1
|
Mount J, Maksaev G, Summers BT, Fitzpatrick JAJ, Yuan P. Structural basis for mechanotransduction in a potassium-dependent mechanosensitive ion channel. Nat Commun 2022; 13:6904. [PMID: 36371466 PMCID: PMC9653487 DOI: 10.1038/s41467-022-34737-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Accepted: 11/04/2022] [Indexed: 11/13/2022] Open
Abstract
Mechanosensitive channels of small conductance, found in many living organisms, open under elevated membrane tension and thus play crucial roles in biological response to mechanical stress. Amongst these channels, MscK is unique in that its activation also requires external potassium ions. To better understand this dual gating mechanism by force and ligand, we elucidate distinct structures of MscK along the gating cycle using cryo-electron microscopy. The heptameric channel comprises three layers: a cytoplasmic domain, a periplasmic gating ring, and a markedly curved transmembrane domain that flattens and expands upon channel opening, which is accompanied by dilation of the periplasmic ring. Furthermore, our results support a potentially unifying mechanotransduction mechanism in ion channels depicted as flattening and expansion of the transmembrane domain.
Collapse
Affiliation(s)
- Jonathan Mount
- grid.4367.60000 0001 2355 7002Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO USA ,grid.4367.60000 0001 2355 7002Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO USA
| | - Grigory Maksaev
- grid.4367.60000 0001 2355 7002Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO USA ,grid.4367.60000 0001 2355 7002Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO USA
| | - Brock T. Summers
- grid.4367.60000 0001 2355 7002Washington University Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO USA
| | - James A. J. Fitzpatrick
- grid.4367.60000 0001 2355 7002Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO USA ,grid.4367.60000 0001 2355 7002Washington University Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO USA ,grid.4367.60000 0001 2355 7002Department of Neuroscience, Washington University School of Medicine, Saint Louis, MO USA ,grid.4367.60000 0001 2355 7002Department of Biomedical Engineering, Washington University in Saint Louis, Saint Louis, MO USA
| | - Peng Yuan
- grid.4367.60000 0001 2355 7002Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO USA ,grid.4367.60000 0001 2355 7002Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO USA
| |
Collapse
|
2
|
Bavi O, Zhou Z, Bavi N, Mehdi Vaez Allaei S, Cox CD, Martinac B. Asymmetric effects of amphipathic molecules on mechanosensitive channels. Sci Rep 2022; 12:9976. [PMID: 35705645 PMCID: PMC9200802 DOI: 10.1038/s41598-022-14446-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Accepted: 06/06/2022] [Indexed: 12/30/2022] Open
Abstract
Mechanosensitive (MS) ion channels are primary transducers of mechanical force into electrical and/or chemical intracellular signals. Many diverse MS channel families have been shown to respond to membrane forces. As a result of this intimate relationship with the membrane and proximal lipids, amphipathic compounds exert significant effects on the gating of MS channels. Here, we performed all-atom molecular dynamics (MD) simulations and employed patch-clamp recording to investigate the effect of two amphipaths, Fluorouracil (5-FU) a chemotherapy agent, and the anaesthetic trifluoroethanol (TFE) on structurally distinct mechanosensitive channels. We show that these amphipaths have a profound effect on the bilayer order parameter as well as transbilayer pressure profile. We used bacterial mechanosensitive channels (MscL/MscS) and a eukaryotic mechanosensitive channel (TREK-1) as force-from-lipids reporters and showed that these amphipaths have differential effects on these channels depending on the amphipaths' size and shape as well as which leaflet of the bilayer they incorporate into. 5-FU is more asymmetric in shape and size than TFE and does not penetrate as deep within the bilayer as TFE. Thereby, 5-FU has a more profound effect on the bilayer and channel activity than TFE at much lower concentrations. We postulate that asymmetric effects of amphipathic molecules on mechanosensitive membrane proteins through the bilayer represents a general regulatory mechanism for these proteins.
Collapse
Affiliation(s)
- Omid Bavi
- grid.444860.a0000 0004 0600 0546Department of Mechanical and Aerospace Engineering, Shiraz University of Technology, Shiraz, Iran
| | - Zijing Zhou
- grid.1057.30000 0000 9472 3971Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010 Australia
| | - Navid Bavi
- grid.170205.10000 0004 1936 7822Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL USA
| | - S. Mehdi Vaez Allaei
- grid.46072.370000 0004 0612 7950Department of Physics, University of Tehran, 1439955961 Tehran, Iran
| | - Charles D. Cox
- grid.1057.30000 0000 9472 3971Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010 Australia ,grid.1005.40000 0004 4902 0432Faculty of Medicine, St Vincent’s Clinical School, University of New South Wales, Darlinghurst, NSW 2010 Australia
| | - B. Martinac
- grid.1057.30000 0000 9472 3971Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010 Australia ,grid.1005.40000 0004 4902 0432Faculty of Medicine, St Vincent’s Clinical School, University of New South Wales, Darlinghurst, NSW 2010 Australia
| |
Collapse
|
3
|
Qiu Y, Chien CC, Maroulis B, Bei J, Gaitas A, Gong B. Extending applications of AFM to fluidic AFM in single living cell studies. J Cell Physiol 2022; 237:3222-3238. [PMID: 35696489 PMCID: PMC9378449 DOI: 10.1002/jcp.30809] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 05/25/2022] [Indexed: 12/30/2022]
Abstract
In this article, a review of a series of applications of atomic force microscopy (AFM) and fluidic Atomic Force Microscopy (fluidic AFM, hereafter fluidFM) in single-cell studies is presented. AFM applications involving single-cell and extracellular vesicle (EV) studies, colloidal force spectroscopy, and single-cell adhesion measurements are discussed. FluidFM is an offshoot of AFM that combines a microfluidic cantilever with AFM and has enabled the research community to conduct biological, pathological, and pharmacological studies on cells at the single-cell level in a liquid environment. In this review, capacities of fluidFM are discussed to illustrate (1) the speed with which sequential measurements of adhesion using coated colloid beads can be done, (2) the ability to assess lateral binding forces of endothelial or epithelial cells in a confluent cell monolayer in an appropriate physiological environment, and (3) the ease of measurement of vertical binding forces of intercellular adhesion between heterogeneous cells. Furthermore, key applications of fluidFM are reviewed regarding to EV absorption, manipulation of a single living cell by intracellular injection, sampling of cellular fluid from a single living cell, patch clamping, and mass measurements of a single living cell.
Collapse
Affiliation(s)
- Yuan Qiu
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Chen-Chi Chien
- The Estelle and Daniel Maggin Department of Neurology, Icahn School of Medicine at Mount Sinai, New York City, New York, USA
| | - Basile Maroulis
- The Estelle and Daniel Maggin Department of Neurology, Icahn School of Medicine at Mount Sinai, New York City, New York, USA
| | - Jiani Bei
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA
| | - Angelo Gaitas
- The Estelle and Daniel Maggin Department of Neurology, Icahn School of Medicine at Mount Sinai, New York City, New York, USA.,BioMedical Engineering & Imaging Institute, Leon and Norma Hess Center for Science and Medicine, New York City, New York, USA
| | - Bin Gong
- Department of Pathology, University of Texas Medical Branch, Galveston, Texas, USA.,Sealy Center for Vector Borne and Zoonotic Diseases, University of Texas Medical Branch, Galveston, Texas, USA.,Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, Texas, USA.,Institute for Human Infectious and Immunity, University of Texas Medical Branch, Galveston, Texas, USA
| |
Collapse
|
4
|
Abstract
Written by someone who has worked in the mechanobiology field for close to 40 years, this commentary describes some historical background to the recent award of one-half of the Nobel Prize for Physiology or Medicine to Ardem Patapoutian for his discovery of the family of mechanosensitive Piezo ion channels, which function as mechanoreceptors feeling the environment in senses such as touch, pain, and proprioception.
Collapse
|
5
|
Golubchik A, Lopes LC, Singh V, Kuss S. Pharma‐molecule Transport across Bacterial Membranes: Detection and Quantification Approaches by Electrochemistry and Bioanalytical Methods. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202101055] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Alon Golubchik
- Department Chemistry University of Manitoba Winnipeg R3T 2N2 Canada
| | | | - Vikram Singh
- Department Chemistry University of Manitoba Winnipeg R3T 2N2 Canada
| | - Sabine Kuss
- Department Chemistry University of Manitoba Winnipeg R3T 2N2 Canada
| |
Collapse
|
6
|
Paternò GM, Bondelli G, Lanzani G. Bringing Microbiology to Light: Toward All-Optical Electrophysiology in Bacteria. Bioelectricity 2021; 3:136-142. [PMID: 34476389 DOI: 10.1089/bioe.2021.0008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The observation of neuron-like behavior in bacteria, such as the occurrence of electric spiking and extended bioelectric signaling, points to the role of membrane dynamics in prokaryotes. Electrophysiology of bacteria, however, has been overlooked for long time, due to the difficulties in monitoring bacterial bioelectric phenomena with those probing techniques that are commonly used for eukaryotes. Optical technologies can allow a paradigm shift in the field of electrophysiology of bacteria, as they would permit to elicit and monitor signaling rapidly, remotely, and with high spatiotemporal precision. In this perspective, we discuss about the potentiality of light interrogation methods in microbiology, encouraging the development of all-optical electrophysiology of bacteria.
Collapse
Affiliation(s)
| | - Gaia Bondelli
- Center for Nanoscience and Technology, Istituto Italiano di Tecnologia, Milano, Italy.,Physics Department, Politecnico di Milano, Milano, Italy
| | - Guglielmo Lanzani
- Center for Nanoscience and Technology, Istituto Italiano di Tecnologia, Milano, Italy.,Physics Department, Politecnico di Milano, Milano, Italy
| |
Collapse
|
7
|
Golubchik A, Lopes LC, Singh V, Kuss S. Pharma-molecule Transport across Bacterial Membranes: Detection and Quantification Approaches by Electrochemistry and Bioanalytical Methods. Angew Chem Int Ed Engl 2021; 60:22112-22124. [PMID: 33979000 DOI: 10.1002/anie.202101055] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Indexed: 11/07/2022]
Abstract
Antibiotic resistance is a significant challenge encountered by healthcare systems on a global scale. Knowledge about membrane transport of antibiotics and other pharmacologically relevant molecules in bacteria is crucial towards understanding and overcoming antibiotic resistance, as drug resistance often depends on drug transport. This comprehensive literature review discusses the detection and quantification of membrane transport of pharma-molecules in bacteria and highlights the importance of molecule transport to antibiotic resistance. This review emphasizes electrochemical and electrophysiological methods of detection and quantification. The results of this literature review reveal a substantial diversity in methods and types of quantitative information collected.
Collapse
Affiliation(s)
- Alon Golubchik
- Department Chemistry, University of Manitoba, Winnipeg, R3T 2N2, Canada
| | | | - Vikram Singh
- Department Chemistry, University of Manitoba, Winnipeg, R3T 2N2, Canada
| | - Sabine Kuss
- Department Chemistry, University of Manitoba, Winnipeg, R3T 2N2, Canada
| |
Collapse
|
8
|
Jiang Y, Idikuda V, Chowdhury S, Chanda B. Activation of the archaeal ion channel MthK is exquisitely regulated by temperature. eLife 2020; 9:e59055. [PMID: 33274718 PMCID: PMC7717905 DOI: 10.7554/elife.59055] [Citation(s) in RCA: 8] [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: 05/18/2020] [Accepted: 11/17/2020] [Indexed: 11/13/2022] Open
Abstract
Physiological response to thermal stimuli in mammals is mediated by a structurally diverse class of ion channels, many of which exhibit polymodal behavior. To probe the diversity of biophysical mechanisms of temperature-sensitivity, we characterized the temperature-dependent activation of MthK, a two transmembrane calcium-activated potassium channel from thermophilic archaebacteria. Our functional complementation studies show that these channels are more efficient at rescuing K+ transport at 37°C than at 24°C. Electrophysiological activity of the purified MthK is extremely sensitive (Q10 >100) to heating particularly at low-calcium concentrations whereas channels lacking the calcium-sensing RCK domain are practically insensitive. By analyzing single-channel activities at limiting calcium concentrations, we find that temperature alters the coupling between the cytoplasmic RCK domains and the pore domain. These findings reveal a hitherto unexplored mechanism of temperature-dependent regulation of ion channel gating and shed light on ancient origins of temperature-sensitivity.
Collapse
Affiliation(s)
- Yihao Jiang
- Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
- Center for the Investigation of Membrane Excitability Diseases (CIMED)St. LouisUnited States
| | - Vinay Idikuda
- Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
- Center for the Investigation of Membrane Excitability Diseases (CIMED)St. LouisUnited States
| | - Sandipan Chowdhury
- Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
- Center for the Investigation of Membrane Excitability Diseases (CIMED)St. LouisUnited States
| | - Baron Chanda
- Department of Anesthesiology, Washington University School of MedicineSt. LouisUnited States
- Center for the Investigation of Membrane Excitability Diseases (CIMED)St. LouisUnited States
| |
Collapse
|
9
|
Deng Z, Maksaev G, Schlegel AM, Zhang J, Rau M, Fitzpatrick JAJ, Haswell ES, Yuan P. Structural mechanism for gating of a eukaryotic mechanosensitive channel of small conductance. Nat Commun 2020; 11:3690. [PMID: 32704140 PMCID: PMC7378837 DOI: 10.1038/s41467-020-17538-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Accepted: 07/07/2020] [Indexed: 01/21/2023] Open
Abstract
Mechanosensitive ion channels transduce physical force into electrochemical signaling that underlies an array of fundamental physiological processes, including hearing, touch, proprioception, osmoregulation, and morphogenesis. The mechanosensitive channels of small conductance (MscS) constitute a remarkably diverse superfamily of channels critical for management of osmotic pressure. Here, we present cryo-electron microscopy structures of a MscS homolog from Arabidopsis thaliana, MSL1, presumably in both the closed and open states. The heptameric MSL1 channel contains an unusual bowl-shaped transmembrane region, which is reminiscent of the evolutionarily and architecturally unrelated mechanosensitive Piezo channels. Upon channel opening, the curved transmembrane domain of MSL1 flattens and expands. Our structures, in combination with functional analyses, delineate a structural mechanism by which mechanosensitive channels open under increased membrane tension. Further, the shared structural feature between unrelated channels suggests the possibility of a unified mechanical gating mechanism stemming from membrane deformation induced by a non-planar transmembrane domain. Mechanosensitive channels transduce physical force into electrochemical signaling in processes such as hearing, touch, proprioception, osmoregulation, and morphogenesis. Here, authors use cryo-electron microscopy to provide structural insights into the mechanical gating mechanism.
Collapse
Affiliation(s)
- Zengqin Deng
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, 63110, USA.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, 63110, USA
| | - Grigory Maksaev
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, 63110, USA.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, 63110, USA
| | - Angela M Schlegel
- Department of Biology, Washington University in Saint Louis, Saint Louis, MO, 63130, USA.,NSF Center for Engineering Mechanobiology, Washington University in Saint Louis, Saint Louis, MO, 63130, USA
| | - Jingying Zhang
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, 63110, USA.,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, 63110, USA
| | - Michael Rau
- Washington University Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO, 63110, USA
| | - James A J Fitzpatrick
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, 63110, USA.,Washington University Center for Cellular Imaging, Washington University School of Medicine, Saint Louis, MO, 63110, USA.,Department of Neuroscience, Washington University School of Medicine, Saint Louis, MO, 63110, USA.,Department of Biomedical Engineering, Washington University in Saint Louis, Saint Louis, MO, 63130, USA
| | - Elizabeth S Haswell
- Department of Biology, Washington University in Saint Louis, Saint Louis, MO, 63130, USA.,NSF Center for Engineering Mechanobiology, Washington University in Saint Louis, Saint Louis, MO, 63130, USA
| | - Peng Yuan
- Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO, 63110, USA. .,Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, 63110, USA.
| |
Collapse
|
10
|
Schlegel AM, Haswell ES. Analyzing plant mechanosensitive ion channels expressed in giant E. coli spheroplasts by single-channel patch-clamp electrophysiology. Methods Cell Biol 2020; 160:61-82. [PMID: 32896333 DOI: 10.1016/bs.mcb.2020.02.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Plants possess numerous ion channels that respond to a range of stimuli, including small molecules, transmembrane voltage, and mechanical force. Many in the latter category, known as mechanosensitive (MS) ion channels, open directly in response to increases in lateral membrane tension. One of the most effective techniques for characterizing ion channel properties is patch-clamp electrophysiology, in which the current through a section of membrane containing ion channels is measured. For MS channels, this technique enables the measurement of key channel properties such as tension sensitivity, conductance, and ion selectivity. These characteristics, along with the phenotypes of genetic mutants, can help reveal the physiological roles of a particular MS channel. In this protocol, we provide detailed instructions on how to study MS ion channels using single-channel patch-clamp electrophysiology in giant E. coli spheroplasts. We first present an optimized method for preparing giant spheroplasts, then describe how to measure MS channel activity using patch-clamp electrophysiology and analyze the resulting data. We also provide recommended equipment lists, setup schematics, and useful conventions.
Collapse
Affiliation(s)
- Angela M Schlegel
- Department of Biology and Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, MO, United States
| | - Elizabeth S Haswell
- Department of Biology and Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, MO, United States.
| |
Collapse
|
11
|
A General Workflow for Characterization of Nernstian Dyes and Their Effects on Bacterial Physiology. Biophys J 2019; 118:4-14. [PMID: 31810660 PMCID: PMC6950638 DOI: 10.1016/j.bpj.2019.10.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 10/08/2019] [Accepted: 10/18/2019] [Indexed: 12/22/2022] Open
Abstract
The electrical membrane potential (Vm) is one of the components of the electrochemical potential of protons across the biological membrane (proton motive force), which powers many vital cellular processes. Because Vm also plays a role in signal transduction, measuring it is of great interest. Over the years, a variety of techniques have been developed for the purpose. In bacteria, given their small size, Nernstian membrane voltage probes are arguably the favorite strategy, and their cytoplasmic accumulation depends on Vm according to the Nernst equation. However, a careful calibration of Nernstian probes that takes into account the tradeoffs between the ease with which the signal from the dye is observed and the dyes’ interactions with cellular physiology is rarely performed. Here, we use a mathematical model to understand such tradeoffs and apply the results to assess the applicability of the Thioflavin T dye as a Vm sensor in Escherichia coli. We identify the conditions in which the dye turns from a Vm probe into an actuator and, based on the model and experimental results, propose a general workflow for the characterization of Nernstian dye candidates.
Collapse
|
12
|
Buck AK, Elmore DE, Darling LEO. Using fluorescence microscopy to shed light on the mechanisms of antimicrobial peptides. Future Med Chem 2019; 11:2445-2458. [PMID: 31517514 PMCID: PMC6787493 DOI: 10.4155/fmc-2019-0095] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 06/18/2019] [Indexed: 12/18/2022] Open
Abstract
Antimicrobial peptides (AMPs) are promising in the fight against increasing bacterial resistance, but the development of AMPs with enhanced activity requires a thorough understanding of their mechanisms of action. Fluorescence microscopy is one of the most flexible and effective tools to characterize AMPs, particularly in its ability to measure the membrane interactions and cellular localization of peptides. Recent advances have increased the scope of research questions that can be addressed via microscopy through improving spatial and temporal resolution. Unique combinations of fluorescent labels and dyes can simultaneously consider different aspects of peptide-membrane interaction mechanisms. This review emphasizes the central role that fluorescence microscopy will continue to play in the interrogation of AMP structure-function relationships and the engineering of more potent peptides.
Collapse
Affiliation(s)
- Anne K Buck
- Biochemistry Program, Wellesley College, Wellesley, MA 02481, USA
| | - Donald E Elmore
- Department of Chemistry & Biochemistry Program, Wellesley College, Wellesley, MA 02481, USA
| | - Louise EO Darling
- Department of Biological Sciences & Biochemistry Program, Wellesley College, Wellesley, MA 02481, USA
| |
Collapse
|
13
|
Morgan JLW, Evans EGB, Zagotta WN. Functional characterization and optimization of a bacterial cyclic nucleotide-gated channel. J Biol Chem 2019; 294:7503-7515. [PMID: 30885945 DOI: 10.1074/jbc.ra119.007699] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 03/15/2019] [Indexed: 02/01/2023] Open
Abstract
Cyclic nucleotide-gated (CNG) channels produce the initial electrical signal in mammalian vision and olfaction. They open in response to direct binding of cyclic nucleotide (cAMP or cGMP) to a cytoplasmic region of the channel. However, the conformational rearrangements occurring upon binding to produce pore opening (i.e. gating) are not well understood. SthK is a bacterial CNG channel that has the potential to serve as an ideal model for structure-function studies of gating but is currently limited by its toxicity, native cysteines, and low open probability (P o). Here, we expressed SthK in giant Escherichia coli spheroplasts and performed patch-clamp recordings to characterize SthK gating in a bacterial membrane. We demonstrated that the P o in cAMP is higher than has been previously published and that cGMP acts as a weak partial SthK agonist. Additionally, we determined that SthK expression is toxic to E. coli because of gating by cytoplasmic cAMP. We overcame this toxicity by developing an adenylate cyclase-knockout E. coli cell line. Finally, we generated a cysteine-free SthK construct and introduced mutations that further increase the P o in cAMP. We propose that this SthK model will help elucidate the gating mechanism of CNG channels.
Collapse
Affiliation(s)
- Jacob L W Morgan
- From the Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195
| | - Eric G B Evans
- From the Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195
| | - William N Zagotta
- From the Department of Physiology and Biophysics, University of Washington, Seattle, Washington 98195
| |
Collapse
|
14
|
Nakayama Y, Hashimoto KI, Sawada Y, Sokabe M, Kawasaki H, Martinac B. Corynebacterium glutamicum mechanosensitive channels: towards unpuzzling "glutamate efflux" for amino acid production. Biophys Rev 2018; 10:1359-1369. [PMID: 30209745 PMCID: PMC6233337 DOI: 10.1007/s12551-018-0452-1] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 08/27/2018] [Indexed: 12/11/2022] Open
Abstract
Corynebacterium glutamicum has been utilized for industrial amino acid production, especially for monosodium glutamate (MSG), the food-additive for the "UMAMI" category of taste sensation, which is one of the five human basic tastes. Glutamate export from these cells is facilitated by the opening of mechanosensitive channels in the cell membrane within the bacterial cell envelope following specific treatments, such as biotin limitation, addition of Tween 40 or penicillin. A long-unsolved puzzle still remains how and why C. glutamicum mechanosensitive channels are activated by these treatments to export glutamate. Unlike mechanosensitive channels in other bacteria, these channels are not simply osmotic safety valves that prevent these bacteria from bursting upon a hypo-osmotic shock. They also function as metabolic valves to continuously release glutamate as components of a pump-and-leak mechanism regulating the cellular turgor pressure. Recent studies have demonstrated that the opening of the mechanosensitive channel, MscCG, mainly facilitates the efflux of glutamate and not of other amino acids and that the "force-from-lipids" gating mechanism of channels also applies to the MscCG channel. The bacterial types of mechanosensitive channels are found in cell-walled organisms from bacteria to land plants, where their physiological functions have been specialized beyond their basic function in bacterial osmoregulation. In the case of the C. glutamicum MscCG channels, they have evolved to function as specialized glutamate exporters.
Collapse
Affiliation(s)
- Yoshitaka Nakayama
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW, 2010, Australia.
| | - Ken-Ichi Hashimoto
- Department of Green and Sustainable Chemistry, Tokyo Denki University, 5 Asahi-cho, Senju, Adachi-ku, Tokyo, 120-8551, Japan
| | - Yasuyuki Sawada
- Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Japan
| | - Masahiro Sokabe
- Mechanobiology Laboratory, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550, Japan
| | - Hisashi Kawasaki
- Department of Green and Sustainable Chemistry, Tokyo Denki University, 5 Asahi-cho, Senju, Adachi-ku, Tokyo, 120-8551, Japan
| | - Boris Martinac
- Molecular Cardiology and Biophysics Division, Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW, 2010, Australia
- St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Darlinghurst, NSW, 2010, Australia
| |
Collapse
|
15
|
Herrera N, Maksaev G, Haswell ES, Rees DC. Elucidating a role for the cytoplasmic domain in the Mycobacterium tuberculosis mechanosensitive channel of large conductance. Sci Rep 2018; 8:14566. [PMID: 30275500 PMCID: PMC6167328 DOI: 10.1038/s41598-018-32536-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 08/31/2018] [Indexed: 12/04/2022] Open
Abstract
Microbial survival in dynamic environments requires the ability to successfully respond to abrupt changes in osmolarity. The mechanosensitive channel of large conductance (MscL) is a ubiquitous channel that facilitates the survival of bacteria and archaea under severe osmotic downshock conditions by relieving excess turgor pressure in response to increased membrane tension. A prominent structural feature of MscL, the cytoplasmic C-terminal domain, has been suggested to influence channel assembly and function. In this report, we describe the X-ray crystal structure and electrophysiological properties of a C-terminal domain truncation of the Mycobacterium tuberculosis MscL (MtMscLΔC). A crystal structure of MtMscLΔC solubilized in the detergent n-dodecyl-β-D-maltopyranoside reveals the pentameric, closed state-like architecture for the membrane spanning region observed in the previously solved full-length MtMscL. Electrophysiological characterization demonstrates that MtMscLΔC retains mechanosensitivity, but with conductance and tension sensitivity more closely resembling full length EcMscL than MtMscL. This study establishes that the C-terminal domain of MtMscL is not required for oligomerization of the full-length channel, but rather influences the tension sensitivity and conductance properties of the channel. The collective picture that emerges from these data is that each MscL channel structure has characteristic features, highlighting the importance of studying multiple homologs.
Collapse
Affiliation(s)
- Nadia Herrera
- Division of Chemistry and Chemical Engineering 114-96, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA, 91125, USA.,Division of Infectious Diseases, Department of Medicine University of California, San Francisco, San Francisco, CA, 94143-0654, USA
| | - Grigory Maksaev
- Department of Biology, NSF Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, MO, 63130, USA.,Department of Cell Biology and Physiology, Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, Saint Louis, MO, 63110, USA
| | - Elizabeth S Haswell
- Department of Biology, NSF Center for Engineering Mechanobiology, Washington University in St. Louis, St. Louis, MO, 63130, USA
| | - Douglas C Rees
- Division of Chemistry and Chemical Engineering 114-96, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA, 91125, USA.
| |
Collapse
|
16
|
Nishino K, Morita Y, Takahashi S, Okumura M, Shiratani S, Umemura K, Narumi I, Kondo C, Ochiai R, Oshima T, Nishida H. Enlargement of Deinococcus grandis spheroplasts requires Mg 2+ or Ca 2. MICROBIOLOGY-SGM 2018; 164:1361-1371. [PMID: 30222092 DOI: 10.1099/mic.0.000716] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
While the cell wall strictly controls cell size and morphology in bacteria, spheroplasts lack cell walls and can become enlarged in growth medium under optimal conditions. Optimal conditions depend on the bacterial species. We frequently observed extreme enlargement of spheroplasts of the radiation-resistant bacterium Deinococcus grandis in Difco Marine Broth 2216, but not in TGY broth (a commonly used growth medium for Deinococcus). Thorough investigation of media components showed that the presence of Mg2+ or Ca2+ promoted extreme spheroplast enlargement, synthesizing the outer membrane. Our findings strongly suggest that Mg2+ or Ca2+ enlarges spheroplasts, which could change the lipid composition of the spheroplast membrane.
Collapse
Affiliation(s)
- Koki Nishino
- 1Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan
| | - Yusuke Morita
- 1Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan
| | - Sawako Takahashi
- 1Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan
| | - Mai Okumura
- 1Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan
| | - Shusaku Shiratani
- 1Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan
| | - Kosuke Umemura
- 1Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan
| | - Issay Narumi
- 2Radiation Microbiology Laboratory, Department of Life Sciences, Faculty of Life Sciences, Toyo University, 1-1-1 Izumino, Gunma 374-0193, Japan
| | - Chie Kondo
- 3Pharmaceuticals and Life Sciences Division, Shimadzu Techno-Research, Inc., 1 Nishinokyoushimoaicho, Nakagyouku, Kyoto 604-8436, Japan
| | - Ryosuke Ochiai
- 3Pharmaceuticals and Life Sciences Division, Shimadzu Techno-Research, Inc., 1 Nishinokyoushimoaicho, Nakagyouku, Kyoto 604-8436, Japan
| | - Taku Oshima
- 1Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan
| | - Hiromi Nishida
- 1Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan
| |
Collapse
|
17
|
Figueroa DM, Wade HM, Montales KP, Elmore DE, Darling LEO. Production and Visualization of Bacterial Spheroplasts and Protoplasts to Characterize Antimicrobial Peptide Localization. J Vis Exp 2018:57904. [PMID: 30148492 PMCID: PMC6126710 DOI: 10.3791/57904] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The use of confocal microscopy as a method to assess peptide localization patterns within bacteria is commonly inhibited by the resolution limits of conventional light microscopes. As the resolution for a given microscope cannot be easily enhanced, we present protocols to transform the small rod-shaped gram-negative Escherichia coli (E. coli) and gram-positive Bacillus megaterium (B. megaterium) into larger, easily imaged spherical forms called spheroplasts or protoplasts. This transformation allows observers to rapidly and clearly determine whether peptides lodge themselves into the bacterial membrane (i.e., membrane localizing) or cross the membrane to enter the cell (i.e., translocating). With this approach, we also present a systematic method to characterize peptides as membrane localizing or translocating. While this method can be used for a variety of membrane-active peptides and bacterial strains, we demonstrate the utility of this protocol by observing the interaction of Buforin II P11A (BF2 P11A), an antimicrobial peptide (AMP), with E. coli spheroplasts and B. megaterium protoplasts.
Collapse
Affiliation(s)
| | - Heidi M Wade
- Biochemistry Program, Wellesley College; Department of Chemistry, Wellesley College
| | | | - Donald E Elmore
- Biochemistry Program, Wellesley College; Department of Chemistry, Wellesley College;
| | - Louise E O Darling
- Biochemistry Program, Wellesley College; Department of Biological Sciences, Wellesley College;
| |
Collapse
|
18
|
O’Sullivan ME, Perez A, Lin R, Sajjadi A, Ricci AJ, Cheng AG. Towards the Prevention of Aminoglycoside-Related Hearing Loss. Front Cell Neurosci 2017; 11:325. [PMID: 29093664 PMCID: PMC5651232 DOI: 10.3389/fncel.2017.00325] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 09/30/2017] [Indexed: 01/08/2023] Open
Abstract
Aminoglycosides are potent antibiotics deployed worldwide despite their known side-effect of sensorineural hearing loss. The main etiology of this sensory deficit is death of inner ear sensory hair cells selectively triggered by aminoglycosides. For decades, research has sought to unravel the molecular events mediating sensory cell demise, emphasizing the roles of reactive oxygen species and their potentials as therapeutic targets. Studies in recent years have revealed candidate transport pathways including the mechanotransducer channel for drug entry into sensory cells. Once inside sensory cells, intracellular targets of aminoglycosides, such as the mitochondrial ribosomes, are beginning to be elucidated. Based on these results, less ototoxic aminoglycoside analogs are being generated and may serve as alternate antimicrobial agents. In this article, we review the latest findings on mechanisms of aminoglycoside entry into hair cells, their intracellular actions and potential therapeutic targets for preventing aminoglycoside ototoxicity.
Collapse
Affiliation(s)
- Mary E. O’Sullivan
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, United States
| | - Adela Perez
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, United States
| | - Randy Lin
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, United States
| | - Autefeh Sajjadi
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, United States
| | - Anthony J. Ricci
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, United States
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, United States
- *Correspondence: Anthony J. Ricci Alan G. Cheng
| | - Alan G. Cheng
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA, United States
- *Correspondence: Anthony J. Ricci Alan G. Cheng
| |
Collapse
|
19
|
Lee CP, Maksaev G, Jensen GS, Murcha MW, Wilson ME, Fricker M, Hell R, Haswell ES, Millar AH, Sweetlove LJ. MSL1 is a mechanosensitive ion channel that dissipates mitochondrial membrane potential and maintains redox homeostasis in mitochondria during abiotic stress. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2016; 88:809-825. [PMID: 27505616 PMCID: PMC5195915 DOI: 10.1111/tpj.13301] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 08/04/2016] [Accepted: 08/05/2016] [Indexed: 05/18/2023]
Abstract
Mitochondria must maintain tight control over the electrochemical gradient across their inner membrane to allow ATP synthesis while maintaining a redox-balanced electron transport chain and avoiding excessive reactive oxygen species production. However, there is a scarcity of knowledge about the ion transporters in the inner mitochondrial membrane that contribute to control of membrane potential. We show that loss of MSL1, a member of a family of mechanosensitive ion channels related to the bacterial channel MscS, leads to increased membrane potential of Arabidopsis mitochondria under specific bioenergetic states. We demonstrate that MSL1 localises to the inner mitochondrial membrane. When expressed in Escherichia coli, MSL1 forms a stretch-activated ion channel with a slight preference for anions and provides protection against hypo-osmotic shock. In contrast, loss of MSL1 in Arabidopsis did not prevent swelling of isolated mitochondria in hypo-osmotic conditions. Instead, our data suggest that ion transport by MSL1 leads to dissipation of mitochondrial membrane potential when it becomes too high. The importance of MSL1 function was demonstrated by the observation of a higher oxidation state of the mitochondrial glutathione pool in msl1-1 mutants under moderate heat- and heavy-metal-stress. Furthermore, we show that MSL1 function is not directly implicated in mitochondrial membrane potential pulsing, but is complementary and appears to be important under similar conditions.
Collapse
Affiliation(s)
- Chun Pong Lee
- ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Bayliss Building M316, 35 Stirling Highway, Crawley, 6009, Western Australia, Australia
| | - Grigory Maksaev
- Department of Biology, Washington University in Saint Louis, One Brookings Drive, Mailcode 1137, Saint Louis, MO, 63130, USA
| | - Gregory S Jensen
- Department of Biology, Washington University in Saint Louis, One Brookings Drive, Mailcode 1137, Saint Louis, MO, 63130, USA
| | - Monika W Murcha
- ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Bayliss Building M316, 35 Stirling Highway, Crawley, 6009, Western Australia, Australia
| | - Margaret E Wilson
- Department of Biology, Washington University in Saint Louis, One Brookings Drive, Mailcode 1137, Saint Louis, MO, 63130, USA
| | - Mark Fricker
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Ruediger Hell
- Department of Plant Molecular Biology, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 360, D-69120, Heidelberg, Germany
| | - Elizabeth S Haswell
- Department of Biology, Washington University in Saint Louis, One Brookings Drive, Mailcode 1137, Saint Louis, MO, 63130, USA
| | - A Harvey Millar
- ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Bayliss Building M316, 35 Stirling Highway, Crawley, 6009, Western Australia, Australia
| | - Lee J Sweetlove
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| |
Collapse
|
20
|
Bacterial Spheroplasts as a Model for Visualizing Membrane Translocation of Antimicrobial Peptides. Antimicrob Agents Chemother 2016; 60:6350-2. [PMID: 27431217 DOI: 10.1128/aac.01008-16] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 06/24/2016] [Indexed: 11/20/2022] Open
Abstract
Studies attempting to characterize the membrane translocation of antimicrobial and cell-penetrating peptides are frequently limited by the resolution of conventional light microscopy. This study shows that spheroplasts provide a valuable approach to overcome these limits. Spheroplasts produce less ambiguous images and allow for more systematic analyses of localization. Data collected with spheroplasts are consistent with studies using normal bacterial cells and imply that a particular peptide may not always follow the same mechanism of action.
Collapse
|
21
|
Perley-Robertson GE, Yadav AK, Winogrodzki JL, Stubbs KA, Mark BL, Vocadlo DJ. A Fluorescent Transport Assay Enables Studying AmpG Permeases Involved in Peptidoglycan Recycling and Antibiotic Resistance. ACS Chem Biol 2016; 11:2626-35. [PMID: 27442597 DOI: 10.1021/acschembio.6b00552] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Inducible AmpC β-lactamases deactivate a broad-spectrum of β-lactam antibiotics and afford antibiotic resistance in many Gram-negative bacteria. The disturbance of peptidoglycan recycling caused by β-lactam antibiotics leads to accumulation of GlcNAc-1,6-anhydroMurNAc-peptides, which are transported by AmpG to the cytoplasm where they are processed into AmpC inducers. AmpG transporters are poorly understood; however, their loss restores susceptibility toward β-lactam antibiotics, highlighting AmpG as a potential target for resistance-attenuating therapeutics. We prepare a GlcNAc-1,6-anhydroMurNAc-fluorophore conjugate and, using live E. coli spheroplasts, quantitatively analyze its transport by AmpG and inhibition of this process by a competing substrate. Further, we use this transport assay to evaluate the function of two AmpG homologues from Pseudomonas aeruginosa and show that P. aeruginosa AmpG (Pa-AmpG) but not AmpP (Pa-AmpP) transports this probe substrate. We corroborate these results by AmpC induction assays with Pa-AmpG and Pa-AmpP. This fluorescent AmpG probe and spheroplast-based transport assay will enable improved understanding of PG recycling and of permeases from the major facilitator superfamily of transport proteins and may aid in identification of AmpG antagonists that combat AmpC-mediated resistance toward β-lactam antibiotics.
Collapse
Affiliation(s)
| | - Anuj K. Yadav
- Department
of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| | - Judith L. Winogrodzki
- Department
of Microbiology, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - Keith A. Stubbs
- School
of Chemistry and Biochemistry, University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Brian L. Mark
- Department
of Microbiology, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada
| | - David J. Vocadlo
- Department
of Chemistry, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
| |
Collapse
|
22
|
Takahashi S, Nishida H. Quantitative analysis of chromosomal and plasmid DNA during the growth of spheroplasts of Escherichia coli. J GEN APPL MICROBIOL 2016; 61:262-5. [PMID: 26782657 DOI: 10.2323/jgam.61.262] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We generated spheroplasts from Escherichia coli carrying a broad-host-range plasmid. In the presence of penicillin, the spheroplasts did not divide but grew and enlarged in marine broth, whereas, in the absence of penicillin, they elongated. We quantified cellular DNA at different time points by using real-time quantitative PCR. Both chromosomal and plasmid DNA had replicated during spheroplast growth not only in the absence but also in the presence of penicillin. Thus, plasmid DNA and chromosomal DNA replication might be regulated synchronously during the growth of spheroplasts.
Collapse
Affiliation(s)
- Sawako Takahashi
- Biotechnology Research Center and Department of Biotechnology, Toyama Prefectural University
| | | |
Collapse
|
23
|
The impact of the C-terminal domain on the gating properties of MscCG from Corynebacterium glutamicum. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:130-8. [PMID: 26494188 DOI: 10.1016/j.bbamem.2015.10.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 10/14/2015] [Accepted: 10/17/2015] [Indexed: 11/20/2022]
Abstract
The mechanosensitive (MS) channel MscCG from the soil bacterium Corynebacterium glutamicum functions as a major glutamate exporter. MscCG belongs to a subfamily of the bacterial MscS-like channels, which play an important role in osmoregulation. To understand the structural and functional features of MscCG, we investigated the role of the carboxyl-terminal domain, whose relevance for the channel gating has been unknown. The chimeric channel MscS-(C-MscCG), which is a fusion protein between the carboxyl terminal domain of MscCG and the MscS channel, was examined by the patch clamp technique. We found that the chimeric channel exhibited MS channel activity in Escherichia coli spheroplasts characterized by a lower activation threshold and slow closing compared to MscS. The chimeric channel MscS-(C-MscCG) was successfully reconstituted into azolectin liposomes and exhibited gating hysteresis in a voltage-dependent manner, especially at high pipette voltages. Moreover, the channel remained open after releasing pipette pressure at membrane potentials physiologically relevant for C. glutamicum. This contribution to the gating hysteresis of the C-terminal domain of MscCG confers to the channel gating properties highly suitable for release of intracellular solutes.
Collapse
|
24
|
Masi E, Ciszak M, Santopolo L, Frascella A, Giovannetti L, Marchi E, Viti C, Mancuso S. Electrical spiking in bacterial biofilms. J R Soc Interface 2015; 12:20141036. [PMID: 25392401 DOI: 10.1098/rsif.2014.1036] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
In nature, biofilms are the most common form of bacterial growth. In biofilms, bacteria display coordinated behaviour to perform specific functions. Here, we investigated electrical signalling as a possible driver in biofilm sociobiology. Using a multi-electrode array system that enables high spatio-temporal resolution, we studied the electrical activity in two biofilm-forming strains and one non-biofilm-forming strain. The action potential rates monitored during biofilm-forming bacterial growth exhibited a one-peak maximum with a long tail, corresponding to the highest biofilm development. This peak was not observed for the non-biofilm-forming strain, demonstrating that the intensity of the electrical activity was not linearly related to the bacterial density, but was instead correlated with biofilm formation. Results obtained indicate that the analysis of the spatio-temporal electrical activity of bacteria during biofilm formation can open a new frontier in the study of the emergence of collective microbial behaviour.
Collapse
Affiliation(s)
- Elisa Masi
- DISPAA-Department of Agrifood and Environmental Science, University of Florence, Florence, Italy
| | - Marzena Ciszak
- DISPAA-Department of Agrifood and Environmental Science, University of Florence, Florence, Italy CNR-Istituto Nazionale di Ottica, Florence, Italy
| | - Luisa Santopolo
- DISPAA-Department of Agrifood and Environmental Science, University of Florence, Florence, Italy
| | - Arcangela Frascella
- DISPAA-Department of Agrifood and Environmental Science, University of Florence, Florence, Italy
| | - Luciana Giovannetti
- DISPAA-Department of Agrifood and Environmental Science, University of Florence, Florence, Italy
| | - Emmanuela Marchi
- DISPAA-Department of Agrifood and Environmental Science, University of Florence, Florence, Italy
| | - Carlo Viti
- DISPAA-Department of Agrifood and Environmental Science, University of Florence, Florence, Italy
| | - Stefano Mancuso
- DISPAA-Department of Agrifood and Environmental Science, University of Florence, Florence, Italy
| |
Collapse
|
25
|
Martinac B, Nomura T, Chi G, Petrov E, Rohde PR, Battle AR, Foo A, Constantine M, Rothnagel R, Carne S, Deplazes E, Cornell B, Cranfield CG, Hankamer B, Landsberg MJ. Bacterial mechanosensitive channels: models for studying mechanosensory transduction. Antioxid Redox Signal 2014; 20:952-69. [PMID: 23834368 DOI: 10.1089/ars.2013.5471] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
SIGNIFICANCE Sensations of touch and hearing are manifestations of mechanical contact and air pressure acting on touch receptors and hair cells of the inner ear, respectively. In bacteria, osmotic pressure exerts a significant mechanical force on their cellular membrane. Bacteria have evolved mechanosensitive (MS) channels to cope with excessive turgor pressure resulting from a hypo-osmotic shock. MS channel opening allows the expulsion of osmolytes and water, thereby restoring normal cellular turgor and preventing cell lysis. RECENT ADVANCES As biological force-sensing systems, MS channels have been identified as the best examples of membrane proteins coupling molecular dynamics to cellular mechanics. The bacterial MS channel of large conductance (MscL) and MS channel of small conductance (MscS) have been subjected to extensive biophysical, biochemical, genetic, and structural analyses. These studies have established MscL and MscS as model systems for mechanosensory transduction. CRITICAL ISSUES In recent years, MS ion channels in mammalian cells have moved into focus of mechanotransduction research, accompanied by an increased awareness of the role they may play in the pathophysiology of diseases, including cardiac hypertrophy, muscular dystrophy, or Xerocytosis. FUTURE DIRECTIONS A recent exciting development includes the molecular identification of Piezo proteins, which function as nonselective cation channels in mechanosensory transduction associated with senses of touch and pain. Since research on Piezo channels is very young, applying lessons learned from studies of bacterial MS channels to establishing the mechanism by which the Piezo channels are mechanically activated remains one of the future challenges toward a better understanding of the role that MS channels play in mechanobiology.
Collapse
Affiliation(s)
- Boris Martinac
- 1 Molecular Cardiology and Biophysics Division/Mechanosensory Biophysics Laboratory, Victor Chang Cardiac Research Institute , Darlinghurst, Australia
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|