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Dayam RM, Saric A, Shilliday RE, Botelho RJ. The Phosphoinositide-Gated Lysosomal Ca2+Channel, TRPML1, Is Required for Phagosome Maturation. Traffic 2015; 16:1010-26. [DOI: 10.1111/tra.12303] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 05/15/2015] [Accepted: 05/17/2015] [Indexed: 12/27/2022]
Affiliation(s)
- Roya M. Dayam
- Department of Chemistry and Biology; Ryerson University; Toronto Ontario M5B2K3 Canada
- Molecular Science Program; Ryerson University; Toronto Ontario M5B2K3 Canada
| | - Amra Saric
- Department of Chemistry and Biology; Ryerson University; Toronto Ontario M5B2K3 Canada
- Molecular Science Program; Ryerson University; Toronto Ontario M5B2K3 Canada
| | - Ryan E. Shilliday
- Department of Chemistry and Biology; Ryerson University; Toronto Ontario M5B2K3 Canada
| | - Roberto J. Botelho
- Department of Chemistry and Biology; Ryerson University; Toronto Ontario M5B2K3 Canada
- Molecular Science Program; Ryerson University; Toronto Ontario M5B2K3 Canada
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52
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Ruas M, Davis LC, Chen CC, Morgan AJ, Chuang KT, Walseth TF, Grimm C, Garnham C, Powell T, Platt N, Platt FM, Biel M, Wahl-Schott C, Parrington J, Galione A. Expression of Ca²⁺-permeable two-pore channels rescues NAADP signalling in TPC-deficient cells. EMBO J 2015; 34:1743-58. [PMID: 25872774 PMCID: PMC4516428 DOI: 10.15252/embj.201490009] [Citation(s) in RCA: 133] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 03/11/2015] [Indexed: 01/26/2023] Open
Abstract
The second messenger NAADP triggers Ca2+ release from endo-lysosomes. Although two-pore channels (TPCs) have been proposed to be regulated by NAADP, recent studies have challenged this. By generating the first mouse line with demonstrable absence of both Tpcn1 and Tpcn2 expression (Tpcn1/2−/−), we show that the loss of endogenous TPCs abolished NAADP-dependent Ca2+ responses as assessed by single-cell Ca2+ imaging or patch-clamp of single endo-lysosomes. In contrast, currents stimulated by PI(3,5)P2 were only partially dependent on TPCs. In Tpcn1/2−/− cells, NAADP sensitivity was restored by re-expressing wild-type TPCs, but not by mutant versions with impaired Ca2+-permeability, nor by TRPML1. Another mouse line formerly reported as TPC-null likely expresses truncated TPCs, but we now show that these truncated proteins still support NAADP-induced Ca2+ release. High-affinity [32P]NAADP binding still occurs in Tpcn1/2−/− tissue, suggesting that NAADP regulation is conferred by an accessory protein. Altogether, our data establish TPCs as Ca2+-permeable channels indispensable for NAADP signalling.
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Affiliation(s)
- Margarida Ruas
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Lianne C Davis
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Cheng-Chang Chen
- Center for Integrated Protein Science CIPS-M and Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, München, Germany
| | | | - Kai-Ting Chuang
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Timothy F Walseth
- Pharmacology Department, University of Minnesota, Minneapolis, MN, USA
| | - Christian Grimm
- Center for Integrated Protein Science CIPS-M and Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, München, Germany
| | - Clive Garnham
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Trevor Powell
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Nick Platt
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Frances M Platt
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Martin Biel
- Center for Integrated Protein Science CIPS-M and Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, München, Germany
| | - Christian Wahl-Schott
- Center for Integrated Protein Science CIPS-M and Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, München, Germany
| | - John Parrington
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Antony Galione
- Department of Pharmacology, University of Oxford, Oxford, UK
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53
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Up-regulation of lysosomal TRPML1 channels is essential for lysosomal adaptation to nutrient starvation. Proc Natl Acad Sci U S A 2015; 112:E1373-81. [PMID: 25733853 DOI: 10.1073/pnas.1419669112] [Citation(s) in RCA: 161] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Upon nutrient starvation, autophagy digests unwanted cellular components to generate catabolites that are required for housekeeping biosynthesis processes. A complete execution of autophagy demands an enhancement in lysosome function and biogenesis to match the increase in autophagosome formation. Here, we report that mucolipin-1 (also known as TRPML1 or ML1), a Ca(2+) channel in the lysosome that regulates many aspects of lysosomal trafficking, plays a central role in this quality-control process. By using Ca(2+) imaging and whole-lysosome patch clamping, lysosomal Ca(2+) release and ML1 currents were detected within hours of nutrient starvation and were potently up-regulated. In contrast, lysosomal Na(+)-selective currents were not up-regulated. Inhibition of mammalian target of rapamycin (mTOR) or activation of transcription factor EB (TFEB) mimicked a starvation effect in fed cells. The starvation effect also included an increase in lysosomal proteostasis and enhanced clearance of lysosomal storage, including cholesterol accumulation in Niemann-Pick disease type C (NPC) cells. However, this effect was not observed when ML1 was pharmacologically inhibited or genetically deleted. Furthermore, overexpression of ML1 mimicked the starvation effect. Hence, lysosomal adaptation to environmental cues such as nutrient levels requires mTOR/TFEB-dependent, lysosome-to-nucleus regulation of lysosomal ML1 channels and Ca(2+) signaling.
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54
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Ezeani M, Omabe M. A New Perspective of Lysosomal Cation Channel-Dependent Homeostasis in Alzheimer's Disease. Mol Neurobiol 2015; 53:1672-1678. [PMID: 25691454 DOI: 10.1007/s12035-015-9108-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Accepted: 01/20/2015] [Indexed: 01/08/2023]
Abstract
Studies have reported typically biophysical lysosomal cation channels including TPCs. Their plausible biological roles are being elucidated by pharmacological, genetic and conventional patch clamp procedures. The best characterized so far among these channels is the ML1 isoform of TRP. The reported TRPs and TPCs are bypass for cation fluxes and are strategic for homeostasis of ionic milieu of the acidic organelles they confine to. Ca(2+) homeostasis and adequate acidic pHL are critically influential for the regulation of a plethora of biological functions these intracellular cation channels perform. In lysosomal ion channel biology, we review: ML1 and TPC2 in Ca(2+) signaling, ML1 and TPC2 in pH(L) regulation. Using Aβ42 and tau proteins found along clathrin endolysosomal internalization pathway (Fig. 3), we proffer a mechanism of abnormal pH(L) and ML1/TPC2-dependent cation homeostasis in AD.
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Affiliation(s)
- Martin Ezeani
- Department of Physiology and Biophysics, Faculty of Medicine, Dalhousie University, Sir Charles Tupper Medical Building, 5850 College Street, Halifax, B3H 4R2, Nova Scotia, Canada.
| | - Maxwell Omabe
- Cancer Research Unit, Saskatchewan Cancer Agency, Department of Oncology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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55
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Miller A, Schafer J, Upchurch C, Spooner E, Huynh J, Hernandez S, McLaughlin B, Oden L, Fares H. Mucolipidosis type IV protein TRPML1-dependent lysosome formation. Traffic 2015; 16:284-97. [PMID: 25491304 DOI: 10.1111/tra.12249] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 12/03/2014] [Accepted: 12/03/2014] [Indexed: 02/05/2023]
Abstract
Lysosomes are dynamic organelles that undergo cycles of fusion and fission with themselves and with other organelles. Following fusion with late endosomes to form hybrid organelles, lysosomes are reformed as discrete organelles. This lysosome reformation or formation is a poorly understood process that has not been systematically analyzed and that lacks known regulators. In this study, we quantitatively define the multiple steps of lysosome formation and identify the first regulator of this process.
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Affiliation(s)
- Austin Miller
- Department of Molecular and Cellular Biology, Life Sciences South Room 531, University of Arizona, Tucson, AZ, 85721, USA
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56
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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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57
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Grishchuk Y, Sri S, Rudinskiy N, Ma W, Stember KG, Cottle MW, Sapp E, Difiglia M, Muzikansky A, Betensky RA, Wong AMS, Bacskai BJ, Hyman BT, Kelleher RJ, Cooper JD, Slaugenhaupt SA. Behavioral deficits, early gliosis, dysmyelination and synaptic dysfunction in a mouse model of mucolipidosis IV. Acta Neuropathol Commun 2014; 2:133. [PMID: 25200117 PMCID: PMC4173007 DOI: 10.1186/s40478-014-0133-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 08/26/2014] [Indexed: 12/04/2022] Open
Abstract
Mucolipidosis IV (MLIV) is caused by mutations in the gene MCOLN1. Patients with MLIV have severe neurologic deficits and very little is known about the brain pathology in this lysosomal disease. Using an accurate mouse model of mucolipidosis IV, we observed early behavioral deficits which were accompanied by activation of microglia and astrocytes. The glial activation that persisted during the course of disease was not accompanied by neuronal loss even at the late stage. In vivo [Ca2+]-imaging revealed no changes in resting [Ca2+] levels in Mcoln1−/− cortical neurons, implying their physiological health. Despite the absence of neuron loss, we observed alterations in synaptic plasticity, as indicated by elevated paired-pulse facilitation and enhanced long-term potentiation. Myelination deficits and severely dysmorphic corpus callosum were present early and resembled white matter pathology in mucolipidosis IV patients. These results indicate the early involvement of glia, and challenge the traditional view of mucolipidosis IV as an overtly neurodegenerative condition.
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58
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Thieleke-Matos C, da Silva ML, Cabrita-Santos L, Pires CF, Ramalho JS, Ikonomov O, Seixas E, Shisheva A, Seabra MC, Barral DC. Host PI(3,5)P2 activity is required for Plasmodium berghei growth during liver stage infection. Traffic 2014; 15:1066-82. [PMID: 24992508 DOI: 10.1111/tra.12190] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2013] [Revised: 06/26/2014] [Accepted: 06/29/2014] [Indexed: 01/18/2023]
Abstract
Malaria parasites go through an obligatory liver stage before they infect erythrocytes and cause disease symptoms. In the host hepatocytes, the parasite is enclosed by a parasitophorous vacuole membrane (PVM). Here, we dissected the interaction between the Plasmodium parasite and the host cell late endocytic pathway and show that parasite growth is dependent on the phosphoinositide 5-kinase (PIKfyve) that converts phosphatidylinositol 3-phosphate [PI(3)P] into phosphatidylinositol 3,5-bisphosphate [PI(3,5)P2 ] in the endosomal system. We found that inhibition of PIKfyve by either pharmacological or non-pharmacological means causes a delay in parasite growth. Moreover, we show that the PI(3,5)P2 effector protein TRPML1 that is involved in late endocytic membrane fusion, is present in vesicles closely contacting the PVM and is necessary for parasite growth. Thus, our studies suggest that the parasite PVM is able to fuse with host late endocytic vesicles in a PI(3,5)P2 -dependent manner, allowing the exchange of material between the host and the parasite, which is essential for successful infection.
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Affiliation(s)
- Carolina Thieleke-Matos
- CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056, Lisboa, Portugal; IGC, Instituto Gulbenkian de Ciência, 2780-156, Oeiras, Portugal
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59
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Chen CC, Keller M, Hess M, Schiffmann R, Urban N, Wolfgardt A, Schaefer M, Bracher F, Biel M, Wahl-Schott C, Grimm C. A small molecule restores function to TRPML1 mutant isoforms responsible for mucolipidosis type IV. Nat Commun 2014; 5:4681. [PMID: 25119295 DOI: 10.1038/ncomms5681] [Citation(s) in RCA: 122] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 07/11/2014] [Indexed: 11/08/2022] Open
Abstract
Mucolipidosis type IV (MLIV) is an autosomal recessive lysosomal storage disorder often characterized by severe neurodevelopmental abnormalities and neuro-retinal degeneration. Mutations in the TRPML1 gene are causative for MLIV. We used lead optimization strategies to identify--and MLIV patient fibroblasts to test--small-molecule activators for their potential to restore TRPML1 mutant channel function. Using the whole-lysosome planar patch-clamp technique, we found that activation of MLIV mutant isoforms by the endogenous ligand PI(3,5)P2 is strongly reduced, while activity can be increased using synthetic ligands. We also found that the F465L mutation renders TRPML1 pH insensitive, while F408Δ impacts synthetic ligand binding. Trafficking defects and accumulation of zinc in lysosomes of MLIV mutant fibroblasts can be rescued by the small molecule treatment. Collectively, our data demonstrate that small molecules can be used to restore channel function and rescue disease associated abnormalities in patient cells expressing specific MLIV point mutations.
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Affiliation(s)
- Cheng-Chang Chen
- 1] Department of Pharmacy-Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, Munchen 81377, Germany [2]
| | - Marco Keller
- 1] Department of Pharmacy, Ludwig-Maximilians-Universität München, Munchen 81377, Germany [2]
| | - Martin Hess
- Department of Biology, Ludwig-Maximilians-Universität München, Munchen 82152, Germany
| | - Raphael Schiffmann
- Institute of Metabolic Disease, Baylor Research Institute, Dallas, Texas, USA
| | - Nicole Urban
- Rudolf-Boehm-Institute for Pharmacology and Toxicolgy, Universität Leipzig, Leipzig 04107, Germany
| | - Annette Wolfgardt
- Department of Pharmacy, Ludwig-Maximilians-Universität München, Munchen 81377, Germany
| | - Michael Schaefer
- Rudolf-Boehm-Institute for Pharmacology and Toxicolgy, Universität Leipzig, Leipzig 04107, Germany
| | - Franz Bracher
- Department of Pharmacy, Ludwig-Maximilians-Universität München, Munchen 81377, Germany
| | - Martin Biel
- Department of Pharmacy-Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, Munchen 81377, Germany
| | - Christian Wahl-Schott
- Department of Pharmacy-Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, Munchen 81377, Germany
| | - Christian Grimm
- 1] Department of Pharmacy-Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, Munchen 81377, Germany [2]
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60
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Liu Z, Zhao S, Wu S, Zhang J, Nie Z, Zeng S. A novel role of transient receptor potential mucolipin1 (TRPML1) in protecting against imidazole-induced cytotoxicity. Biochem Cell Biol 2014; 92:279-86. [DOI: 10.1139/bcb-2014-0044] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Lysosomotropic amines cause serious side effects such as cytoplasmic vacuolation and cell death. TRPML1 (also known as mucolipin1), a member of the transient receptor potential (TRP) protein family, may regulate fusion/fission of vesicles along the endocytic pathway and some aspects of lysosomal ion homeostasis. Nevertheless, it is still unknown whether TRPML1 is involved in death of mammalian cells induced by lysosomotropic agents. In this study, imidazole was used as a model to investigate the role of TRPML1 in the cytotoxicity of lysosomotropic agents. Overexpression of wild-type TRPML1 inhibited imidazole-induced vacuole formation and cell death in human endometrial adenocarcinoma (HEC-1B) cells. In contrast, siRNA-mediated TRPML1 knockdown increased the cell death induced by imidazole. Bafilomycin A1 raises the pH of acidic organelles and therefore suppresses accumulation of weak bases in them. Similarly, lysosomal pH was raised in TRPML1-overexpressing cells; therefore, we inferred that TRPML1 protected against imidazole toxicity by regulating the pH of acidic organelles. We concluded that TRPML1 had a novel role in protecting against lysosomotropic amine toxicity.
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Affiliation(s)
- Zhenxing Liu
- Laboratory of Animal Embryonic Biotechnology, College of Animal Science and Technology, China Agricultural University, Beijing 100193, P.R. China
| | - Shuan Zhao
- Laboratory of Animal Embryonic Biotechnology, College of Animal Science and Technology, China Agricultural University, Beijing 100193, P.R. China
| | - Shuaishuai Wu
- Laboratory of Animal Embryonic Biotechnology, College of Animal Science and Technology, China Agricultural University, Beijing 100193, P.R. China
| | - Jingyou Zhang
- Reproduction and Breeding Research Center, Animal Husbandry and Veterinary 9 Research Institute, Heilongjiang Academy of Agricultural and Reclamation Science, Harbin 150038, P.R. China
| | - Zunyang Nie
- Laboratory of Animal Embryonic Biotechnology, College of Animal Science and Technology, China Agricultural University, Beijing 100193, P.R. China
| | - Shenming Zeng
- Laboratory of Animal Embryonic Biotechnology, College of Animal Science and Technology, China Agricultural University, Beijing 100193, P.R. China
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Jha A, Ahuja M, Patel S, Brailoiu E, Muallem S. Convergent regulation of the lysosomal two-pore channel-2 by Mg²⁺, NAADP, PI(3,5)P₂ and multiple protein kinases. EMBO J 2014; 33:501-11. [PMID: 24502975 DOI: 10.1002/embj.201387035] [Citation(s) in RCA: 150] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Lysosomal Ca(2+) homeostasis is implicated in disease and controls many lysosomal functions. A key in understanding lysosomal Ca(2+) signaling was the discovery of the two-pore channels (TPCs) and their potential activation by NAADP. Recent work concluded that the TPCs function as a PI(3,5)P2 activated channels regulated by mTORC1, but not by NAADP. Here, we identified Mg(2+) and the MAPKs, JNK and P38 as novel regulators of TPC2. Cytoplasmic Mg(2+) specifically inhibited TPC2 outward current, whereas lysosomal Mg(2+) partially inhibited both outward and inward currents in a lysosomal lumen pH-dependent manner. Under controlled Mg(2+), TPC2 is readily activated by NAADP with channel properties identical to those in response to PI(3,5)P2. Moreover, TPC2 is robustly regulated by P38 and JNK. Notably, NAADP-mediated Ca(2+) release in intact cells is regulated by Mg(2+), PI(3,5)P2, and P38/JNK kinases, thus paralleling regulation of TPC2 currents. Our data affirm a key role for TPC2 in NAADP-mediated Ca(2+) signaling and link this pathway to Mg(2+) homeostasis and MAP kinases, pointing to roles for lysosomal Ca(2+) in cell growth, inflammation and cancer.
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Affiliation(s)
- Archana Jha
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, NIDCR NIH, Bethesda, MD, USA
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62
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Martina JA, Diab HI, Lishu L, Jeong-A L, Patange S, Raben N, Puertollano R. The nutrient-responsive transcription factor TFE3 promotes autophagy, lysosomal biogenesis, and clearance of cellular debris. Sci Signal 2014; 7:ra9. [PMID: 24448649 DOI: 10.1126/scisignal.2004754] [Citation(s) in RCA: 456] [Impact Index Per Article: 45.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The discovery of a gene network regulating lysosomal biogenesis and its transcriptional regulator transcription factor EB (TFEB) revealed that cells monitor lysosomal function and respond to degradation requirements and environmental cues. We report the identification of transcription factor E3 (TFE3) as another regulator of lysosomal homeostasis that induced expression of genes encoding proteins involved in autophagy and lysosomal biogenesis in ARPE-19 cells in response to starvation and lysosomal stress. We found that in nutrient-replete cells, TFE3 was recruited to lysosomes through interaction with active Rag guanosine triphosphatases (GTPases) and exhibited mammalian (or mechanistic) target of rapamycin complex 1 (mTORC1)-dependent phosphorylation. Phosphorylated TFE3 was retained in the cytosol through its interaction with the cytosolic chaperone 14-3-3. After starvation, TFE3 rapidly translocated to the nucleus and bound to the CLEAR elements present in the promoter region of many lysosomal genes, thereby inducing lysosomal biogenesis. Depletion of endogenous TFE3 entirely abolished the response of ARPE-19 cells to starvation, suggesting that TFE3 plays a critical role in nutrient sensing and regulation of energy metabolism. Furthermore, overexpression of TFE3 triggered lysosomal exocytosis and resulted in efficient cellular clearance in a cellular model of a lysosomal storage disorder, Pompe disease, thus identifying TFE3 as a potential therapeutic target for the treatment of lysosomal disorders.
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Affiliation(s)
- José A Martina
- 1Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, 9000 Rockville Pike, Building 50/3537, Bethesda, MD 20892, USA
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63
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Abstract
The first member of the mammalian mucolipin TRP channel subfamily (TRPML1) is a cation-permeable channel that is predominantly localized on the membranes of late endosomes and lysosomes (LELs) in all mammalian cell types. In response to the regulatory changes of LEL-specific phosphoinositides or other cellular cues, TRPML1 may mediate the release of Ca(2+) and heavy metal Fe(2+)/Zn(2+)ions into the cytosol from the LEL lumen, which in turn may regulate membrane trafficking events (fission and fusion), signal transduction, and ionic homeostasis in LELs. Human mutations in TRPML1 result in type IV mucolipidosis (ML-IV), a childhood neurodegenerative lysosome storage disease. At the cellular level, loss-of-function mutations of mammalian TRPML1 or its C. elegans or Drosophila homolog gene results in lysosomal trafficking defects and lysosome storage. In this chapter, we summarize recent advances in our understandings of the cell biological and channel functions of TRPML1. Studies on TRPML1's channel properties and its regulation by cellular activities may provide clues for developing new therapeutic strategies to delay neurodegeneration in ML-IV and other lysosome-related pediatric diseases.
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64
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Loss of TRPML1 promotes production of reactive oxygen species: is oxidative damage a factor in mucolipidosis type IV? Biochem J 2013; 457:361-8. [DOI: 10.1042/bj20130647] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
TRPML1 is a lysosomal ion channel permeable to cations, including Fe2+. Our data suggest that TRPML1 redistributes Fe2+ between the lysosomes and the cytoplasm. Loss of TRPML1 leads to production of reactive oxygen species, and to mitochondrial deterioration.
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65
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Abstract
TRP channels constitute a large superfamily of cation channel forming proteins, all related to the gene product of the transient receptor potential (trp) locus in Drosophila. In mammals, 28 different TRP channel genes have been identified, which exhibit a large variety of functional properties and play diverse cellular and physiological roles. In this article, we provide a brief and systematic summary of expression, function, and (patho)physiological role of the mammalian TRP channels.
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Affiliation(s)
- Maarten Gees
- Laboratory Ion Channel Research and TRP Research Platform Leuven (TRPLe), KU Leuven, Campus Gasthuisberg, Leuven, Belgium
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66
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Taylor MC, McLatchie AP, Kelly JM. Evidence that transport of iron from the lysosome to the cytosol in African trypanosomes is mediated by a mucolipin orthologue. Mol Microbiol 2013; 89:420-32. [PMID: 23750752 PMCID: PMC3828870 DOI: 10.1111/mmi.12285] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/02/2013] [Indexed: 11/28/2022]
Abstract
Bloodstream-form Trypanosoma brucei acquire iron by receptor-mediated endocytosis of host transferrin. However, the mechanism(s) by which iron is then transferred from the lysosome to the cytosol are unresolved. Here, we provide evidence for the involvement of a protein (TbMLP) orthologous to the mammalian endolysosomal cation channel Mucolipin 1. In T. brucei, we show that this protein is localized to the single parasite lysosome. TbMLP null mutants could only be generated in the presence of an expressed ectopic copy, suggesting that the protein is essential. RNAi-mediated ablation resulted in a growth defect in vitro and led to a sevenfold increase in susceptibility to the iron-chelators deferoxamine and salicylhydroxamic acid. Conditional null mutants remained viable when the ectopic copy was repressed, but were hypersensitive to deferoxamine and displayed a growth defect similar to that observed following RNAi. The conditional nulls also retained virulence in vivo in the absence of the doxycycline inducer. These data provide strong evidence that TbMLP has a role in import of iron into the cytosol of African trypanosomes. They also indicate that even when expression is greatly reduced, there is sufficient protein, or an alternative mechanism, to provide the parasite with an adequate supply of cytosolic iron.
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Affiliation(s)
- Martin C Taylor
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, Keppel St., London, WC1E 7HT, UK.
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67
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Sillence DJ. Glucosylceramide modulates endolysosomal pH in Gaucher disease. Mol Genet Metab 2013; 109:194-200. [PMID: 23628459 DOI: 10.1016/j.ymgme.2013.03.015] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 03/25/2013] [Accepted: 03/25/2013] [Indexed: 10/27/2022]
Abstract
GlcCer accumulation causes Gaucher disease where GlcCer breakdown is inhibited due to a hereditary deficiency in glucocerebrosidase. Glycolipids are endocytosed and targeted to the Golgi apparatus in normal cells but in Gaucher disease they are mistargeted to lysosomes. To better understand the role of GlcCer in endocytic sorting RAW macrophages were treated with Conduritol B-epoxide to inhibit GlcCer breakdown. Lipid analysis found increases in GlcCer led to accumulation of both triacylglycerol and cholesterol consistent with increased lysosomal pH. Ratio imaging of macrophages using both acridine orange and lysosensor yellow/blue to measure endolysosomal pH revealed increases in Conduritol B-epoxide treated RAW macrophages and Gaucher patient lymphoblasts. Increased endolysosomal pH was restricted to Gaucher lymphoblasts as no significant increases in pH were seen in Fabry, Krabbe, Tay-Sachs and GM1-gangliosidosis lymphoblasts. Substrate reduction therapy utilises inhibitors of GlcCer synthase to reduce storage in Gaucher disease. The addition of inhibitors of GlcCer synthesis to RAW macrophages also led to increases in cholesterol and triacylglycerol and an endolysosomal pH increase of up to 1 pH unit. GlcCer modulation appears specific since glucosylsphingosine but not galactosylsphingosine reversed the effects of GlcCer depletion. Although no acute effects on glycolipid trafficking were observed using bafilomycin A the results are consistent with a multistep model whereby increases in pH lead to altered trafficking via cholesterol accumulation. GlcCer modulates endolysosomal pH in lymphocytes suggesting an important role in normal lysosomes which may be disrupted in Gaucher disease.
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Affiliation(s)
- Dan J Sillence
- Cell Signalling Lab. Leicester School of Pharmacy, De Montfort University, The Gateway, Leicester, LE1 9BH, UK.
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68
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Li PL, Zhang Y, Abais JM, Ritter JK, Zhang F. Cyclic ADP-Ribose and NAADP in Vascular Regulation and Diseases. ACTA ACUST UNITED AC 2013; 2:63-85. [PMID: 24749015 DOI: 10.1166/msr.2013.1022] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cyclic ADP-ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP), two intracellular Ca2+ mobilizing second messengers, have been recognized as a fundamental signaling mechanism regulating a variety of cell or organ functions in different biological systems. Here we reviewed the literature regarding these ADP-ribosylcyclase products in vascular cells with a major focus on their production, physiological roles, and related underlying mechanisms mediating their actions. In particular, several hot topics in this area of research are comprehensively discussed, which may help understand some of the controversial evidence provided by different studies. For example, some new models are emerging for the agonist receptor coupling of CD38 or ADP-ribosylcyclase and for the formation of an acidic microenvironment to facilitate the production of NAADP in vascular cells. We also summarized the evidence regarding the NAADP-mediated two-phase Ca2+ release with a slow Ca2+-induced Ca2+ release (CICR) and corresponding physiological relevance. The possibility of a permanent structural space between lysosomes and sarcoplasmic reticulum (SR), as well as the critical role of lysosome trafficking in phase 2 Ca2+ release in response to some agonists are also explored. With respect to the molecular targets of NAADP within cells, several possible candidates including SR ryanodine receptors (RyRs), lysosomal transient receptor potential-mucolipin 1 (TRP-ML1) and two pore channels (TPCs) are presented with supporting and opposing evidence. Finally, the possible role of NAADP-mediated regulation of lysosome function in autophagy and atherogenesis is discussed, which may indicate a new direction for further studies on the pathological roles of cADPR and NAADP in the vascular system.
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Affiliation(s)
- Pin-Lan Li
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, VA 23298, USA
| | - Yang Zhang
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, VA 23298, USA
| | - Justine M Abais
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, VA 23298, USA
| | - Joseph K Ritter
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, VA 23298, USA
| | - Fan Zhang
- Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, VA 23298, USA
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69
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Spooner E, McLaughlin BM, Lepow T, Durns TA, Randall J, Upchurch C, Miller K, Campbell EM, Fares H. Systematic screens for proteins that interact with the mucolipidosis type IV protein TRPML1. PLoS One 2013; 8:e56780. [PMID: 23418601 PMCID: PMC3572064 DOI: 10.1371/journal.pone.0056780] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 01/15/2013] [Indexed: 11/19/2022] Open
Abstract
Mucolipidosis type IV is a lysosomal storage disorder resulting from mutations in the MCOLN1 gene, which encodes the endosomal/lysosomal Transient Receptor Potential channel protein mucolipin-1/TRPML1. Cells isolated from Mucolipidosis type IV patients and grown in vitro and in in vivo models of this disease both show several lysosome-associated defects. However, it is still unclear how TRPML1 regulates the transport steps implicated by these defects. Identifying proteins that associate with TRPML1 will facilitate the elucidation of its cellular and biochemical functions. We report here two saturation screens for proteins that interact with TRPML1: one that is based on immunoprecipitation/mass spectrometry and the other using a genetic yeast two-hybrid approach. From these screens, we identified largely non-overlapping proteins, which represent potential TRPML1-interactors., Using additional interaction assays on some of the potential interactors from each screen, we validated some proteins as candidate TRPML1 interactors In addition, our analysis indicates that each of the two screens not only identified some false-positive interactors, as expected from any screen, but also failed to uncover potential TRPML1 interactors. Future studies on the true interactors, first identified in these screens, will help elucidate the structure and function of protein complexes containing TRPML1.
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Affiliation(s)
- Ellen Spooner
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, United States of America
| | - Brooke M. McLaughlin
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, United States of America
| | - Talya Lepow
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, United States of America
| | - Tyler A. Durns
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, United States of America
| | - Justin Randall
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, United States of America
| | - Cameron Upchurch
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, United States of America
| | - Katherine Miller
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, United States of America
| | - Erin M. Campbell
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, United States of America
| | - Hanna Fares
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, United States of America
- * E-mail:
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70
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Cang C, Zhou Y, Navarro B, Seo YJ, Aranda K, Shi L, Battaglia-Hsu S, Nissim I, Clapham DE, Ren D. mTOR regulates lysosomal ATP-sensitive two-pore Na(+) channels to adapt to metabolic state. Cell 2013; 152:778-790. [PMID: 23394946 DOI: 10.1016/j.cell.2013.01.023] [Citation(s) in RCA: 292] [Impact Index Per Article: 26.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Revised: 08/31/2012] [Accepted: 01/14/2013] [Indexed: 12/11/2022]
Abstract
Survival in the wild requires organismal adaptations to the availability of nutrients. Endosomes and lysosomes are key intracellular organelles that couple nutrition and metabolic status to cellular responses, but how they detect cytosolic ATP levels is not well understood. Here, we identify an endolysosomal ATP-sensitive Na(+) channel (lysoNa(ATP)). The channel is a complex formed by two-pore channels (TPC1 and TPC2), ion channels previously thought to be gated by nicotinic acid adenine dinucleotide phosphate (NAADP), and the mammalian target of rapamycin (mTOR). The channel complex detects nutrient status, becomes constitutively open upon nutrient removal and mTOR translocation off the lysosomal membrane, and controls the lysosome's membrane potential, pH stability, and amino acid homeostasis. Mutant mice lacking lysoNa(ATP) have much reduced exercise endurance after fasting. Thus, TPCs make up an ion channel family that couples the cell's metabolic state to endolysosomal function and are crucial for physical endurance during food restriction.
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Affiliation(s)
- Chunlei Cang
- Department of Biology, University of Pennsylvania, 415 S. University Ave., Philadelphia, Pennsylvania 19104, USA
| | - Yandong Zhou
- Department of Biology, University of Pennsylvania, 415 S. University Ave., Philadelphia, Pennsylvania 19104, USA
| | - Betsy Navarro
- Howard Hughes Medical Institute, Department of Cardiology, Children's Hospital, Boston, Massachusetts 02115, USA
| | - Young-Jun Seo
- Department of Biology, University of Pennsylvania, 415 S. University Ave., Philadelphia, Pennsylvania 19104, USA
| | - Kimberly Aranda
- Department of Biology, University of Pennsylvania, 415 S. University Ave., Philadelphia, Pennsylvania 19104, USA
| | - Lucy Shi
- Department of Biology, University of Pennsylvania, 415 S. University Ave., Philadelphia, Pennsylvania 19104, USA
| | - Shyuefang Battaglia-Hsu
- INSERM U954, Nutrition Génétique et exposition aux risques environnementaux Faculté de Médecine - BP 184, Université de Lorraine, 54505 VANDOEUVRE LES NANCY CEDEX, FRANCE
| | - Itzhak Nissim
- Division of Child Development and Metabolic Disease, Children's Hospital of Philadelphia, Department of Pediatrics, Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
| | - David E Clapham
- Howard Hughes Medical Institute, Department of Cardiology, Children's Hospital, Boston, Massachusetts 02115, USA
| | - Dejian Ren
- Department of Biology, University of Pennsylvania, 415 S. University Ave., Philadelphia, Pennsylvania 19104, USA
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71
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Wong CO, Li R, Montell C, Venkatachalam K. Drosophila TRPML is required for TORC1 activation. Curr Biol 2012; 22:1616-21. [PMID: 22863314 DOI: 10.1016/j.cub.2012.06.055] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 04/13/2012] [Accepted: 06/15/2012] [Indexed: 02/04/2023]
Abstract
Loss-of-function mutations in TRPML1 (transient receptor potential mucolipin 1) cause the lysosomal storage disorder, mucolipidosis type IV (MLIV). Here, we report that flies lacking the TRPML1 homolog displayed incomplete autophagy and reduced viability during the pupal period--a phase when animals rely on autophagy for nutrients. We show that TRPML was required for fusion of amphisomes with lysosomes, and its absence led to accumulation of vesicles of significantly larger volume and higher luminal Ca(2+). We also found that trpml(1) mutant cells showed decreased TORC1 (target of rapamycin complex 1) signaling and a concomitant upregulation of autophagy induction. Both of these defects in the mutants were reversed by genetically activating TORC1 or by feeding the larvae a high-protein diet. The high-protein diet also reduced the pupal lethality and the increased volume of acidic vesicles. Conversely, further inhibition of TORC1 activity by rapamycin exacerbated the mutant phenotypes. Finally, TORC1 exerted reciprocal control on TRPML function. A high-protein diet caused cortical localization of TRPML, and this effect was blocked by rapamycin. Our findings delineate the interrelationship between the TRPML and TORC1 pathways and raise the intriguing possibility that a high-protein diet might reduce the severity of MLIV.
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Affiliation(s)
- Ching-On Wong
- Department of Integrative Biology and Pharmacology, University of Texas School of Medicine, Houston, TX 77030, USA
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72
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Phosphoinositide isoforms determine compartment-specific ion channel activity. Proc Natl Acad Sci U S A 2012; 109:11384-9. [PMID: 22733759 DOI: 10.1073/pnas.1202194109] [Citation(s) in RCA: 122] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Phosphoinositides serve as address labels for recruiting peripheral cytoplasmic proteins to specific subcellular compartments, and as endogenous factors for modulating the activity of integral membrane proteins. Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) is a plasma-membrane (PM)-specific phosphoinositide and a positive cofactor required for the activity of most PM channels and transporters. This requirement for phosphoinositide cofactors has been proposed to prevent PM channel/transporter activity during passage through the biosynthetic/secretory and endocytic pathways. To determine whether intracellularly localized channels are similarly "inactivated" at the PM, we studied PIP(2) modulation of intracellular TRPML1 channels. TRPML1 channels are primarily localized in lysosomes, but can also be detected temporarily in the PM upon lysosomal exocytosis. By directly patch-clamping isolated lysosomes, we previously found that lysosomal, but not PM-localized, TRPML1 is active with PI(3,5)P(2), a lysosome-specific PIP(2), as the underlying positive cofactor. Here we found that "silent" PM-localized TRPML1 could be activated by depleting PI(4,5)P(2) levels and/or by adding PI(3,5)P(2) to inside-out membrane patches. Unlike PM channels, surface-expressed TRPML1 underwent a unique and characteristic run-up upon patch excision, and was potently inhibited by a low micromolar concentration of PI(4,5)P(2). Conversely, depletion of PI(4,5)P(2) by either depolarization-induced activation or chemically induced translocation of 5'-phosphatase potentiated whole-cell TRPML1 currents. PI(3,5)P(2) activation and PI(4,5)P(2) inhibition of TRPML1 were mediated by distinct basic amino acid residues in a common PIP(2)-interacting domain. Thus, PI(4,5)P(2) may serve as a negative cofactor for intracellular channels such as TRPML1. Based on these results, we propose that phosphoinositide regulation sets compartment-specific activity codes for membrane channels and transporters.
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73
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Shen D, Wang X, Li X, Zhang X, Yao Z, Dibble S, Dong XP, Yu T, Lieberman AP, Showalter HD, Xu H. Lipid storage disorders block lysosomal trafficking by inhibiting a TRP channel and lysosomal calcium release. Nat Commun 2012; 3:731. [PMID: 22415822 DOI: 10.1038/ncomms1735] [Citation(s) in RCA: 364] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 02/07/2012] [Indexed: 11/09/2022] Open
Abstract
Lysosomal lipid accumulation, defects in membrane trafficking and altered Ca(2+) homoeostasis are common features in many lysosomal storage diseases. Mucolipin transient receptor potential channel 1 (TRPML1) is the principle Ca(2+) channel in the lysosome. Here we show that TRPML1-mediated lysosomal Ca(2+) release, measured using a genetically encoded Ca(2+) indicator (GCaMP3) attached directly to TRPML1 and elicited by a potent membrane-permeable synthetic agonist, is dramatically reduced in Niemann-Pick (NP) disease cells. Sphingomyelins (SMs) are plasma membrane lipids that undergo sphingomyelinase (SMase)-mediated hydrolysis in the lysosomes of normal cells, but accumulate distinctively in lysosomes of NP cells. Patch-clamp analyses revealed that TRPML1 channel activity is inhibited by SMs, but potentiated by SMases. In NP-type C cells, increasing TRPML1's expression or activity was sufficient to correct the trafficking defects and reduce lysosome storage and cholesterol accumulation. We propose that abnormal accumulation of luminal lipids causes secondary lysosome storage by blocking TRPML1- and Ca(2+)-dependent lysosomal trafficking.
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Affiliation(s)
- Dongbiao Shen
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 3089 Natural Science Building (Kraus), 830 North University, Ann Arbor 48109, USA
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74
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Lima WC, Leuba F, Soldati T, Cosson P. Mucolipin controls lysosome exocytosis in Dictyostelium. J Cell Sci 2012; 125:2315-22. [PMID: 22357942 DOI: 10.1242/jcs.100362] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mucolipidosis type IV is a poorly understood lysosomal storage disease caused by alterations in the mucolipin lysosomal Ca(2+) channel. In this study, we generated mucolipin-knockout Dictyostelium cells, and observed that lysosome exocytosis was markedly increased in these cells compared with wild-type cells. In addition, mucolipin-knockout cells were more resistant to Ca(2+) deprivation, and the Ca(2+) concentration in their secretory lysosomes was decreased, suggesting that mucolipin transfers Ca(2+) ions from the cytosol to the lumen of secretory lysosomes. We speculate that mucolipin attenuates the fusogenic effect of local cytosolic increases in Ca(2+) by dissipating them into the lumen of lysosomal compartments.
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Affiliation(s)
- Wanessa C Lima
- Department of Cell Physiology and Metabolism, Faculty of Medicine, University of Geneva, 1211 Geneva, Switzerland.
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75
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Abstract
Lysosomes, the terminal organelles on the endocytic pathway, digest macromolecules and make their components available to the cell as nutrients. Hydrolytic enzymes specific to a wide range of targets reside within the lysosome; these enzymes are activated by the highly acidic pH (between 4.5 and 5.0) in the organelles' interior. Lysosomes generate and maintain their pH gradients by using the activity of a proton-pumping V-type ATPase, which uses metabolic energy in the form of ATP to pump protons into the lysosome lumen. Because this activity separates electric charge and generates a transmembrane voltage, another ion must move to dissipate this voltage for net pumping to occur. This so-called counterion may be either a cation (moving out of the lysosome) or an anion (moving into the lysosome). Recent data support the involvement of ClC-7, a Cl(-)/H(+) antiporter, in this process, although many open questions remain as to this transporter's involvement. Although functional results also point to a cation transporter, its molecular identity remains uncertain. Both the V-ATPase and the counterion transporter are likely to be important players in the mechanisms determining the steady-state pH of the lysosome interior. Exciting new results suggest that lysosomal pH may be dynamically regulated in some cell types.
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Affiliation(s)
- Joseph A Mindell
- Membrane Transport Biophysics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
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76
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Marks DL, Holicky EL, Wheatley CL, Frumkin A, Bach G, Pagano RE. Role of protein kinase d in Golgi exit and lysosomal targeting of the transmembrane protein, Mcoln1. Traffic 2012; 13:565-75. [PMID: 22268962 DOI: 10.1111/j.1600-0854.2012.01331.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Revised: 01/19/2012] [Accepted: 01/23/2012] [Indexed: 11/27/2022]
Abstract
The targeting of lysosomal transmembrane (TM) proteins from the Golgi apparatus to lysosomes is a complex process that is only beginning to be understood. Here, the lysosomal targeting of mucolipin-1 (Mcoln1), the TM protein defective in the autosomal recessive disease, mucolipidosis type IV, was studied by overexpressing full-length and truncated forms of the protein in human cells, followed by detection using immunofluorescence and immunoblotting. We demonstrated that a 53-amino acid C-terminal region of Mcoln1 is required for efficient exit from the Golgi. Truncations lacking this region exhibited reduced delivery to lysosomes and decreased proteolytic cleavage of Mcoln1 into characteristic ∼35-kDa fragments, suggesting that this cleavage occurs in lysosomes. In addition, we found that the co-expression of full-length Mcoln1 with kinase-inactive protein kinase D (PKD) 1 or 2 inhibited Mcoln1 Golgi exit and transport to lysosomes and decreased Mcoln1 cleavage. These studies suggest that PKDs play a role in the delivery of some lysosomal resident TM proteins from the Golgi to the lysosomes.
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Affiliation(s)
- David L Marks
- Department of Medicine, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA.
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77
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Colletti GA, Miedel MT, Quinn J, Andharia N, Weisz OA, Kiselyov K. Loss of lysosomal ion channel transient receptor potential channel mucolipin-1 (TRPML1) leads to cathepsin B-dependent apoptosis. J Biol Chem 2012; 287:8082-91. [PMID: 22262857 DOI: 10.1074/jbc.m111.285536] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Mucolipidosis type IV (MLIV) is a lysosomal storage disease caused by mutations in the gene MCOLN1, which codes for the transient receptor potential family ion channel TRPML1. MLIV has an early onset and is characterized by developmental delays, motor and cognitive deficiencies, gastric abnormalities, retinal degeneration, and corneal cloudiness. The degenerative aspects of MLIV have been attributed to cell death, whose mechanisms remain to be delineated in MLIV and in most other storage diseases. Here we report that an acute siRNA-mediated loss of TRPML1 specifically causes a leak of lysosomal protease cathepsin B (CatB) into the cytoplasm. CatB leak is associated with apoptosis, which can be prevented by CatB inhibition. Inhibition of the proapoptotic protein Bax prevents TRPML1 KD-mediated apoptosis but does not prevent cytosolic release of CatB. This is the first evidence of a mechanistic link between acute TRPML1 loss and cell death.
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Affiliation(s)
- Grace A Colletti
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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78
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Abstract
Lysosomes are an important cellular organelle that receive and degrade macromolecules from the secretory, endocytic, autophagic, and phagocytic membrane-trafficking pathways. Defects in lysosome function lead to the development of disease with often-severe consequences to the individual. Since the discovery of lysosomes by Christian de Duve over 50 years ago, research into endocytic and lysosomal biology has allowed for the development of tools to understand further the role of lysosomes in cells. There are now several fluorescent probes that can be used to visualize and assess membrane traffic to the lysosome as well as probes to assess the activity of lysosomal hydrolases in live cells. This chapter describes the current methods used to measure lysosome function in live cells.
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Affiliation(s)
- Paul R Pryor
- Centre for Immunology and Infection, Hull York Medical School and Department of Biology, University of York, York, United Kingdom
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79
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Pyridine nucleotide metabolites and calcium release from intracellular stores. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:305-23. [PMID: 22453948 DOI: 10.1007/978-94-007-2888-2_13] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Ca(2+) signals are probably the most common intracellular signaling elements, controlling an extensive range of responses in virtually all cells. Many cellular stimuli, often acting at cell surface receptors, evoke Ca(2+) signals by mobilizing Ca(2+) from intracellular stores. Inositol trisphosphate (IP₃) was the first messenger shown to link events at the plasma membrane to release of Ca(2+) from the endoplasmic reticulum (ER), through activation of IP₃-gated Ca(2+) release channels (IP₃ receptors). Subsequently, two additional Ca(2+) mobilizing messengers were discovered, cADPR and NAADP. Both are metabolites of pyridine nucleotides, and may be produced by the same class of enzymes, ADP-ribosyl cyclases, such as CD38. Whilst cADPR mobilizes Ca(2+) from the ER by activation of ryanodine receptors (RyRs), NAADP releases Ca(2+) from acidic stores by a mechanism involving the activation of two pore channels (TPCs).
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80
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Iron transport machinery of human cells: players and their interactions. CURRENT TOPICS IN MEMBRANES 2012; 69:67-93. [PMID: 23046647 DOI: 10.1016/b978-0-12-394390-3.00003-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Organisms, like cells, maintain tight control of iron. In humans as well as other mammals, control is achieved through the regulation of iron uptake into the body rather than through the excretion of iron. The mechanisms by which humans and mice regulate both iron uptake and the distribution of iron within the body and cells are reviewed. Special emphasis is given to the iron transporters involved in this process.
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81
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Molecular mechanisms of endolysosomal Ca2+ signalling in health and disease. Biochem J 2011; 439:349-74. [PMID: 21992097 DOI: 10.1042/bj20110949] [Citation(s) in RCA: 295] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Endosomes, lysosomes and lysosome-related organelles are emerging as important Ca2+ storage cellular compartments with a central role in intracellular Ca2+ signalling. Endocytosis at the plasma membrane forms endosomal vesicles which mature to late endosomes and culminate in lysosomal biogenesis. During this process, acquisition of different ion channels and transporters progressively changes the endolysosomal luminal ionic environment (e.g. pH and Ca2+) to regulate enzyme activities, membrane fusion/fission and organellar ion fluxes, and defects in these can result in disease. In the present review we focus on the physiology of the inter-related transport mechanisms of Ca2+ and H+ across endolysosomal membranes. In particular, we discuss the role of the Ca2+-mobilizing messenger NAADP (nicotinic acid adenine dinucleotide phosphate) as a major regulator of Ca2+ release from endolysosomes, and the recent discovery of an endolysosomal channel family, the TPCs (two-pore channels), as its principal intracellular targets. Recent molecular studies of endolysosomal Ca2+ physiology and its regulation by NAADP-gated TPCs are providing exciting new insights into the mechanisms of Ca2+-signal initiation that control a wide range of cellular processes and play a role in disease. These developments underscore a new central role for the endolysosomal system in cellular Ca2+ regulation and signalling.
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82
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Galione A, Parrington J, Funnell T. Physiological roles of NAADP-mediated Ca2+ signaling. SCIENCE CHINA-LIFE SCIENCES 2011; 54:725-32. [PMID: 21786195 DOI: 10.1007/s11427-011-4207-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Accepted: 06/25/2011] [Indexed: 10/18/2022]
Abstract
Nicotinic acid dinucleotide phosphate (NAADP) is unique amongst Ca(2+) mobilizing messengers in that its principal function is to mobilize Ca(2+) from acidic organelles. Early studies indicated that it was likely that NAADP activates a novel Ca(2+) release channel distinct from the well characterized Ca(2+) release channels on the (sarco)-endoplasmic reticulum (ER), inositol trisphosphate and ryanodine receptors. In this review, we discuss the emergence of a novel family of endolysosomal channels, the two-pore channels (TPCs), as likely targets for NAADP, and how molecular and pharmacological manipulation of these channels is enhancing our understanding of the physiological roles of NAADP as an intracellular Ca(2+) mobilizing messenger.
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Affiliation(s)
- Antony Galione
- Department of Pharmacology, University of Oxford, Oxford, UK.
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83
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Lloyd-Evans E, Platt FM. Lysosomal Ca(2+) homeostasis: role in pathogenesis of lysosomal storage diseases. Cell Calcium 2011; 50:200-5. [PMID: 21724254 DOI: 10.1016/j.ceca.2011.03.010] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Revised: 03/21/2011] [Accepted: 03/24/2011] [Indexed: 01/07/2023]
Abstract
Disrupted cellular Ca(2+) signaling is believed to play a role in a number of human diseases including lysosomal storage diseases (LSD). LSDs are a group of ∼50 diseases caused predominantly by mutations in lysosomal proteins that result in accumulation of macromolecules within the lysosome. We recently reported that Niemann-Pick type C (NPC) is the first human disease to be associated with defective lysosomal Ca(2+) uptake and defective NAADP-mediated lysosomal Ca(2+) release. These defects in NPC cells leads to the disruption in endocytosis and subsequent lipid storage that is a feature of this disease. In contrast, Chediak-Higashi Syndrome cells have been reported to have enhanced lysosomal Ca(2+) uptake whilst the TRPML1 protein defective in mucolipidosis type IV is believed to function as a Ca(2+) channel. In this review we provide a summary of the current knowledge on the role of lysosomal Ca(2+) signaling in the pathogenesis of this group of diseases.
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Affiliation(s)
- Emyr Lloyd-Evans
- School of Biosciences, Biomedical Sciences Building, Cardiff University, Museum Avenue, Cardiff CF10 3AX, United Kingdom.
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84
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Abe K, Puertollano R. Role of TRP channels in the regulation of the endosomal pathway. Physiology (Bethesda) 2011; 26:14-22. [PMID: 21357899 DOI: 10.1152/physiol.00048.2010] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Some members of the transient receptor potential (TRP) channel superfamily have proved to be essential in maintaining adequate ion homeostasis, signaling, and membrane trafficking in the endosomal pathway. The unique properties of the TRP channels confer cells the ability to integrate cytosolic and intraluminal stimuli and allow maintained and regulated release of Ca(2+) from endosomes and lysosomes.
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Affiliation(s)
- Ken Abe
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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85
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Zhang F, Xu M, Han WQ, Li PL. Reconstitution of lysosomal NAADP-TRP-ML1 signaling pathway and its function in TRP-ML1(-/-) cells. Am J Physiol Cell Physiol 2011; 301:C421-30. [PMID: 21613607 DOI: 10.1152/ajpcell.00393.2010] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It is well known that the mutation of TRP-ML1 (transient receptor potential-mucolipin-1) causes mucolipidosis IV, a lysosomal storage disease. Given that lysosomal nicotinic acid adenine dinucleotide phosphate (NAADP)-Ca(2+) release channel activity is associated with TRP-ML1, the present study was designed to test the hypothesis that NAADP regulates lysosome function via activation of TRP-ML1 channel activity. Using lysosomal preparations from wild-type (TRP-ML1(+/+)) human fibroblasts, channel reconstitution experiments demonstrated that NAADP (0.01-1.0 μM) produced a concentration-dependent increase in TRP-ML1 channel activity. This NAADP-induced activation of TRP-ML1 channels could not be observed in lysosomes from TRP-ML1(-/-) cells, but was restored by introducing a TRP-ML1 transgene into these cells. Microscopic Ca(2+) fluorescence imaging showed that NAADP significantly increased intracellular Ca(2+) concentration to 302.4 ± 74.28 nM (vs. 180 ± 44.13 nM of the basal) in TRP-ML1(+/+) cells, but it had no effect in TRP-ML1(-/-) cells. If a TRP-ML1 gene was transfected into TRP-ML1(-/-) cells, the Ca(2+) response to NAADP was restored to the level comparable to TRP-ML1(+/+) cells. Functionally, confocal microscopy revealed that NAADP significantly enhanced the dynamic interaction of endosomes and lysosomes and the lipid delivery to lysosomes in TRP-ML1(+/+) cells. This functional action of NAADP was abolished in TRP-ML1(-/-) cells, but restored after TRP-ML1 gene was rescued in these cells. Our results suggest that NAADP increases lysosomal TRP-ML1 channel activity to release Ca(2+), which promotes the interaction of endosomes and lysosomes and thereby regulates lipid transport to lysosomes. Failure of NAADP-TRP-ML1 signaling may be one of the important mechanisms resulting in intracellular lipid trafficking disorder and consequent mucolipidosis.
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Affiliation(s)
- Fan Zhang
- Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298, USA
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86
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Yamaguchi S, Jha A, Li Q, Soyombo AA, Dickinson GD, Churamani D, Brailoiu E, Patel S, Muallem S. Transient receptor potential mucolipin 1 (TRPML1) and two-pore channels are functionally independent organellar ion channels. J Biol Chem 2011; 286:22934-42. [PMID: 21540176 DOI: 10.1074/jbc.m110.210930] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
NAADP is a potent second messenger that mobilizes Ca(2+) from acidic organelles such as endosomes and lysosomes. The molecular basis for Ca(2+) release by NAADP, however, is uncertain. TRP mucolipins (TRPMLs) and two-pore channels (TPCs) are Ca(2+)-permeable ion channels present within the endolysosomal system. Both have been proposed as targets for NAADP. In the present study, we probed possible physical and functional association of these ion channels. Exogenously expressed TRPML1 showed near complete colocalization with TPC2 and partial colocalization with TPC1. TRPML3 overlap with TPC2 was more modest. TRPML1 and to some extent TRPML3 co-immunoprecipitated with TPC2 but less so with TPC1. Current recording, however, showed that TPC1 and TPC2 did not affect the activity of wild-type TRPML1 or constitutively active TRPML1(V432P). N-terminally truncated TPC2 (TPC2delN), which is targeted to the plasma membrane, also failed to affect TRPML1 and TRPML1(V432P) channel function or TRPML1(V432P)-mediated Ca(2+) influx. Whereas overexpression of TPCs enhanced NAADP-mediated Ca(2+) signals, overexpression of TRPML1 did not, and the dominant negative TRPML1(D471K) was without affect on endogenous NAADP-mediated Ca(2+) signals. Furthermore, the single channel properties of NAADP-activated TPC2delN were not affected by TRPML1. Finally, NAADP-evoked Ca(2+) oscillations in pancreatic acinar cells were identical in wild-type and TRPML1(-/-) cells. We conclude that although TRPML1 and TPCs are present in the same complex, they function as two independent organellar ion channels and that TPCs, not TRPMLs, are the targets for NAADP.
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Affiliation(s)
- Soichiro Yamaguchi
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75235, USA
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87
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Shen D, Wang X, Xu H. Pairing phosphoinositides with calcium ions in endolysosomal dynamics: phosphoinositides control the direction and specificity of membrane trafficking by regulating the activity of calcium channels in the endolysosomes. Bioessays 2011; 33:448-57. [PMID: 21538413 DOI: 10.1002/bies.201000152] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The direction and specificity of endolysosomal membrane trafficking is tightly regulated by various cytosolic and membrane-bound factors, including soluble NSF attachment protein receptors (SNAREs), Rab GTPases, and phosphoinositides. Another trafficking regulatory factor is juxta-organellar Ca(2+) , which is hypothesized to be released from the lumen of endolysosomes and to be present at higher concentrations near fusion/fission sites. The recent identification and characterization of several Ca(2+) channel proteins from endolysosomal membranes has provided a unique opportunity to examine the roles of Ca(2+) and Ca(2+) channels in the membrane trafficking of endolysosomes. SNAREs, Rab GTPases, and phosphoinositides have been reported to regulate plasma membrane ion channels, thereby suggesting that these trafficking regulators may also modulate endolysosomal dynamics by controlling Ca(2+) flux across endolysosomal membranes. In this paper, we discuss the roles of phosphoinositides, Ca(2+) , and potential interactions between endolysosomal Ca(2+) channels and phosphoinositides in endolysosomal dynamics.
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Affiliation(s)
- Dongbiao Shen
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
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88
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Korolchuk VI, Saiki S, Lichtenberg M, Siddiqi FH, Roberts EA, Imarisio S, Jahreiss L, Sarkar S, Futter M, Menzies FM, O'Kane CJ, Deretic V, Rubinsztein DC. Lysosomal positioning coordinates cellular nutrient responses. Nat Cell Biol 2011; 13:453-60. [PMID: 21394080 PMCID: PMC3071334 DOI: 10.1038/ncb2204] [Citation(s) in RCA: 649] [Impact Index Per Article: 49.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Accepted: 01/07/2011] [Indexed: 12/14/2022]
Abstract
mTOR (mammalian target of rapamycin) signalling and macroautophagy (henceforth autophagy) regulate numerous pathological and physiological processes, including cellular responses to altered nutrient levels. However, the mechanisms regulating mTOR and autophagy remain incompletely understood. Lysosomes are dynamic intracellular organelles intimately involved both in the activation of mTOR complex 1 (mTORC1) signalling and in degrading autophagic substrates. Here we report that lysosomal positioning coordinates anabolic and catabolic responses with changes in nutrient availability by orchestrating early plasma-membrane signalling events, mTORC1 signalling and autophagy. Activation of mTORC1 by nutrients correlates with its presence on peripheral lysosomes that are physically close to the upstream signalling modules, whereas starvation causes perinuclear clustering of lysosomes, driven by changes in intracellular pH. Lysosomal positioning regulates mTORC1 signalling, which in turn influences autophagosome formation. Lysosome positioning also influences autophagosome-lysosome fusion rates, and thus controls autophagic flux by acting at both the initiation and termination stages of the process. Our findings provide a physiological role for the dynamic state of lysosomal positioning in cells as a coordinator of mTORC1 signalling with autophagic flux.
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Affiliation(s)
- Viktor I. Korolchuk
- Department of Medical Genetics, Cambridge Institute for Medical Genetics, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - Shinji Saiki
- Department of Medical Genetics, Cambridge Institute for Medical Genetics, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - Maike Lichtenberg
- Department of Medical Genetics, Cambridge Institute for Medical Genetics, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - Farah H. Siddiqi
- Department of Medical Genetics, Cambridge Institute for Medical Genetics, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - Esteban A. Roberts
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, Albuquerque, NM, 87131, USA
| | - Sara Imarisio
- Department of Medical Genetics, Cambridge Institute for Medical Genetics, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
- Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK
| | - Luca Jahreiss
- Department of Medical Genetics, Cambridge Institute for Medical Genetics, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - Sovan Sarkar
- Department of Medical Genetics, Cambridge Institute for Medical Genetics, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - Marie Futter
- Department of Medical Genetics, Cambridge Institute for Medical Genetics, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - Fiona M. Menzies
- Department of Medical Genetics, Cambridge Institute for Medical Genetics, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
| | - Cahir J. O'Kane
- Department of Genetics, University of Cambridge, Cambridge, CB2 3EH, UK
| | - Vojo Deretic
- Department of Molecular Genetics and Microbiology, University of New Mexico School of Medicine, Albuquerque, NM, 87131, USA
- Department of Cell Biology and Physiology, University of New Mexico School of Medicine, Albuquerque, NM, 87131, USA
| | - David C. Rubinsztein
- Department of Medical Genetics, Cambridge Institute for Medical Genetics, Wellcome Trust/MRC Building, Hills Road, Cambridge, CB2 0XY, UK
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89
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NAADP as an intracellular messenger regulating lysosomal calcium-release channels. Biochem Soc Trans 2011; 38:1424-31. [PMID: 21118101 DOI: 10.1042/bst0381424] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Recent studies into the mechanisms of action of the Ca(2+)-mobilizing messenger NAADP (nicotinic acid-adenine dinucleotide phosphate) have demonstrated that a novel family of intracellular Ca(2+)-release channels termed TPCs (two-pore channels) are components of the NAADP receptor. TPCs appear to be exclusively localized to the endolysosomal system. These findings confirm previous pharmacological and biochemical studies suggesting that NAADP targets acidic Ca(2+) stores rather than the endoplasmic reticulum, the major site of action of the other two principal Ca(2+)-mobilizing messengers, InsP(3) and cADPR (cADP-ribose). Studies of the messenger roles of NAADP and the function of TPCs highlight the novel role of lysosomes and other organelles of the endocytic pathway as messenger-regulated Ca(2+) stores which also affects the regulation of the endolysosomal system.
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90
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Abstract
Until recently, the mechanisms that regulate endolysosomal calcium homoeostasis were poorly understood. The discovery of the molecular target of NAADP (nicotinic acid-adenine dinucleotide phosphate) as the two-pore channels resident in the endolysosomal system has highlighted this compartment as an important calcium store. The recent findings that dysfunctional NAADP release leads to defective endocytic function which in turn results in secondary lipid accumulation in the lysosomal storage disease Niemann-Pick type C, is the first evidence of a direct connection between a human disease and defective lysosomal calcium release. In the present review, we provide a summary of the current knowledge on mechanisms of calcium homoeostasis within the endolysosomal system and how these mechanisms may be affected in human metabolic disorders.
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91
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Chandra M, Zhou H, Li Q, Muallem S, Hofmann SL, Soyombo AA. A role for the Ca2+ channel TRPML1 in gastric acid secretion, based on analysis of knockout mice. Gastroenterology 2011; 140:857-67. [PMID: 21111738 PMCID: PMC3057336 DOI: 10.1053/j.gastro.2010.11.040] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Revised: 11/03/2010] [Accepted: 11/10/2010] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Mutations in TRPML1, a lysosomal Ca(2+)-permeable TRP channel, lead to mucolipidosis type IV, a neurodegenerative lysosomal storage disease. An unusual feature of mucolipidosis type IV is constitutive achlorhydria. We produced Trpml1(-/-) (null) mice to investigate the requirement for this protein in gastric acid secretion. METHODS Trpml1-null mice were generated by gene targeting. The expression of Trpml1 and its role in acid secretion by gastric parietal cells were analyzed using biochemical, histologic, and ultrastructural approaches. RESULTS Trpml1 is expressed by parietal cells and localizes predominantly to the lysosomes; it was dynamically palmitoylated and dephosphorylated in vivo following histamine stimulation of acid secretion. Trpml1-null mice had significant impairments in basal and histamine-stimulated gastric acid secretion and markedly reduced levels of the gastric proton pump. Histologic and ultrastructural analyses revealed that Trpml1(-/-) parietal cells were enlarged, had multivesicular and multi-lamellated lysosomes, and maintained an abnormal intracellular canalicular membrane. The intralysosomal Ca(2+) content and receptor-mediated Ca(2+) signaling were, however, unaffected in Trpml1(-/-) gastric glands, indicating that Trpml1 does not function in the regulation of lysosomal Ca(2+). CONCLUSIONS Loss of Trpml1 causes reduced levels and mislocalization of the gastric proton pump and alters the secretory canaliculi, causing hypochlorhydria and hypergastrinemia. The lysosomal enlargement and defective intracellular canaliculi formation observed in Trpml1(-/-) parietal cells indicate that Trpml1 functions in the formation and trafficking of the tubulovesicles. This study provides direct evidence for the regulation of gastric acid secretion by a TRP channel; TRPML1 is an important protein in parietal cell apical membrane trafficking.
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Affiliation(s)
- Manjari Chandra
- Department of Internal Medicine, University of Texas, Southwestern Medical Center, 6000 Harry Hines Blvd, Dallas, TX 75390, USA
| | - Hua Zhou
- Department of Internal Medicine, University of Texas, Southwestern Medical Center, 6000 Harry Hines Blvd, Dallas, TX 75390, USA
| | - Qin Li
- Department of Physiology, University of Texas, Southwestern Medical Center, 6000 Harry Hines Blvd, Dallas, TX 75390, USA
| | - Shmuel Muallem
- Department of Physiology, University of Texas, Southwestern Medical Center, 6000 Harry Hines Blvd, Dallas, TX 75390, USA,Molecular Physiology and Therapeutics Branch, NIDCR, NIH, Bethesda, MD 20892, USA
| | - Sandra L. Hofmann
- Department of Internal Medicine, University of Texas, Southwestern Medical Center, 6000 Harry Hines Blvd, Dallas, TX 75390, USA
| | - Abigail A. Soyombo
- Department of Internal Medicine, University of Texas, Southwestern Medical Center, 6000 Harry Hines Blvd, Dallas, TX 75390, USA,Address correspondence to: Abigail A. Soyombo, Ph.D., Department of Internal Medicine, University of Texas, Southwestern Medical Center, 6000 Harry Hines Blvd, Dallas, Texas 75390-8593, USA, Tel: 214-648-1456, Fax: 214-648-4940,
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92
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Vergarajauregui S, Martina JA, Puertollano R. LAPTMs regulate lysosomal function and interact with mucolipin 1: new clues for understanding mucolipidosis type IV. J Cell Sci 2011; 124:459-68. [PMID: 21224396 PMCID: PMC3022000 DOI: 10.1242/jcs.076240] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2010] [Indexed: 11/20/2022] Open
Abstract
Loss-of-function mutations in mucolipin 1 (MCOLN1) result in mucolipidosis type IV (MLIV), a lysosomal storage disorder characterized by severe mental and psychomotor retardation. MCOLN1 is a lysosomal ion channel that belongs to the transient receptor potential (TRP) superfamily. To better understand the cellular function of MCOLN1, a split-ubiquitin yeast two-hybrid screen was performed with the purpose of revealing new MCOLN1 interaction partners. The screen identified two members of the lysosome-associated protein transmembrane (LAPTM) family as novel interaction partners of MCOLN1. The binding between MCOLN1 and LAPTM members (LAPTMs) was confirmed by co-immunoprecipitation and yeast two-hybrid assays. In addition, MCOLN1 and LAPTMs extensively colocalize at late endosomes and lysosomes. Overexpression of LAPTM4b caused enlargement of lysosomes and defective lysosomal degradation, indicating that LAPTMs are important for proper lysosomal function. Interestingly, lysosomal swelling induced by LAPTM4b was rescued by expression of MCOLN1, suggesting a functional connection between the two proteins. Finally, depletion of endogenous LAPTMs by siRNA induced accumulation of concentric multi-lamellar structures and electron-dense inclusions that closely resemble the structures found in MLIV cells. Overall, our data provide new insight into the molecular mechanisms of MCOLN1 function and suggest a potential role for LAPTMs in MLIV pathogenesis.
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Affiliation(s)
- Silvia Vergarajauregui
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jose A. Martina
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Rosa Puertollano
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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93
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LaPlante JM, Falardeau JL, Brown EM, Slaugenhaupt SA, Vassilev PM. The cation channel mucolipin-1 is a bifunctional protein that facilitates membrane remodeling via its serine lipase domain. Exp Cell Res 2011; 317:691-705. [PMID: 21256127 DOI: 10.1016/j.yexcr.2011.01.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Revised: 12/03/2010] [Accepted: 01/05/2011] [Indexed: 11/19/2022]
Abstract
Phospholipase modulators have been shown to affect the topology of lipid bilayers and the formation of tubulo-vesicular structures, but the specific endogenous phospholipases involved have yet to be identified. Here we show that TRPML1 (MLN1), a Ca(2+)-permeable channel, contributes to membrane remodeling through a serine lipase consensus domain, and thus represents a novel type of bifunctional protein. Remarkably, this serine lipase active site determines the ability of MLN1 to generate tubulo-vesicular extensions in mucolipin-1-expressing oocytes, human fibroblasts and model membrane vesicles. Our demonstration that MLN1 is involved in membrane remodeling and the formation of extensions suggests that it may play a role in the formation of cellular processes linked to the late endosome/lysosome (LE/L) pathway. MLN1 is absent or mutated in patients with mucolipidosis IV (MLIV), a lysosomal disorder with devastating neurological and other consequences. This study provides potential insight into the pathophysiology of MLIV.
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Affiliation(s)
- Janice M LaPlante
- Division of Endocrinology, Diabetes and Hypertension and Membrane Biology Program, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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Lelouvier B, Puertollano R. Mucolipin-3 regulates luminal calcium, acidification, and membrane fusion in the endosomal pathway. J Biol Chem 2011; 286:9826-32. [PMID: 21245134 DOI: 10.1074/jbc.m110.169185] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mucolipin-3 (MCOLN3) is a pH-regulated Ca(2+) channel that localizes to the endosomal pathway. Gain-of-function mutation in MCOLN3 causes the varitint-waddler (Va) phenotype in mice, which is characterized by hearing loss, vestibular dysfunction, and coat color dilution. The Va phenotype results from a punctual mutation (A419P) in the pore region of MCOLN3 that locks the channel in an open conformation causing massive entry of Ca(2+) inside cells and inducing cell death by apoptosis. Overexpression of wild-type MCOLN3 produces severe alterations of the endosomal pathway, including enlargement and clustering of endosomes, delayed EGF receptor degradation, and impaired autophagosome maturation, thus suggesting that MCOLN3 plays an important role in the regulation of endosomal function. To understand better the physiological role of MCOLN3, we inhibited MCOLN3 function by expression of a channel-dead dominant negative mutant (458DD/KK) or by knockdown of endogenous MCOLN3. Remarkably, we found that impairment of MCOLN3 activity caused a significant accumulation of luminal Ca(2+) in endosomes. This accumulation led to severe defects in endosomal acidification as well as to increased endosomal fusion. Our findings reveal a prominent role for MCOLN3 in regulating Ca(2+) homeostasis at the endosomal pathway and confirm the importance of luminal Ca(2+) for proper acidification and membrane fusion.
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Affiliation(s)
- Benjamin Lelouvier
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA
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96
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Abstract
Of the established Ca(2+) mobilizing messengers, NAADP is arguably the most tantalizing. It is the most potent, often efficacious at low nanomolar concentrations. Recent studies have identified a new class of calcium release channel, the two-pore channels (TPCs), as the likely targets for NAADP. These channels are endolysosomal in localization where they mediate local Ca(2+) release, and have highlighted a new role of acidic organelles as targets for messenger-evoked Ca(2+) mobilization. Three distinct roles of TPCs have been identified. The first is to effect local Ca(2+) release that may play a role in endolysosomal function including vesicular fusion and trafficking. The second is to trigger global calcium release by recruiting Ca(2+)-induced Ca(2+) release (CICR) channels at lysosomal-ER junctions. The third is to regulate plasma membrane excitability by the targeting of Ca(2+) release from appropriately positioned subplasma membrane stores to regulate plasma membrane Ca(2+)-activated channels. In this review, I discuss the role of NAADP-mediated Ca(2+) release from endolysosomal stores as a widespread trigger for intracellular calcium signaling mechanisms, and how studies of TPCs are beginning to enhance our understanding of the central role of lysosomes in Ca(2+) signaling.
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Affiliation(s)
- Antony Galione
- Department of Pharmacology, University of Oxford, Mansfield Road, Oxford OX1 3QT, United Kingdom.
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97
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98
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Abstract
MLIV (mucolipidosis type IV) is a neurodegenerative lysosomal storage disorder caused by mutations in MCOLN1, a gene that encodes TRPML1 (mucolipin-1), a member of the TRPML (transient receptor potential mucolipin) cation channels. Two additional homologues are TRPML2 and TRPML3 comprising the TRPML subgroup in the TRP superfamily. The three proteins play apparently key roles along the endocytosis process, and thus their cellular localization varies among the different group members. Thus TRPML1 is localized exclusively to late endosomes and lysosomes, TRPML2 is primarily located in the recycling clathrin-independent GPI (glycosylphosphatidylinositol)-anchored proteins and early endosomes, and TRPML3 is primarily located in early endosomes. Apparently, all three proteins' main physiological function underlies Ca2+ channelling, regulating the endocytosis process. Recent findings also indicate that the three TRPML proteins form heteromeric complexes at least in some of their cellular content. The physiological role of these complexes in lysosomal function remains to be elucidated, as well as their effect on the pathophysiology of MLIV. Another open question is whether any one of the TRPMLs bears additional function in channel activity
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99
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Curcio-Morelli C, Charles FA, Micsenyi MC, Cao Y, Venugopal B, Browning MF, Dobrenis K, Cotman SL, Walkley SU, Slaugenhaupt SA. Macroautophagy is defective in mucolipin-1-deficient mouse neurons. Neurobiol Dis 2010; 40:370-7. [PMID: 20600908 PMCID: PMC4392647 DOI: 10.1016/j.nbd.2010.06.010] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Revised: 06/15/2010] [Accepted: 06/22/2010] [Indexed: 11/17/2022] Open
Abstract
Mucolipidosis type IV is a neurodegenerative lysosomal disease clinically characterized by psychomotor retardation, visual impairment, and achlorhydria. In this study we report the development of a neuronal cell model generated from cerebrum of Mcoln1(-/-) embryos. Prior functional characterization of MLIV cells has been limited to fibroblast cultures gleaned from patients. The current availability of the mucolipin-1 knockout mouse model Mcoln1(-/-) allows the study of mucolipin-1-defective neurons, which is important since the disease is characterized by severe neurological impairment. Electron microscopy studies reveal significant membranous intracytoplasmic storage bodies, which correlate with the storage morphology observed in cerebral cortex of Mcoln1(-/-) P7 pups and E17 embryos. The Mcoln1(-/-) neuronal cultures show an increase in size of LysoTracker and Lamp1 positive vesicles. Using this neuronal model system, we show that macroautophagy is defective in mucolipin-1-deficient neurons and that LC3-II levels are significantly elevated. Treatment with rapamycin plus protease inhibitors did not increase levels of LC3-II in Mcoln1(-/-) neuronal cultures, indicating that the lack of mucolipin-1 affects LC3-II clearance. P62/SQSTM1 and ubiquitin levels were also increased in Mcoln1(-/-) neuronal cultures, suggesting an accumulation of protein aggregates and a defect in macroautophagy which could help explain the neurodegeneration observed in MLIV. This study describes, for the first time, a defect in macroautophagy in mucolipin-1-deficient neurons, which corroborates recent findings in MLIV fibroblasts and provides new insight into the neuronal pathogenesis of this disease.
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Affiliation(s)
- Cyntia Curcio-Morelli
- Center for Human Genetic Research, Massachusetts General Hospital/Harvard Medical School, Richard B. Simches Research Center, CPZN-5254, 185 Cambridge Street, Boston, MA 02114
| | - Florie A. Charles
- Center for Human Genetic Research, Massachusetts General Hospital/Harvard Medical School, Richard B. Simches Research Center, CPZN-5254, 185 Cambridge Street, Boston, MA 02114
| | - Matthew C. Micsenyi
- Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Center for Research in Mental Retardation and Human Development, Albert Einstein College of Medicine, Bronx, New York
| | - Yi Cao
- Center for Human Genetic Research, Massachusetts General Hospital/Harvard Medical School, Richard B. Simches Research Center, CPZN-5254, 185 Cambridge Street, Boston, MA 02114
| | - Bhuvarahamurthy Venugopal
- Center for Human Genetic Research, Massachusetts General Hospital/Harvard Medical School, Richard B. Simches Research Center, CPZN-5254, 185 Cambridge Street, Boston, MA 02114
| | - Marsha F. Browning
- Center for Human Genetic Research, Massachusetts General Hospital/Harvard Medical School, Richard B. Simches Research Center, CPZN-5254, 185 Cambridge Street, Boston, MA 02114
| | - Kostantin Dobrenis
- Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Center for Research in Mental Retardation and Human Development, Albert Einstein College of Medicine, Bronx, New York
| | - Susan L. Cotman
- Center for Human Genetic Research, Massachusetts General Hospital/Harvard Medical School, Richard B. Simches Research Center, CPZN-5254, 185 Cambridge Street, Boston, MA 02114
| | - Steven U. Walkley
- Dominick P. Purpura Department of Neuroscience, Rose F. Kennedy Center for Research in Mental Retardation and Human Development, Albert Einstein College of Medicine, Bronx, New York
| | - Susan A. Slaugenhaupt
- Center for Human Genetic Research, Massachusetts General Hospital/Harvard Medical School, Richard B. Simches Research Center, CPZN-5254, 185 Cambridge Street, Boston, MA 02114
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Zeevi DA, Lev S, Frumkin A, Minke B, Bach G. Heteromultimeric TRPML channel assemblies play a crucial role in the regulation of cell viability models and starvation-induced autophagy. J Cell Sci 2010; 123:3112-24. [PMID: 20736310 PMCID: PMC2931605 DOI: 10.1242/jcs.067330] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/05/2010] [Indexed: 11/20/2022] Open
Abstract
The mucolipin (TRPML) subfamily of transient receptor potential (TRP) cation channels consists of three members that play various roles in the regulation of membrane and protein sorting along endo-lysosomal pathways. Loss-of-function mutations in TRPML1 cause the neurodegenerative lysosomal storage disorder, mucolipidosis type IV (MLIV), whereas a gain-of-function mutation in TRPML3 is principally implicated in the hearing-impaired and abnormally pigmented varitint-waddler mouse. Currently, TRPML2 is not implicated in any pathological disorder, but we have recently shown that it is a functional cation channel that physically interacts with TRPML1 and TRPML3 to potentially regulate lysosomal integrity. Here, we show that mutant TRPMLs heteromultimerize with other mutant and wild-type TRPMLs to regulate cell viability and starvation-induced autophagy, a process that mediates macromolecular and organellar turnover under cell starvation conditions. Heteromultimerization of dominant-negative TRPMLs with constitutively active TRPMLs rescues cells from the cytotoxic effects of TRPML constitutive activity. Moreover, dominant-negative TRPML1 channels, including a mutant channel directly implicated in MLIV pathology, also inhibit starvation-induced autophagy by interacting with and affecting native TRPML channel function. Collectively, our results indicate that heteromultimerization of TRPML channels plays a role in various TRPML-regulated mechanisms.
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Affiliation(s)
- David A. Zeevi
- Monique and Jacques Roboh Department of Genetic Research, Institute of Medical Research Israel-Canada (IMRIC), Faculty of Medicine of the Hebrew University and Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Shaya Lev
- Department of Medical Neurobiology, Institute of Medical Research Israel-Canada (IMRIC), Faculty of Medicine of the Hebrew University and Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
- The Kühne Minerva Center for Studies of Visual Transduction, Institute of Medical Research Israel-Canada (IMRIC), Faculty of Medicine of the Hebrew University and Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Ayala Frumkin
- Monique and Jacques Roboh Department of Genetic Research, Institute of Medical Research Israel-Canada (IMRIC), Faculty of Medicine of the Hebrew University and Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Baruch Minke
- Department of Medical Neurobiology, Institute of Medical Research Israel-Canada (IMRIC), Faculty of Medicine of the Hebrew University and Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
- The Kühne Minerva Center for Studies of Visual Transduction, Institute of Medical Research Israel-Canada (IMRIC), Faculty of Medicine of the Hebrew University and Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Gideon Bach
- Monique and Jacques Roboh Department of Genetic Research, Institute of Medical Research Israel-Canada (IMRIC), Faculty of Medicine of the Hebrew University and Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
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