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Zubcevic L, Lee SY. The role of π-helices in TRP channel gating. Curr Opin Struct Biol 2019; 58:314-323. [PMID: 31378426 DOI: 10.1016/j.sbi.2019.06.011] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 06/18/2019] [Accepted: 06/19/2019] [Indexed: 12/21/2022]
Abstract
Transient Receptor Potential (TRP) channels are a large superfamily of polymodal ion channels, which perform important roles in numerous physiological processes. The architecture of their transmembrane (TM) domains closely resembles that of voltage-gated potassium channels (KV). However, recent cryoEM and crystallographic studies of TRP channels have identified π-helices in functionally important regions, and it is increasingly recognized that they utilize a distinct mechanism of gating that relies on α-to-π secondary structure transitions. Here we review our current understanding of the role of π-helices in TRP channel function and their broader impact on different classes of ion channels.
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Affiliation(s)
- Lejla Zubcevic
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, 27710, USA
| | - Seok-Yong Lee
- Department of Biochemistry, Duke University School of Medicine, Durham, NC, 27710, USA.
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52
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Viet KK, Wagner A, Schwickert K, Hellwig N, Brennich M, Bader N, Schirmeister T, Morgner N, Schindelin H, Hellmich UA. Structure of the Human TRPML2 Ion Channel Extracytosolic/Lumenal Domain. Structure 2019; 27:1246-1257.e5. [DOI: 10.1016/j.str.2019.04.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 04/16/2019] [Accepted: 04/29/2019] [Indexed: 11/28/2022]
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53
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Thakore P, Earley S. Transient Receptor Potential Channels and Endothelial Cell Calcium Signaling. Compr Physiol 2019; 9:1249-1277. [PMID: 31187891 DOI: 10.1002/cphy.c180034] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The vascular endothelium is a broadly distributed and highly specialized organ. The endothelium has a number of functions including the control of blood vessels diameter through the production and release of potent vasoactive substances or direct electrical communication with underlying smooth muscle cells, regulates the permeability of the vascular barrier, stimulates the formation of new blood vessels, and influences inflammatory and thrombotic processes. Endothelial cells that make up the endothelium express a variety of cell-surface receptors and ion channels on the plasma membrane that are capable of detecting circulating hormones, neurotransmitters, oxygen tension, and shear stress across the vascular wall. Changes in these stimuli activate signaling cascades that initiate an appropriate physiological response. Increases in the global intracellular Ca2+ concentration and localized Ca2+ signals that occur within specialized subcellular microdomains are fundamentally important components of many signaling pathways in the endothelium. The transient receptor potential (TRP) channels are a superfamily of cation-permeable ion channels that act as a primary means of increasing cytosolic Ca2+ in endothelial cells. Consequently, TRP channels are vitally important for the major functions of the endothelium. In this review, we provide an in-depth discussion of Ca2+ -permeable TRP channels in the endothelium and their role in vascular regulation. © 2019 American Physiological Society. Compr Physiol 9:1249-1277, 2019.
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Affiliation(s)
- Pratish Thakore
- Department of Pharmacology, Center for Cardiovascular Research, University of Nevada, Reno School of Medicine, Reno, Nevada, USA
| | - Scott Earley
- Department of Pharmacology, Center for Cardiovascular Research, University of Nevada, Reno School of Medicine, Reno, Nevada, USA
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54
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Transient Receptor Potential Mucolipin-1 Channels in Glioblastoma: Role in Patient's Survival. Cancers (Basel) 2019; 11:cancers11040525. [PMID: 31013784 PMCID: PMC6521337 DOI: 10.3390/cancers11040525] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Accepted: 04/09/2019] [Indexed: 02/06/2023] Open
Abstract
A link between mucolipin channels and tumors has been recently suggested. Herein, we aim to investigate the transient receptor potential mucolipin (TRPML)-1 relevance in glioblastoma. The expression of this channel was evaluated via qRT-PCR and immunohistochemistry in biopsies from 66 glioblastoma patients and two human glioblastoma cell lines and compared to normal human brain, astrocytes, and epileptic tissues. The subcellular distribution of TRPML-1 was examined via confocal microscopy in the glioma cell lines. Then, to assess the role of TRPML-1, cell viability assays have been conducted in T98 and U251 cell lines treated with the specific TRPML-1 agonist, MK6-83. We found that MK6-83 reduced cell viability and induced caspase-3-dependent apoptosis. Indeed, the TRPML-1 silencing or the blockage of TRPML-1 dependent [Ca2+]i release abrogated these effects. In addition, exposure of glioma cells to the reactive oxygen species (ROS) inducer, carbonyl cyanide m-chlorophenylhydrazone (CCCP), stimulated a TRPML-1-dependent autophagic cell death, as demonstrated by the ability of the autophagic inhibitor bafilomycin A, the TRPML-1 inhibitor sphingomyelin, and the TRPML-1 silencing to completely inhibit the CCCP-mediated effects. To test a possible correlation with patient’s survival, Kaplan–Meier, univariate, and multivariate analysis have been performed. Data showed that the loss/reduction of TRPML-1 mRNA expression strongly correlates with short survival in glioblastoma (GBM) patients, suggesting that the reduction of TRPML-1 expression represents a negative prognostic factor in GBM patients.
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55
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Boudewyn LC, Walkley SU. Current concepts in the neuropathogenesis of mucolipidosis type IV. J Neurochem 2019; 148:669-689. [PMID: 29770442 PMCID: PMC6239999 DOI: 10.1111/jnc.14462] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 04/29/2018] [Accepted: 05/02/2018] [Indexed: 12/11/2022]
Abstract
Mucolipidosis type IV (MLIV) is an autosomal recessive, lysosomal storage disorder causing progressively severe intellectual disability, motor and speech deficits, retinal degeneration often culminating in blindness, and systemic disease causing a shortened lifespan. MLIV results from mutations in the gene MCOLN1 encoding the transient receptor potential channel mucolipin-1. It is an ultra-rare disease and is currently known to affect just over 100 diagnosed individuals. The last decade has provided a wealth of research focused on understanding the role of the enigmatic mucolipin-1 protein in cell and brain function and how its absence causes disease. This review explores our current understanding of the mucolipin-1 protein in relation to neuropathogenesis in MLIV and describes recent findings implicating mucolipin-1's important role in mechanistic target of rapamycin and TFEB (transcription factor EB) signaling feedback loops as well as in the function of the greater endosomal/lysosomal system. In addition to addressing the vital role of mucolipin-1 in the brain, we also report new data on the question of whether haploinsufficiency as would be anticipated in MCOLN1 heterozygotes is associated with any evidence of neuron dysfunction or disease. Greater insights into the role of mucolipin-1 in the nervous system can be expected to shed light not only on MLIV disease but also on numerous processes governing normal brain function. This article is part of the Special Issue "Lysosomal Storage Disorders".
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Affiliation(s)
- Lauren C. Boudewyn
- Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, New York
| | - Steven U. Walkley
- Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Intellectual and Developmental Disabilities Research Center, Albert Einstein College of Medicine, Bronx, New York
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56
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Wheeler S, Schmid R, Sillence DJ. Lipid⁻Protein Interactions in Niemann⁻Pick Type C Disease: Insights from Molecular Modeling. Int J Mol Sci 2019; 20:E717. [PMID: 30736449 PMCID: PMC6387118 DOI: 10.3390/ijms20030717] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 01/31/2019] [Accepted: 02/03/2019] [Indexed: 12/19/2022] Open
Abstract
The accumulation of lipids in the late endosomes and lysosomes of Niemann⁻Pick type C disease (NPCD) cells is a consequence of the dysfunction of one protein (usually NPC1) but induces dysfunction in many proteins. We used molecular docking to propose (a) that NPC1 exports not just cholesterol, but also sphingosine, (b) that the cholesterol sensitivity of big potassium channel (BK) can be traced to a previously unappreciated site on the channel's voltage sensor, (c) that transient receptor potential mucolipin 1 (TRPML1) inhibition by sphingomyelin is likely an indirect effect, and (d) that phosphoinositides are responsible for both the mislocalization of annexin A2 (AnxA2) and a soluble NSF (N-ethylmaleimide Sensitive Fusion) protein attachment receptor (SNARE) recycling defect. These results are set in the context of existing knowledge of NPCD to sketch an account of the endolysosomal pathology key to this disease.
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Affiliation(s)
- Simon Wheeler
- School of Pharmacy, De Montfort University, The Gateway, Leicester LE1 9BH, UK.
| | - Ralf Schmid
- Leicester Institute of Structural and Chemical Biology, Henry Wellcome Building, University of Leicester, Lancaster Road, Leicester LE1 7RH, UK.
| | - Dan J Sillence
- School of Pharmacy, De Montfort University, The Gateway, Leicester LE1 9BH, UK.
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57
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Singh AK, McGoldrick LL, Sobolevsky AI. Expression, Purification, and Crystallization of the Transient Receptor Potential Channel TRPV6. Methods Mol Biol 2019; 1987:23-37. [PMID: 31028671 DOI: 10.1007/978-1-4939-9446-5_2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Transient receptor potential (TRP) channels are polymodal sensory transducers that respond to chemicals, temperature, mechanical stress, and membrane voltage and are involved in vision, taste, olfaction, hearing, touch, thermal perception, and nociception. TRP channels are implicated in numerous devastating diseases, including various forms of cancer, and represent important drug targets. The large sizes, low expression levels, and conformational dynamics of TRP channels make them challenging targets for structural biology. Here, we present the methodology used in structural studies of TRPV6, a TRP channel that is highly selective for calcium and mediates Ca2+ uptake in epithelial tissues. We provide a protocol for the expression, purification, and crystallization of TRPV6. Similar approaches can be used to determine crystal structures of other membrane proteins, including different members of the TRP channel family.
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Affiliation(s)
- Appu K Singh
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA
| | - Luke L McGoldrick
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.,Integrated Program in Cellular, Molecular and Biomedical Studies, Columbia University, New York, NY, USA
| | - Alexander I Sobolevsky
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
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58
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Endolysosomal Ca 2+ Signalling and Cancer Hallmarks: Two-Pore Channels on the Move, TRPML1 Lags Behind! Cancers (Basel) 2018; 11:cancers11010027. [PMID: 30591696 PMCID: PMC6356888 DOI: 10.3390/cancers11010027] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 12/21/2018] [Accepted: 12/21/2018] [Indexed: 12/22/2022] Open
Abstract
The acidic vesicles of the endolysosomal (EL) system are emerging as an intracellular Ca2+ store implicated in the regulation of multiple cellular functions. The EL Ca2+ store releases Ca2+ through a variety of Ca2+-permeable channels, including Transient Receptor Potential (TRP) Mucolipin 1-3 (TRPML1-3) and two-pore channels 1-2 (TPC1-2), whereas EL Ca2+ refilling is sustained by the proton gradient across the EL membrane and/or by the endoplasmic reticulum (ER). EL Ca2+ signals may be either spatially restricted to control vesicle trafficking, autophagy and membrane repair or may be amplified into a global Ca2+ signal through the Ca2+-dependent recruitment of ER-embedded channels. Emerging evidence suggested that nicotinic acid adenine dinucleotide phosphate (NAADP)-gated TPCs sustain multiple cancer hallmarks, such as migration, invasiveness and angiogenesis. Herein, we first survey the EL Ca2+ refilling and release mechanisms and then focus on the oncogenic role of EL Ca2+ signaling. While the evidence in favor of TRPML1 involvement in neoplastic transformation is yet to be clearly provided, TPCs are emerging as an alternative target for anticancer therapies.
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59
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Degradation of TRPML1 in Neurons Reduces Neuron Survival in Transient Global Cerebral Ischemia. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2018; 2018:4612727. [PMID: 30662583 PMCID: PMC6312622 DOI: 10.1155/2018/4612727] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 09/28/2018] [Accepted: 10/15/2018] [Indexed: 11/17/2022]
Abstract
Postcardiac arrest syndrome yields poor neurological outcomes, but the mechanisms underlying this condition remain poorly understood. Autophagy plays an important role in neuronal apoptosis induced by ischemia. However, whether autophagy is involved in neuron apoptosis induced by cardiac arrest has been less studied. This study found that TRPML1 participates in cerebral ischemic reperfusion injury. Primary neurons were isolated and treated with mucolipin synthetic agonist 1 (ML-SA1), as well as infected with the recombinant lentivirus TRPML1 overexpression vector in vitro. ML-SA1 was delivered intracerebroventricularly in transient global ischemia model. Protein expression levels were determined by western blot. Neurological deficit score and the infarct volume were analyzed for the detection of neuronal damage. We found that TRPML1 was significantly downregulated in vivo and in vitro ischemic reperfusion model. We also observed that TRPML1 overexpression or treatment with the ML-SA1 attenuated neuronal death in primary neurons and ameliorated neurological dysfunction in vivo. Our findings suggested that autophagy and apoptosis were activated after transient global ischemia. Administration of ML-SA1 before transient global ischemia ameliorated neurological dysfunction possibly through the promotion of autophagy and the inhibition of apoptosis.
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60
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Identification of Inhibitory Ca 2+ Binding Sites in the Upper Vestibule of the Yeast Vacuolar TRP Channel. iScience 2018; 11:1-12. [PMID: 30572205 PMCID: PMC6299153 DOI: 10.1016/j.isci.2018.11.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Revised: 10/30/2018] [Accepted: 11/29/2018] [Indexed: 01/28/2023] Open
Abstract
By vacuolar patch-clamp and Ca2+ imaging experiments, we show that the yeast vacuolar transient receptor potential (TRPY) channel 1 is activated by cytosolic Ca2+ and inhibited by Ca2+ from the vacuolar lumen. The channel is cooperatively affected by vacuolar Ca2+ (Hill coefficient, 1.5), suggesting that it may accommodate a Ca2+ receptor that can bind two calcium ions. Alanine scanning of six negatively charged amino acid residues in the transmembrane S5 and S6 linker, facing the vacuolar lumen, revealed that two aspartate residues, 401 and 405, are essential for current inhibition and direct binding of 45Ca2+. Expressed in HEK-293 cells, a significant fraction of TRPY1, present in the plasma membrane, retained its Ca2+ sensitivity. Based on these data and on homology with TRPV channels, we conclude that D401 and D405 are key residues within the vacuolar vestibule of the TRPY1 pore that decrease cation access or permeation after Ca2+ binding. The yeast vacuolar TRPY1 channel is inhibited by vacuolar Ca2+ Aspartate residues D401A and D405A are essential for Ca2+-mediated inhibition Aspartate residues D401 and D405 are essential for direct Ca2+ binding Ca2+ binding to D401 and D405 within vacuolar pore vestibule mediates inhibition
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61
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Plesch E, Chen CC, Butz E, Scotto Rosato A, Krogsaeter EK, Yinan H, Bartel K, Keller M, Robaa D, Teupser D, Holdt LM, Vollmar AM, Sippl W, Puertollano R, Medina D, Biel M, Wahl-Schott C, Bracher F, Grimm C. Selective agonist of TRPML2 reveals direct role in chemokine release from innate immune cells. eLife 2018; 7:39720. [PMID: 30479274 PMCID: PMC6257821 DOI: 10.7554/elife.39720] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Accepted: 10/26/2018] [Indexed: 12/21/2022] Open
Abstract
Cytokines and chemokines are produced and secreted by a broad range of immune cells including macrophages. Remarkably, little is known about how these inflammatory mediators are released from the various immune cells. Here, the endolysosomal cation channel TRPML2 is shown to play a direct role in chemokine trafficking and secretion from murine macrophages. To demonstrate acute and direct involvement of TRPML2 in these processes, the first isoform-selective TRPML2 channel agonist was generated, ML2-SA1. ML2-SA1 was not only found to directly stimulate release of the chemokine CCL2 from macrophages but also to stimulate macrophage migration, thus mimicking CCL2 function. Endogenous TRPML2 is expressed in early/recycling endosomes as demonstrated by endolysosomal patch-clamp experimentation and ML2-SA1 promotes trafficking through early/recycling endosomes, suggesting CCL2 being transported and secreted via this pathway. These data provide a direct link between TRPML2 activation, CCL2 release and stimulation of macrophage migration in the innate immune response.
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Affiliation(s)
- Eva Plesch
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich, Ludwig Maximilian University of Munich, Munich, Germany
| | - Cheng-Chang Chen
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich, Ludwig Maximilian University of Munich, Munich, Germany
| | - Elisabeth Butz
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich, Ludwig Maximilian University of Munich, Munich, Germany
| | | | - Einar K Krogsaeter
- Department of Pharmacology and Toxicology, Medical Faculty, Ludwig Maximilian University of Munich, Munich, Germany
| | - Hua Yinan
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Karin Bartel
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich, Ludwig Maximilian University of Munich, Munich, Germany
| | - Marco Keller
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich, Ludwig Maximilian University of Munich, Munich, Germany
| | - Dina Robaa
- Department of Pharmaceutical Chemistry, Institute of Pharmacy, Martin Luther University of Halle-Wittenberg, Halle, Germany
| | - Daniel Teupser
- Institute of Laboratory Medicine, University Hospital Munich, Munich, Germany
| | - Lesca M Holdt
- Institute of Laboratory Medicine, University Hospital Munich, Munich, Germany
| | - Angelika M Vollmar
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich, Ludwig Maximilian University of Munich, Munich, Germany
| | - Wolfgang Sippl
- Department of Pharmaceutical Chemistry, Institute of Pharmacy, Martin Luther University of Halle-Wittenberg, Halle, Germany
| | - Rosa Puertollano
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Diego Medina
- Telethon Institute of Genetics and Medicine, Naples, Italy
| | - Martin Biel
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich, Ludwig Maximilian University of Munich, Munich, Germany
| | | | - Franz Bracher
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich, Ludwig Maximilian University of Munich, Munich, Germany
| | - Christian Grimm
- Department of Pharmacology and Toxicology, Medical Faculty, Ludwig Maximilian University of Munich, Munich, Germany
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62
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Fine M, Schmiege P, Li X. Structural basis for PtdInsP 2-mediated human TRPML1 regulation. Nat Commun 2018; 9:4192. [PMID: 30305615 PMCID: PMC6180102 DOI: 10.1038/s41467-018-06493-7] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 09/05/2018] [Indexed: 12/27/2022] Open
Abstract
Transient receptor potential mucolipin 1 (TRPML1), a lysosomal channel, maintains the low pH and calcium levels for lysosomal function. Several small molecules modulate TRPML1 activity. ML-SA1, a synthetic agonist, binds to the pore region and phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P2), a natural lipid, stimulates channel activity to a lesser extent than ML-SA1; moreover, PtdIns(4,5)P2, another natural lipid, prevents TRPML1-mediated calcium release. Notably, PtdIns(3,5)P2 and ML-SA1 cooperate further increasing calcium efflux. Here we report the structures of human TRPML1 at pH 5.0 with PtdIns(3,5)P2, PtdIns(4,5)P2, or ML-SA1 and PtdIns(3,5)P2, revealing a unique lipid-binding site. PtdIns(3,5)P2 and PtdIns(4,5)P2 bind to the extended helices of S1, S2, and S3. The phosphate group of PtdIns(3,5)P2 induces Y355 to form a π-cation interaction with R403, moving the S4-S5 linker, thus allosterically activating the channel. Our structures and electrophysiological characterizations reveal an allosteric site and provide molecular insight into how lipids regulate TRP channels.
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Affiliation(s)
- Michael Fine
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Philip Schmiege
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Xiaochun Li
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, 75390, USA.
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63
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Freeman SA, Grinstein S. Resolution of macropinosomes, phagosomes and autolysosomes: Osmotically driven shrinkage enables tubulation and vesiculation. Traffic 2018; 19:965-974. [DOI: 10.1111/tra.12614] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2018] [Revised: 08/15/2018] [Accepted: 08/16/2018] [Indexed: 12/14/2022]
Affiliation(s)
- Spencer A. Freeman
- Program in Cell Biology; Peter Gilgan Centre for Research and Learning, Hospital for Sick Children; Toronto Ontario Canada
| | - Sergio Grinstein
- Program in Cell Biology; Peter Gilgan Centre for Research and Learning, Hospital for Sick Children; Toronto Ontario Canada
- Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital; Toronto Ontario Canada
- Department of Biochemistry; University of Toronto; Toronto Ontario Canada
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64
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Wu G, Yang X, Shen Y. Identification of a single aspartate residue critical for both fast and slow calcium-dependent inactivation of the human TRPML1 channel. J Biol Chem 2018; 293:11736-11745. [PMID: 29884771 DOI: 10.1074/jbc.ra118.003250] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Revised: 06/05/2018] [Indexed: 01/16/2023] Open
Abstract
Transient receptor potential mucolipin subfamily 1 (TRPML1) is a nonselective cation channel mainly located in late endosomes and lysosomes. Mutations of the gene encoding human TRPML1 can cause severe lysosomal diseases. The activity of TRPML1 is regulated by both Ca2+ and H+, which are important for its critical physiological functions in membrane trafficking, exocytosis, autophagy, and intracellular signal transduction. However, the molecular mechanism of its dual regulation by Ca2+ and H+ remains elusive. Here, using a mutant screening method in combination with a whole-cell patch clamp technique, we identified a key TRPML1 residue, Asp-472, responsible for both fast calcium-dependent inactivation (FCDI) and slow calcium-dependent inactivation (SCDI) as well as H+ regulation. We also found that, in acidic pH, H+ can significantly delay FCDI and abolish SCDI and thereby presumably facilitate the ion conductance of the human TRPML1 channel. In summary, we have identified a key residue critical for Ca2+-induced inhibition of TRPML1 channel currents and uncovered pH-dependent regulation of this channel, providing vital information regarding the detailed mechanism of action of human TRPML1.
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Affiliation(s)
- Guangyan Wu
- From the State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China and
| | - Xue Yang
- From the State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China and
| | - Yuequan Shen
- From the State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China and .,the Synergetic Innovation Center of Chemical Science and Engineering, 94 Weijin Road, Tianjin 300071, China
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65
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Lu W, Gómez NM, Lim JC, Guha S, O'Brien-Jenkins A, Coffey EE, Campagno KE, McCaughey SA, Laties AM, Carlsson LG, Mitchell CH. The P2Y 12 Receptor Antagonist Ticagrelor Reduces Lysosomal pH and Autofluorescence in Retinal Pigmented Epithelial Cells From the ABCA4 -/- Mouse Model of Retinal Degeneration. Front Pharmacol 2018; 9:242. [PMID: 29725296 PMCID: PMC5917064 DOI: 10.3389/fphar.2018.00242] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 03/05/2018] [Indexed: 11/13/2022] Open
Abstract
The accumulation of partially degraded lipid waste in lysosomal-related organelles may contribute to pathology in many aging diseases. The presence of these lipofuscin granules is particularly evident in the autofluorescent lysosome-associated organelles of the retinal pigmented epithelial (RPE) cells, and may be related to early stages of age-related macular degeneration. While lysosomal enzymes degrade material optimally at acidic pH levels, lysosomal pH is elevated in RPE cells from the ABCA4-/- mouse model of Stargardt's disease, an early onset retinal degeneration. Lowering lysosomal pH through cAMP-dependent pathways decreases accumulation of autofluorescent material in RPE cells in vitro, but identification of an appropriate receptor is crucial for manipulating this pathway in vivo. As the P2Y12 receptor for ADP is coupled to the inhibitory Gi protein, we asked whether blocking the P2Y12 receptor with ticagrelor could restore lysosomal acidity and reduce autofluorescence in compromised RPE cells from ABCA4-/- mice. Oral delivery of ticagrelor giving rise to clinically relevant exposure lowered lysosomal pH in these RPE cells. Ticagrelor also partially reduced autofluorescence in the RPE cells of ABCA4-/- mice. In vitro studies in ARPE-19 cells using more specific antagonists AR-C69931 and AR-C66096 confirmed the importance of the P2Y12 receptor for lowering lysosomal pH and reducing autofluorescence. These observations identify P2Y12 receptor blockade as a potential target to lower lysosomal pH and clear lysosomal waste in RPE cells.
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Affiliation(s)
- Wennan Lu
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, PA, United States
| | - Néstor M Gómez
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, PA, United States
| | - Jason C Lim
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, PA, United States
| | - Sonia Guha
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, PA, United States.,Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA, United States
| | - Ann O'Brien-Jenkins
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, PA, United States
| | - Erin E Coffey
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, PA, United States
| | - Keith E Campagno
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, PA, United States
| | - Stuart A McCaughey
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, PA, United States
| | - Alan M Laties
- Jules Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA, United States
| | - Leif G Carlsson
- Department of Bioscience Heart Failure, Cardiovascular, Renal and Metabolic Diseases, IMED Biotech Unit, AstraZeneca, Gothenburg, Sweden
| | - Claire H Mitchell
- Department of Anatomy and Cell Biology, University of Pennsylvania, Philadelphia, PA, United States.,Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, United States.,Department of Physiology, University of Pennsylvania, Philadelphia, PA, United States
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66
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Schmiege P, Fine M, Li X. The regulatory mechanism of mammalian TRPMLs revealed by cryo-EM. FEBS J 2018; 285:2579-2585. [PMID: 29577631 DOI: 10.1111/febs.14443] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 03/15/2018] [Accepted: 03/20/2018] [Indexed: 01/18/2023]
Abstract
Transient receptor potential mucolipin (TRPML) channels are the most recently identified subfamily of TRP channels and have seen a surge of new reports revealing both structural and functional insight. In 2017, several groups published multiple conformations of TRPML channels using cryo-EM. Similar to other TRP channels, the ML subfamily consists of six transmembrane helices (S1-S6), and a pore region including S5, S6, and two pore helices (PH1 and PH2). However, these reports also reveal distinct structural characteristics of the ML subfamily. Asp residues within the luminal pore may function to control calcium/pH regulation. A synthetic agonist, ML-SA1, can bind to the pore region of TRPMLs to force a direct dilation of the lower gate. Finally, biophysical and electrophysiological characterizations reveal another natural agonist binding site in the unique domain of TRPMLs, presumably regulating the conformation of the S4-S5 linker to open the channel. This work elucidates the molecular architecture and provides insights into how multiple ligands regulate TRPMLs.
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Affiliation(s)
- Philip Schmiege
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Michael Fine
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Xiaochun Li
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
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67
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Mio K, Sato C. Lipid environment of membrane proteins in cryo-EM based structural analysis. Biophys Rev 2018; 10:307-316. [PMID: 29256118 PMCID: PMC5899730 DOI: 10.1007/s12551-017-0371-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 11/20/2017] [Indexed: 12/18/2022] Open
Abstract
Cryoelectron microscopy (cryo-EM) in association with a single particle analysis method (SPA) is now a promising tool to determine the structures of proteins and their macromolecular complexes. The development of direct electron detection cameras and image processing technologies has allowed the structures of many important proteins to be solved at near-atomic resolution or, in some cases, at atomic resolution, by overcoming difficulties in crystallization or low yield of protein production. In the case of membrane-integrated proteins, the proteins were traditionally solubilized and stabilized with various kind of detergents. However, the density of detergent micelles diminished the contrast of membrane proteins in cryo-EM studies and made it difficult to obtain high-resolution structures. To improve the resolution of membrane protein structures in cryo-EM studies, major improvements have been made both in sample preparation techniques and in hardware and software developments. The focus of our review is on improvements which have been made in the various techniques for sample preparation for cryo-EM studies, with a specific interest placed on techniques for mimicking the lipid environment of membrane proteins.
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Affiliation(s)
- Kazuhiro Mio
- AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation Laboratory (OPERANDO-OIL), National Institute of Advanced Industrial Science and Technology (AIST), Chiba, 277-8568, Japan.
- Molecular Profiling Research Center for Drug Discovery (molprof), National Institute of Advanced Industrial Science and Technology (AIST), Tokyo, 135-0064, Japan.
| | - Chikara Sato
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8566, Japan.
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68
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Su Q, Hu F, Liu Y, Ge X, Mei C, Yu S, Shen A, Zhou Q, Yan C, Lei J, Zhang Y, Liu X, Wang T. Cryo-EM structure of the polycystic kidney disease-like channel PKD2L1. Nat Commun 2018; 9:1192. [PMID: 29567962 PMCID: PMC5864754 DOI: 10.1038/s41467-018-03606-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Accepted: 02/28/2018] [Indexed: 02/07/2023] Open
Abstract
PKD2L1, also termed TRPP3 from the TRPP subfamily (polycystic TRP channels), is involved in the sour sensation and other pH-dependent processes. PKD2L1 is believed to be a nonselective cation channel that can be regulated by voltage, protons, and calcium. Despite its considerable importance, the molecular mechanisms underlying PKD2L1 regulations are largely unknown. Here, we determine the PKD2L1 atomic structure at 3.38 Å resolution by cryo-electron microscopy, whereby side chains of nearly all residues are assigned. Unlike its ortholog PKD2, the pore helix (PH) and transmembrane segment 6 (S6) of PKD2L1, which are involved in upper and lower-gate opening, adopt an open conformation. Structural comparisons of PKD2L1 with a PKD2-based homologous model indicate that the pore domain dilation is coupled to conformational changes of voltage-sensing domains (VSDs) via a series of π-π interactions, suggesting a potential PKD2L1 gating mechanism.
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Affiliation(s)
- Qiang Su
- Ministry of Education Key Laboratory of Protein Science, Tsinghua University, Beijing, 100084, China.,School of Life Sciences, Tsinghua University, Beijing, 100084, China.,Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, 100084, China
| | - Feizhuo Hu
- Ministry of Education Key Laboratory of Protein Science, Tsinghua University, Beijing, 100084, China.,Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, 100084, China.,School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Yuxia Liu
- School of Medicine, Tsinghua University, Beijing, 100084, China.,X-Lab for Transmembrane Signaling Research, Department of Biomedical Engineering and McGovern Institute for Brain Research, Tsinghua University, Beijing, 100084, China.,School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China.,Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China, 102402
| | - Xiaofei Ge
- Ministry of Education Key Laboratory of Protein Science, Tsinghua University, Beijing, 100084, China.,School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Changlin Mei
- Department of Nephrology, Changzheng Hospital, Second Military Medical University, Shanghai, 200433, China
| | - Shengqiang Yu
- Department of Nephrology, Changzheng Hospital, Second Military Medical University, Shanghai, 200433, China
| | - Aiwen Shen
- Department of Nephrology, Changzheng Hospital, Second Military Medical University, Shanghai, 200433, China
| | - Qiang Zhou
- Ministry of Education Key Laboratory of Protein Science, Tsinghua University, Beijing, 100084, China.,Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, 100084, China.,School of Medicine, Tsinghua University, Beijing, 100084, China.,Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Chuangye Yan
- Ministry of Education Key Laboratory of Protein Science, Tsinghua University, Beijing, 100084, China.,School of Life Sciences, Tsinghua University, Beijing, 100084, China.,Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, 100084, China.,Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Jianlin Lei
- Ministry of Education Key Laboratory of Protein Science, Tsinghua University, Beijing, 100084, China.,School of Life Sciences, Tsinghua University, Beijing, 100084, China.,Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, 100084, China
| | - Yanqing Zhang
- Ministry of Education Key Laboratory of Protein Science, Tsinghua University, Beijing, 100084, China. .,School of Life Sciences, Tsinghua University, Beijing, 100084, China. .,Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, 100084, China. .,Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, 100084, China.
| | - Xiaodong Liu
- School of Life Sciences, Tsinghua University, Beijing, 100084, China. .,School of Medicine, Tsinghua University, Beijing, 100084, China. .,X-Lab for Transmembrane Signaling Research, Department of Biomedical Engineering and McGovern Institute for Brain Research, Tsinghua University, Beijing, 100084, China. .,School of Biological Science and Medical Engineering, Beihang University, Beijing, 100083, China. .,Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China, 102402.
| | - Tingliang Wang
- Ministry of Education Key Laboratory of Protein Science, Tsinghua University, Beijing, 100084, China. .,Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, 100084, China. .,School of Medicine, Tsinghua University, Beijing, 100084, China. .,Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, 100084, China.
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69
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Sterea AM, Almasi S, El Hiani Y. The hidden potential of lysosomal ion channels: A new era of oncogenes. Cell Calcium 2018; 72:91-103. [PMID: 29748137 DOI: 10.1016/j.ceca.2018.02.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 02/28/2018] [Accepted: 02/28/2018] [Indexed: 01/14/2023]
Abstract
Lysosomes serve as the control centre for cellular clearance. These membrane-bound organelles receive biomolecules destined for degradation from intracellular and extracellular pathways; thus, facilitating the production of energy and shaping the fate of the cell. At the base of their functionality are the lysosomal ion channels which mediate the function of the lysosome through the modulation of ion influx and efflux. Ion channels form pores in the membrane of lysosomes and allow the passage of ions, a seemingly simple task which harbours the potential of overthrowing the cell's stability. Considered the master regulators of ion homeostasis, these integral membrane proteins enable the proper operation of the lysosome. Defects in the structure or function of these ion channels lead to the development of lysosomal storage diseases, neurodegenerative diseases and cancer. Although more than 50 years have passed since their discovery, lysosomes are not yet fully understood, with their ion channels being even less well characterized. However, significant improvements have been made in the development of drugs targeted against these ion channels as a means of combating diseases. In this review, we will examine how Ca2+, K+, Na+ and Cl- ion channels affect the function of the lysosome, their involvement in hereditary and spontaneous diseases, and current ion channel-based therapies.
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Affiliation(s)
- Andra M Sterea
- Departments of Physiology & Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Shekoufeh Almasi
- Departments of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Yassine El Hiani
- Departments of Physiology & Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada.
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70
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Madej MG, Ziegler CM. Dawning of a new era in TRP channel structural biology by cryo-electron microscopy. Pflugers Arch 2018; 470:213-225. [PMID: 29344776 DOI: 10.1007/s00424-018-2107-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Accepted: 01/03/2018] [Indexed: 12/20/2022]
Abstract
Cryo-electron microscopy (cryo-EM) permits the determination of atomic protein structures by averaging large numbers of individual projection images recorded at cryogenic temperatures-a method termed single-particle analysis. The cryo-preservation traps proteins within a thin glass-like ice layer, making literally a freeze image of proteins in solution. Projections of randomly adopted orientations are merged to reconstruct a 3D density map. While atomic resolution for highly symmetric viruses was achieved already in 2009, the development of new sensitive and fast electron detectors has enabled cryo-EM for smaller and asymmetrical proteins including fragile membrane proteins. As one of the most important structural biology methods at present, cryo-EM was awarded in October 2017 with the Nobel Prize in Chemistry. The molecular understanding of Transient-Receptor-Potential (TRP) channels has been boosted tremendously by cryo-EM single-particle analysis. Several near-atomic and atomic structures gave important mechanistic insights, e.g., into ion permeation and selectivity, gating, as well as into the activation of this enigmatic and medically important membrane protein family by various chemical and physical stimuli. Lastly, these structures have set the starting point for the rational design of TRP channel-targeted therapeutics to counteract life-threatening channelopathies. Here, we attempt a brief introduction to the method, review the latest advances in cryo-EM structure determination of TRP channels, and discuss molecular insights into the channel function based on the wealth of TRP channel cryo-EM structures.
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Affiliation(s)
- M Gregor Madej
- Department of Structural Biology, Institute of Biophysics and Physical Biochemistry, University of Regensburg, Universitätsstrasse 31, D-93053, Regensburg, Germany
| | - Christine M Ziegler
- Department of Structural Biology, Institute of Biophysics and Physical Biochemistry, University of Regensburg, Universitätsstrasse 31, D-93053, Regensburg, Germany.
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71
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Hughes TET, Lodowski DT, Huynh KW, Yazici A, Del Rosario J, Kapoor A, Basak S, Samanta A, Han X, Chakrapani S, Zhou ZH, Filizola M, Rohacs T, Han S, Moiseenkova-Bell VY. Structural basis of TRPV5 channel inhibition by econazole revealed by cryo-EM. Nat Struct Mol Biol 2018; 25:53-60. [PMID: 29323279 PMCID: PMC5951624 DOI: 10.1038/s41594-017-0009-1] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2017] [Accepted: 11/13/2017] [Indexed: 12/18/2022]
Abstract
The transient receptor potential vanilloid 5 (TRPV5) channel is a member of the transient receptor potential (TRP) channel family, which is highly selective for Ca2+, that is present primarily at the apical membrane of distal tubule epithelial cells in the kidney and plays a key role in Ca2+ reabsorption. Here we present the structure of the full-length rabbit TRPV5 channel as determined using cryo-EM in complex with its inhibitor econazole. This structure reveals that econazole resides in a hydrophobic pocket analogous to that occupied by phosphatidylinositides and vanilloids in TRPV1, thus suggesting conserved mechanisms for ligand recognition and lipid binding among TRPV channels. The econazole-bound TRPV5 structure adopts a closed conformation with a distinct lower gate that occludes Ca2+ permeation through the channel. Structural comparisons between TRPV5 and other TRPV channels, complemented with molecular dynamics (MD) simulations of the econazole-bound TRPV5 structure, allowed us to gain mechanistic insight into TRPV5 channel inhibition by small molecules.
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Affiliation(s)
- Taylor E T Hughes
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - David T Lodowski
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
- Department of Nutrition, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Kevin W Huynh
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, USA
| | - Aysenur Yazici
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, USA
| | - John Del Rosario
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, USA
| | - Abhijeet Kapoor
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Sandip Basak
- Department of Physiology and Biophysics School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Amrita Samanta
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
- Department of Physiology and Biophysics School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Xu Han
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Sudha Chakrapani
- Department of Physiology and Biophysics School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Z Hong Zhou
- California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, USA
| | - Marta Filizola
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Tibor Rohacs
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Rutgers University, Newark, NJ, USA
| | - Seungil Han
- Pfizer Research and Development, Groton, CT, USA
| | - Vera Y Moiseenkova-Bell
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA.
- Department of Physiology and Biophysics School of Medicine, Case Western Reserve University, Cleveland, OH, USA.
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
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72
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Zhou X, Li M, Su D, Jia Q, Li H, Li X, Yang J. Cryo-EM structures of the human endolysosomal TRPML3 channel in three distinct states. Nat Struct Mol Biol 2017; 24:1146-1154. [PMID: 29106414 PMCID: PMC5747366 DOI: 10.1038/nsmb.3502] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 10/10/2017] [Indexed: 12/23/2022]
Abstract
TRPML3 channels are mainly localized to endolysosomes and play a critical role in the endocytic pathway. Their dysfunction causes deafness and pigmentation defects in mice. TRPML3 activity is inhibited by low endolysosomal pH. Here we present cryo-electron microscopy (cryo-EM) structures of human TRPML3 in the closed, agonist-activated, and low-pH-inhibited states, with resolutions of 4.06, 3.62, and 4.65 Å, respectively. The agonist ML-SA1 lodges between S5 and S6 and opens an S6 gate. A polycystin-mucolipin domain (PMD) forms a luminal cap. S1 extends into this cap, forming a 'gating rod' that connects directly to a luminal pore loop, which undergoes dramatic conformational changes in response to low pH. S2 extends intracellularly and interacts with several intracellular regions to form a 'gating knob'. These unique structural features, combined with the results of electrophysiological studies, indicate a new mechanism by which luminal pH and other physiological modulators such as PIP2 regulate TRPML3 by changing S1 and S2 conformations.
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Affiliation(s)
- Xiaoyuan Zhou
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Minghui Li
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | - Deyuan Su
- Department of Biological Sciences, Columbia University, New York, NY, USA
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, and Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
| | - Qi Jia
- Department of Orthopedic Oncology, Shanghai Changzheng Hospital, The Second Military Medical University, Shanghai 200003, China
| | - Huan Li
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, and Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
- Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, China
| | - Xueming Li
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Jian Yang
- Department of Biological Sciences, Columbia University, New York, NY, USA
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, and Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
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73
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Schmiege P, Fine M, Blobel G, Li X. Human TRPML1 channel structures in open and closed conformations. Nature 2017; 550:366-370. [PMID: 29019983 DOI: 10.1038/nature24036] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2017] [Accepted: 08/24/2017] [Indexed: 12/20/2022]
Abstract
Transient receptor potential mucolipin 1 (TRPML1) is a Ca2+-releasing cation channel that mediates the calcium signalling and homeostasis of lysosomes. Mutations in TRPML1 lead to mucolipidosis type IV, a severe lysosomal storage disorder. Here we report two electron cryo-microscopy structures of full-length human TRPML1: a 3.72-Å apo structure at pH 7.0 in the closed state, and a 3.49-Å agonist-bound structure at pH 6.0 in an open state. Several aromatic and hydrophobic residues in pore helix 1, helices S5 and S6, and helix S6 of a neighbouring subunit, form a hydrophobic cavity to house the agonist, suggesting a distinct agonist-binding site from that found in TRPV1, a TRP channel from a different subfamily. The opening of TRPML1 is associated with distinct dilations of its lower gate together with a slight structural movement of pore helix 1. Our work reveals the regulatory mechanism of TRPML channels, facilitates better understanding of TRP channel activation, and provides insights into the molecular basis of mucolipidosis type IV pathogenesis.
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Affiliation(s)
- Philip Schmiege
- Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, New York 10065, USA.,Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Michael Fine
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
| | - Günter Blobel
- Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, New York 10065, USA
| | - Xiaochun Li
- Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, New York 10065, USA.,Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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74
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Hirschi M, Herzik MA, Wie J, Suo Y, Borschel WF, Ren D, Lander GC, Lee SY. Cryo-electron microscopy structure of the lysosomal calcium-permeable channel TRPML3. Nature 2017; 550:411-414. [PMID: 29019979 PMCID: PMC5762132 DOI: 10.1038/nature24055] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2017] [Accepted: 09/01/2017] [Indexed: 01/09/2023]
Abstract
The modulation of ion channel activity by lipids is increasingly recognized as a fundamental component of cellular signalling. The transient receptor potential mucolipin (TRPML) channel family belongs to the TRP superfamily and is composed of three members: TRPML1-TRPML3. TRPMLs are the major Ca2+-permeable channels on late endosomes and lysosomes (LEL). They regulate the release of Ca2+ from organelles, which is important for various physiological processes, including organelle trafficking and fusion. Loss-of-function mutations in the MCOLN1 gene, which encodes TRPML1, cause the neurodegenerative lysosomal storage disorder mucolipidosis type IV, and a gain-of-function mutation (Ala419Pro) in TRPML3 gives rise to the varitint-waddler (Va) mouse phenotype. Notably, TRPML channels are activated by the low-abundance and LEL-enriched signalling lipid phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P2), whereas other phosphoinositides such as PtdIns(4,5)P2, which is enriched in plasma membranes, inhibit TRPMLs. Conserved basic residues at the N terminus of the channel are important for activation by PtdIns(3,5)P2 and inhibition by PtdIns(4,5)P2. However, owing to a lack of structural information, the mechanism by which TRPML channels recognize PtdIns(3,5)P2 and increase their Ca2+ conductance remains unclear. Here we present the cryo-electron microscopy (cryo-EM) structure of a full-length TRPML3 channel from the common marmoset (Callithrix jacchus) at an overall resolution of 2.9 Å. Our structure reveals not only the molecular basis of ion conduction but also the unique architecture of TRPMLs, wherein the voltage sensor-like domain is linked to the pore via a cytosolic domain that we term the mucolipin domain. Combined with functional studies, these data suggest that the mucolipin domain is responsible for PtdIns(3,5)P2 binding and subsequent channel activation, and that it acts as a 'gating pulley' for lipid-dependent TRPML gating.
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Affiliation(s)
- Marscha Hirschi
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Mark A Herzik
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Jinhong Wie
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Yang Suo
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - William F Borschel
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Dejian Ren
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Gabriel C Lander
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Seok-Yong Lee
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina 27710, USA
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75
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Chen Q, She J, Zeng W, Guo J, Xu H, Bai XC, Jiang Y. Structure of mammalian endolysosomal TRPML1 channel in nanodiscs. Nature 2017; 550:415-418. [PMID: 29019981 PMCID: PMC5901962 DOI: 10.1038/nature24035] [Citation(s) in RCA: 180] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 08/24/2017] [Indexed: 12/14/2022]
Abstract
Transient receptor potential mucolipin 1 (TRPML1) is an endo/lysosomal cation channel ubiquitously expressed in mammalian cells1,2 and its loss-of-function mutations are the direct cause of Type IV mucolipidosis (MLIV), an autosomal recessive lysosomal storage disease3-6. Here we present the single particle cryo-electron microscopy (cryo-EM) structure of the mouse TRPML1 channel embedded in nanodiscs. Combined with mutagenesis, the TRPML1 structure reveals that phosphatidylinositol bisphosphate (PIP2) binds to the N-terminus of the channel – distal from the pore – and the helix-turn-helix extension between S2 and S3 likely couples ligand binding to pore opening. The tightly packed selectivity filter contains multiple ion binding sites and the conserved acidic residues form the luminal Ca2+ blocking site that confers luminal pH and Ca2+ modulation on channel conductance. A luminal linker domain forms a fenestrated canopy atop the channel, providing multiple luminal ion passages to the pore and also creating a negative electrostatic trap – preferably for divalent cations at the luminal entrance. The structure also reveals two equally distributed S4-S5 linker conformations in the closed channel, providing structural implication for the S4-S5 linker-mediated PIP2 gating mechanism among TRPML channels7,8.
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Affiliation(s)
- Qingfeng Chen
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8816, USA.,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA
| | - Ji She
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8816, USA
| | - Weizhong Zeng
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8816, USA.,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA
| | - Jiangtao Guo
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8816, USA
| | - Haoxing Xu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109-1048, USA
| | - Xiao-Chen Bai
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8816, USA
| | - Youxing Jiang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8816, USA.,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA
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Zhang S, Li N, Zeng W, Gao N, Yang M. Cryo-EM structures of the mammalian endo-lysosomal TRPML1 channel elucidate the combined regulation mechanism. Protein Cell 2017; 8:834-847. [PMID: 28936784 PMCID: PMC5676595 DOI: 10.1007/s13238-017-0476-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 09/18/2017] [Indexed: 01/10/2023] Open
Abstract
TRPML1 channel is a non-selective group-2 transient receptor potential (TRP) channel with Ca2+ permeability. Located mainly in late endosome and lysosome of all mammalian cell types, TRPML1 is indispensable in the processes of endocytosis, membrane trafficking, and lysosome biogenesis. Mutations of TRPML1 cause a severe lysosomal storage disorder called mucolipidosis type IV (MLIV). In the present study, we determined the cryo-electron microscopy (cryo-EM) structures of Mus musculus TRPML1 (mTRPML1) in lipid nanodiscs and Amphipols. Two distinct states of mTRPML1 in Amphipols are added to the closed state, on which could represent two different confirmations upon activation and regulation. The polycystin-mucolipin domain (PMD) may sense the luminal/extracellular stimuli and undergo a “move upward” motion during endocytosis, thus triggering the overall conformational change in TRPML1. Based on the structural comparisons, we propose TRPML1 is regulated by pH, Ca2+, and phosphoinositides in a combined manner so as to accommodate the dynamic endocytosis process.
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Affiliation(s)
- Sensen Zhang
- Ministry of Education Key Laboratory of Protein Science, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Ningning Li
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Science, Peking University, Beijing, 100871, China
| | - Wenwen Zeng
- Institute for Immunology and School of Medicine, Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Ning Gao
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Center for Life Sciences, School of Life Science, Peking University, Beijing, 100871, China.
| | - Maojun Yang
- Ministry of Education Key Laboratory of Protein Science, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
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Di Paola S, Scotto-Rosato A, Medina DL. TRPML1: The Ca (2+)retaker of the lysosome. Cell Calcium 2017; 69:112-121. [PMID: 28689729 DOI: 10.1016/j.ceca.2017.06.006] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 06/16/2017] [Accepted: 06/16/2017] [Indexed: 12/27/2022]
Abstract
Efficient functioning of lysosome is necessary to ensure the correct performance of a variety of intracellular processes such as degradation of cargoes coming from the endocytic and autophagic pathways, recycling of organelles, and signaling mechanisms involved in cellular adaptation to nutrient availability. Mutations in lysosomal genes lead to more than 50 lysosomal storage disorders (LSDs). Among them, mutations in the gene encoding TRPML1 (MCOLN1) cause Mucolipidosis type IV (MLIV), a recessive LSD characterized by neurodegeneration, psychomotor retardation, ophthalmologic defects and achlorhydria. At the cellular level, MLIV patient fibroblasts show enlargement and engulfment of the late endo-lysosomal compartment, autophagy impairment, and accumulation of lipids and glycosaminoglycans. TRPML1 is the most extensively studied member of a small family of genes that also includes TRPML2 and TRPML3, and it has been found to participate in vesicular trafficking, lipid and ion homeostasis, and autophagy. In this review we will provide an update on the latest and more novel findings related to the functions of TRPMLs, with particular focus on the emerging role of TRPML1 and lysosomal calcium signaling in autophagy. Moreover, we will also discuss new potential therapeutic approaches for MLIV and LSDs based on the modulation of TRPML1-mediated signaling.
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Affiliation(s)
- Simone Di Paola
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078 Pozzuoli ,NA, Italy
| | - Anna Scotto-Rosato
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078 Pozzuoli ,NA, Italy
| | - Diego Luis Medina
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078 Pozzuoli ,NA, Italy.
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