1
|
Ji J, Zhou X, Lu Y, Shen L, Li L, Chen Z, Shi Y, Liao W, Yu L. SCN1A intronic variants impact on Nav1.1 protein expression and sodium channel function, and associated with epilepsy phenotypic severity. Gene 2025; 932:148876. [PMID: 39173978 DOI: 10.1016/j.gene.2024.148876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 07/18/2024] [Accepted: 08/19/2024] [Indexed: 08/24/2024]
Abstract
High-throughput sequencing has identified numerous intronic variants in the SCN1A gene in epilepsy patients. Abnormal mRNA splicing caused by these variants can lead to significant phenotypic differences, but the mechanisms of epileptogenicity and phenotypic differences remain unknown. Two variants, c.4853-1 G>C and c.4853-25 T>A, were identified in intron 25 of SCN1A, which were associated with severe Dravet syndrome (DS) and mild focal epilepsy with febrile seizures plus (FEFS+), respectively. The impact of these variants on protein expression, electrophysiological properties of sodium channels and their correlation with epilepsy severity was investigated through plasmid construction and transfection based on the aberrant spliced mRNA. We found that the expression of truncated mutant proteins was significantly reduced on the cell membrane, and retained in the cytoplasmic endoplasmic reticulum. The mutants caused a decrease in current density, voltage sensitivity, and an increased vulnerability of channel, leading to a partial impairment of sodium channel function. Notably, the expression of DS-related mutant protein on the cell membrane was higher compared to that of FEFS+-related mutant, whereas the sodium channel function impairment caused by DS-related mutant was comparatively milder than that caused by FEFS+-related mutant. Our study suggests that differences in protein expression levels and altered electrophysiological properties of sodium channels play important roles in the manifestation of diverse epileptic phenotypes. The presence of intronic splice site variants may result in severe phenotypes due to the dominant-negative effects, whereas non-canonical splice site variants leading to haploinsufficiency could potentially cause milder phenotypes.
Collapse
Affiliation(s)
- Jingjing Ji
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Nanning, GX, China
| | - Xijing Zhou
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Nanning, GX, China; Department of Neurology, The First People's Hospital of Nanning, the Fifth Affiliated Hospital of Guangxi Medical University, Nanning, GX, China
| | - Yanting Lu
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Nanning, GX, China
| | - Lang Shen
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Nanning, GX, China
| | - Lixia Li
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Nanning, GX, China
| | - Zirong Chen
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Nanning, GX, China
| | - Yiwu Shi
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, GD, China
| | - Weiping Liao
- Institute of Neuroscience and the Second Affiliated Hospital of Guangzhou Medical University, Guangzhou, GD, China
| | - Lu Yu
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Nanning, GX, China.
| |
Collapse
|
2
|
Tang C, Duran P, Calderon-Rivera A, Loya-Lopez S, Gomez K, Perez-Miller S, Khanna R. Regulating neuronal excitability: The role of S-palmitoylation in Na V1.7 activity and voltage sensitivity. PNAS NEXUS 2024; 3:pgae222. [PMID: 38894876 PMCID: PMC11184981 DOI: 10.1093/pnasnexus/pgae222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 05/29/2024] [Indexed: 06/21/2024]
Abstract
S-palmitoylation, a reversible lipid post-translational modification, regulates the functions of numerous proteins. Voltage-gated sodium channels (NaVs), pivotal in action potential generation and propagation within cardiac cells and sensory neurons, can be directly or indirectly modulated by S-palmitoylation, impacting channel trafficking and function. However, the role of S-palmitoylation in modulating NaV1.7, a significant contributor to pain pathophysiology, has remained unexplored. Here, we addressed this knowledge gap by investigating if S-palmitoylation influences NaV1.7 channel function. Acyl-biotin exchange assays demonstrated that heterologously expressed NaV1.7 channels are modified by S-palmitoylation. Blocking S-palmitoylation with 2-bromopalmitate resulted in reduced NaV1.7 current density and hyperpolarized steady-state inactivation. We identified two S-palmitoylation sites within NaV1.7, both located in the second intracellular loop, which regulated different properties of the channel. Specifically, S-palmitoylation of cysteine 1126 enhanced NaV1.7 current density, while S-palmitoylation of cysteine 1152 modulated voltage-dependent inactivation. Blocking S-palmitoylation altered excitability of rat dorsal root ganglion neurons. Lastly, in human sensory neurons, NaV1.7 undergoes S-palmitoylation, and the attenuation of this post-translational modification results in alterations in the voltage-dependence of activation, leading to decreased neuronal excitability. Our data show, for the first time, that S-palmitoylation affects NaV1.7 channels, exerting regulatory control over their activity and, consequently, impacting rodent and human sensory neuron excitability. These findings provide a foundation for future pharmacological studies, potentially uncovering novel therapeutic avenues in the modulation of S-palmitoylation for NaV1.7 channels.
Collapse
Affiliation(s)
- Cheng Tang
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, NY 10010, USA
- The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha 410081, China
- Peptide and Small Molecule Drug R&D Platform, Furong Laboratory, Hunan Normal University, Changsha 410081, China
| | - Paz Duran
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, NY 10010, USA
| | - Aida Calderon-Rivera
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, NY 10010, USA
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Santiago Loya-Lopez
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, NY 10010, USA
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Kimberly Gomez
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, NY 10010, USA
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Samantha Perez-Miller
- Department of Molecular Pathobiology, College of Dentistry, New York University, New York, NY 10010, USA
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| | - Rajesh Khanna
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL 32610, USA
| |
Collapse
|
3
|
Scott H, Novikov B, Ugur B, Allen B, Mertsalov I, Monagas-Valentin P, Koff M, Baas Robinson S, Aoki K, Veizaj R, Lefeber DJ, Tiemeyer M, Bellen H, Panin V. Glia-neuron coupling via a bipartite sialylation pathway promotes neural transmission and stress tolerance in Drosophila. eLife 2023; 12:e78280. [PMID: 36946697 PMCID: PMC10110239 DOI: 10.7554/elife.78280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 03/16/2023] [Indexed: 03/23/2023] Open
Abstract
Modification by sialylated glycans can affect protein functions, underlying mechanisms that control animal development and physiology. Sialylation relies on a dedicated pathway involving evolutionarily conserved enzymes, including CMP-sialic acid synthetase (CSAS) and sialyltransferase (SiaT) that mediate the activation of sialic acid and its transfer onto glycan termini, respectively. In Drosophila, CSAS and DSiaT genes function in the nervous system, affecting neural transmission and excitability. We found that these genes function in different cells: the function of CSAS is restricted to glia, while DSiaT functions in neurons. This partition of the sialylation pathway allows for regulation of neural functions via a glia-mediated control of neural sialylation. The sialylation genes were shown to be required for tolerance to heat and oxidative stress and for maintenance of the normal level of voltage-gated sodium channels. Our results uncovered a unique bipartite sialylation pathway that mediates glia-neuron coupling and regulates neural excitability and stress tolerance.
Collapse
Affiliation(s)
- Hilary Scott
- Department of Biochemistry and Biophysics, Texas A&M UniversityCollege StationUnited States
| | - Boris Novikov
- Department of Biochemistry and Biophysics, Texas A&M UniversityCollege StationUnited States
| | - Berrak Ugur
- Departments of Molecular and Human Genetics and Neuroscience, Baylor College of Medicine, and Jan and Dan Duncan Neurological Research Institute, Texas Children’s HospitalHoustonUnited States
| | - Brooke Allen
- Department of Biochemistry and Biophysics, Texas A&M UniversityCollege StationUnited States
| | - Ilya Mertsalov
- Department of Biochemistry and Biophysics, Texas A&M UniversityCollege StationUnited States
| | - Pedro Monagas-Valentin
- Department of Biochemistry and Biophysics, Texas A&M UniversityCollege StationUnited States
| | - Melissa Koff
- Department of Biochemistry and Biophysics, Texas A&M UniversityCollege StationUnited States
| | - Sarah Baas Robinson
- Complex Carbohydrate Research Center, University of GeorgiaAthensUnited States
| | - Kazuhiro Aoki
- Complex Carbohydrate Research Center, University of GeorgiaAthensUnited States
| | - Raisa Veizaj
- Translational Metabolic Laboratory, Department of Neurology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical CenterNijmegenNetherlands
| | - Dirk J Lefeber
- Translational Metabolic Laboratory, Department of Neurology, Donders Institute for Brain, Cognition and Behavior, Radboud University Medical CenterNijmegenNetherlands
| | - Michael Tiemeyer
- Complex Carbohydrate Research Center, University of GeorgiaAthensUnited States
| | - Hugo Bellen
- Departments of Molecular and Human Genetics and Neuroscience, Baylor College of Medicine, and Jan and Dan Duncan Neurological Research Institute, Texas Children’s HospitalHoustonUnited States
| | - Vladislav Panin
- Department of Biochemistry and Biophysics, Texas A&M UniversityCollege StationUnited States
| |
Collapse
|
4
|
Valente P, Marte A, Franchi F, Sterlini B, Casagrande S, Corradi A, Baldelli P, Benfenati F. A Push-Pull Mechanism Between PRRT2 and β4-subunit Differentially Regulates Membrane Exposure and Biophysical Properties of NaV1.2 Sodium Channels. Mol Neurobiol 2023; 60:1281-1296. [PMID: 36441479 PMCID: PMC9899197 DOI: 10.1007/s12035-022-03112-x] [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: 04/27/2022] [Accepted: 10/26/2022] [Indexed: 11/29/2022]
Abstract
Proline-rich transmembrane protein 2 (PRRT2) is a neuron-specific protein implicated in the control of neurotransmitter release and neural network stability. Accordingly, PRRT2 loss-of-function mutations associate with pleiotropic paroxysmal neurological disorders, including paroxysmal kinesigenic dyskinesia, episodic ataxia, benign familial infantile seizures, and hemiplegic migraine. PRRT2 is a negative modulator of the membrane exposure and biophysical properties of Na+ channels NaV1.2/NaV1.6 predominantly expressed in brain glutamatergic neurons. NaV channels form complexes with β-subunits that facilitate the membrane targeting and the activation of the α-subunits. The opposite effects of PRRT2 and β-subunits on NaV channels raises the question of whether PRRT2 and β-subunits interact or compete for common binding sites on the α-subunit, generating Na+ channel complexes with distinct functional properties. Using a heterologous expression system, we have observed that β-subunits and PRRT2 do not interact with each other and act as independent non-competitive modulators of NaV1.2 channel trafficking and biophysical properties. PRRT2 antagonizes the β4-induced increase in expression and functional activation of the transient and persistent NaV1.2 currents, without affecting resurgent current. The data indicate that β4-subunit and PRRT2 form a push-pull system that finely tunes the membrane expression and function of NaV channels and the intrinsic neuronal excitability.
Collapse
Affiliation(s)
- Pierluigi Valente
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132, Genova, Italy. .,IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132, Genova, Italy.
| | - Antonella Marte
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy ,IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Francesca Franchi
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy ,Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Bruno Sterlini
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy ,Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Silvia Casagrande
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy
| | - Anna Corradi
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy ,IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Pietro Baldelli
- Department of Experimental Medicine, Section of Physiology, University of Genova, Viale Benedetto XV, 3, 16132 Genova, Italy ,IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132 Genova, Italy
| | - Fabio Benfenati
- IRCCS, Ospedale Policlinico San Martino, Largo Rosanna Benzi 10, 16132, Genova, Italy. .,Center for Synaptic Neuroscience and Technology, Istituto Italiano Di Tecnologia, Largo Rosanna Benzi 10, 16132, Genova, Italy.
| |
Collapse
|
5
|
Hawkinson TR, Clarke HA, Young LEA, Conroy LR, Markussen KH, Kerch KM, Johnson LA, Nelson PT, Wang C, Allison DB, Gentry MS, Sun RC. In situ spatial glycomic imaging of mouse and human Alzheimer's disease brains. Alzheimers Dement 2022; 18:1721-1735. [PMID: 34908231 PMCID: PMC9198106 DOI: 10.1002/alz.12523] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 10/06/2021] [Accepted: 10/10/2021] [Indexed: 01/28/2023]
Abstract
N-linked protein glycosylation in the brain is an understudied facet of glucose utilization that impacts a myriad of cellular processes including resting membrane potential, axon firing, and synaptic vesicle trafficking. Currently, a spatial map of N-linked glycans within the normal and Alzheimer's disease (AD) human brain does not exist. A comprehensive analysis of the spatial N-linked glycome would improve our understanding of brain energy metabolism, linking metabolism to signaling events perturbed during AD progression, and could illuminate new therapeutic strategies. Herein we report an optimized in situ workflow for enzyme-assisted, matrix-assisted laser desorption and ionization (MALDI) mass spectrometry imaging (MSI) of brain N-linked glycans. Using this workflow, we spatially interrogated N-linked glycan heterogeneity in both mouse and human AD brains and their respective age-matched controls. We identified robust regional-specific N-linked glycan changes associated with AD in mice and humans. These data suggest that N-linked glycan dysregulation could be an underpinning of AD pathologies.
Collapse
Affiliation(s)
- Tara R. Hawkinson
- Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, Kentucky, USA
| | - Harrison A. Clarke
- Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, Kentucky, USA
| | - Lyndsay E. A. Young
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, Kentucky, USA
- Markey Cancer Center, University of Kentucky, Lexington, Kentucky, USA
| | - Lindsey R. Conroy
- Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, Kentucky, USA
| | - Kia H. Markussen
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, Kentucky, USA
| | - Kayla M. Kerch
- Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, Kentucky, USA
| | - Lance A. Johnson
- Department of Physiology, College of Medicine, University of Kentucky, Lexington, Kentucky, USA
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, Kentucky, USA
| | - Peter T. Nelson
- Department of Pathology and Laboratory Medicine, University of Kentucky, Lexington, Kentucky, USA
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, Kentucky, USA
| | - Chi Wang
- Markey Cancer Center, University of Kentucky, Lexington, Kentucky, USA
- Department of Biostatistics, College of Medicine, University of Kentucky, Lexington, Kentucky, USA
| | - Derek B. Allison
- Markey Cancer Center, University of Kentucky, Lexington, Kentucky, USA
- Department of Pathology and Laboratory Medicine, University of Kentucky, Lexington, Kentucky, USA
| | - Matthew S. Gentry
- Department of Molecular and Cellular Biochemistry, College of Medicine, University of Kentucky, Lexington, Kentucky, USA
- Markey Cancer Center, University of Kentucky, Lexington, Kentucky, USA
| | - Ramon C. Sun
- Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, Kentucky, USA
- Markey Cancer Center, University of Kentucky, Lexington, Kentucky, USA
- Sanders-Brown Center on Aging, University of Kentucky, Lexington, Kentucky, USA
| |
Collapse
|
6
|
Palmitoylation of Voltage-Gated Ion Channels. Int J Mol Sci 2022; 23:ijms23169357. [PMID: 36012639 PMCID: PMC9409123 DOI: 10.3390/ijms23169357] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 08/11/2022] [Accepted: 08/16/2022] [Indexed: 11/30/2022] Open
Abstract
Protein lipidation is one of the most common forms of posttranslational modification. This alteration couples different lipids, such as fatty acids, phospho- and glycolipids and sterols, to cellular proteins. Lipidation regulates different aspects of the protein’s physiology, including structure, stability and affinity for cellular membranes and protein–protein interactions. In this scenario, palmitoylation is the addition of long saturated fatty acid chains to amino acid residues of the proteins. The enzymes responsible for this modification are acyltransferases and thioesterases, which control the protein’s behavior by performing a series of acylation and deacylation cycles. These enzymes target a broad repertoire of substrates, including ion channels. Thus, protein palmitoylation exhibits a pleiotropic role by differential modulation of the trafficking, spatial organization and electrophysiological properties of ion channels. Considering voltage-gated ion channels (VGICs), dysregulation of lipidation of both the channels and the associated ancillary subunits correlates with the development of various diseases, such as cancer or mental disorders. Therefore, a major role for protein palmitoylation is currently emerging, affecting not only the dynamism and differential regulation of a moiety of cellular proteins but also linking to human health. Therefore, palmitoylation of VGIC, as well as related enzymes, constitutes a novel pharmacological tool for drug development to target related pathologies.
Collapse
|
7
|
Daimi H, Lozano-Velasco E, Aranega A, Franco D. Genomic and Non-Genomic Regulatory Mechanisms of the Cardiac Sodium Channel in Cardiac Arrhythmias. Int J Mol Sci 2022; 23:1381. [PMID: 35163304 PMCID: PMC8835759 DOI: 10.3390/ijms23031381] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 12/30/2021] [Accepted: 01/06/2022] [Indexed: 12/19/2022] Open
Abstract
Nav1.5 is the predominant cardiac sodium channel subtype, encoded by the SCN5A gene, which is involved in the initiation and conduction of action potentials throughout the heart. Along its biosynthesis process, Nav1.5 undergoes strict genomic and non-genomic regulatory and quality control steps that allow only newly synthesized channels to reach their final membrane destination and carry out their electrophysiological role. These regulatory pathways are ensured by distinct interacting proteins that accompany the nascent Nav1.5 protein along with different subcellular organelles. Defects on a large number of these pathways have a tremendous impact on Nav1.5 functionality and are thus intimately linked to cardiac arrhythmias. In the present review, we provide current state-of-the-art information on the molecular events that regulate SCN5A/Nav1.5 and the cardiac channelopathies associated with defects in these pathways.
Collapse
Affiliation(s)
- Houria Daimi
- Biochemistry and Molecular Biology Laboratory, Faculty of Pharmacy, University of Monastir, Monastir 5000, Tunisia
| | - Estefanía Lozano-Velasco
- Department of Experimental Biology, University of Jaen, 23071 Jaen, Spain; (E.L.-V.); (A.A.); (D.F.)
- Medina Foundation, Technology Park of Health Sciences, Av. del Conocimiento, 34, 18016 Granada, Spain
| | - Amelia Aranega
- Department of Experimental Biology, University of Jaen, 23071 Jaen, Spain; (E.L.-V.); (A.A.); (D.F.)
- Medina Foundation, Technology Park of Health Sciences, Av. del Conocimiento, 34, 18016 Granada, Spain
| | - Diego Franco
- Department of Experimental Biology, University of Jaen, 23071 Jaen, Spain; (E.L.-V.); (A.A.); (D.F.)
- Medina Foundation, Technology Park of Health Sciences, Av. del Conocimiento, 34, 18016 Granada, Spain
| |
Collapse
|
8
|
Zybura A, Hudmon A, Cummins TR. Distinctive Properties and Powerful Neuromodulation of Na v1.6 Sodium Channels Regulates Neuronal Excitability. Cells 2021; 10:cells10071595. [PMID: 34202119 PMCID: PMC8307729 DOI: 10.3390/cells10071595] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 06/20/2021] [Accepted: 06/21/2021] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (Navs) are critical determinants of cellular excitability. These ion channels exist as large heteromultimeric structures and their activity is tightly controlled. In neurons, the isoform Nav1.6 is highly enriched at the axon initial segment and nodes, making it critical for the initiation and propagation of neuronal impulses. Changes in Nav1.6 expression and function profoundly impact the input-output properties of neurons in normal and pathological conditions. While mutations in Nav1.6 may cause channel dysfunction, aberrant changes may also be the result of complex modes of regulation, including various protein-protein interactions and post-translational modifications, which can alter membrane excitability and neuronal firing properties. Despite decades of research, the complexities of Nav1.6 modulation in health and disease are still being determined. While some modulatory mechanisms have similar effects on other Nav isoforms, others are isoform-specific. Additionally, considerable progress has been made toward understanding how individual protein interactions and/or modifications affect Nav1.6 function. However, there is still more to be learned about how these different modes of modulation interact. Here, we examine the role of Nav1.6 in neuronal function and provide a thorough review of this channel’s complex regulatory mechanisms and how they may contribute to neuromodulation.
Collapse
Affiliation(s)
- Agnes Zybura
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
- Biology Department, School of Science, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
| | - Andy Hudmon
- Department of Medicinal Chemistry and Molecular Pharmacology, College of Pharmacy, Purdue University, West Lafayette, IN 47907, USA;
| | - Theodore R. Cummins
- Program in Medical Neuroscience, Paul and Carole Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN 46202, USA;
- Biology Department, School of Science, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46202, USA
- Correspondence:
| |
Collapse
|
9
|
Shimell JJ, Shah BS, Cain SM, Thouta S, Kuhlmann N, Tatarnikov I, Jovellar DB, Brigidi GS, Kass J, Milnerwood AJ, Snutch TP, Bamji SX. The X-Linked Intellectual Disability Gene Zdhhc9 Is Essential for Dendrite Outgrowth and Inhibitory Synapse Formation. Cell Rep 2020; 29:2422-2437.e8. [PMID: 31747610 DOI: 10.1016/j.celrep.2019.10.065] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 09/09/2019] [Accepted: 10/13/2019] [Indexed: 11/29/2022] Open
Abstract
Palmitoylation is a reversible post-translational lipid modification that facilitates vesicular transport and subcellular localization of modified proteins. This process is catalyzed by ZDHHC enzymes that are implicated in several neurological and neurodevelopmental disorders. Loss-of-function mutations in ZDHHC9 have been identified in patients with X-linked intellectual disability (XLID) and associated with increased epilepsy risk. Loss of Zdhhc9 function in hippocampal cultures leads to shorter dendritic arbors and fewer inhibitory synapses, altering the ratio of excitatory-to-inhibitory inputs formed onto Zdhhc9-deficient cells. While Zdhhc9 promotes dendrite outgrowth through the palmitoylation of the GTPase Ras, it promotes inhibitory synapse formation through the palmitoylation of another GTPase, TC10. Zdhhc9 knockout mice exhibit seizure-like activity together with increased frequency and amplitude of both spontaneous and miniature excitatory and inhibitory postsynaptic currents. These findings present a plausible mechanism for how the loss of ZDHHC9 function may contribute to XLID and epilepsy.
Collapse
Affiliation(s)
- Jordan J Shimell
- Department of Cellular and Physiological Sciences, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Bhavin S Shah
- Department of Cellular and Physiological Sciences, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Stuart M Cain
- Michael Smith Laboratories, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
| | - Samrat Thouta
- Michael Smith Laboratories, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
| | - Naila Kuhlmann
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, 3801 University Street, Montreal, QC H3A 2B4, Canada
| | - Igor Tatarnikov
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, 3801 University Street, Montreal, QC H3A 2B4, Canada
| | - D Blair Jovellar
- Department of Cellular and Physiological Sciences, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - G Stefano Brigidi
- Department of Cellular and Physiological Sciences, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - Jennifer Kass
- Michael Smith Laboratories, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
| | - Austen J Milnerwood
- Montreal Neurological Institute, Department of Neurology and Neurosurgery, McGill University, 3801 University Street, Montreal, QC H3A 2B4, Canada
| | - Terrance P Snutch
- Michael Smith Laboratories, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2215 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
| | - Shernaz X Bamji
- Department of Cellular and Physiological Sciences, Djavad Mowafaghian Centre for Brain Health, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.
| |
Collapse
|
10
|
Snyder J, Zhai R, Lackey AI, Sato PY. Changes in Myocardial Metabolism Preceding Sudden Cardiac Death. Front Physiol 2020; 11:640. [PMID: 32612538 PMCID: PMC7308560 DOI: 10.3389/fphys.2020.00640] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 05/20/2020] [Indexed: 12/11/2022] Open
Abstract
Heart disease is widely recognized as a major cause of death worldwide and is the leading cause of mortality in the United States. Centuries of research have focused on defining mechanistic alterations that drive cardiac pathogenesis, yet sudden cardiac death (SCD) remains a common unpredictable event that claims lives in every age group. The heart supplies blood to all tissues while maintaining a constant electrical and hormonal feedback communication with other parts of the body. As such, recent research has focused on understanding how myocardial electrical and structural properties are altered by cardiac metabolism and the various signaling pathways associated with it. The importance of cardiac metabolism in maintaining myocardial function, or lack thereof, is exemplified by shifts in cardiac substrate preference during normal development and various pathological conditions. For instance, a shift from fatty acid (FA) oxidation to oxygen-sparing glycolytic energy production has been reported in many types of cardiac pathologies. Compounded by an uncoupling of glycolysis and glucose oxidation this leads to accumulation of undesirable levels of intermediate metabolites. The resulting accumulation of intermediary metabolites impacts cardiac mitochondrial function and dysregulates metabolic pathways through several mechanisms, which will be reviewed here. Importantly, reversal of metabolic maladaptation has been shown to elicit positive therapeutic effects, limiting cardiac remodeling and at least partially restoring contractile efficiency. Therein, the underlying metabolic adaptations in an array of pathological conditions as well as recently discovered downstream effects of various substrate utilization provide guidance for future therapeutic targeting. Here, we will review recent data on alterations in substrate utilization in the healthy and diseased heart, metabolic pathways governing cardiac pathogenesis, mitochondrial function in the diseased myocardium, and potential metabolism-based therapeutic interventions in disease.
Collapse
Affiliation(s)
- J Snyder
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, United States
| | - R Zhai
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, United States
| | - A I Lackey
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, United States
| | - P Y Sato
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA, United States
| |
Collapse
|
11
|
Wiedmann F, Schlund D, Voigt N, Ratte A, Kraft M, Katus HA, Schmidt C. N-glycosylation-dependent regulation of hK 2P17.1 currents. Mol Biol Cell 2019; 30:1425-1436. [PMID: 30969900 PMCID: PMC6724686 DOI: 10.1091/mbc.e18-10-0687] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Two pore-domain potassium (K2P) channels mediate potassium background currents that stabilize the resting membrane potential and facilitate action potential repolarization. In the human heart, hK2P17.1 channels are predominantly expressed in the atria and Purkinje cells. Reduced atrial hK2P17.1 protein levels were described in patients with atrial fibrillation or heart failure. Genetic alterations in hK2P17.1 were associated with cardiac conduction disorders. Little is known about posttranslational modifications of hK2P17.1. Here, we characterized glycosylation of hK2P17.1 and investigated how glycosylation alters its surface expression and activity. Wild-type hK2P17.1 channels and channels lacking specific glycosylation sites were expressed in Xenopus laevis oocytes, HEK-293T cells, and HeLa cells. N-glycosylation was disrupted using N-glycosidase F and tunicamycin. hK2P17.1 expression and activity were assessed using immunoblot analysis and a two-electrode voltage clamp technique. Channel subunits of hK2P17.1 harbor two functional N-glycosylation sites at positions N65 and N94. In hemi-glycosylated hK2P17.1 channels, functionality and membrane trafficking remain preserved. Disruption of both N-glycosylation sites results in loss of hK2P17.1 currents, presumably caused by impaired surface expression. This study confirms diglycosylation of hK2P17.1 channel subunits and its pivotal role in cell-surface targeting. Our findings underline the functional relevance of N-glycosylation in biogenesis and membrane trafficking of ion channels.
Collapse
Affiliation(s)
- Felix Wiedmann
- Department of Cardiology, University of Heidelberg, 69120 Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, 69120 Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, 69120 Heidelberg, Germany
| | - Daniel Schlund
- Department of Cardiology, University of Heidelberg, 69120 Heidelberg, Germany
| | - Niels Voigt
- Institute of Pharmacology and Toxicology, University Medical Center Göttingen, Georg-August University of Göttingen, 37073 Göttingen, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Göttingen, University of Göttingen, 37073 Göttingen, Germany
| | - Antonius Ratte
- Department of Cardiology, University of Heidelberg, 69120 Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, 69120 Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, 69120 Heidelberg, Germany
| | - Manuel Kraft
- Department of Cardiology, University of Heidelberg, 69120 Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, 69120 Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, 69120 Heidelberg, Germany
| | - Hugo A Katus
- Department of Cardiology, University of Heidelberg, 69120 Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, 69120 Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, 69120 Heidelberg, Germany
| | - Constanze Schmidt
- Department of Cardiology, University of Heidelberg, 69120 Heidelberg, Germany.,DZHK (German Center for Cardiovascular Research), Partner Site Heidelberg/Mannheim, University of Heidelberg, 69120 Heidelberg, Germany.,HCR, Heidelberg Center for Heart Rhythm Disorders, University of Heidelberg, 69120 Heidelberg, Germany
| |
Collapse
|
12
|
Co-expression of β Subunits with the Voltage-Gated Sodium Channel Na V1.7: the Importance of Subunit Association and Phosphorylation and Their Effects on Channel Pharmacology and Biophysics. J Mol Neurosci 2018; 65:154-166. [PMID: 29744740 DOI: 10.1007/s12031-018-1082-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 05/01/2018] [Indexed: 12/19/2022]
Abstract
The voltage-gated sodium ion channel NaV1.7 is crucial in pain signaling. We examined how auxiliary β2 and β3 subunits and the phosphorylation state of the channel influence its biophysical properties and pharmacology. The human NaV1.7α subunit was co-expressed with either β2 or β3 subunits in HEK-293 cells. The β2 subunits and the NaV1.7α, however, were barely associated as evidenced by immunoprecipitation. Therefore, the β2 subunits did not change the biophysical properties of the channel. In contrast, β3 subunit was clearly associated with NaV1.7α. This subunit had a significant degree of glycosylation, and only the fully glycosylated β3 subunit was associated with the NaV1.7α. Electrophysiological characterisation revealed that the β3 subunit had small but consistent effects: a right-hand shift of the steady-state inactivation and faster recovery from inactivation. Furthermore, the β3 subunit reduced the susceptibility of NaV1.7α to several sodium channel blockers. In addition, we assessed the functional effect of NaV1.7α phosphorylation. Inhibition of kinase activity increased channel inactivation, while the blocking phosphatases produced the opposite effect. In conclusion, co-expression of β subunits with NaV1.7α, to better mimic the native channel properties, may be ineffective in cases when subunits are not associated, as shown in our experiments with β2. The β3 subunit significantly influences the function of NaV1.7α and, together with the phosphorylation of the channel, regulates its biophysical and pharmacological properties. These are important findings to take into account when considering the role of NaV1.7 channel in pain signaling.
Collapse
|
13
|
Taruno A, Sun H, Nakajo K, Murakami T, Ohsaki Y, Kido MA, Ono F, Marunaka Y. Post-translational palmitoylation controls the voltage gating and lipid raft association of the CALHM1 channel. J Physiol 2017; 595:6121-6145. [PMID: 28734079 DOI: 10.1113/jp274164] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Accepted: 07/14/2017] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS Calcium homeostasis modulator 1 (CALHM1), a new voltage-gated ATP- and Ca2+ -permeable channel, plays important physiological roles in taste perception and memory formation. Regulatory mechanisms of CALHM1 remain unexplored, although the biophysical disparity between CALHM1 gating in vivo and in vitro suggests that there are undiscovered regulatory mechanisms. Here we report that CALHM1 gating and association with lipid microdomains are post-translationally regulated through the process of protein S-palmitoylation, a reversible attachment of palmitate to cysteine residues. Our data also establish cysteine residues and enzymes responsible for CALHM1 palmitoylation. CALHM1 regulation by palmitoylation provides new mechanistic insights into fine-tuning of CALHM1 gating in vivo and suggests a potential layer of regulation in taste and memory. ABSTRACT Emerging roles of CALHM1, a recently discovered voltage-gated ion channel, include purinergic neurotransmission of tastes in taste buds and memory formation in the brain, highlighting its physiological importance. However, the regulatory mechanisms of the CALHM1 channel remain entirely unexplored, hindering full understanding of its contribution in vivo. The different gating properties of CALHM1 in vivo and in vitro suggest undiscovered regulatory mechanisms. Here, in searching for post-translational regulatory mechanisms, we discovered the regulation of CALHM1 gating and association with lipid microdomains via protein S-palmitoylation, the only reversible lipid modification of proteins on cysteine residues. CALHM1 is palmitoylated at two intracellular cysteines located in the juxtamembrane regions of the third and fourth transmembrane domains. Enzymes that catalyse CALHM1 palmitoylation were identified by screening 23 members of the DHHC protein acyltransferase family. Epitope tagging of endogenous CALHM1 proteins in mice revealed that CALHM1 is basally palmitoylated in taste buds in vivo. Functionally, palmitoylation downregulates CALHM1 without effects on its synthesis, degradation and cell surface expression. Mutation of the palmitoylation sites has a profound impact on CALHM1 gating, shifting the conductance-voltage relationship to more negative voltages and accelerating the activation kinetics. The same mutation also reduces CALHM1 association with detergent-resistant membranes. Our results comprehensively uncover a post-translational regulation of the voltage-dependent gating of CALHM1 by palmitoylation.
Collapse
Affiliation(s)
- Akiyuki Taruno
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto, 602-8566, Japan
| | - Hongxin Sun
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto, 602-8566, Japan
| | - Koichi Nakajo
- Department of Physiology, Osaka Medical College, 2-7 Daigakumachi, Takatsuki, 569-8686, Japan
| | - Tatsuro Murakami
- Biotech Research and Innovation Centre, University of Copenhagen, Ole Maaløes Vej 5, DK-2200, Copenhagen N, Denmark
| | - Yasuyoshi Ohsaki
- Department of Molecular Cell Biology and Oral Anatomy, Kyushu University, 3-1-1 Maidashi, Higashi-ward, Fukuoka, 812-8582, Japan
| | - Mizuho A Kido
- Department of Anatomy and Physiology, Saga University, 5-1-1 Nabeshima, Saga, 849-8501, Japan
| | - Fumihito Ono
- Department of Physiology, Osaka Medical College, 2-7 Daigakumachi, Takatsuki, 569-8686, Japan
| | - Yoshinori Marunaka
- Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto, 602-8566, Japan.,Department of Bio-Ionomics, Kyoto Prefectural University of Medicine, 465 Kajiicho Kamigyo-ward, Kyoto, 602-8566, Japan
| |
Collapse
|
14
|
Tong J, Okutani F, Murata Y, Taniguchi M, Namba T, Wang YJ, Kaba H. Tunicamycin impairs olfactory learning and synaptic plasticity in the olfactory bulb. Neuroscience 2017; 344:371-379. [PMID: 28087337 DOI: 10.1016/j.neuroscience.2017.01.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 11/25/2016] [Accepted: 01/02/2017] [Indexed: 01/05/2023]
Abstract
Tunicamycin (TM) induces endoplasmic reticulum (ER) stress and inhibits N-glycosylation in cells. ER stress is associated with neuronal death in neurodegenerative disorders, such as Parkinson's disease and Alzheimer's disease, and most patients complain of the impairment of olfactory recognition. Here we examined the effects of TM on aversive olfactory learning and the underlying synaptic plasticity in the main olfactory bulb (MOB). Behavioral experiments demonstrated that the intrabulbar infusion of TM disabled aversive olfactory learning without affecting short-term memory. Histological analyses revealed that TM infusion upregulated C/EBP homologous protein (CHOP), a marker of ER stress, in the mitral and granule cell layers of MOB. Electrophysiological data indicated that TM inhibited tetanus-induced long-term potentiation (LTP) at the dendrodendritic excitatory synapse from mitral to granule cells. A low dose of TM (250nM) abolished the late phase of LTP, and a high dose (1μM) inhibited the early and late phases of LTP. Further, high-dose, but not low-dose, TM reduced the paired-pulse facilitation ratio, suggesting that the inhibitory effects of TM on LTP are partially mediated through the presynaptic machinery. Thus, our results support the hypothesis that TM-induced ER stress impairs olfactory learning by inhibiting synaptic plasticity via presynaptic and postsynaptic mechanisms in MOB.
Collapse
Affiliation(s)
- Jia Tong
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
| | - Fumino Okutani
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan; Department of Occupational Health, Kochi Medical School, Nankoku, Kochi 783-8505, Japan.
| | - Yoshihiro Murata
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
| | - Mutsuo Taniguchi
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
| | - Toshiharu Namba
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
| | - Yu-Jie Wang
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
| | - Hideto Kaba
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
| |
Collapse
|
15
|
Abstract
Voltage-gated sodium channels (VGSCs) are critical determinants of excitability. The properties of VGSCs are thought to be tightly controlled. However, VGSCs are also subjected to extensive modifications. Multiple posttranslational modifications that covalently modify VGSCs in neurons and muscle have been identified. These include, but are not limited to, phosphorylation, ubiquitination, palmitoylation, nitrosylation, glycosylation, and SUMOylation. Posttranslational modifications of VGSCs can have profound impact on cellular excitability, contributing to normal and abnormal physiology. Despite four decades of research, the complexity of VGSC modulation is still being determined. While some modifications have similar effects on the various VGSC isoforms, others have isoform-specific interactions. In addition, while much has been learned about how individual modifications can impact VGSC function, there is still more to be learned about how different modifications can interact. Here we review what is known about VGSC posttranslational modifications with a focus on the breadth and complexity of the regulatory mechanisms that impact VGSC properties.
Collapse
Affiliation(s)
- Zifan Pei
- Department of Biology, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA.,Department of Pharmacology and Toxicology, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA
| | - Yanling Pan
- Medical Neuroscience Graduate Program, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA
| | - Theodore R Cummins
- Department of Biology, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA. .,Department of Pharmacology and Toxicology, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA. .,Medical Neuroscience Graduate Program, Indiana University - Purdue University Indianapolis, Indianapolis, IN, USA.
| |
Collapse
|
16
|
Benson M, Iñiguez-Lluhí JA, Martens J. Sumo Modification of Ion Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 963:127-141. [PMID: 28197910 DOI: 10.1007/978-3-319-50044-7_8] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Recently, a role for SUMO modification outside of the nucleus has emerged. Although the number of extranuclear proteins known to be sumoylated is comparatively small, ion channels represent one important new class of these proteins. Ion channels are responsible for the control of membrane excitability and therefore are critical for fundamental physiological processes such as muscle contraction, neuronal firing, and cellular homeostasis. As such, these ion-conducting proteins are subject to precise regulation. Recently, several studies have identified sumoylation as a novel mechanism of modulating ion channel function. These studies expand the list of known functions of sumoylation and reveal that, in addition to its more established role in the regulation of nuclear proteins, this modification plays important roles at the cytoplasmic face of membranes.
Collapse
Affiliation(s)
- Mark Benson
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
| | | | - Jeffrey Martens
- Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA.
| |
Collapse
|
17
|
Zheng W, Yang J, Beauchamp E, Cai R, Hussein S, Hofmann L, Li Q, Flockerzi V, Berthiaume LG, Tang J, Chen XZ. Regulation of TRPP3 Channel Function by N-terminal Domain Palmitoylation and Phosphorylation. J Biol Chem 2016; 291:25678-25691. [PMID: 27754867 DOI: 10.1074/jbc.m116.756544] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/16/2016] [Indexed: 01/08/2023] Open
Abstract
Transient receptor potential polycystin-3 (TRPP3) is a cation channel activated by calcium and proton and is involved in hedgehog signaling, intestinal development, and sour tasting. How TRPP3 channel function is regulated remains poorly understood. By N-terminal truncation mutations, electrophysiology, and Xenopus oocyte expression, we first identified fragment Asp-21-Ser-42 to be functionally important. We then found that deletion mutant Δ1-36 (TRPP3 missing fragment Met-1-Arg-36) has a similar function as wild-type TRPP3, whereas Δ1-38 is functionally dead, suggesting the importance of Val-37 or Cys-38. Further studies found that Cys-38, but not Val-37, is functionally critical. Cys-38 is a predicted site of palmitoylation, and indeed TRPP3 channel activity was inhibited by palmitoylation inhibitor 2-bromopalmitate and rescued by palmitoylation substrate palmitic acid. The TRPP3 N terminus (TRPP3NT, Met-1-Leu-95) localized along the plasma membrane of HEK293 cells but stayed in the cytoplasm with 2-bromopalmitate treatment or C38A mutation, indicating that TRPP3NT anchors to the surface membrane through palmitoylation at Cys-38. By acyl-biotin exchange assays, we showed that TRPP3, but not mutant C38A, is indeed palmitoylated. When putative phosphorylation sites near Cys-38 were mutated to Asp or Glu to mimic phosphorylation, only T39D and T39E reduced TRPP3 function. Furthermore, TRPP3NT displayed double bands in which the upper band was abolished by λ phosphatase treatment or T39A mutation. However, palmitoylation at Cys-38 and phosphorylation at Thr-39 independently regulated TRPP3 channel function, in contrast to previous reports about correlated palmitoylation with a proximate phosphorylation. Palmitoylation at Cys-38 represents a novel mechanism of functional regulation for TRPP3.
Collapse
Affiliation(s)
- Wang Zheng
- From the Membrane Protein Disease Research Group, Departments of Physiology and
| | - JungWoo Yang
- From the Membrane Protein Disease Research Group, Departments of Physiology and
| | - Erwan Beauchamp
- Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Ruiqi Cai
- From the Membrane Protein Disease Research Group, Departments of Physiology and
| | - Shaimaa Hussein
- From the Membrane Protein Disease Research Group, Departments of Physiology and
| | - Laura Hofmann
- the Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany, and
| | - Qiang Li
- From the Membrane Protein Disease Research Group, Departments of Physiology and
| | - Veit Flockerzi
- the Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany, and
| | - Luc G Berthiaume
- Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Jingfeng Tang
- the Institute of Biomedical and Pharmaceutical Sciences and Provincial Cooperative Innovation Center, College of Bioengineering, Hubei University of Technology, 430068 Wuhan, China
| | - Xing-Zhen Chen
- From the Membrane Protein Disease Research Group, Departments of Physiology and .,the Institute of Biomedical and Pharmaceutical Sciences and Provincial Cooperative Innovation Center, College of Bioengineering, Hubei University of Technology, 430068 Wuhan, China
| |
Collapse
|
18
|
Pei Z, Xiao Y, Meng J, Hudmon A, Cummins TR. Cardiac sodium channel palmitoylation regulates channel availability and myocyte excitability with implications for arrhythmia generation. Nat Commun 2016; 7:12035. [PMID: 27337590 PMCID: PMC4931030 DOI: 10.1038/ncomms12035] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 05/22/2016] [Indexed: 02/06/2023] Open
Abstract
Cardiac voltage-gated sodium channels (Nav1.5) play an essential role in regulating cardiac electric activity by initiating and propagating action potentials in the heart. Altered Nav1.5 function is associated with multiple cardiac diseases including long-QT3 and Brugada syndrome. Here, we show that Nav1.5 is subject to palmitoylation, a reversible post-translational lipid modification. Palmitoylation increases channel availability and late sodium current activity, leading to enhanced cardiac excitability and prolonged action potential duration. In contrast, blocking palmitoylation increases closed-state channel inactivation and reduces myocyte excitability. We identify four cysteines as possible Nav1.5 palmitoylation substrates. A mutation of one of these is associated with cardiac arrhythmia (C981F), induces a significant enhancement of channel closed-state inactivation and ablates sensitivity to depalmitoylation. Our data indicate that alterations in palmitoylation can substantially control Nav1.5 function and cardiac excitability and this form of post-translational modification is likely an important contributor to acquired and congenital arrhythmias.
Collapse
Affiliation(s)
- Zifan Pei
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, Indiana 46202, USA
| | - Yucheng Xiao
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, Indiana 46202, USA
| | - Jingwei Meng
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, Indiana 46202, USA
| | - Andy Hudmon
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, Indiana 46202, USA.,Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, Indiana 46202, USA.,Stark Neurosciences Research Institute, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, Indiana 46202, USA
| | - Theodore R Cummins
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, Indiana 46202, USA.,Stark Neurosciences Research Institute, Indiana University School of Medicine, 635 Barnhill Drive, Indianapolis, Indiana 46202, USA
| |
Collapse
|
19
|
Inaba H, Kai D, Kida S. N-glycosylation in the hippocampus is required for the consolidation and reconsolidation of contextual fear memory. Neurobiol Learn Mem 2016; 135:57-65. [PMID: 27343988 DOI: 10.1016/j.nlm.2016.06.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Revised: 06/17/2016] [Accepted: 06/21/2016] [Indexed: 01/14/2023]
Abstract
Memory consolidation and reconsolidation have been shown to require new gene expression. N-glycosylation, one of the major post-translational modifications, is known to play essential or regulatory roles in protein function. A previous study suggested that N-glycosylation is required for the maintenance of long-term potentiation in hippocampal CA1 neurons. However, the role of de novo N-glycosylation in learning and memory, such as memory consolidation and reconsolidation, still remains unclear. Here, we show critical roles for N-glycosylation in the consolidation and reconsolidation of contextual fear memory in mice. We examined the effects of pharmacological inhibition of N-glycosylation in the hippocampus on these memory processes using three different inhibitors (tunicamycin, 1-deoxynojirimycin, and swainsonine) that block the enzymatic activity required for N-glycosylation at different steps. Microinfusions of the N-glycosylation inhibitors into the dorsal hippocampus impaired long-term memory (LTM) formation without affecting short-term memory (STM). Similarly, this pharmacological blockade of N-glycosylation in the dorsal hippocampus also disrupted post-reactivation LTM after retrieval without affecting post-reactivation STM. Additionally, a microinfusion of swainsonine blocked c-fos induction in the hippocampus, which is observed when memory is consolidated. Our observations showed that N-glycosylation is required for the consolidation and reconsolidation of contextual fear memory and suggested that N-glycosylation contributes to the new gene expression necessary for these memory processes.
Collapse
Affiliation(s)
- Hiroyoshi Inaba
- Department of Bioscience, Faculty of Applied Bioscience, Tokyo University of Agriculture, Tokyo, Japan
| | - Daisuke Kai
- Department of Bioscience, Faculty of Applied Bioscience, Tokyo University of Agriculture, Tokyo, Japan
| | - Satoshi Kida
- Department of Bioscience, Faculty of Applied Bioscience, Tokyo University of Agriculture, Tokyo, Japan; Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Saitama, Japan.
| |
Collapse
|
20
|
Abstract
The lipid landscapes of cellular membranes are complex and dynamic, are tissue dependent, and can change with the age and the development of a variety of diseases. Researchers are now gaining new appreciation for the regulation of ion channel proteins by the membrane lipids in which they are embedded. Thus, as membrane lipids change, for example, during the development of disease, it is likely that the ionic currents that conduct through the ion channels embedded in these membranes will also be altered. This chapter provides an overview of the complex regulation of prokaryotic and eukaryotic voltage-dependent sodium (Nav) channels by fatty acids, sterols, glycerophospholipids, sphingolipids, and cannabinoids. The impact of lipid regulation on channel gating kinetics, voltage-dependence, trafficking, toxin binding, and structure are explored for Nav channels that have been examined in heterologous expression systems, native tissue, and reconstituted into artificial membranes. Putative mechanisms for Nav regulation by lipids are also discussed.
Collapse
Affiliation(s)
- N D'Avanzo
- Université de Montréal, Montréal, QC, Canada.
| |
Collapse
|
21
|
Laedermann CJ, Abriel H, Decosterd I. Post-translational modifications of voltage-gated sodium channels in chronic pain syndromes. Front Pharmacol 2015; 6:263. [PMID: 26594175 PMCID: PMC4633509 DOI: 10.3389/fphar.2015.00263] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 10/23/2015] [Indexed: 02/06/2023] Open
Abstract
In the peripheral sensory nervous system the neuronal expression of voltage-gated sodium channels (Navs) is very important for the transmission of nociceptive information since they give rise to the upstroke of the action potential (AP). Navs are composed of nine different isoforms with distinct biophysical properties. Studying the mutations associated with the increase or absence of pain sensitivity in humans, as well as other expression studies, have highlighted Nav1.7, Nav1.8, and Nav1.9 as being the most important contributors to the control of nociceptive neuronal electrogenesis. Modulating their expression and/or function can impact the shape of the AP and consequently modify nociceptive transmission, a process that is observed in persistent pain conditions. Post-translational modification (PTM) of Navs is a well-known process that modifies their expression and function. In chronic pain syndromes, the release of inflammatory molecules into the direct environment of dorsal root ganglia (DRG) sensory neurons leads to an abnormal activation of enzymes that induce Navs PTM. The addition of small molecules, i.e., peptides, phosphoryl groups, ubiquitin moieties and/or carbohydrates, can modify the function of Navs in two different ways: via direct physical interference with Nav gating, or via the control of Nav trafficking. Both mechanisms have a profound impact on neuronal excitability. In this review we will discuss the role of Protein Kinase A, B, and C, Mitogen Activated Protein Kinases and Ca++/Calmodulin-dependent Kinase II in peripheral chronic pain syndromes. We will also discuss more recent findings that the ubiquitination of Nav1.7 by Nedd4-2 and the effect of methylglyoxal on Nav1.8 are also implicated in the development of experimental neuropathic pain. We will address the potential roles of other PTMs in chronic pain and highlight the need for further investigation of PTMs of Navs in order to develop new pharmacological tools to alleviate pain.
Collapse
Affiliation(s)
- Cedric J. Laedermann
- F.M. Kirby Neurobiology Research Center, Boston Children’s Hospital, Harvard Medical School, BostonMA, USA
| | - Hugues Abriel
- Department of Clinical Research, University of BernBern, Switzerland
| | - Isabelle Decosterd
- Pain Center, Department of Anesthesiology, Lausanne University Hospital (CHUV) and University of LausanneLausanne, Switzerland
- Department of Fundamental Neurosciences, University of LausanneLausanne, Switzerland
| |
Collapse
|
22
|
Onwuli DO, Beltran-Alvarez P. An update on transcriptional and post-translational regulation of brain voltage-gated sodium channels. Amino Acids 2015; 48:641-651. [PMID: 26503606 PMCID: PMC4752963 DOI: 10.1007/s00726-015-2122-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 10/16/2015] [Indexed: 11/29/2022]
Abstract
Voltage-gated sodium channels are essential proteins in brain physiology, as they generate the sodium currents that initiate neuronal action potentials. Voltage-gated sodium channels expression, localisation and function are regulated by a range of transcriptional and post-translational mechanisms. Here, we review our understanding of regulation of brain voltage-gated sodium channels, in particular SCN1A (NaV1.1), SCN2A (NaV1.2), SCN3A (NaV1.3) and SCN8A (NaV1.6), by transcription factors, by alternative splicing, and by post-translational modifications. Our focus is strongly centred on recent research lines, and newly generated knowledge.
Collapse
Affiliation(s)
- Donatus O Onwuli
- School of Biological, Biomedical and Environmental Sciences, University of Hull, Hardy Building Cottingham Road, Hull, HU6 7RX, UK
| | - Pedro Beltran-Alvarez
- School of Biological, Biomedical and Environmental Sciences, University of Hull, Hardy Building Cottingham Road, Hull, HU6 7RX, UK.
| |
Collapse
|
23
|
Abstract
Protein S-acylation, the only fully reversible posttranslational lipid modification of proteins, is emerging as a ubiquitous mechanism to control the properties and function of a diverse array of proteins and consequently physiological processes. S-acylation results from the enzymatic addition of long-chain lipids, most typically palmitate, onto intracellular cysteine residues of soluble and transmembrane proteins via a labile thioester linkage. Addition of lipid results in increases in protein hydrophobicity that can impact on protein structure, assembly, maturation, trafficking, and function. The recent explosion in global S-acylation (palmitoyl) proteomic profiling as a result of improved biochemical tools to assay S-acylation, in conjunction with the recent identification of enzymes that control protein S-acylation and de-acylation, has opened a new vista into the physiological function of S-acylation. This review introduces key features of S-acylation and tools to interrogate this process, and highlights the eclectic array of proteins regulated including membrane receptors, ion channels and transporters, enzymes and kinases, signaling adapters and chaperones, cell adhesion, and structural proteins. We highlight recent findings correlating disruption of S-acylation to pathophysiology and disease and discuss some of the major challenges and opportunities in this rapidly expanding field.
Collapse
Affiliation(s)
- Luke H Chamberlain
- Strathclyde Institute of Pharmacy and Biomedical Sciences, Strathclyde University, Glasgow, United Kingdom; and Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, United Kingdom
| | - Michael J Shipston
- Strathclyde Institute of Pharmacy and Biomedical Sciences, Strathclyde University, Glasgow, United Kingdom; and Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh, United Kingdom
| |
Collapse
|
24
|
Sialyltransferase7A, a Klf4-responsive gene, promotes cardiomyocyte apoptosis during myocardial infarction. Basic Res Cardiol 2015; 110:28. [PMID: 25860962 DOI: 10.1007/s00395-015-0484-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 03/15/2015] [Accepted: 03/31/2015] [Indexed: 01/01/2023]
Abstract
Myocardial infarction (MI) is one major cause of heart failure through its induction of cardiomyocyte death. However, the molecular mechanisms associated with MI-induced cardiomyocyte apoptosis in the context of sialylation of heart are not yet understood. In this study, we found that sialyltransferase7A (Siat7A), one of the members of sialyltransferase family, was significantly increased in the ischemic myocardium, as well as in the human cardiomyocyte cell line AC16 under hypoxic condition. The Sialyl-Tn antigen (Neu5Acα2-6GalNAc-O-Ser/Thr) synthesized by Siat7A also increased in the AC16 cardiomyocytes following hypoxic stimulus. Increased Siat7A promoted cardiomyocyte apoptosis. The knockdown of Siat7A expression reduced cardiomyocyte apoptosis in both of vivo and vitro. Furthermore, the decreased extracellular signal-regulated kinase ERK1 and ERK2 (ERK1/2) activity was involved in the Siat7A-induced cardiomyocyte apoptosis. Notably, we showed that Krüppel-like factor 4 (Klf4), one of the transcription factors, specifically bound to the Siat7A promoter by ChIP assays. Deletion and mutagenesis analysis identified that Klf4 could transactivate the Siat7A promoter region (nt -655 to -636 bp). The upregulated Siat7A expression, which was paralleled by the increased Klf4 in the ischemic myocardium, contributed to cardiomyocyte apoptosis. Our study suggests Siat7A could be a valuable target for developing treatments for MI patients.
Collapse
|
25
|
Nav1.5 channels can reach the plasma membrane through distinct N-glycosylation states. Biochim Biophys Acta Gen Subj 2015; 1850:1215-23. [PMID: 25721215 DOI: 10.1016/j.bbagen.2015.02.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 01/26/2015] [Accepted: 02/16/2015] [Indexed: 02/06/2023]
Abstract
BACKGROUND Like many voltage-gated sodium channels, the cardiac isoform Nav1.5 is well known as a glycoprotein which necessarily undergoes N-glycosylation processing during its transit to the plasma membrane. In some cardiac disorders, especially the Brugada syndrome (BrS), mutations in Nav1.5 encoding gene lead to intracellular retention and consequently trafficking defect of these proteins. We used two BrS mutants as tools to clarify both Nav1.5 glycosylation states and associated secretory behaviors. METHODS Patch-clamp recordings and surface biotinylation assays of HEK293T cells expressing wild-type (WT) and/or mutant Nav1.5 proteins were performed to assess the impact of mutant co-expression on the membrane activity and localization of WT channels. Enzymatic deglycosylation assays and brefeldin A (BFA) treatments were also employed to further characterize recombinant and native Nav1.5 maturation. RESULTS The present data demonstrate that Nav1.5 channels mainly exist as two differentially glycosylated forms. We reveal that dominant negative effects induced by BrS mutants upon WT channel current result from the abnormal surface expression of the fully-glycosylated forms exclusively. Furthermore, we show that core-glycosylated channels can be found at the surface membrane of BFA-treated or untreated cells, but obviously without generating any sodium current. CONCLUSIONS Our findings provide evidence that native and recombinant Nav1.5 subunits are expressed as two distinct matured forms. Fully-glycosylated state of Nav1.5 seems to determine its functionality whereas core-glycosylated forms might be transported to the plasma membrane through an unconventional Golgi-independent secretory route. GENERAL SIGNIFICANCE This work highlights that N-linked glycosylation processing would be critical for Nav1.5 membrane trafficking and function.
Collapse
|
26
|
Shipston MJ. Ion channel regulation by protein S-acylation. J Gen Physiol 2014; 143:659-78. [PMID: 24821965 PMCID: PMC4035745 DOI: 10.1085/jgp.201411176] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 04/18/2014] [Indexed: 01/09/2023] Open
Abstract
Protein S-acylation, the reversible covalent fatty-acid modification of cysteine residues, has emerged as a dynamic posttranslational modification (PTM) that controls the diversity, life cycle, and physiological function of numerous ligand- and voltage-gated ion channels. S-acylation is enzymatically mediated by a diverse family of acyltransferases (zDHHCs) and is reversed by acylthioesterases. However, for most ion channels, the dynamics and subcellular localization at which S-acylation and deacylation cycles occur are not known. S-acylation can control the two fundamental determinants of ion channel function: (1) the number of channels resident in a membrane and (2) the activity of the channel at the membrane. It controls the former by regulating channel trafficking and the latter by controlling channel kinetics and modulation by other PTMs. Ion channel function may be modulated by S-acylation of both pore-forming and regulatory subunits as well as through control of adapter, signaling, and scaffolding proteins in ion channel complexes. Importantly, cross-talk of S-acylation with other PTMs of both cysteine residues by themselves and neighboring sites of phosphorylation is an emerging concept in the control of ion channel physiology. In this review, I discuss the fundamentals of protein S-acylation and the tools available to investigate ion channel S-acylation. The mechanisms and role of S-acylation in controlling diverse stages of the ion channel life cycle and its effect on ion channel function are highlighted. Finally, I discuss future goals and challenges for the field to understand both the mechanistic basis for S-acylation control of ion channels and the functional consequence and implications for understanding the physiological function of ion channel S-acylation in health and disease.
Collapse
Affiliation(s)
- Michael J Shipston
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD Scotland, UK
| |
Collapse
|
27
|
Abstract
The paralytic agent (+)-saxitoxin (STX), most commonly associated with oceanic red tides and shellfish poisoning, is a potent inhibitor of electrical conduction in cells. Its nefarious effects result from inhibition of voltage-gated sodium channels (Na(V)s), the obligatory proteins responsible for the initiation and propagation of action potentials. In the annals of ion channel research, the identification and characterization of Na(V)s trace to the availability of STX and an allied guanidinium derivative, tetrodotoxin. The mystique of STX is expressed in both its function and form, as this uniquely compact dication boasts more heteroatoms than carbon centers. This Review highlights both the chemistry and chemical biology of this fascinating natural product, and offers a perspective as to how molecular design and synthesis may be used to explore Na(V) structure and function.
Collapse
Affiliation(s)
- Arun P Thottumkara
- Department of Chemistry, Stanford University, Stanford, CA 94305-5080 (USA)
| | | | | |
Collapse
|
28
|
|
29
|
Kim S, Lee BC, Lee AR, Won S, Park CS. Effects of palmitoylation on the diffusional movement of BKCa channels in live cells. FEBS Lett 2014; 588:713-9. [PMID: 24462688 DOI: 10.1016/j.febslet.2014.01.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2013] [Revised: 11/21/2013] [Accepted: 01/08/2014] [Indexed: 01/10/2023]
Abstract
BKCa channels are palmitoylated at a cluster of cysteine residues within the cytosolic linker connecting the 1st and 2nd transmembrane domains, and this lipid modification affects their surface expression. To verify the effects of palmitoylation on the diffusional dynamics of BKCa channels, we investigated their lateral movement. Compared to wild-type channels, the movement of mutant palmitoylation-deficient channels was much less confined and close to random. The diffusion of the mutant channel was also much faster than that of the wild type. Thus, the lateral movement of BKCa channels is greatly influenced by palmitoylation.
Collapse
Affiliation(s)
- Sulgi Kim
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Byoung-Cheol Lee
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea; National Leading Research Laboratory, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea; Cell Dynamics Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - A-Ram Lee
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea; National Leading Research Laboratory, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea; Cell Dynamics Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Sehoon Won
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea
| | - Chul-Seung Park
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea; National Leading Research Laboratory, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea; Cell Dynamics Research Center, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea.
| |
Collapse
|
30
|
|
31
|
Abstract
The pedigree of voltage-gated sodium channels spans the millennia from eukaryotic members that initiate the action potential firing in excitable tissues to primordial ancestors that act as enviro-protective complexes in bacterial extremophiles. Eukaryotic sodium channels (eNavs) are central to electrical signaling throughout the cardiovascular and nervous systems in animals and are established clinical targets for the therapeutic management of epilepsy, cardiac arrhythmia, and painful syndromes as they are inhibited by local anesthetic compounds. Alternatively, bacterial voltage-gated sodium channels (bNavs) likely regulate the survival response against extreme pH conditions, electrophiles, and hypo-osmotic shock and may represent a founder of the voltage-gated cation channel family. Despite apparent differences between eNav and bNav channel physiology, gating, and gene structure, the discovery that bNavs are amenable to crystallographic study opens the door for the possibility of structure-guided rational design of the next generation of therapeutics that target eNavs. Here we summarize the gating behavior of these disparate channel members and discuss mechanisms of local anesthetic inhibition in light of the growing number of bNav structures.
Collapse
Affiliation(s)
- Ben Corry
- Research School of Biology, The Australian National University, Canberra, ACT, Australia
| | | | | |
Collapse
|
32
|
Abstract
Ion channel proteins are regulated by different types of posttranslational modifications. The focus of this review is the regulation of voltage-gated sodium channels (Navs) upon their ubiquitylation. The amiloride-sensitive epithelial sodium channel (ENaC) was the first ion channel shown to be regulated upon ubiquitylation. This modification results from the binding of ubiquitin ligase from the Nedd4 family to a protein-protein interaction domain, known as the PY motif, in the ENaC subunits. Many of the Navs have similar PY motifs, which have been demonstrated to be targets of Nedd4-dependent ubiquitylation, tagging them for internalization from the cell surface. The role of Nedd4-dependent regulation of the Nav membrane density in physiology and disease remains poorly understood. Two recent studies have provided evidence that Nedd4-2 is downregulated in dorsal root ganglion (DRG) neurons in both rat and mouse models of nerve injury-induced neuropathic pain. Using two different mouse models, one with a specific knockout of Nedd4-2 in sensory neurons and another where Nedd4-2 was overexpressed with the use of viral vectors, it was demonstrated that the neuropathy-linked neuronal hyperexcitability was the result of Nav1.7 and Nav1.8 overexpression due to Nedd4-2 downregulation. These studies provided the first in vivo evidence of the role of Nedd4-2-dependent regulation of Nav channels in a disease state. This ubiquitylation pathway may be involved in the development of symptoms and diseases linked to Nav-dependent hyperexcitability, such as pain, cardiac arrhythmias, epilepsy, migraine, and myotonias.
Collapse
Affiliation(s)
- Cédric J Laedermann
- Department of Clinical Research, University of Bern, Murtenstrasse, 35, 3010, Bern, Switzerland,
| | | | | |
Collapse
|
33
|
Nowycky MC, Wu G, Ledeen RW. Glycobiology of ion transport in the nervous system. ADVANCES IN NEUROBIOLOGY 2014; 9:321-42. [PMID: 25151386 DOI: 10.1007/978-1-4939-1154-7_15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The nervous system is richly endowed with large transmembrane proteins that mediate ion transport, including gated ion channels as well as energy-consuming pumps and transporters. Transport proteins undergo N-linked glycosylation which can affect expression, location, stability, and function. The N-linked glycans of ion channels are large, contributing between 5 and 50 % of their molecular weight. Many contain a high density of negatively charged sialic acid residues which modulate voltage-dependent gating of ion channels. Changes in the size and chemical composition of glycans are responsible for developmental and cell-specific variability in the biophysical and functional properties of many ion channels. Glycolipids, principally gangliosides, exert considerable influence on some forms of ion transport, either through direct association with ion transport proteins or indirectly through association with proteins that activate transport through appropriate signaling. Examples of both pumps and ion channels have been revealed which depend on ganglioside regulation. While some of these processes are localized in the plasma membrane, ganglioside-regulated ion transport can also occur at various loci within the cell including the nucleus. This chapter will describe ion channel and ion pump structures with a focus on the functional effects of glycosylation on ion channel availability and function, and effects of alterations in glycosylation on nervous system function. It will also summarize highlights of the research on glycolipid/ganglioside-mediated regulation of ion transport.
Collapse
Affiliation(s)
- Martha C Nowycky
- Department of Pharmacology and Physiology, RBHS, New Jersey Medical School, The State University of New Jersey, 185 South Orange Ave., Newark, NJ, 07103, USA,
| | | | | |
Collapse
|
34
|
Ednie AR, Horton KK, Wu J, Bennett ES. Expression of the sialyltransferase, ST3Gal4, impacts cardiac voltage-gated sodium channel activity, refractory period and ventricular conduction. J Mol Cell Cardiol 2013; 59:117-27. [PMID: 23471032 DOI: 10.1016/j.yjmcc.2013.02.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2012] [Revised: 02/21/2013] [Accepted: 02/25/2013] [Indexed: 12/19/2022]
Abstract
The sequential glycosylation process typically ends with sialic acid residues added through trans-Golgi sialyltransferase activity. Individuals afflicted with congenital disorders of glycosylation often have reduced glycoprotein sialylation and present with multi-system symptoms including hypotonia, seizures, arrhythmia and cardiomyopathy. Cardiac voltage-gated Na(+) channel (Nav) activity can be influenced by sialic acids likely contributing to an external surface potential causing channels to gate at less depolarized voltages. Here, a possible pathophysiological role for reduced sialylation is investigated by questioning the impact of gene deletion of the uniformly expressed beta-galactoside alpha-2,3-sialyltransferase 4 (ST3Gal4) on cardiac Nav activity, cellular refractory period and ventricular conduction. Whole-cell patch-clamp experiments showed that ventricular Nav from ST3Gal4 deficient mice (ST3Gal4(-/-)) gated at more depolarized potentials, inactivated more slowly and recovered from fast inactivation more rapidly than WT controls. Current-clamp recordings indicated a 20% increase in time to action potential peak and a 30ms decrease in ST3Gal4(-/-) myocyte refractory period, concurrent with increased Nav recovery rate. Nav expression, distribution and maximal Na(+) current levels were unaffected by ST3Gal4 expression, indicating that reduced sialylation does not impact Nav surface expression and distribution. However, enzymatic desialylation suggested that ST3Gal4(-/-) ventricular Nav are less sialylated. Consistent with the shortened myocyte refractory period, epicardial conduction experiments using optical mapping techniques demonstrated a 27% reduction in minimum ventricular refractory period and increased susceptibility to arrhythmias in ST3Gal4(-/-) ventricles. Thus, deletion of a single sialyltransferase significantly impacts ventricular myocyte electrical signaling. These studies offer insight into diseases of glycosylation that are often associated with pathological changes in excitability and highlight the importance of glycosylation in cardiac physiology.
Collapse
Affiliation(s)
- Andrew R Ednie
- Department of Molecular Pharmacology and Physiology, University of South Florida Morsani College of Medicine, Tampa, FL 33612, USA
| | | | | | | |
Collapse
|
35
|
Mining the virgin land of neurotoxicology: a novel paradigm of neurotoxic peptides action on glycosylated voltage-gated sodium channels. J Toxicol 2012; 2012:843787. [PMID: 22829817 PMCID: PMC3399347 DOI: 10.1155/2012/843787] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 04/17/2012] [Accepted: 05/24/2012] [Indexed: 12/30/2022] Open
Abstract
Voltage-gated sodium channels (VGSCs) are important membrane protein carrying on the molecular basis for action potentials (AP) in neuronal firings. Even though the structure-function studies were the most pursued spots, the posttranslation modification processes, such as glycosylation, phosphorylation, and alternative splicing associating with channel functions captured less eyesights. The accumulative research suggested an interaction between the sialic acids chains and ion-permeable pores, giving rise to subtle but significant impacts on channel gating. Sodium channel-specific neurotoxic toxins, a family of long-chain polypeptides originated from venomous animals, are found to potentially share the binding sites adjacent to glycosylated region on VGSCs. Thus, an interaction between toxin and glycosylated VGSC might hopefully join the campaign to approach the role of glycosylation in modulating VGSCs-involved neuronal network activity. This paper will cover the state-of-the-art advances of researches on glycosylation-mediated VGSCs function and the possible underlying mechanisms of interactions between toxin and glycosylated VGSCs, which may therefore, fulfill the knowledge in identifying the pharmacological targets and therapeutic values of VGSCs.
Collapse
|
36
|
Palmitoylation influences the function and pharmacology of sodium channels. Proc Natl Acad Sci U S A 2011; 108:20213-8. [PMID: 22123950 DOI: 10.1073/pnas.1108497108] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Palmitoylation is a common lipid modification known to regulate the functional properties of various proteins and is a vital step in the biosynthesis of voltage-activated sodium (Nav) channels. We discovered a mutation in an intracellular loop of rNav1.2a (G1079C), which results in a higher apparent affinity for externally applied PaurTx3 and ProTx-II, two voltage sensor toxins isolated from tarantula venom. To explore whether palmitoylation of the introduced cysteine underlies this observation, we compared channel susceptibility to a range of animal toxins in the absence and presence of 2-Br-palmitate, a palmitate analog that prevents palmitate incorporation into proteins, and found that palmitoylation contributes to the increased affinity of PaurTx3 and ProTx-II for G1079C. Further investigations with 2-Br-palmitate revealed that palmitoylation can regulate the gating and pharmacology of wild-type (wt) rNav1.2a. To identify rNav1.2a palmitoylation sites contributing to these phenomena, we substituted three endogenous cysteines predicted to be palmitoylated and found that the gating behavior of this triple cysteine mutant is similar to wt rNav1.2a treated with 2-Br-palmitate. As with chemically depalmitoylated rNav1.2a channels, this mutant also exhibits an increased susceptibility for PaurTx3. Additional mutagenesis experiments showed that palmitoylation of one cysteine in particular (C1182) primarily influences PaurTx3 sensitivity and may enhance the inactivation process of wt rNav1.2a. Overall, our results demonstrate that lipid modifications are capable of altering the gating and pharmacological properties of rNav1.2a.
Collapse
|
37
|
Granell AEVB, Palter KB, Akan I, Aich U, Yarema KJ, Betenbaugh MJ, Thornhill WB, Recio-Pinto E. DmSAS is required for sialic acid biosynthesis in cultured Drosophila third instar larvae CNS neurons. ACS Chem Biol 2011; 6:1287-95. [PMID: 21919466 DOI: 10.1021/cb200238k] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Sialylation is an important carbohydrate modification of glycoconjugates that has been shown to modulate many cellular/molecular interactions in vertebrates. In Drosophila melanogaster (Dm), using sequence homology, several enzymes of the sialylation pathway have been cloned and their function tested in expression systems. Here we investigated whether sialic acid incorporation in cultured Dm central nervous system (CNS) neurons required endogenously expressed Dm sialic acid synthase (DmSAS). We compared neurons derived from wild type Dm larvae with those containing a DmSAS mutation (148 bp deletion). The ability of these cells to produce Sia5NAz (sialic acid form) from Ac(4)ManNAz (azide-derivatized N-acetylmannosamine) and incorporate it into their glycoconjugates was measured by tagging the azide group of Sia5NAz with fluorescent agents via Click-iT chemistry. We found that most of the wild type Dm CNS neurons incorporated Sia5NAz into their glycoconjugates. Sialic acid incorporation was higher at the soma than at the neurite and could also be detected at perinuclear regions and the plasma membrane. In contrast, neurons from the DmSAS mutant did not incorporate Sia5NAz unless DmSAS was reintroduced (rescue mutant). Most of the neurons expressed α2,6-sialyltransferase. These results confirm that the mutation was a null mutation and that no redundant sialic acid biosynthetic activity exists in Dm cells, i.e., there is only one DmSAS. They also provide the strongest proof to date that DmSAS is a key enzyme in the biosynthesis of sialic acids in Dm CNS neurons, and the observed subcellular distribution of the newly synthesized sialic acids offers insights into their biological function.
Collapse
Affiliation(s)
| | - Karen B. Palter
- Department of Biology, Temple University, Philadelphia, Pennsylvania 19122, United States
| | - Ihan Akan
- Department of Biology, Temple University, Philadelphia, Pennsylvania 19122, United States
| | | | | | | | - William B. Thornhill
- Department of Biological Sciences, Fordham University, Bronx, New York 10458, United States
| | | |
Collapse
|
38
|
Beltran-Alvarez P, Pagans S, Brugada R. The cardiac sodium channel is post-translationally modified by arginine methylation. J Proteome Res 2011; 10:3712-9. [PMID: 21726068 DOI: 10.1021/pr200339n] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The α subunit of the cardiac sodium channel (Na(v)1.5) is an essential protein in the initial depolarization phase of the cardiomyocyte action potential. Post-translational modifications such as phosphorylation are known to regulate Na(v)1.5 function. Here, we used a proteomic approach for the study of the post-translational modifications of Na(v)1.5 using tsA201 cells as a model system. We generated a stable cell line expressing Na(v)1.5, purified the sodium channel, and analyzed Na(v)1.5 by MALDI-TOF and LC-MS/MS. We report the identification of arginine methylation as a novel post-translational modification of Na(v)1.5. R513, R526, and R680, located in the linker between domains I and II in Na(v)1.5, were found in mono- or dimethylated states. The functional relevance of arginine methylation in Na(v)1.5 is underscored by the fact that R526H and R680H are known Na(v)1.5 mutations causing Brugada and long QT type 3 syndromes, respectively. Our work describes for the first time arginine methylation in the voltage-gated ion channel superfamily.
Collapse
Affiliation(s)
- Pedro Beltran-Alvarez
- Cardiovascular Genetics Center, Institut d'Investigació Biomèdica de Girona, Hospital Dr. Josep Trueta, Girona, Spain
| | | | | |
Collapse
|
39
|
Unconventional myristoylation of large-conductance Ca²⁺-activated K⁺ channel (Slo1) via serine/threonine residues regulates channel surface expression. Proc Natl Acad Sci U S A 2011; 108:10744-9. [PMID: 21670298 DOI: 10.1073/pnas.1008863108] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Protein myristoylation is a means by which cells anchor proteins into membranes. The most common type of myristoylation occurs at an N-terminal glycine. However, myristoylation rarely occurs at an internal amino acid residue. Here we tested whether the α-subunit of the human large-conductance voltage- and Ca(2+)-activated K(+) channel (hSlo1) might undergo internal myristoylation. hSlo1 expressed in HEK293T cells incorporated [(3)H]myristic acid via a posttranslational mechanism, which is insensitive to cycloheximide, an inhibitor of protein biosynthesis. In-gel hydrolysis of [(3)H]myristoyl-hSlo1 with alkaline NH(2)OH (which cleaves hydroxyesters) but not neutral NH(2)OH (which cleaves thioesters) completely removed [(3)H]myristate from hSlo1, suggesting the involvement of a hydroxyester bond between hSlo1's hydroxyl-bearing serine, threonine, and/or tyrosine residues and myristic acid; this type of esterification was further confirmed by its resistance to alkaline Tris·HCl. Treatment of cells expressing hSlo1 with 100 μM myristic acid caused alteration of hSlo1 activation kinetics and a 40% decrease in hSlo1 current density from 20 to 12 nA*MΩ. Immunocytochemistry confirmed a decrease in hSlo1 plasmalemma localization by myristic acid. Replacement of the six serines or the seven threonines (but not of the single tyrosine) of hSlo1 intracellular loops 1 and 3 with alanines decreased hSlo1 direct myristoylation by 40-44%, whereas in combination decreased myristoylation by nearly 90% and abolished the myristic acid-induced change in current density. Our data demonstrate that an ion channel, hSlo1, is internally and posttranslationally myristoylated. Myristoylation occurs mainly at hSlo1 intracellular loop 1 or 3, and is an additional mechanism for channel surface expression regulation.
Collapse
|
40
|
Abstract
Protein S-palmitoylation, the reversible thioester linkage of a 16-carbon palmitate lipid to an intracellular cysteine residue, is rapidly emerging as a fundamental, dynamic, and widespread post-translational mechanism to control the properties and function of ligand- and voltage-gated ion channels. Palmitoylation controls multiple stages in the ion channel life cycle, from maturation to trafficking and regulation. An emerging concept is that palmitoylation is an important determinant of channel regulation by other signaling pathways. The elucidation of enzymes controlling palmitoylation and developments in proteomics tools now promise to revolutionize our understanding of this fundamental post-translational mechanism in regulating ion channel physiology.
Collapse
Affiliation(s)
- Michael J Shipston
- Centre for Integrative Physiology, College of Medicine and Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom.
| |
Collapse
|
41
|
Schwetz TA, Norring SA, Ednie AR, Bennett ES. Sialic acids attached to O-glycans modulate voltage-gated potassium channel gating. J Biol Chem 2010; 286:4123-32. [PMID: 21115483 DOI: 10.1074/jbc.m110.171322] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Neuronal, cardiac, and skeletal muscle action potentials are produced and conducted through the highly regulated activity of several types of voltage-gated ion channels. Voltage-gated potassium (K(v)) channels are responsible for action potential repolarization. Glycans can be attached to glycoproteins through N- and O-linkages. Previous reports described the impact of N-glycans on voltage-gated ion channel function. Here, we show that sialic acids attached through O-linkages modulate gating of K(v)2.1, K(v)4.2, and K(v)4.3. The conductance-voltage (G-V) relationships for each isoform were shifted uniquely by a depolarizing 8-16 mV under conditions of reduced sialylation. The data indicate that sialic acids modulate K(v) channel activation through apparent electrostatic mechanisms that promote channel activity. Voltage-dependent steady-state inactivation was unaffected by changes in sialylation. N-Linked sialic acids cannot be responsible for the G-V shifts because K(v)4.2 and K(v)4.3 cannot be N-glycosylated, and immunoblot analysis confirmed K(v)2.1 is not N-glycosylated. Glycosidase gel shift analysis suggested that K(v)2.1, K(v)4.2, and K(v)4.3 were O-glycosylated and sialylated. To confirm this, azide-modified sugar residues involved specifically in O-glycan and sialic acid biosynthesis were shown to incorporate into all three K(v) channel isoforms using Cu(I)-catalyzed cycloaddition chemistry. Together, the data indicate that sialic acids attached to O-glycans uniquely modulate gating of three K(v) channel isoforms that are not N-glycosylated. These data provide the first evidence that external O-glycans, with core structures distinct from N-glycans in type and number of sugar residues, can modulate K(v) channel function and thereby contribute to changes in electrical signaling that result from regulated ion channel expression and/or O-glycosylation.
Collapse
Affiliation(s)
- Tara A Schwetz
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida 33612, USA
| | | | | | | |
Collapse
|
42
|
Jeffries O, Geiger N, Rowe ICM, Tian L, McClafferty H, Chen L, Bi D, Knaus HG, Ruth P, Shipston MJ. Palmitoylation of the S0-S1 linker regulates cell surface expression of voltage- and calcium-activated potassium (BK) channels. J Biol Chem 2010; 285:33307-33314. [PMID: 20693285 PMCID: PMC2963414 DOI: 10.1074/jbc.m110.153940] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Revised: 07/14/2010] [Indexed: 11/18/2022] Open
Abstract
S-palmitoylation is rapidly emerging as an important post-translational mechanism to regulate ion channels. We have previously demonstrated that large conductance calcium- and voltage-activated potassium (BK) channels are palmitoylated within an alternatively spliced (STREX) insert. However, these studies also revealed that additional site(s) for palmitoylation must exist outside of the STREX insert, although the identity or the functional significance of these palmitoylated cysteine residues are unknown. Here, we demonstrate that BK channels are palmitoylated at a cluster of evolutionary conserved cysteine residues (Cys-53, Cys-54, and Cys-56) within the intracellular linker between the S0 and S1 transmembrane domains. Mutation of Cys-53, Cys-54, and Cys-56 completely abolished palmitoylation of BK channels lacking the STREX insert (ZERO variant). Palmitoylation allows the S0-S1 linker to associate with the plasma membrane but has no effect on single channel conductance or the calcium/voltage sensitivity. Rather, S0-S1 linker palmitoylation is a critical determinant of cell surface expression of BK channels, as steady state surface expression levels are reduced by ∼55% in the C53:54:56A mutant. STREX variant channels that could not be palmitoylated in the S0-S1 linker also displayed significantly reduced cell surface expression even though STREX insert palmitoylation was unaffected. Thus our work reveals the functional independence of two distinct palmitoylation-dependent membrane interaction domains within the same channel protein and demonstrates the critical role of S0-S1 linker palmitoylation in the control of BK channel cell surface expression.
Collapse
Affiliation(s)
- Owen Jeffries
- From the Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - Nina Geiger
- From the Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom; Pharmacology and Toxicology, Institute of Pharmacy, University Tuebingen, 72076 Tuebingen, Germany
| | - Iain C M Rowe
- From the Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - Lijun Tian
- From the Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - Heather McClafferty
- From the Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - Lie Chen
- From the Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - Danlei Bi
- From the Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom
| | - Hans Guenther Knaus
- Division for Molecular and Cellular Pharmacology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Medical University Innsbruck, Peter-Mayr Strasse 1, 6020 Innsbruck, Austria
| | - Peter Ruth
- Pharmacology and Toxicology, Institute of Pharmacy, University Tuebingen, 72076 Tuebingen, Germany
| | - Michael J Shipston
- From the Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, Hugh Robson Building, University of Edinburgh, Edinburgh EH8 9XD, United Kingdom.
| |
Collapse
|
43
|
Tian L, McClafferty H, Jeffries O, Shipston MJ. Multiple palmitoyltransferases are required for palmitoylation-dependent regulation of large conductance calcium- and voltage-activated potassium channels. J Biol Chem 2010; 285:23954-62. [PMID: 20507996 PMCID: PMC2911306 DOI: 10.1074/jbc.m110.137802] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Palmitoylation is emerging as an important and dynamic regulator of ion channel function; however, the specificity with which the large family of acyl palmitoyltransferases (zinc finger Asp-His-His-Cys type-containing acyl palmitoyltransferase (DHHCs)) control channel palmitoylation is poorly understood. We have previously demonstrated that the alternatively spliced stress-regulated exon (STREX) variant of the intracellular C-terminal domain of the large conductance calcium- and voltage-activated potassium (BK) channels is palmitoylated and targets the STREX domain to the plasma membrane. Using a combined imaging, biochemical, and functional approach coupled with loss-of-function (small interfering RNA knockdown of endogenous DHHCs) and gain-of-function (overexpression of recombinant DHHCs) assays, we demonstrate that multiple DHHCs control palmitoylation of the C terminus of STREX channels, the association of the STREX domain with the plasma membrane, and functional channel regulation. Cysteine residues 12 and 13 within the STREX insert were the only endogenously palmitoylated residues in the entire C terminus of the STREX channel. Palmitoylation of this dicysteine motif was controlled by DHHCs 3, 5, 7, 9, and 17, although DHHC17 showed the greatest specificity for this site upon overexpression of the cognate DHHC. DHHCs that palmitoylated the channel also co-assembled with the channel in co-immunoprecipitation experiments, and knockdown of any of these DHHCs blocked regulation of the channel by protein kinase A-dependent phosphorylation. Taken together our data reveal that a subset of DHHCs controls STREX palmitoylation and function and suggest that DHHC17 may preferentially target cysteine-rich domains. Finally, our approach may prove useful in elucidating the specificity of DHHC palmitoylation of intracellular domains of other ion channels and transmembrane proteins.
Collapse
Affiliation(s)
- Lijun Tian
- Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, University of Edinburgh, Edinburgh EH89XD, Scotland, United Kingdom
| | | | | | | |
Collapse
|
44
|
Quamme GA. Molecular identification of ancient and modern mammalian magnesium transporters. Am J Physiol Cell Physiol 2010; 298:C407-29. [DOI: 10.1152/ajpcell.00124.2009] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
A large number of mammalian Mg2+ transporters have been hypothesized on the basis of physiological data, but few have been investigated at the molecular level. The recent identification of a number of novel proteins that mediate Mg2+ transport has enhanced our understanding of how Mg2+ is translocated across mammalian membranes. Some of these transporters have some similarity to those found in prokaryocytes and yeast cells. Human Mrs2, a mitochondrial Mg2+ channel, shares many of the properties of the bacterial CorA and yeast Alr1 proteins. The SLC41 family of mammalian Mg2+ transporters has a similarity with some regions of the bacterial MgtE transporters. The mammalian ancient conserved domain protein (ACDP) Mg2+ transporters are found in prokaryotes, suggesting an ancient origin. However, other newly identified mammalian transporters, including TRPM6/7, MagT, NIPA, MMgT, and HIP14 families, are not represented in prokaryotic genomes, suggesting more recent development. MagT, NIPA, MMgT, and HIP14 transporters were identified by differential gene expression using microarray analysis. These proteins, which are found in many different tissues and subcellular organelles, demonstrate a diversity of structural properties and biophysical functions. The mammalian Mg2+ transporters have no obvious amino acid similarities, indicating that there are many ways to transport Mg2+ across membranes. Most of these proteins transport a number of divalent cations across membranes. Only MagT1 and NIPA2 are selective for Mg2+. Many of the identified mammalian Mg2+ transporters are associated with a number of congenital disorders encompassing a wide range of tissues, including intestine, kidney, brain, nervous system, and skin. It is anticipated that future research will identify other novel Mg2+ transporters and reveal other diseases.
Collapse
Affiliation(s)
- Gary A. Quamme
- Vancouver Hospital, University of British Columbia, Vancouver, British Columbia, Canada
| |
Collapse
|
45
|
N-glycans modulate Kv1.5 gating but have no effect on Kv1.4 gating. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:367-75. [DOI: 10.1016/j.bbamem.2009.11.018] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Revised: 11/12/2009] [Accepted: 11/16/2009] [Indexed: 12/13/2022]
|
46
|
Hines RM, Kang R, Goytain A, Quamme GA. Golgi-specific DHHC zinc finger protein GODZ mediates membrane Ca2+ transport. J Biol Chem 2009; 285:4621-8. [PMID: 19955568 DOI: 10.1074/jbc.m109.069849] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The Golgi-specific zinc finger protein GODZ (palmitoyl acyltransferase/DHHC-3) mediates the palmitoylation and post-translational modification of many protein substrates that regulate membrane-protein interactions. Here, we show that GODZ also mediates Ca(2+) transport in expressing Xenopus laevis oocytes. Two-electrode voltage-clamp, fluorescence, and (45)Ca(2+) isotopic uptake determinations demonstrated voltage- and concentration-dependent, saturable, and substrate-inhibitable Ca(2+) transport in oocytes expressing GODZ cRNA but not in oocytes injected with water alone. Moreover, we show that GODZ-mediated Ca(2+) transport is regulated by palmitoylation, as the palmitoyl acyltransferase inhibitor 2-bromopalmitate or alteration of the acyltransferase DHHC motif (GODZ-DHHS) diminished GODZ-mediated Ca(2+) transport by approximately 80%. The GODZ mutation V61R abolished Ca(2+) transport but did not affect palmitoyl acyltransferase activity. Coexpression of GODZ-V61R with GODZ-DHHS restored GODZ-DHHS-mediated Ca(2+) uptake to values observed with wild-type GODZ, excluding an endogenous effect of palmitoylation. Coexpression of an independent palmitoyl acyltransferase (HIP14) with the GODZ-DHHS mutant also rescued Ca(2+) transport. HIP14 did not mediate Ca(2+) transport when expressed alone. Immunocytochemistry studies showed that GODZ and HIP14 co-localized to the Golgi and the same post-Golgi vesicles, suggesting that heteropalmitoylation might play a physiological role in addition to a biochemical function. We conclude that GODZ encodes a Ca(2+) transport protein in addition to its ability to palmitoylate protein substrates.
Collapse
Affiliation(s)
- Rochelle M Hines
- Department of Psychiatry, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | | | | | | |
Collapse
|
47
|
Hayashi T, Thomas GM, Huganir RL. Dual palmitoylation of NR2 subunits regulates NMDA receptor trafficking. Neuron 2009; 64:213-26. [PMID: 19874789 DOI: 10.1016/j.neuron.2009.08.017] [Citation(s) in RCA: 183] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Revised: 08/18/2009] [Accepted: 08/21/2009] [Indexed: 11/15/2022]
Abstract
Modification of NMDA receptor function and trafficking contributes to the regulation of synaptic transmission and is important for several forms of synaptic plasticity. Here, we report that NMDA receptor subunits NR2A and NR2B have two distinct clusters of palmitoylation sites in their C-terminal region. Palmitoylation within the first cluster on a membrane-proximal region increases tyrosine phosphorylation of tyrosine-based internalization motifs by Src family protein tyrosine kinases, leading to enhanced stable surface expression of NMDA receptors. In addition, palmitoylation of these sites regulates constitutive internalization of the NMDA receptor in developing neurons. In marked contrast, palmitoylation of the second cluster in the middle of C terminus by distinct palmitoyl transferases causes receptors to accumulate in the Golgi apparatus and reduces receptor surface expression. These data suggest that regulated palmitoylation of NR2 subunits differentially modulates receptor trafficking and might be important for NMDA-receptor-dependent synaptic plasticity.
Collapse
Affiliation(s)
- Takashi Hayashi
- Howard Hughes Medical Institute, Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | | | | |
Collapse
|
48
|
Jay CM, Levonyak N, Nemunaitis G, Maples PB, Nemunaitis J. Hereditary Inclusion Body Myopathy (HIBM2). GENE REGULATION AND SYSTEMS BIOLOGY 2009; 3:181-90. [PMID: 20054407 PMCID: PMC2796972 DOI: 10.4137/grsb.s2594] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hereditary inclusion body myopathy type 2 (HIBM2) is a myopathy characterized by progressive muscle weakness with early adult onset. The disease is the result of a recessive mutation in the Glucosamine (UDP-N-acetyl)-2-epimerase/N-acetylmannosamine kinase gene (GNE), which results in reduced enzyme function and sialic acid levels. A majority of individuals with HIBM2 are from Iranian-Jewish or Japanese decent, but isolated cases have been identified world wide. This article reviews the diagnostic criteria for HIBM2. Current research with a highlight on the biology of the disease and the role of GNE in the sialic acid pathway are assessed. Finally, therapeutic investigations and animal models are discussed with a focus on future studies to better understand the pathology of Hereditary Inclusion Body Myopathy and move therapeutic agents towards clinical trials.
Collapse
|
49
|
Regulated and aberrant glycosylation modulate cardiac electrical signaling. Proc Natl Acad Sci U S A 2009; 106:16517-22. [PMID: 19666501 DOI: 10.1073/pnas.0905414106] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Millions afflicted with Chagas disease and other disorders of aberrant glycosylation suffer symptoms consistent with altered electrical signaling such as arrhythmias, decreased neuronal conduction velocity, and hyporeflexia. Cardiac, neuronal, and muscle electrical signaling is controlled and modulated by changes in voltage-gated ion channel activity that occur through physiological and pathological processes such as development, epilepsy, and cardiomyopathy. Glycans attached to ion channels alter channel activity through isoform-specific mechanisms. Here we show that regulated and aberrant glycosylation modulate cardiac ion channel activity and electrical signaling through a cell-specific mechanism. Data show that nearly half of 239 glycosylation-associated genes (glycogenes) were significantly differentially expressed among neonatal and adult atrial and ventricular myocytes. The N-glycan structures produced among cardiomyocyte types were markedly variable. Thus, the cardiac glycome, defined as the complete set of glycan structures produced in the heart, is remodeled. One glycogene, ST8sia2, a polysialyltransferase, is expressed only in the neonatal atrium. Cardiomyocyte electrical signaling was compared in control and ST8sia2((-/-)) neonatal atrial and ventricular myocytes. Action potential waveforms and gating of less sialylated voltage-gated Na+ channels were altered consistently in ST8sia2((-/-)) atrial myocytes. ST8sia2 expression had no effect on ventricular myocyte excitability. Thus, the regulated (between atrium and ventricle) and aberrant (knockout in the neonatal atrium) expression of a single glycogene was sufficient to modulate cardiomyocyte excitability. A mechanism is described by which cardiac function is controlled and modulated through physiological and pathological processes that involve regulated and aberrant glycosylation.
Collapse
|
50
|
Usuki S, Nakatani Y, Taguchi K, Fujita T, Tanabe S, Ustunomiya I, Gu Y, Cawthraw SA, Newell DG, Pajaniappan M, Thompson SA, Ariga T, Yu RK. Topology and patch-clamp analysis of the sodium channel in relationship to the anti-lipid a antibody in campylobacteriosis. J Neurosci Res 2009; 86:3359-74. [PMID: 18627035 DOI: 10.1002/jnr.21781] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
An infecting strain VLA2/18 of Campylobacter jejuni was obtained from an individual with campylobacteriosis and used to prepare chicken sera by experimental infection to investigate the role of serum anti-ganglioside antibodies in Guillain-Barré syndrome. Both sera of the patient and chicken contained anti-ganglioside antibodies and anti-Lipid A (anti-Kdo2-Lipid A) antibodies directed against the lipid A portion of the bacterial lipooligosaccharide. The anti-Kdo2-Lipid A activities inhibited voltage-gated Na (Nav) channel of NSC-34 cells in culture. We hypothesized that anti-Kdo2-Lipid A antibody acts on the functional inhibition of Nav1.4. To test this possibility, a rabbit peptide antibody (anti-Nav1.4 pAb) against a 19-mer peptide (KELKDNHILNHVGLTDGPR) on the alpha subunit of Nav1.4 was produced. Anti-Nav1.4 pAb was cross-reactive to Kdo2-Lipid A. Anti-Kdo2-lipid A antibody activity in the chicken serum was tested for the Na(+) current inhibition in NSC-34 cells in combination with mu-Conotoxin and tetrodotoxin. Contrary to our expectations, the anti-Kdo2-Lipid A antibody activity was extended to Nav channels other than Nav1.4. By overlapping structural analysis, it was found that there might be multiple peptide epitopes containing certain dipeptides showing a structural similarity with v-Lipid A. Thus, our study suggests the possibility that there are multiple epitopic peptides on the extracellular domains of Nav1.1 to 1.9, and some of them may represent target sites for anti-Kdo2-Lipid A antibody, to induce neurophysiological changes in GBS by disrupting the normal function of the Nav channels.
Collapse
Affiliation(s)
- Seigo Usuki
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30912-2697, USA
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|