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Arancibia F, De Giorgis D, Medina F, Hermosilla T, Simon F, Varela D. Role of the Ca V1.2 distal carboxy terminus in the regulation of L-type current. Channels (Austin) 2024; 18:2338782. [PMID: 38691022 PMCID: PMC11067984 DOI: 10.1080/19336950.2024.2338782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2024] [Accepted: 03/31/2024] [Indexed: 05/03/2024] Open
Abstract
L-type calcium channels are essential for the excitation-contraction coupling in cardiac muscle. The CaV1.2 channel is the most predominant isoform in the ventricle which consists of a multi-subunit membrane complex that includes the CaV1.2 pore-forming subunit and auxiliary subunits like CaVα2δ and CaVβ2b. The CaV1.2 channel's C-terminus undergoes proteolytic cleavage, and the distal C-terminal domain (DCtermD) associates with the channel core through two domains known as proximal and distal C-terminal regulatory domain (PCRD and DCRD, respectively). The interaction between the DCtermD and the remaining C-terminus reduces the channel activity and modifies voltage- and calcium-dependent inactivation mechanisms, leading to an autoinhibitory effect. In this study, we investigate how the interaction between DCRD and PCRD affects the inactivation processes and CaV1.2 activity. We expressed a 14-amino acid peptide miming the DCRD-PCRD interaction sequence in both heterologous systems and cardiomyocytes. Our results show that overexpression of this small peptide can displace the DCtermD and replicate the effects of the entire DCtermD on voltage-dependent inactivation and channel inhibition. However, the effect on calcium-dependent inactivation requires the full DCtermD and is prevented by overexpression of calmodulin. In conclusion, our results suggest that the interaction between DCRD and PCRD is sufficient to bring about the current inhibition and alter the voltage-dependent inactivation, possibly in an allosteric manner. Additionally, our data suggest that the DCtermD competitively modifies the calcium-dependent mechanism. The identified peptide sequence provides a valuable tool for further dissecting the molecular mechanisms that regulate L-type calcium channels' basal activity in cardiomyocytes.
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Affiliation(s)
- Felipe Arancibia
- Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Chile, Santiago, Chile
- Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Daniela De Giorgis
- Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Chile, Santiago, Chile
- Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Franco Medina
- Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Chile, Santiago, Chile
- Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Tamara Hermosilla
- Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Chile, Santiago, Chile
- Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Felipe Simon
- Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Chile, Santiago, Chile
- Laboratory of Integrative Physiopathology, Faculty of Life Sciences, Universidad Andres Bello, Santiago, Chile
- Millennium Institute on Immunology and Immunotherapy, Santiago, Chile
| | - Diego Varela
- Millennium Nucleus of Ion Channels-Associated Diseases (MiNICAD), Universidad de Chile, Santiago, Chile
- Programa de Fisiología y Biofísica, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile
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2
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Ezell KM, Tinker RJ, Furuta Y, Gulsevin A, Bastarache L, Hamid R, Cogan JD, Rives L, Neumann S, Corner B, Kozuria M, Phillips JA. Undiagnosed Disease Network collaborative approach in diagnosing rare disease in a patient with a mosaic CACNA1D variant. Am J Med Genet A 2024; 194:e63597. [PMID: 38511854 PMCID: PMC11161305 DOI: 10.1002/ajmg.a.63597] [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: 01/08/2024] [Revised: 02/23/2024] [Accepted: 03/08/2024] [Indexed: 03/22/2024]
Abstract
The Undiagnosed Disease Network (UDN) is comprised of clinical and research experts collaborating to diagnose rare disease. The UDN is funded by the National Institutes of Health and includes 12 different clinical sites (About Us, 2022). Here we highlight the success of collaborative efforts within the UDN Clinical Site at Vanderbilt University Medical Center (VUMC) in utilizing a cohort of experts in bioinformatics, structural biology, and genetics specialists in diagnosing rare disease. Our UDN team identified a de novo mosaic CACNA1D variant c.2299T>C in a 5-year-old female with a history of global developmental delay, dystonia, dyskinesis, and seizures. Using a collaborative multidisciplinary approach, our VUMC UDN team diagnosed the participant with Primary Aldosteronism, Seizures, and Neurologic abnormalities (PASNA) OMIM: 615474 due to a rare mosaic CACNA1D variant (O'Neill, 2013). Interestingly, this patient was mosaic, a phenotypic trait previously unreported in PASNA cases. This report highlights the importance of a multidisciplinary approach in diagnosing rare disease.
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Affiliation(s)
- Kimberly M. Ezell
- Department of Pediatrics, Division of Medical Genetics and Genomic Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Rory J. Tinker
- Department of Pediatrics, Division of Medical Genetics and Genomic Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Yutaka Furuta
- Department of Pediatrics, Division of Medical Genetics and Genomic Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Alican Gulsevin
- Department of Chemistry, Center for Structural Biology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Butler University, Indianapolis, Indiana, USA
| | - Lisa Bastarache
- Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Rizwan Hamid
- Department of Pediatrics, Division of Medical Genetics and Genomic Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Joy D. Cogan
- Department of Pediatrics, Division of Medical Genetics and Genomic Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Lynette Rives
- Department of Pediatrics, Division of Medical Genetics and Genomic Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Serena Neumann
- Department of Pediatrics, Division of Medical Genetics and Genomic Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Brian Corner
- Department of Pediatrics, Division of Medical Genetics and Genomic Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Mary Kozuria
- Department of Pediatrics, Division of Medical Genetics and Genomic Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - John A. Phillips
- Department of Pediatrics, Division of Medical Genetics and Genomic Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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Moser T, Karagulyan N, Neef J, Jaime Tobón LM. Diversity matters - extending sound intensity coding by inner hair cells via heterogeneous synapses. EMBO J 2023; 42:e114587. [PMID: 37800695 PMCID: PMC10690447 DOI: 10.15252/embj.2023114587] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 06/26/2023] [Accepted: 08/07/2023] [Indexed: 10/07/2023] Open
Abstract
Our sense of hearing enables the processing of stimuli that differ in sound pressure by more than six orders of magnitude. How to process a wide range of stimulus intensities with temporal precision is an enigmatic phenomenon of the auditory system. Downstream of dynamic range compression by active cochlear micromechanics, the inner hair cells (IHCs) cover the full intensity range of sound input. Yet, the firing rate in each of their postsynaptic spiral ganglion neurons (SGNs) encodes only a fraction of it. As a population, spiral ganglion neurons with their respective individual coding fractions cover the entire audible range. How such "dynamic range fractionation" arises is a topic of current research and the focus of this review. Here, we discuss mechanisms for generating the diverse functional properties of SGNs and formulate testable hypotheses. We postulate that an interplay of synaptic heterogeneity, molecularly distinct subtypes of SGNs, and efferent modulation serves the neural decomposition of sound information and thus contributes to a population code for sound intensity.
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Affiliation(s)
- Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Cluster of Excellence “Multiscale Bioimaging of Excitable Cells”GöttingenGermany
| | - Nare Karagulyan
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Hertha Sponer CollegeCluster of Excellence “Multiscale Bioimaging of Excitable Cells” Cluster of ExcellenceGöttingenGermany
| | - Jakob Neef
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
| | - Lina María Jaime Tobón
- Institute for Auditory Neuroscience and InnerEarLabUniversity Medical Center GöttingenGöttingenGermany
- Auditory Neuroscience and Synaptic Nanophysiology GroupMax Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Hertha Sponer CollegeCluster of Excellence “Multiscale Bioimaging of Excitable Cells” Cluster of ExcellenceGöttingenGermany
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4
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Ortner NJ, Sah A, Paradiso E, Shin J, Stojanovic S, Hammer N, Haritonova M, Hofer NT, Marcantoni A, Guarina L, Tuluc P, Theiner T, Pitterl F, Ebner K, Oberacher H, Carbone E, Stefanova N, Ferraguti F, Singewald N, Roeper J, Striessnig J. The human channel gating-modifying A749G CACNA1D (Cav1.3) variant induces a neurodevelopmental syndrome-like phenotype in mice. JCI Insight 2023; 8:e162100. [PMID: 37698939 PMCID: PMC10619503 DOI: 10.1172/jci.insight.162100] [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: 06/09/2022] [Accepted: 09/06/2023] [Indexed: 09/14/2023] Open
Abstract
Germline de novo missense variants of the CACNA1D gene, encoding the pore-forming α1 subunit of Cav1.3 L-type Ca2+ channels (LTCCs), have been found in patients with neurodevelopmental and endocrine dysfunction, but their disease-causing potential is unproven. These variants alter channel gating, enabling enhanced Cav1.3 activity, suggesting Cav1.3 inhibition as a potential therapeutic option. Here we provide proof of the disease-causing nature of such gating-modifying CACNA1D variants using mice (Cav1.3AG) containing the A749G variant reported de novo in a patient with autism spectrum disorder (ASD) and intellectual impairment. In heterozygous mutants, native LTCC currents in adrenal chromaffin cells exhibited gating changes as predicted from heterologous expression. The A749G mutation induced aberrant excitability of dorsomedial striatum-projecting substantia nigra dopamine neurons and medium spiny neurons in the dorsal striatum. The phenotype observed in heterozygous mutants reproduced many of the abnormalities described within the human disease spectrum, including developmental delay, social deficit, and pronounced hyperactivity without major changes in gross neuroanatomy. Despite an approximately 7-fold higher sensitivity of A749G-containing channels to the LTCC inhibitor isradipine, oral pretreatment over 2 days did not rescue the hyperlocomotion. Cav1.3AG mice confirm the pathogenicity of the A749G variant and point toward a pathogenetic role of altered signaling in the dopamine midbrain system.
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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
| | - Anupam Sah
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Enrica Paradiso
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck, Austria
| | - Josef Shin
- Institute for Neurophysiology, Goethe University, Frankfurt, Germany
| | | | - Niklas Hammer
- Institute for Neurophysiology, Goethe University, Frankfurt, Germany
| | - Maria Haritonova
- 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
| | - Andrea Marcantoni
- Department of Drug Science, N.I.S. Centre, University of Torino, Torino, Italy
| | - Laura Guarina
- Department of Drug Science, N.I.S. Centre, University of Torino, Torino, Italy
| | - Petronel Tuluc
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Tamara Theiner
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Florian Pitterl
- Institute of Legal Medicine and Core Facility Metabolomics and
| | - Karl Ebner
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | | | - Emilio Carbone
- Department of Drug Science, N.I.S. Centre, University of Torino, Torino, Italy
| | - Nadia Stefanova
- Department of Neurology, Medical University of Innsbruck, Innsbruck, Austria
| | - Francesco Ferraguti
- Department of Pharmacology, Medical University of Innsbruck, Innsbruck, Austria
| | - Nicolas Singewald
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Jochen Roeper
- Institute for Neurophysiology, Goethe University, Frankfurt, 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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Karema-Jokinen V, Koskela A, Hytti M, Hongisto H, Viheriälä T, Liukkonen M, Torsti T, Skottman H, Kauppinen A, Nymark S, Kaarniranta K. Crosstalk of protein clearance, inflammasome, and Ca 2+ channels in retinal pigment epithelium derived from age-related macular degeneration patients. J Biol Chem 2023:104770. [PMID: 37137441 DOI: 10.1016/j.jbc.2023.104770] [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: 11/07/2022] [Revised: 04/21/2023] [Accepted: 04/23/2023] [Indexed: 05/05/2023] Open
Abstract
Degeneration and/or dysfunction of retinal pigment epithelium (RPE) is generally detected as the formation of intra- and extracellular protein aggregates, called lipofuscin and drusen, respectively, in patients with age-related macular degeneration (AMD), the leading cause of blindness in the elderly population. These clinical hallmarks are linked to dysfunctional protein homeostasis and inflammation, and furthermore, are both regulated by changes in intracellular Ca2+ concentration. While many other cellular mechanisms have been considered in the investigations of AMD-RPE, there has been relatively little work on understanding the interactions of protein clearance, inflammation, and Ca2+ dynamics in disease pathogenesis. Here we established induced pluripotent stem cell-derived RPE from two patients with advanced AMD and from an age- and gender-matched control subject. We studied autophagy and inflammasome activation under disturbed proteostasis in these cell lines and investigated changes in their intracellular Ca2+ concentration and L-type voltage-gated Ca2+ channels. Our work demonstrated dysregulated autophagy and inflammasome activation in AMD-RPE accompanied by reduced intracellular free Ca2+ levels. Interestingly, we found currents through L-type voltage-gated Ca2+ channels to be diminished and showed these channels to be significantly localized to intracellular compartments in AMD-RPE. Taken together, the alterations in Ca2+ dynamics in AMD-RPE together with dysregulated autophagy and inflammasome activation indicate an important role for Ca2+ signaling in AMD pathogenesis, providing new avenues for the development of therapeutic approaches.
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Affiliation(s)
| | - Ali Koskela
- Department of Ophthalmology, University of Eastern Finland, Kuopio, Finland
| | - Maria Hytti
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, Kuopio, Finland
| | - Heidi Hongisto
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland; Department of Ophthalmology, University of Eastern Finland, Kuopio, Finland
| | - Taina Viheriälä
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Mikko Liukkonen
- Department of Ophthalmology, University of Eastern Finland, Kuopio, Finland
| | - Tommi Torsti
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, Kuopio, Finland
| | - Heli Skottman
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland
| | - Anu Kauppinen
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, Kuopio, Finland
| | - Soile Nymark
- Faculty of Medicine and Health Technology, Tampere University, Tampere, Finland.
| | - Kai Kaarniranta
- Department of Ophthalmology, University of Eastern Finland, Kuopio, Finland; Department of Ophthalmology, Kuopio University Hospital, Finland, Immuno-Ophthalmology, School of Pharmacy, University of Eastern Finland, Kuopio, Finland; Department of Molecular Genetics, University of Lodz, Lodz, Poland.
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6
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Kameyama M, Minobe E, Shao D, Xu J, Gao Q, Hao L. Regulation of Cardiac Cav1.2 Channels by Calmodulin. Int J Mol Sci 2023; 24:ijms24076409. [PMID: 37047381 PMCID: PMC10094977 DOI: 10.3390/ijms24076409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 03/19/2023] [Accepted: 03/23/2023] [Indexed: 03/31/2023] Open
Abstract
Cav1.2 Ca2+ channels, a type of voltage-gated L-type Ca2+ channel, are ubiquitously expressed, and the predominant Ca2+ channel type, in working cardiac myocytes. Cav1.2 channels are regulated by the direct interactions with calmodulin (CaM), a Ca2+-binding protein that causes Ca2+-dependent facilitation (CDF) and inactivation (CDI). Ca2+-free CaM (apoCaM) also contributes to the regulation of Cav1.2 channels. Furthermore, CaM indirectly affects channel activity by activating CaM-dependent enzymes, such as CaM-dependent protein kinase II and calcineurin (a CaM-dependent protein phosphatase). In this article, we review the recent progress in identifying the role of apoCaM in the channel ‘rundown’ phenomena and related repriming of channels, and CDF, as well as the role of Ca2+/CaM in CDI. In addition, the role of CaM in channel clustering is reviewed.
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Affiliation(s)
- Masaki Kameyama
- Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, Sakura-ga-oka, Kagoshima 890-8544, Japan
- Correspondence:
| | - Etsuko Minobe
- Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, Sakura-ga-oka, Kagoshima 890-8544, Japan
| | - Dongxue Shao
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110012, China (L.H.)
| | - Jianjun Xu
- Department of Physiology, Graduate School of Medical & Dental Sciences, Kagoshima University, Sakura-ga-oka, Kagoshima 890-8544, Japan
| | - Qinghua Gao
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110012, China (L.H.)
| | - Liying Hao
- Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110012, China (L.H.)
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7
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Ortner NJ. CACNA1D-Related Channelopathies: From Hypertension to Autism. Handb Exp Pharmacol 2023. [PMID: 36592224 DOI: 10.1007/164_2022_626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Tightly controlled Ca2+ influx through voltage-gated Ca2+ channels (Cavs) is indispensable for proper physiological function. Thus, it is not surprising that Cav loss and/or gain of function have been implicated in human pathology. Deficiency of Cav1.3 L-type Ca2+ channels (LTCCs) causes deafness and bradycardia, whereas several genetic variants of CACNA1D, the gene encoding the pore-forming α1 subunit of Cav1.3, have been linked to various disease phenotypes, such as hypertension, congenital hypoglycemia, or autism. These variants include not only common polymorphisms associated with an increased disease risk, but also rare de novo missense variants conferring high risk. This review provides a concise summary of disease-associated CACNA1D variants, whereas the main focus lies on de novo germline variants found in individuals with a neurodevelopmental disorder of variable severity. Electrophysiological recordings revealed activity-enhancing gating changes induced by these de novo variants, and tools to predict their pathogenicity and to study the resulting pathophysiological consequences will be discussed. Despite the low number of affected patients, potential phenotype-genotype correlations and factors that could impact the severity of symptoms will be covered. Since increased channel activity is assumed as the disease-underlying mechanism, pharmacological inhibition could be a treatment option. In the absence of Cav1.3-selective blockers, dihydropyridine LTCC inhibitors clinically approved for the treatment of hypertension may be used for personalized off-label trials. Findings from in vitro studies and treatment attempts in some of the patients seem promising as outlined. Taken together, due to advances in diagnostic sequencing techniques the number of reported CACNA1D variants in human diseases is constantly rising. Evidence from in silico, in vitro, and in vivo disease models can help to predict the pathogenic potential of such variants and to guide diagnosis and treatment in the clinical practice when confronted with patients harboring CACNA1D variants.
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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.
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8
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Zaveri S, Srivastava U, Qu YS, Chahine M, Boutjdir M. Pathophysiology of Ca v1.3 L-type calcium channels in the heart. Front Physiol 2023; 14:1144069. [PMID: 37025382 PMCID: PMC10070707 DOI: 10.3389/fphys.2023.1144069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 03/07/2023] [Indexed: 04/08/2023] Open
Abstract
Ca2+ plays a crucial role in excitation-contraction coupling in cardiac myocytes. Dysfunctional Ca2+ regulation alters the force of contraction and causes cardiac arrhythmias. Ca2+ entry into cardiomyocytes is mediated mainly through L-type Ca2+ channels, leading to the subsequent Ca2+ release from the sarcoplasmic reticulum. L-type Ca2+ channels are composed of the conventional Cav1.2, ubiquitously expressed in all heart chambers, and the developmentally regulated Cav1.3, exclusively expressed in the atria, sinoatrial node, and atrioventricular node in the adult heart. As such, Cav1.3 is implicated in the pathogenesis of sinoatrial and atrioventricular node dysfunction as well as atrial fibrillation. More recently, Cav1.3 de novo expression was suggested in heart failure. Here, we review the functional role, expression levels, and regulation of Cav1.3 in the heart, including in the context of cardiac diseases. We believe that the elucidation of the functional and molecular pathways regulating Cav1.3 in the heart will assist in developing novel targeted therapeutic interventions for the aforementioned arrhythmias.
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Affiliation(s)
- Sahil Zaveri
- Cardiovascular Research Program, VA New York Harbor Healthcare System, New York, NY, United States
- Department of Medicine, Cell Biology and Pharmacology, State University of New York Downstate Health Sciences University, Brooklyn, New York, NY, United States
| | - Ujala Srivastava
- Cardiovascular Research Program, VA New York Harbor Healthcare System, New York, NY, United States
| | - Yongxia Sarah Qu
- Cardiovascular Research Program, VA New York Harbor Healthcare System, New York, NY, United States
- Department of Medicine, Cell Biology and Pharmacology, State University of New York Downstate Health Sciences University, Brooklyn, New York, NY, United States
- Department of Cardiology, New York Presbyterian Brooklyn Methodist Hospital, New York, NY, United States
| | - Mohamed Chahine
- CERVO Brain Research Center, Institut Universitaire en Santé Mentale de Québec, Québec, QC, Canada
- Department of Medicine, Faculté de Médecine, Université Laval, Quebec, QC, Canada
| | - Mohamed Boutjdir
- Cardiovascular Research Program, VA New York Harbor Healthcare System, New York, NY, United States
- Department of Medicine, Cell Biology and Pharmacology, State University of New York Downstate Health Sciences University, Brooklyn, New York, NY, United States
- Division of Cardiology, Department of Medicine, NYU Grossman School of Medicine, New York, NY, United States
- *Correspondence: Mohamed Boutjdir,
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9
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Rinné S, Stallmeyer B, Pinggera A, Netter MF, Matschke LA, Dittmann S, Kirchhefer U, Neudorf U, Opp J, Striessnig J, Decher N, Schulze-Bahr E. Whole Exome Sequencing Identifies a Heterozygous Variant in the Cav1.3 Gene CACNA1D Associated with Familial Sinus Node Dysfunction and Focal Idiopathic Epilepsy. Int J Mol Sci 2022; 23:ijms232214215. [PMID: 36430690 PMCID: PMC9693521 DOI: 10.3390/ijms232214215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 11/04/2022] [Accepted: 11/11/2022] [Indexed: 11/18/2022] Open
Abstract
Cav1.3 voltage-gated L-type calcium channels (LTCCs) are involved in cardiac pacemaking, hearing and hormone secretion, but are also expressed postsynaptically in neurons. So far, homozygous loss of function mutations in CACNA1D encoding the Cav1.3 α1-subunit are described in congenital sinus node dysfunction and deafness. In addition, germline mutations in CACNA1D have been linked to neurodevelopmental syndromes including epileptic seizures, autism, intellectual disability and primary hyperaldosteronism. Here, a three-generation family with a syndromal phenotype of sinus node dysfunction, idiopathic epilepsy and attention deficit hyperactivity disorder (ADHD) is investigated. Whole genome sequencing and functional heterologous expression studies were used to identify the disease-causing mechanisms in this novel syndromal disorder. We identified a heterozygous non-synonymous variant (p.Arg930His) in the CACNA1D gene that cosegregated with the combined clinical phenotype in an autosomal dominant manner. Functional heterologous expression studies showed that the CACNA1D variant induces isoform-specific alterations of Cav1.3 channel gating: a gain of ion channel function was observed in the brain-specific short CACNA1D isoform (Cav1.3S), whereas a loss of ion channel function was seen in the long (Cav1.3L) isoform. The combined gain-of-function (GOF) and loss-of-function (LOF) induced by the R930H variant are likely to be associated with the rare combined clinical and syndromal phenotypes in the family. The GOF in the Cav1.3S variant with high neuronal expression is likely to result in epilepsy, whereas the LOF in the long Cav1.3L variant results in sinus node dysfunction.
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Affiliation(s)
- Susanne Rinné
- Institute of Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, 35037 Marburg, Germany
| | - Birgit Stallmeyer
- Institute for Genetics of Heart Diseases (IfGH), University Hospital Muenster, 48149 Muenster, Germany
| | - Alexandra Pinggera
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences, University of Innsbruck, 6020 Innsbruck, Austria
| | - Michael F. Netter
- Institute of Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, 35037 Marburg, Germany
| | - Lina A. Matschke
- Institute of Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, 35037 Marburg, Germany
| | - Sven Dittmann
- Institute for Genetics of Heart Diseases (IfGH), University Hospital Muenster, 48149 Muenster, Germany
| | - Uwe Kirchhefer
- Institute of Pharmacology and Toxicology, University Hospital Muenster, 48149 Muenster, Germany
| | - Ulrich Neudorf
- Zentrum für Kinder-und Jugendmedizin, Klinik für Kinderheilkunde III-Bereich Kardiologie, University Hospital Essen, 45147 Essen, Germany
| | - Joachim Opp
- Ev. Krankenhaus Oberhausen, 46047 Oberhausen, Germany
| | - Jörg Striessnig
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences, University of Innsbruck, 6020 Innsbruck, Austria
| | - Niels Decher
- Institute of Physiology and Pathophysiology, Vegetative Physiology, University of Marburg, 35037 Marburg, Germany
- Correspondence: (N.D.); (E.S.-B.); Tel.: +49-(0)6421/28-62148 (N.D.); +49-(0)251/83-55326 (E.S.-B.)
| | - Eric Schulze-Bahr
- Institute for Genetics of Heart Diseases (IfGH), University Hospital Muenster, 48149 Muenster, Germany
- Correspondence: (N.D.); (E.S.-B.); Tel.: +49-(0)6421/28-62148 (N.D.); +49-(0)251/83-55326 (E.S.-B.)
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10
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Hofer NT, Pinggera A, Nikonishyna YV, Tuluc P, Fritz EM, Obermair GJ, Striessnig J. Stabilization of negative activation voltages of Cav1.3 L-Type Ca 2+-channels by alternative splicing. Channels (Austin) 2021; 15:38-52. [PMID: 33380256 PMCID: PMC7781618 DOI: 10.1080/19336950.2020.1859260] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 11/30/2020] [Indexed: 11/30/2022] Open
Abstract
-->Low voltage-activated Cav1.3 L-type Ca2+-channels are key regulators of neuronal excitability controlling neuronal development and different types of learning and memory. Their physiological functions are enabled by their negative activation voltage-range, which allows Cav1.3 to be active at subthreshold voltages. Alternative splicing in the C-terminus of their pore-forming α1-subunits gives rise to C-terminal long (Cav1.3L) and short (Cav1.3S) splice variants allowing Cav1.3S to activate at even more negative voltages than Cav1.3L. We discovered that inclusion of exons 8b, 11, and 32 in Cav1.3S further shifts activation (-3 to -4 mV) and inactivation (-4 to -6 mV) to more negative voltages as revealed by functional characterization in tsA-201 cells. We found transcripts of these exons in mouse chromaffin cells, the cochlea, and the brain. Our data further suggest that Cav1.3-containing exons 11 and 32 constitute a significant part of native channels in the brain. We therefore investigated the effect of these splice variants on human disease variants. Splicing did not prevent the gating defects of the previously reported human pathogenic variant S652L, which further shifted the voltage-dependence of activation of exon 11-containing channels by more than -12 mV. In contrast, we found no evidence for gating changes of the CACNA1D missense variant R498L, located in exon 11, which has recently been identified in a patient with an epileptic syndrome. Our data demonstrate that alternative splicing outside the C-terminus involving exons 11 and 32 contributes to channel fine-tuning by stabilizing negative activation and inactivation gating properties of wild-type and mutant Cav1.3 channels.
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Affiliation(s)
- Nadja T. Hofer
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Austria
| | - Alexandra Pinggera
- Neurobiology Division, MRC Laboratory of Molecular Biology, Cambridge, UK
| | - Yuliia V. Nikonishyna
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Austria
| | - Petronel Tuluc
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Austria
| | - Eva M. Fritz
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Austria
| | - Gerald J. Obermair
- Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria
- Division Physiology, Karl Landsteiner University of Health Sciences, Krems, Austria
| | - Jörg Striessnig
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Austria
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11
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Jeong S, Rhee JS, Lee JH. Snapin Specifically Up-Regulates Ca v1.3 Ca 2+ Channel Variant with a Long Carboxyl Terminus. Int J Mol Sci 2021; 22:ijms222011268. [PMID: 34681928 PMCID: PMC8537452 DOI: 10.3390/ijms222011268] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 10/14/2021] [Accepted: 10/15/2021] [Indexed: 11/16/2022] Open
Abstract
Ca2+ entry through Cav1.3 Ca2+ channels plays essential roles in diverse physiological events. We employed yeast-two-hybrid (Y2H) assays to mine novel proteins interacting with Cav1.3 and found Snapin2, a synaptic protein, as a partner interacting with the long carboxyl terminus (CTL) of rat Cav1.3L variant. Co-expression of Snapin with Cav1.3L/Cavβ3/α2δ2 subunits increased the peak current density or amplitude by about 2-fold in HEK-293 cells and Xenopus oocytes, without affecting voltage-dependent gating properties and calcium-dependent inactivation. However, the Snapin up-regulation effect was not found for rat Cav1.3S containing a short CT (CTS) in which a Snapin interaction site in the CTL was deficient. Luminometry and electrophysiology studies uncovered that Snapin co-expression did not alter the membrane expression of HA tagged Cav1.3L but increased the slope of tail current amplitudes plotted against ON-gating currents, indicating that Snapin increases the opening probability of Cav1.3L. Taken together, our results strongly suggest that Snapin directly interacts with the CTL of Cav1.3L, leading to up-regulation of Cav1.3L channel activity via facilitating channel opening probability.
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Affiliation(s)
- Sua Jeong
- Department of Life Science, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107, Korea;
| | - Jeong-Seop Rhee
- Synaptic Physiology Group, Department of Molecular Neurobiology, Max Planck Institute for Experimental Medicine, Hermann-Rein-Str. 3, 37075 Göttingen, Germany;
| | - Jung-Ha Lee
- Department of Life Science, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul 04107, Korea;
- Correspondence: ; Tel.: +82-2-705-8791; Fax: +82-3-704-3601
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12
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Sodium background currents in endocrine/neuroendocrine cells: Towards unraveling channel identity and contribution in hormone secretion. Front Neuroendocrinol 2021; 63:100947. [PMID: 34592201 DOI: 10.1016/j.yfrne.2021.100947] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 09/03/2021] [Accepted: 09/23/2021] [Indexed: 02/04/2023]
Abstract
In endocrine/neuroendocrine tissues, excitability of secretory cells is patterned by the repertoire of ion channels and there is clear evidence that extracellular sodium (Na+) ions contribute to hormone secretion. While voltage-gated channels involved in action potential generation are well-described, the background 'leak' channels operating near the resting membrane potential are much less known, and in particular the channels supporting a background entry of Na+ ions. These background Na+ currents (called here 'INab') have the ability to modulate the resting membrane potential and subsequently affect action potential firing. Here we compile and analyze the data collected from three endocrine/neuroendocrine tissues: the anterior pituitary gland, the adrenal medulla and the endocrine pancreas. We also model how INab can be functionally involved in cellular excitability. Finally, towards deciphering the physiological role of INab in endocrine/neuroendocrine cells, its implication in hormone release is also discussed.
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13
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Koschak A, Fernandez-Quintero ML, Heigl T, Ruzza M, Seitter H, Zanetti L. Cav1.4 dysfunction and congenital stationary night blindness type 2. Pflugers Arch 2021; 473:1437-1454. [PMID: 34212239 PMCID: PMC8370969 DOI: 10.1007/s00424-021-02570-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 04/14/2021] [Accepted: 04/18/2021] [Indexed: 12/04/2022]
Abstract
Cav1.4 L-type Ca2+ channels are predominantly expressed in retinal neurons, particularly at the photoreceptor terminals where they mediate sustained Ca2+ entry needed for continuous neurotransmitter release at their ribbon synapses. Cav1.4 channel gating properties are controlled by accessory subunits, associated regulatory proteins, and also alternative splicing. In humans, mutations in the CACNA1F gene encoding for Cav1.4 channels are associated with X-linked retinal disorders such as congenital stationary night blindness type 2. Mutations in the Cav1.4 protein result in a spectrum of altered functional channel activity. Several mouse models broadened our understanding of the role of Cav1.4 channels not only as Ca2+ source at retinal synapses but also as synaptic organizers. In this review, we highlight different structural and functional phenotypes of Cav1.4 mutations that might also occur in patients with congenital stationary night blindness type 2. A further important yet mostly neglected aspect that we discuss is the influence of alternative splicing on channel dysfunction. We conclude that currently available functional phenotyping strategies should be refined and summarize potential specific therapeutic options for patients carrying Cav1.4 mutations. Importantly, the development of new therapeutic approaches will permit a deeper understanding of not only the disease pathophysiology but also the physiological function of Cav1.4 channels in the retina.
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MESH Headings
- 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester/pharmacology
- Animals
- Calcium Channel Agonists/pharmacology
- Calcium Channels, L-Type/genetics
- Calcium Channels, L-Type/metabolism
- Eye Diseases, Hereditary/genetics
- Eye Diseases, Hereditary/metabolism
- Genetic Diseases, X-Linked/genetics
- Genetic Diseases, X-Linked/metabolism
- Humans
- Mutation/physiology
- Myopia/genetics
- Myopia/metabolism
- Night Blindness/genetics
- Night Blindness/metabolism
- Retina/drug effects
- Retina/metabolism
- Synapses/drug effects
- Synapses/genetics
- Synapses/metabolism
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Affiliation(s)
- Alexandra Koschak
- Institute of Pharmacy, Pharmacology and Toxicology, Center for Chemistry and Biomedicine, University of Innsbruck, Innrain 80-82/III, 6020, Innsbruck, Austria.
| | - Monica L Fernandez-Quintero
- Institute of General, Inorganic and Theoretical Chemistry, Center for Chemistry and Biomedicine, University of Innsbruck, Innrain 80-82/III, 6020, Innsbruck, Austria
| | - Thomas Heigl
- Institute of Pharmacy, Pharmacology and Toxicology, Center for Chemistry and Biomedicine, University of Innsbruck, Innrain 80-82/III, 6020, Innsbruck, Austria
| | - Marco Ruzza
- Institute of Pharmacy, Pharmacology and Toxicology, Center for Chemistry and Biomedicine, University of Innsbruck, Innrain 80-82/III, 6020, Innsbruck, Austria
| | - Hartwig Seitter
- Institute of Pharmacy, Pharmacology and Toxicology, Center for Chemistry and Biomedicine, University of Innsbruck, Innrain 80-82/III, 6020, Innsbruck, Austria
| | - Lucia Zanetti
- Institute of Pharmacy, Pharmacology and Toxicology, Center for Chemistry and Biomedicine, University of Innsbruck, Innrain 80-82/III, 6020, Innsbruck, Austria
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Effertz T, Moser T, Oliver D. Recent advances in cochlear hair cell nanophysiology: subcellular compartmentalization of electrical signaling in compact sensory cells. Fac Rev 2021; 9:24. [PMID: 33659956 PMCID: PMC7886071 DOI: 10.12703/r/9-24] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In recent years, genetics, physiology, and structural biology have advanced into the molecular details of the sensory physiology of auditory hair cells. Inner hair cells (IHCs) and outer hair cells (OHCs) mediate two key functions: active amplification and non-linear compression of cochlear vibrations by OHCs and sound encoding by IHCs at their afferent synapses with the spiral ganglion neurons. OHCs and IHCs share some molecular physiology, e.g. mechanotransduction at the apical hair bundles, ribbon-type presynaptic active zones, and ionic conductances in the basolateral membrane. Unique features enabling their specific function include prestin-based electromotility of OHCs and indefatigable transmitter release at the highest known rates by ribbon-type IHC active zones. Despite their compact morphology, the molecular machineries that either generate electrical signals or are driven by these signals are essentially all segregated into local subcellular structures. This review provides a brief account on recent insights into the molecular physiology of cochlear hair cells with a specific focus on organization into membrane domains.
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Affiliation(s)
- Thomas Effertz
- InnerEarLab, Department of Otorhinolaryngology, University Medical Center Göttingen, 37099 Göttingen, Germany
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, 37099 Göttingen, Germany
- Auditory Neuroscience Group, Max Planck Institute for Experimental Medicine, 37075 Göttingen, Germany
- Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
- Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, 37075 Göttingen, Germany
| | - Dominik Oliver
- Institute for Physiology and Pathophysiology, Philipps University, Deutschhausstraße 2, 35037 Marburg, Germany
- Center for Mind, Brain and Behavior (CMBB), Universities of Marburg and Giessen, 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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Hofer NT, Tuluc P, Ortner NJ, Nikonishyna YV, Fernándes-Quintero ML, Liedl KR, Flucher BE, Cox H, Striessnig J. Biophysical classification of a CACNA1D de novo mutation as a high-risk mutation for a severe neurodevelopmental disorder. Mol Autism 2020; 11:4. [PMID: 31921405 PMCID: PMC6950833 DOI: 10.1186/s13229-019-0310-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Accepted: 12/24/2019] [Indexed: 12/27/2022] Open
Abstract
Background There is increasing evidence that de novo CACNA1D missense mutations inducing increased Cav1.3 L-type Ca2+-channel-function confer a high risk for neurodevelopmental disorders (autism spectrum disorder with and without neurological and endocrine symptoms). Electrophysiological studies demonstrating the presence or absence of typical gain-of-function gating changes could therefore serve as a tool to distinguish likely disease-causing from non-pathogenic de novo CACNA1D variants in affected individuals. We tested this hypothesis for mutation S652L, which has previously been reported in twins with a severe neurodevelopmental disorder in the Deciphering Developmental Disorder Study, but has not been classified as a novel disease mutation. Methods For functional characterization, wild-type and mutant Cav1.3 channel complexes were expressed in tsA-201 cells and tested for typical gain-of-function gating changes using the whole-cell patch-clamp technique. Results Mutation S652L significantly shifted the voltage-dependence of activation and steady-state inactivation to more negative potentials (~ 13-17 mV) and increased window currents at subthreshold voltages. Moreover, it slowed tail currents and increased Ca2+-levels during action potential-like stimulations, characteristic for gain-of-function changes. To provide evidence that only gain-of-function variants confer high disease risk, we also studied missense variant S652W reported in apparently healthy individuals. S652W shifted activation and inactivation to more positive voltages, compatible with a loss-of-function phenotype. Mutation S652L increased the sensitivity of Cav1.3 for inhibition by the dihydropyridine L-type Ca2+-channel blocker isradipine by 3-4-fold.Conclusions and limitationsOur data provide evidence that gain-of-function CACNA1D mutations, such as S652L, but not loss-of-function mutations, such as S652W, cause high risk for neurodevelopmental disorders including autism. This adds CACNA1D to the list of novel disease genes identified in the Deciphering Developmental Disorder Study. Although our study does not provide insight into the cellular mechanisms of pathological Cav1.3 signaling in neurons, we provide a unifying mechanism of gain-of-function CACNA1D mutations as a predictor for disease risk, which may allow the establishment of a more reliable diagnosis of affected individuals. Moreover, the increased sensitivity of S652L to isradipine encourages a therapeutic trial in the two affected individuals. This can address the important question to which extent symptoms are responsive to therapy with Ca2+-channel blockers.
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Affiliation(s)
- Nadja T. Hofer
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Petronel Tuluc
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Nadine J. Ortner
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Yuliia V. Nikonishyna
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
| | - Monica L. Fernándes-Quintero
- Institute of General, Inorganic and Theoretical Chemistry, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Klaus R. Liedl
- Institute of General, Inorganic and Theoretical Chemistry, Centre for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Bernhard E. Flucher
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Helen Cox
- West Midlands Regional Clinical Genetics Service, Birmingham Women’s and Children’s Hospital, National Health Service Foundation Trust, B15 2TG, Birmingham, UK
| | - Jörg Striessnig
- Department of Pharmacology and Toxicology, Centre for Molecular Biosciences, University of Innsbruck, Innrain 80/82, 6020 Innsbruck, Austria
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16
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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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17
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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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18
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Carbone E, Borges R, Eiden LE, García AG, Hernández‐Cruz A. Chromaffin Cells of the Adrenal Medulla: Physiology, Pharmacology, and Disease. Compr Physiol 2019; 9:1443-1502. [DOI: 10.1002/cphy.c190003] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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19
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Beggs MR, Lee JJ, Busch K, Raza A, Dimke H, Weissgerber P, Engel J, Flockerzi V, Alexander RT. TRPV6 and Ca v1.3 Mediate Distal Small Intestine Calcium Absorption Before Weaning. Cell Mol Gastroenterol Hepatol 2019; 8:625-642. [PMID: 31398491 PMCID: PMC6889763 DOI: 10.1016/j.jcmgh.2019.07.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 07/15/2019] [Accepted: 07/17/2019] [Indexed: 12/12/2022]
Abstract
BACKGROUND & AIMS Intestinal Ca2+ absorption early in life is vital to achieving optimal bone mineralization. The molecular details of intestinal Ca2+ absorption have been defined in adults after peak bone mass is obtained, but they are largely unexplored during development. We sought to delineate the molecular details of transcellular Ca2+ absorption during this critical period. METHODS Expression of small intestinal and renal calcium transport genes was assessed by using quantitative polymerase chain reaction. Net calcium flux across small intestinal segments was measured in Ussing chambers, including after pharmacologic inhibition or genetic manipulation of TRPV6 or Cav1.3 calcium channels. Femurs were analyzed by using micro-computed tomography and histology. RESULTS Net TRPV6-mediated Ca2+ flux across the duodenum was absent in pre-weaned (P14) mice but present after weaning. In contrast, we found significant transcellular Ca2+ absorption in the jejunum at 2 weeks but not 2 months of age. Net jejunal Ca2+ absorption observed at P14 was not present in either Trpv6 mutant (D541A) mice or Cav1.3 knockout mice. We observed significant nifedipine-sensitive transcellular absorption across the ileum at P14 but not 2 months. Cav1.3 knockout pups exhibited delayed bone mineral accrual, compensatory nifedipine-insensitive Ca2+ absorption in the ileum, and increased expression of renal Ca2+ reabsorption mediators at P14. Moreover, weaning pups at 2 weeks reduced jejunal and ileal Cav1.3 expression. CONCLUSIONS We have detailed novel pathways contributing to transcellular Ca2+ transport across the distal small intestine of mice during development, highlighting the complexity of the multiple mechanisms involved in achieving a positive Ca2+ balance early in life.
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Affiliation(s)
- Megan R. Beggs
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada,The Women’s & Children’s Health Research Institute, Edmonton, Alberta, Canada
| | - Justin J. Lee
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada,The Women’s & Children’s Health Research Institute, Edmonton, Alberta, Canada
| | - Kai Busch
- Experimentelle und Klinische Pharmakologie und Toxikologie, Saarland University, Homburg, Germany
| | - Ahsan Raza
- Experimentelle und Klinische Pharmakologie und Toxikologie, Saarland University, Homburg, Germany
| | - Henrik Dimke
- Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Petra Weissgerber
- Experimentelle und Klinische Pharmakologie und Toxikologie, Saarland University, Homburg, Germany
| | - Jutta Engel
- Department of Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, School of Medicine, Homburg, Germany
| | - Veit Flockerzi
- Experimentelle und Klinische Pharmakologie und Toxikologie, Saarland University, Homburg, Germany
| | - R. Todd Alexander
- Department of Physiology, University of Alberta, Edmonton, Alberta, Canada,The Women’s & Children’s Health Research Institute, Edmonton, Alberta, Canada,Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada,Correspondence Address correspondence to: R. Todd Alexander, MD, PhD, Department of Pediatrics, 4-585 Edmonton Clinic Health Academy, 11405 – 87 Avenue, University of Alberta, Edmonton, Alberta T6G 2R7, Canada. fax: (780) 248-5556.
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Eckrich S, Hecker D, Sorg K, Blum K, Fischer K, Münkner S, Wenzel G, Schick B, Engel J. Cochlea-Specific Deletion of Ca v1.3 Calcium Channels Arrests Inner Hair Cell Differentiation and Unravels Pitfalls of Conditional Mouse Models. Front Cell Neurosci 2019; 13:225. [PMID: 31178698 PMCID: PMC6538774 DOI: 10.3389/fncel.2019.00225] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 05/03/2019] [Indexed: 12/29/2022] Open
Abstract
Inner hair cell (IHC) Cav1.3 Ca2+ channels are multifunctional channels mediating Ca2+ influx for exocytosis at ribbon synapses, the generation of Ca2+ action potentials in pre-hearing IHCs and gene expression. IHCs of deaf systemic Cav1.3-deficient (Cav1.3-/-) mice stay immature because they fail to up-regulate voltage- and Ca2+-activated K+ (BK) channels but persistently express small conductance Ca2+-activated K+ (SK2) channels. In pre-hearing wildtype mice, cholinergic neurons from the superior olivary complex (SOC) exert efferent inhibition onto spontaneously active immature IHCs by activating their SK2 channels. Because Cav1.3 plays an important role for survival, health and function of SOC neurons, SK2 channel persistence and lack of BK channels in systemic Cav1.3-/- IHCs may result from malfunctioning neurons of the SOC. Here we analyze cochlea-specific Cav1.3 knockout mice with green fluorescent protein (GFP) switch reporter function, Pax2::cre;Cacna1d-eGFPflex/flexand Pax2::cre;Cacna1d-eGFPflex/-. Profound hearing loss, lack of BK channels and persistence of SK2 channels in Pax2::cre;Cacna1d-eGFPflex/- mice recapitulated the phenotype of systemic Cav1.3-/- mice, indicating that in wildtype mice, regulation of SK2 and BK channel expression is independent of Cav1.3 expression in SOC neurons. In addition, we noticed dose-dependent GFP toxicity leading to death of basal coil IHCs of Pax2::cre;Cacna1d-eGFPflex/flex mice, likely because of high GFP concentration and small repair capacity. This and the slower time course of Pax2-driven Cre recombinase in switching two rather than one Cacna1d-eGFPflex allele lead us to study Pax2::cre;Cacna1d-eGFPflex/- mice. Notably, control Cacna1d-eGFPflex/- IHCs showed a significant reduction in Cav1.3 channel cluster sizes and currents, suggesting that the intronic construct interfered with gene translation or splicing. These pitfalls are likely to be a frequent problem of many genetically modified mice with complex or multiple gene-targeting constructs or fluorescent proteins. Great caution and appropriate controls are therefore required.
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Affiliation(s)
- Stephanie Eckrich
- Department of Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, Homburg, Germany
| | - Dietmar Hecker
- Department of Otorhinolaryngology, Saarland University, Homburg, Germany
| | - Katharina Sorg
- Department of Otorhinolaryngology, Saarland University, Homburg, Germany
| | - Kerstin Blum
- Department of Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, Homburg, Germany
| | - Kerstin Fischer
- Department of Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, Homburg, Germany
| | - Stefan Münkner
- Department of Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, Homburg, Germany
| | - Gentiana Wenzel
- Department of Otorhinolaryngology, Saarland University, Homburg, Germany
| | - Bernhard Schick
- Department of Otorhinolaryngology, Saarland University, Homburg, Germany
| | - Jutta Engel
- Department of Biophysics, Center for Integrative Physiology and Molecular Medicine (CIPMM), School of Medicine, Saarland University, Homburg, Germany
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Single-Channel Resolution of the Interaction between C-Terminal Ca V1.3 Isoforms and Calmodulin. Biophys J 2019; 116:836-846. [PMID: 30773296 DOI: 10.1016/j.bpj.2019.01.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2018] [Revised: 01/05/2019] [Accepted: 01/16/2019] [Indexed: 12/21/2022] Open
Abstract
Voltage-dependent calcium (CaV) 1.3 channels are involved in the control of cellular excitability and pacemaking in neuronal, cardiac, and sensory cells. Various proteins interact with the alternatively spliced channel C-terminus regulating gating of CaV1.3 channels. Binding of a regulatory calcium-binding protein calmodulin (CaM) to the proximal C-terminus leads to the boosting of channel activity and promotes calcium-dependent inactivation (CDI). The C-terminal modulator domain (CTM) of CaV1.3 channels can interfere with the CaM binding, thereby inhibiting channel activity and CDI. Here, we compared single-channel gating behavior of two natural CaV1.3 splice isoforms: the long CaV1.342 with the full-length CTM and the short CaV1.342A with the C-terminus truncated before the CTM. We found that CaM regulation of CaV1.3 channels is dynamic on a minute timescale. We observed that at equilibrium, single CaV1.342 channels occasionally switched from low to high open probability, which perhaps reflects occasional binding of CaM despite the presence of CTM. Similarly, when the amount of the available CaM in the cell was reduced, the short CaV1.342A isoform showed patterns of the low channel activity. CDI also underwent periodic changes with corresponding kinetics in both isoforms. Our results suggest that the competition between CTM and CaM is influenced by calcium, allowing further fine-tuning of CaV1.3 channel activity for particular cellular needs.
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Viral Transfer of Mini-Otoferlins Partially Restores the Fast Component of Exocytosis and Uncovers Ultrafast Endocytosis in Auditory Hair Cells of Otoferlin Knock-Out Mice. J Neurosci 2019; 39:3394-3411. [PMID: 30833506 DOI: 10.1523/jneurosci.1550-18.2018] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 10/24/2018] [Accepted: 11/02/2018] [Indexed: 01/06/2023] Open
Abstract
Transmitter release at auditory inner hair cell (IHC) ribbon synapses involves exocytosis of glutamatergic vesicles during voltage activation of L-type Cav1.3 calcium channels. At these synapses, the fast and indefatigable release of synaptic vesicles by IHCs is controlled by otoferlin, a six-C2-domain (C2-ABCDEF) protein that functions as a high-affinity Ca2+ sensor. The molecular events by which each otoferlin C2 domain contributes to the regulation of the synaptic vesicle cycle in IHCs are still incompletely understood. Here, we investigate their role using a cochlear viral cDNA transfer approach in vivo, where IHCs of mouse lacking otoferlin (Otof -/- mice of both sexes) were virally transduced with cDNAs of various mini-otoferlins. Using patch-clamp recordings and membrane capacitance measurements, we show that the viral transfer of mini-otoferlin containing C2-ACEF, C2-EF, or C2-DEF partially restores the fast exocytotic component in Otof -/- mouse IHCs. The restoration was much less efficient with C2-ACDF, underlining the importance of the C2-EF domain. None of the mini-otoferlins tested restored the sustained component of vesicle release, explaining the absence of hearing recovery. The restoration of the fast exocytotic component in the transduced Otof -/- IHCs was also associated with a recovery of Ca2+ currents with normal amplitude and fast time inactivation, confirming that the C-terminal C2 domains of otoferlin are essential for normal gating of Cav1.3 channels. Finally, the reintroduction of the mini-otoferlins C2-EF, C2-DEF, or C2-ACEF allowed us to uncover and characterize for the first time a dynamin-dependent ultrafast endocytosis in IHCs.SIGNIFICANCE STATEMENT Otoferlin, a large six-C2-domain protein, is essential for synaptic vesicle exocytosis at auditory hair cell ribbon synapses. Here, we show that the viral expression of truncated forms of otoferlin (C2-EF, C2-DEF, and C2-ACEF) can partially rescue the fast and transient release component of exocytosis in mouse hair cells lacking otoferlin, yet cannot sustain exocytosis after long repeated stimulation. Remarkably, these hair cells also display a dynamin-dependent ultrafast endocytosis. Overall, our study uncovers the pleiotropic role of otoferlin in the hair cell synaptic vesicle cycle, notably in triggering both ultrafast exocytosis and endocytosis and recruiting synaptic vesicles to the active zone.
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23
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Calorio C, Gavello D, Guarina L, Salio C, Sassoè-Pognetto M, Riganti C, Bianchi FT, Hofer NT, Tuluc P, Obermair GJ, Defilippi P, Balzac F, Turco E, Bett GC, Rasmusson RL, Carbone E. Impaired chromaffin cell excitability and exocytosis in autistic Timothy syndrome TS2-neo mouse rescued by L-type calcium channel blockers. J Physiol 2019; 597:1705-1733. [PMID: 30629744 DOI: 10.1113/jp277487] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 12/19/2018] [Indexed: 12/30/2022] Open
Abstract
KEY POINTS Tymothy syndrome (TS) is a multisystem disorder featuring cardiac arrhythmias, autism and adrenal gland dysfunction that originates from a de novo point mutation in the gene encoding the Cav1.2 (CACNA1C) L-type channel. To study the role of Cav1.2 channel signals in autism, the autistic TS2-neo mouse has been generated bearing the G406R point-mutation associated with TS type-2. Using heterozygous TS2-neo mice, we report that the G406R mutation reduces the rate of inactivation and shifts leftward the activation and inactivation of L-type channels, causing marked increase of resting Ca2+ influx ('window' Ca2+ current). The increased 'window current' causes marked reduction of NaV channel density, switches normal tonic firing to abnormal burst firing, reduces mitochondrial metabolism, induces cell swelling and decreases catecholamine release. Overnight incubations with nifedipine rescue NaV channel density, normal firing and the quantity of catecholamine released. We provide evidence that chromaffin cell malfunction derives from altered Cav1.2 channel gating. ABSTRACT L-type voltage-gated calcium (Cav1) channels have a key role in long-term synaptic plasticity, sensory transduction, muscle contraction and hormone release. A point mutation in the gene encoding Cav1.2 (CACNA1C) causes Tymothy syndrome (TS), a multisystem disorder featuring cardiac arrhythmias, autism spectrum disorder (ASD) and adrenal gland dysfunction. In the more severe type-2 form (TS2), the missense mutation G406R is on exon 8 coding for the IS6-helix of the Cav1.2 channel. The mutation causes reduced inactivation and induces autism. How this occurs and how Cav1.2 gating-changes alter cell excitability, neuronal firing and hormone release on a molecular basis is still largely unknown. Here, using the TS2-neo mouse model of TS we show that the G406R mutation altered excitability and reduced secretory activity in adrenal chromaffin cells (CCs). Specifically, the TS2 mutation reduced the rate of voltage-dependent inactivation and shifted leftward the activation and steady-state inactivation of L-type channels. This markedly increased the resting 'window' Ca2+ current that caused an increased percentage of CCs undergoing abnormal action potential (AP) burst firing, cell swelling, reduced mitochondrial metabolism and decreased catecholamine release. The increased 'window' Ca2+ current caused also decreased NaV channel density and increased steady-state inactivation, which contributed to the increased abnormal burst firing. Overnight incubation with the L-type channel blocker nifedipine rescued the normal AP firing of CCs, the density of functioning NaV channels and their steady-state inactivation. We provide evidence that CC malfunction derives from the altered Cav1.2 channel gating and that dihydropyridines are potential therapeutics for ASD.
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Affiliation(s)
- Chiara Calorio
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Daniela Gavello
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Laura Guarina
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Chiara Salio
- Department of Veterinary Sciences, University of Torino, Torino, Italy
| | - Marco Sassoè-Pognetto
- Department of Neuroscience Rita Levi Montalcini, University of Torino, Torino, Italy
| | - Chiara Riganti
- Department of Oncology, University of Torino, Torino, Italy
| | | | - Nadja T Hofer
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Petronel Tuluc
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Gerald J Obermair
- Department of Physiology & Medical Physics, Medical University of Innsbruck, Innsbruck, Austria
| | - Paola Defilippi
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Fiorella Balzac
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Emilia Turco
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Glenna C Bett
- Department of Physiology & Biophysics, State University of New York, Buffalo, NY, USA
| | - Randall L Rasmusson
- Department of Physiology & Biophysics, State University of New York, Buffalo, NY, USA
| | - Emilio Carbone
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
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24
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Pangrsic T, Singer JH, Koschak A. Voltage-Gated Calcium Channels: Key Players in Sensory Coding in the Retina and the Inner Ear. Physiol Rev 2019; 98:2063-2096. [PMID: 30067155 DOI: 10.1152/physrev.00030.2017] [Citation(s) in RCA: 60] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Calcium influx through voltage-gated Ca (CaV) channels is the first step in synaptic transmission. This review concerns CaV channels at ribbon synapses in primary sense organs and their specialization for efficient coding of stimuli in the physical environment. Specifically, we describe molecular, biochemical, and biophysical properties of the CaV channels in sensory receptor cells of the retina, cochlea, and vestibular apparatus, and we consider how such properties might change over the course of development and contribute to synaptic plasticity. We pay particular attention to factors affecting the spatial arrangement of CaV channels at presynaptic, ribbon-type active zones, because the spatial relationship between CaV channels and release sites has been shown to affect synapse function critically in a number of systems. Finally, we review identified synaptopathies affecting sensory systems and arising from dysfunction of L-type, CaV1.3, and CaV1.4 channels or their protein modulatory elements.
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Affiliation(s)
- Tina Pangrsic
- Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen and Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine , Göttingen, Germany ; Department of Biology, University of Maryland , College Park, Maryland ; and Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck , Innsbruck , Austria
| | - Joshua H Singer
- Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen and Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine , Göttingen, Germany ; Department of Biology, University of Maryland , College Park, Maryland ; and Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck , Innsbruck , Austria
| | - Alexandra Koschak
- Synaptic Physiology of Mammalian Vestibular Hair Cells Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen and Auditory Neuroscience Group, Max Planck Institute of Experimental Medicine , Göttingen, Germany ; Department of Biology, University of Maryland , College Park, Maryland ; and Pharmacology and Toxicology, Institute of Pharmacy, University of Innsbruck , Innsbruck , Austria
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25
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Niu J, Dick IE, Yang W, Bamgboye MA, Yue DT, Tomaselli G, Inoue T, Ben-Johny M. Allosteric regulators selectively prevent Ca 2+-feedback of Ca V and Na V channels. eLife 2018; 7:35222. [PMID: 30198845 PMCID: PMC6156082 DOI: 10.7554/elife.35222] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Accepted: 09/09/2018] [Indexed: 12/31/2022] Open
Abstract
Calmodulin (CaM) serves as a pervasive regulatory subunit of CaV1, CaV2, and NaV1 channels, exploiting a functionally conserved carboxy-tail element to afford dynamic Ca2+-feedback of cellular excitability in neurons and cardiomyocytes. Yet this modularity counters functional adaptability, as global changes in ambient CaM indiscriminately alter its targets. Here, we demonstrate that two structurally unrelated proteins, SH3 and cysteine-rich domain (stac) and fibroblast growth factor homologous factors (fhf) selectively diminish Ca2+/CaM-regulation of CaV1 and NaV1 families, respectively. The two proteins operate on allosteric sites within upstream portions of respective channel carboxy-tails, distinct from the CaM-binding interface. Generalizing this mechanism, insertion of a short RxxK binding motif into CaV1.3 carboxy-tail confers synthetic switching of CaM regulation by Mona SH3 domain. Overall, our findings identify a general class of auxiliary proteins that modify Ca2+/CaM signaling to individual targets allowing spatial and temporal orchestration of feedback, and outline strategies for engineering Ca2+/CaM signaling to individual targets.
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Affiliation(s)
- Jacqueline Niu
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, United States
| | - Ivy E Dick
- Department of Physiology, University of Maryland, Baltimore, United States
| | - Wanjun Yang
- Department of Cardiology, Johns Hopkins University, Baltimore, United States
| | | | - David T Yue
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, United States
| | - Gordon Tomaselli
- Department of Cardiology, Johns Hopkins University, Baltimore, United States
| | - Takanari Inoue
- Department of Cell Biology, Johns Hopkins University, Baltimore, United States.,Center for Cell Dynamics, Institute for Basic Biomedical Sciences, Johns Hopkins University, Baltimore, United States
| | - Manu Ben-Johny
- Department of Physiology and Cellular Biophysics, College of Physicians and Surgeons, Columbia University, New York, United States
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26
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Roles of Na +, Ca 2+, and K + channels in the generation of repetitive firing and rhythmic bursting in adrenal chromaffin cells. Pflugers Arch 2017; 470:39-52. [PMID: 28776261 DOI: 10.1007/s00424-017-2048-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 07/23/2017] [Indexed: 12/30/2022]
Abstract
Adrenal chromaffin cells (CCs) are the main source of circulating catecholamines (CAs) that regulate the body response to stress. Release of CAs is controlled neurogenically by the activity of preganglionic sympathetic neurons through trains of action potentials (APs). APs in CCs are generated by robust depolarization following the activation of nicotinic and muscarinic receptors that are highly expressed in CCs. Bovine, rat, mouse, and human CCs also express a composite array of Na+, K+, and Ca2+ channels that regulate the resting potential, shape the APs, and set the frequency of AP trains. AP trains of increasing frequency induce enhanced release of CAs. If the primary role of CCs is simply to relay preganglionic nerve commands to CA secretion, why should they express such a diverse set of ion channels? An answer to this comes from recent observations that, like in neurons, CCs undergo complex firing patterns of APs suggesting the existence of an intrinsic CC excitability (non-neurogenically controlled). Recent work has shown that CCs undergo occasional or persistent burst firing elicited by altered physiological conditions or deletion of pore-regulating auxiliary subunits. In this review, we aim to give a rationale to the role of the many ion channel types regulating CC excitability. We will first describe their functional properties and then analyze how they contribute to pacemaking, AP shape, and burst waveforms. We will also furnish clear indications on missing ion conductances that may be involved in pacemaking and highlight the contribution of the crucial channels involved in burst firing.
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27
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Grassmeyer JJ, Thoreson WB. Synaptic Ribbon Active Zones in Cone Photoreceptors Operate Independently from One Another. Front Cell Neurosci 2017; 11:198. [PMID: 28744203 PMCID: PMC5504102 DOI: 10.3389/fncel.2017.00198] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Accepted: 06/26/2017] [Indexed: 12/04/2022] Open
Abstract
Cone photoreceptors depolarize in darkness to release glutamate-laden synaptic vesicles. Essential to release is the synaptic ribbon, a structure that helps organize active zones by clustering vesicles near proteins that mediate exocytosis, including voltage-gated Ca2+ channels. Cone terminals have many ribbon-style active zones at which second-order neurons receive input. We asked whether there are functionally significant differences in local Ca2+ influx among ribbons in individual cones. We combined confocal Ca2+ imaging to measure Ca2+ influx at individual ribbons and patch clamp recordings to record whole-cell ICa in salamander cones. We found that the voltage for half-maximal activation (V50) of whole cell ICa in cones averaged −38.1 mV ± 3.05 mV (standard deviation [SD]), close to the cone membrane potential in darkness of ca. −40 mV. Ca2+ signals at individual ribbons varied in amplitude from one another and showed greater variability in V50 values than whole-cell ICa, suggesting that Ca2+ signals can differ significantly among ribbons within cones. After accounting for potential sources of technical variability in measurements of Ca2+ signals and for contributions from cone-to-cone differences in ICa, we found that the variability in V50 values for ribbon Ca2+ signals within individual cones showed a SD of 2.5 mV. Simulating local differences in Ca2+ channel activity at two ribbons by shifting the V50 value of ICa by ±2.5 mV (1 SD) about the mean suggests that when the membrane depolarizes to −40 mV, two ribbons could experience differences in Ca2+ influx of >45%. Further evidence that local Ca2+ changes at ribbons can be regulated independently was obtained in experiments showing that activation of inhibitory feedback from horizontal cells (HCs) to cones in paired recordings changed both amplitude and V50 of Ca2+ signals at individual ribbons. By varying the strength of synaptic output, differences in voltage dependence and amplitude of Ca2+ signals at individual ribbons shape the information transmitted from cones to downstream neurons in vision.
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Affiliation(s)
- Justin J Grassmeyer
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical CenterOmaha, NE, United States.,Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical CenterOmaha, NE, United States
| | - Wallace B Thoreson
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical CenterOmaha, NE, United States.,Truhlsen Eye Institute and Department of Ophthalmology and Visual Sciences, University of Nebraska Medical CenterOmaha, NE, United States
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28
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Lyu L, Gao Q, Xu J, Minobe E, Zhu T, Kameyama M. A new interaction between proximal and distal C-terminus of Cav1.2 channels. J Pharmacol Sci 2017; 133:240-246. [DOI: 10.1016/j.jphs.2017.03.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Revised: 02/16/2017] [Accepted: 03/03/2017] [Indexed: 11/16/2022] Open
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29
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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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30
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Ca 2+-binding protein 2 inhibits Ca 2+-channel inactivation in mouse inner hair cells. Proc Natl Acad Sci U S A 2017; 114:E1717-E1726. [PMID: 28183797 DOI: 10.1073/pnas.1617533114] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Ca2+-binding protein 2 (CaBP2) inhibits the inactivation of heterologously expressed voltage-gated Ca2+ channels of type 1.3 (CaV1.3) and is defective in human autosomal-recessive deafness 93 (DFNB93). Here, we report a newly identified mutation in CABP2 that causes a moderate hearing impairment likely via nonsense-mediated decay of CABP2-mRNA. To study the mechanism of hearing impairment resulting from CABP2 loss of function, we disrupted Cabp2 in mice (Cabp2LacZ/LacZ ). CaBP2 was expressed by cochlear hair cells, preferentially in inner hair cells (IHCs), and was lacking from the postsynaptic spiral ganglion neurons (SGNs). Cabp2LacZ/LacZ mice displayed intact cochlear amplification but impaired auditory brainstem responses. Patch-clamp recordings from Cabp2LacZ/LacZ IHCs revealed enhanced Ca2+-channel inactivation. The voltage dependence of activation and the number of Ca2+ channels appeared normal in Cabp2LacZ/LacZ mice, as were ribbon synapse counts. Recordings from single SGNs showed reduced spontaneous and sound-evoked firing rates. We propose that CaBP2 inhibits CaV1.3 Ca2+-channel inactivation, and thus sustains the availability of CaV1.3 Ca2+ channels for synaptic sound encoding. Therefore, we conclude that human deafness DFNB93 is an auditory synaptopathy.
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31
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Liu N, Yang Y, Ge L, Liu M, Colecraft HM, Liu X. Cooperative and acute inhibition by multiple C-terminal motifs of L-type Ca 2+ channels. eLife 2017; 6. [PMID: 28059704 PMCID: PMC5279948 DOI: 10.7554/elife.21989] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 01/05/2017] [Indexed: 12/31/2022] Open
Abstract
Inhibitions and antagonists of L-type Ca2+ channels are important to both research and therapeutics. Here, we report C-terminus mediated inhibition (CMI) for CaV1.3 that multiple motifs coordinate to tune down Ca2+ current and Ca2+ influx toward the lower limits determined by end-stage CDI (Ca2+-dependent inactivation). Among IQV (preIQ3-IQ domain), PCRD and DCRD (proximal or distal C-terminal regulatory domain), spatial closeness of any two modules, e.g., by constitutive fusion, facilitates the trio to form the complex, compete against calmodulin, and alter the gating. Acute CMI by rapamycin-inducible heterodimerization helps reconcile the concurrent activation/inactivation attenuations to ensure Ca2+ influx is reduced, in that Ca2+ current activated by depolarization is potently (~65%) inhibited at the peak (full activation), but not later on (end-stage inactivation, ~300 ms). Meanwhile, CMI provides a new paradigm to develop CaV1 inhibitors, the therapeutic potential of which is implied by computational modeling of CaV1.3 dysregulations related to Parkinson’s disease. DOI:http://dx.doi.org/10.7554/eLife.21989.001 All cells need calcium ions to stay healthy, but having too many calcium ions can interfere with important processes in the cell and cause severe problems. Proteins known as calcium channels on the cell surface allow calcium ions to flow into the cell from the surrounding environment. Cells carefully control the opening and closing of these channels to prevent too many calcium ions entering the cell at once. CaV1.3 channels are a type of calcium channel that are important for the heart and brain to work properly. Defects in CaV1.3 channels can lead to irregular heart rhythms and neurodegenerative diseases such as Parkinson’s disease. Studies have shown that part of the CaV1.3 channel that sits inside the cell – known as the “tail” – responds to increases in the levels of calcium ions inside the cell by closing the channel. The tail region of CaV1.3 contains three modules, but how these modules work together to regulate channel activity is not clear. Liu, Yang et al. investigated whether the three modules need to be physically connected to each other in the channel protein. For the experiments, several versions of the protein were constructed with different combinations of tail modules being directly linked as part of the same molecule or present as separate molecules. When any two modules were directly linked, the third module could bind to them and this was enough to close the CaV1.3 channel. However, the channel did not close if the modules were totally isolated from each other as three separate molecules. Certain types of neurons in the brain produce electrical signals in a rhythmic fashion that depends on CaV1.3 channels. In Parkinson’s disease, increased movement of calcium ions into these neurons via CaV1.3 channels interferes with the rhythms of the signals and can cause these cells to die. Liu, Yang et al. performed computer simulations to analyse the effects of closing CaV1.3 channels in these neurons. The results suggest that this can restore normal rhythms of electrical activity and prevent these cells from dying. The next step is to understand the molecular details of how the tail region closes CaV1.3 channels and its role in healthy and diseased cells. This may lead to new ways to block CaV1.3 channels in different types of diseases. DOI:http://dx.doi.org/10.7554/eLife.21989.002
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Affiliation(s)
- Nan Liu
- X-Lab for Transmembrane Signaling Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China
| | - Yaxiong Yang
- X-Lab for Transmembrane Signaling Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China
| | - Lin Ge
- X-Lab for Transmembrane Signaling Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China
| | - Min Liu
- X-Lab for Transmembrane Signaling Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China
| | - Henry M Colecraft
- Department of Physiology and Cellular Biophysics, Columbia University, New York, United States
| | - Xiaodong Liu
- X-Lab for Transmembrane Signaling Research, Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China.,School of Life Sciences, Tsinghua University, Beijing, China.,IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, China
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Stanika R, Campiglio M, Pinggera A, Lee A, Striessnig J, Flucher BE, Obermair GJ. Splice variants of the Ca V1.3 L-type calcium channel regulate dendritic spine morphology. Sci Rep 2016; 6:34528. [PMID: 27708393 PMCID: PMC5052568 DOI: 10.1038/srep34528] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 09/15/2016] [Indexed: 01/13/2023] Open
Abstract
Dendritic spines are the postsynaptic compartments of glutamatergic synapses in the brain. Their number and shape are subject to change in synaptic plasticity and neurological disorders including autism spectrum disorders and Parkinson’s disease. The L-type calcium channel CaV1.3 constitutes an important calcium entry pathway implicated in the regulation of spine morphology. Here we investigated the importance of full-length CaV1.3L and two C-terminally truncated splice variants (CaV1.342A and CaV1.343S) and their modulation by densin-180 and shank1b for the morphology of dendritic spines of cultured hippocampal neurons. Live-cell immunofluorescence and super-resolution microscopy of epitope-tagged CaV1.3L revealed its localization at the base-, neck-, and head-region of dendritic spines. Expression of the short splice variants or deletion of the C-terminal PDZ-binding motif in CaV1.3L induced aberrant dendritic spine elongation. Similar morphological alterations were induced by co-expression of densin-180 or shank1b with CaV1.3L and correlated with increased CaV1.3 currents and dendritic calcium signals in transfected neurons. Together, our findings suggest a key role of CaV1.3 in regulating dendritic spine structure. Under physiological conditions it may contribute to the structural plasticity of glutamatergic synapses. Conversely, altered regulation of CaV1.3 channels may provide an important mechanism in the development of postsynaptic aberrations associated with neurodegenerative disorders.
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Affiliation(s)
- Ruslan Stanika
- Division of Physiology, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Marta Campiglio
- Division of Physiology, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Alexandra Pinggera
- Department of Pharmacology and Toxicology, University of Innsbruck, 6020 Innsbruck, Austria
| | - Amy Lee
- Department of Molecular Physiology and Biophysics, Otolaryngology Head-Neck Surgery, and Neurology, University of Iowa, Iowa City, IA 52242, USA
| | - Jörg Striessnig
- Department of Pharmacology and Toxicology, University of Innsbruck, 6020 Innsbruck, Austria
| | - Bernhard E Flucher
- Division of Physiology, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Gerald J Obermair
- Division of Physiology, Medical University Innsbruck, 6020 Innsbruck, Austria
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Hair cells use active zones with different voltage dependence of Ca2+ influx to decompose sounds into complementary neural codes. Proc Natl Acad Sci U S A 2016; 113:E4716-25. [PMID: 27462107 DOI: 10.1073/pnas.1605737113] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
For sounds of a given frequency, spiral ganglion neurons (SGNs) with different thresholds and dynamic ranges collectively encode the wide range of audible sound pressures. Heterogeneity of synapses between inner hair cells (IHCs) and SGNs is an attractive candidate mechanism for generating complementary neural codes covering the entire dynamic range. Here, we quantified active zone (AZ) properties as a function of AZ position within mouse IHCs by combining patch clamp and imaging of presynaptic Ca(2+) influx and by immunohistochemistry. We report substantial AZ heterogeneity whereby the voltage of half-maximal activation of Ca(2+) influx ranged over ∼20 mV. Ca(2+) influx at AZs facing away from the ganglion activated at weaker depolarizations. Estimates of AZ size and Ca(2+) channel number were correlated and larger when AZs faced the ganglion. Disruption of the deafness gene GIPC3 in mice shifted the activation of presynaptic Ca(2+) influx to more hyperpolarized potentials and increased the spontaneous SGN discharge. Moreover, Gipc3 disruption enhanced Ca(2+) influx and exocytosis in IHCs, reversed the spatial gradient of maximal Ca(2+) influx in IHCs, and increased the maximal firing rate of SGNs at sound onset. We propose that IHCs diversify Ca(2+) channel properties among AZs and thereby contribute to decomposing auditory information into complementary representations in SGNs.
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Haeseleer F, Williams B, Lee A. Characterization of C-terminal Splice Variants of Cav1.4 Ca2+ Channels in Human Retina. J Biol Chem 2016; 291:15663-73. [PMID: 27226626 DOI: 10.1074/jbc.m116.731737] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2016] [Indexed: 11/06/2022] Open
Abstract
Voltage-gated Ca(2+) channels (Cav) undergo extensive alternative splicing that greatly enhances their functional diversity in excitable cells. Here, we characterized novel splice variants of the cytoplasmic C-terminal domain of Cav1.4 Ca(2+) channels that regulate neurotransmitter release in photoreceptors in the retina. These variants lack a portion of exon 45 and/or the entire exon 47 (Cav1.4Δex p45, Cav1.4Δex 47, Cav1.4Δex p45,47) and are expressed in the retina of primates but not mice. Although the electrophysiological properties of Cav1.4Δex p45 are similar to those of full-length channels (Cav1.4FL), skipping of exon 47 dramatically alters Cav1.4 function. Deletion of exon 47 removes part of a C-terminal automodulatory domain (CTM) previously shown to suppress Ca(2+)-dependent inactivation (CDI) and to cause a positive shift in the voltage dependence of channel activation. Exon 47 is crucial for these effects of the CTM because variants lacking this exon show intense CDI and activate at more hyperpolarized voltages than Cav1.4FL The robust CDI of Cav1.4Δex 47 is suppressed by CaBP4, a regulator of Cav1.4 channels in photoreceptors. Although CaBP4 enhances activation of Cav1.4FL, Cav1.4Δex 47 shows similar voltage-dependent activation in the presence and absence of CaBP4. We conclude that exon 47 encodes structural determinants that regulate CDI and voltage-dependent activation of Cav1.4, and is necessary for modulation of channel activation by CaBP4.
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Affiliation(s)
- Françoise Haeseleer
- From the Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195 and
| | - Brittany Williams
- the Departments of Molecular Physiology and Biophysics, Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, Iowa 52242
| | - Amy Lee
- the Departments of Molecular Physiology and Biophysics, Otolaryngology Head-Neck Surgery, Neurology, and
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Duda J, Pötschke C, Liss B. Converging roles of ion channels, calcium, metabolic stress, and activity pattern of Substantia nigra dopaminergic neurons in health and Parkinson's disease. J Neurochem 2016; 139 Suppl 1:156-178. [PMID: 26865375 PMCID: PMC5095868 DOI: 10.1111/jnc.13572] [Citation(s) in RCA: 100] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 02/03/2016] [Accepted: 02/05/2016] [Indexed: 12/18/2022]
Abstract
Dopamine‐releasing neurons within the Substantia nigra (SN DA) are particularly vulnerable to degeneration compared to other dopaminergic neurons. The age‐dependent, progressive loss of these neurons is a pathological hallmark of Parkinson's disease (PD), as the resulting loss of striatal dopamine causes its major movement‐related symptoms. SN DA neurons release dopamine from their axonal terminals within the dorsal striatum, and also from their cell bodies and dendrites within the midbrain in a calcium‐ and activity‐dependent manner. Their intrinsically generated and metabolically challenging activity is created and modulated by the orchestrated function of different ion channels and dopamine D2‐autoreceptors. Here, we review increasing evidence that the mechanisms that control activity patterns and calcium homeostasis of SN DA neurons are not only crucial for their dopamine release within a physiological range but also modulate their mitochondrial and lysosomal activity, their metabolic stress levels, and their vulnerability to degeneration in PD. Indeed, impaired calcium homeostasis, lysosomal and mitochondrial dysfunction, and metabolic stress in SN DA neurons represent central converging trigger factors for idiopathic and familial PD. We summarize double‐edged roles of ion channels, activity patterns, calcium homeostasis, and related feedback/feed‐forward signaling mechanisms in SN DA neurons for maintaining and modulating their physiological function, but also for contributing to their vulnerability in PD‐paradigms. We focus on the emerging roles of maintained neuronal activity and calcium homeostasis within a physiological bandwidth, and its modulation by PD‐triggers, as well as on bidirectional functions of voltage‐gated L‐type calcium channels and metabolically gated ATP‐sensitive potassium (K‐ATP) channels, and their probable interplay in health and PD.
We propose that SN DA neurons possess several feedback and feed‐forward mechanisms to protect and adapt their activity‐pattern and calcium‐homeostasis within a physiological bandwidth, and that PD‐trigger factors can narrow this bandwidth. We summarize roles of ion channels in this view, and findings documenting that both, reduced as well as elevated activity and associated calcium‐levels can trigger SN DA degeneration.
This article is part of a special issue on Parkinson disease.
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Affiliation(s)
- Johanna Duda
- Department of Applied Physiology, Ulm University, Ulm, Germany
| | | | - Birgit Liss
- Department of Applied Physiology, Ulm University, Ulm, Germany.
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Barrett PQ, Guagliardo NA, Klein PM, Hu C, Breault DT, Beenhakker MP. Role of voltage-gated calcium channels in the regulation of aldosterone production from zona glomerulosa cells of the adrenal cortex. J Physiol 2016; 594:5851-5860. [PMID: 26845064 DOI: 10.1113/jp271896] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 11/28/2015] [Indexed: 11/08/2022] Open
Abstract
Zona glomerulosa cells (ZG) of the adrenal gland constantly integrate fluctuating ionic, hormonal and paracrine signals to control the synthesis and secretion of aldosterone. These signals modulate Ca2+ levels, which provide the critical second messenger to drive steroid hormone production. Angiotensin II is a hormone known to modulate the activity of voltage-dependent L- and T-type Ca2+ channels that are expressed on the plasma membrane of ZG cells in many species. Because the ZG cell maintains a resting membrane voltage of approximately -85 mV and has been considered electrically silent, low voltage-activated T-type Ca2+ channels are assumed to provide the primary Ca2+ signal that drives aldosterone production. However, this view has recently been challenged by human genetic studies identifying somatic gain-of-function mutations in L-type CaV 1.3 channels in aldosterone-producing adenomas of patients with primary hyperaldosteronism. We provide a review of these assumptions and challenges, and update our understanding of the state of the ZG cell in a layer in which native cellular associations are preserved. This updated view of Ca2+ signalling in ZG cells provides a unifying mechanism that explains how transiently activating CaV 3.2 channels can generate a significant and recurring Ca2+ signal, and how CaV 1.3 channels may contribute to the Ca2+ signal that drives aldosterone production.
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Affiliation(s)
- Paula Q Barrett
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22947, USA
| | - Nick A Guagliardo
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22947, USA
| | - Peter M Klein
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22947, USA
| | - Changlong Hu
- Department of Physiology and Biophysics, School of Life Sciences, Institutes of Brain Science, Fudan University, Shanghai, 200433, China
| | - David T Breault
- Division of Endocrinology, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Mark P Beenhakker
- Department of Pharmacology, University of Virginia, Charlottesville, VA, 22947, USA.
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