1
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Yang Y, Murtha K, Climer LK, Ceriani F, Thompson P, Hornak AJ, Marcotti W, Simmons DD. Oncomodulin regulates spontaneous calcium signalling and maturation of afferent innervation in cochlear outer hair cells. J Physiol 2023; 601:4291-4308. [PMID: 37642186 PMCID: PMC10621907 DOI: 10.1113/jp284690] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 08/08/2023] [Indexed: 08/31/2023] Open
Abstract
Cochlear outer hair cells (OHCs) are responsible for the exquisite frequency selectivity and sensitivity of mammalian hearing. During development, the maturation of OHC afferent connectivity is refined by coordinated spontaneous Ca2+ activity in both sensory and non-sensory cells. Calcium signalling in neonatal OHCs can be modulated by oncomodulin (OCM, β-parvalbumin), an EF-hand calcium-binding protein. Here, we investigated whether OCM regulates OHC spontaneous Ca2+ activity and afferent connectivity during development. Using a genetically encoded Ca2+ sensor (GCaMP6s) expressed in OHCs in wild-type (Ocm+/+ ) and Ocm knockout (Ocm-/- ) littermates, we found increased spontaneous Ca2+ activity and upregulation of purinergic receptors in OHCs from Ocm-/- cochlea immediately following birth. The afferent synaptic maturation of OHCs was delayed in the absence of OCM, leading to an increased number of ribbon synapses and afferent fibres on Ocm-/- OHCs before hearing onset. We propose that OCM regulates the spontaneous Ca2+ signalling in the developing cochlea and the maturation of OHC afferent innervation. KEY POINTS: Cochlear outer hair cells (OHCs) exhibit spontaneous Ca2+ activity during a narrow period of neonatal development. OHC afferent maturation and connectivity requires spontaneous Ca2+ activity. Oncomodulin (OCM, β-parvalbumin), an EF-hand calcium-binding protein, modulates Ca2+ signals in immature OHCs. Using transgenic mice that endogenously expressed a Ca2+ sensor, GCaMP6s, we found increased spontaneous Ca2+ activity and upregulated purinergic receptors in Ocm-/- OHCs. The maturation of afferent synapses in Ocm-/- OHCs was also delayed, leading to an upregulation of ribbon synapses and afferent fibres in Ocm-/- OHCs before hearing onset. We propose that OCM plays an important role in modulating Ca2+ activity, expression of Ca2+ channels and afferent innervation in developing OHCs.
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Affiliation(s)
- Yang Yang
- Department of Biology, Baylor University, 101 Bagby Ave, Waco, TX
| | - Kaitlin Murtha
- Department of Biology, Baylor University, 101 Bagby Ave, Waco, TX
| | - Leslie K. Climer
- Department of Biology, Baylor University, 101 Bagby Ave, Waco, TX
| | - Federico Ceriani
- School of Biosciences, University of Sheffield, S10 2TN Sheffield, United Kingdom
| | - Pierce Thompson
- Department of Biology, Baylor University, 101 Bagby Ave, Waco, TX
| | - Aubrey J. Hornak
- Department of Biology, Baylor University, 101 Bagby Ave, Waco, TX
| | - Walter Marcotti
- School of Biosciences, University of Sheffield, S10 2TN Sheffield, United Kingdom
- Sheffield Neuroscience Institute, University of Sheffield, Sheffield, S10 2TN, UK
| | - Dwayne D. Simmons
- Department of Biology, Baylor University, 101 Bagby Ave, Waco, TX
- School of Biosciences, University of Sheffield, S10 2TN Sheffield, United Kingdom
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA
- Department of Psychology and Neuroscience, Baylor University, Waco, TX
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2
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Ritzer A, Roeschl T, Nay S, Rudakova E, Volk T. Rapid Pacing Decreases L-type Ca 2+ Current and Alters Cacna1c Isogene Expression in Primary Cultured Rat Left Ventricular Myocytes. J Membr Biol 2023; 256:257-269. [PMID: 36995425 DOI: 10.1007/s00232-023-00284-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 03/14/2023] [Indexed: 03/31/2023]
Abstract
The L-type calcium current (ICaL) is the first step in cardiac excitation-contraction-coupling and plays an important role in regulating contractility, but also in electrical and mechanical remodeling. Primary culture of cardiomyocytes, a widely used tool in cardiac ion channel research, is associated with substantial morphological, functional and electrical changes some of which may be prevented by electrical pacing. We therefore investigated ICaL directly after cell isolation and after 24 h of primary culture with and without regular pacing at 1 and 3 Hz in rat left ventricular myocytes. Moreover, we analyzed total mRNA expression of the pore forming subunit of the L-type Ca2+ channel (cacna1c) as well as the expression of splice variants of its exon 1 that contribute to specificity of ICaL in different tissue such as cardiac myocytes or smooth muscle. 24 h incubation without pacing decreased ICaL density by ~ 10% only. Consistent with this decrease we observed a decrease in the expression of total cacna1c and of exon 1a, the dominant variant of cardiomyocytes, while expression of exon 1b and 1c increased. Pacing for 24 h at 1 and 3 Hz led to a substantial decrease in ICaL density by 30%, mildly slowed ICaL inactivation and shifted steady-state inactivation to more negative potentials. Total cacna1c mRNA expression was substantially decreased by pacing, as was the expression of exon 1b and 1c. Taken together, electrical silence introduces fewer alterations in ICaL density and cacna1c mRNA expression than pacing for 24 h and should therefore be the preferred approach for primary culture of cardiomyocytes.
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Affiliation(s)
- Anne Ritzer
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany
| | - Tobias Roeschl
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany
| | - Sandra Nay
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany
| | - Elena Rudakova
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany
| | - Tilmann Volk
- Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstraße 6, 91054, Erlangen, Germany.
- Muscle Research Center Erlangen (MURCE), Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054, Erlangen, Germany.
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3
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McKerr N, Mohd-Sarip A, Dorrian H, Breen C, A James J, McQuaid S, Mills IG, McCloskey KD. CACNA1D overexpression and voltage-gated calcium channels in prostate cancer during androgen deprivation. Sci Rep 2023; 13:4683. [PMID: 36949059 PMCID: PMC10033880 DOI: 10.1038/s41598-023-28693-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 01/23/2023] [Indexed: 03/24/2023] Open
Abstract
Prostate cancer is often treated by perturbing androgen receptor signalling. CACNA1D, encoding CaV1.3 ion channels is upregulated in prostate cancer. Here we show how hormone therapy affects CACNA1D expression and CaV1.3 function. Human prostate cells (LNCaP, VCaP, C4-2B, normal RWPE-1) and a tissue microarray were used. Cells were treated with anti-androgen drug, Enzalutamide (ENZ) or androgen-removal from media, mimicking androgen-deprivation therapy (ADT). Proliferation assays, qPCR, Western blot, immunofluorescence, Ca2+-imaging and patch-clamp electrophysiology were performed. Nifedipine, Bay K 8644 (CaV1.3 inhibitor, activator), mibefradil, Ni2+ (CaV3.2 inhibitors) and high K+ depolarising solution were employed. CACNA1D and CaV1.3 protein are overexpressed in prostate tumours and CACNA1D was overexpressed in androgen-sensitive prostate cancer cells. In LNCaP, ADT or ENZ increased CACNA1D time-dependently whereas total protein showed little change. Untreated LNCaP were unresponsive to depolarising high K+/Bay K (to activate CaV1.3); moreover, currents were rarely detected. ADT or ENZ-treated LNCaP exhibited nifedipine-sensitive Ca2+-transients; ADT-treated LNCaP exhibited mibefradil-sensitive or, occasionally, nifedipine-sensitive inward currents. CACNA1D knockdown reduced the subpopulation of treated-LNCaP with CaV1.3 activity. VCaP displayed nifedipine-sensitive high K+/Bay K transients (responding subpopulation was increased by ENZ), and Ni2+-sensitive currents. Hormone therapy enables depolarization/Bay K-evoked Ca2+-transients and detection of CaV1.3 and CaV3.2 currents. Physiological and genomic CACNA1D/CaV1.3 mechanisms are likely active during hormone therapy-their modulation may offer therapeutic advantage.
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Affiliation(s)
- Niamh McKerr
- Patrick G Johnston Centre for Cancer Research, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, Northern Ireland, BT9 7AE, UK
| | - Adone Mohd-Sarip
- Patrick G Johnston Centre for Cancer Research, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, Northern Ireland, BT9 7AE, UK
| | - Hannah Dorrian
- Patrick G Johnston Centre for Cancer Research, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, Northern Ireland, BT9 7AE, UK
| | - Conor Breen
- Patrick G Johnston Centre for Cancer Research, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, Northern Ireland, BT9 7AE, UK
| | - Jacqueline A James
- Patrick G Johnston Centre for Cancer Research, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, Northern Ireland, BT9 7AE, UK
| | - Stephen McQuaid
- Patrick G Johnston Centre for Cancer Research, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, Northern Ireland, BT9 7AE, UK
| | - Ian G Mills
- Patrick G Johnston Centre for Cancer Research, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, Northern Ireland, BT9 7AE, UK
- Centre for Cancer Biomarkers (CCBIO), University of Bergen, Bergen, Norway
- Nuffield Department of Surgical Sciences, John Radcliffe Hospital, University of Oxford, Headley Way, OX3 9DU, UK
| | - Karen D McCloskey
- Patrick G Johnston Centre for Cancer Research, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, Northern Ireland, BT9 7AE, UK.
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4
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Yang Y, Murtha K, Climer LK, Ceriani F, Thompson P, Hornak AJ, Marcotti W, Simmons DD. Oncomodulin Regulates Spontaneous Calcium Signaling and Maturation of Afferent Innervation in Cochlear Outer Hair Cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.01.529895. [PMID: 36909575 PMCID: PMC10002690 DOI: 10.1101/2023.03.01.529895] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
Abstract
Cochlear outer hair cells (OHCs) are responsible for the exquisite frequency selectivity and sensitivity of mammalian hearing. During development, the maturation of OHC afferent connectivity is refined by coordinated spontaneous Ca 2+ activity in both sensory and non-sensory cells. Calcium signaling in neonatal OHCs can be modulated by Oncomodulin (OCM, β-parvalbumin), an EF-hand calcium-binding protein. Here, we investigated whether OCM regulates OHC spontaneous Ca 2+ activity and afferent connectivity during development. Using a genetically encoded Ca 2+ sensor (GCaMP6s) expressed in OHCs in wild-type (Ocm +/+ ) and Ocm knockout (Ocm -/- ) littermates, we found increased spontaneous Ca 2+ activity and upregulation of purinergic receptors in OHCs from GCaMP6s Ocm -/- cochlea immediately following birth. The afferent synaptic maturation of OHCs was delayed in the absence of OCM, leading to an increased number of ribbon synapses and afferent fibers on GCaMP6s Ocm -/- OHCs before hearing onset. We propose that OCM regulates the spontaneous Ca 2+ signaling in the developing cochlea and the maturation of OHC afferent innervation.
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5
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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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6
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Vega R, García-Garibay O, Soto E. Opioid receptor activation modulates the calcium current in the cochlear outer hair cells of the rat. Eur J Neurosci 2022; 56:3543-3552. [PMID: 35501117 DOI: 10.1111/ejn.15682] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 04/10/2022] [Accepted: 04/25/2022] [Indexed: 12/01/2022]
Abstract
Previous works showed that opioid peptides are produced by olivocochlear efferent neurons, while cochlear hair cells express opioid receptors. It has been proposed that opioids protect the auditory system from damage by intense stimulation, although their use for therapeutic or illicit purposes links to hearing impairment. Therefore, it is relevant to study the effect of opioids in the auditory system to define their functional expression and mechanism of action. This study investigated the modulation of the Ca2+ currents by opioid peptides in the rat outer hair cells (OHC) using the whole-cell patch-clamp technique. The influence of agonists of the three opioid receptor subtypes (μ, δ, and κ) was studied. The κ opioid receptor agonist U-50488 inhibits the Ca2+ currents in a partially reversible form. Coincidently, norbinaltorphimine (a κ receptor antagonist) blocked the U-50488 inhibitory effect on the Ca2+ current. The δ- and the μ opioid receptor agonists did not significantly affect the Ca2+ currents. These results indicate that the κ opioid receptor activation inhibits the Ca2+ current in OHC, modulating the intracellular Ca2+ concentration when OHCs depolarize. The modulation of the auditory function by opioids constitutes a relevant mechanism with a potential role in the physiopathology of auditory disturbances.
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Affiliation(s)
- Rosario Vega
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, México
| | | | - Enrique Soto
- Instituto de Fisiología, Benemérita Universidad Autónoma de Puebla, México
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7
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Manca M, Yen P, Spaiardi P, Russo G, Giunta R, Johnson SL, Marcotti W, Masetto S. Current Response in Ca V 1.3 -/- Mouse Vestibular and Cochlear Hair Cells. Front Neurosci 2021; 15:749483. [PMID: 34955713 PMCID: PMC8694397 DOI: 10.3389/fnins.2021.749483] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 11/01/2021] [Indexed: 11/24/2022] Open
Abstract
Signal transmission by sensory auditory and vestibular hair cells relies upon Ca2+-dependent exocytosis of glutamate. The Ca2+ current in mammalian inner ear hair cells is predominantly carried through CaV1.3 voltage-gated Ca2+ channels. Despite this, CaV1.3 deficient mice (CaV1.3–/–) are deaf but do not show any obvious vestibular phenotype. Here, we compared the Ca2+ current (ICa) in auditory and vestibular hair cells from wild-type and CaV1.3–/– mice, to assess whether differences in the size of the residual ICa could explain, at least in part, the two phenotypes. Using 5 mM extracellular Ca2+ and near-body temperature conditions, we investigated the cochlear primary sensory receptors inner hair cells (IHCs) and both type I and type II hair cells of the semicircular canals. We found that the residual ICa in both auditory and vestibular hair cells from CaV1.3–/– mice was less than 20% (12–19%, depending on the hair cell type and age investigated) compared to controls, indicating a comparable expression of CaV1.3 Ca2+ channels in both sensory organs. We also showed that, different from IHCs, type I and type II hair cells from CaV1.3–/– mice were able to acquire the adult-like K+ current profile in their basolateral membrane. Intercellular K+ accumulation was still present in CaV1.3–/– mice during IK,L activation, suggesting that the K+-based, non-exocytotic, afferent transmission is still functional in these mice. This non-vesicular mechanism might contribute to the apparent normal vestibular functions in CaV1.3–/– mice.
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Affiliation(s)
- Marco Manca
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy.,School of Biosciences, University of Sheffield, Sheffield, United Kingdom
| | - Piece Yen
- School of Biosciences, University of Sheffield, Sheffield, United Kingdom
| | - Paolo Spaiardi
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Giancarlo Russo
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Roberta Giunta
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Stuart L Johnson
- School of Biosciences, University of Sheffield, Sheffield, United Kingdom.,Sheffield Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom
| | - Walter Marcotti
- School of Biosciences, University of Sheffield, Sheffield, United Kingdom.,Sheffield Neuroscience Institute, University of Sheffield, Sheffield, United Kingdom
| | - Sergio Masetto
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
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8
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Functional Postnatal Maturation of the Medial Olivocochlear Efferent-Outer Hair Cell Synapse. J Neurosci 2020; 40:4842-4857. [PMID: 32430293 DOI: 10.1523/jneurosci.2409-19.2020] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 04/19/2020] [Accepted: 05/11/2020] [Indexed: 01/07/2023] Open
Abstract
The organ of Corti, the auditory mammalian sensory epithelium, contains two types of mechanotransducer cells, inner hair cells (IHCs) and outer hair cells (OHCs). IHCs are involved in conveying acoustic stimuli to the CNS, while OHCs are implicated in the fine tuning and amplification of sounds. OHCs are innervated by medial olivocochlear (MOC) cholinergic efferent fibers. The functional characteristics of the MOC-OHC synapse during maturation were assessed by electrophysiological and pharmacological methods in mouse organs of Corti at postnatal day 11 (P11)-P13, hearing onset in altricial rodents, and at P20-P22 when the OHCs are morphologically and functionally mature. Synaptic currents were recorded in whole-cell voltage-clamped OHCs while electrically stimulating the MOC fibers. A progressive increase in the number of functional MOC-OHC synapses, as well as in their strength and efficacy, was observed between P11-13 and P20-22. At hearing onset, the MOC-OHC synapse presented facilitation during MOC fibers high-frequency stimulation that disappeared at mature stages. In addition, important changes were found in the VGCC that are coupled to transmitter release. Ca2+ flowing in through L-type VGCCs contribute to trigger ACh release together with P/Q- and R-type VGCCs at P11-P13, but not at P20-P22. Interestingly, N-type VGCCs were found to be involved in this process at P20-P22, but not at hearing onset. Moreover, the degree of compartmentalization of calcium channels with respect to BK channels and presynaptic release components significantly increased from P11-P13 to P20-P22. These results suggest that the MOC-OHC synapse is immature at the onset of hearing.SIGNIFICANCE STATEMENT The functional expression of both VGCCs and BK channels, as well as their localization with respect to the presynaptic components involved in transmitter release, are key elements in determining synaptic efficacy. In this work, we show dynamic changes in the expression of VGCCs and Ca2+-dependent BK K+ channels coupled to ACh release at the MOC-OHC synapse and their shift in compartmentalization during postnatal maturation. These processes most likely set the short-term plasticity pattern and reliability of the MOC-OHC synapse on high-frequency activity.
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9
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Jeng JY, Ceriani F, Hendry A, Johnson SL, Yen P, Simmons DD, Kros CJ, Marcotti W. Hair cell maturation is differentially regulated along the tonotopic axis of the mammalian cochlea. J Physiol 2019; 598:151-170. [PMID: 31661723 PMCID: PMC6972525 DOI: 10.1113/jp279012] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 10/24/2019] [Indexed: 12/15/2022] Open
Abstract
Key points Outer hair cells (OHCs) enhance the sensitivity and the frequency tuning of the mammalian cochlea. Similar to the primary sensory receptor, the inner hair cells (IHCs), the mature functional characteristics of OHCs are acquired before hearing onset. We found that OHCs, like IHCs, fire spontaneous Ca2+‐induced action potentials (APs) during immature stages of development, which are driven by CaV1.3 Ca2+ channels. We also showed that the development of low‐ and high‐frequency hair cells is differentially regulated during pre‐hearing stages, with the former cells being more strongly dependent on experience‐independent Ca2+ action potential activity.
Abstract Sound amplification within the mammalian cochlea depends upon specialized hair cells, the outer hair cells (OHCs), which possess both sensory and motile capabilities. In various altricial rodents, OHCs become functionally competent from around postnatal day 7 (P7), before the primary sensory inner hair cells (IHCs), which become competent at about the onset of hearing (P12). The mechanisms responsible for the maturation of OHCs and their synaptic specialization remain poorly understood. We report that spontaneous Ca2+ activity in the immature cochlea, which is generated by CaV1.3 Ca2+ channels, differentially regulates the maturation of hair cells along the cochlea. Under near‐physiological recording conditions we found that, similar to IHCs, immature OHCs elicited spontaneous Ca2+ action potentials (APs), but only during the first few postnatal days. Genetic ablation of these APs in vivo, using CaV1.3−/− mice, prevented the normal developmental acquisition of mature‐like basolateral membrane currents in low‐frequency (apical) hair cells, such as IK,n (carried by KCNQ4 channels), ISK2 and IACh (α9α10nAChRs) in OHCs and IK,n and IK,f (BK channels) in IHCs. Electromotility and prestin expression in OHCs were normal in CaV1.3−/− mice. The maturation of high‐frequency (basal) hair cells was also affected in CaV1.3−/− mice, but to a much lesser extent than apical cells. However, a characteristic feature in CaV1.3−/− mice was the reduced hair cell size irrespective of their cochlear location. We conclude that the development of low‐ and high‐frequency hair cells is differentially regulated during development, with apical cells being more strongly dependent on experience‐independent Ca2+ APs. Outer hair cells (OHCs) enhance the sensitivity and the frequency tuning of the mammalian cochlea. Similar to the primary sensory receptor, the inner hair cells (IHCs), the mature functional characteristics of OHCs are acquired before hearing onset. We found that OHCs, like IHCs, fire spontaneous Ca2+‐induced action potentials (APs) during immature stages of development, which are driven by CaV1.3 Ca2+ channels. We also showed that the development of low‐ and high‐frequency hair cells is differentially regulated during pre‐hearing stages, with the former cells being more strongly dependent on experience‐independent Ca2+ action potential activity.
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Affiliation(s)
- Jing-Yi Jeng
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Federico Ceriani
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Aenea Hendry
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Stuart L Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | - Piece Yen
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
| | | | - Corné J Kros
- School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 9QG, UK
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, S10 2TN, UK
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10
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Ortner NJ, Pinggera A, Hofer NT, Siller A, Brandt N, Raffeiner A, Vilusic K, Lang I, Blum K, Obermair GJ, Stefan E, Engel J, Striessnig J. RBP2 stabilizes slow Cav1.3 Ca 2+ channel inactivation properties of cochlear inner hair cells. Pflugers Arch 2019; 472:3-25. [PMID: 31848688 PMCID: PMC6960213 DOI: 10.1007/s00424-019-02338-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 10/18/2019] [Accepted: 12/04/2019] [Indexed: 01/31/2023]
Abstract
Cav1.3 L-type Ca2+ channels (LTCCs) in cochlear inner hair cells (IHCs) are essential for hearing as they convert sound-induced graded receptor potentials into tonic postsynaptic glutamate release. To enable fast and indefatigable presynaptic Ca2+ signaling, IHC Cav1.3 channels exhibit a negative activation voltage range and uniquely slow inactivation kinetics. Interaction with CaM-like Ca2+-binding proteins inhibits Ca2+-dependent inactivation, while the mechanisms underlying slow voltage-dependent inactivation (VDI) are not completely understood. Here we studied if the complex formation of Cav1.3 LTCCs with the presynaptic active zone proteins RIM2α and RIM-binding protein 2 (RBP2) can stabilize slow VDI. We detected both RIM2α and RBP isoforms in adult mouse IHCs, where they co-localized with Cav1.3 and synaptic ribbons. Using whole-cell patch-clamp recordings (tsA-201 cells), we assessed their effect on the VDI of the C-terminal full-length Cav1.3 (Cav1.3L) and a short splice variant (Cav1.342A) that lacks the C-terminal RBP2 interaction site. When co-expressed with the auxiliary β3 subunit, RIM2α alone (Cav1.342A) or RIM2α/RBP2 (Cav1.3L) reduced Cav1.3 VDI to a similar extent as observed in IHCs. Membrane-anchored β2 variants (β2a, β2e) that inhibit inactivation on their own allowed no further modulation of inactivation kinetics by RIM2α/RBP2. Moreover, association with RIM2α and/or RBP2 consolidated the negative Cav1.3 voltage operating range by shifting the channel's activation threshold toward more hyperpolarized potentials. Taken together, the association with "slow" β subunits (β2a, β2e) or presynaptic scaffolding proteins such as RIM2α and RBP2 stabilizes physiological gating properties of IHC Cav1.3 LTCCs in a splice variant-dependent manner ensuring proper IHC function.
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Affiliation(s)
- Nadine J Ortner
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria.
| | - Alexandra Pinggera
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Nadja T Hofer
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Anita Siller
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Niels Brandt
- Department of Biophysics and CIPMM, Saarland University, Homburg, Germany
| | - Andrea Raffeiner
- Institute of Biochemistry, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Kristina Vilusic
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Isabelle Lang
- Department of Biophysics and CIPMM, Saarland University, Homburg, Germany
| | - Kerstin Blum
- Department of Biophysics and CIPMM, Saarland University, Homburg, Germany
| | - Gerald J Obermair
- Division of Physiology, Medical University Innsbruck, Innsbruck, Austria.,Division Physiology, Karl Landsteiner University of Health Sciences, Krems, Austria
| | - Eduard Stefan
- Institute of Biochemistry, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Jutta Engel
- Department of Biophysics and CIPMM, Saarland University, Homburg, Germany
| | - Jörg Striessnig
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria.
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11
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Johnson SL, Safieddine S, Mustapha M, Marcotti W. Hair Cell Afferent Synapses: Function and Dysfunction. Cold Spring Harb Perspect Med 2019; 9:a033175. [PMID: 30617058 PMCID: PMC6886459 DOI: 10.1101/cshperspect.a033175] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
To provide a meaningful representation of the auditory landscape, mammalian cochlear hair cells are optimized to detect sounds over an incredibly broad range of frequencies and intensities with unparalleled accuracy. This ability is largely conferred by specialized ribbon synapses that continuously transmit acoustic information with high fidelity and sub-millisecond precision to the afferent dendrites of the spiral ganglion neurons. To achieve this extraordinary task, ribbon synapses employ a unique combination of molecules and mechanisms that are tailored to sounds of different frequencies. Here we review the current understanding of how the hair cell's presynaptic machinery and its postsynaptic afferent connections are formed, how they mature, and how their function is adapted for an accurate perception of sound.
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Affiliation(s)
- Stuart L Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Saaid Safieddine
- UMRS 1120, Institut Pasteur, Paris, France
- Sorbonne Universités, UPMC Université Paris 06, Complexité du Vivant, Paris, France
| | - Mirna Mustapha
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, Stanford, California 94035
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, United Kingdom
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12
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Lundt A, Soós J, Seidel R, Henseler C, Müller R, Raj Ginde V, Imran Arshaad M, Ehninger D, Hescheler J, Sachinidis A, Broich K, Wormuth C, Papazoglou A, Weiergräber M. Functional implications of Ca v 2.3 R-type voltage-gated calcium channels in the murine auditory system - novel vistas from brainstem-evoked response audiometry. Eur J Neurosci 2019; 51:1583-1604. [PMID: 31603587 DOI: 10.1111/ejn.14591] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 09/11/2019] [Accepted: 10/08/2019] [Indexed: 12/25/2022]
Abstract
Voltage-gated Ca2+ channels (VGCCs) are considered to play a key role in auditory perception and information processing within the murine inner ear and brainstem. In the past, Cav 1.3 L-type VGCCs gathered most attention as their ablation causes congenital deafness. However, isolated patch-clamp investigation and localization studies repetitively suggested that Cav 2.3 R-type VGCCs are also expressed in the cochlea and further components of the ascending auditory tract, pointing to a potential functional role of Cav 2.3 in hearing physiology. Thus, we performed auditory profiling of Cav 2.3+/+ controls, heterozygous Cav 2.3+/- mice and Cav 2.3 null mutants (Cav 2.3-/- ) using brainstem-evoked response audiometry. Interestingly, click-evoked auditory brainstem responses (ABRs) revealed increased hearing thresholds in Cav 2.3+/- mice from both genders, whereas no alterations were observed in Cav 2.3-/- mice. Similar observations were made for tone burst-related ABRs in both genders. However, Cav 2.3 ablation seemed to prevent mutant mice from total hearing loss particularly in the higher frequency range (36-42 kHz). Amplitude growth function analysis revealed, i.a., significant reduction in ABR wave WI and WIII amplitude in mutant animals. In addition, alterations in WI -WIV interwave interval were observed in female Cav 2.3+/- mice whereas absolute latencies remained unchanged. In summary, our results demonstrate that Cav 2.3 VGCCs are mandatory for physiological auditory information processing in the ascending auditory tract.
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Affiliation(s)
- Andreas Lundt
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany
| | - Julien Soós
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany
| | - Robin Seidel
- Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany
| | - Christina Henseler
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany
| | - Ralf Müller
- Cognitive Neurophysiology, Department of Psychiatry and Psychotherapy and University Hospital Cologne, Faculty of Medicine, University of Cologne, Cologne, Germany
| | - Varun Raj Ginde
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany
| | - Muhammad Imran Arshaad
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany
| | - Dan Ehninger
- Molecular and Cellular Cognition, German Center for Neurodegenerative Diseases, (Deutsches Zentrum für Neurodegenerative Erkrankungen, DZNE), Bonn, Germany
| | - Jürgen Hescheler
- Institute of Neurophysiology, Faculty of Medicine, University of Cologne, Cologne, Germany
| | - Agapios Sachinidis
- Institute of Neurophysiology, Faculty of Medicine, University of Cologne, Cologne, Germany
| | - Karl Broich
- Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany
| | - Carola Wormuth
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany
| | - Anna Papazoglou
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany
| | - Marco Weiergräber
- Experimental Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (Bundesinstitut für Arzneimittel und Medizinprodukte, BfArM), Bonn, Germany
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13
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Lang I, Jung M, Niemeyer BA, Ruth P, Engel J. Expression of the LRRC52 γ subunit (γ2) may provide Ca 2+-independent activation of BK currents in mouse inner hair cells. FASEB J 2019; 33:11721-11734. [PMID: 31348683 DOI: 10.1096/fj.201900701rr] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Mammalian inner hair cells (IHCs) transduce sound into depolarization and transmitter release. Big conductance and voltage- and Ca2+-activated K+ (BK) channels are responsible for fast membrane repolarization and small time constants of mature IHCs. For unknown reasons, they activate at around -75 mV with a voltage of half-maximum activation (Vhalf) of -50 mV although being largely insensitive to Ca2+ influx. Ca2+-independent activation of BK channels was observed by others in heterologous expression systems if γ subunits leucine-rich repeat-containing protein (LRRC)26 (γ1) and LRRC52 (γ2) were coexpressed with the pore-forming BKα subunit, which shifted Vhalf by -140 and -100 mV, respectively. Using nested PCR, we consistently detected transcripts for LRRC52 but not for LRRC26 in IHCs of 3-wk-old mice. Confocal immunohistochemistry showed synchronous up-regulation of LRRC52 protein with BKα at the onset of hearing. Colocalization of LRRC52 protein and BKα at the IHC neck within ≤40 nm was specified using an in situ proximity ligation assay. Mice deficient for the voltage-gated Cav1.3 Ca2+ channel encoded by Cacna1d do not express BKα protein. LRRC52 protein was neither expressed in IHCs of BKα nor in IHCs of Cav1.3 knockout mice. Together, LRRC52 is a γ2 subunit of BK channel complexes and is a strong candidate for causing the Ca2+-independent activation of BK currents at negative membrane potentials in mouse IHCs.-Lang, I., Jung, M., Niemeyer, B. A., Ruth, P., Engel, J. Expression of the LRRC52 γ subunit (γ2) may provide Ca2+-independent activation of BK currents in mouse inner hair cells.
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Affiliation(s)
- Isabelle Lang
- Hearing Research, Department of Biophysics and Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Martin Jung
- Department of Biochemistry and Molecular Biology, Saarland University, Homburg, Germany
| | - Barbara A Niemeyer
- Molecular Biophysics, Department of Biophysics and Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Peter Ruth
- Institute of Pharmacy, Department of Pharmacology, Toxicology and Clinical Pharmacy, University of Tübingen, Tübingen, Germany
| | - Jutta Engel
- Hearing Research, Department of Biophysics and Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
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14
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Leitner MG, Oliver D. A choreography of intracellular Ca 2+ and extracellular ATP to refine auditory nociceptors before hearing. EMBO J 2019; 38:embj.2019101980. [PMID: 30975689 DOI: 10.15252/embj.2019101980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Michael G Leitner
- Division of Physiology, Department of Physiology and Medical Physics, Medical University of Innsbruck, Innsbruck, Austria
| | - Dominik Oliver
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps-University Marburg, Marburg, Germany.,Center for Mind, Brain and Behavior (CMBB), University of Marburg, Marburg, Germany.,DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodelling, GRK 2213, Philipps University, Marburg, Germany
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15
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Ceriani F, Hendry A, Jeng JY, Johnson SL, Stephani F, Olt J, Holley MC, Mammano F, Engel J, Kros CJ, Simmons DD, Marcotti W. Coordinated calcium signalling in cochlear sensory and non-sensory cells refines afferent innervation of outer hair cells. EMBO J 2019; 38:embj.201899839. [PMID: 30804003 PMCID: PMC6484507 DOI: 10.15252/embj.201899839] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 12/11/2018] [Accepted: 01/18/2019] [Indexed: 12/12/2022] Open
Abstract
Outer hair cells (OHCs) are highly specialized sensory cells conferring the fine‐tuning and high sensitivity of the mammalian cochlea to acoustic stimuli. Here, by genetically manipulating spontaneous Ca2+ signalling in mice in vivo, through a period of early postnatal development, we find that the refinement of OHC afferent innervation is regulated by complementary spontaneous Ca2+ signals originating in OHCs and non‐sensory cells. OHCs fire spontaneous Ca2+ action potentials during a narrow period of neonatal development. Simultaneously, waves of Ca2+ activity in the non‐sensory cells of the greater epithelial ridge cause, via ATP‐induced activation of P2X3 receptors, the increase and synchronization of the Ca2+ activity in nearby OHCs. This synchronization is required for the refinement of their immature afferent innervation. In the absence of connexin channels, Ca2+ waves are impaired, leading to a reduction in the number of ribbon synapses and afferent fibres on OHCs. We propose that the correct maturation of the afferent connectivity of OHCs requires experience‐independent Ca2+ signals from sensory and non‐sensory cells.
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Affiliation(s)
- Federico Ceriani
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Aenea Hendry
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Jing-Yi Jeng
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Stuart L Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Friederike Stephani
- Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Jennifer Olt
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Matthew C Holley
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
| | - Fabio Mammano
- Department of Physics and Astronomy "G. Galilei", University of Padua, Padova, Italy.,Department of Biomedical Sciences, Institute of Cell Biology and Neurobiology, Italian National Research Council, Monterotondo, Italy
| | - Jutta Engel
- Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
| | - Corné J Kros
- School of Life Sciences, University of Sussex, Brighton, UK
| | | | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, UK
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16
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Yang T, Hu N, Pangršič T, Green S, Hansen M, Lee A. Functions of CaBP1 and CaBP2 in the peripheral auditory system. Hear Res 2018; 364:48-58. [PMID: 29661613 DOI: 10.1016/j.heares.2018.04.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2018] [Revised: 03/13/2018] [Accepted: 04/02/2018] [Indexed: 12/29/2022]
Abstract
CaBPs are a family of Ca2+ binding proteins related to calmodulin. Two CaBP family members, CaBP1 and CaBP2, are highly expressed in the cochlea. Here, we investigated the significance of CaBP1 and CaBP2 for hearing in mice lacking expression of these proteins (CaBP1 KO and CaBP2 KO) using auditory brain responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). In CaBP1 KO mice, ABR wave I was larger in amplitude, and shorter in latency and faster in decay, suggestive of enhanced synchrony of auditory nerve fibers. This interpretation was supported by the greater excitability of CaBP1 KO than WT neurons in whole-cell patch clamp recordings of spiral ganglion neurons in culture, and normal presynaptic function of CaBP1 KO IHCs. DPOAEs and ABR thresholds were normal in 4-week old CaBP1 KO mice, but elevated ABR thresholds became evident at 32 kHz at 9 weeks, and at 8 and 16 kHz by 6 months of age. In contrast, CaBP2 KO mice exhibited significant ABR threshold elevations at 4 weeks of age that became more severe in the mid-frequency range by 9 weeks. Though normal at 4 weeks, DPOAEs in CaBP2 KO mice were significantly reduced in the mid-frequency range by 9 weeks. Our results reveal requirements for CaBP1 and CaBP2 in the peripheral auditory system and highlight the diverse modes by which CaBPs influence sensory processing.
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Affiliation(s)
- Tian Yang
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA; Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, IA 52242, USA
| | - Ning Hu
- Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Department of Biology, University of Iowa, Iowa City, IA 52242, USA
| | - Tina Pangršič
- Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
| | - Steven Green
- Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Department of Biology, University of Iowa, Iowa City, IA 52242, USA
| | - Marlan Hansen
- Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Department of Neurosurgery, University of Iowa, Iowa City, IA 52242, USA
| | - Amy Lee
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA; Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Department of Neurology, University of Iowa, Iowa City, IA 52242, USA.
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17
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Möhrle D, Reimann K, Wolter S, Wolters M, Varakina K, Mergia E, Eichert N, Geisler HS, Sandner P, Ruth P, Friebe A, Feil R, Zimmermann U, Koesling D, Knipper M, Rüttiger L. NO-Sensitive Guanylate Cyclase Isoforms NO-GC1 and NO-GC2 Contribute to Noise-Induced Inner Hair Cell Synaptopathy. Mol Pharmacol 2017; 92:375-388. [DOI: 10.1124/mol.117.108548] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 07/18/2017] [Indexed: 12/21/2022] Open
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18
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Vivas O, Moreno CM, Santana LF, Hille B. Proximal clustering between BK and Ca V1.3 channels promotes functional coupling and BK channel activation at low voltage. eLife 2017; 6. [PMID: 28665272 PMCID: PMC5503510 DOI: 10.7554/elife.28029] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Accepted: 06/28/2017] [Indexed: 01/09/2023] Open
Abstract
CaV-channel dependent activation of BK channels is critical for feedback control of both calcium influx and cell excitability. Here we addressed the functional and spatial interaction between BK and CaV1.3 channels, unique CaV1 channels that activate at low voltages. We found that when BK and CaV1.3 channels were co-expressed in the same cell, BK channels started activating near −50 mV, ~30 mV more negative than for activation of co-expressed BK and high-voltage activated CaV2.2 channels. In addition, single-molecule localization microscopy revealed striking clusters of CaV1.3 channels surrounding clusters of BK channels and forming a multi-channel complex both in a heterologous system and in rat hippocampal and sympathetic neurons. We propose that this spatial arrangement allows tight tracking between local BK channel activation and the gating of CaV1.3 channels at quite negative membrane potentials, facilitating the regulation of neuronal excitability at voltages close to the threshold to fire action potentials. DOI:http://dx.doi.org/10.7554/eLife.28029.001
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Affiliation(s)
- Oscar Vivas
- Department of Physiology and Biophysics, University of Washington, Seattle, United States.,Department of Physiology and Membrane Biology, University of California, Davis, Davis, United States
| | - Claudia M Moreno
- Department of Physiology and Biophysics, University of Washington, Seattle, United States.,Department of Physiology and Membrane Biology, University of California, Davis, Davis, United States
| | - Luis F Santana
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, United States
| | - Bertil Hille
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
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19
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Modrell MS, Lyne M, Carr AR, Zakon HH, Buckley D, Campbell AS, Davis MC, Micklem G, Baker CV. Insights into electrosensory organ development, physiology and evolution from a lateral line-enriched transcriptome. eLife 2017; 6. [PMID: 28346141 PMCID: PMC5429088 DOI: 10.7554/elife.24197] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 03/23/2017] [Indexed: 01/22/2023] Open
Abstract
The anamniote lateral line system, comprising mechanosensory neuromasts and electrosensory ampullary organs, is a useful model for investigating the developmental and evolutionary diversification of different organs and cell types. Zebrafish neuromast development is increasingly well understood, but neither zebrafish nor Xenopus is electroreceptive and our molecular understanding of ampullary organ development is rudimentary. We have used RNA-seq to generate a lateral line-enriched gene-set from late-larval paddlefish (Polyodon spathula). Validation of a subset reveals expression in developing ampullary organs of transcription factor genes critical for hair cell development, and genes essential for glutamate release at hair cell ribbon synapses, suggesting close developmental, physiological and evolutionary links between non-teleost electroreceptors and hair cells. We identify an ampullary organ-specific proneural transcription factor, and candidates for the voltage-sensing L-type Cav channel and rectifying Kv channel predicted from skate (cartilaginous fish) ampullary organ electrophysiology. Overall, our results illuminate ampullary organ development, physiology and evolution.
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Affiliation(s)
- Melinda S Modrell
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Mike Lyne
- Cambridge Systems Biology Centre, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Adrian R Carr
- Cambridge Systems Biology Centre, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Harold H Zakon
- Department of Neuroscience, The University of Texas at Austin, Austin, United States.,Department of Integrative Biology, The University of Texas at Austin, Austin, United States
| | - David Buckley
- Departmento de Biodiversidad y Biología Evolutiva, Museo Nacional de Ciencias Naturales-MNCN-CSIC, Madrid, Spain.,Department of Natural Sciences, Saint Louis University - Madrid Campus, Madrid, Spain
| | - Alexander S Campbell
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Marcus C Davis
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, United States
| | - Gos Micklem
- Cambridge Systems Biology Centre, University of Cambridge, Cambridge, United Kingdom.,Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Clare Vh Baker
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
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20
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Different Ca V1.3 Channel Isoforms Control Distinct Components of the Synaptic Vesicle Cycle in Auditory Inner Hair Cells. J Neurosci 2017; 37:2960-2975. [PMID: 28193694 DOI: 10.1523/jneurosci.2374-16.2017] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 01/27/2017] [Accepted: 02/01/2017] [Indexed: 12/16/2022] Open
Abstract
The mechanisms orchestrating transient and sustained exocytosis in auditory inner hair cells (IHCs) remain largely unknown. These exocytotic responses are believed to mobilize sequentially a readily releasable pool of vesicles (RRP) underneath the synaptic ribbons and a slowly releasable pool of vesicles (SRP) at farther distance from them. They are both governed by Cav1.3 channels and require otoferlin as Ca2+ sensor, but whether they use the same Cav1.3 isoforms is still unknown. Using whole-cell patch-clamp recordings in posthearing mice, we show that only a proportion (∼25%) of the total Ca2+ current in IHCs displaying fast inactivation and resistance to 20 μm nifedipine, a l-type Ca2+ channel blocker, is sufficient to trigger RRP but not SRP exocytosis. This Ca2+ current is likely conducted by short C-terminal isoforms of Cav1.3 channels, notably Cav1.342A and Cav1.343S, because their mRNA is highly expressed in wild-type IHCs but poorly expressed in Otof-/- IHCs, the latter having Ca2+ currents with considerably reduced inactivation. Nifedipine-resistant RRP exocytosis was poorly affected by 5 mm intracellular EGTA, suggesting that the Cav1.3 short isoforms are closely associated with the release site at the synaptic ribbons. Conversely, our results suggest that Cav1.3 long isoforms, which carry ∼75% of the total IHC Ca2+ current with slow inactivation and confer high sensitivity to nifedipine and to internal EGTA, are essentially involved in recruiting SRP vesicles. Intracellular Ca2+ imaging showed that Cav1.3 long isoforms support a deep intracellular diffusion of Ca2+SIGNIFICANCE STATEMENT Auditory inner hair cells (IHCs) encode sounds into nerve impulses through fast and indefatigable Ca2+-dependent exocytosis at their ribbon synapses. We show that this synaptic process involves long and short C-terminal isoforms of the Cav1.3 Ca2+ channel that differ in the kinetics of their Ca2+-dependent inactivation and their relative sensitivity to the l-type Ca2+ channel blocker nifedipine. The short C-terminal isoforms, having fast inactivation and low sensitivity to nifedipine, mainly control the fast fusion of the readily releasable pool (RRP); that is, they encode the phasic exocytotic component. The long isoforms, with slow inactivation and great sensitivity to nifedipine, mainly regulate the vesicular replenishment of the RRP; that is, the sustained or tonic exocytosis.
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21
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Excessive activation of ionotropic glutamate receptors induces apoptotic hair-cell death independent of afferent and efferent innervation. Sci Rep 2017; 7:41102. [PMID: 28112265 PMCID: PMC5255535 DOI: 10.1038/srep41102] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 12/15/2016] [Indexed: 02/07/2023] Open
Abstract
Accumulation of excess glutamate plays a central role in eliciting the pathological events that follow intensely loud noise exposures and ischemia-reperfusion injury. Glutamate excitotoxicity has been characterized in cochlear nerve terminals, but much less is known about whether excess glutamate signaling also contributes to pathological changes in sensory hair cells. I therefore examined whether glutamate excitotoxicity damages hair cells in zebrafish larvae exposed to drugs that mimic excitotoxic trauma. Exposure to ionotropic glutamate receptor (iGluR) agonists, kainic acid (KA) or N-methyl-D-aspartate (NMDA), contributed to significant, progressive hair cell loss in zebrafish lateral-line organs. To examine whether hair-cell loss was a secondary effect of excitotoxic damage to innervating neurons, I exposed neurog1a morphants-fish whose hair-cell organs are devoid of afferent and efferent innervation-to KA or NMDA. Significant, dose-dependent hair-cell loss occurred in neurog1a morphants exposed to either agonist, and the loss was comparable to wild-type siblings. A survey of iGluR gene expression revealed AMPA-, Kainate-, and NMDA-type subunits are expressed in zebrafish hair cells. Finally, hair cells exposed to KA or NMDA appear to undergo apoptotic cell death. Cumulatively, these data reveal that excess glutamate signaling through iGluRs induces hair-cell death independent of damage to postsynaptic terminals.
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22
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Wormuth C, Lundt A, Henseler C, Müller R, Broich K, Papazoglou A, Weiergräber M. Review: Ca v2.3 R-type Voltage-Gated Ca 2+ Channels - Functional Implications in Convulsive and Non-convulsive Seizure Activity. Open Neurol J 2016; 10:99-126. [PMID: 27843503 PMCID: PMC5080872 DOI: 10.2174/1874205x01610010099] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 05/16/2016] [Accepted: 06/24/2016] [Indexed: 11/22/2022] Open
Abstract
Background: Researchers have gained substantial insight into mechanisms of synaptic transmission, hyperexcitability, excitotoxicity and neurodegeneration within the last decades. Voltage-gated Ca2+ channels are of central relevance in these processes. In particular, they are key elements in the etiopathogenesis of numerous seizure types and epilepsies. Earlier studies predominantly targeted on Cav2.1 P/Q-type and Cav3.2 T-type Ca2+ channels relevant for absence epileptogenesis. Recent findings bring other channels entities more into focus such as the Cav2.3 R-type Ca2+ channel which exhibits an intriguing role in ictogenesis and seizure propagation. Cav2.3 R-type voltage gated Ca2+ channels (VGCC) emerged to be important factors in the pathogenesis of absence epilepsy, human juvenile myoclonic epilepsy (JME), and cellular epileptiform activity, e.g. in CA1 neurons. They also serve as potential target for various antiepileptic drugs, such as lamotrigine and topiramate. Objective: This review provides a summary of structure, function and pharmacology of VGCCs and their fundamental role in cellular Ca2+ homeostasis. We elaborate the unique modulatory properties of Cav2.3 R-type Ca2+ channels and point to recent findings in the proictogenic and proneuroapoptotic role of Cav2.3 R-type VGCCs in generalized convulsive tonic–clonic and complex-partial hippocampal seizures and its role in non-convulsive absence like seizure activity. Conclusion: Development of novel Cav2.3 specific modulators can be effective in the pharmacological treatment of epilepsies and other neurological disorders.
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Affiliation(s)
- Carola Wormuth
- Department of Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Andreas Lundt
- Department of Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Christina Henseler
- Department of Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Ralf Müller
- Department of Psychiatry and Psychotherapy, University of Cologne, Faculty of Medicine, Cologne, Germany
| | - Karl Broich
- Department of Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Anna Papazoglou
- Department of Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
| | - Marco Weiergräber
- Department of Neuropsychopharmacology, Federal Institute for Drugs and Medical Devices (BfArM), Kurt-Georg-Kiesinger-Allee 3, 53175 Bonn, Germany
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Striessnig J, Ortner NJ, Pinggera A. Pharmacology of L-type Calcium Channels: Novel Drugs for Old Targets? Curr Mol Pharmacol 2016; 8:110-22. [PMID: 25966690 PMCID: PMC5384371 DOI: 10.2174/1874467208666150507105845] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Revised: 02/10/2015] [Accepted: 04/20/2015] [Indexed: 11/22/2022]
Abstract
Inhibition of voltage-gated L-type calcium channels by organic calcium channel blockers is a well-established pharmacodynamic concept for the treatment of hypertension and cardiac ischemia. Since decades these antihypertensives (such as the dihydropyridines amlodipine, felodipine or nifedipine) belong to the most widely prescribed drugs
world-wide. Their tolerability is excellent because at therapeutic doses their pharmacological effects in humans are limited to the cardiovascular system. During the last years substantial progress has been made to reveal the physiological role of different L-type calcium channel isoforms in many other tissues, including the brain, endocrine and sensory cells.
Moreover, there is accumulating evidence about their involvement in various human diseases, such as Parkinson's disease, neuropsychiatric disorders and hyperaldosteronism. In this review we discuss the pathogenetic role of L-type calcium channels, potential new indications for existing or isoform-selective compounds and strategies to minimize potential side effects.
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Affiliation(s)
- Jörg Striessnig
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck, A-6020 Innsbruck, Austria.
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Yang T, Scholl ES, Pan N, Fritzsch B, Haeseleer F, Lee A. Expression and Localization of CaBP Ca2+ Binding Proteins in the Mouse Cochlea. PLoS One 2016; 11:e0147495. [PMID: 26809054 PMCID: PMC4725724 DOI: 10.1371/journal.pone.0147495] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 01/05/2016] [Indexed: 11/19/2022] Open
Abstract
CaBPs are a family of EF-hand Ca2+ binding proteins that are structurally similar to calmodulin. CaBPs can interact with, and yet differentially modulate, effectors that are regulated by calmodulin, such as Cav1 voltage-gated Ca2+ channels. Immunolabeling studies suggest that multiple CaBP family members (CaBP1, 2, 4, and 5) are expressed in the cochlea. To gain insights into the respective auditory functions of these CaBPs, we characterized the expression and cellular localization of CaBPs in the mouse cochlea. By quantitative reverse transcription PCR, we show that CaBP1 and CaBP2 are the major CaBPs expressed in mouse cochlea both before and after hearing onset. Of the three alternatively spliced variants of CaBP1 (caldendrin, CaBP1-L, and CaBP1-S) and CaBP2 (CaBP2-alt, CaBP2-L, CaBP2-S), caldendrin and CaBP2-alt are the most abundant. By in situ hybridization, probes recognizing caldendrin strongly label the spiral ganglion, while probes designed to recognize all three isoforms of CaBP1 weakly label both the inner and outer hair cells as well as the spiral ganglion. Within the spiral ganglion, caldendrin/CaBP1 labeling is associated with cells resembling satellite glial cells. CaBP2-alt is strongly expressed in inner hair cells both before and after hearing onset. Probes designed to recognize all three variants of CaBP2 strongly label inner hair cells before hearing onset and outer hair cells after the onset of hearing. Thus, CaBP1 and CaBP2 may have overlapping roles in regulating Ca2+ signaling in the hair cells, and CaBP1 may have an additional function in the spiral ganglion. Our findings provide a framework for understanding the role of CaBP family members in the auditory periphery.
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Affiliation(s)
- Tian Yang
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, United States of America
- Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, Iowa, United States of America
- Department of Neurology, University of Iowa, Iowa City, Iowa, United States of America
| | - Elizabeth S. Scholl
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, United States of America
- Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, Iowa, United States of America
- Department of Neurology, University of Iowa, Iowa City, Iowa, United States of America
| | - Ning Pan
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Bernd Fritzsch
- Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, Iowa, United States of America
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Françoise Haeseleer
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, United States of America
| | - Amy Lee
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, United States of America
- Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, Iowa, United States of America
- Department of Neurology, University of Iowa, Iowa City, Iowa, United States of America
- * E-mail:
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25
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Cochlear afferent innervation development. Hear Res 2015; 330:157-69. [DOI: 10.1016/j.heares.2015.07.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 06/02/2015] [Accepted: 07/21/2015] [Indexed: 01/11/2023]
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Sundaresan S, Kong JH, Fang Q, Salles FT, Wangsawihardja F, Ricci AJ, Mustapha M. Thyroid hormone is required for pruning, functioning and long-term maintenance of afferent inner hair cell synapses. Eur J Neurosci 2015; 43:148-61. [PMID: 26386265 DOI: 10.1111/ejn.13081] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 09/09/2015] [Accepted: 09/14/2015] [Indexed: 12/16/2022]
Abstract
Functional maturation of afferent synaptic connections to inner hair cells (IHCs) involves pruning of excess synapses formed during development, as well as the strengthening and survival of the retained synapses. These events take place during the thyroid hormone (TH)-critical period of cochlear development, which is in the perinatal period for mice and in the third trimester for humans. Here, we used the hypothyroid Snell dwarf mouse (Pit1(dw)) as a model to study the role of TH in afferent type I synaptic refinement and functional maturation. We observed defects in afferent synaptic pruning and delays in calcium channel clustering in the IHCs of Pit1(dw) mice. Nevertheless, calcium currents and capacitance reached near normal levels in Pit1(dw) IHCs by the age of onset of hearing, despite the excess number of retained synapses. We restored normal synaptic pruning in Pit1(dw) IHCs by supplementing with TH from postnatal day (P)3 to P8, establishing this window as being critical for TH action on this process. Afferent terminals of older Pit1(dw) IHCs showed evidence of excitotoxic damage accompanied by a concomitant reduction in the levels of the glial glutamate transporter, GLAST. Our results indicate that a lack of TH during a critical period of inner ear development causes defects in pruning and long-term homeostatic maintenance of afferent synapses.
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Affiliation(s)
- Srividya Sundaresan
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, 300 Pasteur Drive, Room R111A, Stanford, CA, 94035, USA
| | - Jee-Hyun Kong
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, 300 Pasteur Drive, Room R111A, Stanford, CA, 94035, USA
| | - Qing Fang
- Department of Human Genetics, University of Michigan, Ann Arbor, MI, USA
| | - Felipe T Salles
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, 300 Pasteur Drive, Room R111A, Stanford, CA, 94035, USA
| | - Felix Wangsawihardja
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, 300 Pasteur Drive, Room R111A, Stanford, CA, 94035, USA
| | - Anthony J Ricci
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, 300 Pasteur Drive, Room R111A, Stanford, CA, 94035, USA
| | - Mirna Mustapha
- Department of Otolaryngology-Head & Neck Surgery, Stanford University, 300 Pasteur Drive, Room R111A, Stanford, CA, 94035, USA
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27
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Scharinger A, Eckrich S, Vandael DH, Schönig K, Koschak A, Hecker D, Kaur G, Lee A, Sah A, Bartsch D, Benedetti B, Lieb A, Schick B, Singewald N, Sinnegger-Brauns MJ, Carbone E, Engel J, Striessnig J. Cell-type-specific tuning of Cav1.3 Ca(2+)-channels by a C-terminal automodulatory domain. Front Cell Neurosci 2015; 9:309. [PMID: 26379493 PMCID: PMC4547004 DOI: 10.3389/fncel.2015.00309] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 07/27/2015] [Indexed: 11/13/2022] Open
Abstract
Cav1.3 L-type Ca(2+)-channel function is regulated by a C-terminal automodulatory domain (CTM). It affects channel binding of calmodulin and thereby tunes channel activity by interfering with Ca(2+)- and voltage-dependent gating. Alternative splicing generates short C-terminal channel variants lacking the CTM resulting in enhanced Ca(2+)-dependent inactivation and stronger voltage-sensitivity upon heterologous expression. However, the role of this modulatory domain for channel function in its native environment is unkown. To determine its functional significance in vivo, we interrupted the CTM with a hemagglutinin tag in mutant mice (Cav1.3DCRD(HA/HA)). Using these mice we provide biochemical evidence for the existence of long (CTM-containing) and short (CTM-deficient) Cav1.3 α1-subunits in brain. The long (HA-labeled) Cav1.3 isoform was present in all ribbon synapses of cochlear inner hair cells. CTM-elimination impaired Ca(2+)-dependent inactivation of Ca(2+)-currents in hair cells but increased it in chromaffin cells, resulting in hyperpolarized resting potentials and reduced pacemaking. CTM disruption did not affect hearing thresholds. We show that the modulatory function of the CTM is affected by its native environment in different cells and thus occurs in a cell-type specific manner in vivo. It stabilizes gating properties of Cav1.3 channels required for normal electrical excitability.
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Affiliation(s)
- Anja Scharinger
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Stephanie Eckrich
- Department of Biophysics, Center for Integrative Physiology and Molecular Medicine, Saarland University Homburg, Germany
| | - David H Vandael
- Laboratory of Cellular and Molecular Neuroscience, Department of Drug Science, Nanostructured Interfaces and Surfaces Center, University of Torino Torino, Italy
| | - Kai Schönig
- Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University Mannheim, Germany
| | - Alexandra Koschak
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Dietmar Hecker
- Department of Otorhinolaryngology, Saarland University Homburg, Germany
| | - Gurjot Kaur
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Amy Lee
- Department of Molecular Physiology and Biophysics, University of Iowa Iowa City, IA, USA
| | - Anupam Sah
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Dusan Bartsch
- Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University Mannheim, Germany
| | - Bruno Benedetti
- Department of Physiology and Medical Physics, Innsbruck Medical University Innsbruck, Austria
| | - Andreas Lieb
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Bernhard Schick
- Department of Otorhinolaryngology, Saarland University Homburg, Germany
| | - Nicolas Singewald
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Martina J Sinnegger-Brauns
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Emilio Carbone
- Laboratory of Cellular and Molecular Neuroscience, Department of Drug Science, Nanostructured Interfaces and Surfaces Center, University of Torino Torino, Italy
| | - Jutta Engel
- Department of Biophysics, Center for Integrative Physiology and Molecular Medicine, Saarland University Homburg, Germany
| | - Jörg Striessnig
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
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Nicolson T. Ribbon synapses in zebrafish hair cells. Hear Res 2015; 330:170-7. [PMID: 25916266 DOI: 10.1016/j.heares.2015.04.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Revised: 03/20/2015] [Accepted: 04/13/2015] [Indexed: 12/31/2022]
Abstract
The basic architecture and functionality of ribbon synapses of mechanosensitive hair cells are well conserved among vertebrates. Forward and reverse genetic methods in zebrafish (Danio rerio) have identified components that are critical for the development and function of ribbon synapses. This review will focus on the findings of these genetic approaches, and discuss some emergent concepts on the role of the ribbon body and calcium in synapse development, and how perturbations in synaptic vesicles lead to a loss of temporal fidelity at ribbon synapses. This article is part of a Special Issue entitled <Auditory Synaptology>.
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Affiliation(s)
- T Nicolson
- Oregon Hearing Research Center and Vollum Institute, 3181 SW Sam Jackson Park Road, Oregon Health & Science University, Portland, OR 97239, USA.
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29
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Willaredt MA, Schlüter T, Nothwang HG. The gene regulatory networks underlying formation of the auditory hindbrain. Cell Mol Life Sci 2015; 72:519-535. [PMID: 25332098 PMCID: PMC11113740 DOI: 10.1007/s00018-014-1759-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 09/24/2014] [Accepted: 10/09/2014] [Indexed: 01/28/2023]
Abstract
Development and evolution of auditory hindbrain nuclei are two major unsolved issues in hearing research. Recent characterization of transgenic mice identified the rhombomeric origins of mammalian auditory nuclei and unraveled genes involved in their formation. Here, we provide an overview on these data by assembling them into rhombomere-specific gene regulatory networks (GRNs), as they underlie developmental and evolutionary processes. To explore evolutionary mechanisms, we compare the GRNs operating in the mammalian auditory hindbrain with data available from the inner ear and other vertebrate groups. Finally, we propose that the availability of genomic sequences from all major vertebrate taxa and novel genetic techniques for non-model organisms provide an unprecedented opportunity to investigate development and evolution of the auditory hindbrain by comparative molecular approaches. The dissection of the molecular mechanisms leading to auditory structures will also provide an important framework for auditory processing disorders, a clinical problem difficult to tackle so far. These data will, therefore, foster basic and clinical hearing research alike.
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Affiliation(s)
- Marc A Willaredt
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany.
| | - Tina Schlüter
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany
| | - Hans Gerd Nothwang
- Neurogenetics group, Center of Excellence Hearing4All, School of Medicine and Health Sciences, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany.
- Research Center for Neurosensory Science, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany.
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30
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Katz E, Elgoyhen AB. Short-term plasticity and modulation of synaptic transmission at mammalian inhibitory cholinergic olivocochlear synapses. Front Syst Neurosci 2014; 8:224. [PMID: 25520631 PMCID: PMC4251319 DOI: 10.3389/fnsys.2014.00224] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 11/06/2014] [Indexed: 12/23/2022] Open
Abstract
The organ of Corti, the mammalian sensory epithelium of the inner ear, has two types of mechanoreceptor cells, inner hair cells (IHCs) and outer hair cells (OHCs). In this sensory epithelium, vibrations produced by sound waves are transformed into electrical signals. When depolarized by incoming sounds, IHCs release glutamate and activate auditory nerve fibers innervating them and OHCs, by virtue of their electromotile property, increase the amplification and fine tuning of sound signals. The medial olivocochlear (MOC) system, an efferent feedback system, inhibits OHC activity and thereby reduces the sensitivity and sharp tuning of cochlear afferent fibers. During neonatal development, IHCs fire Ca2+ action potentials which evoke glutamate release promoting activity in the immature auditory system in the absence of sensory stimuli. During this period, MOC fibers also innervate IHCs and are thought to modulate their firing rate. Both the MOC-OHC and the MOC-IHC synapses are cholinergic, fast and inhibitory and mediated by the α9α10 nicotinic cholinergic receptor (nAChR) coupled to the activation of calcium-activated potassium channels that hyperpolarize the hair cells. In this review we discuss the biophysical, functional and molecular data which demonstrate that at the synapses between MOC efferent fibers and cochlear hair cells, modulation of transmitter release as well as short term synaptic plasticity mechanisms, operating both at the presynaptic terminal and at the postsynaptic hair-cell, determine the efficacy of these synapses and shape the hair cell response pattern.
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Affiliation(s)
- Eleonora Katz
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) Buenos Aires, Argentina ; Departamento de Fisiología, Biología Molecular y Celular "Prof. Héctor Maldonado", Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires Buenos Aires, Argentina
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres" (INGEBI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) Buenos Aires, Argentina ; Tercera Cátedra de Farmacología, Facultad de Medicina, Universidad de Buenos Aires Buenos Aires, Argentina
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31
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Genetic, cellular, and functional evidence for Ca2+ inflow through Cav1.2 and Cav1.3 channels in murine spiral ganglion neurons. J Neurosci 2014; 34:7383-93. [PMID: 24849370 DOI: 10.1523/jneurosci.5416-13.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Spiral ganglion neurons (SGNs) of the eighth nerve serve as the bridge between hair cells and the cochlear nucleus. Hair cells use Cav1.3 as the primary channel for Ca(2+) inflow to mediate transmitter release. In contrast, SGNs are equipped with multiple Ca(2+) channels to mediate Ca(2+)-dependent functions. We examined directly the role of Cav1.3 channels in SGNs using Cav1.3-deficient mice (Cav1.3(-/-)). We revealed a surprising finding that SGNs functionally express the cardiac-specific Cav1.2, as well as neuronal Cav1.3 channels. We show that evoked action potentials recorded from SGNs show a significant decrease in the frequency of firing in Cav1.3(-/-) mice compared with wild-type (Cav1.3(+/+)) littermates. Although Cav1.3 is the designated L-type channel in neurons, whole-cell currents recorded in isolated SGNs from Cav1.3(-/-) mice showed a surprising remnant current with sensitivity toward the dihydropyridine (DHP) agonist and antagonist, and a depolarization shift in the voltage-dependent activation compared with that in the Cav1.3(+/+) mice. Indeed, direct measurement of the elementary properties of Ca(2+) channels, in Cav1.3(+/+) neurons, confirmed the existence of two DHP-sensitive single-channel currents, with distinct open probabilities and conductances. We demonstrate that the DHP-sensitive current in Cav1.3(-/-) mice is derived from Cav1.2 channel activity, providing for the first time, to our knowledge, functional data for the expression of Cav1.2 currents in neurons. Finally, using shRNA gene knockdown methodology, and histological analyses of SGNs from Cav1.2(+/-) and Cav1.3(+/-) mice, we were able to establish the differential roles of Cav1.2 and Cav1.3 in SGNs.
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32
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Pochaev VA, Krasnyi AM, Ozernyuk ND. Influx of Ca2+ via Cav1.3 calcium channels in satellite cells of muscle fibers in rats. BIOL BULL+ 2013. [DOI: 10.1134/s1062359013050129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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33
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Gregory FD, Pangrsic T, Calin-Jageman IE, Moser T, Lee A. Harmonin enhances voltage-dependent facilitation of Cav1.3 channels and synchronous exocytosis in mouse inner hair cells. J Physiol 2013; 591:3253-69. [PMID: 23613530 DOI: 10.1113/jphysiol.2013.254367] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cav1.3 channels mediate Ca(2+) influx that triggers exocytosis of glutamate at cochlear inner hair cell (IHC) synapses. Harmonin is a PDZ-domain-containing protein that interacts with the C-terminus of the Cav1.3 α1 subunit (α11.3) and controls cell surface Cav1.3 levels by promoting ubiquitin-dependent proteosomal degradation. However, PDZ-domain-containing proteins have diverse functions and regulate other Cav1.3 properties, which could collectively influence presynaptic transmitter release. Here, we report that harmonin binding to the α11.3 distal C-terminus (dCT) enhances voltage-dependent facilitation (VDF) of Cav1.3 currents both in transfected HEK293T cells and in mouse inner hair cells. In HEK293T cells, this effect of harmonin was greater for Cav1.3 channels containing the auxiliary Cav β1 than with the β2 auxiliary subunit. Cav1.3 channels lacking the α11.3 dCT were insensitive to harmonin modulation. Moreover, the 'deaf-circler' dfcr mutant form of harmonin, which does not interact with the α11.3 dCT, did not promote VDF. In mature IHCs from mice expressing the dfcr harmonin mutant, Cav1.3 VDF was less than in control IHCs. This difference was not observed between control and dfcr IHCs prior to hearing onset. Membrane capacitance recordings from dfcr IHCs revealed a role for harmonin in synchronous exocytosis and in increasing the efficiency of Ca(2+) influx for triggering exocytosis. Collectively, our results indicate a multifaceted presynaptic role of harmonin in IHCs in regulating Cav1.3 Ca(2+) channels and exocytosis.
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Affiliation(s)
- Frederick D Gregory
- Department of Molecular Physiology and Biophysics, University of Iowa, 5-610 Bowen Science Building, 51 Newton Rd, Iowa City, IA 52242, USA
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34
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Downregulation of Cav1.3 calcium channel expression in the cochlea is associated with age-related hearing loss in C57BL/6J mice. Neuroreport 2013; 24:313-7. [DOI: 10.1097/wnr.0b013e32835fa79c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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35
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Posthearing Ca(2+) currents and their roles in shaping the different modes of firing of spiral ganglion neurons. J Neurosci 2013; 32:16314-30. [PMID: 23152615 DOI: 10.1523/jneurosci.2097-12.2012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Whereas prehearing spiral ganglion neurons (SGNs) rely faithfully on outputs from spontaneously active developing hair cells, the electrical phenotypes of posthearing neurons are shaped by distinct rapid and graded receptor potentials from hair cells. To date, technical difficulties in isolation of fragile posthearing neurons from the rigid bony labyrinth of the inner ear have hindered analyses of the electrical phenotype of SGNs. Therefore, we have recently developed new strategies to isolate posthearing mouse SGNs for functional analyses. Here, we describe the coarse and fine properties of Ca(2+) currents, which sculpt the firing properties of posthearing SGNs. Murine SGNs express multiple Ca(2+) channel currents to enable diverse functions. We have demonstrated that suppression of Ca(2+) currents results in significant hyperpolarization of the resting membrane potential (rmp) of basal SGNs, suggesting that Ca(2+) influx primes rmp for excitation. In contrast, removal of external Ca(2+) has modest effects on rmp of apical SGNs. The blockade of Ca(2+) currents with a mixture of specific blockers attenuates spontaneously active SGNs. Paradoxically, different subtypes of Ca(2+) currents, such as R-type currents, may activate resting outward conductances since blockage of the current results in depolarization of rmp. In keeping with whole-cell current data, single-channel records revealed multiple diverse Ca(2+) channels in SGNs. Additionally, there were differential expressions of distinct Ca(2+) current densities in the apicobasal contour of the adult cochlea. This report provides invaluable insights into Ca(2+)-dependent processes in adult SGNs.
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Levels of Ca(V)1.2 L-Type Ca(2+) Channels Peak in the First Two Weeks in Rat Hippocampus Whereas Ca(V)1.3 Channels Steadily Increase through Development. JOURNAL OF SIGNAL TRANSDUCTION 2012; 2012:597214. [PMID: 23097697 PMCID: PMC3477797 DOI: 10.1155/2012/597214] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Accepted: 06/04/2012] [Indexed: 12/20/2022]
Abstract
Influx of calcium through voltage-dependent channels regulates processes throughout the nervous system. Specifically, influx through L-type channels plays a variety of roles in early neuronal development and is commonly modulated by G-protein-coupled receptors such as GABA(B) receptors. Of the four isoforms of L-type channels, only Ca(V)1.2 and Ca(V)1.3 are predominately expressed in the nervous system. Both isoforms are inhibited by the same pharmacological agents, so it has been difficult to determine the role of specific isoforms in physiological processes. In the present study, Western blot analysis and confocal microscopy were utilized to study developmental expression levels and patterns of Ca(V)1.2 and Ca(V)1.3 in the CA1 region of rat hippocampus. Steady-state expression of Ca(V)1.2 predominated during the early neonatal period decreasing by day 12. Steady-state expression of Ca(V)1.3 was low at birth and gradually rose to adult levels by postnatal day 15. In immunohistochemical studies, antibodies against Ca(V)1.2 and Ca(V)1.3 demonstrated the highest intensity of labeling in the proximal dendrites at all ages studied (P1-72). Immunohistochemical studies on one-week-old hippocampi demonstrated significantly more colocalization of GABA(B) receptors with Ca(V)1.2 than with Ca(V)1.3, suggesting that modulation of L-type calcium current in early development is mediated through Ca(V)1.2 channels.
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Bulankina AV, Moser T. Neural circuit development in the mammalian cochlea. Physiology (Bethesda) 2012; 27:100-12. [PMID: 22505666 DOI: 10.1152/physiol.00036.2011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The organ of Corti, the sensory epithelium of the mammalian auditory system, uses afferent and efferent synapses for encoding auditory signals and top-down modulation of cochlear function. During development, the final precisely ordered sensorineural circuit is established following excessive formation of afferent and efferent synapses and subsequent refinement. Here, we review the development of innervation of the mouse organ of Corti and its regulation.
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Affiliation(s)
- A V Bulankina
- InnerEarLab, Department of Otolaryngology, University of Goettingen School of Medicine, Goettingen, Germany
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Ceriani F, Mammano F. Calcium signaling in the cochlea - Molecular mechanisms and physiopathological implications. Cell Commun Signal 2012; 10:20. [PMID: 22788415 PMCID: PMC3408374 DOI: 10.1186/1478-811x-10-20] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 07/12/2012] [Indexed: 12/20/2022] Open
Abstract
Calcium ions (Ca2+) regulate numerous and diverse aspects of cochlear and vestibular physiology. This review focuses on the Ca2+ control of mechanotransduction and synaptic transmission in sensory hair cells, as well as on Ca2+ signalling in non-sensory cells of the developing cochlea.
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Affiliation(s)
- Federico Ceriani
- Dipartimento di Fisica e Astronomia "G, Galilei", Università di Padova, 35131, Padova, Italy.
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Föller M, Jaumann M, Dettling J, Saxena A, Pakladok T, Munoz C, Ruth P, Sopjani M, Seebohm G, Rüttiger L, Knipper M, Lang F. AMP-activated protein kinase in BK-channel regulation and protection against hearing loss following acoustic overstimulation. FASEB J 2012; 26:4243-53. [PMID: 22767231 DOI: 10.1096/fj.12-208132] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The energy-sensing AMP-activated serine/threonine protein kinase (AMPK) confers cell survival in part by stimulation of cellular energy production and limitation of cellular energy utilization. AMPK-sensitive functions further include activities of epithelial Na+ channel ENaC and voltage-gated K+ channel KCNE1/KCNQ1. AMPK is activated by an increased cytosolic Ca2+ concentration. The present study explored whether AMPK regulates the Ca2+-sensitive large conductance and voltage-gated potassium (BK) channel. cRNA encoding BK channel was injected into Xenopus oocytes with and without additional injection of wild-type AMPK (AMPKα1+AMPKβ1+AMPKγ1), constitutively active AMPKγR70Q, or inactive AMPKαK45R. BK-channel activity was determined utilizing the 2-electrode voltage-clamp. Moreover, BK-channel protein abundance in the cell membrane was determined by confocal immunomicroscopy. As BK channels are expressed in outer hair cells (OHC) of the inner ear and lack of BK channels increases noise vulnerability, OHC BK-channel expression was examined by immunohistochemistry and hearing function analyzed by auditory brain stem response measurements in AMPKα1-deficient mice (ampk-/-) and in wild-type mice (ampk+/+). As a result, coexpression of AMPK or AMPKγR70Q but not of AMPKαK45R significantly enhanced BK-channel-mediated currents and BK-channel protein abundance in the oocyte cell membrane. BK-channel expression in the inner ear was lower in ampk-/- mice than in ampk+/+ mice. The hearing thresholds prior to and immediately after an acoustic overexposure were similar in ampk-/- and ampk+/+ mice. However, the recovery from the acoustic trauma was significantly impaired in ampk-/- mice compared to ampk+/+ mice. In summary, AMPK is a potent regulator of BK channels. It may thus participate in the signaling cascades that protect the inner ear from damage following acoustic overstimulation.
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Affiliation(s)
- Michael Föller
- Department of Physiology, University of Tübingen, Gmelinstr. 5, D-72076 Tübingen, Germany
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Chen J, Chu H, Xiong H, Chen Q, Zhou L, Bing D, Liu Y, Gao Y, Wang S, Huang X, Cui Y. Expression patterns of Ca(V)1.3 channels in the rat cochlea. Acta Biochim Biophys Sin (Shanghai) 2012; 44:513-8. [PMID: 22495160 DOI: 10.1093/abbs/gms024] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Although Ca(V)1.3 channels are known to be essential for neuronal excitation and signal transduction in the auditory system, their expression patterns in the cochlea are still not fully understood, particularly in the regions where non-sensory cells are located. We performed immunohistochemistry, western blotting and reverse transcription-polymerase chain reaction (RT-PCR) to identify the expression and distribution of Ca(V)1.3 channels in the rat cochlea. Immunohistochemistry revealed that Ca(V)1.3 channels were localized in the outer hair cells (OHCs), inner hair cells (IHCs), limbus laminae spiralis, spiral ganglion cell, spiral ligament (SL), and stria vascularis (STV). The results of RT-PCR and western blotting demonstrated Ca(V)1.3 channels had a tissue-specific expression pattern. Ca(V)1.3 mRNA and protein were intensively expressed in the basilar membrane and spiral ganglion while moderate level of Ca(V)1.3 channels was observed in SL and STV. Our study preliminarily revealed the expression patterns of Ca(V)1.3 channels in the rat cochlea, providing a theoretical basis for further research on the role of Ca(V)1.3 channels in the periphery auditory system.
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Affiliation(s)
- Jin Chen
- Department of Otorhinolaryngology-Head and Neck Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
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Lieb A, Scharinger A, Sartori S, Sinnegger-Brauns MJ, Striessnig J. Structural determinants of CaV1.3 L-type calcium channel gating. Channels (Austin) 2012; 6:197-205. [PMID: 22760075 PMCID: PMC3431584 DOI: 10.4161/chan.21002] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
A C-terminal modulatory domain (CTM) tightly regulates the biophysical properties of Ca(v)1.3 L-type Ca(2+) channels, in particular the voltage dependence of activation (V(0.5)) and Ca(2+) dependent inactivation (CDI). A functional CTM is present in the long C-terminus of human and mouse Ca(v)1.3 (Ca(v)1.3(L)), but not in a rat long cDNA clone isolated from superior cervical ganglia neurons (rCa(v)1.3(scg)). We therefore addressed the question if this represents a species-difference and compared the biophysical properties of rCa(v)1.3(scg) with a rat cDNA isolated from rat pancreas (rCa(v)1.3(L)). When expressed in tsA-201 cells under identical experimental conditions rCa(v)1.3(L) exhibited Ca(2+) current properties indistinguishable from human and mouse Ca(v)1.3(L), compatible with the presence of a functional CTM. In contrast, rCa(v)1.3(scg) showed gating properties similar to human short splice variants lacking a CTM. rCa(v)1.3(scg) differs from rCa(v)1.3(L) at three single amino acid (aa) positions, one alternative spliced exon (exon31), and a N-terminal polymethionine stretch with two additional lysines. Two aa (S244, A2075) in rCa(v)1.3(scg) explained most of the functional differences to rCa(v)1.3(L). Their mutation to the corresponding residues in rCa(v)1.3(L) (G244, V2075) revealed that both contributed to the more negative V 0.5, but caused opposite effects on CDI. A2075 (located within a region forming the CTM) additionally permitted higher channel open probability. The cooperative action in the double-mutant restored gating properties similar to rCa(v)1.3(L). We found no evidence for transcripts containing one of the single rCa(v)1.3(scg) mutations in rat superior cervical ganglion preparations. However, the rCa(v)1.3(scg) variant provided interesting insight into the structural machinery involved in Ca(v)1.3 gating.
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Affiliation(s)
- Andreas Lieb
- Institute of Pharmacy and Center for Molecular Biosciences, University of Innsbruck, Austria
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cGMP-Prkg1 signaling and Pde5 inhibition shelter cochlear hair cells and hearing function. Nat Med 2012; 18:252-9. [PMID: 22270721 DOI: 10.1038/nm.2634] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 12/07/2011] [Indexed: 02/07/2023]
Abstract
Noise-induced hearing loss (NIHL) is a global health hazard with considerable pathophysiological and social consequences that has no effective treatment. In the heart, lung and other organs, cyclic guanosine monophosphate (cGMP) facilitates protective processes in response to traumatic events. We therefore analyzed NIHL in mice with a genetic deletion of the gene encoding cGMP-dependent protein kinase type I (Prkg1) and found a greater vulnerability to and markedly less recovery from NIHL in these mice as compared to mice without the deletion. Prkg1 was expressed in the sensory cells and neurons of the inner ear of wild-type mice, and its expression partly overlapped with the expression profile of cGMP-hydrolyzing phosphodiesterase 5 (Pde5). Treatment of rats and wild-type mice with the Pde5 inhibitor vardenafil almost completely prevented NIHL and caused a Prkg1-dependent upregulation of poly (ADP-ribose) in hair cells and the spiral ganglion, suggesting an endogenous protective cGMP-Prkg1 signaling pathway that culminates in the activation of poly (ADP-ribose) polymerase. These data suggest vardenafil or related drugs as possible candidates for the treatment of NIHL.
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Voltage-Gated Ca2+ Channel Mediated Ca2+ Influx in Epileptogenesis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:1219-47. [DOI: 10.1007/978-94-007-2888-2_55] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Abstract
Hair cells in the mammalian inner ear convert sound into electrical signals that are relayed to the nervous system by the chemical neurotransmitter glutamate. Electrical information encoding sound is then passed through the central nervous system to the higher auditory centres in the brain, where it is used to construct a temporally and spatially accurate representation of the auditory landscape. To achieve this, hair cells must encode fundamental properties of sound stimuli at extremely high rates, not only during mechano-electrical transduction, which occurs in the hair bundles at the cell apex, but also during electrochemical transduction at the specialized ribbon synapses at the cell base. How is the development of such a sophisticated cell regulated? More specifically, to what extent does physiological activity contribute to the progression of the intrinsic genetic programmes that drive cell differentiation? Hair cell differentiation takes about 3 weeks in most rodents, from terminal mitosis during embryonic development to the onset of hearing around 2 weeks after birth. Until recent years, most of the molecules involved in hair cell development and function were unknown, which was mainly due to difficulties in working with the mammalian cochlea and the very small number of hair cells, about 16,000 in humans, present in the auditory organ. Recent advances in the ability to record from the acutely isolated cochlea maintained in near-physiological conditions, combined with the use of genetically modified mouse models, has allowed the identification of several proteins and molecular mechanisms that are crucial for the maturation and function of hair cells. In this article, I highlight recent findings from my laboratory that have furthered our understanding of how developing hair cells acquire the remarkable sensitivity of adult auditory sensory receptors.
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Affiliation(s)
- Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield S10 2TN, UK.
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Patuzzi R. Ion flow in cochlear hair cells and the regulation of hearing sensitivity. Hear Res 2011; 280:3-20. [DOI: 10.1016/j.heares.2011.04.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2010] [Revised: 03/28/2011] [Accepted: 04/11/2011] [Indexed: 12/22/2022]
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Abstract
Within the Ca(v)1 family of voltage-gated calcium channels, Ca(v)1.2 and Ca(v)1.3 channels are the predominant subtypes in the brain. Whereas specific functions for each subtype were described in the adult brain, their role in brain development is poorly understood. Here we assess the role of Ca(v)1.3 subunits in the activity-dependent development of the auditory brainstem. We used Ca(v)1.3-deficient (Ca(v)1.3(-/-)) mice because these mice lack cochlea-driven activity that deprives the auditory centers from peripheral input. We found a drastically reduced volume in all auditory brainstem centers (range 25-59%, total 35%), which was manifest before hearing onset. A reduction was not obvious outside the auditory system. The lateral superior olive (LSO) was strikingly malformed in Ca(v)1.3(-/-) mice and had fewer neurons (1/3 less). The remaining LSO neurons displayed normal dendritic trees and received functional glutamatergic input, yet they fired action potentials predominantly with a multiple pattern upon depolarization, in contrast to the single firing pattern prevalent in controls. The latter finding appears to be due to a reduction of dendrototoxin-sensitive potassium conductances, presumably mediated through the K(v)1.2 subtype. Fura2 imaging provided evidence for functional Ca(v)1.3 channels in the LSO of wild-type mice. Our results imply that Ca(v)1.3 channels are indispensable for the development of the central auditory system. We propose that the unique LSO phenotype in Ca(v)1.3(-/-) mice, which hitherto was not described in other hereditary deafness models, is caused by the synergistic contribution of two factors: on-site loss of Ca(v)1.3 channels in the neurons plus lack of peripheral input.
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Defourny J, Lallemend F, Malgrange B. Structure and development of cochlear afferent innervation in mammals. Am J Physiol Cell Physiol 2011; 301:C750-61. [PMID: 21753183 DOI: 10.1152/ajpcell.00516.2010] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
In mammals, sensorineural deafness results from damage to the auditory receptors of the inner ear, the nerve pathways to the brain or the cortical area that receives sound information. In this review, we first focused on the cellular and molecular events taking part to spiral ganglion axon growth, extension to the organ of Corti, and refinement. In the second half, we considered the functional maturation of synaptic contacts between sensory hair cells and their afferent projections. A better understanding of all these processes could open insights into novel therapeutic strategies aimed to re-establish primary connections from sound transducers to the ascending auditory nerve pathways.
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Molecular cloning and characterization of a hamster Cav1.3 Ca2+ channel variant with a long carboxyl terminus. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:1629-38. [DOI: 10.1016/j.bbamem.2010.11.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2010] [Revised: 11/09/2010] [Accepted: 11/09/2010] [Indexed: 11/22/2022]
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Milenkovic VM, Krejcova S, Reichhart N, Wagner A, Strauß O. Interaction of bestrophin-1 and Ca2+ channel β-subunits: identification of new binding domains on the bestrophin-1 C-terminus. PLoS One 2011; 6:e19364. [PMID: 21559412 PMCID: PMC3084833 DOI: 10.1371/journal.pone.0019364] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 04/01/2011] [Indexed: 12/21/2022] Open
Abstract
Bestrophin-1 modulates currents through voltage-dependent L-type Ca2+ channels by physically interacting with the β-subunits of Ca2+ channels. The main function of β-subunits is to regulate the number of pore-forming CaV-subunits in the cell membrane and modulate Ca2+ channel currents. To understand the influence of full-length bestrophin-1 on β-subunit function, we studied binding and localization of bestrophin-1 and Ca2+ channel subunits, together with modulation of CaV1.3 Ca2+ channels currents. In heterologeous expression, bestrophin-1 showed co-immunoprecipitation with either, β3-, or β4-subunits. We identified a new highly conserved cluster of proline-rich motifs on the bestrophin-1 C-terminus between amino acid position 468 and 486, which enables possible binding to SH3-domains of β-subunits. A bestrophin-1 that lacks these proline-rich motifs (ΔCT-PxxP bestrophin-1) showed reduced efficiency to co-immunoprecipitate with β3 and β4-subunits. In the presence of ΔCT-PxxP bestrophin-1, β4-subunits and CaV1.3 subunits partly lost membrane localization. Currents from CaV1.3 subunits were modified in the presence of β4-subunit and wild-type bestrophin-1: accelerated time-dependent activation and reduced current density. With ΔCTPxxP bestrophin-1, currents showed the same time-dependent activation as with wild-type bestrophin-1, but the current density was further reduced due to decreased number of Ca2+ channels proteins in the cell membrane. In summary, we described new proline-rich motifs on bestrophin-1 C-terminus, which help to maintain the ability of β-subunits to regulate surface expression of pore-forming CaV Ca2+-channel subunits.
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Affiliation(s)
- Vladimir M. Milenkovic
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany
| | - Sarka Krejcova
- Experimentelle Ophthalmologie, Klinik und Poliklinik für Augenheilkunde, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
| | - Nadine Reichhart
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany
| | - Andrea Wagner
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany
| | - Olaf Strauß
- Experimental Ophthalmology, Eye Hospital, University Medical Center Regensburg, Regensburg, Germany
- * E-mail:
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Pérez-Alvarez A, Hernández-Vivanco A, Caba-González JC, Albillos A. Different roles attributed to Cav1 channel subtypes in spontaneous action potential firing and fine tuning of exocytosis in mouse chromaffin cells. J Neurochem 2010; 116:105-21. [PMID: 21054386 PMCID: PMC7197458 DOI: 10.1111/j.1471-4159.2010.07089.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
J. Neurochem. (2011) 116, 105–121. Abstract This study examines the Cav1 isoforms expressed in mouse chromaffin cells and compares their biophysical properties and roles played in cell excitability and exocytosis. Using immunocytochemical and electrophysiological techniques in mice lacking the Cav1.3α1 subunit (Cav1.3−/−) or the high sensitivity of Cav1.2α1 subunits to dihydropyridines, Cav1.2 and Cav1.3 channels were identified as the only Cav1 channel subtypes expressed in mouse chromaffin cells. Cav1.3 channels were activated at more negative membrane potentials and inactivated more slowly than Cav1.2 channels. Cav1 channels, mainly Cav1.2, control cell excitability by functional coupling to BK channels, revealed by nifedipine blockade of BK channels in wild type (WT) and Cav1.3−/− cells (53% and 35%, respectively), and by the identical change in the shape of the spontaneous action potentials elicited by the dihydropyridine in both strains of mice. Cav1.2 channels also play a major role in spontaneous action potential firing, supported by the following evidence: (i) a similar percentage of WT and Cav1.3−/− cells fired spontaneous action potentials; (ii) firing frequency did not vary between WT and Cav1.3−/− cells; (iii) mostly Cav1.2 channels contributed to the inward current preceding the action potential threshold; and (iv) in the presence of tetrodotoxin, WT or Cav1.3−/− cells exhibited spontaneous oscillatory activity, which was fully abolished by nifedipine perfusion. Finally, Cav1.2 and Cav1.3 channels were essential for controlling the exocytotic process at potentials above and below −10 mV, respectively. Our data reveal the key yet differential roles of Cav1.2 and Cav1.3 channels in mediating action potential firing and exocytotic events in the neuroendocrine chromaffin cell.
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Affiliation(s)
- Alberto Pérez-Alvarez
- Department of Pharmacology and Therapeutics, Faculty of Medicine, Universidad Autónoma de Madrid, Madrid, Spain
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