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Walid MKI, Rahman S, Smith EA. Reciprocal effect on lateral diffusion of receptor for advanced glycation endproducts and toll-like receptor 4 in the HEK293 cell membrane. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2024; 53:327-338. [PMID: 39066956 DOI: 10.1007/s00249-024-01717-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2024] [Revised: 06/28/2024] [Accepted: 07/18/2024] [Indexed: 07/30/2024]
Abstract
Receptor for advanced glycation endproducts (RAGE) and toll-like receptor 4 (TLR4) are pattern-recognition receptors that bind to molecular patterns associated with pathogens, stress, and cellular damage. Diffusion plays an important role in receptor functionality in the cell membrane. However, there has been no prior investigation of the reciprocal effect of RAGE and TLR4 diffusion properties in the presence and absence of each receptor. This study reports how RAGE and TLR4 affect the mobility of each other in the human embryonic kidney (HEK) 293 cell membrane. Diffusion properties were measured using single-particle tracking (SPT) with quantum dots (QDs) that are selectively attached to RAGE or TLR4. The Brownian diffusion coefficients of RAGE and TLR4 are affected by the presence of the other receptor, leading to similar diffusion coefficients when both receptors coexist in the cell. When TLR4 is present, the average Brownian diffusion coefficient of RAGE increases by 40%, while the presence of RAGE decreases the average Brownian diffusion coefficient of TLR4 by 32%. Diffusion in confined membrane domains is not altered by the presence of the other receptor. The mobility of the cell membrane lipid remains constant whether one or both receptors are present. Overall, this work shows that the presence of each receptor can affect a subset of diffusion properties of the other receptor without affecting the mobility of the membrane.
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Affiliation(s)
| | - Sharifur Rahman
- Department of Chemistry, Iowa State University, Ames, IA, 50011, USA
| | - Emily A Smith
- Department of Chemistry, Iowa State University, Ames, IA, 50011, USA.
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2
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Abstract
Ca2+ is a universal second messenger that plays a wide variety of fundamental roles in cellular physiology. Thus, to warrant selective responses and to allow rapid mobilization upon specific stimuli, Ca2+ is accumulated in organelles to keep it at very low levels in the cytoplasm during resting conditions. Major Ca2+ storage organelles include the endoplasmic reticulum (ER), the mitochondria, and as recently demonstrated, the lysosome (Xu and Ren, Annu Rev Physiol 77:57-80, 2015). The importance of Ca2+ signaling deregulation in human physiology is underscored by its involvement in several human diseases, including lysosomal storage disorders, neurodegenerative disease and cancer (Shen et al., Nat Commun 3:731, 2012; Bae et al., J Neurosci 34:11485-11503, 2014). Recent evidence strongly suggests that lysosomal Ca2+ plays a major role in the regulation of lysosomal adaptation to nutrient availability through a lysosomal signaling pathway involving the lysosomal Ca2+ channel TRPML1 and the transcription factor TFEB, a master regulator for lysosomal function and autophagy (Sardiello et al., Science 325:473-477, 2009; Settembre et al., Science 332:1429-1433, 2011; Medina et al., Nat Cell Biol 17:288-299, 2015; Di Paola et al., Cell Calcium 69:112-121, 2018). Due to the tight relationship of this lysosomal Ca2+ channel and TFEB, in this chapter, we will focus on the role of the TRPML1/TFEB pathway in the regulation of lysosomal function and autophagy.
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Affiliation(s)
- Diego Luis Medina
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Naples, Italy.
- Medical Genetics Unit, Department of Medical and Translational Science, Federico II University, Naples, Italy.
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3
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Allan CY, Fisher PR. The Dictyostelium Model for Mucolipidosis Type IV. Front Cell Dev Biol 2022; 10:741967. [PMID: 35493081 PMCID: PMC9043695 DOI: 10.3389/fcell.2022.741967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 03/21/2022] [Indexed: 12/02/2022] Open
Abstract
Mucolipidosis type IV, a devastating neurological lysosomal disease linked to mutations in the transient receptor potential channel mucolipin 1, TRPML1, a calcium permeable channel in the membranes of vesicles in endolysosomal system. TRPML1 function is still being elucidated and a better understanding of the molecular pathogenesis of Mucolipidosis type IV, may facilitate development of potential treatments. We have created a model to study mucolipin function in the eukaryotic slime mould Dictyostelium discoideum by altering expression of its single mucolipin homologue, mcln. We show that in Dictyostelium mucolipin overexpression contributes significantly to global chemotactic calcium responses in vegetative and differentiated cells. Knockdown of mucolipin also enhances calcium responses in vegetative cells but does not affect responses in 6–7 h developed cells, suggesting that in developed cells mucolipin may help regulate local calcium signals rather than global calcium waves. We found that both knocking down and overexpressing mucolipin often, but not always, presented the same phenotypes. Altering mucolipin expression levels caused an accumulation or increased acidification of Lysosensor Blue stained vesicles in vegetative cells. Nutrient uptake by phagocytosis and macropinocytosis were increased but growth rates were not, suggesting defects in catabolism. Both increasing and decreasing mucolipin expression caused the formation of smaller slugs and larger numbers of fruiting bodies during multicellular development, suggesting that mucolipin is involved in initiation of aggregation centers. The fruiting bodies that formed from these smaller aggregates had proportionately larger basal discs and thickened stalks, consistent with a regulatory role for mucolipin-dependent Ca2+ signalling in the autophagic cell death pathways involved in stalk and basal disk differentiation in Dictyostelium. Thus, we have provided evidence that mucolipin contributes to chemotactic calcium signalling and that Dictyostelium is a useful model to study the molecular mechanisms involved in the cytopathogenesis of Mucolipidosis type IV.
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Tedeschi V, Sisalli MJ, Petrozziello T, Canzoniero LMT, Secondo A. Lysosomal calcium is modulated by STIM1/TRPML1 interaction which participates to neuronal survival during ischemic preconditioning. FASEB J 2021; 35:e21277. [PMID: 33484198 DOI: 10.1096/fj.202001886r] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Revised: 11/02/2020] [Accepted: 11/30/2020] [Indexed: 11/11/2022]
Abstract
A robust activity of the lysosomal Ca2+ channel TRPML1 is sufficient to correct cellular defects in neurodegeneration. Importantly, lysosomes are refilled by the endoplasmic reticulum (ER). However, it is unclear how TRPML1 function could be modulated by the ER. Here, we deal with this issue in rat primary cortical neurons exposed to different oxygen conditions affecting neuronal survival. Under normoxic conditions, TRPML1: (1) showed a wide distribution within soma and along neuronal processes; (2) was stimulated by the synthetic agonist ML-SA1 and the analog of its endogenous modulator, PI(3,5)P2 diC8; (3) its knockdown by siRNA strategy produced an ER Ca2+ accumulation; (4) co-localized and co-immunoprecipitated with the ER-located Ca2+ sensor stromal interacting molecule 1 (STIM1). In cortical neurons lacking STIM1, ML-SA1 and PI(3,5)P2 diC8 failed to induce Ca2+ release and, more deeply, they induced a negligible Ca2+ passage through the channel in neurons transfected with the genetically encoded Ca2+ indicator GCaMP3-ML1. Moreover, TRPML1/STIM1 interplay changed at low-oxygen conditions: both proteins were downregulated during the ischemic preconditioning (IPC) while during IPC followed by 1 hour of normoxia, at which STIM1 is upregulated, TRPML1 protein was reduced. However, during oxygen and glucose deprivation (OGD) followed by reoxygenation, TRPML1 and STIM1 proteins peaked at 8 hours of reoxygenation, when the proteins were co-immunoprecipitated and reactive oxygen species (ROS) hyperproduction was measured in cortical neurons. This may lead to a persistent TRPML1 Ca2+ release and lysosomal Ca2+ loss. Collectively, we showed a new modulation exerted by STIM1 on TRPML1 activity that may differently intervene during hypoxia to regulate organellar Ca2+ homeostasis.
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Affiliation(s)
- Valentina Tedeschi
- Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Naples, Italy
| | - Maria José Sisalli
- Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Naples, Italy
| | - Tiziana Petrozziello
- Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Naples, Italy
| | | | - Agnese Secondo
- Division of Pharmacology, Department of Neuroscience, Reproductive and Odontostomatological Sciences, School of Medicine, "Federico II" University of Naples, Naples, Italy
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5
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Abstract
Lysosomal calcium is emerging as a modulator of autophagy and lysosomal compartment, an obligatory partner to complete the autophagic pathway. A variety of specific signals such as nutrient deprivation or oxidative stress can trigger lysosomal calcium-mediated nuclear translocation of the transcription factor EB (TFEB), a master regulator of global lysosomal function. Also, lysosomal calcium can promote the formation of autophagosome vesicles (AVs) by a mechanism that requires the production of the phosphoinositide PI3P by the VPS34 autophagic complex and the activation of the energy-sensing kinase AMPK. Additionally, lysosomal calcium plays a role in membrane fusion and fission events involved in cellular processes such as endocytic maturation, autophagosome-lysosome fusion, lysosomal exocytosis, and lysosomal reformation upon autophagy completion. Lysosomal calcium-dependent functions are defective in cellular and animal models of the non-selective cation channel TRPML1, whose mutations in humans cause the neurodegenerative lysosomal storage disease mucolipidosis type IV (MLIV). Lysosomal calcium is not only acting as a positive regulator of autophagy, but it is also responsible for turning-off this process through the reactivation of the mTOR kinase during prolonged starvation. More recently, it has been described the role of lysosomal calcium on an elegant sequence of intracellular signaling events such as membrane repair, lysophagy, and lysosomal biogenesis upon the induction of different grades of lysosomal membrane damage. Here, we will discuss these novel findings that re-define the importance of the lysosome and lysosomal calcium signaling at regulating cellular metabolism.
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6
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Li G, Li PL. Lysosomal TRPML1 Channel: Implications in Cardiovascular and Kidney Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1349:275-301. [PMID: 35138619 PMCID: PMC9899368 DOI: 10.1007/978-981-16-4254-8_13] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Lysosomal ion channels mediate ion flux from lysosomes and regulate membrane potential across the lysosomal membrane, which are essential for lysosome biogenesis, nutrient sensing, lysosome trafficking, lysosome enzyme activity, and cell membrane repair. As a cation channel, the transient receptor potential mucolipin 1 (TRPML1) channel is mainly expressed on lysosomes and late endosomes. Recently, the normal function of TRPML1 channels has been demonstrated to be important for the maintenance of cardiovascular and renal glomerular homeostasis and thereby involved in the pathogenesis of some cardiovascular and kidney diseases. In arterial myocytes, it has been found that Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP), an intracellular second messenger, can induce Ca2+ release through the lysosomal TRPML1 channel, leading to a global Ca2+ release response from the sarcoplasmic reticulum (SR). In podocytes, it has been demonstrated that lysosomal TRPML1 channels control lysosome trafficking and exosome release, which contribute to the maintenance of podocyte functional integrity. The defect or functional deficiency of lysosomal TRPML1 channels has been shown to critically contribute to the initiation and development of some chronic degeneration or diseases in the cardiovascular system or kidneys. Here we briefly summarize the current evidence demonstrating the regulation of lysosomal TRPML1 channel activity and related signaling mechanisms. We also provide some insights into the canonical and noncanonical roles of TRPML1 channel dysfunction as a potential pathogenic mechanism for certain cardiovascular and kidney diseases and associated therapeutic strategies.
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Affiliation(s)
- Guangbi Li
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA
| | - Pin-Lan Li
- Department of Pharmacology and Toxicology, School of Medicine, Virginia Commonwealth University, Richmond, VA, USA.
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7
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Lavanderos B, Silva I, Cruz P, Orellana-Serradell O, Saldías MP, Cerda O. TRP Channels Regulation of Rho GTPases in Brain Context and Diseases. Front Cell Dev Biol 2020; 8:582975. [PMID: 33240883 PMCID: PMC7683514 DOI: 10.3389/fcell.2020.582975] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 10/05/2020] [Indexed: 12/13/2022] Open
Abstract
Neurological and neuropsychiatric disorders are mediated by several pathophysiological mechanisms, including developmental and degenerative abnormalities caused primarily by disturbances in cell migration, structural plasticity of the synapse, and blood-vessel barrier function. In this context, critical pathways involved in the pathogenesis of these diseases are related to structural, scaffolding, and enzymatic activity-bearing proteins, which participate in Ca2+- and Ras Homologs (Rho) GTPases-mediated signaling. Rho GTPases are GDP/GTP binding proteins that regulate the cytoskeletal structure, cellular protrusion, and migration. These proteins cycle between GTP-bound (active) and GDP-bound (inactive) states due to their intrinsic GTPase activity and their dynamic regulation by GEFs, GAPs, and GDIs. One of the most important upstream inputs that modulate Rho GTPases activity is Ca2+ signaling, positioning ion channels as pivotal molecular entities for Rho GTPases regulation. Multiple non-selective cationic channels belonging to the Transient Receptor Potential (TRP) family participate in cytoskeletal-dependent processes through Ca2+-mediated modulation of Rho GTPases. Moreover, these ion channels have a role in several neuropathological events such as neuronal cell death, brain tumor progression and strokes. Although Rho GTPases-dependent pathways have been extensively studied, how they converge with TRP channels in the development or progression of neuropathologies is poorly understood. Herein, we review recent evidence and insights that link TRP channels activity to downstream Rho GTPase signaling or modulation. Moreover, using the TRIP database, we establish associations between possible mediators of Rho GTPase signaling with TRP ion channels. As such, we propose mechanisms that might explain the TRP-dependent modulation of Rho GTPases as possible pathways participating in the emergence or maintenance of neuropathological conditions.
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Affiliation(s)
- Boris Lavanderos
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - Ian Silva
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - Pablo Cruz
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - Octavio Orellana-Serradell
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - María Paz Saldías
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile
| | - Oscar Cerda
- Program of Cellular and Molecular Biology, Institute of Biomedical Sciences, Faculty of Medicine, Universidad de Chile, Santiago, Chile.,Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Santiago, Chile.,The Wound Repair, Treatment and Health (WoRTH) Initiative, Santiago, Chile
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8
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Two-pore and TRPML cation channels: Regulators of phagocytosis, autophagy and lysosomal exocytosis. Pharmacol Ther 2020; 220:107713. [PMID: 33141027 DOI: 10.1016/j.pharmthera.2020.107713] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Accepted: 10/19/2020] [Indexed: 02/07/2023]
Abstract
The old Greek saying "Panta Rhei" ("everything flows") is true for all life and all living things in general. It also becomes nicely evident when looking closely into cells. There, material from the extracellular space is taken up by endocytic processes and transported to endosomes where it is sorted either for recycling or degradation. Cargo is also packaged for export through exocytosis involving the Golgi network, lysosomes and other organelles. Everything in this system is in constant motion and many proteins are necessary to coordinate transport along the different intracellular pathways to avoid chaos. Among these proteins are ion channels., in particular TRPML channels (mucolipins) and two-pore channels (TPCs) which reside on endosomal and lysosomal membranes to speed up movement between organelles, e.g. by regulating fusion and fission; they help readjust pH and osmolarity changes due to such processes, or they promote exocytosis of export material. Pathophysiologically, these channels are involved in neurodegenerative, metabolic, retinal and infectious diseases, cancer, pigmentation defects, and immune cell function, and thus have been proposed as novel pharmacological targets, e.g. for the treatment of lysosomal storage disorders, Duchenne muscular dystrophy, or different types of cancer. Here, we discuss the similarities but also differences of TPCs and TRPMLs in regulating phagocytosis, autophagy and lysosomal exocytosis, and we address the contradictions and open questions in the field relating to the roles TPCs and TRPMLs play in these different processes.
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9
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Santoni G, Maggi F, Amantini C, Marinelli O, Nabissi M, Morelli MB. Pathophysiological Role of Transient Receptor Potential Mucolipin Channel 1 in Calcium-Mediated Stress-Induced Neurodegenerative Diseases. Front Physiol 2020; 11:251. [PMID: 32265740 PMCID: PMC7105868 DOI: 10.3389/fphys.2020.00251] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Accepted: 03/05/2020] [Indexed: 12/15/2022] Open
Abstract
Mucolipins (TRPML) are endosome/lysosome Ca2+ permeable channels belonging to the family of transient receptor potential channels. In mammals, there are three TRPML proteins, TRPML1, 2, and 3, encoded by MCOLN1-3 genes. Among these channels, TRPML1 is a reactive oxygen species sensor localized on the lysosomal membrane that is able to control intracellular oxidative stress due to the activation of the autophagic process. Moreover, genetic or pharmacological inhibition of the TRPML1 channel stimulates oxidative stress signaling pathways. Experimental data suggest that elevated levels of reactive species play a role in several neurological disorders. There is a need to gain better understanding of the molecular mechanisms behind these neurodegenerative diseases, considering that the main sources of free radicals are mitochondria, that mitochondria/endoplasmic reticulum and lysosomes are coupled, and that growing evidence links neurodegenerative diseases to the gain or loss of function of proteins related to lysosome homeostasis. This review examines the significant roles played by the TRPML1 channel in the alterations of calcium signaling responsible for stress-mediated neurodegenerative disorders and its potential as a new therapeutic target for ameliorating neurodegeneration in our ever-aging population.
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Affiliation(s)
- Giorgio Santoni
- Immunopathology Laboratory, School of Pharmacy, University of Camerino, Camerino, Italy
| | - Federica Maggi
- Immunopathology Laboratory, School of Pharmacy, University of Camerino, Camerino, Italy.,Department of Molecular Medicine, Sapienza University, Rome, Italy
| | - Consuelo Amantini
- Immunopathology Laboratory, School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy
| | - Oliviero Marinelli
- Immunopathology Laboratory, School of Pharmacy, University of Camerino, Camerino, Italy.,Immunopathology Laboratory, School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy
| | - Massimo Nabissi
- Immunopathology Laboratory, School of Pharmacy, University of Camerino, Camerino, Italy
| | - Maria Beatrice Morelli
- Immunopathology Laboratory, School of Pharmacy, University of Camerino, Camerino, Italy.,Immunopathology Laboratory, School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy
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10
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Sub-nanomolar sensitive GZnP3 reveals TRPML1-mediated neuronal Zn 2+ signals. Nat Commun 2019; 10:4806. [PMID: 31641116 PMCID: PMC6805855 DOI: 10.1038/s41467-019-12761-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2019] [Accepted: 09/27/2019] [Indexed: 02/07/2023] Open
Abstract
Although numerous fluorescent Zn2+ sensors have been reported, it is unclear whether and how Zn2+ can be released from the intracellular compartments into the cytosol due to a lack of probes that can detect physiological dynamics of cytosolic Zn2+. Here, we create a genetically encoded sensor, GZnP3, which demonstrates unprecedented sensitivity for Zn2+ at sub-nanomolar concentrations. Using GZnP3 as well as GZnP3-derived vesicular targeted probes, we provide the first direct evidence that Zn2+ can be released from endolysosomal vesicles to the cytosol in primary hippocampal neurons through the TRPML1 channel. Such TRPML1-mediated Zn2+ signals are distinct from Ca2+ in that they are selectively present in neurons, sustain longer, and are significantly higher in neurites as compared to the soma. Together, our work not only creates highly sensitive probes for investigating sub-nanomolar Zn2+ dynamics, but also reveals new pools of Zn2+ signals that can play critical roles in neuronal function. Numerous fluorescent Zn2+ sensors are available but most are unsuitable to detect physiological dynamics of cytosolic Zn2+. In this study, the authors present a genetically encoded sensor with sub-nanomolar sensitivity and show that Zn2 + is released from endolysosomal vesicles via TRPML1 in neurons.
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11
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Jin W, Dai Y, Li F, Zhu L, Huang Z, Liu W, Li J, Zhang M, Du J, Zhang W, Wen Z. Dysregulation of Microglial Function Contributes to Neuronal Impairment in Mcoln1a-Deficient Zebrafish. iScience 2019; 13:391-401. [PMID: 30897512 PMCID: PMC6426713 DOI: 10.1016/j.isci.2019.02.031] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 10/28/2018] [Accepted: 02/26/2019] [Indexed: 01/21/2023] Open
Abstract
Type IV mucolipidosis (ML-IV) is a neurodegenerative lysosome storage disorder caused by mutations in the MCOLN1 gene. However, the cellular and molecular bases underlying the neuronal phenotypes of ML-IV disease remain elusive. Using a forward genetic screening, we identified a zebrafish mutant, biluo, that harbors a hypomorphic mutation in mcoln1a, one of the two zebrafish homologs of mammalian MCOLN1. The mcoln1a-deficient mutants display phenotypes partially recapitulating the key features of ML-IV disorder, including the accumulation of enlarged late endosomes in microglia and aberrant neuronal activities in both spontaneous and visual-evoking conditions in optic tectal neurons. We further show that the accumulation of enlarged late endosomes in microglia is caused by the impairment of late endosome and lysosome fusion and the aberrant neuronal activities can be partially rescued by the reconstitution of Mcoln1a function in microglia. Our findings suggest that dysregulation of microglial function may contribute to the development and progression of ML-IV disease. mcoln1a-deficient fish display microglia impairment and aberrant neuronal activity The aberrant neuronal activity can be rescued by expressing WT mcoln1a in microglia Impairment of microglia-neuron contact contributes to the aberrant neuronal activity
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Affiliation(s)
- Wan Jin
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Center of Systems Biology and Human Health, the Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR. China
| | - Yimei Dai
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Center of Systems Biology and Human Health, the Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR. China
| | - Funing Li
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, PR. China
| | - Lu Zhu
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Center of Systems Biology and Human Health, the Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR. China
| | - Zhibin Huang
- Department of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou 510006, PR. China
| | - Wei Liu
- Department of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou 510006, PR. China
| | - Jianchao Li
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Center of Systems Biology and Human Health, the Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR. China
| | - Mingjie Zhang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Center of Systems Biology and Human Health, the Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR. China
| | - Jiulin Du
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, 320 Yue-Yang Road, Shanghai 200031, PR. China
| | - Wenqing Zhang
- Department of Cell, Developmental and Integrative Biology, School of Medicine, South China University of Technology, Guangzhou 510006, PR. China.
| | - Zilong Wen
- Division of Life Science, State Key Laboratory of Molecular Neuroscience and Center of Systems Biology and Human Health, the Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR. China; Shenzhen Key Laboratory for Neuronal Structural Biology, Biomedical Research Institute, Shenzhen Peking University-Hong Kong University of Science and Technology Medical Center, Shenzhen 518036, PR. China.
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12
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Wu G, Yang X, Shen Y. Identification of a single aspartate residue critical for both fast and slow calcium-dependent inactivation of the human TRPML1 channel. J Biol Chem 2018; 293:11736-11745. [PMID: 29884771 DOI: 10.1074/jbc.ra118.003250] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Revised: 06/05/2018] [Indexed: 01/16/2023] Open
Abstract
Transient receptor potential mucolipin subfamily 1 (TRPML1) is a nonselective cation channel mainly located in late endosomes and lysosomes. Mutations of the gene encoding human TRPML1 can cause severe lysosomal diseases. The activity of TRPML1 is regulated by both Ca2+ and H+, which are important for its critical physiological functions in membrane trafficking, exocytosis, autophagy, and intracellular signal transduction. However, the molecular mechanism of its dual regulation by Ca2+ and H+ remains elusive. Here, using a mutant screening method in combination with a whole-cell patch clamp technique, we identified a key TRPML1 residue, Asp-472, responsible for both fast calcium-dependent inactivation (FCDI) and slow calcium-dependent inactivation (SCDI) as well as H+ regulation. We also found that, in acidic pH, H+ can significantly delay FCDI and abolish SCDI and thereby presumably facilitate the ion conductance of the human TRPML1 channel. In summary, we have identified a key residue critical for Ca2+-induced inhibition of TRPML1 channel currents and uncovered pH-dependent regulation of this channel, providing vital information regarding the detailed mechanism of action of human TRPML1.
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Affiliation(s)
- Guangyan Wu
- From the State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China and
| | - Xue Yang
- From the State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China and
| | - Yuequan Shen
- From the State Key Laboratory of Medicinal Chemical Biology and College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China and .,the Synergetic Innovation Center of Chemical Science and Engineering, 94 Weijin Road, Tianjin 300071, China
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13
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Di Paola S, Scotto-Rosato A, Medina DL. TRPML1: The Ca (2+)retaker of the lysosome. Cell Calcium 2017; 69:112-121. [PMID: 28689729 DOI: 10.1016/j.ceca.2017.06.006] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 06/16/2017] [Accepted: 06/16/2017] [Indexed: 12/27/2022]
Abstract
Efficient functioning of lysosome is necessary to ensure the correct performance of a variety of intracellular processes such as degradation of cargoes coming from the endocytic and autophagic pathways, recycling of organelles, and signaling mechanisms involved in cellular adaptation to nutrient availability. Mutations in lysosomal genes lead to more than 50 lysosomal storage disorders (LSDs). Among them, mutations in the gene encoding TRPML1 (MCOLN1) cause Mucolipidosis type IV (MLIV), a recessive LSD characterized by neurodegeneration, psychomotor retardation, ophthalmologic defects and achlorhydria. At the cellular level, MLIV patient fibroblasts show enlargement and engulfment of the late endo-lysosomal compartment, autophagy impairment, and accumulation of lipids and glycosaminoglycans. TRPML1 is the most extensively studied member of a small family of genes that also includes TRPML2 and TRPML3, and it has been found to participate in vesicular trafficking, lipid and ion homeostasis, and autophagy. In this review we will provide an update on the latest and more novel findings related to the functions of TRPMLs, with particular focus on the emerging role of TRPML1 and lysosomal calcium signaling in autophagy. Moreover, we will also discuss new potential therapeutic approaches for MLIV and LSDs based on the modulation of TRPML1-mediated signaling.
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Affiliation(s)
- Simone Di Paola
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078 Pozzuoli ,NA, Italy
| | - Anna Scotto-Rosato
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078 Pozzuoli ,NA, Italy
| | - Diego Luis Medina
- Telethon Institute of Genetics and Medicine (TIGEM), Via Campi Flegrei 34, 80078 Pozzuoli ,NA, Italy.
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14
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Structural basis of dual Ca 2+/pH regulation of the endolysosomal TRPML1 channel. Nat Struct Mol Biol 2017; 24:205-213. [PMID: 28112729 PMCID: PMC5336481 DOI: 10.1038/nsmb.3362] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 12/12/2016] [Indexed: 12/01/2022]
Abstract
Organellar ion channels are essential for cell physiology. Their activities are often regulated by Ca2+ and H+, which are concentrated in many organelles. Here we report a novel structural element critical for Ca2+/pH dual regulation of TRPML1, a Ca2+ release channel crucial for endolysosomal functions. TRPML1 mutations cause mucolipidosis type IV (MLIV), a severe lysosomal storage disorder characterized by neurodegeneration, mental retardation and blindness. We obtained high-resolution crystal structures of a 213-amino acid luminal domain of human TRPML1 that harbors three missense MLIV-causing mutations. This domain forms a tetramer with a highly electronegative central pore formed by a novel luminal pore-loop. Cysteine crosslinking and cryo-EM confirm this structure in the full-length channel. Structure-function studies demonstrate that Ca2+ and H+ interact with the luminal pore to exert physiologically important regulation. The MLIV-causing mutations disrupt the luminal domain structure and cause TRPML1 mislocalization. Our study provides a structural underpinning for TRPML1's regulation, assembly and pathogenesis.
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15
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Beck A, Fecher-Trost C, Wolske K, Philipp SE, Flockerzi V, Wissenbach U. Identification of Sidt2 as a lysosomal cation-conducting protein. FEBS Lett 2017; 591:76-87. [PMID: 27987306 DOI: 10.1002/1873-3468.12528] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 11/25/2016] [Accepted: 12/01/2016] [Indexed: 12/18/2022]
Abstract
A screen to identify lysosomal-expressed ion channels led to the discovery of the human Sidt2 protein. Sidt2 is expressed within lysosomal organelles but as a result of heterologous overexpression the protein is also detectable within the plasma membrane of human embryonic kidney cells. The overexpressed protein leads to cell depolarization upon sodium addition. Accordingly in whole-cell patch clamp experiments a spontaneous noninactivating monovalent cation current can be detected in Sidt2-overexpressing cells. Strong overexpression of Sidt2 in HEK293 cells is attended by a significant reduction/loss of detectable lysosomes, indicating that the overexpressed protein leads to lysosomal dysfunction, a hallmark of Alzheimer's disease. Sidt2 is located on chromosome 11q23, a locus repeatedly found by chromosomal mapping of Alzheimer's disease-related genes.
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Affiliation(s)
- Andreas Beck
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, Homburg/Saar, Germany
| | - Claudia Fecher-Trost
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, Homburg/Saar, Germany
| | - Karin Wolske
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, Homburg/Saar, Germany
| | - Stephan E Philipp
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, Homburg/Saar, Germany
| | - Veit Flockerzi
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, Homburg/Saar, Germany
| | - Ulrich Wissenbach
- Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, Homburg/Saar, Germany
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16
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Grishchuk Y, Stember KG, Matsunaga A, Olivares AM, Cruz NM, King VE, Humphrey DM, Wang SL, Muzikansky A, Betensky RA, Thoreson WB, Haider N, Slaugenhaupt SA. Retinal Dystrophy and Optic Nerve Pathology in the Mouse Model of Mucolipidosis IV. THE AMERICAN JOURNAL OF PATHOLOGY 2015; 186:199-209. [PMID: 26608452 DOI: 10.1016/j.ajpath.2015.09.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 08/31/2015] [Accepted: 09/10/2015] [Indexed: 11/19/2022]
Abstract
Mucolipidosis IV is a debilitating developmental lysosomal storage disorder characterized by severe neuromotor retardation and progressive loss of vision, leading to blindness by the second decade of life. Mucolipidosis IV is caused by loss-of-function mutations in the MCOLN1 gene, which encodes the transient receptor potential channel protein mucolipin-1. Ophthalmic pathology in patients includes corneal haze and progressive retinal and optic nerve atrophy. Herein, we report ocular pathology in Mcoln1(-/-) mouse, a good phenotypic model of the disease. Early, but non-progressive, thinning of the photoreceptor layer, reduced levels of rhodopsin, disrupted rod outer segments, and widespread accumulation of the typical storage inclusion bodies were the major histological findings in the Mcoln1(-/-) retina. Electroretinograms showed significantly decreased functional response (scotopic a- and b-wave amplitudes) in the Mcoln1(-/-) mice. At the ultrastructural level, we observed formation of axonal spheroids and decreased density of axons in the optic nerve of the aged (6-month-old) Mcoln1(-/-) mice, which indicates progressive axonal degeneration. Our data suggest that mucolipin-1 plays a role in postnatal development of photoreceptors and provides a set of outcome measures that can be used for ocular therapy development for mucolipidosis IV.
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Affiliation(s)
- Yulia Grishchuk
- Department of Neurology, Center for Human Genetic Research, Harvard Medical School, Boston, Massachusetts.
| | - Katherine G Stember
- Department of Neurology, Center for Human Genetic Research, Harvard Medical School, Boston, Massachusetts
| | - Aya Matsunaga
- Department of Neurology, Center for Human Genetic Research, Harvard Medical School, Boston, Massachusetts
| | - Ana M Olivares
- Schepens Eye Research Institute, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts
| | - Nelly M Cruz
- Schepens Eye Research Institute, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts
| | - Victoria E King
- Department of Neurology, Center for Human Genetic Research, Harvard Medical School, Boston, Massachusetts
| | - Daniel M Humphrey
- Department of Neurology, Center for Human Genetic Research, Harvard Medical School, Boston, Massachusetts
| | - Shirley L Wang
- Department of Neurology, Center for Human Genetic Research, Harvard Medical School, Boston, Massachusetts
| | - Alona Muzikansky
- Massachusetts General Hospital Biostatistics Center, Massachusetts General Hospital, Boston, Massachusetts
| | - Rebecca A Betensky
- Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts
| | - Wallace B Thoreson
- Department of Ophthalmology & Visual Sciences, University of Nebraska Medical Center, Omaha, Nebraska
| | - Neena Haider
- Schepens Eye Research Institute, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts
| | - Susan A Slaugenhaupt
- Department of Neurology, Center for Human Genetic Research, Harvard Medical School, Boston, Massachusetts
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17
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Liang XH, Sun H, Shen W, Crooke ST. Identification and characterization of intracellular proteins that bind oligonucleotides with phosphorothioate linkages. Nucleic Acids Res 2015; 43:2927-45. [PMID: 25712094 PMCID: PMC4357732 DOI: 10.1093/nar/gkv143] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Although the RNase H-dependent mechanism of inhibition of gene expression by chemically modified antisense oligonucleotides (ASOs) has been well characterized, little is known about the interactions between ASOs and intracellular proteins that may alter cellular localization and/or potency of ASOs. Here, we report the identification of 56 intracellular ASO-binding proteins using multi-step affinity selection approaches. Many of the tested proteins had no significant effect on ASO activity; however, some proteins, including La/SSB, NPM1, ANXA2, VARS and PC4, appeared to enhance ASO activities, likely through mechanisms related to subcellular distribution. VARS and ANXA2 co-localized with ASOs in endocytic organelles, and reduction in the level of VARS altered lysosome/ASO localization patterns, implying that these proteins may facilitate ASO release from the endocytic pathway. Depletion of La and NPM1 reduced nuclear ASO levels, suggesting potential roles in ASO nuclear accumulation. On the other hand, Ku70 and Ku80 proteins inhibited ASO activity, most likely by competition with RNase H1 for ASO/RNA duplex binding. Our results demonstrate that phosphorothioate-modified ASOs bind a set of cellular proteins that affect ASO activity via different mechanisms.
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Affiliation(s)
- Xue-hai Liang
- Department of Core Antisense Research, ISIS Pharmaceuticals, Carlsbad, CA 92010, USA
| | - Hong Sun
- Department of Core Antisense Research, ISIS Pharmaceuticals, Carlsbad, CA 92010, USA
| | - Wen Shen
- Department of Core Antisense Research, ISIS Pharmaceuticals, Carlsbad, CA 92010, USA
| | - Stanley T Crooke
- Department of Core Antisense Research, ISIS Pharmaceuticals, Carlsbad, CA 92010, USA
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18
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Inoue K, O'Bryant Z, Xiong ZG. Zinc-permeable ion channels: effects on intracellular zinc dynamics and potential physiological/pathophysiological significance. Curr Med Chem 2015; 22:1248-57. [PMID: 25666796 PMCID: PMC4363167 DOI: 10.2174/0929867322666150209153750] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Revised: 10/14/2014] [Accepted: 02/02/2015] [Indexed: 02/08/2023]
Abstract
Zinc (Zn(2+)) is one of the most important trace metals in the body. It is necessary for the normal function of a large number of protein s including enzymes and transcription factors. While extracellular fluid may contain up to micromolar Zn(2+), intracellular Zn(2+) concentration is generally maintained at a subnanomolar level; this steep gradient across the cell membrane is primarily attributable to Zn(2+) extrusion by Zn(2+) transporting systems. Interestingly, systematic investigation has revealed that activities, previously believed to be dependent on calcium (Ca(2+)), may be partially mediated by Zn(2+). This is also supported by new findings that some Ca(2+)-permeable channels such as voltage-dependent calcium channels (VDCCs), N-methyl-D-aspartate receptors (NMDA), and amino-3- hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPA-Rs) are also permeable to Zn(2+). Thus, the importance of Zn(2+) in physiological and pathophysiological processes is now more widely appreciated. In this review, we describe Zn(2+)- permeable membrane molecules, especially Zn(2+)-permeable ion channels, in intracellular Zn(2+)dynamics and Zn(2+) mediated physiology/pathophysiology.
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Affiliation(s)
- Koichi Inoue
- Neuroscience Institute, Morehouse School of Medicine, Atlanta, USA.
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19
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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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20
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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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21
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Cuajungco MP, Basilio LC, Silva J, Hart T, Tringali J, Chen CC, Biel M, Grimm C. Cellular zinc levels are modulated by TRPML1-TMEM163 interaction. Traffic 2014; 15:1247-65. [PMID: 25130899 DOI: 10.1111/tra.12205] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Revised: 08/02/2014] [Accepted: 08/04/2014] [Indexed: 02/05/2023]
Abstract
Mucolipidosis type IV (MLIV) is caused by loss of function mutations in the TRPML1 ion channel. We previously reported that tissue zinc levels in MLIV were abnormally elevated; however, the mechanism behind this pathologic accumulation remains unknown. Here, we identify transmembrane (TMEM)-163 protein, a putative zinc transporter, as a novel interacting partner for TRPML1. Evidence from yeast two-hybrid, tissue expression pattern, co-immunoprecipitation, mass spectrometry and confocal microscopy studies confirmed the physical association of TMEM163 with TRPML1. This interaction is disrupted when a part of TMEM163's N-terminus was deleted. Further studies to define the relevance of their interaction revealed that the plasma membrane (PM) levels of TMEM163 significantly decrease when TRPML1 is co-expressed in HEK-293 cells, while it mostly localizes within the PM when co-expressed with a mutant TRPML1 that distributes mostly in the PM. Meanwhile, co-expression of TMEM163 does not alter TRPML1 channel activity, but its expression levels in MLIV patient fibroblasts are reduced, which correlate with marked accumulation of zinc in lysosomes when these cells are acutely exposed to exogenous zinc (100 μM). When TMEM163 is knocked down or when TMEM163 and TRPML1 are co-knocked down in HEK-293 cells treated overnight with 100 nm zinc, the cells have significantly higher intracellular zinc levels than untreated control. Overall, these findings suggest that TMEM163 and TRPML1 proteins play a critical role in cellular zinc homeostasis, and thus possibly explain a novel mechanism for the pathological overload of zinc in MLIV disease.
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Affiliation(s)
- Math P Cuajungco
- Department of Biological Science and Center for Applied Biotechnology Studies, California State University, Fullerton, CA, 92831, USA; Mental Health Research Institute, Melbourne Brain Centre, Parkville, VIC, 3052, Australia
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22
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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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23
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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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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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Vandewauw I, Owsianik G, Voets T. Systematic and quantitative mRNA expression analysis of TRP channel genes at the single trigeminal and dorsal root ganglion level in mouse. BMC Neurosci 2013; 14:21. [PMID: 23410158 PMCID: PMC3576292 DOI: 10.1186/1471-2202-14-21] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Accepted: 01/31/2013] [Indexed: 11/30/2022] Open
Abstract
Background Somatosensory nerve fibres arising from cell bodies within the trigeminal ganglia (TG) in the head and from a string of dorsal root ganglia (DRG) located lateral to the spinal cord convey endogenous and environmental stimuli to the central nervous system. Although several members of the transient receptor potential (TRP) superfamily of cation channels have been implicated in somatosensation, the expression levels of TRP channel genes in the individual sensory ganglia have never been systematically studied. Results Here, we used quantitative real-time PCR to analyse and compare mRNA expression of all TRP channels in TG and individual DRGs from 27 anatomically defined segments of the spinal cord of the mouse. At the mRNA level, 17 of the 28 TRP channel genes, TRPA1, TRPC1, TRPC3, TRPC4, TRPC5, TRPM2, TRPM3, TRPM4, TRPM5, TRPM6, TRPM7, TRPM8, TRPV1, TRPV2, TRPV4, TRPML1 and TRPP2, were detectable in every tested ganglion. Notably, four TRP channels, TRPC4, TRPM4, TRPM8 and TRPV1, showed statistically significant variation in mRNA levels between DRGs from different segments, suggesting ganglion-specific regulation of TRP channel gene expression. These ganglion-to-ganglion differences in TRP channel transcript levels may contribute to the variability in sensory responses in functional studies. Conclusions We developed, compared and refined techniques to quantitatively analyse the relative mRNA expression of all TRP channel genes at the single ganglion level. This study also provides for the first time a comparative mRNA distribution profile in TG and DRG along the entire vertebral column for the mammalian TRP channel family.
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Affiliation(s)
- Ine Vandewauw
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine and TRP Research Platform Leuven, KU Leuven, Leuven, Belgium
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26
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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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Drosophila TRP channels and animal behavior. Life Sci 2012; 92:394-403. [PMID: 22877650 DOI: 10.1016/j.lfs.2012.07.029] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 07/09/2012] [Accepted: 07/16/2012] [Indexed: 11/24/2022]
Abstract
Multiple classes of cell surface receptors and ion channels participate in the detection of changes in environmental stimuli, and thereby influence animal behavior. Among the many classes of ion channels, Transient Receptor Potential (TRP) cation channels are notable in contributing to virtually every sensory modality, and in controlling a daunting array of behaviors. TRP channels appear to be conserved in all metazoan organisms including worms, insects and humans. Flies encode 13 TRPs, most of which are expressed and function in sensory neurons, and impact behaviors ranging from phototaxis to thermotaxis, gravitaxis, the avoidance of noxious tastants and smells and proprioception. Multiple diseases result from defects in TRPs, and flies provide an excellent animal model for dissecting the mechanisms underlying "TRPopathies." Drosophila TRPs also function in the sensation of botanically derived insect repellents, and related TRPs in insect pests are potential targets for the development of improved repellents to combat insect-borne diseases.
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Freichel M, Almering J, Tsvilovskyy V. The Role of TRP Proteins in Mast Cells. Front Immunol 2012; 3:150. [PMID: 22701456 PMCID: PMC3372879 DOI: 10.3389/fimmu.2012.00150] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 05/22/2012] [Indexed: 01/16/2023] Open
Abstract
Transient receptor potential (TRP) proteins form cation channels that are regulated through strikingly diverse mechanisms including multiple cell surface receptors, changes in temperature, in pH and osmolarity, in cytosolic free Ca(2+) concentration ([Ca(2+)](i)), and by phosphoinositides which makes them polymodal sensors for fine tuning of many cellular and systemic processes in the body. The 28 TRP proteins identified in mammals are classified into six subfamilies: TRPC, TRPV, TRPM, TRPA, TRPML, and TRPP. When activated, they contribute to cell depolarization and Ca(2+) entry. In mast cells, the increase of [Ca(2+)](i) is fundamental for their biological activity, and several entry pathways for Ca(2+) and other cations were described including Ca(2+) release activated Ca(2+) (CRAC) channels. Like in other non-excitable cells, TRP channels could directly contribute to Ca(2+) influx via the plasma membrane as constituents of Ca(2+) conducting channel complexes or indirectly by shifting the membrane potential and regulation of the driving force for Ca(2+) entry through independent Ca(2+) entry channels. Here, we summarize the current knowledge about the expression of individual Trp genes with the majority of the 28 members being yet identified in different mast cell models, and we highlight mechanisms how they can regulate mast cell functions. Since specific agonists or blockers are still lacking for most members of the TRP family, studies to unravel their function and activation mode still rely on experiments using genetic approaches and transgenic animals. RNAi approaches suggest a functional role for TRPC1, TRPC5, and TRPM7 in mast cell derived cell lines or primary mast cells, and studies using Trp gene knock-out mice reveal a critical role for TRPM4 in mast cell activation and for mast cell mediated cutaneous anaphylaxis, whereas a direct role of cold- and menthol-activated TRPM8 channels seems to be unlikely for the development of cold urticaria at least in mice.
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Affiliation(s)
- Marc Freichel
- Pharmakologisches Institut, Universität HeidelbergHeidelberg, Germany
| | - Julia Almering
- Pharmakologisches Institut, Universität HeidelbergHeidelberg, Germany
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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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30
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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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31
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Chen C, Paw BH. Cellular and mitochondrial iron homeostasis in vertebrates. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1459-67. [PMID: 22285816 DOI: 10.1016/j.bbamcr.2012.01.003] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 01/07/2012] [Accepted: 01/07/2012] [Indexed: 02/08/2023]
Abstract
Iron plays an essential role in cellular metabolism and biological processes. However, due to its intrinsic redox activity, free iron is a potentially toxic molecule in cellular biochemistry. Thus, organisms have developed sophisticated ways to import, sequester, and utilize iron. The transferrin cycle is a well-studied iron uptake pathway that is important for most vertebrate cells. Circulating iron can also be imported into cells by mechanisms that are independent of transferrin. Once imported into erythroid cells, iron is predominantly consumed by the mitochondria for the biosynthesis of heme and iron sulfur clusters. This review focuses on canonical transferrin-mediated and the newly discovered, non-transferrin mediated iron uptake pathways, as well as, mitochondrial iron homeostasis in higher eukaryotes. This article is part of a Special Issue entitled: Cell Biology of Metals.
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Affiliation(s)
- Caiyong Chen
- Department of Medicine, Hematology Division, Brigham & Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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32
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33
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Wakabayashi K, Gustafson AM, Sidransky E, Goldin E. Mucolipidosis type IV: an update. Mol Genet Metab 2011; 104:206-13. [PMID: 21763169 PMCID: PMC3205274 DOI: 10.1016/j.ymgme.2011.06.006] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/09/2011] [Accepted: 06/09/2011] [Indexed: 11/28/2022]
Abstract
Mucolipidosis type IV (MLIV) is a neurodevelopmental as well as neurodegenerative disorder with severe psychomotor developmental delay, progressive visual impairment, and achlorydria. It is characterized by the presence of lysosomal inclusions in many cell types in patients. MLIV is an autosomal recessive disease caused by mutations in MCOLN1, which encodes for mucolipin-1, a member of the transient receptor potential (TRP) cation channel family. Although approximately 70-80% of patients identified are Ashkenazi Jewish, MLIV is a pan-ethnic disorder. Importantly, while MLIV is thought to be a rare disease, its frequency may be greater than currently appreciated, for its common presentation as a cerebral palsy-like encephalopathy can lead to misdiagnosis. Moreover, patients with milder variants are often not recognized as having MLIV. This review provides an update on the ethnic distribution, clinical manifestations, laboratory findings, methods of diagnosis, molecular genetics, differential diagnosis, and treatment of patients with MLIV. An enhanced awareness of the manifestations of this disorder may help to elucidate the true frequency and range of symptoms associated with MLIV, providing insight into the pathogenesis of this multi-system disease.
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Affiliation(s)
| | | | - Ellen Sidransky
- Section on Molecular Neurogenetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Building 35, Room 1A213, 35 Convent Dr., MSC 3708, Bethesda, MD 20892-3708
| | - Ehud Goldin
- Section on Molecular Neurogenetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Building 35, Room 1A213, 35 Convent Dr., MSC 3708, Bethesda, MD 20892-3708
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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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35
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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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36
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Wu LJ, Sweet TB, Clapham DE. International Union of Basic and Clinical Pharmacology. LXXVI. Current progress in the mammalian TRP ion channel family. Pharmacol Rev 2010; 62:381-404. [PMID: 20716668 DOI: 10.1124/pr.110.002725] [Citation(s) in RCA: 426] [Impact Index Per Article: 30.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Transient receptor potential (TRP) channels are a large family of ion channel proteins, surpassed in number in mammals only by voltage-gated potassium channels. TRP channels are activated and regulated through strikingly diverse mechanisms, making them suitable candidates for cellular sensors. They respond to environmental stimuli such as temperature, pH, osmolarity, pheromones, taste, and plant compounds, and intracellular stimuli such as Ca(2+) and phosphatidylinositol signal transduction pathways. However, it is still largely unknown how TRP channels are activated in vivo. Despite the uncertainties, emerging evidence using TRP channel knockout mice indicates that these channels have broad function in physiology. Here we review the recent progress on the physiology, pharmacology and pathophysiological function of mammalian TRP channels.
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Affiliation(s)
- Long-Jun Wu
- Howard Hughes Medical Institute, Department of Cardiology, Children's Hospital Boston, 320 Longwood Avenue, Boston, MA 02115, USA
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37
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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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38
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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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39
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Patel S, Marchant JS, Brailoiu E. Two-pore channels: Regulation by NAADP and customized roles in triggering calcium signals. Cell Calcium 2010; 47:480-90. [PMID: 20621760 DOI: 10.1016/j.ceca.2010.05.001] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Revised: 04/30/2010] [Accepted: 05/03/2010] [Indexed: 01/11/2023]
Abstract
NAADP is a potent regulator of cytosolic calcium levels. Much evidence suggests that NAADP activates a novel channel located on an acidic (lysosomal-like) calcium store, the mobilisation of which results in further calcium release from the endoplasmic reticulum. Here, we discuss the recent identification of a family of poorly characterized ion channels (the two-pore channels) as endo-lysosomal NAADP receptors. The generation of calcium signals by these channels is likened to those evoked by depolarisation during excitation-contraction coupling in muscle. We discuss the idea that two-pore channels can mediate a trigger release of calcium which is then amplified by calcium-induced calcium release from the endoplasmic reticulum. This is similar to the activation of voltage-sensitive calcium channels and subsequent mobilisation of sarcoplasmic reticulum calcium stores in cardiac tissue. We suggest that two-pore channels may physically interact with ryanodine receptors to account for more direct release of calcium from the endoplasmic reticulum in analogy with the conformational coupling of voltage-sensitive calcium channels and ryanodine receptors in skeletal muscle. Interaction of two-pore channels with other calcium release channels likely occurs between stores "trans-chatter" and possibly within the same store "cis-chatter". We also speculate that trafficking of two-pore channels through the endo-lysosomal system facilitates interactions with calcium entry channels. Strategic placing of two-pore channels thus provides a versatile means of generating spatiotemporally complex cellular calcium signals.
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Affiliation(s)
- Sandip Patel
- Department of Cell and Developmental Biology, University College London, UK.
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40
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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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41
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Lev S, Zeevi DA, Frumkin A, Offen-Glasner V, Bach G, Minke B. Constitutive activity of the human TRPML2 channel induces cell degeneration. J Biol Chem 2010; 285:2771-82. [PMID: 19940139 PMCID: PMC2807332 DOI: 10.1074/jbc.m109.046508] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 11/19/2009] [Indexed: 01/01/2023] Open
Abstract
The mucolipin (TRPML) ion channel proteins represent a distinct subfamily of channel proteins within the transient receptor potential (TRP) superfamily of cation channels. Mucolipin 1, 2, and 3 (TRPML1, -2, and -3, respectively) are channel proteins that share high sequence homology with each other and homology in the transmembrane domain with other TRPs. Mutations in the TRPML1 protein are implicated in mucolipidosis type IV, whereas mutations in TRPML3 are found in the varitint-waddler mouse. The properties of the wild type TRPML2 channel are not well known. Here we show functional expression of the wild type human TRPML2 channel (h-TRPML2). The channel is functional at the plasma membrane and characterized by a significant inward rectification similar to other constitutively active TRPML mutant isoforms. The h-TRPML2 channel displays nonselective cation permeability, which is Ca(2+)-permeable and inhibited by low extracytosolic pH but not Ca(2+) regulated. In addition, constitutively active h-TRPML2 leads to cell death by causing Ca(2+) overload. Furthermore, we demonstrate by functional mutation analysis that h-TRPML2 shares similar characteristics and structural similarities with other TRPML channels that regulate the channel in a similar manner. Hence, in addition to overall structure, all three TRPML channels also share common modes of regulation.
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Affiliation(s)
- Shaya Lev
- From the Department of Medical Neurobiology and the Kühne Minerva Center for Studies of Visual Transduction, Faculty of Medicine of the Hebrew University, and
| | - David A. Zeevi
- the Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Ayala Frumkin
- the Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Vered Offen-Glasner
- the Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Gideon Bach
- the Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem 91120, Israel
| | - Baruch Minke
- From the Department of Medical Neurobiology and the Kühne Minerva Center for Studies of Visual Transduction, Faculty of Medicine of the Hebrew University, and
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42
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Vergarajauregui S, Martina JA, Puertollano R. Identification of the penta-EF-hand protein ALG-2 as a Ca2+-dependent interactor of mucolipin-1. J Biol Chem 2009; 284:36357-36366. [PMID: 19864416 DOI: 10.1074/jbc.m109.047241] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Loss of function mutations in mucolipin-1 (MCOLN1) have been linked to mucolipidosis type IV (MLIV), a recessive lysosomal storage disease characterized by severe neurological and ophthalmological abnormalities. MCOLN1 is an ion channel that regulates membrane transport along the endolysosomal pathway. It has been suggested that MCOLN1 participates in several Ca(2+)-dependent processes, including fusion of lysosomes with the plasma membrane, fusion of late endosomes and autophagosomes with lysosomes, and lysosomal biogenesis. Here, we searched for proteins that interact with MCOLN1 in a Ca(2+)-dependent manner. We found that the penta-EF-hand protein ALG-2 binds to the NH-terminal cytosolic tail of MCOLN1. The interaction is direct, strictly dependent on Ca(2+), and mediated by a patch of charged and hydrophobic residues located between MCOLN1 residues 37 and 49. We further show that MCOLN1 and ALG-2 co-localize to enlarged endosomes induced by overexpression of an ATPase-defective dominant-negative form of Vps4B (Vps4B(E235Q)). In agreement with the proposed role of MCOLN1 in the regulation of fusion/fission events, we found that overexpression of MCOLN1 caused accumulation of enlarged, aberrant endosomes that contain both early and late endosome markers. Interestingly, aggregation of abnormal endosomes was greatly reduced when the ALG-2-binding domain in MCOLN1 was mutated, suggesting that ALG-2 regulates MCOLN1 function. Overall, our data provide new insight into the molecular mechanisms that regulate MCOLN1 activity. We propose that ALG-2 acts as a Ca(2+) sensor that modulates the function of MCOLN1 along the late endosomal-lysosomal pathway.
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Affiliation(s)
- Silvia Vergarajauregui
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892
| | - Jose A Martina
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892
| | - Rosa Puertollano
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892.
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Zeevi DA, Frumkin A, Offen-Glasner V, Kogot-Levin A, Bach G. A potentially dynamic lysosomal role for the endogenous TRPML proteins. J Pathol 2009; 219:153-62. [PMID: 19557826 DOI: 10.1002/path.2587] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Accepted: 05/28/2009] [Indexed: 11/10/2022]
Abstract
Lysosomal storage disorders (LSDs) constitute a diverse group of inherited diseases that result from lysosomal storage of compounds occurring in direct consequence to deficiencies of proteins implicated in proper lysosomal function. Pathology in the LSD mucolipidosis type IV (MLIV), is characterized by lysosomal storage of lipids together with water-soluble materials in cells from every tissue and organ of affected patients. Mutations in the mucolipin 1 (TRPML1) protein cause MLIV and TRPML1 has also been shown to interact with two of its paralogous proteins, mucolipin 2 (TRPML2) and mucolipin 3 (TRPML3), in heterologous expression systems. Heterogeneous lysosomal storage is readily identified in electron micrographs of MLIV patient cells, suggesting that proper TRPML1 function is essential for the maintenance of lysosomal integrity. In order to investigate whether TRPML2 and TRPML3 also play a role in the maintenance of lysosomal integrity, we conducted gene-specific knockdown assays against these protein targets. Ultrastructural analysis revealed lysosomal inclusions in both TRPML2 and TRPML3 knockdown cells, suggestive of a common mechanism for these proteins, in parallel with TRPML1, in the regulation of lysosomal integrity. However, co-immunoprecipitation assays revealed that physical interactions between each of the endogenous TRPML proteins are quite limited. In addition, we found that all three endogenous proteins only partially co-localize with each other in lysosomal as well as extra-lysosomal compartments. This suggests that native TRPML2 and TRPML3 might participate with native TRPML1 in a dynamic form of lysosomal regulation. Given that depletion of TRPML2/3 led to lysosomal storage typical to an LSD, we propose that depletion of these proteins might also underlie novel LSD pathologies not described hitherto.
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Affiliation(s)
- David A Zeevi
- Department of Human Genetics, Hadassah Hebrew University Hospital, Jerusalem, Israel
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44
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Kim HJ, Soyombo AA, Tjon-Kon-Sang S, So I, Muallem S. The Ca(2+) channel TRPML3 regulates membrane trafficking and autophagy. Traffic 2009; 10:1157-67. [PMID: 19522758 PMCID: PMC2993507 DOI: 10.1111/j.1600-0854.2009.00924.x] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
TRPML3 is an inward rectifying Ca(2+) channel that is regulated by extracytosolic H(+). Although gain-of-function mutation in TRPML3 causes the varitint-waddler phenotype, the role of TRPML3 in cellular physiology is not known. In this study, we report that TRPML3 is a prominent regulator of endocytosis, membrane trafficking and autophagy. Gradient fractionation and confocal localization reveal that TRPML3 is expressed in the plasma membrane and multiple intracellular compartments. However, expression of TRPML3 is dynamic, with accumulation of TRPML3 in the plasma membrane upon inhibition of endocytosis, and recruitment of TRPML3 to autophagosomes upon induction of autophagy. Accordingly, overexpression of TRPML3 leads to reduced constitutive and regulated endocytosis, increased autophagy and marked exacerbation of autophagy evoked by various cell stressors with nearly complete recruitment of TRPML3 into the autophagosomes. Importantly, both knockdown of TRPML3 by siRNA and expression of the channel-dead dominant negative TRPML3(D458K) have a reciprocal effect, reducing endocytosis and autophagy. These findings reveal a prominent role for TRPML3 in regulating endocytosis, membrane trafficking and autophagy, perhaps by controlling the Ca(2+) in the vicinity of cellular organelles that is necessary to regulate these cellular events.
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Affiliation(s)
- Hyun Jin Kim
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Abigail A. Soyombo
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Sandra Tjon-Kon-Sang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Insuk So
- Department of Physiology and Biophysics, Seoul National University College of Medicine, Seoul 110-799, Korea
| | - Shmuel Muallem
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390
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45
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Kogot-Levin A, Zeigler M, Ornoy A, Bach G. Mucolipidosis type IV: the effect of increased lysosomal pH on the abnormal lysosomal storage. Pediatr Res 2009; 65:686-90. [PMID: 19247216 DOI: 10.1203/pdr.0b013e3181a1681a] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Mucolipidosis type IV (MLIV) is a neurodegenerative channelopathy that is caused by the deficiency of TRPML1 activity, a nonselective cation channel. TRPML1 is a lysosomal membrane protein, and thus, MLIV is a lysosomal storage disorder. The basic, specific function of TRPML1 has not been yet clarified. A recent report (Soyombo AA, Tjon-Kon-Sang S, Rbaibi Y, Bashllari E, Bisceglia J, Muallem S, Kiselyov K: J Biol Chem 281:7294-7301, 2006) indicated that TRPML1 functions as an outwardly proton channel whose function is the prevention of overacidification of these organelles. Thus, in MLIV the lysosomal pH is lower than normal. Furthermore, attempts by these investigators to increase slightly the lysososmal pH with either Nigericin or Chloroquine suggested corrective effect of the abnormal storage in MLIV cells. We investigated this approach using these agents with cultured fibroblasts from severely affected and milder patients. Our data indicated that there was no reduction in the total number of storage vesicles by either agent, although Nigericin resulted in a change in the nature of the storage materials, reducing the presence of lamellated substances (lipids) so that the storage vesicles contained predominantly granulated substances. On the other hand, transfection with the normal MCOLN1 cDNA (the gene coding for TRPML1) resulted in the removal of almost all the storage materials.
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Affiliation(s)
- Aviram Kogot-Levin
- Department of Human Genetics, Hadassah University Hospital, Jerusalem, Israel
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46
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Venugopal B, Mesires NT, Kennedy JC, Curcio-Morelli C, Laplante JM, Dice JF, Slaugenhaupt SA. Chaperone-mediated autophagy is defective in mucolipidosis type IV. J Cell Physiol 2009; 219:344-53. [PMID: 19117012 DOI: 10.1002/jcp.21676] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Mucolipidosis type IV (MLIV) is a lysosomal storage disorder caused by mutations in the MCOLN1 gene, a member of the transient receptor potential (TRP) cation channel gene family. The encoded protein, transient receptor potential mucolipin-1 (TRPML1), has been localized to lysosomes and late endosomes but the pathogenic mechanism by which loss of TRPML1 leads to abnormal cellular storage and neuronal cell death is still poorly understood. Yeast two-hybrid and co-immunoprecipitation (coIP) experiments identified interactions between TRPML1 and Hsc70 as well as TRPML1 and Hsp40. Hsc70 and Hsp40 are members of a molecular chaperone complex required for protein transport into the lysosome during chaperone-mediated autophagy (CMA). To determine the functional relevance of this interaction, we compared fibroblasts from MLIV patients to those from sex- and age-matched controls and show a defect in CMA in response to serum withdrawal. This defect in CMA was subsequently confirmed in purified lysosomes isolated from control and MLIV fibroblasts. We further show that the amount of lysosomal-associated membrane protein type 2A (LAMP-2A) is reduced in lysosomal membranes of MLIV fibroblasts. As a result of decreased CMA, MLIV fibroblasts have increased levels of oxidized proteins compared to control fibroblasts. We hypothesize that TRPML1 may act as a docking site for intralysosomal Hsc70 (ly-Hsc70) allowing it to more efficiently pull in substrates for CMA. It is also possible that TRPML1 channel activity may be required for CMA. Understanding the role of TRPML1 in CMA will undoubtedly help to characterize the pathogenesis of MLIV.
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Affiliation(s)
- Bhuvarahamurthy Venugopal
- Center for Human Genetic Research, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA
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47
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Ruivo R, Anne C, Sagné C, Gasnier B. Molecular and cellular basis of lysosomal transmembrane protein dysfunction. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1793:636-49. [DOI: 10.1016/j.bbamcr.2008.12.008] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Revised: 12/10/2008] [Accepted: 12/11/2008] [Indexed: 02/04/2023]
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48
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Venkatachalam K, Long AA, Elsaesser R, Nikolaeva D, Broadie K, Montell C. Motor deficit in a Drosophila model of mucolipidosis type IV due to defective clearance of apoptotic cells. Cell 2008; 135:838-51. [PMID: 19041749 DOI: 10.1016/j.cell.2008.09.041] [Citation(s) in RCA: 162] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2008] [Revised: 07/25/2008] [Accepted: 09/17/2008] [Indexed: 11/27/2022]
Abstract
Disruption of the Transient Receptor Potential (TRP) mucolipin 1 (TRPML1) channel results in the neurodegenerative disorder mucolipidosis type IV (MLIV), a lysosomal storage disease with severe motor impairments. The mechanisms underlying MLIV are poorly understood and there is no treatment. Here, we report a Drosophila MLIV model, which recapitulates the key disease features, including abnormal intracellular accumulation of macromolecules, motor defects, and neurodegeneration. The basis for the buildup of macromolecules was defective autophagy, which resulted in oxidative stress and impaired synaptic transmission. Late-apoptotic cells accumulated in trpml mutant brains, suggesting diminished cell clearance. The accumulation of late-apoptotic cells and motor deficits were suppressed by expression of trpml(+) in neurons, glia, or hematopoietic cells. We conclude that the neurodegeneration and motor defects result primarily from decreased clearance of apoptotic cells. Since hematopoietic cells in humans are involved in clearance of apoptotic cells, our results raise the possibility that bone marrow transplantation may limit the progression of MLIV.
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Affiliation(s)
- Kartik Venkatachalam
- Departments of Biological Chemistry and Neuroscience, Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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49
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van Aken AFJ, Atiba-Davies M, Marcotti W, Goodyear RJ, Bryant JE, Richardson GP, Noben-Trauth K, Kros CJ. TRPML3 mutations cause impaired mechano-electrical transduction and depolarization by an inward-rectifier cation current in auditory hair cells of varitint-waddler mice. J Physiol 2008; 586:5403-18. [PMID: 18801844 PMCID: PMC2655368 DOI: 10.1113/jphysiol.2008.156992] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
TRPML3 (mucolipin-3) belongs to one of the transient-receptor-potential (TRP) ion channel families. Mutations in the Trpml3 gene cause disorganization of the stereociliary hair bundle, structural aberrations in outer and inner hair cells and stria vascularis defects, leading to deafness in the varitint-waddler (Va) mouse. Here we refined the stereociliary localization of TRPML3 and investigated cochlear hair cell function in varitint-waddler (Va(J)) mice carrying the TRPML3<I362T/A419P> mutations. Using a TRPML3-specific antibody we detected a approximately 68 kDa protein with near-equal expression levels in cochlea and vestibule of wild-type and Va(J) mutants. At postnatal days 3 and 5, we observed abundant localization of TRPML3 at the base of stereocilia near the position of the ankle links. This stereociliary localization domain was absent in Va(J) heterozygotes and homozygotes. Electrophysiological recordings revealed reduced mechano-electrical transducer currents in hair cells from Va(J)/+ and Va(J)/Va(J) mice. Furthermore, FM1-43 uptake and [(3)H]gentamicin accumulation were decreased in hair cells in cultured organs of Corti from Va(J)/+ and Va(J)/Va(J) mice. We propose that TRPML3 plays a critical role at the ankle-link region during hair-bundle growth and that an adverse effect of mutant TRPML3 on bundle development and mechano-electrical transduction is the main cause of hearing loss in Va(J)/+ mutant mice. Outer hair cells of Va(J)/Va(J) mice additionally had depolarized resting potentials due to an inwardly rectifying leak conductance formed by the mutant channels, leading over time to hair-cell degeneration and contributing to their deafness. Our findings argue against TRPML3 being a component of the hair-cell transducer channel.
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50
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A novel mode of TRPML3 regulation by extracytosolic pH absent in the varitint-waddler phenotype. EMBO J 2008; 27:1197-205. [PMID: 18369318 DOI: 10.1038/emboj.2008.56] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 02/27/2008] [Indexed: 11/08/2022] Open
Abstract
TRPML3 belongs to the TRPML subfamily of the transient receptor potential (TRP) channels. The A419P mutation in TRPML3 causes the varitint-waddler phenotype as a result of gain-of-function mutation (GOF). Regulation of the channels and the mechanism by which the A419P mutation leads to GOF are not known. We report here that TRPML3 is a Ca(2+)-permeable channel with a unique form of regulation by extracytosolic (luminal) H(+) (H(+)(e-cyto)). Regulation by H(+)(e-cyto) is mediated by a string of three histidines (H252, H273, H283) in the large extracytosolic loop between transmembrane domains (TMD) 1 and 2. Each of the histidines has a unique role, whereby H252 and H273 retard access of H(+)(e-cyto) to the inhibitory H283. Notably, the H283A mutation has the same phenotype as A419P and locks the channel in an open state, whereas the H283R mutation inactivates the channel. Accordingly, A419P eliminates regulation of TRPML3 by H(+)(e-cyto), and confers full activation to TRPML3(H283R). Activation of TRPML3 and regulation by H(+)(e-cyto) are altered by both the alpha-helix-destabilizing A419G and the alpha-helix-favouring A419M and A419K. These findings suggest that regulation of TRPML3 by H(+)(e-cyto) is due to an effect of the large extracytosolic loop on the orientation of fifth TMD and thus pore opening and show that the GOF of TRPML3(A419P) is due to disruption of this communication.
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