51
|
Lin H, Jun I, Woo JH, Lee MG, Kim SJ, Nam JH. Temperature-dependent increase in the calcium sensitivity and acceleration of activation of ANO6 chloride channel variants. Sci Rep 2019; 9:6706. [PMID: 31040335 PMCID: PMC6491614 DOI: 10.1038/s41598-019-43162-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 04/12/2019] [Indexed: 02/08/2023] Open
Abstract
Anoctamin-6 (ANO6) belongs to a family of calcium (Ca2+)-activated chloride channels (CaCCs), with three splicing variants (V1, V2, and V5) showing plasma membrane expression. Unlike other CaCCs, ANO6 requires a non-physiological intracellular free calcium concentration ([Ca2+]i > 1 μM) and several minutes for full activation under a whole-cell patch clamp. Therefore, its physiological role as an ion channel is uncertain and it is more commonly considered a Ca2+-dependent phospholipid scramblase. Here, we demonstrate that physiological temperature (37 °C) increases ANO6 Ca2+ sensitivity under a whole-cell patch clamp; V1 was activated by 1 μM [Ca2+]i, whereas V2 and V5 were activated by 300 nM [Ca2+]i. Increasing the temperature to 42 °C led to activation of all ANO6 variants by 100 nM [Ca2+]i. The delay time for activation of the three variants was significantly shortened at 37 °C. Notably, the temperature-dependent Ca2+-sensitisation of ANO6 became insignificant under inside-out patch clamp, suggesting critical roles of unknown cytosolic factors. Unlike channel activity, 27 °C but not 37 °C (physiological temperature) induced the scramblase activity of ANO6 at submicromolar [Ca2+]i (300 nM), irrespective of variant type. Our results reveal a physiological ion conducting property of ANO6 at 37 °C and suggest that ANO6 channel function acts separately from its scramblase activity.
Collapse
Affiliation(s)
- Haiyue Lin
- Department of Physiology, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080, Republic of Korea
| | - Ikhyun Jun
- The Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea
- Department of Pharmacology and Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Joo Han Woo
- Department of Physiology, Dongguk University College of Medicine, 123 Dongdae-ro, Gyeongju, 38066, Republic of Korea
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, 32 Dongguk-ro, Ilsan Dong-gu, Goyang, Gyeonggi-do, 10326, Republic of Korea
| | - Min Goo Lee
- Department of Pharmacology and Brain Korea 21 PLUS Project for Medical Sciences, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea
| | - Sung Joon Kim
- Department of Physiology, Seoul National University College of Medicine, 103 Daehak-ro, Jongno-gu, Seoul, 03080, Republic of Korea.
| | - Joo Hyun Nam
- Department of Physiology, Dongguk University College of Medicine, 123 Dongdae-ro, Gyeongju, 38066, Republic of Korea.
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, 32 Dongguk-ro, Ilsan Dong-gu, Goyang, Gyeonggi-do, 10326, Republic of Korea.
| |
Collapse
|
52
|
Watanabe R. Microsystem for the single molecule analysis of membrane transport proteins. Biochim Biophys Acta Gen Subj 2019; 1864:129330. [PMID: 30926442 DOI: 10.1016/j.bbagen.2019.03.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 03/19/2019] [Accepted: 03/22/2019] [Indexed: 12/31/2022]
Abstract
Micro-chamber arrays enable highly sensitive and quantitative bioassays at the single-molecule level. Accordingly, they are widely used for ultra-sensitive biomedical applications, e.g., digital PCR and digital ELISA. However, the versatility of micro-chambers is generally limited to reactions in aqueous solutions, although various functions of membrane proteins are extremely important. To address this issue, microsystems using arrayed micro-sized chambers sealed with lipid bilayers, referred to here as a "biomembrane microsystems", have been developed by many research groups for the analysis of membrane proteins. In this review, I would like to introduce recent progress on the single molecule analysis of membrane transport proteins using a biomembrane microsystem, and discuss the future prospects for its use in analytical and pharmacological applications.
Collapse
|
53
|
Contribution of Anoctamins to Cell Survival and Cell Death. Cancers (Basel) 2019; 11:cancers11030382. [PMID: 30893776 PMCID: PMC6468699 DOI: 10.3390/cancers11030382] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 03/13/2019] [Accepted: 03/16/2019] [Indexed: 02/07/2023] Open
Abstract
Before anoctamins (TMEM16 proteins) were identified as a family of Ca2+-activated chloride channels and phospholipid scramblases, the founding member anoctamin 1 (ANO1, TMEM16A) was known as DOG1, a marker protein for gastrointestinal stromal tumors (GIST). Meanwhile, ANO1 has been examined in more detail, and the role of ANO1 in cell proliferation and the development of different types of malignomas is now well established. While ANO5, ANO7, and ANO9 may also be relevant for growth of cancers, evidence has been provided for a role of ANO6 (TMEM16F) in regulated cell death. The cellular mechanisms by which anoctamins control cell proliferation and cell death, respectively, are just emerging; however, the pronounced effects of anoctamins on intracellular Ca2+ levels are likely to play a significant role. Recent results suggest that some anoctamins control membrane exocytosis by setting Ca2+i levels near the plasma membrane, and/or by controlling the intracellular Cl- concentration. Exocytosis and increased membrane trafficking induced by ANO1 and ANO6 may enhance membrane expression of other chloride channels, such as CFTR and volume activated chloride channels (VRAC). Notably, ANO6-induced phospholipid scrambling with exposure of phosphatidylserine is pivotal for the sheddase function of disintegrin and metalloproteinase (ADAM). This may support cell death and tumorigenic activity of IL-6 by inducing IL-6 trans-signaling. The reported anticancer effects of the anthelminthic drug niclosamide are probably related to the potent inhibitory effect on ANO1, apart from inducing cell cycle arrest through the Let-7d/CDC34 axis. On the contrary, pronounced activation of ANO6 due to a large increase in intracellular calcium, activation of phospholipase A2 or lipid peroxidation, can lead to ferroptotic death of cancer cells. It therefore appears reasonable to search for both inhibitors and potent activators of TMEM16 in order to interfere with cancer growth and metastasis.
Collapse
|
54
|
Alvadia C, Lim NK, Clerico Mosina V, Oostergetel GT, Dutzler R, Paulino C. Cryo-EM structures and functional characterization of the murine lipid scramblase TMEM16F. eLife 2019; 8:44365. [PMID: 30785399 PMCID: PMC6414204 DOI: 10.7554/elife.44365] [Citation(s) in RCA: 95] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 02/19/2019] [Indexed: 12/13/2022] Open
Abstract
The lipid scramblase TMEM16F initiates blood coagulation by catalyzing the exposure of phosphatidylserine in platelets. The protein is part of a family of membrane proteins, which encompasses calcium-activated channels for ions and lipids. Here, we reveal features of murine TMEM16F (mTMEM16F) that underlie its function as a lipid scramblase and an ion channel. The cryo-EM data of mTMEM16F in absence and presence of Ca2+ define the ligand-free closed conformation of the protein and the structure of a Ca2+-bound intermediate. Both conformations resemble their counterparts of the scrambling-incompetent anion channel mTMEM16A, yet with distinct differences in the region of ion and lipid permeation. In conjunction with functional data, we demonstrate the relationship between ion conduction and lipid scrambling. Although activated by a common mechanism, both functions appear to be mediated by alternate protein conformations that are at equilibrium in the ligand-bound state.
Collapse
Affiliation(s)
- Carolina Alvadia
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Novandy K Lim
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Vanessa Clerico Mosina
- Department of Structural Biology at the Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, Netherlands
| | - Gert T Oostergetel
- Department of Structural Biology at the Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, Netherlands
| | - Raimund Dutzler
- Department of Biochemistry, University of Zurich, Zurich, Switzerland
| | - Cristina Paulino
- Department of Structural Biology at the Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, Netherlands
| |
Collapse
|
55
|
Corradi V, Sejdiu BI, Mesa-Galloso H, Abdizadeh H, Noskov SY, Marrink SJ, Tieleman DP. Emerging Diversity in Lipid-Protein Interactions. Chem Rev 2019; 119:5775-5848. [PMID: 30758191 PMCID: PMC6509647 DOI: 10.1021/acs.chemrev.8b00451] [Citation(s) in RCA: 245] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
![]()
Membrane
lipids interact with proteins in a variety of ways, ranging
from providing a stable membrane environment for proteins to being
embedded in to detailed roles in complicated and well-regulated protein
functions. Experimental and computational advances are converging
in a rapidly expanding research area of lipid–protein interactions.
Experimentally, the database of high-resolution membrane protein structures
is growing, as are capabilities to identify the complex lipid composition
of different membranes, to probe the challenging time and length scales
of lipid–protein interactions, and to link lipid–protein
interactions to protein function in a variety of proteins. Computationally,
more accurate membrane models and more powerful computers now enable
a detailed look at lipid–protein interactions and increasing
overlap with experimental observations for validation and joint interpretation
of simulation and experiment. Here we review papers that use computational
approaches to study detailed lipid–protein interactions, together
with brief experimental and physiological contexts, aiming at comprehensive
coverage of simulation papers in the last five years. Overall, a complex
picture of lipid–protein interactions emerges, through a range
of mechanisms including modulation of the physical properties of the
lipid environment, detailed chemical interactions between lipids and
proteins, and key functional roles of very specific lipids binding
to well-defined binding sites on proteins. Computationally, despite
important limitations, molecular dynamics simulations with current
computer power and theoretical models are now in an excellent position
to answer detailed questions about lipid–protein interactions.
Collapse
Affiliation(s)
- Valentina Corradi
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| | - Besian I Sejdiu
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| | - Haydee Mesa-Galloso
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| | - Haleh Abdizadeh
- Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials , University of Groningen , Nijenborgh 7 , 9747 AG Groningen , The Netherlands
| | - Sergei Yu Noskov
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| | - Siewert J Marrink
- Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials , University of Groningen , Nijenborgh 7 , 9747 AG Groningen , The Netherlands
| | - D Peter Tieleman
- Centre for Molecular Simulation and Department of Biological Sciences , University of Calgary , 2500 University Drive NW , Calgary , Alberta T2N 1N4 , Canada
| |
Collapse
|
56
|
Bricogne C, Fine M, Pereira PM, Sung J, Tijani M, Wang Y, Henriques R, Collins MK, Hilgemann DW. TMEM16F activation by Ca 2+ triggers plasma membrane expansion and directs PD-1 trafficking. Sci Rep 2019; 9:619. [PMID: 30679690 PMCID: PMC6345885 DOI: 10.1038/s41598-018-37056-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 12/03/2018] [Indexed: 12/22/2022] Open
Abstract
TMEM16F is a Ca2+ -gated ion channel that is required for Ca2+ -activated phosphatidylserine exposure on the surface of many eukaryotic cells. TMEM16F is widely expressed and has roles in platelet activation during blood clotting, bone formation and T cell activation. By combining microscopy and patch clamp recording we demonstrate that activation of TMEM16F by Ca2+ ionophores in Jurkat T cells triggers large-scale surface membrane expansion in parallel with phospholipid scrambling. With continued ionophore application,TMEM16F-expressing cells then undergo extensive shedding of ectosomes. The T cell co-receptor PD-1 is selectively incorporated into ectosomes. This selectivity depends on its transmembrane sequence. Surprisingly, cells lacking TMEM16F not only fail to expand surface membrane in response to elevated cytoplasmic Ca2+, but instead undergo rapid massive endocytosis with PD-1 internalisation. These results establish a new role for TMEM16F as a regulator of Ca2+ activated membrane trafficking.
Collapse
Affiliation(s)
| | - Michael Fine
- University of Texas Southwestern Medical Center, Department of Physiology, Dallas, Texas, USA
| | - Pedro M Pereira
- MRC Laboratory for Molecular Cell Biology, University College London, Gower St, London, UK
| | - Julia Sung
- National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Herts, UK
| | - Maha Tijani
- National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Herts, UK
| | - Youxue Wang
- University of Texas Southwestern Medical Center, Department of Physiology, Dallas, Texas, USA
| | - Ricardo Henriques
- MRC Laboratory for Molecular Cell Biology, University College London, Gower St, London, UK
| | - Mary K Collins
- UCL Cancer Institute, University College London, Gower St, London, UK.
- National Institute for Biological Standards and Control, Blanche Lane, South Mimms, Herts, UK.
- Okinawa Institute of Science and Technology, Onna-son, Okinawa, Japan.
| | - Donald W Hilgemann
- University of Texas Southwestern Medical Center, Department of Physiology, Dallas, Texas, USA.
| |
Collapse
|
57
|
Han TW, Ye W, Bethel NP, Zubia M, Kim A, Li KH, Burlingame AL, Grabe M, Jan YN, Jan LY. Chemically induced vesiculation as a platform for studying TMEM16F activity. Proc Natl Acad Sci U S A 2019; 116:1309-1318. [PMID: 30622179 PMCID: PMC6347726 DOI: 10.1073/pnas.1817498116] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Calcium-activated phospholipid scramblase mediates the energy-independent bidirectional translocation of lipids across the bilayer, leading to transient or, in the case of apoptotic scrambling, sustained collapse of membrane asymmetry. Cells lacking TMEM16F-dependent lipid scrambling activity are deficient in generation of extracellular vesicles (EVs) that shed from the plasma membrane in a Ca2+-dependent manner, namely microvesicles. We have adapted chemical induction of giant plasma membrane vesicles (GPMVs), which require both TMEM16F-dependent phospholipid scrambling and calcium influx, as a kinetic assay to investigate the mechanism of TMEM16F activity. Using the GPMV assay, we identify and characterize both inactivating and activating mutants that elucidate the mechanism for TMEM16F activation and facilitate further investigation of TMEM16F-mediated lipid translocation and its role in extracellular vesiculation.
Collapse
Affiliation(s)
- Tina W Han
- Howard Hughes Medical Institute, University of California, San Francisco, CA 94143
- Department of Physiology, University of California, San Francisco, CA 94143
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143
| | - Wenlei Ye
- Howard Hughes Medical Institute, University of California, San Francisco, CA 94143
- Department of Physiology, University of California, San Francisco, CA 94143
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143
| | - Neville P Bethel
- Department of Pharmaceutical Chemistry, Cardiovascular Research Institute, University of California, San Francisco, CA 94143
| | - Mario Zubia
- Howard Hughes Medical Institute, University of California, San Francisco, CA 94143
- Department of Physiology, University of California, San Francisco, CA 94143
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143
| | - Andrew Kim
- Howard Hughes Medical Institute, University of California, San Francisco, CA 94143
- Department of Physiology, University of California, San Francisco, CA 94143
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143
| | - Kathy H Li
- Mass Spectrometry Facility, University of California, San Francisco, CA 94143
| | - Alma L Burlingame
- Mass Spectrometry Facility, University of California, San Francisco, CA 94143
| | - Michael Grabe
- Department of Pharmaceutical Chemistry, Cardiovascular Research Institute, University of California, San Francisco, CA 94143
| | - Yuh Nung Jan
- Howard Hughes Medical Institute, University of California, San Francisco, CA 94143
- Department of Physiology, University of California, San Francisco, CA 94143
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143
| | - Lily Y Jan
- Howard Hughes Medical Institute, University of California, San Francisco, CA 94143;
- Department of Physiology, University of California, San Francisco, CA 94143
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94143
| |
Collapse
|
58
|
Brunner JD, Schenck S. Preparation of Proteoliposomes with Purified TMEM16 Protein for Accurate Measures of Lipid Scramblase Activity. Methods Mol Biol 2019; 1949:181-199. [PMID: 30790257 DOI: 10.1007/978-1-4939-9136-5_14] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The distribution of different lipid species between the two leaflets is tightly regulated and underlies the concerted action of distinct catalytic entities. While flippases and floppases establish membrane asymmetry, scramblases randomize the lipid distribution and play pivotal roles during blood clotting, apoptosis, and in processes such as N-linked glycosylation of proteins. The recent discovery of TMEM16 family members acting as scramblases has led to an increasing demand for developing protocols tailored for TMEM16 proteins to enable functional investigations of their scrambling activity. Here we describe a protocol for the expression, purification, and functional reconstitution of TMEM16 proteins into preformed liposomes and measurement of their scrambling activity using fluorescence-labeled lipid derivatives. The reconstitution involves extrusion of liposomes through a membrane, destabilization of liposomes using Triton X-100, and stepwise detergent removal by adsorption on styryl-beads. The scrambling assay is based on the selective bleaching of nitrobenzoxadiazol fluorescent lipids on the outer leaflet of liposomes by the membrane-impermeant reducing agent sodium dithionite. The assay allows conclusions on the substrate specificity and on the kinetics of the transported lipids as shown with the example of a Ca2+-activated TMEM16 scramblase from the fungus Nectria haematococca (nhTMEM16).
Collapse
Affiliation(s)
- Janine Denise Brunner
- Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institut, Villigen, Switzerland.
| | - Stephan Schenck
- Laboratory of Biomolecular Research, Division of Biology and Chemistry, Paul Scherrer Institut, Villigen, Switzerland
| |
Collapse
|
59
|
Wang L, Iwasaki Y, Andra KK, Pandey K, Menon AK, Bütikofer P. Scrambling of natural and fluorescently tagged phosphatidylinositol by reconstituted G protein-coupled receptor and TMEM16 scramblases. J Biol Chem 2018; 293:18318-18327. [PMID: 30287690 PMCID: PMC6254352 DOI: 10.1074/jbc.ra118.004213] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 10/03/2018] [Indexed: 12/12/2022] Open
Abstract
Members of the G protein-coupled receptor and TMEM16 (transmembrane protein 16) protein families are phospholipid scramblases that facilitate rapid, bidirectional movement of phospholipids across a membrane bilayer in an ATP-independent manner. On reconstitution into large unilamellar vesicles, these proteins scramble more than 10,000 lipids/protein/s as measured with co-reconstituted fluorescent nitrobenzoxadiazole (NBD)-labeled phospholipids. Although NBD-labeled phospholipids are ubiquitously used as reporters of scramblase activity, it remains unclear whether the NBD modification influences the quantitative outcomes of the scramblase assay. We now report a refined biochemical approach for measuring the activity of scramblase proteins with radiolabeled natural phosphatidylinositol ([3H]PI) and exploiting the hydrolytic activity of bacterial PI-specific phospholipase C (PI-PLC) to detect the transbilayer movement of PI. PI-PLC rapidly hydrolyzed 50% of [3H]PI in large symmetric, unilamellar liposomes, corresponding to the lipid pool in the outer leaflet. On reconstitution of a crude preparation of yeast endoplasmic reticulum scramblase, purified bovine opsin, or purified Nectria haematococca TMEM16, the extent of [3H]PI hydrolysis increased, indicating that [3H]PI from the inner leaflet had been scrambled to the outer leaflet. Using transphosphatidylation, we synthesized acyl-NBD-PI and used it to compare our PI-PLC-based assay with conventional fluorescence-based methods. Our results revealed quantitative differences between the two assays that we attribute to the specific features of the assays themselves rather than to the nature of the phospholipid. In summary, we have developed an assay that measures scrambling of a chemically unmodified phospholipid by a reconstituted scramblase.
Collapse
Affiliation(s)
- Lei Wang
- From the Institute of Biochemistry and Molecular Medicine and; Graduate School for Cellular and Biochemical Sciences, University of Bern, 3012 Bern, Switzerland
| | - Yugo Iwasaki
- the Laboratory of Molecular Biotechnology, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Nagoya 464-8601, Japan, and
| | - Kiran K Andra
- the Department of Biochemistry, Weill Cornell Medical College, New York, New York 10065
| | - Kalpana Pandey
- the Department of Biochemistry, Weill Cornell Medical College, New York, New York 10065
| | - Anant K Menon
- the Department of Biochemistry, Weill Cornell Medical College, New York, New York 10065.
| | - Peter Bütikofer
- From the Institute of Biochemistry and Molecular Medicine and.
| |
Collapse
|
60
|
Ono T, Ichiki T, Noji H. Digital enzyme assay using attoliter droplet array. Analyst 2018; 143:4923-4929. [PMID: 30221644 PMCID: PMC6180314 DOI: 10.1039/c8an01152d] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 08/18/2018] [Indexed: 01/12/2023]
Abstract
Single-molecule digital enzyme assay using micron-sized droplet array is a promising analysis method to quantify biomolecules at extremely low concentrations. However, multiplex digital enzyme assays are still difficult to access because the best buffer conditions can vary largely among enzymes. In addition, the best conditions for flurogenic compounds to retain high quantum efficiency and to avoid leakage into the oil phase can be also very different. In this study, digital enzyme assay was performed using an array of nanometer-sized droplets of 200 aL volume, termed 'nanocell'. Due to the small reaction volume, nanocell enhanced the accumulation rate of fluorescent products by a factor of 100 when compared with micron-sized reactors. Nanocell also enabled oil-free sealing of reactors: when flushed with an air flow, nanocell displayed water droplets under air, allowing enzymes to catalyze the reaction at the same rate as in oil-sealed reactors. Dual digital enzyme assay was also demonstrated using β-galactosidase and alkaline phosphatase (ALP) at pH 7.4, which is far from the optimum condition for ALP. Even under such a non-optimum condition, ALP molecules were successfully detected. Nanocell could largely expand the applicability of digital bioassay for enzymes under non-optimum conditions or enzymes of low turnover rate. The sealing of the reactor with air would also expand the applicability, allowing the use of fluorescent dyes that leak into oil.
Collapse
Affiliation(s)
- Takao Ono
- Department of Applied Chemistry
, Graduate School of Engineering
, The University of Tokyo
,
Japan
.
| | - Takanori Ichiki
- Department of Materials Engineering
, Graduate School of Engineering
, The University of Tokyo
,
Japan
| | - Hiroyuki Noji
- Department of Applied Chemistry
, Graduate School of Engineering
, The University of Tokyo
,
Japan
.
- ImPACT Program
, Japan Science and Technology Agency
,
Saitama 332-0012
, Japan
| |
Collapse
|
61
|
Watanabe R, Komatsu T, Sakamoto S, Urano Y, Noji H. High-throughput single-molecule bioassay using micro-reactor arrays with a concentration gradient of target molecules. LAB ON A CHIP 2018; 18:2849-2853. [PMID: 30091771 DOI: 10.1039/c8lc00535d] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Micro-reactor arrays enable highly sensitive and quantitative bioassays at a single-molecule level. Accordingly, they are widely used for sensitive "digital" bioassays, e.g., digital PCR and digital ELISA. Despite high integration, individual reactors in digital bioassays are filled with a uniform reaction solution, thus limiting the ability to simultaneously conduct multiple bioassays under different conditions using integrated reactors in parallel, resulting in the loss of potential throughput. We developed micro-reactor arrays with a concentration gradient of target molecules, in which individual reactors sealed with a lipid-bilayer membrane contained a precise amount of target molecules. Using the arrays, we successfully demonstrated multiple single-molecule bioassays in parallel using alkaline phosphatase or α-hemolysin, key components in various biomedical sensors. This new platform extends the versatility of micro-reactor arrays and could enable further analytical and pharmacological applications.
Collapse
Affiliation(s)
- Rikiya Watanabe
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
| | | | | | | | | |
Collapse
|
62
|
Falzone ME, Malvezzi M, Lee BC, Accardi A. Known structures and unknown mechanisms of TMEM16 scramblases and channels. J Gen Physiol 2018; 150:933-947. [PMID: 29915161 PMCID: PMC6028493 DOI: 10.1085/jgp.201711957] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 05/29/2018] [Indexed: 12/25/2022] Open
Abstract
Falzone et al. interpret the mechanisms underlying the activity of TMEM16 family members from recent structural and functional work. The TMEM16 family of membrane proteins is composed of both Ca2+-gated Cl− channels and Ca2+-dependent phospholipid scramblases. The functional diversity of TMEM16s underlies their involvement in numerous signal transduction pathways that connect changes in cytosolic Ca2+ levels to cellular signaling networks. Indeed, defects in the function of several TMEM16s cause a variety of genetic disorders, highlighting their fundamental pathophysiological importance. Here, we review how our mechanistic understanding of TMEM16 function has been shaped by recent functional and structural work. Remarkably, the recent determination of near-atomic-resolution structures of TMEM16 proteins of both functional persuasions has revealed how relatively minimal rearrangements in the substrate translocation pathway are sufficient to precipitate the dramatic functional differences that characterize the family. These structures, when interpreted in the light of extensive functional analysis, point to an unusual mechanism for Ca2+-dependent activation of TMEM16 proteins in which substrate permeation is regulated by a combination of conformational rearrangements and electrostatics. These breakthroughs pave the way to elucidate the mechanistic bases of ion and lipid transport by the TMEM16 proteins and unravel the molecular links between these transport activities and their function in human pathophysiology.
Collapse
Affiliation(s)
- Maria E Falzone
- Department of Biochemistry, Weill Cornell Medical School, New York, NY
| | - Mattia Malvezzi
- Department of Anesthesiology, Weill Cornell Medical School, New York, NY
| | - Byoung-Cheol Lee
- Department of Anesthesiology, Weill Cornell Medical School, New York, NY
| | - Alessio Accardi
- Department of Biochemistry, Weill Cornell Medical School, New York, NY .,Department of Anesthesiology, Weill Cornell Medical School, New York, NY.,Department of Physiology, Biophysics and Systems Biology, Weill Cornell Medical School, New York, NY
| |
Collapse
|