1
|
Zhang Z, Chen M, Zhan W, Chen Y, Wang T, Chen Z, Fu Y, Zhao G, Mao D, Ruan J, Yuan FL. Acid-sensing ion channel 1a modulation of apoptosis in acidosis-related diseases: implications for therapeutic intervention. Cell Death Discov 2023; 9:330. [PMID: 37666823 PMCID: PMC10477349 DOI: 10.1038/s41420-023-01624-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 07/28/2023] [Accepted: 08/22/2023] [Indexed: 09/06/2023] Open
Abstract
Acid-sensing ion channel 1a (ASIC1a), a prominent member of the acid-sensing ion channel (ASIC) superfamily activated by extracellular protons, is ubiquitously expressed throughout the human body, including the nervous system and peripheral tissues. Excessive accumulation of Ca2+ ions via ASIC1a activation may occur in the acidified microenvironment of blood or local tissues. ASIC1a-mediated Ca2+‑induced apoptosis has been implicated in numerous pathologies, including neurological disorders, cancer, and rheumatoid arthritis. This review summarizes the role of ASIC1a in the modulation of apoptosis via various signaling pathways across different disease states to provide insights for future studies on the underlying mechanisms and development of therapeutic strategies.
Collapse
Affiliation(s)
- Zhenyu Zhang
- Institute of Integrated Chinese and Western Medicine, Affiliated to Jiangnan University, Wuxi, Jiangsu, 214041, China
| | - Minnan Chen
- Nantong First People's Hospital, Nantong, 226001, China
| | - Wenjing Zhan
- The Key Laboratory of Anti-Inflammatory and Immune Medicine, Anhui Medical University, Hefei, 230032, China
| | - Yuechun Chen
- Institute of Integrated Chinese and Western Medicine, Affiliated to Jiangnan University, Wuxi, Jiangsu, 214041, China
| | - Tongtong Wang
- Institute of Integrated Chinese and Western Medicine, Affiliated to Jiangnan University, Wuxi, Jiangsu, 214041, China
| | - Zhonghua Chen
- Institute of Integrated Chinese and Western Medicine, Affiliated to Jiangnan University, Wuxi, Jiangsu, 214041, China
| | - Yifei Fu
- Institute of Integrated Chinese and Western Medicine, Affiliated to Jiangnan University, Wuxi, Jiangsu, 214041, China
| | - Gang Zhao
- Orthopaedic Institute, Wuxi 9th People's Hospital Affiliated to Soochow University, Wuxi, 214062, China
| | - Dong Mao
- Orthopaedic Institute, Wuxi 9th People's Hospital Affiliated to Soochow University, Wuxi, 214062, China.
| | - Jingjing Ruan
- Nantong First People's Hospital, Nantong, 226001, China.
- Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, 230022, People's Republic of China.
| | - Feng-Lai Yuan
- Institute of Integrated Chinese and Western Medicine, Affiliated to Jiangnan University, Wuxi, Jiangsu, 214041, China.
| |
Collapse
|
2
|
Mayse LA, Movileanu L. Gating of β-Barrel Protein Pores, Porins, and Channels: An Old Problem with New Facets. Int J Mol Sci 2023; 24:12095. [PMID: 37569469 PMCID: PMC10418385 DOI: 10.3390/ijms241512095] [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: 07/03/2023] [Revised: 07/23/2023] [Accepted: 07/25/2023] [Indexed: 08/13/2023] Open
Abstract
β barrels are ubiquitous proteins in the outer membranes of mitochondria, chloroplasts, and Gram-negative bacteria. These transmembrane proteins (TMPs) execute a wide variety of tasks. For example, they can serve as transporters, receptors, membrane-bound enzymes, as well as adhesion, structural, and signaling elements. In addition, multimeric β barrels are common structural scaffolds among many pore-forming toxins. Significant progress has been made in understanding the functional, structural, biochemical, and biophysical features of these robust and versatile proteins. One frequently encountered fundamental trait of all β barrels is their voltage-dependent gating. This process consists of reversible or permanent conformational transitions between a large-conductance, highly permeable open state and a low-conductance, solute-restrictive closed state. Several intrinsic molecular mechanisms and environmental factors modulate this universal property of β barrels. This review article outlines the typical signatures of voltage-dependent gating. Moreover, we discuss recent developments leading to a better qualitative understanding of the closure dynamics of these TMPs.
Collapse
Affiliation(s)
- Lauren A. Mayse
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244, USA;
- Department of Biomedical and Chemical Engineering, Syracuse University, 223 Link Hall, Syracuse, NY 13244, USA
| | - Liviu Movileanu
- Department of Physics, Syracuse University, 201 Physics Building, Syracuse, NY 13244, USA;
- Department of Biomedical and Chemical Engineering, Syracuse University, 223 Link Hall, Syracuse, NY 13244, USA
- The BioInspired Institute, Syracuse University, Syracuse, NY 13244, USA
| |
Collapse
|
3
|
Cheng Q, Chen A, Du Q, Liao Q, Shuai Z, Chen C, Yang X, Hu Y, Zhao J, Liu S, Wen GR, An J, Jing H, Tuo B, Xie R, Xu J. Novel insights into ion channels in cancer stem cells (Review). Int J Oncol 2018; 53:1435-1441. [PMID: 30066845 DOI: 10.3892/ijo.2018.4500] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 06/28/2018] [Indexed: 11/06/2022] Open
Abstract
Cancer stem cells (CSCs) are immortal cells in tumor tissues that have been proposed as the driving force of tumorigenesis and tumor invasion. Previously, ion channels were revealed to contribute to cancer cell proliferation, migration and apoptosis. Recent studies have demonstrated that ion channels are present in various CSCs; however, the functions of ion channels and their mechanisms in CSCs remain unknown. The present review aimed to focus on the roles of ion channels in the regulation of CSC behavior and the CSC-like properties of cancer cells. Evaluation of the relationship between ion channels and CSCs is critically important for understanding malignancy.
Collapse
Affiliation(s)
- Qijiao Cheng
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Anhai Chen
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Qian Du
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Qiushi Liao
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Zhangli Shuai
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Changmei Chen
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Xinrong Yang
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Yaxia Hu
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Ju Zhao
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Songpo Liu
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Guo Rong Wen
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Jiaxin An
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Hai Jing
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Biguang Tuo
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Rui Xie
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| | - Jingyu Xu
- Department of Gastroenterology, Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou 563003, P.R. China
| |
Collapse
|
4
|
Abstract
Exciting new technological developments have pushed the boundaries of structural biology, and have enabled studies of biological macromolecules and assemblies that would have been unthinkable not long ago. Yet, the enhanced capabilities of structural biologists to pry into the complex molecular world have also placed new demands on the abilities of protein engineers to reproduce this complexity into the test tube. With this challenge in mind, we review the contents of the modern molecular engineering toolbox that allow the manipulation of proteins in a site-specific and chemically well-defined fashion. Thus, we cover concepts related to the modification of cysteines and other natural amino acids, native chemical ligation, intein and sortase-based approaches, amber suppression, as well as chemical and enzymatic bio-conjugation strategies. We also describe how these tools can be used to aid methodology development in X-ray crystallography, nuclear magnetic resonance, cryo-electron microscopy and in the studies of dynamic interactions. It is our hope that this monograph will inspire structural biologists and protein engineers alike to apply these tools to novel systems, and to enhance and broaden their scope to meet the outstanding challenges in understanding the molecular basis of cellular processes and disease.
Collapse
|
5
|
Kahlstatt J, Reiß P, Halbritter T, Essen LO, Koert U, Heckel A. A light-triggered transmembrane porin. Chem Commun (Camb) 2018; 54:9623-9626. [DOI: 10.1039/c8cc05221b] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Porins are ideal model systems for channel engineering. Here, we present a photocaged diethylaminocoumarin (DEACM) hybrid of the transmembrane porin OmpG.
Collapse
Affiliation(s)
- J. Kahlstatt
- Goethe University Frankfurt
- Institute for Organic Chemistry and Chemical Biology
- 60438 Frankfurt am Main
- Germany
| | - P. Reiß
- Philipps-University Marburg
- Department of Chemistry
- 35032 Marburg
- Germany
| | - T. Halbritter
- Goethe University Frankfurt
- Institute for Organic Chemistry and Chemical Biology
- 60438 Frankfurt am Main
- Germany
| | - L.-O. Essen
- Philipps-University Marburg
- Department of Chemistry
- 35032 Marburg
- Germany
- Philipps-University Marburg
| | - U. Koert
- Philipps-University Marburg
- Department of Chemistry
- 35032 Marburg
- Germany
| | - A. Heckel
- Goethe University Frankfurt
- Institute for Organic Chemistry and Chemical Biology
- 60438 Frankfurt am Main
- Germany
| |
Collapse
|
6
|
Chandramouli B, Di Maio D, Mancini G, Brancato G. Introducing an artificial photo-switch into a biological pore: A model study of an engineered α-hemolysin. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:689-97. [DOI: 10.1016/j.bbamem.2015.12.030] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Revised: 12/06/2015] [Accepted: 12/24/2015] [Indexed: 12/21/2022]
|
7
|
Einfalt T, Goers R, Dinu IA, Najer A, Spulber M, Onaca-Fischer O, Palivan CG. Stimuli-Triggered Activity of Nanoreactors by Biomimetic Engineering Polymer Membranes. NANO LETTERS 2015; 15:7596-7603. [PMID: 26428033 DOI: 10.1021/acs.nanolett.5b03386] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The development of advanced stimuli-responsive systems for medicine, catalysis, or technology requires compartmentalized reaction spaces with triggered activity. Only very few stimuli-responsive systems preserve the compartment architecture, and none allows a triggered activity in situ. We present here a biomimetic strategy to molecular transmembrane transport by engineering synthetic membranes equipped with channel proteins so that they are stimuli-responsive. Nanoreactors with triggered activity were designed by simultaneously encapsulating an enzyme inside polymer compartments, and inserting protein "gates" in the membrane. The outer membrane protein F (OmpF) porin was chemically modified with a pH-responsive molecular cap to serve as "gate" producing pH-driven molecular flow through the membrane and control the in situ enzymatic activity. This strategy provides complex reaction spaces necessary in "smart" medicine and for biomimetic engineering of artificial cells.
Collapse
Affiliation(s)
- Tomaž Einfalt
- Department of Chemistry, University of Basel , Klingelbergstrasse 80 CH-4056 Basel, Switzerland
| | - Roland Goers
- Department of Chemistry, University of Basel , Klingelbergstrasse 80 CH-4056 Basel, Switzerland
- Department of Biosystems Science and Engineering, ETH Zürich , CH-4058 Basel, Switzerland
| | - Ionel Adrian Dinu
- Department of Chemistry, University of Basel , Klingelbergstrasse 80 CH-4056 Basel, Switzerland
| | - Adrian Najer
- Department of Chemistry, University of Basel , Klingelbergstrasse 80 CH-4056 Basel, Switzerland
| | - Mariana Spulber
- Department of Chemistry, University of Basel , Klingelbergstrasse 80 CH-4056 Basel, Switzerland
| | - Ozana Onaca-Fischer
- Department of Chemistry, University of Basel , Klingelbergstrasse 80 CH-4056 Basel, Switzerland
| | - Cornelia G Palivan
- Department of Chemistry, University of Basel , Klingelbergstrasse 80 CH-4056 Basel, Switzerland
| |
Collapse
|
8
|
Volkov V. Salinity tolerance in plants. Quantitative approach to ion transport starting from halophytes and stepping to genetic and protein engineering for manipulating ion fluxes. FRONTIERS IN PLANT SCIENCE 2015; 6:873. [PMID: 26579140 PMCID: PMC4621421 DOI: 10.3389/fpls.2015.00873] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 10/01/2015] [Indexed: 05/18/2023]
Abstract
Ion transport is the fundamental factor determining salinity tolerance in plants. The Review starts from differences in ion transport between salt tolerant halophytes and salt-sensitive plants with an emphasis on transport of potassium and sodium via plasma membranes. The comparison provides introductory information for increasing salinity tolerance. Effects of salt stress on ion transport properties of membranes show huge opportunities for manipulating ion fluxes. Further steps require knowledge about mechanisms of ion transport and individual genes of ion transport proteins. Initially, the Review describes methods to measure ion fluxes, the independent set of techniques ensures robust and reliable basement for quantitative approach. The Review briefly summarizes current data concerning Na(+) and K(+) concentrations in cells, refers to primary thermodynamics of ion transport and gives special attention to individual ion channels and transporters. Simplified scheme of a plant cell with known transport systems at the plasma membrane and tonoplast helps to imagine the complexity of ion transport and allows choosing specific transporters for modulating ion transport. The complexity is enhanced by the influence of cell size and cell wall on ion transport. Special attention is given to ion transporters and to potassium and sodium transport by HKT, HAK, NHX, and SOS1 proteins. Comparison between non-selective cation channels and ion transporters reveals potential importance of ion transporters and the balance between the two pathways of ion transport. Further on the Review describes in detail several successful attempts to overexpress or knockout ion transporters for changing salinity tolerance. Future perspectives are questioned with more attention given to promising candidate ion channels and transporters for altered expression. Potential direction of increasing salinity tolerance by modifying ion channels and transporters using single point mutations is discussed and questioned. An alternative approach from synthetic biology is to create new regulation networks using novel transport proteins with desired properties for transforming agricultural crops. The approach had not been widely used earlier; it leads also to theoretical and pure scientific aspects of protein chemistry, structure-function relations of membrane proteins, systems biology and physiology of stress and ion homeostasis. Summarizing, several potential ways are aimed at required increase in salinity tolerance of plants of interest.
Collapse
Affiliation(s)
- Vadim Volkov
- Faculty of Life Sciences and Computing, London Metropolitan UniversityLondon, UK
| |
Collapse
|
9
|
Semisynthetic protein nanoreactor for single-molecule chemistry. Proc Natl Acad Sci U S A 2015; 112:13768-73. [PMID: 26504203 DOI: 10.1073/pnas.1510565112] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The covalent chemistry of individual reactants bound within a protein pore can be monitored by observing the ionic current flow through the pore, which acts as a nanoreactor responding to bond-making and bond-breaking events. In the present work, we incorporated an unnatural amino acid into the α-hemolysin (αHL) pore by using solid-phase peptide synthesis to make the central segment of the polypeptide chain, which forms the transmembrane β-barrel of the assembled heptamer. The full-length αHL monomer was obtained by native chemical ligation of the central synthetic peptide to flanking recombinant polypeptides. αHL pores with one semisynthetic subunit were then used as nanoreactors for single-molecule chemistry. By introducing an amino acid with a terminal alkyne group, we were able to visualize click chemistry at the single-molecule level, which revealed a long-lived (4.5-s) reaction intermediate. Additional side chains might be introduced in a similar fashion, thereby greatly expanding the range of single-molecule covalent chemistry that can be investigated by the nanoreactor approach.
Collapse
|
10
|
Pittel I, Alper N, Yonai S, Basch S, Blum L, Bachur A, Paas Y. Computational and biochemical design of a nanopore cleavable by a cancer-secreted enzyme. Chembiochem 2015; 16:463-71. [PMID: 25581099 DOI: 10.1002/cbic.201402378] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Indexed: 11/11/2022]
Abstract
Many proteinaceous macromolecules selectively transport substrates across lipid bilayers and effectively serve as gated nanopores. Here, we engineered cleavage-site motifs for human matrix metalloprotease 7 (MMP-7) into the extracellular and pore-constricting loops of OprD, a bacterial substrate-specific transmembrane channel. Concurrent removal of two extracellular loops allowed MMP-7 to access and hydrolyze a cleavage-site motif engineered within the pore's major constricting loop, in both membrane-incorporated and detergent-solubilized OprDs. Import of antibiotics by the engineered OprDs into living bacteria pointed to their proper folding and integration in biological membranes. Purified engineered OprDs were also found to be properly folded in detergent. Hence, this study demonstrates the design of nanopores with a constriction cleavable by tumor-secreted enzymes (like MMP-7) for their potential incorporation in lipid-based nanoparticles to accelerate drug release at the tumor site.
Collapse
Affiliation(s)
- Ilya Pittel
- Laboratory of Ion Channels, The Mina and Everard Goodman Faculty of Life Sciences, The Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat Gan 52900 (Israel)
| | | | | | | | | | | | | |
Collapse
|
11
|
Grosse W, Psakis G, Mertins B, Reiss P, Windisch D, Brademann F, Bürck J, Ulrich A, Koert U, Essen LO. Structure-based engineering of a minimal porin reveals loop-independent channel closure. Biochemistry 2014; 53:4826-38. [PMID: 24988371 DOI: 10.1021/bi500660q] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Porins, like outer membrane protein G (OmpG) of Escherichia coli, are ideal templates among ion channels for protein and chemical engineering because of their robustness and simple architecture. OmpG shows fast transitions between open and closed states, which were attributed to loop 6 (L6). As flickering limits single-channel-based applications, we pruned L6 by either 8 or 12 amino acids. While the open probabilities of both L6 variants resemble that of native OmpG, their gating frequencies were reduced by 63 and 81%, respectively. Using the 3.2 Å structure of the shorter L6 variant in the open state, we engineered a minimal porin (220 amino acids), where all remaining extramembranous loops were truncated. Unexpectedly, this minimized porin still exhibited gating, but it was 5-fold less frequent than in OmpG. The residual gating of the minimal pore is hence independent of L6 rearrangements and involves narrowing of the ion conductance pathway most probably driven by global stretching-flexing deformations of the membrane-embedded β-barrel.
Collapse
Affiliation(s)
- Wolfgang Grosse
- Department of Chemistry, Philipps-University Marburg , Hans-Meerwein-Straße, 35032 Marburg, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Affiliation(s)
- Shigehiko Hayashi
- Department of Chemistry, Graduate School of Science, Kyoto University, Japan
| |
Collapse
|
13
|
Yu Z, Li J, Zhu J, Zhu M, Jiang F, Zhang J, Li Z, Zhong M, Kaye JB, Du J, Shen B. A synthetic transmembrane segment derived from TRPV4 channel self-assembles into potassium-like channels to regulate vascular smooth muscle cell membrane potential. J Mater Chem B 2014; 2:3809-3818. [DOI: 10.1039/c3tb21645d] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A synthetic K+-like channel mediates K+outward flow to regulate vascular smooth muscle cell membrane potential, blood vessel tone and blood pressure.
Collapse
Affiliation(s)
- Zhiqiang Yu
- Center for BioEnergetics
- The Biodesign Institute
- Department of Chemistry and Biochemistry
- Arizona State University
- Tempe, USA
| | - Jie Li
- Department of Physiology
- Anhui Medical University
- Hefei, China
| | - Jinhang Zhu
- Department of Physiology
- Anhui Medical University
- Hefei, China
| | - Min Zhu
- Hefei Institutes of Science
- Chinese Academy of Sciences
- Hefei, China
| | - Feifei Jiang
- Department of Physiology
- Anhui Medical University
- Hefei, China
| | - Jin Zhang
- Department of Physiology
- Anhui Medical University
- Hefei, China
| | - Zhongwen Li
- Department of Physiology
- Anhui Medical University
- Hefei, China
| | - Mingkui Zhong
- Department of Physiology
- Anhui Medical University
- Hefei, China
| | - Justin Boy Kaye
- Center for BioEnergetics
- The Biodesign Institute
- Department of Chemistry and Biochemistry
- Arizona State University
- Tempe, USA
| | - Juan Du
- Department of Physiology
- Anhui Medical University
- Hefei, China
| | - Bing Shen
- Department of Physiology
- Anhui Medical University
- Hefei, China
| |
Collapse
|
14
|
Abstract
Ion channels provide a conductance pathway for the passive transport of ions across membranes. These functional molecules perform key tasks in biological systems such as neuronal signaling, muscular control, and sensing. Recently, function-oriented synthesis researchers began to focus on ion channels with the goal of modifying the function of existing ion channels (ion selectivity, gating) or creating new channels with novel functions. Both approaches, ion channel engineering and de novo design, have involved synthetic chemists, biochemists, structural biologists, and neurochemists. Researchers characterize the function of ion channels by measuring their conductance in samples of biological membranes (patch clamp) or artificial membranes (planar lipid bilayers). At the single molecule level, these measurements require special attention to the purity of the sample, a challenge that synthetic chemists should be aware of. Ideally, researchers study the function of channels while also acquiring structural data (X-ray, NMR) to understand and predict how synthetic modifications alter channel function. Long-term oriented researchers would like to apply synthetic ion channels to single molecule sensing and to implantat these synthetic systems in living organisms as tools or for the treatment of channelopathies. In this Account, we discuss our own work on synthetic ion channels and explain the shift of our research focus from a de novo design of oligo-THFs and oligo-THF-amino acids to ion channel engineering. We introduce details about two biological lead structures for ion channel engineering: the gramicidin β(6,3) helix as an example of a channel with a narrow ion conductance pathway and the outer membrane porins (OmpF, OmpG) with their open β-barrel structure. The increase and the reversal of ion selectivity of these systems and the hydrophobic match/mismatch of the channel with the phospholipid bilayer are of particular interest. For engineering ion channels, we need to supplement the single-point attachment of a synthetic modulator with the synthesis of a more challenging two-point attachment. The successful function-oriented synthesis of ion channels will require interdisciplinary efforts that include new electrophysiology techniques, efficient synthesis (peptide/protein/organic), and good structural analysis.
Collapse
Affiliation(s)
- Philipp Reiß
- Fachbereich Chemie, Philipps-Universität Marburg, Hans Meerwein Strasse, 35032 Marburg, Germany
| | - Ulrich Koert
- Fachbereich Chemie, Philipps-Universität Marburg, Hans Meerwein Strasse, 35032 Marburg, Germany
| |
Collapse
|
15
|
Otis F, Auger M, Voyer N. Exploiting peptide nanostructures to construct functional artificial ion channels. Acc Chem Res 2013; 46:2934-43. [PMID: 23627544 DOI: 10.1021/ar400044k] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Natural ion channel proteins possess remarkable properties that researchers could exploit to develop nanochemotherapeutics and diagnostic devices. Unfortunately, the poor stability, limited availability, and complexity of these structures have precluded their use in practical devices. One solution to these limitations is to develop simpler molecular systems through chemical synthesis that mimic the salient properties of artificial ion channels. Inspired by natural channel proteins, our group has developed a family of peptide nanostructures thatcreate channels for ions by aligning crown ethers on top of each other when they adopt an α-helical conformation. Advantages to this crown ether/peptide framework approach include the ease of synthesis, the predictability of their conformations, and the ability to fine-tune and engineer their properties. We have synthesized these structures using solid phase methods from artificial crown ether amino acids made from L-DOPA. Circular dichroism and FTIR spectroscopy studies in different media confirmed that the nanostructures adopt the predicted α-helical conformation. Fluorescence studies verified the crown ether stacking arrangement. We confirmed the channel activity by single-channel measurements using a modified patch-clamp technique, planar lipid bilayer (PLB) assays, and various vesicle experiments. From the results, we estimate that a 6 Å distance between two relays is ideal for sodium cation transport, but relatively efficient ion transport can still occur with an 11 Å distance between two crown ethers. Biophysical studies demonstrated that peptide channels operate as monomers in an equilibrium between adsorption at the surface and an active, transmembrane orientation. Toward practical applications of these systems, we have prepared channel analogs that bear a biotin moiety, and we have used them as nanotransducers successfully to detect avidin. Analogs of channel peptide nanostructures showed cytotoxicity against breast and leukemia cancer cells. Overall, we have prepared well-defined nanostructures with designed properties, demonstrated their transport abilities, and described their mechanism of action. We have also illustrated the advantages and the versatility of polypeptides for the construction of functional nanoscale artificial ion channels.
Collapse
Affiliation(s)
- François Otis
- Département de Chimie and PROTEO, Faculté des Sciences et de Génie, Université Laval, Pavillon Alexandre-Vachon, 1045 avenue de la Médecine, Québec, Québec G1V 0A6, Canada
| | - Michèle Auger
- Département de Chimie and PROTEO, Faculté des Sciences et de Génie, Université Laval, Pavillon Alexandre-Vachon, 1045 avenue de la Médecine, Québec, Québec G1V 0A6, Canada
| | - Normand Voyer
- Département de Chimie and PROTEO, Faculté des Sciences et de Génie, Université Laval, Pavillon Alexandre-Vachon, 1045 avenue de la Médecine, Québec, Québec G1V 0A6, Canada
| |
Collapse
|
16
|
Balleza D. Mechanical properties of lipid bilayers and regulation of mechanosensitive function: from biological to biomimetic channels. Channels (Austin) 2012; 6:220-33. [PMID: 22790280 DOI: 10.4161/chan.21085] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Material properties of lipid bilayers, including thickness, intrinsic curvature and compressibility regulate the function of mechanosensitive (MS) channels. This regulation is dependent on phospholipid composition, lateral packing and organization within the membrane. Therefore, a more complete framework to understand the functioning of MS channels requires insights into bilayer structure, thermodynamics and phospholipid structure, as well as lipid-protein interactions. Phospholipids and MS channels interact with each other mainly through electrostatic forces and hydrophobic matching, which are also crucial for antimicrobial peptides. They are excellent models for studying the formation and stabilization of membrane pores. Importantly, they perform equivalent responses as MS channels: (1) tilting in response to tension and (2) dissipation of osmotic gradients. Lessons learned from pore forming peptides could enrich our knowledge of mechanisms of action and evolution of these channels. Here, the current state of the art is presented and general principles of membrane regulation of mechanosensitive function are discussed.
Collapse
Affiliation(s)
- Daniel Balleza
- Unidad de Biofísica, CSIC, UPV/EHU, Universidad del País Vasco, Leioa, Spain.
| |
Collapse
|
17
|
Hsieh D, Davis A, Nanda V. A knowledge-based potential highlights unique features of membrane α-helical and β-barrel protein insertion and folding. Protein Sci 2011; 21:50-62. [PMID: 22031179 DOI: 10.1002/pro.758] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 09/06/2011] [Accepted: 10/19/2011] [Indexed: 12/16/2022]
Abstract
Outer membrane β-barrel proteins differ from α-helical inner membrane proteins in lipid environment, secondary structure, and the proposed processes of folding and insertion. It is reasonable to expect that outer membrane proteins may contain primary sequence information specific for their folding and insertion behavior. In previous work, a depth-dependent insertion potential, E(z) , was derived for α-helical inner membrane proteins. We have generated an equivalent potential for TM β-barrel proteins. The similarities and differences between these two potentials provide insight into unique aspects of the folding and insertion of β-barrel membrane proteins. This potential can predict orientation within the membrane and identify functional residues involved in intermolecular interactions.
Collapse
Affiliation(s)
- Daniel Hsieh
- BioMaPS Institute and the Graduate Program in Computational Biology and Molecular Biophysics, Rutgers University, Piscataway, NJ 08854, USA
| | | | | |
Collapse
|