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Miller KK, Wang P, Grillet N. SUB-Immunogold-SEM reveals nanoscale distribution of submembranous epitopes. RESEARCH SQUARE 2024:rs.3.rs-3876898. [PMID: 38343799 PMCID: PMC10854333 DOI: 10.21203/rs.3.rs-3876898/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/17/2024]
Abstract
Electron microscopy paired with immunogold labeling is the most precise tool for protein localization. However, these methods are either cumbersome, resulting in small sample numbers and restricted quantification, or limited to identifying protein epitopes external to the membrane. Here, we introduce SUB-immunogold-SEM, a scanning electron microscopy technique that detects intracellular protein epitopes proximal to the membrane. We identified four critical sample preparation factors that contribute to the method's sensitivity and validate its efficacy through precise localization and high-powered quantification of cytoskeletal and transmembrane proteins. We evaluated the capabilities of SUB-immunogold-SEM on cells with highly differentiated apical surfaces: (i) auditory hair cells, revealing the presence of nanoscale Myosin rings at the tip of stereocilia; and (ii) respiratory multiciliate cells, mapping the distribution of the SARS-CoV-2 receptor ACE2 along the motile cilia. SUB-immunogold-SEM provides a novel solution for nanoscale protein localization at the exposed surface of any cell.
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Affiliation(s)
- Katharine K. Miller
- Department of Otolaryngology-Head & Neck Surgery, School of Medicine, 240 Pasteur Drive, Stanford University, Stanford, CA 94305, USA
| | - Pei Wang
- Department of Otolaryngology-Head & Neck Surgery, School of Medicine, 240 Pasteur Drive, Stanford University, Stanford, CA 94305, USA
| | - Nicolas Grillet
- Department of Otolaryngology-Head & Neck Surgery, School of Medicine, 240 Pasteur Drive, Stanford University, Stanford, CA 94305, USA
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2
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Tao Y, Lamas V, Du W, Zhu W, Li Y, Whittaker MN, Zuris JA, Thompson DB, Rameshbabu AP, Shu Y, Gao X, Hu JH, Pei C, Kong WJ, Liu X, Wu H, Kleinstiver BP, Liu DR, Chen ZY. Treatment of monogenic and digenic dominant genetic hearing loss by CRISPR-Cas9 ribonucleoprotein delivery in vivo. Nat Commun 2023; 14:4928. [PMID: 37582836 PMCID: PMC10427623 DOI: 10.1038/s41467-023-40476-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 07/31/2023] [Indexed: 08/17/2023] Open
Abstract
Mutations in Atp2b2, an outer hair cell gene, cause dominant hearing loss in humans. Using a mouse model Atp2b2Obl/+, with a dominant hearing loss mutation (Oblivion), we show that liposome-mediated in vivo delivery of CRISPR-Cas9 ribonucleoprotein complexes leads to specific editing of the Obl allele. Large deletions encompassing the Obl locus and indels were identified as the result of editing. In vivo genome editing promotes outer hair cell survival and restores their function, leading to hearing recovery. We further show that in a double-dominant mutant mouse model, in which the Tmc1 Beethoven mutation and the Atp2b2 Oblivion mutation cause digenic genetic hearing loss, Cas9/sgRNA delivery targeting both mutations leads to partial hearing recovery. These findings suggest that liposome-RNP delivery can be used as a strategy to recover hearing with dominant mutations in OHC genes and with digenic mutations in the auditory hair cells, potentially expanding therapeutics of gene editing to treat hearing loss.
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Affiliation(s)
- Yong Tao
- Department of Otolaryngology-Head and Neck Surgery, Graduate Program in Speech and Hearing Bioscience and Technology and Program in Neuroscience, Harvard Medical School, Boston, MA, 02115, USA
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114, USA
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
| | - Veronica Lamas
- Department of Otolaryngology-Head and Neck Surgery, Graduate Program in Speech and Hearing Bioscience and Technology and Program in Neuroscience, Harvard Medical School, Boston, MA, 02115, USA
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114, USA
- Salk Institute for Biological Studies, La Jolla, CA, 92037, USA
| | - Wan Du
- Department of Otolaryngology-Head and Neck Surgery, Graduate Program in Speech and Hearing Bioscience and Technology and Program in Neuroscience, Harvard Medical School, Boston, MA, 02115, USA
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114, USA
| | - Wenliang Zhu
- Department of Otolaryngology-Head and Neck Surgery, Graduate Program in Speech and Hearing Bioscience and Technology and Program in Neuroscience, Harvard Medical School, Boston, MA, 02115, USA
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114, USA
| | - Yiran Li
- Department of Otolaryngology-Head and Neck Surgery, Graduate Program in Speech and Hearing Bioscience and Technology and Program in Neuroscience, Harvard Medical School, Boston, MA, 02115, USA
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114, USA
- C.S. Mott Children's Hospital, Ann Harbor, MI, USA
| | - Madelynn N Whittaker
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Pathology, Massachusetts General hospital, Boston, MA, 02114, USA
| | - John A Zuris
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA
| | - David B Thompson
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA
| | - Arun Prabhu Rameshbabu
- Department of Otolaryngology-Head and Neck Surgery, Graduate Program in Speech and Hearing Bioscience and Technology and Program in Neuroscience, Harvard Medical School, Boston, MA, 02115, USA
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114, USA
| | - Yilai Shu
- Department of Otolaryngology-Head and Neck Surgery, Graduate Program in Speech and Hearing Bioscience and Technology and Program in Neuroscience, Harvard Medical School, Boston, MA, 02115, USA
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114, USA
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, NHC Key Laboratory of Hearing Medicine, Institutes of Biomedical Sciences, Fudan University, Shanghai, 200031, China
| | - Xue Gao
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA
| | - Johnny H Hu
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA
| | - Charles Pei
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114, USA
| | - Wei-Jia Kong
- Department of Otorhinolaryngology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Xuezhong Liu
- Department of Otolaryngology, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Hao Wu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, China
| | - Benjamin P Kleinstiver
- Center for Genomic Medicine, Massachusetts General Hospital, Boston, MA, 02114, USA
- Department of Pathology, Massachusetts General hospital, Boston, MA, 02114, USA
- Department of Pathology, Harvard Medical School, Boston, MA, 02115, USA
| | - David R Liu
- Merkin Institute of Transformative Technologies in Healthcare, Broad Institute of MIT and Harvard, Cambridge, MA, USA.
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
- Howard Hughes Medical Institute, Harvard University, Cambridge, MA, USA.
| | - Zheng-Yi Chen
- Department of Otolaryngology-Head and Neck Surgery, Graduate Program in Speech and Hearing Bioscience and Technology and Program in Neuroscience, Harvard Medical School, Boston, MA, 02115, USA.
- Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles St., Boston, MA, 02114, USA.
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3
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Calcium signaling and genetic rare diseases: An auditory perspective. Cell Calcium 2023; 110:102702. [PMID: 36791536 DOI: 10.1016/j.ceca.2023.102702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 02/01/2023] [Accepted: 02/02/2023] [Indexed: 02/07/2023]
Abstract
Deafness is a highly heterogeneous disorder which stems, for 50%, from genetic origins. Sensory transduction relies mainly on sensory hair cells of the cochlea, in the inner ear. Calcium is key for the function of these cells and acts as a fundamental signal transduction. Its homeostasis depends on three factors: the calcium influx, through the mechanotransduction channel at the apical pole of the hair cell as well as the voltage-gated calcium channel at the base of the cells; the calcium buffering via Ca2+-binding proteins in the cytoplasm, but also in organelles such as mitochondria and the reticulum endoplasmic mitochondria-associated membranes with specialized proteins; and the calcium extrusion through the Ca-ATPase pump, located all over the plasma membrane. In addition, the synaptic transmission to the central nervous system is also controlled by calcium. Genetic studies of inherited deafness have tremendously helped understand the underlying molecular pathways of calcium signaling. In this review, we discuss these different factors in light of the associated genetic diseases (syndromic and non-syndromic deafness) and the causative genes.
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O'Sullivan JDB, Bullen A, Mann ZF. Mitochondrial form and function in hair cells. Hear Res 2023; 428:108660. [PMID: 36525891 DOI: 10.1016/j.heares.2022.108660] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 11/07/2022] [Accepted: 11/23/2022] [Indexed: 11/27/2022]
Abstract
Hair cells (HCs) are specialised sensory receptors residing in the neurosensory epithelia of inner ear sense organs. The precise morphological and physiological properties of HCs allow us to perceive sound and interact with the world around us. Mitochondria play a significant role in normal HC function and are also intricately involved in HC death. They generate ATP essential for sustaining the activity of ion pumps, Ca2+ transporters and the integrity of the stereociliary bundle during transduction as well as regulating cytosolic calcium homoeostasis during synaptic transmission. Advances in imaging techniques have allowed us to study mitochondrial populations throughout the HC, and how they interact with other organelles. These analyses have identified distinct mitochondrial populations between the apical and basolateral portions of the HC, in which mitochondrial morphology appears determined by the physiological processes in the different cellular compartments. Studies in HCs across species show that ototoxic agents, ageing and noise damage directly impact mitochondrial structure and function resulting in HC death. Deciphering the molecular mechanisms underlying this mitochondrial sensitivity, and how their morphology relates to their function during HC death, requires that we first understand this relationship in the context of normal HC function.
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Affiliation(s)
- James D B O'Sullivan
- Centre for Craniofacial and Regenerative Biology, Faculty of Dentistry, Oral, Craniofacial Sciences, King's College London, London SE1 9RT, U.K
| | - Anwen Bullen
- UCL Ear Institute, University College London, London WC1×8EE, U.K.
| | - Zoë F Mann
- Centre for Craniofacial and Regenerative Biology, Faculty of Dentistry, Oral, Craniofacial Sciences, King's College London, London SE1 9RT, U.K.
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5
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Lysakowski A, Govindaraju AC, Raphael RM. Structural and Functional Diversity of Mitochondria in Vestibular/Cochlear Hair Cells and Vestibular Calyx Afferents. Hear Res 2022; 426:108612. [DOI: 10.1016/j.heares.2022.108612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 07/21/2022] [Accepted: 09/19/2022] [Indexed: 11/30/2022]
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6
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Wu F, Hill K, Fang Q, He Z, Zheng H, Wang X, Xiong H, Sha SH. Traumatic-noise-induced hair cell death and hearing loss is mediated by activation of CaMKKβ. Cell Mol Life Sci 2022; 79:249. [PMID: 35438341 PMCID: PMC9844253 DOI: 10.1007/s00018-022-04268-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 03/14/2022] [Accepted: 03/20/2022] [Indexed: 01/19/2023]
Abstract
BACKGROUND The Ca2+/calmodulin-dependent protein kinase kinases (CaMKKs) are serine/threonine-directed protein kinases that are activated following increases in intracellular calcium, playing a critical role in neuronal signaling. Inner-ear-trauma-induced calcium overload in sensory hair cells has been well documented in the pathogenesis of traumatic noise-induced hair cell death and hearing loss, but there are no established pharmaceutical therapies available due to a lack of specific therapeutic targets. In this study, we investigated the activation of CaMKKβ in the inner ear after traumatic noise exposure and assessed the prevention of noise-induced hearing loss (NIHL) with RNA silencing. RESULTS Treatment with short hairpin RNA of CaMKKβ (shCaMKKβ) via adeno-associated virus transduction significantly knocked down CaMKKβ expression in the inner ear. Knockdown of CaMKKβ significantly attenuated noise-induced hair cell loss and hearing loss (NIHL). Additionally, pretreatment with naked CaMKKβ small interfering RNA (siCaMKKβ) attenuated noise-induced losses of inner hair cell synapses and OHCs and NIHL. Furthermore, traumatic noise exposure activates CaMKKβ in OHCs as demonstrated by immunolabeling for p-CaMKI. CaMKKβ mRNA assessed by fluorescence in-situ hybridization and immunolabeling for CaMKKβ in OHCs also increased after the exposure. Finally, pretreatment with siCaMKKβ diminished noise-induced activation of AMPKα in OHCs. CONCLUSIONS These findings demonstrate that traumatic-noise-induced OHC loss and hearing loss occur primarily via activation of CaMKKβ. Targeting CaMKKβ is a key strategy for prevention of noise-induced hearing loss. Furthermore, our data suggest that noise-induced activation of AMPKα in OHCs occurs via the CaMKKβ pathway.
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Affiliation(s)
- Fan Wu
- Department of Pathology and Laboratory Medicine, The Medical University of South Carolina, Charleston, SC 29425, USA.,Department of Otolaryngology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Kayla Hill
- Department of Pathology and Laboratory Medicine, The Medical University of South Carolina, Charleston, SC 29425, USA
| | - Qiaojun Fang
- Department of Pathology and Laboratory Medicine, The Medical University of South Carolina, Charleston, SC 29425, USA.,School of Life Sciences and Technology, Southeast University, Nanjing 210096, China
| | - Zuhong He
- Department of Pathology and Laboratory Medicine, The Medical University of South Carolina, Charleston, SC 29425, USA
| | - Hongwei Zheng
- Department of Pathology and Laboratory Medicine, The Medical University of South Carolina, Charleston, SC 29425, USA
| | - Xianren Wang
- Department of Pathology and Laboratory Medicine, The Medical University of South Carolina, Charleston, SC 29425, USA
| | - Hao Xiong
- Department of Pathology and Laboratory Medicine, The Medical University of South Carolina, Charleston, SC 29425, USA
| | - Su-Hua Sha
- Department of Pathology and Laboratory Medicine, The Medical University of South Carolina, Charleston, SC 29425, USA.,Correspondence should be addressed to: Dr. Su-Hua Sha • Department of Pathology and Laboratory Medicine • Medical University of South Carolina • Walton Research Building, Room 403-E • 39 Sabin Street, Charleston, SC 29425, USA. Telephone: 843-792-8324; Fax: 843-792-0368;
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7
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Newton S, Kong F, Carlton AJ, Aguilar C, Parker A, Codner GF, Teboul L, Wells S, Brown SDM, Marcotti W, Bowl MR. Neuroplastin genetically interacts with Cadherin 23 and the encoded isoform Np55 is sufficient for cochlear hair cell function and hearing. PLoS Genet 2022; 18:e1009937. [PMID: 35100259 PMCID: PMC8830789 DOI: 10.1371/journal.pgen.1009937] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Revised: 02/10/2022] [Accepted: 01/13/2022] [Indexed: 11/25/2022] Open
Abstract
Mammalian hearing involves the mechanoelectrical transduction (MET) of sound-induced fluid waves in the cochlea. Essential to this process are the specialised sensory cochlear cells, the inner (IHCs) and outer hair cells (OHCs). While genetic hearing loss is highly heterogeneous, understanding the requirement of each gene will lead to a better understanding of the molecular basis of hearing and also to therapeutic opportunities for deafness. The Neuroplastin (Nptn) gene, which encodes two protein isoforms Np55 and Np65, is required for hearing, and homozygous loss-of-function mutations that affect both isoforms lead to profound deafness in mice. Here we have utilised several distinct mouse models to elaborate upon the spatial, temporal, and functional requirement of Nptn for hearing. While we demonstrate that both Np55 and Np65 are present in cochlear cells, characterisation of a Np65-specific mouse knockout shows normal hearing thresholds indicating that Np65 is functionally redundant for hearing. In contrast, we find that Nptn-knockout mice have significantly reduced maximal MET currents and MET channel open probabilities in mature OHCs, with both OHCs and IHCs also failing to develop fully mature basolateral currents. Furthermore, comparing the hearing thresholds and IHC synapse structure of Nptn-knockout mice with those of mice that lack Nptn only in IHCs and OHCs shows that the majority of the auditory deficit is explained by hair cell dysfunction, with abnormal afferent synapses contributing only a small proportion of the hearing loss. Finally, we show that continued expression of Neuroplastin in OHCs of adult mice is required for membrane localisation of Plasma Membrane Ca2+ ATPase 2 (PMCA2), which is essential for hearing function. Moreover, Nptn haploinsufficiency phenocopies Atp2b2 (encodes PMCA2) mutations, with heterozygous Nptn-knockout mice exhibiting hearing loss through genetic interaction with the Cdh23ahl allele. Together, our findings provide further insight to the functional requirement of Neuroplastin for mammalian hearing.
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Affiliation(s)
- Sherylanne Newton
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Fanbo Kong
- School of Sciences, University of Sheffield, Sheffield, United Kingdom
| | - Adam J. Carlton
- School of Sciences, University of Sheffield, Sheffield, United Kingdom
| | - Carlos Aguilar
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Andrew Parker
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Gemma F. Codner
- Mary Lyon Centre, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Lydia Teboul
- Mary Lyon Centre, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Sara Wells
- Mary Lyon Centre, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Steve D. M. Brown
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Oxford, United Kingdom
| | - Walter Marcotti
- School of Sciences, University of Sheffield, Sheffield, United Kingdom
- Sheffield Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom
| | - Michael R. Bowl
- Mammalian Genetics Unit, MRC Harwell Institute, Harwell Oxford, United Kingdom
- UCL Ear Institute, University College London, London, United Kingdom
- * E-mail:
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8
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Mitochondrial calcium uniporter is essential for hearing and hair cell preservation in congenic FVB/NJ mice. Sci Rep 2021; 11:9660. [PMID: 33958614 PMCID: PMC8102556 DOI: 10.1038/s41598-021-88841-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 04/13/2021] [Indexed: 12/12/2022] Open
Abstract
Mitochondrial Ca2+ regulates a wide range of cell processes, including morphogenesis, metabolism, excitotoxicity, and survival. In cochlear hair cells, the activation of mechano-electrical transduction and voltage-gated Ca2+ channels result in a large influx of Ca2+. The intracellular rise in Ca2+ is partly balanced by the mitochondria which rapidly uptakes Ca2+ via a highly selective channel comprised of the main pore-forming subunit, the mitochondrial Ca2+ uniporter (MCU), and associated regulatory proteins. MCU thus contributes to Ca2+ buffering, ensuring cytosolic homeostasis, and is posited to have a critical role in hair cell function and hearing. To test this hypothesis, Ca2+ homeostasis in hair cells and cochlear function were investigated in FVB/NJ mice carrying the knockout allele of Mcu (Mcu+/− or Mcu−/−). The Mcu knockout allele, which originated in C57BL/6 strain cosegregated along with Cdh23ahl allele to the FVB/NJ strain, due to the close proximity of these genes. Neither Mcu+/− nor Mcu−/− genotypes affected cochlear development, morphology, or Ca2+ homeostasis of auditory hair cells in the first two postnatal weeks. However, Mcu−/− mice displayed high-frequency hearing impairment as early as 3 weeks postnatal, which then progressed to profound hearing loss at all frequencies in about 6 months. In Mcu+/− mice, significantly elevated ABR thresholds were observed at 6 months and 9 months of age only at 32 kHz frequency. In three-month-old Mcu−/− mice, up to 18% of the outer hair cells and occasionally some inner hair cells were missing in the mid-cochlear region. In conclusion, mitochondrial Ca2+ uniporter is not required for the development of cochlea in mice, but is essential for hearing and hair cell preservation in congenic FVB/NJ mice.
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9
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Mulhall EM, Ward A, Yang D, Koussa MA, Corey DP, Wong WP. Single-molecule force spectroscopy reveals the dynamic strength of the hair-cell tip-link connection. Nat Commun 2021; 12:849. [PMID: 33558532 PMCID: PMC7870652 DOI: 10.1038/s41467-021-21033-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Accepted: 01/08/2021] [Indexed: 01/11/2023] Open
Abstract
The conversion of auditory and vestibular stimuli into electrical signals is initiated by force transmitted to a mechanotransduction channel through the tip link, a double stranded protein filament held together by two adhesion bonds in the middle. Although thought to form a relatively static structure, the dynamics of the tip-link connection has not been measured. Here, we biophysically characterize the strength of the tip-link connection at single-molecule resolution. We show that a single tip-link bond is more mechanically stable relative to classic cadherins, and our data indicate that the double stranded tip-link connection is stabilized by single strand rebinding facilitated by strong cis-dimerization domains. The measured lifetime of seconds suggests the tip-link is far more dynamic than previously thought. We also show how Ca2+ alters tip-link lifetime through elastic modulation and reveal the mechanical phenotype of a hereditary deafness mutation. Together, these data show how the tip link is likely to function during mechanical stimuli.
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Affiliation(s)
- Eric M Mulhall
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Program in Neuroscience, Harvard University, Cambridge, MA, USA
| | - Andrew Ward
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
| | - Darren Yang
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA
| | - Mounir A Koussa
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
- Program in Neuroscience, Harvard University, Cambridge, MA, USA
| | - David P Corey
- Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
| | - Wesley P Wong
- Program in Cellular and Molecular Medicine, Boston Children's Hospital, Boston, MA, USA.
- Department of Biological Chemistry and Molecular Pharmacology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
- Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, USA.
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10
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Cochlear homeostasis: a molecular physiological perspective on maintenance of sound transduction and auditory neurotransmission with noise and ageing. CURRENT OPINION IN PHYSIOLOGY 2020. [DOI: 10.1016/j.cophys.2020.09.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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11
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Disruption of Atg7-dependent autophagy causes electromotility disturbances, outer hair cell loss, and deafness in mice. Cell Death Dis 2020; 11:913. [PMID: 33099575 PMCID: PMC7585579 DOI: 10.1038/s41419-020-03110-8] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 10/04/2020] [Accepted: 10/06/2020] [Indexed: 12/11/2022]
Abstract
Atg7 is an indispensable factor that plays a role in canonical nonselective autophagy. Here we show that genetic ablation of Atg7 in outer hair cells (OHCs) in mice caused stereocilium damage, somatic electromotility disturbances, and presynaptic ribbon degeneration over time, which led to the gradual wholesale loss of OHCs and subsequent early-onset profound hearing loss. Impaired autophagy disrupted OHC mitochondrial function and triggered the accumulation of dysfunctional mitochondria that would otherwise be eliminated in a timely manner. Atg7-independent autophagy/mitophagy processes could not compensate for Atg7 deficiency and failed to rescue the terminally differentiated, non-proliferating OHCs. Our results show that OHCs orchestrate intricate nonselective and selective autophagic/mitophagy pathways working in concert to maintain cellular homeostasis. Overall, our results demonstrate that Atg7-dependent autophagy plays a pivotal cytoprotective role in preserving OHCs and maintaining hearing function.
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12
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Mechanotransduction-Dependent Control of Stereocilia Dimensions and Row Identity in Inner Hair Cells. Curr Biol 2020; 30:442-454.e7. [PMID: 31902726 DOI: 10.1016/j.cub.2019.11.076] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 11/08/2019] [Accepted: 11/26/2019] [Indexed: 02/07/2023]
Abstract
Actin-rich structures, like stereocilia and microvilli, are assembled with precise control of length, diameter, and relative spacing. By quantifying actin-core dimensions of stereocilia from phalloidin-labeled mouse cochleas, we demonstrated that inner hair cell stereocilia developed in specific stages, where a widening phase is sandwiched between two lengthening phases. Moreover, widening of the second-tallest stereocilia rank (row 2) occurred simultaneously with the appearance of mechanotransduction. Correspondingly, Tmc1KO/KO;Tmc2KO/KO or TmieKO/KO hair cells, which lack transduction, have significantly altered stereocilia lengths and diameters, including a narrowed row 2. EPS8 and the short splice isoform of MYO15A, identity markers for mature row 1 (the tallest row), lost their row exclusivity in transduction mutants. GNAI3, another member of the mature row 1 complex, accumulated at mutant row 1 tips at considerably lower levels than in wild-type bundles. Alterations in stereocilia dimensions and in EPS8 distribution seen in transduction mutants were mimicked by block of transduction channels of cochlear explants in culture. In addition, proteins normally concentrated at mature row 2 tips were also distributed differently in transduction mutants; the heterodimeric capping protein subunit CAPZB and its partner TWF2 never concentrated at row 2 tips like they do in wild-type bundles. The altered distribution of marker proteins in transduction mutants was accompanied by increased variability in stereocilia length. Transduction channels thus specify and maintain row identity, control addition of new actin filaments to increase stereocilia diameter, and coordinate stereocilia height within rows.
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13
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Du H, Zou L, Ren R, Li N, Li J, Wang Y, Sun J, Yang J, Xiong W, Xu Z. Lack of PDZD7 long isoform disrupts ankle-link complex and causes hearing loss in mice. FASEB J 2019; 34:1136-1149. [PMID: 31914662 DOI: 10.1096/fj.201901657rr] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 09/28/2019] [Accepted: 11/14/2019] [Indexed: 12/12/2022]
Abstract
Usher syndrome (USH) is the most frequent form of combined hereditary deafness-blindness, characterized by hearing loss and retinitis pigmentosa, with or without vestibular dysfunction. PDZD7 is a PDZ domain-containing scaffold protein that was suggested to be a USH modifier and a contributor to digenic USH. In the inner ear hair cells, PDZD7 localizes at the ankle region of the stereocilia and constitutes the so-called ankle-link complex together with three other USH proteins Usherin, WHRN, and ADGRV1. PDZD7 gene is subjected to alternative splicing, which gives rise to two types of PDZD7 isoforms, namely the long and short isoforms. At present, little is known which specific isoform is involved in ankle-link formation and stereocilia development. In this work, we showed that PDZD7 long isoform, but not short isoforms, localizes at the ankle region of the stereocilia. Moreover, we established Pdzd7 mutant mice by introducing deletions into exon 14 of the Pdzd7 gene, which causes potential premature translational stop in the long isoform but leaves short isoforms unaffected. We found that lack of PDZD7 long isoform affects the localization of other ankle-link complex components in the stereocilia. Consequently, Pdzd7 mutant mice showed stereocilia development deficits and hearing loss as well as reduced mechanotransduction (MET) currents, suggesting that PDZD7 long isoform is indispensable for hair cells. Furthermore, by performing yeast two-hybrid screening, we identified a PDZD7 long isoform-specific binding partner PIP5K1C, which has been shown to play important roles in hearing and might participate in the function and/or transportation of PDZD7.
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Affiliation(s)
- Haibo Du
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology, School of Life Sciences, Shandong University, Qingdao, China
| | - Linzhi Zou
- School of Life Sciences, IDG/McGovern Institute for Brain Research at Tsinghua, Tsinghua University, Beijing, China
| | - Rui Ren
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology, School of Life Sciences, Shandong University, Qingdao, China
| | - Nana Li
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology, School of Life Sciences, Shandong University, Qingdao, China
| | - Jie Li
- School of Life Sciences, IDG/McGovern Institute for Brain Research at Tsinghua, Tsinghua University, Beijing, China
| | - Yanfei Wang
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology, School of Life Sciences, Shandong University, Qingdao, China
| | - Jinpeng Sun
- Key Laboratory Experimental Teratology of the Ministry of Education, Department of Biochemistry and Molecular Biology, Shandong University School of Medicine, Jinan, China
| | - Jun Yang
- Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah, Salt Lake City, Utah
| | - Wei Xiong
- School of Life Sciences, IDG/McGovern Institute for Brain Research at Tsinghua, Tsinghua University, Beijing, China
| | - Zhigang Xu
- Shandong Provincial Key Laboratory of Animal Cell and Developmental Biology, School of Life Sciences, Shandong University, Qingdao, China.,Shandong Provincial Collaborative Innovation Center of Cell Biology, Shandong Normal University, Jinan, China
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14
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Bortolozzi M, Mammano F. PMCA2 pump mutations and hereditary deafness. Neurosci Lett 2019; 663:18-24. [PMID: 29452611 DOI: 10.1016/j.neulet.2017.09.059] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2017] [Revised: 09/25/2017] [Accepted: 09/28/2017] [Indexed: 01/21/2023]
Abstract
Hair cells of the inner ear detect sound stimuli, inertial or gravitational forces by deflection of their apical stereocilia. A small number of stereociliary cation-selective mechanotransduction (MET) channels admit K+ and Ca2+ ions into the cytoplasm promoting hair cell membrane depolarization and, consequently, neurotransmitter release at the cell basolateral pole. Ca2+ influx into the stereocilia compartment is counteracted by the unusual w/a splicing variant of plasma-membrane calcium-pump isoform 2 (PMCA2) which, unlike other PMCA2 variants, increases only marginally its activity in response to a rapid variation of the cytoplasmic free Ca2+ concentration ([Ca2+]c). Missense mutations of PMCA2w/a cause deafness and loss of balance in humans. Mouse models in which the pump is genetically ablated or mutated show hearing and balance impairment, which correlates with defects in homeostatic regulation of stereociliary [Ca2+]c, decreased sensitivity of mechanotransduction channels to hair bundle displacement and progressive degeneration of the organ of Corti. These results highlight a critical role played by the PMCA2w/a pump in the control of hair cell function and survival, and provide mechanistic insight into the etiology of deafness and vestibular disorders.
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Affiliation(s)
- Mario Bortolozzi
- University of Padua, Department of Physics and Astronomy "G. Galilei", Padua, Italy; Venetian Institute of Molecular Medicine (VIMM), Padua, Italy; CNR Institute of Protein Biochemistry, Naples, Italy.
| | - Fabio Mammano
- University of Padua, Department of Physics and Astronomy "G. Galilei", Padua, Italy; Venetian Institute of Molecular Medicine (VIMM), Padua, Italy; CNR Institute of Cell Biology and Neurobiology, Monterotondo Scalo, Rome, Italy
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15
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Krey JF, Barr-Gillespie PG. Molecular Composition of Vestibular Hair Bundles. Cold Spring Harb Perspect Med 2019; 9:cshperspect.a033209. [PMID: 29844221 DOI: 10.1101/cshperspect.a033209] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The vertebrate hair bundle, responsible for transduction of mechanical signals into receptor potentials in sensory hair cells, is an evolutionary masterpiece. Composed of actin-filled stereocilia of precisely regulated length, width, and number, the structure of the hair bundle is optimized for sensing auditory and vestibular stimuli. Recent developments in identifying the lipids and proteins constituting the hair bundle, obtained through genetics, biochemistry, and imaging, now permit a description of the consensus composition of vestibular bundles of mouse, rat, and chick.
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Affiliation(s)
- Jocelyn F Krey
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, Oregon 97239
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16
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Vélez-Ortega AC, Frolenkov GI. Building and repairing the stereocilia cytoskeleton in mammalian auditory hair cells. Hear Res 2019; 376:47-57. [PMID: 30638948 DOI: 10.1016/j.heares.2018.12.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 12/19/2018] [Accepted: 12/28/2018] [Indexed: 10/27/2022]
Abstract
Despite all recent achievements in identification of the molecules that are essential for the structure and mechanosensory function of stereocilia bundles in the auditory hair cells of mammalian species, we still have only a rudimentary understanding of the mechanisms of stereocilia formation, maintenance, and repair. Important molecular differences distinguishing mammalian auditory hair cells from hair cells of other types and species have been recently revealed. In addition, we are beginning to solve the puzzle of the apparent life-long stability of the stereocilia bundles in these cells. New data link the stability of the cytoskeleton in the mammalian auditory stereocilia with the normal activity of mechanotransduction channels. These data suggest new ideas on how a terminally-differentiated non-regenerating hair cell in the mammalian cochlea may repair and tune its stereocilia bundle throughout the life span of the organism.
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Affiliation(s)
- A Catalina Vélez-Ortega
- Department of Physiology, University of Kentucky, 800 Rose St., Lexington, KY, 40536-0298, USA.
| | - Gregory I Frolenkov
- Department of Physiology, University of Kentucky, 800 Rose St., Lexington, KY, 40536-0298, USA.
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17
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Fettiplace R, Nam JH. Tonotopy in calcium homeostasis and vulnerability of cochlear hair cells. Hear Res 2018; 376:11-21. [PMID: 30473131 DOI: 10.1016/j.heares.2018.11.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 11/05/2018] [Accepted: 11/08/2018] [Indexed: 12/18/2022]
Abstract
Ototoxicity, noise overstimulation, or aging, can all produce hearing loss with similar properties, in which outer hair cells (OHCs), principally those at the high-frequency base of the cochlea, are preferentially affected. We suggest that the differential vulnerability may partly arise from differences in Ca2+ balance among cochlear locations. Homeostasis is determined by three factors: Ca2+ influx mainly via mechanotransducer (MET) channels; buffering by calcium-binding proteins and organelles like mitochondria; and extrusion by the plasma membrane CaATPase pump. We review quantification of these parameters and use our experimentally-determined values to model changes in cytoplasmic and mitochondrial Ca2+ during Ca2+ influx through the MET channels. We suggest that, in OHCs, there are two distinct micro-compartments for Ca2+ handling, one in the hair bundle and the other in the cell soma. One conclusion of the modeling is that there is a tonotopic gradient in the ability of OHCs to handle the Ca2+ load, which correlates with their vulnerability to environmental challenges. High-frequency basal OHCs are the most susceptible because they have much larger MET currents and have smaller dimensions than low-frequency apical OHCs.
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Affiliation(s)
- Robert Fettiplace
- Department of Neuroscience, University of Wisconsin, Madison, WI, 53706, USA.
| | - Jong-Hoon Nam
- Departments of Mechanical Engineering and Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
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18
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Takahashi S, Sun W, Zhou Y, Homma K, Kachar B, Cheatham MA, Zheng J. Prestin Contributes to Membrane Compartmentalization and Is Required for Normal Innervation of Outer Hair Cells. Front Cell Neurosci 2018; 12:211. [PMID: 30079013 PMCID: PMC6062617 DOI: 10.3389/fncel.2018.00211] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 06/27/2018] [Indexed: 12/16/2022] Open
Abstract
Outer hair cells (OHC) act as amplifiers and their function is modified by medial olivocochlear (MOC) efferents. The unique OHC motor protein, prestin, provides the molecular basis for somatic electromotility, which is required for sensitivity and frequency selectivity, the hallmarks of mammalian hearing. Prestin proteins are the major component of the lateral membrane of mature OHCs, which separates apical and basal domains. To investigate the contribution of prestin to this unique arrangement, we compared the distribution of membrane proteins in OHCs of wildtype (WT) and prestin-knockout (KO) mice. In WT, the apical protein PMCA2 was exclusively localized to the hair bundles, while it was also found at the lateral membrane in KOs. Similarly, a basal protein KCNQ4 did not coalesce at the base of OHCs but was widely dispersed in mice lacking prestin. Since the expression levels of PMCA2 and KCNQ4 remained unchanged in KOs, the data indicate that prestin is required for the normal distribution of apical and basal membrane proteins in OHCs. Since OHC synapses predominate in the basal subnuclear region, we also examined the synaptic architecture in prestin-KO mice. Although neurite densities were not affected, MOC efferent terminals in prestin-KO mice were no longer constrained to the basal pole as in WT. This trend was evident as early as at postnatal day 12. Furthermore, terminals were often enlarged and frequently appeared as singlets when compared to the multiple clusters of individual terminals in WT. This abnormality in MOC synaptic morphology in prestin-KO mice is similar to defects in mice lacking MOC pathway proteins such as α9/α10 nicotinic acetylcholine receptors and BK channels, indicating a role for prestin in the proper establishment of MOC synapses. To investigate the contribution of prestin’s electromotility, we also examined OHCs from a mouse model that expresses non-functional prestin (499-prestin). We found no changes in PMCA2 localization and MOC synaptic morphology in OHCs from 499-prestin mice. Taken together, these results indicate that prestin, independent of its motile function, plays an important structural role in membrane compartmentalization, which is required for the formation of normal efferent-OHC synapses in mature OHCs.
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Affiliation(s)
- Satoe Takahashi
- Department of Otolaryngology - Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Willy Sun
- Section on Structural Cell Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
| | - Yingjie Zhou
- Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL, United States
| | - Kazuaki Homma
- Department of Otolaryngology - Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States.,The Knowles Hearing Center, Northwestern University, Evanston, IL, United States
| | - Bechara Kachar
- Section on Structural Cell Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, United States
| | - Mary Ann Cheatham
- Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL, United States.,The Knowles Hearing Center, Northwestern University, Evanston, IL, United States
| | - Jing Zheng
- Department of Otolaryngology - Head and Neck Surgery, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States.,Department of Communication Sciences and Disorders, Northwestern University, Evanston, IL, United States.,The Knowles Hearing Center, Northwestern University, Evanston, IL, United States
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19
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Ellwanger DC, Scheibinger M, Dumont RA, Barr-Gillespie PG, Heller S. Transcriptional Dynamics of Hair-Bundle Morphogenesis Revealed with CellTrails. Cell Rep 2018; 23:2901-2914.e13. [PMID: 29874578 PMCID: PMC6089258 DOI: 10.1016/j.celrep.2018.05.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 03/19/2018] [Accepted: 05/01/2018] [Indexed: 11/30/2022] Open
Abstract
Protruding from the apical surface of inner ear sensory cells, hair bundles carry out mechanotransduction. Bundle growth involves sequential and overlapping cellular processes, which are concealed within gene expression profiles of individual cells. To dissect such processes, we developed CellTrails, a tool for uncovering, analyzing, and visualizing single-cell gene-expression dynamics. Utilizing quantitative gene-expression data for key bundle proteins from single cells of the developing chick utricle, we reconstructed de novo a bifurcating trajectory that spanned from progenitor cells to mature striolar and extrastriolar hair cells. Extraction and alignment of developmental trails and association of pseudotime with bundle length measurements linked expression dynamics of individual genes with bundle growth stages. Differential trail analysis revealed high-resolution dynamics of transcripts that control striolar and extrastriolar bundle development, including those that encode proteins that regulate [Ca2+]i or mediate crosslinking and lengthening of actin filaments.
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Affiliation(s)
- Daniel C Ellwanger
- Department of Otolaryngology, Head & Neck Surgery and Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Mirko Scheibinger
- Department of Otolaryngology, Head & Neck Surgery and Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Rachel A Dumont
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center and Vollum Institute, Oregon Health & Science University, Portland, OR 97239, USA.
| | - Stefan Heller
- Department of Otolaryngology, Head & Neck Surgery and Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.
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20
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Lin LY, Yeh YH, Hung GY, Lin CH, Hwang PP, Horng JL. Role of Calcium-Sensing Receptor in Mechanotransducer-Channel-Mediated Ca 2+ Influx in Hair Cells of Zebrafish Larvae. Front Physiol 2018; 9:649. [PMID: 29899708 PMCID: PMC5988855 DOI: 10.3389/fphys.2018.00649] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 05/14/2018] [Indexed: 01/16/2023] Open
Abstract
The calcium-sensing receptor (CaSR) is an extracellular Ca2+ sensor that plays a critical role in maintaining Ca2+ homeostasis in several organs, including the parathyroid gland and kidneys. In this study, through in situ hybridization, the expression of CaSR mRNA was found in the neuromasts of zebrafish larvae. Immunohistochemistry further demonstrated that the CaSR protein was present in neuromast hair cell stereocilia and basolateral membranes. Based on the expression and subcellular localization of the CaSR in hair cells, we hypothesized that the CaSR is expressed in zebrafish lateral-line hair cells to regulate mechanotransducer (MET)-channel-mediated Ca2+ entry. Using the scanning ion-selective electrode technique, MET-channel-mediated Ca2+ influx at the stereocilia of hair cells was measured in intact larvae. Ca2+ influx was suppressed after larvae were pretreated with a CaSR activator (R-568) or high-Ca2+ (HCa) medium. Gene knockdown by using morpholino oligonucleotides decreased CaSR expression in hair cells and eliminated the effects of R-568 and HCa on Ca2+ influx. In addition, we found that treatment with R-568 attenuated neomycin-induced hair cell death. This study is the first to demonstrate that the CaSR is involved in mechanotransduction in zebrafish hair cells.
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Affiliation(s)
- Li-Yih Lin
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Ya-Hsin Yeh
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan
| | - Giun-Yi Hung
- Department of Life Science, National Taiwan Normal University, Taipei, Taiwan.,Department of Pediatrics, Taipei Veterans General Hospital, Taipei, Taiwan.,Department of Pediatrics, Faculty of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Chia-Hao Lin
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan.,Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
| | - Pung-Pung Hwang
- Institute of Cellular and Organismic Biology, Academia Sinica, Taipei, Taiwan
| | - Jiun-Lin Horng
- Department of Anatomy and Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan
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21
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Vicario M, Zanni G, Vallese F, Santorelli F, Grinzato A, Cieri D, Berto P, Frizzarin M, Lopreiato R, Zonta F, Ferro S, Sandre M, Marin O, Ruzzene M, Bertini E, Zanotti G, Brini M, Calì T, Carafoli E. A V1143F mutation in the neuronal-enriched isoform 2 of the PMCA pump is linked with ataxia. Neurobiol Dis 2018; 115:157-166. [PMID: 29655659 DOI: 10.1016/j.nbd.2018.04.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 03/21/2018] [Accepted: 04/09/2018] [Indexed: 12/13/2022] Open
Abstract
The fine regulation of intracellular calcium is fundamental for all eukaryotic cells. In neurons, Ca2+ oscillations govern the synaptic development, the release of neurotransmitters and the expression of several genes. Alterations of Ca2+ homeostasis were found to play a pivotal role in neurodegenerative progression. The maintenance of proper Ca2+ signaling in neurons demands the continuous activity of Ca2+ pumps and exchangers to guarantee physiological cytosolic concentration of the cation. The plasma membrane Ca2+ATPases (PMCA pumps) play a key role in the regulation of Ca2+ handling in selected sub-plasma membrane microdomains. Among the four basic PMCA pump isoforms existing in mammals, isoforms 2 and 3 are particularly enriched in the nervous system. In humans, genetic mutations in the PMCA2 gene in association with cadherin 23 mutations have been linked to hearing loss phenotypes, while those occurring in the PMCA3 gene were associated with X-linked congenital cerebellar ataxias. Here we describe a novel missense mutation (V1143F) in the calmodulin binding domain (CaM-BD) of the PMCA2 protein. The mutant pump was present in a patient showing congenital cerebellar ataxia but no overt signs of deafness, in line with the absence of mutations in the cadherin 23 gene. Biochemical and molecular dynamics studies on the mutated PMCA2 have revealed that the V1143F substitution alters the binding of calmodulin to the CaM-BD leading to impaired Ca2+ ejection.
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Affiliation(s)
- Mattia Vicario
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Ginevra Zanni
- Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Francesca Vallese
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | | | - Alessandro Grinzato
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Domenico Cieri
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Paola Berto
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Martina Frizzarin
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Raffaele Lopreiato
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Francesco Zonta
- Shanghai Institute of Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China; Department of Biomedical Sciences, Institute of Cell Biology and Neurobiology, Italian National Research Council, 00015 Monterotondo, Rome, Italy
| | - Stefania Ferro
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Michele Sandre
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Oriano Marin
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Maria Ruzzene
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Enrico Bertini
- Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Giuseppe Zanotti
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Marisa Brini
- Department of Biology, University of Padova, Italy.
| | - Tito Calì
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy; Padua Neuroscience Center (PNC), University of Padua, 35122 Padova, Italy.
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22
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Zorio DAR, Monsma S, Sanes DH, Golding NL, Rubel EW, Wang Y. De novo sequencing and initial annotation of the Mongolian gerbil (Meriones unguiculatus) genome. Genomics 2018. [PMID: 29526484 DOI: 10.1016/j.ygeno.2018.03.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The Mongolian gerbil (Meriones unguiculatus) is a member of the rodent family that displays several features not found in mice or rats, including sensory specializations and social patterns more similar to those in humans. These features have made gerbils a valuable animal for research studies of auditory and visual processing, brain development, learning and memory, and neurological disorders. Here, we report the whole gerbil annotated genome sequence, and identify important similarities and differences to the human and mouse genomes. We further analyze the chromosomal structure of eight genes with high relevance for controlling neural signaling and demonstrate a high degree of homology between these genes in mouse and gerbil. This homology increases the likelihood that individual genes can be rapidly identified in gerbil and used for genetic manipulations. The availability of the gerbil genome provides a foundation for advancing our knowledge towards understanding evolution, behavior and neural function in mammals. ACCESSION NUMBER: The Whole Genome Shotgun sequence data from this project has been deposited at DDBJ/ENA/GenBank under the accession NHTI00000000. The version described in this paper is version NHTI01000000. The fragment reads, and mate pair reads have been deposited in the Sequence Read Archive under BioSample accession SAMN06897401.
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Affiliation(s)
- Diego A R Zorio
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA.
| | | | - Dan H Sanes
- Center for Neural Science, New York University, New York, NY, USA
| | - Nace L Golding
- University of Texas at Austin, Department of Neuroscience, Center for Learning and Memory, Austin, TX, USA
| | - Edwin W Rubel
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, University of Washington, Seattle, WA, USA
| | - Yuan Wang
- Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, FL, USA; Program in Neuroscience, Florida State University, Tallahassee, FL, USA.
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23
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Regulation of the Plasma Membrane Calcium ATPases by the actin cytoskeleton. Biochem Biophys Res Commun 2017; 506:347-354. [PMID: 29180009 DOI: 10.1016/j.bbrc.2017.11.151] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 11/22/2017] [Indexed: 01/08/2023]
Abstract
Associations between the cortical cytoskeleton and the components of the plasma membrane are no longer considered to be merely of structural and mechanical nature but are nowadays recognized as dynamic interactions that modulate a plethora of cellular responses. Reorganization of actin filaments upon diverse stimuli - among which is the rise in cytosolic Ca2+ - is involved in cell motility and adhesion, phagocytosis, cytokinesis, and secretion. Actin dynamics also participates in the regulation of ion transport across the membranes where it not only plays a key role in the delivery and stabilization of channels and transporters in the plasma membrane but also in the regulation of their activity. The recently described functional interaction between actin and the Plasma Membrane Ca2+-ATPase (PMCA) represents a novel regulatory mechanism of the pump at the time that unveils a new pathway by which the cortical actin cytoskeleton participates in the regulation of cytosolic Ca2+ homeostasis. In this review, we summarize the current knowledge on the interaction between the cortical actin cytoskeleton and the PMCA and discuss the possible mechanisms that may explain the pump's modulation.
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24
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Fettiplace R. Hair Cell Transduction, Tuning, and Synaptic Transmission in the Mammalian Cochlea. Compr Physiol 2017; 7:1197-1227. [PMID: 28915323 DOI: 10.1002/cphy.c160049] [Citation(s) in RCA: 189] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Sound pressure fluctuations striking the ear are conveyed to the cochlea, where they vibrate the basilar membrane on which sit hair cells, the mechanoreceptors of the inner ear. Recordings of hair cell electrical responses have shown that they transduce sound via submicrometer deflections of their hair bundles, which are arrays of interconnected stereocilia containing the mechanoelectrical transducer (MET) channels. MET channels are activated by tension in extracellular tip links bridging adjacent stereocilia, and they can respond within microseconds to nanometer displacements of the bundle, facilitated by multiple processes of Ca2+-dependent adaptation. Studies of mouse mutants have produced much detail about the molecular organization of the stereocilia, the tip links and their attachment sites, and the MET channels localized to the lower end of each tip link. The mammalian cochlea contains two categories of hair cells. Inner hair cells relay acoustic information via multiple ribbon synapses that transmit rapidly without rundown. Outer hair cells are important for amplifying sound-evoked vibrations. The amplification mechanism primarily involves contractions of the outer hair cells, which are driven by changes in membrane potential and mediated by prestin, a motor protein in the outer hair cell lateral membrane. Different sound frequencies are separated along the cochlea, with each hair cell being tuned to a narrow frequency range; amplification sharpens the frequency resolution and augments sensitivity 100-fold around the cell's characteristic frequency. Genetic mutations and environmental factors such as acoustic overstimulation cause hearing loss through irreversible damage to the hair cells or degeneration of inner hair cell synapses. © 2017 American Physiological Society. Compr Physiol 7:1197-1227, 2017.
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Affiliation(s)
- Robert Fettiplace
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
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25
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Stafford N, Wilson C, Oceandy D, Neyses L, Cartwright EJ. The Plasma Membrane Calcium ATPases and Their Role as Major New Players in Human Disease. Physiol Rev 2017; 97:1089-1125. [PMID: 28566538 DOI: 10.1152/physrev.00028.2016] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 01/20/2017] [Accepted: 01/23/2017] [Indexed: 02/07/2023] Open
Abstract
The Ca2+ extrusion function of the four mammalian isoforms of the plasma membrane calcium ATPases (PMCAs) is well established. There is also ever-increasing detail known of their roles in global and local Ca2+ homeostasis and intracellular Ca2+ signaling in a wide variety of cell types and tissues. It is becoming clear that the spatiotemporal patterns of expression of the PMCAs and the fact that their abundances and relative expression levels vary from cell type to cell type both reflect and impact on their specific functions in these cells. Over recent years it has become increasingly apparent that these genes have potentially significant roles in human health and disease, with PMCAs1-4 being associated with cardiovascular diseases, deafness, autism, ataxia, adenoma, and malarial resistance. This review will bring together evidence of the variety of tissue-specific functions of PMCAs and will highlight the roles these genes play in regulating normal physiological functions and the considerable impact the genes have on human disease.
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Affiliation(s)
- Nicholas Stafford
- Division of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom
| | - Claire Wilson
- Division of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom
| | - Delvac Oceandy
- Division of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom
| | - Ludwig Neyses
- Division of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom
| | - Elizabeth J Cartwright
- Division of Cardiovascular Sciences, University of Manchester, Manchester, United Kingdom
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26
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Nurbaeva MK, Eckstein M, Feske S, Lacruz RS. Ca 2+ transport and signalling in enamel cells. J Physiol 2017; 595:3015-3039. [PMID: 27510811 PMCID: PMC5430215 DOI: 10.1113/jp272775] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 07/21/2016] [Indexed: 01/02/2023] Open
Abstract
Dental enamel is one of the most remarkable examples of matrix-mediated biomineralization. Enamel crystals form de novo in a rich extracellular environment in a stage-dependent manner producing complex microstructural patterns that are visually stunning. This process is orchestrated by specialized epithelial cells known as ameloblasts which themselves undergo striking morphological changes, switching function from a secretory role to a cell primarily engaged in ionic transport. Ameloblasts are supported by a host of cell types which combined represent the enamel organ. Fully mineralized enamel is the hardest tissue found in vertebrates owing its properties partly to the unique mixture of ionic species represented and their highly organized assembly in the crystal lattice. Among the main elements found in enamel, Ca2+ is the most abundant ion, yet how ameloblasts modulate Ca2+ dynamics remains poorly known. This review describes previously proposed models for passive and active Ca2+ transport, the intracellular Ca2+ buffering systems expressed in ameloblasts and provides an up-dated view of current models concerning Ca2+ influx and extrusion mechanisms, where most of the recent advances have been made. We also advance a new model for Ca2+ transport by the enamel organ.
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Affiliation(s)
- Meerim K. Nurbaeva
- Department of Basic Science and Craniofacial BiologyNew York University College of DentistryNew YorkUSA
| | - Miriam Eckstein
- Department of Basic Science and Craniofacial BiologyNew York University College of DentistryNew YorkUSA
| | - Stefan Feske
- Department of PathologyNew York University School of MedicineNew YorkNY10016USA
| | - Rodrigo S. Lacruz
- Department of Basic Science and Craniofacial BiologyNew York University College of DentistryNew YorkUSA
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27
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Vélez-Ortega AC, Freeman MJ, Indzhykulian AA, Grossheim JM, Frolenkov GI. Mechanotransduction current is essential for stability of the transducing stereocilia in mammalian auditory hair cells. eLife 2017; 6. [PMID: 28350294 PMCID: PMC5407859 DOI: 10.7554/elife.24661] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Accepted: 03/27/2017] [Indexed: 01/02/2023] Open
Abstract
Mechanotransducer channels at the tips of sensory stereocilia of inner ear hair cells are gated by the tension of 'tip links' interconnecting stereocilia. To ensure maximal sensitivity, tip links are tensioned at rest, resulting in a continuous influx of Ca2+ into the cell. Here, we show that this constitutive Ca2+ influx, usually considered as potentially deleterious for hair cells, is in fact essential for stereocilia stability. In the auditory hair cells of young postnatal mice and rats, a reduction in mechanotransducer current, via pharmacological channel blockers or disruption of tip links, leads to stereocilia shape changes and shortening. These effects occur only in stereocilia that harbor mechanotransducer channels, recover upon blocker washout or tip link regeneration and can be replicated by manipulations of extracellular Ca2+ or intracellular Ca2+ buffering. Thus, our data provide the first experimental evidence for the dynamic control of stereocilia morphology by the mechanotransduction current. DOI:http://dx.doi.org/10.7554/eLife.24661.001 Our sense of hearing depends on cells known as hair cells that line the inner ear. Each hair cell has tiny projections called stereocilia, which are arranged in a bundle with rows of increasing height like a staircase and are connected to each other by tiny filaments called tip-links. When sound waves hit the stereocilia, the tension on the tip-links increases, which opens “mechanotransduction” channels on the shorter stereocilia that allow calcium ions to flow into the cells. To ensure that the ears can detect even the softest sounds, the tip-links always have a small amount of tension which allows a small, but continuous flow of calcium ions into the cell. Scientists generally consider this continuous flow of calcium ions as a potentially harmful byproduct of sensitive hearing. Vélez-Ortega et al. isolated inner ear tissues from young mice and rats and exposed them to drugs that either block the flow of calcium ions through the mechanotransduction channels or break the tip-links on stereocilia. Surprisingly, these drugs made profound changes in the shape of individual stereocilia and the staircase architecture of the stereocilia bundle. When the drugs were rinsed out of the hair cells, the stereocilia went back to their normal shape. Sequestering of free calcium ions inside the hair cells had a similar effect on the shape of stereocilia. These findings show that the flow of calcium ions into the sterocilia via mechanotransduction channels controls the exquisite staircase-like architecture of the stereocilia bundle. More research is needed to identify which structural proteins cause the stereocilia shape changes and to work out exactly how calcium ions are involved. DOI:http://dx.doi.org/10.7554/eLife.24661.002
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Affiliation(s)
- A Catalina Vélez-Ortega
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, United States
| | - Mary J Freeman
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, United States
| | - Artur A Indzhykulian
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, United States
| | - Jonathan M Grossheim
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, United States
| | - Gregory I Frolenkov
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, United States
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28
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Calì T, Brini M, Carafoli E. Regulation of Cell Calcium and Role of Plasma Membrane Calcium ATPases. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2017; 332:259-296. [PMID: 28526135 DOI: 10.1016/bs.ircmb.2017.01.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The plasma membrane Ca2+ ATPase (PMCA pump) is a member of the superfamily of P-type pumps. It has 10 transmembrane helices and 2 cytosolic loops, one of which contains the catalytic center. Its most distinctive feature is a C-terminal tail that contains most of the regulatory sites including that for calmodulin. The pump is also regulated by acidic phospholipids, kinases, a dimerization process, and numerous protein interactors. In mammals, four genes code for the four basic isoforms. Isoform complexity is increased by alternative splicing of primary transcripts. Pumps 2 and 3 are expressed preferentially in the nervous system. The pumps coexist with more powerful systems that clear Ca2+ from the bulk cytosol: their role is thus the regulation of Ca2+ in selected subplasma membrane microdomains, where a number of important Ca2+-dependent enzymes interact with them. Malfunctions of the pump lead to disease phenotypes that affect the nervous system preferentially.
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Affiliation(s)
- T Calì
- University of Padova, Padova, Italy
| | - M Brini
- University of Padova, Padova, Italy
| | - E Carafoli
- Venetian Institute of Molecular Medicine, Padova, Italy.
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29
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Bucks SA, Cox BC, Vlosich BA, Manning JP, Nguyen TB, Stone JS. Supporting cells remove and replace sensory receptor hair cells in a balance organ of adult mice. eLife 2017; 6:e18128. [PMID: 28263708 PMCID: PMC5338920 DOI: 10.7554/elife.18128] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 01/20/2017] [Indexed: 01/20/2023] Open
Abstract
Vestibular hair cells in the inner ear encode head movements and mediate the sense of balance. These cells undergo cell death and replacement (turnover) throughout life in non-mammalian vertebrates. However, there is no definitive evidence that this process occurs in mammals. We used fate-mapping and other methods to demonstrate that utricular type II vestibular hair cells undergo turnover in adult mice under normal conditions. We found that supporting cells phagocytose both type I and II hair cells. Plp1-CreERT2-expressing supporting cells replace type II hair cells. Type I hair cells are not restored by Plp1-CreERT2-expressing supporting cells or by Atoh1-CreERTM-expressing type II hair cells. Destruction of hair cells causes supporting cells to generate 6 times as many type II hair cells compared to normal conditions. These findings expand our understanding of sensorineural plasticity in adult vestibular organs and further elucidate the roles that supporting cells serve during homeostasis and after injury.
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Affiliation(s)
- Stephanie A Bucks
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, United States
| | - Brandon C Cox
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, United States,Department of Surgery, Division of Otolaryngology, Southern Illinois University School of Medicine, Springfield, United States
| | - Brittany A Vlosich
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, United States
| | - James P Manning
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, United States
| | - Tot B Nguyen
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, United States
| | - Jennifer S Stone
- Department of Otolaryngology-Head and Neck Surgery, Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, United States,
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30
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The Plasma Membrane Calcium Pump (PMCA): Regulation of Cytosolic Ca2+, Genetic Diversities and Its Role in Sub-plasma Membrane Microdomains. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 981:3-21. [DOI: 10.1007/978-3-319-55858-5_1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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31
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Weatherstone JH, Kopp-Scheinpflug C, Pilati N, Wang Y, Forsythe ID, Rubel EW, Tempel BL. Maintenance of neuronal size gradient in MNTB requires sound-evoked activity. J Neurophysiol 2016; 117:756-766. [PMID: 27881722 PMCID: PMC5304411 DOI: 10.1152/jn.00528.2016] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 11/21/2016] [Indexed: 12/12/2022] Open
Abstract
Neurons of the medial nucleus of the trapezoid body (MNTB) act as fast-spiking inhibitory interneurons within the auditory brain stem. The MNTB is topographically organized, with low sound frequencies encoded laterally and high frequencies medially. We discovered a cell size gradient along this axis: lateral neurons are larger than medial neurons. The absence of this gradient in deaf mice lacking plasma membrane calcium ATPase 2 suggests an activity-dependent, calcium-mediated mechanism that controls neuronal soma size. The medial nucleus of the trapezoid body (MNTB) is an important source of inhibition during the computation of sound location. It transmits fast and precisely timed action potentials at high frequencies; this requires an efficient calcium clearance mechanism, in which plasma membrane calcium ATPase 2 (PMCA2) is a key component. Deafwaddler (dfw2J) mutant mice have a null mutation in PMCA2 causing deafness in homozygotes (dfw2J/dfw2J) and high-frequency hearing loss in heterozygotes (+/dfw2J). Despite the deafness phenotype, no significant differences in MNTB volume or cell number were observed in dfw2J homozygous mutants, suggesting that PMCA2 is not required for MNTB neuron survival. The MNTB tonotopic axis encodes high to low sound frequencies across the medial to lateral dimension. We discovered a cell size gradient along this axis: lateral neuronal somata are significantly larger than medially located somata. This size gradient is decreased in +/dfw2J and absent in dfw2J/dfw2J. The lack of acoustically driven input suggests that sound-evoked activity is required for maintenance of the cell size gradient. This hypothesis was corroborated by selective elimination of auditory hair cell activity with either hair cell elimination in Pou4f3 DTR mice or inner ear tetrodotoxin (TTX) treatment. The change in soma size was reversible and recovered within 7 days of TTX treatment, suggesting that regulation of the gradient is dependent on synaptic activity and that these changes are plastic rather than permanent. NEW & NOTEWORTHY Neurons of the medial nucleus of the trapezoid body (MNTB) act as fast-spiking inhibitory interneurons within the auditory brain stem. The MNTB is topographically organized, with low sound frequencies encoded laterally and high frequencies medially. We discovered a cell size gradient along this axis: lateral neurons are larger than medial neurons. The absence of this gradient in deaf mice lacking plasma membrane calcium ATPase 2 suggests an activity-dependent, calcium-mediated mechanism that controls neuronal soma size.
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Affiliation(s)
- Jessica H Weatherstone
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, and Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington.,Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, and Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington
| | - Conny Kopp-Scheinpflug
- Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, United Kingdom; .,Division of Neurobiology, Department Biology II, Ludwig-Maximilians University Munich, Planegg-Martinsried, Germany
| | - Nadia Pilati
- Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, United Kingdom.,Autifony Srl Laboratories, Medicines Research Centre, Verona, Italy; and
| | - Yuan Wang
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, and Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington.,Department of Biomedical Sciences, College of Medicine, Florida State University, Tallahassee, Florida
| | - Ian D Forsythe
- Department of Neuroscience, Psychology and Behaviour, University of Leicester, Leicester, United Kingdom
| | - Edwin W Rubel
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, and Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington
| | - Bruce L Tempel
- Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, and Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington.,Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surgery, and Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington
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32
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McLean WJ, McLean DT, Eatock RA, Edge ASB. Distinct capacity for differentiation to inner ear cell types by progenitor cells of the cochlea and vestibular organs. Development 2016; 143:4381-4393. [PMID: 27789624 DOI: 10.1242/dev.139840] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 10/11/2016] [Indexed: 01/16/2023]
Abstract
Disorders of hearing and balance are most commonly associated with damage to cochlear and vestibular hair cells or neurons. Although these cells are not capable of spontaneous regeneration, progenitor cells in the hearing and balance organs of the neonatal mammalian inner ear have the capacity to generate new hair cells after damage. To investigate whether these cells are restricted in their differentiation capacity, we assessed the phenotypes of differentiated progenitor cells isolated from three compartments of the mouse inner ear - the vestibular and cochlear sensory epithelia and the spiral ganglion - by measuring electrophysiological properties and gene expression. Lgr5+ progenitor cells from the sensory epithelia gave rise to hair cell-like cells, but not neurons or glial cells. Newly created hair cell-like cells had hair bundle proteins, synaptic proteins and membrane proteins characteristic of the compartment of origin. PLP1+ glial cells from the spiral ganglion were identified as neural progenitors, which gave rise to neurons, astrocytes and oligodendrocytes, but not hair cells. Thus, distinct progenitor populations from the neonatal inner ear differentiate to cell types associated with their organ of origin.
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Affiliation(s)
- Will J McLean
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02114, USA.,Eaton-Peabody Laboratories of Auditory Physiology, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA.,Program in Speech and Hearing Bioscience and Technology, Division of Health Sciences and Technology, Harvard & MIT, Cambridge, MA 02139, USA
| | - Dalton T McLean
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02114, USA.,Eaton-Peabody Laboratories of Auditory Physiology, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA
| | - Ruth Anne Eatock
- Department of Neurobiology, University of Chicago, Chicago, IL 60637, USA
| | - Albert S B Edge
- Department of Otology and Laryngology, Harvard Medical School, Boston, MA 02114, USA .,Eaton-Peabody Laboratories of Auditory Physiology, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA.,Program in Speech and Hearing Bioscience and Technology, Division of Health Sciences and Technology, Harvard & MIT, Cambridge, MA 02139, USA.,Harvard Stem Cell Institute, Cambridge, MA 02138, USA
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33
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Calì T, Frizzarin M, Luoni L, Zonta F, Pantano S, Cruz C, Bonza MC, Bertipaglia I, Ruzzene M, De Michelis MI, Damiano N, Marin O, Zanni G, Zanotti G, Brini M, Lopreiato R, Carafoli E. The ataxia related G1107D mutation of the plasma membrane Ca 2+ ATPase isoform 3 affects its interplay with calmodulin and the autoinhibition process. Biochim Biophys Acta Mol Basis Dis 2016; 1863:165-173. [PMID: 27632770 DOI: 10.1016/j.bbadis.2016.09.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 09/05/2016] [Accepted: 09/09/2016] [Indexed: 11/20/2022]
Abstract
The plasma membrane Ca2+ ATPases (PMCA pumps) have a long, cytosolic C-terminal regulatory region where a calmodulin-binding domain (CaM-BD) is located. Under basal conditions (low Ca2+), the C-terminal tail of the pump interacts with autoinhibitory sites proximal to the active center of the enzyme. In activating conditions (i.e., high Ca2+), Ca2+-bound CaM displaces the C-terminal tail from the autoinhibitory sites, restoring activity. We have recently identified a G1107D replacement within the CaM-BD of isoform 3 of the PMCA pump in a family affected by X-linked congenital cerebellar ataxia. Here, we investigate the effects of the G1107D replacement on the interplay of the mutated CaM-BD with both CaM and the pump core, by combining computational, biochemical and functional approaches. We provide evidence that the affinity of the isolated mutated CaM-BD for CaM is significantly reduced with respect to the wild type (wt) counterpart, and that the ability of CaM to activate the pump in vitro is thus decreased. Multiscale simulations support the conclusions on the detrimental effect of the mutation, indicating reduced stability of the CaM binding. We further show that the G1107D replacement impairs the autoinhibition mechanism of the PMCA3 pump as well, as the introduction of a negative charge perturbs the contacts between the CaM-BD and the pump core. Thus, the mutation affects both the ability of the pump to optimally transport Ca2+ in the activated state, and the autoinhibition mechanism in its resting state.
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Affiliation(s)
- Tito Calì
- Department of Biomedical Sciences, University of Padova, Italy
| | | | - Laura Luoni
- Department of Biosciences, University of Milano, Italy
| | - Francesco Zonta
- Shanghai Institute of Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China
| | | | - Carlos Cruz
- Aggeu Magalhães Research Center - CpqAM, Oswaldo Cruz Foundation - FioCruz, Rio de Janeiro, Brazil; Institut Pasteur de Montevideo, Uruguay
| | | | | | - Maria Ruzzene
- Department of Biomedical Sciences, University of Padova, Italy
| | | | - Nunzio Damiano
- Department of Biomedical Sciences, University of Padova, Italy
| | - Oriano Marin
- Department of Biomedical Sciences, University of Padova, Italy
| | - Ginevra Zanni
- Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | | | - Marisa Brini
- Department of Biology, University of Padova, Italy
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34
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Morgan CP, Krey JF, Grati M, Zhao B, Fallen S, Kannan-Sundhari A, Liu XZ, Choi D, Müller U, Barr-Gillespie PG. PDZD7-MYO7A complex identified in enriched stereocilia membranes. eLife 2016; 5:e18312. [PMID: 27525485 PMCID: PMC5005036 DOI: 10.7554/elife.18312] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 08/14/2016] [Indexed: 12/15/2022] Open
Abstract
While more than 70 genes have been linked to deafness, most of which are expressed in mechanosensory hair cells of the inner ear, a challenge has been to link these genes into molecular pathways. One example is Myo7a (myosin VIIA), in which deafness mutations affect the development and function of the mechanically sensitive stereocilia of hair cells. We describe here a procedure for the isolation of low-abundance protein complexes from stereocilia membrane fractions. Using this procedure, combined with identification and quantitation of proteins with mass spectrometry, we demonstrate that MYO7A forms a complex with PDZD7, a paralog of USH1C and DFNB31. MYO7A and PDZD7 interact in tissue-culture cells, and co-localize to the ankle-link region of stereocilia in wild-type but not Myo7a mutant mice. Our data thus describe a new paradigm for the interrogation of low-abundance protein complexes in hair cell stereocilia and establish an unanticipated link between MYO7A and PDZD7.
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Affiliation(s)
- Clive P Morgan
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, United States
| | - Jocelyn F Krey
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, United States
| | - M'hamed Grati
- Department of Otolaryngology, Miller School of Medicine, University of Miami, Miami, United States
| | - Bo Zhao
- Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, United States
| | - Shannon Fallen
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, United States
| | | | - Xue Zhong Liu
- Department of Otolaryngology, Miller School of Medicine, University of Miami, Miami, United States
| | - Dongseok Choi
- OHSU-PSU School of Public Health, Oregon Health and Science University, Portland, United States
- Graduate School of Dentistry, Kyung Hee University, Seoul, Korea
| | - Ulrich Müller
- Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, United States
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, United States
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35
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Beurg M, Goldring AC, Fettiplace R. The effects of Tmc1 Beethoven mutation on mechanotransducer channel function in cochlear hair cells. ACTA ACUST UNITED AC 2016; 146:233-43. [PMID: 26324676 PMCID: PMC4555472 DOI: 10.1085/jgp.201511458] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Analyses of the Tmc1 Beethoven mouse mutant indicate that hair cell mechanotransducer channel adaptation in mammals is mainly regulated by changes in intracellular Ca2+. Sound stimuli are converted into electrical signals via gating of mechano-electrical transducer (MT) channels in the hair cell stereociliary bundle. The molecular composition of the MT channel is still not fully established, although transmembrane channel–like protein isoform 1 (TMC1) may be one component. We found that in outer hair cells of Beethoven mice containing a M412K point mutation in TMC1, MT channels had a similar unitary conductance to that of wild-type channels but a reduced selectivity for Ca2+. The Ca2+-dependent adaptation that adjusts the operating range of the channel was also impaired in Beethoven mutants, with reduced shifts in the relationship between MT current and hair bundle displacement for adapting steps or after lowering extracellular Ca2+; these effects may be attributed to the channel’s reduced Ca2+ permeability. Moreover, the density of stereociliary CaATPase pumps for Ca2+ extrusion was decreased in the mutant. The results suggest that a major component of channel adaptation is regulated by changes in intracellular Ca2+. Consistent with this idea, the adaptive shift in the current–displacement relationship when hair bundles were bathed in endolymph-like Ca2+ saline was usually abolished by raising the intracellular Ca2+ concentration.
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Affiliation(s)
- Maryline Beurg
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706
| | - Adam C Goldring
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706
| | - Robert Fettiplace
- Department of Neuroscience, University of Wisconsin School of Medicine and Public Health, Madison, WI 53706
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36
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Bortolozzi M, Mammano F. PMCA2w/a Splice Variant: A Key Regulator of Hair Cell Mechano-transduction Machinery. REGULATION OF CA2+-ATPASES,V-ATPASES AND F-ATPASES 2016:27-45. [DOI: 10.1007/978-3-319-24780-9_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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37
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Multifaceted plasma membrane Ca(2+) pumps: From structure to intracellular Ca(2+) handling and cancer. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1863:1351-63. [PMID: 26707182 DOI: 10.1016/j.bbamcr.2015.12.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 11/25/2015] [Accepted: 12/12/2015] [Indexed: 11/20/2022]
Abstract
Plasma membrane Ca(2+) ATPases (PMCAs) are intimately involved in the control of intracellular Ca(2+) concentration. They reduce Ca(2+) in the cytosol not only by direct ejection, but also by controlling the formation of inositol-1,4,5-trisphosphate and decreasing Ca(2+) release from the endoplasmic reticulum Ca(2+) pool. In mammals four genes (PMCA1-4) are expressed, and alternative RNA splicing generates more than twenty variants. The variants differ in their regulatory characteristics. They localize into highly specialized membrane compartments and respond to the incoming Ca(2+) with distinct temporal resolution. The expression pattern of variants depends on cell type; a change in this pattern can result in perturbed Ca(2+) homeostasis and thus altered cell function. Indeed, PMCAs undergo remarkable changes in their expression pattern during tumorigenesis that might significantly contribute to the unbalanced Ca(2+) homeostasis of cancer cells. This article is part of a Special Issue entitled: Calcium and Cell Fate. Guest Editors: Jacques Haiech, Claus Heizmann, Joachim Krebs, Thierry Capiod and Olivier Mignen.
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Calì T, Lopreiato R, Shimony J, Vineyard M, Frizzarin M, Zanni G, Zanotti G, Brini M, Shinawi M, Carafoli E. A Novel Mutation in Isoform 3 of the Plasma Membrane Ca2+ Pump Impairs Cellular Ca2+ Homeostasis in a Patient with Cerebellar Ataxia and Laminin Subunit 1α Mutations. J Biol Chem 2015; 290:16132-41. [PMID: 25953895 DOI: 10.1074/jbc.m115.656496] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Indexed: 11/06/2022] Open
Abstract
The particular importance of Ca(2+) signaling to neurons demands its precise regulation within their cytoplasm. Isoform 3 of the plasma membrane Ca(2+) ATPase (the PMCA3 pump), which is highly expressed in brain and cerebellum, plays an important role in the regulation of neuronal Ca(2+). A genetic defect of the PMCA3 pump has been described in one family with X-linked congenital cerebellar ataxia. Here we describe a novel mutation in the ATP2B3 gene in a patient with global developmental delay, generalized hypotonia and cerebellar ataxia. The mutation (a R482H replacement) impairs the Ca(2+) ejection function of the pump. It reduces the ability of the pump expressed in model cells to control Ca(2+) transients generated by cell stimulation and impairs its Ca(2+) extrusion function under conditions of low resting cytosolic Ca(2+) as well. In silico analysis of the structural effect of the mutation suggests a reduced stabilization of the portion of the pump surrounding the mutated residue in the Ca(2+)-bound state. The patient also carries two missense mutations in LAMA1, encoding laminin subunit 1α. On the basis of the family pedigree of the patient, the presence of both PMCA3 and laminin subunit 1α mutations appears to be necessary for the development of the disease. Considering the observed defect in cellular Ca(2+) homeostasis and the previous finding that PMCAs act as digenic modulators in Ca(2+)-linked pathologies, the PMCA3 dysfunction along with LAMA1 mutations could act synergistically to cause the neurological phenotype.
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Affiliation(s)
| | | | | | - Marisa Vineyard
- Department of Pediatrics, Division of Genetics and Genomic Medicine, Washington University School of Medicine, St. Louis, Missouri 63110-1093
| | | | - Ginevra Zanni
- Unit of Molecular Medicine for Neuromuscular and Neurodegenerative Disorders, Department of Neurosciences, Bambino Gesù Children's Hospital, Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS), 00165 Rome, Italy, and
| | | | | | - Marwan Shinawi
- Department of Pediatrics, Division of Genetics and Genomic Medicine, Washington University School of Medicine, St. Louis, Missouri 63110-1093,
| | - Ernesto Carafoli
- Venetian Institute of Molecular Medicine (VIMM), 35131 Padova, Italy
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Azaiez H, Decker AR, Booth KT, Simpson AC, Shearer AE, Huygen PLM, Bu F, Hildebrand MS, Ranum PT, Shibata SB, Turner A, Zhang Y, Kimberling WJ, Cornell RA, Smith RJH. HOMER2, a stereociliary scaffolding protein, is essential for normal hearing in humans and mice. PLoS Genet 2015; 11:e1005137. [PMID: 25816005 PMCID: PMC4376867 DOI: 10.1371/journal.pgen.1005137] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 03/10/2015] [Indexed: 12/29/2022] Open
Abstract
Hereditary hearing loss is a clinically and genetically heterogeneous disorder. More than 80 genes have been implicated to date, and with the advent of targeted genomic enrichment and massively parallel sequencing (TGE+MPS) the rate of novel deafness-gene identification has accelerated. Here we report a family segregating post-lingual progressive autosomal dominant non-syndromic hearing loss (ADNSHL). After first excluding plausible variants in known deafness-causing genes using TGE+MPS, we completed whole exome sequencing in three hearing-impaired family members. Only a single variant, p.Arg185Pro in HOMER2, segregated with the hearing-loss phenotype in the extended family. This amino acid change alters a highly conserved residue in the coiled-coil domain of HOMER2 that is essential for protein multimerization and the HOMER2-CDC42 interaction. As a scaffolding protein, HOMER2 is involved in intracellular calcium homeostasis and cytoskeletal organization. Consistent with this function, we found robust expression in stereocilia of hair cells in the murine inner ear and observed that over-expression of mutant p.Pro185 HOMER2 mRNA causes anatomical changes of the inner ear and neuromasts in zebrafish embryos. Furthermore, mouse mutants homozygous for the targeted deletion of Homer2 present with early-onset rapidly progressive hearing loss. These data provide compelling evidence that HOMER2 is required for normal hearing and that its sequence alteration in humans leads to ADNSHL through a dominant-negative mode of action. The most frequent sensory disorder worldwide is hearing impairment. It impacts over 5% of the world population (360 million persons), and is characterized by extreme genetic heterogeneity. Over 80 genes have been implicated in isolated (also referred to as ‘non-syndromic’) hearing loss, and abundant evidence supports the existence of many more ‘deafness-causing’ genes. In this study, we used a sequential screening strategy to first exclude causal mutations in known deafness-causing genes in a family segregating autosomal dominant non-syndromic hearing loss. We next turned to whole exome sequencing and identified a single variant—p.Arg185Pro in HOMER2—that segregated with the phenotype in the extended family. To validate the pathological significance of this mutation, we studied two animal models. In zebrafish, we overexpressed mutant HOMER2 and observed inner ear defects; and in mice we documented robust expression in stereocilia of cochlear hair cells and demonstrated that its absence causes early-onset progressive deafness. Our data offer novel insights into gene pathways essential for normal auditory function and the maintenance of cochlear hair cells.
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Affiliation(s)
- Hela Azaiez
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology University of Iowa, Iowa City, Iowa, United States of America
| | - Amanda R. Decker
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Kevin T. Booth
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology University of Iowa, Iowa City, Iowa, United States of America
| | - Allen C. Simpson
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology University of Iowa, Iowa City, Iowa, United States of America
| | - A. Eliot Shearer
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology University of Iowa, Iowa City, Iowa, United States of America
| | - Patrick L. M. Huygen
- Department of Otorhinolaryngology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands
| | - Fengxiao Bu
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology University of Iowa, Iowa City, Iowa, United States of America
| | - Michael S. Hildebrand
- Austin Health, Department of Medicine, University of Melbourne, Melbourne, Australia
| | - Paul T. Ranum
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology University of Iowa, Iowa City, Iowa, United States of America
| | - Seiji B. Shibata
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology University of Iowa, Iowa City, Iowa, United States of America
| | - Ann Turner
- Self-employed physician, Menlo Park, California, United States of America
| | - Yuzhou Zhang
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology University of Iowa, Iowa City, Iowa, United States of America
| | - William J. Kimberling
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology University of Iowa, Iowa City, Iowa, United States of America
| | - Robert A. Cornell
- Department of Anatomy and Cell Biology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, United States of America
| | - Richard J. H. Smith
- Molecular Otolaryngology and Renal Research Laboratories, Department of Otolaryngology University of Iowa, Iowa City, Iowa, United States of America
- Interdepartmental PhD Program in Genetics, University of Iowa, Iowa City, Iowa, United States of America
- * E-mail:
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Krebs J. The plethora of PMCA isoforms: Alternative splicing and differential expression. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:2018-24. [PMID: 25535949 DOI: 10.1016/j.bbamcr.2014.12.020] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Revised: 12/08/2014] [Accepted: 12/15/2014] [Indexed: 10/24/2022]
Abstract
In this review the four different genes of the mammalian plasma membrane calcium ATPase (PMCA) and their spliced isoforms are discussed with respect to their tissue distribution, their differences during development and their importance for regulating Ca²⁺ homeostasis under different conditions. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.
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Affiliation(s)
- Joachim Krebs
- NMR-Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.
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Lundberg YW, Xu Y, Thiessen KD, Kramer KL. Mechanisms of otoconia and otolith development. Dev Dyn 2014; 244:239-53. [PMID: 25255879 DOI: 10.1002/dvdy.24195] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 08/25/2014] [Accepted: 08/26/2014] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Otoconia are bio-crystals that couple mechanic forces to the sensory hair cells in the utricle and saccule, a process essential for us to sense linear acceleration and gravity for the purpose of maintaining bodily balance. In fish, structurally similar bio-crystals called otoliths mediate both balance and hearing. Otoconia abnormalities are common and can cause vertigo and imbalance in humans. However, the molecular etiology of these illnesses is unknown, as investigators have only begun to identify genes important for otoconia formation in recent years. RESULTS To date, in-depth studies of selected mouse otoconial proteins have been performed, and about 75 zebrafish genes have been identified to be important for otolith development. CONCLUSIONS This review will summarize recent findings as well as compare otoconia and otolith development. It will provide an updated brief review of otoconial proteins along with an overview of the cells and cellular processes involved. While continued efforts are needed to thoroughly understand the molecular mechanisms underlying otoconia and otolith development, it is clear that the process involves a series of temporally and spatially specific events that are tightly coordinated by numerous proteins. Such knowledge will serve as the foundation to uncover the molecular causes of human otoconia-related disorders.
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Affiliation(s)
- Yunxia Wang Lundberg
- Vestibular Genetics Laboratory, Boys Town National Research Hospital, Omaha, Nebraska
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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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43
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Watson CJ, Lies SM, Minich RR, Tempel BL. Changes in cochlear PMCA2 expression correlate with the maturation of auditory sensitivity. J Assoc Res Otolaryngol 2014; 15:543-54. [PMID: 24799196 PMCID: PMC4141437 DOI: 10.1007/s10162-014-0454-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 03/26/2014] [Indexed: 10/25/2022] Open
Abstract
The plasma membrane Ca(2+) ATPase 2 (PMCA2) is necessary for auditory transduction and serves as the primary Ca(2+) extrusion mechanism in auditory stereocilia bundles. To date, studies examining PMCA2 in auditory function using mutant mice have focused on the phenotype of late adolescent and adult mice. Here, we focus on the changes of PMCA2 in the maturation of auditory sensitivity by comparing auditory responses to RNA and protein expression levels in haploinsufficient PMCA2 and wild-type mice from P16 into adulthood. Auditory sensitivity in wild-type mice improves between P16 and 3 weeks of age, when it becomes stable through adolescence. In haploinsufficient mice, there are frequency-dependent loss of sensitivity and subsequent recovery of thresholds between P16 and adulthood. RNA analysis demonstrates that α-Atp2b2 transcript levels increase in both wild-type and heterozygous cochleae between P16 and 5 weeks. The increases reported for the α-Atp2b2 transcript type during this stage in development support the requisite usage of this transcript for mature auditory transduction. PMCA2 expression also increases in wild-type cochleae between P16 and 5 weeks suggesting that this critical auditory protein may be involved in normal maturation of auditory sensitivity after the onset of hearing. We also characterize expression levels of two long noncoding RNA genes, Gm15082 (lnc82) and Gm15083 (lnc83), which are transcribed on the opposite strand in the 5' region of Atp2b2 and propose that the lnc83 transcript may be involved in regulating α-Atp2b2 expression.
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Affiliation(s)
- Claire J. Watson
- />Department of Otolaryngology—Head and Neck Surgery, University of Washington, Box 356515, Seattle, WA 98195 USA
- />Department of Pharmacology, University of Washington, Box 357280, Seattle, WA 98195 USA
- />The Virginia Merrill Bloedel Hearing Research Center, University of Washington, Box 357923, Seattle, WA 98195 USA
| | - Sarah M. Lies
- />Department of Speech and Hearing Sciences, University of Washington, 1417 NE 42nd St., Seattle, WA 98105 USA
- />The Virginia Merrill Bloedel Hearing Research Center, University of Washington, Box 357923, Seattle, WA 98195 USA
| | - Rebecca R. Minich
- />Department of Pharmacology, University of Washington, Box 357280, Seattle, WA 98195 USA
- />The Virginia Merrill Bloedel Hearing Research Center, University of Washington, Box 357923, Seattle, WA 98195 USA
| | - Bruce L Tempel
- />Department of Otolaryngology—Head and Neck Surgery, University of Washington, Box 356515, Seattle, WA 98195 USA
- />Department of Pharmacology, University of Washington, Box 357280, Seattle, WA 98195 USA
- />The Virginia Merrill Bloedel Hearing Research Center, University of Washington, Box 357923, Seattle, WA 98195 USA
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Bullen A, Taylor RR, Kachar B, Moores C, Fleck RA, Forge A. Inner ear tissue preservation by rapid freezing: improving fixation by high-pressure freezing and hybrid methods. Hear Res 2014; 315:49-60. [PMID: 25016142 PMCID: PMC4152001 DOI: 10.1016/j.heares.2014.06.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 06/09/2014] [Accepted: 06/24/2014] [Indexed: 11/29/2022]
Abstract
In the preservation of tissues in as ‘close to life’ state as possible, rapid freeze fixation has many benefits over conventional chemical fixation. One technique by which rapid freeze-fixation can be achieved, high pressure freezing (HPF), has been shown to enable ice crystal artefact-free freezing and tissue preservation to greater depths (more than 40 μm) than other quick-freezing methods. Despite increasingly becoming routine in electron microscopy, the use of HPF for the fixation of inner ear tissue has been limited. Assessment of the quality of preservation showed routine HPF techniques were suitable for preparation of inner ear tissues in a variety of species. Good preservation throughout the depth of sensory epithelia was achievable. Comparison to chemically fixed tissue indicated that fresh frozen preparations exhibited overall superior structural preservation of cells. However, HPF fixation caused characteristic artefacts in stereocilia that suggested poor quality freezing of the actin bundles. The hybrid technique of pre-fixation and high pressure freezing was shown to produce cellular preservation throughout the tissue, similar to that seen in HPF alone. Pre-fixation HPF produced consistent high quality preservation of stereociliary actin bundles. Optimising the preparation of samples with minimal artefact formation allows analysis of the links between ultrastructure and function in inner ear tissues. Routine high pressure freezing can preserve large depths of inner ear tissue. Stereocilial actin preserved by rapid freezing exhibits characteristic artefacts. Hybrid methods of fixation improved structural preservation of stereocilial actin. Improved fixation will reduce artefacts in ultrastructural studies of the inner ear.
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Affiliation(s)
- A Bullen
- Centre for Auditory Research, UCL Ear Institute, London WC1X 8EE, UK.
| | - R R Taylor
- Centre for Auditory Research, UCL Ear Institute, London WC1X 8EE, UK
| | - B Kachar
- Laboratory of Cell Structure and Dynamics, NIDCD, National Institutes for Health, Bethesda, MD 20892-8027, USA
| | - C Moores
- Institute of Structural and Molecular Biology, Birkbeck College, London WC1E 7HX, UK
| | - R A Fleck
- National Institute for Biological Standards and Control, Potters Bar EN6 3QG, UK
| | - A Forge
- Centre for Auditory Research, UCL Ear Institute, London WC1X 8EE, UK
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45
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Ex vivo visualization of the mouse otoconial layer compared with micro-computed tomography. Otol Neurotol 2014; 36:311-7. [PMID: 24892370 DOI: 10.1097/mao.0000000000000376] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
HYPOTHESIS Micro-computed tomography (micro-CT) is useful for assessing the 3-dimensional (3D) morphology and age-related changes of the otoconial layer. BACKGROUND Wriggle mouse Sagami (WMS) is a mutant of the plasma membrane Ca2+ ATPase type2 gene (Atp2b2) with deficits in the saccular otoconia. We examined the effectiveness of micro-CT in evaluating the otoconial layer of WMS and C57BL/6J mice. METHODS Otic capsules of C57BL/6J mice at different fixation time were examined using micro-CT to evaluate the effects of the fixation time on the otoconial layer. Otic capsules of Atp2b2(wri/wri), Atp2b2(wri/+), and Atp2b2(+/+) mice at P14, P21, and the age of 3 months were used to analyze age-related changes in the otoconial layer. A series of cross-section and 3D reconstructed images of the otoconial layer were obtained. The micro-CT findings were compared with the otic capsule findings cleared in methyl salicylate using stereomicroscopy. RESULTS Micro-CT produced high-resolution images of the otoconial layer, thereby providing information regarding the spatial configuration and 3D curvature. There were no changes between the different fixation times. In the Atp2b2(wri/+) and Atp2b2(+/+) mice, the saccular and utricular otoconial layers were normal among all age groups. In the Atp2b2(wri/wri) mice, the saccular otoconial layer decreased on P14 and was absent on P21, whereas the utricular otoconial layer disappeared at 3 months of age. CONCLUSION We obtained precise information regarding the mouse otoconial layer with minimum artifacts. This method is expected to improve our understanding of the physiologic function and age-related changes in otolith organs.
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Carpinelli MR, Manning MG, Kile BT, Burt RA. Two ENU-induced alleles of Atp2b2 cause deafness in mice. PLoS One 2013; 8:e67479. [PMID: 23826306 PMCID: PMC3691321 DOI: 10.1371/journal.pone.0067479] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 05/14/2013] [Indexed: 12/12/2022] Open
Abstract
Over 120 loci are known to cause inherited hearing loss in humans. The deafness gene has been identified for only half of these loci. With the aim of identifying some of the remaining deafness genes, we performed an ethylnitrosourea mutagenesis screen for deaf mice. We isolated two mutants with semi-dominant hearing loss, Deaf11 and Deaf13. Both contained causative mutations in Atp2b2, which encodes the plasma membrane calcium ATPase 2. The Atp2b2Deaf11 mutation leads to a p. I1023S substitution in the tenth transmembrane domain. The Atp2b2Deaf13 mutation leads to a p. R561S substitution in the catalytic core. Mice homozygous for these mutations display profound hearing loss. Heterozygotes display mild to moderate, progressive hearing loss.
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Affiliation(s)
- Marina R Carpinelli
- Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Victoria, Australia.
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Watson CJ, Tempel BL. A new Atp2b2 deafwaddler allele, dfw(i5), interacts strongly with Cdh23 and other auditory modifiers. Hear Res 2013; 304:41-8. [PMID: 23792079 DOI: 10.1016/j.heares.2013.06.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Revised: 05/22/2013] [Accepted: 06/08/2013] [Indexed: 12/24/2022]
Abstract
Tight regulation of calcium (Ca2+) concentrations in the stereocilia bundles of auditory hair cells of the inner ear is critical to normal auditory transduction. The plasma membrane Ca2+ ATPase 2 (PMCA2), encoded by the Atp2b2 gene, is the primary mechanism for clearance of Ca2+ from auditory stereocilia, keeping intracellular levels low, and also contributes to maintaining adequate levels of extracellular Ca2+ in the endolymph. This study characterizes a novel null Atp2b2 allele, dfw(i5), by examining cochlear anatomy, vestibular function and auditory physiology in mutant mice. Loss of auditory function in PMCA2 mutants can be attributed to dysregulation of intracellular Ca2+ inside the stereocilia bundles. However, extracellular Ca2+ ions surrounding the stereocilia are also required for rigidity of cadherin 23, a component of the stereocilia tip-link encoded by the Cdh23 gene. This study further resolves the interaction between Atp2b2 and Cdh23 in a gene dosage and frequency-dependent manner, and finds that low frequencies are significantly affected by the interaction. In +/dfw(i5) mice, one mutant copy of Cdh23 is sufficient to cause broad frequency hearing impairment. Additionally, we report another modifying interaction with Atp2b2 on auditory sensitivity, possibly caused by an unidentified hearing loss gene in mice.
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Affiliation(s)
- Claire J Watson
- The Virginia Merrill Bloedel Hearing Research Center, Department of Pharmacology, University of Washington, Box 357280, Seattle, WA 98195, USA
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Brini M, Calì T, Ottolini D, Carafoli E. The plasma membrane calcium pump in health and disease. FEBS J 2013; 280:5385-97. [PMID: 23413890 DOI: 10.1111/febs.12193] [Citation(s) in RCA: 121] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 02/04/2013] [Accepted: 02/13/2013] [Indexed: 12/12/2022]
Abstract
The Ca(2+) ATPases of the plasma membrane (PMCA pumps) export Ca(2+) from all eukaryotic cells. In mammals they are the products of four separate genes. PMCA types 1 and 4 are distributed ubiquitously; PMCA types 2 and 3 are restricted to some tissues, the most important being the nervous system. Alternative splicing at two sites greatly increases the number of pump isoforms. The two ubiquitous isoforms are no longer considered as only housekeeping pumps as they also perform tissue-specific functions. The PMCAs are classical P-type pumps, their reaction cycle repeating that of all other pumps of the family. Their 3D structure has not been solved, but molecular modeling on SERCA pump templates shows the essential structural pattern of the latter. PMCAs are regulated by calmodulin, which interacts with high affinity with their cytosolic C-terminal tail. A second calmodulin-binding domain with lower affinity is present in some splicing variants of the pump. The PMCAs are essential to the regulation of cellular Ca(2+), but the all-important Ca(2+) signal is ambivalent: defects in its control generate various pathologies, the most thoroughly studied being those of genetic origin. Genetic defects of PMCA function produce disease phenotypes: the best characterized is a form of deafness in mice and in humans linked to PMCA2 mutations. A cerebellar X-linked human ataxia has recently been found to be caused by a mutation in the calmodulin-binding domain of PMCA3.
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Affiliation(s)
- Marisa Brini
- Department of Comparative Biomedicine and Food Science, University of Padova, Italy
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Wong ACY, Birnbaumer L, Housley GD. Canonical transient receptor potential channel subtype 3-mediated hair cell Ca2+entry regulates sound transduction and auditory neurotransmission. Eur J Neurosci 2013; 37:1478-86. [DOI: 10.1111/ejn.12158] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Revised: 01/09/2013] [Accepted: 01/16/2013] [Indexed: 12/20/2022]
Affiliation(s)
- Ann Chi Yan Wong
- Translational Neuroscience Facility and Department of Physiology; School of Medical Sciences; University of New South Wales; Sydney; 2052; NSW; Australia
| | - Lutz Birnbaumer
- Laboratory of Neurobiology, National Institute of Environmental Health Sciences, NIH, Building 101, Room F180, 111 TW Alexander Dr; Research Triangle Park; NC 27709; USA
| | - Gary D. Housley
- Translational Neuroscience Facility and Department of Physiology; School of Medical Sciences; University of New South Wales; Sydney; 2052; NSW; Australia
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50
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Tan X, Beurg M, Hackney C, Mahendrasingam S, Fettiplace R. Electrical tuning and transduction in short hair cells of the chicken auditory papilla. J Neurophysiol 2013; 109:2007-20. [PMID: 23365177 DOI: 10.1152/jn.01028.2012] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The avian auditory papilla contains two classes of sensory receptor, tall hair cells (THCs) and short hair cells (SHCs), the latter analogous to mammalian outer hair cells with large efferent but sparse afferent innervation. Little is known about the tuning, transduction, or electrical properties of SHCs. To address this problem, we made patch-clamp recordings from hair cells in an isolated chicken basilar papilla preparation at 33°C. We found that SHCs are electrically tuned by a Ca(2+)-activated K(+) current, their resonant frequency varying along the papilla in tandem with that of the THCs, which also exhibit electrical tuning. The tonotopic map for THCs was similar to maps previously described from auditory nerve fiber measurements. SHCs also possess an A-type K(+) current, but electrical tuning was observed only at resting potentials positive to -45 mV, where the A current is inactivated. We predict that the resting potential in vivo is approximately -40 mV, depolarized by a standing inward current through mechanotransducer (MT) channels having a resting open probability of ∼0.26. The resting open probability stems from a low endolymphatic Ca(2+) concentration (0.24 mM) and a high intracellular mobile Ca(2+) buffer concentration, estimated from perforated-patch recordings as equivalent to 0.5 mM BAPTA. The high buffer concentration was confirmed by quantifying parvalbumin-3 and calbindin D-28K with calibrated postembedding immunogold labeling, demonstrating >1 mM calcium-binding sites. Both proteins displayed an apex-to-base gradient matching that in the MT current amplitude, which increased exponentially along the papilla. Stereociliary bundles also labeled heavily with antibodies against the Ca(2+) pump isoform PMCA2a.
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Affiliation(s)
- Xiaodong Tan
- Department of Neuroscience, University of Wisconsin Medical School, Madison, Wisconsin, USA
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