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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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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3
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Sumalde AAM, Scholes MA, Kalmanson OA, Terhune EA, Frejo L, Wethey CI, Roman-Naranjo P, Carry PM, Gubbels SP, Lopez-Escamez JA, Hadley-Miller N, Santos-Cortez RLP. Rare Coding Variants in Patients with Non-Syndromic Vestibular Dysfunction. Genes (Basel) 2023; 14:831. [PMID: 37107589 PMCID: PMC10137884 DOI: 10.3390/genes14040831] [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: 03/08/2023] [Revised: 03/25/2023] [Accepted: 03/27/2023] [Indexed: 04/29/2023] Open
Abstract
Vertigo due to vestibular dysfunction is rare in children. The elucidation of its etiology will improve clinical management and the quality of life of patients. Genes for vestibular dysfunction were previously identified in patients with both hearing loss and vertigo. This study aimed to identify rare, coding variants in children with peripheral vertigo but no hearing loss, and in patients with potentially overlapping phenotypes, namely, Meniere's disease or idiopathic scoliosis. Rare variants were selected from the exome sequence data of 5 American children with vertigo, 226 Spanish patients with Meniere's disease, and 38 European-American probands with scoliosis. In children with vertigo, 17 variants were found in 15 genes involved in migraine, musculoskeletal phenotypes, and vestibular development. Three genes, OTOP1, HMX3, and LAMA2, have knockout mouse models for vestibular dysfunction. Moreover, HMX3 and LAMA2 were expressed in human vestibular tissues. Rare variants within ECM1, OTOP1, and OTOP2 were each identified in three adult patients with Meniere's disease. Additionally, an OTOP1 variant was identified in 11 adolescents with lateral semicircular canal asymmetry, 10 of whom have scoliosis. We hypothesize that peripheral vestibular dysfunction in children may be due to multiple rare variants within genes that are involved in the inner ear structure, migraine, and musculoskeletal disease.
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Affiliation(s)
- Angelo Augusto M. Sumalde
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Department of Otolaryngology-Head and Neck Surgery, University of the Philippines Manila College of Medicine, Philippine General Hospital, Manila 1000, Philippines
| | - Melissa A. Scholes
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Department of Pediatric Otolaryngology, Children’s Hospital Colorado, Aurora, CO 80045, USA
- Department of Otolaryngology-Head and Neck Surgery, University of Mississippi Medical Center, Jackson, MS 39216, USA
| | - Olivia A. Kalmanson
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Elizabeth A. Terhune
- Department of Orthopedics, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Lidia Frejo
- Otology and Neurotology Group CTS495, Department of Genomic Medicine, GENYO-Centre for Genomics and Oncological Research-Pfizer-University of Granada-Junta de Andalucia, PTS, 18016 Granada, Spain
- Division of Otolaryngology, Department of Surgery, Instituto de Investigación Biosanitaria, ibs.GRANADA, Universidad de Granada, 18071 Granada, Spain
| | - Cambria I. Wethey
- Department of Orthopedics, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Pablo Roman-Naranjo
- Otology and Neurotology Group CTS495, Department of Genomic Medicine, GENYO-Centre for Genomics and Oncological Research-Pfizer-University of Granada-Junta de Andalucia, PTS, 18016 Granada, Spain
- Division of Otolaryngology, Department of Surgery, Instituto de Investigación Biosanitaria, ibs.GRANADA, Universidad de Granada, 18071 Granada, Spain
| | - Patrick M. Carry
- Department of Orthopedics, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Musculoskeletal Research Center, Children’s Hospital Colorado, Aurora, CO 80045, USA
| | - Samuel P. Gubbels
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Jose A. Lopez-Escamez
- Otology and Neurotology Group CTS495, Department of Genomic Medicine, GENYO-Centre for Genomics and Oncological Research-Pfizer-University of Granada-Junta de Andalucia, PTS, 18016 Granada, Spain
- Division of Otolaryngology, Department of Surgery, Instituto de Investigación Biosanitaria, ibs.GRANADA, Universidad de Granada, 18071 Granada, Spain
- Meniere’s Disease Neuroscience Research Program, Faculty of Medicine & Health, School of Medical Sciences, The Kolling Institute, University of Sydney, Sydney, NSW 2006, Australia
| | - Nancy Hadley-Miller
- Department of Orthopedics, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Musculoskeletal Research Center, Children’s Hospital Colorado, Aurora, CO 80045, USA
| | - Regie Lyn P. Santos-Cortez
- Department of Otolaryngology-Head and Neck Surgery, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Center for Children’s Surgery, Children’s Hospital Colorado, Aurora, CO 80045, USA
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4
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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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5
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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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6
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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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7
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Abstract
Sour taste, the taste of acids, is one of the most enigmatic of the five basic taste qualities; its function is unclear and its receptor was until recently unknown. Sour tastes are transduced in taste buds on the tongue and palate epithelium by a subset of taste receptor cells, known as type III cells. Type III cells express a number of unique markers, including the PKD2L1 gene, which allow for their identification and manipulation. These cells respond to acid stimuli with action potentials and release neurotransmitters onto afferent nerve fibers, with cell bodies in geniculate and petrosal ganglia. Here, we review classical studies of sour taste leading up to the identification of the sour receptor as the proton channel, OTOP1. Expected final online publication date for the Annual Review of Physiology, Volume 84 is February 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Heather N Turner
- Department of Biological Sciences, Section of Neurobiology, University of Southern California, Los Angeles, California, USA; ,
| | - Emily R Liman
- Department of Biological Sciences, Section of Neurobiology, University of Southern California, Los Angeles, California, USA; ,
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8
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Chen Q, Zeng W, She J, Bai XC, Jiang Y. Structural and functional characterization of an otopetrin family proton channel. eLife 2019; 8:46710. [PMID: 30973323 PMCID: PMC6483595 DOI: 10.7554/elife.46710] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Accepted: 04/11/2019] [Indexed: 12/14/2022] Open
Abstract
The otopetrin (OTOP) proteins were recently characterized as proton channels. Here we present the cryo-EM structure of OTOP3 from Xenopus tropicalis (XtOTOP3) along with functional characterization of the channel. XtOTOP3 forms a homodimer with each subunit containing 12 transmembrane helices that can be divided into two structurally homologous halves; each half assembles as an α-helical barrel that could potentially serve as a proton conduction pore. Both pores open from the extracellular half before becoming occluded at a central constriction point consisting of three highly conserved residues - Gln232/585-Asp262/Asn623-Tyr322/666 (the constriction triads). Mutagenesis shows that the constriction triad from the second pore is less amenable to perturbation than that of the first pore, suggesting an unequal contribution between the two pores to proton transport. We also identified several key residues at the interface between the two pores that are functionally important, particularly Asp509, which confers intracellular pH-dependent desensitization to OTOP channels.
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Affiliation(s)
- Qingfeng Chen
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
| | - Weizhong Zeng
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
| | - Ji She
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
| | - Xiao-Chen Bai
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, United States
| | - Youxing Jiang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States.,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, United States
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9
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RNA sequencing-based analysis of the laying hen uterus revealed the novel genes and biological pathways involved in the eggshell biomineralization. Sci Rep 2018; 8:16853. [PMID: 30443032 PMCID: PMC6237962 DOI: 10.1038/s41598-018-35203-y] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 11/01/2018] [Indexed: 01/04/2023] Open
Abstract
Eggshell is the outermost calcified covering of an egg that protects it from microbial invasion and physical damage, and is critical for egg quality. However, understanding of the genes/proteins and the biological pathways regulating the eggshell formation is still obscure. We hypothesized that the transcriptomic analysis of the chicken uteri using RNA-sequencing may reveal novel genes and biological pathways involved in the eggshell biomineralization. RNA-sequence analysis using uteri of laying hens at 15–20 h post-ovulation (layers, n = 3) and non-laying (non-layers, n = 3) hens was carried out. About 229 differentially expressed genes (DEGs) were up-regulated in the layers compared to the non-layers. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Ingenuity Pathway Analysis (IPA) revealed more than ten novel genes and biological pathways related to calcium transport and mineralization in the uterus. Based on the enriched pathways and molecular function analysis, 12 DEGs related to eggshell mineralization were further analyzed in the uteri of layers (3 h and 15–20 h post-ovulation), non-layers and molters using qPCR. Expressions of OC-116 (regulator of mineralization), OTOP2 (modulator of cellular calcium influx), CALCB (intracellular release of Ca-ions), STC2 (increases alkaline phosphatase activity), and ATP2C2 (cellular import of Ca-ions) were significantly higher in the uteri of laying hen at 15–20 h post-ovulation. This study identified the involvement of novel genes and their proposed biological pathways in the regulation of eggshell formation.
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10
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Behavioral and neurochemical characterization of the mlh mutant mice lacking otoconia. Behav Brain Res 2018; 359:958-966. [PMID: 29913187 DOI: 10.1016/j.bbr.2018.06.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 05/30/2018] [Accepted: 06/14/2018] [Indexed: 01/28/2023]
Abstract
Otoconia are crucial for the correct processing of positional information and orientation. Mice lacking otoconia cannot sense the direction of the gravity vector and cannot swim properly. This study aims to characterize the behavior of mergulhador (mlh), otoconia-deficient mutant mice. Additionally, the central catecholamine levels were evaluated to investigate possible correlations between behaviors and central neurotransmitters. A sequence of behavioral tests was used to evaluate the parameters related to the general activity, sensory nervous system, psychomotor system, and autonomous nervous system, in addition to measuring the acquisition of spatial and declarative memory, anxiety-like behavior, motor coordination, and swimming behavior of the mlh mutant mice. As well, the neurotransmitter levels in the cerebellum, striatum, frontal cortex, and hippocampus were measured. Relative to BALB/c mice, the mutant mlh mice showed 1) reduced locomotor and rearing behavior, increased auricular and touch reflexes, decreased motor coordination and increased micturition; 2) decreased responses in the T-maze and aversive wooden beam tests; 3) increased time of immobility in the tail suspension test; 4) no effects in the elevated plus maze or object recognition test; 5) an inability to swim; and 6) reduced turnover of dopaminergic system in the cerebellum, striatum, and frontal cortex. Thus, in our mlh mutant mice, otoconia deficiency reduced the motor, sensory and spatial learning behaviors likely by impairing balance. We did not rule out the role of the dopaminergic system in all behavioral deficits of the mlh mutant mice.
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11
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Mohajeri K, Cantsilieris S, Huddleston J, Nelson BJ, Coe BP, Campbell CD, Baker C, Harshman L, Munson KM, Kronenberg ZN, Kremitzki M, Raja A, Catacchio CR, Graves TA, Wilson RK, Ventura M, Eichler EE. Interchromosomal core duplicons drive both evolutionary instability and disease susceptibility of the Chromosome 8p23.1 region. Genome Res 2016; 26:1453-1467. [PMID: 27803192 PMCID: PMC5088589 DOI: 10.1101/gr.211284.116] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2016] [Accepted: 09/12/2016] [Indexed: 12/13/2022]
Abstract
Recurrent rearrangements of Chromosome 8p23.1 are associated with congenital heart defects and developmental delay. The complexity of this region has led to inconsistencies in the current reference assembly, confounding studies of genetic variation. Using comparative sequence-based approaches, we generated a high-quality 6.3-Mbp alternate reference assembly of an inverted Chromosome 8p23.1 haplotype. Comparison with nonhuman primates reveals a 746-kbp duplicative transposition and two separate inversion events that arose in the last million years of human evolution. The breakpoints associated with these rearrangements map to an ape-specific interchromosomal core duplicon that clusters at sites of evolutionary inversion (P = 7.8 × 10−5). Refinement of microdeletion breakpoints identifies a subgroup of patients that map to the same interchromosomal core involved in the evolutionary formation of the duplication blocks. Our results define a higher-order genomic instability element that has shaped the structure of specific chromosomes during primate evolution contributing to rearrangements associated with inversion and disease.
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Affiliation(s)
- Kiana Mohajeri
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA
| | - Stuart Cantsilieris
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA
| | - John Huddleston
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA.,Howard Hughes Medical Institute, University of Washington, Seattle, Washington 98195, USA
| | - Bradley J Nelson
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA
| | - Bradley P Coe
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA
| | - Catarina D Campbell
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA
| | - Carl Baker
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA
| | - Lana Harshman
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA
| | - Katherine M Munson
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA
| | - Zev N Kronenberg
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA
| | - Milinn Kremitzki
- The McDonnell Genome Institute at Washington University, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Archana Raja
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA.,Howard Hughes Medical Institute, University of Washington, Seattle, Washington 98195, USA
| | | | - Tina A Graves
- The McDonnell Genome Institute at Washington University, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Richard K Wilson
- The McDonnell Genome Institute at Washington University, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Mario Ventura
- Dipartimento di Biologia, Università degli Studi di Bari Aldo Moro, Bari 70125, Italy
| | - Evan E Eichler
- Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA.,Howard Hughes Medical Institute, University of Washington, Seattle, Washington 98195, USA
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12
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Wang GX, Cho KW, Uhm M, Hu CR, Li S, Cozacov Z, Xu AE, Cheng JX, Saltiel AR, Lumeng CN, Lin JD. Otopetrin 1 protects mice from obesity-associated metabolic dysfunction through attenuating adipose tissue inflammation. Diabetes 2014; 63:1340-52. [PMID: 24379350 PMCID: PMC3964504 DOI: 10.2337/db13-1139] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Chronic low-grade inflammation is emerging as a pathogenic link between obesity and metabolic disease. Persistent immune activation in white adipose tissue (WAT) impairs insulin sensitivity and systemic metabolism, in part, through the actions of proinflammatory cytokines. Whether obesity engages an adaptive mechanism to counteract chronic inflammation in adipose tissues has not been elucidated. Here we identified otopetrin 1 (Otop1) as a component of a counterinflammatory pathway that is induced in WAT during obesity. Otop1 expression is markedly increased in obese mouse WAT and is stimulated by tumor necrosis factor-α in cultured adipocytes. Otop1 mutant mice respond to high-fat diet with pronounced insulin resistance and hepatic steatosis, accompanied by augmented adipose tissue inflammation. Otop1 attenuates interferon-γ (IFN-γ) signaling in adipocytes through selective downregulation of the transcription factor STAT1. Using a tagged vector, we found that Otop1 physically interacts with endogenous STAT1. Thus, Otop1 defines a unique target of cytokine signaling that attenuates obesity-induced adipose tissue inflammation and plays an adaptive role in maintaining metabolic homeostasis in obesity.
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Affiliation(s)
- Guo-Xiao Wang
- Life Sciences Institute, University of Michigan Medical School, Ann Arbor, MI
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI
| | - Kae Won Cho
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI
- Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI
| | - Maeran Uhm
- Life Sciences Institute, University of Michigan Medical School, Ann Arbor, MI
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI
| | - Chun-Rui Hu
- Weldon School of Biomedical Engineering, Department of Chemistry, Purdue University, West Lafayette, IN
| | - Siming Li
- Life Sciences Institute, University of Michigan Medical School, Ann Arbor, MI
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI
| | - Zoharit Cozacov
- Life Sciences Institute, University of Michigan Medical School, Ann Arbor, MI
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI
| | - Acer E. Xu
- Life Sciences Institute, University of Michigan Medical School, Ann Arbor, MI
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI
| | - Ji-Xin Cheng
- Weldon School of Biomedical Engineering, Department of Chemistry, Purdue University, West Lafayette, IN
| | - Alan R. Saltiel
- Life Sciences Institute, University of Michigan Medical School, Ann Arbor, MI
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI
| | - Carey N. Lumeng
- Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI
- Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI
| | - Jiandie D. Lin
- Life Sciences Institute, University of Michigan Medical School, Ann Arbor, MI
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI
- Corresponding author: Jiandie D. Lin,
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13
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Powers TR, Virk SM, Trujillo-Provencio C, Serrano EE. Probing the Xenopus laevis inner ear transcriptome for biological function. BMC Genomics 2012; 13:225. [PMID: 22676585 PMCID: PMC3532188 DOI: 10.1186/1471-2164-13-225] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Accepted: 05/21/2012] [Indexed: 01/27/2023] Open
Abstract
Background The senses of hearing and balance depend upon mechanoreception, a process that originates in the inner ear and shares features across species. Amphibians have been widely used for physiological studies of mechanotransduction by sensory hair cells. In contrast, much less is known of the genetic basis of auditory and vestibular function in this class of animals. Among amphibians, the genus Xenopus is a well-characterized genetic and developmental model that offers unique opportunities for inner ear research because of the amphibian capacity for tissue and organ regeneration. For these reasons, we implemented a functional genomics approach as a means to undertake a large-scale analysis of the Xenopus laevis inner ear transcriptome through microarray analysis. Results Microarray analysis uncovered genes within the X. laevis inner ear transcriptome associated with inner ear function and impairment in other organisms, thereby supporting the inclusion of Xenopus in cross-species genetic studies of the inner ear. The use of gene categories (inner ear tissue; deafness; ion channels; ion transporters; transcription factors) facilitated the assignment of functional significance to probe set identifiers. We enhanced the biological relevance of our microarray data by using a variety of curation approaches to increase the annotation of the Affymetrix GeneChip® Xenopus laevis Genome array. In addition, annotation analysis revealed the prevalence of inner ear transcripts represented by probe set identifiers that lack functional characterization. Conclusions We identified an abundance of targets for genetic analysis of auditory and vestibular function. The orthologues to human genes with known inner ear function and the highly expressed transcripts that lack annotation are particularly interesting candidates for future analyses. We used informatics approaches to impart biologically relevant information to the Xenopus inner ear transcriptome, thereby addressing the impediment imposed by insufficient gene annotation. These findings heighten the relevance of Xenopus as a model organism for genetic investigations of inner ear organogenesis, morphogenesis, and regeneration.
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Affiliation(s)
- TuShun R Powers
- Biology Department, New Mexico State University, Las Cruces, USA
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