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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 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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Charan M, Jones TH, Ahirwar DK, Acharya N, Subramaniam VV, Ganju RK, Song JW. Induced electric fields inhibit breast cancer growth and metastasis by modulating the immune tumor microenvironment. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.14.589256. [PMID: 38659909 PMCID: PMC11042207 DOI: 10.1101/2024.04.14.589256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Despite tremendous advances in oncology, metastatic triple-negative breast cancer remains difficult to treat and manage with established therapies. Here, we show in mice with orthotopic triple-negative breast tumors that alternating (100 kHz), and low intensity (<1 mV/cm) induced electric fields (iEFs) significantly reduced primary tumor growth and distant lung metastases. Non-contact iEF treatment can be delivered safely and non-invasively in vivo via a hollow, rectangular solenoid coil. We discovered that iEF treatment enhances anti-tumor immune responses at both the primary breast and secondary lung sites. In addition, iEF reduces immunosuppressive TME by reducing effector CD8+ T cell exhaustion and the infiltration of immunosuppressive immune cells. Furthermore, iEF treatment reduced lung metastasis by increasing CD8+ T cells and reducing immunosuppressive Gr1+ neutrophils in the lung microenvironment. We also observed that iEFs reduced the metastatic potential of cancer cells by inhibiting epithelial-to-mesenchymal transition. By introducing a non-invasive and non-toxic electrotherapeutic for inhibiting metastatic outgrowth and enhancing anti-tumor immune response in vivo, treatment with iEF technology could add to a paradigm-shifting strategy for cancer therapy.
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Castillo-Velasquez C, Matamala E, Becerra D, Orio P, Brauchi SE. Optical recordings of organellar membrane potentials and the components of membrane conductance in lysosomes. J Physiol 2024; 602:1637-1654. [PMID: 38625711 DOI: 10.1113/jp283825] [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: 06/14/2023] [Accepted: 03/20/2024] [Indexed: 04/17/2024] Open
Abstract
The eukaryotic cell is highly compartmentalized with organelles. Owing to their function in transporting metabolites, metabolic intermediates and byproducts of metabolic activity, organelles are important players in the orchestration of cellular function. Recent advances in optical methods for interrogating the different aspects of organellar activity promise to revolutionize our ability to dissect cellular processes with unprecedented detail. The transport activity of organelles is usually coupled to the transport of charged species; therefore, it is not only associated with the metabolic landscape but also entangled with membrane potentials. In this context, the targeted expression of fluorescent probes for interrogating organellar membrane potential (Ψorg) emerges as a powerful approach, offering less-invasive conditions and technical simplicity to interrogate cellular signalling and metabolism. Different research groups have made remarkable progress in adapting a variety of optical methods for measuring and monitoring Ψorg. These approaches include using potentiometric dyes, genetically encoded voltage indicators, hybrid fluorescence resonance energy transfer sensors and photoinduced electron transfer systems. These studies have provided consistent values for the resting potential of single-membrane organelles, such as lysosomes, the Golgi and the endoplasmic reticulum. We can foresee the use of dynamic measurements of Ψorg to study fundamental problems in organellar physiology that are linked to serious cellular disorders. Here, we present an overview of the available techniques, a survey of the resting membrane potential of internal membranes and, finally, an open-source mathematical model useful to interpret and interrogate membrane-bound structures of small volume by using the lysosome as an example.
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Affiliation(s)
- Cristian Castillo-Velasquez
- Department of Physiology, Faculty of Medicine, Universidad Austral de Chile, Valdivia, Chile
- Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Valdivia, Chile
| | - Ella Matamala
- Department of Physiology, Faculty of Medicine, Universidad Austral de Chile, Valdivia, Chile
- Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Valdivia, Chile
| | - Diego Becerra
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - Patricio Orio
- Centro Interdisciplinario de Neurociencia de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
- Instituto de Neurociencias, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
| | - Sebastian E Brauchi
- Department of Physiology, Faculty of Medicine, Universidad Austral de Chile, Valdivia, Chile
- Millennium Nucleus of Ion Channel-Associated Diseases (MiNICAD), Valdivia, Chile
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4
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Chen C, Li H, Zhang J, Cheng SC. Exploring the limitations of mitochondrial dye as a genuine horizontal mitochondrial transfer surrogate. Commun Biol 2024; 7:281. [PMID: 38448655 PMCID: PMC10917768 DOI: 10.1038/s42003-024-05964-6] [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: 10/19/2023] [Accepted: 02/23/2024] [Indexed: 03/08/2024] Open
Abstract
Rosamine-based mitochondrial dyes, such as Mitotracker Red, have commonly been employed to visualize mitochondrial localization within cells due to their preferential accumulation in organelles with membrane potential. Consequently, Mitotracker Red has often served as a surrogate indicator for tracking mitochondrial movement between neighboring cells. However, it is important to note that the presence of membrane potential in the cell membrane and other organelles may lead to the non-specific partial enrichment of Mitotracker Red in locations other than mitochondria. This study comprehensively investigates the reliability of mitochondrial dye as a marker for studying horizontal mitochondrial transfer (HMT). By meticulous replicating of previous experiments and comparing the efficiency of mitochondrial dye transfer with that of mito-targeted GFP, our findings confirm that HMT occurs at significantly lower efficiency than previously indicated by Mitotracker dye. Subsequent experiments involving mitochondria-deficient cells robustly demonstrates the non-specificity of mitochondrial dye as indicator for mitochondria. We advocate for a thorough reevaluation of existing literature in this field and propose exploration of alternative techniques to enhance the investigation of HMT. By addressing these pivotal aspects, we can advance our understanding of cellular dynamics and pave the way for future explorations in this captivating field.
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Affiliation(s)
- Chuanfang Chen
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University; Xiamen, Fujian, 361102, China.
| | - Haige Li
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University; Xiamen, Fujian, 361102, China
| | - Jia Zhang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University; Xiamen, Fujian, 361102, China
| | - Shih-Chin Cheng
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University; Xiamen, Fujian, 361102, China.
- Department of Gastroenterology, The National Key Clinical Specialty, Zhongshan Hospital of Xiamen University, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China.
- Department of Digestive Disease, School of Medicine, Xiamen University, Xiamen, Fujian, 361004, China.
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5
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Li T, Gong X, Guo H, Xi L. Photoacoustic expansion microscopy of melanosomes. OPTICS LETTERS 2024; 49:798-801. [PMID: 38359185 DOI: 10.1364/ol.509831] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 01/13/2024] [Indexed: 02/17/2024]
Abstract
Optical resolution photoacoustic microscopy (OR-PAM) is a hybrid imaging method for visualizing organelles due to the high spatial resolution and abundant optical contrast. Usually, OR-PAM employs high numerical aperture (NA) objectives and high-frequency ultrasonic detectors to resolve three-dimensional (3D) microstructures of cells. Expansion microscopy (ExM) provides a nanoscale resolution by isotropically enlarging cells instead of utilizing ultrahigh NA objectives. In this Letter, we report the development of photoacoustic expansion microscopy (PA-ExM) that combines the advantages of OR-PAM and ExM for 3D organelle imaging using near-infrared light. We evaluate the performance of PA-ExM using label-free melanoma cells, where the image quality of melanosome distributions in expanded cells using a 40× objective is comparable to that of unexpanded cells using an oil-immersed 100× objective. The results suggest that PA-ExM possesses the great potential to study organelles.
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Moreddu R. Nanotechnology and Cancer Bioelectricity: Bridging the Gap Between Biology and Translational Medicine. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2304110. [PMID: 37984883 PMCID: PMC10767462 DOI: 10.1002/advs.202304110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 09/25/2023] [Indexed: 11/22/2023]
Abstract
Bioelectricity is the electrical activity that occurs within living cells and tissues. This activity is critical for regulating homeostatic cellular function and communication, and disruptions of the same can lead to a variety of conditions, including cancer. Cancer cells are known to exhibit abnormal electrical properties compared to their healthy counterparts, and this has driven researchers to investigate the potential of harnessing bioelectricity as a tool in cancer diagnosis, prognosis, and treatment. In parallel, bioelectricity represents one of the means to gain fundamental insights on how electrical signals and charges play a role in cancer insurgence, growth, and progression. This review provides a comprehensive analysis of the literature in this field, addressing the fundamentals of bioelectricity in single cancer cells, cancer cell cohorts, and cancerous tissues. The emerging role of bioelectricity in cancer proliferation and metastasis is introduced. Based on the acknowledgement that this biological information is still hard to access due to the existing gap between biological findings and translational medicine, the latest advancements in the field of nanotechnologies for cellular electrophysiology are examined, as well as the most recent developments in micro- and nano-devices for cancer diagnostics and therapy targeting bioelectricity.
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7
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Sim SI, Park E. P5-ATPases: Structure, substrate specificities, and transport mechanisms. Curr Opin Struct Biol 2023; 79:102531. [PMID: 36724561 DOI: 10.1016/j.sbi.2023.102531] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Revised: 11/30/2022] [Accepted: 12/19/2022] [Indexed: 02/01/2023]
Abstract
P5A- and P5B- ATPases, or collectively P5-ATPases, are eukaryotic-specific ATP-dependent transporters that are important for the function of the endoplasmic reticulum (ER) and endo-/lysosomes. However, their substrate specificities had remained enigmatic for many years. Recent cryo-electron microscopy (cryo-EM) and biochemical studies of P5-ATPases have revealed their substrate specificities and transport mechanisms, which were found to be markedly different from other members of the P-type ATPase superfamily. The P5A-ATPase extracts mistargeted or mis-inserted transmembrane helices from the ER membrane for protein quality control, while the P5B-ATPases mediate export of polyamines from late endo-/lysosomes into the cytosol. In this review, we discuss the mechanisms of their substrate recognition and transport based on the cryo-EM structures of the yeast and human P5-ATPases. We highlight how structural diversification of the transmembrane domain has enabled the P5-ATPase subfamily to adapt for transport of atypical substrates.
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Affiliation(s)
- Sue Im Sim
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Eunyong Park
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA.
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8
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Deschamps A, Thines L, Colinet AS, Stribny J, Morsomme P. The yeast Gdt1 protein mediates the exchange of H + for Ca 2+ and Mn 2+ influencing the Golgi pH. J Biol Chem 2023; 299:104628. [PMID: 36963491 PMCID: PMC10148156 DOI: 10.1016/j.jbc.2023.104628] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 02/24/2023] [Accepted: 03/16/2023] [Indexed: 03/26/2023] Open
Abstract
The GDT1 family is broadly spread and highly conserved among living organisms. GDT1 members have functions in key processes like glycosylation in humans and yeasts, and photosynthesis in plants. These functions are mediated by their ability to transport ions. While transport of Ca2+ or Mn2+ is well established for several GDT1 members, their transport mechanism is poorly understood. Here, we demonstrate that H+ ions are transported in exchange for Ca2+ and Mn2+ cations by the Golgi-localized yeast Gdt1 protein. We performed direct transport measurement across a biological membrane by expressing Gdt1p in Lactococcus lactis bacterial cells and by recording either the extracellular pH or the intracellular pH during the application of Ca2+, Mn2+ or H+ gradients. Besides, in vivo cytosolic and Golgi pH measurements were performed in Saccharomyces cerevisiae with genetically encoded pH probes targeted to those subcellular compartments. These data point out that the flow of H+ ions carried by Gdt1p could be reversed according to the physiological conditions. Together, our experiments unravel the influence of the relative concentration gradients for Gdt1p-mediated H+ transport and pave the way to decipher the regulatory mechanisms driving the activity of GDT1 orthologs in various biological contexts.
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Affiliation(s)
- Antoine Deschamps
- UCLouvain, Louvain Institute of Biomolecular Science and Technology (LIBST), Group of Molecular Physiology, Croix du Sud 4-5, B-1348 Louvain-la-Neuve, Belgium
| | - Louise Thines
- UCLouvain, Louvain Institute of Biomolecular Science and Technology (LIBST), Group of Molecular Physiology, Croix du Sud 4-5, B-1348 Louvain-la-Neuve, Belgium
| | - Anne-Sophie Colinet
- UCLouvain, Louvain Institute of Biomolecular Science and Technology (LIBST), Group of Molecular Physiology, Croix du Sud 4-5, B-1348 Louvain-la-Neuve, Belgium
| | - Jiri Stribny
- UCLouvain, Louvain Institute of Biomolecular Science and Technology (LIBST), Group of Molecular Physiology, Croix du Sud 4-5, B-1348 Louvain-la-Neuve, Belgium
| | - Pierre Morsomme
- UCLouvain, Louvain Institute of Biomolecular Science and Technology (LIBST), Group of Molecular Physiology, Croix du Sud 4-5, B-1348 Louvain-la-Neuve, Belgium.
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9
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Campbell EP, Abushawish AA, Valdez LA, Bell MK, Haryono M, Rangamani P, Bloodgood BL. Electrical signals in the ER are cell type and stimulus specific with extreme spatial compartmentalization in neurons. Cell Rep 2023; 42:111943. [PMID: 36640310 PMCID: PMC10033362 DOI: 10.1016/j.celrep.2022.111943] [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: 01/12/2022] [Revised: 10/04/2022] [Accepted: 12/15/2022] [Indexed: 01/06/2023] Open
Abstract
The endoplasmic reticulum (ER) is a tortuous organelle that spans throughout a cell with a continuous membrane containing ion channels, pumps, and transporters. It is unclear if stimuli that gate ER ion channels trigger substantial membrane potential fluctuations and if those fluctuations spread beyond their site of origin. Here, we visualize ER membrane potential dynamics in HEK cells and cultured rat hippocampal neurons by targeting a genetically encoded voltage indicator specifically to the ER membrane. We report the existence of clear cell-type- and stimulus-specific ER membrane potential fluctuations. In neurons, direct stimulation of ER ryanodine receptors generates depolarizations that scale linearly with stimulus strength and reach tens of millivolts. However, ER potentials do not spread beyond the site of receptor activation, exhibiting steep attenuation that is exacerbated by intracellular large conductance K+ channels. Thus, segments of ER can generate large depolarizations that are actively restricted from impacting nearby, contiguous membrane.
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Affiliation(s)
- Evan P Campbell
- Neurobiology Department, School of Biological Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Ahmed A Abushawish
- Neurobiology Department, School of Biological Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Lauren A Valdez
- Neurobiology Department, School of Biological Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Miriam K Bell
- Department of Mechanical and Aerospace Engineering, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Melita Haryono
- Neurobiology Department, School of Biological Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Brenda L Bloodgood
- Neurobiology Department, School of Biological Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
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10
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Nikolaev DM, Mironov VN, Shtyrov AA, Kvashnin ID, Mereshchenko AS, Vasin AV, Panov MS, Ryazantsev MN. Fluorescence Imaging of Cell Membrane Potential: From Relative Changes to Absolute Values. Int J Mol Sci 2023; 24:ijms24032435. [PMID: 36768759 PMCID: PMC9916766 DOI: 10.3390/ijms24032435] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 01/20/2023] [Accepted: 01/23/2023] [Indexed: 01/28/2023] Open
Abstract
Membrane potential is a fundamental property of biological cells. Changes in membrane potential characterize a vast number of vital biological processes, such as the activity of neurons and cardiomyocytes, tumorogenesis, cell-cycle progression, etc. A common strategy to record membrane potential changes that occur in the process of interest is to utilize organic dyes or genetically-encoded voltage indicators with voltage-dependent fluorescence. Sensors are introduced into target cells, and alterations of fluorescence intensity are recorded with optical methods. Techniques that allow recording relative changes of membrane potential and do not take into account fluorescence alterations due to factors other than membrane voltage are already widely used in modern biological and biomedical studies. Such techniques have been reviewed previously in many works. However, in order to investigate a number of processes, especially long-term processes, the measured signal must be corrected to exclude the contribution from voltage-independent factors or even absolute values of cell membrane potential have to be evaluated. Techniques that enable such measurements are the subject of this review.
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Affiliation(s)
- Dmitrii M. Nikolaev
- Institute of Biomedical Systems and Biotechnologies, Peter the Great Saint Petersburg Polytechnic University, 29 Polytechnicheskaya str., 195251 Saint Petersburg, Russia
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina str., 194021 Saint Petersburg, Russia
| | - Vladimir N. Mironov
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina str., 194021 Saint Petersburg, Russia
| | - Andrey A. Shtyrov
- Institute of Biomedical Systems and Biotechnologies, Peter the Great Saint Petersburg Polytechnic University, 29 Polytechnicheskaya str., 195251 Saint Petersburg, Russia
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina str., 194021 Saint Petersburg, Russia
| | - Iaroslav D. Kvashnin
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina str., 194021 Saint Petersburg, Russia
| | - Andrey S. Mereshchenko
- Institute of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, 198504 Saint Petersburg, Russia
| | - Andrey V. Vasin
- Institute of Biomedical Systems and Biotechnologies, Peter the Great Saint Petersburg Polytechnic University, 29 Polytechnicheskaya str., 195251 Saint Petersburg, Russia
| | - Maxim S. Panov
- Institute of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, 198504 Saint Petersburg, Russia
- Center for Biophysical Studies, Saint Petersburg State Chemical Pharmaceutical University, 14 Professor Popov str., lit. A, 197022 Saint Petersburg, Russia
| | - Mikhail N. Ryazantsev
- Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, 8/3 Khlopina str., 194021 Saint Petersburg, Russia
- Institute of Chemistry, Saint Petersburg State University, 26 Universitetskii pr, 198504 Saint Petersburg, Russia
- Correspondence:
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11
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Riederer E, Cang C, Ren D. Lysosomal Ion Channels: What Are They Good For and Are They Druggable Targets? Annu Rev Pharmacol Toxicol 2023; 63:19-41. [PMID: 36151054 DOI: 10.1146/annurev-pharmtox-051921-013755] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Lysosomes play fundamental roles in material digestion, cellular clearance, recycling, exocytosis, wound repair, Ca2+ signaling, nutrient signaling, and gene expression regulation. The organelle also serves as a hub for important signaling networks involving the mTOR and AKT kinases. Electrophysiological recording and molecular and structural studies in the past decade have uncovered several unique lysosomal ion channels and transporters, including TPCs, TMEM175, TRPMLs, CLN7, and CLC-7. They underlie the organelle's permeability to major ions, including K+, Na+, H+, Ca2+, and Cl-. The channels are regulated by numerous cellular factors, ranging from H+ in the lumen and voltage across the lysosomal membrane to ATP in the cytosol to growth factors outside the cell. Genetic variations in the channel/transporter genes are associated with diseases that include lysosomal storage diseases and neurodegenerative diseases. Recent studies with human genetics and channel activators suggest that lysosomal channels may be attractive targets for the development of therapeutics for the prevention of and intervention in human diseases.
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Affiliation(s)
- Erika Riederer
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA; ,
| | - Chunlei Cang
- CAS Key Laboratory of Innate Immunity and Chronic Disease, Neurodegenerative Disorder Research Center, School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China;
| | - Dejian Ren
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA; ,
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12
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Klier PEZ, Roo R, Miller EW. Fluorescent indicators for imaging membrane potential of organelles. Curr Opin Chem Biol 2022; 71:102203. [PMID: 36084425 PMCID: PMC10259174 DOI: 10.1016/j.cbpa.2022.102203] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 07/18/2022] [Accepted: 07/21/2022] [Indexed: 01/27/2023]
Abstract
Plasma membrane potential is a key driver of the physiology of excitable cells like neurons and cardiomyocytes. Voltage-sensitive fluorescent indicators offer a powerful complement to traditional electrode-based approaches to measuring and monitoring membrane potential. Intracellular organelles can also generate membrane potential, yet the electrode- and fluorescent indicator-based approaches used for plasma membrane potential imaging are difficult to implement on intact organelles in their native environment. Here, we survey recent advances in developing and deploying voltage-sensitive fluorescent indicators to interrogate organelle membrane potential in intact cells.
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Affiliation(s)
- Pavel E Z Klier
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA
| | - Ryan Roo
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA
| | - Evan W Miller
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA; Department of Molecular & Cell Biology, University of California, Berkeley, CA, 94720, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, CA, 94720, USA.
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13
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Zapevalova MV, Shchegravina ES, Fonareva IP, Salnikova DI, Sorokin DV, Scherbakov AM, Maleev AA, Ignatov SK, Grishin ID, Kuimov AN, Konovalova MV, Svirshchevskaya EV, Fedorov AY. Synthesis, Molecular Docking, In Vitro and In Vivo Studies of Novel Dimorpholinoquinazoline-Based Potential Inhibitors of PI3K/Akt/mTOR Pathway. Int J Mol Sci 2022; 23:ijms231810854. [PMID: 36142768 PMCID: PMC9503112 DOI: 10.3390/ijms231810854] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Revised: 09/11/2022] [Accepted: 09/13/2022] [Indexed: 11/18/2022] Open
Abstract
A (series) range of potential dimorpholinoquinazoline-based inhibitors of the PI3K/Akt/mTOR cascade was synthesized. Several compounds exhibited cytotoxicity towards a panel of cancer cell lines in the low and sub-micromolar range. Compound 7c with the highest activity and moderate selectivity towards MCF7 cells which express the mutant type of PI3K was also tested for the ability to inhibit PI3K-(signaling pathway) downstream effectors and associated proteins. Compound 7c inhibited the phosphorylation of Akt, mTOR, and S6K at 125–250 nM. It also triggered PARP1 cleavage, ROS production, and cell death via several mechanisms. Inhibition of PI3Kα was observed at a concentration of 7b 50 µM and of 7c 500 µM and higher, that can indicate minority PI3Kα as a target among other kinases in the titled cascade for 7c. In vivo studies demonstrated an inhibition of tumor growth in the colorectal tumor model. According to the docking studies, the replacement of the triazine core in gedatolisib (8) by a quinazoline fragment, and incorporation of a (hetero)aromatic unit connected with the carbamide group via a flexible spacer, can result in more selective inhibition of the PI3Kα isoform.
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Affiliation(s)
- Maria V. Zapevalova
- Department of Organic Chemistry, Nizhny Novgorod State University, Gagarina Av. 23, 603950 Nizhny Novgorod, Russia
| | - Ekaterina S. Shchegravina
- Department of Organic Chemistry, Nizhny Novgorod State University, Gagarina Av. 23, 603950 Nizhny Novgorod, Russia
- N.D. Zelinsky Insitute of Organic Chemistry RAS, Leninsky Prospect 47, 119991 Moscow, Russia
- Correspondence: (E.S.S.); (A.Y.F.)
| | - Irina P. Fonareva
- Department of Organic Chemistry, Nizhny Novgorod State University, Gagarina Av. 23, 603950 Nizhny Novgorod, Russia
| | - Diana I. Salnikova
- Department of Experimental Tumor Biology, Blokhin N.N. National Medical Research Center of Oncology, Kashirskoye Sh. 24, 115522 Moscow, Russia
| | - Danila V. Sorokin
- Department of Experimental Tumor Biology, Blokhin N.N. National Medical Research Center of Oncology, Kashirskoye Sh. 24, 115522 Moscow, Russia
| | - Alexander M. Scherbakov
- Department of Experimental Tumor Biology, Blokhin N.N. National Medical Research Center of Oncology, Kashirskoye Sh. 24, 115522 Moscow, Russia
| | - Alexander A. Maleev
- Department of Organic Chemistry, Nizhny Novgorod State University, Gagarina Av. 23, 603950 Nizhny Novgorod, Russia
| | - Stanislav K. Ignatov
- Department of Organic Chemistry, Nizhny Novgorod State University, Gagarina Av. 23, 603950 Nizhny Novgorod, Russia
| | - Ivan D. Grishin
- Department of Organic Chemistry, Nizhny Novgorod State University, Gagarina Av. 23, 603950 Nizhny Novgorod, Russia
| | - Alexander N. Kuimov
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, Leninskye Gory, House 1, Building 40, 119992 Moscow, Russia
| | - Maryia V. Konovalova
- Department of Immunology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Miklukho-Maklaya 16/10, 117997 Moscow, Russia
| | - Elena V. Svirshchevskaya
- Department of Immunology, Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Miklukho-Maklaya 16/10, 117997 Moscow, Russia
| | - Alexey Yu. Fedorov
- Department of Organic Chemistry, Nizhny Novgorod State University, Gagarina Av. 23, 603950 Nizhny Novgorod, Russia
- N.D. Zelinsky Insitute of Organic Chemistry RAS, Leninsky Prospect 47, 119991 Moscow, Russia
- Correspondence: (E.S.S.); (A.Y.F.)
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14
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Klier PEZ, Gest AMM, Martin JG, Roo R, Navarro MX, Lesiak L, Deal PE, Dadina N, Tyson J, Schepartz A, Miller EW. Bioorthogonal, Fluorogenic Targeting of Voltage-Sensitive Fluorophores for Visualizing Membrane Potential Dynamics in Cellular Organelles. J Am Chem Soc 2022; 144:12138-12146. [PMID: 35776693 DOI: 10.1021/jacs.2c02664] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Electrical potential differences across lipid bilayers play foundational roles in cellular physiology. Plasma membrane voltage is the most widely studied; however, the bilayers of organelles like mitochondria, lysosomes, nuclei, and the endoplasmic reticulum (ER) also provide opportunities for ionic compartmentalization and the generation of transmembrane potentials. Unlike plasma membranes, organellar bilayers, cloistered within the cell, remain recalcitrant to traditional approaches like patch-clamp electrophysiology. To address the challenge of monitoring changes in organelle membrane potential, we describe the design, synthesis, and application of the LUnAR RhoVR (Ligation Unquenched for Activation and Redistribution Rhodamine-based Voltage Reporter) for optically monitoring membrane potential changes in the ER of living cells. We pair a tetrazine-quenched RhoVR for voltage sensing with a transcyclooctene (TCO)-conjugated ceramide (Cer-TCO) for targeting to the ER. Bright fluorescence is observed only at the coincidence of the LUnAR RhoVR and TCO in the ER, minimizing non-specific, off-target fluorescence. We show that the product of the LUnAR RhoVR and Cer-TCO is voltage-sensitive and that the LUnAR RhoVR can be targeted to an intact ER in living cells. Using the LUnAR RhoVR, we use two-color, ER-localized, fast voltage imaging coupled with cytosolic Ca2+ imaging to validate the electroneutrality of Ca2+ release from internal stores. Finally, we use the LUnAR RhoVR to directly visualize functional coupling between the plasma-ER membranes in patch clamped cell lines, providing the first direct evidence of the sign of the ER potential response to plasma membrane potential changes. We envision that the LUnAR RhoVR, along with other existing organelle-targeting TCO probes, could be applied widely for exploring organelle physiology.
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Affiliation(s)
- Pavel E Z Klier
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Anneliese M M Gest
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Julia G Martin
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Ryan Roo
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Marisol X Navarro
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Lauren Lesiak
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Parker E Deal
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Neville Dadina
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Jonathan Tyson
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Alanna Schepartz
- Department of Chemistry, University of California, Berkeley, California 94720, United States.,Department of Molecular & Cell Biology, University of California, Berkeley, California 94720, United States
| | - Evan W Miller
- Department of Chemistry, University of California, Berkeley, California 94720, United States.,Department of Molecular & Cell Biology, University of California, Berkeley, California 94720, United States.,Helen Wills Neuroscience Institute, University of California, Berkeley, California 94720, United States
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15
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Kramer RH, Miller EW, Abdelfattah A, Baker B. Fluorescent Reporters for Sensing Membrane Potential: Tools for Bioelectricity. Bioelectricity 2022. [DOI: 10.1089/bioe.2022.0017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Richard H. Kramer
- Department of Molecular & Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA
| | - Evan W. Miller
- Departments of Chemistry and Molecular & Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, California, USA
| | - Ahmed Abdelfattah
- Department of Neuroscience, Brown University, Providence, Rhode Island, USA
| | - Bradley Baker
- Brain Science Institute, Korea Institute of Science and Technology, Seoul, South Korea
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16
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Puri NM, Romano GR, Lin TY, Mai QN, Irannejad R. The organic cation Transporter 2 regulates dopamine D1 receptor signaling at the Golgi apparatus. eLife 2022; 11:75468. [PMID: 35467530 PMCID: PMC9098220 DOI: 10.7554/elife.75468] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Accepted: 04/22/2022] [Indexed: 11/13/2022] Open
Abstract
Dopamine is a key catecholamine in the brain and kidney, where it is involved in a number of physiological functions such as locomotion, cognition, emotion, endocrine regulation, and renal function. As a membrane-impermeant hormone and neurotransmitter, dopamine is thought to signal by binding and activating dopamine receptors, members of the G protein coupled receptor (GPCR) family, only on the plasma membrane. Here, using novel nanobody-based biosensors, we demonstrate for the first time that the dopamine D1 receptor (D1DR), the primary mediator of dopaminergic signaling in the brain and kidney, not only functions on the plasma membrane but becomes activated at the Golgi apparatus in the presence of its ligand. We present evidence that activation of the Golgi pool of D1DR is dependent on organic cation transporter 2 (OCT2), a dopamine transporter, providing an explanation for how the membrane-impermeant dopamine accesses subcellular pools of D1DR. We further demonstrate that dopamine activates Golgi-D1DR in murine striatal medium spiny neurons, and this activity depends on OCT2 function. We also introduce a new approach to selectively interrogate compartmentalized D1DR signaling by inhibiting Gαs coupling using a nanobody-based chemical recruitment system. Using this strategy, we show that Golgi-localized D1DRs regulate cAMP production and mediate local protein kinase A activation. Together, our data suggest that spatially compartmentalized signaling hubs are previously unappreciated regulatory aspects of D1DR signaling. Our data provide further evidence for the role of transporters in regulating subcellular GPCR activity.
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Affiliation(s)
- Natasha M Puri
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - Giovanna R Romano
- Biochemistry Department, Weill Cornell Medicine, New York, United States
| | - Ting-Yu Lin
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, United States
| | - Quynh N Mai
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, United States
| | - Roshanak Irannejad
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, United States
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17
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Sun A, Ji Y, Li Y, Xie W, Liu Z, Li T, Jin T, Qi W, Li K, Wu C, Xi L. Multicolor Photoacoustic Volumetric Imaging of Subcellular Structures. ACS NANO 2022; 16:3231-3238. [PMID: 35080378 DOI: 10.1021/acsnano.1c11103] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Photoacoustic imaging (PAI) has been widely used in multiscale and multicontrast imaging of biological structures and functions. Optical resolution photoacoustic microscopy (OR-PAM), an emerging submodality of PAI, features high lateral resolution and rich optical contrast, indicating great potential in visualizing cellular and subcellular structures. However, three-dimensional (3D) imaging of subcellular structures using OR-PAM has remained a challenge due to the limited axial resolution. In this study, we propose a multicolor 3D photoacoustic microscopy with high lateral/axial resolutions of 0.42/2 and 0.5/2.5 μm at 532 and 780 nm excitation, respectively. Owing to the significantly increased axial resolution, we could visualize the volumetric subcellular structures of melanoma cells using intrinsic contrast. In addition, we carried out multicolor imaging of labeled microtubules/clathrin-coated pits (CCP) and microtubules/mitochondria, respectively, with one scanning by using two different excitation wavelengths. The internal connections between different subcellular structures are revealed by quantitatively comparing the spatial distributions of microtubules/CCP and microtubules/mitochondria in a single cell. Current results suggest that the proposed OR-PAM may serve as an efficient tool for subcellular and cytophysiological studies.
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Affiliation(s)
- Aihui Sun
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yaoyao Ji
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Yaxi Li
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Wenhui Xie
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Zhihe Liu
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Tingting Li
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Tian Jin
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Weizhi Qi
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen 518055, China
- Shenzhen Bay Laboratory, Shenzhen 518132, China
| | - Kai Li
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Changfeng Wu
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen 518055, China
| | - Lei Xi
- Department of Biomedical Engineering, Southern University of Science and Technology, Shenzhen 518055, China
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18
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Ion Channels and Pumps in Autophagy: A Reciprocal Relationship. Cells 2021; 10:cells10123537. [PMID: 34944044 PMCID: PMC8700256 DOI: 10.3390/cells10123537] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 12/07/2021] [Accepted: 12/08/2021] [Indexed: 12/24/2022] Open
Abstract
Autophagy, the process of cellular self-degradation, is intrinsically tied to the degradative function of the lysosome. Several diseases have been linked to lysosomal degradative defects, including rare lysosomal storage disorders and neurodegenerative diseases. Ion channels and pumps play a major regulatory role in autophagy. Importantly, calcium signaling produced by TRPML1 (transient receptor potential cation channel, mucolipin subfamily) has been shown to regulate autophagic progression through biogenesis of autophagic-lysosomal organelles, activation of mTORC1 (mechanistic target of rapamycin complex 1) and degradation of autophagic cargo. ER calcium channels such as IP3Rs supply calcium for the lysosome, and lysosomal function is severely disrupted in the absence of lysosomal calcium replenishment by the ER. TRPML1 function is also regulated by LC3 (microtubule-associated protein light chain 3) and mTORC1, two critical components of the autophagic network. Here we provide an overview of the current knowledge about ion channels and pumps-including lysosomal V-ATPase (vacuolar proton-ATPase), which is required for acidification and hence proper enzymatic activity of lysosomal hydrolases-in the regulation of autophagy, and discuss how functional impairment of some of these leads to diseases.
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19
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Grupi A, Shapira Z, Yudovich S, Degani-Katzav N, Weiss S. Point-localized, site-specific membrane potential optical recording by single fluorescent nanodiscs. ACTA ACUST UNITED AC 2021; 1:None. [PMID: 34568861 PMCID: PMC8448295 DOI: 10.1016/j.bpr.2021.100007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 07/20/2021] [Indexed: 01/02/2023]
Abstract
Nanodisc technology was implemented as a platform for voltage nanosensors. A fluorescence (Förster) resonance energy transfer (FRET)- based voltage-sensing scheme employing fluorescent nanodiscs and the hydrophobic ion dipicrylamine was developed and utilized to optically record membrane potentials on the single-nanodisc level. Ensemble and single-nanosensor recordings were demonstrated for HEK293 cells and primary cortical neuron cells. Conjugation of nanodiscs to anti-GABAA antibodies allowed for site-specific membrane potential measurements from postsynaptic sites.
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Affiliation(s)
- Asaf Grupi
- Department of Physics, Institute for Nanotechnology and Advanced Materials.,Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, Israel
| | - Zehavit Shapira
- Department of Physics, Institute for Nanotechnology and Advanced Materials.,Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, Israel
| | - Shimon Yudovich
- Department of Physics, Institute for Nanotechnology and Advanced Materials.,Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, Israel
| | - Nurit Degani-Katzav
- Department of Physics, Institute for Nanotechnology and Advanced Materials.,Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, Israel
| | - Shimon Weiss
- Department of Physics, Institute for Nanotechnology and Advanced Materials.,Institute for Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan, Israel.,Department of Chemistry and Biochemistry.,California NanoSystems Institute, University of California Los Angeles, Los Angeles, California
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20
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Cabrera‐Garcia D, Bekdash R, Abbott GW, Yazawa M, Harrison NL. The envelope protein of SARS-CoV-2 increases intra-Golgi pH and forms a cation channel that is regulated by pH. J Physiol 2021; 599:2851-2868. [PMID: 33709461 PMCID: PMC8251088 DOI: 10.1113/jp281037] [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: 10/28/2020] [Accepted: 03/02/2021] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS We report a novel method for the transient expression of SARS-CoV-2 envelope (E) protein in intracellular organelles and the plasma membrane of mammalian cells and Xenopus oocytes. Intracellular expression of SARS-CoV-2 E protein increases intra-Golgi pH. By targeting the SARS-CoV-2 E protein to the plasma membrane, we show that it forms a cation channel, viroporin, that is modulated by changes of pH. This method for studying the activity of viroporins may facilitate screening for new antiviral drugs to identify novel treatments for COVID-19. ABSTRACT The envelope (E) protein of coronaviruses such as SARS-CoV-1 is proposed to form an ion channel or viroporin that participates in viral propagation and pathogenesis. Here we developed a technique to study the E protein of SARS-CoV-2 in mammalian cells by directed targeting using a carboxyl-terminal fluorescent protein tag, mKate2. The wild-type SARS-CoV-2 E protein can be trafficked to intracellular organelles, notably the endoplasmic reticulum-Golgi intermediate complex, where its expression increases pH inside the organelle. We also succeeded in targeting SARS-CoV-2 E to the plasma membrane, which enabled biophysical analysis using whole-cell patch clamp recording in a mammalian cell line, HEK 293 cells, and two-electrode voltage clamp electrophysiology in Xenopus oocytes. The results suggest that the E protein forms an ion channel that is permeable to monovalent cations such as Na+ , Cs+ and K+ . The E current is nearly time- and voltage-independent when E protein is expressed in mammalian cells, and is modulated by changes of pH. At pH 6.0 and 7.4, the E protein current is activated, whereas at pH 8.0 and 9.0, the amplitude of E protein current is reduced, and in oocytes the inward E current fades at pH 9 in a time- and voltage-dependent manner. Using this directed targeting method and electrophysiological recordings, potential inhibitors of the E protein can be screened and subsequently investigated for antiviral activity against SARS-CoV-2 in vitro and possible efficacy in treating COVID-19.
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Affiliation(s)
| | - Ramsey Bekdash
- Department of Molecular Pharmacology and TherapeuticsColumbia UniversityNew YorkNYUSA
- Columbia Stem Cell Initiative, Department of Rehabilitation and Regenerative MedicineColumbia UniversityNew YorkNYUSA
| | - Geoffrey W. Abbott
- Bioelectricity Laboratory, Department of Physiology and Biophysics, School of MedicineUniversity of CaliforniaIrvineCAUSA
| | - Masayuki Yazawa
- Department of Molecular Pharmacology and TherapeuticsColumbia UniversityNew YorkNYUSA
- Columbia Stem Cell Initiative, Department of Rehabilitation and Regenerative MedicineColumbia UniversityNew YorkNYUSA
| | - Neil L. Harrison
- Department of AnesthesiologyColumbia UniversityNew YorkNYUSA
- Department of Molecular Pharmacology and TherapeuticsColumbia UniversityNew YorkNYUSA
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