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Mathur PD, Zou J, Neiswanger G, Zhu D, Wang Y, Almishaal AA, Vashist D, Hammond HK, Park AH, Yang J. Adenylyl cyclase 6 plays a minor role in the mouse inner ear and retina. Sci Rep 2023; 13:7075. [PMID: 37127773 PMCID: PMC10151359 DOI: 10.1038/s41598-023-34361-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Accepted: 04/28/2023] [Indexed: 05/03/2023] Open
Abstract
Adenylyl cyclase 6 (AC6) synthesizes second messenger cAMP in G protein-coupled receptor (GPCR) signaling. In cochlear hair cells, AC6 distribution relies on an adhesion GPCR, ADGRV1, which is associated with Usher syndrome (USH), a condition of combined hearing and vision loss. ADGRV1 is a component of the USH type 2 (USH2) protein complex in hair cells and photoreceptors. However, the role of AC6 in the inner ear and retina has not been explored. Here, we found that AC6 distribution in hair cells depends on the USH2 protein complex integrity. Several known AC6 regulators and effectors, which were previously reported to participate in ADGRV1 signaling in vitro, are localized to the stereociliary compartments that overlap with AC6 distribution in hair cells. In young AC6 knockout (Adcy6-/-) mice, the activity of cAMP-dependent protein kinase, but not Akt kinase, is altered in cochleas, while both kinases are normal in vestibular organs. Adult Adcy6-/- mice however exhibit normal hearing function. AC6 is expressed in mouse retinas but rarely in photoreceptors. Adcy6-/- mice have slightly enhanced photopic but normal scotopic vision. Therefore, AC6 may participate in the ADGRV1 signaling in hair cells but AC6 is not essential for cochlear and retinal development and maintenance.
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Affiliation(s)
- Pranav Dinesh Mathur
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA
- Department of Neurobiology, University of Utah, Salt Lake City, UT, 84132, USA
- Vecprobio Inc., San Diego, CA, 92126, USA
| | - Junhuang Zou
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA
| | - Grace Neiswanger
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA
| | - Daniel Zhu
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA
| | - Yong Wang
- Division of Otolaryngology, Department of Surgery, University of Utah, Salt Lake City, UT, 84132, USA
| | - Ali A Almishaal
- Department of Communication Sciences and Disorders, University of Utah, Salt Lake City, UT, 84112, USA
- Department of Speech-Language Pathology and Audiology, College of Applied Medical Sciences, University of Hail, Hail, 81451, Saudi Arabia
| | - Deepti Vashist
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA
| | - H Kirk Hammond
- Division of Cardiovascular Medicine, Department of Medicine, University of California, San Diego, VA San Diego Healthcare System, San Diego, CA, 92161, USA
| | - Albert H Park
- Division of Otolaryngology, Department of Surgery, University of Utah, Salt Lake City, UT, 84132, USA
| | - Jun Yang
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, UT, 84132, USA.
- Department of Neurobiology, University of Utah, Salt Lake City, UT, 84132, USA.
- Division of Otolaryngology, Department of Surgery, University of Utah, Salt Lake City, UT, 84132, USA.
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cAMP and voltage modulate rat auditory mechanotransduction by decreasing the stiffness of gating springs. Proc Natl Acad Sci U S A 2022; 119:e2107567119. [PMID: 35858439 PMCID: PMC9335186 DOI: 10.1073/pnas.2107567119] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Regulation of auditory sensitivity contributes to the precision, dynamic range, and protection of the auditory system. Regulation of the hair cell mechanotransduction channel is a major contributor to controlling the sensitivity of the auditory transduction process. The gating spring is a critical piece of the mechanotransduction machinery because it opens and closes the mechanotransduction channel, and its stiffness regulates the sensitivity of the mechanotransduction process. In the present work, we characterize the effect of the second-messenger signaling molecule cyclic adenosine monophosphate (cAMP) and identify that it reduces gating spring stiffness likely through an exchange protein directly activated by cAMP (EPAC)-mediated pathway. This is a unique physiologic mechanism to regulate gating spring stiffness. Hair cells of the auditory and vestibular systems transform mechanical input into electrical potentials through the mechanoelectrical transduction process (MET). Deflection of the mechanosensory hair bundle increases tension in the gating springs that open MET channels. Regulation of MET channel sensitivity contributes to the auditory system’s precision, wide dynamic range and, potentially, protection from overexcitation. Modulating the stiffness of the gating spring modulates the sensitivity of the MET process. Here, we investigated the role of cyclic adenosine monophosphate (cAMP) in rat outer hair cell MET and found that cAMP up-regulation lowers the sensitivity of the channel in a manner consistent with decreasing gating spring stiffness. Direct measurements of the mechanical properties of the hair bundle confirmed a decrease in gating spring stiffness with cAMP up-regulation. In parallel, we found that prolonged depolarization mirrored the effects of cAMP. Finally, a limited number of experiments implicate that cAMP activates the exchange protein directly activated by cAMP to mediate the changes in MET sensitivity. These results reveal that cAMP signaling modulates gating spring stiffness to affect auditory sensitivity.
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Wang L, Feng Y, Yan D, Qin L, Grati M, Mittal R, Li T, Sundhari AK, Liu Y, Chapagain P, Blanton SH, Liao S, Liu X. A dominant variant in the PDE1C gene is associated with nonsyndromic hearing loss. Hum Genet 2018; 137:437-446. [PMID: 29860631 PMCID: PMC6560636 DOI: 10.1007/s00439-018-1895-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 05/26/2018] [Indexed: 01/02/2023]
Abstract
Identification of genes with variants causing non-syndromic hearing loss (NSHL) is challenging due to genetic heterogeneity. The difficulty is compounded by technical limitations that in the past prevented comprehensive gene identification. Recent advances in technology, using targeted capture and next-generation sequencing (NGS), is changing the face of gene identification and making it possible to rapidly and cost-effectively sequence the whole human exome. Here, we characterize a five-generation Chinese family with progressive, postlingual autosomal dominant nonsyndromic hearing loss (ADNSHL). By combining population-specific mutation arrays, targeted deafness genes panel, whole exome sequencing (WES), we identified PDE1C (Phosphodiesterase 1C) c.958G>T (p.A320S) as the disease-associated variant. Structural modeling insights into p.A320S strongly suggest that the sequence alteration will likely affect the substrate-binding pocket of PDE1C. By whole-mount immunofluorescence on postnatal day 3 mouse cochlea, we show its expression in outer (OHC) and inner (IHC) hair cells cytosol co-localizing with Lamp-1 in lysosomes. Furthermore, we provide evidence that the variant alters the PDE1C hydrolytic activity for both cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Collectively, our findings indicate that the c.958G>T variant in PDE1C may disrupt the cross talk between cGMP-signaling and cAMP pathways in Ca2+ homeostasis.
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Affiliation(s)
- Li Wang
- Institute of Medical Genetics, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou, China
- Department of Otolaryngology (D-48), Miller School of Medicine, University of Miami, 1666 NW 12th Avenue, Miami, FL, 33136, USA
| | - Yong Feng
- Department of Otolaryngology, Xiangya Hospital, Central South University, Changsha, China
| | - Denise Yan
- Department of Otolaryngology (D-48), Miller School of Medicine, University of Miami, 1666 NW 12th Avenue, Miami, FL, 33136, USA
| | - Litao Qin
- Institute of Medical Genetics, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - M'hamed Grati
- Department of Otolaryngology (D-48), Miller School of Medicine, University of Miami, 1666 NW 12th Avenue, Miami, FL, 33136, USA
- Laboratory of Cell Structure and Dynamics, NIDCD, NIH, Bethesda, MD, 20892, USA
| | - Rahul Mittal
- Department of Otolaryngology (D-48), Miller School of Medicine, University of Miami, 1666 NW 12th Avenue, Miami, FL, 33136, USA
| | - Tao Li
- Institute of Medical Genetics, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Abhiraami Kannan Sundhari
- Department of Otolaryngology (D-48), Miller School of Medicine, University of Miami, 1666 NW 12th Avenue, Miami, FL, 33136, USA
| | - Yalan Liu
- Department of Otolaryngology (D-48), Miller School of Medicine, University of Miami, 1666 NW 12th Avenue, Miami, FL, 33136, USA
| | - Prem Chapagain
- Department of Physics, Florida International University, Miami, FL, USA
- Biomolecular Sciences Institute, Florida International University, Miami, FL, USA
| | - Susan H Blanton
- Department of Otolaryngology (D-48), Miller School of Medicine, University of Miami, 1666 NW 12th Avenue, Miami, FL, 33136, USA
- Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
| | - Shixiu Liao
- Institute of Medical Genetics, Henan Provincial People's Hospital, People's Hospital of Zhengzhou University, Zhengzhou, China
| | - Xuezhong Liu
- Department of Otolaryngology (D-48), Miller School of Medicine, University of Miami, 1666 NW 12th Avenue, Miami, FL, 33136, USA.
- Department of Otolaryngology, Xiangya Hospital, Central South University, Changsha, China.
- Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami Miller School of Medicine, Miami, FL, 33136, USA.
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Nishio SY, Hattori M, Moteki H, Tsukada K, Miyagawa M, Naito T, Yoshimura H, Iwasa YI, Mori K, Shima Y, Sakuma N, Usami SI. Gene expression profiles of the cochlea and vestibular endorgans: localization and function of genes causing deafness. Ann Otol Rhinol Laryngol 2015; 124 Suppl 1:6S-48S. [PMID: 25814645 DOI: 10.1177/0003489415575549] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVES We sought to elucidate the gene expression profiles of the causative genes as well as the localization of the encoded proteins involved in hereditary hearing loss. METHODS Relevant articles (as of September 2014) were searched in PubMed databases, and the gene symbols of the genes reported to be associated with deafness were located on the Hereditary Hearing Loss Homepage using localization, expression, and distribution as keywords. RESULTS Our review of the literature allowed us to systematize the gene expression profiles for genetic deafness in the inner ear, clarifying the unique functions and specific expression patterns of these genes in the cochlea and vestibular endorgans. CONCLUSIONS The coordinated actions of various encoded molecules are essential for the normal development and maintenance of auditory and vestibular function.
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Affiliation(s)
- Shin-Ya Nishio
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan Department of Hearing Implant Sciences, Shinshu University School of Medicine, Matsumoto, Japan
| | - Mitsuru Hattori
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Hideaki Moteki
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Keita Tsukada
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Maiko Miyagawa
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan Department of Hearing Implant Sciences, Shinshu University School of Medicine, Matsumoto, Japan
| | - Takehiko Naito
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Hidekane Yoshimura
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Yoh-Ichiro Iwasa
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Kentaro Mori
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Yutaka Shima
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan
| | - Naoko Sakuma
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan Department of Otorhinolaryngology and Head and Neck Surgery, Yokohama City University School of Medicine, Yokohama, Japan
| | - Shin-Ichi Usami
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan Department of Hearing Implant Sciences, Shinshu University School of Medicine, Matsumoto, Japan
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5
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Fettiplace R, Kim KX. The physiology of mechanoelectrical transduction channels in hearing. Physiol Rev 2014; 94:951-86. [PMID: 24987009 DOI: 10.1152/physrev.00038.2013] [Citation(s) in RCA: 176] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Much is known about the mechanotransducer (MT) channels mediating transduction in hair cells of the vertrbrate inner ear. With the use of isolated preparations, it is experimentally feasible to deliver precise mechanical stimuli to individual cells and record the ensuing transducer currents. This approach has shown that small (1-100 nm) deflections of the hair-cell stereociliary bundle are transmitted via interciliary tip links to open MT channels at the tops of the stereocilia. These channels are cation-permeable with a high selectivity for Ca(2+); two channels are thought to be localized at the lower end of the tip link, each with a large single-channel conductance that increases from the low- to high-frequency end of the cochlea. Ca(2+) influx through open channels regulates their resting open probability, which may contribute to setting the hair cell resting potential in vivo. Ca(2+) also controls transducer fast adaptation and force generation by the hair bundle, the two coupled processes increasing in speed from cochlear apex to base. The molecular intricacy of the stereocilary bundle and the transduction apparatus is reflected by the large number of single-gene mutations that are linked to sensorineural deafness, especially those in Usher syndrome. Studies of such mutants have led to the discovery of many of the molecules of the transduction complex, including the tip link and its attachments to the stereociliary core. However, the MT channel protein is still not firmly identified, nor is it known whether the channel is activated by force delivered through accessory proteins or by deformation of the lipid bilayer.
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Affiliation(s)
- Robert Fettiplace
- Department of Neuroscience, University of Wisconsin-Madison, Madison, Wisconsin
| | - Kyunghee X Kim
- Department of Neuroscience, University of Wisconsin-Madison, Madison, Wisconsin
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6
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Santos-Cortez RLP, Lee K, Giese AP, Ansar M, Amin-Ud-Din M, Rehn K, Wang X, Aziz A, Chiu I, Hussain Ali R, Smith JD, Shendure J, Bamshad M, Nickerson DA, Ahmed ZM, Ahmad W, Riazuddin S, Leal SM. Adenylate cyclase 1 (ADCY1) mutations cause recessive hearing impairment in humans and defects in hair cell function and hearing in zebrafish. Hum Mol Genet 2014; 23:3289-98. [PMID: 24482543 DOI: 10.1093/hmg/ddu042] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Cyclic AMP (cAMP) production, which is important for mechanotransduction within the inner ear, is catalyzed by adenylate cyclases (AC). However, knowledge of the role of ACs in hearing is limited. Previously, a novel autosomal recessive non-syndromic hearing impairment locus DFNB44 was mapped to chromosome 7p14.1-q11.22 in a consanguineous family from Pakistan. Through whole-exome sequencing of DNA samples from hearing-impaired family members, a nonsense mutation c.3112C>T (p.Arg1038*) within adenylate cyclase 1 (ADCY1) was identified. This stop-gained mutation segregated with hearing impairment within the family and was not identified in ethnically matched controls or within variant databases. This mutation is predicted to cause the loss of 82 amino acids from the carboxyl tail, including highly conserved residues within the catalytic domain, plus a calmodulin-stimulation defect, both of which are expected to decrease enzymatic efficiency. Individuals who are homozygous for this mutation had symmetric, mild-to-moderate mixed hearing impairment. Zebrafish adcy1b morphants had no FM1-43 dye uptake and lacked startle response, indicating hair cell dysfunction and gross hearing impairment. In the mouse, Adcy1 expression was observed throughout inner ear development and maturation. ADCY1 was localized to the cytoplasm of supporting cells and hair cells of the cochlea and vestibule and also to cochlear hair cell nuclei and stereocilia. Ex vivo studies in COS-7 cells suggest that the carboxyl tail of ADCY1 is essential for localization to actin-based microvilli. These results demonstrate that ADCY1 has an evolutionarily conserved role in hearing and that cAMP signaling is important to hair cell function within the inner ear.
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Affiliation(s)
| | - Kwanghyuk Lee
- Department of Molecular and Human Genetics, Center for Statistical Genetics and
| | - Arnaud P Giese
- Division of Pediatric Ophthalmology and Division of Pediatric Otolaryngology-Head and Neck Surgery, Cincinnati Children's Hospital Research Foundation, University of Cincinnati, Cincinnati, OH 45221, USA
| | - Muhammad Ansar
- Department of Molecular and Human Genetics, Center for Statistical Genetics and Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan
| | | | - Kira Rehn
- Division of Pediatric Otolaryngology-Head and Neck Surgery, Cincinnati Children's Hospital Research Foundation, University of Cincinnati, Cincinnati, OH 45221, USA
| | - Xin Wang
- Department of Molecular and Human Genetics, Center for Statistical Genetics and
| | - Abdul Aziz
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan
| | - Ilene Chiu
- Bobby R. Alford Department of Otolaryngology-Head and Neck Surgery, Baylor College of Medicine, Houston, TX 77030, USA
| | - Raja Hussain Ali
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan
| | - Joshua D Smith
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | | | - Jay Shendure
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Michael Bamshad
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Deborah A Nickerson
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | | | - Wasim Ahmad
- Department of Biochemistry, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad 45320, Pakistan
| | - Saima Riazuddin
- Division of Pediatric Otolaryngology-Head and Neck Surgery, Cincinnati Children's Hospital Research Foundation, University of Cincinnati, Cincinnati, OH 45221, USA
| | - Suzanne M Leal
- Department of Molecular and Human Genetics, Center for Statistical Genetics and
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Abstract
The very large G protein coupled receptor (Vlgr1) is a member of adhesion receptors or large N-terminal family B-7 transmembrane helixes (LNB7TM) receptors within the seven trans-membrane receptor superfamily. Vlgr1 is the largest GPCR identified to date; its mRNA spans 19 kb and encodes 6,300 amino acids. Vlgr1 is a core component of ankle-link complex in inner ear hair cells. Knock-out and mutation mouse models show that loss of Vlgr1 function leads to abnormal stereociliary development and hearing loss, indicating crucial roles of Vlgr1 in hearing transduction or auditory system development. Over the past 10 or so years, human genetics data suggested that Vlgr1 mutations cause Usher syndromes and seizures. Although significant progresses have been made, the details of Vlgr1's function in hair cells, its signaling cascade, and the mechanisms underlying causative effects of Vlgr1 mutations in human diseases remain elusive and ask for further investigation.
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Ceriani F, Mammano F. Calcium signaling in the cochlea - Molecular mechanisms and physiopathological implications. Cell Commun Signal 2012; 10:20. [PMID: 22788415 PMCID: PMC3408374 DOI: 10.1186/1478-811x-10-20] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 07/12/2012] [Indexed: 12/20/2022] Open
Abstract
Calcium ions (Ca2+) regulate numerous and diverse aspects of cochlear and vestibular physiology. This review focuses on the Ca2+ control of mechanotransduction and synaptic transmission in sensory hair cells, as well as on Ca2+ signalling in non-sensory cells of the developing cochlea.
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Affiliation(s)
- Federico Ceriani
- Dipartimento di Fisica e Astronomia "G, Galilei", Università di Padova, 35131, Padova, Italy.
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An adenylyl cyclase signaling pathway predicts direct dopaminergic input to vestibular hair cells. Neuroscience 2010; 171:1054-74. [PMID: 20883745 DOI: 10.1016/j.neuroscience.2010.09.051] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Revised: 09/23/2010] [Accepted: 09/23/2010] [Indexed: 11/20/2022]
Abstract
Adenylyl cyclase (AC) signaling pathways have been identified in a model hair cell preparation from the trout saccule, for which the hair cell is the only intact cell type. The use of degenerate primers targeting cDNA sequence conserved across AC isoforms, and reverse transcription-polymerase chain reaction (RT-PCR), coupled with cloning of amplification products, indicated expression of AC9, AC7 and AC5/6, with cloning efficiencies of 11:5:2. AC9 and AC5/6 are inhibited by Ca(2+), the former in conjunction with calcineurin, and message for calcineurin has also been identified in the trout saccular hair cell layer. AC7 is independent of Ca(2+). Given the lack of detection of calcium/calmodulin-activated isoforms previously suggested to mediate AC activation in the absence of Gαs in mammalian cochlear hair cells, the issue of hair-cell Gαs mRNA expression was re-examined in the teleost vestibular hair cell model. Two full-length coding sequences were obtained for Gαs/olf in the vestibular type II-like hair cells of the trout saccule. Two messages for Gαi have also been detected in the hair cell layer, one with homology to Gαi1 and the second with homology to Gαi3 of higher vertebrates. Both Gαs/olf protein and Gαi1/Gαi3 protein were immunolocalized to stereocilia and to the base of the hair cell, the latter consistent with sites of efferent input. Although a signaling event coupling to Gαs/olf and Gαi1/Gαi3 in the stereocilia is currently unknown, signaling with Gαs/olf, Gαi3, and AC5/6 at the base of the hair cell would be consistent with transduction pathways activated by dopaminergic efferent input. mRNA for dopamine receptors D1A4 and five forms of dopamine D2 were found to be expressed in the teleost saccular hair cell layer, representing information on vestibular hair cell expression not directly available for higher vertebrates. Dopamine D1A receptor would couple to Gαolf and activation of AC5/6. Co-expression with dopamine D2 receptor, which itself couples to Gαi3 and AC5/6, will down-modulate levels of cAMP, thus fine-tuning and gradating the hair-cell response to dopamine D1A. As predicted by the trout saccular hair cell model, evidence has been obtained for the first time that hair cells of mammalian otolithic vestibular end organs (rat/mouse saccule/utricle) express dopamine D1A and D2L receptors, and each receptor co-localizes with AC5/6, with a marked presence of all three proteins in subcuticular regions of type I vestibular hair cells. A putative efferent, presynaptic source of dopamine was identified in tyrosine hydroxylase-positive nerve fibers which passed from underlying connective tissue to the sensory epithelia, ending on type I and type II vestibular hair cells and on afferent calyces.
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10
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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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11
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Michalski N, Michel V, Bahloul A, Lefèvre G, Barral J, Yagi H, Chardenoux S, Weil D, Martin P, Hardelin JP, Sato M, Petit C. Molecular characterization of the ankle-link complex in cochlear hair cells and its role in the hair bundle functioning. J Neurosci 2007; 27:6478-88. [PMID: 17567809 PMCID: PMC6672440 DOI: 10.1523/jneurosci.0342-07.2007] [Citation(s) in RCA: 160] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Several lines of evidence indicate that very large G-protein-coupled receptor 1 (Vlgr1) makes up the ankle links that connect the stereocilia of hair cells at their base. Here, we show that the transmembrane protein usherin, the putative transmembrane protein vezatin, and the PDZ (postsynaptic density-95/Discs large/zona occludens-1) domain-containing submembrane protein whirlin are colocalized with Vlgr1 at the stereocilia base in developing cochlear hair cells and are absent in Vlgr1-/- mice that lack the ankle links. Direct in vitro interactions between these four proteins further support their involvement in a molecular complex associated with the ankle links and scaffolded by whirlin. In addition, the delocalization of these proteins in myosin VIIa defective mutant mice as well as the myosin VIIa tail direct interactions with vezatin, whirlin, and, we show, Vlgr1 and usherin, suggest that myosin VIIa conveys proteins of the ankle-link complex to the stereocilia. Adenylyl cyclase 6, which was found at the base of stereocilia, was both overexpressed and mislocated in Vlgr1-/- mice. In postnatal day 7 Vlgr1-/- mice, mechanoelectrical transduction currents evoked by displacements of the hair bundle toward the tallest stereocilia (i.e., in the excitatory direction) were reduced in outer but not inner hair cells. In both cell types, stimulation of the hair bundle in the opposite direction paradoxically resulted in significant transduction currents. The absence of ankle-link-mediated cohesive forces within hair bundles lacking Vlgr1 may account for the electrophysiological results. However, because some long cadherin-23 isoforms could no longer be detected in Vlgr1-/- mice shortly after birth, the loss of some apical links could be involved too. The premature disappearance of these cadherin isoforms in the Vlgr1-/- mutant argues in favor of a signaling function of the ankle links in hair bundle differentiation.
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MESH Headings
- Adenylyl Cyclases/metabolism
- Animals
- Animals, Newborn
- Carrier Proteins/metabolism
- Chelating Agents/pharmacology
- Cilia/physiology
- Cochlea/cytology
- Egtazic Acid/analogs & derivatives
- Egtazic Acid/pharmacology
- Embryo, Mammalian
- Extracellular Matrix Proteins/metabolism
- Gene Expression Regulation, Developmental/physiology
- Hair Cells, Auditory/metabolism
- Hair Cells, Auditory/ultrastructure
- Mechanotransduction, Cellular/genetics
- Mechanotransduction, Cellular/physiology
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Membrane Potentials/radiation effects
- Membrane Proteins/metabolism
- Mice
- Mice, Knockout
- Microscopy, Electron, Scanning/methods
- Organ Culture Techniques
- Patch-Clamp Techniques
- Receptors, G-Protein-Coupled/deficiency
- Subtilisin/pharmacology
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Affiliation(s)
- Nicolas Michalski
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 587, Collège de France, Institut Pasteur, 75724 Paris cedex 15, France
| | - Vincent Michel
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 587, Collège de France, Institut Pasteur, 75724 Paris cedex 15, France
| | - Amel Bahloul
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 587, Collège de France, Institut Pasteur, 75724 Paris cedex 15, France
| | - Gaëlle Lefèvre
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 587, Collège de France, Institut Pasteur, 75724 Paris cedex 15, France
| | - Jérémie Barral
- Centre National de la Recherche Scientifique Unité Mixte de Recherche 168, Institut Curie, 75248 Paris cedex 05, France
| | - Hideshi Yagi
- Division of Cell Biology and Neuroscience, Department of Morphological and Physiological Sciences, Research and Education Program for Life Science, University of Fukui, Eiheiji, Fukui 910-1193, Japan, and
| | - Sébastien Chardenoux
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 587, Collège de France, Institut Pasteur, 75724 Paris cedex 15, France
| | - Dominique Weil
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 587, Collège de France, Institut Pasteur, 75724 Paris cedex 15, France
| | - Pascal Martin
- Centre National de la Recherche Scientifique Unité Mixte de Recherche 168, Institut Curie, 75248 Paris cedex 05, France
| | - Jean-Pierre Hardelin
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 587, Collège de France, Institut Pasteur, 75724 Paris cedex 15, France
| | - Makoto Sato
- Division of Cell Biology and Neuroscience, Department of Morphological and Physiological Sciences, Research and Education Program for Life Science, University of Fukui, Eiheiji, Fukui 910-1193, Japan, and
| | - Christine Petit
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche en Santé 587, Collège de France, Institut Pasteur, 75724 Paris cedex 15, France
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12
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Abstract
The inner ear contains delicate sensory receptors that have adapted to detect the minutest mechanical disturbances. Ca(2+) ions are implicated in all steps of the transduction process, as well as in its regulation by an impressive ensemble of finely tuned feedback control mechanisms. Recent studies have unveiled some of the key players, but things do not sound quite right yet.
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Affiliation(s)
- Fabio Mammano
- Istituto Veneto di Medicina Molecolare, Fondazione per la Ricerca Biomedica Avanzata, Padua, Italy.
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13
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Chang LC, Wang CJ, Lin YL, Wang JP. Expression of adenylyl cyclase isoforms in neutrophils. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1640:53-60. [PMID: 12676354 DOI: 10.1016/s0167-4889(03)00003-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In the present study, we have identified the expression of adenylyl cyclase (AC) isoforms in rat neutrophils according to the mRNA analysis and the distinct mode of regulation of isoform activity. Agarose gel electrophoresis of reverse transcription-polymerase chain reaction (RT-PCR)-amplified products resulted in a single band of the expected size for each product with nucleotide sequences corresponding to AC1 to AC9. AC1 was abundant, while AC2, 6 and 9 were of moderate expression among the AC isoforms in neutrophils based on the quantitative real-time RT-PCR analysis. Exposure of neutrophils to Ca(2+) ionophore A23187, isoproterenol and forskolin stimulated cellular cyclic AMP accumulation. EDTA and the calmodulin (CaM) antagonist, trifluoperazine, prevented the A23187-induced response. Pretreatment with pertussis toxin (PTX) inhibited the alpha(2)-adrenergic agonist, UK14304-induced cellular cyclic AMP elevation. In addition, UK14304 augmented the cyclic AMP elevation when cells were stimulated by isoproterenol. Phorbol 12-myristate 13-acetate (PMA) attenuated the augmentation response of UK14304 and isoproterenol. Treatment of the membrane preparations from rat neutrophils with Ca(2+)/CaM, forskolin, isoproterenol, GTPgammaS or Gbetagamma all increased cyclic AMP production. The addition of protein kinase C (PKC) catalytic fragment and Gbetagamma augmented the Ca(2+)/CaM- and isoproterenol-stimulated AC activity, respectively. However, forskolin and the activated protein kinase A (PKA) attenuated the GTPgammaS- and isoproterenol-stimulated AC activity, respectively. KT5720, a PKA inhibitor, reversed the inhibition by PKA. Taken together, these data suggest the presence of four groups of AC isoforms in rat neutrophils.
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Affiliation(s)
- Ling-Chu Chang
- Department of Education and Research, Taichung Veterans General Hospital, 160, Chung Kang Road, Sec. 3, 407, Taichung, Taiwan, ROC
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14
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Tremblay F, Abdel-Majid R, Neumann PE. Electroretinographic oscillatory potentials are reduced in adenylyl cyclase type I deficient mice. Vision Res 2002; 42:1715-25. [PMID: 12127105 DOI: 10.1016/s0042-6989(02)00113-x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Electroretinography (ERG) of adult Adcy1(brl) mutant mice, which are deficient in adenylyl cyclase type 1 (AC1) activity, revealed decreased amplitude of the oscillatory potentials (OP) and of the primary rising phase of the b-wave intensity-response function in scotopic conditions. These abnormalities were less discernable in 3-6 week old mutants. No abnormalities were detected in the ERG signal obtained in photopic conditions or in the dark adaptation dynamics. The mutants displayed no histologic evidence of retinal degeneration. Retinal output, as measured by visual evoked potentials, was not different from heterozygous control mice. AC1-dependent pathways contribute to the generation of the retinal response to light. They may be necessary for the maintenance of the neural generators of the ERG OP.
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Affiliation(s)
- François Tremblay
- Department of Ophthalmology, Dalhousie University, Halifax, NS, Canada B3H 4H7.
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15
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Drescher MJ, Barretto RL, Chaturvedi D, Beisel KW, Hatfield JS, Khan KM, Drescher DG. Expression of subunits for the cAMP-sensitive 'olfactory' cyclic nucleotide-gated ion channel in the cochlea: implications for signal transduction. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2002; 98:1-14. [PMID: 11834291 DOI: 10.1016/s0169-328x(01)00289-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cyclic nucleotide-gated (CNG) ion channels have been implicated as functioning in sensory transduction and in second-messenger modulation of synaptic neurotransmitter release. The olfactory, cAMP-sensitive CNG ion channel in vivo is considered to comprise the pore-forming CNG2 subunit together with CNG5 and CNG4.3 modulatory subunits. The expression of these 'olfactory' CNG subunit transcripts in microdissected subfractions of the rat cochlea and hair cell libraries has been investigated with RT-PCR. Unmodified transcripts of CNG2 were detected in the organ of Corti, lateral wall and spiral ganglion subfractions. CNG5 message was found in both the sensory organ of Corti and the non-sensory lateral wall subfractions but not in the spiral ganglion subfraction. The CNG5 sequence obtained for the organ of Corti fraction encompassed 78% of the olfactory CNG5 cDNA sequence. CNG5 message has also been detected in an inner hair cell cDNA library. In the lateral wall, unmodified CNG5 sequence was observed as well as truncated versions of CNG5 transcripts, one of which was also found in the rat brain. The truncated versions were characterized by deletions that resulted in a shift in reading frame and the premature appearance of a stop codon. The 'olfactory' CNG4.3 cDNA was amplified from all three subfractions. Within the cochlea, CNG2 immunoreactivity was selectively distributed in a pattern similar to that of adenylyl cyclase type I. Immunoreactivity to CNG2 has been localized to stereocilia of inner hair cells. CNG5 immunoreactivity was associated with stereocilia and lateral plasma membranes of outer hair cells. We conclude that transcripts necessary for a functional cAMP-sensitive CNG ion channel are present in the cochlea resulting from combinations of CNG2 with CNG5 and CNG4.3. Further, the localization of CNG2 and CNG5 immunoreactivity to hair cell stereocilia suggests a role for cAMP-sensitive CNG channels in hair cell signal transduction.
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Affiliation(s)
- Marian J Drescher
- Laboratory of Bio-otology, Department of Otolaryngology, Wayne State University, 261 Lande Medical Research Building, 540 E. Canfield, Detroit, MI 48201, USA.
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16
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Drescher MJ, Khan KM, Hatfield JS, Shakir AH, Drescher DG. Immunohistochemical localization of adenylyl cyclase isoforms in the lateral wall of the rat cochlea. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2000; 76:289-98. [PMID: 10762704 DOI: 10.1016/s0169-328x(00)00008-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The enzymatic activity of adenylyl cyclase (AC) is attributable to nine isoforms with individual pharmacology and tissue distribution. Polyclonal antibodies for AC isoforms I-IV, VII and VIII were applied to sections of cochlear lateral wall, a tissue involved in ion transport contributing to the unique ion content of endolymph and electrical potential of scala media. Within the stria vascularis, immunoreactivity primarily to Ca(2+)/calmodulin-independent isoforms II, IV and VII was localized to sites consistent in position to the basolateral extensions of marginal cells. Little immunoreactivity was observed in the stria vascularis for Ca(2+)/calmodulin-dependent isoforms I, III and VIII. Within the spiral ligament, type II and type IV fibrocytes exhibited moderate staining for ACII, IV and VII, less staining for VIII and little for I and III. Immunoreactivity to ACII, IV, VII and VIII was observed in type I fibrocytes. The outer sulcus cells and root processes were highly immunoreactive for isoforms I and VIII, but not for III or the Ca(2+)/calmodulin-independent isoforms. The differential pattern of immunoreactivity in the lateral wall overall appears to reflect subfamily-specific expression with Ca(2+)/calmodulin-independent isoforms expressed in the stria vascularis and Ca(2+)/calmodulin-dependent isoforms expressed in the outer sulcus cells and root processes. cAMP-mediated modulation of ion transport by marginal cells is predicted to exhibit, in the microenvironment of basolateral membrane infoldings, pharmacological characteristics of the AC type II subfamily (II, IV and VII), including activation by protein kinase C (II and VII).
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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 E. Canfield Ave., Detroit, MI 48201, USA.
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17
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Wackym PA, Troyanovskaya M, Popper P. Adenylyl cyclase isoforms in the vestibular periphery of the rat. Brain Res 2000; 859:378-80. [PMID: 10719090 DOI: 10.1016/s0006-8993(00)02007-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The expression of adenylyl cyclase (AC) isoforms in the adult rat vestibular periphery was investigated using reverse transcription polymerase chain reaction (RT-PCR). AC II, IV and V mRNAs were expressed in both Scarpa's ganglion and vestibular end organs. In addition, in the vestibular end organs, an AC mRNA not previously reported in the rat was identified. The cloned sequence (GenBank accession no. AF184150) represented 95 amino acids with 100% similarity to the human AC VII and 94% to the bovine AC VII. AC VII mRNA also was found in the cerebellum but was undetectable in heart, kidney, liver and Scarpa's ganglion.
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Affiliation(s)
- P A Wackym
- Department of Otolaryngology, Medical College of Wisconsin, 9200 W. Wisconsin Avenue, Milwaukee, WI, USA.
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18
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Oh CK, Drescher MJ, Hatfield JS, Drescher DG. Selective expression of serotonin receptor transcripts in the mammalian cochlea and its subdivisions. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1999; 70:135-40. [PMID: 10381551 DOI: 10.1016/s0169-328x(99)00110-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Expression of serotonin receptor (5-HTR) mRNA has been determined in the mammalian cochlea and its subdivisions by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Specific primers targeting individual 5-HTRs 1-7 directed amplification of 5-HTR subtypes 1A, 1B, 2B, 2C, 3, 5B, and 6 from mouse cochlea cDNA. No evidence of expression was obtained for 5-HTRs 1D, 2A, 4 (L and S), 5A, and 7. The distribution of receptor mRNA within the cochlea was determined with application of RT-PCR to morphologically defined microdissected subfractions of the rat cochlea. Messages for 5-HTR subtypes 1A, 1B, 2B, and 6 were present in the organ of Corti, lateral wall, and spiral ganglion subfractions. Messages for 5-HTR subtypes 2C, 3 and 5B were found in the spiral ganglion, but not in the organ of Corti or lateral wall fractions. The existence of transcripts for 5-HTRs 1A, 1B, 2B and 6 in the organ of Corti is consistent with a role for these receptors in serotonin-mediated modulation of the mechanosensory signal.
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Affiliation(s)
- C K Oh
- Laboratory of Bio-otology, Department of Otolaryngology, Wayne State University, Detroit, MI, USA
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19
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Kumagami H, Beitz E, Wild K, Zenner HP, Ruppersberg JP, Schultz JE. Expression pattern of adenylyl cyclase isoforms in the inner ear of the rat by RT-PCR and immunochemical localization of calcineurin in the organ of Corti. Hear Res 1999; 132:69-75. [PMID: 10392549 DOI: 10.1016/s0378-5955(99)00035-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Most studies concerning adenylyl cyclases in the inner ear were carried out before the advent of molecular biology. In a PCR approach using cDNAs of six inner ear tissues (stria vascularis, endolymphatic sac, organ of Corti, vestibulum, cochlear and vestibular nerve) we found tissue specific expression of adenylyl cyclase isoforms. Adenylyl cyclases types 2 and 4 are predominant in the fluid controlling tissues, i.e. in the stria vascularis and endolymphatic sac. In the organ of Corti and vestibulum the Ca2+-modulated isoforms types 1, 6 and 9 were expressed. The regulation of adenylyl cyclase 9, which is the major isoform expressed in the organ of Corti, proceeds via the Ca2+-activated protein phosphatase 2B (calcineurin, PPP3). PCR with specific primers for calcineurin demonstrated its abundant expression in the organ of Corti. Using a monoclonal antibody we localized calcineurin immunochemically to the cochlear nerve, the nerve fibers and the inner hair cells. In the cochlear and vestibular nerves a characteristic neuronal expression pattern of adenylyl cyclase isoforms was observed, i.e. adenylyl cyclases types 2, 3 and 8. The functional consequences of the adenylyl cyclase expression pattern in the inner ear are discussed in conjunction with its unique sensory performance.
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Affiliation(s)
- H Kumagami
- Department of Otorhinolaryngology, University of Tübingen, Germany
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20
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Barritt LC, Fritzsch B, Beisel KW. Characterization of G-protein betagamma expression in inner ear. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1999; 68:42-54. [PMID: 10320782 DOI: 10.1016/s0169-328x(99)00078-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Heterotrimeric guanine nucleotide binding proteins (G-proteins) are composed of a diverse set of alpha, beta, and gamma subunits, which couple cell surface receptors to intracellular effectors, such as adenylyl cyclase, phospholipase Cbeta, and ion channels. Both the Galpha and the Gbetagamma dimers mediate effector activity and are believed to contribute to the complexity of the signaling pathway. Molecular and immunocytochemical techniques were employed to determine diversity of Gbeta and Ggamma subunit expression in the murine inner ear. PCR-based assessment of lambdaZAP unidirectional cDNA libraries, representing the cochlea and inner ear hair cells, indicated all five known Gbeta subunits were present in the cochlea, while only a subset of Ggamma isoforms were found. New or novel G-protein beta and gamma subunits were not detected. cDNAs representing Gbeta1-4 and Ggamma2, Ggamma3, Ggamma5, Ggamma8olf subunit transcripts were isolated. In addition, cDNAs corresponding to the Gbeta5 and Ggamma11 isoforms exhibited restricted expression to inner and outer hair cells, respectively. Antisera specific for Gbeta3, Gbeta4, Ggamma3, Ggamma5 and Ggamma11 stained spiral ganglion and neurosensory hair cells. A unique finding was the variable topological distribution of Ggamma3 in the spiral ganglion cells along the cochlear axis. Collectively, our results demonstrate a complementary as well as differential distribution pattern for Gbeta and Ggamma isoforms exists in the inner ear. The co-localization of various G-protein isoforms within the same cell type suggests specific combinatorial Gbeta and Ggamma subunit associations may preferentially be formed. Thus, the detection of multiple subunits presumably reflects the extent of the functional diversity of inner ear signaling pathways and should provide specificity of G-protein mediated pathways.
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Affiliation(s)
- L C Barritt
- Center for Hereditary Communication Disorders, Boys Town National Research Hospital, Omaha, NE 68131, USA
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