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Hackney CM, Furness DN. The composition and role of cross links in mechanoelectrical transduction in vertebrate sensory hair cells. J Cell Sci 2013; 126:1721-31. [DOI: 10.1242/jcs.106120] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The key components of acousticolateralis systems (lateral line, hearing and balance) are sensory hair cells. At their apex, these cells have a bundle of specialized cellular protrusions, which are modified actin-containing microvilli, connected together by extracellular filaments called cross links. Stereociliary deflections open nonselective cation channels allowing ions from the extracellular environment into the cell, a process called mechanoelectrical transduction. This produces a receptor potential that causes the release of the excitatory neurotransmitter glutamate onto the terminals of the sensory nerve fibres, which connect to the cell base, causing nerve signals to be sent to the brain. Identification of the cellular mechanisms underlying mechanoelectrical transduction and of some of the proteins involved has been assisted by research into the genetics of deafness, molecular biology and mechanical measurements of function. It is thought that one type of cross link, the tip link, is composed of cadherin 23 and protocadherin 15, and gates the transduction channel when the bundle is deflected. Another type of link, called lateral (or horizontal) links, maintains optimal bundle cohesion and stiffness for transduction. This Commentary summarizes the information currently available about the structure, function and composition of the links and how they might be relevant to human hearing impairment.
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Pan B, Waguespack J, Schnee ME, LeBlanc C, Ricci AJ. Permeation properties of the hair cell mechanotransducer channel provide insight into its molecular structure. J Neurophysiol 2012; 107:2408-20. [PMID: 22323630 DOI: 10.1152/jn.01178.2011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Mechanoelectric transducer (MET) channels, located near stereocilia tips, are opened by deflecting the hair bundle of sensory hair cells. Defects in this process result in deafness. Despite this critical function, the molecular identity of MET channels remains a mystery. Inherent channel properties, particularly those associated with permeation, provide the backbone for the molecular identification of ion channels. Here, a novel channel rectification mechanism is identified, resulting in a reduced pore size at positive potentials. The apparent difference in pore dimensions results from Ca(2+) binding within the pore, occluding permeation. Driving force for permeation at hyperpolarized potentials is increased because Ca(2+) can more easily be removed from binding within the pore due to the presence of an electronegative external vestibule that dehydrates and concentrates permeating ions. Alterations in Ca(2+) binding may underlie tonotopic and Ca(2+)-dependent variations in channel conductance. This Ca(2+)-dependent rectification provides targets for identifying the molecular components of the MET channel.
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Affiliation(s)
- B Pan
- Department of Otolaryngology, Stanford University, 300 Pasteur Dr., Stanford, CA 94305, USA
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Abstract
The epithelial Na(+) channel (ENaC) and acid-sensitive ion channel (ASIC) branches of the ENaC/degenerin superfamily of cation channels have drawn increasing attention as potential therapeutic targets in a variety of diseases and conditions. Originally thought to be solely expressed in fluid absorptive epithelia and in neurons, it has become apparent that members of this family exhibit nearly ubiquitous expression. Therapeutic opportunities range from hypertension, due to the role of ENaC in maintaining whole body salt and water homeostasis, to anxiety disorders and pain associated with ASIC activity. As a physiologist intrigued by the fundamental mechanics of salt and water transport, it was natural that Dale Benos, to whom this series of reviews is dedicated, should have been at the forefront of research into the amiloride-sensitive sodium channel. The cloning of ENaC and subsequently the ASIC channels has revealed a far wider role for this channel family than was previously imagined. In this review, we will discuss the known and potential roles of ENaC and ASIC subunits in the wide variety of pathologies in which these channels have been implicated. Some of these, such as the role of ENaC in Liddle's syndrome are well established, others less so; however, all are related in that the fundamental defect is due to inappropriate channel activity.
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Affiliation(s)
- Yawar J Qadri
- Department of Physiology and Biophysics, University of Alabama at Birmingham, AL 35294, USA
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Guan Z, Pollock JS, Cook AK, Hobbs JL, Inscho EW. Effect of epithelial sodium channel blockade on the myogenic response of rat juxtamedullary afferent arterioles. Hypertension 2009; 54:1062-9. [PMID: 19720952 DOI: 10.1161/hypertensionaha.109.137992] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The mechanotransduction mechanism underlying the myogenic response is poorly understood, but evidence implicates participation of epithelial sodium channel (ENaC)-like proteins. Therefore, the role of ENaC on the afferent arteriolar myogenic response was investigated in vitro using the blood-perfused juxtamedullary nephron technique. Papillectomy was used to isolate myogenic influences by eliminating tubuloglomerular feedback signals. Autoregulatory responses were assessed by manipulating perfusion pressure in 30-mm Hg steps. Under control conditions, arteriolar diameter increased by 15% from 13.0+/-1.3 to 14.7+/-1.2 microm (P<0.05) after reducing perfusion pressure from 100 to 70 mm Hg. Diameter decreased to 11.3+/-1.1 and 10.6+/-1.0 microm after increasing pressure to 130 and 160 mm Hg (88+/-1 and 81+/-2% of control diameter, P<0.05), respectively. Pressure-mediated autoregulatory responses were significantly inhibited by superfusion of 10 micromol/L amiloride (102+/-2, 97+/-4, and 94+/-3% of control diameter), or 10 micromol/L benzamil (106+/-5, 100+/-3, and 103+/-3% of control diameter), and when perfusing with blood containing 5 micromol/L amiloride (106+/-2, 97+/-4, and 97+/-4% of control diameter). Vasoconstrictor responses to 55 mmol/L KCl were preserved as diameters decreased by 67+/-4, 55+/-8, and 60+/-4% in afferent arterioles superfused with amiloride or benzamil, and perfused with amiloride, respectively. These responses were similar to responses obtained from control afferent arterioles (64+/-6%, P>0.05). Immunofluorescence revealed expression of the alpha, beta, and gamma subunits of ENaC in freshly isolated preglomerular microvascular smooth muscle cells. These results demonstrate that selective ENaC inhibitors attenuate afferent arteriolar myogenic responses and suggest that ENaC may function as mechanosensitive ion channels initiating pressure-dependent myogenic responses in rat juxtamedullary afferent arterioles.
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Affiliation(s)
- Zhengrong Guan
- Department of Physiology, Medical College of Georgia, Augusta, GA 30912, USA
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Ricci AJ, Kachar B. Hair cell mechanotransduction: the dynamic interplay between structure and function. CURRENT TOPICS IN MEMBRANES 2007; 59:339-74. [PMID: 25168142 DOI: 10.1016/s1063-5823(06)59012-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
Hair cells are capable of detecting mechanical vibrations of molecular dimensions at frequencies in the 10s to 100s of kHz. This remarkable feat is accomplished by the interplay of mechanically gated ion channels located near the top of a complex and dynamic sensory hair bundle. The hair bundle is composed of a series of actin-filled stereocilia that has both active and passive mechanical components as well as a highly active turnover process, whereby the components of the hair bundle are rapidly and continually recycled. Hair bundle mechanical properties have significant impact on the gating of the mechanically activated channels, and delineating between attributes intrinsic to the ion channel and those imposed by the channel's microenvironment is often difficult. This chapter describes what is known and accepted regarding hair-cell mechanotransduction and what remains to be explored, particularly, in relation to the interplay between hair bundle properties and mechanotransducer channel response. The interplay between hair bundle dynamics and mechanotransduction are discussed.
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Affiliation(s)
- Anthony J Ricci
- Department of Otolaryngology, Stanford University, Stanford, California 94305
| | - Bechara Kachar
- Section of Structural Biology, National Institutes of Deafness and Communicative Disorders, Bethesda, Maryland 20892
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Ricci AJ, Kachar B, Gale J, Van Netten SM. Mechano-electrical transduction: new insights into old ideas. J Membr Biol 2006; 209:71-88. [PMID: 16773495 PMCID: PMC1839004 DOI: 10.1007/s00232-005-0834-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2005] [Indexed: 11/26/2022]
Abstract
The gating-spring theory of hair cell mechanotransduction channel activation was first postulated over twenty years ago. The basic tenets of this hypothesis have been reaffirmed in hair cells from both auditory and vestibular systems and across species. In fact, the basic findings have been reproduced in every hair cell type tested. A great deal of information regarding the structural, mechanical, molecular and biophysical properties of the sensory hair bundle and the mechanotransducer channel has accumulated over the past twenty years. The goal of this review is to investigate new data, using the gating spring hypothesis as the framework for discussion. Mechanisms of channel gating are presented in reference to the need for a molecular gating spring or for tethering to the intra- or extracellular compartments. Dynamics of the sensory hair bundle and the presence of motor proteins are discussed in reference to passive contributions of the hair bundle to gating compliance. And finally, the molecular identity of the channel is discussed in reference to known intrinsic properties of the native transducer channel.
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Affiliation(s)
- A J Ricci
- Neuroscience Center, Louisiana State University, New Orleans, LA 70112, USA.
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Myrdal SE, Johnson KC, Steyger PS. Cytoplasmic and intra-nuclear binding of gentamicin does not require endocytosis. Hear Res 2006; 204:156-69. [PMID: 15925201 PMCID: PMC2736065 DOI: 10.1016/j.heares.2005.02.002] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2004] [Accepted: 02/02/2005] [Indexed: 11/16/2022]
Abstract
Understanding the cellular mechanism(s) by which the oto- and nephrotoxic aminoglycoside antibiotics penetrate cells, and the precise intracellular distribution of these molecules, will enable identification of aminoglycoside-sensitive targets, and potential uptake blockers. Clones of two kidney cell lines, OK and MDCK, were treated with the aminoglycoside gentamicin linked to the fluorophore Texas Red (GTTR). As in earlier reports, endosomal accumulation was observed in live cells, or cells fixed with formaldehyde only. However, delipidation of fixed cells revealed GTTR fluorescence in cytoplasmic and nuclear compartments. Immunolabeling of both GTTR and unconjugated gentamicin corresponded to the cytoplasmic distribution of GTTR fluorescence. Intra-nuclear GTTR binding co-localized with labeled RNA in the nucleoli and trans-nuclear tubules. Cytoplasmic and nuclear distribution of GTTR was quenched by phosphatidylinositol-bisphosphate (PIP2), a known ligand for gentamicin. Cytoplasmic and nuclear GTTR binding increased over time (at 37 degrees C, or on ice to inhibit endocytosis), and was serially competed off by increasing concentrations of unconjugated gentamicin, i.e., GTTR binding is saturable. In contrast, little or no reduction of endocytotic GTTR uptake was observed when cells were co-incubated with up to 4 mg/mL unconjugated gentamicin. Thus, cytoplasmic and nuclear GTTR uptake is time-dependent, weakly temperature-dependent and saturable, suggesting that it occurs via an endosome-independent mechanism, implicating ion channels, transporters or pores in the plasma membrane as bioregulatory routes for gentamicin entry into cells.
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MESH Headings
- Animals
- Anti-Bacterial Agents/adverse effects
- Anti-Bacterial Agents/metabolism
- Binding Sites/drug effects
- Cell Line
- Dogs
- Dose-Response Relationship, Drug
- Endocytosis/physiology
- Fluorescent Dyes
- Gentamicins/adverse effects
- Gentamicins/metabolism
- Immunohistochemistry
- Kidney Tubules, Distal/cytology
- Kidney Tubules, Distal/drug effects
- Kidney Tubules, Distal/metabolism
- Kidney Tubules, Proximal/cytology
- Kidney Tubules, Proximal/drug effects
- Kidney Tubules, Proximal/metabolism
- Microscopy, Confocal
- Neurons/drug effects
- Opossums
- Phosphatidylinositol 4,5-Diphosphate/metabolism
- Phosphatidylinositol 4,5-Diphosphate/pharmacology
- Xanthenes
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Affiliation(s)
- Sigrid E Myrdal
- Oregon Hearing Research Center, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
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Hildebrand MS, de Silva MG, Klockars T, Rose E, Price M, Smith RJH, McGuirt WT, Christopoulos H, Petit C, Dahl HHM. Characterisation of DRASIC in the mouse inner ear. Hear Res 2004; 190:149-60. [PMID: 15051137 DOI: 10.1016/s0378-5955(04)00015-2] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2003] [Accepted: 12/15/2003] [Indexed: 01/10/2023]
Abstract
Within the cochlea, the hair cells detect sound waves and transduce them into receptor potential. The molecular architecture of the highly specialised cochlea is complex and until recently little was known about the molecular interactions which underlie its function. It is now clear that the coordinated expression and interplay of hundreds of genes and the integrity of cochlear cells regulate this function. It was hypothesised that transcripts expressed highly or specifically in the cochlea are likely to have important roles in normal hearing. Microarray analyses of the Soares NMIE library, consisting of 1536 cDNA clones isolated from the mouse inner ear, suggested that the expression of the mechanoreceptor DRASIC was enriched in the cochlea compared to other tissues. This amiloride-sensitive ion channel is a member of the DEG/ENaC superfamily and a potential candidate for the unidentified mechanoelectrical transduction channel of the sensory hair cells of the cochlea. The cochlear-enriched expression of amiloride-sensitive cation channel 3 (ACCN3) was confirmed by quantitative real-time polymerase chain reaction. Using in situ hybridisation and immunofluorescence, DRASIC expression was localised to the cells and neural fibre region of the spiral ganglion. DRASIC protein was also detected in cells of the organ of Corti. DRASIC may be present in cochlear hair cells as the ACCN3 transcript was shown to be expressed in immortalised cell lines that exhibit characteristics of hair cells. The normal mouse ACCN3 cDNA and an alternatively spliced transcript were elucidated by reverse transcription polymerase chain reaction from mouse inner ear RNA. This transcript may represent a new protein isoform with an as yet unknown function. A DRASIC knockout mouse model was tested for a hearing loss phenotype and was found to have normal hearing at 2 months of age but appeared to develop hearing loss early in life. The human homologue of ACCN3, acid-sensing ion channel 3, maps to the same chromosomal region as the autosomal recessive hearing loss locus DFNB13. However, we did not detect mutations in this gene in a family with DFNB13 hearing loss.
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Affiliation(s)
- Michael S Hildebrand
- Department of Gene Identification and Expression, Murdoch Childrens Research Institute, Royal Children's Hospital, Flemington Road, Parkville, Vic. 3052, Australia
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Ricci A. Differences in mechano-transducer channel kinetics underlie tonotopic distribution of fast adaptation in auditory hair cells. J Neurophysiol 2002; 87:1738-48. [PMID: 11929895 DOI: 10.1152/jn.00574.2001] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The first step in audition is a deflection of the sensory hair bundle that opens mechanically gated channels, depolarizing the sensory hair cells. Two mechanism of adaptation of mechano-electric transducer (MET) channels have been identified in turtle auditory hair cells. The rate of fast adaptation varies tonotopically and is postulated to underlie a mechanical tuning mechanism in turtle auditory hair cells. Fast adaptation is driven by a calcium-dependent feedback process associated with MET channels. The purpose of this paper is to test the hypothesis that fast adaptation contributes to MET channel kinetics and that variations in channel kinetics underlie the tonotopic distribution of fast adaptation. To test for kinetic differences, the open channel blocker dihydrostreptomycin (DHS) was used. DHS blocked MET currents from low-frequency cells (IC(50) = 14 +/- 2 microM) more effectively than high-frequency cells (IC(50) = 75 +/- 5 microM), suggesting differences in MET channel properties. DHS block showed similar calcium sensitivities at both papilla locations. No difference in calcium permeation or block of the transducer channels was observed, indicating that the DHS effect was not due to differences in the channel pore. Slowing adaptation increased DHS efficacy, and speeding adaptation decreased DHS efficacy, suggesting that adaptation was influencing DHS block. DHS block of MET channels slowed adaptation, most likely by reducing the peak intraciliary calcium concentration achieved, supporting the hypothesis that the rate of adaptation varies with the calcium load per stereocilia. Another channel blocker, amiloride showed similar efficacy for high- and low-frequency cells with an IC(50) of 24.2 +/- 0.5 microM and a Hill coefficient of 2 but appeared to block high-frequency channels faster than low-frequency channels. To further explore MET channel differences between papilla locations, stationary noise analysis was performed. Spectral analysis of the noise gave half power frequencies of 1,185 +/- 148 Hz (n = 6) and 551 +/- 145 Hz (n = 5) for high- and low-frequency cells in 2.8 mM external calcium. The half power frequency showed similar calcium sensitivity to that of adaptation shifting to 768 +/- 205 Hz (n = 4) and 289 +/- 63 Hz (n = 4) for high- and low-frequency cells in 0.25 mM external calcium. Both the pharmacological data and the noise analysis data are consistent with the hypothesis that the tonotopic distribution of fast adaptation is in part due to differences in MET channel kinetics. An increase in the number of MET channels per stereocilia (termed summation) and or intrinsic differences in MET channel kinetics may be the underlying mechanism involved in establishing the gradient.
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Affiliation(s)
- Anthony Ricci
- Neuroscience Center and Kresge Hearing Laboratories, Louisiana State University, New Orleans, Louisiana 70112, USA.
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Schulte CC, Meyer J, Furness DN, Hackney CM, Kleyman TR, Gummer AW. Functional effects of a monoclonal antibody on mechanoelectrical transduction in outer hair cells. Hear Res 2002; 164:190-205. [PMID: 11950538 DOI: 10.1016/s0378-5955(01)00431-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The functional effect of a monoclonal antibody, RA6.3, on mechanoelectrical transduction (MET) of outer hair cells (OHCs) isolated from the adult guinea-pig cochlea was investigated. This antibody was raised by an antiidiotypic approach against amiloride binding sites. RA6.3 irreversibly reduced the receptor current, independent of membrane potential. The time course of the functional block was independent of dilution (1:100, 50 and 10), beginning 1.2+/-0.5 min after the start of application and decreasing exponentially with a time constant of 0.29+/-0.18 min to 53+/-8% of the control current. The residual current was reversibly blocked by amiloride (300 microM), mainly at negative membrane potentials. Block of control current by amiloride was competitively inhibited by simultaneous application of RA6.3. These results suggest that RA6.3 binds to or in close proximity to amiloride receptor sites associated with the MET channels. Irreversibility, incompleteness, independence of membrane potential and independence of antibody dilution of the functional block can all be explained by irreversible binding of one antibody molecule to a receptor site, yielding a non-blocked state, followed by a relatively slow, reversible transition to a blocked state. It is proposed that the reversible transition might represent intramolecular binding of the second antibody combining site to the second receptor site.
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MESH Headings
- Amiloride/metabolism
- Amiloride/pharmacology
- Animals
- Antibodies, Anti-Idiotypic
- Antibodies, Monoclonal
- Binding Sites
- Binding, Competitive
- Biomechanical Phenomena
- Electrophysiology
- Guinea Pigs
- Hair Cells, Auditory, Outer/drug effects
- Hair Cells, Auditory, Outer/immunology
- Hair Cells, Auditory, Outer/physiology
- In Vitro Techniques
- Keratan Sulfate/antagonists & inhibitors
- Keratan Sulfate/metabolism
- Mechanoreceptors/drug effects
- Mechanoreceptors/immunology
- Mechanoreceptors/physiology
- Models, Biological
- Molecular Mimicry
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Affiliation(s)
- Claudia C Schulte
- Section of Physiological Acoustics and Communication, Department of Otolaryngology, University of Tübingen, Silcherstr. 5, 72076, Germany
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Stacey DJ, McLean WG. Cytoskeletal protein mRNA expression in the chick utricle after treatment in vitro with aminoglycoside antibiotics: effects of insulin, iron chelators and cyclic nucleotides. Brain Res 2000; 871:319-32. [PMID: 10899298 DOI: 10.1016/s0006-8993(00)02488-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In birds, spontaneous recovery of the hair cells of the inner ear can occur after damage induced by aminoglycoside antibiotics. The factors that influence this recovery and the process of hair cell regeneration itself have until recently been investigated largely by morphological and histological methods. The aim of this work was to use a molecular biological approach to the analysis of hair cell regeneration by measuring the changes that occur in expression of mRNA for hair cell-specific cytoskeletal proteins fimbrin and class III beta-tubulin, along with that for beta-actin, in the utricle of chicks after hair cell damage both in vitro and in vivo. Utricles were removed from 1-day-old chicks and incubated with the aminoglycoside antibiotics gentamicin or neomycin (both 1 mM), or chicks were injected intraperitoneally with 100 mg/kg gentamicin or neomycin for 4 consecutive days. At the end of the treatment periods, total RNA was extracted from single utricles, reverse transcribed to cDNA and the cDNA amplified by PCR with primers for beta-actin, fimbrin and class III beta-tubulin. Co-amplification allowed quantitative comparison of mRNA between fimbrin, or class III beta-tubulin and beta-actin from the same utricle. Both aminoglycosides, either after 48 h in vitro or immediately after treatment in vivo, caused a significant decrease in the expression of fimbrin mRNA and class III beta-tubulin mRNA, relative to beta-actin mRNA, which itself increased. Light and electron microscopy confirmed that this corresponded to loss of, and damage to, hair cells. The relative expression of fimbrin and class III beta-tubulin mRNAs was partly restored almost to control levels 4 days after cessation of treatment in vivo and fully normalised by 4 weeks, by which time hair cells appeared normal. However, their relative expression remained depressed 4 days after removal of antibiotic in vitro. The iron chelator desferrioxamine (100 microM) in vitro prevented the aminoglycoside-induced reduction in relative expression of mRNA for both fimbrin and class III beta-tubulin. Neither insulin (5 microM) nor a combination of dibutyryl cyclic AMP (5 mM) and the phosphodiesterase inhibitor IBMX (0.5 mM) prevented the decrease in relative expression of the mRNAs for the hair cell-specific proteins, but both treatments allowed their partial recovery in vitro during the 4-day-period after removal of aminoglycoside. It is concluded that the cells of the sensory epithelium of the chick utricle subjected to aminoglycoside-induced damage undergo a process in which mRNA expression is switched away from the production of functional proteins and towards proteins necessary for structural re-organisation. The restoration of mRNA expression to a normal pattern is promoted by the growth factor insulin and by cyclic AMP.
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MESH Headings
- Actins/metabolism
- Aminoglycosides
- Animals
- Animals, Newborn
- Anti-Bacterial Agents/adverse effects
- Cell Death/drug effects
- Cell Death/physiology
- Cell Survival/drug effects
- Cell Survival/physiology
- Chelating Agents/pharmacology
- Chickens/anatomy & histology
- Chickens/metabolism
- Cytoskeletal Proteins/drug effects
- Cytoskeletal Proteins/genetics
- Cytoskeletal Proteins/metabolism
- Hair Cells, Auditory/drug effects
- Hair Cells, Auditory/pathology
- Hair Cells, Auditory/physiopathology
- Hair Cells, Auditory/ultrastructure
- Insulin/metabolism
- Insulin/pharmacology
- Iron/metabolism
- Membrane Glycoproteins/drug effects
- Membrane Glycoproteins/metabolism
- Microfilament Proteins
- Microscopy, Electron
- Nucleotides, Cyclic/metabolism
- Nucleotides, Cyclic/pharmacology
- Polymerase Chain Reaction
- RNA, Messenger/drug effects
- RNA, Messenger/isolation & purification
- RNA, Messenger/metabolism
- Regeneration/drug effects
- Regeneration/physiology
- Saccule and Utricle/drug effects
- Saccule and Utricle/pathology
- Saccule and Utricle/physiopathology
- Saccule and Utricle/ultrastructure
- Tubulin/drug effects
- Tubulin/metabolism
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Affiliation(s)
- D J Stacey
- Department of Pharmacology and Therapeutics, University of Liverpool, L69 3BX, Liverpool, UK
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Wiersinga-Post JEC, van Netten SM. Amiloride causes changes in the mechanical properties of hair cell bundles in the fish lateral line similar to those induced by dihydrostreptomycin. Proc Biol Sci 1998. [DOI: 10.1098/rspb.1998.0339] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- J. Esther C Wiersinga-Post
- Department of Biophysics, Graduate School for Behavioural and Cognitive Neurosciences, University of Groningen, Nijenborgh 4, NL–9747 AG Groningen, The Netherlands
| | - Sietse M van Netten
- Department of Biophysics, Graduate School for Behavioural and Cognitive Neurosciences, University of Groningen, Nijenborgh 4, NL–9747 AG Groningen, The Netherlands
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van Netten SM. Hair cell mechano-transduction: its influence on the gross mechanical characteristics of a hair cell sense organ. Biophys Chem 1997; 68:43-52. [PMID: 9468609 DOI: 10.1016/s0301-4622(97)00006-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The complex mechanical behaviour of a hair cell bundle appears to be a direct consequence of the gating forces on the individual transduction channels. The mechanical molecular interactions involved in transduction channel gating, therefore, also bear a reciprocal influence, via the hair bundles, on the mechanical properties of accessory structures driving them. This allows for the possibility to investigate, under in vivo conditions, the mechanical gating machinery of ion channels via the dynamics of accessory structures. We have performed such studies on the lateral line organ of fish and were thus able to relate the mechanics of elementary molecular events to the macroscopical dynamics of an intact organ.
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Affiliation(s)
- S M van Netten
- Department of Biophysics, University of Groningen, The Netherlands.
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Killick R, Richardson G. Isolation of chicken alpha ENaC splice variants from a cochlear cDNA library. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1350:33-7. [PMID: 9003454 DOI: 10.1016/s0167-4781(96)00197-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Three splice variants of the alpha subunit of the amiloride-sensitive epithelial sodium channel (alpha ENaC) have been isolated from a chicken cochlear cDNA library. A PCR product, generated from the cochlear library using degenerate primers to regions of homology between the rat alpha ENaC and the degenerin Mec-4, was used as a probe. The three splice variant cDNAs with sizes of 2321, 3399 and 3845 bp correspond to transcripts of 2.5, 3.5 and 3.9 kb as detected by Northern blot analysis. The 3399 bp clone differs from the 2321 clone solely by the addition of 1079 bases in the 3'-non-coding region. Both these cDNAs code for an identical predicted protein of 637 amino acids which has 68% similarity to the rat alpha ENaC, and is probably the chicken homologue of alpha ENaC. The third cDNA of 3845 bp is similar to the 3399 bp clone but includes two exons within the open reading frame. The first of these exons introduces a premature stop codon resulting in a truncated predicted protein of 434 amino acids. Northern blot analysis shows expression of the 2.5 and 3.5 kb transcripts in cochlea and colon, the 2.5 kb transcript in cartilage, whilst the 3.9 kb transcript is only detected in cochlea. No expression is detected in brain, liver, and heart nor, most notably, in lung or kidney.
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Affiliation(s)
- R Killick
- School of Biological Sciences, Sussex University, Falmer, Brighton, UK.
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