1
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Liv N, Fermie J, Ten Brink CBM, de Heus C, Klumperman J. Functional characterization of endo-lysosomal compartments by correlative live-cell and volume electron microscopy. Methods Cell Biol 2023; 177:301-326. [PMID: 37451771 DOI: 10.1016/bs.mcb.2022.12.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2023]
Abstract
Fluorescent biosensors are valuable tools to monitor protein activities and the functional state of organelles in live cells. However, the information provided by fluorescent microscopy (FM) is mostly limited in resolution and lacks ultrastructural context information. Protein activities are confined to organelle zones with a distinct membrane morphology, which can only be seen by electron microscopy (EM). EM, however, intrinsically lacks information on protein activities. The lack of methods to integrate these two imaging modalities has hampered understanding the functional organization of cellular organelles. Here we introduce "functional correlative microscopy" (functional CLEM) to directly infer functional information from live cells to EM with nanometer resolution. We label and visualize live cells with fluorescent biosensors after which they are processed for EM and imaged using a volume electron microscopy technique. Within a single dataset we correlate hundreds of fluorescent spots enabling quantitative analysis of the functional-ultrastructural data. We employ our method to monitor essential functional parameters of late endo-lysosomal compartments, i.e., pH, calcium, enzyme activities and cholesterol content. Our data reveal a steep functional difference in enzyme activity between late endosomes and lysosomes and unexpectedly high calcium levels in late endosomes. The presented CLEM workflow is compatible with a large repertoire of probes and paves the way for large scale functional studies of all types of cellular structures.
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Affiliation(s)
- Nalan Liv
- Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands.
| | - Job Fermie
- Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands; Molecular Biophysics, Debye Institute for Nanomaterials Science, Utrecht University, Utrecht, The Netherlands
| | - Corlinda B M Ten Brink
- Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Cecilia de Heus
- Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
| | - Judith Klumperman
- Center for Molecular Medicine, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
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2
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Wahl-Schott C, Freichel M, Hennis K, Philippaert K, Ottenheijm R, Tsvilovskyy V, Varbanov H. Characterization of Endo-Lysosomal Cation Channels Using Calcium Imaging. Handb Exp Pharmacol 2023; 278:277-304. [PMID: 36894791 DOI: 10.1007/164_2023_637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
Endo-lysosomes are membrane-bound acidic organelles that are involved in endocytosis, recycling, and degradation of extracellular and intracellular material. The membranes of endo-lysosomes express several Ca2+-permeable cation ion channels, including two-pore channels (TPC1-3) and transient receptor potential mucolipin channels (TRPML1-3). In this chapter, we will describe four different state-of-the-art Ca2+ imaging approaches, which are well-suited to investigate the function of endo-lysosomal cation channels. These techniques include (1) global cytosolic Ca2+ measurements, (2) peri-endo-lysosomal Ca2+ imaging using genetically encoded Ca2+ sensors that are directed to the cytosolic endo-lysosomal membrane surface, (3) Ca2+ imaging of endo-lysosomal cation channels, which are engineered in order to redirect them to the plasma membrane in combination with approaches 1 and 2, and (4) Ca2+ imaging by directing Ca2+ indicators to the endo-lysosomal lumen. Moreover, we will review useful small molecules, which can be used as valuable tools for endo-lysosomal Ca2+ imaging. Rather than providing complete protocols, we will discuss specific methodological issues related to endo-lysosomal Ca2+ imaging.
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Affiliation(s)
- Christian Wahl-Schott
- Institut für Kardiovaskuläre Physiologie und Pathophysiologie, Lehrstuhl für Vegetative Physiologie, Biomedizinisches Zentrum, Ludwig-Maximilians-Universität München, München, Germany.
| | - Marc Freichel
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany. .,DZHK (German Centre for Cardiovascular Research), Heidelberg/Mannheim, Germany.
| | - Konstantin Hennis
- Institut für Kardiovaskuläre Physiologie und Pathophysiologie, Lehrstuhl für Vegetative Physiologie, Biomedizinisches Zentrum, Ludwig-Maximilians-Universität München, München, Germany
| | - Koenraad Philippaert
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg/Mannheim, Germany
| | - Roger Ottenheijm
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg/Mannheim, Germany
| | - Volodymyr Tsvilovskyy
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Heidelberg/Mannheim, Germany
| | - Hristo Varbanov
- Institut für Neurophysiologie, Medizinische Hochschule Hannover(MHH), Hannover, Germany
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3
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Sargsyan Y, Thoms S. Live-Cell Imaging of Peroxisomal Calcium Levels and Dynamics. Methods Mol Biol 2023; 2643:199-206. [PMID: 36952187 DOI: 10.1007/978-1-0716-3048-8_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/24/2023]
Abstract
Calcium (Ca2+) is an intracellular messenger that plays an essential role in a variety of cellular processes ranging from early embryonic events to muscle contraction and neuron excitability. Measurement of cytosolic, endoplasmic reticulum (ER), and mitochondrial Ca2+ has contributed immensely to our understanding of cellular physiology. Here we describe the measurement of peroxisomal Ca2+ using ratiometric Ca2+ sensors, enabling measurement of absolute Ca2+ concentration and its dynamics in living cells.
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Affiliation(s)
- Yelena Sargsyan
- Department of Child and Adolescent Health, University Medical Center, Göttingen, Germany
| | - Sven Thoms
- Department of Child and Adolescent Health, University Medical Center, Göttingen, Germany.
- Department for Biochemistry and Molecular Medicine, Medical School EWL, Bielefeld University, Bielefeld, Germany.
- German Center of Cardiovascular Research (DZHK), Partner site Göttingen, Göttingen, Germany.
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4
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Zajac M, Modi S, Krishnan Y. The evolution of organellar calcium mapping technologies. Cell Calcium 2022; 108:102658. [PMID: 36274564 PMCID: PMC10224794 DOI: 10.1016/j.ceca.2022.102658] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Revised: 10/05/2022] [Accepted: 10/08/2022] [Indexed: 01/25/2023]
Abstract
Intracellular Ca2+ fluxes are dynamically controlled by the co-involvement of multiple organellar pools of stored Ca2+. Endolysosomes are emerging as physiologically critical, yet underexplored, sources and sinks of intracellular Ca2+. Delineating the role of organelles in Ca2+ signaling has relied on chemical fluorescent probes and electrophysiological strategies. However, the acidic endolysosomal environment presents unique issues, which preclude the use of traditional chemical reporter strategies to map lumenal Ca2+. Here, we broadly address the current state of knowledge about organellar Ca2+ pools. We then outline the application of traditional probes, and their sensing paradigms. We then discuss how a new generation of probes overcomes the limitations of traditional Ca2+probes, emphasizing their ability to offer critical insights into endolysosomal Ca2+, and its feedback with other organellar pools.
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Affiliation(s)
- Matthew Zajac
- Department of Chemistry, The University of Chicago, Chicago, Illinois, 60637, USA; Neuroscience Institute, The University of Chicago, Chicago, IL, 60637, USA
| | - Souvik Modi
- Esya Labs, Translation and Innovation Hub, Imperial College White City Campus, 84 Wood Lane, London, W12 0BZ, UK
| | - Yamuna Krishnan
- Department of Chemistry, The University of Chicago, Chicago, Illinois, 60637, USA; Neuroscience Institute, The University of Chicago, Chicago, IL, 60637, USA; Institute for Biophysical Dynamics, The University of Chicago, Chicago, Illinois, 60637, USA.
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5
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Barral DC, Staiano L, Guimas Almeida C, Cutler DF, Eden ER, Futter CE, Galione A, Marques ARA, Medina DL, Napolitano G, Settembre C, Vieira OV, Aerts JMFG, Atakpa‐Adaji P, Bruno G, Capuozzo A, De Leonibus E, Di Malta C, Escrevente C, Esposito A, Grumati P, Hall MJ, Teodoro RO, Lopes SS, Luzio JP, Monfregola J, Montefusco S, Platt FM, Polishchuck R, De Risi M, Sambri I, Soldati C, Seabra MC. Current methods to analyze lysosome morphology, positioning, motility and function. Traffic 2022; 23:238-269. [PMID: 35343629 PMCID: PMC9323414 DOI: 10.1111/tra.12839] [Citation(s) in RCA: 37] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 03/21/2022] [Accepted: 03/22/2022] [Indexed: 01/09/2023]
Abstract
Since the discovery of lysosomes more than 70 years ago, much has been learned about the functions of these organelles. Lysosomes were regarded as exclusively degradative organelles, but more recent research has shown that they play essential roles in several other cellular functions, such as nutrient sensing, intracellular signalling and metabolism. Methodological advances played a key part in generating our current knowledge about the biology of this multifaceted organelle. In this review, we cover current methods used to analyze lysosome morphology, positioning, motility and function. We highlight the principles behind these methods, the methodological strategies and their advantages and limitations. To extract accurate information and avoid misinterpretations, we discuss the best strategies to identify lysosomes and assess their characteristics and functions. With this review, we aim to stimulate an increase in the quantity and quality of research on lysosomes and further ground-breaking discoveries on an organelle that continues to surprise and excite cell biologists.
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Affiliation(s)
- Duarte C. Barral
- CEDOC, NOVA Medical School, NMS, Universidade NOVA de LisboaLisbonPortugal
| | - Leopoldo Staiano
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
- Institute for Genetic and Biomedical ResearchNational Research Council (CNR)MilanItaly
| | | | - Dan F. Cutler
- MRC Laboratory for Molecular Cell BiologyUniversity College LondonLondonUK
| | - Emily R. Eden
- University College London (UCL) Institute of OphthalmologyLondonUK
| | - Clare E. Futter
- University College London (UCL) Institute of OphthalmologyLondonUK
| | | | | | - Diego Luis Medina
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
- Medical Genetics Unit, Department of Medical and Translational ScienceFederico II UniversityNaplesItaly
| | - Gennaro Napolitano
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
- Medical Genetics Unit, Department of Medical and Translational ScienceFederico II UniversityNaplesItaly
| | - Carmine Settembre
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
- Clinical Medicine and Surgery DepartmentFederico II UniversityNaplesItaly
| | - Otília V. Vieira
- CEDOC, NOVA Medical School, NMS, Universidade NOVA de LisboaLisbonPortugal
| | | | | | - Gemma Bruno
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
| | | | - Elvira De Leonibus
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
- Institute of Biochemistry and Cell Biology, CNRRomeItaly
| | - Chiara Di Malta
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
- Medical Genetics Unit, Department of Medical and Translational ScienceFederico II UniversityNaplesItaly
| | | | | | - Paolo Grumati
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
| | - Michael J. Hall
- CEDOC, NOVA Medical School, NMS, Universidade NOVA de LisboaLisbonPortugal
| | - Rita O. Teodoro
- CEDOC, NOVA Medical School, NMS, Universidade NOVA de LisboaLisbonPortugal
| | - Susana S. Lopes
- CEDOC, NOVA Medical School, NMS, Universidade NOVA de LisboaLisbonPortugal
| | - J. Paul Luzio
- Cambridge Institute for Medical ResearchUniversity of CambridgeCambridgeUK
| | | | | | | | | | - Maria De Risi
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
| | - Irene Sambri
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
- Medical Genetics Unit, Department of Medical and Translational ScienceFederico II UniversityNaplesItaly
| | - Chiara Soldati
- Telethon Institute of Genetics and Medicine (TIGEM)PozzuoliItaly
| | - Miguel C. Seabra
- CEDOC, NOVA Medical School, NMS, Universidade NOVA de LisboaLisbonPortugal
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6
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Zhang YL, Moran SP, Allen A, Baez-Nieto D, Xu Q, Wang LA, Martenis WE, Sacher JR, Gale JP, Weïwer M, Wagner FF, Pan JQ. Novel Fluorescence-Based High-Throughput FLIPR Assay Utilizing Membrane-Tethered Genetic Calcium Sensors to Identify T-Type Calcium Channel Modulators. ACS Pharmacol Transl Sci 2022; 5:156-168. [PMID: 35311021 PMCID: PMC8923061 DOI: 10.1021/acsptsci.1c00233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Indexed: 11/28/2022]
Abstract
T-type voltage-gated Ca2+ channels have been implicated in many human disorders, and there has been increasing interest in developing highly selective and potent T-type Ca2+ channel modulators for potential clinical use. However, the unique biophysical properties of T-type Ca2+ channels are not conducive for developing high-throughput screening (HTS) assays to identify modulators, particularly potentiators. To illustrate, T-type Ca2+ channels are largely inactivated and unable to open to allow Ca2+ influx at -25 mV, the typical resting membrane potential of the cell lines commonly used in cellular screening assays. To address this issue, we developed cell lines that express Kir2.3 channels to hyperpolarize the membrane potential to -70 mV, thus allowing T-type channels to return to their resting state where they can be subsequently activated by membrane depolarization in the presence of extracellular KCl. Furthermore, to simplify the HTS assay and to reduce reagent cost, we stably expressed a membrane-tethered genetic calcium sensor, GCaMP6s-CAAX, that displays superior signal to the background compared to the untethered GCaMP6s or the synthetic Ca2+ sensor Fluo-4AM. Here, we describe a novel GCaMP6s-CAAX-based calcium assay utilizing a high-throughput fluorometric imaging plate reader (Molecular Devices, Sunnyvale, CA) format that can identify both activators and inhibitors of T-type Ca2+ channels. Lastly, we demonstrate the utility of this novel fluorescence-based assay to evaluate the activities of two distinct G-protein-coupled receptors, thus expanding the use of GCaMP6s-CAAX to a wide range of applications relevant for developing cellular assays in drug discovery.
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Affiliation(s)
- Yan-Ling Zhang
- Stanley Center for Psychiatric
Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
| | - Sean P. Moran
- Stanley Center for Psychiatric
Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
| | - Andrew Allen
- Stanley Center for Psychiatric
Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
| | - David Baez-Nieto
- Stanley Center for Psychiatric
Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
| | - Qihong Xu
- Stanley Center for Psychiatric
Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
| | - Lei A. Wang
- Stanley Center for Psychiatric
Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
| | - William E. Martenis
- Stanley Center for Psychiatric
Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
| | - Joshua R. Sacher
- Stanley Center for Psychiatric
Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
| | - Jennifer P. Gale
- Stanley Center for Psychiatric
Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
| | - Michel Weïwer
- Stanley Center for Psychiatric
Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
| | - Florence F. Wagner
- Stanley Center for Psychiatric
Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
| | - Jen Q. Pan
- Stanley Center for Psychiatric
Research, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, United States
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7
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Burgstaller S, Bischof H, Matt L, Lukowski R. Assessing K + ions and K + channel functions in cancer cell metabolism using fluorescent biosensors. Free Radic Biol Med 2022; 181:43-51. [PMID: 35091062 DOI: 10.1016/j.freeradbiomed.2022.01.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Revised: 01/15/2022] [Accepted: 01/24/2022] [Indexed: 12/17/2022]
Abstract
Cancer represents a leading cause of death worldwide. Hence, a better understanding of the molecular mechanisms causing and propelling the disease is of utmost importance. Several cancer entities are associated with altered K+ channel expression which is frequently decisive for malignancy and disease outcome. The impact of such oncogenic K+ channels on cell patho-/physiology and homeostasis and their roles in different subcellular compartments is, however, far from being understood. A refined method to simultaneously investigate metabolic and ionic signaling events on the level of individual cells and their organelles represent genetically encoded fluorescent biosensors, that allow a high-resolution investigation of compartmentalized metabolite or ion dynamics in a non-invasive manner. This feature of these probes makes them versatile tools to visualize and understand subcellular consequences of aberrant K+ channel expression and activity in K+ channel related cancer research.
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Affiliation(s)
- Sandra Burgstaller
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Germany; NMI Natural and Medical Sciences Institute at the University of Tübingen, Reutlingen, 72770, Germany.
| | - Helmut Bischof
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Germany
| | - Lucas Matt
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Germany
| | - Robert Lukowski
- Department of Pharmacology, Toxicology and Clinical Pharmacy, Institute of Pharmacy, University of Tübingen, Germany.
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8
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Sargsyan Y, Bickmeyer U, Gibhardt CS, Streckfuss-Bömeke K, Bogeski I, Thoms S. Peroxisomes contribute to intracellular calcium dynamics in cardiomyocytes and non-excitable cells. Life Sci Alliance 2021; 4:4/9/e202000987. [PMID: 34330788 PMCID: PMC8326789 DOI: 10.26508/lsa.202000987] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 07/09/2021] [Accepted: 07/12/2021] [Indexed: 11/24/2022] Open
Abstract
Peroxisomes communicate with other cellular compartments by transfer of various metabolites. However, whether peroxisomes are sites for calcium handling and exchange has remained contentious. Here we generated sensors for assessment of peroxisomal calcium and applied them for single cell-based calcium imaging in HeLa cells and cardiomyocytes. We found that peroxisomes in HeLa cells take up calcium upon depletion of intracellular calcium stores and upon calcium influx across the plasma membrane. Furthermore, we show that peroxisomes of neonatal rat cardiomyocytes and human induced pluripotent stem cell-derived cardiomyocytes can take up calcium. Our results indicate that peroxisomal and cytosolic calcium signals are tightly interconnected both in HeLa cells and in cardiomyocytes. Cardiac peroxisomes take up calcium on beat-to-beat basis. Hence, peroxisomes may play an important role in shaping cellular calcium dynamics of cardiomyocytes.
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Affiliation(s)
- Yelena Sargsyan
- Department of Child and Adolescent Health, University Medical Center, Göttingen, Germany
| | - Uta Bickmeyer
- Department of Child and Adolescent Health, University Medical Center, Göttingen, Germany
| | - Christine S Gibhardt
- Molecular Physiology, Institute of Cardiovascular Physiology, University Medical Center, Göttingen, Germany
| | - Katrin Streckfuss-Bömeke
- Clinic for Cardiology and Pneumology, University Medical Center, Göttingen, Germany.,Institute of Pharmacology and Toxicology, Würzburg University, Würzburg, Germany.,German Center of Cardiovascular Research (DZHK), Partner Site Göttingen, Germany
| | - Ivan Bogeski
- Molecular Physiology, Institute of Cardiovascular Physiology, University Medical Center, Göttingen, Germany
| | - Sven Thoms
- Department of Child and Adolescent Health, University Medical Center, Göttingen, Germany .,Department of Biochemistry and Molecular Medicine, Medical School, Bielefeld University, Bielefeld, Germany.,German Center of Cardiovascular Research (DZHK), Partner Site Göttingen, Germany
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9
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Hong S, Pawel GT, Pei R, Lu Y. Recent progress in developing fluorescent probes for imaging cell metabolites. Biomed Mater 2021; 16. [PMID: 33915523 DOI: 10.1088/1748-605x/abfd11] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Accepted: 04/29/2021] [Indexed: 01/12/2023]
Abstract
Cellular metabolites play a crucial role in promoting and regulating cellular activities, but it has been difficult to monitor these cellular metabolites in living cells and in real time. Over the past decades, iterative development and improvements of fluorescent probes have been made, resulting in the effective monitoring of metabolites. In this review, we highlight recent progress in the use of fluorescent probes for tracking some key metabolites, such as adenosine triphosphate, cyclic adenosine monophosphate, cyclic guanosine 5'-monophosphate, Nicotinamide adenine dinucleotide (NADH), reactive oxygen species, sugar, carbon monoxide, and nitric oxide for both whole cell and subcellular imaging.
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Affiliation(s)
- Shanni Hong
- Department of Medical Imaging Technology, School of Medical Technology and Engineering, Fujian Medical University, Fuzhou, People's Republic of China.,Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, United States of America.,CAS Key Laboratory of Nano-Bio Interfaces, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, People's Republic of China
| | - Gregory T Pawel
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, United States of America
| | - Renjun Pei
- CAS Key Laboratory of Nano-Bio Interfaces, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, People's Republic of China
| | - Yi Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, United States of America
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10
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Sharma V, Makhdoomi M, Singh L, Kumar P, Khan N, Singh S, Verma HN, Luthra K, Sarkar S, Kumar D. Trehalose limits opportunistic mycobacterial survival during HIV co-infection by reversing HIV-mediated autophagy block. Autophagy 2021; 17:476-495. [PMID: 32079455 PMCID: PMC7610453 DOI: 10.1080/15548627.2020.1725374] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 01/27/2020] [Accepted: 01/29/2020] [Indexed: 02/07/2023] Open
Abstract
Opportunistic bacterial infections amongst HIV-infected individuals contribute significantly to HIV-associated mortality. The role of HIV-mediated modulation of innate mechanisms like autophagy in promoting opportunistic infections, however, remains obscure. Here we show, HIV reactivation in or infection of macrophages inhibits autophagy and helps the survival of pathogenic Mycobacterium tuberculosis (Mtb) and nonpathogenic non-tuberculous mycobacterial strains (NTMs). The HIV-mediated impairment of xenophagy flux facilitated bacterial survival. Activation of autophagy by trehalose could induce xenophagy flux and kill intracellular Mtb or NTMs either during single or co-infections. Trehalose, we delineate, activates PIKFYVE leading to TFEB nuclear translocation in MCOLN1-dependent manner to induce autophagy. Remarkably, trehalose significantly reduced HIV-p24 levels in ex-vivo-infected PBMCs or PBMCs from treatment-naive HIV patients and also controlled mycobacterial survival within Mtb-infected animals. To conclude, we report leveraging of HIV-mediated perturbed host innate-immunity by opportunistic bacterial pathogens and show an attractive therapeutic strategy for HIV and associated co-morbidities.Abbreviations: AIDS: acquired immune deficiency syndrome; AMPK: AMP-activated protein kinase; ATG5: autophagy related 5; BafA1: bafilomycin A1; CFU: colony forming unit; CTSD: cathepsin D; CD63: CD63 molecule; EGFP: enhanced green fluorescent protein; FRET: Förster resonance energy transfer; GABARAP: gamma-aminobutyric acid receptor-associated protein; GAPDH: glyceraldehyde 3-phosphate dehydrogenase; GLUT: glucose transporter; HIV: human immunodeficiency virus; hMDMs: human monocyte derived macrophages; IL2: interleukin 2; LAMP1: lysosomal-associated membrane protein 1; LC3B-II: lipidated microtubule-associated proteins 1A/1B light chain 3B; Mtb: Mycobacterium tuberculosis; MTOR: mechanistic target of rapamycin; mRFP: monomeric red fluorescent protein; M6PR: mannose-6-phosphate receptor; NAC: N- acetyl- L -cysteine; NTM's: non-tuberculous mycobacteria; PBMC: Peripheral Blood Mononuclear cells; PIKFYVE: phosphoinositide kinase; FYVE-Type Zinc Finger; PHA: phytohemagglutinin; PMA: phorbol 12-myristate 13-acetate; PtdIns(3,5)P2: Phosphatidylinositol 3,5-bisphosphate; ptfLC3: pEGFP-mRFP-LC3; ROS: reactive oxygen species; SQSTM1: sequestosome1; TFEB: transcription factor EB; MCOLN1/TRPML1: mucolipin 1; PIP4P1/TMEM55B: Human trans-membrane Protein 55B; UVRAG: UV Radiation Resistance Associate; VPS35: vacuolar protein sorting associated protein 35; WDR45: WD repeat domain 45; YCAM: Yellow Chameleon.
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Affiliation(s)
- Vartika Sharma
- Cellular Immunology Group, International Center for Genetic Engineering and Biotechnology, New Delhi, India
| | - Muzamil Makhdoomi
- Department of Biochemistry, All India Institute of Medical Sciences, New Delhi, India
| | - Lakshyaveer Singh
- Cellular Immunology Group, International Center for Genetic Engineering and Biotechnology, New Delhi, India
| | - Purnima Kumar
- Cellular Immunology Group, International Center for Genetic Engineering and Biotechnology, New Delhi, India
| | - Nabab Khan
- Cellular Immunology Group, International Center for Genetic Engineering and Biotechnology, New Delhi, India
| | - Sarman Singh
- Division of Clinical Microbiology & Molecular Medicine, Department of Laboratory Medicine, All India Institute of Medical Sciences, New Delhi, India
| | - H N Verma
- School of Life Sciences, Jaipur National University, Jaipur, India
| | - Kalpana Luthra
- Department of Biochemistry, All India Institute of Medical Sciences, New Delhi, India
| | - Sovan Sarkar
- Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Dhiraj Kumar
- Cellular Immunology Group, International Center for Genetic Engineering and Biotechnology, New Delhi, India
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11
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Cavinato M, Madreiter-Sokolowski CT, Büttner S, Schosserer M, Zwerschke W, Wedel S, Grillari J, Graier WF, Jansen-Dürr P. Targeting cellular senescence based on interorganelle communication, multilevel proteostasis, and metabolic control. FEBS J 2020; 288:3834-3854. [PMID: 33200494 PMCID: PMC7611050 DOI: 10.1111/febs.15631] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 11/02/2020] [Accepted: 11/13/2020] [Indexed: 02/06/2023]
Abstract
Cellular senescence, a stable cell division arrest caused by severe damage and stress, is a hallmark of aging in vertebrates including humans. With progressing age, senescent cells accumulate in a variety of mammalian tissues, where they contribute to tissue aging, identifying cellular senescence as a major target to delay or prevent aging. There is an increasing demand for the discovery of new classes of small molecules that would either avoid or postpone cellular senescence by selectively eliminating senescent cells from the body (i.e., ‘senolytics’) or inactivating/switching damage‐inducing properties of senescent cells (i.e., ‘senostatics/senomorphics’), such as the senescence‐associated secretory phenotype. Whereas compounds with senolytic or senostatic activity have already been described, their efficacy and specificity has not been fully established for clinical use yet. Here, we review mechanisms of senescence that are related to mitochondria and their interorganelle communication, and the involvement of proteostasis networks and metabolic control in the senescent phenotype. These cellular functions are associated with cellular senescence in in vitro and in vivo models but have not been fully exploited for the search of new compounds to counteract senescence yet. Therefore, we explore possibilities to target these mechanisms as new opportunities to selectively eliminate and/or disable senescent cells with the aim of tissue rejuvenation. We assume that this research will provide new compounds from the chemical space which act as mimetics of caloric restriction, modulators of calcium signaling and mitochondrial physiology, or as proteostasis optimizers, bearing the potential to counteract cellular senescence, thereby allowing healthy aging.
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Affiliation(s)
- Maria Cavinato
- Institute for Biomedical Aging Research, Leopold-Franzens Universität Innsbruck, Austria.,Center for Molecular Biosciences Innsbruck (CMBI), Leopold-Franzens Universität Innsbruck, Austria
| | - Corina T Madreiter-Sokolowski
- Department of Health Sciences and Technology, Institute of Translational Medicine, Swiss Federal Institute of Technology (ETH), Zurich, Switzerland.,Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Austria
| | - Sabrina Büttner
- Institute of Molecular Biosciences, University of Graz, Austria.,Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Sweden
| | - Markus Schosserer
- Christian Doppler Laboratory for Skin Multimodal Analytical Imaging of Aging and Senescence, Institute of Molecular Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Medical University of Vienna, Austria
| | - Werner Zwerschke
- Institute for Biomedical Aging Research, Leopold-Franzens Universität Innsbruck, Austria.,Center for Molecular Biosciences Innsbruck (CMBI), Leopold-Franzens Universität Innsbruck, Austria
| | - Sophia Wedel
- Institute for Biomedical Aging Research, Leopold-Franzens Universität Innsbruck, Austria.,Center for Molecular Biosciences Innsbruck (CMBI), Leopold-Franzens Universität Innsbruck, Austria
| | - Johannes Grillari
- Christian Doppler Laboratory for Skin Multimodal Analytical Imaging of Aging and Senescence, Institute of Molecular Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria.,Austrian Cluster for Tissue Regeneration, Medical University of Vienna, Austria.,Ludwig Boltzmann Institute for Experimental and Clinical Traumatology, Vienna, Austria
| | - Wolfgang F Graier
- Molecular Biology and Biochemistry, Gottfried Schatz Research Center, Medical University of Graz, Austria.,BioTechMed Graz, Austria
| | - Pidder Jansen-Dürr
- Institute for Biomedical Aging Research, Leopold-Franzens Universität Innsbruck, Austria.,Center for Molecular Biosciences Innsbruck (CMBI), Leopold-Franzens Universität Innsbruck, Austria
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12
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Lloyd-Evans E, Waller-Evans H. Lysosomal Ca 2+ Homeostasis and Signaling in Health and Disease. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a035311. [PMID: 31653642 DOI: 10.1101/cshperspect.a035311] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Calcium (Ca2+) signaling is an essential process in all cells that is maintained by a plethora of channels, pumps, transporters, receptors, and intracellular Ca2+ sequestering stores. Changes in cytosolic Ca2+ concentration govern processes as far reaching as fertilization, cell growth, and motility through to cell death. In recent years, lysosomes have emerged as a major intracellular Ca2+ storage organelle with an increasing involvement in triggering or regulating cellular functions such as endocytosis, autophagy, and Ca2+ release from the endoplasmic reticulum. This review will summarize recent work in the area of lysosomal Ca2+ signaling and homeostasis, including newly identified functions, and the involvement of lysosome-derived Ca2+ signals in human disease. In addition, we explore recent controversies in the techniques used for measurement of lysosomal Ca2+ content.
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Affiliation(s)
- Emyr Lloyd-Evans
- School of Biosciences, Cardiff University, Cardiff CF10 3AX, United Kingdom
| | - Helen Waller-Evans
- Medicines Discovery Institute, Cardiff University, Cardiff CF10 3AT, United Kingdom
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13
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Atakpa P, Thillaiappan NB, Mataragka S, Prole DL, Taylor CW. IP 3 Receptors Preferentially Associate with ER-Lysosome Contact Sites and Selectively Deliver Ca 2+ to Lysosomes. Cell Rep 2019; 25:3180-3193.e7. [PMID: 30540949 PMCID: PMC6302550 DOI: 10.1016/j.celrep.2018.11.064] [Citation(s) in RCA: 121] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Revised: 07/30/2018] [Accepted: 11/15/2018] [Indexed: 12/22/2022] Open
Abstract
Inositol 1,4,5-trisphosphate (IP3) receptors (IP3Rs) allow extracellular stimuli to redistribute Ca2+ from the ER to cytosol or other organelles. We show, using small interfering RNA (siRNA) and vacuolar H+-ATPase (V-ATPase) inhibitors, that lysosomes sequester Ca2+ released by all IP3R subtypes, but not Ca2+ entering cells through store-operated Ca2+ entry (SOCE). A low-affinity Ca2+ sensor targeted to lysosomal membranes reports large, local increases in cytosolic [Ca2+] during IP3-evoked Ca2+ release, but not during SOCE. Most lysosomes associate with endoplasmic reticulum (ER) and dwell at regions populated by IP3R clusters, but IP3Rs do not assemble ER-lysosome contacts. Increasing lysosomal pH does not immediately prevent Ca2+ uptake, but it causes lysosomes to slowly redistribute and enlarge, reduces their association with IP3Rs, and disrupts Ca2+ exchange with ER. In a "piston-like" fashion, ER concentrates cytosolic Ca2+ and delivers it, through large-conductance IP3Rs, to a low-affinity lysosomal uptake system. The involvement of IP3Rs allows extracellular stimuli to regulate Ca2+ exchange between the ER and lysosomes.
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Affiliation(s)
- Peace Atakpa
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | | | - Stefania Mataragka
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - David L Prole
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
| | - Colin W Taylor
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
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14
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Helassa N, Nugues C, Rajamanoharan D, Burgoyne RD, Haynes LP. A centrosome-localized calcium signal is essential for mammalian cell mitosis. FASEB J 2019; 33:14602-14610. [PMID: 31682764 PMCID: PMC6910830 DOI: 10.1096/fj.201901662r] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Accepted: 09/23/2019] [Indexed: 02/02/2023]
Abstract
Mitosis defects can lead to premature ageing and cancer. Understanding mitosis regulation therefore has important implications for human disease. Early data suggested that calcium (Ca2+) signals could influence mitosis, but these have hitherto not been observed in mammalian cells. Here, we reveal a prolonged yet spatially restricted Ca2+ signal at the centrosomes of actively dividing cells. Local buffering of the centrosomal Ca2+ signals, by flash photolysis of the caged Ca2+ chelator diazo-2-acetoxymethyl ester, arrests mitosis. We also provide evidence that this Ca2+ signal emanates from the endoplasmic reticulum. In summary, we characterize a unique centrosomal Ca2+ signal as a functionally essential input into mitosis.-Helassa, N., Nugues, C., Rajamanoharan, D., Burgoyne, R. D., Haynes, L. P. A centrosome-localized calcium signal is essential for mammalian cell mitosis.
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Affiliation(s)
- Nordine Helassa
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Charlotte Nugues
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Dayani Rajamanoharan
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Robert D. Burgoyne
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
| | - Lee P. Haynes
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom
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15
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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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16
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Nelson HA, Roe MW. Molecular physiology and pathophysiology of stromal interaction molecules. Exp Biol Med (Maywood) 2018; 243:451-472. [PMID: 29363328 DOI: 10.1177/1535370218754524] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Ca2+ release from the endoplasmic reticulum is an important component of Ca2+ signal transduction that controls numerous physiological processes in eukaryotic cells. Release of Ca2+ from the endoplasmic reticulum is coupled to the activation of store-operated Ca2+ entry into cells. Store-operated Ca2+ entry provides Ca2+ for replenishing depleted endoplasmic reticulum Ca2+ stores and a Ca2+ signal that regulates Ca2+-dependent intracellular biochemical events. Central to connecting discharge of endoplasmic reticulum Ca2+ stores following G protein-coupled receptor activation with the induction of store-operated Ca2+ entry are stromal interaction molecules (STIM1 and STIM2). These highly homologous endoplasmic reticulum transmembrane proteins function as sensors of the Ca2+ concentration within the endoplasmic reticulum lumen and activators of Ca2+ release-activated Ca2+ channels. Emerging evidence indicates that in addition to their role in Ca2+ release-activated Ca2+ channel gating and store-operated Ca2+ entry, STIM1 and STIM2 regulate other cellular signaling events. Recent studies have shown that disruption of STIM expression and function is associated with the pathogenesis of several diseases including autoimmune disorders, cancer, cardiovascular disease, and myopathies. Here, we provide an overview of the latest developments in the molecular physiology and pathophysiology of STIM1 and STIM2. Impact statement Intracellular Ca2+ signaling is a fundamentally important regulator of cell physiology. Recent studies have revealed that Ca2+-binding stromal interaction molecules (Stim1 and Stim2) expressed in the membrane of the endoplasmic reticulum (ER) are essential components of eukaryote Ca2+ signal transduction that control the activity of ion channels and other signaling effectors present in the plasma membrane. This review summarizes the most recent information on the molecular physiology and pathophysiology of stromal interaction molecules. We anticipate that the work presented in our review will provide new insights into molecular interactions that participate in interorganelle signaling crosstalk, cell function, and the pathogenesis of human diseases.
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Affiliation(s)
- Heather A Nelson
- 1 Department of Cell and Developmental Biology, 12302 SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Michael W Roe
- 1 Department of Cell and Developmental Biology, 12302 SUNY Upstate Medical University, Syracuse, NY 13210, USA.,2 Department of Medicine, 12302 SUNY Upstate Medical University, Syracuse, NY 13210, USA
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17
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Vervliet T, Pintelon I, Welkenhuyzen K, Bootman MD, Bannai H, Mikoshiba K, Martinet W, Nadif Kasri N, Parys JB, Bultynck G. Basal ryanodine receptor activity suppresses autophagic flux. Biochem Pharmacol 2017; 132:133-142. [DOI: 10.1016/j.bcp.2017.03.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 03/14/2017] [Indexed: 01/29/2023]
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18
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Pendin D, Greotti E, Lefkimmiatis K, Pozzan T. Exploring cells with targeted biosensors. J Gen Physiol 2016; 149:1-36. [PMID: 28028123 PMCID: PMC5217087 DOI: 10.1085/jgp.201611654] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 10/26/2016] [Accepted: 12/01/2016] [Indexed: 01/10/2023] Open
Abstract
Cellular signaling networks are composed of multiple pathways, often interconnected, that form complex networks with great potential for cross-talk. Signal decoding depends on the nature of the message as well as its amplitude, temporal pattern, and spatial distribution. In addition, the existence of membrane-bound organelles, which are both targets and generators of messages, add further complexity to the system. The availability of sensors that can localize to specific compartments in live cells and monitor their targets with high spatial and temporal resolution is thus crucial for a better understanding of cell pathophysiology. For this reason, over the last four decades, a variety of strategies have been developed, not only to generate novel and more sensitive probes for ions, metabolites, and enzymatic activity, but also to selectively deliver these sensors to specific intracellular compartments. In this review, we summarize the principles that have been used to target organic or protein sensors to different cellular compartments and their application to cellular signaling.
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Affiliation(s)
- Diana Pendin
- Neuroscience Institute, National Research Council, Padua Section, 35121 Padua, Italy.,Department of Biomedical Sciences, University of Padua, 35121 Padua, Italy
| | - Elisa Greotti
- Neuroscience Institute, National Research Council, Padua Section, 35121 Padua, Italy.,Department of Biomedical Sciences, University of Padua, 35121 Padua, Italy
| | - Konstantinos Lefkimmiatis
- Neuroscience Institute, National Research Council, Padua Section, 35121 Padua, Italy.,Venetian Institute of Molecular Medicine, 35129 Padua, Italy
| | - Tullio Pozzan
- Neuroscience Institute, National Research Council, Padua Section, 35121 Padua, Italy.,Venetian Institute of Molecular Medicine, 35129 Padua, Italy.,Department of Biomedical Sciences, University of Padua, 35121 Padua, Italy
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19
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Kilpatrick BS, Yates E, Grimm C, Schapira AH, Patel S. Endo-lysosomal TRP mucolipin-1 channels trigger global ER Ca2+ release and Ca2+ influx. J Cell Sci 2016; 129:3859-3867. [PMID: 27577094 PMCID: PMC5087663 DOI: 10.1242/jcs.190322] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 08/19/2016] [Indexed: 12/20/2022] Open
Abstract
Transient receptor potential (TRP) mucolipins (TRPMLs), encoded by the MCOLN genes, are patho-physiologically relevant endo-lysosomal ion channels crucial for membrane trafficking. Several lines of evidence suggest that TRPMLs mediate localised Ca2+ release but their role in Ca2+ signalling is not clear. Here, we show that activation of endogenous and recombinant TRPMLs with synthetic agonists evoked global Ca2+ signals in human cells. These signals were blocked by a dominant-negative TRPML1 construct and a TRPML antagonist. We further show that, despite a predominant lysosomal localisation, TRPML1 supports both Ca2+ release and Ca2+ entry. Ca2+ release required lysosomal and ER Ca2+ stores suggesting that TRPMLs, like other endo-lysosomal Ca2+ channels, are capable of ‘chatter’ with ER Ca2+ channels. Our data identify new modalities for TRPML1 action. Summary: The endolysosomal ion channel TRP mucolipin 1 was thought to mediate local Ca2+ signals. However, as reported here, it can also mediate global elevations in Ca2+.
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Affiliation(s)
- Bethan S Kilpatrick
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Elizabeth Yates
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
| | - Christian Grimm
- Center for Integrated Protein Science CIPSM and Department of Pharmacy - Center for Drug Research, Ludwig-Maximilians-Universität München, München 81377, Germany
| | - Anthony H Schapira
- Department of Clinical Neurosciences, Institute of Neurology, University College London, London NW3 2PF, UK
| | - Sandip Patel
- Department of Cell and Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK
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20
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Garrity AG, Wang W, Collier CM, Levey SA, Gao Q, Xu H. The endoplasmic reticulum, not the pH gradient, drives calcium refilling of lysosomes. eLife 2016; 5. [PMID: 27213518 PMCID: PMC4909396 DOI: 10.7554/elife.15887] [Citation(s) in RCA: 154] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Accepted: 05/20/2016] [Indexed: 12/15/2022] Open
Abstract
Impaired homeostasis of lysosomal Ca2+ causes lysosome dysfunction and lysosomal storage diseases (LSDs), but the mechanisms by which lysosomes acquire and refill Ca2+ are not known. We developed a physiological assay to monitor lysosomal Ca2+ store refilling using specific activators of lysosomal Ca2+ channels to repeatedly induce lysosomal Ca2+ release. In contrast to the prevailing view that lysosomal acidification drives Ca2+ into the lysosome, inhibiting the V-ATPase H+ pump did not prevent Ca2+ refilling. Instead, pharmacological depletion or chelation of Endoplasmic Reticulum (ER) Ca2+ prevented lysosomal Ca2+ stores from refilling. More specifically, antagonists of ER IP3 receptors (IP3Rs) rapidly and completely blocked Ca2+ refilling of lysosomes, but not in cells lacking IP3Rs. Furthermore, reducing ER Ca2+ or blocking IP3Rs caused a dramatic LSD-like lysosome storage phenotype. By closely apposing each other, the ER may serve as a direct and primary source of Ca2+for the lysosome. DOI:http://dx.doi.org/10.7554/eLife.15887.001
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Affiliation(s)
- Abigail G Garrity
- Neuroscience Program, University of Michigan, Ann Arbor, United States
| | - Wuyang Wang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Crystal Md Collier
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Sara A Levey
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Qiong Gao
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Haoxing Xu
- Neuroscience Program, University of Michigan, Ann Arbor, United States.,Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, United States
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21
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Abstract
Extracellular stimuli evoke the synthesis of intracellular second messengers, several of which couple to the release of Ca2+ from Ca2+-storing organelles via activation of cognate organellar Ca2+-channel complexes. The archetype is the inositol 1,4,5-trisphosphate (IP3) and IP3 receptor (IP3R) on the endoplasmic reticulum (ER). A less understood, parallel Ca2+ signalling cascade is that involving the messenger nicotinic acid adenine dinucleotide phosphate (NAADP) that couples to Ca2+ release from acidic Ca2+ stores [e.g. endo-lysosomes, secretory vesicles, lysosome-related organelles (LROs)]. NAADP-induced Ca2+ release absolutely requires organellar TPCs (two-pore channels). This review discusses how ER and acidic Ca2+ stores physically and functionally interact to generate and shape global and local Ca2+ signals, with particular emphasis on the two-way dialogue between these two organelles.
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22
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Intracellular calcium dynamics dependent on defined microtopographical features of titanium. Biomaterials 2015; 46:48-57. [DOI: 10.1016/j.biomaterials.2014.12.016] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 12/10/2014] [Accepted: 12/16/2014] [Indexed: 02/06/2023]
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23
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Penny CJ, Kilpatrick BS, Eden ER, Patel S. Coupling acidic organelles with the ER through Ca²⁺ microdomains at membrane contact sites. Cell Calcium 2015; 58:387-96. [PMID: 25866010 DOI: 10.1016/j.ceca.2015.03.006] [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: 12/18/2014] [Revised: 03/13/2015] [Accepted: 03/14/2015] [Indexed: 10/23/2022]
Abstract
Acidic organelles such as lysosomes serve as non-canonical Ca(2+) stores. The Ca(2+) mobilising messenger NAADP is thought to trigger local Ca(2+) release from such stores. These events are then amplified by Ca(2+) channels on canonical ER Ca(2+) stores to generate physiologically relevant global Ca(2+) signals. Coupling likely occurs at microdomains formed at membrane contact sites between acidic organelles and the ER. Molecular analyses and computational modelling suggest heterogeneity in the composition of these contacts and predicted Ca(2+) microdomain behaviour. Conversely, acidic organelles might also locally amplify and temper ER-evoked Ca(2+) signals. Ca(2+) microdomains between distinct Ca(2+) stores are thus likely to be integral to the genesis of complex Ca(2+) signals.
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Affiliation(s)
- Christopher J Penny
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK
| | - Bethan S Kilpatrick
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK
| | - Emily R Eden
- Department of Cell Biology, Institute of Ophthalmology, University College London, London EC1V 9EL, UK
| | - Sandip Patel
- Department of Cell and Developmental Biology, University College London, London WC1E 6BT, UK.
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24
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Rajamanoharan D, McCue HV, Burgoyne RD, Haynes LP. Modulation of phosphatidylinositol 4-phosphate levels by CaBP7 controls cytokinesis in mammalian cells. Mol Biol Cell 2015; 26:1428-39. [PMID: 25717182 PMCID: PMC4395124 DOI: 10.1091/mbc.e14-07-1243] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 02/13/2015] [Indexed: 12/29/2022] Open
Abstract
For more than 25 years, lysosomes have been known to cluster at the intercellular bridge during cytokinesis, but why has remained a mystery. This study provides evidence that phosphoinositide metabolism is important for this clustering and that lysosome activity is required for cytokinesis. Calcium and phosphoinositide signaling regulate cell division in model systems, but their significance in mammalian cells is unclear. Calcium-binding protein-7 (CaBP7) is a phosphatidylinositol 4-kinaseIIIβ (PI4KIIIβ) inhibitor required during cytokinesis in mammalian cells, hinting at a link between these pathways. Here we characterize a novel association of CaBP7 with lysosomes that cluster at the intercellular bridge during cytokinesis in HeLa cells. We show that CaBP7 regulates lysosome clustering and that PI4KIIIβ is essential for normal cytokinesis. CaBP7 depletion induces lysosome mislocalization, extension of intercellular bridge lifetime, and cytokinesis failure. These data connect phosphoinositide and calcium pathways to lysosome localization and normal cytokinesis in mammalian cells.
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Affiliation(s)
- Dayani Rajamanoharan
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3BX, United Kingdom
| | - Hannah V McCue
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3BX, United Kingdom
| | - Robert D Burgoyne
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3BX, United Kingdom
| | - Lee P Haynes
- Department of Cellular and Molecular Physiology, Institute of Translational Medicine, University of Liverpool, Liverpool L69 3BX, United Kingdom
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25
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Mehta S, Zhang J. Dynamic visualization of calcium-dependent signaling in cellular microdomains. Cell Calcium 2015; 58:333-41. [PMID: 25703691 DOI: 10.1016/j.ceca.2015.01.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 01/20/2015] [Accepted: 01/21/2015] [Indexed: 11/17/2022]
Abstract
Cells rely on the coordinated action of diverse signaling molecules to sense, interpret, and respond to their highly dynamic external environment. To ensure the specific and robust flow of information, signaling molecules are often spatially organized to form distinct signaling compartments, and our understanding of the molecular mechanisms that guide intracellular signaling hinges on the ability to directly probe signaling events within these cellular microdomains. Ca(2+) signaling in particular owes much of its functional versatility to this type of exquisite spatial regulation. As discussed below, a number of methods have been developed to investigate the mechanistic and functional implications of microdomains of Ca(2+) signaling, ranging from the application of Ca(2+) buffers to the direct and targeted visualization of Ca(2+) signaling microdomains using genetically encoded fluorescent reporters.
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Affiliation(s)
- Sohum Mehta
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Jin Zhang
- Department of Pharmacology and Molecular Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, USA; The Solomon H. Snyder Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Oncology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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26
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Morgan AJ, Davis LC, Galione A. Imaging approaches to measuring lysosomal calcium. Methods Cell Biol 2015; 126:159-95. [DOI: 10.1016/bs.mcb.2014.10.031] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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27
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Guerrero-Hernandez A, Gallegos-Gomez ML, Sanchez-Vazquez VH, Lopez-Mendez MC. Acidic intracellular Ca(2+) stores and caveolae in Ca(2+) signaling and diabetes. Cell Calcium 2014; 56:323-31. [PMID: 25182518 DOI: 10.1016/j.ceca.2014.08.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 08/07/2014] [Indexed: 12/19/2022]
Abstract
Acidic Ca(2+) stores, particularly lysosomes, are newly discovered players in the well-orchestrated arena of Ca(2+) signaling and we are at the verge of understanding how lysosomes accumulate Ca(2+) and how they release it in response to different chemical, such as NAADP, and physical signals. Additionally, it is now clear that lysosomes play a key role in autophagy, a process that allows cells to recycle components or to eliminate damaged structures to ensure cellular well-being. Moreover, lysosomes are being unraveled as hubs that coordinate both anabolism via insulin signaling and catabolism via AMPK. These acidic vesicles have close contact with the ER and there is a bidirectional movement of information between these two organelles that exquisitely regulates cell survival. Lysosomes also connect with plasma membrane where caveolae are located as specialized regions involved in Ca(2+) and insulin signaling. Alterations of all these signaling pathways are at the core of insulin resistance and diabetes.
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Fameli N, Ogunbayo OA, van Breemen C, Evans AM. Cytoplasmic nanojunctions between lysosomes and sarcoplasmic reticulum are required for specific calcium signaling. F1000Res 2014; 3:93. [PMID: 25126414 PMCID: PMC4126599 DOI: 10.12688/f1000research.3720.1] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/08/2014] [Indexed: 01/21/2023] Open
Abstract
Herein we demonstrate how nanojunctions between lysosomes and sarcoplasmic reticulum (L-SR junctions) serve to couple lysosomal activation to regenerative, ryanodine receptor-mediated cellular Ca
2+ waves. In pulmonary artery smooth muscle cells (PASMCs) it has been proposed that nicotinic acid adenine dinucleotide phosphate (NAADP) triggers increases in cytoplasmic Ca
2+ via L-SR junctions, in a manner that requires initial Ca
2+ release from lysosomes and subsequent Ca
2+-induced Ca
2+ release (CICR) via ryanodine receptor (RyR) subtype 3 on the SR membrane proximal to lysosomes. L-SR junction membrane separation has been estimated to be < 400 nm and thus beyond the resolution of light microscopy, which has restricted detailed investigations of the junctional coupling process. The present study utilizes standard and tomographic transmission electron microscopy to provide a thorough ultrastructural characterization of the L-SR junctions in PASMCs. We show that L-SR nanojunctions are prominent features within these cells and estimate that the junctional membrane separation and extension are about 15 nm and 300 nm, respectively. Furthermore, we develop a quantitative model of the L-SR junction using these measurements, prior kinetic and specific Ca
2+ signal information as input data. Simulations of NAADP-dependent junctional Ca
2+ transients demonstrate that the magnitude of these signals can breach the threshold for CICR via RyR3. By correlation analysis of live cell Ca
2+ signals and simulated Ca
2+ transients within L-SR junctions, we estimate that “trigger zones” comprising 60–100 junctions are required to confer a signal of similar magnitude. This is compatible with the 110 lysosomes/cell estimated from our ultrastructural observations. Most importantly, our model shows that increasing the L-SR junctional width above 50 nm lowers the magnitude of junctional [Ca
2+] such that there is a failure to breach the threshold for CICR via RyR3. L-SR junctions are therefore a pre-requisite for efficient Ca
2+signal coupling and may contribute to cellular function in health and disease.
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Affiliation(s)
- Nicola Fameli
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, V6T 1Z3, Canada.,Centre for Integrative Physiology, University of Edinburgh, Edinburgh, EH8 9XD, UK.,Current address: Institute for Biophysics, Medical University of Graz, Graz, 8010, Austria
| | - Oluseye A Ogunbayo
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, EH8 9XD, UK
| | - Cornelis van Breemen
- Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, Vancouver, V6T 1Z3, Canada
| | - A Mark Evans
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh, EH8 9XD, UK
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Rasmussen JE, Sheridan JT, Polk W, Davies CM, Tarran R. Cigarette smoke-induced Ca2+ release leads to cystic fibrosis transmembrane conductance regulator (CFTR) dysfunction. J Biol Chem 2014; 289:7671-81. [PMID: 24448802 DOI: 10.1074/jbc.m113.545137] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Chronic obstructive pulmonary disease affects 64 million people and is currently the fourth leading cause of death worldwide. Chronic obstructive pulmonary disease includes both emphysema and chronic bronchitis, and in the case of chronic bronchitis represents an inflammatory response of the airways that is associated with mucus hypersecretion and obstruction of small airways. Recently, it has emerged that exposure to cigarette smoke (CS) leads to an inhibition of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel, causing airway surface liquid dehydration, which may play a role in the development of chronic bronchitis. CS rapidly clears CFTR from the plasma membrane and causes it to be deposited into aggresome-like compartments. However, little is known about the mechanism(s) responsible for the internalization of CFTR following CS exposure. Our studies revealed that CS triggered a rise in cytoplasmic Ca(2+) that may have emanated from lysosomes. Furthermore, chelation of cytoplasmic Ca(2+), but not inhibition of protein kinases/phosphatases, prevented CS-induced CFTR internalization. The macrolide antibiotic bafilomycin A1 inhibited CS-induced Ca(2+) release and prevented CFTR clearance from the plasma membrane, further linking cytoplasmic Ca(2+) and CFTR internalization. We hypothesize that CS-induced Ca(2+) release prevents normal sorting/degradation of CFTR and causes internalized CFTR to reroute to aggresomes. Our data provide mechanistic insight into the potentially deleterious effects of CS on airway epithelia and outline a hitherto unrecognized signaling event triggered by CS that may affect the long term transition of the lung into a hyper-inflammatory/dehydrated environment.
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Hill JM, De Stefani D, Jones AWE, Ruiz A, Rizzuto R, Szabadkai G. Measuring baseline Ca(2+) levels in subcellular compartments using genetically engineered fluorescent indicators. Methods Enzymol 2014; 543:47-72. [PMID: 24924127 DOI: 10.1016/b978-0-12-801329-8.00003-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Intracellular Ca(2+) signaling is involved in a series of physiological and pathological processes. In particular, an intimate crosstalk between bioenergetic metabolism and Ca(2+) homeostasis has been shown to determine cell fate in resting conditions as well as in response to stress. The endoplasmic reticulum and mitochondria represent key hubs of cellular metabolism and Ca(2+) signaling. However, it has been challenging to specifically detect highly localized Ca(2+) fluxes such as those bridging these two organelles. To circumvent this issue, various recombinant Ca(2+) indicators that can be targeted to specific subcellular compartments have been developed over the past two decades. While the use of these probes for measuring agonist-induced Ca(2+) signals in various organelles has been extensively described, the assessment of basal Ca(2+) concentrations within specific organelles is often disregarded, in spite of the fact that this parameter is vital for several metabolic functions, including the enzymatic activity of mitochondrial dehydrogenases of the Krebs cycle and protein folding in the endoplasmic reticulum. Here, we provide an overview on genetically engineered, organelle-targeted fluorescent Ca(2+) probes and outline their evolution. Moreover, we describe recently developed protocols to quantify baseline Ca(2+) concentrations in specific subcellular compartments. Among several applications, this method is suitable for assessing how changes in basal Ca(2+) levels affect the metabolic profile of cancer cells.
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Affiliation(s)
- Julia M Hill
- Department of Cell and Developmental Biology, Consortium for Mitochondrial Research, University College London, London, United Kingdom
| | - Diego De Stefani
- Department of Biomedical Sciences, CNR Neuroscience Institute, University of Padua, Padua, Italy
| | - Aleck W E Jones
- Department of Cell and Developmental Biology, Consortium for Mitochondrial Research, University College London, London, United Kingdom
| | - Asier Ruiz
- Department of Neurosciences, University of the Basque Country (UPV/EHU), Achúcarro Basque Center for Neuroscience-UPV/EHU, Leioa, Spain; Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas, (CIBERNED), Madrid, Spain
| | - Rosario Rizzuto
- Department of Biomedical Sciences, CNR Neuroscience Institute, University of Padua, Padua, Italy
| | - Gyorgy Szabadkai
- Department of Cell and Developmental Biology, Consortium for Mitochondrial Research, University College London, London, United Kingdom; Department of Biomedical Sciences, CNR Neuroscience Institute, University of Padua, Padua, Italy.
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31
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Lam AK, Galione A. The endoplasmic reticulum and junctional membrane communication during calcium signaling. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2542-59. [DOI: 10.1016/j.bbamcr.2013.06.004] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 06/03/2013] [Accepted: 06/03/2013] [Indexed: 12/13/2022]
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Gene expression profiling as a tool to investigate the molecular machinery activated during hippocampal neurodegeneration induced by trimethyltin (TMT) administration. Int J Mol Sci 2013; 14:16817-35. [PMID: 23955266 PMCID: PMC3759937 DOI: 10.3390/ijms140816817] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 08/06/2013] [Accepted: 08/08/2013] [Indexed: 12/31/2022] Open
Abstract
Trimethyltin (TMT) is an organotin compound exhibiting neurotoxicant effects selectively localized in the limbic system and especially marked in the hippocampus, in both experimental animal models and accidentally exposed humans. TMT administration causes selective neuronal death involving either the granular neurons of the dentate gyrus or the pyramidal cells of the Cornu Ammonis, with a different pattern of localization depending on the different species studied or the dosage schedule. TMT is broadly used to realize experimental models of hippocampal neurodegeneration associated with cognitive impairment and temporal lobe epilepsy, though the molecular mechanisms underlying the associated selective neuronal death are still not conclusively clarified. Experimental evidence indicates that TMT-induced neurodegeneration is a complex event involving different pathogenetic mechanisms, probably acting differently in animal and cell models, which include neuroinflammation, intracellular calcium overload, and oxidative stress. Microarray-based, genome-wide expression analysis has been used to investigate the molecular scenario occurring in the TMT-injured brain in different in vivo and in vitro models, producing an overwhelming amount of data. The aim of this review is to discuss and rationalize the state-of-the-art on TMT-associated genome wide expression profiles in order to identify comparable and reproducible data that may allow focusing on significantly involved pathways.
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Li X, Garrity AG, Xu H. Regulation of membrane trafficking by signalling on endosomal and lysosomal membranes. J Physiol 2013; 591:4389-401. [PMID: 23878375 DOI: 10.1113/jphysiol.2013.258301] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Endosomal and lysosomal membrane trafficking requires the coordination of multiple signalling events to control cargo sorting and processing, and endosome maturation. The initiation and termination of signalling events in endosomes and lysosomes is not well understood, but several key regulators have been identified, which include small GTPases, phosphoinositides, and Ca2+. Small GTPases act as master regulators and molecular switches in a GTP-dependent manner, initiating signalling cascades to regulate the direction and specificity of endosomal trafficking. Phosphoinositides are membrane-bound lipids that indicate vesicular identities for recruiting specific cytoplasmic proteins to endosomal membranes, thus allowing specificity of membrane fusion, fission, and cargo sorting to occur within and between specific vesicle compartments. In addition, phosphoinositides regulate the function of membrane proteins such as ion channels and transporters in a compartment-specific manner to mediate transport and signalling. Finally, Ca2+, a locally acting second messenger released from intracellular ion channels, may provide precise spatiotemporal regulation of endosomal signalling and trafficking events. Small GTPase signalling can regulate phosphoinositide conversion during endosome maturation, and electrophysiological studies on isolated endosomes have shown that endosomal and lysosomal Ca2+ channels are directly modulated by endosomal lipids. Thus trafficking and maturation of endosomes and lysosomes can be precisely regulated by dynamic changes in GTPases and membrane lipids, as well as Ca2+ signalling. Importantly, impaired phosphoinositide and Ca2+ signalling can cause endosomal and lysosomal trafficking defects at the cellular level, and a spectrum of lysosome storage diseases.
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Affiliation(s)
- Xinran Li
- H. Xu: University of Michigan, MCDB, 3089 Natural Science Building (Kraus), 830 North University, Ann Arbor, MI 48109, USA.
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