1
|
Maciąg F, Chhikara A, Heine M. Calcium channel signalling at neuronal endoplasmic reticulum-plasma membrane junctions. Biochem Soc Trans 2024:BST20230819. [PMID: 38934485 DOI: 10.1042/bst20230819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Revised: 05/22/2024] [Accepted: 06/07/2024] [Indexed: 06/28/2024]
Abstract
Neurons are highly specialised cells that need to relay information over long distances and integrate signals from thousands of synaptic inputs. The complexity of neuronal function is evident in the morphology of their plasma membrane (PM), by far the most intricate of all cell types. Yet, within the neuron lies an organelle whose architecture adds another level to this morphological sophistication - the endoplasmic reticulum (ER). Neuronal ER is abundant in the cell body and extends to distant axonal terminals and postsynaptic dendritic spines. It also adopts specialised structures like the spine apparatus in the postsynapse and the cisternal organelle in the axon initial segment. At membrane contact sites (MCSs) between the ER and the PM, the two membranes come in close proximity to create hubs of lipid exchange and Ca2+ signalling called ER-PM junctions. The development of electron and light microscopy techniques extended our knowledge on the physiological relevance of ER-PM MCSs. Equally important was the identification of ER and PM partners that interact in these junctions, most notably the STIM-ORAI and VAP-Kv2.1 pairs. The physiological functions of ER-PM junctions in neurons are being increasingly explored, but their molecular composition and the role in the dynamics of Ca2+ signalling are less clear. This review aims to outline the current state of research on the topic of neuronal ER-PM contacts. Specifically, we will summarise the involvement of different classes of Ca2+ channels in these junctions, discuss their role in neuronal development and neuropathology and propose directions for further research.
Collapse
Affiliation(s)
- Filip Maciąg
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University, Hanns-Dieter Hüsch Weg 15, 55128 Mainz, Germany
| | - Arun Chhikara
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University, Hanns-Dieter Hüsch Weg 15, 55128 Mainz, Germany
| | - Martin Heine
- Institute of Developmental Biology and Neurobiology, Johannes Gutenberg University, Hanns-Dieter Hüsch Weg 15, 55128 Mainz, Germany
| |
Collapse
|
2
|
Murage B, Tan H, Mashimo T, Jackson M, Skehel PA. Spinal cord neurone loss and foot placement changes in a rat knock-in model of amyotrophic lateral sclerosis Type 8. Brain Commun 2024; 6:fcae184. [PMID: 38846532 PMCID: PMC11154649 DOI: 10.1093/braincomms/fcae184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 04/10/2024] [Accepted: 05/23/2024] [Indexed: 06/09/2024] Open
Abstract
Amyotrophic lateral sclerosis is an age-dependent cell type-selective degenerative disease. Genetic studies indicate that amyotrophic lateral sclerosis is part of a spectrum of disorders, ranging from spinal muscular atrophy to frontotemporal dementia that share common pathological mechanisms. Amyotrophic lateral sclerosis Type 8 is a familial disease caused by mis-sense mutations in VAPB. VAPB is localized to the cytoplasmic surface of the endoplasmic reticulum, where it serves as a docking point for cytoplasmic proteins and mediates inter-organelle interactions with the endoplasmic reticulum membrane. A gene knock-in model of amyotrophic lateral sclerosis Type 8 based on the VapBP56S mutation and VapB gene deletion has been generated in rats. These animals display a range of age-dependent phenotypes distinct from those previously reported in mouse models of amyotrophic lateral sclerosis Type 8. A loss of motor neurones in VapBP56S/+ and VapBP56S/P56S animals is indicated by a reduction in the number of large choline acetyl transferase-staining cells in the spinal cord. VapB-/- animals exhibit a relative increase in cytoplasmic TDP-43 levels compared with the nucleus, but no large protein aggregates. Concomitant with these spinal cord pathologies VapBP56S/+ , VapBP56S/P56S and VapB-/- animals exhibit age-dependent changes in paw placement and exerted pressures when traversing a CatWalk apparatus, consistent with a somatosensory dysfunction. Extramotor dysfunction is reported in half the cases of motor neurone disease, and this is the first indication of an associated sensory dysfunction in a rodent model of amyotrophic lateral sclerosis. Different rodent models may offer complementary experimental platforms with which to understand the human disease.
Collapse
Affiliation(s)
- Brenda Murage
- Centre for Discovery Brain Sciences, Edinburgh University, Edinburgh EH8 9XD, UK
- Euan MacDonald Centre for MND Research, Edinburgh University, Edinburgh EH16 4SB, UK
| | - Han Tan
- Centre for Discovery Brain Sciences, Edinburgh University, Edinburgh EH8 9XD, UK
| | - Tomoji Mashimo
- Division of Animal Genetics, Laboratory Animal Research Center, Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan
| | - Mandy Jackson
- Centre for Discovery Brain Sciences, Edinburgh University, Edinburgh EH8 9XD, UK
- Euan MacDonald Centre for MND Research, Edinburgh University, Edinburgh EH16 4SB, UK
| | - Paul A Skehel
- Centre for Discovery Brain Sciences, Edinburgh University, Edinburgh EH8 9XD, UK
- Euan MacDonald Centre for MND Research, Edinburgh University, Edinburgh EH16 4SB, UK
| |
Collapse
|
3
|
Landry C, Costanzo J, Mitne-Neto M, Zatz M, Schaffer A, Hatzoglou M, Muotri A, Miranda HC. Mitochondrial dysfunction heightens the integrated stress response to drive ALS pathogenesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.13.594000. [PMID: 38798645 PMCID: PMC11118434 DOI: 10.1101/2024.05.13.594000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Vesicle-associated membrane protein-associated protein-B (VAPB) is an ER membrane bound protein. VAPB P56S causes a dominant, familial form of amyotrophic lateral sclerosis (ALS), however, the mechanism through which this mutation causes motor neuron (MN) disease remains unknown. Using inducible wild type (WT) and VAPB P56S expressing iPSC-derived MNs we show that VAPB P56S, but not WT, protein decreased neuronal firing and mitochondrial-ER contact (MERC) with an associated age-dependent decrease in mitochondrial membrane potential (MMP); all typical characteristics of MN-disease. We further show that VAPB P56S expressing iPSC-derived MNs have enhanced age-dependent sensitivity to ER stress. We identified elevated expression of the master regulator of the Integrated Stress Response (ISR) marker ATF4 and decreased protein synthesis in the VAPB P56S iPSC-derived MNs. Chemical inhibition of ISR with the compound, ISRIB, rescued all MN disease phenotype in VAPB P56S MNs. Thus, our results not only support ISR inhibition as a potential therapeutic target for ALS patients, but also provides evidence to pathogenesis.
Collapse
|
4
|
Casas M, Dickson EJ. Unraveling the Connection: Cholesterol, Calcium Signaling, and Neurodegeneration. Neurosci Insights 2024; 19:26331055241252772. [PMID: 38737295 PMCID: PMC11088808 DOI: 10.1177/26331055241252772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 04/19/2024] [Indexed: 05/14/2024] Open
Abstract
Cholesterol and calcium play crucial roles as integral structural components and functional signaling entities within the central nervous system. Disruption in cholesterol homeostasis has been linked to Alzheimer's, Parkinson's, and Huntington's Disease while alterations in calcium signaling is hypothesized to be a key substrate for neurodegeneration across many disorders. Despite the importance of regulated cholesterol and calcium homeostasis for brain health there has been an absence of research investigating the interdependence of these signaling molecules and how they can tune each other's abundance at membranes to influence membrane identity. Here, we discuss the role of cholesterol in shaping calcium dynamics in a neurodegenerative disorder that arises due to mutations in the lysosomal cholesterol transporter, Niemann Pick Type C1 (NPC1). We discuss the molecular mechanisms through which altered lysosomal cholesterol transport influences calcium signaling pathways through remodeling of ion channel distribution at organelle-organelle membrane contacts leading to neurodegeneration. This scientific inquiry not only sheds light on NPC disease but also holds implications for comprehending other cholesterol-associated neurodegenerative disorders.
Collapse
Affiliation(s)
- Maria Casas
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Eamonn J Dickson
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| |
Collapse
|
5
|
Wang Y, Yang J. ER-organelle contacts: A signaling hub for neurological diseases. Pharmacol Res 2024; 203:107149. [PMID: 38518830 DOI: 10.1016/j.phrs.2024.107149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 03/07/2024] [Accepted: 03/19/2024] [Indexed: 03/24/2024]
Abstract
Neuronal health is closely linked to the homeostasis of intracellular organelles, and organelle dysfunction affects the pathological progression of neurological diseases. In contrast to isolated cellular compartments, a growing number of studies have found that organelles are largely interdependent structures capable of communicating through membrane contact sites (MCSs). MCSs have been identified as key pathways mediating inter-organelle communication crosstalk in neurons, and their alterations have been linked to neurological disease pathology. The endoplasmic reticulum (ER) is a membrane-bound organelle capable of forming an extensive network of pools and tubules with important physiological functions within neurons. There are multiple MCSs between the ER and other organelles and the plasma membrane (PM), which regulate a variety of cellular processes. In this review, we focus on ER-organelle MCSs and their role in a variety of neurological diseases. We compared the biological effects between different tethering proteins and the effects of their respective disease counterparts. We also discuss how altered ER-organelle contacts may affect disease pathogenesis. Therefore, understanding the molecular mechanisms of ER-organelle MCSs in neuronal homeostasis will lay the foundation for the development of new therapies targeting ER-organelle contacts.
Collapse
Affiliation(s)
- Yunli Wang
- Key Laboratory of Environmental Stress and Chronic Disease Control & Prevention (China Medical University), Ministry of Education, PR China; Department of Toxicology, School of Public Health, China Medical University, Shenyang 110122, PR China
| | - Jinghua Yang
- Key Laboratory of Environmental Stress and Chronic Disease Control & Prevention (China Medical University), Ministry of Education, PR China; Department of Toxicology, School of Public Health, China Medical University, Shenyang 110122, PR China.
| |
Collapse
|
6
|
Sun S, Zhao G, Jia M, Jiang Q, Li S, Wang H, Li W, Wang Y, Bian X, Zhao YG, Huang X, Yang G, Cai H, Pastor-Pareja JC, Ge L, Zhang C, Hu J. Stay in touch with the endoplasmic reticulum. SCIENCE CHINA. LIFE SCIENCES 2024; 67:230-257. [PMID: 38212460 DOI: 10.1007/s11427-023-2443-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Accepted: 08/28/2023] [Indexed: 01/13/2024]
Abstract
The endoplasmic reticulum (ER), which is composed of a continuous network of tubules and sheets, forms the most widely distributed membrane system in eukaryotic cells. As a result, it engages a variety of organelles by establishing membrane contact sites (MCSs). These contacts regulate organelle positioning and remodeling, including fusion and fission, facilitate precise lipid exchange, and couple vital signaling events. Here, we systematically review recent advances and converging themes on ER-involved organellar contact. The molecular basis, cellular influence, and potential physiological functions for ER/nuclear envelope contacts with mitochondria, Golgi, endosomes, lysosomes, lipid droplets, autophagosomes, and plasma membrane are summarized.
Collapse
Affiliation(s)
- Sha Sun
- National Laboratory of Biomacromolecules, Institute of Biophysics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100101, China
| | - Gan Zhao
- The Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing, 100871, China
| | - Mingkang Jia
- The Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing, 100871, China
| | - Qing Jiang
- The Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing, 100871, China
| | - Shulin Li
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Haibin Wang
- National Laboratory of Biomacromolecules, Institute of Biophysics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100101, China
| | - Wenjing Li
- Laboratory of Computational Biology & Machine Intelligence, School of Artificial Intelligence, University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yunyun Wang
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, 300071, China
| | - Xin Bian
- State Key Laboratory of Medicinal Chemical Biology, College of Life Sciences, Nankai University, Tianjin, 300071, China.
| | - Yan G Zhao
- Brain Research Center, Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, 518055, China.
| | - Xun Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Ge Yang
- Laboratory of Computational Biology & Machine Intelligence, School of Artificial Intelligence, University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Huaqing Cai
- National Laboratory of Biomacromolecules, Institute of Biophysics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Jose C Pastor-Pareja
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
- Institute of Neurosciences, Consejo Superior de Investigaciones Cientfflcas-Universidad Miguel Hernandez, San Juan de Alicante, 03550, Spain.
| | - Liang Ge
- State Key Laboratory of Membrane Biology, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
| | - Chuanmao Zhang
- The Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, College of Life Sciences, Peking University, Beijing, 100871, China.
| | - Junjie Hu
- National Laboratory of Biomacromolecules, Institute of Biophysics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, 100101, China.
| |
Collapse
|
7
|
Leek AN, Quinn JA, Krapf D, Tamkun MM. GLT-1a glutamate transporter nanocluster localization is associated with astrocytic actin and neuronal Kv2 clusters at sites of neuron-astrocyte contact. Front Cell Dev Biol 2024; 12:1334861. [PMID: 38362041 PMCID: PMC10867268 DOI: 10.3389/fcell.2024.1334861] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 01/16/2024] [Indexed: 02/17/2024] Open
Abstract
Introduction: Astrocytic GLT-1 glutamate transporters ensure the fidelity of glutamic neurotransmission by spatially and temporally limiting glutamate signals. The ability to limit neuronal hyperactivity relies on the localization and diffusion of GLT-1 on the astrocytic surface, however, little is known about the underlying mechanisms. We show that two isoforms of GLT-1, GLT-1a and GLT-1b, form nanoclusters on the surface of transfected astrocytes and HEK-293 cells. Methods: We used both fixed and live cell super-resolution imaging of fluorescent protein and epitope tagged proteins in co-cultures of rat astrocytes and neurons. Immunofluorescence techniques were also used. GLT1 diffusion was assessed via single particle tracking and fluorescence recovery after photobleach (FRAP). Results: We found GLT-1a, but not GLT-1b, nanoclusters concentrated adjacent to actin filaments which was maintained after addition of glutamate. GLT-1a nanocluster concentration near actin filaments was prevented by expression of a cytosolic GLT-1a C-terminus, suggesting the C-terminus is involved in the localization adjacent to cortical actin. Using super-resolution imaging, we show that astrocytic GLT-1a and actin co-localize in net-like structures around neuronal Kv2.1 clusters at points of neuron/astrocyte contact. Conclusion: Overall, these data describe a novel relationship between GLT-1a and cortical actin filaments, which localizes GLT-1a near neuronal structures responsive to ischemic insult.
Collapse
Affiliation(s)
- Ashley N. Leek
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, United States
- Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO, United States
| | - Josiah A. Quinn
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, United States
| | - Diego Krapf
- Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, CO, United States
| | - Michael M. Tamkun
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, United States
- Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO, United States
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO, United States
| |
Collapse
|
8
|
Ferns M, van der List D, Vierra NC, Lacey T, Murray K, Kirmiz M, Stewart RG, Sack JT, Trimmer JS. Electrically silent KvS subunits associate with native Kv2 channels in brain and impact diverse properties of channel function. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.25.577135. [PMID: 38328147 PMCID: PMC10849721 DOI: 10.1101/2024.01.25.577135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Voltage-gated K+ channels of the Kv2 family are highly expressed in brain and play dual roles in regulating neuronal excitability and in organizing endoplasmic reticulum - plasma membrane (ER-PM) junctions. Studies in heterologous cells suggest that the two pore-forming alpha subunits Kv2.1 and Kv2.2 assemble with "electrically silent" KvS subunits to form heterotetrameric channels with distinct biophysical properties. Here, using mass spectrometry-based proteomics, we identified five KvS subunits as components of native Kv2.1 channels immunopurified from mouse brain, the most abundant being Kv5.1. We found that Kv5.1 co-immunoprecipitates with Kv2.1 and to a lesser extent with Kv2.2 from brain lysates, and that Kv5.1 protein levels are decreased by 70% in Kv2.1 knockout mice and 95% in Kv2.1/2.2 double knockout mice. Multiplex immunofluorescent labelling of rodent brain sections revealed that in neocortex Kv5.1 immunolabeling is apparent in a large percentage of Kv2.1 and Kv2.2-positive layer 2/3 neurons, and in a smaller percentage of layer 5 and 6 neurons. At the subcellular level, Kv5.1 is co-clustered with Kv2.1 and Kv2.2 at ER-PM junctions in cortical neurons, although clustering of Kv5.1-containing channels is reduced relative to homomeric Kv2 channels. We also found that in heterologous cells coexpression with Kv5.1 reduces the clustering and alters the pharmacological properties of Kv2.1 channels. Together, these findings demonstrate that the Kv5.1 electrically silent subunit is a component of a substantial fraction of native brain Kv2 channels, and that its incorporation into heteromeric channels can impact diverse aspects of Kv2 channel function.
Collapse
Affiliation(s)
- Michael Ferns
- Dept. of Anesthesiology and Pain Medicine, University of California Davis, One Shields Ave, Davis, CA 95616, USA
- Dept. of Physiology and Membrane Biology, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - Deborah van der List
- Dept. of Physiology and Membrane Biology, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - Nicholas C. Vierra
- Dept. of Physiology and Membrane Biology, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - Taylor Lacey
- Dept. of Anesthesiology and Pain Medicine, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - Karl Murray
- Dept. of Physiology and Membrane Biology, University of California Davis, One Shields Ave, Davis, CA 95616, USA
- Dept. of Psychiatry and Behavioral Sciences, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - Michael Kirmiz
- Dept. of Physiology and Membrane Biology, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - Robert G. Stewart
- Dept. of Physiology and Membrane Biology, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - Jon T. Sack
- Dept. of Physiology and Membrane Biology, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - James S. Trimmer
- Dept. of Physiology and Membrane Biology, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| |
Collapse
|
9
|
Stewart RG, Camacena M, Copits BA, Sack JT. Distinct cellular expression and subcellular localization of Kv2 voltage-gated K + channel subtypes in dorsal root ganglion neurons conserved between mice and humans. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.01.530679. [PMID: 38187582 PMCID: PMC10769185 DOI: 10.1101/2023.03.01.530679] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
The distinct organization of Kv2 voltage-gated potassium channels on and near the cell body of brain neurons enables their regulation of action potentials and specialized membrane contact sites. Somatosensory neurons have a pseudounipolar morphology and transmit action potentials from peripheral nerve endings through axons that bifurcate to the spinal cord and the cell body within ganglia including the dorsal root ganglia (DRG). Kv2 channels regulate action potentials in somatosensory neurons, yet little is known about where Kv2 channels are located. Here we define the cellular and subcellular localization of the Kv2 paralogs, Kv2.1 and Kv2.2, in DRG somatosensory neurons with a panel of antibodies, cell markers, and genetically modified mice. We find that relative to spinal cord neurons, DRG neurons have similar levels of detectable Kv2.1, and higher levels of Kv2.2. In older mice, detectable Kv2.2 remains similar while detectable Kv2.1 decreases. Both Kv2 subtypes adopt clustered subcellular patterns that are distinct from central neurons. Most DRG neurons co-express Kv2.1 and Kv2.2, although neuron subpopulations show preferential expression of Kv2.1 or Kv2.2. We find that Kv2 protein expression and subcellular localization is similar between mouse and human DRG neurons. We conclude that the organization of both Kv2 channels is consistent with physiological roles in the somata and stem axons of DRG neurons. The general prevalence of Kv2.2 in DRG as compared to central neurons and the enrichment of Kv2.2 relative to detectable Kv2.1, in older mice, proprioceptors, and axons suggest more widespread roles for Kv2.2 in DRG neurons.
Collapse
Affiliation(s)
- Robert G Stewart
- Department of Physiology and Membrane Biology, University of California Davis, Davis, CA 95616, USA
| | - Miriam Camacena
- Department of Physiology and Membrane Biology, University of California Davis, Davis, CA 95616, USA
| | - Bryan A Copits
- Washington University Pain Center, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Jon T Sack
- Department of Physiology and Membrane Biology, University of California Davis, Davis, CA 95616, USA
- Department of Anesthesiology and Pain Medicine, University of California Davis, Davis, CA 95616, USA
| |
Collapse
|
10
|
Matsumoto C, O'Dwyer SC, Manning D, Hernandez-Hernandez G, Rhana P, Fong Z, Sato D, Clancy CE, Vierra NC, Trimmer JS, Fernando Santana L. The formation of K V2.1 macro-clusters is required for sex-specific differences in L-type Ca V1.2 clustering and function in arterial myocytes. Commun Biol 2023; 6:1165. [PMID: 37963972 PMCID: PMC10645748 DOI: 10.1038/s42003-023-05527-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2023] [Accepted: 10/31/2023] [Indexed: 11/16/2023] Open
Abstract
In arterial myocytes, the canonical function of voltage-gated CaV1.2 and KV2.1 channels is to induce myocyte contraction and relaxation through their responses to membrane depolarization, respectively. Paradoxically, KV2.1 also plays a sex-specific role by promoting the clustering and activity of CaV1.2 channels. However, the impact of KV2.1 protein organization on CaV1.2 function remains poorly understood. We discovered that KV2.1 forms micro-clusters, which can transform into large macro-clusters when a critical clustering site (S590) in the channel is phosphorylated in arterial myocytes. Notably, female myocytes exhibit greater phosphorylation of S590, and macro-cluster formation compared to males. Contrary to current models, the activity of KV2.1 channels seems unrelated to density or macro-clustering in arterial myocytes. Disrupting the KV2.1 clustering site (KV2.1S590A) eliminated KV2.1 macro-clustering and sex-specific differences in CaV1.2 cluster size and activity. We propose that the degree of KV2.1 clustering tunes CaV1.2 channel function in a sex-specific manner in arterial myocytes.
Collapse
Affiliation(s)
- Collin Matsumoto
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Samantha C O'Dwyer
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Declan Manning
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | | | - Paula Rhana
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Zhihui Fong
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Daisuke Sato
- Department of Pharmacology, School of Medicine, University of California, Davis, CA, USA
| | - Colleen E Clancy
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Nicholas C Vierra
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - James S Trimmer
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - L Fernando Santana
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA.
| |
Collapse
|
11
|
Bortolami A, Sesti F. Ion channels in neurodevelopment: lessons from the Integrin-KCNB1 channel complex. Neural Regen Res 2023; 18:2365-2369. [PMID: 37282454 PMCID: PMC10360111 DOI: 10.4103/1673-5374.371347] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023] Open
Abstract
Ion channels modulate cellular excitability by regulating ionic fluxes across biological membranes. Pathogenic mutations in ion channel genes give rise to epileptic disorders that are among the most frequent neurological diseases affecting millions of individuals worldwide. Epilepsies are triggered by an imbalance between excitatory and inhibitory conductances. However, pathogenic mutations in the same allele can give rise to loss-of-function and/or gain-of-function variants, all able to trigger epilepsy. Furthermore, certain alleles are associated with brain malformations even in the absence of a clear electrical phenotype. This body of evidence argues that the underlying epileptogenic mechanisms of ion channels are more diverse than originally thought. Studies focusing on ion channels in prenatal cortical development have shed light on this apparent paradox. The picture that emerges is that ion channels play crucial roles in landmark neurodevelopmental processes, including neuronal migration, neurite outgrowth, and synapse formation. Thus, pathogenic channel mutants can not only cause epileptic disorders by altering excitability, but further, by inducing morphological and synaptic abnormalities that are initiated during neocortex formation and may persist into the adult brain.
Collapse
Affiliation(s)
- Alessandro Bortolami
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, West Piscataway, NJ, USA
| | - Federico Sesti
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, West Piscataway, NJ, USA
| |
Collapse
|
12
|
Sarhadi TR, Panse JS, Nagotu S. Mind the gap: Methods to study membrane contact sites. Exp Cell Res 2023; 431:113756. [PMID: 37633408 DOI: 10.1016/j.yexcr.2023.113756] [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: 03/28/2023] [Revised: 08/11/2023] [Accepted: 08/13/2023] [Indexed: 08/28/2023]
Abstract
Organelles are dynamic entities whose functions are essential for the optimum functioning of cells. It is now known that the juxtaposition of organellar membranes is essential for the exchange of metabolites and their communication. These functional apposition sites are termed membrane contact sites. Dynamic membrane contact sites between various sub-cellular structures such as mitochondria, endoplasmic reticulum, peroxisomes, Golgi apparatus, lysosomes, lipid droplets, plasma membrane, endosomes, etc. have been reported in various model systems. The burgeoning area of research on membrane contact sites has witnessed several manuscripts in recent years that identified the contact sites and components involved. Several methods have been developed to identify, measure and analyze the membrane contact sites. In this manuscript, we aim to discuss important methods developed to date that are used to study membrane contact sites.
Collapse
Affiliation(s)
- Tanveera Rounaque Sarhadi
- Organelle Biology and Cellular Ageing Lab, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India
| | - Janhavee Shirish Panse
- Organelle Biology and Cellular Ageing Lab, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India
| | - Shirisha Nagotu
- Organelle Biology and Cellular Ageing Lab, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India.
| |
Collapse
|
13
|
Sesti F, Bortolami A, Kathera-Ibarra EF. Non-conducting functions of potassium channels in cancer and neurological disease. CURRENT TOPICS IN MEMBRANES 2023; 92:199-231. [PMID: 38007268 DOI: 10.1016/bs.ctm.2023.09.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2023]
Abstract
Cancer and neurodegenerative disease, albeit fundamental differences, share some common pathogenic mechanisms. Accordingly, both conditions are associated with aberrant cell proliferation and migration. Here, we review the causative role played by potassium (K+) channels, a fundamental class of proteins, in cancer and neurodegenerative disease. The concept that emerges from the review of the literature is that K+ channels can promote the development and progression of cancerous and neurodegenerative pathologies by dysregulating cell proliferation and migration. K+ channels appear to control these cellular functions in ways that not necessarily depend on their conducting properties and that involve the ability to directly or indirectly engage growth and survival signaling pathways. As cancer and neurodegenerative disease represent global health concerns, identifying commonalities may help understand the molecular basis for those devastating conditions and may facilitate the design of new drugs or the repurposing of existing drugs.
Collapse
Affiliation(s)
- Federico Sesti
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, Hoes Ln. West, Piscataway, NJ, United States.
| | - Alessandro Bortolami
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, Hoes Ln. West, Piscataway, NJ, United States
| | - Elena Forzisi Kathera-Ibarra
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, Hoes Ln. West, Piscataway, NJ, United States
| |
Collapse
|
14
|
Vierra NC, Ribeiro-Silva L, Kirmiz M, van der List D, Bhandari P, Mack OA, Carroll J, Le Monnier E, Aicher SA, Shigemoto R, Trimmer JS. Neuronal ER-plasma membrane junctions couple excitation to Ca 2+-activated PKA signaling. Nat Commun 2023; 14:5231. [PMID: 37633939 PMCID: PMC10460453 DOI: 10.1038/s41467-023-40930-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 08/16/2023] [Indexed: 08/28/2023] Open
Abstract
Junctions between the endoplasmic reticulum (ER) and the plasma membrane (PM) are specialized membrane contacts ubiquitous in eukaryotic cells. Concentration of intracellular signaling machinery near ER-PM junctions allows these domains to serve critical roles in lipid and Ca2+ signaling and homeostasis. Subcellular compartmentalization of protein kinase A (PKA) signaling also regulates essential cellular functions, however, no specific association between PKA and ER-PM junctional domains is known. Here, we show that in brain neurons type I PKA is directed to Kv2.1 channel-dependent ER-PM junctional domains via SPHKAP, a type I PKA-specific anchoring protein. SPHKAP association with type I PKA regulatory subunit RI and ER-resident VAP proteins results in the concentration of type I PKA between stacked ER cisternae associated with ER-PM junctions. This ER-associated PKA signalosome enables reciprocal regulation between PKA and Ca2+ signaling machinery to support Ca2+ influx and excitation-transcription coupling. These data reveal that neuronal ER-PM junctions support a receptor-independent form of PKA signaling driven by membrane depolarization and intracellular Ca2+, allowing conversion of information encoded in electrical signals into biochemical changes universally recognized throughout the cell.
Collapse
Affiliation(s)
- Nicholas C Vierra
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA, USA.
| | - Luisa Ribeiro-Silva
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA, USA
| | - Michael Kirmiz
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA, USA
| | - Deborah van der List
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA, USA
| | - Pradeep Bhandari
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Olivia A Mack
- Chemical Physiology and Biochemistry Department, Oregon Health & Science University, Portland, OR, USA
| | - James Carroll
- Chemical Physiology and Biochemistry Department, Oregon Health & Science University, Portland, OR, USA
| | - Elodie Le Monnier
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Sue A Aicher
- Chemical Physiology and Biochemistry Department, Oregon Health & Science University, Portland, OR, USA
| | - Ryuichi Shigemoto
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - James S Trimmer
- Department of Physiology and Membrane Biology, University of California Davis School of Medicine, Davis, CA, USA.
| |
Collapse
|
15
|
Casas M, Murray KD, Hino K, Vierra NC, Simó S, Trimmer JS, Dixon RE, Dickson EJ. NPC1-dependent alterations in K V2.1-Ca V1.2 nanodomains drive neuronal death in models of Niemann-Pick Type C disease. Nat Commun 2023; 14:4553. [PMID: 37507375 PMCID: PMC10382591 DOI: 10.1038/s41467-023-39937-w] [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: 08/17/2022] [Accepted: 07/04/2023] [Indexed: 07/30/2023] Open
Abstract
Lysosomes communicate through cholesterol transfer at endoplasmic reticulum (ER) contact sites. At these sites, the Niemann Pick C1 cholesterol transporter (NPC1) facilitates the removal of cholesterol from lysosomes, which is then transferred to the ER for distribution to other cell membranes. Mutations in NPC1 result in cholesterol buildup within lysosomes, leading to Niemann-Pick Type C (NPC) disease, a progressive and fatal neurodegenerative disorder. The molecular mechanisms connecting NPC1 loss to NPC-associated neuropathology remain unknown. Here we show both in vitro and in an animal model of NPC disease that the loss of NPC1 function alters the distribution and activity of voltage-gated calcium channels (CaV). Underlying alterations in calcium channel localization and function are KV2.1 channels whose interactions drive calcium channel clustering to enhance calcium entry and fuel neurotoxic elevations in mitochondrial calcium. Targeted disruption of KV2-CaV interactions rescues aberrant CaV1.2 clustering, elevated mitochondrial calcium, and neurotoxicity in vitro. Our findings provide evidence that NPC is a nanostructural ion channel clustering disease, characterized by altered distribution and activity of ion channels at membrane contacts, which contribute to neurodegeneration.
Collapse
Affiliation(s)
- Maria Casas
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Karl D Murray
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
- Department of Psychiatry & Behavioral Sciences, School of Medicine, University of California, Davis, CA, USA
| | - Keiko Hino
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis, CA, USA
| | - Nicholas C Vierra
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Sergi Simó
- Department of Cell Biology and Human Anatomy, School of Medicine, University of California, Davis, CA, USA
| | - James S Trimmer
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Rose E Dixon
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA
| | - Eamonn J Dickson
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, CA, USA.
| |
Collapse
|
16
|
Matsumoto C, O'Dwyer SC, Manning D, Hernandez-Hernandez G, Rhana P, Fong Z, Sato D, Clancy CE, Vierra NC, Trimmer JS, Santana LF. The formation of K V 2.1 macro-clusters is required for sex-specific differences in L-type Ca V 1.2 clustering and function in arterial myocytes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.27.546725. [PMID: 37425816 PMCID: PMC10327069 DOI: 10.1101/2023.06.27.546725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
In arterial myocytes, the canonical function of voltage-gated Ca V 1.2 and K V 2.1 channels is to induce myocyte contraction and relaxation through their responses to membrane depolarization, respectively. Paradoxically, K V 2.1 also plays a sex-specific role by promoting the clustering and activity of Ca V 1.2 channels. However, the impact of K V 2.1 protein organization on Ca V 1.2 function remains poorly understood. We discovered that K V 2.1 forms micro-clusters, which can transform into large macro-clusters when a critical clustering site (S590) in the channel is phosphorylated in arterial myocytes. Notably, female myocytes exhibit greater phosphorylation of S590, and macro-cluster formation compared to males. Contrary to current models, the activity of K V 2.1 channels seems unrelated to density or macro-clustering in arterial myocytes. Disrupting the K V 2.1 clustering site (K V 2.1 S590A ) eliminated K V 2.1 macro-clustering and sex-specific differences in Ca V 1.2 cluster size and activity. We propose that the degree of K V 2.1 clustering tunes Ca V 1.2 channel function in a sex-specific manner in arterial myocytes.
Collapse
|
17
|
Guillén-Samander A, De Camilli P. Endoplasmic Reticulum Membrane Contact Sites, Lipid Transport, and Neurodegeneration. Cold Spring Harb Perspect Biol 2023; 15:a041257. [PMID: 36123033 PMCID: PMC10071438 DOI: 10.1101/cshperspect.a041257] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Endoplasmic Reticulum (ER) is an endomembrane system that plays a multiplicity of roles in cell physiology and populates even the most distal cell compartments, including dendritic tips and axon terminals of neurons. Some of its functions are achieved by a cross talk with other intracellular membranous organelles and with the plasma membrane at membrane contacts sites (MCSs). As the ER synthesizes most membrane lipids, lipid exchanges mediated by lipid transfer proteins at MCSs are a particularly important aspect of this cross talk, which synergizes with the cross talk mediated by vesicular transport. Several mutations of genes that encode proteins localized at ER MCSs result in familial neurodegenerative diseases, emphasizing the importance of the normal lipid traffic within cells for a healthy brain. Here, we provide an overview of such diseases, with a specific focus on proteins that directly or indirectly impact lipid transport.
Collapse
Affiliation(s)
- Andrés Guillén-Samander
- Departments of Neuroscience and of Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut 06520, USA
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, Maryland 20815, USA
| | - Pietro De Camilli
- Departments of Neuroscience and of Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut 06520, USA
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, Maryland 20815, USA
| |
Collapse
|
18
|
Wang P, Duckney P, Gao E, Hussey PJ, Kriechbaumer V, Li C, Zang J, Zhang T. Keep in contact: multiple roles of endoplasmic reticulum-membrane contact sites and the organelle interaction network in plants. THE NEW PHYTOLOGIST 2023; 238:482-499. [PMID: 36651025 DOI: 10.1111/nph.18745] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Accepted: 12/02/2022] [Indexed: 06/17/2023]
Abstract
Functional regulation and structural maintenance of the different organelles in plants contribute directly to plant development, reproduction and stress responses. To ensure these activities take place effectively, cells have evolved an interconnected network amongst various subcellular compartments, regulating rapid signal transduction and the exchange of biomaterial. Many proteins that regulate membrane connections have recently been identified in plants, and this is the first step in elucidating both the mechanism and function of these connections. Amongst all organelles, the endoplasmic reticulum is the key structure, which likely links most of the different subcellular compartments through membrane contact sites (MCS) and the ER-PM contact sites (EPCS) have been the most intensely studied in plants. However, the molecular composition and function of plant MCS are being found to be different from other eukaryotic systems. In this article, we will summarise the most recent advances in this field and discuss the mechanism and biological relevance of these essential links in plants.
Collapse
Affiliation(s)
- Pengwei Wang
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture & Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, China
- Hubei Hongshan Laboratory, Wuhan, 430070, China
| | - Patrick Duckney
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Erlin Gao
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture & Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, China
- Hubei Hongshan Laboratory, Wuhan, 430070, China
| | - Patrick J Hussey
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Verena Kriechbaumer
- Endomembrane Structure and Function Research Group, Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Chengyang Li
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture & Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, China
- Hubei Hongshan Laboratory, Wuhan, 430070, China
| | - Jingze Zang
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture & Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, China
- Hubei Hongshan Laboratory, Wuhan, 430070, China
| | - Tong Zhang
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, College of Horticulture & Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, China
- Hubei Hongshan Laboratory, Wuhan, 430070, China
| |
Collapse
|
19
|
Dixon RE, Trimmer JS. Endoplasmic Reticulum-Plasma Membrane Junctions as Sites of Depolarization-Induced Ca 2+ Signaling in Excitable Cells. Annu Rev Physiol 2023; 85:217-243. [PMID: 36202100 PMCID: PMC9918718 DOI: 10.1146/annurev-physiol-032122-104610] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Membrane contact sites between endoplasmic reticulum (ER) and plasma membrane (PM), or ER-PM junctions, are found in all eukaryotic cells. In excitable cells they play unique roles in organizing diverse forms of Ca2+ signaling as triggered by membrane depolarization. ER-PM junctions underlie crucial physiological processes such as excitation-contraction coupling, smooth muscle contraction and relaxation, and various forms of activity-dependent signaling and plasticity in neurons. In many cases the structure and molecular composition of ER-PM junctions in excitable cells comprise important regulatory feedback loops linking depolarization-induced Ca2+ signaling at these sites to the regulation of membrane potential. Here, we describe recent findings on physiological roles and molecular composition of native ER-PM junctions in excitable cells. We focus on recent studies that provide new insights into canonical forms of depolarization-induced Ca2+ signaling occurring at junctional triads and dyads of striated muscle, as well as the diversity of ER-PM junctions in these cells and in smooth muscle and neurons.
Collapse
Affiliation(s)
- Rose E Dixon
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, California, USA;
| | - James S Trimmer
- Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis, California, USA;
| |
Collapse
|
20
|
Vullhorst D, Bloom MS, Akella N, Buonanno A. ER-PM Junctions on GABAergic Interneurons Are Organized by Neuregulin 2/VAP Interactions and Regulated by NMDA Receptors. Int J Mol Sci 2023; 24:2908. [PMID: 36769244 PMCID: PMC9917868 DOI: 10.3390/ijms24032908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 01/24/2023] [Accepted: 01/27/2023] [Indexed: 02/05/2023] Open
Abstract
Neuregulins (NRGs) signal via ErbB receptors to regulate neural development, excitability, synaptic and network activity, and behaviors relevant to psychiatric disorders. Bidirectional signaling between NRG2/ErbB4 and NMDA receptors is thought to homeostatically regulate GABAergic interneurons in response to increased excitatory neurotransmission or elevated extracellular glutamate levels. Unprocessed proNRG2 forms discrete clusters on cell bodies and proximal dendrites that colocalize with the potassium channel Kv2.1 at specialized endoplasmic reticulum-plasma membrane (ER-PM) junctions, and NMDA receptor activation triggers rapid dissociation from ER-PM junctions and ectodomain shedding by ADAM10. Here, we elucidate the mechanistic basis of proNRG2 clustering at ER-PM junctions and its regulation by NMDA receptors. Importantly, we demonstrate that proNRG2 promotes the formation of ER-PM junctions by directly binding the ER-resident membrane tether VAP, like Kv2.1. The proNRG2 intracellular domain harbors two non-canonical, low-affinity sites that cooperatively mediate VAP binding. One of these is a cryptic and phosphorylation-dependent VAP binding motif that is dephosphorylated following NMDA receptor activation, thus revealing how excitatory neurotransmission promotes the dissociation of proNRG2 from ER-PM junctions. Therefore, proNRG2 and Kv2.1 can independently function as VAP-dependent organizers of neuronal ER-PM junctions. Based on these and prior studies, we propose that proNRG2 and Kv2.1 serve as co-regulated downstream effectors of NMDA receptors to homeostatically regulate GABAergic interneurons.
Collapse
Affiliation(s)
- Detlef Vullhorst
- Section on Molecular Neurobiology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD 20892, USA
| | | | | | | |
Collapse
|
21
|
Fyffe REW, Deardorff AS. Another novel non-conducting functional role for Kv2 channels – regulation of calcium signaling. Cell Calcium 2022; 107:102650. [DOI: 10.1016/j.ceca.2022.102650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 08/28/2022] [Indexed: 11/02/2022]
|
22
|
Piccialli I, Sisalli MJ, de Rosa V, Boscia F, Tedeschi V, Secondo A, Pannaccione A. Increased K V2.1 Channel Clustering Underlies the Reduction of Delayed Rectifier K + Currents in Hippocampal Neurons of the Tg2576 Alzheimer's Disease Mouse. Cells 2022; 11:cells11182820. [PMID: 36139395 PMCID: PMC9497218 DOI: 10.3390/cells11182820] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 09/01/2022] [Accepted: 09/07/2022] [Indexed: 11/30/2022] Open
Abstract
Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by the progressive deterioration of cognitive functions. Cortical and hippocampal hyperexcitability intervenes in the pathological derangement of brain activity leading to cognitive decline. As key regulators of neuronal excitability, the voltage-gated K+ channels (KV) might play a crucial role in the AD pathophysiology. Among them, the KV2.1 channel, the main α subunit mediating the delayed rectifier K+ currents (IDR) and controlling the intrinsic excitability of pyramidal neurons, has been poorly examined in AD. In the present study, we investigated the KV2.1 protein expression and activity in hippocampal neurons from the Tg2576 mouse, a widely used transgenic model of AD. To this aim we performed whole-cell patch-clamp recordings, Western blotting, and immunofluorescence analyses. Our Western blotting results reveal that KV2.1 was overexpressed in the hippocampus of 3-month-old Tg2576 mice and in primary hippocampal neurons from Tg2576 mouse embryos compared with the WT counterparts. Electrophysiological experiments unveiled that the whole IDR were reduced in the Tg2576 primary neurons compared with the WT neurons, and that this reduction was due to the loss of the KV2.1 current component. Moreover, we found that the reduction of the KV2.1-mediated currents was due to increased channel clustering, and that glutamate, a stimulus inducing KV2.1 declustering, was able to restore the IDR to levels comparable to those of the WT neurons. These findings add new information about the dysregulation of ionic homeostasis in the Tg2576 AD mouse model and identify KV2.1 as a possible player in the AD-related alterations of neuronal excitability.
Collapse
|
23
|
Activity-dependent endoplasmic reticulum Ca 2+ uptake depends on Kv2.1-mediated endoplasmic reticulum/plasma membrane junctions to promote synaptic transmission. Proc Natl Acad Sci U S A 2022; 119:e2117135119. [PMID: 35862456 PMCID: PMC9335237 DOI: 10.1073/pnas.2117135119] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The endoplasmic reticulum (ER) extends throughout the neuron as a continuous organelle, and its dysfunction is associated with several neurological disorders. During electrical activity, the ER takes up Ca2+ from the cytosol, which has been shown to support synaptic transmission. This close choreography of ER Ca2+ uptake with electrical activity suggests functional coupling of the ER to sources of voltage-gated Ca2+ entry through an unknown mechanism. We report that a nonconducting role for Kv2.1 through its ER binding domain is necessary for ER Ca2+ uptake during neuronal activity. Loss of Kv2.1 profoundly disables neurotransmitter release without altering presynaptic voltage. This suggests that Kv2.1-mediated signaling hubs play an important neurobiological role in Ca2+ handling and synaptic transmission independent of ion conduction. The endoplasmic reticulum (ER) forms a continuous and dynamic network throughout a neuron, extending from dendrites to axon terminals, and axonal ER dysfunction is implicated in several neurological disorders. In addition, tight junctions between the ER and plasma membrane (PM) are formed by several molecules including Kv2 channels, but the cellular functions of many ER-PM junctions remain unknown. Recently, dynamic Ca2+ uptake into the ER during electrical activity was shown to play an essential role in synaptic transmission. Our experiments demonstrate that Kv2.1 channels are necessary for enabling ER Ca2+ uptake during electrical activity, as knockdown (KD) of Kv2.1 rendered both the somatic and axonal ER unable to accumulate Ca2+ during electrical stimulation. Moreover, our experiments demonstrate that the loss of Kv2.1 in the axon impairs synaptic vesicle fusion during stimulation via a mechanism unrelated to voltage. Thus, our data demonstrate that a nonconducting role of Kv2.1 exists through its binding to the ER protein VAMP-associated protein (VAP), which couples ER Ca2+ uptake with electrical activity. Our results further suggest that Kv2.1 has a critical function in neuronal cell biology for Ca2+ handling independent of voltage and reveals a critical pathway for maintaining ER lumen Ca2+ levels and efficient neurotransmitter release. Taken together, these findings reveal an essential nonclassical role for both Kv2.1 and the ER-PM junctions in synaptic transmission.
Collapse
|
24
|
Three-dimensional SEM, TEM, and STEM for analysis of large-scale biological systems. Histochem Cell Biol 2022; 158:203-211. [PMID: 35829815 PMCID: PMC9399040 DOI: 10.1007/s00418-022-02117-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/07/2022] [Indexed: 12/12/2022]
Abstract
A major aim in structural cell biology is to analyze intact cells in three dimensions, visualize subcellular structures, and even localize proteins at the best possible resolution in three dimensions. Though recently developed electron microscopy tools such as electron tomography, or three-dimensional (3D) scanning electron microscopy, offer great resolution in three dimensions, the challenge is that, the better the resolution, usually the smaller the volume under investigation. Several different approaches to overcome this challenge were presented at the Microscopy Conference in Vienna in 2021. These tools include array tomography, batch tomography, or scanning transmission electron tomography, all of which can nowadays be extended toward correlative light and electron tomography, with greatly increased 3D information. Here, we review these tools, describe the underlying procedures, and discuss their advantages and limits.
Collapse
|
25
|
Zouiouich M, Di Mattia T, Martinet A, Eichler J, Wendling C, Tomishige N, Grandgirard E, Fuggetta N, Fromental-Ramain C, Mizzon G, Dumesnil C, Carpentier M, Reina-San-Martin B, Mathelin C, Schwab Y, Thiam AR, Kobayashi T, Drin G, Tomasetto C, Alpy F. MOSPD2 is an endoplasmic reticulum-lipid droplet tether functioning in LD homeostasis. J Cell Biol 2022; 221:213116. [PMID: 35389430 DOI: 10.1083/jcb.202110044] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 02/11/2022] [Accepted: 03/16/2022] [Indexed: 12/28/2022] Open
Abstract
Membrane contact sites between organelles are organized by protein bridges. Among the components of these contacts, the VAP family comprises ER-anchored proteins, such as MOSPD2, that function as major ER-organelle tethers. MOSPD2 distinguishes itself from the other members of the VAP family by the presence of a CRAL-TRIO domain. In this study, we show that MOSPD2 forms ER-lipid droplet (LD) contacts, thanks to its CRAL-TRIO domain. MOSPD2 ensures the attachment of the ER to LDs through a direct protein-membrane interaction. The attachment mechanism involves an amphipathic helix that has an affinity for lipid packing defects present at the surface of LDs. Remarkably, the absence of MOSPD2 markedly disturbs the assembly of lipid droplets. These data show that MOSPD2, in addition to being a general ER receptor for inter-organelle contacts, possesses an additional tethering activity and is specifically implicated in the biology of LDs via its CRAL-TRIO domain.
Collapse
Affiliation(s)
- Mehdi Zouiouich
- IGBMC, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Inserm, UMR-S 1258, Illkirch, France.,CNRS, UMR 7104, Illkirch, France.,Université de Strasbourg, IGBMC UMR 7104- UMR-S 1258, Illkirch, France
| | - Thomas Di Mattia
- IGBMC, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Inserm, UMR-S 1258, Illkirch, France.,CNRS, UMR 7104, Illkirch, France.,Université de Strasbourg, IGBMC UMR 7104- UMR-S 1258, Illkirch, France
| | - Arthur Martinet
- IGBMC, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Inserm, UMR-S 1258, Illkirch, France.,CNRS, UMR 7104, Illkirch, France.,Université de Strasbourg, IGBMC UMR 7104- UMR-S 1258, Illkirch, France
| | - Julie Eichler
- IGBMC, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Inserm, UMR-S 1258, Illkirch, France.,CNRS, UMR 7104, Illkirch, France.,Université de Strasbourg, IGBMC UMR 7104- UMR-S 1258, Illkirch, France
| | - Corinne Wendling
- IGBMC, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Inserm, UMR-S 1258, Illkirch, France.,CNRS, UMR 7104, Illkirch, France.,Université de Strasbourg, IGBMC UMR 7104- UMR-S 1258, Illkirch, France
| | - Nario Tomishige
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France
| | - Erwan Grandgirard
- IGBMC, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Inserm, UMR-S 1258, Illkirch, France.,CNRS, UMR 7104, Illkirch, France.,Université de Strasbourg, IGBMC UMR 7104- UMR-S 1258, Illkirch, France
| | - Nicolas Fuggetta
- Université Côte d'Azur, Centre National de la Recherche Scientifique, Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne, France
| | - Catherine Fromental-Ramain
- IGBMC, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Inserm, UMR-S 1258, Illkirch, France.,CNRS, UMR 7104, Illkirch, France.,Université de Strasbourg, IGBMC UMR 7104- UMR-S 1258, Illkirch, France
| | - Giulia Mizzon
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Heidelberg, Germany
| | - Calvin Dumesnil
- Laboratoire de Physique de l'École Normale Supérieure, Université Paris Sciences and Lettres, Centre National de la Recherche Scientifique, Sorbonne Université, Université de Paris, Paris, France
| | - Maxime Carpentier
- Laboratoire de Physique de l'École Normale Supérieure, Université Paris Sciences and Lettres, Centre National de la Recherche Scientifique, Sorbonne Université, Université de Paris, Paris, France
| | - Bernardo Reina-San-Martin
- IGBMC, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Inserm, UMR-S 1258, Illkirch, France.,CNRS, UMR 7104, Illkirch, France.,Université de Strasbourg, IGBMC UMR 7104- UMR-S 1258, Illkirch, France
| | - Carole Mathelin
- IGBMC, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Inserm, UMR-S 1258, Illkirch, France.,CNRS, UMR 7104, Illkirch, France.,Université de Strasbourg, IGBMC UMR 7104- UMR-S 1258, Illkirch, France.,Institut de Cancérologie Strasbourg Europe, Strasbourg, France
| | - Yannick Schwab
- European Molecular Biology Laboratory, Cell Biology and Biophysics Unit, Heidelberg, Germany
| | - Abdou Rachid Thiam
- Laboratoire de Physique de l'École Normale Supérieure, Université Paris Sciences and Lettres, Centre National de la Recherche Scientifique, Sorbonne Université, Université de Paris, Paris, France
| | - Toshihide Kobayashi
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, Illkirch, France
| | - Guillaume Drin
- Université Côte d'Azur, Centre National de la Recherche Scientifique, Institut de Pharmacologie Moléculaire et Cellulaire, Valbonne, France
| | - Catherine Tomasetto
- IGBMC, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Inserm, UMR-S 1258, Illkirch, France.,CNRS, UMR 7104, Illkirch, France.,Université de Strasbourg, IGBMC UMR 7104- UMR-S 1258, Illkirch, France
| | - Fabien Alpy
- IGBMC, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Inserm, UMR-S 1258, Illkirch, France.,CNRS, UMR 7104, Illkirch, France.,Université de Strasbourg, IGBMC UMR 7104- UMR-S 1258, Illkirch, France
| |
Collapse
|
26
|
Xu Z, Khan S, Schnicker NJ, Baker S. Pentameric assembly of the Kv2.1 tetramerization domain. ACTA CRYSTALLOGRAPHICA SECTION D STRUCTURAL BIOLOGY 2022; 78:792-802. [PMID: 35647925 PMCID: PMC9159280 DOI: 10.1107/s205979832200568x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Accepted: 05/25/2022] [Indexed: 11/25/2022]
Abstract
The selective assembly of Kv subunits into one of four subfamilies of tetrameric, voltage-gated potassium channels is mediated by the T1 tetramerization domain. Here, it was found that unlike the other Kv T1 domains that have been studied to date, the human Kv2.1 T1 domain forms a pentamer, and that zinc binding and electrostatics contribute to the stability of the proteins. The Kv family of voltage-gated potassium channels regulate neuronal excitability. The biophysical characteristics of Kv channels can be matched to the needs of different neurons by forming homotetrameric or heterotetrameric channels within one of four subfamilies. The cytoplasmic tetramerization (T1) domain plays a major role in dictating the compatibility of different Kv subunits. The only Kv subfamily lacking a representative structure of the T1 domain is the Kv2 family. Here, X-ray crystallography was used to solve the structure of the human Kv2.1 T1 domain. The structure is similar to those of other T1 domains, but surprisingly formed a pentamer instead of a tetramer. In solution the Kv2.1 T1 domain also formed a pentamer, as determined by inline SEC–MALS–SAXS and negative-stain electron microscopy. The Kv2.1 T1–T1 interface involves electrostatic interactions, including a salt bridge formed by the negative charges in a previously described CDD motif, and inter-subunit coordination of zinc. It is shown that zinc binding is important for stability. In conclusion, the Kv2.1 T1 domain behaves differently from the other Kv T1 domains, which may reflect the versatility of Kv2.1, which can assemble with the regulatory KvS subunits and scaffold ER–plasma membrane contacts.
Collapse
|
27
|
Abstract
KCNQ2 and KCNQ3 channels are associated with multiple neurodevelopmental disorders and are also therapeutic targets for neurological and neuropsychiatric diseases. For more than two decades, it has been thought that most KCNQ channels in the brain are either KCNQ2/3 or KCNQ3/5 heteromers. Here, we investigated the potential heteromeric compositions of KCNQ2-containing channels. We applied split-intein protein trans-splicing to form KCNQ2/5 tandems and coexpressed these with and without KCNQ3. Unexpectedly, we found that KCNQ2/5 tandems form functional channels independent of KCNQ3 in heterologous cells. Using mass spectrometry, we went on to demonstrate that KCNQ2 associates with KCNQ5 in native channels in the brain, even in the absence of KCNQ3. Additionally, our functional heterologous expression data are consistent with the formation of KCNQ2/3/5 heteromers. Thus, the composition of KCNQ channels is more diverse than has been previously recognized, necessitating a re-examination of the genotype/phenotype relationship of KCNQ2 pathogenic variants.
Collapse
|
28
|
Kors S, Hacker C, Bolton C, Maier R, Reimann L, Kitchener EJA, Warscheid B, Costello JL, Schrader M. Regulating peroxisome-ER contacts via the ACBD5-VAPB tether by FFAT motif phosphorylation and GSK3β. J Cell Biol 2022; 221:212956. [PMID: 35019937 DOI: 10.1083/jcb.202003143/212956] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 11/12/2021] [Accepted: 12/15/2021] [Indexed: 05/25/2023] Open
Abstract
Peroxisomes and the endoplasmic reticulum (ER) cooperate in cellular lipid metabolism. They form membrane contacts through interaction of the peroxisomal membrane protein ACBD5 (acyl-coenzyme A-binding domain protein 5) and the ER-resident protein VAPB (vesicle-associated membrane protein-associated protein B). ACBD5 binds to the major sperm protein domain of VAPB via its FFAT-like (two phenylalanines [FF] in an acidic tract) motif. However, molecular mechanisms, which regulate formation of these membrane contact sites, are unknown. Here, we reveal that peroxisome-ER associations via the ACBD5-VAPB tether are regulated by phosphorylation. We show that ACBD5-VAPB binding is phosphatase-sensitive and identify phosphorylation sites in the flanking regions and core of the FFAT-like motif, which alter interaction with VAPB-and thus peroxisome-ER contact sites-differently. Moreover, we demonstrate that GSK3β (glycogen synthase kinase-3 β) regulates this interaction. Our findings reveal for the first time a molecular mechanism for the regulation of peroxisome-ER contacts in mammalian cells and expand the current model of FFAT motifs and VAP interaction.
Collapse
Affiliation(s)
- Suzan Kors
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, UK
| | - Christian Hacker
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, UK
| | - Chloe Bolton
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, UK
| | - Renate Maier
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Lena Reimann
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Emily J A Kitchener
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, UK
| | - Bettina Warscheid
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, Freiburg, Germany
- Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Joseph L Costello
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, UK
| | - Michael Schrader
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, UK
| |
Collapse
|
29
|
Kors S, Hacker C, Bolton C, Maier R, Reimann L, Kitchener EJA, Warscheid B, Costello JL, Schrader M. Regulating peroxisome-ER contacts via the ACBD5-VAPB tether by FFAT motif phosphorylation and GSK3β. J Cell Biol 2022; 221:212956. [PMID: 35019937 PMCID: PMC8759595 DOI: 10.1083/jcb.202003143] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 11/12/2021] [Accepted: 12/15/2021] [Indexed: 12/18/2022] Open
Abstract
Peroxisomes and the endoplasmic reticulum (ER) cooperate in cellular lipid metabolism. They form membrane contacts through interaction of the peroxisomal membrane protein ACBD5 (acyl-coenzyme A–binding domain protein 5) and the ER-resident protein VAPB (vesicle-associated membrane protein–associated protein B). ACBD5 binds to the major sperm protein domain of VAPB via its FFAT-like (two phenylalanines [FF] in an acidic tract) motif. However, molecular mechanisms, which regulate formation of these membrane contact sites, are unknown. Here, we reveal that peroxisome–ER associations via the ACBD5-VAPB tether are regulated by phosphorylation. We show that ACBD5-VAPB binding is phosphatase-sensitive and identify phosphorylation sites in the flanking regions and core of the FFAT-like motif, which alter interaction with VAPB—and thus peroxisome–ER contact sites—differently. Moreover, we demonstrate that GSK3β (glycogen synthase kinase-3 β) regulates this interaction. Our findings reveal for the first time a molecular mechanism for the regulation of peroxisome–ER contacts in mammalian cells and expand the current model of FFAT motifs and VAP interaction.
Collapse
Affiliation(s)
- Suzan Kors
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, UK
| | - Christian Hacker
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, UK
| | - Chloe Bolton
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, UK
| | - Renate Maier
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Lena Reimann
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, Freiburg, Germany
| | - Emily J A Kitchener
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, UK
| | - Bettina Warscheid
- Institute of Biology II, Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, Freiburg, Germany.,Centre for Integrative Biological Signalling Studies, University of Freiburg, Freiburg, Germany
| | - Joseph L Costello
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, UK
| | - Michael Schrader
- College of Life and Environmental Sciences, Biosciences, University of Exeter, Exeter, UK
| |
Collapse
|
30
|
Sepela RJ, Stewart RG, Valencia LA, Thapa P, Wang Z, Cohen BE, Sack JT. The AMIGO1 adhesion protein activates Kv2.1 voltage sensors. Biophys J 2022; 121:1395-1416. [PMID: 35314141 PMCID: PMC9072587 DOI: 10.1016/j.bpj.2022.03.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 11/11/2021] [Accepted: 03/16/2022] [Indexed: 11/30/2022] Open
Abstract
Kv2 voltage-gated potassium channels are modulated by amphoterin-induced gene and open reading frame (AMIGO) neuronal adhesion proteins. Here, we identify steps in the conductance activation pathway of Kv2.1 channels that are modulated by AMIGO1 using voltage-clamp recordings and spectroscopy of heterologously expressed Kv2.1 and AMIGO1 in mammalian cell lines. AMIGO1 speeds early voltage-sensor movements and shifts the gating charge-voltage relationship to more negative voltages. The gating charge-voltage relationship indicates that AMIGO1 exerts a larger energetic effect on voltage-sensor movement than is apparent from the midpoint of the conductance-voltage relationship. When voltage sensors are detained at rest by voltage-sensor toxins, AMIGO1 has a greater impact on the conductance-voltage relationship. Fluorescence measurements from voltage-sensor toxins bound to Kv2.1 indicate that with AMIGO1, the voltage sensors enter their earliest resting conformation, yet this conformation is less stable upon voltage stimulation. We conclude that AMIGO1 modulates the Kv2.1 conductance activation pathway by destabilizing the earliest resting state of the voltage sensors.
Collapse
Affiliation(s)
- Rebecka J Sepela
- Department of Physiology and Membrane Biology, University of California, Davis, California
| | - Robert G Stewart
- Department of Physiology and Membrane Biology, University of California, Davis, California
| | - Luis A Valencia
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Parashar Thapa
- Department of Physiology and Membrane Biology, University of California, Davis, California
| | - Zeming Wang
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Bruce E Cohen
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California; Division of Molecular Biophysics & Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, California
| | - Jon T Sack
- Department of Physiology and Membrane Biology, University of California, Davis, California; Department of Anesthesiology and Pain Medicine, University of California, Davis, California.
| |
Collapse
|
31
|
Ion Channel Partnerships: Odd and Not-So-Odd Couples Controlling Neuronal Ion Channel Function. Int J Mol Sci 2022; 23:ijms23041953. [PMID: 35216068 PMCID: PMC8878034 DOI: 10.3390/ijms23041953] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Revised: 02/05/2022] [Accepted: 02/08/2022] [Indexed: 12/04/2022] Open
Abstract
The concerted function of the large number of ion channels expressed in excitable cells, including brain neurons, shapes diverse signaling events by controlling the electrical properties of membranes. It has long been recognized that specific groups of ion channels are functionally coupled in mediating ionic fluxes that impact membrane potential, and that these changes in membrane potential impact ion channel gating. Recent studies have identified distinct sets of ion channels that can also physically and functionally associate to regulate the function of either ion channel partner beyond that afforded by changes in membrane potential alone. Here, we review canonical examples of such ion channel partnerships, in which a Ca2+ channel is partnered with a Ca2+-activated K+ channel to provide a dedicated route for efficient coupling of Ca2+ influx to K+ channel activation. We also highlight examples of non-canonical ion channel partnerships between Ca2+ channels and voltage-gated K+ channels that are not intrinsically Ca2+ sensitive, but whose partnership nonetheless yields enhanced regulation of one or the other ion channel partner. We also discuss how these ion channel partnerships can be shaped by the subcellular compartments in which they are found and provide perspectives on how recent advances in techniques to identify proteins in close proximity to one another in native cells may lead to an expanded knowledge of other ion channel partnerships.
Collapse
|
32
|
Dickson EJ. Phosphoinositide transport and metabolism at membrane contact sites. Biochim Biophys Acta Mol Cell Biol Lipids 2022; 1867:159107. [PMID: 34995791 DOI: 10.1016/j.bbalip.2021.159107] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 12/06/2021] [Accepted: 12/09/2021] [Indexed: 11/18/2022]
Abstract
Phosphoinositides are a family of signaling lipids that play a profound role in regulating protein function at the membrane-cytosol interface of all cellular membranes. Underscoring their importance, mutations or alterations in phosphoinositide metabolizing enzymes lead to host of developmental, neurodegenerative, and metabolic disorders that are devastating for human health. In addition to lipid enzymes, phosphoinositide metabolism is regulated and controlled at membrane contact sites (MCS). Regions of close opposition typically between the ER and other cellular membranes, MCS are non-vesicular lipid transport portals that engage in extensive communication to influence organelle homeostasis. This review focuses on lipid transport, specifically phosphoinositide lipid transport and metabolism at MCS.
Collapse
Affiliation(s)
- Eamonn J Dickson
- Department of Physiology and Membrane Biology, University of California, Davis, CA 95616, United States of America.
| |
Collapse
|
33
|
Kors S, Costello JL, Schrader M. VAP Proteins - From Organelle Tethers to Pathogenic Host Interactors and Their Role in Neuronal Disease. Front Cell Dev Biol 2022; 10:895856. [PMID: 35756994 PMCID: PMC9213790 DOI: 10.3389/fcell.2022.895856] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 04/25/2022] [Indexed: 12/26/2022] Open
Abstract
Vesicle-associated membrane protein (VAMP)-associated proteins (VAPs) are ubiquitous ER-resident tail-anchored membrane proteins in eukaryotic cells. Their N-terminal major sperm protein (MSP) domain faces the cytosol and allows them to interact with a wide variety of cellular proteins. Therefore, VAP proteins are vital to many cellular processes, including organelle membrane tethering, lipid transfer, autophagy, ion homeostasis and viral defence. Here, we provide a timely overview of the increasing number of VAPA/B binding partners and discuss the role of VAPA/B in maintaining organelle-ER interactions and cooperation. Furthermore, we address how viruses and intracellular bacteria hijack VAPs and their binding partners to induce interactions between the host ER and pathogen-containing compartments and support pathogen replication. Finally, we focus on the role of VAP in human disease and discuss how mutated VAPB leads to the disruption of cellular homeostasis and causes amyotrophic lateral sclerosis.
Collapse
Affiliation(s)
- Suzan Kors
- *Correspondence: Suzan Kors, ; Michael Schrader,
| | | | | |
Collapse
|
34
|
Dixon RE, Navedo MF, Binder MD, Santana LF. Mechanisms and Physiological Implications of Cooperative Gating of Ion Channels Clusters. Physiol Rev 2021; 102:1159-1210. [PMID: 34927454 DOI: 10.1152/physrev.00022.2021] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Ion channels play a central role in the regulation of nearly every cellular process. Dating back to the classic 1952 Hodgkin-Huxley model of the generation of the action potential, ion channels have always been thought of as independent agents. A myriad of recent experimental findings exploiting advances in electrophysiology, structural biology, and imaging techniques, however, have posed a serious challenge to this long-held axiom as several classes of ion channels appear to open and close in a coordinated, cooperative manner. Ion channel cooperativity ranges from variable-sized oligomeric cooperative gating in voltage-gated, dihydropyridine-sensitive Cav1.2 and Cav1.3 channels to obligatory dimeric assembly and gating of voltage-gated Nav1.5 channels. Potassium channels, transient receptor potential channels, hyperpolarization cyclic nucleotide-activated channels, ryanodine receptors (RyRs), and inositol trisphosphate receptors (IP3Rs) have also been shown to gate cooperatively. The implications of cooperative gating of these ion channels range from fine tuning excitation-contraction coupling in muscle cells to regulating cardiac function and vascular tone, to modulation of action potential and conduction velocity in neurons and cardiac cells, and to control of pace-making activity in the heart. In this review, we discuss the mechanisms leading to cooperative gating of ion channels, their physiological consequences and how alterations in cooperative gating of ion channels may induce a range of clinically significant pathologies.
Collapse
Affiliation(s)
- Rose Ellen Dixon
- Department of Physiology and Membrane Biology, University of California, Davis, CA, United States
| | - Manuel F Navedo
- Department of Pharmacology, University of California, Davis, CA, United States
| | - Marc D Binder
- Department of Physiology and Biophysics, University of Washington, Seattle, WA, United States
| | - L Fernando Santana
- Department of Physiology and Membrane Biology, University of California, Davis, CA, United States
| |
Collapse
|
35
|
Ptak C, Saik NO, Premashankar A, Lapetina DL, Aitchison JD, Montpetit B, Wozniak RW. Phosphorylation-dependent mitotic SUMOylation drives nuclear envelope-chromatin interactions. J Cell Biol 2021; 220:212843. [PMID: 34787675 PMCID: PMC8641411 DOI: 10.1083/jcb.202103036] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 07/30/2021] [Accepted: 09/22/2021] [Indexed: 12/15/2022] Open
Abstract
In eukaryotes, chromatin binding to the inner nuclear membrane (INM) and nuclear pore complexes (NPCs) contributes to spatial organization of the genome and epigenetic programs important for gene expression. In mitosis, chromatin–nuclear envelope (NE) interactions are lost and then formed again as sister chromosomes segregate to postmitotic nuclei. Investigating these processes in S. cerevisiae, we identified temporally and spatially controlled phosphorylation-dependent SUMOylation events that positively regulate postmetaphase chromatin association with the NE. Our work establishes a phosphorylation-mediated targeting mechanism of the SUMO ligase Siz2 to the INM during mitosis, where Siz2 binds to and SUMOylates the VAP protein Scs2. The recruitment of Siz2 through Scs2 is further responsible for a wave of SUMOylation along the INM that supports the assembly and anchorage of subtelomeric chromatin at the INM and localization of an active gene (INO1) to NPCs during the later stages of mitosis and into G1-phase.
Collapse
Affiliation(s)
- Christopher Ptak
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada
| | - Natasha O Saik
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada
| | | | - Diego L Lapetina
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada
| | | | - Ben Montpetit
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada.,Department of Viticulture and Enology, University of California Davis, Davis, CA
| | - Richard W Wozniak
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada
| |
Collapse
|
36
|
Regulation of neuronal excitation-transcription coupling by Kv2.1-induced clustering of somatic L-type Ca 2+ channels at ER-PM junctions. Proc Natl Acad Sci U S A 2021; 118:2110094118. [PMID: 34750263 PMCID: PMC8609631 DOI: 10.1073/pnas.2110094118] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2021] [Indexed: 11/18/2022] Open
Abstract
In hippocampal neurons, gene expression is triggered by electrical activity and Ca2+ entry via L-type Cav1.2 channels in a process called excitation–transcription coupling. We identified a domain on the voltage-gated K+ channel Kv2.1 that promotes the clustering of L-type Cav1.2 channels at endoplasmic reticulum–plasma membrane junctions in the soma of neurons. Importantly, we discovered by disrupting this domain that the Kv2.1-mediated clustering of Cav1.2 at this somatic microdomain is critical for depolarization-induced excitation–transcription coupling. In mammalian brain neurons, membrane depolarization leads to voltage-gated Ca2+ channel-mediated Ca2+ influx that triggers diverse cellular responses, including gene expression, in a process termed excitation–transcription coupling. Neuronal L-type Ca2+ channels, which have prominent populations on the soma and distal dendrites of hippocampal neurons, play a privileged role in excitation–transcription coupling. The voltage-gated K+ channel Kv2.1 organizes signaling complexes containing the L-type Ca2+ channel Cav1.2 at somatic endoplasmic reticulum–plasma membrane junctions. This leads to enhanced clustering of Cav1.2 channels, increasing their activity. However, the downstream consequences of the Kv2.1-mediated regulation of Cav1.2 localization and function on excitation–transcription coupling are not known. Here, we have identified a region between residues 478 to 486 of Kv2.1’s C terminus that mediates the Kv2.1-dependent clustering of Cav1.2. By disrupting this Ca2+ channel association domain with either mutations or with a cell-penetrating interfering peptide, we blocked the Kv2.1-mediated clustering of Cav1.2 at endoplasmic reticulum–plasma membrane junctions and the subsequent enhancement of its channel activity and somatic Ca2+ signals without affecting the clustering of Kv2.1. These interventions abolished the depolarization-induced and L-type Ca2+ channel-dependent phosphorylation of the transcription factor CREB and the subsequent expression of c-Fos in hippocampal neurons. Our findings support a model whereby the Kv2.1-Ca2+ channel association domain-mediated clustering of Cav1.2 channels imparts a mechanism to control somatic Ca2+ signals that couple neuronal excitation to gene expression.
Collapse
|
37
|
Thapa P, Stewart R, Sepela RJ, Vivas O, Parajuli LK, Lillya M, Fletcher-Taylor S, Cohen BE, Zito K, Sack JT. EVAP: A two-photon imaging tool to study conformational changes in endogenous Kv2 channels in live tissues. J Gen Physiol 2021; 153:212666. [PMID: 34581724 PMCID: PMC8480965 DOI: 10.1085/jgp.202012858] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Accepted: 09/03/2021] [Indexed: 12/29/2022] Open
Abstract
A primary goal of molecular physiology is to understand how conformational changes of proteins affect the function of cells, tissues, and organisms. Here, we describe an imaging method for measuring the conformational changes of the voltage sensors of endogenous ion channel proteins within live tissue, without genetic modification. We synthesized GxTX-594, a variant of the peptidyl tarantula toxin guangxitoxin-1E, conjugated to a fluorophore optimal for two-photon excitation imaging through light-scattering tissue. We term this tool EVAP (Endogenous Voltage-sensor Activity Probe). GxTX-594 targets the voltage sensors of Kv2 proteins, which form potassium channels and plasma membrane–endoplasmic reticulum junctions. GxTX-594 dynamically labels Kv2 proteins on cell surfaces in response to voltage stimulation. To interpret dynamic changes in fluorescence intensity, we developed a statistical thermodynamic model that relates the conformational changes of Kv2 voltage sensors to degree of labeling. We used two-photon excitation imaging of rat brain slices to image Kv2 proteins in neurons. We found puncta of GxTX-594 on hippocampal CA1 neurons that responded to voltage stimulation and retain a voltage response roughly similar to heterologously expressed Kv2.1 protein. Our findings show that EVAP imaging methods enable the identification of conformational changes of endogenous Kv2 voltage sensors in tissue.
Collapse
Affiliation(s)
- Parashar Thapa
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Robert Stewart
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Rebecka J Sepela
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Oscar Vivas
- Center for Neuroscience, University of California, Davis, Davis, CA
| | - Laxmi K Parajuli
- Center for Neuroscience, University of California, Davis, Davis, CA
| | - Mark Lillya
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA
| | - Sebastian Fletcher-Taylor
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA.,The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA
| | - Bruce E Cohen
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA.,Division of Molecular Biophysics and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA
| | - Karen Zito
- Center for Neuroscience, University of California, Davis, Davis, CA
| | - Jon T Sack
- Department of Physiology and Membrane Biology, University of California, Davis, Davis, CA.,Department of Anesthesiology and Pain Medicine, University of California, Davis, Davis, CA
| |
Collapse
|
38
|
Borgese N, Iacomino N, Colombo SF, Navone F. The Link between VAPB Loss of Function and Amyotrophic Lateral Sclerosis. Cells 2021; 10:1865. [PMID: 34440634 PMCID: PMC8392409 DOI: 10.3390/cells10081865] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 07/16/2021] [Accepted: 07/16/2021] [Indexed: 02/06/2023] Open
Abstract
The VAP proteins are integral adaptor proteins of the endoplasmic reticulum (ER) membrane that recruit a myriad of interacting partners to the ER surface. Through these interactions, the VAPs mediate a large number of processes, notably the generation of membrane contact sites between the ER and essentially all other cellular membranes. In 2004, it was discovered that a mutation (p.P56S) in the VAPB paralogue causes a rare form of dominantly inherited familial amyotrophic lateral sclerosis (ALS8). The mutant protein is aggregation-prone, non-functional and unstable, and its expression from a single allele appears to be insufficient to support toxic gain-of-function effects within motor neurons. Instead, loss-of-function of the single wild-type allele is required for pathological effects, and VAPB haploinsufficiency may be the main driver of the disease. In this article, we review the studies on the effects of VAPB deficit in cellular and animal models. Several basic cell physiological processes are affected by downregulation or complete depletion of VAPB, impinging on phosphoinositide homeostasis, Ca2+ signalling, ion transport, neurite extension, and ER stress. In the future, the distinction between the roles of the two VAP paralogues (A and B), as well as studies on motor neurons generated from induced pluripotent stem cells (iPSC) of ALS8 patients will further elucidate the pathogenic basis of p.P56S familial ALS, as well as of other more common forms of the disease.
Collapse
Affiliation(s)
- Nica Borgese
- CNR Institute of Neuroscience, Via Follereau 3, Bldg U28, 20854 Vedano al Lambro, Italy; (N.I.); (S.F.C.)
| | | | | | - Francesca Navone
- CNR Institute of Neuroscience, Via Follereau 3, Bldg U28, 20854 Vedano al Lambro, Italy; (N.I.); (S.F.C.)
| |
Collapse
|
39
|
Chen J, Bassot A, Giuliani F, Simmen T. Amyotrophic Lateral Sclerosis (ALS): Stressed by Dysfunctional Mitochondria-Endoplasmic Reticulum Contacts (MERCs). Cells 2021; 10:cells10071789. [PMID: 34359958 PMCID: PMC8304209 DOI: 10.3390/cells10071789] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 07/12/2021] [Accepted: 07/13/2021] [Indexed: 02/06/2023] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease for which there is currently no cure. Progress in the characterization of other neurodegenerative mechanisms has shifted the spotlight onto an intracellular structure called mitochondria-endoplasmic reticulum (ER) contacts (MERCs) whose ER portion can be biochemically isolated as mitochondria-associated membranes (MAMs). Within the central nervous system (CNS), these structures control the metabolic output of mitochondria and keep sources of oxidative stress in check via autophagy. The most relevant MERC controllers in the ALS pathogenesis are vesicle-associated membrane protein-associated protein B (VAPB), a mitochondria-ER tether, and the ubiquitin-specific chaperone valosin containing protein (VCP). These two systems cooperate to maintain mitochondrial energy output and prevent oxidative stress. In ALS, mutant VAPB and VCP take a central position in the pathology through MERC dysfunction that ultimately alters or compromises mitochondrial bioenergetics. Intriguingly, both proteins are targets themselves of other ALS mutant proteins, including C9orf72, FUS, or TDP-43. Thus, a new picture emerges, where different triggers cause MERC dysfunction in ALS, subsequently leading to well-known pathological changes including endoplasmic reticulum (ER) stress, inflammation, and motor neuron death.
Collapse
Affiliation(s)
- Junsheng Chen
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G2H7, Canada; (J.C.); (A.B.)
| | - Arthur Bassot
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G2H7, Canada; (J.C.); (A.B.)
| | - Fabrizio Giuliani
- Department of Medicine (Neurology), Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G2H7, Canada;
| | - Thomas Simmen
- Department of Cell Biology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G2H7, Canada; (J.C.); (A.B.)
- Correspondence: ; Tel.: +1-780-492-1546
| |
Collapse
|
40
|
Maverick EE, Leek AN, Tamkun MM. Kv2 channel-AMIGO β-subunit assembly modulates both channel function and cell adhesion molecule surface trafficking. J Cell Sci 2021; 134:jcs256339. [PMID: 34137443 PMCID: PMC8255027 DOI: 10.1242/jcs.256339] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 05/17/2021] [Indexed: 11/20/2022] Open
Abstract
The Kv2 channels encode delayed rectifier currents that regulate membrane potential in many tissues. They also have a non-conducting function to form stable junctions between the endoplasmic reticulum and plasma membranes, creating membrane contact sites that mediate functions distinct from membrane excitability. Therefore, proteins that interact with Kv2.1 and Kv2.2 channels can alter conducting and/or non-conducting channel properties. One member of the AMIGO family of proteins is an auxiliary β-subunit for Kv2 channels and modulates Kv2.1 electrical activity. However, the AMIGO family has two additional members of ∼50% similarity that have not yet been characterized as Kv2 β-subunits. In this work, we show that the surface trafficking and localization of all three AMIGOs are controlled by their assembly with both Kv2 channels. Additionally, assembly of each AMIGO with either Kv2.1 or Kv2.2 hyperpolarizes the channel activation midpoint by -10 mV. However, only AMIGO2 significantly slows inactivation and deactivation, leading to a prolonged open state of Kv2 channels. The co-regulatory effects of Kv2s and AMIGOs likely fine-tune both the electrical and non-electrical properties of the cells in which they are expressed.
Collapse
Affiliation(s)
- Emily E. Maverick
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
- Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO 80523, USA
| | - Ashley N. Leek
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
- Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO 80523, USA
| | - Michael M. Tamkun
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
- Molecular, Cellular and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO 80523, USA
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA
| |
Collapse
|
41
|
Almeida C. A potential third-order role of the host endoplasmic reticulum as a contact site in interkingdom microbial endosymbiosis and viral infection. ENVIRONMENTAL MICROBIOLOGY REPORTS 2021; 13:255-271. [PMID: 33559322 DOI: 10.1111/1758-2229.12938] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 02/04/2021] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
The normal functioning of eukaryotic cells depends on the compartmentalization of metabolic processes within specific organelles. Interactions among organelles, such as those between the endoplasmic reticulum (ER) - considered the largest single structure in eukaryotic cells - and other organelles at membrane contact sites (MCSs) have also been suggested to trigger synergisms, including intracellular immune responses against pathogens. In addition to the ER-endogenous functions and ER-organelle MCSs, we present the perspective of a third-order role of the ER as a host contact site for endosymbiotic microbial non-pathogens and pathogens, from endosymbiont bacteria to parasitic protists and viruses. Although understudied, ER-endosymbiont interactions have been observed in a range of eukaryotic hosts, including protists, plants, algae, and metazoans. Host ER interactions with endosymbionts could be an ER function built from ancient, conserved mechanisms selected for communicating with mutualistic endosymbionts in specific life cycle stages, and they may be exploited by pathogens and parasites. The host ER-'guest' interactome and traits in endosymbiotic biology are briefly discussed. The acknowledgment and understanding of these possible mechanisms might reveal novel evolutionary perspectives, uncover the causes of unexplained cellular disorders and suggest new pharmacological targets.
Collapse
Affiliation(s)
- Celso Almeida
- ENDOBIOS Biotech®, Praceta Progresso Clube n° 6, 2725-110 Mem-Martins, Portugal
| |
Collapse
|
42
|
Essential Role of Somatic Kv2 Channels in High-Frequency Firing in Cartwheel Cells of the Dorsal Cochlear Nucleus. eNeuro 2021; 8:ENEURO.0515-20.2021. [PMID: 33837049 PMCID: PMC8116111 DOI: 10.1523/eneuro.0515-20.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 03/23/2021] [Accepted: 03/24/2021] [Indexed: 11/29/2022] Open
Abstract
Among all voltage-gated potassium (Kv) channels, Kv2 channels are the most widely expressed in the mammalian brain. However, studying Kv2 in neurons has been challenging because of a lack of high-selective blockers. Recently, a peptide toxin, guangxitoxin-1E (GxTX), has been identified as a specific inhibitor of Kv2, thus facilitating the study of Kv2 in neurons. The mammalian dorsal cochlear nucleus (DCN) integrates auditory and somatosensory information. In the DCN, cartwheel inhibitory interneurons receive excitatory synaptic inputs from parallel fibers conveying somatosensory information. The activation of parallel fibers drives action potentials in the cartwheel cells up to 130 Hz in vivo, and the excitation of cartwheel cells leads to the strong inhibition of principal cells. Therefore, cartwheel cells play crucial roles in monaural sound localization and cancelling detection of self-generated sounds. However, how Kv2 controls the high-frequency firing in cartwheel cells is unknown. In this study, we performed immunofluorescence labeling with anti-Kv2.1 and anti-Kv2.2 antibodies using fixed mouse brainstem slice preparations. The results revealed that Kv2.1 and Kv2.2 were largely present on the cartwheel cell body membrane but not on the axon initial segment (AIS) nor the proximal dendrite. Whole-cell patch-clamp recordings using mouse brainstem slice preparation and GxTX demonstrated that blockade of Kv2 induced failure of parallel fiber-induced action potentials when parallel fibers were stimulated at high frequencies (30–100 Hz). Thus, somatic Kv2 in cartwheel cells regulates the action potentials in a frequency-dependent manner and may play important roles in the DCN function.
Collapse
|
43
|
Kissane RWP, Ghaffari-Rafi A, Tickle PG, Chakrabarty S, Egginton S, Brownstone RM, Smith CC. C-bouton components on rat extensor digitorum longus motoneurons are resistant to chronic functional overload. J Anat 2021; 241:1157-1168. [PMID: 33939175 PMCID: PMC9558151 DOI: 10.1111/joa.13439] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 02/06/2023] Open
Abstract
Mammalian motor systems adapt to the demands of their environment. For example, muscle fibre types change in response to increased load or endurance demands. However, for adaptations to be effective, motoneurons must adapt such that their properties match those of the innervated muscle fibres. We used a rat model of chronic functional overload to assess adaptations to both motoneuron size and a key modulatory synapse responsible for amplification of motor output, C‐boutons. Overload of extensor digitorum longus (EDL) muscles was induced by removal of their synergists, tibialis anterior muscles. Following 21 days survival, EDL muscles showed an increase in fatigue resistance and a decrease in force output, indicating a shift to a slower phenotype. These changes were reflected by a decrease in motoneuron size. However, C‐bouton complexes remained largely unaffected by overload. The C‐boutons themselves, quantified by expression of vesicular acetylcholine transporter, were similar in size and density in the control and overload conditions. Expression of the post‐synaptic voltage‐gated potassium channel (KV2.1) was also unchanged. Small conductance calcium‐activated potassium channels (SK3) were expressed in most EDL motoneurons, despite this being an almost exclusively fast motor pool. Overload induced a decrease in the proportion of SK3+ cells, however, there was no change in density or size of clusters. We propose that reductions in motoneuron size may promote early recruitment of EDL motoneurons, but that C‐bouton plasticity is not necessary to increase the force output required in response to muscle overload.
Collapse
Affiliation(s)
- Roger W P Kissane
- Institute of Ageing & Chronic Disease, University of Liverpool, Liverpool, UK.,School of Biomedical Sciences, University of Leeds, Leeds, UK
| | - Arash Ghaffari-Rafi
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Peter G Tickle
- School of Biomedical Sciences, University of Leeds, Leeds, UK
| | | | - Stuart Egginton
- School of Biomedical Sciences, University of Leeds, Leeds, UK
| | - Robert M Brownstone
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
| | - Calvin C Smith
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, University College London, London, UK
| |
Collapse
|
44
|
Guillén-Samander A, Leonzino M, Hanna MG, Tang N, Shen H, De Camilli P. VPS13D bridges the ER to mitochondria and peroxisomes via Miro. J Cell Biol 2021; 220:e202010004. [PMID: 33891013 PMCID: PMC8077184 DOI: 10.1083/jcb.202010004] [Citation(s) in RCA: 76] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 01/08/2021] [Accepted: 02/17/2021] [Indexed: 12/12/2022] Open
Abstract
Mitochondria, which are excluded from the secretory pathway, depend on lipid transport proteins for their lipid supply from the ER, where most lipids are synthesized. In yeast, the outer mitochondrial membrane GTPase Gem1 is an accessory factor of ERMES, an ER-mitochondria tethering complex that contains lipid transport domains and that functions, partially redundantly with Vps13, in lipid transfer between the two organelles. In metazoa, where VPS13, but not ERMES, is present, the Gem1 orthologue Miro was linked to mitochondrial dynamics but not to lipid transport. Here we show that Miro, including its peroxisome-enriched splice variant, recruits the lipid transport protein VPS13D, which in turn binds the ER in a VAP-dependent way and thus could provide a lipid conduit between the ER and mitochondria. These findings reveal a so far missing link between function(s) of Gem1/Miro in yeast and higher eukaryotes, where Miro is a Parkin substrate, with potential implications for Parkinson's disease pathogenesis.
Collapse
Affiliation(s)
- Andrés Guillén-Samander
- Departments of Neuroscience and of Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD
| | - Marianna Leonzino
- Departments of Neuroscience and of Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD
| | - Michael G. Hanna
- Departments of Neuroscience and of Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT
| | - Ni Tang
- Departments of Neuroscience and of Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD
| | - Hongying Shen
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT
- Systems Biology Institute, Yale West Campus, West Haven, CT
| | - Pietro De Camilli
- Departments of Neuroscience and of Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, CT
- Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, MD
| |
Collapse
|
45
|
Venditti R, Wilson C, De Matteis MA. Regulation and physiology of membrane contact sites. Curr Opin Cell Biol 2021; 71:148-157. [PMID: 33932623 DOI: 10.1016/j.ceb.2021.03.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 03/18/2021] [Accepted: 03/22/2021] [Indexed: 12/14/2022]
Abstract
Membrane contact sites (MCSs) in addition to impacting the functions of membrane-limited organelles also have a role in the spatial and functional organization of cells, tissues and whole organisms. MCSs have been identified between all organelles and the identification of their molecular composition has progressed significantly in recent years. Equally important is how MCSs respond dynamically to physiological stimuli, how this is regulated, and the physiological roles of MCSs in tissues and at the organismal level, an area that still remains relatively unexplored. In the present review, we focus on the regulation of MCSs, considerations of their function at the organismal level, and how mutations of MCS components linked to genetic diseases might inform us about their physiological relevance.
Collapse
Affiliation(s)
- Rossella Venditti
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy; Department of Molecular Medicine and Medical Biotechnology, University of Napoli Federico II-Medical School, Naples, Italy
| | - Cathal Wilson
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy
| | - Maria Antonietta De Matteis
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy; Department of Molecular Medicine and Medical Biotechnology, University of Napoli Federico II-Medical School, Naples, Italy.
| |
Collapse
|
46
|
Li C, Qian T, He R, Wan C, Liu Y, Yu H. Endoplasmic Reticulum-Plasma Membrane Contact Sites: Regulators, Mechanisms, and Physiological Functions. Front Cell Dev Biol 2021; 9:627700. [PMID: 33614657 PMCID: PMC7889955 DOI: 10.3389/fcell.2021.627700] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 01/13/2021] [Indexed: 12/13/2022] Open
Abstract
The endoplasmic reticulum (ER) forms direct membrane contact sites with the plasma membrane (PM) in eukaryotic cells. These ER-PM contact sites play essential roles in lipid homeostasis, ion dynamics, and cell signaling, which are carried out by protein-protein or protein-lipid interactions. Distinct tethering factors dynamically control the architecture of ER-PM junctions in response to intracellular signals or external stimuli. The physiological roles of ER-PM contact sites are dependent on a variety of regulators that individually or cooperatively perform functions in diverse cellular processes. This review focuses on proteins functioning at ER-PM contact sites and highlights the recent progress in their mechanisms and physiological roles.
Collapse
Affiliation(s)
- Chenlu Li
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Tiantian Qian
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Ruyue He
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Chun Wan
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, CO, United States
| | - Yinghui Liu
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - Haijia Yu
- Jiangsu Key Laboratory for Molecular and Medical Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| |
Collapse
|
47
|
Deardorff AS, Romer SH, Fyffe RE. Location, location, location: the organization and roles of potassium channels in mammalian motoneurons. J Physiol 2021; 599:1391-1420. [DOI: 10.1113/jp278675] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 01/08/2021] [Indexed: 11/08/2022] Open
Affiliation(s)
- Adam S. Deardorff
- Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine Dayton OH 45435 USA
- Department of Neurology and Internal Medicine, Wright State University Boonshoft School of Medicine Dayton OH 45435 USA
| | - Shannon H. Romer
- Odyssey Systems Environmental Health Effects Laboratory, Navy Medical Research Unit‐Dayton Wright‐Patterson Air Force Base OH 45433 USA
| | - Robert E.W. Fyffe
- Department of Neuroscience, Cell Biology and Physiology, Wright State University Boonshoft School of Medicine Dayton OH 45435 USA
| |
Collapse
|
48
|
TSUBOI M, HIRABAYASHI Y. New insights into the regulation of synaptic transmission and plasticity by the endoplasmic reticulum and its membrane contacts. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2021; 97:559-572. [PMID: 34897182 PMCID: PMC8687855 DOI: 10.2183/pjab.97.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2021] [Accepted: 10/18/2021] [Indexed: 06/14/2023]
Abstract
Mammalian neurons are highly compartmentalized yet very large cells. To provide each compartment with its distinct properties, metabolic homeostasis and molecular composition need to be precisely coordinated in a compartment-specific manner. Despite the importance of the endoplasmic reticulum (ER) as a platform for various biochemical reactions, such as protein synthesis, protein trafficking, and intracellular calcium control, the contribution of the ER to neuronal compartment-specific functions and plasticity remains elusive. Recent advances in the development of live imaging and serial scanning electron microscopy (sSEM) analysis have revealed that the neuronal ER is a highly dynamic organelle with compartment-specific structures. sSEM studies also revealed that the ER forms contacts with other membranes, such as the mitochondria and plasma membrane, although little is known about the functions of these ER-membrane contacts. In this review, we discuss the mechanisms and physiological roles of the ER structure and ER-mitochondria contacts in synaptic transmission and plasticity, thereby highlighting a potential link between organelle ultrastructure and neuronal functions.
Collapse
Affiliation(s)
- Masafumi TSUBOI
- Graduate School of Engineering, The University of Tokyo, Tokyo, Japan
| | | |
Collapse
|
49
|
Lin S, Meng T, Huang H, Zhuang H, He Z, Yang H, Feng D. Molecular machineries and physiological relevance of ER-mediated membrane contacts. Theranostics 2021; 11:974-995. [PMID: 33391516 PMCID: PMC7738843 DOI: 10.7150/thno.51871] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 10/22/2020] [Indexed: 02/06/2023] Open
Abstract
Membrane contact sites (MCSs) are defined as regions where two organelles are closely apposed, and most MCSs associated with each other via protein-protein or protein-lipid interactions. A number of key molecular machinery systems participate in mediating substance exchange and signal transduction, both of which are essential processes in terms of cellular physiology and pathophysiology. The endoplasmic reticulum (ER) is the largest reticulum network within the cell and has extensive communication with other cellular organelles, including the plasma membrane (PM), mitochondria, Golgi, endosomes and lipid droplets (LDs). The contacts and reactions between them are largely mediated by various protein tethers and lipids. Ions, lipids and even proteins can be transported between the ER and neighboring organelles or recruited to the contact site to exert their functions. This review focuses on the key molecules involved in the formation of different contact sites as well as their biological functions.
Collapse
|
50
|
Klemm RW. Getting in Touch Is an Important Step: Control of Metabolism at Organelle Contact Sites. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2021; 4:2515256421993708. [PMID: 37366381 PMCID: PMC10243586 DOI: 10.1177/2515256421993708] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 01/19/2021] [Accepted: 01/19/2021] [Indexed: 06/28/2023]
Abstract
Metabolic pathways are often spread over several organelles and need to be functionally integrated by controlled organelle communication. Physical organelle contact-sites have emerged as critical hubs in the regulation of cellular metabolism, but the molecular understanding of mechanisms that mediate formation or regulation of organelle interfaces was until recently relatively limited. Mitochondria are central organelles in anabolic and catabolic pathways and therefore interact with a number of other cellular compartments including the endoplasmic reticulum (ER) and lipid droplets (LDs). An interesting set of recent work has shed new light on the molecular basis forming these contact sites. This brief overview describes the discovery of unanticipated functions of contact sites between the ER, mitochondria and LDs in de novo synthesis of storage lipids of brown and white adipocytes. Interestingly, the factors involved in mediating the interaction between these organelles are subject to unexpected modes of regulation through newly uncovered Phospho-FFAT motifs. These results suggest dynamic regulation of contact sites between organelles and indicate that spatial organization of organelles within the cell contributes to the control of metabolism.
Collapse
Affiliation(s)
- Robin W. Klemm
- Department of Physiology,
Anatomy and Genetics, University of Oxford, UK
| |
Collapse
|