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TPC2 polymorphisms associated with a hair pigmentation phenotype in humans result in gain of channel function by independent mechanisms. Proc Natl Acad Sci U S A 2017; 114:E8595-E8602. [PMID: 28923947 DOI: 10.1073/pnas.1705739114] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Two-pore channels (TPCs) are endolysosomal cation channels. Two members exist in humans, TPC1 and TPC2. Functional roles associated with the ubiquitously expressed TPCs include VEGF-induced neoangiogenesis, LDL-cholesterol trafficking and degradation, physical endurance under fasting conditions, autophagy regulation, the acrosome reaction in sperm, cancer cell migration, and intracellular trafficking of pathogens such as Ebola virus or bacterial toxins (e.g., cholera toxin). In a genome-wide association study for variants associated with human pigmentation characteristics two coding variants of TPC2, rs35264875 (encoding M484L) and rs3829241 (encoding G734E), have been found to be associated with a shift from brown to blond hair color. In two recent follow-up studies a role for TPC2 in pigmentation has been further confirmed. However, these human polymorphic variants have not been functionally characterized until now. The development of endolysosomal patch-clamp techniques has made it possible to investigate directly ion channel activities and characteristics in isolated endolysosomal organelles. We applied this technique here to scrutinize channel characteristics of the polymorphic TPC2 variants in direct comparison with WT. We found that both polymorphisms lead to a gain of channel function by independent mechanisms. We next conducted a clinical study with more than 100 blond- and brown/black-haired individuals. We performed a genotype/phenotype analysis and subsequently isolated fibroblasts from WT and polymorphic variant carriers for endolysosomal patch-clamp experimentation to confirm key in vitro findings.
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102
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Patch-clamp technique to characterize ion channels in enlarged individual endolysosomes. Nat Protoc 2017; 12:1639-1658. [PMID: 28726848 DOI: 10.1038/nprot.2017.036] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
According to proteomics analyses, more than 70 different ion channels and transporters are harbored in membranes of intracellular compartments such as endosomes and lysosomes. Malfunctioning of these channels has been implicated in human diseases such as lysosomal storage disorders, neurodegenerative diseases and metabolic pathologies, as well as in the progression of certain infectious diseases. As a consequence, these channels have engendered very high interest as future drug targets. Detailed electrophysiological characterization of intracellular ion channels is lacking, mainly because standard methods to analyze plasma membrane ion channels, such as the patch-clamp technique, are not readily applicable to intracellular organelles. Here we present a protocol detailing how to implement a manual patch-clamp technique for endolysosomal compartments. In contrast to the alternatively used planar endolysosomal patch-clamp technique, this method is a visually controlled, direct patch-clamp technique similar to conventional patch-clamping. The protocol assumes basic knowledge and experience with patch-clamp methods. Implementation of the method requires up to 1 week, and material preparation takes ∼2-4 d. An individual experiment (i.e., measurement of channel currents across the endolysosomal membrane), including control experiments, can be completed within 1 h. This excludes the time for endolysosome enlargement, which takes between 1 and 48 h, depending on the approach and cell type used. Data analysis requires an additional hour.
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103
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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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104
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Methods for monitoring Ca 2+ and ion channels in the lysosome. Cell Calcium 2017; 64:20-28. [DOI: 10.1016/j.ceca.2016.12.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2016] [Revised: 12/07/2016] [Accepted: 12/07/2016] [Indexed: 12/22/2022]
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105
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Grimm C, Butz E, Chen CC, Wahl-Schott C, Biel M. From mucolipidosis type IV to Ebola: TRPML and two-pore channels at the crossroads of endo-lysosomal trafficking and disease. Cell Calcium 2017; 67:148-155. [PMID: 28457591 DOI: 10.1016/j.ceca.2017.04.003] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/05/2017] [Accepted: 04/05/2017] [Indexed: 01/05/2023]
Abstract
What do lysosomal storage disorders such as mucolipidosis type IV have in common with Ebola, cancer cell migration, or LDL-cholesterol trafficking? LDL-cholesterol, certain bacterial toxins and viruses, growth factors, receptors, integrins, macromolecules destined for degradation or secretion are all sorted and transported via the endolysosomal system (ES). There are several pathways known in the ES, e.g. the degradation, the recycling, or the retrograde trafficking pathway. The ES comprises early and late endosomes, lysosomes and recycling endosomes as well as autophagosomes and lysosome related organelles. Contact sites between the ES and the endoplasmic reticulum or the Golgi apparatus may also be considered part of it. Dysfunction of this complex intracellular machinery can cause or contribute to the development of a number of diseases ranging from neurodegenerative, infectious, or metabolic diseases to retinal and pigmentation disorders as well as cancer and autophagy-related diseases. Endolysosomal ion channels such as mucolipins (TRPMLs) and two-pore channels (TPCs) play an important role in intracellular cation/calcium signaling and homeostasis and appear to critically contribute to the proper function of the endolysosomal trafficking network.
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Affiliation(s)
- Christian Grimm
- Munich Center for Integrated Protein Science CIPSM, Center for Drug Research, Ludwig-Maximilians-Universität, München, Germany; Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Germany.
| | - Elisabeth Butz
- Munich Center for Integrated Protein Science CIPSM, Center for Drug Research, Ludwig-Maximilians-Universität, München, Germany; Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Germany
| | - Cheng-Chang Chen
- Munich Center for Integrated Protein Science CIPSM, Center for Drug Research, Ludwig-Maximilians-Universität, München, Germany; Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Germany
| | - Christian Wahl-Schott
- Munich Center for Integrated Protein Science CIPSM, Center for Drug Research, Ludwig-Maximilians-Universität, München, Germany; Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Germany
| | - Martin Biel
- Munich Center for Integrated Protein Science CIPSM, Center for Drug Research, Ludwig-Maximilians-Universität, München, Germany; Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Germany.
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106
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Recombinant tandem of pore-domains in a Weakly Inward rectifying K + channel 2 (TWIK2) forms active lysosomal channels. Sci Rep 2017; 7:649. [PMID: 28381826 PMCID: PMC5428834 DOI: 10.1038/s41598-017-00640-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 03/07/2017] [Indexed: 12/27/2022] Open
Abstract
Recombinant TWIK2 channels produce weak basal background K+ currents. Current amplitudes depend on the animal species the channels have been isolated from and on the heterologous system used for their re-expression. Here we show that this variability is due to a unique cellular trafficking. We identified three different sequence signals responsible for the preferential expression of TWIK2 in the Lamp1-positive lysosomal compartment. Sequential inactivation of tyrosine-based (Y308ASIP) and di-leucine-like (E266LILL and D282EDDQVDIL) trafficking motifs progressively abolishes the targeting of TWIK2 to lysosomes, and promotes its functional relocation at the plasma membrane. In addition, TWIK2 contains two N-glycosylation sites (N79AS and N85AS) on its luminal side, and glycosylation is necessary for expression in lysosomes. As shown by electrophysiology and electron microscopy, TWIK2 produces functional background K+ currents in the endolysosomes, and its expression affects the number and mean size of the lysosomes. These results show that TWIK2 is expressed in lysosomes, further expanding the registry of ion channels expressed in these organelles.
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107
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Hofmann L, Wang H, Zheng W, Philipp SE, Hidalgo P, Cavalié A, Chen XZ, Beck A, Flockerzi V. The S4---S5 linker - gearbox of TRP channel gating. Cell Calcium 2017; 67:156-165. [PMID: 28416203 DOI: 10.1016/j.ceca.2017.04.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/03/2017] [Accepted: 04/03/2017] [Indexed: 10/19/2022]
Abstract
Transient receptor potential (TRP) channels are cation channels which participate in a wide variety of physiological processes in organisms ranging from fungi to humans. They fulfill roles in body homeostasis, are sensors for noxious chemicals and temperature in the mammalian somatosensory system and are activated by light stimulated phospholipase C activity in Drosophila or by hypertonicity in yeast. The transmembrane topology of TRP channels is similar to that of voltage-gated cation channels. TRP proteins assemble as tetramers with each subunit containing six transmembrane helices (S1-S6) and intracellular N- and C-termini. Here we focus on the emerging functions of the cytosolic S4-S5 linker on TRP channel gating. Most of this knowledge comes from pathogenic mutations within the S4-S5 linker that alter TRP channel activities. This knowledge has stimulated forward genetic approaches to identify additional residues around this region which are essential for channel gating and is supported, in part, by recent structures obtained for TRPV1, TRPV2, TRPV6, TRPA1, and TRPP2.
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Affiliation(s)
- Laura Hofmann
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Hongmei Wang
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Wang Zheng
- Membrane Protein Disease Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, T6G 2H7, Edmonton, AB, Canada
| | - Stephan E Philipp
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Patricia Hidalgo
- Institute of Complex Systems 4, Zelluläre Biophysik, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Adolfo Cavalié
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Xing-Zhen Chen
- Membrane Protein Disease Research Group, Department of Physiology, Faculty of Medicine and Dentistry, University of Alberta, T6G 2H7, Edmonton, AB, Canada
| | - Andreas Beck
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany
| | - Veit Flockerzi
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany.
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108
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Matalonga L, Gort L, Ribes A. Small molecules as therapeutic agents for inborn errors of metabolism. J Inherit Metab Dis 2017; 40:177-193. [PMID: 27966099 DOI: 10.1007/s10545-016-0005-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 11/22/2016] [Accepted: 11/23/2016] [Indexed: 01/03/2023]
Abstract
Most inborn errors of metabolism (IEM) remain without effective treatment mainly due to the incapacity of conventional therapeutic approaches to target the neurological symptomatology and to ameliorate the multisystemic involvement frequently observed in these patients. However, in recent years, the therapeutic use of small molecules has emerged as a promising approach for treating this heterogeneous group of disorders. In this review, we focus on the use of therapeutically active small molecules to treat IEM, including readthrough agents, pharmacological chaperones, proteostasis regulators, substrate inhibitors, and autophagy inducers. The small molecules reviewed herein act at different cellular levels, and this knowledge provides new tools to set up innovative treatment approaches for particular IEM. We review the molecular mechanism underlying therapeutic properties of small molecules, methodologies used to screen for these compounds, and their applicability in preclinical and clinical practice.
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Affiliation(s)
- Leslie Matalonga
- Secció Errors Congènits del Metabolisme-IBC. Servei de Bioquímica i Genètica Molecular, Hospital Clínic, CIBERER-U737; IDIBAPS, C/ Mejía Lequerica s/n, 08028, Barcelona, Spain.
| | - Laura Gort
- Secció Errors Congènits del Metabolisme-IBC. Servei de Bioquímica i Genètica Molecular, Hospital Clínic, CIBERER-U737; IDIBAPS, C/ Mejía Lequerica s/n, 08028, Barcelona, Spain
| | - Antonia Ribes
- Secció Errors Congènits del Metabolisme-IBC. Servei de Bioquímica i Genètica Molecular, Hospital Clínic, CIBERER-U737; IDIBAPS, C/ Mejía Lequerica s/n, 08028, Barcelona, Spain
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109
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Nguyen ONP, Grimm C, Schneider LS, Chao YK, Atzberger C, Bartel K, Watermann A, Ulrich M, Mayr D, Wahl-Schott C, Biel M, Vollmar AM. Two-Pore Channel Function Is Crucial for the Migration of Invasive Cancer Cells. Cancer Res 2017; 77:1427-1438. [PMID: 28108508 DOI: 10.1158/0008-5472.can-16-0852] [Citation(s) in RCA: 102] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Revised: 12/22/2016] [Accepted: 12/22/2016] [Indexed: 11/16/2022]
Abstract
Metastatic invasion is the major cause of cancer-related deaths. In this study, we introduce two-pore channels (TPC), a recently described class of NAADP- and PI(3,5)P2-sensitive Ca2+-permeable cation channels in the endolysosomal system of cells, as candidate targets for the treatment of invasive cancers. Inhibition of the channel abrogated migration of metastatic cancer cells in vitro Silencing or pharmacologic inhibition of the two-pore channel TPC2 reduced lung metastasis of mammary mouse cancer cells. Disrupting TPC function halted trafficking of β1-integrin, leading to its accumulation in EEA1-positive early endosomes. As a consequence, invasive cancer cells were no longer able to form leading edges, which are required for adequate migration. Our findings link TPC to cancer cell migration and provide a preclinical proof of concept for their candidacy as targets to treat metastatic cancers. Cancer Res; 77(6); 1427-38. ©2017 AACR.
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Affiliation(s)
- Ong Nam Phuong Nguyen
- Department of Pharmacy, Pharmaceutical Biology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Christian Grimm
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-University Munich, Munich, Germany
| | - Lina S Schneider
- Department of Pharmacy, Pharmaceutical Biology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Yu-Kai Chao
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-University Munich, Munich, Germany
| | - Carina Atzberger
- Department of Pharmacy, Pharmaceutical Biology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Karin Bartel
- Department of Pharmacy, Pharmaceutical Biology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Anna Watermann
- Department of Pharmacy, Pharmaceutical Biology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Melanie Ulrich
- Department of Pharmacy, Pharmaceutical Biology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Doris Mayr
- Pathological Institute, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Christian Wahl-Schott
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-University Munich, Munich, Germany
| | - Martin Biel
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-University Munich, Munich, Germany.
| | - Angelika M Vollmar
- Department of Pharmacy, Pharmaceutical Biology, Ludwig-Maximilians-University Munich, Munich, Germany.
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110
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Cui C, Merritt R, Fu L, Pan Z. Targeting calcium signaling in cancer therapy. Acta Pharm Sin B 2017; 7:3-17. [PMID: 28119804 PMCID: PMC5237760 DOI: 10.1016/j.apsb.2016.11.001] [Citation(s) in RCA: 377] [Impact Index Per Article: 53.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Accepted: 10/28/2016] [Indexed: 12/15/2022] Open
Abstract
The intracellular calcium ions (Ca2+) act as second messenger to regulate gene transcription, cell proliferation, migration and death. Accumulating evidences have demonstrated that intracellular Ca2+ homeostasis is altered in cancer cells and the alteration is involved in tumor initiation, angiogenesis, progression and metastasis. Targeting derailed Ca2+ signaling for cancer therapy has become an emerging research area. This review summarizes some important Ca2+ channels, transporters and Ca2+-ATPases, which have been reported to be altered in human cancer patients. It discusses the current research effort toward evaluation of the blockers, inhibitors or regulators for Ca2+ channels/transporters or Ca2+-ATPase pumps as anti-cancer drugs. This review is also aimed to stimulate interest in, and support for research into the understanding of cellular mechanisms underlying the regulation of Ca2+ signaling in different cancer cells, and to search for novel therapies to cure these malignancies by targeting Ca2+ channels or transporters.
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Key Words
- 20-GPPD, 20-O-β-D-glucopyranosyl-20(S)-protopanaxadiol
- Apoptosis
- CBD, cannabidiol
- CBG, cannabigerol
- CPZ, capsazepine
- CRAC, Ca2+ release-activated Ca2+ channel
- CTL, cytotoxic T cells
- CYP3A4, cytochrome P450 3A4
- Ca2+ channels
- CaM, calmodulin
- CaMKII, calmodulin-dependent protein kinase II
- Cancer therapy
- Cell proliferation
- Channel blockers;
- ER/SR, endoplasmic/sarcoplasmic reticulum
- HCX, H+/Ca2+ exchangers
- IP3, inositol 1,4,5-trisphosphate
- IP3R (1, 2, 3), IP3 receptor (type 1, type 2, type 3)
- MCU, mitochondrial Ca2+ uniporter
- MCUR1, MCU uniporter regulator 1
- MICU (1, 2, 3), mitochondrial calcium uptake (type 1, type 2, type 3)
- MLCK, myosin light-chain kinase
- Migration
- NCX, Na+/Ca2+ exchanger
- NF-κB, nuclear factor-κB
- NFAT, nuclear factor of activated T cells
- NSCLC, non-small cell lung cancer
- OSCC, oral squamous cell carcinoma cells
- PKC, protein kinase C
- PM, plasma membrane
- PMCA, plasma membrane Ca2+-ATPase
- PTP, permeability transition pore
- ROS, reactive oxygen species
- RyR, ryanodine receptor
- SERCA, SR/ER Ca2+-ATPase
- SOCE, store-operated Ca2+ entry
- SPCA, secretory pathway Ca2+-ATPase
- Store-operated Ca2+ entry
- TEA, tetraethylammonium
- TG, thapsigargin
- TPC2, two-pore channel 2
- TRIM, 1-(2-(trifluoromethyl) phenyl) imidazole
- TRP (A, C, M, ML, N, P, V), transient receptor potential (ankyrin, canonical, melastatin, mucolipin, no mechanoreceptor potential C, polycystic, vanilloid)
- VGCC, voltage-gated Ca2+ channel
- mAb, monoclonal antibody
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Affiliation(s)
- Chaochu Cui
- State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou 510060, China
- Department of Surgery, Division of Thoracic Surgery, The Ohio State University, Columbus, OH 43210, USA
| | - Robert Merritt
- Department of Surgery, Division of Thoracic Surgery, The Ohio State University, Columbus, OH 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210, USA
| | - Liwu Fu
- State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine, Sun Yat-sen University Cancer Center, Guangzhou 510060, China
| | - Zui Pan
- Department of Surgery, Division of Thoracic Surgery, The Ohio State University, Columbus, OH 43210, USA
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH 43210, USA
- College of Nursing and Health Innovation, The University of Texas at Arlington, Arlington, TX 76019, USA
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111
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Zhong XZ, Sun X, Cao Q, Dong G, Schiffmann R, Dong XP. BK channel agonist represents a potential therapeutic approach for lysosomal storage diseases. Sci Rep 2016; 6:33684. [PMID: 27670435 PMCID: PMC5037385 DOI: 10.1038/srep33684] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 08/31/2016] [Indexed: 12/21/2022] Open
Abstract
Efficient lysosomal Ca2+ release plays an essential role in lysosomal trafficking. We have recently shown that lysosomal big conductance Ca2+-activated potassium (BK) channel forms a physical and functional coupling with the lysosomal Ca2+ release channel Transient Receptor Potential Mucolipin-1 (TRPML1). BK and TRPML1 forms a positive feedback loop to facilitate lysosomal Ca2+ release and subsequent lysosome membrane trafficking. However, it is unclear whether the positive feedback mechanism is common for other lysosomal storage diseases (LSDs) and whether BK channel agonists rescue abnormal lysosomal storage in LSDs. In this study, we assessed the effect of BK agonist, NS1619 and NS11021 in a number of LSDs including NPC1, mild cases of mucolipidosis type IV (ML4) (TRPML1-F408∆), Niemann-Pick type A (NPA) and Fabry disease. We found that TRPML1-mediated Ca2+ release was compromised in these LSDs. BK activation corrected the impaired Ca2+ release in these LSDs and successfully rescued the abnormal lysosomal storage of these diseases by promoting TRPML1-mediated lysosomal exocytosis. Our study suggests that BK channel activation stimulates the TRPML1-BK positive reinforcing loop to correct abnormal lysosomal storage in LSDs. Drugs targeting BK channel represent a potential therapeutic approach for LSDs.
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Affiliation(s)
- Xi Zoë Zhong
- Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, B3H 4R2, Nova Scotia, Canada
| | - Xue Sun
- Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, B3H 4R2, Nova Scotia, Canada
| | - Qi Cao
- Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, B3H 4R2, Nova Scotia, Canada
| | - Gaofeng Dong
- Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, B3H 4R2, Nova Scotia, Canada
| | - Raphael Schiffmann
- Institute of Metabolic Disease, Baylor Research Institute, 3812 Elm Street, Dallas, TX, 75226, USA
| | - Xian-Ping Dong
- Department of Physiology and Biophysics, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, B3H 4R2, Nova Scotia, Canada
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112
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Kilpatrick BS, Yates E, Grimm C, Schapira AH, Patel S. Endo-lysosomal TRP mucolipin-1 channels trigger global ER Ca2+ release and Ca2+ influx. J Cell Sci 2016; 129:3859-3867. [PMID: 27577094 PMCID: PMC5087663 DOI: 10.1242/jcs.190322] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 08/19/2016] [Indexed: 12/20/2022] Open
Abstract
Transient receptor potential (TRP) mucolipins (TRPMLs), encoded by the MCOLN genes, are patho-physiologically relevant endo-lysosomal ion channels crucial for membrane trafficking. Several lines of evidence suggest that TRPMLs mediate localised Ca2+ release but their role in Ca2+ signalling is not clear. Here, we show that activation of endogenous and recombinant TRPMLs with synthetic agonists evoked global Ca2+ signals in human cells. These signals were blocked by a dominant-negative TRPML1 construct and a TRPML antagonist. We further show that, despite a predominant lysosomal localisation, TRPML1 supports both Ca2+ release and Ca2+ entry. Ca2+ release required lysosomal and ER Ca2+ stores suggesting that TRPMLs, like other endo-lysosomal Ca2+ channels, are capable of ‘chatter’ with ER Ca2+ channels. Our data identify new modalities for TRPML1 action. Summary: The endolysosomal ion channel TRP mucolipin 1 was thought to mediate local Ca2+ signals. However, as reported here, it can also mediate global elevations in Ca2+.
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Affiliation(s)
- Bethan S Kilpatrick
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Elizabeth Yates
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Christian Grimm
- Center for Integrated Protein Science CIPSM and Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, München 81377, Germany
| | - Anthony H Schapira
- Department of Clinical Neurosciences, Institute of Neurology, University College London, London NW3 2PF, UK
| | - Sandip Patel
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
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113
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Regulation of lysosomal ion homeostasis by channels and transporters. SCIENCE CHINA-LIFE SCIENCES 2016; 59:777-91. [PMID: 27430889 PMCID: PMC5147046 DOI: 10.1007/s11427-016-5090-x] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 06/02/2016] [Indexed: 02/05/2023]
Abstract
Lysosomes are the major organelles that carry out degradation functions. They integrate and digest materials compartmentalized by endocytosis, phagocytosis or autophagy. In addition to more than 60 hydrolases residing in the lysosomes, there are also ion channels and transporters that mediate the flux or transport of H+, Ca2+, Na+, K+, and Cl− across the lysosomal membranes. Defects in ionic exchange can lead to abnormal lysosome morphology, defective vesicle trafficking, impaired autophagy, and diseases such as neurodegeneration and lysosomal storage disorders. The latter are characterized by incomplete lysosomal digestion and accumulation of toxic materials inside enlarged intracellular vacuoles. In addition to degradation, recent studies have revealed the roles of lysosomes in metabolic pathways through kinases such as mechanistic target of rapamycin (mTOR) and transcriptional regulation through calcium signaling molecules such as transcription factor EB (TFEB) and calcineurin. Owing to the development of new approaches including genetically encoded fluorescence probes and whole endolysosomal patch clamp recording techniques, studies on lysosomal ion channels have made remarkable progress in recent years. In this review, we will focus on the current knowledge of lysosome-resident ion channels and transporters, discuss their roles in maintaining lysosomal function, and evaluate how their dysfunction can result in disease.
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114
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Walker MT, Montell C. Suppression of the motor deficit in a mucolipidosis type IV mouse model by bone marrow transplantation. Hum Mol Genet 2016; 25:2752-2761. [PMID: 27270598 DOI: 10.1093/hmg/ddw132] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 04/04/2016] [Accepted: 04/25/2016] [Indexed: 11/13/2022] Open
Abstract
Mucolipidosis IV (MLIV) is a severe lysosomal storage disorder, which results from loss of the TRPML1 channel. MLIV causes multiple impairments in young children, including severe motor deficits. Currently, there is no effective treatment. Using a Drosophila MLIV model, we showed previously that introduction of trpml+ in phagocytic glia rescued the locomotor deficit by removing early dying neurons, thereby preventing amplification of neuronal death from cytotoxicity. Because microglia, which are phagocytic cells in the mammalian brain, are bone marrow derived, and cross the blood-brain barrier, we used a mouse MLIV model to test the efficacy of bone marrow transplantation (BMT). We found that BMT suppressed the reduced myelination and the increased caspase-3 activity due to loss of TRPML1. Using a rotarod test, we demonstrated that early BMT greatly delayed the motor impairment in the mutant mice. These data offer the possibility that BMT might provide the first therapy for MLIV.
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Affiliation(s)
- Marquis T Walker
- Neuroscience Research Institute.,Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA.,Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Craig Montell
- Neuroscience Research Institute .,Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA.,Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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115
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Abstract
Lysosomes are key acidic Ca2+ stores. The principle Ca2+-permeable channels of the lysosome are TRP mucolipins (TRPMLs) and NAADP-regulated two-pore channels (TPCs). Recent studies, reviewed in this collection, have linked numerous neurodegenerative diseases to both gain and loss of function of TRPMLs/TPCs, as well as to defects in acidic Ca2+ store content. These diseases span rare lysosomal storage disorders such as Mucolipidosis Type IV and Niemann-Pick disease, type C, through to more common ones such as Alzheimer and Parkinson disease. Cellular phenotypes, underpinned by endo-lysosomal trafficking defects, are reversed by chemical or molecular targeting of TRPMLs and TPCs. Lysosomal Ca2+ channels therefore emerge as potential druggable targets in combatting neurodegeneration.
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Affiliation(s)
- Sandip Patel
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT
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116
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Abstract
The neurodegenerative movement disorder Parkinson disease (PD) is prevalent in the aged population. However, the underlying mechanisms that trigger disease are unclear. Increasing work implicates both impaired Ca2+ signalling and lysosomal dysfunction in neuronal demise. Here I aim to connect these distinct processes by exploring the evidence that lysosomal Ca2+ signalling is disrupted in PD. In particular, I highlight defects in lysosomal Ca2+ content and signalling through NAADP-regulated two-pore channels in patient fibroblasts harbouring mutations in the PD-linked genes, GBA1 and LRRK2. As an emerging contributor to PD pathogenesis, the lysosomal Ca2+ signalling apparatus could represent a novel therapeutic target.
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Affiliation(s)
- Bethan S Kilpatrick
- Department of Cell and Developmental Biology, University College London, London, WC1E 6BT, UK
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117
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Ward C, Martinez-Lopez N, Otten EG, Carroll B, Maetzel D, Singh R, Sarkar S, Korolchuk VI. Autophagy, lipophagy and lysosomal lipid storage disorders. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:269-84. [DOI: 10.1016/j.bbalip.2016.01.006] [Citation(s) in RCA: 165] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 01/07/2016] [Accepted: 01/12/2016] [Indexed: 12/30/2022]
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118
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Kiselyov K, Muallem S. ROS and intracellular ion channels. Cell Calcium 2016; 60:108-14. [PMID: 26995054 DOI: 10.1016/j.ceca.2016.03.004] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 03/03/2016] [Accepted: 03/04/2016] [Indexed: 12/15/2022]
Abstract
Oxidative stress is a well-known driver of numerous pathological processes involving protein and lipid peroxidation and DNA damage. The resulting increase of pro-apoptotic pressure drives tissue damage in a host of conditions, including ischemic stroke and reperfusion injury, diabetes, death in acute pancreatitis and neurodegenerative diseases. Somewhat less frequently discussed, but arguably as important, is the signaling function of oxidative stress stemming from the ability of oxidative stress to modulate ion channel activity. The evidence for the modulation of the intracellular ion channels and transporters by oxidative stress is constantly emerging and such evidence suggests new regulatory and pathological circuits that can be explored towards new treatments for diseases in which oxidative stress is an issue. In this review we summarize the current knowledge on the effects of oxidative stress on the intracellular ion channels and transporters and their role in cell function.
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Affiliation(s)
- Kirill Kiselyov
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, United States; Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch NIH, NIDCR, Bethesda, MD 20892, United States.
| | - Shmuel Muallem
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, United States; Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch NIH, NIDCR, Bethesda, MD 20892, United States.
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119
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Abstract
TRPML1 is a ubiquitously expressed cation channel found on lysosomes and late endosomes. Mutations in TRPML1 cause mucolipidosis type IV and it has been implicated in Alzheimer's disease and HIV. However, the mechanisms by which TRPML1 activity is regulated are not well understood. This review summarizes the current understanding of TRPML1 activation and regulation.
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120
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Grishchuk Y, Peña KA, Coblentz J, King VE, Humphrey DM, Wang SL, Kiselyov KI, Slaugenhaupt SA. Impaired myelination and reduced brain ferric iron in the mouse model of mucolipidosis IV. Dis Model Mech 2015; 8:1591-601. [PMID: 26398942 PMCID: PMC4728313 DOI: 10.1242/dmm.021154] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 09/08/2015] [Indexed: 12/11/2022] Open
Abstract
Mucolipidosis type IV (MLIV) is a lysosomal storage disease caused by mutations in the MCOLN1 gene, which encodes the lysosomal transient receptor potential ion channel mucolipin-1 (TRPML1). MLIV causes impaired motor and cognitive development, progressive loss of vision and gastric achlorhydria. How loss of TRPML1 leads to severe psychomotor retardation is currently unknown, and there is no therapy for MLIV. White matter abnormalities and a hypoplastic corpus callosum are the major hallmarks of MLIV brain pathology. Here, we report that loss of TRPML1 in mice results in developmental aberrations of brain myelination as a result of deficient maturation and loss of oligodendrocytes. Defective myelination is evident in Mcoln1(-/-) mice at postnatal day 10, an active stage of postnatal myelination in the mouse brain. Expression of mature oligodendrocyte markers is reduced in Mcoln1(-/-) mice at postnatal day 10 and remains lower throughout the course of the disease. We observed reduced Perls' staining in Mcoln1(-/-) brain, indicating lower levels of ferric iron. Total iron content in unperfused brain is not significantly different between Mcoln1(-/-) and wild-type littermate mice, suggesting that the observed maturation delay or loss of oligodendrocytes might be caused by impaired iron handling, rather than by global iron deficiency. Overall, these data emphasize a developmental rather than a degenerative disease course in MLIV, and suggest that there should be a stronger focus on oligodendrocyte maturation and survival to better understand MLIV pathogenesis and aid treatment development.
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Affiliation(s)
- Yulia Grishchuk
- Center for Human Genetic Research and Department of Neurology, Massachusetts General Hospital and Harvard Medical School, 185 Cambridge Street, Boston, MA 02114, USA
| | - Karina A Peña
- Department of Biological Sciences, University of Pittsburgh, 519 Langley Hall, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Jessica Coblentz
- Department of Biological Sciences, University of Pittsburgh, 519 Langley Hall, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Victoria E King
- Center for Human Genetic Research and Department of Neurology, Massachusetts General Hospital and Harvard Medical School, 185 Cambridge Street, Boston, MA 02114, USA
| | - Daniel M Humphrey
- Center for Human Genetic Research and Department of Neurology, Massachusetts General Hospital and Harvard Medical School, 185 Cambridge Street, Boston, MA 02114, USA
| | - Shirley L Wang
- Center for Human Genetic Research and Department of Neurology, Massachusetts General Hospital and Harvard Medical School, 185 Cambridge Street, Boston, MA 02114, USA
| | - Kirill I Kiselyov
- Department of Biological Sciences, University of Pittsburgh, 519 Langley Hall, 4249 Fifth Avenue, Pittsburgh, PA 15260, USA
| | - Susan A Slaugenhaupt
- Center for Human Genetic Research and Department of Neurology, Massachusetts General Hospital and Harvard Medical School, 185 Cambridge Street, Boston, MA 02114, USA
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121
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Abstract
Two-pore channels (TPCs) are evolutionarily important members of the voltage-gated ion channel superfamily. TPCs localize to acidic Ca(2+) stores within the endolysosomal system. Most evidence indicate that TPCs mediate Ca(2+) signals through the Ca(2+)-mobilizing messenger nicotinic acid adenine dinucleotide phosphate (NAADP) to control a range of Ca(2+)-dependent events. Recent studies clarify the mechanism of TPC activation and identify roles for TPCs in disease, highlighting the regulation of endolysosomal membrane traffic by local Ca(2+) fluxes. Chemical targeting of TPCs to maintain endolysosomal "well-being" may be beneficial in disorders as diverse as Parkinson's disease, fatty liver disease, and Ebola virus infection.
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Affiliation(s)
- Sandip Patel
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK. E-mail:
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122
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Cao Q, Zhong XZ, Zou Y, Zhang Z, Toro L, Dong XP. BK Channels Alleviate Lysosomal Storage Diseases by Providing Positive Feedback Regulation of Lysosomal Ca2+ Release. Dev Cell 2015; 33:427-41. [PMID: 25982675 DOI: 10.1016/j.devcel.2015.04.010] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 03/25/2015] [Accepted: 04/10/2015] [Indexed: 11/25/2022]
Abstract
Promoting lysosomal trafficking represents a promising therapeutic approach for lysosome storage diseases. Efficient Ca(2+) mobilization from lysosomes is important for lysosomal trafficking. Ca(2+) release from lysosomes could generate a negative potential in the lumen to disturb subsequent Ca(2+) release in the absence of counter ion flux. Here we report that lysosomes express big-conductance Ca(2+)-activated potassium (BK) channels that form physical and functional coupling with the lysosomal Ca(2+) release channel, TRPML1. Ca(2+) release via TRPML1 causes BK activation, which in turn facilitates further lysosomal Ca(2+) release and membrane trafficking. Importantly, BK overexpression rescues the impaired TRPML1-mediated Ca(2+) release and abnormal lysosomal storage in cells from Niemann-Pick C1 patients. Therefore, we have identified a lysosomal K(+) channel that provides a positive feedback mechanism to facilitate TRPML1-mediated Ca(2+) release and membrane trafficking. Our findings suggest that upregulating BK may be a potential therapeutic strategy for certain lysosomal storage diseases and common neurodegenerative disorders.
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Affiliation(s)
- Qi Cao
- Department of Physiology and Biophysics, Sir Charles Tupper Medical Building, Dalhousie University, 5850 College Street, Halifax, NS B3H 4R2, Canada
| | - Xi Zoë Zhong
- Department of Physiology and Biophysics, Sir Charles Tupper Medical Building, Dalhousie University, 5850 College Street, Halifax, NS B3H 4R2, Canada
| | - Yuanjie Zou
- Department of Physiology and Biophysics, Sir Charles Tupper Medical Building, Dalhousie University, 5850 College Street, Halifax, NS B3H 4R2, Canada
| | - Zhu Zhang
- Division of Molecular Medicine, Department of Anesthesiology and Department of Molecular & Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-7115, USA
| | - Ligia Toro
- Division of Molecular Medicine, Department of Anesthesiology and Department of Molecular & Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-7115, USA
| | - Xian-Ping Dong
- Department of Physiology and Biophysics, Sir Charles Tupper Medical Building, Dalhousie University, 5850 College Street, Halifax, NS B3H 4R2, Canada.
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123
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Waugh MG. PIPs in neurological diseases. Biochim Biophys Acta Mol Cell Biol Lipids 2015; 1851:1066-82. [PMID: 25680866 DOI: 10.1016/j.bbalip.2015.02.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 01/29/2015] [Accepted: 02/01/2015] [Indexed: 12/19/2022]
Abstract
Phosphoinositide (PIP) lipids regulate many aspects of cell function in the nervous system including receptor signalling, secretion, endocytosis, migration and survival. Levels of PIPs such as PI4P, PI(4,5)P2 and PI(3,4,5)P3 are normally tightly regulated by phosphoinositide kinases and phosphatases. Deregulation of these biochemical pathways leads to lipid imbalances, usually on intracellular endosomal membranes, and these changes have been linked to a number of major neurological diseases including Alzheimer's, Parkinson's, epilepsy, stroke, cancer and a range of rarer inherited disorders including brain overgrowth syndromes, Charcot-Marie-Tooth neuropathies and neurodevelopmental conditions such as Lowe's syndrome. This article analyses recent progress in this area and explains how PIP lipids are involved, to varying degrees, in almost every class of neurological disease. This article is part of a Special Issue entitled Brain Lipids.
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Affiliation(s)
- Mark G Waugh
- Lipid and Membrane Biology Group, Institute for Liver and Digestive Health, UCL, Royal Free Campus, Rowland Hill Street, London NW3 2PF, United Kingdom.
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124
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The role of TRPMLs in endolysosomal trafficking and function. Cell Calcium 2014; 58:48-56. [PMID: 25465891 DOI: 10.1016/j.ceca.2014.10.008] [Citation(s) in RCA: 140] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 10/15/2014] [Accepted: 10/17/2014] [Indexed: 12/24/2022]
Abstract
Members of the Transient Receptor Potential-Mucolipin (TRPML) constitute a family of evolutionarily conserved cation channels that function predominantly in endolysosomal vesicles. Whereas loss-of-function mutations in human TRPML1 were first identified as being causative for the lysosomal storage disease, Mucolipidosis type IV, most mammals also express two other TRPML isoforms called TRPML2 and TRPML3. All three mammalian TRPMLs as well as TRPML related genes in other species including Caenorhabditis elegans and Drosophila exhibit overlapping functional and biophysical properties. The functions of TRPML proteins include roles in vesicular trafficking and biogenesis, maintenance of neuronal development, function, and viability, and regulation of intracellular and organellar ionic homeostasis. Biophysically, TRPML channels are non-selective cation channels exhibiting variable permeability to a host of cations including Na(+), Ca(2+), Fe(2+), and Zn(2+), and are activated by a phosphoinositide species, PI(3,5)P2, that is mostly found in endolysosomal membranes. Here, we review the functional and biophysical properties of these enigmatic cation channels, which represent the most ancient and archetypical TRP channels.
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125
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Feng X, Xiong J, Lu Y, Xia X, Zhu MX. Differential mechanisms of action of the mucolipin synthetic agonist, ML-SA1, on insect TRPML and mammalian TRPML1. Cell Calcium 2014; 56:446-56. [PMID: 25266962 DOI: 10.1016/j.ceca.2014.09.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 09/08/2014] [Accepted: 09/10/2014] [Indexed: 10/24/2022]
Abstract
Mucolipin synthetic agonist 1 (ML-SA1) was recently identified to activate mammalian TRPML channels and shown to alleviate lipid accumulation in lysosomes of cellular models of lysosome storage diseases, mucolipidosis type IV (MLIV) and Niemann-Pick's disease type C (NPC). Owning to its potential use in complimenting genetic studies in Drosophila melanogaster to elucidate the cellular and physiological functions of TRPML channels, we examined the effect of ML-SA1 on Drosophila TRPML expressed in HEK293 cells using whole-cell, inside-out, and whole-lysosome electrophysiological recordings. We previously showed that when expressed in HEK293 cells, Drosophila TRPML was localized and functional on both plasma membrane and endolysosome. We show here that in both inside-out patches excised from the plasma membrane and whole-lysosome recordings from enlarged endolysosome vacuoles, ML-SA1 failed to activate TRPML unless exogenous phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2] was applied. At 1 μM ML-SA1, the sensitivity of TRPML to PI(3,5)P2 increased approximately by 10-fold and at 10 μM ML-SA1, the deactivation of PI(3,5)P2-evoked TRPML currents was markedly slowed. On the other hand, constitutive activation of TRPML by a mutation that mimics the varitint-waddler (Va) mutation of mouse TRPML3 rendered the insect channel sensitive to activation by ML-SA1 alone. Moreover, different from the insect TRPML, mouse TRPML1 was readily activated by ML-SA1 independent of PI(3,5)P2. Thus, our data reveal that while ML-SA1 acts as a true agonist at mouse TRPML1, it behaves as an allosteric activator of the Drosophila TRPML, showing dependence on and the ability to stabilize open conformation of the insect channels.
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Affiliation(s)
- Xinghua Feng
- The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou 510150, China; Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Jian Xiong
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; Graduate Program in Cell and Regulatory Biology, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Yungang Lu
- The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou 510150, China; Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA
| | - Xuefeng Xia
- The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou 510150, China; Center for Genomic Medicine, Houston Methodist Research Institute, Houston, TX 77030, USA.
| | - Michael X Zhu
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA; Graduate Program in Cell and Regulatory Biology, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA.
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