 35920807 PMCID: PMC9348849 DOI: 10.7554/elife.77946] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 07/19/2022] [Indexed: 01/05/2023] Open
Abstract
Otopetrin (OTOP) channels are proton-selective ion channels conserved among vertebrates and invertebrates, with no structural similarity to other ion channels. There are three vertebrate OTOP channels (OTOP1, OTOP2, and OTOP3), of which one (OTOP1) functions as a sour taste receptor. Whether extracellular protons gate OTOP channels, in addition to permeating them, was not known. Here, we compare the functional properties of the three murine OTOP channels using patch-clamp recording and cytosolic pH microfluorimetry. We find that OTOP1 and OTOP3 are both steeply activated by extracellular protons, with thresholds of pHo <6.0 and 5.5, respectively, and kinetics that are pH-dependent. In contrast, OTOP2 channels are broadly active over a large pH range (pH 5 pH 10) and carry outward currents in response to extracellular alkalinization (>pH 9.0). Strikingly, we could change the pH-sensitive gating of OTOP2 and OTOP3 channels by swapping extracellular linkers that connect transmembrane domains. Swaps of extracellular linkers in the N domain, comprising transmembrane domains 1-6, tended to change the relative conductance at alkaline pH of chimeric channels, while swaps within the C domain, containing transmembrane domains 7-12, tended to change the rates of OTOP3 current activation. We conclude that members of the OTOP channel family are proton-gated (acid-sensitive) proton channels and that the gating apparatus is distributed across multiple extracellular regions within both the N and C domains of the channels. In addition to the taste system, OTOP channels are expressed in the vertebrate vestibular and digestive systems. The distinct gating properties we describe may allow them to subserve varying cell-type specific functions in these and other biological systems.
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Affiliation(s)
- Bochuan Teng
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States,Program in Neuroscience, University of Southern CaliforniaLos AngelesUnited States
| | - Joshua P Kaplan
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States,Program in Neuroscience, University of Southern CaliforniaLos AngelesUnited States
| | - Ziyu Liang
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States,Program in Neuroscience, University of Southern CaliforniaLos AngelesUnited States
| | - Zachary Krieger
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States
| | - Yu-Hsiang Tu
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesdaUnited States
| | - Batuujin Burendei
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
| | - Andrew B Ward
- Department of Integrative Structural and Computational Biology, The Scripps Research InstituteLa JollaUnited States
| | - Emily R Liman
- Section of Neurobiology, Department of Biological Sciences, University of Southern CaliforniaLos AngelesUnited States,Program in Neuroscience, University of Southern CaliforniaLos AngelesUnited States
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15
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Requirement for an Otopetrin-like protein for acid taste in Drosophila. Proc Natl Acad Sci U S A 2021; 118:2110641118. [PMID: 34911758 PMCID: PMC8713817 DOI: 10.1073/pnas.2110641118] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/01/2021] [Indexed: 11/18/2022] Open
Abstract
Receptors for bitter, sugar, and other tastes have been identified in the fruit fly Drosophila melanogaster, while a broadly tuned receptor for the taste of acid has been elusive. Previous work showed that such a receptor was unlikely to be encoded by a gene within one of the two major families of taste receptors in Drosophila, the "gustatory receptors" and "ionotropic receptors." Here, to identify the acid taste receptor, we tested the contributions of genes encoding proteins distantly related to the mammalian Otopertrin1 (OTOP1) proton channel that functions as a sour receptor in mice. RNA interference (RNAi) knockdown or mutation by CRISPR/Cas9 of one of the genes, Otopetrin-Like A (OtopLA), but not of the others (OtopLB or OtopLC) severely impaired the behavioral rejection to a sweet solution laced with high levels of HCl or carboxylic acids and greatly reduced acid-induced action potentials measured from taste hairs. An isoform of OtopLA that we isolated from the proboscis was sufficient to restore behavioral sensitivity and acid-induced action potential firing in OtopLA mutant flies. At lower concentrations, HCl was attractive to the flies, and this attraction was abolished in the OtopLA mutant. Cell type-specific rescue experiments showed that OtopLA functions in distinct subsets of gustatory receptor neurons for repulsion and attraction to high and low levels of protons, respectively. This work highlights a functional conservation of a sensory receptor in flies and mammals and shows that the same receptor can function in both appetitive and repulsive behaviors.
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