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Kersbergen CJ, Bergles DE. Priming central sound processing circuits through induction of spontaneous activity in the cochlea before hearing onset. Trends Neurosci 2024; 47:522-537. [PMID: 38782701 PMCID: PMC11236524 DOI: 10.1016/j.tins.2024.04.007] [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: 12/22/2023] [Revised: 04/02/2024] [Accepted: 04/26/2024] [Indexed: 05/25/2024]
Abstract
Sensory systems experience a period of intrinsically generated neural activity before maturation is complete and sensory transduction occurs. Here we review evidence describing the mechanisms and functions of this 'spontaneous' activity in the auditory system. Both ex vivo and in vivo studies indicate that this correlated activity is initiated by non-sensory supporting cells within the developing cochlea, which induce depolarization and burst firing of groups of nearby hair cells in the sensory epithelium, activity that is conveyed to auditory neurons that will later process similar sound features. This stereotyped neural burst firing promotes cellular maturation, synaptic refinement, acoustic sensitivity, and establishment of sound-responsive domains in the brain. While sensitive to perturbation, the developing auditory system exhibits remarkable homeostatic mechanisms to preserve periodic burst firing in deaf mice. Preservation of this early spontaneous activity in the context of deafness may enhance the efficacy of later interventions to restore hearing.
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Affiliation(s)
- Calvin J Kersbergen
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA
| | - Dwight E Bergles
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, Baltimore, MD, USA; Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, USA; Department of Otolaryngology - Head and Neck Surgery, Johns Hopkins University, Baltimore, MD, USA; Kavli Neuroscience Discovery Institute, Johns Hopkins University, Baltimore, MD, USA.
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2
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van der Valk WH, van Beelen ESA, Steinhart MR, Nist-Lund C, Osorio D, de Groot JCMJ, Sun L, van Benthem PPG, Koehler KR, Locher H. A single-cell level comparison of human inner ear organoids with the human cochlea and vestibular organs. Cell Rep 2023; 42:112623. [PMID: 37289589 PMCID: PMC10592453 DOI: 10.1016/j.celrep.2023.112623] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 02/21/2023] [Accepted: 05/23/2023] [Indexed: 06/10/2023] Open
Abstract
Inner ear disorders are among the most common congenital abnormalities; however, current tissue culture models lack the cell type diversity to study these disorders and normal otic development. Here, we demonstrate the robustness of human pluripotent stem cell-derived inner ear organoids (IEOs) and evaluate cell type heterogeneity by single-cell transcriptomics. To validate our findings, we construct a single-cell atlas of human fetal and adult inner ear tissue. Our study identifies various cell types in the IEOs including periotic mesenchyme, type I and type II vestibular hair cells, and developing vestibular and cochlear epithelium. Many genes linked to congenital inner ear dysfunction are confirmed to be expressed in these cell types. Additional cell-cell communication analysis within IEOs and fetal tissue highlights the role of endothelial cells on the developing sensory epithelium. These findings provide insights into this organoid model and its potential applications in studying inner ear development and disorders.
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Affiliation(s)
- Wouter H van der Valk
- OtoBiology Leiden, Department of Otorhinolaryngology and Head & Neck Surgery, Leiden University Medical Center, 2333 ZA Leiden, the Netherlands; The Novo Nordisk Foundation Center for Stem Cell Medicine (reNEW), Leiden University Medical Center, 2333 ZA Leiden, the Netherlands; Department of Otolaryngology, Boston Children's Hospital, Boston, MA 02115, USA; F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA; Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA 02115, USA.
| | - Edward S A van Beelen
- OtoBiology Leiden, Department of Otorhinolaryngology and Head & Neck Surgery, Leiden University Medical Center, 2333 ZA Leiden, the Netherlands
| | - Matthew R Steinhart
- Department of Otolaryngology, Boston Children's Hospital, Boston, MA 02115, USA; F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA; Department of Otolaryngology-Head and Neck Surgery, Indiana University School of Medicine, Indianapolis, IN 46202, USA; Medical Neuroscience Graduate Program, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Carl Nist-Lund
- Department of Otolaryngology, Boston Children's Hospital, Boston, MA 02115, USA; F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA; Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA
| | - Daniel Osorio
- Research Computing, Department of Information Technology, Boston Children's Hospital, Boston, MA 02115, USA
| | - John C M J de Groot
- OtoBiology Leiden, Department of Otorhinolaryngology and Head & Neck Surgery, Leiden University Medical Center, 2333 ZA Leiden, the Netherlands
| | - Liang Sun
- Research Computing, Department of Information Technology, Boston Children's Hospital, Boston, MA 02115, USA
| | - Peter Paul G van Benthem
- OtoBiology Leiden, Department of Otorhinolaryngology and Head & Neck Surgery, Leiden University Medical Center, 2333 ZA Leiden, the Netherlands
| | - Karl R Koehler
- Department of Otolaryngology, Boston Children's Hospital, Boston, MA 02115, USA; F.M. Kirby Neurobiology Center, Boston Children's Hospital, Boston, MA 02115, USA; Department of Otolaryngology-Head and Neck Surgery, Harvard Medical School, Boston, MA 02115, USA; Department of Plastic and Oral Surgery, Boston Children's Hospital, Boston, MA 02115, USA.
| | - Heiko Locher
- OtoBiology Leiden, Department of Otorhinolaryngology and Head & Neck Surgery, Leiden University Medical Center, 2333 ZA Leiden, the Netherlands; The Novo Nordisk Foundation Center for Stem Cell Medicine (reNEW), Leiden University Medical Center, 2333 ZA Leiden, the Netherlands.
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3
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Vlajkovic SM, Thorne PR. Purinergic Signalling in the Cochlea. Int J Mol Sci 2022; 23:ijms232314874. [PMID: 36499200 PMCID: PMC9741428 DOI: 10.3390/ijms232314874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 11/24/2022] [Accepted: 11/25/2022] [Indexed: 11/29/2022] Open
Abstract
The mammalian cochlea is the sensory organ of hearing with a delicate, highly organised structure that supports unique operating mechanisms. ATP release from the secretory tissues of the cochlear lateral wall (stria vascularis) triggers numerous physiological responses by activating P2 receptors in sensory, supporting and neural tissues. Two families of P2 receptors, ATP-gated ion channels (P2X receptors) and G protein-coupled P2Y receptors, activate intracellular signalling pathways that regulate cochlear development, homeostasis, sensory transduction, auditory neurotransmission and response to stress. Of particular interest is a purinergic hearing adaptation, which reflects the critical role of the P2X2 receptor in adaptive cochlear response to elevated sound levels. Other P2 receptors are involved in the maturation of neural processes and frequency selectivity refinement in the developing cochlea. Extracellular ATP signalling is regulated by a family of surface-located enzymes collectively known as "ectonucleotidases" that hydrolyse ATP to adenosine. Adenosine is a constitutive cell metabolite with an established role in tissue protection and regeneration. The differential activation of A1 and A2A adenosine receptors defines the cochlear response to injury caused by oxidative stress, inflammation, and activation of apoptotic pathways. A1 receptor agonism, A2A receptor antagonism, and increasing adenosine levels in cochlear fluids all represent promising therapeutic tools for cochlear rescue from injury and prevention of hearing loss.
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Affiliation(s)
- Srdjan M. Vlajkovic
- Department of Physiology and The Eisdell Moore Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
- Correspondence: ; Tel.: +64-9-9239782
| | - Peter R. Thorne
- Department of Physiology and The Eisdell Moore Centre, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
- Section of Audiology, School of Population Health, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
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Köles L, Szepesy J, Berekméri E, Zelles T. Purinergic Signaling and Cochlear Injury-Targeting the Immune System? Int J Mol Sci 2019; 20:ijms20122979. [PMID: 31216722 PMCID: PMC6627352 DOI: 10.3390/ijms20122979] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Revised: 06/14/2019] [Accepted: 06/14/2019] [Indexed: 02/06/2023] Open
Abstract
Hearing impairment is the most common sensory deficit, affecting more than 400 million people worldwide. Sensorineural hearing losses currently lack any specific or efficient pharmacotherapy largely due to the insufficient knowledge of the pathomechanism. Purinergic signaling plays a substantial role in cochlear (patho)physiology. P2 (ionotropic P2X and the metabotropic P2Y) as well as adenosine receptors expressed on cochlear sensory and non-sensory cells are involved mostly in protective mechanisms of the cochlea. They are implicated in the sensitivity adjustment of the receptor cells by a K+ shunt and can attenuate the cochlear amplification by modifying cochlear micromechanics. Cochlear blood flow is also regulated by purines. Here, we propose to comprehend this field with the purine-immune interactions in the cochlea. The role of harmful immune mechanisms in sensorineural hearing losses has been emerging in the horizon of cochlear pathologies. In addition to decreasing hearing sensitivity and increasing cochlear blood supply, influencing the immune system can be the additional avenue for pharmacological targeting of purinergic signaling in the cochlea. Elucidating this complexity of purinergic effects on cochlear functions is necessary and it can result in development of new therapeutic approaches in hearing disabilities, especially in the noise-induced ones.
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Affiliation(s)
- László Köles
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary.
| | - Judit Szepesy
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary.
| | - Eszter Berekméri
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary.
- Department of Ecology, University of Veterinary Medicine, H-1078 Budapest, Hungary.
| | - Tibor Zelles
- Department of Pharmacology and Pharmacotherapy, Semmelweis University, H-1089 Budapest, Hungary.
- Department of Pharmacology, Institute of Experimental Medicine, Hungarian Academy of Sciences, H-1083 Budapest, Hungary.
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Kipper FC, Tamajusuku ASK, Minussi DC, Vargas JE, Battastini AMO, Kaczmarek E, Robson SC, Lenz G, Wink MR. Analysis of NTPDase2 in the cell membrane using fluorescence recovery after photobleaching (FRAP). Cytometry A 2018; 93:232-238. [DOI: 10.1002/cyto.a.23317] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Revised: 12/09/2016] [Accepted: 12/28/2016] [Indexed: 12/21/2022]
Affiliation(s)
- Franciele Cristina Kipper
- Departamento de Ciências Básicas da Saúde e Laboratório de Biologia Celular; Universidade Federal de Ciências da Saúde de Porto Alegre - UFCSPA; Porto Alegre RS Brazil
- Departamento de Biofísica e Centro de Biotecnologia; Universidade Federal do Rio Grande do Sul - UFRGS; Porto Alegre RS Brazil
| | | | - Darlan Conterno Minussi
- Departamento de Ciências Básicas da Saúde e Laboratório de Biologia Celular; Universidade Federal de Ciências da Saúde de Porto Alegre - UFCSPA; Porto Alegre RS Brazil
- Departamento de Biofísica e Centro de Biotecnologia; Universidade Federal do Rio Grande do Sul - UFRGS; Porto Alegre RS Brazil
| | - José Eduardo Vargas
- Instituto de Ciências Biológicas (ICB) - Universidade de Passo Fundo; RS Brazil
| | - Ana Maria Oliveira Battastini
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde; Universidade Federal do Rio Grande do Sul-UFRGS; Porto Alegre RS Brazil
| | - Elzbieta Kaczmarek
- Center for Vascular Biology Research, Department of Surgery; Beth Israel Deaconess Medical Center, Harvard Medical School; Boston Massachusetts
| | - Simon Christopher Robson
- Department of Medicine, Beth Israel Deaconess Medical Center; Harvard Medical School; Boston Massachusetts
| | - Guido Lenz
- Departamento de Biofísica e Centro de Biotecnologia; Universidade Federal do Rio Grande do Sul - UFRGS; Porto Alegre RS Brazil
| | - Márcia Rosângela Wink
- Departamento de Ciências Básicas da Saúde e Laboratório de Biologia Celular; Universidade Federal de Ciências da Saúde de Porto Alegre - UFCSPA; Porto Alegre RS Brazil
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Putative role of border cells in generating spontaneous morphological activity within Kölliker's organ. Hear Res 2015; 330:90-7. [PMID: 26119178 DOI: 10.1016/j.heares.2015.06.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 05/21/2015] [Accepted: 06/23/2015] [Indexed: 11/21/2022]
Abstract
Kölliker's organ is a transient epithelial structure, comprising a major part of the organ of Corti during pre-hearing stages of development. The auditory system is spontaneously active during development, which serves to retain and refine neural connections. Kölliker's organ is considered a key candidate for generating such spontaneous activity, most likely through purinergic (P2 receptor) signalling and inner hair cell (IHC) activation. Associated with the spontaneous neural activity, ATP released locally by epithelial cells induces rhythmic morphological changes within Kölliker's organ, the purpose of which is not understood. These changes are accompanied by a shift in cellular refractive index, allowing optical detection of this activity in real-time. Using this principle, we investigated the origin of spontaneous morphological activity within Kölliker's organ. Apical turns of Wistar rat cochleae (P9-11) were dissected, and the purinergic involvement was studied following acute tissue exposure to a P2 receptor agonist (ATPγS) and antagonist (suramin). ATPγS induced a sustained darkening throughout Kölliker's organ, reversed by suramin. This effect was most pronounced in the region closest to the inner hair cells, which also displayed the highest frequency of intrinsic morphological events. Additionally, suramin alone induced swelling of this region, suggesting a tight regulation of cell volume by ATP-mediated mechanisms. Histological analysis of cochlear tissues demonstrates the most profound volume changes in the border cell region immediately adjacent to the IHCs. Together, these results underline the role of purinergic signalling in initiating morphological events within Kölliker's organ, and suggest a key involvement of border cells surrounding IHCs in regulating this spontaneous activity.
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Ceriani F, Mammano F. Calcium signaling in the cochlea - Molecular mechanisms and physiopathological implications. Cell Commun Signal 2012; 10:20. [PMID: 22788415 PMCID: PMC3408374 DOI: 10.1186/1478-811x-10-20] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 07/12/2012] [Indexed: 12/20/2022] Open
Abstract
Calcium ions (Ca2+) regulate numerous and diverse aspects of cochlear and vestibular physiology. This review focuses on the Ca2+ control of mechanotransduction and synaptic transmission in sensory hair cells, as well as on Ca2+ signalling in non-sensory cells of the developing cochlea.
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Affiliation(s)
- Federico Ceriani
- Dipartimento di Fisica e Astronomia "G, Galilei", Università di Padova, 35131, Padova, Italy.
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8
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Distribution of NTPDase5 and NTPDase6 and the regulation of P2Y receptor signalling in the rat cochlea. Purinergic Signal 2010; 6:249-61. [PMID: 20806016 DOI: 10.1007/s11302-010-9190-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Accepted: 05/26/2010] [Indexed: 10/19/2022] Open
Abstract
Membrane-bound ectonucleoside triphosphate diphosphohydrolases (E-NTPDases) in the inner ear regulate complex extracellular purinergic type-2 (P2) receptor signalling pathways through hydrolysis of extracellular nucleoside 5'-triphosphates and diphosphates. This study investigated the distribution of NTPDase5 and NTPDase6, two intracellular members of the E-NTPDase family, and linked this to regulation of P2 receptor signalling in the adult rat cochlea. These extracellular ectonucleotidases preferentially hydrolyse nucleoside 5'-diphosphates such as UDP and GDP. Expression of both enzymes at mRNA and protein level was detected in cochlear tissues and there was in vivo release of soluble NTPDase5 and 6 into cochlear fluids. Strong NTPDase5 immunostaining was found in the spiral ganglion neurones and supporting Deiters' cells of the organ of Corti, while NTPDase6 was confined to the inner hair cells. Upregulation of NTPDase5 after exposure to loud sound indicates a dynamic role for NTPDase5 in cochlear response to stress, whereas NTPDase6 may have more limited extracellular roles. Noise-induced upregulation of co-localised UDP-preferring P2Y(6) receptors in the spiral ganglion neurons further supports the involvement of NTPDase5 in regulation of P2Y receptor signalling. Noise stress also induced P2Y(14) (UDP- and UDP-glucose preferring) receptor expression in the root processes of the outer sulcus cells, but this was not associated with localization of the E-NTPDases.
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Differential expression of P2Y receptors in the rat cochlea during development. Purinergic Signal 2010; 6:231-48. [PMID: 20806015 DOI: 10.1007/s11302-010-9191-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Accepted: 05/26/2010] [Indexed: 01/16/2023] Open
Abstract
Purinergic signaling has broad physiological significance to the hearing organ, involving signal transduction via ionotropic P2X receptors and metabotropic G-protein-coupled P2Y and P1 (adenosine), alongside conversion of nucleotides and nucleosides by ecto-nucleotidases and ecto-nucleoside diphosphokinase. In addition, ATP release is modulated by acoustic overstimulation or stress and involves feedback regulation. Many of these principal elements of the purinergic signaling complex have been well characterized in the cochlea, while the characterization of P2Y receptor expression is emerging. The present study used immunohistochemistry to evaluate the expression of five P2Y receptors, P2Y(1), P2Y(2), P2Y(4), P2Y(6), and P2Y(12), during development of the rat cochlea. Commencing in the late embryonic period, the P2Y receptors studied were found in the cells lining the cochlear partition, associated with establishment of the electrochemical environment which provides the driving force for sound transduction. In addition, early postnatal P2Y(2) and P2Y(4) protein expression in the greater epithelial ridge, part of the developing hearing organ, supports the view that initiation and regulation of spontaneous activity in the hair cells prior to hearing onset is mediated by purinergic signaling. Sub-cellular compartmentalization of P2Y receptor expression in sensory hair cells, and diversity of receptor expression in the spiral ganglion neurons and their satellite cells, indicates roles for P2Y receptor-mediated Ca(2+)-signaling in sound transduction and auditory neuron excitability. Overall, the dynamics of P2Y receptor expression during development of the cochlea complement the other elements of the purinergic signaling complex and reinforce the significance of extracellular nucleotide and nucleoside signaling to hearing.
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Tritsch NX, Zhang YX, Ellis-Davies G, Bergles DE. ATP-induced morphological changes in supporting cells of the developing cochlea. Purinergic Signal 2010; 6:155-66. [PMID: 20806009 DOI: 10.1007/s11302-010-9189-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2009] [Accepted: 05/23/2010] [Indexed: 01/20/2023] Open
Abstract
The developing cochlea of mammals contains a large group of columnar-shaped cells, which together form a structure known as Kölliker's organ. Prior to the onset of hearing, these inner supporting cells periodically release adenosine 5'-triphosphate (ATP), which activates purinergic receptors in surrounding supporting cells, inner hair cells and the dendrites of primary auditory neurons. Recent studies indicate that purinergic signaling between inner supporting cells and inner hair cells initiates bursts of action potentials in auditory nerve fibers before the onset of hearing. ATP also induces prominent effects in inner supporting cells, including an increase in membrane conductance, a rise in intracellular Ca(2+), and dramatic changes in cell shape, although the importance of ATP signaling in non-sensory cells of the developing cochlea remains unknown. Here, we review current knowledge pertaining to purinergic signaling in supporting cells of Kölliker's organ and focus on the mechanisms by which ATP induces changes in their morphology. We show that these changes in cell shape are preceded by increases in cytoplasmic Ca(2+), and provide new evidence indicating that elevation of intracellular Ca(2+) and IP(3) are sufficient to initiate shape changes. In addition, we discuss the possibility that these ATP-mediated morphological changes reflect crenation following the activation of Ca(2+)-activated Cl(-) channels, and speculate about the possible functions of these changes in cell morphology for maturation of the cochlea.
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Purinergic signaling in cochleovestibular hair cells and afferent neurons. Purinergic Signal 2010; 6:201-9. [PMID: 20806012 DOI: 10.1007/s11302-010-9183-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Accepted: 04/27/2010] [Indexed: 02/04/2023] Open
Abstract
Purinergic signaling in the mammalian cochleovestibular hair cells and afferent neurons is reviewed. The scope includes P2 and P1 receptors in the inner hair cells (IHCs) of the cochlea, the type I spiral ganglion neurons (SGNs) that convey auditory signals from IHCs, the vestibular hair cells (VHCs) in the vestibular end organs (macula in the otolith organs and crista in the semicircular canals), and the vestibular ganglion neurons (VGNs) that transmit postural and rotatory information from VHCs. Various subtypes of P2X ionotropic receptors are expressed in IHCs as well as P2Y metabotropic receptors that mobilize intracellular calcium. Their functional roles still remain speculative, but adenosine 5'-triphosphate (ATP) could regulate the spontaneous activity of the hair cells during development and the receptor potentials of mature hair cells during sound stimulation. In SGNs, P2Y metabotropic receptors activate a nonspecific cation conductance that is permeable to large cations as NMDG(+) and TEA(+). Remarkably, this depolarizing nonspecific conductance in SGNs can also be activated by other metabotropic processes evoked by acetylcholine and tachykinin. The molecular nature and the role of this depolarizing channel are unknown, but its electrophysiological properties suggest that it could lie within the transient receptor potential channel family and could regulate the firing properties of the afferent neurons. Studies on the vestibular partition (VHC and VGN) are sparse but have also shown the expression of P2X and P2Y receptors. There is still little evidence of functional P1 (adenosine) receptors in the afferent system of the inner ear.
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O'Keeffe MG, Thorne PR, Housley GD, Robson SC, Vlajkovic SM. Developmentally regulated expression of ectonucleotidases NTPDase5 and NTPDase6 and UDP-responsive P2Y receptors in the rat cochlea. Histochem Cell Biol 2010; 133:425-36. [PMID: 20217113 DOI: 10.1007/s00418-010-0682-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/15/2010] [Indexed: 12/31/2022]
Abstract
Ectonucleoside triphosphate diphosphohydrolases (E-NTPDases) regulate complex extracellular P2 receptor signalling pathways in mammalian tissues by hydrolysing extracellular nucleotides to the respective nucleosides. All enzymes from this family (NTPDase1-8) are expressed in the adult rat cochlea. This study reports the changes in expression of NTPDase5 and NTPDase6 in the developing rat cochlea. These two intracellular members of the E-NTPDase family can be released in a soluble form and show preference for nucleoside 5'-diphosphates, such as UDP and GDP. Here, we demonstrate differential spatial and temporal patterns for NTPDase5 and NTPDase6 expression during cochlear development, which are indicative of both cytosolic and extracellular action via pyrimidines. NTPDase5 is noted during the early postnatal period in developing sensory hair cells and supporting Deiters' cells of the organ of Corti, and primary auditory neurons located in the spiral ganglion. In contrast, NTPDase6 is confined to the embryonic and early postnatal hair cell bundles. NTPDase6 immunolocalisation in the developing cochlea underpins its putative role in hair cell bundle development, probably via cytosolic action, whilst NTPDase5 may have a broader extracellular role in the development of sensory and neural tissues in the rat cochlea. Both NTPDase5 and NTPDase6 colocalize with UDP-preferring P2Y(4), P2Y(6) and P2Y(14) receptors during cochlear development, but this strong association was lost in the adult cochlea. Spatiotemporal topographic expression of NTPDase5 and NTPDase6 and P2Y receptors in adult and developing cochlear tissues provide strong support for the role of pyrimidinergic signalling in cochlear development.
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Affiliation(s)
- Mary G O'Keeffe
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand
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Duarte-Araújo M, Nascimento C, Timóteo MA, Magalhães-Cardoso MT, Correia-de-Sá P. Relative contribution of ecto-ATPase and ecto-ATPDase pathways to the biphasic effect of ATP on acetylcholine release from myenteric motoneurons. Br J Pharmacol 2009; 156:519-33. [PMID: 19154428 DOI: 10.1111/j.1476-5381.2008.00058.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE The relative contribution of distinct ecto-nucleotidases to the modulation of purinergic signalling may depend on differential tissue distribution and substrate preference. EXPERIMENTAL APPROACH Extracellular ATP catabolism (assessed by high-performance liquid chromatography) and its influence on [(3)H]acetylcholine ([(3)H]ACh) release were investigated in the myenteric plexus of rat ileum in vitro. KEY RESULTS ATP was primarily metabolized via ecto-ATPDase (adenosine 5'-triphosphate diphosphohydrolase) into AMP, which was then dephosphorylated into adenosine by ecto-5'-nucleotidase. Alternative conversion of ATP into ADP by ecto-ATPase (adenosine 5'-triphosphatase) was more relevant at high ATP concentrations. ATP transiently increased basal [(3)H]ACh outflow in a 2',3'-O-(2,4,6-trinitrophenyl)adenosine-5'-triphosphate (TNP-ATP)-dependent, tetrodotoxin-independent manner. ATP and ATPgammaS (adenosine 5'-[gamma-thio]triphosphate), but not alpha,beta-methyleneATP, decreased [(3)H]ACh release induced by electrical stimulation. ADP and ADPbetaS (adenosine 5'[beta-thio]diphosphate) only decreased evoked [(3)H]ACh release. Inhibition by ADPbetaS was prevented by MRS 2179 (2'-deoxy-N(6)-methyl adenosine 3',5'-diphosphate diammonium salt, a selective P2Y(1) antagonist); blockade of ADP inhibition required co-application of MRS 2179 plus adenosine deaminase (which inactivates endogenous adenosine). Blockade of adenosine A(1) receptors with 1,3-dipropyl-8-cyclopentyl xanthine enhanced ADPbetaS inhibition, indicating that P2Y(1) stimulation is cut short by tonic adenosine A(1) receptor activation. MRS 2179 facilitated evoked [(3)H]ACh release, an effect reversed by the ecto-ATPase inhibitor, ARL67156, which delayed ATP conversion into ADP without affecting adenosine levels. CONCLUSIONS AND IMPLICATIONS ATP transiently facilitated [(3)H]ACh release from non-stimulated nerve terminals via prejunctional P2X (probably P2X(2)) receptors. Hydrolysis of ATP directly into AMP by ecto-ATPDase and subsequent formation of adenosine by ecto-5'-nucleotidase reduced [(3)H]ACh release via inhibitory adenosine A(1) receptors. Stimulation of inhibitory P2Y(1) receptors by ADP generated alternatively via ecto-ATPase might be relevant in restraining ACh exocytosis when ATP saturates ecto-ATPDase activity.
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Affiliation(s)
- M Duarte-Araújo
- Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Portugal
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14
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Lee JH, Marcus DC. Purinergic signaling in the inner ear. Hear Res 2007; 235:1-7. [PMID: 17980525 DOI: 10.1016/j.heares.2007.09.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2007] [Revised: 09/17/2007] [Accepted: 09/22/2007] [Indexed: 10/22/2022]
Abstract
Epithelial cells of the inner ear coordinate their ion transport activity through a number of mechanisms. One important mechanism is the autocrine and paracrine signaling among neighboring cells in the ear via nucleotides, such as adenosine, ATP and UTP. This review summarizes observations on the release, detection and degradation of nucleotides by epithelial cells of the inner ear. Purinergic signaling is thought to be important for endolymph ion homeostasis and for protection from acoustic over-stimulation.
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Affiliation(s)
- Jun Ho Lee
- Department of Otorhinolaryngology, Seoul National University College of Medicine, Chongro-gu, Seoul 110-744, Republic of Korea.
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15
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Lee JH, Heo JH, Kim CH, Chang SO, Kim CS, Oh SH. Changes in P2Y4 receptor expression in rat cochlear outer sulcus cells during development. Hear Res 2007; 228:201-11. [PMID: 17433586 DOI: 10.1016/j.heares.2007.02.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2006] [Revised: 01/24/2007] [Accepted: 02/26/2007] [Indexed: 11/29/2022]
Abstract
Extracellular adenosine triphosphate (ATP) released from cellular sources plays an important role in variety of the cochlear physiologic processes. The primary purinergic receptor subtype in the cochlea is the P2X2 receptor, which is a subtype of P2X receptor. This receptor appears to mediate a protective decrease in the electrical driving force in response to acoustic overstimulation. Outer sulcus cells (OSCs) in the cochlear lateral wall appear to maintain an adequate K+ concentration in the cochlear endolymph in response to varying intensities of auditory stimulation. However, little is known about developing OSCs. The purpose of this study was to investigate subtypes of purinergic receptors in developing rat OSCs using a voltage-sensitive vibrating probe. Results showed that only two P2 receptors (P2Y4 and P2X2) contributed to the regulation of short circuit currents in neonatal OSCs. ATP increased cation absorption via apical nonselective cation channels after activating P2Y4 receptors in early neonatal OSCs. P2Y4 expression rapidly declined postnatally and reached near adult levels on postnatal day 14. P2X2 was co-expressed with P2Y4 in early neonatal OSCs. Temporal changes in P2Y4 during OSC development might be involved in the establishment of the endolymphatic ion composition needed for normal auditory transduction and/or specific cellular differentiation.
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Affiliation(s)
- Jun Ho Lee
- Department of Otolaryngology-Head and Neck Surgery, Seoul National University College of Medicine, Seoul National University Hospital, 28 Yeongon-dong, Chongro-gu, Seoul 110-744, Republic of Korea.
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16
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Khan AF, Thorne PR, Muñoz DJB, Wang CJH, Housley GD, Vlajkovic SM. Nucleoside transporter expression and adenosine uptake in the rat cochlea. Neuroreport 2007; 18:235-9. [PMID: 17314663 DOI: 10.1097/wnr.0b013e3280115918] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Even though extracellular adenosine plays multiple roles in the cochlea, the mechanisms that control extracellular adenosine concentrations in this organ are unclear. This study investigated the expression of nucleoside transporters and adenosine uptake in the rat cochlea. Reverse transcription-polymerase chain reaction revealed the expression of mRNA transcripts for two equilibrative (ENT1 and ENT2) and two concentrative (CNT1 and CNT2) nucleoside transporters. Exogenous adenosine perfused through the cochlear perilymphatic compartment was taken up by cells lining the compartment. Adenosine uptake was sensitive to changes in extracellular Na concentrations and inhibited by nitrobenzylthioinosine (an adenosine uptake blocker). The study suggests that the bi-directional nucleoside transport supports the uptake and recycling of purines and regulates the activation of adenosine receptors by altering adenosine concentrations in cochlear fluid spaces.
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Affiliation(s)
- Abdul F Khan
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
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17
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Vlajkovic SM, Abi S, Wang CJH, Housley GD, Thorne PR. Differential distribution of adenosine receptors in rat cochlea. Cell Tissue Res 2007; 328:461-71. [PMID: 17285327 DOI: 10.1007/s00441-006-0374-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2006] [Accepted: 12/22/2006] [Indexed: 12/21/2022]
Abstract
Adenosine is a constitutive cell metabolite that can be released from cells via specific bi-directional transporters and is an end-point for nucleotide hydrolysis. In the extracellular space, adenosine becomes a signalling molecule for P1 (adenosine) receptors that modulate physiological responses in a wide range of mammalian tissues. Whereas adenosine signalling has been implicated in the regulation of cochlear blood flow and in cochlear protection from oxidative damage, the potential roles for adenosine signalling in the modulation of sound transduction and auditory neurotransmission have not been established. We have characterised the expression and distribution of adenosine receptors in the rat cochlea. mRNA transcripts for all four subtypes of adenosine receptors (A(1), A(2A), A(2B) and A(3)) were detected in dissected cochlear tissue by using reverse transcription/polymerase chain reaction analysis. The protein distribution for the A(1), A(2A) and A(3) receptor subtypes was identified by immunoperoxidase histochemistry and confocal immunofluorescence labelling. These receptors were differentially expressed in the organ of Corti, spiral ganglion neurones, lateral wall tissues and cochlear blood vessels. The distribution of adenosine receptors in sensory and neural tissues and in the vasculature coincided with other elements of purinergic signalling (P2X and P2Y receptors, ectonucleotidases), consistent with the integrative regulation of many physiological processes in the cochlea by extracellular nucleotides and nucleosides. Our study provides a framework for further investigation of adenosine signalling in the inner ear, including putative roles in oxidative stress responses.
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MESH Headings
- Animals
- Antibody Specificity
- Cochlea/metabolism
- Gene Expression Regulation
- Male
- RNA, Messenger/metabolism
- Rats
- Rats, Wistar
- Receptor, Adenosine A1/genetics
- Receptor, Adenosine A1/metabolism
- Receptor, Adenosine A2A/genetics
- Receptor, Adenosine A2A/metabolism
- Receptor, Adenosine A3/genetics
- Receptor, Adenosine A3/metabolism
- Receptors, Purinergic P1/genetics
- Receptors, Purinergic P1/metabolism
- Tissue Distribution
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Affiliation(s)
- Srdjan M Vlajkovic
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand.
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18
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Vlajkovic SM, Vinayagamoorthy A, Thorne PR, Robson SC, Wang CJH, Housley GD. Noise-induced up-regulation of NTPDase3 expression in the rat cochlea: Implications for auditory transmission and cochlear protection. Brain Res 2006; 1104:55-63. [PMID: 16815340 DOI: 10.1016/j.brainres.2006.05.094] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2005] [Revised: 05/15/2006] [Accepted: 05/21/2006] [Indexed: 10/24/2022]
Abstract
Stimuli such as noise or hypoxia can induce a release of ATP into the cochlear fluid spaces. At nanomolar concentrations, ATP affects neurotransmission and electrochemical regulation of sound transduction. At higher concentrations, ATP may exert cytotoxicity acting on specific P2X(7) receptor subunits, thus contributing to the pathophysiology of noise-induced cochlear injury. Ectonucleoside triphosphate diphosphohydrolases (E-NTPDases) are pivotal to regulation of extracellular nucleotide concentrations and therefore P2 receptor signaling in the cochlea. Here, we characterize the distribution of NTPDase3 ectonucleotidase (preferentially hydrolyzes ATP over ADP) in cochlear tissues and investigate the effect of noise exposure on NTPDase3 expression. Marked NTPDase3 immunoreactivity in the primary afferent neurones of the spiral ganglion, extending in the distal neurite processes to the synapses beneath the inner and outer hair cells, suggests involvement in auditory neurotransmission. Immunolabeling in the lateral wall and epithelial cells lining the cochlear partition was also evident. Semi-quantitative immunohistochemistry revealed increased NTPDase3 immunolabeling in the synaptic regions of the inner and outer hair cells at sound intensities that induce temporary threshold shift. The results suggest a role for NTPDase3 in regulating ATP signaling associated primarily with auditory neurotransmission, and the potential neuroprotective nature of noise-induced up-regulation of this ectonucleotidase in the cochlea.
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Affiliation(s)
- Srdjan M Vlajkovic
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
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19
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Robson SC, Sévigny J, Zimmermann H. The E-NTPDase family of ectonucleotidases: Structure function relationships and pathophysiological significance. Purinergic Signal 2006; 2:409-30. [PMID: 18404480 PMCID: PMC2254478 DOI: 10.1007/s11302-006-9003-5] [Citation(s) in RCA: 712] [Impact Index Per Article: 39.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Accepted: 01/23/2006] [Indexed: 12/17/2022] Open
Abstract
Ectonucleotidases are ectoenzymes that hydrolyze extracellular nucleotides to the respective nucleosides. Within the past decade, ectonucleotidases belonging to several enzyme families have been discovered, cloned and characterized. In this article, we specifically address the cell surface-located members of the ecto-nucleoside triphosphate diphosphohydrolase (E-NTPDase/CD39) family (NTPDase1,2,3, and 8). The molecular identification of individual NTPDase subtypes, genetic engineering, mutational analyses, and the generation of subtype-specific antibodies have resulted in considerable insights into enzyme structure and function. These advances also allow definition of physiological and patho-physiological implications of NTPDases in a considerable variety of tissues. Biological actions of NTPDases are a consequence (at least in part) of the regulated phosphohydrolytic activity on extracellular nucleotides and consequent effects on P2-receptor signaling. It further appears that the spatial and temporal expression of NTPDases by various cell types within the vasculature, the nervous tissues and other tissues impacts on several patho-physiological processes. Examples include acute effects on cellular metabolism, adhesion, activation and migration with other protracted impacts upon developmental responses, inclusive of cellular proliferation, differentiation and apoptosis, as seen with atherosclerosis, degenerative neurological diseases and immune rejection of transplanted organs and cells. Future clinical applications are expected to involve the development of new therapeutic strategies for transplantation and various inflammatory cardiovascular, gastrointestinal and neurological diseases.
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Affiliation(s)
- Simon C. Robson
- Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts USA
| | - Jean Sévigny
- Centre de Recherche en Rhumatologie et Immunologie, Université Laval, Québec, Québec Canada
| | - Herbert Zimmermann
- Institut fuer Zellbiologie und Neurowissenschaft, Biozentrum der J.W. Goethe-Universitaet, Marie-Curie-Str. 9, D-60439 Frankfurt am Main, Germany
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20
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Housley GD, Marcotti W, Navaratnam D, Yamoah EN. Hair Cells – Beyond the Transducer. J Membr Biol 2006; 209:89-118. [PMID: 16773496 DOI: 10.1007/s00232-005-0835-7] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2005] [Indexed: 02/06/2023]
Abstract
OVERVIEW This review considers the "tween twixt and twain" of hair cell physiology, specifically the signaling elements and membrane conductances which underpin forward and reverse transduction at the input stage of hair cell function and neurotransmitter release at the output stage. Other sections of this review series outline the advances which have been made in understanding the molecular physiology of mechanoelectrical transduction and outer hair cell electromotility. Here we outline the contributions of a considerable array of ion channels and receptor signaling pathways that define the biophysical status of the sensory hair cells, contributing to hair cell development and subsequently defining the operational condition of the hair cells across the broad dynamic range of physiological function.
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Affiliation(s)
- G D Housley
- Department of Physiology, University of Auckland, Private Bag, 92019, Auckland, New Zealand.
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21
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Dulon D, Jagger DJ, Lin X, Davis RL. Neuromodulation in the Spiral Ganglion: Shaping Signals from the Organ of Corti to the CNS. J Membr Biol 2006; 209:167-75. [PMID: 16773500 DOI: 10.1007/s00232-005-0841-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Indexed: 11/25/2022]
Affiliation(s)
- D Dulon
- Laboratoire de Biologie Cellulaire et Moléculaire de l'Audition, Hôpital Pellegrin, INSERM et EA 3665 Université de Bordeaux 2, 33076, Bordeaux, France
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22
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Bobbin RP, Bledsoe SC. Asphyxia and depolarization increase adenosine levels in perilymph. Hear Res 2006; 205:110-4. [PMID: 15953520 DOI: 10.1016/j.heares.2005.03.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2004] [Accepted: 03/10/2005] [Indexed: 11/27/2022]
Abstract
Extracellular adenosine has been suggested as a modulator of cochlear function. To date the release of adenosine into the extracellular spaces of the cochlea has not been demonstrated. Therefore, experiments were designed to examine whether adenosine release into perilymph could be detected in response to depolarization by high potassium concentrations or in response to asphyxia. For this purpose, the perilymph compartment of guinea pigs was perfused with an artificial perilymph and the effluent assayed for ATP, ADP, AMP and adenosine. Results indicate that potassium induced a slight, significant increase and asphyxia induced a very large, significant increase in adenosine levels in perilymph effluent. No changes in the levels of the other compounds were measured. It is concluded that depolarization and asphyxia can induce the release of adenosine into perilymph.
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Affiliation(s)
- Richard P Bobbin
- Kresge Hearing Research Laboratory, Department of Otolaryngology, Louisiana State University Health Sciences Center, New Orleans, LA 70112-2234, USA.
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23
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Belcher SM, Zsarnovszky A, Crawford PA, Hemani H, Spurling L, Kirley TL. Immunolocalization of ecto-nucleoside triphosphate diphosphohydrolase 3 in rat brain: Implications for modulation of multiple homeostatic systems including feeding and sleep–wake behaviors. Neuroscience 2006; 137:1331-46. [PMID: 16338080 DOI: 10.1016/j.neuroscience.2005.08.086] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2004] [Revised: 08/18/2005] [Accepted: 08/28/2005] [Indexed: 12/01/2022]
Abstract
Three anti-peptide antisera were raised against three distinct amino acid sequences of ecto-nucleoside triphosphate diphosphohydrolase 3 (NTPDase3), characterized by Western blot analyses, and used to determine the distribution of NTPDase3 protein in adult rat brain. The three antisera all yielded similar immunolocalization data, leading to increased reliability of the results obtained. Unlike NTPDase1 and NTPDase2, NTPDase3 immunoreactivity was detected exclusively in neurons. Immunoreactivity was localized primarily to axon-like structures with prominent staining of presynaptic elements. Specific perikaryal immunostaining was detected primarily in scattered neurons near the lateral hypothalamic area and the perifornical nucleus. High densities of immunoreactive axon-like fibers were present in midline regions of the forebrain and midbrain. Highly scattered NTPDase3 positive fibers were observed in the cerebral cortex, the hippocampal formation, and the basal ganglia. Moreover, very high densities of immunostained fibers were detected in the mediobasal hypothalamus, with the overall mesencephalic pattern of staining associated closely with hormone responsive nuclei. High densities of NTPDase3 positive terminals were also associated with noradrenergic neurons. However, co-immunolocalization studies revealed clearly that NTPDase3 immunoreactivity was not localized within the noradrenaline cells or terminals. In contrast, nearly all of the NTPDase3 immunopositive hypothalamic cells, and most fibers in the mid- and hindbrain, also expressed hypocretin-1/orexin-A. The overall pattern of expression and co-localization with hypocretin-1/orexin-A suggests that NTPDase3, by regulating the extracellular turnover of ATP, may modulate feeding, sleep-wake, and other behaviors through diverse homeostatic systems.
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Affiliation(s)
- S M Belcher
- Department of Pharmacology and Cell Biophysics, University of Cincinnati, 231 Albert Sabin Way, P.O. Box 670575, Cincinnati, OH 45267-0575, USA
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24
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Wang C, Vlajkovic S, Housley G, Braun N, Zimmermann H, Robson S, Sévigny J, Soeller C, Thorne P. C-terminal splicing of NTPDase2 provides distinctive catalytic properties, cellular distribution and enzyme regulation. Biochem J 2005; 385:729-36. [PMID: 15362980 PMCID: PMC1134748 DOI: 10.1042/bj20040852] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The present study provides functional characterization of alternative splicing of the NTPDase2 (ecto-nucleoside triphosphate diphosphohydrolase-2) involved in the regulation of extracellular nucleotide concentrations in a range of organ systems. A novel NTPDase2beta isoform produced by alternative splicing of the rat NTPDase2 gene provides an extended intracellular C-terminus and distinguishes itself from NTPDase2alpha isoform in gaining several intracellular protein kinase CK2 (casein kinase 2) phosphorylation sites and losing the intracellular protein kinase C motif. The plasmids containing NTPDase2alpha or NTPDase2beta cDNA were used to stably transfect Chinese-hamster ovary-S cells. Imaging studies showed that NTPDase2alpha was predominantly membrane-bound, whereas NTPDase2beta had combined cell surface and intracellular localization. alpha and beta isoforms showed variations in divalent cation dependence and substrate specificity for nucleoside-5'-triphosphates and nucleoside-5'-diphosphates. NTPDase2beta exhibited reduced ATPase activity and no apparent ADPase activity. NTPDase2 isoforms demonstrated similar sensitivity to inhibitors such as suramin and pyridoxal phosphate-6-azophenyl-2',4'-disulphonic acid, and differential regulation by protein kinases. NTPDase2beta was up-regulated by intracellular protein kinase CK2 phosphorylation, whereas NTPDase2alpha activity was down-regulated by protein kinase C phosphorylation. The results demonstrate that alternative coding of the intracellular C-terminal domain contributes distinctive phenotypic variation with respect to extracellular nucleotide specificity, hydrolysis kinetics, protein kinase-dependent intracellular regulation and protein trafficking. These findings advance the molecular physiology of this enzyme system by characterizing the contribution of the C-terminal domain to many of the enzyme's signature properties.
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Affiliation(s)
- Carol J. H. Wang
- *Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Park Road, Grafton, Private Bag 92019, Auckland, New Zealand
| | - Srdjan M. Vlajkovic
- *Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Park Road, Grafton, Private Bag 92019, Auckland, New Zealand
- To whom correspondence should be addressed (email )
| | - Gary D. Housley
- *Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Park Road, Grafton, Private Bag 92019, Auckland, New Zealand
| | - Norbert Braun
- †Biozentrum der J. W. Goethe-Universität, AK Neurochemie, Frankfurt am Main, Germany
| | - Herbert Zimmermann
- †Biozentrum der J. W. Goethe-Universität, AK Neurochemie, Frankfurt am Main, Germany
| | - Simon C. Robson
- ‡Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, U.S.A
| | - Jean Sévigny
- §Centre de Recherche en Rhumatologie et Immunologie, CHUQ, Université Laval, Sainte-Foy, Québec, Canada
| | - Christian Soeller
- *Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Park Road, Grafton, Private Bag 92019, Auckland, New Zealand
| | - Peter R. Thorne
- ∥Discipline of Audiology, Faculty of Medical and Health Sciences, The University of Auckland, Park Road, Grafton, Private Bag 92019, Auckland, New Zealand
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Buffon A, Ribeiro VB, Fürstenau CR, Battastini AMO, Sarkis JJF. Acetylsalicylic acid inhibits ATP diphosphohydrolase activity by platelets from adult rats. Clin Chim Acta 2005; 349:53-60. [PMID: 15469855 DOI: 10.1016/j.cccn.2004.06.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Revised: 05/31/2004] [Accepted: 06/01/2004] [Indexed: 12/11/2022]
Abstract
BACKGROUND AND METHODS The in vitro effect of the nonsteroidal anti-inflammatory drug, acetylsalicylic acid (ASA), on the extracellular adenine nucleotide hydrolysis by intact rat blood platelets was studied. RESULTS Our results demonstrate that aspirin, at final concentrations of 2.0 and 3.0 mM, inhibits ATP extracellular hydrolysis in vitro by approximately 17% and 21%, respectively. Aspirin, at a final concentration of 3.0 mM, also inhibited in vitro extracellular ADP hydrolysis by approximately 41%. The same concentrations of this drug, however, did not alter AMP hydrolysis by intact rat blood platelets under similar assay conditions. The kinetic analysis demonstrated that the inhibition of ADP and ATP hydrolysis by aspirin in rat platelets is of the uncompetitive type. CONCLUSION In this study, we demonstrated an inhibitory effect of ASA upon E-NTPDase 3 activity of platelets from adult rats and discussed the significance of our findings.
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Affiliation(s)
- Andréia Buffon
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600, ANEXO, CEP Porto Alegre, RS, Brazil.
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26
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Kukulski F, Sévigny J, Komoszyński M. Comparative hydrolysis of extracellular adenine nucleotides and adenosine in synaptic membranes from porcine brain cortex, hippocampus, cerebellum and medulla oblongata. Brain Res 2005; 1030:49-56. [PMID: 15567336 DOI: 10.1016/j.brainres.2004.09.044] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/24/2004] [Indexed: 11/17/2022]
Abstract
We have investigated the metabolism of extracellular adenine nucleotides and adenosine in porcine brain. The cortex synaptic plasma membranes hydrolyzed ATP to ADP, AMP and adenosine. We also observed a slow hydrolysis of adenosine with the concomitant accumulation of inosine. These results indicate that NTPDase1, NTPDase2, ecto-5'-nucleotidase, and adenosine deaminase are present in cortex synaptic membranes from porcine brain. We further showed that all these enzymes are also abundant in synaptic membranes from hippocampus, cerebellum, and medulla oblongata and compared their specific activities. Brain cortex and hippocampus exhibited higher activities of NTPDase1 and NTPDase2 than cerebellum and medulla oblongata. It was consistent with the high level of the expression of NTPDases in the two first structures. Adenosine deaminase activity was found in all brain structures analyzed; however, it was lower than the activity of ecto-nucleotidases. Taken together, our data suggest that investigated enzymes have a ubiquitous abundance in porcine brain, and observed differences in their activities in cortex, hippocampus, cerebellum, and medulla oblongata may correlate with the pattern of P2 receptor expression in these brain areas. In addition, low activity of adenosine deaminase may indicate that nonenzymatic mechanism(s) are responsible for the termination of P1 receptor signaling in porcine brain.
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Affiliation(s)
- Filip Kukulski
- Department of Biochemistry, Institute of General and Molecular Biology, N. Copernicus University of Toruń, Toruń, Poland.
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27
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Kishore BK, Isaac J, Fausther M, Tripp SR, Shi H, Gill PS, Braun N, Zimmermann H, Sévigny J, Robson SC. Expression of NTPDase1 and NTPDase2 in murine kidney: relevance to regulation of P2 receptor signaling. Am J Physiol Renal Physiol 2005; 288:F1032-43. [PMID: 15632415 DOI: 10.1152/ajprenal.00108.2004] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The regulation of renal function by extracellular nucleotides encompasses alterations in glomerular hemodynamics, microvascular function, tubuloglomerular feedback, tubular transport, cell growth or apoptosis, and transport of water and solutes in the medullary collecting duct. Nearly all cells can release ATP or other nucleotides that are then rapidly hydrolyzed in the extracellular milieu. However, little information is available on the cellular expression of ectoenzymes that hydrolyze extracellular nucleotides within the kidney. Nucleoside triphosphate diphosphohydrolases (NTPDases) are plasma membrane-bound ectonucleotidases. NTPDase1 has identity with CD39, a B lymphocyte activation marker, and hydrolyzes extracellular ATP and ADP to AMP within the vasculature, whereas NTPDase2/CD39L(ike)1 preferentially converts ATP to ADP outside of blood vessels. Using immunohistochemical and in situ hybridization approaches, we localized the protein and mRNA of NTPDase1 and 2 in murine renal tissues. In the renal cortex, NTPDase1 is expressed by vascular smooth muscle cells and endothelium in interlobular arteries, afferent glomerular arterioles, and peritubular capillaries. In the inner medulla, NTPDase1 is expressed in ascending thin limbs of Henle's loop, ducts of Bellini, and in the pelvic wall. In contrast, NTPDase2 is expressed in Bowman's capsule, glomerular arterioles, adventitia of blood vessels, and pelvic wall. Thus the distribution patterns of NTPDases have parallels to the known distribution of P2 receptors within the kidney. NTPDases may modulate regulatory effects of ATP and degradation products within the vasculature and other sites and thereby potentially influence physiological as well as multiple pathological events in the kidney.
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Affiliation(s)
- Bellamkonda K Kishore
- Department of Internal Medicine, University of Utah Health Sciences Center, Salt Lake CIty, Utah, USA.
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28
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Alvarado-Castillo C, Harden TK, Boyer JL. Regulation of P2Y1 receptor-mediated signaling by the ectonucleoside triphosphate diphosphohydrolase isozymes NTPDase1 and NTPDase2. Mol Pharmacol 2004; 67:114-22. [PMID: 15496502 DOI: 10.1124/mol.104.006908] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ectonucleoside triphosphate diphosphohydrolases (NTPDases) control the concentration of released extracellular nucleotides, but the precise physiological roles played by these isozymes in modulation of P2 receptor signaling remain unclear. Activation of the human P2Y(1) receptor was studied in the presence of NTPDase1 or NTPDase2 expressed either in the same cell as the receptor or in P2Y(1) receptor-expressing cells cocultured with NTPDaseexpressing cells. Coexpression of NTPDase1 with the P2Y(1) receptor resulted in increases in the EC(50) for 2'-methylthioadenosine 5'-diphosphate (2MeSADP; 12-fold), ADP (50-fold), and ATP (10-fold) for activation of phospholipase C. Similar effects were observed when the P2Y(1) receptor and NTPDase1 were expressed on different cells. These results are explained by the capacity of NTPDase1 to hydrolyze both nucleoside triphosphates and diphosphates. NTPDase2 preferentially hydrolyzes nucleoside triphosphates, and the presence of NTPDase2 under either coexpression or coculture conditions did not change the EC(50) of 2MeSADP, ADP, or adenosine 5'-O-(2-thiodiphosphate) for activation of the P2Y(1) receptor. However, the EC(50) for ATP was 15-fold lower in the presence of NTPDase2 than in cells expressing the P2Y(1) receptor alone. Whereas expression of NTPDase1 decreased basal activity of the P2Y(1) receptor, the presence of the NTPDase2 resulted in P2Y(1) receptor-dependent increases in basal activity. These results suggest that basal activity of the P2Y(1) receptor is maintained by paracrine or autocrine release of receptor agonists and that the biological and/or pharmacological response mediated by P2Y receptors in target tissues is highly dependent on the types of ectonucleotidases expressed in the vicinity of the receptor.
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Affiliation(s)
- Claudia Alvarado-Castillo
- Department of Pharmacology, University of North Carolina School of Medicine, CB#7365, Chapel Hill, NC 27599-7365, USA
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Vlajkovic SM, Housley GD, Muñoz DJB, Robson SC, Sévigny J, Wang CJH, Thorne PR. Noise exposure induces up-regulation of ecto-nucleoside triphosphate diphosphohydrolases 1 and 2 in rat cochlea. Neuroscience 2004; 126:763-73. [PMID: 15183524 DOI: 10.1016/j.neuroscience.2004.04.023] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/07/2004] [Indexed: 12/01/2022]
Abstract
Extracellular ATP acting via P2 receptors in the inner ear initiates a variety of signaling pathways that may be involved in noise-induced cochlear injury. Nucleoside triphosphate diphosphohydrolase (NTPDase)1/CD39 and NTPDase2/CD39L1 are key elements for regulation of extracellular nucleotide concentrations and P2 receptor signaling in the cochlea. This study characterized the effect of noise exposure on regulation of NTPDase1 and NTPDase2 expression in the cochlea using a combination of real-time RT-PCR, immunohistochemistry and functional studies. Adult Wistar rats were exposed to broad band noise at 90 dB and 110 dB sound pressure level (SPL) for 72 h. Exposure to 90 dB SPL induced a small and temporary change of auditory thresholds (temporary threshold shift), while exposure to 110 dB SPL induced a robust and permanent change of auditory thresholds (permanent threshold shift). NTPDase1 and NTPDase2 mRNA transcripts were upregulated in the cochlea exposed to 110 dB SPL, while mild noise (90 dB SPL) altered only NTPDase1 mRNA expression levels. Changes in NTPDases expression did not correlate with levels of circulating corticosterone, implying that the up-regulation of NTPDases expression was not stress-related. Semi-quantitative immunohistochemistry in the cochlea exposed to 110 dB SPL localized the increased NTPDase1 and NTPDase2 immunostaining in the stria vascularis and up-regulation of NTPDase2 in the intraganglionic spiral bundle. In contrast, NTPDase1 was down-regulated in the cell bodies of the spiral ganglion neurones. Distribution of NTPDases was not altered in the cochlea exposed to 90 dB SPL. Functional studies revealed increased ectonucleotidase activities in the cochlea after exposure to 110 dB SPL, consistent with up-regulation of NTPDases. The changes in NTPDases expression may reflect adaptive response of cochlear tissues to limit ATP signaling during noise exposure.
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Affiliation(s)
- S M Vlajkovic
- Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand
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Fürstenau CR, Spier AP, Rücker B, Luisa Berti S, Battastini AMO, Sarkis JJF. The effect of ebselen on adenine nucleotide hydrolysis by platelets from adult rats. Chem Biol Interact 2004; 148:93-9. [PMID: 15223359 DOI: 10.1016/j.cbi.2004.04.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2003] [Revised: 04/16/2004] [Accepted: 04/20/2004] [Indexed: 10/26/2022]
Abstract
The extracellular hydrolysis of adenine nucleotides by intact rat blood platelets occurs by the action of a cascade of enzymes constituted by an NTPDase 3 (CD39, EC 3.6.1.5, apyrase) and a 5'-nucleotidase (CD73, EC 3.5.7.3), whose final product is adenosine. Ebselen is a seleno-organic compound that possesses low toxicity and exhibits antioxidant, anti-inflammatory, anti-atherosclerotic, and cytoprotective properties. The main objective of this study was to evaluate if the anti-inflammatory drug ebselen can modulate the extracellular adenine nucleotide hydrolysis by platelets from rats. Our results showed that ebselen, at final concentrations of 30 and 100 microM, inhibits in vitro ATP extracellular hydrolysis by 48 and 60%, respectively. Ebselen, at final concentrations of 100 and 130 microM, also inhibited the in vitro extracellular hydrolysis of ADP by 28 and 35%, respectively. However, this drug did not alter AMP hydrolysis by platelets in the appropriate assay conditions. Kinetic analysis showed that the inhibition of ADP and ATP hydrolysis by ebselen, in rat platelets, is of the uncompetitive type. The IC50 calculated from the results were 99 +/- 10 and 186 +/- 47 microM (mean +/- S.D., n = 3) for ATP and ADP hydrolysis, respectively.
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Affiliation(s)
- Cristina Ribas Fürstenau
- Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, ICBS, Rua Ramiro Barcelos, 2600-ANEXO, CEP 90035-003, Porto Alegre, RS, Brazil
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Kukulski F, Komoszyński M. Purification and characterization of NTPDase1 (ecto-apyrase) and NTPDase2 (ecto-ATPase) from porcine brain cortex synaptosomes. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:3447-54. [PMID: 12899702 DOI: 10.1046/j.1432-1033.2003.03734.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We purified to homogeneity and characterized NTPDase1 and NTPDase2 from porcine brain cortex synaptosomes. SDS/PAGE and immunoblotting with antibodies specific to these enzymes revealed a molecular mass estimated at 72 kDa for NTPDase1 and 66 for NTPDase2. Both enzymes exhibited kinetic properties typical for all members of the NTPDase family, e.g. low substrate specificity for tri- and diphosphonucleosides, divalent cations dependency and insensitivity towards ATPase inhibitors. The calculated Km value for NTPDase1 in respect to ATP as a substrate (97 microm) was three times lower in comparison to analogous values for NTPDase2 (270 microm). Additionally, NTPDase1 had a three times higher Kcat/Km coefficient than NTPDase2 (860 and 833 micromol product.s(-1), respectively). We have also demonstrated that in spite of differences in the affinity of ATP for both hydrolases, these enzymes have similar molecular activity. Taken together, these results indicate that NTPDase1 would terminate P2 receptor-mediated signal transmission whereas activity of NTPDase2 may contribute to decreasing high (toxic) concentrations of ATP and/or to production of another signal molecule, ADP.
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Affiliation(s)
- Filip Kukulski
- Department of Biochemistry, Institute of General and Molecular Biology, N. Copernicus University, Toruń, Poland
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