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Tyagi S, Higerd-Rusli GP, Akin EJ, Baker CA, Liu S, Dib-Hajj FB, Waxman SG, Dib-Hajj SD. Real-time imaging of axonal membrane protein life cycles. Nat Protoc 2024:10.1038/s41596-024-00997-x. [PMID: 38831222 DOI: 10.1038/s41596-024-00997-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 02/12/2024] [Indexed: 06/05/2024]
Abstract
The construction of neuronal membranes is a dynamic process involving the biogenesis, vesicular packaging, transport, insertion and recycling of membrane proteins. Optical imaging is well suited for the study of protein spatial organization and transport. However, various shortcomings of existing imaging techniques have prevented the study of specific types of proteins and cellular processes. Here we describe strategies for protein tagging and labeling, cell culture and microscopy that enable the real-time imaging of axonal membrane protein trafficking and subcellular distribution as they progress through some stages of their life cycle. First, we describe a process for engineering membrane proteins with extracellular self-labeling tags (either HaloTag or SNAPTag), which can be labeled with fluorescent ligands of various colors and cell permeability, providing flexibility for investigating the trafficking and spatiotemporal regulation of multiple membrane proteins in neuronal compartments. Next, we detail the dissection, transfection and culture of dorsal root ganglion sensory neurons in microfluidic chambers, which physically compartmentalizes cell bodies and distal axons. Finally, we describe four labeling and imaging procedures that utilize these enzymatically tagged proteins, flexible fluorescent labels and compartmentalized neuronal cultures to study axonal membrane protein anterograde and retrograde transport, the cotransport of multiple proteins, protein subcellular localization, exocytosis and endocytosis. Additionally, we generated open-source software for analyzing the imaging data in a high throughput manner. The experimental and analysis workflows provide an approach for studying the dynamics of neuronal membrane protein homeostasis, addressing longstanding challenges in this area. The protocol requires 5-7 days and expertise in cell culture and microscopy.
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Affiliation(s)
- Sidharth Tyagi
- Medical Scientist Training Program, Yale School of Medicine, New Haven, CT, USA
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA
| | - Grant P Higerd-Rusli
- Medical Scientist Training Program, Yale School of Medicine, New Haven, CT, USA
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA
| | - Elizabeth J Akin
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA
- Department of Pharmacology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Christopher A Baker
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA
| | - Shujun Liu
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA
| | - Fadia B Dib-Hajj
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA
| | - Stephen G Waxman
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA.
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA.
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA.
| | - Sulayman D Dib-Hajj
- Center for Neuroscience and Regeneration Research, West Haven, CT, USA.
- Department of Neurology, Yale School of Medicine, New Haven, CT, USA.
- Center for Restoration of Nervous System Function, VA Connecticut Healthcare System, West Haven, CT, USA.
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2
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Hansson KA, Eftestøl E. Scaling of nuclear numbers and their spatial arrangement in skeletal muscle cell size regulation. Mol Biol Cell 2023; 34:pe3. [PMID: 37339435 PMCID: PMC10398882 DOI: 10.1091/mbc.e22-09-0424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 03/29/2023] [Accepted: 04/28/2023] [Indexed: 06/22/2023] Open
Abstract
Many cells display considerable functional plasticity and depend on the regulation of numerous organelles and macromolecules for their maintenance. In large cells, organelles also need to be carefully distributed to supply the cell with essential resources and regulate intracellular activities. Having multiple copies of the largest eukaryotic organelle, the nucleus, epitomizes the importance of scaling gene products to large cytoplasmic volumes in skeletal muscle fibers. Scaling of intracellular constituents within mammalian muscle fibers is, however, poorly understood, but according to the myonuclear domain hypothesis, a single nucleus supports a finite amount of cytoplasm and is thus postulated to act autonomously, causing the nuclear number to be commensurate with fiber volume. In addition, the orderly peripheral distribution of myonuclei is a hallmark of normal cell physiology, as nuclear mispositioning is associated with impaired muscle function. Because underlying structures of complex cell behaviors are commonly formalized by scaling laws and thus emphasize emerging principles of size regulation, the work presented herein offers more of a unified conceptual platform based on principles from physics, chemistry, geometry, and biology to explore cell size-dependent correlations of the largest mammalian cell by means of scaling.
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Affiliation(s)
- Kenth-Arne Hansson
- Section for Health and Exercise Physiology, Inland Norway University of Applied Sciences, 2624 Lillehammer, Norway
| | - Einar Eftestøl
- Department of Biosciences, University of Oslo, 0371 Oslo, Norway
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3
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Antunes FTT, De Souza AH, Figueira J, Binda NS, Carvalho VPR, Vieira LB, Gomez MV. Targeting N-type calcium channels in young-onset of some neurological diseases. Front Cell Dev Biol 2022; 10:1090765. [PMID: 36601540 PMCID: PMC9806183 DOI: 10.3389/fcell.2022.1090765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Accepted: 12/08/2022] [Indexed: 12/24/2022] Open
Abstract
Calcium (Ca 2+) is an important second messenger in charge of many critical processes in the central nervous system (CNS), including membrane excitability, neurotransmission, learning, memory, cell proliferation, and apoptosis. In this way, the voltage-gated calcium channels (VGCCs) act as a key supply for Ca2+ entry into the cytoplasm and organelles. Importantly, the dysregulation of these channels has been reported in many neurological diseases of young-onset, with associated genetic factors, such as migraine, multiple sclerosis, and Huntington's disease. Notably, the literature has pointed to the role of N-type Ca2+ channels (NTCCs) in controlling a variety of processes, including pain, inflammation, and excitotoxicity. Moreover, several Ca2+ channel blockers that are used for therapeutic purposes have been shown to act on the N-type channels. Therefore, this review provides an overview of the NTCCs in neurological disorders focusing mainly on Huntington's disease, multiple sclerosis, and migraine. It will discuss possible strategies to generate novel therapeutic strategies.
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Affiliation(s)
- Flavia Tasmin Techera Antunes
- Department of Physiology and Pharmacology, University of Calgary, Calgary, AB, Canada,Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | - Alessandra Hubner De Souza
- Post-Graduate Program of Health Sciences, Faculdade de Ciências Médicas de, Belo Horizonte, Minas Gerais, Brazil,*Correspondence: Alessandra Hubner De Souza, ; Marcus Vinícius Gomez,
| | - Juliana Figueira
- Pharmacology Department, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais, Brazil
| | - Nancy Scardua Binda
- Pharmacology Department, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais, Brazil
| | | | - Luciene Bruno Vieira
- Pharmacology Departament, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Marcus Vinícius Gomez
- Graduate Program in Health Sciences, Faculty Santa Casa BH, Belo Horizonte, Minas Gerais, Brazil,*Correspondence: Alessandra Hubner De Souza, ; Marcus Vinícius Gomez,
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4
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Sanderson JL, Freund RK, Castano AM, Benke TA, Dell'Acqua ML. The Ca V1.2 G406R mutation decreases synaptic inhibition and alters L-type Ca 2+ channel-dependent LTP at hippocampal synapses in a mouse model of Timothy Syndrome. Neuropharmacology 2022; 220:109271. [PMID: 36162529 PMCID: PMC9644825 DOI: 10.1016/j.neuropharm.2022.109271] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 09/09/2022] [Accepted: 09/20/2022] [Indexed: 11/17/2022]
Abstract
Genetic alterations in autism spectrum disorders (ASD) frequently disrupt balance between synaptic excitation and inhibition and alter plasticity in the hippocampal CA1 region. Individuals with Timothy Syndrome (TS), a genetic disorder caused by CaV1.2 L-type Ca2+ channel (LTCC) gain-of function mutations, such as G406R, exhibit social deficits, repetitive behaviors, and cognitive impairments characteristic of ASD that are phenocopied in TS2-neo mice expressing G406R. Here, we characterized hippocampal CA1 synaptic function in male TS2-neo mice and found basal excitatory transmission was slightly increased and inhibitory transmission strongly decreased. We also found distinct impacts on two LTCC-dependent forms of long-term potentiation (LTP) synaptic plasticity that were not readily consistent with LTCC gain-of-function. LTP induced by high-frequency stimulation (HFS) was strongly impaired in TS2-neo mice, suggesting decreased LTCC function. Yet, CaV1.2 expression, basal phosphorylation, and current density were similar for WT and TS2-neo. However, this HFS-LTP also required GABAA receptor activity, and thus may be impaired in TS2-neo due to decreased inhibitory transmission. In contrast, LTP induced in WT mice by prolonged theta-train (PTT) stimulation in the presence of a β-adrenergic receptor agonist to increase CaV1.2 phosphorylation was partially induced in TS2-neo mice by PTT stimulation alone, consistent with increased LTCC function. Overall, our findings provide insights regarding how altered CaV1.2 channel function disrupts basal transmission and plasticity that could be relevant for neurobehavioral alterations in ASD.
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Affiliation(s)
- Jennifer L Sanderson
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 E. 19th Ave, Mail Stop 8303, Aurora, CO, 80045, USA
| | - Ronald K Freund
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 E. 19th Ave, Mail Stop 8303, Aurora, CO, 80045, USA
| | - Anna M Castano
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 E. 19th Ave, Mail Stop 8303, Aurora, CO, 80045, USA
| | - Timothy A Benke
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 E. 19th Ave, Mail Stop 8303, Aurora, CO, 80045, USA; Departments of Pediatrics, Neurology, and Otolaryngology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 E. 19th Ave, Mail Stop 8303, Aurora, CO, 80045, USA
| | - Mark L Dell'Acqua
- Department of Pharmacology, University of Colorado School of Medicine, Anschutz Medical Campus, 12800 E. 19th Ave, Mail Stop 8303, Aurora, CO, 80045, USA.
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5
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Tuinte WE, Török E, Mahlknecht I, Tuluc P, Flucher BE, Campiglio M. STAC3 determines the slow activation kinetics of Ca V 1.1 currents and inhibits its voltage-dependent inactivation. J Cell Physiol 2022; 237:4197-4214. [PMID: 36161458 DOI: 10.1002/jcp.30870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 08/23/2022] [Indexed: 11/06/2022]
Abstract
The skeletal muscle CaV 1.1 channel functions as the voltage-sensor of excitation-contraction (EC) coupling. Recently, the adaptor protein STAC3 was found to be essential for both CaV 1.1 functional expression and EC coupling. Interestingly, STAC proteins were also reported to inhibit calcium-dependent inactivation (CDI) of L-type calcium channels (LTCC), an important negative feedback mechanism in calcium signaling. The same could not be demonstrated for CaV 1.1, as STAC3 is required for its functional expression. However, upon strong membrane depolarization, CaV 1.1 conducts calcium currents characterized by very slow kinetics of activation and inactivation. Therefore, we hypothesized that the negligible inactivation observed in CaV 1.1 currents reflects the inhibitory effect of STAC3. Here, we inserted a triple mutation in the linker region of STAC3 (ETLAAA), as the analogous mutation abolished the inhibitory effect of STAC2 on CDI of CaV 1.3 currents. When coexpressed in CaV 1.1/STAC3 double knockout myotubes, the mutant STAC3-ETLAAA failed to colocalize with CaV 1.1 in the sarcoplasmic reticulum/membrane junctions. However, combined patch-clamp and calcium recording experiments revealed that STAC3-ETLAAA supports CaV 1.1 functional expression and EC coupling, although at a reduced extent compared to wild-type STAC3. Importantly, STAC3-ETLAAA coexpression dramatically accelerated the kinetics of activation and inactivation of CaV 1.1 currents, suggesting that STAC3 determines the slow CaV 1.1 currents kinetics. To examine if STAC3 specifically inhibits the CDI of CaV 1.1 currents, we performed patch-clamp recordings using calcium and barium as charge carriers in HEK cells. While CaV 1.1 displayed negligible CDI with STAC3, this did not increase in the presence of STAC3-ETLAAA. On the contrary, our data demonstrate that STAC3 specifically inhibits the voltage-dependent inactivation (VDI) of CaV 1.1 currents. Altogether, these results designate STAC3 as a crucial determinant for the slow activation kinetics of CaV 1.1 currents and implicate STAC proteins as modulators of both components of inactivation of LTCC.
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Affiliation(s)
- Wietske E Tuinte
- Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria
| | - Enikő Török
- Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria
| | - Irene Mahlknecht
- Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria
| | - Petronel Tuluc
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences Innsbruck, University of Innsbruck, Innsbruck, Austria
| | - Bernhard E Flucher
- Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria
| | - Marta Campiglio
- Institute of Physiology, Medical University Innsbruck, Innsbruck, Austria
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6
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Ferron L, Guderyan SD, Smith EJ, Zamponi GW. CaVβ-subunit dependence of forward and reverse trafficking of CaV1.2 calcium channels. Mol Brain 2022; 15:43. [PMID: 35534894 PMCID: PMC9082888 DOI: 10.1186/s13041-022-00930-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 05/02/2022] [Indexed: 11/10/2022] Open
Abstract
AbstractAuxiliary CaVβ subunits interact with the pore forming CaVα1 subunit to promote the plasma membrane expression of high voltage-activated calcium channels and to modulate the biophysical properties of Ca2+ currents. However, the effect of CaVβ subunits on channel trafficking to and from the plasma membrane is still controversial. Here, we have investigated the impact of CaVβ1b and CaVβ2a subunits on plasma membrane trafficking of CaV1.2 using a live-labeling strategy. We show that the CaVβ1b subunit is more potent in increasing CaV1.2 expression at the plasma membrane than the CaVβ2a subunit and that this effect is not related to modification of intracellular trafficking of the channel (i.e. neither forward trafficking, nor recycling, nor endocytosis). We conclude that the differential effect of CaVβ subunit subtypes on CaV1.2 surface expression is likely due to their differential ability to protect CaV1.2 from degradation.
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7
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Dixon RE, Navedo MF, Binder MD, Santana LF. Mechanisms and Physiological Implications of Cooperative Gating of Ion Channels Clusters. Physiol Rev 2021; 102:1159-1210. [PMID: 34927454 DOI: 10.1152/physrev.00022.2021] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ion channels play a central role in the regulation of nearly every cellular process. Dating back to the classic 1952 Hodgkin-Huxley model of the generation of the action potential, ion channels have always been thought of as independent agents. A myriad of recent experimental findings exploiting advances in electrophysiology, structural biology, and imaging techniques, however, have posed a serious challenge to this long-held axiom as several classes of ion channels appear to open and close in a coordinated, cooperative manner. Ion channel cooperativity ranges from variable-sized oligomeric cooperative gating in voltage-gated, dihydropyridine-sensitive Cav1.2 and Cav1.3 channels to obligatory dimeric assembly and gating of voltage-gated Nav1.5 channels. Potassium channels, transient receptor potential channels, hyperpolarization cyclic nucleotide-activated channels, ryanodine receptors (RyRs), and inositol trisphosphate receptors (IP3Rs) have also been shown to gate cooperatively. The implications of cooperative gating of these ion channels range from fine tuning excitation-contraction coupling in muscle cells to regulating cardiac function and vascular tone, to modulation of action potential and conduction velocity in neurons and cardiac cells, and to control of pace-making activity in the heart. In this review, we discuss the mechanisms leading to cooperative gating of ion channels, their physiological consequences and how alterations in cooperative gating of ion channels may induce a range of clinically significant pathologies.
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Affiliation(s)
- Rose Ellen Dixon
- Department of Physiology and Membrane Biology, University of California, Davis, CA, United States
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, CA, United States
| | - Marc D Binder
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, United States
| | - L Fernando Santana
- Department of Physiology and Membrane Biology, University of California, Davis, CA, United States
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8
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Gómez-Oca R, Cowling BS, Laporte J. Common Pathogenic Mechanisms in Centronuclear and Myotubular Myopathies and Latest Treatment Advances. Int J Mol Sci 2021; 22:11377. [PMID: 34768808 PMCID: PMC8583656 DOI: 10.3390/ijms222111377] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Accepted: 10/18/2021] [Indexed: 01/18/2023] Open
Abstract
Centronuclear myopathies (CNM) are rare congenital disorders characterized by muscle weakness and structural defects including fiber hypotrophy and organelle mispositioning. The main CNM forms are caused by mutations in: the MTM1 gene encoding the phosphoinositide phosphatase myotubularin (myotubular myopathy), the DNM2 gene encoding the mechanoenzyme dynamin 2, the BIN1 gene encoding the membrane curvature sensing amphiphysin 2, and the RYR1 gene encoding the skeletal muscle calcium release channel/ryanodine receptor. MTM1, BIN1, and DNM2 proteins are involved in membrane remodeling and trafficking, while RyR1 directly regulates excitation-contraction coupling (ECC). Several CNM animal models have been generated or identified, which confirm shared pathological anomalies in T-tubule remodeling, ECC, organelle mispositioning, protein homeostasis, neuromuscular junction, and muscle regeneration. Dynamin 2 plays a crucial role in CNM physiopathology and has been validated as a common therapeutic target for three CNM forms. Indeed, the promising results in preclinical models set up the basis for ongoing clinical trials. Another two clinical trials to treat myotubular myopathy by MTM1 gene therapy or tamoxifen repurposing are also ongoing. Here, we review the contribution of the different CNM models to understanding physiopathology and therapy development with a focus on the commonly dysregulated pathways and current therapeutic targets.
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Affiliation(s)
- Raquel Gómez-Oca
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), 67400 Illkirch, France;
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1258, 67400 Illkirch, France
- Centre National de la Recherche Scientifique (CNRS), UMR7104, 67400 Illkirch, France
- Strasbourg University, 67081 Strasbourg, France
- Dynacure, 67400 Illkirch, France;
| | | | - Jocelyn Laporte
- Department of Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), 67400 Illkirch, France;
- Institut National de la Santé et de la Recherche Médicale (INSERM), U1258, 67400 Illkirch, France
- Centre National de la Recherche Scientifique (CNRS), UMR7104, 67400 Illkirch, France
- Strasbourg University, 67081 Strasbourg, France
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Morgenstern TJ, Colecraft HM. Controlling ion channel trafficking by targeted ubiquitination and deubiquitination. Methods Enzymol 2021; 654:139-167. [PMID: 34120711 DOI: 10.1016/bs.mie.2021.03.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Plasma membrane-localized ion channels are essential for diverse physiological processes such as neurotransmission, muscle contraction, and osmotic homeostasis. The surface density of such ion channels is a major determinant of their function, and tuning this variable is a powerful way to regulate physiology. Dysregulation of ion channel surface density due to inherited or de novo mutations underlies many serious diseases, and molecules that can correct trafficking deficits are potential therapeutics and useful research tools. We have developed targeted ubiquitination and deubiquitination approaches that enable selective posttranslational down- or up-regulation, respectively, of desired ion channels. The method employs bivalent molecules comprised of an ion-channel-targeted nanobody fused to catalytic domains of either an E3 ubiquitin ligase or a deubiquitinase. Here, we use two examples to provide detailed protocols that illustrate the utility of the approach-rescued surface expression of a trafficking-deficient mutant KV7.1 (KCNQ1) channel that causes long QT syndrome, and selective elimination of the CaV2.2 voltage-gated calcium channel from the plasma membrane using targeted ubiquitination. Important aspects of the approach include having a robust assay to measure ion channel surface density and generating nanobody binders to cytosolic domains or subunits of targeted ion channels. Accordingly, we also review available methods for determining ion channel surface density and nanobody selection.
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Affiliation(s)
- Travis J Morgenstern
- Department of Molecular Pharmacology and Therapeutics, Columbia University, Vagelos College of Physicians and Surgeons, New York, NY, United States
| | - Henry M Colecraft
- Department of Molecular Pharmacology and Therapeutics, Columbia University, Vagelos College of Physicians and Surgeons, New York, NY, United States; Department of Physiology and Cellular Biophysics, Columbia University, Vagelos College of Physicians and Surgeons, New York, NY, United States.
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10
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Schöpf CL, Ablinger C, Geisler SM, Stanika RI, Campiglio M, Kaufmann WA, Nimmervoll B, Schlick B, Brockhaus J, Missler M, Shigemoto R, Obermair GJ. Presynaptic α 2δ subunits are key organizers of glutamatergic synapses. Proc Natl Acad Sci U S A 2021; 118:e1920827118. [PMID: 33782113 PMCID: PMC8040823 DOI: 10.1073/pnas.1920827118] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In nerve cells the genes encoding for α2δ subunits of voltage-gated calcium channels have been linked to synaptic functions and neurological disease. Here we show that α2δ subunits are essential for the formation and organization of glutamatergic synapses. Using a cellular α2δ subunit triple-knockout/knockdown model, we demonstrate a failure in presynaptic differentiation evidenced by defective presynaptic calcium channel clustering and calcium influx, smaller presynaptic active zones, and a strongly reduced accumulation of presynaptic vesicle-associated proteins (synapsin and vGLUT). The presynaptic defect is associated with the downscaling of postsynaptic AMPA receptors and the postsynaptic density. The role of α2δ isoforms as synaptic organizers is highly redundant, as each individual α2δ isoform can rescue presynaptic calcium channel trafficking and expression of synaptic proteins. Moreover, α2δ-2 and α2δ-3 with mutated metal ion-dependent adhesion sites can fully rescue presynaptic synapsin expression but only partially calcium channel trafficking, suggesting that the regulatory role of α2δ subunits is independent from its role as a calcium channel subunit. Our findings influence the current view on excitatory synapse formation. First, our study suggests that postsynaptic differentiation is secondary to presynaptic differentiation. Second, the dependence of presynaptic differentiation on α2δ implicates α2δ subunits as potential nucleation points for the organization of synapses. Finally, our results suggest that α2δ subunits act as transsynaptic organizers of glutamatergic synapses, thereby aligning the synaptic active zone with the postsynaptic density.
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Affiliation(s)
- Clemens L Schöpf
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Cornelia Ablinger
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Stefanie M Geisler
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
- Department of Pharmacology and Toxicology, University of Innsbruck, A-6020 Innsbruck, Austria
| | - Ruslan I Stanika
- Division of Physiology, Karl Landsteiner University of Health Sciences, A-3500 Krems, Austria
| | - Marta Campiglio
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Walter A Kaufmann
- Institute of Science and Technology Austria, A-3400 Klosterneuburg, Austria
| | - Benedikt Nimmervoll
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Bettina Schlick
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria
| | - Johannes Brockhaus
- Institute of Anatomy and Molecular Neurobiology, Westfälische Wilhelms University, 48149 Münster, Germany
| | - Markus Missler
- Institute of Anatomy and Molecular Neurobiology, Westfälische Wilhelms University, 48149 Münster, Germany
| | - Ryuichi Shigemoto
- Institute of Science and Technology Austria, A-3400 Klosterneuburg, Austria
| | - Gerald J Obermair
- Institute of Physiology, Medical University of Innsbruck, A-6020 Innsbruck, Austria;
- Division of Physiology, Karl Landsteiner University of Health Sciences, A-3500 Krems, Austria
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11
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Autism-associated mutations in the CaVβ2 calcium-channel subunit increase Ba2+-currents and lead to differential modulation by the RGK-protein Gem. Neurobiol Dis 2020; 136:104721. [DOI: 10.1016/j.nbd.2019.104721] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Revised: 12/06/2019] [Accepted: 12/26/2019] [Indexed: 12/26/2022] Open
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12
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Listeria monocytogenes exploits host exocytosis to promote cell-to-cell spread. Proc Natl Acad Sci U S A 2020; 117:3789-3796. [PMID: 32015134 DOI: 10.1073/pnas.1916676117] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The facultative intracellular pathogen Listeria monocytogenes uses an actin-based motility process to spread within human tissues. Filamentous actin from the human cell forms a tail behind bacteria, propelling microbes through the cytoplasm. Motile bacteria remodel the host plasma membrane into protrusions that are internalized by neighboring cells. A critical unresolved question is whether generation of protrusions by Listeria involves stimulation of host processes apart from actin polymerization. Here we demonstrate that efficient protrusion formation in polarized epithelial cells involves bacterial subversion of host exocytosis. Confocal microscopy imaging indicated that exocytosis is up-regulated in protrusions of Listeria in a manner that depends on the host exocyst complex. Depletion of components of the exocyst complex by RNA interference inhibited the formation of Listeria protrusions and subsequent cell-to-cell spread of bacteria. Additional genetic studies indicated important roles for the exocyst regulators Rab8 and Rab11 in bacterial protrusion formation and spread. The secreted Listeria virulence factor InlC associated with the exocyst component Exo70 and mediated the recruitment of Exo70 to bacterial protrusions. Depletion of exocyst proteins reduced the length of Listeria protrusions, suggesting that the exocyst complex promotes protrusion elongation. Collectively, these results demonstrate that Listeria exploits host exocytosis to stimulate intercellular spread of bacteria.
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13
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Sato D, Hernández-Hernández G, Matsumoto C, Tajada S, Moreno CM, Dixon RE, O'Dwyer S, Navedo MF, Trimmer JS, Clancy CE, Binder MD, Santana LF. A stochastic model of ion channel cluster formation in the plasma membrane. J Gen Physiol 2019; 151:1116-1134. [PMID: 31371391 PMCID: PMC6719406 DOI: 10.1085/jgp.201912327] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 07/05/2019] [Accepted: 07/08/2019] [Indexed: 12/24/2022] Open
Abstract
Ion channels are often found arranged into dense clusters in the plasma membranes of excitable cells, but the mechanisms underlying the formation and maintenance of these functional aggregates are unknown. Here, we tested the hypothesis that channel clustering is the consequence of a stochastic self-assembly process and propose a model by which channel clusters are formed and regulated in size. Our hypothesis is based on statistical analyses of the size distributions of the channel clusters we measured in neurons, ventricular myocytes, arterial smooth muscle, and heterologous cells, which in all cases were described by exponential functions, indicative of a Poisson process (i.e., clusters form in a continuous, independent, and memory-less fashion). We were able to reproduce the observed cluster distributions of five different types of channels in the membrane of excitable and tsA-201 cells in simulations using a computer model in which channels are "delivered" to the membrane at randomly assigned locations. The model's three parameters represent channel cluster nucleation, growth, and removal probabilities, the values of which were estimated based on our experimental measurements. We also determined the time course of cluster formation and membrane dwell time for CaV1.2 and TRPV4 channels expressed in tsA-201 cells to constrain our model. In addition, we elaborated a more complex version of our model that incorporated a self-regulating feedback mechanism to shape channel cluster formation. The strong inference we make from our results is that CaV1.2, CaV1.3, BK, and TRPV4 proteins are all randomly inserted into the plasma membranes of excitable cells and that they form homogeneous clusters that increase in size until they reach a steady state. Further, it appears likely that cluster size for a diverse set of membrane-bound proteins and a wide range of cell types is regulated by a common feedback mechanism.
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Affiliation(s)
- Daisuke Sato
- Department of Pharmacology, University of California School of Medicine, Davis, CA
| | | | - Collin Matsumoto
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA
| | - Sendoa Tajada
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA
| | - Claudia M Moreno
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA
| | - Rose E Dixon
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA
| | - Samantha O'Dwyer
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA
| | - Manuel F Navedo
- Department of Pharmacology, University of California School of Medicine, Davis, CA
| | - James S Trimmer
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA
| | - Colleen E Clancy
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA
| | - Marc D Binder
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA
| | - L Fernando Santana
- Department of Physiology and Membrane Biology, University of California School of Medicine, Davis, CA
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14
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Syed AU, Reddy GR, Ghosh D, Prada MP, Nystoriak MA, Morotti S, Grandi E, Sirish P, Chiamvimonvat N, Hell JW, Santana LF, Xiang YK, Nieves-Cintrón M, Navedo MF. Adenylyl cyclase 5-generated cAMP controls cerebral vascular reactivity during diabetic hyperglycemia. J Clin Invest 2019; 129:3140-3152. [PMID: 31162142 PMCID: PMC6668679 DOI: 10.1172/jci124705] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 05/14/2019] [Indexed: 12/20/2022] Open
Abstract
Elevated blood glucose (hyperglycemia) is a hallmark metabolic abnormality in diabetes. Hyperglycemia is associated with protein kinase A (PKA)-mediated stimulation of L-type Ca2+ channels in arterial myocytes resulting in increased vasoconstriction. However, the mechanisms by which glucose activates PKA remain unclear. Here, we showed that elevating extracellular glucose stimulates cAMP production in arterial myocytes, and that this was specifically dependent on adenylyl cyclase 5 (AC5) activity. Super-resolution imaging suggested nanometer proximity between subpopulations of AC5 and the L-type Ca2+ channel pore-forming subunit CaV1.2. In vitro, in silico, ex vivo and in vivo experiments revealed that this close association is critical for stimulation of L-type Ca2+ channels in arterial myocytes and increased myogenic tone upon acute hyperglycemia. This pathway supported the increase in L-type Ca2+ channel activity and myogenic tone in two animal models of diabetes. Our collective findings demonstrate a unique role for AC5 in PKA-dependent modulation of L-type Ca2+ channel activity and vascular reactivity during acute hyperglycemia and diabetes.
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MESH Headings
- Adenylyl Cyclases/genetics
- Adenylyl Cyclases/metabolism
- Animals
- Calcium Channels, L-Type/biosynthesis
- Calcium Channels, L-Type/genetics
- Cerebral Arteries/enzymology
- Cerebral Arteries/pathology
- Cyclic AMP/genetics
- Cyclic AMP/metabolism
- Cyclic AMP-Dependent Protein Kinases/genetics
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Diabetes Mellitus, Experimental/enzymology
- Diabetes Mellitus, Experimental/genetics
- Diabetes Mellitus, Experimental/pathology
- Hyperglycemia/enzymology
- Hyperglycemia/genetics
- Hyperglycemia/pathology
- Mice
- Mice, Knockout
- Muscle, Smooth, Vascular/enzymology
- Muscle, Smooth, Vascular/pathology
- Myocytes, Smooth Muscle/enzymology
- Myocytes, Smooth Muscle/pathology
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Affiliation(s)
- Arsalan U. Syed
- Department of Pharmacology, University of California, Davis, Davis, California, USA
| | - Gopireddy R. Reddy
- Department of Pharmacology, University of California, Davis, Davis, California, USA
| | - Debapriya Ghosh
- Department of Pharmacology, University of California, Davis, Davis, California, USA
| | - Maria Paz Prada
- Department of Pharmacology, University of California, Davis, Davis, California, USA
| | - Matthew A. Nystoriak
- Diabetes and Obesity Center, Department of Medicine, University of Louisville, Louisville, Kentucky, USA
| | - Stefano Morotti
- Department of Pharmacology, University of California, Davis, Davis, California, USA
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Davis, California, USA
| | - Padmini Sirish
- Department of Internal Medicine, University of California, Davis, Davis, California, USA
| | - Nipavan Chiamvimonvat
- Department of Pharmacology, University of California, Davis, Davis, California, USA
- Department of Internal Medicine, University of California, Davis, Davis, California, USA
- VA Northern California Health Care System, Mather, California, USA
| | - Johannes W. Hell
- Department of Pharmacology, University of California, Davis, Davis, California, USA
| | - Luis F. Santana
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, California, USA
| | - Yang K. Xiang
- Department of Pharmacology, University of California, Davis, Davis, California, USA
- VA Northern California Health Care System, Mather, California, USA
| | | | - Manuel F. Navedo
- Department of Pharmacology, University of California, Davis, Davis, California, USA
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15
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Heine M, Heck J, Ciuraszkiewicz A, Bikbaev A. Dynamic compartmentalization of calcium channel signalling in neurons. Neuropharmacology 2019; 169:107556. [PMID: 30851307 DOI: 10.1016/j.neuropharm.2019.02.038] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 02/16/2019] [Accepted: 02/27/2019] [Indexed: 12/13/2022]
Abstract
Calcium fluxes through the neuronal membrane are strictly limited in time due to biophysical properties of voltage-gated and ligand-activated ion channels and receptors. Being embedded into the crowded dynamic environment of biological membranes, Ca2+-permeable receptors and channels undergo perpetual spatial rearrangement, which enables their temporary association and formation of transient signalling complexes. Thus, efficient calcium-mediated signal transduction requires mechanisms to support very precise spatiotemporal alignment of the calcium source and Ca2+-binding lipids and proteins in a highly dynamic environment. The mobility of calcium channels and calcium-sensing proteins themselves can be considered as a physiologically meaningful variable that affects calcium-mediated signalling in neurons. In this review, we will focus on voltage-gated calcium channels (VGCCs) and activity-induced relocation of stromal interaction molecules (STIMs) in the endoplasmic reticulum (ER) to show that particularly in time ranges between milliseconds to minutes, dynamic rearrangement of calcium conducting channels and sensor molecules is of physiological relevance. This article is part of the special issue entitled 'Mobility and trafficking of neuronal membrane proteins'.
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Affiliation(s)
- Martin Heine
- RG Molecular Physiology, Leibniz Institute for Neurobiology, Magdeburg, 39118, Germany; Center for Behavioral Brain Sciences, Otto-von-Guericke University, Magdeburg, 39106, Germany; RG Functional Neurobiology, Institute for Development Biology and Neurobiology, Johannes Gutenberg University Mainz, Germany.
| | - Jennifer Heck
- RG Molecular Physiology, Leibniz Institute for Neurobiology, Magdeburg, 39118, Germany
| | - Anna Ciuraszkiewicz
- RG Molecular Physiology, Leibniz Institute for Neurobiology, Magdeburg, 39118, Germany; Center for Behavioral Brain Sciences, Otto-von-Guericke University, Magdeburg, 39106, Germany
| | - Arthur Bikbaev
- RG Molecular Physiology, Leibniz Institute for Neurobiology, Magdeburg, 39118, Germany
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16
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Zhang Z, Wang Y, Zhang Q, Zhao W, Chen X, Zhai J, Chen M, Du B, Deng X, Ji F, Wang C, Xiang Y, Li D, Wu H, Dong Q, Chen C, Li J. The effects of CACNA1C gene polymorphism on prefrontal cortex in both schizophrenia patients and healthy controls. Schizophr Res 2019; 204:193-200. [PMID: 30268820 DOI: 10.1016/j.schres.2018.09.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Revised: 11/28/2017] [Accepted: 09/09/2018] [Indexed: 11/28/2022]
Abstract
CACNA1C gene polymorphism rs2007044 has been reported to be associated with schizophrenia, but its underlying brain mechanism is not clear. First, we conducted an exploratory functional magnetic resonance imaging (fMRI) study using an N-BACK task and a Stroop task in 194 subjects (55 schizophrenia patients and 139 healthy controls). Our whole brain analysis found that the risk allele was associated with reduced activation of the left inferior frontal gyrus (IFG) during the Stroop task (cluster size = 390 voxels, P < 0.05 TFCE-FWE corrected; peak MNI coordinates: x = -57, y = -6, z = 30). We also conducted a functional near-infrared spectroscopy (fNIRS) study using the same Stroop task in an independent sample of 126 healthy controls to validate the fMRI finding. Our repeated-measures ANCOVA on the six channels (20, 27, 33, 34, 40 and 46) within the left IFG also found significant result. The polymorphism rs2007044 showed significant effect on the oxy-Hb data (F = 5.072, P = 0.026) and showed significant interaction effect with channels on the deoxy-Hb data (F = 2.841, P = 0.015). Taken together, results of this study suggested that rs2007044 could affect the activation of the left IFG, which was a possible brain mechanism underlying the association between CACNA1C gene polymorphism and schizophrenia.
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Affiliation(s)
- Zhifang Zhang
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, PR China
| | - Yanyan Wang
- Department of Psychiatry, HePing Hospital of Chang Zhou, Jiangsu 213003, China
| | - Qiumei Zhang
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, PR China; School of Mental Health, Jining Medical University, 45# Jianshe South Road, Jining 272013, Shandong Province, PR China
| | - Wan Zhao
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, PR China
| | - Xiongying Chen
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, PR China
| | - Jinguo Zhai
- School of Mental Health, Jining Medical University, 45# Jianshe South Road, Jining 272013, Shandong Province, PR China
| | - Min Chen
- School of Mental Health, Jining Medical University, 45# Jianshe South Road, Jining 272013, Shandong Province, PR China
| | - Boqi Du
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, PR China
| | - Xiaoxiang Deng
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, PR China
| | - Feng Ji
- School of Mental Health, Jining Medical University, 45# Jianshe South Road, Jining 272013, Shandong Province, PR China
| | | | - Yutao Xiang
- Beijing Anding Hospital, Beijing 100088, PR China; Faculty of Health Sciences, University of Macau, Avenida da Universidade, Taipa, Macau
| | - Dawei Li
- Center for Cognitive Neuroscience, Duke University, Durham, NC, USA
| | - Hongjie Wu
- Shengli Hospital of Shengli Petroleum Administration Bureau, Dongying 257022, Shandong Province, PR China
| | - Qi Dong
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, PR China
| | - Chuansheng Chen
- Department of Psychology and Social Behavior, University of California, Irvine, CA 92697, United States
| | - Jun Li
- State Key Laboratory of Cognitive Neuroscience and Learning & IDG/McGovern Institute for Brain Research, Beijing Normal University, PR China.
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17
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Calorio C, Gavello D, Guarina L, Salio C, Sassoè-Pognetto M, Riganti C, Bianchi FT, Hofer NT, Tuluc P, Obermair GJ, Defilippi P, Balzac F, Turco E, Bett GC, Rasmusson RL, Carbone E. Impaired chromaffin cell excitability and exocytosis in autistic Timothy syndrome TS2-neo mouse rescued by L-type calcium channel blockers. J Physiol 2019; 597:1705-1733. [PMID: 30629744 DOI: 10.1113/jp277487] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Accepted: 12/19/2018] [Indexed: 12/30/2022] Open
Abstract
KEY POINTS Tymothy syndrome (TS) is a multisystem disorder featuring cardiac arrhythmias, autism and adrenal gland dysfunction that originates from a de novo point mutation in the gene encoding the Cav1.2 (CACNA1C) L-type channel. To study the role of Cav1.2 channel signals in autism, the autistic TS2-neo mouse has been generated bearing the G406R point-mutation associated with TS type-2. Using heterozygous TS2-neo mice, we report that the G406R mutation reduces the rate of inactivation and shifts leftward the activation and inactivation of L-type channels, causing marked increase of resting Ca2+ influx ('window' Ca2+ current). The increased 'window current' causes marked reduction of NaV channel density, switches normal tonic firing to abnormal burst firing, reduces mitochondrial metabolism, induces cell swelling and decreases catecholamine release. Overnight incubations with nifedipine rescue NaV channel density, normal firing and the quantity of catecholamine released. We provide evidence that chromaffin cell malfunction derives from altered Cav1.2 channel gating. ABSTRACT L-type voltage-gated calcium (Cav1) channels have a key role in long-term synaptic plasticity, sensory transduction, muscle contraction and hormone release. A point mutation in the gene encoding Cav1.2 (CACNA1C) causes Tymothy syndrome (TS), a multisystem disorder featuring cardiac arrhythmias, autism spectrum disorder (ASD) and adrenal gland dysfunction. In the more severe type-2 form (TS2), the missense mutation G406R is on exon 8 coding for the IS6-helix of the Cav1.2 channel. The mutation causes reduced inactivation and induces autism. How this occurs and how Cav1.2 gating-changes alter cell excitability, neuronal firing and hormone release on a molecular basis is still largely unknown. Here, using the TS2-neo mouse model of TS we show that the G406R mutation altered excitability and reduced secretory activity in adrenal chromaffin cells (CCs). Specifically, the TS2 mutation reduced the rate of voltage-dependent inactivation and shifted leftward the activation and steady-state inactivation of L-type channels. This markedly increased the resting 'window' Ca2+ current that caused an increased percentage of CCs undergoing abnormal action potential (AP) burst firing, cell swelling, reduced mitochondrial metabolism and decreased catecholamine release. The increased 'window' Ca2+ current caused also decreased NaV channel density and increased steady-state inactivation, which contributed to the increased abnormal burst firing. Overnight incubation with the L-type channel blocker nifedipine rescued the normal AP firing of CCs, the density of functioning NaV channels and their steady-state inactivation. We provide evidence that CC malfunction derives from the altered Cav1.2 channel gating and that dihydropyridines are potential therapeutics for ASD.
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Affiliation(s)
- Chiara Calorio
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Daniela Gavello
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Laura Guarina
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
| | - Chiara Salio
- Department of Veterinary Sciences, University of Torino, Torino, Italy
| | - Marco Sassoè-Pognetto
- Department of Neuroscience Rita Levi Montalcini, University of Torino, Torino, Italy
| | - Chiara Riganti
- Department of Oncology, University of Torino, Torino, Italy
| | | | - Nadja T Hofer
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Petronel Tuluc
- Department of Pharmacology and Toxicology, Center for Molecular Biosciences, University of Innsbruck, Innsbruck, Austria
| | - Gerald J Obermair
- Department of Physiology & Medical Physics, Medical University of Innsbruck, Innsbruck, Austria
| | - Paola Defilippi
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Fiorella Balzac
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Emilia Turco
- Department of Molecular Biotechnology and Health Sciences, University of Torino, Torino, Italy
| | - Glenna C Bett
- Department of Physiology & Biophysics, State University of New York, Buffalo, NY, USA
| | - Randall L Rasmusson
- Department of Physiology & Biophysics, State University of New York, Buffalo, NY, USA
| | - Emilio Carbone
- Department of Drug Science, NIS Centre, University of Torino, Torino, Italy
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18
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Basheer WA, Shaw RM. Connexin 43 and CaV1.2 Ion Channel Trafficking in Healthy and Diseased Myocardium. Circ Arrhythm Electrophysiol 2018; 9:e001357. [PMID: 27266274 DOI: 10.1161/circep.115.001357] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 04/29/2016] [Indexed: 11/16/2022]
Affiliation(s)
- Wassim A Basheer
- From the Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA (W.A.B., R.M.S.); and Department of Medicine, University of California Los Angeles (R.M.S.)
| | - Robin M Shaw
- From the Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA (W.A.B., R.M.S.); and Department of Medicine, University of California Los Angeles (R.M.S.).
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19
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Ghosh D, Nieves-Cintrón M, Tajada S, Brust-Mascher I, Horne MC, Hell JW, Dixon RE, Santana LF, Navedo MF. Dynamic L-type Ca V1.2 channel trafficking facilitates Ca V1.2 clustering and cooperative gating. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1865:1341-1355. [PMID: 29959960 PMCID: PMC6407617 DOI: 10.1016/j.bbamcr.2018.06.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2018] [Revised: 06/22/2018] [Accepted: 06/26/2018] [Indexed: 11/21/2022]
Abstract
L-type CaV1.2 channels are key regulators of gene expression, cell excitability and muscle contraction. CaV1.2 channels organize in clusters throughout the plasma membrane. This channel organization has been suggested to contribute to the concerted activation of adjacent CaV1.2 channels (e.g. cooperative gating). Here, we tested the hypothesis that dynamic intracellular and perimembrane trafficking of CaV1.2 channels is critical for formation and dissolution of functional channel clusters mediating cooperative gating. We found that CaV1.2 moves in vesicular structures of circular and tubular shape with diverse intracellular and submembrane trafficking patterns. Both microtubules and actin filaments are required for dynamic movement of CaV1.2 vesicles. These vesicles undergo constitutive homotypic fusion and fission events that sustain CaV1.2 clustering, channel activity and cooperative gating. Our study suggests that CaV1.2 clusters and activity can be modulated by diverse and unique intracellular and perimembrane vesicular dynamics to fine-tune Ca2+ signals.
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Affiliation(s)
- Debapriya Ghosh
- Department of Pharmacology, School of Medicine, One Shields Avenue, University of California, Davis, CA 95616, USA
| | - Madeline Nieves-Cintrón
- Department of Pharmacology, School of Medicine, One Shields Avenue, University of California, Davis, CA 95616, USA
| | - Sendoa Tajada
- Department of Physiology & Membrane Biology, School of Medicine, One Shields Avenue, University of California, Davis, CA 95616, USA
| | - Ingrid Brust-Mascher
- Advanced Imaging Facility, School of Veterinary Medicine, One Shields Avenue, University of California, Davis, CA 95616, USA
| | - Mary C Horne
- Department of Pharmacology, School of Medicine, One Shields Avenue, University of California, Davis, CA 95616, USA
| | - Johannes W Hell
- Department of Pharmacology, School of Medicine, One Shields Avenue, University of California, Davis, CA 95616, USA
| | - Rose E Dixon
- Department of Physiology & Membrane Biology, School of Medicine, One Shields Avenue, University of California, Davis, CA 95616, USA
| | - Luis F Santana
- Department of Physiology & Membrane Biology, School of Medicine, One Shields Avenue, University of California, Davis, CA 95616, USA
| | - Manuel F Navedo
- Department of Pharmacology, School of Medicine, One Shields Avenue, University of California, Davis, CA 95616, USA.
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20
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STAC proteins associate to the IQ domain of Ca V1.2 and inhibit calcium-dependent inactivation. Proc Natl Acad Sci U S A 2018; 115:1376-1381. [PMID: 29363593 PMCID: PMC5819422 DOI: 10.1073/pnas.1715997115] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Association of the adaptor protein STAC3 to the calcium channel was recently identified as essential for skeletal muscle contraction. While STAC3 is expressed exclusively in skeletal muscle, the other two isoforms, STAC1 and STAC2, are found in the brain, but their function has not yet been investigated. Recently we identified the C1 domain of STAC as crucial for its association with calcium channels. However, the corresponding binding domain remained unknown. Here, we demonstrate that STAC proteins associate with the C terminus of CaV1.2 at the IQ domain, and that this interaction results in the inhibition of calcium-dependent inactivation. Taken together, our data identify a functionally important STAC interaction domain and suggest that STAC proteins modulate calcium entry through CaV1 channels. The adaptor proteins STAC1, STAC2, and STAC3 represent a newly identified family of regulators of voltage-gated calcium channel (CaV) trafficking and function. The skeletal muscle isoform STAC3 is essential for excitation–contraction coupling and its mutation causes severe muscle disease. Recently, two distinct molecular domains in STAC3 were identified, necessary for its functional interaction with CaV1.1: the C1 domain, which recruits STAC proteins to the calcium channel complex in skeletal muscle triads, and the SH3-1 domain, involved in excitation–contraction coupling. These interaction sites are conserved in the three STAC proteins. However, the molecular domain in CaV1 channels interacting with the STAC C1 domain and the possible role of this interaction in neuronal CaV1 channels remained unknown. Using CaV1.2/2.1 chimeras expressed in dysgenic (CaV1.1−/−) myotubes, we identified the amino acids 1,641–1,668 in the C terminus of CaV1.2 as necessary for association of STAC proteins. This sequence contains the IQ domain and alanine mutagenesis revealed that the amino acids important for STAC association overlap with those making contacts with the C-lobe of calcium-calmodulin (Ca/CaM) and mediating calcium-dependent inactivation of CaV1.2. Indeed, patch-clamp analysis demonstrated that coexpression of either one of the three STAC proteins with CaV1.2 opposed calcium-dependent inactivation, although to different degrees, and that substitution of the CaV1.2 IQ domain with that of CaV2.1, which does not interact with STAC, abolished this effect. These results suggest that STAC proteins associate with the CaV1.2 C terminus at the IQ domain and thus inhibit calcium-dependent feedback regulation of CaV1.2 currents.
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21
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Bedenk BT, Almeida-Corrêa S, Jurik A, Dedic N, Grünecker B, Genewsky AJ, Kaltwasser SF, Riebe CJ, Deussing JM, Czisch M, Wotjak CT. Mn 2+ dynamics in manganese-enhanced MRI (MEMRI): Ca v1.2 channel-mediated uptake and preferential accumulation in projection terminals. Neuroimage 2017; 169:374-382. [PMID: 29277401 DOI: 10.1016/j.neuroimage.2017.12.054] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 11/27/2017] [Accepted: 12/18/2017] [Indexed: 12/11/2022] Open
Abstract
Manganese-enhanced magnetic resonance imaging (MEMRI) exploits the biophysical similarity of Ca2+ and Mn2+ to map the brain's activity in vivo. However, to what extent different Ca2+ channels contribute to the enhanced signal that MEMRI provides and how Mn2+ dynamics influence Mn2+ brain accumulation after systemic administration of MnCl2 are not yet fully understood. Here, we demonstrate that mice lacking the L-type Ca2+ channel 1.2 (Cav1.2) in the CNS show approximately 50% less increase in MEMRI contrast after repeated systemic MnCl2 injections, as compared to control mice. In contrast, genetic deletion of L-type Ca2+ channel 1.3 (Cav1.3) did not reduce signal. Brain structure- or cell type-specific deletion of Cav1.2 in combination with voxel-wise MEMRI analysis revealed a preferential accumulation of Mn2+ in projection terminals, which was confirmed by local MnCl2 administration to defined brain areas. Taken together, we provide unequivocal evidence that Cav1.2 represents an important channel for neuronal Mn2+ influx after systemic injections. We also show that after neuronal uptake, Mn2+ preferentially accumulates in projection terminals.
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Affiliation(s)
- Benedikt T Bedenk
- Max Planck Institute of Psychiatry, Dept. Stress Neurobiology & Neurogenetics, Kraepelinstr. 2-10, 80804 Munich, Germany; Max Planck Institute of Psychiatry, Core Unit Neuroimaging, Kraepelinstr. 2-10, 80804 Munich, Germany
| | - Suellen Almeida-Corrêa
- Max Planck Institute of Psychiatry, Dept. Stress Neurobiology & Neurogenetics, Kraepelinstr. 2-10, 80804 Munich, Germany
| | - Angela Jurik
- Max Planck Institute of Psychiatry, Dept. Stress Neurobiology & Neurogenetics, Kraepelinstr. 2-10, 80804 Munich, Germany
| | - Nina Dedic
- Max Planck Institute of Psychiatry, Dept. Stress Neurobiology & Neurogenetics, Kraepelinstr. 2-10, 80804 Munich, Germany
| | - Barbara Grünecker
- Max Planck Institute of Psychiatry, Core Unit Neuroimaging, Kraepelinstr. 2-10, 80804 Munich, Germany
| | - Andreas J Genewsky
- Max Planck Institute of Psychiatry, Dept. Stress Neurobiology & Neurogenetics, Kraepelinstr. 2-10, 80804 Munich, Germany
| | - Sebastian F Kaltwasser
- Max Planck Institute of Psychiatry, Dept. Stress Neurobiology & Neurogenetics, Kraepelinstr. 2-10, 80804 Munich, Germany
| | - Caitlin J Riebe
- Max Planck Institute of Psychiatry, Dept. Stress Neurobiology & Neurogenetics, Kraepelinstr. 2-10, 80804 Munich, Germany
| | - Jan M Deussing
- Max Planck Institute of Psychiatry, Dept. Stress Neurobiology & Neurogenetics, Kraepelinstr. 2-10, 80804 Munich, Germany
| | - Michael Czisch
- Max Planck Institute of Psychiatry, Core Unit Neuroimaging, Kraepelinstr. 2-10, 80804 Munich, Germany
| | - Carsten T Wotjak
- Max Planck Institute of Psychiatry, Dept. Stress Neurobiology & Neurogenetics, Kraepelinstr. 2-10, 80804 Munich, Germany.
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22
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Folci A, Steinberger A, Lee B, Stanika R, Scheruebel S, Campiglio M, Ramprecht C, Pelzmann B, Hell JW, Obermair GJ, Heine M, Di Biase V. Molecular mimicking of C-terminal phosphorylation tunes the surface dynamics of Ca V1.2 calcium channels in hippocampal neurons. J Biol Chem 2017; 293:1040-1053. [PMID: 29180451 PMCID: PMC5777246 DOI: 10.1074/jbc.m117.799585] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 11/03/2017] [Indexed: 11/26/2022] Open
Abstract
L-type voltage-gated CaV1.2 calcium channels (CaV1.2) are key regulators of neuronal excitability, synaptic plasticity, and excitation-transcription coupling. Surface-exposed CaV1.2 distributes in clusters along the dendrites of hippocampal neurons. A permanent exchange between stably clustered and laterally diffusive extra-clustered channels maintains steady-state levels of CaV1.2 at dendritic signaling domains. A dynamic equilibrium between anchored and diffusive receptors is a common feature among ion channels and is crucial to modulate signaling transduction. Despite the importance of this fine regulatory system, the molecular mechanisms underlying the surface dynamics of CaV1.2 are completely unexplored. Here, we examined the dynamic states of CaV1.2 depending on phosphorylation on Ser-1700 and Ser-1928 at the channel C terminus. Phosphorylation at these sites is strongly involved in CaV1.2-mediated nuclear factor of activated T cells (NFAT) signaling, long-term potentiation, and responsiveness to adrenergic stimulation. We engineered CaV1.2 constructs mimicking phosphorylation at Ser-1700 and Ser-1928 and analyzed their behavior at the membrane by immunolabeling protocols, fluorescence recovery after photobleaching, and single particle tracking. We found that the phosphomimetic S1928E variant increases the mobility of CaV1.2 without altering the steady-state maintenance of cluster in young neurons and favors channel stabilization later in differentiation. Instead, mimicking phosphorylation at Ser-1700 promoted the diffusive state of CaV1.2 irrespective of the differentiation stage. Together, these results reveal that phosphorylation could contribute to the establishment of channel anchoring mechanisms depending on the neuronal differentiation state. Finally, our findings suggest a novel mechanism by which phosphorylation at the C terminus regulates calcium signaling by tuning the content of CaV1.2 at signaling complexes.
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Affiliation(s)
- Alessandra Folci
- From the Institute of Biophysics, Medical University of Graz, 8010 Graz, Austria
| | - Angela Steinberger
- From the Institute of Biophysics, Medical University of Graz, 8010 Graz, Austria
| | - Boram Lee
- the Department of Pharmacology, University of California, Davis, California 95616
| | - Ruslan Stanika
- the Department of Physiology and Medical Physics, Medical University of Innsbruck, 6020 Innsbruck, Austria, and
| | - Susanne Scheruebel
- From the Institute of Biophysics, Medical University of Graz, 8010 Graz, Austria
| | - Marta Campiglio
- the Department of Physiology and Medical Physics, Medical University of Innsbruck, 6020 Innsbruck, Austria, and
| | - Claudia Ramprecht
- From the Institute of Biophysics, Medical University of Graz, 8010 Graz, Austria
| | - Brigitte Pelzmann
- From the Institute of Biophysics, Medical University of Graz, 8010 Graz, Austria
| | - Johannes W Hell
- the Department of Pharmacology, University of California, Davis, California 95616
| | - Gerald J Obermair
- the Department of Physiology and Medical Physics, Medical University of Innsbruck, 6020 Innsbruck, Austria, and
| | - Martin Heine
- the Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany
| | - Valentina Di Biase
- From the Institute of Biophysics, Medical University of Graz, 8010 Graz, Austria,
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23
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Kutchukian C, Szentesi P, Allard B, Trochet D, Beuvin M, Berthier C, Tourneur Y, Guicheney P, Csernoch L, Bitoun M, Jacquemond V. Impaired excitation-contraction coupling in muscle fibres from the dynamin2 R465W mouse model of centronuclear myopathy. J Physiol 2017; 595:7369-7382. [PMID: 29071728 DOI: 10.1113/jp274990] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 10/20/2017] [Indexed: 01/25/2023] Open
Abstract
KEY POINTS Dynamin 2 is a ubiquitously expressed protein involved in membrane trafficking processes. Mutations in the gene encoding dynamin 2 are responsible for a congenital myopathy associated with centrally located nuclei in the muscle fibres. Using muscle fibres from a mouse model of the most common mutation responsible for this disease in humans, we tested whether altered Ca2+ signalling and excitation-contraction coupling contribute to muscle weakness. The plasma membrane network that carries the electrical excitation is moderately perturbed in the diseased muscle fibres. The excitation-activated Ca2+ input fluxes across both the plasma membrane and the membrane of the sarcoplasmic reticulum are defective in the diseased fibres, which probably contributes to muscle weakness in patients. ABSTRACT Mutations in the gene encoding dynamin 2 (DNM2) are responsible for autosomal dominant centronuclear myopathy (AD-CNM). We studied the functional properties of Ca2+ signalling and excitation-contraction (EC) coupling in muscle fibres isolated from a knock-in (KI) mouse model of the disease, using confocal imaging and the voltage clamp technique. The transverse-tubule network organization appeared to be unaltered in the diseased fibres, although its density was reduced by ∼10% compared to that in control fibres. The density of Ca2+ current through CaV1.1 channels and the rate of voltage-activated sarcoplasmic reticulum Ca2+ release were reduced by ∼60% and 30%, respectively, in KI vs. control fibres. In addition, Ca2+ release in the KI fibres reached its peak value 10-50 ms later than in control ones. Activation of Ca2+ transients along the longitudinal axis of the fibres was more heterogeneous in the KI than in the control fibres, with the difference being exacerbated at intermediate membrane voltages. KI fibres exhibited spontaneous Ca2+ release events that were almost absent from control fibres. Overall, the results of the present study demonstrate that Ca2+ signalling and EC coupling exhibit a number of dysfunctions likely contributing to muscle weakness in DNM2-related AD-CNM.
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Affiliation(s)
- Candice Kutchukian
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR-5310, INSERM U-1217, Institut NeuroMyoGène, Villeurbanne, France
| | - Peter Szentesi
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Bruno Allard
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR-5310, INSERM U-1217, Institut NeuroMyoGène, Villeurbanne, France
| | - Delphine Trochet
- Research Center for Myology, UPMC Univ Paris 06 and INSERM UMR_S974, Institute of Myology, Paris, France
| | - Maud Beuvin
- Research Center for Myology, UPMC Univ Paris 06 and INSERM UMR_S974, Institute of Myology, Paris, France
| | - Christine Berthier
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR-5310, INSERM U-1217, Institut NeuroMyoGène, Villeurbanne, France
| | - Yves Tourneur
- CarMeN, INSERM U1060, Faculté de Médecine Lyon Sud, Oullins, France.,UFPE Dept Nutrição, Av. Prof. Moraes Rego, Cidade Universitária, Recife, Brazil
| | - Pascale Guicheney
- Sorbonne Universités, UPMC Univ Paris 06, INSERM UMR_S1166, Institute of Cardiometabolism and Nutrition (ICAN), Paris, France
| | - Laszlo Csernoch
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Marc Bitoun
- Research Center for Myology, UPMC Univ Paris 06 and INSERM UMR_S974, Institute of Myology, Paris, France
| | - Vincent Jacquemond
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS UMR-5310, INSERM U-1217, Institut NeuroMyoGène, Villeurbanne, France
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24
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Dynamics of surface neurotransmitter receptors and transporters in glial cells: Single molecule insights. Cell Calcium 2017; 67:46-52. [PMID: 29029790 DOI: 10.1016/j.ceca.2017.08.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 08/21/2017] [Accepted: 08/21/2017] [Indexed: 11/22/2022]
Abstract
The surface dynamics of neurotransmitter receptors and transporters, as well as ion channels, has been well-documented in neurons, revealing complex molecular behaviour and key physiological functions. However, our understanding of the membrane trafficking and dynamics of the signalling molecules located at the plasma membrane of glial cells is still in its infancy. Yet, recent breakthroughs in the field of glial cells have been obtained using combination of superresolution microscopy, single molecule imaging, and electrophysiological recordings. Here, we review our current knowledge on the surface dynamics of neurotransmitter receptors, transporters and ion channels, in glial cells. It has emerged that the brain cell network activity, synaptic activity, and calcium signalling, regulate the surface distribution and dynamics of these molecules. Remarkably, the dynamics of a given neurotransmitter receptor/transporter at the plasma membrane of a glial cell or neuron is unique, revealing the existence of cell-type specific regulatory pathways. Thus, investigating the dynamics of signalling proteins at the surface of glial cells will likely shed new light on our understanding of glial cell physiology and pathology.
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25
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Tseng PY, Henderson PB, Hergarden AC, Patriarchi T, Coleman AM, Lillya MW, Montagut-Bordas C, Lee B, Hell JW, Horne MC. α-Actinin Promotes Surface Localization and Current Density of the Ca 2+ Channel Ca V1.2 by Binding to the IQ Region of the α1 Subunit. Biochemistry 2017; 56:3669-3681. [PMID: 28613835 DOI: 10.1021/acs.biochem.7b00359] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The voltage-gated L-type Ca2+ channel CaV1.2 is crucial for initiating heartbeat and control of a number of neuronal functions such as neuronal excitability and long-term potentiation. Mutations of CaV1.2 subunits result in serious health problems, including arrhythmia, autism spectrum disorders, immunodeficiency, and hypoglycemia. Thus, precise control of CaV1.2 surface expression and localization is essential. We previously reported that α-actinin associates and colocalizes with neuronal CaV1.2 channels and that shRNA-mediated depletion of α-actinin significantly reduces localization of endogenous CaV1.2 in dendritic spines in hippocampal neurons. Here we investigated the hypothesis that direct binding of α-actinin to CaV1.2 supports its surface expression. Using two-hybrid screens and pull-down assays, we identified three point mutations (K1647A, Y1649A, and I1654A) in the central, pore-forming α11.2 subunit of CaV1.2 that individually impaired α-actinin binding. Surface biotinylation and flow cytometry assays revealed that CaV1.2 channels composed of the corresponding α-actinin-binding-deficient mutants result in a 35-40% reduction in surface expression compared to that of wild-type channels. Moreover, the mutant CaV1.2 channels expressed in HEK293 cells exhibit a 60-75% decrease in current density. The larger decrease in current density as compared to surface expression imparted by these α11.2 subunit mutations hints at the possibility that α-actinin not only stabilizes surface localization of CaV1.2 but also augments its ion conducting activity.
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Affiliation(s)
- Pang-Yen Tseng
- Department of Pharmacology, School of Medicine, University of California , Davis, California 95615-8636, United States
| | - Peter B Henderson
- Department of Pharmacology, School of Medicine, University of California , Davis, California 95615-8636, United States
| | - Anne C Hergarden
- Department of Pharmacology, School of Medicine, University of California , Davis, California 95615-8636, United States
| | - Tommaso Patriarchi
- Department of Pharmacology, School of Medicine, University of California , Davis, California 95615-8636, United States
| | - Andrea M Coleman
- Department of Pharmacology, School of Medicine, University of California , Davis, California 95615-8636, United States
| | - Mark W Lillya
- Department of Pharmacology, School of Medicine, University of California , Davis, California 95615-8636, United States
| | - Carlota Montagut-Bordas
- Department of Pharmacology, School of Medicine, University of California , Davis, California 95615-8636, United States
| | - Boram Lee
- Department of Pharmacology, School of Medicine, University of California , Davis, California 95615-8636, United States
| | - Johannes W Hell
- Department of Pharmacology, School of Medicine, University of California , Davis, California 95615-8636, United States
| | - Mary C Horne
- Department of Pharmacology, School of Medicine, University of California , Davis, California 95615-8636, United States
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26
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Densin-180 Controls the Trafficking and Signaling of L-Type Voltage-Gated Ca v1.2 Ca 2+ Channels at Excitatory Synapses. J Neurosci 2017; 37:4679-4691. [PMID: 28363979 DOI: 10.1523/jneurosci.2583-16.2017] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 03/23/2017] [Accepted: 03/27/2017] [Indexed: 11/21/2022] Open
Abstract
Voltage-gated Cav1.2 and Cav1.3 (L-type) Ca2+ channels regulate neuronal excitability, synaptic plasticity, and learning and memory. Densin-180 (densin) is an excitatory synaptic protein that promotes Ca2+-dependent facilitation of voltage-gated Cav1.3 Ca2+ channels in transfected cells. Mice lacking densin (densin KO) exhibit defects in synaptic plasticity, spatial memory, and increased anxiety-related behaviors-phenotypes that more closely match those in mice lacking Cav1.2 than Cav1.3. Therefore, we investigated the functional impact of densin on Cav1.2. We report that densin is an essential regulator of Cav1.2 in neurons, but has distinct modulatory effects compared with its regulation of Cav1.3. Densin binds to the N-terminal domain of Cav1.2, but not that of Cav1.3, and increases Cav1.2 currents in transfected cells and in neurons. In transfected cells, densin accelerates the forward trafficking of Cav1.2 channels without affecting their endocytosis. Consistent with a role for densin in increasing the number of postsynaptic Cav1.2 channels, overexpression of densin increases the clustering of Cav1.2 in dendrites of hippocampal neurons in culture. Compared with wild-type mice, the cell surface levels of Cav1.2 in the brain, as well as Cav1.2 current density and signaling to the nucleus, are reduced in neurons from densin KO mice. We conclude that densin is an essential regulator of neuronal Cav1 channels and ensures efficient Cav1.2 Ca2+ signaling at excitatory synapses.SIGNIFICANCE STATEMENT The number and localization of voltage-gated Cav Ca2+ channels are crucial determinants of neuronal excitability and synaptic transmission. We report that the protein densin-180 is highly enriched at excitatory synapses in the brain and enhances the cell surface trafficking and postsynaptic localization of Cav1.2 L-type Ca2+ channels in neurons. This interaction promotes coupling of Cav1.2 channels to activity-dependent gene transcription. Our results reveal a mechanism that may contribute to the roles of Cav1.2 in regulating cognition and mood.
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27
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Minobe E, Mori MX, Kameyama M. Calmodulin and ATP support activity of the Cav1.2 channel through dynamic interactions with the channel. J Physiol 2017; 595:2465-2477. [PMID: 28130847 PMCID: PMC5390892 DOI: 10.1113/jp273736] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 01/06/2017] [Indexed: 11/08/2022] Open
Abstract
Key points Cav1.2 channels maintain activity through interactions with calmodulin (CaM). In this study, activities of the Cav1.2 channel (α1C) and of mutant‐derivatives, C‐terminal deleted (α1CΔ) and α1CΔ linked with CaM (α1CΔCaM), were compared in the inside‐out mode. α1CΔ with CaM, but not without CaM, and α1CΔCaM were active, suggesting that CaM induced channel activity through a dynamic interaction with the channel, even without the distal C‐tail. ATP induced α1C activity with CaM and enhanced activity of the mutant channels. Okadaic acid mimicked the effect of ATP on the wildtype but not mutant channels. These results supported the hypothesis that CaM and ATP maintain activity of Cav1.2 channels through their dynamic interactions. ATP effects involve mechanisms both related and unrelated to channel phosphorylation. CaM‐linked channels are useful tools for investigating Cav1.2 channels in the inside‐out mode; the fast run‐down is prevented by only ATP and the slow run‐down is nearly absent.
Abstract Calmodulin (CaM) plays a critical role in regulation of Cav1.2 Ca2+ channels. CaM binds to the channel directly, maintaining channel activity and regulating it in a Ca2+‐dependent manner. To explore the molecular mechanisms involved, we compared the activity of the wildtype channel (α1C) and mutant derivatives, C‐terminal deleted (α1C∆) and α1C∆ linked to CaM (α1C∆CaM). These were co‐expressed with β2a and α2δ subunits in HEK293 cells. In the inside‐out mode, α1C and α1C∆ showed minimal open‐probabilities in a basic internal solution (run‐down), whereas α1C∆ with CaM and α1C∆CaM maintained detectable channel activity, confirming that CaM was necessary, but not sufficient, for channel activity. Previously, we reported that ATP was required to maintain channel activity of α1C. Unlike α1C, the mutant channels did not require ATP for activation in the early phase (3–5 min). However, α1C∆ with CaM + ATP and α1C∆CaM with ATP maintained activity, even in the late phase (after 7–9 min). These results suggested that CaM and ATP interacted dynamically with the proximal C‐terminal tail of the channel and, thereby, produced channel activity. In addition, okadaic acid, a protein phosphatase inhibitor, could substitute for the effects of ATP on α1C but not on the mutant channels. These results supported the hypothesis that CaM and ATP maintain activity of Cav1.2 channels, further indicating that ATP has dual effects. One maintains phosphorylation of the channel and the other becomes apparent when the distal carboxyl‐terminal tail is removed. Cav1.2 channels maintain activity through interactions with calmodulin (CaM). In this study, activities of the Cav1.2 channel (α1C) and of mutant‐derivatives, C‐terminal deleted (α1CΔ) and α1CΔ linked with CaM (α1CΔCaM), were compared in the inside‐out mode. α1CΔ with CaM, but not without CaM, and α1CΔCaM were active, suggesting that CaM induced channel activity through a dynamic interaction with the channel, even without the distal C‐tail. ATP induced α1C activity with CaM and enhanced activity of the mutant channels. Okadaic acid mimicked the effect of ATP on the wildtype but not mutant channels. These results supported the hypothesis that CaM and ATP maintain activity of Cav1.2 channels through their dynamic interactions. ATP effects involve mechanisms both related and unrelated to channel phosphorylation. CaM‐linked channels are useful tools for investigating Cav1.2 channels in the inside‐out mode; the fast run‐down is prevented by only ATP and the slow run‐down is nearly absent.
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Affiliation(s)
- Etsuko Minobe
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, 890-8544, Japan
| | - Masayuki X Mori
- Laboratory of Molecular Biology, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan
| | - Masaki Kameyama
- Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, 890-8544, Japan
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28
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Abstract
Unique to striated muscle cells, transverse tubules (t-tubules) are membrane organelles that consist of sarcolemma penetrating into the myocyte interior, forming a highly branched and interconnected network. Mature t-tubule networks are found in mammalian ventricular cardiomyocytes, with the transverse components of t-tubules occurring near sarcomeric z-discs. Cardiac t-tubules contain membrane microdomains enriched with ion channels and signaling molecules. The microdomains serve as key signaling hubs in regulation of cardiomyocyte function. Dyad microdomains formed at the junctional contact between t-tubule membrane and neighboring sarcoplasmic reticulum are critical in calcium signaling and excitation-contraction coupling necessary for beat-to-beat heart contraction. In this review, we provide an overview of the current knowledge in gross morphology and structure, membrane and protein composition, and function of the cardiac t-tubule network. We also review in detail current knowledge on the formation of functional membrane subdomains within t-tubules, with a particular focus on the cardiac dyad microdomain. Lastly, we discuss the dynamic nature of t-tubules including membrane turnover, trafficking of transmembrane proteins, and the life cycles of membrane subdomains such as the cardiac BIN1-microdomain, as well as t-tubule remodeling and alteration in diseased hearts. Understanding cardiac t-tubule biology in normal and failing hearts is providing novel diagnostic and therapeutic opportunities to better treat patients with failing hearts.
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Affiliation(s)
- TingTing Hong
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California; and Department of Medicine, University of California Los Angeles, Los Angeles, California
| | - Robin M Shaw
- Cedars-Sinai Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California; and Department of Medicine, University of California Los Angeles, Los Angeles, California
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29
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Nystoriak MA, Nieves-Cintrón M, Patriarchi T, Buonarati OR, Prada MP, Morotti S, Grandi E, Fernandes JDS, Forbush K, Hofmann F, Sasse KC, Scott JD, Ward SM, Hell JW, Navedo MF. Ser1928 phosphorylation by PKA stimulates the L-type Ca2+ channel CaV1.2 and vasoconstriction during acute hyperglycemia and diabetes. Sci Signal 2017; 10:10/463/eaaf9647. [PMID: 28119464 DOI: 10.1126/scisignal.aaf9647] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Hypercontractility of arterial myocytes and enhanced vascular tone during diabetes are, in part, attributed to the effects of increased glucose (hyperglycemia) on L-type CaV1.2 channels. In murine arterial myocytes, kinase-dependent mechanisms mediate the increase in CaV1.2 activity in response to increased extracellular glucose. We identified a subpopulation of the CaV1.2 channel pore-forming subunit (α1C) within nanometer proximity of protein kinase A (PKA) at the sarcolemma of murine and human arterial myocytes. This arrangement depended upon scaffolding of PKA by an A-kinase anchoring protein 150 (AKAP150) in mice. Glucose-mediated increases in CaV1.2 channel activity were associated with PKA activity, leading to α1C phosphorylation at Ser1928 Compared to arteries from low-fat diet (LFD)-fed mice and nondiabetic patients, arteries from high-fat diet (HFD)-fed mice and from diabetic patients had increased Ser1928 phosphorylation and CaV1.2 activity. Arterial myocytes and arteries from mice lacking AKAP150 or expressing mutant AKAP150 unable to bind PKA did not exhibit increased Ser1928 phosphorylation and CaV1.2 current density in response to increased glucose or to HFD. Consistent with a functional role for Ser1928 phosphorylation, arterial myocytes and arteries from knockin mice expressing a CaV1.2 with Ser1928 mutated to alanine (S1928A) lacked glucose-mediated increases in CaV1.2 activity and vasoconstriction. Furthermore, the HFD-induced increases in CaV1.2 current density and myogenic tone were prevented in S1928A knockin mice. These findings reveal an essential role for α1C phosphorylation at Ser1928 in stimulating CaV1.2 channel activity and vasoconstriction by AKAP-targeted PKA upon exposure to increased glucose and in diabetes.
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Affiliation(s)
- Matthew A Nystoriak
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | | | - Tommaso Patriarchi
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Olivia R Buonarati
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Maria Paz Prada
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Stefano Morotti
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | | | - Katherine Forbush
- Howard Hughes Medical Institute and Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Franz Hofmann
- Department of Pharmacology and Toxicology, Technical University of Munich, Munich D80802, Germany
| | | | - John D Scott
- Howard Hughes Medical Institute and Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Sean M Ward
- Department of Physiology and Cell Biology, University of Nevada, Reno, NV 89557, USA
| | - Johannes W Hell
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA.
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30
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Fraysse B, Guicheney P, Bitoun M. Calcium homeostasis alterations in a mouse model of the Dynamin 2-related centronuclear myopathy. Biol Open 2016; 5:1691-1696. [PMID: 27870637 PMCID: PMC5155535 DOI: 10.1242/bio.020263] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Autosomal dominant centronuclear myopathy (CNM) is a rare congenital myopathy characterized by centrally located nuclei in muscle fibers. CNM results from mutations in the gene encoding dynamin 2 (DNM2), a large GTPase involved in endocytosis, intracellular membrane trafficking, and cytoskeleton regulation. We developed a knock-in mouse model expressing the most frequent DNM2-CNM mutation; i.e. the KI-Dnm2R465W model. Heterozygous (HTZ) KI-Dnm2 mice progressively develop muscle atrophy, impairment of contractile properties, histopathological abnormalities, and elevated cytosolic calcium concentration. Here, we aim at better characterizing the calcium homeostasis impairment in extensor digitorum longus (EDL) and soleus muscles from adult HTZ KI-Dnm2 mice. We demonstrate abnormal contractile properties and cytosolic Ca2+ concentration in EDL but not soleus muscles showing that calcium impairment is correlated with muscle weakness and might be a determinant factor of the spatial muscle involvement. In addition, the elevated cytosolic Ca2+ concentration in EDL muscles is associated with an increased sarcolemmal permeability to Ca2+ and releasable Ca2+ content from the sarcoplasmic reticulum. However, amplitude and kinetics characteristics of the calcium transient appear unchanged. This suggests that calcium defect is probably not a primary cause of decreased force generation by compromised sarcomere shortening but may be involved in long-term deleterious consequences on muscle physiology. Our results highlight the first pathomechanism which may explain the spatial muscle involvement occurring in DNM2-related CNM and open the way toward development of a therapeutic approach to normalize calcium content. Summary: Dynamin 2 mutations cause centronuclear myopathy via unclear mechanisms. We show in a mouse model that changes in cytosolic calcium via incorrect membrane permeability correlate with muscle weakness.
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Affiliation(s)
- Bodvaël Fraysse
- Atlantic Gene Therapies, INSERM UMR 1089, Université de Nantes, CHU de Nantes, Nantes 44200, France
| | - Pascale Guicheney
- INSERM, UMR_S1166, Sorbonne Universités, UPMC Univ Paris 06, UMR_S1166, Institute of Cardiometabolism and Nutrition (ICAN), Paris 75013, France
| | - Marc Bitoun
- Research Center for Myology, UPMC Univ Paris 06 and INSERM UMR_S974, CNRS FRE 3617, Institute of Myology, Paris 75013, France
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Stanika R, Campiglio M, Pinggera A, Lee A, Striessnig J, Flucher BE, Obermair GJ. Splice variants of the Ca V1.3 L-type calcium channel regulate dendritic spine morphology. Sci Rep 2016; 6:34528. [PMID: 27708393 PMCID: PMC5052568 DOI: 10.1038/srep34528] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 09/15/2016] [Indexed: 01/13/2023] Open
Abstract
Dendritic spines are the postsynaptic compartments of glutamatergic synapses in the brain. Their number and shape are subject to change in synaptic plasticity and neurological disorders including autism spectrum disorders and Parkinson’s disease. The L-type calcium channel CaV1.3 constitutes an important calcium entry pathway implicated in the regulation of spine morphology. Here we investigated the importance of full-length CaV1.3L and two C-terminally truncated splice variants (CaV1.342A and CaV1.343S) and their modulation by densin-180 and shank1b for the morphology of dendritic spines of cultured hippocampal neurons. Live-cell immunofluorescence and super-resolution microscopy of epitope-tagged CaV1.3L revealed its localization at the base-, neck-, and head-region of dendritic spines. Expression of the short splice variants or deletion of the C-terminal PDZ-binding motif in CaV1.3L induced aberrant dendritic spine elongation. Similar morphological alterations were induced by co-expression of densin-180 or shank1b with CaV1.3L and correlated with increased CaV1.3 currents and dendritic calcium signals in transfected neurons. Together, our findings suggest a key role of CaV1.3 in regulating dendritic spine structure. Under physiological conditions it may contribute to the structural plasticity of glutamatergic synapses. Conversely, altered regulation of CaV1.3 channels may provide an important mechanism in the development of postsynaptic aberrations associated with neurodegenerative disorders.
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Affiliation(s)
- Ruslan Stanika
- Division of Physiology, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Marta Campiglio
- Division of Physiology, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Alexandra Pinggera
- Department of Pharmacology and Toxicology, University of Innsbruck, 6020 Innsbruck, Austria
| | - Amy Lee
- Department of Molecular Physiology and Biophysics, Otolaryngology Head-Neck Surgery, and Neurology, University of Iowa, Iowa City, IA 52242, USA
| | - Jörg Striessnig
- Department of Pharmacology and Toxicology, University of Innsbruck, 6020 Innsbruck, Austria
| | - Bernhard E Flucher
- Division of Physiology, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Gerald J Obermair
- Division of Physiology, Medical University Innsbruck, 6020 Innsbruck, Austria
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Voigt A, Freund R, Heck J, Missler M, Obermair GJ, Thomas U, Heine M. Dynamic association of calcium channel subunits at the cellular membrane. NEUROPHOTONICS 2016; 3:041809. [PMID: 27872869 PMCID: PMC5093230 DOI: 10.1117/1.nph.3.4.041809] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/10/2016] [Indexed: 05/25/2023]
Abstract
High voltage gated calcium channels (VGCCs) are composed of at least three subunits, one pore forming [Formula: see text]-subunit, an intracellular [Formula: see text]-variant, and a mostly extracellular [Formula: see text]-variant. Interactions between these subunits determine the kinetic properties of VGCCs. It is unclear whether these interactions are stable over time or rather transient. Here, we used single-molecule tracking to investigate the surface diffusion of [Formula: see text]- and [Formula: see text]-subunits at the cell surface. We found that [Formula: see text]-subunits show higher surface mobility than [Formula: see text]-subunits, and that they are only transiently confined together, suggesting a weak association between [Formula: see text]- and [Formula: see text]-subunits. Moreover, we observed that different [Formula: see text]-subunits engage in different degrees of association with the [Formula: see text]-subunit, revealing the tighter interaction of [Formula: see text] with [Formula: see text]. These data indicate a distinct regulation of the [Formula: see text] interaction in VGCC subtypes. We modeled their membrane dynamics in a Monte Carlo simulation using experimentally determined diffusion constants. Our modeling predicts that the ratio of associated [Formula: see text]- and [Formula: see text]-subunits mainly depends on their expression density and confinement in the membrane. Based on the different motilities of particular [Formula: see text]-subunit combinations, we propose that their dynamic assembly and disassembly represent an important mechanism to regulate the signaling properties of VGCC.
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Affiliation(s)
- Andreas Voigt
- Otto-von-Guericke-University of Magdeburg, Lehrstuhl Systemverfahrenstechnik, Universitätsplatz 2, Magdeburg D-39106, Germany
| | - Romy Freund
- Leibniz-Institute of Neurobiology, Research Group Molecular Physiology, Brenneckestrasse 6, Magdeburg D-39118, Germany
| | - Jennifer Heck
- Leibniz-Institute of Neurobiology, Research Group Molecular Physiology, Brenneckestrasse 6, Magdeburg D-39118, Germany
| | - Markus Missler
- Westfälische Wilhelms-University, Institute of Anatomy and Molecular Neurobiology, Vesaliusweg 2, Münster 48149, Germany
| | - Gerald J. Obermair
- Medical University Innsbruck, Division of Physiology, Department of Physiology and Medical Physics, Schöpfstrasse 41, Innsbruck 6020, Austria
| | - Ulrich Thomas
- Leibniz-Institute of Neurobiology, Department Neurochemistry, Brenneckestrasse 6, Magdeburg D-39118, Germany
| | - Martin Heine
- Leibniz-Institute of Neurobiology, Research Group Molecular Physiology, Brenneckestrasse 6, Magdeburg D-39118, Germany
- Otto-von-Guericke-University Magdeburg, Center for Behavioral Brain Sciences (CBBS), Universitätsplatz 2, Magdeburg D-39106, Germany
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Heine M, Ciuraszkiewicz A, Voigt A, Heck J, Bikbaev A. Surface dynamics of voltage-gated ion channels. Channels (Austin) 2016; 10:267-81. [PMID: 26891382 DOI: 10.1080/19336950.2016.1153210] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Neurons encode information in fast changes of the membrane potential, and thus electrical membrane properties are critically important for the integration and processing of synaptic inputs by a neuron. These electrical properties are largely determined by ion channels embedded in the membrane. The distribution of most ion channels in the membrane is not spatially uniform: they undergo activity-driven changes in the range of minutes to days. Even in the range of milliseconds, the composition and topology of ion channels are not static but engage in highly dynamic processes including stochastic or activity-dependent transient association of the pore-forming and auxiliary subunits, lateral diffusion, as well as clustering of different channels. In this review we briefly discuss the potential impact of mobile sodium, calcium and potassium ion channels and the functional significance of this for individual neurons and neuronal networks.
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Affiliation(s)
- Martin Heine
- a RG Molecular Physiology, Leibniz Institute for Neurobiology, Center for Behavioral Brain Science, Otto-von-Guericke-University of Magdeburg , Magdeburg , Germany
| | - Anna Ciuraszkiewicz
- a RG Molecular Physiology, Leibniz Institute for Neurobiology, Center for Behavioral Brain Science, Otto-von-Guericke-University of Magdeburg , Magdeburg , Germany
| | - Andreas Voigt
- b Lehrstuhl Systemverfahrenstechnik, Otto-von-Guericke-University of Magdeburg , Magdeburg , Germany
| | - Jennifer Heck
- a RG Molecular Physiology, Leibniz Institute for Neurobiology, Center for Behavioral Brain Science, Otto-von-Guericke-University of Magdeburg , Magdeburg , Germany
| | - Arthur Bikbaev
- a RG Molecular Physiology, Leibniz Institute for Neurobiology, Center for Behavioral Brain Science, Otto-von-Guericke-University of Magdeburg , Magdeburg , Germany
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Abstract
UNLABELLED Synapses depend on trafficking of key membrane proteins by lateral diffusion from surface populations and by exocytosis from intracellular pools. The cell adhesion molecule neurexin (Nrxn) plays essential roles in synapses, but the dynamics and regulation of its trafficking are unknown. Here, we performed single-particle tracking and live imaging of transfected, epitope-tagged Nrxn variants in cultured rat and mouse wild-type or knock-out neurons. We observed that structurally larger αNrxn molecules are more mobile in the plasma membrane than smaller βNrxns because αNrxns displayed higher diffusion coefficients in extrasynaptic regions and excitatory or inhibitory terminals. We found that well characterized interactions with extracellular binding partners regulate the surface mobility of Nrxns. Binding to neurexophilin-1 (Nxph1) reduced the surface diffusion of αNrxns when both molecules were coexpressed. Conversely, impeding other interactions by insertion of splice sequence #4 or removal of extracellular Ca(2+) augmented the mobility of αNrxns and βNrxns. We also determined that fast axonal transport delivers Nrxns to the neuronal surface because Nrxns comigrate as cargo on synaptic vesicle protein transport vesicles (STVs). Unlike surface mobility, intracellular transport of βNrxn(+) STVs was faster than that of αNrxns, but both depended on the microtubule motor protein KIF1A and neuronal activity regulated the velocity. Large spontaneous fusion of Nrxn(+) STVs occurred simultaneously with synaptophysin on axonal membranes mostly outside of active presynaptic terminals. Surface Nrxns enriched at synaptic terminals where αNrxns and Nxph1/αNrxns recruited GABAAR subunits. Therefore, our results identify regulated dynamic trafficking as an important property of Nrxns that corroborates their function at synapses. SIGNIFICANCE STATEMENT Synapses mediate most functions in our brains and depend on the precise and timely delivery of key molecules throughout life. Neurexins (Nrxns) are essential synaptic cell adhesion molecules that are involved in synaptic transmission and differentiation of synaptic contacts. In addition, Nrxns have been linked to neuropsychiatric diseases such as autism. Because little is known about the dynamic aspects of trafficking of neurexins to synapses, we investigated this important question using single-molecule tracking and time-lapse imaging. We identify distinct differences between major Nrxn variants both in surface mobility and during intracellular transport. Because their dynamic behavior is highly regulated, for example, by different binding activities, these processes have immediate consequences for the function of Nrxns at synapses.
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Chen-Izu Y, Shaw RM, Pitt GS, Yarov-Yarovoy V, Sack JT, Abriel H, Aldrich RW, Belardinelli L, Cannell MB, Catterall WA, Chazin WJ, Chiamvimonvat N, Deschenes I, Grandi E, Hund TJ, Izu LT, Maier LS, Maltsev VA, Marionneau C, Mohler PJ, Rajamani S, Rasmusson RL, Sobie EA, Clancy CE, Bers DM. Na+ channel function, regulation, structure, trafficking and sequestration. J Physiol 2015; 593:1347-60. [PMID: 25772290 DOI: 10.1113/jphysiol.2014.281428] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 11/02/2014] [Indexed: 12/19/2022] Open
Abstract
This paper is the second of a series of three reviews published in this issue resulting from the University of California Davis Cardiovascular Symposium 2014: Systems approach to understanding cardiac excitation-contraction coupling and arrhythmias: Na(+) channel and Na(+) transport. The goal of the symposium was to bring together experts in the field to discuss points of consensus and controversy on the topic of sodium in the heart. The present review focuses on Na(+) channel function and regulation, Na(+) channel structure and function, and Na(+) channel trafficking, sequestration and complexing.
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Affiliation(s)
- Ye Chen-Izu
- Department of Pharmacology, University of California, Davis, USA; Department of Biomedical Engineering, University of California, Davis, USA; Department of Internal Medicine/Cardiology, University of California, Davis, USA
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Heyes S, Pratt WS, Rees E, Dahimene S, Ferron L, Owen MJ, Dolphin AC. Genetic disruption of voltage-gated calcium channels in psychiatric and neurological disorders. Prog Neurobiol 2015; 134:36-54. [PMID: 26386135 PMCID: PMC4658333 DOI: 10.1016/j.pneurobio.2015.09.002] [Citation(s) in RCA: 164] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 09/08/2015] [Accepted: 09/08/2015] [Indexed: 12/15/2022]
Abstract
Voltage-gated calcium channel classification—genes and proteins. Genetic analysis of neuropsychiatric syndromes. Calcium channel genes identified from GWA studies of psychiatric disorders. Rare mutations in calcium channel genes in psychiatric disorders. Pathophysiological sequelae of CACNA1C mutations and polymorphisms. Monogenic disorders resulting from harmful mutations in other voltage-gated calcium channel genes. Changes in calcium channel gene expression in disease. Involvement of voltage-gated calcium channels in early brain development.
This review summarises genetic studies in which calcium channel genes have been connected to the spectrum of neuropsychiatric syndromes, from bipolar disorder and schizophrenia to autism spectrum disorders and intellectual impairment. Among many other genes, striking numbers of the calcium channel gene superfamily have been implicated in the aetiology of these diseases by various DNA analysis techniques. We will discuss how these relate to the known monogenic disorders associated with point mutations in calcium channels. We will then examine the functional evidence for a causative link between these mutations or single nucleotide polymorphisms and the disease processes. A major challenge for the future will be to translate the expanding psychiatric genetic findings into altered physiological function, involvement in the wider pathology of the diseases, and what potential that provides for personalised and stratified treatment options for patients.
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Affiliation(s)
- Samuel Heyes
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Wendy S Pratt
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Elliott Rees
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Neuroscience and Mental Health Research Institute, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Shehrazade Dahimene
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Laurent Ferron
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK
| | - Michael J Owen
- Medical Research Council Centre for Neuropsychiatric Genetics and Genomics, Neuroscience and Mental Health Research Institute, Institute of Psychological Medicine and Clinical Neurosciences, Cardiff University, Cardiff CF24 4HQ, UK
| | - Annette C Dolphin
- Department of Neuroscience, Physiology and Pharmacology, University College London, London WC1E 6BT, UK.
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Palacio S, Velázquez-Marrero C, Marrero HG, Seale GE, Yudowski GA, Treistman SN. Time-Dependent Effects of Ethanol on BK Channel Expression and Trafficking in Hippocampal Neurons. Alcohol Clin Exp Res 2015; 39:1619-31. [PMID: 26247146 DOI: 10.1111/acer.12808] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 06/09/2015] [Indexed: 01/06/2023]
Abstract
BACKGROUND The large conductance Ca(2+) - and voltage-activated K(+) channel (BK) is an important player in molecular and behavioral alcohol tolerance. Trafficking and surface expression of ion channels contribute to the development of addictive behaviors. We have previously reported that internalization of the BK channel is a component of molecular tolerance to ethanol (EtOH). METHODS Using primary cultures of hippocampal neurons, we combine total internal reflection fluorescence microscopy, electrophysiology, and biochemical techniques to explore how exposure to EtOH affects the expression and subcellular localization of endogenous BK channels over time. RESULTS Exposure to EtOH changed the expression of endogenous BK channels in a time-dependent manner at the perimembrane area (plasma membrane and/or the area adjacent to it), while total protein levels of BK remain unchanged. These results suggest a redistribution of the channel within the neurons rather than changes in synthesis or degradation rates. Our results showed a temporally nonlinear effect of EtOH on perimembrane expression of BK. First, there was an increase in BK perimembrane expression after 10 minutes of EtOH exposure that remained evident after 3 hours, although not correlated to increases in functional channel expression. In contrast, after 6 hours of EtOH exposure, we observed a significant decrease in both BK perimembrane expression and functional channel expression. Furthermore, after 24 hours of EtOH exposure, perimembrane levels of BK had returned to baseline. CONCLUSIONS We report a complex time-dependent pattern in the effect of EtOH on BK channel trafficking, including successive increases and decreases in perimembrane expression and a reduction in active BK channels after 3 and 6 hours of EtOH exposure. Possible mechanisms underlying this multiphasic trafficking are discussed. As molecular tolerance necessarily underlies behavioral tolerance, the time-dependent alterations we see at the level of the channel may be relevant to the influence of drinking patterns on the development of behavioral tolerance.
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Affiliation(s)
- Stephanie Palacio
- Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico.,Department of Anatomy and Neurobiology, Medical Science Campus, University of Puerto Rico, San Juan, Puerto Rico
| | | | - Héctor G Marrero
- Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico
| | - Garrett E Seale
- Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico
| | - Guillermo A Yudowski
- Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico.,Department of Anatomy and Neurobiology, Medical Science Campus, University of Puerto Rico, San Juan, Puerto Rico
| | - Steven N Treistman
- Institute of Neurobiology, University of Puerto Rico, San Juan, Puerto Rico.,Department of Anatomy and Neurobiology, Medical Science Campus, University of Puerto Rico, San Juan, Puerto Rico
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Campiglio M, Flucher BE. The role of auxiliary subunits for the functional diversity of voltage-gated calcium channels. J Cell Physiol 2015; 230:2019-31. [PMID: 25820299 PMCID: PMC4672716 DOI: 10.1002/jcp.24998] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 03/23/2015] [Indexed: 11/18/2022]
Abstract
Voltage-gated calcium channels (VGCCs) represent the sole mechanism to convert membrane depolarization into cellular functions like secretion, contraction, or gene regulation. VGCCs consist of a pore-forming α1 subunit and several auxiliary channel subunits. These subunits come in multiple isoforms and splice-variants giving rise to a stunning molecular diversity of possible subunit combinations. It is generally believed that specific auxiliary subunits differentially regulate the channels and thereby contribute to the great functional diversity of VGCCs. If auxiliary subunits can associate and dissociate from pre-existing channel complexes, this would allow dynamic regulation of channel properties. However, most auxiliary subunits modulate current properties very similarly, and proof that any cellular calcium channel function is indeed modulated by the physiological exchange of auxiliary subunits is still lacking. In this review we summarize available information supporting a differential modulation of calcium channel functions by exchange of auxiliary subunits, as well as experimental evidence in support of alternative functions of the auxiliary subunits. At the heart of the discussion is the concept that, in their native environment, VGCCs function in the context of macromolecular signaling complexes and that the auxiliary subunits help to orchestrate the diverse protein–protein interactions found in these calcium channel signalosomes. Thus, in addition to a putative differential modulation of current properties, differential subcellular targeting properties and differential protein–protein interactions of the auxiliary subunits may explain the need for their vast molecular diversity. J. Cell. Physiol. 999: 00–00, 2015. © 2015 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc. J. Cell. Physiol. 230: 2019–2031, 2015. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Marta Campiglio
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
| | - Bernhard E Flucher
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, Innsbruck, Austria
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Schneider R, Hosy E, Kohl J, Klueva J, Choquet D, Thomas U, Voigt A, Heine M. Mobility of calcium channels in the presynaptic membrane. Neuron 2015; 86:672-9. [PMID: 25892305 DOI: 10.1016/j.neuron.2015.03.050] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 02/03/2015] [Accepted: 03/09/2015] [Indexed: 12/20/2022]
Abstract
Unravelling principles underlying neurotransmitter release are key to understand neural signaling. Here, we describe how surface mobility of voltage-dependent calcium channels (VDCCs) modulates release probabilities (P(r)) of synaptic vesicles (SVs). Coupling distances of <10 to >100 nm have been reported for SVs and VDCCs in different synapses. Tracking individual VDCCs revealed that within hippocampal synapses, ∼60% of VDCCs are mobile while confined to presynaptic membrane compartments. Intracellular Ca(2+) chelation decreased VDCC mobility. Increasing VDCC surface populations by co-expression of the α2δ1 subunit did not alter channel mobility but led to enlarged active zones (AZs) rather than higher channel densities. VDCCs thus scale presynaptic scaffolds to maintain local mobility. We propose that dynamic coupling based on mobile VDCCs supports calcium domain cooperativity and tunes neurotransmitter release by equalizing Pr for docked SVs within AZs.
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Affiliation(s)
- Romy Schneider
- Molecular Physiology Group, Leibniz Institute for Neurobiology, D-39118 Magdeburg, Germany
| | - Eric Hosy
- University of Bordeaux, F-33000 Bordeaux, France; CNRS, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000 Bordeaux, France
| | - Johannes Kohl
- Harvard University, Department Molecular and Cellular Biology, Cambridge, MA 02138, USA
| | - Julia Klueva
- Molecular Physiology Group, Leibniz Institute for Neurobiology, D-39118 Magdeburg, Germany; Presynaptic Plasticity Group, Leibniz Institute for Neurobiology, D-39118 Magdeburg, Germany
| | - Daniel Choquet
- University of Bordeaux, F-33000 Bordeaux, France; CNRS, Interdisciplinary Institute for Neuroscience, UMR 5297, F-33000 Bordeaux, France; Bordeaux Imaging Center, UMS 3420 CNRS, US4 INSERM, University of Bordeaux, F-33000 Bordeaux, France
| | - Ulrich Thomas
- Department Neurochemistry, Leibniz Institute for Neurobiology, D-39118 Magdeburg, Germany
| | - Andreas Voigt
- Otto-von-Guericke-University Magdeburg, Systemverfahrenstechnik, Universitätsplatz 2, D-39106 Magdeburg, Germany
| | - Martin Heine
- Molecular Physiology Group, Leibniz Institute for Neurobiology, D-39118 Magdeburg, Germany.
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Yamamura H, Suzuki Y, Imaizumi Y. New light on ion channel imaging by total internal reflection fluorescence (TIRF) microscopy. J Pharmacol Sci 2015; 128:1-7. [PMID: 26002253 DOI: 10.1016/j.jphs.2015.04.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2015] [Revised: 03/30/2015] [Accepted: 04/06/2015] [Indexed: 11/28/2022] Open
Abstract
Ion channels play pivotal roles in a wide variety of cellular functions; therefore, their physiological characteristics, pharmacological responses, and molecular structures have been extensively investigated. However, the mobility of an ion channel itself in the cell membrane has not been examined in as much detail. A total internal reflection fluorescence (TIRF) microscope allows fluorophores to be imaged in a restricted region within an evanescent field of less than 200 nm from the interface of the coverslip and plasma membrane in living cells. Thus the TIRF microscope is useful for selectively visualizing the plasmalemmal surface and subplasmalemmal zone. In this review, we focused on a single-molecule analysis of the dynamic movement of ion channels in the plasma membrane using TIRF microscopy. We also described two single-molecule imaging techniques under TIRF microscopy: fluorescence resonance energy transfer (FRET) for the identification of molecules that interact with ion channels, and subunit counting for the determination of subunit stoichiometry in a functional channel. TIRF imaging can also be used to analyze spatiotemporal Ca(2+) events in the subplasmalemma. Single-molecule analyses of ion channels and localized Ca(2+) signals based on TIRF imaging provide beneficial pharmacological and physiological information concerning the functions of ion channels.
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Affiliation(s)
- Hisao Yamamura
- Department of Molecular & Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan.
| | - Yoshiaki Suzuki
- Department of Molecular & Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Yuji Imaizumi
- Department of Molecular & Cellular Pharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
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Abstract
The neurexin family of cell adhesion proteins consists of three members in
vertebrates and has homologs in several invertebrate species. In mammals, each
neurexin gene encodes an α-neurexin in which the extracellular portion is long,
and a β-neurexin in which the extracellular portion is short. As a result of
alternative splicing, both major isoforms can be transcribed in many variants,
contributing to distinct structural domains and variability. Neurexins act
predominantly at the presynaptic terminal in neurons and play essential roles in
neurotransmission and differentiation of synapses. Some of these functions require
the formation of trans-synaptic complexes with postsynaptic proteins such as
neuroligins, LRRTM proteins or cerebellin. In addition, rare mutations and
copy-number variations of human neurexin genes have been linked to autism and
schizophrenia, indicating that impairments of synaptic function sustained by
neurexins and their binding partners may be relevant to the pathomechanism of these
debilitating diseases.
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Xiao S, Shaw RM. Cardiomyocyte protein trafficking: Relevance to heart disease and opportunities for therapeutic intervention. Trends Cardiovasc Med 2014; 25:379-89. [PMID: 25649302 DOI: 10.1016/j.tcm.2014.12.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 12/18/2014] [Accepted: 12/20/2014] [Indexed: 11/30/2022]
Abstract
Cardiomyocytes, the individual contractile units of heart muscle, are long-lived and robust. Given the longevity of these cells, it can be easy to overlook their dynamic intracellular environment that contain rapid protein movements and frequent protein turnover. Critical gene transcription and protein translation occur continuously, as well as trafficking and localization of proteins to specific functional zones of cell membrane. As heart failure becomes an increasingly important clinical entity, growing numbers of investigative teams are examining the cell biology of healthy and diseased cardiomyocytes. In this review, we introduce the major architectural structures and types of protein movements within cardiac cells, and then review recent studies that explore the regulation of such movements. We conclude by introducing current translational directions of the basic studies with a focus on novel areas of therapeutic development.
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Affiliation(s)
- Shaohua Xiao
- Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA
| | - Robin M Shaw
- Heart Institute and Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA; Department of Medicine, University of California Los Angeles, Los Angeles, CA.
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Geisler S, Schöpf CL, Obermair GJ. Emerging evidence for specific neuronal functions of auxiliary calcium channel α₂δ subunits. Gen Physiol Biophys 2014; 34:105-118. [PMID: 25504062 DOI: 10.4149/gpb_2014037] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 11/06/2014] [Indexed: 11/08/2022]
Abstract
In nerve cells the ubiquitous second messenger calcium regulates a variety of vitally important functions including neurotransmitter release, gene regulation, and neuronal plasticity. The entry of calcium into cells is tightly regulated by voltage-gated calcium channels, which consist of a heteromultimeric complex of a pore forming α₁, and the auxiliary β and α₂δ subunits. Four genes (Cacna2d1-4) encode for the extracellular membrane-attached α₂δ subunits (α₂δ-1 to α₂δ-4), out of which three isoforms (α₂δ-1 to -3) are strongly expressed in the central nervous system. Over the years a wealth of studies has demonstrated the classical role of α₂δ subunits in channel trafficking and calcium current modulation. Recent studies in specialized neuronal cell systems propose roles of α₂δ subunits beyond the classical view and implicate α₂δ subunits as important regulators of synapse formation. These findings are supported by the identification of novel human disease mutations associated with α₂δ subunits and by the fact that α₂δ subunits are the target of the anti-epileptic and anti-allodynic drugs gabapentin and pregabalin. Here we review the recently emerging evidence for specific as well as redundant neuronal roles of α₂δ subunits and discuss the mechanisms for establishing and maintaining specificity.
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Affiliation(s)
- Stefanie Geisler
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Clemens L Schöpf
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
| | - Gerald J Obermair
- Division of Physiology, Department of Physiology and Medical Physics, Medical University Innsbruck, 6020 Innsbruck, Austria
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Age-related homeostatic midchannel proteolysis of neuronal L-type voltage-gated Ca²⁺ channels. Neuron 2014; 82:1045-57. [PMID: 24908485 DOI: 10.1016/j.neuron.2014.04.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/01/2014] [Indexed: 12/11/2022]
Abstract
Neural circuitry and brain activity depend critically on proper function of voltage-gated calcium channels (VGCCs), whose activity must be tightly controlled. We show that the main body of the pore-forming α1 subunit of neuronal L-type VGCCs, Cav1.2, is proteolytically cleaved, resulting in Cav1.2 fragment channels that separate but remain on the plasma membrane. This "midchannel" proteolysis is regulated by channel activity, involves the Ca(2+)-dependent protease calpain and the ubiquitin-proteasome system, and causes attenuation and biophysical alterations of VGCC currents. Recombinant Cav1.2 fragment channels mimicking the products of midchannel proteolysis do not form active channels on their own but, when properly paired, produce currents with distinct biophysical properties. Midchannel proteolysis increases dramatically with age and can be attenuated with an L-type VGCC blocker in vivo. Midchannel proteolysis represents a novel form of homeostatic negative-feedback processing of VGCCs that could profoundly affect neuronal excitability, neurotransmission, neuroprotection, and calcium signaling in physiological and disease states.
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Campiglio M, Di Biase V, Tuluc P, Flucher BE. Stable incorporation versus dynamic exchange of β subunits in a native Ca2+ channel complex. J Cell Sci 2013; 126:2092-101. [PMID: 23447673 DOI: 10.1242/jcs.jcs124537] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Voltage-gated Ca(2+) channels are multi-subunit membrane proteins that transduce depolarization into cellular functions such as excitation-contraction coupling in muscle or neurotransmitter release in neurons. The auxiliary β subunits function in membrane targeting of the channel and modulation of its gating properties. However, whether β subunits can reversibly interact with, and thus differentially modulate, channels in the membrane is still unresolved. In the present study we applied fluorescence recovery after photobleaching (FRAP) of GFP-tagged α1 and β subunits expressed in dysgenic myotubes to study the relative dynamics of these Ca(2+) channel subunits for the first time in a native functional signaling complex. Identical fluorescence recovery rates of both subunits indicate stable interactions, distinct recovery rates indicate dynamic interactions. Whereas the skeletal muscle β1a isoform formed stable complexes with CaV1.1 and CaV1.2, the non-skeletal muscle β2a and β4b isoforms dynamically interacted with both α1 subunits. Neither replacing the I-II loop of CaV1.1 with that of CaV2.1, nor deletions in the proximal I-II loop, known to change the orientation of β relative to the α1 subunit, altered the specific dynamic properties of the β subunits. In contrast, a single residue substitution in the α interaction pocket of β1aM293A increased the FRAP rate threefold. Taken together, these findings indicate that in skeletal muscle triads the homologous β1a subunit forms a stable complex, whereas the heterologous β2a and β4b subunits form dynamic complexes with the Ca(2+) channel. The distinct binding properties are not determined by differences in the I-II loop sequences of the α1 subunits, but are intrinsic properties of the β subunit isoforms.
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Affiliation(s)
- Marta Campiglio
- Department of Physiology and Medical Physics, Medical University Innsbruck, A-6020 Innsbruck, Austria
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Altier C, Dubel SJ, Barrere C, Jarvis SE, Stotz SC, Scott JD, Nargeot J, Zamponi GW, Bourinet E. AKAP79 modulation of L-type channels involves disruption of intramolecular interactions in the CaV1.2 subunit. Channels (Austin) 2012; 6:157-65. [PMID: 22677788 DOI: 10.4161/chan.20865] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
L-type voltage gated calcium channels (VGCCs) interact with a variety of proteins that modulate both their function and localization. A-Kinase Anchoring Proteins (AKAPs) facilitate L-type calcium channel phosphorylation through β adrenergic stimulation. Our previous work indicated a role of neuronal AKAP79/150 in the membrane targeting of Ca(V)1.2 L-type calcium channels, which involved a proline rich domain (PRD) in the intracellular II-III loop of the channel.(1) Here, we show that mutation of proline 857 to alanine (P857A) into the PRD does not disrupt the AKAP79-induced increase in Ca(v)1.2 membrane expression. Furthermore, deletion of two other PRDs into the carboxy terminal domain of Ca(V)1.2 did not alter the targeting role of AKAP79. In contrast, the distal carboxy terminus region of the channel directly interacts with AKAP79. This protein-protein interaction competes with a direct association of the channel II-III linker on the carboxy terminal tail and modulates membrane targeting of Ca(V)1.2. Thus, our results suggest that the effects of AKAP79 occur through relief of an autoinhibitory mechanism mediated by intramolecular interactions of Ca(v)1.2 intracellular regions.
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Affiliation(s)
- Christophe Altier
- Department of Physiology and Pharmacology, University of Calgary, Alberta, Canada
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The role of metaplasticity mechanisms in regulating memory destabilization and reconsolidation. Neurosci Biobehav Rev 2012; 36:1667-707. [PMID: 22484475 DOI: 10.1016/j.neubiorev.2012.03.008] [Citation(s) in RCA: 144] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 03/09/2012] [Accepted: 03/21/2012] [Indexed: 12/13/2022]
Abstract
Memory allows organisms to predict future events based on prior experiences. This requires encoded information to persist once important predictors are extracted, while also being modifiable in response to changes within the environment. Memory reconsolidation may allow stored information to be modified in response to related experience. However, there are many boundary conditions beyond which reconsolidation may not occur. One interpretation of these findings is that the event triggering memory retrieval must contain new information about a familiar stimulus in order to induce reconsolidation. Presently, the mechanisms that affect the likelihood of reconsolidation occurring under these conditions are not well understood. Here we speculate on a number of systems that may play a role in protecting memory from being destabilized during retrieval. We conclude that few memories may enter a state in which they cannot be modified. Rather, metaplasticity mechanisms may serve to alter the specific reactivation cues necessary to destabilize a memory. This might imply that destabilization mechanisms can differ depending on learning conditions.
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Shetty PK, Galeffi F, Turner DA. Cellular Links between Neuronal Activity and Energy Homeostasis. Front Pharmacol 2012; 3:43. [PMID: 22470340 PMCID: PMC3308331 DOI: 10.3389/fphar.2012.00043] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 02/24/2012] [Indexed: 12/20/2022] Open
Abstract
Neuronal activity, astrocytic responses to this activity, and energy homeostasis are linked together during baseline, conscious conditions, and short-term rapid activation (as occurs with sensory or motor function). Nervous system energy homeostasis also varies during long-term physiological conditions (i.e., development and aging) and with adaptation to pathological conditions, such as ischemia or low glucose. Neuronal activation requires increased metabolism (i.e., ATP generation) which leads initially to substrate depletion, induction of a variety of signals for enhanced astrocytic function, and increased local blood flow and substrate delivery. Energy generation (particularly in mitochondria) and use during ATP hydrolysis also lead to considerable heat generation. The local increases in blood flow noted following neuronal activation can both enhance local substrate delivery but also provides a heat sink to help cool the brain and removal of waste by-products. In this review we highlight the interactions between short-term neuronal activity and energy metabolism with an emphasis on signals and factors regulating astrocyte function and substrate supply.
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Affiliation(s)
- Pavan K Shetty
- Neurosurgery and Neurobiology, Research and Surgery Services, Durham VA Medical Center, Duke University Durham, NC, USA
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