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Hu M, Feng X, Liu Q, Liu S, Huang F, Xu H. The ion channels of endomembranes. Physiol Rev 2024; 104:1335-1385. [PMID: 38451235 PMCID: PMC11381013 DOI: 10.1152/physrev.00025.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2023] [Revised: 02/20/2024] [Accepted: 02/25/2024] [Indexed: 03/08/2024] Open
Abstract
The endomembrane system consists of organellar membranes in the biosynthetic pathway [endoplasmic reticulum (ER), Golgi apparatus, and secretory vesicles] as well as those in the degradative pathway (early endosomes, macropinosomes, phagosomes, autophagosomes, late endosomes, and lysosomes). These endomembrane organelles/vesicles work together to synthesize, modify, package, transport, and degrade proteins, carbohydrates, and lipids, regulating the balance between cellular anabolism and catabolism. Large ion concentration gradients exist across endomembranes: Ca2+ gradients for most endomembrane organelles and H+ gradients for the acidic compartments. Ion (Na+, K+, H+, Ca2+, and Cl-) channels on the organellar membranes control ion flux in response to cellular cues, allowing rapid informational exchange between the cytosol and organelle lumen. Recent advances in organelle proteomics, organellar electrophysiology, and luminal and juxtaorganellar ion imaging have led to molecular identification and functional characterization of about two dozen endomembrane ion channels. For example, whereas IP3R1-3 channels mediate Ca2+ release from the ER in response to neurotransmitter and hormone stimulation, TRPML1-3 and TMEM175 channels mediate lysosomal Ca2+ and H+ release, respectively, in response to nutritional and trafficking cues. This review aims to summarize the current understanding of these endomembrane channels, with a focus on their subcellular localizations, ion permeation properties, gating mechanisms, cell biological functions, and disease relevance.
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Affiliation(s)
- Meiqin Hu
- Department of Neurology and Department of Cardiology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, People's Republic of China
- New Cornerstone Science Laboratory, Liangzhu Laboratory and School of Basic Medical Sciences, Zhejiang University, Hangzhou, People's Republic of China
| | - Xinghua Feng
- Department of Neurology and Department of Cardiology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, People's Republic of China
- New Cornerstone Science Laboratory, Liangzhu Laboratory and School of Basic Medical Sciences, Zhejiang University, Hangzhou, People's Republic of China
| | - Qiang Liu
- New Cornerstone Science Laboratory, Liangzhu Laboratory and School of Basic Medical Sciences, Zhejiang University, Hangzhou, People's Republic of China
| | - Siyu Liu
- New Cornerstone Science Laboratory, Liangzhu Laboratory and School of Basic Medical Sciences, Zhejiang University, Hangzhou, People's Republic of China
| | - Fangqian Huang
- New Cornerstone Science Laboratory, Liangzhu Laboratory and School of Basic Medical Sciences, Zhejiang University, Hangzhou, People's Republic of China
| | - Haoxing Xu
- Department of Neurology and Department of Cardiology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, People's Republic of China
- New Cornerstone Science Laboratory, Liangzhu Laboratory and School of Basic Medical Sciences, Zhejiang University, Hangzhou, People's Republic of China
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States
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Xu M, Zhong XZ, Huang P, Jaślan D, Wang P, Sun X, Weiden EM, EL Hiani Y, Grimm C, Dong XP. TRPML3/BK complex promotes autophagy and bacterial clearance by providing a positive feedback regulation of mTOR via PI3P. Proc Natl Acad Sci U S A 2023; 120:e2215777120. [PMID: 37585464 PMCID: PMC10450854 DOI: 10.1073/pnas.2215777120] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 06/22/2023] [Indexed: 08/18/2023] Open
Abstract
TRPML3 is a Ca2+/Na+ release channel residing in both phagophores and endolysosomal membranes. It is activated by PI3P and PI3,5P2. Its activity can be enhanced by high luminal pH and by replacing luminal Na+ with K+. Here, we report that big-conductance Ca2+-activated potassium (BK) channels form a positive feedback loop with TRPML3. Ca2+ release via TRPML3 activates BK, which in turn facilitates TRPML3-mediated Ca2+ release, potentially through removing luminal Na+ inhibition. We further show that TRPML3/BK and mammalian target of rapamycin (mTOR) form another positive feedback loop to facilitate autophagy induction in response to nutrient starvation, i.e., mTOR inhibition upon nutrient starvation activates TRPML3/BK, and this further reduces mTOR activity, thereby increasing autophagy induction. Mechanistically, the feedback regulation between TRPML3/BK and mTOR is mediated by PI3P, an endogenous TRPML3 activator that is enriched in phagophores and is up-regulated by mTOR reduction. Importantly, bacterial infection activates TRPML3 in a BK-dependent manner, and both TRPML3 and BK are required for mTOR suppression and autophagy induction responding to bacterial infection. Suppressing either TRPML3 or BK helps bacteria survival whereas increasing either TRPML3 or BK favors bacterial clearance. Considering that TRPML3/BK is inhibited by low luminal pH but activated by high luminal pH and PI3P in phagophores, we suggest that TRPML3/BK and mTOR form a positive feedback loop via PI3P to ensure efficient autophagy induction in response to nutrient deprivation and bacterial infection. Our study reveals a role of TRPML3-BK coupling in controlling cellular homeostasis and intracellular bacterial clearance via regulating mTOR signaling.
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Affiliation(s)
- Mengnan Xu
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NSB3H 4R2, Canada
| | - Xi Zoë Zhong
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NSB3H 4R2, Canada
| | - Peng Huang
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NSB3H 4R2, Canada
- Chongming Hospital, Shanghai University of Medicine and Health Sciences, Shanghai202150, China
| | - Dawid Jaślan
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, Ludwig-Maximilians-Universität, Munich80336, Germany
| | - Pingping Wang
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NSB3H 4R2, Canada
| | - Xue Sun
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NSB3H 4R2, Canada
- Department of Developmental Cell Biology, China Medical University, Shenbei New District, Shenyang110122, China
| | - Eva-Maria Weiden
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, Ludwig-Maximilians-Universität, Munich80336, Germany
| | - Yassine EL Hiani
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NSB3H 4R2, Canada
| | - Christian Grimm
- Walther Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, Ludwig-Maximilians-Universität, Munich80336, Germany
- Immunology, Infection and Pandemic Research, Fraunhofer Institute for Translational Medicine and Pharmacology, Munich80799, Germany
| | - Xian-Ping Dong
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NSB3H 4R2, Canada
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Rautenberg S, Keller M, Leser C, Chen CC, Bracher F, Grimm C. Expanding the Toolbox: Novel Modulators of Endolysosomal Cation Channels. Handb Exp Pharmacol 2023; 278:249-276. [PMID: 35902436 DOI: 10.1007/164_2022_605] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
Functional characterization of endolysosomal ion channels is challenging due to their intracellular location. With recent advances in endolysosomal patch clamp technology, it has become possible to directly measure ion channel currents across endolysosomal membranes. Members of the transient receptor potential (TRP) cation channel family, namely the endolysosomal TRPML channels (TRPML1-3), also called mucolipins, as well as the distantly related two-pore channels (TPCs) have recently been characterized in more detail with endolysosomal patch clamp techniques. However, answers to many physiological questions require work in intact cells or animal models. One major obstacle thereby is that the known endogenous ligands of TRPMLs and TPCs are anionic in nature and thus impermeable for cell membranes. Microinjection, on the other hand, is technically demanding. There is also a risk of losing essential co-factors for channel activation or inhibition in isolated preparations. Therefore, lipophilic, membrane-permeable small-molecule activators and inhibitors for TRPMLs and TPCs are urgently needed. Here, we describe and discuss the currently available small-molecule modulators of TRPMLs and TPCs.
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Affiliation(s)
- Susanne Rautenberg
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-University, Munich, Germany
| | - Marco Keller
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-University, Munich, Germany
| | - Charlotte Leser
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-University, Munich, Germany
| | - Cheng-Chang Chen
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-University, Munich, Germany
| | - Franz Bracher
- Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-University, Munich, Germany.
| | - Christian Grimm
- Department of Pharmacology and Toxicology, Medical Faculty, Ludwig-Maximilians-University, Munich, Germany.
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Abstract
This chapter explores the existing structural and functional studies on the endo-lysosomal channel TRPML1 and its analogs TRPML2, TRPML3. These channels represent the mucolipin subfamily of the TRP channel superfamily comprising important roles in sensory physiology, ion homeostasis, and signal transduction. Since 2016, numerous structures have been determined for all three members using either cryo-EM or X-ray crystallography. These studies along with recent functional analysis have considerably strengthened our knowledge on TRPML channels and its related endo-lysosomal function. This chapter, together with relevant reports in other chapters from this handbook, provides an informative and detailed tool to study the endo-lysosomal cation channels.
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Affiliation(s)
- Michael Fine
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Xiaochun Li
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
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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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The intracellular Ca 2+ channel TRPML3 is a PI3P effector that regulates autophagosome biogenesis. Proc Natl Acad Sci U S A 2022; 119:e2200085119. [PMID: 36252030 PMCID: PMC9618060 DOI: 10.1073/pnas.2200085119] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Autophagy is a multiple fusion event, initiating with autophagosome formation and culminating with fusion with endo-lysosomes in a Ca2+-dependent manner. The source of Ca2+ and the molecular mechanism by which Ca2+ is provided for this process are not known. The intracellular Ca2+ permeable channel transient receptor potential mucolipin 3 (TRPML3) localizes in the autophagosome and interacts with the mammalian autophagy-related protein 8 (ATG8) homolog GATE16. Here, we show that lipid-regulated TRPML3 is the Ca2+ release channel in the phagophore that provides the Ca2+ necessary for autophagy progress. We generated a TRPML3-GCaMP6 fusion protein as a targeted reporter of TRPML3 compartment localization and channel function. Notably, TRPML3-GCaMP6 localized in the phagophores, the level of which increased in response to nutrient starvation. Importantly, phosphatidylinositol-3-phosphate (PI3P), an essential lipid for autophagosome formation, is a selective regulator of TRPML3. TRPML3 interacted with PI3P, which is a direct activator of TRPML3 current and Ca2+ release from the phagophore, to promote and increase autophagy. Inhibition of TRPML3 suppressed autophagy even in the presence of excess PI3P, while activation of TRPML3 reversed the autophagy inhibition caused by blocking PI3P. Moreover, disruption of the TRPML3-PI3P interaction abolished both TRPML3 activation by PI3P and the increase in autophagy. Taken together, these results reveal that TRPML3 is a downstream effector of PI3P and a key regulator of autophagy. Activation of TRPML3 by PI3P is the critical step providing Ca2+ from the phagophore for the fusion process, which is essential for autophagosome biogenesis.
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7
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Chen CC, Krogsaeter E, Kuo CY, Huang MC, Chang SY, Biel M. Endolysosomal cation channels point the way towards precision medicine of cancer and infectious diseases. Biomed Pharmacother 2022; 148:112751. [PMID: 35240524 DOI: 10.1016/j.biopha.2022.112751] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Revised: 02/21/2022] [Accepted: 02/23/2022] [Indexed: 11/02/2022] Open
Abstract
Infectious diseases and cancer are among the key medical challenges that humankind is facing today. A growing amount of evidence suggests that ion channels in the endolysosomal system play a crucial role in the pathology of both groups of diseases. The development of advanced patch-clamp technologies has allowed us to directly characterize ion fluxes through endolysosomal ion channels in their native environments. Endolysosomes are essential organelles for intracellular transport, digestion and metabolism, and maintenance of homeostasis. The endolysosomal ion channels regulate the function of the endolysosomal system through four basic mechanisms: calcium release, control of membrane potential, pH change, and osmolarity regulation. In this review, we put particular emphasis on the endolysosomal cation channels, including TPC2 and TRPML2, which are particularly important in monocyte function. We discuss existing endogenous and synthetic ligands of these channels and summarize current knowledge of their impact on channel activity and function in different cell types. Moreover, we summarize recent findings on the importance of TPC2 and TRPML2 channels as potential drug targets for the prevention and treatment of the emerging infectious diseases and cancer.
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Affiliation(s)
- Cheng-Chang Chen
- Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan; Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan.
| | | | - Ching-Ying Kuo
- Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan; Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Min-Chuan Huang
- Graduate Institute of Anatomy and Cell Biology, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Sui-Yuan Chang
- Department of Clinical Laboratory Sciences and Medical Biotechnology, College of Medicine, National Taiwan University, Taipei, Taiwan; Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan
| | - Martin Biel
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, Germany
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8
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Gan N, Jiang Y. Structural biology of cation channels important for lysosomal calcium release. Cell Calcium 2022; 101:102519. [PMID: 34952412 PMCID: PMC8752501 DOI: 10.1016/j.ceca.2021.102519] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 12/10/2021] [Accepted: 12/11/2021] [Indexed: 01/03/2023]
Abstract
Calcium is one of the most important second messengers in cells. The uptake and release of calcium ions are conducted by channels and transporters. Inside a eukaryotic cell, calcium is stored in intracellular organelles including the endoplasmic reticulum (ER), mitochondrion, and lysosome. Lysosomes are acid membrane-bounded organelles serving as the crucial degradation and recycling center of the cell. Lysosomes involve in multiple important signaling events, including nutrient sensing, lipid metabolism, and trafficking. Hitherto, two lysosomal cation channel families have been suggested to function as calcium release channels, namely the Two-pore Channel (TPC) family, and the Transient Receptor Potential Channel Mucolipin (TRPML) family. Additionally, a few plasma membrane calcium channels have also been found in the lysosomal membrane under certain circumstances. In this review, we will discuss the structural mechanism of the cation channels that may be important for lysosomal calcium release, primarily focusing on the TPCs and TRPMLs.
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Affiliation(s)
- Ninghai Gan
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390 USA,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390 USA
| | - Youxing Jiang
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390 USA,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390 USA
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9
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Sirés-Campos J, Lambertos A, Delevoye C, Raposo G, Bennett DC, Sviderskaya E, Jiménez-Cervantes C, Olivares C, García-Borrón JC. Mahogunin Ring Finger 1 regulates pigmentation by controlling the pH of melanosomes in melanocytes and melanoma cells. Cell Mol Life Sci 2021; 79:47. [PMID: 34921635 PMCID: PMC8738503 DOI: 10.1007/s00018-021-04053-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 11/18/2021] [Accepted: 11/19/2021] [Indexed: 12/29/2022]
Abstract
Mahogunin Ring Finger 1 (MGRN1) is an E3-ubiquitin ligase absent in dark-furred mahoganoid mice. We investigated the mechanisms of hyperpigmentation in Mgrn1-null melan-md1 melanocytes, Mgrn1-KO cells obtained by CRISPR-Cas9-mediated knockdown of Mgrn1 in melan-a6 melanocytes, and melan-a6 cells depleted of MGRN1 by siRNA treatment. Mgrn1-deficient melanocytes showed higher melanin content associated with increased melanosome abundance and higher fraction of melanosomes in highly melanized maturation stages III-IV. Expression, post-translational processing and enzymatic activity of the rate-limiting melanogenic enzyme tyrosinase measured in cell-free extracts were comparable in control and MGRN1-depleted cells. However, tyrosinase activity measured in situ in live cells and expression of genes associated with regulation of pH increased upon MGRN1 repression. Using pH-sensitive fluorescent probes, we found that downregulation of MGRN1 expression in melanocytes and melanoma cells increased the pH of acidic organelles, including melanosomes, strongly suggesting a previously unknown role of MGRN1 in the regulation of melanosomal pH. Among the pH regulatory genes upregulated by Mgrn1 knockdown, we identified those encoding several subunits of the vacuolar adenosine triphosphatase V-ATPase (mostly Atp6v0d2) and a calcium channel of the transient receptor potential channel family, Mucolipin 3 (Mcoln3). Manipulation of expression of the Mcoln3 gene showed that overexpression of Mcoln3 played a significant role in neutralization of the pH of acidic organelles and activation of tyrosinase in MGRN1-depleted cells. Therefore, lack of MGRN1 led to cell-autonomous stimulation of pigment production in melanocytes mostly by increasing tyrosinase specific activity through neutralization of the melanosomal pH in a MCOLN3-dependent manner.
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Affiliation(s)
- Julia Sirés-Campos
- University of Murcia, Murcia, Spain.,Institut Curie, UMR144, Structure and Membrane Compartments, PSL Research University, CNRS, 75005, Paris, France
| | | | - Cédric Delevoye
- Institut Curie, UMR144, Structure and Membrane Compartments, PSL Research University, CNRS, 75005, Paris, France.,Institut Curie, UMR144, Cell and Tissue Imaging Facility (PICT-IBiSA), PSL Research University, CNRS, 75005, Paris, France
| | - Graça Raposo
- Institut Curie, UMR144, Structure and Membrane Compartments, PSL Research University, CNRS, 75005, Paris, France.,Institut Curie, UMR144, Cell and Tissue Imaging Facility (PICT-IBiSA), PSL Research University, CNRS, 75005, Paris, France
| | - Dorothy C Bennett
- Molecular and Clinical Sciences Research Institute, St. George's, University of London, London, SW17 0RE, UK
| | - Elena Sviderskaya
- Molecular and Clinical Sciences Research Institute, St. George's, University of London, London, SW17 0RE, UK
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Endolysosomal TRPMLs in Cancer. Biomolecules 2021; 11:biom11010065. [PMID: 33419007 PMCID: PMC7825278 DOI: 10.3390/biom11010065] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 12/31/2020] [Accepted: 12/31/2020] [Indexed: 12/13/2022] Open
Abstract
Lysosomes, the degradative endpoints and sophisticated cellular signaling hubs, are emerging as intracellular Ca2+ stores that govern multiple cellular processes. Dys-homeostasis of lysosomal Ca2+ is intimately associated with a variety of human diseases including cancer. Recent studies have suggested that the Ca2+-permeable channels Transient Receptor Potential (TRP) Mucolipins (TRPMLs, TRPML1-3) integrate multiple processes of cell growth, division and metabolism. Dysregulation of TRPMLs activity has been implicated in cancer development. In this review, we provide a summary of the latest development of TRPMLs in cancer. The expression of TRPMLs in cancer, TRPMLs in cancer cell nutrient sensing, TRPMLs-mediated lysosomal exocytosis in cancer development, TRPMLs in TFEB-mediated gene transcription of cancer cells, TRPMLs in bacteria-related cancer development and TRPMLs-regulated antitumor immunity are discussed. We hope to guide readers toward a more in-depth discussion of the importance of lysosomal TRPMLs in cancer progression and other human diseases.
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11
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Structural insights into group II TRP channels. Cell Calcium 2019; 86:102107. [PMID: 31841954 DOI: 10.1016/j.ceca.2019.102107] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/29/2019] [Accepted: 10/29/2019] [Indexed: 01/01/2023]
Abstract
The seven members of the TRP channel superfamily are divided into two main groups with five members comprising group I (TRPC/V/M/N/A) and TRPML (TRP MucoLipin) and TRPP (TRP Polycystin) making up group II. Group II channels share a high sequence homology on their transmembrane domains and are distinct from group I members as they contain a large luminal/extracellular domain between transmembrane helix 1 (S1) and S2. Since 2016, there are more than ten research papers reporting various structures of group II channels by either cryo-EM or X-ray crystallography. These studies along with recent functional analysis by the other groups have considerably strengthened our knowledge on TRPML and TRPP channels. In this review, we summarize and discuss these reports providing molecular insights into the group II TRP channel family.
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Viet KK, Wagner A, Schwickert K, Hellwig N, Brennich M, Bader N, Schirmeister T, Morgner N, Schindelin H, Hellmich UA. Structure of the Human TRPML2 Ion Channel Extracytosolic/Lumenal Domain. Structure 2019; 27:1246-1257.e5. [DOI: 10.1016/j.str.2019.04.016] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2018] [Revised: 04/16/2019] [Accepted: 04/29/2019] [Indexed: 11/28/2022]
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Westman J, Grinstein S, Maxson ME. Revisiting the role of calcium in phagosome formation and maturation. J Leukoc Biol 2019; 106:837-851. [DOI: 10.1002/jlb.mr1118-444r] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 04/24/2019] [Accepted: 04/25/2019] [Indexed: 12/19/2022] Open
Affiliation(s)
- Johannes Westman
- Program in Cell BiologyHospital for Sick Children Toronto Ontario Canada
| | - Sergio Grinstein
- Program in Cell BiologyHospital for Sick Children Toronto Ontario Canada
- Department of BiochemistryUniversity of Toronto Toronto Ontario Canada
- Keenan Research Centre of the Li Ka Shing Knowledge InstituteSt. Michael's Hospital Toronto Ontario Canada
| | - Michelle E. Maxson
- Program in Cell BiologyHospital for Sick Children Toronto Ontario Canada
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Endolysosomal Ca 2+ Signalling and Cancer Hallmarks: Two-Pore Channels on the Move, TRPML1 Lags Behind! Cancers (Basel) 2018; 11:cancers11010027. [PMID: 30591696 PMCID: PMC6356888 DOI: 10.3390/cancers11010027] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 12/21/2018] [Accepted: 12/21/2018] [Indexed: 12/22/2022] Open
Abstract
The acidic vesicles of the endolysosomal (EL) system are emerging as an intracellular Ca2+ store implicated in the regulation of multiple cellular functions. The EL Ca2+ store releases Ca2+ through a variety of Ca2+-permeable channels, including Transient Receptor Potential (TRP) Mucolipin 1-3 (TRPML1-3) and two-pore channels 1-2 (TPC1-2), whereas EL Ca2+ refilling is sustained by the proton gradient across the EL membrane and/or by the endoplasmic reticulum (ER). EL Ca2+ signals may be either spatially restricted to control vesicle trafficking, autophagy and membrane repair or may be amplified into a global Ca2+ signal through the Ca2+-dependent recruitment of ER-embedded channels. Emerging evidence suggested that nicotinic acid adenine dinucleotide phosphate (NAADP)-gated TPCs sustain multiple cancer hallmarks, such as migration, invasiveness and angiogenesis. Herein, we first survey the EL Ca2+ refilling and release mechanisms and then focus on the oncogenic role of EL Ca2+ signaling. While the evidence in favor of TRPML1 involvement in neoplastic transformation is yet to be clearly provided, TPCs are emerging as an alternative target for anticancer therapies.
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Kim SW, Kim DH, Park KS, Kim MK, Park YM, Muallem S, So I, Kim HJ. Palmitoylation controls trafficking of the intracellular Ca 2+ channel MCOLN3/TRPML3 to regulate autophagy. Autophagy 2018; 15:327-340. [PMID: 30215288 PMCID: PMC6333453 DOI: 10.1080/15548627.2018.1518671] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
MCOLN3/TRPML3 is a Ca2+-permeable cation channel that is expressed in multiple subcellular compartments with dynamic localization. Our previous studies suggest that upon macroautophagy/autophagy induction MCOLN3/TRPML3 is recruited and provides Ca2+ for the fusion process in autophagosome biogenesis. However, how intracellular trafficking and the Ca2+ channel function of MCOLN3/TRPML3 are related to autophagy are not known. Here we report that MCOLN3/TRPML3 undergoes palmitoylation at its C-terminal region, which is required for dynamic trafficking and cellular function of MCOLN3/TRPML3 in autophagy. Palmitoylation regulated MCOLN3/TRPML3 surface expression and trafficking, but not channel properties or localization and function of intracellular MCOLN3/TRPML3. Activation of intracellular MCOLN3/TRPML3 induced robust Ca2+ release, which solely increased autophagy in Ca2+- and palmitoylation-dependent manners. Palmitoylation regulated not only intracellular MCOLN3/TRPML3 trafficking to autophagic structures but also autophagic flux in induced autophagy. Importantly, nutrient starvation activated MCOLN3/TRPML3 to release Ca2+ and increased the level of MCOLN3/TRPML3 palmitoylation. Disruption of MCOLN3/TRPML3 palmitoylation, however, abolished the starvation-induced MCOLN3/TRPML3 activation without affecting channel activity. These results suggest that trafficking and channel function of MCOLN3/TRPML3 are regulated in the context of autophagy, and palmitoylation is a prerequisite for the function of MCOLN3/TRPML3 as a Ca2+ channel in autophagosome formation by controlling its trafficking between subcellular compartments. Abbreviations: 17-ODYA, 17-octadecynoic acid; 2-BP, 2-bromopalmitate; BFA, brefeldin A; DN, dominant-negative; GPN, glycyl-L-phenylalanine-beta-naphthylamide; HN, hydroxylamine; KD, knockdown; MCOLN3/TRPML3, mucolipin 3; MS, mass spectrometry; PAT, palmitoyl acyltransferase; PM, plasma membrane; WT, wild type; ZDHHC, a zinc-finger motif and an Asp-His-His-Cys sequence.
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Affiliation(s)
- So Woon Kim
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Dong Hyun Kim
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Kyoung Sun Park
- Wide River Institute of Immunology, Seoul National University College of Medicine, Gangwon-do, Korea
| | - Mi Kyung Kim
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Yun Min Park
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Shmuel Muallem
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Insuk So
- Department of Physiology and Biophysics, Seoul National University College of Medicine, Seoul, Korea
| | - Hyun Jin Kim
- Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea,Samsung Biomedical Research Institute, Samsung Medical Center, Seoul, Korea,CONTACT Hyun Jin Kim Department of Physiology, Sungkyunkwan University School of Medicine, Suwon, Korea; Insuk So Department of Physiology and Biophysics, Seoul National University College of Medicine, Seoul, Korea
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16
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Sterea AM, Almasi S, El Hiani Y. The hidden potential of lysosomal ion channels: A new era of oncogenes. Cell Calcium 2018; 72:91-103. [PMID: 29748137 DOI: 10.1016/j.ceca.2018.02.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 02/28/2018] [Accepted: 02/28/2018] [Indexed: 01/14/2023]
Abstract
Lysosomes serve as the control centre for cellular clearance. These membrane-bound organelles receive biomolecules destined for degradation from intracellular and extracellular pathways; thus, facilitating the production of energy and shaping the fate of the cell. At the base of their functionality are the lysosomal ion channels which mediate the function of the lysosome through the modulation of ion influx and efflux. Ion channels form pores in the membrane of lysosomes and allow the passage of ions, a seemingly simple task which harbours the potential of overthrowing the cell's stability. Considered the master regulators of ion homeostasis, these integral membrane proteins enable the proper operation of the lysosome. Defects in the structure or function of these ion channels lead to the development of lysosomal storage diseases, neurodegenerative diseases and cancer. Although more than 50 years have passed since their discovery, lysosomes are not yet fully understood, with their ion channels being even less well characterized. However, significant improvements have been made in the development of drugs targeted against these ion channels as a means of combating diseases. In this review, we will examine how Ca2+, K+, Na+ and Cl- ion channels affect the function of the lysosome, their involvement in hereditary and spontaneous diseases, and current ion channel-based therapies.
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Affiliation(s)
- Andra M Sterea
- Departments of Physiology & Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Shekoufeh Almasi
- Departments of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Yassine El Hiani
- Departments of Physiology & Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada.
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17
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Rinkenberger N, Schoggins JW. Mucolipin-2 Cation Channel Increases Trafficking Efficiency of Endocytosed Viruses. mBio 2018; 9:e02314-17. [PMID: 29382735 PMCID: PMC5790917 DOI: 10.1128/mbio.02314-17] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 01/03/2018] [Indexed: 12/26/2022] Open
Abstract
Receptor-mediated endocytosis is a cellular process commonly hijacked by viruses to enter cells. The stages of entry are well described for certain viruses, but the host factors that mediate each step are less well characterized. We previously identified endosomal cation channel mucolipin-2 (MCOLN2) as a host factor that promotes viral infection. Here, we assign a role for MCOLN2 in modulating viral entry. We show that MCOLN2 specifically promotes viral vesicular trafficking and subsequent escape from endosomal compartments. This mechanism requires channel activity, occurs independently of antiviral signaling, and broadly applies to enveloped RNA viruses that require transport to late endosomes for infection, including influenza A virus, yellow fever virus, and Zika virus. We further identify a rare allelic variant of human MCOLN2 that has a loss-of-function phenotype with respect to viral enhancement. These findings establish a mechanistic link between an endosomal cation channel and late stages of viral entry.IMPORTANCE Viruses must co-opt cellular processes to complete their life cycle. To enter cells, viruses frequently take advantage of cellular receptor-mediated endocytosis pathways. A growing number of host proteins are implicated in these viral uptake pathways. Here, we describe a new role for the gated cation channel MCOLN2 in viral entry. This endosomal protein modulates viral entry by enhancing the efficiency of viral trafficking through the endosomal system. Thus, MCOLN2-mediated enhancement of infection may represent a key vulnerability in the viral life cycle that could be targeted for therapeutic intervention.
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Affiliation(s)
- Nicholas Rinkenberger
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - John W Schoggins
- Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
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18
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Podinovskaia M, Spang A. The Endosomal Network: Mediators and Regulators of Endosome Maturation. ENDOCYTOSIS AND SIGNALING 2018; 57:1-38. [DOI: 10.1007/978-3-319-96704-2_1] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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19
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Zhou X, Li M, Su D, Jia Q, Li H, Li X, Yang J. Cryo-EM structures of the human endolysosomal TRPML3 channel in three distinct states. Nat Struct Mol Biol 2017; 24:1146-1154. [PMID: 29106414 PMCID: PMC5747366 DOI: 10.1038/nsmb.3502] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 10/10/2017] [Indexed: 12/23/2022]
Abstract
TRPML3 channels are mainly localized to endolysosomes and play a critical role in the endocytic pathway. Their dysfunction causes deafness and pigmentation defects in mice. TRPML3 activity is inhibited by low endolysosomal pH. Here we present cryo-electron microscopy (cryo-EM) structures of human TRPML3 in the closed, agonist-activated, and low-pH-inhibited states, with resolutions of 4.06, 3.62, and 4.65 Å, respectively. The agonist ML-SA1 lodges between S5 and S6 and opens an S6 gate. A polycystin-mucolipin domain (PMD) forms a luminal cap. S1 extends into this cap, forming a 'gating rod' that connects directly to a luminal pore loop, which undergoes dramatic conformational changes in response to low pH. S2 extends intracellularly and interacts with several intracellular regions to form a 'gating knob'. These unique structural features, combined with the results of electrophysiological studies, indicate a new mechanism by which luminal pH and other physiological modulators such as PIP2 regulate TRPML3 by changing S1 and S2 conformations.
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Affiliation(s)
- Xiaoyuan Zhou
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Minghui Li
- Department of Biological Sciences, Columbia University, New York, NY, USA
| | - Deyuan Su
- Department of Biological Sciences, Columbia University, New York, NY, USA
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, and Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
| | - Qi Jia
- Department of Orthopedic Oncology, Shanghai Changzheng Hospital, The Second Military Medical University, Shanghai 200003, China
| | - Huan Li
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, and Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
- Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming, China
| | - Xueming Li
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Jian Yang
- Department of Biological Sciences, Columbia University, New York, NY, USA
- Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences/Key Laboratory of Bioactive Peptides of Yunnan Province, and Ion Channel Research and Drug Development Center, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, China
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20
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Hirschi M, Herzik MA, Wie J, Suo Y, Borschel WF, Ren D, Lander GC, Lee SY. Cryo-electron microscopy structure of the lysosomal calcium-permeable channel TRPML3. Nature 2017; 550:411-414. [PMID: 29019979 PMCID: PMC5762132 DOI: 10.1038/nature24055] [Citation(s) in RCA: 86] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2017] [Accepted: 09/01/2017] [Indexed: 01/09/2023]
Abstract
The modulation of ion channel activity by lipids is increasingly recognized as a fundamental component of cellular signalling. The transient receptor potential mucolipin (TRPML) channel family belongs to the TRP superfamily and is composed of three members: TRPML1-TRPML3. TRPMLs are the major Ca2+-permeable channels on late endosomes and lysosomes (LEL). They regulate the release of Ca2+ from organelles, which is important for various physiological processes, including organelle trafficking and fusion. Loss-of-function mutations in the MCOLN1 gene, which encodes TRPML1, cause the neurodegenerative lysosomal storage disorder mucolipidosis type IV, and a gain-of-function mutation (Ala419Pro) in TRPML3 gives rise to the varitint-waddler (Va) mouse phenotype. Notably, TRPML channels are activated by the low-abundance and LEL-enriched signalling lipid phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P2), whereas other phosphoinositides such as PtdIns(4,5)P2, which is enriched in plasma membranes, inhibit TRPMLs. Conserved basic residues at the N terminus of the channel are important for activation by PtdIns(3,5)P2 and inhibition by PtdIns(4,5)P2. However, owing to a lack of structural information, the mechanism by which TRPML channels recognize PtdIns(3,5)P2 and increase their Ca2+ conductance remains unclear. Here we present the cryo-electron microscopy (cryo-EM) structure of a full-length TRPML3 channel from the common marmoset (Callithrix jacchus) at an overall resolution of 2.9 Å. Our structure reveals not only the molecular basis of ion conduction but also the unique architecture of TRPMLs, wherein the voltage sensor-like domain is linked to the pore via a cytosolic domain that we term the mucolipin domain. Combined with functional studies, these data suggest that the mucolipin domain is responsible for PtdIns(3,5)P2 binding and subsequent channel activation, and that it acts as a 'gating pulley' for lipid-dependent TRPML gating.
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Affiliation(s)
- Marscha Hirschi
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Mark A Herzik
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Jinhong Wie
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Yang Suo
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - William F Borschel
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Dejian Ren
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Gabriel C Lander
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Seok-Yong Lee
- Department of Biochemistry, Duke University School of Medicine, Durham, North Carolina 27710, USA
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21
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Chen CC, Butz ES, Chao YK, Grishchuk Y, Becker L, Heller S, Slaugenhaupt SA, Biel M, Wahl-Schott C, Grimm C. Small Molecules for Early Endosome-Specific Patch Clamping. Cell Chem Biol 2017; 24:907-916.e4. [PMID: 28732201 DOI: 10.1016/j.chembiol.2017.05.025] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 03/30/2017] [Accepted: 05/26/2017] [Indexed: 12/31/2022]
Abstract
To resolve the subcellular distribution of endolysosomal ion channels, we have established a novel experimental approach to selectively patch clamp Rab5 positive early endosomes (EE) versus Rab7/LAMP1-positive late endosomes/lysosomes (LE/LY). To functionally characterize ion channels in endolysosomal membranes with the patch-clamp technique, it is important to develop techniques to selectively enlarge the respective organelles. We found here that two small molecules, wortmannin and latrunculin B, enlarge Rab5-positive EE when combined but not Rab7-, LAMP1-, or Rab11 (RE)-positive vesicles. The two compounds act rapidly, specifically, and are readily applicable in contrast to genetic approaches or previously used compounds such as vacuolin, which enlarges EE, RE, and LE/LY. We apply this approach here to measure currents mediated by TRPML channels, in particular TRPML3, which we found to be functionally active in both EE and LE/LY in overexpressing cells as well as in endogenously expressing CD11b+ lung-tissue macrophages.
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Affiliation(s)
- Cheng-Chang Chen
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Elisabeth S Butz
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Yu-Kai Chao
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Yulia Grishchuk
- Department of Neurology, Center for Human Genetic Research, Massachusetts General Hospital, Harvard University, Boston, MA 02114, USA
| | - Lars Becker
- Departments of Otolaryngology - HNS and Molecular & Cellular Physiology, Stanford University School of Medicine, Palo Alto, CA 94304, USA
| | - Stefan Heller
- Departments of Otolaryngology - HNS and Molecular & Cellular Physiology, Stanford University School of Medicine, Palo Alto, CA 94304, USA
| | - Susan A Slaugenhaupt
- Department of Neurology, Center for Human Genetic Research, Massachusetts General Hospital, Harvard University, Boston, MA 02114, USA
| | - Martin Biel
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, 81377 Munich, Germany
| | - Christian Wahl-Schott
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, 81377 Munich, Germany.
| | - Christian Grimm
- Department of Pharmacy, Center for Drug Research and Center for Integrated Protein Science Munich (CIPSM), Ludwig-Maximilians-Universität München, 81377 Munich, Germany.
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22
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Regulation of lysosomal ion homeostasis by channels and transporters. SCIENCE CHINA-LIFE SCIENCES 2016; 59:777-91. [PMID: 27430889 PMCID: PMC5147046 DOI: 10.1007/s11427-016-5090-x] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 06/02/2016] [Indexed: 02/05/2023]
Abstract
Lysosomes are the major organelles that carry out degradation functions. They integrate and digest materials compartmentalized by endocytosis, phagocytosis or autophagy. In addition to more than 60 hydrolases residing in the lysosomes, there are also ion channels and transporters that mediate the flux or transport of H+, Ca2+, Na+, K+, and Cl− across the lysosomal membranes. Defects in ionic exchange can lead to abnormal lysosome morphology, defective vesicle trafficking, impaired autophagy, and diseases such as neurodegeneration and lysosomal storage disorders. The latter are characterized by incomplete lysosomal digestion and accumulation of toxic materials inside enlarged intracellular vacuoles. In addition to degradation, recent studies have revealed the roles of lysosomes in metabolic pathways through kinases such as mechanistic target of rapamycin (mTOR) and transcriptional regulation through calcium signaling molecules such as transcription factor EB (TFEB) and calcineurin. Owing to the development of new approaches including genetically encoded fluorescence probes and whole endolysosomal patch clamp recording techniques, studies on lysosomal ion channels have made remarkable progress in recent years. In this review, we will focus on the current knowledge of lysosome-resident ion channels and transporters, discuss their roles in maintaining lysosomal function, and evaluate how their dysfunction can result in disease.
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23
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Wu X, Indzhykulian AA, Niksch PD, Webber RM, Garcia-Gonzalez M, Watnick T, Zhou J, Vollrath MA, Corey DP. Hair-Cell Mechanotransduction Persists in TRP Channel Knockout Mice. PLoS One 2016; 11:e0155577. [PMID: 27196058 PMCID: PMC4873267 DOI: 10.1371/journal.pone.0155577] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Accepted: 05/01/2016] [Indexed: 12/17/2022] Open
Abstract
Members of the TRP superfamily of ion channels mediate mechanosensation in some organisms, and have been suggested as candidates for the mechanotransduction channel in vertebrate hair cells. Some TRP channels can be ruled out based on lack of an inner ear phenotype in knockout animals or pore properties not similar to the hair-cell channel. Such studies have excluded Trpv4, Trpa1, Trpml3, Trpm1, Trpm3, Trpc1, Trpc3, Trpc5, and Trpc6. However, others remain reasonable candidates. We used data from an RNA-seq analysis of gene expression in hair cells as well as data on TRP channel conductance to narrow the candidate group. We then characterized mice lacking functional Trpm2, Pkd2, Pkd2l1, Pkd2l2 and Pkd1l3, using scanning electron microscopy, auditory brainstem response, permeant dye accumulation, and single-cell electrophysiology. In all of these TRP-deficient mice, and in double and triple knockouts, mechanotransduction persisted. Together with published studies, these results argue against the participation of any of the 33 mouse TRP channels in hair cell transduction.
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MESH Headings
- Animals
- Calcium Channels/genetics
- Cochlea/physiology
- Ear, Inner/physiology
- Evoked Potentials, Auditory, Brain Stem/genetics
- Gene Expression Profiling
- Gene Expression Regulation
- Hair Cells, Auditory/physiology
- Hearing
- Mechanotransduction, Cellular
- Membrane Glycoproteins/genetics
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microscopy, Electron, Scanning
- Patch-Clamp Techniques
- Receptors, Cell Surface/genetics
- TRPM Cation Channels/genetics
- TRPP Cation Channels/genetics
- Transient Receptor Potential Channels/genetics
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Affiliation(s)
- Xudong Wu
- Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, Massachusetts, United States of America
| | - Artur A. Indzhykulian
- Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, Massachusetts, United States of America
| | - Paul D. Niksch
- Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, Massachusetts, United States of America
| | - Roxanna M. Webber
- Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, Massachusetts, United States of America
| | - Miguel Garcia-Gonzalez
- Department of Medicine, Division of Nephrology, University of Maryland, Baltimore, Maryland, United States of America
| | - Terry Watnick
- Department of Medicine, Division of Nephrology, University of Maryland, Baltimore, Maryland, United States of America
| | - Jing Zhou
- Renal Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, United States of America
| | - Melissa A. Vollrath
- Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, Massachusetts, United States of America
- Department of Physiology, McGill University Montréal, Québec, Canada
| | - David P. Corey
- Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, Massachusetts, United States of America
- * E-mail:
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24
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Calcium signaling in membrane repair. Semin Cell Dev Biol 2015; 45:24-31. [PMID: 26519113 DOI: 10.1016/j.semcdb.2015.10.031] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 10/20/2015] [Accepted: 10/20/2015] [Indexed: 11/21/2022]
Abstract
Resealing allows cells to mend damaged membranes rapidly when plasma membrane (PM) disruptions occur. Models of PM repair mechanisms include the "lipid-patch", "endocytic removal", and "macro-vesicle shedding" models, all of which postulate a dependence on local increases in intracellular Ca(2+) at injury sites. Multiple calcium sensors, including synaptotagmin (Syt) VII, dysferlin, and apoptosis-linked gene-2 (ALG-2), are involved in PM resealing, suggesting that Ca(2+) may regulate multiple steps of the repair process. Although earlier studies focused exclusively on external Ca(2+), recent studies suggest that Ca(2+) release from intracellular stores may also be important for PM resealing. Hence, depending on injury size and the type of injury, multiple sources of Ca(2+) may be recruited to trigger and orchestrate repair processes. In this review, we discuss the mechanisms by which the resealing process is promoted by vesicular Ca(2+) channels and Ca(2+) sensors that accumulate at damage sites.
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25
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PKD2L1/PKD1L3 channel complex with an alkali-activated mechanism and calcium-dependent inactivation. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2015; 44:483-92. [PMID: 26066678 DOI: 10.1007/s00249-015-1040-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 04/20/2015] [Accepted: 05/07/2015] [Indexed: 10/23/2022]
Abstract
Polycystic kidney disease-like (PKDL) genes that are expressed in sour taste cells have been proposed to be involved in the transduction of sourness by producing off-responses, which shows a large inward current after withdrawing the acid stimuli. However, the underlying mechanisms of off-responses are still unclear. Here, we demonstrate that an alkali-activated mechanism is responsible for eliciting off-responses, as evidenced by both experimental and theoretical analyses. In addition, we showed that the decaying phase of offset responses in PKD2L1/PKD1L3 channels was substantially accelerated by extracellular Ca(2+).
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26
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Miao Y, Li G, Zhang X, Xu H, Abraham SN. A TRP Channel Senses Lysosome Neutralization by Pathogens to Trigger Their Expulsion. Cell 2015; 161:1306-19. [PMID: 26027738 PMCID: PMC4458218 DOI: 10.1016/j.cell.2015.05.009] [Citation(s) in RCA: 207] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 01/28/2015] [Accepted: 03/27/2015] [Indexed: 02/01/2023]
Abstract
Vertebrate cells have evolved elaborate cell-autonomous defense programs to monitor subcellular compartments for infection and to evoke counter-responses. These programs are activated by pathogen-associated pattern molecules and by various strategies intracellular pathogens employ to alter cellular microenvironments. Here, we show that, when uropathogenic E. coli (UPEC) infect bladder epithelial cells (BECs), they are targeted by autophagy but avoid degradation because of their capacity to neutralize lysosomal pH. This change is detected by mucolipin TRP channel 3 (TRPML3), a transient receptor potential cation channel localized to lysosomes. TRPML3 activation then spontaneously initiates lysosome exocytosis, resulting in expulsion of exosome-encased bacteria. These studies reveal a cellular default system for lysosome homeostasis that has been co-opted by the autonomous defense program to clear recalcitrant pathogens.
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Affiliation(s)
- Yuxuan Miao
- Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Guojie Li
- Department of Pathology, Duke University Medical Center, Durham, NC 27710, USA
| | - Xiaoli Zhang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Haoxing Xu
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Soman N Abraham
- Department of Molecular Genetics & Microbiology, Duke University Medical Center, Durham, NC 27710, USA; Department of Pathology, Duke University Medical Center, Durham, NC 27710, USA; Department of Immunology, Duke University Medical Center, Durham, NC 27710, USA; Program in Emerging Infectious Diseases, Duke-National University of Singapore, Singapore 169857, Singapore.
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27
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Yue Z, Xie J, Yu AS, Stock J, Du J, Yue L. Role of TRP channels in the cardiovascular system. Am J Physiol Heart Circ Physiol 2015; 308:H157-82. [PMID: 25416190 PMCID: PMC4312948 DOI: 10.1152/ajpheart.00457.2014] [Citation(s) in RCA: 126] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 11/14/2014] [Indexed: 12/12/2022]
Abstract
The transient receptor potential (TRP) superfamily consists of a large number of nonselective cation channels with variable degree of Ca(2+)-permeability. The 28 mammalian TRP channel proteins can be grouped into six subfamilies: canonical, vanilloid, melastatin, ankyrin, polycystic, and mucolipin TRPs. The majority of these TRP channels are expressed in different cell types including both excitable and nonexcitable cells of the cardiovascular system. Unlike voltage-gated ion channels, TRP channels do not have a typical voltage sensor, but instead can sense a variety of other stimuli including pressure, shear stress, mechanical stretch, oxidative stress, lipid environment alterations, hypertrophic signals, and inflammation products. By integrating multiple stimuli and transducing their activity to downstream cellular signal pathways via Ca(2+) entry and/or membrane depolarization, TRP channels play an essential role in regulating fundamental cell functions such as contraction, relaxation, proliferation, differentiation, and cell death. With the use of targeted deletion and transgenic mouse models, recent studies have revealed that TRP channels are involved in numerous cellular functions and play an important role in the pathophysiology of many diseases in the cardiovascular system. Moreover, several TRP channels are involved in inherited diseases of the cardiovascular system. This review presents an overview of current knowledge concerning the physiological functions of TRP channels in the cardiovascular system and their contributions to cardiovascular diseases. Ultimately, TRP channels may become potential therapeutic targets for cardiovascular diseases.
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Affiliation(s)
- Zhichao Yue
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut
| | - Jia Xie
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut
| | - Albert S Yu
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut
| | - Jonathan Stock
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut
| | - Jianyang Du
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut
| | - Lixia Yue
- Calhoun Cardiology Center, Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut
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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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29
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Permeation, regulation and control of expression of TRP channels by trace metal ions. Pflugers Arch 2014; 467:1143-64. [PMID: 25106481 PMCID: PMC4435931 DOI: 10.1007/s00424-014-1590-3] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 07/10/2014] [Accepted: 07/13/2014] [Indexed: 01/26/2023]
Abstract
Transient receptor potential (TRP) channels form a diverse family of cation channels comprising 28 members in mammals. Although some TRP proteins can only be found on intracellular membranes, most of the TRP protein isoforms reach the plasma membrane where they form ion channels and control a wide number of biological processes. There, their involvement in the transport of cations such as calcium and sodium has been well documented. However, a growing number of studies have started to expand our understanding of these proteins by showing that they also transport other biologically relevant metal ions like zinc, magnesium, manganese and cobalt. In addition to this newly recognized property, the activity and expression of TRP channels can be regulated by metal ions like magnesium, gadolinium, lanthanum or cisplatin. The aim of this review is to highlight the complex relationship between metal ions and TRP channels.
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Abstract
Hearing is a particularly sensitive form of mechanosensation that relies on dedicated ion channels transducing sound-induced vibrations that hardly exceed Brownian motion. Attempts to molecularly identify these auditory transduction channels have put the focus on TRPs in ears. In Drosophila, hearing has been shown to involve TRPA, TRPC, TRPN, and TRPV subfamily members, with candidate auditory transduction channels including NOMPC (=TRPN1) and the TRPVs Nan and Iav. In vertebrates, TRPs are unlikely to form auditory transduction channels, yet most TRPs are expressed in inner ear tissues, and mutations in TRPN1, TRPVA1, TRPML3, TRPV4, and TRPC3/TRPC6 have been implicated in inner ear function. Starting with a brief introduction of fly and vertebrate auditory anatomies and transduction mechanisms, this review summarizes our current understanding of the auditory roles of TRPs.
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Affiliation(s)
- Damiano Zanini
- Department of Cellular Neurobiology, University of Göttingen, Julia-Lermontowa-Weg 3, 37077, Göttingen, Germany
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31
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Abstract
TRPML3 belongs to the MCOLN (TRPML) subfamily of transient receptor potential (TRP) channels comprising three genes in mammals. Since the discovery of the pain sensing, capsaicin- and heat-activated vanilloid receptor (TRPV1), TRP channels have been found to be involved in regulating almost all kinds of our sensory modalities. Thus, TRP channel members are sensitive to heat or cold; they are involved in pain or osmosensation, vision, hearing, or taste sensation. Loss or mutation of TRPML1 can cause retina degeneration and eventually blindness in mice and men (mucolipidosis type IV). Gain-of-function mutations in TRPML3 cause deafness and circling behavior in mice. A special feature of TRPML channels is their intracellular expression. They mostly reside in membranes of organelles of the endolysosomal system such as early and late endosomes, recycling endosomes, lysosomes, or lysosome-related organelles. Although the physiological roles of TRPML channels within the endolysosomal system are far from being fully understood, it is speculated that they are involved in the regulation of endolysosomal pH, fusion/fission processes, trafficking, autophagy, and/or (hormone) secretion and exocytosis.
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The Ca2+ channel TRPML3 specifically interacts with the mammalian ATG8 homologue GATE16 to regulate autophagy. Biochem Biophys Res Commun 2014; 443:56-61. [DOI: 10.1016/j.bbrc.2013.11.044] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 11/11/2013] [Indexed: 11/24/2022]
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Feng X, Huang Y, Lu Y, Xiong J, Wong CO, Yang P, Xia J, Chen D, Du G, Venkatachalam K, Xia X, Zhu MX. Drosophila TRPML forms PI(3,5)P2-activated cation channels in both endolysosomes and plasma membrane. J Biol Chem 2013; 289:4262-72. [PMID: 24375408 DOI: 10.1074/jbc.m113.506501] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transient Receptor Potential mucolipin (TRPML) channels are implicated in endolysosomal trafficking, lysosomal Ca(2+) and Fe(2+) release, lysosomal biogenesis, and autophagy. Mutations in human TRPML1 cause the lysosome storage disease, mucolipidosis type IV (MLIV). Unlike vertebrates, which express three TRPML genes, TRPML1-3, the Drosophila genome encodes a single trpml gene. Although the trpml-deficient flies exhibit cellular defects similar to those in mammalian TRPML1 mutants, the biophysical properties of Drosophila TRPML channel remained uncharacterized. Here, we show that transgenic expression of human TRPML1 in the neurons of Drosophila trpml mutants partially suppressed the pupal lethality phenotype. When expressed in HEK293 cells, Drosophila TRPML was localized in both endolysosomes and plasma membrane and was activated by phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) applied to the cytoplasmic side in whole lysosomes and inside-out patches excised from plasma membrane. The PI(3,5)P2-evoked currents were blocked by phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), but not other phosphoinositides. Using TRPML A487P, which mimics the varitint-waddler (Va) mutant of mouse TRPML3 with constitutive whole-cell currents, we show that TRPML is biphasically regulated by extracytosolic pH, with an optimal pH about 0.6 pH unit higher than that of human TRPML1. In addition to monovalent cations, TRPML exhibits high permeability to Ca(2+), Mn(2+), and Fe(2+), but not Fe(3+). The TRPML currents were inhibited by trivalent cations Fe(3+), La(3+), and Gd(3+). These features resemble more closely to mammalian TRPML1 than TRPML2 and TRPML3, but with some obvious differences. Together, our data support the use of Drosophila for assessing functional significance of TRPML1 in cell physiology.
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Affiliation(s)
- Xinghua Feng
- From the Third Affiliated Hospital of Guangzhou Medical University, Guangzhou, China, 510150
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Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Catterall WA, Spedding M, Peters JA, Harmar AJ. The Concise Guide to PHARMACOLOGY 2013/14: ion channels. Br J Pharmacol 2013; 170:1607-51. [PMID: 24528239 PMCID: PMC3892289 DOI: 10.1111/bph.12447] [Citation(s) in RCA: 224] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. Ion channels are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.
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Affiliation(s)
- Stephen PH Alexander
- School of Life Sciences, University of Nottingham Medical SchoolNottingham, NG7 2UH, UK
- *
Author for correspondence;
| | - Helen E Benson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Elena Faccenda
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Adam J Pawson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Joanna L Sharman
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - William A Catterall
- University of Washington, School of Medicine, Department of PharmacologyBox 357280, Seattle, WA 98195-7280, USA
| | | | - John A Peters
- Neuroscience Division, Medical Education Institute, Ninewells Hospital and Medical School, University of DundeeDundee, DD1 9SY, UK
| | - Anthony J Harmar
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
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Abstract
TRP channels constitute a large superfamily of cation channel forming proteins, all related to the gene product of the transient receptor potential (trp) locus in Drosophila. In mammals, 28 different TRP channel genes have been identified, which exhibit a large variety of functional properties and play diverse cellular and physiological roles. In this article, we provide a brief and systematic summary of expression, function, and (patho)physiological role of the mammalian TRP channels.
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Affiliation(s)
- Maarten Gees
- Laboratory Ion Channel Research and TRP Research Platform Leuven (TRPLe), KU Leuven, Campus Gasthuisberg, Leuven, Belgium
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36
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Guo Z, Grimm C, Becker L, Ricci AJ, Heller S. A novel ion channel formed by interaction of TRPML3 with TRPV5. PLoS One 2013; 8:e58174. [PMID: 23469151 PMCID: PMC3585263 DOI: 10.1371/journal.pone.0058174] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Accepted: 01/31/2013] [Indexed: 01/15/2023] Open
Abstract
TRPML3 and TRPV5 are members of the mucolipin (TRPML) and TRPV subfamilies of transient receptor potential (TRP) cation channels. Based on sequence similarities of the pore forming regions and on structure-function evidence, we hypothesized that the pore forming domains of TRPML and TRPV5/TRPV6 channels have similarities that indicate possible functional interactions between these TRP channel subfamilies. Here we show that TRPML3 and TRPV5 associate to form a novel heteromeric ion channel. This novel conductance is detectable under conditions that do not activate either TRPML3 or TRPV5. It has pharmacological similarity with TRPML3 and requires functional TRPML3 as well as functional TRPV5. Single channel analyses revealed that TRPML3 and TRPV5 heteromers have different features than the respective homomers, and furthermore, that they occur in potentially distinct stoichiometric configurations. Based on overlapping expression of TRPML3 and TRPV5 in the kidney and the inner ear, we propose that TRPML3 and TRPV5 heteromers could have a biological function in these organs.
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Affiliation(s)
- Zhaohua Guo
- Departments of Otolaryngology – HNS and Molecular & Cellular Physiology, Stanford University School of Medicine, Palo Alto, California, United States of America
| | - Christian Grimm
- Department of Pharmacy – Center for Drug Research and Center for Integrated Protein Science Munich, Ludwig-Maximilians-Universität, München, Germany
| | - Lars Becker
- Departments of Otolaryngology – HNS and Molecular & Cellular Physiology, Stanford University School of Medicine, Palo Alto, California, United States of America
| | - Anthony J. Ricci
- Departments of Otolaryngology – HNS and Molecular & Cellular Physiology, Stanford University School of Medicine, Palo Alto, California, United States of America
| | - Stefan Heller
- Departments of Otolaryngology – HNS and Molecular & Cellular Physiology, Stanford University School of Medicine, Palo Alto, California, United States of America
- * E-mail:
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37
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Kilch T, Alansary D, Peglow M, Dörr K, Rychkov G, Rieger H, Peinelt C, Niemeyer BA. Mutations of the Ca2+-sensing stromal interaction molecule STIM1 regulate Ca2+ influx by altered oligomerization of STIM1 and by destabilization of the Ca2+ channel Orai1. J Biol Chem 2012; 288:1653-64. [PMID: 23212906 DOI: 10.1074/jbc.m112.417246] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A drop of endoplasmic reticulum Ca(2+) concentration triggers its Ca(2+) ssensor protein stromal interaction molecule 1 (STIM1) to oligomerize and accumulate within endoplasmic reticulum-plasma membrane junctions where it activates Orai1 channels, providing store-operated Ca(2+) entry. To elucidate the functional significance of N-glycosylation sites of STIM1, we created different mutations of asparagine-131 and asparagine-171. STIM1 NN/DQ resulted in a strong gain of function. Patch clamp, Total Internal Reflection Fluorescent (TIRF) microscopy, and fluorescence recovery after photobleaching (FRAP) analyses revealed that expression of STIM1 DQ mutants increases the number of active Orai1 channels and the rate of STIM1 translocation to endoplasmic reticulum-plasma membrane junctions with a decrease in current latency. Surprisingly, co-expression of STIM1 DQ decreased Orai1 protein, altering the STIM1:Orai1 stoichiometry. We describe a novel mathematical tool to delineate the effects of altered STIM1 or Orai1 diffusion parameters from stoichiometrical changes. The mutant uncovers a novel mechanism whereby "superactive" STIM1 DQ leads to altered oligomerization rate constants and to degradation of Orai1 with a change in stoichiometry of activator (STIM1) to effector (Orai1) ratio leading to altered Ca(2+) homeostasis.
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Affiliation(s)
- Tatiana Kilch
- Department of Biophysics, Saarland University, D-66421 Homburg, Germany
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38
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Grimm C, Jörs S, Guo Z, Obukhov AG, Heller S. Constitutive activity of TRPML2 and TRPML3 channels versus activation by low extracellular sodium and small molecules. J Biol Chem 2012; 287:22701-8. [PMID: 22753890 DOI: 10.1074/jbc.m112.368876] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The transient receptor potential channels TRPML2 and TRPML3 (MCOLN2 and MCOLN3) are nonselective cation channels. They are widely expressed in mammals. However, little is known about their physiological function(s) and activation mechanism(s). TRPML3 can be activated or rather de-inhibited by exposing it first to sodium-free extracellular solution and subsequently to high extracellular sodium. TRPML3 can also be activated by a variety of small chemical compounds identified in a high throughput screen and is inhibited by low pH. Furthermore, it was found that TRPML3 is constitutively active in low or no sodium-containing extracellular solution. This constitutive activity is independent of the intracellular presence of sodium, and whole-cell current densities are similar with pipette solutions containing cesium, potassium, or sodium. Here, we present mutagenesis data generated based on the hypothesis that negatively charged amino acids in the extracellular loops of TRPML3 may interfere with the observed sodium inhibition. We systematically mutated negatively charged amino acids in the first and second extracellular loops and found that mutating Glu-361 in the second loop has a significant impact on the sodium-mediated block of TRPML3. We further demonstrate that the TRPML3-related cation channel TRPML2 is also activated by lowering the extracellular sodium concentration as well as by a subset of small chemical compounds that were previously identified as activators of TRPML3, thus confirming the functional activity of TRPML2 at the plasma membrane and suggesting similar gating mechanisms for both TRPML channels.
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Affiliation(s)
- Christian Grimm
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, D-80802 München, Germany.
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Kiselyov KK, Ahuja M, Rybalchenko V, Patel S, Muallem S. The intracellular Ca²⁺ channels of membrane traffic. Channels (Austin) 2012; 6:344-51. [PMID: 22907062 DOI: 10.4161/chan.21723] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Regulation of organellar fusion and fission by Ca ( 2+) has emerged as a central paradigm in intracellular membrane traffic. Originally formulated for Ca ( 2+) -driven SNARE-mediated exocytosis in the presynaptic terminals, it was later expanded to explain membrane traffic in other exocytic events within the endo-lysosomal system. The list of processes and conditions that depend on the intracellular membrane traffic includes aging, antigen and lipid processing, growth factor signaling and enzyme secretion. Characterization of the ion channels that regulate intracellular membrane fusion and fission promises novel pharmacological approaches in these processes when their function becomes aberrant. The recent identification of Ca ( 2+) permeability through the intracellular ion channels comprising the mucolipin (TRPMLs) and the two-pore channels (TPCs) families pinpoints the candidates for the Ca ( 2+) channel that drive intracellular membrane traffic. The present review summarizes the recent developments and the current questions relevant to this topic.
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Affiliation(s)
- Kirill K Kiselyov
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
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40
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Grimm C, Jörs S, Guo Z, Obukhov AG, Heller S. Constitutive Activity of TRPML2 and TRPML3 Channels versus Activation by Low Extracellular Sodium and Small Molecules. J Biol Chem 2012. [DOI: 10.1074/jbc.m112.369876] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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41
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Grimm C, Hassan S, Wahl-Schott C, Biel M. Role of TRPML and two-pore channels in endolysosomal cation homeostasis. J Pharmacol Exp Ther 2012; 342:236-44. [PMID: 22518024 DOI: 10.1124/jpet.112.192880] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The transient receptor potential (TRP) channels TRPML1, TRPML2, and TRPML3 (also called mucolipins 1-3 or MCOLN1-3) are nonselective cation channels. Mutations in the Trpml1 gene cause mucolipidosis type IV in humans with clinical features including psychomotor retardation, corneal clouding, and retinal degeneration, whereas mutations in the Trpml3 gene cause deafness, circling behavior, and coat color dilution in mice. No disease-causing mutations are reported for the Trpml2 gene. Like TRPML channels, which are expressed in the endolysosomal pathway, two-pore channels (TPCs), namely TPC1, TPC2, and TPC3, are found in intracellular organelles, in particular in endosomes and lysosomes. Both TRPML channels and TPCs may function as calcium/cation release channels in endosomes, lysosomes, and lysosome-related organelles with TRPMLs being activated by phosphatidylinositol 3,5-bisphosphate and regulated by pH and TPCs being activated by nicotinic acid adenine dinucleotide phosphate in a calcium- and pH-dependent manner. They may also be involved in endolysosomal transport and fusion processes, e.g., as intracellular calcium sources. Currently, however, the exact physiological roles of TRPML channels and TPCs remain quite elusive, and whether TRPML channels are purely endolysosomal ion channels or whether they may also be functionally active at the plasma membrane in vivo remains to be determined.
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Affiliation(s)
- Christian Grimm
- Department of Pharmacy, Center for Drug Research, Ludwig-Maximilians-Universität München, Munich, 81377 Germany.
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42
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Rybalchenko V, Ahuja M, Coblentz J, Churamani D, Patel S, Kiselyov K, Muallem S. Membrane potential regulates nicotinic acid adenine dinucleotide phosphate (NAADP) dependence of the pH- and Ca2+-sensitive organellar two-pore channel TPC1. J Biol Chem 2012; 287:20407-16. [PMID: 22500018 DOI: 10.1074/jbc.m112.359612] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Nicotinic acid adenine dinucleotide phosphate (NAADP) is a potent second messenger that mobilizes Ca(2+) from the acidic endolysosomes by activation of the two-pore channels TPC1 and TPC2. The channel properties of human TPC1 have not been studied before, and its cellular function is not known. In the present study, we characterized TPC1 incorporated into lipid bilayers. The native and recombinant TPC1 channels are activated by NAADP. TPC1 activity requires acidic luminal pH and high luminal Ca(2+). With Ba(2+) as the permeable ion, luminal Ca(2+) activates TPC1 with an apparent K(m) of 180 μm. TPC1 operates in two tightly coupled conductance states of 47 ± 8 and 200 ± 9 picosiemens. Importantly, opening of the large conductance markedly increases the small conductance mean open time. Changes in membrane potential from 0 to -60 mV increased linearly both the small and the large conductances and NP(o), indicating that TPC1 is regulated by voltage. Intriguingly, the apparent affinity for activation of TPC1 by its ligand NAADP is not constant. Rather, hyperpolarization increases the apparent affinity of TPC1 for NAADP by 10 nm/mV. The concerted regulation of TPC1 activity by luminal Ca(2+) and by membrane potential thus provides a potential mechanism to explain NAADP-induced Ca(2+) oscillations. These findings reveal unique properties of TPC1 to explain its role in Ca(2+) oscillations and cell function.
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Affiliation(s)
- Volodymyr Rybalchenko
- Epithelial Signaling and Transport Section, Molecular Physiology and Therapeutics Branch, NIDCR, National Institutes of Health, Bethesda, Maryland 20892, USA
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Abe K, Puertollano R. Role of TRP channels in the regulation of the endosomal pathway. Physiology (Bethesda) 2011; 26:14-22. [PMID: 21357899 DOI: 10.1152/physiol.00048.2010] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Some members of the transient receptor potential (TRP) channel superfamily have proved to be essential in maintaining adequate ion homeostasis, signaling, and membrane trafficking in the endosomal pathway. The unique properties of the TRP channels confer cells the ability to integrate cytosolic and intraluminal stimuli and allow maintained and regulated release of Ca(2+) from endosomes and lysosomes.
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Affiliation(s)
- Ken Abe
- Laboratory of Cell Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
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44
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Kiselyov K, Colletti GA, Terwilliger A, Ketchum K, Lyons CWP, Quinn J, Muallem S. TRPML: transporters of metals in lysosomes essential for cell survival? Cell Calcium 2011; 50:288-94. [PMID: 21621258 DOI: 10.1016/j.ceca.2011.04.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Accepted: 04/29/2011] [Indexed: 01/09/2023]
Abstract
Key aspects of lysosomal function are affected by the ionic content of the lysosomal lumen and, therefore, by the ion permeability in the lysosomal membrane. Such functions include regulation of lysosomal acidification, a critical process in delivery and activation of the lysosomal enzymes, release of metals from lysosomes into the cytoplasm and the Ca(2+)-dependent component of membrane fusion events in the endocytic pathway. While the basic mechanisms of lysosomal acidification have been largely defined, the lysosomal metal transport system is not well understood. TRPML1 is a lysosomal ion channel whose malfunction is implicated in the lysosomal storage disease Mucolipidosis Type IV. Recent evidence suggests that TRPML1 is involved in Fe(2+), Ca(2+) and Zn(2+) transport across the lysosomal membrane, ascribing novel physiological roles to this ion channel, and perhaps to its relatives TRPML2 and TRPML3 and illuminating poorly understood aspects of lysosomal function. Further, alterations in metal transport by the TRPMLs due to mutations or environmental factors may contribute to their role in the disease phenotype and cell death.
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Affiliation(s)
- Kirill Kiselyov
- Department of Biological Science, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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Yamaguchi S, Jha A, Li Q, Soyombo AA, Dickinson GD, Churamani D, Brailoiu E, Patel S, Muallem S. Transient receptor potential mucolipin 1 (TRPML1) and two-pore channels are functionally independent organellar ion channels. J Biol Chem 2011; 286:22934-42. [PMID: 21540176 DOI: 10.1074/jbc.m110.210930] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
NAADP is a potent second messenger that mobilizes Ca(2+) from acidic organelles such as endosomes and lysosomes. The molecular basis for Ca(2+) release by NAADP, however, is uncertain. TRP mucolipins (TRPMLs) and two-pore channels (TPCs) are Ca(2+)-permeable ion channels present within the endolysosomal system. Both have been proposed as targets for NAADP. In the present study, we probed possible physical and functional association of these ion channels. Exogenously expressed TRPML1 showed near complete colocalization with TPC2 and partial colocalization with TPC1. TRPML3 overlap with TPC2 was more modest. TRPML1 and to some extent TRPML3 co-immunoprecipitated with TPC2 but less so with TPC1. Current recording, however, showed that TPC1 and TPC2 did not affect the activity of wild-type TRPML1 or constitutively active TRPML1(V432P). N-terminally truncated TPC2 (TPC2delN), which is targeted to the plasma membrane, also failed to affect TRPML1 and TRPML1(V432P) channel function or TRPML1(V432P)-mediated Ca(2+) influx. Whereas overexpression of TPCs enhanced NAADP-mediated Ca(2+) signals, overexpression of TRPML1 did not, and the dominant negative TRPML1(D471K) was without affect on endogenous NAADP-mediated Ca(2+) signals. Furthermore, the single channel properties of NAADP-activated TPC2delN were not affected by TRPML1. Finally, NAADP-evoked Ca(2+) oscillations in pancreatic acinar cells were identical in wild-type and TRPML1(-/-) cells. We conclude that although TRPML1 and TPCs are present in the same complex, they function as two independent organellar ion channels and that TPCs, not TRPMLs, are the targets for NAADP.
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Affiliation(s)
- Soichiro Yamaguchi
- Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75235, USA
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Lelouvier B, Puertollano R. Mucolipin-3 regulates luminal calcium, acidification, and membrane fusion in the endosomal pathway. J Biol Chem 2011; 286:9826-32. [PMID: 21245134 DOI: 10.1074/jbc.m110.169185] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mucolipin-3 (MCOLN3) is a pH-regulated Ca(2+) channel that localizes to the endosomal pathway. Gain-of-function mutation in MCOLN3 causes the varitint-waddler (Va) phenotype in mice, which is characterized by hearing loss, vestibular dysfunction, and coat color dilution. The Va phenotype results from a punctual mutation (A419P) in the pore region of MCOLN3 that locks the channel in an open conformation causing massive entry of Ca(2+) inside cells and inducing cell death by apoptosis. Overexpression of wild-type MCOLN3 produces severe alterations of the endosomal pathway, including enlargement and clustering of endosomes, delayed EGF receptor degradation, and impaired autophagosome maturation, thus suggesting that MCOLN3 plays an important role in the regulation of endosomal function. To understand better the physiological role of MCOLN3, we inhibited MCOLN3 function by expression of a channel-dead dominant negative mutant (458DD/KK) or by knockdown of endogenous MCOLN3. Remarkably, we found that impairment of MCOLN3 activity caused a significant accumulation of luminal Ca(2+) in endosomes. This accumulation led to severe defects in endosomal acidification as well as to increased endosomal fusion. Our findings reveal a prominent role for MCOLN3 in regulating Ca(2+) homeostasis at the endosomal pathway and confirm the importance of luminal Ca(2+) for proper acidification and membrane fusion.
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Affiliation(s)
- Benjamin Lelouvier
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892, USA
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The TRPML3 Channel: From Gene to Function. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 704:229-37. [DOI: 10.1007/978-94-007-0265-3_13] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Jörs S, Grimm C, Becker L, Heller S. Genetic inactivation of Trpml3 does not lead to hearing and vestibular impairment in mice. PLoS One 2010; 5:e14317. [PMID: 21179200 PMCID: PMC3001452 DOI: 10.1371/journal.pone.0014317] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Accepted: 11/21/2010] [Indexed: 11/23/2022] Open
Abstract
TRPML3, a member of the transient receptor potential (TRP) family, is an inwardly rectifying, non-selective Ca2+-permeable cation channel that is regulated by extracytosolic Na+ and H+ and can be activated by a variety of small molecules. The severe auditory and vestibular phenotype of the TRPML3(A419P) varitint-waddler mutation made this protein particularly interesting for inner ear biology. To elucidate the physiological role of murine TRPML3, we conditionally inactivated Trpml3 in mice. Surprisingly, lack of functional TRPML3 did not lead to circling behavior, balance impairment or hearing loss.
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Affiliation(s)
- Simone Jörs
- Departments of Otolaryngology – Head and Neck Surgery and Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Christian Grimm
- Departments of Otolaryngology – Head and Neck Surgery and Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Lars Becker
- Departments of Otolaryngology – Head and Neck Surgery and Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California, United States of America
| | - Stefan Heller
- Departments of Otolaryngology – Head and Neck Surgery and Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, California, United States of America
- * E-mail:
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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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