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Zhang C, Burger RM. Cholinergic modulation in the vertebrate auditory pathway. Front Cell Neurosci 2024; 18:1414484. [PMID: 38962512 PMCID: PMC11220170 DOI: 10.3389/fncel.2024.1414484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Accepted: 06/06/2024] [Indexed: 07/05/2024] Open
Abstract
Acetylcholine (ACh) is a prevalent neurotransmitter throughout the nervous system. In the brain, ACh is widely regarded as a potent neuromodulator. In neurons, ACh signals are conferred through a variety of receptors that influence a broad range of neurophysiological phenomena such as transmitter release or membrane excitability. In sensory circuitry, ACh modifies neural responses to stimuli and coordinates the activity of neurons across multiple levels of processing. These factors enable individual neurons or entire circuits to rapidly adapt to the dynamics of complex sensory stimuli, underscoring an essential role for ACh in sensory processing. In the auditory system, histological evidence shows that acetylcholine receptors (AChRs) are expressed at virtually every level of the ascending auditory pathway. Despite its apparent ubiquity in auditory circuitry, investigation of the roles of this cholinergic network has been mainly focused on the inner ear or forebrain structures, while less attention has been directed at regions between the cochlear nuclei and midbrain. In this review, we highlight what is known about cholinergic function throughout the auditory system from the ear to the cortex, but with a particular emphasis on brainstem and midbrain auditory centers. We will focus on receptor expression, mechanisms of modulation, and the functional implications of ACh for sound processing, with the broad goal of providing an overview of a newly emerging view of impactful cholinergic modulation throughout the auditory pathway.
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Affiliation(s)
- Chao Zhang
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, United States
| | - R. Michael Burger
- Department of Biological Sciences, Lehigh University, Bethlehem, PA, United States
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2
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Trenaman SC, Bowles SK, Andrew MK, Goralski K. The role of sex, age and genetic polymorphisms of CYP enzymes on the pharmacokinetics of anticholinergic drugs. Pharmacol Res Perspect 2021; 9:e00775. [PMID: 34003603 PMCID: PMC8130657 DOI: 10.1002/prp2.775] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 03/23/2021] [Accepted: 03/24/2021] [Indexed: 12/20/2022] Open
Abstract
There is evidence that use of drugs with anticholinergic properties increases the risk of cognitive impairment, and increased exposure to these drugs potentiates this risk. Anticholinergic drugs are commonly used even with associated risk of adverse events. Aging, sex, and genetic polymorphisms of cytochrome P450 (CYP) enzymes are associated with alterations in pharmacokinetic processes, which increase drug exposure and may further increase the risk of adverse drug events. Due to the increasing burden of cognitive impairment in our aging population and the future of personalized medicine, the objective of this review was to provide a critical clinical perspective on age, sex, and CYP genetic polymorphisms and their role in the metabolism and exposure to anticholinergic drugs. Age-related changes that may increase anticholinergic drug exposure include pseudocapillarization of liver sinusoidal endothelial cells, an approximate 3.5% decline in CYP content for each decade of life, and a reduction in kidney function. Sex-related differences that may be influenced by anticholinergic drug exposure include women having delayed gastric and colonic emptying, higher gastric pH, reduced catechol-O-methyl transferase activity, reduced glucuronidation, and reduced renal clearance and men having larger stomachs which may affect medication absorption. The overlay of poor metabolism phenotypes for CYP2D6 and CYP2C19 may further modify anticholinergic drug exposure in a significant proportion of the population. These factors help explain findings of clinical trials that show older adults and specifically older women achieve higher plasma concentrations of anticholinergic drugs and that poor metabolizers of CYP2D6 experience increased drug exposure. Despite this knowledge neither age, sex nor CYP phenotype are routinely considered when making decisions about the use or dosing of anticholinergic medications. Future study of anticholinergic medication needs to account for age, sex and CYP polymorphisms so that we may better approach personalized medicine for optimal outcomes and avoidance of medication-related cognitive impairment.
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Affiliation(s)
- Shanna C Trenaman
- Department of Medicine (Division of Geriatric Medicine), Nova Scotia Health, Halifax, Nova Scotia, Canada.,Department of Medicine (Geriatrics), Dalhousie University, Halifax, Nova Scotia, Canada
| | - Susan K Bowles
- Department of Medicine (Division of Geriatric Medicine), Nova Scotia Health, Halifax, Nova Scotia, Canada.,Department of Medicine (Geriatrics), Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Pharmacy, Nova Scotia Health, Halifax, Nova Scotia, Canada.,College of Pharmacy, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Melissa K Andrew
- Department of Medicine (Division of Geriatric Medicine), Nova Scotia Health, Halifax, Nova Scotia, Canada.,Department of Medicine (Geriatrics), Dalhousie University, Halifax, Nova Scotia, Canada
| | - Kerry Goralski
- College of Pharmacy, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada.,Department of Pediatrics, Dalhousie University, Halifax, Nova Scotia, Canada.,Division of Pediatric Hematology and Oncology, IWK Health Centre, Halifax, Nova Scotia, Canada
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3
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Gu S, Olszewski R, Taukulis I, Wei Z, Martin D, Morell RJ, Hoa M. Characterization of rare spindle and root cell transcriptional profiles in the stria vascularis of the adult mouse cochlea. Sci Rep 2020; 10:18100. [PMID: 33093630 PMCID: PMC7581811 DOI: 10.1038/s41598-020-75238-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 10/12/2020] [Indexed: 12/20/2022] Open
Abstract
The stria vascularis (SV) in the cochlea generates and maintains the endocochlear potential, thereby playing a pivotal role in normal hearing. Knowing transcriptional profiles and gene regulatory networks of SV cell types establishes a basis for studying the mechanism underlying SV-related hearing loss. While we have previously characterized the expression profiles of major SV cell types in the adult mouse, transcriptional profiles of rare SV cell types remained elusive due to the limitation of cell capture in single-cell RNA-Seq. The role of these rare cell types in the homeostatic function of the adult SV remain largely undefined. In this study, we performed single-nucleus RNA-Seq on the adult mouse SV in conjunction with sample preservation treatments during the isolation steps. We distinguish rare SV cell types, including spindle cells and root cells, from other cell types, and characterize their transcriptional profiles. Furthermore, we also identify and validate novel specific markers for these rare SV cell types. Finally, we identify homeostatic gene regulatory networks within spindle and root cells, establishing a basis for understanding the functional roles of these cells in hearing. These novel findings will provide new insights for future work in SV-related hearing loss and hearing fluctuation.
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Affiliation(s)
- Shoujun Gu
- Auditory Development and Restoration Program, National Institutes on Deafness and Other Communication Disorders, National Institutes of Health, Porter Neuroscience Research Center, 35 Convent Dr., Room 1F-226, Bethesda, MD, 20892, USA
| | - Rafal Olszewski
- Auditory Development and Restoration Program, National Institutes on Deafness and Other Communication Disorders, National Institutes of Health, Porter Neuroscience Research Center, 35 Convent Dr., Room 1F-226, Bethesda, MD, 20892, USA
| | - Ian Taukulis
- Auditory Development and Restoration Program, National Institutes on Deafness and Other Communication Disorders, National Institutes of Health, Porter Neuroscience Research Center, 35 Convent Dr., Room 1F-226, Bethesda, MD, 20892, USA
| | - Zheng Wei
- Biomedical Research Informatics Office, National Institute of Dental and Craniofacial Research, NIH, Bethesda, MD, 20892, USA
| | - Daniel Martin
- Biomedical Research Informatics Office, National Institute of Dental and Craniofacial Research, NIH, Bethesda, MD, 20892, USA
| | - Robert J Morell
- Computational Biology and Genomics Core, National Institutes on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Michael Hoa
- Auditory Development and Restoration Program, National Institutes on Deafness and Other Communication Disorders, National Institutes of Health, Porter Neuroscience Research Center, 35 Convent Dr., Room 1F-226, Bethesda, MD, 20892, USA.
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4
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Sabbir MG, Calcutt NA, Fernyhough P. Muscarinic Acetylcholine Type 1 Receptor Activity Constrains Neurite Outgrowth by Inhibiting Microtubule Polymerization and Mitochondrial Trafficking in Adult Sensory Neurons. Front Neurosci 2018; 12:402. [PMID: 29997469 PMCID: PMC6029366 DOI: 10.3389/fnins.2018.00402] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 05/24/2018] [Indexed: 11/13/2022] Open
Abstract
The muscarinic acetylcholine type 1 receptor (M1R) is a metabotropic G protein-coupled receptor. Knockout of M1R or exposure to selective or specific receptor antagonists elevates neurite outgrowth in adult sensory neurons and is therapeutic in diverse models of peripheral neuropathy. We tested the hypothesis that endogenous M1R activation constrained neurite outgrowth via a negative impact on the cytoskeleton and subsequent mitochondrial trafficking. We overexpressed M1R in primary cultures of adult rat sensory neurons and cell lines and studied the physiological and molecular consequences related to regulation of cytoskeletal/mitochondrial dynamics and neurite outgrowth. In adult primary neurons, overexpression of M1R caused disruption of the tubulin, but not actin, cytoskeleton and significantly reduced neurite outgrowth. Over-expression of a M1R-DREADD mutant comparatively increased neurite outgrowth suggesting that acetylcholine released from cultured neurons interacts with M1R to suppress neurite outgrowth. M1R-dependent constraint on neurite outgrowth was removed by selective (pirenzepine) or specific (muscarinic toxin 7) M1R antagonists. M1R-dependent disruption of the cytoskeleton also diminished mitochondrial abundance and trafficking in distal neurites, a disorder that was also rescued by pirenzepine or muscarinic toxin 7. M1R activation modulated cytoskeletal dynamics through activation of the G protein (Gα13) that inhibited tubulin polymerization and thus reduced neurite outgrowth. Our study provides a novel mechanism of M1R control of Gα13 protein-dependent modulation of the tubulin cytoskeleton, mitochondrial trafficking and neurite outgrowth in axons of adult sensory neurons. This novel pathway could be harnessed to treat dying-back neuropathies since anti-muscarinic drugs are currently utilized for other clinical conditions.
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Affiliation(s)
- Mohammad G Sabbir
- Division of Neurodegenerative Disorders, St. Boniface Hospital Research Centre, Winnipeg, MB, Canada
| | - Nigel A Calcutt
- Department of Pathology, University of California, San Diego, San Diego, CA, United States
| | - Paul Fernyhough
- Division of Neurodegenerative Disorders, St. Boniface Hospital Research Centre, Winnipeg, MB, Canada.,Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, MB, Canada
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5
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Reijntjes DO, Pyott SJ. The afferent signaling complex: Regulation of type I spiral ganglion neuron responses in the auditory periphery. Hear Res 2016; 336:1-16. [DOI: 10.1016/j.heares.2016.03.011] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 02/12/2016] [Accepted: 03/07/2016] [Indexed: 12/19/2022]
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Eckhard A, Dos Santos A, Liu W, Bassiouni M, Arnold H, Gleiser C, Hirt B, Harteneck C, Müller M, Rask-Andersen H, Löwenheim H. Regulation of the perilymphatic-endolymphatic water shunt in the cochlea by membrane translocation of aquaporin-5. Pflugers Arch 2015; 467:2571-88. [PMID: 26208470 PMCID: PMC4646919 DOI: 10.1007/s00424-015-1720-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2015] [Revised: 07/01/2015] [Accepted: 07/04/2015] [Indexed: 12/02/2022]
Abstract
Volume homeostasis of the cochlear endolymph depends on radial and longitudinal endolymph movements (LEMs). LEMs measured in vivo have been exclusively recognized under physiologically challenging conditions, such as experimentally induced alterations of perilymph osmolarity or endolymph volume. The regulatory mechanisms that adjust LEMs to the physiological requirements of endolymph volume homeostasis remain unknown. Here, we describe the formation of an aquaporin (AQP)-based "water shunt" during the postnatal development of the mouse cochlea and its regulation by different triggers. The final complementary expression pattern of AQP5 (apical membrane) and AQP4 (basolateral membrane) in outer sulcus cells (OSCs) of the cochlear apex is acquired at the onset of hearing function (postnatal day (p)8-p12). In vitro, hyperosmolar perfusion of the perilymphatic fluid spaces or the administration of the muscarinic agonist pilocarpine in cochlear explants (p14) induced the translocation of AQP5 channel proteins into the apical membranes of OSCs. AQP5 membrane translocation was blocked by the muscarinic antagonist atropine. The muscarinic M3 acetylcholine (ACh) receptor (M3R) was identified in murine OSCs via mRNA expression, immunolabeling, and in vitro binding studies using an M3R-specific fluorescent ligand. Finally, the water shunt elements AQP4, AQP5, and M3R were also demonstrated in OSCs of the human cochlea. The regulation of the AQP4/AQP5 water shunt in OSCs of the cochlear apex provides a molecular basis for regulated endolymphatic volume homeostasis. Moreover, its dysregulation or disruption may have pathophysiologic implications for clinical conditions related to endolymphatic hydrops, such as Ménière's disease.
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Affiliation(s)
- A Eckhard
- Department of Otorhinolaryngology-Head & Neck Surgery, University of Tübingen Medical Centre, Tübingen, Germany
- Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
| | - A Dos Santos
- Department of Otorhinolaryngology-Head & Neck Surgery, University of Tübingen Medical Centre, Tübingen, Germany
| | - W Liu
- Department of Surgical Sciences, Section of Otolaryngology, Uppsala University Hospital, Uppsala, Sweden
| | - M Bassiouni
- Department of Otorhinolaryngology-Head & Neck Surgery, University of Tübingen Medical Centre, Tübingen, Germany
| | - H Arnold
- Department of Otorhinolaryngology-Head & Neck Surgery, University of Tübingen Medical Centre, Tübingen, Germany
| | - C Gleiser
- Institute of Anatomy, University of Tübingen, Tübingen, Germany
| | - B Hirt
- Institute of Anatomy, University of Tübingen, Tübingen, Germany
| | - C Harteneck
- Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Interfaculty Center of Pharmacogenomics and Pharmaceutical Research (ICePhA), University of Tübingen, Tübingen, Germany
| | - M Müller
- School of Medicine and Health Sciences - European Medical School, University Hospital of Otorhinolaryngology, Medical Campus University of Oldenburg, Steinweg 13-17, 26122, Oldenburg, Germany
- Research Center of Neurosensory Science, University of Oldenburg, 26111, Oldenburg, Germany
- Cluster of Excellence Hearing4all, University of Oldenburg, 26111, Oldenburg, Germany
| | - H Rask-Andersen
- Department of Surgical Sciences, Section of Otolaryngology, Uppsala University Hospital, Uppsala, Sweden
| | - H Löwenheim
- School of Medicine and Health Sciences - European Medical School, University Hospital of Otorhinolaryngology, Medical Campus University of Oldenburg, Steinweg 13-17, 26122, Oldenburg, Germany.
- Research Center of Neurosensory Science, University of Oldenburg, 26111, Oldenburg, Germany.
- Cluster of Excellence Hearing4all, University of Oldenburg, 26111, Oldenburg, Germany.
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Liu W, Davis RL. Calretinin and calbindin distribution patterns specify subpopulations of type I and type II spiral ganglion neurons in postnatal murine cochlea. J Comp Neurol 2014; 522:2299-318. [PMID: 24414968 DOI: 10.1002/cne.23535] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 12/27/2013] [Accepted: 01/04/2014] [Indexed: 01/02/2023]
Abstract
As the first neural element in the auditory pathway, neurons in the spiral ganglion shape the initial coding of sound stimuli for subsequent processing. Within the ganglion, type I and type II neurons form divergent and convergent innervation patterns, respectively, with their hair cell sensory receptors, indicating that very different information is gathered and conveyed. Layered onto these basic innervation patterns are structural and electrophysiological features that provide additional levels of processing multifaceted sound stimuli. To understand the nature of this additional complexity of signal coding, we characterized the distribution of calretinin and calbindin, two regulators of intracellular calcium that serve as markers for neuronal subpopulations. We showed in acute preparations and in vitro that calretinin and calbindin staining levels were heterogeneous. Immunocytochemical analysis of colocalization further showed that high levels of staining for the two molecules rarely overlapped. Although varied amounts of calbindin and calretinin were found within each tonotopic location and neuronal type, some distinct subdistributions were noted. For example, calretinin levels were highest in neurons innervating the midcochlea region, whereas calbindin levels were similar across the entire ganglion. Furthermore, we noted that apical type II neurons, identified by antiperipherin labeling, had significantly lower levels of calretinin and higher levels of calbindin. We also established that the endogenous firing feature of onset tau of the subthreshold response showed a pattern related to quantified calretinin and calbindin staining levels. Taken together, our results suggest an additional dimension of complexity within the spiral ganglion beyond that currently categorized.
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Affiliation(s)
- Wenke Liu
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, 08854
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8
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Kanzaki J, Masuda M. Correlation between stress and acute sensorineural hearing loss: stress and sudden deafness. ACTA ACUST UNITED AC 2013. [DOI: 10.4295/audiology.56.137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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9
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Water channel proteins in the inner ear and their link to hearing impairment and deafness. Mol Aspects Med 2012; 33:612-37. [DOI: 10.1016/j.mam.2012.06.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 06/11/2012] [Accepted: 06/17/2012] [Indexed: 11/24/2022]
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10
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Rogers SW, Myers EJ, Gahring LC. The expression of nicotinic receptor alpha7 during cochlear development. Brain Behav 2012; 2:628-39. [PMID: 23139908 PMCID: PMC3489815 DOI: 10.1002/brb3.84] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 07/09/2012] [Indexed: 01/24/2023] Open
Abstract
Nicotinic acetylcholine receptor alpha7 expression was examined in the developing and adult auditory system using mice that were modified through homologous recombination to coexpress either GFP (alpha7GFP) or Cre (alpha7Cre), respectively. The expression of alpha7GFP is first detected at embryonic (E) day E13.5 in cells of the spiral prominence. By E14.5, sensory regions including the putative outer hair cells and Deiters' cells express alpha7GFP as do solitary efferent fibers. This pattern diminishes after E16.5 in a basal to apex progression, as Hensen's cells and cells of the spiral ligament acquire alpha7GFP expression. At birth and thereafter alpha7GFP also identifies a subset of spiral ganglion cells whose processes terminate on inner hair cells. Efferent fibers identified by peripherin or calcitonin gene-related protein do not coexpress alpha7GFP. In addition to cochlear structures, there is strong expression of alpha7GFP by cells of the central auditory pathways including the ventral posterior cochlear nucleus, lateral lemniscus, central inferior colliculus, and the medial geniculate nucleus. Our findings suggest that alpha7 expression by both neuronal and non-neuronal cells has the potential to impact multiple auditory functions through mechanisms that are not traditionally attributed to this receptor.
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Affiliation(s)
- Scott W Rogers
- Salt Lake City VA Geriatric Research, Education and Clinical Center, University of Utah Salt Lake City, Utah, 84132 ; Department of Neurobiology and Anatomy, University of Utah School of Medicine Salt Lake City, Utah, 84132
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Yao Q, Cheng H, Guo C, Zhou T, Huang X, Kong W. Muscarinic acetylcholine receptor subtype expression in type vestibular hair cells of guinea pigs. ACTA ACUST UNITED AC 2011; 31:682. [PMID: 22038361 DOI: 10.1007/s11596-011-0582-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Indexed: 10/16/2022]
Abstract
Recent studies have demonstrated that five subtypes (M1-M5) of muscarinic acetylcholine receptor (mAChR) are expressed in the vestibular periphery. However, the exact cellular location of the mAChRs is not clear. In this study, we investigated whether there is the expression of M1-M5 muscarinic receptor mRNA in isolated type II vestibular hair cells of guinea pig by using single-cell RT-PCR. In vestibular end-organ, cDNA of the expected size was obtained by RT-PCR. Moreover, mRNA was identified by RT-PCR from individually isolated type II vestibular hair cells (single-cell RT-PCR). Sequence analysis confirmed that the products were M1-M5 mAChR. These results demonstrated that M1-M5 mAChR was expressed in the type II vestibular hair cells of the guinea pig, which lends further support for the role of M1-M5 mAChR as a mediator of efferent cholinergic signalling pathway in vestibular hair cells.
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Affiliation(s)
- Qi Yao
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Huamao Cheng
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Changkai Guo
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Tao Zhou
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Xiang Huang
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Weijia Kong
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.
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Wersinger E, Fuchs PA. Modulation of hair cell efferents. Hear Res 2010; 279:1-12. [PMID: 21187136 DOI: 10.1016/j.heares.2010.12.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Revised: 12/10/2010] [Accepted: 12/20/2010] [Indexed: 02/01/2023]
Abstract
Outer hair cells (OHCs) amplify the sound-evoked motion of the basilar membrane to enhance acoustic sensitivity and frequency selectivity. Medial olivocochlear (MOC) efferents inhibit OHCs to reduce the sound-evoked response of cochlear afferent neurons. OHC inhibition occurs through the activation of postsynaptic α9α10 nicotinic receptors tightly coupled to calcium-dependent SK2 channels that hyperpolarize the hair cell. MOC neurons are cholinergic but a number of other neurotransmitters and neuromodulators have been proposed to participate in efferent transmission, with emerging evidence for both pre- and postsynaptic effects. Cochlear inhibition in vivo is maximized by repetitive activation of the efferents, reflecting facilitation and summation of transmitter release onto outer hair cells. This review summarizes recent studies on cellular and molecular mechanisms of cholinergic inhibition and the regulation of those molecular components, in particular the involvement of intracellular calcium. Facilitation at the efferent synapse is compared in a variety of animals, as well as other possible mechanisms of modulation of ACh release. These results suggest that short-term plasticity contributes to effective cholinergic inhibition of hair cells.
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Affiliation(s)
- Eric Wersinger
- The Center for Hearing and Balance, Department of Otolaryngology Head and Neck Surgery, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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The subcellular distribution of aquaporin 5 in the cochlea reveals a water shunt at the perilymph–endolymph barrier. Neuroscience 2010; 168:957-70. [DOI: 10.1016/j.neuroscience.2009.09.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2009] [Revised: 08/30/2009] [Accepted: 09/01/2009] [Indexed: 11/23/2022]
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15
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Muscarinic signaling in the cochlea: presynaptic and postsynaptic effects on efferent feedback and afferent excitability. J Neurosci 2010; 30:6751-62. [PMID: 20463237 DOI: 10.1523/jneurosci.5080-09.2010] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Acetylcholine is the major neurotransmitter of the olivocochlear efferent system, which provides feedback to cochlear hair cells and sensory neurons. To study the role of cochlear muscarinic receptors, we studied receptor localization with immunohistochemistry and reverse transcription-PCR and measured olivocochlear function, cochlear responses, and histopathology in mice with targeted deletion of each of the five receptor subtypes. M2, M4, and M5 were detected in microdissected immature (postnatal days 10-13) inner hair cells and spiral ganglion cells but not outer hair cells. In the adult (6 weeks), the same transcripts were found in microdissected organ of Corti and spiral ganglion samples. M2 protein was found, by immunohistochemistry, in olivocochlear fibers in both outer and inner hair cell areas. M3 mRNA was amplified only from whole cochleas, and M1 message was never seen in wild-type ears. Auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs) were unaffected by loss of Gq-coupled receptors (M1, M3, or M5), as were shock-evoked olivocochlear effects and vulnerability to acoustic injury. In contrast, loss of Gi-coupled receptors (M2 and/or M4) decreased neural responses without affecting DPOAEs (at low frequencies). This phenotype and the expression pattern are consistent with excitatory muscarinic signaling in cochlear sensory neurons. At high frequencies, both ABRs and DPOAEs were attenuated by loss of M2 and/or M4, and the vulnerability to acoustic injury was dramatically decreased. This aspect of the phenotype and the expression pattern are consistent with a presynaptic role for muscarinic autoreceptors in decreasing ACh release from olivocochlear terminals during high-level acoustic stimulation and suggest that muscarinic antagonists could enhance the resistance of the inner ear to noise-induced hearing loss.
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Takumida M, Anniko M. Expression of canonical transient receptor potential channel (TRPC) 1-7 in the mouse inner ear. Acta Otolaryngol 2009; 129:1351-8. [PMID: 19922081 DOI: 10.3109/00016480902798350] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
CONCLUSION It is suggested that TRPCs play a functional role in the sensory cell transduction system in the inner ear. OBJECTIVE To study expression of TRPC 1-7 in the mouse inner ear. MATERIALS AND METHODS The localization of TRPC 1-7 in the inner ear of CBA/J mice was investigated by immunohistochemistry. RESULTS TRPC immunoreactivity was observed generally in the inner ear, e.g. in the lateral wall of the cochlea, organ of Corti, spiral ganglion, vestibular end organs and vestibular ganglion. The immunofluorescent reaction to TRPC 3, 4, 5, and 7 in the stria vascularis was more intense than in the spiral prominence or spiral ligament. In the organ of Corti, TRPC immunoreactivity was observed in the outer hair cells (OHCs), inner hair cells (IHCs) and some supporting cells. TRPC 1-7 were all present in the ganglion cell body, TRPC 1 and 3 showing intense fluorescence, TRPC 2 and 7 moderate fluorescence and TRPC 4, 5 and 6 weak staining in ganglion fibres. In the vestibular end organs, vestibular hair cells (VHCs) showed immunoreactivity to all TRPCs. Nerve fibres in the subepithelial tissue were stained by TRPC 1, 3, 5, 6 and 7. Immunofluorescence to TRPC 1, 3, 4, 5, 6 and 7 was observed in the dark cells. In the vestibular ganglion, TRPC 1-7 were all present in the ganglion cell body. TRPC 1-4 and 7 elicited immunofluorescence in ganglion fibres.
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Affiliation(s)
- Masaya Takumida
- Department of Otolaryngology, Hiroshima University Faculty of Medicine, Hiroshima, Japan.
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Ramakrishnan NA, Drescher MJ, Barretto RL, Beisel KW, Hatfield JS, Drescher DG. Calcium-dependent binding of HCN1 channel protein to hair cell stereociliary tip link protein protocadherin 15 CD3. J Biol Chem 2008; 284:3227-3238. [PMID: 19008224 DOI: 10.1074/jbc.m806177200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cytoplasmic amino terminus of HCN1, the primary full-length HCN isoform expressed in trout saccular hair cells, was found by yeast two-hybrid protocols to bind the cytoplasmic carboxyl-terminal domain of a protocadherin 15a-like protein. HCN1 was immunolocalized to discrete sites on saccular hair cell stereocilia, consistent with gradated distribution expected for tip link sites of protocadherin 15a. HCN1 message was also detected in cDNA libraries of rat cochlear inner and outer hair cells, and HCN1 protein was immunolocalized to cochlear hair cell stereocilia. As predicted by the trout hair cell model, the amino terminus of rat organ of Corti HCN1 was found by yeast two-hybrid analysis to bind the carboxyl terminus of protocadherin 15 CD3, a tip link protein implicated in mechanosensory transduction. Specific binding between HCN1 and protocadherin 15 CD3 was confirmed with pull-down assays and surface plasmon resonance analysis, both predicting dependence on Ca(2+). In the presence of calcium chelators, binding between HCN1 and protocadherin 15 CD3 was characterized by a K(D) = 2.39 x 10(-7) m. Ca(2+) at 26.5-68.0 microm promoted binding, with K(D) = 5.26 x 10(-8) m (at 61 microm Ca(2+)). Binding by deletion mutants of protocadherin 15 CD3 pointed to amino acids 158-179 (GenBank accession number XP_238200), with homology to the comparable region in trout hair cell protocadherin 15a-like protein, as necessary for binding to HCN1. Amino terminus binding of HCN1 to HCN1, hypothesized to underlie HCN1 channel formation, was also found to be Ca(2+)-dependent, although the binding was skewed toward a lower effective maximum [Ca(2+)] than for the HCN1 interaction with protocadherin 15 CD3. Competition may therefore exist in vivo between the two binding sites for HCN1, with binding of HCN1 to protocadherin 15 CD3 favored between 26.5 and 68 microm Ca(2+). Taken together, the evidence supports a role for HCN1 in mechanosensory transduction of inner ear hair cells.
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Affiliation(s)
- Neeliyath A Ramakrishnan
- Department of Otolaryngology, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - Marian J Drescher
- Department of Otolaryngology, Wayne State University School of Medicine, Detroit, Michigan 48201.
| | - Roberto L Barretto
- Department of Otolaryngology, Wayne State University School of Medicine, Detroit, Michigan 48201
| | - Kirk W Beisel
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68178
| | - James S Hatfield
- Electron Microscopy Laboratory, Veterans Affairs Medical Center, Detroit, Michigan 48201
| | - Dennis G Drescher
- Department of Otolaryngology, Wayne State University School of Medicine, Detroit, Michigan 48201; Departments of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan 48201
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18
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Li GQ, Kevetter GA, Leonard RB, Prusak DJ, Wood TG, Correia MJ. Muscarinic acetylcholine receptor subtype expression in avian vestibular hair cells, nerve terminals and ganglion cells. Neuroscience 2007; 146:384-402. [PMID: 17391855 PMCID: PMC1986736 DOI: 10.1016/j.neuroscience.2007.02.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2007] [Revised: 01/31/2007] [Accepted: 02/08/2007] [Indexed: 10/23/2022]
Abstract
Muscarinic acetylcholine receptors (mAChRs) are widely expressed in the CNS and peripheral nervous system and play an important role in modulating the cell activity and function. We have shown that the cholinergic agonist carbachol reduces the pigeon's inwardly rectifying potassium channel (pKir2.1) ionic currents in native vestibular hair cells. We have cloned and sequenced pigeon mAChR subtypes M2-M5 and we have studied the expression of all five mAChR subtypes (M1-M5) in the pigeon vestibular end organs (semicircular canal ampullary cristae and utricular maculae), vestibular nerve fibers and the vestibular (Scarpa's) ganglion using tissue immunohistochemistry (IH), dissociated single cell immunocytochemistry (IC) and Western blotting (WB). We found that vestibular hair cells, nerve fibers and ganglion cells each expressed all five (M1-M5) mAChR subtypes. Two of the three odd-numbered mAChRs (M1, M5) were present on the hair cell cilia, supporting cells and nerve terminals. And all three odd numbered mAChRs (M1, M3 and M5) were expressed on cuticular plates, myelin sheaths and Schwann cells. Even-numbered mAChRs were seen on the nerve terminals. M2 was also shown on the cuticular plates and supporting cells. Vestibular efferent fibers and terminals were not identified in our studies. Results from WB of the dissociated vestibular epithelia, nerve fibers and vestibular ganglia were consistent with the results from IH and IC. Our findings suggest that there is considerable co-expression of the subtypes on the neural elements of the labyrinth. Further electrophysiological and pharmacological studies should delineate the mechanisms of action of muscarinic acetylcholine receptors on structures in the labyrinth.
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Affiliation(s)
- Gang Q. Li
- Department of Otolaryngologyy, University of Texas Medical Branch at Galveston, Galveston Texas, 77550-1063 U.S.A
- Department of Neuroscience and Cell Biologyy, University of Texas Medical Branch at Galveston, Galveston Texas, 77550-1063 U.S.A
| | - Golda A. Kevetter
- Department of Otolaryngologyy, University of Texas Medical Branch at Galveston, Galveston Texas, 77550-1063 U.S.A
- Department of Neuroscience and Cell Biologyy, University of Texas Medical Branch at Galveston, Galveston Texas, 77550-1063 U.S.A
| | - Robert B. Leonard
- Department of Otolaryngologyy, University of Texas Medical Branch at Galveston, Galveston Texas, 77550-1063 U.S.A
- Department of Neuroscience and Cell Biologyy, University of Texas Medical Branch at Galveston, Galveston Texas, 77550-1063 U.S.A
| | - Deborah J Prusak
- Sealy Center for Molecular Medicine, University of Texas Medical Branch at Galveston, Galveston Texas, 77550-1063 U.S.A
| | - Thomas G. Wood
- Sealy Center for Molecular Medicine, University of Texas Medical Branch at Galveston, Galveston Texas, 77550-1063 U.S.A
- Department of Molecular Biology and Biochemistry, University of Texas Medical Branch at Galveston, Galveston Texas, 77550-1063 U.S.A
| | - Manning J. Correia
- Department of Otolaryngologyy, University of Texas Medical Branch at Galveston, Galveston Texas, 77550-1063 U.S.A
- Department of Neuroscience and Cell Biologyy, University of Texas Medical Branch at Galveston, Galveston Texas, 77550-1063 U.S.A
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19
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Raybould NP, Jagger DJ, Kanjhan R, Greenwood D, Laslo P, Hoya N, Soeller C, Cannell MB, Housley GD. TRPC-like conductance mediates restoration of intracellular Ca2+ in cochlear outer hair cells in the guinea pig and rat. J Physiol 2006; 579:101-13. [PMID: 17158171 PMCID: PMC2075380 DOI: 10.1113/jphysiol.2006.122929] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Ca2+ signalling is central to cochlear sensory hair cell physiology through its influence on sound transduction, membrane filter properties and neurotransmission. However, the mechanism for establishing Ca2+ homeostasis in these cells remains unresolved. Canonical transient receptor potential (TRPC) Ca2+ entry channels provide an important pathway for maintaining intracellular Ca2+ levels. TRPC3 subunit expression was detected in guinea pig and rat organ of Corti by RT-PCR, and localized to the sensory and neural poles of the inner and outer hair cells (OHCs) by confocal immunofluorescence imaging. A cation entry current with a TRPC-like phenotype was identified in guinea pig and rat OHCs by whole-cell voltage clamp. This slowly activating current was induced by the lowering of cytosolic Ca2+ levels ([Ca2+]i) following a period in nominally Ca2+-free solution. Activation was dependent upon the [Ca2+]o and was sustained until [Ca(2+)]i was restored. Ca2+ entry was confirmed by confocal fluorescence imaging, and rapidly recruited secondary charybdotoxin- and apamin-sensitive K(Ca) currents. Dual activation by the G protein-coupled receptor (GPCR)-phospholipase C-diacylglycerol (DAG) second messenger pathway was confirmed using the analogue 1-oleoyl-2-acetyl-sn-glycerol (OAG). Ion substitution experiments showed that the putative TRPC Ca2+ entry current was selective for Na+ > K+ with a ratio of 1: 0.6. The Ca2+ entry current was inhibited by the TRPC channel blocker 2-aminoethyl diphenylborate (2APB) and the tyrosine kinase inhibitor, erbstatin analogue. We conclude that TRPC Ca2+ entry channels, most likely incorporating TRPC3 subunits, support cochlear hair cell Ca2+ homeostasis and GPCR signalling.
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Affiliation(s)
- Nicholas P Raybould
- Department of Physiology, University of Auckland, Private Bag 92019, Auckland, New Zealand
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20
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Stoffel MH, Monnard CW, Steiner A, Mevissen M, Meylan M. Distribution of muscarinic receptor subtypes and interstitial cells of Cajal in the gastrointestinal tract of healthy dairy cows. Am J Vet Res 2006; 67:1992-7. [PMID: 17144799 DOI: 10.2460/ajvr.67.12.1992] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To describe the distribution of muscarinic receptor subtypes M(1) to M(5) and interstitial cells of Cajal (ICCs) in the gastrointestinal tract of healthy dairy cows. SAMPLE POPULATION Full-thickness samples were collected from the fundus, corpus, and pyloric part of the abomasum and from the duodenum, ileum, cecum, proximal loop of the ascending colon, and both external loops of the spiral colon of 5 healthy dairy cows after slaughter. PROCEDURES Samples were fixed in paraformaldehyde and embedded in paraffin. Muscarinic receptor subtypes and ICCs were identified by immunohistochemical analysis. RESULTS Staining for M(1) receptors was found in the submucosal plexus and myenteric plexus. Antibodies against M(2) receptors stained nuclei of smooth muscle cells only. Evidence of M(3) receptors was found in the lamina propria, in intramuscular neuronal terminals, on intermuscular nerve fibers, and on myocytes of microvessels. There was no staining for M(4) receptors. Staining for M(5) receptors was evident in the myocytes of microvessels and in smooth muscle cells. The ICCs were detected in the myenteric plexus and within smooth muscle layers. Distribution among locations of the bovine gastrointestinal tract did not differ for muscarinic receptor subtypes or ICCs. CONCLUSIONS AND CLINICAL RELEVANCE The broad distribution of M(1), M(3), M(5), and ICCs in the bovine gastrointestinal tract indicated that these components are likely to play an important role in the regulation of gastrointestinal tract motility in healthy dairy cows. Muscarinic receptors and ICCs may be implicated in the pathogenesis of motility disorders, such as abomasal displacement and cecal dilatation-dislocation.
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Affiliation(s)
- Michael H Stoffel
- Division of Veterinary Anatomy, Vetsuisse Faculty, University of Berne, 3001 Berne, Switzerland
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21
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Khan KM, Sarfaraz N, Siddiqui S, Nawaz H. Immunohistochemical localization of G protein betagamma subunits in the lateral wall of the rat cochlea. J Anat 2006; 208:205-18. [PMID: 16441565 PMCID: PMC2100195 DOI: 10.1111/j.1469-7580.2006.00526.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
The role of G protein-mediated signal transduction in the production of endolymph, an extracellular fluid of unusual ionic composition, is beginning to be understood. The identity of Galpha subunits in the stria vascularis and the spiral ligament of the lateral wall of the cochlear duct is well established. However, little is known about the presence of betagamma subunits. This study used immunohistochemistry to investigate the distribution of G protein betagamma subunits in the lateral wall of the cochlea. Temporal bones of 6- to 8-week-old rats were fixed in 4% paraformaldehyde and 0.1% glutaraldehyde and processed for embedding in paraffin wax. The dewaxed, midmodiolar sections of the cochlea were incubated with subunit-specific polyclonal antibodies. The results show that the pattern of immunoreactivity varies for the G protein beta1-4 and gamma1-3, 5 and 7 subunits in the stria vascularis and spiral ligament. In the stria vascularis, immunoreactivity was detected for beta2, beta3, beta4, gamma1, gamma2 and gamma7 subunits. All five types of fibrocytes in the spiral ligament exhibited positive staining for gamma2 and gamma7. However, immunoreactivity for beta1-4 subunits was variable. Immunoreactivity for gamma3 and gamma5 subunits was not detected in the lateral cochlear wall. The expression pattern of G protein betagamma subunits in lateral wall provides a basis for interpreting the functions of G protein-coupled receptors in cochlear fluid homeostasis.
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Affiliation(s)
- Khalid M Khan
- Department of Biological & Biomedical Sciences, Faculty of Health Sciences, The Aga Khan University, Karachi, Pakistan.
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22
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Drescher MJ, Drescher DG, Khan KM, Hatfield JS, Ramakrishnan NA, Abu-Hamdan MD, Lemonnier LA. Pituitary adenylyl cyclase-activating polypeptide (PACAP) and its receptor (PAC1-R) are positioned to modulate afferent signaling in the cochlea. Neuroscience 2006; 142:139-64. [PMID: 16876955 DOI: 10.1016/j.neuroscience.2006.05.065] [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: 01/16/2006] [Revised: 05/02/2006] [Accepted: 05/09/2006] [Indexed: 10/24/2022]
Abstract
Pituitary adenylyl cyclase-activating polypeptide (PACAP), via its specific receptor pituitary adenylyl cyclase-activating polypeptide receptor 1 (PAC1-R), is known to have roles in neuromodulation and neuroprotection associated with glutamatergic and cholinergic neurotransmission, which, respectively, are believed to form the primary basis for afferent and efferent signaling in the organ of Corti. Previously, we identified transcripts for PACAP preprotein and multiple splice variants of its receptor, PAC1-R, in microdissected cochlear subfractions. In the present work, neural localizations of PACAP and PAC1-R within the organ of Corti and spiral ganglion were examined, defining sites of PACAP action. Immunolocalization of PACAP and PAC1-R in the organ of Corti and spiral ganglion was compared with immunolocalization of choline acetyltransferase (ChAT) and synaptophysin as efferent neuronal markers, and glutamate receptor 2/3 (GluR2/3) and neurofilament 200 as afferent neuronal markers, for each of the three cochlear turns. Brightfield microscopy giving morphological detail for individual immunolocalizations was followed by immunofluorescence detection of co-localizations. PACAP was found to be co-localized with ChAT in nerve fibers of the intraganglionic spiral bundle and beneath the inner and outer hair cells within the organ of Corti. Further, evidence was obtained that PACAP is expressed in type I afferent axons leaving the spiral ganglion en route to the auditory nerve, potentially serving as a neuromodulator in axonal terminals. In contrast to the efferent localization of PACAP within the organ of Corti, PAC1-R immunoreactivity was co-localized with afferent dendritic neuronal marker GluR2/3 in nerve fibers passing beneath and lateral to the inner hair cell and in fibers at supranuclear and basal sites on outer hair cells. Given the known association of PACAP with catecholaminergic neurotransmission in sympathoadrenal function, we also re-examined the issue of whether the organ of Corti receives adrenergic innervation. We now demonstrate the existence of nerve fibers within the organ of Corti which are immunoreactive for the adrenergic marker dopamine beta-hydroxylase (DBH). DBH immunoreactivity was particularly prominent in nerve fibers both at the base and near the cuticular plate of outer hair cells of the apical turn, extending to the non-sensory Hensen's cell region. Evidence was obtained for limited co-localization of DBH with PAC1-R and PACAP. In the process of this investigation, we obtained evidence that efferent and afferent nerve fibers, in addition to adrenergic nerve fibers, are present at supranuclear sites on outer hair cells and distributed within the non-sensory epithelium of the apical cochlear turn for rat, based upon immunoreactivity for the corresponding neuronal markers. Overall, PACAP is hypothesized to act within the organ of Corti as an efferent neuromodulator of afferent signaling via PAC1-R that is present on type I afferent dendrites, in position to afford protection from excitotoxicity. Additionally, PACAP/PAC1-R may modulate secretion of catecholamines from adrenergic terminals within the organ of Corti.
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Affiliation(s)
- M J Drescher
- Laboratory of Bio-otology, Department of Otolaryngology, Wayne State University School of Medicine, 261 Lande Medical Research Building, 540 East Canfield Avenue, Detroit, MI 48201, USA.
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23
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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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24
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Mazzone SB, Mori N, Burman M, Palovich M, Belmonte KE, Canning BJ. Fluorescent styryl dyes FM1-43 and FM2-10 are muscarinic receptor antagonists: intravital visualization of receptor occupancy. J Physiol 2006; 575:23-35. [PMID: 16728454 PMCID: PMC1819419 DOI: 10.1113/jphysiol.2006.106351] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The fluorescent styryl dyes FM1-43 and FM2-10 have been used to visualize the endocytic and exocytic processes involved in neurotransmission in a variety of central and peripheral nerve preparations. Their utility is limited to some extent by a poorly understood vesicular-independent labelling of cells and tissues. We show here that one likely cause of this troublesome background labelling is that FM1-43 and FM2-10 are selective and competitive antagonists at both cloned and endogenously expressed muscarinic acetylcholine receptors. In radioligand binding studies, FM1-43 and FM2-10 bound with moderate affinity (23-220 nM) to membranes of Chinese hamster ovary (CHO) cells expressing cloned human muscarinic receptors (M1-M5). In functional studies in vitro, FM1-43 and FM2-10 inhibited electrical field stimulation (EFS) and acetylcholine-induced cholinergic contractions of guinea-pig tracheal strips (IC50: FM1-43, 0.4 +/- 0.1; FM2-10, 1.6 +/- 0.1 microM; concentration of antagonist producing a 2-fold leftward shift in the acetylcholine concentration-response curve (Kb): FM1-43, 0.3 +/- 0.1; FM2-10, 15.8 +/- 10.1 microM). Neither compound inhibited EFS-evoked, non-adrenergic non-cholinergic nerve-mediated relaxations or contractions of the airways, or contractions mediated by histamine H1 receptor or tachykinin NK2 receptor activation. Incubating freshly excised tracheal whole-mount preparations with 5 microM FM1-43 resulted in intense fluorescence labelling of the smooth muscle that was reduced by up to 90% in the presence of selective M2 and M3 receptor antagonists. The potency of the FM dyes as muscarinic receptor antagonists is within the concentration range used to study vesicular cycling at nerve terminals. Given that muscarinic receptors play a key role in the regulation of neurotransmitter release from a variety of neurones, the anticholinergic properties of FM dyes may have important implications when studying vesicular events in the nervous system. In addition, these dyes may provide a novel tool for visualizing muscarinic receptor occupancy in living tissue or cell preparations.
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25
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Hamamura M, Maróstica E, de Avellar MCW, Porto CS. Muscarinic acetylcholine receptor subtypes in the rat seminal vesicle. Mol Cell Endocrinol 2006; 247:192-8. [PMID: 16481100 DOI: 10.1016/j.mce.2006.01.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Revised: 12/19/2005] [Accepted: 01/05/2006] [Indexed: 11/21/2022]
Abstract
The aim of the present study was to identify the muscarinic acetylcholine receptor (mAChR) mRNA subtypes in the rat seminal vesicle. Furthermore, the mAChR subtypes involved in the contraction of the seminal vesicle were also explored. Reverse transcriptase-polymerase chain reaction (PCR) was performed and five PCR products corresponding to M1-M5 mAChR mRNA subtypes were detected in this tissue. Functional pharmacological studies indicated that the rank order of mAChR antagonists in blocking the contractile effects of carbachol was p-fluoro-hexahydro-sila-difenidol (pF-HHSiD) >> tropicamide > methoctramine = pirenzepine. This antagonist profile indicates that M3 mAChR subtype is predominantly involved in the seminal vesicle contraction. Furthermore, immunohistochemical studies confirmed the presence of the M3 mAChR subtype in the smooth muscle layers. M2 mAChR subtype was also immunolocalized in smooth muscle cells and may be involved in the contraction of this tissue. The presence of M2 and M3 mAChR subtypes in the epithelial cells suggests that these receptors could be involved in the protein secretion. Taken together, the cholinergic neurotransmitter may be a factor controlling contractility and protein secretion in this tissue.
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Affiliation(s)
- Margarete Hamamura
- Section of Experimental Endocrinology, Department of Pharmacology, Universidade Federal de São Paulo, Escola Paulista de Medicina, Rua Três de maio 100, INFAR, Vila Clementino, São Paulo, SP 04044-020, Brazil
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26
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Jin YM, Godfrey DA. Effects of cochlear ablation on muscarinic acetylcholine receptor binding in the rat cochlear nucleus. J Neurosci Res 2006; 83:157-66. [PMID: 16307447 DOI: 10.1002/jnr.20706] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cholinergic synapses in the cochlear nucleus (CN) have been reported to modulate spontaneous activity via muscarinic acetylcholine receptors. In this study, muscarinic receptor binding was measured as specific binding of 1-[N-methyl-(3)H]scopolamine in CN regions of control rats and 7 days, 1 month, and 2 months after unilateral cochlear ablation. In control rats, the strongest binding was found in granular regions, followed in order by fusiform soma, molecular, and deep layers of the dorsal cochlear nucleus (DCN), with much lower binding in the anteroventral CN (AVCN) and posteroventral CN (PVCN). After unilateral cochlear ablation, binding in the AVCN, PVCN, and their associated granular regions on the lesion side became progressively greater than on the control side through 2 months after lesion. A significant asymmetry, with binding higher on the lesion side, was also found in the DCN fusiform soma layer at 7 days, and there and in the DCN deep layer at 1 and 2 months after lesion. There was also evidence of increased binding on the control side in most CN regions. By contrast, binding in the ipsilateral facial nucleus decreased, compared with the control side, by 7 days after the lesion and showed some recovery toward symmetry by 2 months after lesion, and there was no evidence for contralateral changes. These muscarinic receptor binding changes reflect receptor plasticity after loss of auditory nerve innervation. Such plasticity may underlie some of the central auditory functional changes that occur following peripheral lesions, such as tinnitus and hyperacusis.
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Affiliation(s)
- Yong-Ming Jin
- Division of Otolaryngology, Department of Surgery, Medical University of Ohio, Toledo, 43614-5807, USA
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27
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Abu-Hamdan MD, Drescher MJ, Ramakrishnan NA, Khan KM, Toma VS, Hatfield JS, Drescher DG. Pituitary Adenylyl Cyclase-Activating Polypeptide (PACAP) and its receptor (PAC1-R) in the cochlea: Evidence for specific transcript expression of PAC1-R splice variants in rat microdissected cochlear subfractions. Neuroscience 2006; 140:147-61. [PMID: 16626868 DOI: 10.1016/j.neuroscience.2006.01.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2005] [Revised: 12/28/2005] [Accepted: 01/06/2006] [Indexed: 11/26/2022]
Abstract
Pituitary adenylyl cyclase-activating polypeptide (PACAP) is a neuropeptide originally isolated from the hypothalamus, named for its high potency in stimulating adenylyl cyclase in pituitary cells. PACAP acts through the specific receptor PAC1-R to modulate the action of neurotransmitters, and additionally, to regulate cell viability via autocrine/intracrine mechanisms. Evidence has now been obtained that PACAP and multiple splice variants of PAC1-R are expressed in the rat cochlea. mRNA for PACAP precursor protein is found by reverse transcription-polymerase chain reaction (RT-PCR) in microdissected cochlear lateral wall, organ of Corti, and spiral ganglion subfractions. A specific pattern of expression of mRNA for PAC1-R splice variants, which mediate the response to PACAP, has been revealed by RT-PCR and cloning for the cochlear subfractions. Transcript for the short form of PAC1-R is found in all three subfractions. Four additional splice variants -- hop1, hop2, hip, and a novel hop1 splice variant -- are expressed in the lateral wall. For the amino terminus splice region of PAC1-R, a new splice variant has been detected in the organ of Corti, representing a deletion of the first 7 of 21 amino acids detected in the PAC1-R very-short sequence. Overall, from message determinations in cochlear subfractions, there are five PAC1-R splice variants in the lateral wall, two in the organ of Corti and one in the spiral ganglion, indicating multiple possible responses to PACAP and/or mechanisms to modulate the response to PACAP in the cochlea. The variety of PAC1-R splice variants expressed may reflect the diversity in cell function between subfractions that is modulated by PACAP. The neuropeptide and its specific receptor have been immunolocalized in the lateral wall, the source of the largest number of cochlear PAC1-R splice variants. The receptor was targeted by primary antibodies which would elicit immunoreactivity for all splice variants of PAC1-R detected with RT-PCR, and evidence has been obtained with Western blot analysis suggesting that PAC1-R is glycosylated in vivo. Within the lateral wall, PACAP and PAC1-R were immunolocalized primarily to the stria vascularis, with immunoreactivity for both neuropeptide and receptor increasing from the basal to apical cochlear turns. Within the stria, PACAP immunoreactivity was localized to the basolateral extensions of marginal cells, while PAC1-R was clearly associated with tight junctions between the marginal cells close to the endolymphatic compartment. In addition, evidence was obtained that PAC1-R was associated with endothelial cells of the capillaries in the stria vascularis. The large number of splice variants expressed, coupled to the specificity in linkage between PAC1-R splice variants and G-protein-coupled second messenger pathways, could provide a mechanism to closely modulate tight junction integrity in the stria vascularis, impacting the endolymphatic potential.
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Affiliation(s)
- M D Abu-Hamdan
- Laboratory of Bio-otology, Department of Otolaryngology, Wayne State University School of Medicine, 261 Lande Medical Research Building, 540 East Canfield Avenue, Detroit, MI 48201, USA
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28
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Siu ER, Yasuhara F, Maróstica E, Avellar MCW, Porto CS. Expression and localization of muscarinic acetylcholine receptor subtypes in rat efferent ductules and epididymis. Cell Tissue Res 2005; 323:157-66. [PMID: 16160857 DOI: 10.1007/s00441-005-0054-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2005] [Accepted: 07/18/2005] [Indexed: 11/27/2022]
Abstract
The expression of muscarinic acetylcholine receptor (mAChR) subtypes (M(1)-M(5)) was studied in the rat efferent ductules and epididymis at the mRNA and protein levels. The relative abundance of each mAChR transcript subtype differed depending on the tissue and the epididymal region analyzed. The M(1) mAChR mRNA level was more abundant in the efferent ductules than in the caput and cauda of the epididymis. The M(2) mAChR mRNA level was similar between the efferent ductules and caput of the epididymis and higher in the cauda region. The M(3) mAChR mRNA level was low in the efferent ductules and caput of the epididymis, but high levels were detected in the cauda region. mRNAs for M(4) and M(5) mAChRs were not detected in these tissues. Our studies indicated a variable degree of immunostaining for each mAChR subtype in a cell-type and tissue-specific pattern. M(1) mAChR was detected over the efferent ductule epithelium. M(2) and M(3) mAChRs were observed in the apical region of the ciliated cells. Apical and narrow cells of the initial segment showed distinct staining by M(1) antibody, whereas a supranuclear reaction was noted in the principal cells of the caput of the epididymis. In addition, staining for M(1) and M(2) mAChRs was visible in the apical membrane of some epithelial cells of the cauda region. M(3) mAChR was detected in the peritubular smooth muscle of the efferent ductules and epididymis. Functional studies suggested the involvement of this subtype in epididymal tubule contraction. Thus, the cell-specific expression of the various mAChR subtypes in the efferent ductules and epididymis suggests that these receptors play a role in the modulation of luminal fluid composition and smooth muscle contraction.
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Affiliation(s)
- Erica R Siu
- Section of Experimental Endocrinology, Department of Pharmacology, Universidade Federal de São Paulo-Escola Paulista de Medicina, Rua Três de maio 100, INFAR, Vila Clementino, 04044-020 São Paulo, Brazil
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Maison SF, Emeson RB, Adams JC, Luebke AE, Liberman MC. Loss of alpha CGRP reduces sound-evoked activity in the cochlear nerve. J Neurophysiol 2003; 90:2941-9. [PMID: 12904337 DOI: 10.1152/jn.00596.2003] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
alpha-Calcitonin gene-related peptide (alphaCGRP) is one of several neurotransmitters immunolocalized in the unmyelinated component of the cochlear efferent innervation, the lateral olivocochlear (OC) system, which makes axo-dendritic synapses with cochlear sensory neurons. In rodents, CGRP is also immunocolocalized in the myelinated medial OC system, which contacts cochlear outer hair cells (OHCs). To understand the role(s) of this neuropeptide in the OC system, we characterized the auditory phenotype of alphaCGRP-null mice. Cochlear threshold sensitivity was normal in mutant mice, both via a neural metric, the auditory brain stem response (ABR), and an OHC-based metric, distortion product otoacoustic emissions (DPOAEs). Medial OC function and resistance to acoustic injury were also unaffected by alphaCGRP deletion: the former was assessed by measuring cochlear response suppression with electrical stimulation of the OC bundle, the latter by measuring temporary threshold shifts after exposure to high level sound. However, significant abnormality in alphaCGRP-null mice was seen in the growth of cochlear neural responses with increasing stimulus level. This observation, contrasted with normal amplitude-versus-level functions for DPOAEs, is consistent with a selective, postsynaptic effect on cochlear neurons via alphaCGRP release from lateral OC terminals. This constitutes the most direct evidence to date for a functional role of the lateral OC system in the auditory periphery.
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Affiliation(s)
- Stephane F Maison
- Department of Otology and Laryngology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts 02114, USA.
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Khan KM, Sarfaraz N, Siddiqui S, Malik ZA, Salim Z. Expression of G protein alpha subunits in the lateral wall of the rat cochlea. J Anat 2003; 202:293-301. [PMID: 12713269 PMCID: PMC1571081 DOI: 10.1046/j.1469-7580.2003.00159.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/17/2002] [Indexed: 11/20/2022] Open
Abstract
Expression of five G protein alpha subunits was investigated in the rat cochlea by reverse transcription-polymerase chain reaction (RT-PCR) in order to understand their role in the cochlear signal transduction mechanisms. Immunohistochemical techniques were employed to study their distribution in the lateral wall of the cochlea. Total RNA was extracted with guanidine thiocyanate from cochleas and brains of 14-21-day-old rats. The extract was treated with DNase to degrade genomic DNA. After RT, the resulting cDNA was amplified by PCR using primers specific for the nucleotide sequences representing alpha subunits of heterotrimeric G proteins. The results indicated that mRNA for all five alpha subunits was expressed in the brain and cochlear samples. For immunohistochemical localization, temporal bones of 6-week-old rats were fixed in 4% paraformaldehyde and 0.1% glutaraldehyde and processed for embedding in paraffin wax. The dewaxed, midmodiolar sections of the cochlea were incubated with subunit-specific polyclonal antibodies. The pattern of immunoreactivity varied for the five G protein alpha subunits studied in the stria vascularis and spiral ligament. The significance of these findings and the role of G protein alpha subunits in cochlear fluid homeostasis are discussed.
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Affiliation(s)
- Khalid M Khan
- Department of Biological & Biomedical Sciences, Faculty of Health Sciences, The Aga Khan University, Karachi, Pakistan.
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Ramakrishnan NA, Green GE, Pasha R, Drescher MJ, Swanson GS, Perin PC, Lakhani RS, Ahsan SF, Hatfield JS, Khan KM, Drescher DG. Voltage-gated Ca2+ channel Ca(V)1.3 subunit expressed in the hair cell epithelium of the sacculus of the trout Oncorhynchus mykiss: cloning and comparison across vertebrate classes. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2002; 109:69-83. [PMID: 12531517 DOI: 10.1016/s0169-328x(02)00522-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Full-length sequence (>6.5 kb) has been determined for the Ca(V)1.3 pore-forming subunit of the voltage-gated Ca(2+) channel from the saccular hair cells of the rainbow trout (Oncorhynchus mykiss). Primary structure was obtained from overlapping PCR and cloned fragments, amplified by primers based on teleost, avian, and mammalian sources. Trout saccular Ca(V)1.3 was localized to hair cells, as evidenced by its isolation from an epithelial layer in which the hair cell is the only intact cell type. The predicted amino acid sequence of the trout hair cell Ca(V)1.3 is approximately 70% identical to the sequences of avian and mammalian Ca(V)1.3 subunits and shows L-type characteristics. The trout hair cell Ca(V)1.3 expresses a 26-aa insert in the I-II cytoplasmic loop (exon 9a) and a 10-aa insert in the IVS2-IVS3 cytoplasmic loop (exon 30a), neither of which is appreciably represented in trout brain. The exon 9a insert also occurs in hair cell organs of chick and rat, and appears as an exon in human genomic Ca(V)1.3 sequence (but not in the Ca(V)1.3 coding sequence expressed in human brain or pancreas). The exon 30a insert, although expressed in hair cells of chick as well as trout, does not appear in comparable rat or human tissues. Further, the IIIS2 region shows a splice choice (exon 22a) that is associated with the hair cell organs of trout, chick, and rat, but is not found in human genomic sequence. The elucidation of the primary structure of the voltage-gated Ca(2+) channel Ca(V)1.3 subunit from hair cells of the teleost, representing the lowest of the vertebrate classes, suggests a generality of sensory mechanism for Ca(V)1.3 across hair cell systems. In particular, the exon 9a insert of this channel appears to be the molecular feature most consistently associated with hair cells from fish to mammal, consonant with the hypothesis that the latter region may be a signature for the hair cell.
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Affiliation(s)
- Neeliyath A Ramakrishnan
- Laboratory of Bio-otology, Department of Otolaryngology, Wayne State University School of Medicine, 259 Lande Medical Research Building, 540 East Canfield Avenue, Detroit, MI 48201, USA
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