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Chen C, Sun T, Yin M, Yan Z, Yu W, Long H, Wang L, Liao X, Yan Z, Li W, Lyu Q. Ionomycin-induced mouse oocyte activation can disrupt preimplantation embryo development through increased reactive oxygen species reaction and DNA damage. Mol Hum Reprod 2021; 26:773-783. [PMID: 32697831 DOI: 10.1093/molehr/gaaa056] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 07/01/2020] [Indexed: 12/19/2022] Open
Abstract
Oocyte activation induced by calcium oscillations is an important process in normal fertilization and subsequent embryogenesis. In the clinical-assisted reproduction, artificial oocyte activation (AOA) is an effective method to improve the clinical outcome of patients with null or low fertilization rate after ICSI. However, little is known about the effect of AOA on preimplantation embryo development in cases with normal fertilization by ICSI. Here, we used ionomycin at different concentrations to activate oocytes after ICSI with normal sperm and evaluated energy metabolism and preimplantation embryo development. We found that a high concentration of ionomycin increased the frequency and amplitude of calcium oscillation patterns, affecting the balance of mitochondrial energy metabolism, leading to increased reactive oxygen species (ROS) and decreased ATP. Eventually, it increases DNA damage and decreases blastocyst formation. In addition, the addition of vitamin C to the culture medium ameliorated the increase in ROS and DNA damage and rescued the abnormal embryo development caused by excessive ionomycin activation. This study provides a perspective that the improper application of AOA may have adverse effects on preimplantation embryo development. Thus, clinical AOA treatment should be cautiously administered.
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Affiliation(s)
- Chen Chen
- Department of Assisted Reproduction, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Tingye Sun
- Department of Assisted Reproduction, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China.,Department of Gynaecology, Guangdong Second Provincial General Hospital, Guangzhou, People's Republic of China
| | - Mingru Yin
- Department of Assisted Reproduction, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Zhiguang Yan
- Department of Assisted Reproduction, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Weina Yu
- Department of Assisted Reproduction, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Hui Long
- Department of Assisted Reproduction, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Li Wang
- Department of Assisted Reproduction, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Xiaoyu Liao
- Department of Assisted Reproduction, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Zheng Yan
- Department of Assisted Reproduction, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Wenzhi Li
- Department of Assisted Reproduction, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
| | - Qifeng Lyu
- Department of Assisted Reproduction, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China
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2
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Rivas S, Hanif K, Chakouri N, Ben-Johny M. Probing ion channel macromolecular interactions using fluorescence resonance energy transfer. Methods Enzymol 2021; 653:319-347. [PMID: 34099178 DOI: 10.1016/bs.mie.2021.01.047] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Ion channels are macromolecular complexes whose functions are exquisitely tuned by interacting proteins. Fluorescence resonance energy transfer (FRET) is a powerful methodology that is adept at quantifying ion channel protein-protein interactions in living cells. For FRET experiments, the interacting partners are tagged with appropriate donor and acceptor fluorescent proteins. If the fluorescently-labeled molecules are in close proximity, then photoexcitation of the donor results in non-radiative energy transfer to the acceptor, and subsequent fluorescence emission of the acceptor. The stoichiometry of ion channel interactions and their relative binding affinities can be deduced by quantifying both the FRET efficiency and the total number of donors and acceptors in a given cell. In this chapter, we discuss general considerations for FRET analysis of biological interactions, various strategies for estimating FRET efficiencies, and detailed protocols for construction of binding curves and determination of stoichiometry. We focus on implementation of FRET assays using a flow cytometer given its amenability for high-throughput data acquisition, enhanced accessibility, and robust analysis. This versatile methodology permits mechanistic dissection of dynamic changes in ion channel interactions.
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Affiliation(s)
- Sharen Rivas
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, United States
| | | | - Nourdine Chakouri
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, United States
| | - Manu Ben-Johny
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY, United States.
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3
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Sang L, Vieira DCO, Yue DT, Ben-Johny M, Dick IE. The molecular basis of the inhibition of Ca V1 calcium-dependent inactivation by the distal carboxy tail. J Biol Chem 2021; 296:100502. [PMID: 33667546 PMCID: PMC8054141 DOI: 10.1016/j.jbc.2021.100502] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 02/25/2021] [Accepted: 03/01/2021] [Indexed: 12/26/2022] Open
Abstract
Ca2+/calmodulin-dependent inactivation (CDI) of CaV channels is a critical regulatory process that tunes the kinetics of Ca2+ entry for different cell types and physiologic responses. CDI is mediated by calmodulin (CaM), which is bound to the IQ domain of the CaV carboxy tail. This modulatory process is tailored by alternative splicing such that select splice variants of CaV1.3 and CaV1.4 contain a long distal carboxy tail (DCT). The DCT harbors an inhibitor of CDI (ICDI) module that competitively displaces CaM from the IQ domain, thereby diminishing CDI. While this overall mechanism is now well described, the detailed interactions required for ICDI binding to the IQ domain are yet to be elucidated. Here, we perform alanine-scanning mutagenesis of the IQ and ICDI domains and evaluate the contribution of neighboring regions to CDI inhibition. Through FRET binding analysis, we identify functionally relevant residues within the CaV1.3 IQ domain and the CaV1.4 ICDI and nearby A region, which are required for high-affinity IQ/ICDI binding. Importantly, patch-clamp recordings demonstrate that disruption of this interaction commensurately diminishes ICDI function resulting in the re-emergence of CDI in mutant channels. Furthermore, CaV1.2 channels harbor a homologous DCT; however, the ICDI region of this channel does not appear to appreciably modulate CaV1.2 CDI. Yet coexpression of CaV1.2 ICDI with select CaV1.3 splice variants significantly disrupts CDI, implicating a cross-channel modulatory scheme in cells expressing both channel subtypes. In all, these findings provide new insights into a molecular rheostat that fine-tunes Ca2+-entry and supports normal neuronal and cardiac function.
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Affiliation(s)
- Lingjie Sang
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Daiana C O Vieira
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - David T Yue
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Manu Ben-Johny
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Department of Physiology and Cellular Biophysics, Columbia University, New York, New York, USA
| | - Ivy E Dick
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
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4
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Chakouri N, Diaz J, Yang PS, Ben-Johny M. Ca V channels reject signaling from a second CaM in eliciting Ca 2+-dependent feedback regulation. J Biol Chem 2020; 295:14948-14962. [PMID: 32820053 DOI: 10.1074/jbc.ra120.013777] [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: 04/06/2020] [Revised: 08/18/2020] [Indexed: 11/06/2022] Open
Abstract
Calmodulin (CaM) regulation of voltage-gated calcium (CaV1-2) channels is a powerful Ca2+-feedback mechanism to adjust channel activity in response to Ca2+ influx. Despite progress in resolving mechanisms of CaM-CaV feedback, the stoichiometry of CaM interaction with CaV channels remains ambiguous. Functional studies that tethered CaM to CaV1.2 suggested that a single CaM sufficed for Ca2+ feedback, yet biochemical, FRET, and structural studies showed that multiple CaM molecules interact with distinct interfaces within channel cytosolic segments, suggesting that functional Ca2+ regulation may be more nuanced. Resolving this ambiguity is critical as CaM is enriched in subcellular domains where CaV channels reside, such as the cardiac dyad. We here localized multiple CaMs to the CaV nanodomain by tethering either WT or mutant CaM that lack Ca2+-binding capacity to the pore-forming α-subunit of CaV1.2, CaV1.3, and CaV2.1 and/or the auxiliary β2A subunit. We observed that a single CaM tethered to either the α or β2A subunit tunes Ca2+ regulation of CaV channels. However, when multiple CaMs are localized concurrently, CaV channels preferentially respond to signaling from the α-subunit-tethered CaM. Mechanistically, the introduction of a second IQ domain to the CaV1.3 carboxyl tail switched the apparent functional stoichiometry, permitting two CaMs to mediate functional regulation. In all, Ca2+ feedback of CaV channels depends exquisitely on a single CaM preassociated with the α-subunit carboxyl tail. Additional CaMs that colocalize with the channel complex are unable to trigger Ca2+-dependent feedback of channel gating but may support alternate regulatory functions.
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Affiliation(s)
- Nourdine Chakouri
- Department of Physiology and Cellular Biophysics, Columbia University, New York, New York, USA
| | - Johanna Diaz
- Department of Physiology and Cellular Biophysics, Columbia University, New York, New York, USA
| | - Philemon S Yang
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, USA
| | - Manu Ben-Johny
- Department of Physiology and Cellular Biophysics, Columbia University, New York, New York, USA.
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5
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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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6
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Van Hook MJ, Nawy S, Thoreson WB. Voltage- and calcium-gated ion channels of neurons in the vertebrate retina. Prog Retin Eye Res 2019; 72:100760. [PMID: 31078724 PMCID: PMC6739185 DOI: 10.1016/j.preteyeres.2019.05.001] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/25/2019] [Accepted: 05/01/2019] [Indexed: 02/06/2023]
Abstract
In this review, we summarize studies investigating the types and distribution of voltage- and calcium-gated ion channels in the different classes of retinal neurons: rods, cones, horizontal cells, bipolar cells, amacrine cells, interplexiform cells, and ganglion cells. We discuss differences among cell subtypes within these major cell classes, as well as differences among species, and consider how different ion channels shape the responses of different neurons. For example, even though second-order bipolar and horizontal cells do not typically generate fast sodium-dependent action potentials, many of these cells nevertheless possess fast sodium currents that can enhance their kinetic response capabilities. Ca2+ channel activity can also shape response kinetics as well as regulating synaptic release. The L-type Ca2+ channel subtype, CaV1.4, expressed in photoreceptor cells exhibits specific properties matching the particular needs of these cells such as limited inactivation which allows sustained channel activity and maintained synaptic release in darkness. The particular properties of K+ and Cl- channels in different retinal neurons shape resting membrane potentials, response kinetics and spiking behavior. A remaining challenge is to characterize the specific distributions of ion channels in the more than 100 individual cell types that have been identified in the retina and to describe how these particular ion channels sculpt neuronal responses to assist in the processing of visual information by the retina.
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Affiliation(s)
- Matthew J Van Hook
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE, USA
| | - Scott Nawy
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE, USA; Department Pharmacology & Experimental Neuroscience(2), University of Nebraska Medical Center, Omaha, NE, USA
| | - Wallace B Thoreson
- Truhlsen Eye Institute, Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, NE, USA; Department Pharmacology & Experimental Neuroscience(2), University of Nebraska Medical Center, Omaha, NE, USA.
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7
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Burgoyne RD, Helassa N, McCue HV, Haynes LP. Calcium Sensors in Neuronal Function and Dysfunction. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a035154. [PMID: 30833454 DOI: 10.1101/cshperspect.a035154] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Calcium signaling in neurons as in other cell types can lead to varied changes in cellular function. Neuronal Ca2+ signaling processes have also become adapted to modulate the function of specific pathways over a wide variety of time domains and these can have effects on, for example, axon outgrowth, neuronal survival, and changes in synaptic strength. Ca2+ also plays a key role in synapses as the trigger for fast neurotransmitter release. Given its physiological importance, abnormalities in neuronal Ca2+ signaling potentially underlie many different neurological and neurodegenerative diseases. The mechanisms by which changes in intracellular Ca2+ concentration in neurons can bring about diverse responses is underpinned by the roles of ubiquitous or specialized neuronal Ca2+ sensors. It has been established that synaptotagmins have key functions in neurotransmitter release, and, in addition to calmodulin, other families of EF-hand-containing neuronal Ca2+ sensors, including the neuronal calcium sensor (NCS) and the calcium-binding protein (CaBP) families, play important physiological roles in neuronal Ca2+ signaling. It has become increasingly apparent that these various Ca2+ sensors may also be crucial for aspects of neuronal dysfunction and disease either indirectly or directly as a direct consequence of genetic variation or mutations. An understanding of the molecular basis for the regulation of the targets of the Ca2+ sensors and the physiological roles of each protein in identified neurons may contribute to future approaches to the development of treatments for a variety of human neuronal disorders.
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Affiliation(s)
- Robert D Burgoyne
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Nordine Helassa
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Hannah V McCue
- Centre for Genomic Research, University of Liverpool, Liverpool, United Kingdom
| | - Lee P Haynes
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
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8
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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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9
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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: 62] [Impact Index Per Article: 12.4] [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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10
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Williams B, Haeseleer F, Lee A. Splicing of an automodulatory domain in Ca v1.4 Ca 2+ channels confers distinct regulation by calmodulin. J Gen Physiol 2018; 150:1676-1687. [PMID: 30355583 PMCID: PMC6279360 DOI: 10.1085/jgp.201812140] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 10/03/2018] [Indexed: 12/17/2022] Open
Abstract
Cav1.4 Ca2+ channels provide maintained Ca2+ entry to support sustained neurotransmitter release, but a retinal splice variant exhibits calmodulin-dependent inactivation. Williams et al. show that the N lobe of calmodulin is involved in this process as well as Ca2+-dependent enhancement of channel activation. Ca2+ influx through Cav1.4 L-type Ca2+ channels supports the sustained release of glutamate from photoreceptor synaptic terminals in darkness, a process that is critical for vision. Consistent with this role, Cav1.4 exhibits weak Ca2+-dependent inactivation (CDI)—a negative feedback regulation mediated by Ca2+-bound calmodulin (CaM). CaM binds to a conserved IQ domain in the proximal C-terminal domain of Cav channels, but in Cav1.4, a C-terminal modulatory domain (CTM) disrupts interactions with CaM. Exon 47 encodes a portion of the CTM and is deleted in a Cav1.4 splice variant (Cav1.4Δex47) that is highly expressed in the human retina. Cav1.4Δex47 exhibits CDI and enhanced voltage-dependent activation, similar to that caused by a mutation that is associated with congenital stationary night blindness type 2, in which the CTM is deleted (K1591X). The presence of CDI and very negative activation thresholds in a naturally occurring variant of Cav1.4 are perplexing considering that these properties are expected to be maladaptive for visual signaling and result in night blindness in the case of K1591X. Here we show that Cav1.4Δex47 and K1591X exhibit fundamental differences in their regulation by CaM. In Cav1.4Δex47, CDI requires both the N-terminal (N lobe) and C-terminal (C lobe) lobes of CaM to bind Ca2+, whereas CDI in K1591X is driven mainly by Ca2+ binding to the C lobe. Moreover, the CaM N lobe causes a Ca2+-dependent enhancement of activation of Cav1.4Δex47 but not K1591X. We conclude that the residual CTM in Cav1.4Δex47 enables a form of CaM N lobe regulation of activation and CDI that is absent in K1591X. Interaction with the N lobe of CaM, which is more sensitive to global elevations in cytosolic Ca2+ than the C lobe, may allow Cav1.4Δex47 to be modulated by a wider range of synaptic Ca2+ concentrations than K1591X; this may distinguish the normal physiological function of Cav1.4Δex47 from the pathological consequences of K1591X.
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Affiliation(s)
- Brittany Williams
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA.,Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA.,Iowa Neuroscience Institute, University of Iowa, Iowa City, IA
| | - Françoise Haeseleer
- Department of Physiology and Biophysics, University of Washington, Seattle, WA
| | - Amy Lee
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA .,Interdisciplinary Graduate Program in Neuroscience, University of Iowa, Iowa City, IA.,Iowa Neuroscience Institute, University of Iowa, Iowa City, IA.,Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, IA.,Department of Neurology, University of Iowa, Iowa City, IA
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11
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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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12
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Niu J, Yang W, Yue DT, Inoue T, Ben-Johny M. Duplex signaling by CaM and Stac3 enhances Ca V1.1 function and provides insights into congenital myopathy. J Gen Physiol 2018; 150:1145-1161. [PMID: 29950399 PMCID: PMC6080896 DOI: 10.1085/jgp.201812005] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2018] [Revised: 03/23/2018] [Accepted: 05/11/2018] [Indexed: 01/24/2023] Open
Abstract
CaV1.1 is essential for skeletal muscle excitation-contraction coupling. Its functional expression is tuned by numerous regulatory proteins, yet underlying modulatory mechanisms remain ambiguous as CaV1.1 fails to function in heterologous systems. In this study, by dissecting channel trafficking versus gating, we evaluated the requirements for functional CaV1.1 in heterologous systems. Although coexpression of the auxiliary β subunit is sufficient for surface-membrane localization, this baseline trafficking is weak, and channels elicit a diminished open probability. The regulatory proteins calmodulin and stac3 independently enhance channel trafficking and gating via their interaction with the CaV1.1 carboxy terminus. Myopathic stac3 mutations weaken channel binding and diminish trafficking. Our findings demonstrate that multiple regulatory proteins orchestrate CaV1.1 function via duplex mechanisms. Our work also furnishes insights into the pathophysiology of stac3-associated congenital myopathy and reveals novel avenues for pharmacological intervention.
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Affiliation(s)
- Jacqueline Niu
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD
| | - Wanjun Yang
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD
| | | | - Takanari Inoue
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD
- Department of Cell Biology, Johns Hopkins University, Baltimore, MD
- Center for Cell Dynamics, Institute for Basic Biomedical Sciences, Johns Hopkins University, Baltimore, MD
| | - Manu Ben-Johny
- Department of Physiology and Cellular Biophysics, Columbia University, New York, NY
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13
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Waldner DM, Bech-Hansen NT, Stell WK. Channeling Vision: Ca V1.4-A Critical Link in Retinal Signal Transmission. BIOMED RESEARCH INTERNATIONAL 2018; 2018:7272630. [PMID: 29854783 PMCID: PMC5966690 DOI: 10.1155/2018/7272630] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Accepted: 02/15/2018] [Indexed: 01/09/2023]
Abstract
Voltage-gated calcium channels (VGCC) are key to many biological functions. Entry of Ca2+ into cells is essential for initiating or modulating important processes such as secretion, cell motility, and gene transcription. In the retina and other neural tissues, one of the major roles of Ca2+-entry is to stimulate or regulate exocytosis of synaptic vesicles, without which synaptic transmission is impaired. This review will address the special properties of one L-type VGCC, CaV1.4, with particular emphasis on its role in transmission of visual signals from rod and cone photoreceptors (hereafter called "photoreceptors," to the exclusion of intrinsically photoreceptive retinal ganglion cells) to the second-order retinal neurons, and the pathological effects of mutations in the CACNA1F gene which codes for the pore-forming α1F subunit of CaV1.4.
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Affiliation(s)
- D. M. Waldner
- Department of Neuroscience, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - N. T. Bech-Hansen
- Department of Medical Genetics and Department of Surgery, Alberta Children's Hospital Research Institute, and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - W. K. Stell
- Department of Cell Biology and Anatomy and Department of Surgery, Hotchkiss Brain Institute, and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
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14
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Zhang Q, Li S, Wong HTC, He XJ, Beirl A, Petralia RS, Wang YX, Kindt KS. Synaptically silent sensory hair cells in zebrafish are recruited after damage. Nat Commun 2018; 9:1388. [PMID: 29643351 PMCID: PMC5895622 DOI: 10.1038/s41467-018-03806-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 03/09/2018] [Indexed: 01/31/2023] Open
Abstract
Analysis of mechanotransduction among ensembles of sensory hair cells in vivo is challenging in many species. To overcome this challenge, we used optical indicators to investigate mechanotransduction among collections of hair cells in intact zebrafish. Our imaging reveals a previously undiscovered disconnect between hair-cell mechanosensation and synaptic transmission. We show that saturating mechanical stimuli able to open mechanically gated channels are unexpectedly insufficient to evoke vesicle fusion in the majority of hair cells. Although synaptically silent, latent hair cells can be rapidly recruited after damage, demonstrating that they are synaptically competent. Therefore synaptically silent hair cells may be an important reserve that acts to maintain sensory function. Our results demonstrate a previously unidentified level of complexity in sculpting sensory transmission from the periphery.
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Affiliation(s)
- Qiuxiang Zhang
- Section on Sensory Cell Development and Function, NIDCD/National Institutes of Health, Bethesda, MD, 20892, USA
| | - Suna Li
- Section on Sensory Cell Development and Function, NIDCD/National Institutes of Health, Bethesda, MD, 20892, USA
| | - Hiu-Tung C Wong
- Section on Sensory Cell Development and Function, NIDCD/National Institutes of Health, Bethesda, MD, 20892, USA
| | - Xinyi J He
- Section on Sensory Cell Development and Function, NIDCD/National Institutes of Health, Bethesda, MD, 20892, USA
| | - Alisha Beirl
- Section on Sensory Cell Development and Function, NIDCD/National Institutes of Health, Bethesda, MD, 20892, USA
| | - Ronald S Petralia
- Advanced Imaging Core, NIDCD/National Institutes of Health, Bethesda, MD, 20892, USA
| | - Ya-Xian Wang
- Advanced Imaging Core, NIDCD/National Institutes of Health, Bethesda, MD, 20892, USA
| | - Katie S Kindt
- Section on Sensory Cell Development and Function, NIDCD/National Institutes of Health, Bethesda, MD, 20892, USA.
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15
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Yang T, Choi JE, Soh D, Tobin K, Joiner ML, Hansen M, Lee A. CaBP1 regulates Ca v1 L-type Ca 2+ channels and their coupling to neurite growth and gene transcription in mouse spiral ganglion neurons. Mol Cell Neurosci 2018; 88:342-352. [PMID: 29548764 DOI: 10.1016/j.mcn.2018.03.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 03/07/2018] [Accepted: 03/12/2018] [Indexed: 12/19/2022] Open
Abstract
CaBP1 is a Ca2+ binding protein that is widely expressed in neurons in the brain, retina, and cochlea. In heterologous expression systems, CaBP1 interacts with and regulates voltage-gated Cav Ca2+ channels but whether this is the case in neurons is unknown. Here, we investigated the cellular functions of CaBP1 in cochlear spiral ganglion neurons (SGNs), which express high levels of CaBP1. Consistent with the role of CaBP1 as a suppressor of Ca2+-dependent inactivation (CDI) of Cav1 (L-type) channels, Cav1 currents underwent greater CDI in SGNs from mice lacking CaBP1 (C-KO) than in wild-type (WT) SGNs. The coupling of Cav1 channels to downstream signaling pathways was also disrupted in C-KO SGNs. Activity-dependent repression of neurite growth was significantly blunted and unresponsive to Cav1 antagonists in C-KO SGNs in contrast to WT SGNs. Moreover, Cav1-mediated Ca2+ signals and phosphorylation of cAMP-response element binding protein were reduced in C-KO SGNs compared to WT SGNs. Our findings establish a role for CaBP1 as an essential regulator of Cav1 channels in SGNs and their coupling to downstream pathways controlling activity-dependent transcription and neurite growth.
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Affiliation(s)
- Tian Yang
- Departments of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA
| | - Ji-Eun Choi
- Departments of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA
| | - Daniel Soh
- Departments of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA
| | - Kevin Tobin
- Departments of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA
| | - Mei-Ling Joiner
- Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, IA 52242, USA
| | - Marlan Hansen
- Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Neurosurgery, University of Iowa, Iowa City, IA 52242, USA
| | - Amy Lee
- Departments of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA; Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Neurology, University of Iowa, Iowa City, IA 52242, USA.
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16
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Abstract
Calmodulin (CaM) regulation of voltage-gated calcium (CaV) channels is a powerful Ca2+ feedback mechanism that adjusts Ca2+ influx, affording rich mechanistic insights into Ca2+ decoding. CaM possesses a dual-lobed architecture, a salient feature of the myriad Ca2+-sensing proteins, where two homologous lobes that recognize similar targets hint at redundant signaling mechanisms. Here, by tethering CaM lobes, we demonstrate that bilobal architecture is obligatory for signaling to CaV channels. With one lobe bound, CaV carboxy tail rearranges itself, resulting in a preinhibited configuration precluded from Ca2+ feedback. Reconstitution of two lobes, even as separate molecules, relieves preinhibition and restores Ca2+ feedback. CaV channels thus detect the coincident binding of two Ca2+-free lobes to promote channel opening, a molecular implementation of a logical NOR operation that processes spatiotemporal Ca2+ signals bifurcated by CaM lobes. Overall, a unified scheme of CaV channel regulation by CaM now emerges, and our findings highlight the versatility of CaM to perform exquisite Ca2+ computations.
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17
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Chemin J, Taiakina V, Monteil A, Piazza M, Guan W, Stephens RF, Kitmitto A, Pang ZP, Dolphin AC, Perez-Reyes E, Dieckmann T, Guillemette JG, Spafford JD. Calmodulin regulates Ca v3 T-type channels at their gating brake. J Biol Chem 2017; 292:20010-20031. [PMID: 28972185 PMCID: PMC5723990 DOI: 10.1074/jbc.m117.807925] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 09/19/2017] [Indexed: 01/10/2023] Open
Abstract
Calcium (Cav1 and Cav2) and sodium channels possess homologous CaM-binding motifs, known as IQ motifs in their C termini, which associate with calmodulin (CaM), a universal calcium sensor. Cav3 T-type channels, which serve as pacemakers of the mammalian brain and heart, lack a C-terminal IQ motif. We illustrate that T-type channels associate with CaM using co-immunoprecipitation experiments and single particle cryo-electron microscopy. We demonstrate that protostome invertebrate (LCav3) and human Cav3.1, Cav3.2, and Cav3.3 T-type channels specifically associate with CaM at helix 2 of the gating brake in the I-II linker of the channels. Isothermal titration calorimetry results revealed that the gating brake and CaM bind each other with high-nanomolar affinity. We show that the gating brake assumes a helical conformation upon binding CaM, with associated conformational changes to both CaM lobes as indicated by amide chemical shifts of the amino acids of CaM in 1H-15N HSQC NMR spectra. Intact Ca2+-binding sites on CaM and an intact gating brake sequence (first 39 amino acids of the I-II linker) were required in Cav3.2 channels to prevent the runaway gating phenotype, a hyperpolarizing shift in voltage sensitivities and faster gating kinetics. We conclude that the presence of high-nanomolar affinity binding sites for CaM at its universal gating brake and its unique form of regulation via the tuning of the voltage range of activity could influence the participation of Cav3 T-type channels in heart and brain rhythms. Our findings may have implications for arrhythmia disorders arising from mutations in the gating brake or CaM.
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Affiliation(s)
- Jean Chemin
- Institut de Génomique Fonctionnelle, CNRS, INSERM, Université de Montpellier, Montpellier F-34094, France
| | | | - Arnaud Monteil
- Institut de Génomique Fonctionnelle, CNRS, INSERM, Université de Montpellier, Montpellier F-34094, France
| | - Michael Piazza
- Departments of Chemistry, Waterloo, Ontario N2L 3G1, Canada
| | - Wendy Guan
- Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | | | - Ashraf Kitmitto
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9NT, United Kingdom
| | - Zhiping P Pang
- Department of Neuroscience and Cell Biology, Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey 08901
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, United Kingdom
| | - Edward Perez-Reyes
- Department of Pharmacology, University of Virginia, Charlottesville, Virginia 22908
| | | | | | - J David Spafford
- Biology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
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18
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Piazza M, Taiakina V, Dieckmann T, Guillemette JG. Structural Consequences of Calmodulin EF Hand Mutations. Biochemistry 2017; 56:944-956. [PMID: 28121131 DOI: 10.1021/acs.biochem.6b01296] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Calmodulin (CaM) is a cytosolic Ca2+-binding protein that serves as a control element for many enzymes. It consists of two globular domains, each containing two EF hand pairs capable of binding Ca2+, joined by a flexible central linker region. CaM is able to bind and activate its target proteins in the Ca2+-replete and Ca2+-deplete forms. To study the Ca2+-dependent/independent properties of binding and activation of target proteins by CaM, CaM constructs with Ca2+-binding disrupting mutations of Asp to Ala at position one of each EF hand have been used. These CaM mutant proteins are deficient in binding Ca2+ in either the N-lobe EF hands (CaM12), C-lobe EF hands (CaM34), or all four EF hands (CaM1234). To investigate potential structural changes these mutations may cause, we performed detailed NMR studies of CaM12, CaM34, and CaM1234 including determining the solution structure of CaM1234. We then investigated if these CaM mutants affected the interaction of CaM with a target protein known to interact with apoCaM by determining the solution structure of CaM34 bound to the iNOS CaM binding domain peptide. The structures provide direct structural evidence of changes that are present in these Ca2+-deficient CaM mutants and show these mutations increase the hydrophobic exposed surface and decrease the electronegative surface potential throughout each lobe of CaM. These Ca2+-deficient CaM mutants may not be a true representation of apoCaM and may not allow for native-like interactions of apoCaM with its target proteins.
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Affiliation(s)
- Michael Piazza
- Department of Chemistry, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Valentina Taiakina
- Department of Chemistry, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - Thorsten Dieckmann
- Department of Chemistry, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
| | - J Guy Guillemette
- Department of Chemistry, University of Waterloo , Waterloo, Ontario N2L 3G1, Canada
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19
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Blacker T, Chen W, Avezov E, Marsh RJ, Duchen MR, Kaminski CF, Bain AJ. Investigating State Restriction in Fluorescent Protein FRET Using Time-Resolved Fluorescence and Anisotropy. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2017; 121:1507-1514. [PMID: 28217242 PMCID: PMC5309863 DOI: 10.1021/acs.jpcc.6b11235] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 12/23/2016] [Indexed: 05/14/2023]
Abstract
Most fluorescent proteins exhibit multiexponential fluorescence decays, indicating a heterogeneous excited state population. FRET between fluorescent proteins should therefore involve multiple energy transfer pathways. We recently demonstrated the FRET pathways between EGFP and mCherry (mC), upon the dimerization of 3-phosphoinositide dependent protein kinase 1 (PDK1), to be highly restricted. A mechanism for FRET restriction based on a highly unfavorable κ2 orientation factor arising from differences in donor-acceptor transition dipole moment angles in a far from coplanar and near static interaction geometry was proposed. Here this is tested via FRET to mC arising from the association of glutathione (GSH) and glutathione S-transferase (GST) with an intrinsically homogeneous and more mobile donor Oregon Green 488 (OG). A new analysis of the acceptor window intensity, based on the turnover point of the sensitized fluorescence, is combined with donor window intensity and anisotropy measurements which show that unrestricted FRET to mC takes place. However, a long-lived anisotropy decay component in the donor window reveals a GST-GSH population in which FRET does not occur, explaining previous discrepancies between quantitative FRET measurements of GST-GSH association and their accepted values. This reinforces the importance of the local donor-acceptor environment in mediating energy transfer and the need to perform spectrally resolved intensity and anisotropy decay measurements in the accurate quantification of fluorescent protein FRET.
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Affiliation(s)
- Thomas
S. Blacker
- Department
of Physics & Astronomy, Centre for Mathematics and Physics
in the Life Sciences and Experimental Biology, and Department of Cell & Developmental
Biology, University College London, Gower Street, London WC1E 6BT, United
Kingdom
| | - WeiYue Chen
- Department
of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom
| | - Edward Avezov
- Cambridge
Institute for Medical Research, University
of Cambridge, Cambridge CB2 0XY, United Kingdom
| | - Richard J. Marsh
- Department
of Physics & Astronomy, Centre for Mathematics and Physics
in the Life Sciences and Experimental Biology, and Department of Cell & Developmental
Biology, University College London, Gower Street, London WC1E 6BT, United
Kingdom
| | - Michael R. Duchen
- Department
of Physics & Astronomy, Centre for Mathematics and Physics
in the Life Sciences and Experimental Biology, and Department of Cell & Developmental
Biology, University College London, Gower Street, London WC1E 6BT, United
Kingdom
| | - Clemens F. Kaminski
- Department
of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge CB2 3RA, United Kingdom
| | - Angus J. Bain
- Department
of Physics & Astronomy, Centre for Mathematics and Physics
in the Life Sciences and Experimental Biology, and Department of Cell & Developmental
Biology, University College London, Gower Street, London WC1E 6BT, United
Kingdom
- E-mail:
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20
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Ben-Johny M, Yue DN, Yue DT. Detecting stoichiometry of macromolecular complexes in live cells using FRET. Nat Commun 2016; 7:13709. [PMID: 27922011 PMCID: PMC5150656 DOI: 10.1038/ncomms13709] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 10/25/2016] [Indexed: 11/10/2022] Open
Abstract
The stoichiometry of macromolecular interactions is fundamental to cellular signalling yet challenging to detect from living cells. Fluorescence resonance energy transfer (FRET) is a powerful phenomenon for characterizing close-range interactions whereby a donor fluorophore transfers energy to a closely juxtaposed acceptor. Recognizing that FRET measured from the acceptor's perspective reports a related but distinct quantity versus the donor, we utilize the ratiometric comparison of the two to obtain the stoichiometry of a complex. Applying this principle to the long-standing controversy of calmodulin binding to ion channels, we find a surprising Ca2+-induced switch in calmodulin stoichiometry with Ca2+ channels—one calmodulin binds at basal cytosolic Ca2+ levels while two calmodulins interact following Ca2+ elevation. This feature is curiously absent for the related Na channels, also potently regulated by calmodulin. Overall, our assay adds to a burgeoning toolkit to pursue quantitative biochemistry of dynamic signalling complexes in living cells. Measuring the in vivo stoichiometry of protein-protein interactions is challenging. Here the authors take a FRET-based approach, quantifying stoichiometry based on ratiometric comparison of donor and acceptor fluorescence, and apply their method to report on a Ca2+-induced switch in calmodulin binding to Ca2+ ion channels.
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Affiliation(s)
- Manu Ben-Johny
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, Maryland 21205, USA
| | - Daniel N Yue
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, Maryland 21205, USA
| | - David T Yue
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, Maryland 21205, USA
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21
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Butz ES, Ben-Johny M, Shen M, Yang PS, Sang L, Biel M, Yue DT, Wahl-Schott C. Quantifying macromolecular interactions in living cells using FRET two-hybrid assays. Nat Protoc 2016; 11:2470-2498. [DOI: 10.1038/nprot.2016.128] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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22
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Sang L, Dick IE, Yue DT. Protein kinase A modulation of CaV1.4 calcium channels. Nat Commun 2016; 7:12239. [PMID: 27456671 PMCID: PMC4963476 DOI: 10.1038/ncomms12239] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Accepted: 06/07/2016] [Indexed: 11/19/2022] Open
Abstract
The regulation of L-type Ca2+ channels by protein kinase A (PKA) represents a crucial element within cardiac, skeletal muscle and neurological systems. Although much work has been done to understand this regulation in cardiac CaV1.2 Ca2+ channels, relatively little is known about the closely related CaV1.4 L-type Ca2+ channels, which feature prominently in the visual system. Here we find that CaV1.4 channels are indeed modulated by PKA phosphorylation within the inhibitor of Ca2+-dependent inactivation (ICDI) motif. Phosphorylation of this region promotes the occupancy of calmodulin on the channel, thus increasing channel open probability (PO) and Ca2+-dependent inactivation. Although this interaction seems specific to CaV1.4 channels, introduction of ICDI1.4 to CaV1.3 or CaV1.2 channels endows these channels with a form of PKA modulation, previously unobserved in heterologous systems. Thus, this mechanism may not only play an important role in the visual system but may be generalizable across the L-type channel family. Phosphorylation of L-type calcium CaV channels by protein kinase A is essential for several physiological events. Here, the authors show how this kinase regulates CaV1.4 activity, suggesting a general regulatory mechanism for all L-type calcium channels.
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Affiliation(s)
- Lingjie Sang
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, Maryland 21205, USA
| | - Ivy E Dick
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, Maryland 21205, USA
| | - David T Yue
- Calcium Signals Laboratory, Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, Maryland 21205, USA.,Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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23
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Ben-Johny M, Dick IE, Sang L, Limpitikul WB, Kang PW, Niu J, Banerjee R, Yang W, Babich JS, Issa JB, Lee SR, Namkung H, Li J, Zhang M, Yang PS, Bazzazi H, Adams PJ, Joshi-Mukherjee R, Yue DN, Yue DT. Towards a Unified Theory of Calmodulin Regulation (Calmodulation) of Voltage-Gated Calcium and Sodium Channels. Curr Mol Pharmacol 2016; 8:188-205. [PMID: 25966688 DOI: 10.2174/1874467208666150507110359] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Revised: 01/29/2015] [Accepted: 04/20/2015] [Indexed: 12/13/2022]
Abstract
Voltage-gated Na and Ca(2+) channels represent two major ion channel families that enable myriad biological functions including the generation of action potentials and the coupling of electrical and chemical signaling in cells. Calmodulin regulation (calmodulation) of these ion channels comprises a vital feedback mechanism with distinct physiological implications. Though long-sought, a shared understanding of the channel families remained elusive for two decades as the functional manifestations and the structural underpinnings of this modulation often appeared to diverge. Here, we review recent advancements in the understanding of calmodulation of Ca(2+) and Na channels that suggest a remarkable similarity in their regulatory scheme. This interrelation between the two channel families now paves the way towards a unified mechanistic framework to understand vital calmodulin-dependent feedback and offers shared principles to approach related channelopathic diseases. An exciting era of synergistic study now looms.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - David T Yue
- Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Ross Building, Room 713, 720 Rutland Avenue, Baltimore, MD 21205, USA.
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24
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Moreno CM, Dixon RE, Tajada S, Yuan C, Opitz-Araya X, Binder MD, Santana LF. Ca(2+) entry into neurons is facilitated by cooperative gating of clustered CaV1.3 channels. eLife 2016; 5. [PMID: 27187148 PMCID: PMC4869912 DOI: 10.7554/elife.15744] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 04/09/2016] [Indexed: 11/13/2022] Open
Abstract
CaV1.3 channels regulate excitability in many neurons. As is the case for all voltage-gated channels, it is widely assumed that individual CaV1.3 channels behave independently with respect to voltage-activation, open probability, and facilitation. Here, we report the results of super-resolution imaging, optogenetic, and electrophysiological measurements that refute this long-held view. We found that the short channel isoform (CaV1.3S), but not the long (CaV1.3L), associates in functional clusters of two or more channels that open cooperatively, facilitating Ca(2+) influx. CaV1.3S channels are coupled via a C-terminus-to-C-terminus interaction that requires binding of the incoming Ca(2+) to calmodulin (CaM) and subsequent binding of CaM to the pre-IQ domain of the channels. Physically-coupled channels facilitate Ca(2+) currents as a consequence of their higher open probabilities, leading to increased firing rates in rat hippocampal neurons. We propose that cooperative gating of CaV1.3S channels represents a mechanism for the regulation of Ca(2+) signaling and electrical activity.
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Affiliation(s)
- Claudia M Moreno
- Department of Physiology and Membrane Biology, University of California, Davis, United States
| | - Rose E Dixon
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Sendoa Tajada
- Department of Physiology and Membrane Biology, University of California, Davis, United States
| | - Can Yuan
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Ximena Opitz-Araya
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Marc D Binder
- Department of Physiology and Biophysics, University of Washington, Seattle, United States
| | - Luis F Santana
- Department of Physiology and Membrane Biology, University of California, Davis, United States
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25
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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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26
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Yang T, Scholl ES, Pan N, Fritzsch B, Haeseleer F, Lee A. Expression and Localization of CaBP Ca2+ Binding Proteins in the Mouse Cochlea. PLoS One 2016; 11:e0147495. [PMID: 26809054 PMCID: PMC4725724 DOI: 10.1371/journal.pone.0147495] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 01/05/2016] [Indexed: 11/19/2022] Open
Abstract
CaBPs are a family of EF-hand Ca2+ binding proteins that are structurally similar to calmodulin. CaBPs can interact with, and yet differentially modulate, effectors that are regulated by calmodulin, such as Cav1 voltage-gated Ca2+ channels. Immunolabeling studies suggest that multiple CaBP family members (CaBP1, 2, 4, and 5) are expressed in the cochlea. To gain insights into the respective auditory functions of these CaBPs, we characterized the expression and cellular localization of CaBPs in the mouse cochlea. By quantitative reverse transcription PCR, we show that CaBP1 and CaBP2 are the major CaBPs expressed in mouse cochlea both before and after hearing onset. Of the three alternatively spliced variants of CaBP1 (caldendrin, CaBP1-L, and CaBP1-S) and CaBP2 (CaBP2-alt, CaBP2-L, CaBP2-S), caldendrin and CaBP2-alt are the most abundant. By in situ hybridization, probes recognizing caldendrin strongly label the spiral ganglion, while probes designed to recognize all three isoforms of CaBP1 weakly label both the inner and outer hair cells as well as the spiral ganglion. Within the spiral ganglion, caldendrin/CaBP1 labeling is associated with cells resembling satellite glial cells. CaBP2-alt is strongly expressed in inner hair cells both before and after hearing onset. Probes designed to recognize all three variants of CaBP2 strongly label inner hair cells before hearing onset and outer hair cells after the onset of hearing. Thus, CaBP1 and CaBP2 may have overlapping roles in regulating Ca2+ signaling in the hair cells, and CaBP1 may have an additional function in the spiral ganglion. Our findings provide a framework for understanding the role of CaBP family members in the auditory periphery.
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Affiliation(s)
- Tian Yang
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, United States of America
- Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, Iowa, United States of America
- Department of Neurology, University of Iowa, Iowa City, Iowa, United States of America
| | - Elizabeth S. Scholl
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, United States of America
- Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, Iowa, United States of America
- Department of Neurology, University of Iowa, Iowa City, Iowa, United States of America
| | - Ning Pan
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Bernd Fritzsch
- Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, Iowa, United States of America
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Françoise Haeseleer
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, United States of America
| | - Amy Lee
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, United States of America
- Department of Otolaryngology Head-Neck Surgery, University of Iowa, Iowa City, Iowa, United States of America
- Department of Neurology, University of Iowa, Iowa City, Iowa, United States of America
- * E-mail:
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27
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Scharinger A, Eckrich S, Vandael DH, Schönig K, Koschak A, Hecker D, Kaur G, Lee A, Sah A, Bartsch D, Benedetti B, Lieb A, Schick B, Singewald N, Sinnegger-Brauns MJ, Carbone E, Engel J, Striessnig J. Cell-type-specific tuning of Cav1.3 Ca(2+)-channels by a C-terminal automodulatory domain. Front Cell Neurosci 2015; 9:309. [PMID: 26379493 PMCID: PMC4547004 DOI: 10.3389/fncel.2015.00309] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 07/27/2015] [Indexed: 11/13/2022] Open
Abstract
Cav1.3 L-type Ca(2+)-channel function is regulated by a C-terminal automodulatory domain (CTM). It affects channel binding of calmodulin and thereby tunes channel activity by interfering with Ca(2+)- and voltage-dependent gating. Alternative splicing generates short C-terminal channel variants lacking the CTM resulting in enhanced Ca(2+)-dependent inactivation and stronger voltage-sensitivity upon heterologous expression. However, the role of this modulatory domain for channel function in its native environment is unkown. To determine its functional significance in vivo, we interrupted the CTM with a hemagglutinin tag in mutant mice (Cav1.3DCRD(HA/HA)). Using these mice we provide biochemical evidence for the existence of long (CTM-containing) and short (CTM-deficient) Cav1.3 α1-subunits in brain. The long (HA-labeled) Cav1.3 isoform was present in all ribbon synapses of cochlear inner hair cells. CTM-elimination impaired Ca(2+)-dependent inactivation of Ca(2+)-currents in hair cells but increased it in chromaffin cells, resulting in hyperpolarized resting potentials and reduced pacemaking. CTM disruption did not affect hearing thresholds. We show that the modulatory function of the CTM is affected by its native environment in different cells and thus occurs in a cell-type specific manner in vivo. It stabilizes gating properties of Cav1.3 channels required for normal electrical excitability.
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Affiliation(s)
- Anja Scharinger
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Stephanie Eckrich
- Department of Biophysics, Center for Integrative Physiology and Molecular Medicine, Saarland University Homburg, Germany
| | - David H Vandael
- Laboratory of Cellular and Molecular Neuroscience, Department of Drug Science, Nanostructured Interfaces and Surfaces Center, University of Torino Torino, Italy
| | - Kai Schönig
- Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University Mannheim, Germany
| | - Alexandra Koschak
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Dietmar Hecker
- Department of Otorhinolaryngology, Saarland University Homburg, Germany
| | - Gurjot Kaur
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Amy Lee
- Department of Molecular Physiology and Biophysics, University of Iowa Iowa City, IA, USA
| | - Anupam Sah
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Dusan Bartsch
- Department of Molecular Biology, Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University Mannheim, Germany
| | - Bruno Benedetti
- Department of Physiology and Medical Physics, Innsbruck Medical University Innsbruck, Austria
| | - Andreas Lieb
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Bernhard Schick
- Department of Otorhinolaryngology, Saarland University Homburg, Germany
| | - Nicolas Singewald
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Martina J Sinnegger-Brauns
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
| | - Emilio Carbone
- Laboratory of Cellular and Molecular Neuroscience, Department of Drug Science, Nanostructured Interfaces and Surfaces Center, University of Torino Torino, Italy
| | - Jutta Engel
- Department of Biophysics, Center for Integrative Physiology and Molecular Medicine, Saarland University Homburg, Germany
| | - Jörg Striessnig
- Department of Pharmacology and Toxicology, Institute of Pharmacy, Center for Molecular Biosciences, University of Innsbruck Innsbruck, Austria
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28
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Abstract
Ca2+-dependent inactivation (CDI) is a negative feedback regulation of voltage-gated Cav1 and Cav2 channels that is mediated by the Ca2+ sensing protein, calmodulin (CaM), binding to the pore-forming Cav α1 subunit. David Yue and his colleagues made seminal contributions to our understanding of this process, as well as factors that regulate CDI. Important in this regard are members of a family of Ca2+ binding proteins (CaBPs) that are related to calmodulin. CaBPs are expressed mainly in neural tissues and can antagonize CaM-dependent CDI for Cav1 L-type channels. This review will focus on the roles of CaBPs as Cav1-interacting proteins, and the significance of these interactions for vision, hearing, and neuronal Ca2+ signaling events.
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Affiliation(s)
- Jason Hardie
- a Departments of Molecular Physiology and Biophysics ; Otolaryngology-Head and Neck Surgery and Neurology; University of Iowa ; Iowa City , IA USA
| | - Amy Lee
- a Departments of Molecular Physiology and Biophysics ; Otolaryngology-Head and Neck Surgery and Neurology; University of Iowa ; Iowa City , IA USA
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29
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Adams PJ, Ben-Johny M, Dick IE, Inoue T, Yue DT. Apocalmodulin itself promotes ion channel opening and Ca(2+) regulation. Cell 2015; 159:608-22. [PMID: 25417111 DOI: 10.1016/j.cell.2014.09.047] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 07/25/2014] [Accepted: 09/26/2014] [Indexed: 11/16/2022]
Abstract
The Ca(2+)-free form of calmodulin (apoCaM) often appears inert, modulating target molecules only upon conversion to its Ca(2+)-bound form. This schema has appeared to govern voltage-gated Ca(2+) channels, where apoCaM has been considered a dormant Ca(2+) sensor, associated with channels but awaiting the binding of Ca(2+) ions before inhibiting channel opening to provide vital feedback inhibition. Using single-molecule measurements of channels and chemical dimerization to elevate apoCaM, we find that apoCaM binding on its own markedly upregulates opening, rivaling the strongest forms of modulation. Upon Ca(2+) binding to this CaM, inhibition may simply reverse the initial upregulation. As RNA-edited and -spliced channel variants show different affinities for apoCaM, the apoCaM-dependent control mechanisms may underlie the functional diversity of these variants and explain an elongation of neuronal action potentials by apoCaM. More broadly, voltage-gated Na channels adopt this same modulatory principle. ApoCaM thus imparts potent and pervasive ion-channel regulation. PAPERCLIP:
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Affiliation(s)
- Paul J Adams
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, Center for Cell Dynamics, The Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA
| | - Manu Ben-Johny
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, Center for Cell Dynamics, The Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA
| | - Ivy E Dick
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, Center for Cell Dynamics, The Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA
| | - Takanari Inoue
- Department of Cell Biology and Center for Cell Dynamics, The Johns Hopkins University School of Medicine, 855 N. Wolfe Street, Baltimore, MD 21205, USA; Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan
| | - David T Yue
- Calcium Signals Laboratory, Departments of Biomedical Engineering and Neuroscience, Center for Cell Dynamics, The Johns Hopkins University School of Medicine, 720 Rutland Avenue, Baltimore, MD 21205, USA.
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30
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Abstract
Voltage- and ligand-gated ion channels form the molecular basis of cellular excitability. With >400 members and accounting for ∼1.5% of the human genome, ion channels are some of the most well studied of all proteins in heterologous expression systems. Yet, ion channels often exhibit unexpected properties in vivo because of their interaction with a variety of signaling/scaffolding proteins. Such interactions can influence the function and localization of ion channels, as well as their coupling to intracellular second messengers and pathways, thus increasing the signaling potential of these ion channels in neurons. Moreover, functions have been ascribed to ion channels that are largely independent of their ion-conducting roles. Molecular and functional dissection of the ion channel proteome/interactome has yielded new insights into the composition of ion channel complexes and how their dysregulation leads to human disease.
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31
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Ben-Johny M, Yue DT. Calmodulin regulation (calmodulation) of voltage-gated calcium channels. ACTA ACUST UNITED AC 2014; 143:679-92. [PMID: 24863929 PMCID: PMC4035741 DOI: 10.1085/jgp.201311153] [Citation(s) in RCA: 147] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Calmodulin regulation (calmodulation) of the family of voltage-gated CaV1-2 channels comprises a prominent prototype for ion channel regulation, remarkable for its powerful Ca(2+) sensing capabilities, deep in elegant mechanistic lessons, and rich in biological and therapeutic implications. This field thereby resides squarely at the epicenter of Ca(2+) signaling biology, ion channel biophysics, and therapeutic advance. This review summarizes the historical development of ideas in this field, the scope and richly patterned organization of Ca(2+) feedback behaviors encompassed by this system, and the long-standing challenges and recent developments in discerning a molecular basis for calmodulation. We conclude by highlighting the considerable synergy between mechanism, biological insight, and promising therapeutics.
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Affiliation(s)
- Manu Ben-Johny
- Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - David T Yue
- Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205Calcium Signals Laboratory, Department of Biomedical Engineering, Department of Neuroscience, and Center for Cell Dynamics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
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32
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Burgoyne RD, Haynes LP. Sense and specificity in neuronal calcium signalling. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:1921-32. [PMID: 25447549 PMCID: PMC4728190 DOI: 10.1016/j.bbamcr.2014.10.029] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Revised: 10/25/2014] [Accepted: 10/29/2014] [Indexed: 11/02/2022]
Abstract
Changes in the intracellular free calcium concentration ([Ca²⁺]i) in neurons regulate many and varied aspects of neuronal function over time scales from microseconds to days. The mystery is how a single signalling ion can lead to such diverse and specific changes in cell function. This is partly due to aspects of the Ca²⁺ signal itself, including its magnitude, duration, localisation and persistent or oscillatory nature. The transduction of the Ca²⁺ signal requires Ca²⁺binding to various Ca²⁺ sensor proteins. The different properties of these sensors are important for differential signal processing and determine the physiological specificity of Ca(2+) signalling pathways. A major factor underlying the specific roles of particular Ca²⁺ sensor proteins is the nature of their interaction with target proteins and how this mediates unique patterns of regulation. We review here recent progress from structural analyses and from functional analyses in model organisms that have begun to reveal the rules that underlie Ca²⁺ sensor protein specificity for target interaction. We discuss three case studies exemplifying different aspects of Ca²⁺ sensor/target interaction. This article is part of a special issue titled the 13th European Symposium on Calcium.
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Affiliation(s)
- Robert D Burgoyne
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, United Kingdom.
| | - Lee P Haynes
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, University of Liverpool, Crown Street, Liverpool, L69 3BX, United Kingdom
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33
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Park S, Li C, Haeseleer F, Palczewski K, Ames JB. Structural insights into activation of the retinal L-type Ca²⁺ channel (Cav1.4) by Ca²⁺-binding protein 4 (CaBP4). J Biol Chem 2014; 289:31262-73. [PMID: 25258313 DOI: 10.1074/jbc.m114.604439] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
CaBP4 modulates Ca(2+)-dependent activity of L-type voltage-gated Ca(2+) channels (Cav1.4) in retinal photoreceptor cells. Mg(2+) binds to the first and third EF-hands (EF1 and EF3), and Ca(2+) binds to EF1, EF3, and EF4 of CaBP4. Here we present NMR structures of CaBP4 in both Mg(2+)-bound and Ca(2+)-bound states and model the CaBP4 structural interaction with Cav1.4. CaBP4 contains an unstructured N-terminal region (residues 1-99) and four EF-hands in two separate lobes. The N-lobe consists of EF1 and EF2 in a closed conformation with either Mg(2+) or Ca(2+) bound at EF1. The C-lobe binds Ca(2+) at EF3 and EF4 and exhibits a Ca(2+)-induced closed-to-open transition like that of calmodulin. Exposed residues in Ca(2+)-bound CaBP4 (Phe(137), Glu(168), Leu(207), Phe(214), Met(251), Phe(264), and Leu(268)) make contacts with the IQ motif in Cav1.4, and the Cav1.4 mutant Y1595E strongly impairs binding to CaBP4. We conclude that CaBP4 forms a collapsed structure around the IQ motif in Cav1.4 that we suggest may promote channel activation by disrupting an interaction between IQ and the inhibitor of Ca(2+)-dependent inactivation domain.
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Affiliation(s)
- Saebomi Park
- From the Department of Chemistry, University of California, Davis, California 95616
| | - Congmin Li
- From the Department of Chemistry, University of California, Davis, California 95616
| | - Françoise Haeseleer
- the Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195, and
| | - Krzysztof Palczewski
- the Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965
| | - James B Ames
- From the Department of Chemistry, University of California, Davis, California 95616,
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34
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Lu S, Huang W, Zhang J. Recent computational advances in the identification of allosteric sites in proteins. Drug Discov Today 2014; 19:1595-600. [PMID: 25107670 DOI: 10.1016/j.drudis.2014.07.012] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 07/10/2014] [Accepted: 07/30/2014] [Indexed: 01/08/2023]
Abstract
Allosteric modulators have the potential to fine-tune protein functional activity. Therefore, the targeting of allosteric sites, as a strategy in drug design, is gaining increasing attention. Currently, it is not trivial to find and characterize new allosteric sites by experimental approaches. Alternatively, computational approaches are useful in helping researchers analyze and select potential allosteric sites for drug discovery. Here, we review state-of-the-art computational approaches directed at predicting putative allosteric sites in proteins, along with examples of successes in identifying allosteric sites utilizing these methods. We also discuss the challenges in developing reliable methods for predicting allosteric sites and tactics to resolve demanding tasks.
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Affiliation(s)
- Shaoyong Lu
- Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai JiaoTong University, School of Medicine (SJTU-SM), Shanghai 200025, China
| | - Wenkang Huang
- Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai JiaoTong University, School of Medicine (SJTU-SM), Shanghai 200025, China
| | - Jian Zhang
- Department of Pathophysiology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai JiaoTong University, School of Medicine (SJTU-SM), Shanghai 200025, China.
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35
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Simms BA, Zamponi GW. Neuronal voltage-gated calcium channels: structure, function, and dysfunction. Neuron 2014; 82:24-45. [PMID: 24698266 DOI: 10.1016/j.neuron.2014.03.016] [Citation(s) in RCA: 420] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Voltage-gated calcium channels are the primary mediators of depolarization-induced calcium entry into neurons. There is great diversity of calcium channel subtypes due to multiple genes that encode calcium channel α1 subunits, coassembly with a variety of ancillary calcium channel subunits, and alternative splicing. This allows these channels to fulfill highly specialized roles in specific neuronal subtypes and at particular subcellular loci. While calcium channels are of critical importance to brain function, their inappropriate expression or dysfunction gives rise to a variety of neurological disorders, including, pain, epilepsy, migraine, and ataxia. This Review discusses salient aspects of voltage-gated calcium channel function, physiology, and pathophysiology.
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Affiliation(s)
- Brett A Simms
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N 4N1, Canada
| | - Gerald W Zamponi
- Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, AB T2N 4N1, Canada.
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36
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Kim KY, Scholl ES, Liu X, Shepherd A, Haeseleer F, Lee A. Localization and expression of CaBP1/caldendrin in the mouse brain. Neuroscience 2014; 268:33-47. [PMID: 24631676 DOI: 10.1016/j.neuroscience.2014.02.052] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 02/26/2014] [Accepted: 02/27/2014] [Indexed: 12/31/2022]
Abstract
Ca(2+) binding protein 1 (CaBP1) and caldendrin are alternatively spliced variants of a subfamily of CaBPs with high homology to calmodulin. Although CaBP1 and caldendrin regulate effectors including plasma membrane and intracellular Ca(2+) channels in heterologous expression systems, little is known about their functions in vivo. Therefore, we generated mice deficient in CaBP1/caldendrin expression (C-KO) and analyzed the expression and cellular localization of CaBP1 and caldendrin in the mouse brain. Immunoperoxidase labeling with antibodies recognizing both CaBP1 and caldendrin was absent in the brain of C-KO mice, but was intense in multiple brain regions of wild-type mice. By Western blot, the antibodies detected two proteins that were absent in the C-KO mouse and consistent in size with caldendrin variants originating from alternative translation initiation sites. By quantitative PCR, caldendrin transcript levels were far greater than those for CaBP1, particularly in the cerebral cortex and hippocampus. In the frontal cortex but not in the hippocampus, caldendrin expression increased steadily from birth. By double-label immunofluorescence, CaBP1/caldendrin was localized in principal neurons and parvalbumin-positive interneurons. In the cerebellum, CaBP1/caldendrin antibodies labeled interneurons in the molecular layer and in basket cell terminals surrounding the soma and axon initial segment of Purkinje neurons, but immunolabeling was absent in Purkinje neurons. We conclude that CaBP1/caldendrin is localized both pre- and postsynaptically where it may regulate Ca(2+) signaling and excitability in select groups of excitatory and inhibitory neurons.
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Affiliation(s)
- K Y Kim
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA; Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Department of Neurology, University of Iowa, Iowa City, IA 52242, USA
| | - E S Scholl
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA; Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Department of Neurology, University of Iowa, Iowa City, IA 52242, USA
| | - X Liu
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA; Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Department of Neurology, University of Iowa, Iowa City, IA 52242, USA
| | - A Shepherd
- Department of Pharmacology, University of Iowa, Iowa City, IA 52242, USA
| | - F Haeseleer
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
| | - A Lee
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA 52242, USA; Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, IA 52242, USA; Department of Neurology, University of Iowa, Iowa City, IA 52242, USA.
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