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Shoyer TC, Collins KL, Ham TR, Blanchard AT, Malavade JN, Johns BA, West JL, Hoffman BD. Detection of fluorescent protein mechanical switching in cellulo. CELL REPORTS METHODS 2024; 4:100815. [PMID: 38986612 DOI: 10.1016/j.crmeth.2024.100815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2024] [Revised: 05/03/2024] [Accepted: 06/17/2024] [Indexed: 07/12/2024]
Abstract
The ability of cells to sense and respond to mechanical forces is critical in many physiological and pathological processes. However, determining the mechanisms by which forces affect protein function inside cells remains challenging. Motivated by in vitro demonstrations of fluorescent proteins (FPs) undergoing reversible mechanical switching of fluorescence, we investigated whether force-sensitive changes in FP function could be visualized in cells. Guided by a computational model of FP mechanical switching, we develop a formalism for its detection in Förster resonance energy transfer (FRET)-based biosensors and demonstrate its occurrence in cellulo within a synthetic actin crosslinker and the mechanical linker protein vinculin. We find that in cellulo mechanical switching is reversible and altered by manipulation of cell force generation, external stiffness, and force-sensitive bond dynamics of the biosensor. This work describes a framework for assessing FP mechanical stability and provides a means of probing force-sensitive protein function inside cells.
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Affiliation(s)
- T Curtis Shoyer
- Department of Biomedical Engineering, Duke University, Durham NC 27708, USA
| | - Kasie L Collins
- Department of Chemistry, Duke University, Durham NC 27708, USA
| | - Trevor R Ham
- Department of Biomedical Engineering, Duke University, Durham NC 27708, USA
| | - Aaron T Blanchard
- Department of Biomedical Engineering, Duke University, Durham NC 27708, USA
| | - Juilee N Malavade
- Department of Biomedical Engineering, Duke University, Durham NC 27708, USA
| | - Benjamin A Johns
- Department of Biomedical Engineering, Duke University, Durham NC 27708, USA
| | - Jennifer L West
- Department of Biomedical Engineering, Duke University, Durham NC 27708, USA; Department of Biomedical Engineering, University of Virginia, Charlottesville, VA 22908, USA
| | - Brenton D Hoffman
- Department of Biomedical Engineering, Duke University, Durham NC 27708, USA.
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2
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Shoyer TC, Collins KL, Ham TR, Blanchard AT, Malavade JN, West JL, Hoffman BD. Detection of Fluorescent Protein Mechanical Switching in Cellulo. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.10.575065. [PMID: 38260589 PMCID: PMC10802509 DOI: 10.1101/2024.01.10.575065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
The ability of cells to sense and respond to mechanical forces is critical in many physiological and pathological processes. However, the mechanisms by which forces affect protein function inside cells remain unclear. Motivated by in vitro demonstrations of fluorescent proteins (FPs) undergoing reversible mechanical switching of fluorescence, we investigated if force-sensitive changes in FP function could be visualized in cells. Guided by a computational model of FP mechanical switching, we develop a formalism for its detection in Förster resonance energy transfer (FRET)-based biosensors and demonstrate its occurrence in cellulo in a synthetic actin-crosslinker and the mechanical linker protein vinculin. We find that in cellulo mechanical switching is reversible and altered by manipulation of cellular force generation as well as force-sensitive bond dynamics of the biosensor. Together, this work describes a new framework for assessing FP mechanical stability and provides a means of probing force-sensitive protein function inside cells. MOTIVATION The ability of cells to sense mechanical forces is critical in developmental, physiological, and pathological processes. Cells sense mechanical cues via force-induced alterations in protein structure and function, but elucidation of the molecular mechanisms is hindered by the lack of approaches to directly probe the effect of forces on protein structure and function inside cells. Motivated by in vitro observations of reversible fluorescent protein mechanical switching, we developed an approach for detecting fluorescent protein mechanical switching in cellulo . This enables the visualization of force-sensitive protein function inside living cells.
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3
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Strobl K, Selivanovitch E, Ibáñez-Freire P, Moreno-Madrid F, Schaap IAT, Delgado-Buscalioni R, Douglas T, de Pablo PJ. Electromechanical Photophysics of GFP Packed Inside Viral Protein Cages Probed by Force-Fluorescence Hybrid Single-Molecule Microscopy. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2200059. [PMID: 35718881 PMCID: PMC9528512 DOI: 10.1002/smll.202200059] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 04/29/2022] [Indexed: 06/15/2023]
Abstract
Packing biomolecules inside virus capsids has opened new avenues for the study of molecular function in confined environments. These systems not only mimic the highly crowded conditions in nature, but also allow their manipulation at the nanoscale for technological applications. Here, green fluorescent proteins are packed in virus-like particles derived from P22 bacteriophage procapsids. The authors explore individual virus cages to monitor their emission signal with total internal reflection fluorescence microscopy while simultaneously changing the microenvironment with the stylus of atomic force microscopy. The mechanical and electronic quenching can be decoupled by ≈10% each using insulator and conductive tips, respectively. While with conductive tips the fluorescence quenches and recovers regardless of the structural integrity of the capsid, with the insulator tips quenching only occurs if the green fluorescent proteins remain organized inside the capsid. The electronic quenching is associated with the coupling of the protein fluorescence emission with the tip surface plasmon resonance. In turn, the mechanical quenching is a consequence of the unfolding of the aggregated proteins during the mechanical disruption of the capsid.
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Affiliation(s)
- Klara Strobl
- Department of Condensed Matter Physics, Universidad Autónoma de Madrid, Madrid, 28049, Spain
| | | | - Pablo Ibáñez-Freire
- Department of Condensed Matter Physics, Universidad Autónoma de Madrid, Madrid, 28049, Spain
| | - Francisco Moreno-Madrid
- Department of Condensed Matter Physics, Universidad Autónoma de Madrid, Madrid, 28049, Spain
| | | | - Rafael Delgado-Buscalioni
- Department of Condensed Matter Physics, Universidad Autónoma de Madrid, Madrid, 28049, Spain
- Institute of Condensed Matter Physics (IFIMAC), Universidad Autónoma de Madrid, Madrid, 28049, Spain
| | - Trevor Douglas
- Department of Chemistry, Indiana University, Bloomington, IN, 47405, USA
| | - Pedro J de Pablo
- Department of Condensed Matter Physics, Universidad Autónoma de Madrid, Madrid, 28049, Spain
- Institute of Condensed Matter Physics (IFIMAC), Universidad Autónoma de Madrid, Madrid, 28049, Spain
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4
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Traeger H, Kiebala DJ, Weder C, Schrettl S. From Molecules to Polymers-Harnessing Inter- and Intramolecular Interactions to Create Mechanochromic Materials. Macromol Rapid Commun 2020; 42:e2000573. [PMID: 33191595 DOI: 10.1002/marc.202000573] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 10/16/2020] [Indexed: 12/30/2022]
Abstract
The development of mechanophores as building blocks that serve as predefined weak linkages has enabled the creation of mechanoresponsive and mechanochromic polymer materials, which are interesting for a range of applications including the study of biological specimens or advanced security features. In typical mechanophores, covalent bonds are broken when polymers that contain these chemical motifs are exposed to mechanical forces, and changes of the optical properties upon bond scission can be harnessed as a signal that enables the detection of applied mechanical stresses and strains. Similar chromic effects upon mechanical deformation of polymers can also be achieved without relying on the scission of covalent bonds. The dissociation of motifs that feature directional noncovalent interactions, the disruption of aggregated molecules, and conformational changes in molecules or polymers constitute an attractive element for the design of mechanoresponsive and mechanochromic materials. In this article, it is reviewed how such alterations of molecules and polymers can be exploited for the development of mechanochromic materials that signal deformation without breaking covalent bonds. Recent illustrative examples are highlighted that showcase how the use of such mechanoresponsive motifs enables the visual mapping of stresses and damage in a reversible and highly sensitive manner.
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Affiliation(s)
- Hanna Traeger
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, Fribourg, CH-1700, Switzerland
| | - Derek J Kiebala
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, Fribourg, CH-1700, Switzerland
| | - Christoph Weder
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, Fribourg, CH-1700, Switzerland
| | - Stephen Schrettl
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, Fribourg, CH-1700, Switzerland
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5
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Liu L, He F, Yu Y, Wang Y. Application of FRET Biosensors in Mechanobiology and Mechanopharmacological Screening. Front Bioeng Biotechnol 2020; 8:595497. [PMID: 33240867 PMCID: PMC7680962 DOI: 10.3389/fbioe.2020.595497] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 10/19/2020] [Indexed: 12/15/2022] Open
Abstract
Extensive studies have shown that cells can sense and modulate the biomechanical properties of the ECM within their resident microenvironment. Thus, targeting the mechanotransduction signaling pathways provides a promising way for disease intervention. However, how cells perceive these mechanical cues of the microenvironment and transduce them into biochemical signals remains to be answered. Förster or fluorescence resonance energy transfer (FRET) based biosensors are a powerful tool that can be used in live-cell mechanotransduction imaging and mechanopharmacological drug screening. In this review, we will first introduce FRET principle and FRET biosensors, and then, recent advances on the integration of FRET biosensors and mechanobiology in normal and pathophysiological conditions will be discussed. Furthermore, we will summarize the current applications and limitations of FRET biosensors in high-throughput drug screening and the future improvement of FRET biosensors. In summary, FRET biosensors have provided a powerful tool for mechanobiology studies to advance our understanding of how cells and matrices interact, and the mechanopharmacological screening for disease intervention.
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Affiliation(s)
| | | | | | - Yingxiao Wang
- Department of Bioengineering, Institute of Engineering in Medicine, University of California, San Diego, La Jolla, CA, United States
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6
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Ham TR, Collins KL, Hoffman BD. Molecular Tension Sensors: Moving Beyond Force. CURRENT OPINION IN BIOMEDICAL ENGINEERING 2019; 12:83-94. [PMID: 32864525 DOI: 10.1016/j.cobme.2019.10.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Nearly all cellular processes are sensitive to mechanical inputs, and this plays a major role in diverse physiological processes. Mechanical stimuli are thought to be primarily detected through force-induced changes in protein structure. Approximately a decade ago, molecular tension sensors were created to measure forces across proteins within cells. Since then, an impressive assortment of sensors has been created and provided key insights into mechanotransduction, but comparisons of measurements between various sensors are challenging. In this review, we discuss the different types of molecular tension sensors, provide a system of classification based on their molecular-scale mechanical properties, and highlight how new applications of these sensors are enabling measurements beyond the magnitude of tensile load. We suggest that an expanded understanding of the functionality of these sensors, as well as integration with other techniques, will lead to consensus amongst measurements as well as critical insights into the underlying mechanisms of mechanotransduction.
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Affiliation(s)
- Trevor R Ham
- Duke University, Room 1379 CIEMAS, 101 Science Drive, 27710, United States
| | - Kasie L Collins
- Duke University, Room 1379 CIEMAS, 101 Science Drive, 27710, United States
| | - Brenton D Hoffman
- Duke University, Room 1379 CIEMAS, 101 Science Drive, 27710, United States
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7
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Abstract
Cells need to be anchored to extracellular matrix (ECM) to survive, yet the role of ECM in guiding developmental processes, tissue homeostasis, and aging has long been underestimated. How ECM orchestrates the deterioration of healthy to pathological tissues, including fibrosis and cancer, also remains poorly understood. Inquiring how alterations in ECM fiber tension might drive these processes is timely, as mechanobiology is a rapidly growing field, and many novel mechanisms behind the mechanical forces that can regulate protein, cell, and tissue functions have recently been deciphered. The goal of this article is to review how forces can switch protein functions, and thus cell signaling, and thereby inspire new approaches to exploit the mechanobiology of ECM in regenerative medicine as well as for diagnostic and therapeutic applications. Some of the mechanochemical switching concepts described here for ECM proteins are more general and apply to intracellular proteins as well.
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Affiliation(s)
- Viola Vogel
- Laboratory of Applied Mechanobiology, Institute of Translational Medicine, Department for Health Sciences and Technology, ETH Zürich, CH-8093 Zürich, Switzerland;
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8
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Verma D, Grigoryan G, Bailey-Kellogg C. Pareto Optimization of Combinatorial Mutagenesis Libraries. IEEE/ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2019; 16:1143-1153. [PMID: 30040654 PMCID: PMC8262366 DOI: 10.1109/tcbb.2018.2858794] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
In order to increase the hit rate of discovering diverse, beneficial protein variants via high-throughput screening, we have developed a computational method to optimize combinatorial mutagenesis libraries for overall enrichment in two distinct properties of interest. Given scoring functions for evaluating individual variants, POCoM (Pareto Optimal Combinatorial Mutagenesis) scores entire libraries in terms of averages over their constituent members, and designs optimal libraries as sets of mutations whose combinations make the best trade-offs between average scores. This represents the first general-purpose method to directly design combinatorial libraries for multiple objectives characterizing their constituent members. Despite being rigorous in mapping out the Pareto frontier, it is also very fast even for very large libraries (e.g., designing 30 mutation, billion-member libraries in only hours). We here instantiate POCoM with scores based on a target's protein structure and its homologs' sequences, enabling the design of libraries containing variants balancing these two important yet quite different types of information. We demonstrate POCoM's generality and power in case study applications to green fluorescent protein, cytochrome P450, and β-lactamase. Analysis of the POCoM library designs provides insights into the trade-offs between structure- and sequence-based scores, as well as the impacts of experimental constraints on library designs. POCoM libraries incorporate mutations that have previously been found favorable experimentally, while diversifying the contexts in which these mutations are situated and maintaining overall variant quality.
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9
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Jöhr R, Bauer MS, Schendel LC, Kluger C, Gaub HE. Dronpa: A Light-Switchable Fluorescent Protein for Opto-Biomechanics. NANO LETTERS 2019; 19:3176-3181. [PMID: 30912662 DOI: 10.1021/acs.nanolett.9b00639] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Since the development of the green fluorescent protein, fluorescent proteins (FP) are indispensable tools in molecular biology. Some FPs change their structure under illumination, which affects their interaction with other biomolecules or proteins. In particular, FPs that are able to form switchable dimers became an important tool in the field of optogenetics. They are widely used for the investigation of signaling pathways, the control of surface recruitment, as well as enzyme and gene regulation. However, optogenetics did not yet develop tools for the investigation of biomechanical processes. This could be leveraged if one could find a light-switchable FP dimer that is able to withstand sufficiently high forces. In this work, we measure the rupture force of the switchable interface in pdDronpa1.2 dimers using atomic force microscopy-based single molecule force spectroscopy. The most probable dimer rupture force amounts to around 80 pN at a pulling speed of 1600 nm/s. After switching of the dimer using illumination at 488 nm, there are hardly any measurable interface interactions, which indicates the successful dissociation of the dimers. Hence this Dronpa dimer could expand the current toolbox in optogenetics with new opto-biomechanical applications like the control of tension in adhesion processes.
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Affiliation(s)
- Res Jöhr
- Lehrstuhl für Angewandte Physik and Center for Nanoscience , Ludwig-Maximilians-Universität , Munich 80799 , Germany
| | - Magnus S Bauer
- Lehrstuhl für Angewandte Physik and Center for Nanoscience , Ludwig-Maximilians-Universität , Munich 80799 , Germany
| | - Leonard C Schendel
- Lehrstuhl für Angewandte Physik and Center for Nanoscience , Ludwig-Maximilians-Universität , Munich 80799 , Germany
| | - Carleen Kluger
- Lehrstuhl für Angewandte Physik and Center for Nanoscience , Ludwig-Maximilians-Universität , Munich 80799 , Germany
| | - Hermann E Gaub
- Lehrstuhl für Angewandte Physik and Center for Nanoscience , Ludwig-Maximilians-Universität , Munich 80799 , Germany
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10
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Atanaskovic I, Kleanthous C. Tools and Approaches for Dissecting Protein Bacteriocin Import in Gram-Negative Bacteria. Front Microbiol 2019; 10:646. [PMID: 31001227 PMCID: PMC6455109 DOI: 10.3389/fmicb.2019.00646] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 03/14/2019] [Indexed: 12/30/2022] Open
Abstract
Bacteriocins of Gram-negative bacteria are typically multi-domain proteins that target and kill bacteria of the same or closely related species. There is increasing interest in protein bacteriocin import; from a fundamental perspective to understand how folded proteins are imported into bacteria and from an applications perspective as species-specific antibiotics to combat multidrug resistant bacteria. In order to translocate across the cell envelope and cause cell death, protein bacteriocins hijack nutrient uptake pathways. Their import is energized by parasitizing intermembrane protein complexes coupled to the proton motive force, which delivers a toxic domain into the cell. A plethora of genetic, structural, biochemical, and biophysical methods have been applied to find cell envelope components involved in bacteriocin import since their discovery almost a century ago. Here, we review the various approaches that now exist for investigating how protein bacteriocins translocate into Gram-negative bacteria and highlight areas of research that will need methodological innovations to fully understand this process. We also highlight recent studies demonstrating how bacteriocins can be used to probe organization and architecture of the Gram-negative cell envelope itself.
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Affiliation(s)
| | - Colin Kleanthous
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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11
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Rifaie-Graham O, Apebende EA, Bast LK, Bruns N. Self-Reporting Fiber-Reinforced Composites That Mimic the Ability of Biological Materials to Sense and Report Damage. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1705483. [PMID: 29573286 DOI: 10.1002/adma.201705483] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Revised: 11/29/2017] [Indexed: 06/08/2023]
Abstract
Sensing of damage, deformation, and mechanical forces is of vital importance in many applications of fiber-reinforced polymer composites, as it allows the structural health and integrity of composite components to be monitored and microdamage to be detected before it leads to catastrophic material failure. Bioinspired and biomimetic approaches to self-sensing and self-reporting materials are reviewed. Examples include bruising coatings and bleeding composites based on dye-filled microcapsules, hollow fibers, and vascular networks. Force-induced changes in color, fluorescence, or luminescence are achieved by mechanochromic epoxy resins, or by mechanophores and force-responsive proteins located at the interface of glass/carbon fibers and polymers. Composites can also feel strain, stress, and damage through embedded optical and electrical sensors, such as fiber Bragg grating sensors, or by resistance measurements of dispersed carbon fibers and carbon nanotubes. Bioinspired composites with the ability to show autonomously if and where they have been damaged lead to a multitude of opportunities for aerospace, automotive, civil engineering, and wind-turbine applications. They range from safety features for the detection of barely visible impact damage, to the real-time monitoring of deformation of load-bearing components.
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Affiliation(s)
- Omar Rifaie-Graham
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700, Fribourg, Switzerland
| | - Edward A Apebende
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700, Fribourg, Switzerland
| | - Livia K Bast
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700, Fribourg, Switzerland
| | - Nico Bruns
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700, Fribourg, Switzerland
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12
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High Efficiency Gene Correction in Hematopoietic Cells by Donor-Template-Free CRISPR/Cas9 Genome Editing. MOLECULAR THERAPY-NUCLEIC ACIDS 2017; 10:1-8. [PMID: 29499925 PMCID: PMC5723376 DOI: 10.1016/j.omtn.2017.11.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Revised: 11/06/2017] [Accepted: 11/06/2017] [Indexed: 01/22/2023]
Abstract
The CRISPR/Cas9 prokaryotic adaptive immune system and its swift repurposing for genome editing enables modification of any prespecified genomic sequence with unprecedented accuracy and efficiency, including targeted gene repair. We used the CRISPR/Cas9 system for targeted repair of patient-specific point mutations in the Cytochrome b-245 heavy chain gene (CYBB), whose inactivation causes chronic granulomatous disease (XCGD)—a life-threatening immunodeficiency disorder characterized by the inability of neutrophils and macrophages to produce microbicidal reactive oxygen species (ROS). We show that frameshift mutations can be effectively repaired in hematopoietic cells by non-integrating lentiviral vectors carrying RNA-guided Cas9 endonucleases (RGNs). Because about 25% of most inherited blood disorders are caused by frameshift mutations, our results suggest that up to a quarter of all patients suffering from monogenic blood disorders could benefit from gene therapy employing personalized, donor template-free RGNs.
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13
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Mechanically switching single-molecule fluorescence of GFP by unfolding and refolding. Proc Natl Acad Sci U S A 2017; 114:11052-11056. [PMID: 29073015 DOI: 10.1073/pnas.1704937114] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Green fluorescent protein (GFP) variants are widely used as genetically encoded fluorescent fusion tags, and there is an increasing interest in engineering their structure to develop in vivo optical sensors, such as for optogenetics and force transduction. Ensemble experiments have shown that the fluorescence of GFP is quenched upon denaturation. Here we study the dependence of fluorescence on protein structure by driving single molecules of GFP into different conformational states with optical tweezers and simultaneously probing the chromophore with fluorescence. Our results show that fluorescence is lost during the earliest events in unfolding, 3.5 ms before secondary structure is disrupted. No fluorescence is observed from the unfolding intermediates or the ensemble of compact and extended states populated during refolding. We further demonstrate that GFP can be mechanically switched between emissive and dark states. These data definitively establish that complete structural integrity is necessary to observe single-molecule fluorescence of GFP.
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14
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Araujo JV, Rifaie-Graham O, Apebende EA, Bruns N. Self-reporting Polymeric Materials with Mechanochromic Properties. BIO-INSPIRED POLYMERS 2016. [DOI: 10.1039/9781782626664-00354] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The mechanical transduction of force onto molecules is an essential feature of many biological processes that results in the senses of touch and hearing, gives important cues for cellular interactions and can lead to optically detectable signals, such as a change in colour, fluorescence or chemoluminescence. Polymeric materials that are able to visually indicate deformation, stress, strain or the occurrence of microdamage draw inspiration from these biological events. The field of self-reporting (or self-assessing) materials is reviewed. First, mechanochromic events in nature are discussed, such as the formation of bruises on skin, the bleeding of a wound, or marine glow caused by dinoflagellates. Then, materials based on force-responsive mechanophores, such as spiropyrans, cyclobutanes, cyclooctanes, Diels–Alder adducts, diarylbibenzofuranone and bis(adamantyl)-1,2-dioxetane are reviewed, followed by mechanochromic blends, chromophores stabilised by hydrogen bonds, and pressure sensors based on ionic interactions between fluorescent dyes and polyelectrolyte brushes. Mechanobiochemistry is introduced as an important tool to create self-reporting hybrid materials that combine polymers with the force-responsive properties of fluorescent proteins, protein FRET pairs, and other biomacromolecules. Finally, dye-filled microcapsules, microvascular networks, and hollow fibres are demonstrated to be important technologies to create damage-indicating coatings, self-reporting fibre-reinforced composites and self-healing materials.
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Affiliation(s)
- Jose V. Araujo
- Adolphe Merkle Institute, University of Fribourg Chemin des Verdiers 4 1700 Fribourg Switzerland
| | - Omar Rifaie-Graham
- Adolphe Merkle Institute, University of Fribourg Chemin des Verdiers 4 1700 Fribourg Switzerland
| | - Edward A. Apebende
- Adolphe Merkle Institute, University of Fribourg Chemin des Verdiers 4 1700 Fribourg Switzerland
| | - Nico Bruns
- Adolphe Merkle Institute, University of Fribourg Chemin des Verdiers 4 1700 Fribourg Switzerland
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15
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Galior K, Liu Y, Yehl K, Vivek S, Salaita K. Titin-Based Nanoparticle Tension Sensors Map High-Magnitude Integrin Forces within Focal Adhesions. NANO LETTERS 2016; 16:341-8. [PMID: 26598972 PMCID: PMC5592801 DOI: 10.1021/acs.nanolett.5b03888] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Mechanical forces transmitted through integrin transmembrane receptors play important roles in a variety of cellular processes ranging from cell development to tumorigenesis. Despite the importance of mechanics in integrin function, the magnitude of integrin forces within adhesions remains unclear. Literature suggests a range from 1 to 50 pN, but the upper limit of integrin forces remains unknown. Herein we challenge integrins with the most mechanically stable molecular tension probe, which is comprised of the immunoglobulin 27th (I27) domain of cardiac titin flanked with a fluorophore and gold nanoparticle. Cell experiments show that integrin forces unfold the I27 domain, suggesting that integrin forces exceed ∼30-40 pN. The addition of a disulfide bridge within I27 "clamps" the probe and resists mechanical unfolding. Importantly, incubation with a reducing agent initiates SH exchange, thus unclamping I27 at a rate that is dependent on the applied force. By recording the rate of S-S reduction in clamped I27, we infer that integrins apply 110 ± 9 pN within focal adhesions of rat embryonic fibroblasts. The rates of S-S exchange are heterogeneous and integrin subtype-dependent. Nanoparticle titin tension sensors along with kinetic analysis of unfolding demonstrate that a subset of integrins apply tension many fold greater than previously reported.
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Affiliation(s)
- Kornelia Galior
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, GA 30322, USA
| | - Yang Liu
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, GA 30322, USA
| | - Kevin Yehl
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, GA 30322, USA
| | - Skanda Vivek
- Department of Physics, Emory University, 400 Dowman Drive, Atlanta, GA 30322, USA
| | - Khalid Salaita
- Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, GA 30322, USA
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16
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Abstract
Cells generate and experience mechanical forces that may shape tissues and regulate signaling pathways in a variety of physiological or pathological situations. How forces propagate and transduce signals at the molecular level is poorly understood. The advent of FRET-based Molecular Tension Microscopy now allows to achieve mechanical force measurements at a molecular scale with molecular specificity in situ, and thereby better understand the mechanical architecture of cells and tissues, and mechanotransduction pathways. In this review, we will first expose the basic principles of FRET-based MTM and its various incarnations. We will describe different ways of measuring FRET, their advantages and drawbacks. Then, throughout the range of proteins of interest, cells and organisms to which it has been applied, we will review the tests developed to validate the approach, how molecular tension was related to cell functions, and conclude with possible developments and offshoots.
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Affiliation(s)
- Charlène Gayrard
- Institut Jacques Monod, Unité Mixe de Recherche 7592, Centre national de la recherche scientifique, Université Paris-Diderot, Paris 75013, France
| | - Nicolas Borghi
- Institut Jacques Monod, Unité Mixe de Recherche 7592, Centre national de la recherche scientifique, Université Paris-Diderot, Paris 75013, France.
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Shawky JH, Davidson LA. Tissue mechanics and adhesion during embryo development. Dev Biol 2015; 401:152-64. [PMID: 25512299 PMCID: PMC4402132 DOI: 10.1016/j.ydbio.2014.12.005] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 12/02/2014] [Accepted: 12/04/2014] [Indexed: 10/24/2022]
Abstract
During development cells interact mechanically with their microenvironment through cell-cell and cell-matrix adhesions. Many proteins involved in these adhesions serve both mechanical and signaling roles. In this review we will focus on the mechanical roles of these proteins and their complexes in transmitting force or stress from cell to cell or from cell to the extracellular matrix. As forces operate against tissues they establish tissue architecture, extracellular matrix assembly, and pattern cell shapes. As tissues become more established, adhesions play a major role integrating cells with the mechanics of their local environment. Adhesions may serve as both a molecular-specific glue, holding defined populations of cells together, and as a lubricant, allowing tissues to slide past one another. We review the biophysical principles and experimental tools used to study adhesion so that we may aid efforts to understand how adhesions guide these movements and integrate their signaling functions with mechanical function. As we conclude we review efforts to develop predictive models of adhesion that can be used to interpret experiments and guide future efforts to control and direct the process of tissue self-assembly during development.
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Affiliation(s)
- Joseph H Shawky
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Lance A Davidson
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Developmental Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA; Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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18
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Longo J, Yao C, Rios C, Chau NTT, Boulmedais F, Hemmerlé J, Lavalle P, Schiller SM, Schaaf P, Jierry L. Reversible biomechano-responsive surface based on green fluorescent protein genetically modified with unnatural amino acids. Chem Commun (Camb) 2015; 51:232-5. [DOI: 10.1039/c4cc07486f] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Uniaxial stretching of modified GFP “clicked” onto an elastomer leads to a repeatable and reversible decrease of its fluorescence intensity.
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Affiliation(s)
| | - Chunyan Yao
- Universität Freiburg
- Freiburg im Breisgau
- Germany
| | | | | | | | | | | | - Stefan M. Schiller
- Universität Freiburg
- Freiburg im Breisgau
- Germany
- Institute for Pharmaceutical Sciences
- Germany
| | | | - Loïc Jierry
- ICS (UPR22-CNRS)
- Strasbourg
- France
- USIAS
- 67083 Strasbourg
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19
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Cost AL, Ringer P, Chrostek-Grashoff A, Grashoff C. How to Measure Molecular Forces in Cells: A Guide to Evaluating Genetically-Encoded FRET-Based Tension Sensors. Cell Mol Bioeng 2014; 8:96-105. [PMID: 25798203 PMCID: PMC4361753 DOI: 10.1007/s12195-014-0368-1] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 11/21/2014] [Indexed: 12/16/2022] Open
Abstract
The ability of cells to sense and respond to mechanical forces is central to a wide range of biological processes and plays an important role in numerous pathologies. The molecular mechanisms underlying cellular mechanotransduction, however, have remained largely elusive because suitable methods to investigate subcellular force propagation were missing. Here, we review recent advances in the development of biosensors that allow molecular force measurements. We describe the underlying principle of currently available techniques and propose a strategy to systematically evaluate new Förster resonance energy transfer (FRET)-based biosensors.
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Affiliation(s)
- Anna-Lena Cost
- Group of Molecular Mechanotransduction, Max Planck Institute of Biochemistry, Am Klopferspitz 18, Martinsried, 82152 Germany
| | - Pia Ringer
- Group of Molecular Mechanotransduction, Max Planck Institute of Biochemistry, Am Klopferspitz 18, Martinsried, 82152 Germany
| | - Anna Chrostek-Grashoff
- Group of Molecular Mechanotransduction, Max Planck Institute of Biochemistry, Am Klopferspitz 18, Martinsried, 82152 Germany
| | - Carsten Grashoff
- Group of Molecular Mechanotransduction, Max Planck Institute of Biochemistry, Am Klopferspitz 18, Martinsried, 82152 Germany
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20
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Klotzsch E, Stiegler J, Ben-Ishay E, Gaus K. Do mechanical forces contribute to nanoscale membrane organisation in T cells? BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:822-9. [PMID: 25447546 DOI: 10.1016/j.bbamcr.2014.10.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Revised: 09/26/2014] [Accepted: 10/25/2014] [Indexed: 12/23/2022]
Abstract
Mechanotransduction describes how a cell senses and interacts with its environment. The concept originated in adhesion biology where adhesion receptors, integrins, facilitate force transmission between the extracellular matrix and the intracellular actin cytoskeleton. Indeed, during any adhesive contacts, cells do exert mechanical force. Hence, the probing of the local environment by cells results in mechanical cues that contribute to cellular functions and cell fate decisions such as migration, proliferation, differentiation and apoptosis. On the molecular level, mechanical forces can rearrange proteins laterally within the membrane, regulate their activity by inducing conformational changes and probe the mechanical properties and bond strength of receptor-ligands. From this point of view, it appears surprising that molecular forces have been largely overlooked in membrane organisation and ligand discrimination processes in lymphocytes. During T cell activation, the T cell receptor recognises and distinguishes antigenic from benign endogenous peptides to initiate the reorganisation of membrane proteins into signalling clusters within the immunological synapse. In this review, we asked whether characteristics of fibroblast force sensing could be applied to immune cell antigen recognition and signalling, and outline state-of-the-art experimental strategies for studying forces in the context of membrane organisation. This article is part of a Special Issue entitled: Nanoscale membrane orgainisation and signalling.
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Affiliation(s)
- Enrico Klotzsch
- Centre for Vascular Research, ARC Centre of Excellence in Advanced Molecular Imaging and Australian Centre for Nanomedicine, University of New South Wales, Sydney, Australia.
| | - Johannes Stiegler
- Centre for Vascular Research, ARC Centre of Excellence in Advanced Molecular Imaging and Australian Centre for Nanomedicine, University of New South Wales, Sydney, Australia
| | - Eldad Ben-Ishay
- Centre for Vascular Research, ARC Centre of Excellence in Advanced Molecular Imaging and Australian Centre for Nanomedicine, University of New South Wales, Sydney, Australia
| | - Katharina Gaus
- Centre for Vascular Research, ARC Centre of Excellence in Advanced Molecular Imaging and Australian Centre for Nanomedicine, University of New South Wales, Sydney, Australia.
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21
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Guo J, Sachs F, Meng F. Fluorescence-based force/tension sensors: a novel tool to visualize mechanical forces in structural proteins in live cells. Antioxid Redox Signal 2014; 20:986-99. [PMID: 24205787 PMCID: PMC3924807 DOI: 10.1089/ars.2013.5708] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
SIGNIFICANCE Three signaling systems, chemical, electrical, and mechanical, ubiquitously contribute to cellular activities. There is limited information on the mechanical signaling system because of a lack of tools to measure stress in specific proteins. Although significant advances in methodologies such as atomic force microscopy and laser tweezers have achieved great success in single molecules and measuring the mean properties of cells and tissues, they cannot deal with specific proteins in live cells. RECENT ADVANCES To remedy the situation, we developed a family of genetically encoded optical force sensors to measure the stress in structural proteins in living cells. The sensors can be incorporated into specific proteins and are not harmful in transgenic animals. The chimeric proteins distribute and function as their wild-type counterparts, and local stress can be read out from changes in Förster resonance energy transfer (FRET). CRITICAL ISSUES Our original sensor used two mutant green fluorescence proteins linked by an alpha helix that served as a linking spring. Ever since, we have improved the probe design in a number of ways. For example, we replaced the helical linker with more common elastic protein domains to better match the compliance of the wild-type hosts. We greatly improved sensitivity by using the angular dependence of FRET rather than the distance dependence as the transduction mechanism, because that has nearly 100% efficiency at rest and nearly zero when stretched. FUTURE DIRECTIONS These probes enable researchers to investigate the roles of mechanical force in cellular activities at the level of single molecules, cells, tissues, and whole animals.
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Affiliation(s)
- Jun Guo
- 1 Department of Biochemistry, Nanjing Medical University , Nanjing, People's Republic of China
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22
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Jacobs MJ, Blank K. Joining forces: integrating the mechanical and optical single molecule toolkits. Chem Sci 2014. [DOI: 10.1039/c3sc52502c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Combining single molecule force measurements with fluorescence detection opens up exciting new possibilities for the characterization of mechanoresponsive molecules in Biology and Materials Science.
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Affiliation(s)
- Monique J. Jacobs
- Radboud University Nijmegen
- Institute for Molecules and Materials
- Department of Molecular Materials
- 6525 AJ Nijmegen, The Netherlands
| | - Kerstin Blank
- Radboud University Nijmegen
- Institute for Molecules and Materials
- Department of Molecular Materials
- 6525 AJ Nijmegen, The Netherlands
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