1
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Engl W, Kunstar-Thomas A, Chen S, Ng WS, Sielaff H, Zhao ZW. Single-molecule imaging of SWI/SNF chromatin remodelers reveals bromodomain-mediated and cancer-mutants-specific landscape of multi-modal DNA-binding dynamics. Nat Commun 2024; 15:7646. [PMID: 39223123 PMCID: PMC11369179 DOI: 10.1038/s41467-024-52040-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Accepted: 08/22/2024] [Indexed: 09/04/2024] Open
Abstract
Despite their prevalent cancer implications, the in vivo dynamics of SWI/SNF chromatin remodelers and how misregulation of such dynamics underpins cancer remain poorly understood. Using live-cell single-molecule tracking, we quantify the intranuclear diffusion and chromatin-binding of three key subunits common to all major human SWI/SNF remodeler complexes (BAF57, BAF155 and BRG1), and resolve two temporally distinct stable binding modes for the fully assembled complex. Super-resolved density mapping reveals heterogeneous, nanoscale remodeler binding "hotspots" across the nucleoplasm where multiple binding events (especially longer-lived ones) preferentially cluster. Importantly, we uncover distinct roles of the bromodomain in modulating chromatin binding/targeting in a DNA-accessibility-dependent manner, pointing to a model where successive longer-lived binding within "hotspots" leads to sustained productive remodeling. Finally, systematic comparison of six common BRG1 mutants implicated in various cancers unveils alterations in chromatin-binding dynamics unique to each mutant, shedding insight into a multi-modal landscape regulating the spatio-temporal organizational dynamics of SWI/SNF remodelers.
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Affiliation(s)
- Wilfried Engl
- Department of Chemistry, Faculty of Science, National University of Singapore, Singapore, 119543, Singapore
- Centre for BioImaging Sciences, Faculty of Science, National University of Singapore, Singapore, 117557, Singapore
| | - Aliz Kunstar-Thomas
- Department of Chemistry, Faculty of Science, National University of Singapore, Singapore, 119543, Singapore
- Centre for BioImaging Sciences, Faculty of Science, National University of Singapore, Singapore, 117557, Singapore
| | - Siyi Chen
- Department of Chemistry, Faculty of Science, National University of Singapore, Singapore, 119543, Singapore
- Centre for BioImaging Sciences, Faculty of Science, National University of Singapore, Singapore, 117557, Singapore
| | - Woei Shyuan Ng
- Department of Chemistry, Faculty of Science, National University of Singapore, Singapore, 119543, Singapore
- Centre for BioImaging Sciences, Faculty of Science, National University of Singapore, Singapore, 117557, Singapore
| | - Hendrik Sielaff
- Department of Chemistry, Faculty of Science, National University of Singapore, Singapore, 119543, Singapore
- Centre for BioImaging Sciences, Faculty of Science, National University of Singapore, Singapore, 117557, Singapore
| | - Ziqing Winston Zhao
- Department of Chemistry, Faculty of Science, National University of Singapore, Singapore, 119543, Singapore.
- Centre for BioImaging Sciences, Faculty of Science, National University of Singapore, Singapore, 117557, Singapore.
- Mechanobiology Institute, National University of Singapore, Singapore, 117411, Singapore.
- Integrative Sciences and Engineering Programme, National University of Singapore, Singapore, 119077, Singapore.
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2
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Gong T, McNally KL, Konanoor S, Peraza A, Bailey C, Redemann S, McNally FJ. Roles of Tubulin Concentration during Prometaphase and Ran-GTP during Anaphase of Caenorhabditis elegans Meiosis. Life Sci Alliance 2024; 7:e202402884. [PMID: 38960623 PMCID: PMC11222656 DOI: 10.26508/lsa.202402884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2024] [Revised: 06/25/2024] [Accepted: 06/26/2024] [Indexed: 07/05/2024] Open
Abstract
In many animal species, the oocyte meiotic spindle, which is required for chromosome segregation, forms without centrosomes. In some systems, Ran-GEF on chromatin initiates spindle assembly. We found that in Caenorhabditis elegans oocytes, endogenously-tagged Ran-GEF dissociates from chromatin during spindle assembly but re-associates during meiotic anaphase. Meiotic spindle assembly occurred after auxin-induced degradation of Ran-GEF, but anaphase I was faster than controls and extrusion of the first polar body frequently failed. In search of a possible alternative pathway for spindle assembly, we found that soluble tubulin concentrates in the nuclear volume during germinal vesicle breakdown. We found that the concentration of soluble tubulin in the metaphase spindle region is enclosed by ER sheets which exclude cytoplasmic organelles including mitochondria and yolk granules. Measurement of the volume occupied by yolk granules and mitochondria indicated that volume exclusion would be sufficient to explain the concentration of tubulin in the spindle volume. We suggest that this concentration of soluble tubulin may be a redundant mechanism promoting spindle assembly near chromosomes.
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Affiliation(s)
- Ting Gong
- https://ror.org/05rrcem69 Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Karen L McNally
- https://ror.org/05rrcem69 Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Siri Konanoor
- https://ror.org/05rrcem69 Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Alma Peraza
- https://ror.org/05rrcem69 Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Cynthia Bailey
- https://ror.org/05rrcem69 Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
| | - Stefanie Redemann
- https://ror.org/0153tk833 Department of Cell Biology, University of Virginia, School of Medicine, Charlottesville, VA, USA
| | - Francis J McNally
- https://ror.org/05rrcem69 Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, USA
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3
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Choi AA, Zhou CY, Tabo A, Heald R, Xu K. Single-molecule diffusivity quantification in Xenopus egg extracts elucidates physicochemical properties of the cytoplasm. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.24.609541. [PMID: 39253443 PMCID: PMC11383024 DOI: 10.1101/2024.08.24.609541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/11/2024]
Abstract
The living cell creates a unique internal molecular environment that is challenging to characterize. By combining single-molecule displacement/diffusivity mapping (SM d M) with physiologically active extracts prepared from Xenopus laevis eggs, we sought to elucidate molecular properties of the cytoplasm. Quantification of the diffusion coefficients of 15 diverse proteins in extract showed that, compared to in water, negatively charged proteins diffused ∼50% slower, while diffusion of positively charged proteins was reduced by ∼80-90%. Adding increasing concentrations of salt progressively alleviated the suppressed diffusion observed for positively charged proteins, signifying electrostatic interactions within a predominately negatively charged macromolecular environment. To investigate the contribution of RNA, an abundant, negatively charged component of cytoplasm, extracts were treated with ribonuclease, which resulted in low diffusivity domains indicative of aggregation, likely due to the liberation of positively charged RNA-binding proteins such as ribosomal proteins, since this effect could be mimicked by adding positively charged polypeptides. Interestingly, negatively charged proteins of different sizes showed similar diffusivity suppression in extract, which are typically prepared under conditions that inhibit actin polymerization. Restoring or enhancing actin polymerization progressively suppressed the diffusion of larger proteins, recapitulating behaviors observed in cells. Together, these results indicate that molecular interactions in the crowded cell are defined by an overwhelmingly negatively charged macromolecular environment containing cytoskeletal networks. Significance Statement The complex intracellular molecular environment is notably challenging to elucidate and recapitulate. Xenopus egg extracts provide a native yet manipulatable cytoplasm model. Through single-molecule microscopy, here we decipher the cytoplasmic environment and molecular interactions by examining the diffusion patterns of diverse proteins in Xenopus egg extracts with strategic manipulations. These experiments reveal an overwhelmingly negatively charged macromolecular environment with crosslinked meshworks, offering new insight into the inner workings of the cell.
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4
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Xia C, Colognori D, Jiang X, Xu K, Doudna JA. Single-molecule live-cell RNA imaging with CRISPR-Csm. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.14.603457. [PMID: 39071319 PMCID: PMC11275710 DOI: 10.1101/2024.07.14.603457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/30/2024]
Abstract
High-resolution, real-time imaging of RNA is essential for understanding the diverse, dynamic behaviors of individual RNA molecules in single cells. However, single-molecule live-cell imaging of unmodified endogenous RNA has not yet been achieved. Here, we present single-molecule live-cell fluorescence in situ hybridization (smLiveFISH), a robust approach that combines the programmable RNA-guided, RNA-targeting CRISPR-Csm complex with multiplexed guide RNAs for efficient, direct visualization of single RNA molecules in a range of cell types, including primary cells. Using smLiveFISH, we tracked individual endogenous NOTCH2 and MAP1B mRNA transcripts in living cells and identified two distinct localization mechanisms: co-translational translocation of NOTCH2 mRNA at the endoplasmic reticulum, and directional transport of MAP1B mRNA toward the cell periphery. This method has the potential to unlock principles governing the spatiotemporal organization of native transcripts in health and disease.
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Affiliation(s)
- Chenglong Xia
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA USA
- Innovative Genomics Institute, University of California, Berkeley, CA, USA
| | - David Colognori
- Innovative Genomics Institute, University of California, Berkeley, CA, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
| | - Xueyang Jiang
- Innovative Genomics Institute, University of California, Berkeley, CA, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
| | - Ke Xu
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA USA
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA
| | - Jennifer A. Doudna
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA USA
- Innovative Genomics Institute, University of California, Berkeley, CA, USA
- Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA
- Howard Hughes Medical Institute, University of California, Berkeley, CA, USA
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5
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Unger BA, Wu CY, Choi AA, He C, Xu K. Hypersensitivity of the vimentin cytoskeleton to net-charge states and Coulomb repulsion. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.08.602555. [PMID: 39026705 PMCID: PMC11257561 DOI: 10.1101/2024.07.08.602555] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
As with most intermediate filament systems, the hierarchical self-assembly of vimentin into nonpolar filaments requires no nucleators or energy input. Utilizing a set of live-cell, single-molecule, and super-resolution microscopy tools, here we show that in mammalian cells, the assembly and disassembly of the vimentin cytoskeleton is highly sensitive to the protein net charge state. Starting with the intriguing observation that the vimentin cytoskeleton fully disassembles under hypotonic stress yet reassembles within seconds upon osmotic pressure recovery, we pinpoint ionic strength as its underlying driving factor. Further modulating the pH and expressing differently charged constructs, we converge on a model in which the vimentin cytoskeleton is destabilized by Coulomb repulsion when its mass-accumulated negative charges (-18 per vimentin protein) along the filament are less screened or otherwise intensified, and stabilized when the charges are better screened or otherwise reduced. Generalizing this model to other intermediate filaments, we further show that whereas the negatively charged GFAP cytoskeleton is similarly subject to fast disassembly under hypotonic stress, the cytokeratin, as a copolymer of negatively and positively charged subunits, does not exhibit this behavior. Thus, in cells containing both vimentin and keratin cytoskeletons, hypotonic stress disassembles the former but not the latter. Together, our results both provide new handles for modulating cell behavior and call for new attention to the effects of net charges in intracellular protein interactions.
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Affiliation(s)
- Bret A. Unger
- Department of Chemistry & California Institute for Quantitative Biosciences
- University of California, Berkeley, California 94720, United States
| | - Chun Ying Wu
- Department of Chemistry & California Institute for Quantitative Biosciences
- University of California, Berkeley, California 94720, United States
| | - Alexander A. Choi
- Department of Chemistry & California Institute for Quantitative Biosciences
- University of California, Berkeley, California 94720, United States
| | - Changdong He
- Department of Chemistry & California Institute for Quantitative Biosciences
- University of California, Berkeley, California 94720, United States
| | - Ke Xu
- Corresponding author: (K.X.)
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6
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Gong T, McNally KL, Konanoor S, Peraza A, Bailey C, Redemann S, McNally FJ. Roles of Tubulin Concentration during Prometaphase and Ran-GTP during Anaphase of C. elegans meiosis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.19.590357. [PMID: 38659754 PMCID: PMC11042349 DOI: 10.1101/2024.04.19.590357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
In many animal species, the oocyte meiotic spindle, which is required for chromosome segregation, forms without centrosomes. In some systems, Ran-GEF on chromatin initiates spindle assembly. We found that in C. elegans oocytes, endogenously-tagged Ran-GEF dissociates from chromatin during spindle assembly but re-associates during meiotic anaphase. Meiotic spindle assembly occurred after auxin-induced degradation of Ran-GEF but anaphase I was faster than controls and extrusion of the first polar body frequently failed. In search of a possible alternative pathway for spindle assembly, we found that soluble tubulin concentrates in the nuclear volume during germinal vesicle breakdown. We found that the concentration of soluble tubulin in the metaphase spindle region is enclosed by ER sheets which exclude cytoplasmic organelles including mitochondria and yolk granules. Measurement of the volume occupied by yolk granules and mitochondria indicated that volume exclusion would be sufficient to explain the concentration of tubulin in the spindle volume. We suggest that this concentration of soluble tubulin may be a redundant mechanism promoting spindle assembly near chromosomes.
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Affiliation(s)
- Ting Gong
- Department of Molecular and Cellular Biology, university of California, Davis, Davis, CA 95616, USA
| | - Karen L McNally
- Department of Molecular and Cellular Biology, university of California, Davis, Davis, CA 95616, USA
| | - Siri Konanoor
- Department of Molecular and Cellular Biology, university of California, Davis, Davis, CA 95616, USA
| | - Alma Peraza
- Department of Molecular and Cellular Biology, university of California, Davis, Davis, CA 95616, USA
| | - Cynthia Bailey
- Department of Molecular and Cellular Biology, university of California, Davis, Davis, CA 95616, USA
| | - Stefanie Redemann
- Department of Cell Biology, University of Virginia, School of Medicine, Charlottesville, VA, USA
| | - Francis J McNally
- Department of Molecular and Cellular Biology, university of California, Davis, Davis, CA 95616, USA
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7
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Raja Venkatesh A, Le KH, Weld DM, Brandman O. Diffusive lensing as a mechanism of intracellular transport and compartmentalization. eLife 2024; 12:RP89794. [PMID: 38896469 PMCID: PMC11186627 DOI: 10.7554/elife.89794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2024] Open
Abstract
While inhomogeneous diffusivity has been identified as a ubiquitous feature of the cellular interior, its implications for particle mobility and concentration at different length scales remain largely unexplored. In this work, we use agent-based simulations of diffusion to investigate how heterogeneous diffusivity affects the movement and concentration of diffusing particles. We propose that a nonequilibrium mode of membrane-less compartmentalization arising from the convergence of diffusive trajectories into low-diffusive sinks, which we call 'diffusive lensing,' is relevant for living systems. Our work highlights the phenomenon of diffusive lensing as a potentially key driver of mesoscale dynamics in the cytoplasm, with possible far-reaching implications for biochemical processes.
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Affiliation(s)
- Achuthan Raja Venkatesh
- Department of Biochemistry, Stanford UniversityStanfordUnited States
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER) MohaliMohaliIndia
| | - Kathy H Le
- Department of Biochemistry, Stanford UniversityStanfordUnited States
| | - David M Weld
- Department of Physics, University of California, Santa BarbaraSanta BarbaraUnited States
| | - Onn Brandman
- Department of Biochemistry, Stanford UniversityStanfordUnited States
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8
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Steves MA, He C, Xu K. Single-Molecule Spectroscopy and Super-Resolution Mapping of Physicochemical Parameters in Living Cells. Annu Rev Phys Chem 2024; 75:163-183. [PMID: 38360526 DOI: 10.1146/annurev-physchem-070623-034225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2024]
Abstract
By superlocalizing the positions of millions of single molecules over many camera frames, a class of super-resolution fluorescence microscopy methods known as single-molecule localization microscopy (SMLM) has revolutionized how we understand subcellular structures over the past decade. In this review, we highlight emerging studies that transcend the outstanding structural (shape) information offered by SMLM to extract and map physicochemical parameters in living mammalian cells at single-molecule and super-resolution levels. By encoding/decoding high-dimensional information-such as emission and excitation spectra, motion, polarization, fluorescence lifetime, and beyond-for every molecule, and mass accumulating these measurements for millions of molecules, such multidimensional and multifunctional super-resolution approaches open new windows into intracellular architectures and dynamics, as well as their underlying biophysical rules, far beyond the diffraction limit.
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Affiliation(s)
- Megan A Steves
- Department of Chemistry, University of California, Berkeley, California, USA;
| | - Changdong He
- Department of Chemistry, University of California, Berkeley, California, USA;
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, California, USA;
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9
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Linnik D, Maslov I, Punter CM, Poolman B. Dynamic structure of E. coli cytoplasm: supramolecular complexes and cell aging impact spatial distribution and mobility of proteins. Commun Biol 2024; 7:508. [PMID: 38678067 PMCID: PMC11055878 DOI: 10.1038/s42003-024-06216-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Accepted: 04/18/2024] [Indexed: 04/29/2024] Open
Abstract
Protein diffusion is a critical factor governing the functioning and organization of a cell's cytoplasm. In this study, we investigate the influence of (poly)ribosome distribution, cell aging, protein aggregation, and biomolecular condensate formation on protein mobility within the E. coli cytoplasm. We employ nanoscale single-molecule displacement mapping (SMdM) to determine the spatial distribution of the proteins and to meticulously track their diffusion. We show that the distribution of polysomes does not impact the lateral diffusion coefficients of proteins. However, the degradation of mRNA induced by rifampicin treatment leads to an increase in protein mobility within the cytoplasm. Additionally, we establish a significant correlation between cell aging, the asymmetric localization of protein aggregates and reduced diffusion coefficients at the cell poles. Notably, we observe variations in the hindrance of diffusion at the poles and the central nucleoid region for small and large proteins, and we reveal differences between the old and new pole of the cell. Collectively, our research highlights cellular processes and mechanisms responsible for spatially organizing the bacterial cytoplasm into domains with different structural features and apparent viscosity.
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Affiliation(s)
- Dmitrii Linnik
- Department of Biochemistry, University of Groningen, Groningen, Nijenborgh 4, 9747 AG, the Netherlands
| | - Ivan Maslov
- Department of Biochemistry, University of Groningen, Groningen, Nijenborgh 4, 9747 AG, the Netherlands
| | - Christiaan Michiel Punter
- Department of Biochemistry, University of Groningen, Groningen, Nijenborgh 4, 9747 AG, the Netherlands
| | - Bert Poolman
- Department of Biochemistry, University of Groningen, Groningen, Nijenborgh 4, 9747 AG, the Netherlands.
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10
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Choi AA, Xu K. Single-Molecule Diffusivity Quantification Unveils Ubiquitous Net Charge-Driven Protein-Protein Interaction. J Am Chem Soc 2024; 146:10973-10978. [PMID: 38576203 PMCID: PMC11023747 DOI: 10.1021/jacs.4c02475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
Recent microscopy and nuclear magnetic resonance (NMR) studies have noticed substantial suppression of intracellular diffusion for positively charged proteins, suggesting an overlooked role of electrostatic attraction in nonspecific protein interactions in a predominantly negatively charged intracellular environment. Utilizing single-molecule detection and statistics, here, we quantify in aqueous solutions how protein diffusion, in the limit of low diffuser concentration to avoid aggregate/coacervate formation, is modulated by differently charged interactor proteins over wide concentration ranges. We thus report substantially suppressed diffusion when oppositely charged interactors are added at parts per million levels, yet unvaried diffusivities when same-charge interactors are added beyond 1%. The electrostatic attraction-driven suppression of diffusion is sensitive to the protein net charge states, as probed by varying the solution pH and ionic strength or chemically modifying the proteins and is robust across different diffuser-interactor pairs. By converting the measured diffusivities to diffuser diameters, we further show that in the limit of excess interactors, a positively charged diffuser molecule effectively drags along just one monolayer of negatively charged interactors, where further interactions stop. We thus unveil ubiquitous, net charge-driven protein-protein interactions and shed new light on the mechanism of charge-based diffusion suppression in living cells.
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Affiliation(s)
- Alexander A. Choi
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, California 94720, United States
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11
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Bock A, Irannejad R, Scott JD. cAMP signaling: a remarkably regional affair. Trends Biochem Sci 2024; 49:305-317. [PMID: 38310024 PMCID: PMC11175624 DOI: 10.1016/j.tibs.2024.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 12/22/2023] [Accepted: 01/10/2024] [Indexed: 02/05/2024]
Abstract
Louis Pasteur once famously said 'in the fields of observation chance favors only the prepared mind'. Much of chance is being in the right place at the right time. This is particularly true in the crowded molecular environment of the cell where being in the right place is often more important than timing. Although Brownian motion argues that enzymes will eventually bump into substrates, this probability is greatly enhanced if both molecules reside in the same subcellular compartment. However, activation of cell signaling enzymes often requires the transmission of chemical signals from extracellular stimuli to intracellular sites of action. This review highlights new developments in our understanding of cAMP generation and the 3D utilization of this second messenger inside cells.
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Affiliation(s)
- Andreas Bock
- Rudolf Boehm Institute of Pharmacology and Toxicology, Medical Faculty, Leipzig University, 04107 Leipzig, Germany.
| | - Roshanak Irannejad
- Cardiovascular Research Institute, University of California, San Francisco, San Francisco, CA 94158, USA; Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94158, USA.
| | - John D Scott
- Department of Pharmacology, University of Washington Medical Center, Seattle, WA 98195, USA.
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12
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Monterroso B, Margolin W, Boersma AJ, Rivas G, Poolman B, Zorrilla S. Macromolecular Crowding, Phase Separation, and Homeostasis in the Orchestration of Bacterial Cellular Functions. Chem Rev 2024; 124:1899-1949. [PMID: 38331392 PMCID: PMC10906006 DOI: 10.1021/acs.chemrev.3c00622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 12/01/2023] [Accepted: 01/10/2024] [Indexed: 02/10/2024]
Abstract
Macromolecular crowding affects the activity of proteins and functional macromolecular complexes in all cells, including bacteria. Crowding, together with physicochemical parameters such as pH, ionic strength, and the energy status, influences the structure of the cytoplasm and thereby indirectly macromolecular function. Notably, crowding also promotes the formation of biomolecular condensates by phase separation, initially identified in eukaryotic cells but more recently discovered to play key functions in bacteria. Bacterial cells require a variety of mechanisms to maintain physicochemical homeostasis, in particular in environments with fluctuating conditions, and the formation of biomolecular condensates is emerging as one such mechanism. In this work, we connect physicochemical homeostasis and macromolecular crowding with the formation and function of biomolecular condensates in the bacterial cell and compare the supramolecular structures found in bacteria with those of eukaryotic cells. We focus on the effects of crowding and phase separation on the control of bacterial chromosome replication, segregation, and cell division, and we discuss the contribution of biomolecular condensates to bacterial cell fitness and adaptation to environmental stress.
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Affiliation(s)
- Begoña Monterroso
- Department
of Structural and Chemical Biology, Centro de Investigaciones Biológicas
Margarita Salas, Consejo Superior de Investigaciones
Científicas (CSIC), 28040 Madrid, Spain
| | - William Margolin
- Department
of Microbiology and Molecular Genetics, McGovern Medical School, UTHealth-Houston, Houston, Texas 77030, United States
| | - Arnold J. Boersma
- Cellular
Protein Chemistry, Bijvoet Centre for Biomolecular Research, Faculty
of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
| | - Germán Rivas
- Department
of Structural and Chemical Biology, Centro de Investigaciones Biológicas
Margarita Salas, Consejo Superior de Investigaciones
Científicas (CSIC), 28040 Madrid, Spain
| | - Bert Poolman
- Department
of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Silvia Zorrilla
- Department
of Structural and Chemical Biology, Centro de Investigaciones Biológicas
Margarita Salas, Consejo Superior de Investigaciones
Científicas (CSIC), 28040 Madrid, Spain
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13
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Tran BM, Punter CM, Linnik D, Iyer A, Poolman B. Single-protein Diffusion in the Periplasm of Escherichia coli. J Mol Biol 2024; 436:168420. [PMID: 38143021 DOI: 10.1016/j.jmb.2023.168420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 12/13/2023] [Accepted: 12/19/2023] [Indexed: 12/26/2023]
Abstract
The width of the periplasmic space of Gram-negative bacteria is only about 25-30 nm along the long axis of the cell, which affects free diffusion of (macro)molecules. We have performed single-particle displacement measurements and diffusion simulation studies to determine the impact of confinement on the apparent mobility of proteins in the periplasm of Escherichia coli. The diffusion of a reporter protein and of OsmY, an osmotically regulated periplasmic protein, is characterized by a fast and slow component regardless of the osmotic conditions. The diffusion coefficient of the fast fraction increases upon osmotic upshift, in agreement with a decrease in macromolecular crowding of the periplasm, but the mobility of the slow (immobile) fraction is not affected by the osmotic stress. We observe that the confinement created by the inner and outer membranes results in a lower apparent diffusion coefficient, but this can only partially explain the slow component of diffusion in the particle displacement measurements, suggesting that a fraction of the proteins is hindered in its mobility by large periplasmic structures. Using particle-based simulations, we have determined the confinement effect on the apparent diffusion coefficient of the particles for geometries akin the periplasmic space of Gram-negative bacteria.
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Affiliation(s)
- Buu Minh Tran
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands
| | - Christiaan Michiel Punter
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands
| | - Dmitrii Linnik
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands
| | - Aditya Iyer
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands
| | - Bert Poolman
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands.
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14
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Udupa A, Kotha SR, Staller MV. Commonly asked questions about transcriptional activation domains. Curr Opin Struct Biol 2024; 84:102732. [PMID: 38056064 PMCID: PMC11193542 DOI: 10.1016/j.sbi.2023.102732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Revised: 10/23/2023] [Accepted: 10/27/2023] [Indexed: 12/08/2023]
Abstract
Eukaryotic transcription factors activate gene expression with their DNA-binding domains and activation domains. DNA-binding domains bind the genome by recognizing structurally related DNA sequences; they are structured, conserved, and predictable from protein sequences. Activation domains recruit chromatin modifiers, coactivator complexes, or basal transcriptional machinery via structurally diverse protein-protein interactions. Activation domains and DNA-binding domains have been called independent, modular units, but there are many departures from modularity, including interactions between these regions and overlap in function. Compared to DNA-binding domains, activation domains are poorly understood because they are poorly conserved, intrinsically disordered, and difficult to predict from protein sequences. This review, organized around commonly asked questions, describes recent progress that the field has made in understanding the sequence features that control activation domains and predicting them from sequence.
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Affiliation(s)
- Aditya Udupa
- Department of Molecular and Cell Biology, University of California, Berkeley, 94720, USA
| | - Sanjana R Kotha
- Department of Molecular and Cell Biology, University of California, Berkeley, 94720, USA; Center for Computational Biology, University of California, Berkeley, 94720, USA
| | - Max V Staller
- Department of Molecular and Cell Biology, University of California, Berkeley, 94720, USA; Center for Computational Biology, University of California, Berkeley, 94720, USA; Chan Zuckerberg Biohub-San Francisco, San Francisco, CA 94158, USA.
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15
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He C, Wu CY, Li W, Xu K. Multidimensional Super-Resolution Microscopy Unveils Nanoscale Surface Aggregates in the Aging of FUS Condensates. J Am Chem Soc 2023; 145:24240-24248. [PMID: 37782826 PMCID: PMC10691933 DOI: 10.1021/jacs.3c08674] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
The intracellular liquid-liquid phase separation (LLPS) of biomolecules gives rise to condensates that act as membrane-less organelles with vital functions. FUS, an RNA-binding protein, natively forms condensates through LLPS and further provides a model system for the often disease-linked liquid-to-solid transition of biomolecular condensates during aging. However, the mechanism of such maturation processes, as well as the structural and physical properties of the system, remains unclear, partly attributable to difficulties in resolving the internal structures of the micrometer-sized condensates with diffraction-limited optical microscopy. Harnessing a set of multidimensional super-resolution microscopy tools that uniquely map out local physicochemical parameters through single-molecule spectroscopy, here, we uncover nanoscale heterogeneities in FUS condensates and elucidate their evolution over aging. Through spectrally resolved single-molecule localization microscopy (SR-SMLM) with a solvatochromic dye, we unveil distinct hydrophobic nanodomains at the condensate surface. Through SMLM with a fluorogenic amyloid probe, we identify these nanodomains as amyloid aggregates. Through single-molecule displacement/diffusivity mapping (SMdM), we show that such nanoaggregates drastically impede local diffusion. Notably, upon aging or mechanical shears, these nanoaggregates progressively expand on the condensate surface, thus leading to a growing low-diffusivity shell while leaving the condensate interior diffusion-permitting. Together, beyond uncovering fascinating structural arrangements and aging mechanisms in the single-component FUS condensates, the demonstrated synergy of multidimensional super-resolution approaches in this study opens new paths for understanding LLPS systems at the nanoscale.
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Affiliation(s)
- Changdong He
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Chun Ying Wu
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Wan Li
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, California 94720, United States
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16
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Zhai F, Hao L, Chen X, Jiang T, Guo Q, Xie L, Ma Y, Du X, Zheng Z, Chen K, Fan J. Single-molecule tracking of PprI in D. radiodurans without interference of autoblinking. Front Microbiol 2023; 14:1256711. [PMID: 38029090 PMCID: PMC10652783 DOI: 10.3389/fmicb.2023.1256711] [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: 07/11/2023] [Accepted: 10/10/2023] [Indexed: 12/01/2023] Open
Abstract
Autoblinking is a widespread phenomenon and exhibits high level of intensity in some bacteria. In Deinococcus radiodurans (D. radiodurans), strong autoblinking was found to be indistinguishable from PAmCherry and greatly prevented single-molecule tracking of proteins of interest. Here we employed the bright photoswitchable fluorescent protein mMaple3 to label PprI, one essential DNA repair factor, and characterized systematically the fluorescence intensity and bleaching kinetics of both autoblinking and PprI-mMaple3 molecules within cells grown under three different conditions. Under minimal media, we can largely separate autoblinking from mMaple3 molecules and perform reliably single-molecule tracking of PprI in D. radiodurans, by means of applying signal-to-noise ratio and constraining the minimal length for linking the trajectories. We observed three states of PprI molecules, which bear different subcellular localizations and distinct functionalities. Our strategy provides a useful means to study the dynamics and distributions of proteins of interest in bacterial cells with high level of autoblinking.
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Affiliation(s)
- Fanfan Zhai
- School of Life Sciences and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan, China
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
- NHC Key Laboratory of Nuclear Technology Medical Transformation (Mianyang Central Hospital), Mianyang, Sichuan, China
| | - Li Hao
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
| | - Xiaomin Chen
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
| | - Ting Jiang
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
| | - Qianhong Guo
- School of Life Sciences and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan, China
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
| | - Liping Xie
- School of Life Sciences and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan, China
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
| | - Ying Ma
- NHC Key Laboratory of Nuclear Technology Medical Transformation (Mianyang Central Hospital), Mianyang, Sichuan, China
| | - Xiaobo Du
- NHC Key Laboratory of Nuclear Technology Medical Transformation (Mianyang Central Hospital), Mianyang, Sichuan, China
| | - Zhiqin Zheng
- School of Life Sciences and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan, China
- NHC Key Laboratory of Nuclear Technology Medical Transformation (Mianyang Central Hospital), Mianyang, Sichuan, China
- School of Biological Engineering and Wuliangye Liquor, Sichuan University of Science and Engineering, Yibin, Sichuan, China
| | - Kun Chen
- School of Optoelectronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
- Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou, Zhejiang, China
| | - Jun Fan
- Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
- Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou, Zhejiang, China
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17
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Mantovanelli L, Linnik DS, Punter M, Kojakhmetov HJ, Śmigiel WM, Poolman B. Simulation-based Reconstructed Diffusion unveils the effect of aging on protein diffusion in Escherichia coli. PLoS Comput Biol 2023; 19:e1011093. [PMID: 37695774 PMCID: PMC10513214 DOI: 10.1371/journal.pcbi.1011093] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 09/21/2023] [Accepted: 08/24/2023] [Indexed: 09/13/2023] Open
Abstract
We have developed Simulation-based Reconstructed Diffusion (SbRD) to determine diffusion coefficients corrected for confinement effects and for the bias introduced by two-dimensional models describing a three-dimensional motion. We validate the method on simulated diffusion data in three-dimensional cell-shaped compartments. We use SbRD, combined with a new cell detection method, to determine the diffusion coefficients of a set of native proteins in Escherichia coli. We observe slower diffusion at the cell poles than in the nucleoid region of exponentially growing cells, which is independent of the presence of polysomes. Furthermore, we show that the newly formed pole of dividing cells exhibits a faster diffusion than the old one. We hypothesize that the observed slowdown at the cell poles is caused by the accumulation of aggregated or damaged proteins, and that the effect is asymmetric due to cell aging.
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Affiliation(s)
- Luca Mantovanelli
- Department of Biochemistry, University of Groningen, Groningen, the Netherlands
| | - Dmitrii S. Linnik
- Department of Biochemistry, University of Groningen, Groningen, the Netherlands
| | - Michiel Punter
- Department of Biochemistry, University of Groningen, Groningen, the Netherlands
| | | | - Wojciech M. Śmigiel
- Department of Biochemistry, University of Groningen, Groningen, the Netherlands
| | - Bert Poolman
- Department of Biochemistry, University of Groningen, Groningen, the Netherlands
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18
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Liu Y, Shahid MA, Mao H, Chen J, Waddington M, Song KH, Zhang Y. Switchable and Functional Fluorophores for Multidimensional Single-Molecule Localization Microscopy. CHEMICAL & BIOMEDICAL IMAGING 2023; 1:403-413. [PMID: 37655169 PMCID: PMC10466381 DOI: 10.1021/cbmi.3c00045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 06/05/2023] [Accepted: 06/08/2023] [Indexed: 09/02/2023]
Abstract
Multidimensional single-molecule localization microscopy (mSMLM) represents a paradigm shift in the realm of super-resolution microscopy techniques. It affords the simultaneous detection of single-molecule spatial locations at the nanoscale and functional information by interrogating the emission properties of switchable fluorophores. The latter is finely tuned to report its local environment through carefully manipulated laser illumination and single-molecule detection strategies. This Perspective highlights recent strides in mSMLM with a focus on fluorophore designs and their integration into mSMLM imaging systems. Particular interests are the accomplishments in simultaneous multiplexed super-resolution imaging, nanoscale polarity and hydrophobicity mapping, and single-molecule orientational imaging. Challenges and prospects in mSMLM are also discussed, which include the development of more vibrant and functional fluorescent probes, the optimization of optical implementation to judiciously utilize the photon budget, and the advancement of imaging analysis and machine learning techniques.
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Affiliation(s)
- Yunshu Liu
- Molecular
Analytics and Photonics (MAP) Laboratory, Department of Textile Engineering,
Chemistry and Science, North Carolina State
University, Raleigh, North Carolina 27606, United States
| | - Md Abul Shahid
- Molecular
Analytics and Photonics (MAP) Laboratory, Department of Textile Engineering,
Chemistry and Science, North Carolina State
University, Raleigh, North Carolina 27606, United States
| | - Hongjing Mao
- Molecular
Analytics and Photonics (MAP) Laboratory, Department of Textile Engineering,
Chemistry and Science, North Carolina State
University, Raleigh, North Carolina 27606, United States
| | - Jiahui Chen
- Molecular
Analytics and Photonics (MAP) Laboratory, Department of Textile Engineering,
Chemistry and Science, North Carolina State
University, Raleigh, North Carolina 27606, United States
| | - Michael Waddington
- Molecular
Analytics and Photonics (MAP) Laboratory, Department of Textile Engineering,
Chemistry and Science, North Carolina State
University, Raleigh, North Carolina 27606, United States
| | - Ki-Hee Song
- Quantum
Optics Research Division, Korea Atomic Energy
Research Institute, Yuseong-gu, Daejeon 34057, Republic of Korea
| | - Yang Zhang
- Molecular
Analytics and Photonics (MAP) Laboratory, Department of Textile Engineering,
Chemistry and Science, North Carolina State
University, Raleigh, North Carolina 27606, United States
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19
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Prindle JR, de Cuba OIC, Gahlmann A. Single-molecule tracking to determine the abundances and stoichiometries of freely-diffusing protein complexes in living cells: Past applications and future prospects. J Chem Phys 2023; 159:071002. [PMID: 37589409 PMCID: PMC10908566 DOI: 10.1063/5.0155638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Accepted: 07/06/2023] [Indexed: 08/18/2023] Open
Abstract
Most biological processes in living cells rely on interactions between proteins. Live-cell compatible approaches that can quantify to what extent a given protein participates in homo- and hetero-oligomeric complexes of different size and subunit composition are therefore critical to advance our understanding of how cellular physiology is governed by these molecular interactions. Biomolecular complex formation changes the diffusion coefficient of constituent proteins, and these changes can be measured using fluorescence microscopy-based approaches, such as single-molecule tracking, fluorescence correlation spectroscopy, and fluorescence recovery after photobleaching. In this review, we focus on the use of single-molecule tracking to identify, resolve, and quantify the presence of freely-diffusing proteins and protein complexes in living cells. We compare and contrast different data analysis methods that are currently employed in the field and discuss experimental designs that can aid the interpretation of the obtained results. Comparisons of diffusion rates for different proteins and protein complexes in intracellular aqueous environments reported in the recent literature reveal a clear and systematic deviation from the Stokes-Einstein diffusion theory. While a complete and quantitative theoretical explanation of why such deviations manifest is missing, the available data suggest the possibility of weighing freely-diffusing proteins and protein complexes in living cells by measuring their diffusion coefficients. Mapping individual diffusive states to protein complexes of defined molecular weight, subunit stoichiometry, and structure promises to provide key new insights into how protein-protein interactions regulate protein conformational, translational, and rotational dynamics, and ultimately protein function.
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Affiliation(s)
- Joshua Robert Prindle
- Department of Chemistry, University of Virginia, Charlottesville, Virginia 22904, USA
| | - Olivia Isabella Christiane de Cuba
- Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia 22903, USA
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20
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Choi AA, Xiang L, Li W, Xu K. Single-Molecule Displacement Mapping Indicates Unhindered Intracellular Diffusion of Small (≲1 kDa) Solutes. J Am Chem Soc 2023; 145:10.1021/jacs.3c00597. [PMID: 37027457 PMCID: PMC10558625 DOI: 10.1021/jacs.3c00597] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
Abstract
While fundamentally important, the intracellular diffusion of small (≲1 kDa) solutes has been difficult to elucidate due to challenges in both labeling and measurement. Here we quantify and spatially map the translational diffusion patterns of small solutes in mammalian cells by integrating several recent advances. In particular, by executing tandem stroboscopic illumination pulses down to 400 μs separation, we extend single-molecule displacement/diffusivity mapping (SMdM), a super-resolution diffusion quantification tool, to small solutes with high diffusion coefficients D of >300 μm2/s. We thus show that for multiple water-soluble dyes and dye-tagged nucleotides, intracellular diffusion is dominated by vast regions of high diffusivity ∼60-70% of that in vitro, up to ∼250 μm2/s in the fastest cases. Meanwhile, we also visualize sub-micrometer foci of substantial slowdowns in diffusion, thus underscoring the importance of spatially resolving the local diffusion behavior. Together, these results suggest that the intracellular diffusion of small solutes is only modestly scaled down by the slightly higher viscosity of the cytosol over water but otherwise not further hindered by macromolecular crowding. We thus lift a paradoxically low speed limit for intracellular diffusion suggested by previous experiments.
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Affiliation(s)
- Alexander A. Choi
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Limin Xiang
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Wan Li
- Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, California 94720, United States
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21
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Park HH, Choi AA, Xu K. Size-Dependent Suppression of Molecular Diffusivity in Expandable Hydrogels: A Single-Molecule Study. J Phys Chem B 2023; 127:3333-3339. [PMID: 37011131 DOI: 10.1021/acs.jpcb.3c00761] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/05/2023]
Abstract
By repurposing the recently popularized expansion microscopy to control the meshwork size of hydrogels, we examine the size-dependent suppression of molecular diffusivity in the resultant tuned hydrogel nanomatrices over a wide range of polymer fractions of ∼0.14-7 wt %. With our recently developed single-molecule displacement/diffusivity mapping (SMdM) microscopy methods, we thus show that with a fixed meshwork size, larger molecules exhibit more impeded diffusion and that, for the same molecule, diffusion is progressively more suppressed as the meshwork size is reduced; this effect is more prominent for the larger molecules. Moreover, we show that the meshwork-induced obstruction of diffusion is uncoupled from the suppression of diffusion due to increased solution viscosities. Thus, the two mechanisms, respectively, being diffuser-size-dependent and independent, may separately scale down molecular diffusivity to produce the final diffusion slowdown in complex systems like the cell.
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Affiliation(s)
- Ha H Park
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Alexander A Choi
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
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22
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Park HH, Wang B, Moon S, Jepson T, Xu K. Machine-learning-powered extraction of molecular diffusivity from single-molecule images for super-resolution mapping. Commun Biol 2023; 6:336. [PMID: 36977778 PMCID: PMC10050076 DOI: 10.1038/s42003-023-04729-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Accepted: 03/17/2023] [Indexed: 03/30/2023] Open
Abstract
While critical to biological processes, molecular diffusion is difficult to quantify, and spatial mapping of local diffusivity is even more challenging. Here we report a machine-learning-enabled approach, pixels-to-diffusivity (Pix2D), to directly extract the diffusion coefficient D from single-molecule images, and consequently enable super-resolved D spatial mapping. Working with single-molecule images recorded at a fixed framerate under typical single-molecule localization microscopy (SMLM) conditions, Pix2D exploits the often undesired yet evident motion blur, i.e., the convolution of single-molecule motion trajectory during the frame recording time with the diffraction-limited point spread function (PSF) of the microscope. Whereas the stochastic nature of diffusion imprints diverse diffusion trajectories to different molecules diffusing at the same given D, we construct a convolutional neural network (CNN) model that takes a stack of single-molecule images as the input and evaluates a D-value as the output. We thus validate robust D evaluation and spatial mapping with simulated data, and with experimental data successfully characterize D differences for supported lipid bilayers of different compositions and resolve gel and fluidic phases at the nanoscale.
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Affiliation(s)
- Ha H Park
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA
| | - Bowen Wang
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA
| | - Suhong Moon
- Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA, 94720, USA
| | - Tyler Jepson
- QB3-Berkeley, University of California, Berkeley, CA, 94720, USA
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, CA, 94720, USA.
- QB3-Berkeley, University of California, Berkeley, CA, 94720, USA.
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23
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Sun N, Jia Y, Bai S, Li Q, Dai L, Li J. The power of super-resolution microscopy in modern biomedical science. Adv Colloid Interface Sci 2023; 314:102880. [PMID: 36965225 DOI: 10.1016/j.cis.2023.102880] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 03/08/2023] [Accepted: 03/08/2023] [Indexed: 03/14/2023]
Abstract
Super-resolution microscopy (SRM) technology that breaks the diffraction limit has revolutionized the field of cell biology since its appearance, which enables researchers to visualize cellular structures with nanometric resolution, multiple colors and single-molecule sensitivity. With the flourishing development of hardware and the availability of novel fluorescent probes, the impact of SRM has already gone beyond cell biology and extended to nanomedicine, material science and nanotechnology, and remarkably boosted important breakthroughs in these fields. In this review, we will mainly highlight the power of SRM in modern biomedical science, discussing how these SRM techniques revolutionize the way we understand cell structures, biomaterials assembly and how assembled biomaterials interact with cellular organelles, and finally their promotion to the clinical pre-diagnosis. Moreover, we also provide an outlook on the current technical challenges and future improvement direction of SRM. We hope this review can provide useful information, inspire new ideas and propel the development both from the perspective of SRM techniques and from the perspective of SRM's applications.
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Affiliation(s)
- Nan Sun
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Lab of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049
| | - Yi Jia
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Lab of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
| | - Shiwei Bai
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Lab of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049
| | - Qi Li
- State Key Laboratory of Biochemical Engineering Institute of Process Engineering Chinese Academy of Sciences, Beijing 100190, China
| | - Luru Dai
- Wenzhou Institute and Wenzhou Key Laboratory of Biophysics, University of Chinese Academy of Sciences, Wenzhou, Zhejiang 325001, China
| | - Junbai Li
- Beijing National Laboratory for Molecular Sciences (BNLMS), CAS Key Lab of Colloid, Interface and Chemical Thermodynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100049.
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24
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Xiang L, Yan R, Chen K, Li W, Xu K. Single-Molecule Displacement Mapping Unveils Sign-Asymmetric Protein Charge Effects on Intraorganellar Diffusion. NANO LETTERS 2023; 23:1711-1716. [PMID: 36802676 PMCID: PMC10044514 DOI: 10.1021/acs.nanolett.2c04379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Using single-molecule displacement/diffusivity mapping (SMdM), an emerging super-resolution microscopy method, here we quantify, at nanoscale resolution, the diffusion of a typical fluorescent protein (FP) in the endoplasmic reticulum (ER) and mitochondrion of living mammalian cells. We thus show that the diffusion coefficients D in both organelles are ∼40% of that in the cytoplasm, with the latter exhibiting higher spatial inhomogeneities. Moreover, we unveil that diffusions in the ER lumen and the mitochondrial matrix are markedly impeded when the FP is given positive, but not negative, net charges. Calculation shows most intraorganellar proteins as negatively charged, hence a mechanism to impede the diffusion of positively charged proteins. However, we further identify the ER protein PPIB as an exception with a positive net charge and experimentally show that the removal of this positive charge elevates its intra-ER diffusivity. We thus unveil a sign-asymmetric protein charge effect on the nanoscale intraorganellar diffusion.
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Affiliation(s)
- Limin Xiang
- Department of Chemistry & California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA, 94720
- College of Chemistry and Molecular Sciences & TaiKang Center for Life and Medical Sciences, Wuhan University, Wuhan 430072, China
| | - Rui Yan
- Department of Chemistry & California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA, 94720
| | - Kun Chen
- Department of Chemistry & California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA, 94720
| | - Wan Li
- Department of Chemistry & California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA, 94720
| | - Ke Xu
- Department of Chemistry & California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA, 94720
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25
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Garner RM, Molines AT, Theriot JA, Chang F. Vast heterogeneity in cytoplasmic diffusion rates revealed by nanorheology and Doppelgänger simulations. Biophys J 2023; 122:767-783. [PMID: 36739478 PMCID: PMC10027447 DOI: 10.1016/j.bpj.2023.01.040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 12/22/2022] [Accepted: 01/30/2023] [Indexed: 02/05/2023] Open
Abstract
The cytoplasm is a complex, crowded, actively driven environment whose biophysical characteristics modulate critical cellular processes such as cytoskeletal dynamics, phase separation, and stem cell fate. Little is known about the variance in these cytoplasmic properties. Here, we employed particle-tracking nanorheology on genetically encoded multimeric 40 nm nanoparticles (GEMs) to measure diffusion within the cytoplasm of individual fission yeast (Schizosaccharomyces pombe) cellscells. We found that the apparent diffusion coefficients of individual GEM particles varied over a 400-fold range, while the differences in average particle diffusivity among individual cells spanned a 10-fold range. To determine the origin of this heterogeneity, we developed a Doppelgänger simulation approach that uses stochastic simulations of GEM diffusion that replicate the experimental statistics on a particle-by-particle basis, such that each experimental track and cell had a one-to-one correspondence with their simulated counterpart. These simulations showed that the large intra- and inter-cellular variations in diffusivity could not be explained by experimental variability but could only be reproduced with stochastic models that assume a wide intra- and inter-cellular variation in cytoplasmic viscosity. The simulation combining intra- and inter-cellular variation in viscosity also predicted weak nonergodicity in GEM diffusion, consistent with the experimental data. To probe the origin of this variation, we found that the variance in GEM diffusivity was largely independent of factors such as temperature, the actin and microtubule cytoskeletons, cell-cyle stage, and spatial locations, but was magnified by hyperosmotic shocks. Taken together, our results provide a striking demonstration that the cytoplasm is not "well-mixed" but represents a highly heterogeneous environment in which subcellular components at the 40 nm size scale experience dramatically different effective viscosities within an individual cell, as well as in different cells in a genetically identical population. These findings carry significant implications for the origins and regulation of biological noise at cellular and subcellular levels.
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Affiliation(s)
- Rikki M Garner
- Biophysics Program, Stanford University School of Medicine, Stanford, California; Department of Biology and Howard Hughes Medical Institute, University of Washington, Seattle, Washington; Marine Biological Laboratory, Woods Hole, Massachusetts.
| | - Arthur T Molines
- Department of Cell and Tissue Biology, University of California San Francisco, San Francisco, California; Marine Biological Laboratory, Woods Hole, Massachusetts.
| | - Julie A Theriot
- Biophysics Program, Stanford University School of Medicine, Stanford, California; Department of Biology and Howard Hughes Medical Institute, University of Washington, Seattle, Washington; Marine Biological Laboratory, Woods Hole, Massachusetts
| | - Fred Chang
- Department of Cell and Tissue Biology, University of California San Francisco, San Francisco, California; Marine Biological Laboratory, Woods Hole, Massachusetts
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26
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Xiang L, Yan R, Chen K, Li W, Xu K. Single-molecule displacement mapping unveils sign-asymmetric protein charge effects on intraorganellar diffusion. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.26.525611. [PMID: 36747807 PMCID: PMC9900983 DOI: 10.1101/2023.01.26.525611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Using single-molecule displacement/diffusivity mapping (SM d M), an emerging super-resolution microscopy method, here we quantify, at nanoscale resolution, the diffusion of a typical fluorescent protein (FP) in the endoplasmic reticulum (ER) and mitochondrion of living mammalian cells. We thus show that the diffusion coefficients D in both organelles are ~40% of that in the cytoplasm, with the latter exhibiting higher spatial inhomogeneities. Moreover, we unveil that diffusions in the ER lumen and the mitochondrial matrix are markedly impeded when the FP is given positive, but not negative, net charges. Calculation shows most intraorganellar proteins as negatively charged, thus a mechanism to impede the diffusion of positively charged proteins. However, we further identify the ER protein PPIB as an exception with a positive net charge, and experimentally show that the removal of this positive charge elevates its intra-ER diffusivity. We thus unveil a sign-asymmetric protein charge effect on the nanoscale intraorganellar diffusion.
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Choi AA, Xiang L, Li W, Xu K. Single-molecule displacement mapping indicates unhindered intracellular diffusion of small (<~1 kDa) solutes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.26.525579. [PMID: 36747694 PMCID: PMC9900885 DOI: 10.1101/2023.01.26.525579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
While fundamentally important, the intracellular diffusion of small (<~1 kDa) solutes has been difficult to elucidate due to challenges in both labeling and measurement. Here we quantify and spatially map the translational diffusion patterns of small solutes in mammalian cells by integrating several recent advances. In particular, by executing tandem stroboscopic illumination pulses down to 400-μs separation, we extend single-molecule displacement/diffusivity mapping (SM d M), a super-resolution diffusion quantification tool, to small solutes with high diffusion coefficients D of >300 μm 2 /s. We thus show that for multiple water-soluble dyes and dye-tagged nucleotides, intracellular diffusion is dominated by vast regions of high diffusivity ~60-70% of that in vitro , up to ~250 μm 2 /s in the fastest cases. Meanwhile, we also visualize sub-micrometer foci of substantial slowdowns in diffusion, thus underscoring the importance of spatially resolving the local diffusion behavior. Together, these results suggest that the intracellular diffusion of small solutes is only modestly scaled down by the slightly higher viscosity of the cytosol over water, but otherwise not further hindered by macromolecular crowding. We thus lift a paradoxically low speed limit for intracellular diffusion suggested by previous experiments. Abstract Graphic
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Geometric deep learning reveals the spatiotemporal features of microscopic motion. NAT MACH INTELL 2023. [DOI: 10.1038/s42256-022-00595-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
AbstractThe characterization of dynamical processes in living systems provides important clues for their mechanistic interpretation and link to biological functions. Owing to recent advances in microscopy techniques, it is now possible to routinely record the motion of cells, organelles and individual molecules at multiple spatiotemporal scales in physiological conditions. However, the automated analysis of dynamics occurring in crowded and complex environments still lags behind the acquisition of microscopic image sequences. Here we present a framework based on geometric deep learning that achieves the accurate estimation of dynamical properties in various biologically relevant scenarios. This deep-learning approach relies on a graph neural network enhanced by attention-based components. By processing object features with geometric priors, the network is capable of performing multiple tasks, from linking coordinates into trajectories to inferring local and global dynamic properties. We demonstrate the flexibility and reliability of this approach by applying it to real and simulated data corresponding to a broad range of biological experiments.
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Tran BM, Linnik DS, Punter CM, Śmigiel WM, Mantovanelli L, Iyer A, O’Byrne C, Abee T, Johansson J, Poolman B. Super-resolving microscopy reveals the localizations and movement dynamics of stressosome proteins in Listeria monocytogenes. Commun Biol 2023; 6:51. [PMID: 36641529 PMCID: PMC9840623 DOI: 10.1038/s42003-023-04423-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 01/04/2023] [Indexed: 01/15/2023] Open
Abstract
The human pathogen Listeria monocytogenes can cope with severe environmental challenges, for which the high molecular weight stressosome complex acts as the sensing hub in a complicated signal transduction pathway. Here, we show the dynamics and functional roles of the stressosome protein RsbR1 and its paralogue, the blue-light receptor RsbL, using photo-activated localization microscopy combined with single-particle tracking and single-molecule displacement mapping and supported by physiological studies. In live cells, RsbR1 is present in multiple states: in protomers with RsbS, large clusters of stressosome complexes, and in connection with the plasma membrane via Prli42. RsbL diffuses freely in the cytoplasm but forms clusters upon exposure to light. The clustering of RsbL is independent of the presence of Prli42. Our work provides a comprehensive view of the spatial organization and intracellular dynamics of the stressosome proteins in L. monocytogenes, which paves the way towards uncovering the stress-sensing mechanism of this signal transduction pathway.
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Affiliation(s)
- Buu Minh Tran
- grid.4830.f0000 0004 0407 1981Department of Biochemistry, University of Groningen, Groningen, the Netherlands
| | - Dmitrii Sergeevich Linnik
- grid.4830.f0000 0004 0407 1981Department of Biochemistry, University of Groningen, Groningen, the Netherlands
| | - Christiaan Michiel Punter
- grid.4830.f0000 0004 0407 1981Department of Biochemistry, University of Groningen, Groningen, the Netherlands
| | - Wojciech Mikołaj Śmigiel
- grid.4830.f0000 0004 0407 1981Department of Biochemistry, University of Groningen, Groningen, the Netherlands
| | - Luca Mantovanelli
- grid.4830.f0000 0004 0407 1981Department of Biochemistry, University of Groningen, Groningen, the Netherlands
| | - Aditya Iyer
- grid.4830.f0000 0004 0407 1981Department of Biochemistry, University of Groningen, Groningen, the Netherlands
| | - Conor O’Byrne
- Microbiology, School of Biological & Chemical Sciences, Ryan Institute, University of Galway, Galway, Ireland
| | - Tjakko Abee
- grid.4818.50000 0001 0791 5666Laboratory of Food Microbiology, Wageningen University & Research, Wageningen, the Netherlands
| | - Jörgen Johansson
- grid.12650.300000 0001 1034 3451Department of Molecular Biology, Umeå University, Umeå, Sweden
| | - Bert Poolman
- grid.4830.f0000 0004 0407 1981Department of Biochemistry, University of Groningen, Groningen, the Netherlands
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Choosing the Probe for Single-Molecule Fluorescence Microscopy. Int J Mol Sci 2022; 23:ijms232314949. [PMID: 36499276 PMCID: PMC9735909 DOI: 10.3390/ijms232314949] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 11/18/2022] [Accepted: 11/24/2022] [Indexed: 12/03/2022] Open
Abstract
Probe choice in single-molecule microscopy requires deeper evaluations than those adopted for less sensitive fluorescence microscopy studies. Indeed, fluorophore characteristics can alter or hide subtle phenomena observable at the single-molecule level, wasting the potential of the sophisticated instrumentation and algorithms developed for advanced single-molecule applications. There are different reasons for this, linked, e.g., to fluorophore aspecific interactions, brightness, photostability, blinking, and emission and excitation spectra. In particular, these spectra and the excitation source are interdependent, and the latter affects the autofluorescence of sample substrate, medium, and/or biological specimen. Here, we review these and other critical points for fluorophore selection in single-molecule microscopy. We also describe the possible kinds of fluorophores and the microscopy techniques based on single-molecule fluorescence. We explain the importance and impact of the various issues in fluorophore choice, and discuss how this can become more effective and decisive for increasingly demanding experiments in single- and multiple-color applications.
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31
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Chen Y, Cattoglio C, Dailey GM, Zhu Q, Tjian R, Darzacq X. Mechanisms governing target search and binding dynamics of hypoxia-inducible factors. eLife 2022; 11:e75064. [PMID: 36322456 PMCID: PMC9681212 DOI: 10.7554/elife.75064] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2021] [Accepted: 11/01/2022] [Indexed: 11/07/2022] Open
Abstract
Transcription factors (TFs) are classically attributed a modular construction, containing well-structured sequence-specific DNA-binding domains (DBDs) paired with disordered activation domains (ADs) responsible for protein-protein interactions targeting co-factors or the core transcription initiation machinery. However, this simple division of labor model struggles to explain why TFs with identical DNA-binding sequence specificity determined in vitro exhibit distinct binding profiles in vivo. The family of hypoxia-inducible factors (HIFs) offer a stark example: aberrantly expressed in several cancer types, HIF-1α and HIF-2α subunit isoforms recognize the same DNA motif in vitro - the hypoxia response element (HRE) - but only share a subset of their target genes in vivo, while eliciting contrasting effects on cancer development and progression under certain circumstances. To probe the mechanisms mediating isoform-specific gene regulation, we used live-cell single particle tracking (SPT) to investigate HIF nuclear dynamics and how they change upon genetic perturbation or drug treatment. We found that HIF-α subunits and their dimerization partner HIF-1β exhibit distinct diffusion and binding characteristics that are exquisitely sensitive to concentration and subunit stoichiometry. Using domain-swap variants, mutations, and a HIF-2α specific inhibitor, we found that although the DBD and dimerization domains are important, another main determinant of chromatin binding and diffusion behavior is the AD-containing intrinsically disordered region (IDR). Using Cut&Run and RNA-seq as orthogonal genomic approaches, we also confirmed IDR-dependent binding and activation of a specific subset of HIF target genes. These findings reveal a previously unappreciated role of IDRs in regulating the TF search and binding process that contribute to functional target site selectivity on chromatin.
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Affiliation(s)
- Yu Chen
- Department of Molecular and Cell Biology, University of California, BerkeleyBerkeleyUnited States
- Howard Hughes Medical Institute, University of California, BerkeleyBerkeleyUnited States
- Li Ka Shing Center for Biomedical & Health Sciences, University of California, BerkeleyBerkeleyUnited States
| | - Claudia Cattoglio
- Department of Molecular and Cell Biology, University of California, BerkeleyBerkeleyUnited States
- Howard Hughes Medical Institute, University of California, BerkeleyBerkeleyUnited States
- Li Ka Shing Center for Biomedical & Health Sciences, University of California, BerkeleyBerkeleyUnited States
| | - Gina M Dailey
- Department of Molecular and Cell Biology, University of California, BerkeleyBerkeleyUnited States
- Li Ka Shing Center for Biomedical & Health Sciences, University of California, BerkeleyBerkeleyUnited States
| | - Qiulin Zhu
- Department of Molecular and Cell Biology, University of California, BerkeleyBerkeleyUnited States
- Li Ka Shing Center for Biomedical & Health Sciences, University of California, BerkeleyBerkeleyUnited States
| | - Robert Tjian
- Department of Molecular and Cell Biology, University of California, BerkeleyBerkeleyUnited States
- Howard Hughes Medical Institute, University of California, BerkeleyBerkeleyUnited States
- Li Ka Shing Center for Biomedical & Health Sciences, University of California, BerkeleyBerkeleyUnited States
| | - Xavier Darzacq
- Department of Molecular and Cell Biology, University of California, BerkeleyBerkeleyUnited States
- Li Ka Shing Center for Biomedical & Health Sciences, University of California, BerkeleyBerkeleyUnited States
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Liu X, Jiang Y, Cui Y, Yuan J, Fang X. Deep learning in single-molecule imaging and analysis: recent advances and prospects. Chem Sci 2022; 13:11964-11980. [PMID: 36349113 PMCID: PMC9600384 DOI: 10.1039/d2sc02443h] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 09/19/2022] [Indexed: 09/19/2023] Open
Abstract
Single-molecule microscopy is advantageous in characterizing heterogeneous dynamics at the molecular level. However, there are several challenges that currently hinder the wide application of single molecule imaging in bio-chemical studies, including how to perform single-molecule measurements efficiently with minimal run-to-run variations, how to analyze weak single-molecule signals efficiently and accurately without the influence of human bias, and how to extract complete information about dynamics of interest from single-molecule data. As a new class of computer algorithms that simulate the human brain to extract data features, deep learning networks excel in task parallelism and model generalization, and are well-suited for handling nonlinear functions and extracting weak features, which provide a promising approach for single-molecule experiment automation and data processing. In this perspective, we will highlight recent advances in the application of deep learning to single-molecule studies, discuss how deep learning has been used to address the challenges in the field as well as the pitfalls of existing applications, and outline the directions for future development.
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Affiliation(s)
- Xiaolong Liu
- Key Laboratory of Molecular Nanostructure and Nanotechnology, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences Beijing 100190 China
- University of Chinese Academy of Sciences Beijing 100049 P. R. China
| | - Yifei Jiang
- Institute of Basic Medicine and Cancer, Chinese Academy of Sciences Hangzhou 310022 Zhejiang China
| | - Yutong Cui
- Key Laboratory of Molecular Nanostructure and Nanotechnology, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences Beijing 100190 China
- University of Chinese Academy of Sciences Beijing 100049 P. R. China
| | - Jinghe Yuan
- Key Laboratory of Molecular Nanostructure and Nanotechnology, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences Beijing 100190 China
| | - Xiaohong Fang
- Key Laboratory of Molecular Nanostructure and Nanotechnology, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences Beijing 100190 China
- University of Chinese Academy of Sciences Beijing 100049 P. R. China
- Institute of Basic Medicine and Cancer, Chinese Academy of Sciences Hangzhou 310022 Zhejiang China
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Theillet FX, Luchinat E. In-cell NMR: Why and how? PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2022; 132-133:1-112. [PMID: 36496255 DOI: 10.1016/j.pnmrs.2022.04.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 04/19/2022] [Accepted: 04/27/2022] [Indexed: 06/17/2023]
Abstract
NMR spectroscopy has been applied to cells and tissues analysis since its beginnings, as early as 1950. We have attempted to gather here in a didactic fashion the broad diversity of data and ideas that emerged from NMR investigations on living cells. Covering a large proportion of the periodic table, NMR spectroscopy permits scrutiny of a great variety of atomic nuclei in all living organisms non-invasively. It has thus provided quantitative information on cellular atoms and their chemical environment, dynamics, or interactions. We will show that NMR studies have generated valuable knowledge on a vast array of cellular molecules and events, from water, salts, metabolites, cell walls, proteins, nucleic acids, drugs and drug targets, to pH, redox equilibria and chemical reactions. The characterization of such a multitude of objects at the atomic scale has thus shaped our mental representation of cellular life at multiple levels, together with major techniques like mass-spectrometry or microscopies. NMR studies on cells has accompanied the developments of MRI and metabolomics, and various subfields have flourished, coined with appealing names: fluxomics, foodomics, MRI and MRS (i.e. imaging and localized spectroscopy of living tissues, respectively), whole-cell NMR, on-cell ligand-based NMR, systems NMR, cellular structural biology, in-cell NMR… All these have not grown separately, but rather by reinforcing each other like a braided trunk. Hence, we try here to provide an analytical account of a large ensemble of intricately linked approaches, whose integration has been and will be key to their success. We present extensive overviews, firstly on the various types of information provided by NMR in a cellular environment (the "why", oriented towards a broad readership), and secondly on the employed NMR techniques and setups (the "how", where we discuss the past, current and future methods). Each subsection is constructed as a historical anthology, showing how the intrinsic properties of NMR spectroscopy and its developments structured the accessible knowledge on cellular phenomena. Using this systematic approach, we sought i) to make this review accessible to the broadest audience and ii) to highlight some early techniques that may find renewed interest. Finally, we present a brief discussion on what may be potential and desirable developments in the context of integrative studies in biology.
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Affiliation(s)
- Francois-Xavier Theillet
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France.
| | - Enrico Luchinat
- Dipartimento di Scienze e Tecnologie Agro-Alimentari, Alma Mater Studiorum - Università di Bologna, Piazza Goidanich 60, 47521 Cesena, Italy; CERM - Magnetic Resonance Center, and Neurofarba Department, Università degli Studi di Firenze, 50019 Sesto Fiorentino, Italy
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34
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Aparin IO, Yan R, Pelletier R, Choi AA, Danylchuk DI, Xu K, Klymchenko AS. Fluorogenic Dimers as Bright Switchable Probes for Enhanced Super-Resolution Imaging of Cell Membranes. J Am Chem Soc 2022; 144:18043-18053. [PMID: 36153973 DOI: 10.1021/jacs.2c07542] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Super-resolution fluorescence imaging based on single-molecule localization microscopy (SMLM) enables visualizing cellular structures with nanometric precision. However, its spatial and temporal resolution largely relies on the brightness of ON/OFF switchable fluorescent dyes. Moreover, in cell plasma membranes, the single-molecule localization is hampered by the fast lateral diffusion of membrane probes. Here, to address these two fundamental problems, we propose a concept of ON/OFF switchable probes for SMLM (points accumulation for imaging in nanoscale topography, PAINT) based on fluorogenic dimers of bright cyanine dyes. In these probes, the two cyanine units connected with a linker were modified at their extremities with low-affinity membrane anchors. Being self-quenched in water due to intramolecular dye H-aggregation, they displayed light up on reversible binding to lipid membranes. The charged group in the linker further decreased the probe affinity to the lipid membranes, thus accelerating its dynamic reversible ON/OFF switching. The concept was validated on cyanines 3 and 5. SMLM of live cells revealed that the new probes provided higher brightness and ∼10-fold slower diffusion at the cell surface, compared to reference probes Nile Red and DiD, which boosted axial localization precision >3-fold down to 31 nm. The new probe allowed unprecedented observation of nanoscale fibrous protrusions on plasma membranes of live cells with 40 s time resolution, revealing their fast dynamics. Thus, going beyond the brightness limit of single switchable dyes by cooperative dequenching in fluorogenic dimers and slowing down probe diffusion in biomembranes open the route to significant enhancement of super-resolution fluorescence microscopy of live cells.
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Affiliation(s)
- Ilya O Aparin
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Université de Strasbourg, 74 Route du Rhin, 67401 Illkirch, France
| | - Rui Yan
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.,Chan Zuckerberg Biohub, San Francisco, California 94158, United States
| | - Rémi Pelletier
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Université de Strasbourg, 74 Route du Rhin, 67401 Illkirch, France
| | - Alexander A Choi
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.,Chan Zuckerberg Biohub, San Francisco, California 94158, United States
| | - Dmytro I Danylchuk
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Université de Strasbourg, 74 Route du Rhin, 67401 Illkirch, France
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States.,Chan Zuckerberg Biohub, San Francisco, California 94158, United States
| | - Andrey S Klymchenko
- Laboratoire de Bioimagerie et Pathologies, UMR 7021 CNRS, Université de Strasbourg, 74 Route du Rhin, 67401 Illkirch, France
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Stress induced TDP-43 mobility loss independent of stress granules. Nat Commun 2022; 13:5480. [PMID: 36123343 PMCID: PMC9485239 DOI: 10.1038/s41467-022-32939-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2022] [Accepted: 08/24/2022] [Indexed: 11/25/2022] Open
Abstract
TAR DNA binding protein 43 (TDP-43) is closely related to the pathogenesis of amyotrophic lateral sclerosis (ALS) and translocates to stress granules (SGs). The role of SGs as aggregation-promoting “crucibles” for TDP-43, however, is still under debate. We analyzed TDP-43 mobility and localization under different stress and recovery conditions using live cell single-molecule tracking and super-resolution microscopy. Besides reduced mobility within SGs, a stress induced decrease of TDP-43 mobility in the cytoplasm and the nucleus was observed. Stress removal led to a recovery of TDP-43 mobility, which strongly depended on the stress duration. ‘Stimulated-emission depletion microscopy’ (STED) and ‘tracking and localization microscopy’ (TALM) revealed not only TDP-43 substructures within stress granules but also numerous patches of slow TDP-43 species throughout the cytoplasm. This work provides insights into the aggregation of TDP-43 in living cells and provide evidence suggesting that TDP-43 oligomerization and aggregation takes place in the cytoplasm separate from SGs. Amyotrophic Lateral Sclerosis related TDP-43 protein translocates to stress granules with a concomitant reduction in mobility. Here, the authors use single molecule tracking and find a stress-induced reduction in TDP-43 mobility also in the cytoplasm potentially relevant for TDP-43 aggregation.
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Heckert A, Dahal L, Tjian R, Darzacq X. Recovering mixtures of fast-diffusing states from short single-particle trajectories. eLife 2022; 11:e70169. [PMID: 36066004 PMCID: PMC9451534 DOI: 10.7554/elife.70169] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 08/04/2022] [Indexed: 12/15/2022] Open
Abstract
Single-particle tracking (SPT) directly measures the dynamics of proteins in living cells and is a powerful tool to dissect molecular mechanisms of cellular regulation. Interpretation of SPT with fast-diffusing proteins in mammalian cells, however, is complicated by technical limitations imposed by fast image acquisition. These limitations include short trajectory length due to photobleaching and shallow depth of field, high localization error due to the low photon budget imposed by short integration times, and cell-to-cell variability. To address these issues, we investigated methods inspired by Bayesian nonparametrics to infer distributions of state parameters from SPT data with short trajectories, variable localization precision, and absence of prior knowledge about the number of underlying states. We discuss the advantages and disadvantages of these approaches relative to other frameworks for SPT analysis.
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Affiliation(s)
- Alec Heckert
- Department of Molecular and Cell Biology, Li Ka Shing Center for Biomedical and Health Sciences, University of California, BerkeleyBerkeleyUnited States
| | - Liza Dahal
- Department of Molecular and Cell Biology, Li Ka Shing Center for Biomedical and Health Sciences, University of California, BerkeleyBerkeleyUnited States
- CIRM Center of Excellence, University of California, BerkeleyBerkeleyUnited States
| | - Robert Tjian
- CIRM Center of Excellence, University of California, BerkeleyBerkeleyUnited States
- Howard Hughes Medical InstituteBerkeleyUnited States
| | - Xavier Darzacq
- Department of Molecular and Cell Biology, Li Ka Shing Center for Biomedical and Health Sciences, University of California, BerkeleyBerkeleyUnited States
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Huang D, Haddad L, Rahman F, Palma M, Sapelkin A. Engineering a DNA origami mediated multicolour quantum dot platform for sub-diffraction spectral separation imaging. RSC Adv 2022; 12:23778-23785. [PMID: 36093241 PMCID: PMC9394590 DOI: 10.1039/d2ra04316e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 08/04/2022] [Indexed: 12/04/2022] Open
Abstract
The validation of super-resolution optical imaging techniques requires well-defined reference samples that can be used repeatedly and reliably as model standards. Here, we engineer a DNA origami scaffold-mediated multicolour quantum dot hybrid nanostructure and test it using a recently proposed Quantum Dot-based spectral separation technique. We show that multivalent DNA structures offer a robust and precise nanoscale quantum dot placement scaffold, while the spectral resolution method provides relatively simple and fast image acquisition capabilities using any standard confocal or fluorescence microscope capable of spectral signal separation and a single excitation laser wavelength.
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Affiliation(s)
- Da Huang
- Department of Chemistry, Queen Mary University of London London E1 4NS UK
| | - Lucy Haddad
- Department of Physics and Astronomy, Queen Mary University of London London E1 4NS UK
| | - Fahmida Rahman
- Department of Physics and Astronomy, Queen Mary University of London London E1 4NS UK
| | - Matteo Palma
- Department of Chemistry, Queen Mary University of London London E1 4NS UK
| | - Andrei Sapelkin
- Department of Physics and Astronomy, Queen Mary University of London London E1 4NS UK
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Angert I, Karuka SR, Mansky LM, Mueller JD. Partitioning of ribonucleoprotein complexes from the cellular actin cortex. SCIENCE ADVANCES 2022; 8:eabj3236. [PMID: 35984883 PMCID: PMC9390997 DOI: 10.1126/sciadv.abj3236] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 07/08/2022] [Indexed: 06/15/2023]
Abstract
The cell cortex plays a crucial role in cell mechanics, signaling, and development. However, little is known about the influence of the cortical meshwork on the spatial distribution of cytoplasmic biomolecules. Here, we describe a fluorescence microscopy method with the capacity to infer the intracellular distribution of labeled biomolecules with subresolution accuracy. Unexpectedly, we find that RNA binding proteins are partially excluded from the cytoplasmic volume adjacent to the plasma membrane that corresponds to the actin cortex. Complementary diffusion measurements of RNA-protein complexes suggest that a rudimentary model based on excluded volume interactions can explain this partitioning effect. Our results suggest the actin cortex meshwork may play a role in regulating the biomolecular content of the volume immediately adjacent to the plasma membrane.
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Affiliation(s)
- Isaac Angert
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
- Institute of Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA
- Division of Basic Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA
| | - Siddarth Reddy Karuka
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
| | - Louis M. Mansky
- Institute of Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA
- Division of Basic Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN 55455, USA
- Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA
| | - Joachim D. Mueller
- School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455, USA
- Institute of Molecular Virology, University of Minnesota, Minneapolis, MN 55455, USA
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
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39
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Śmigiel WM, Mantovanelli L, Linnik DS, Punter M, Silberberg J, Xiang L, Xu K, Poolman B. Protein diffusion in Escherichia coli cytoplasm scales with the mass of the complexes and is location dependent. SCIENCE ADVANCES 2022; 8:eabo5387. [PMID: 35960807 PMCID: PMC9374337 DOI: 10.1126/sciadv.abo5387] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 06/28/2022] [Indexed: 05/30/2023]
Abstract
We analyze the structure of the cytoplasm by performing single-molecule displacement mapping on a diverse set of native cytoplasmic proteins in exponentially growing Escherichia coli. We evaluate the method for application in small compartments and find that confining effects of the cell membrane affect the diffusion maps. Our analysis reveals that protein diffusion at the poles is consistently slower than in the center of the cell, i.e., to an extent greater than the confining effect of the cell membrane. We also show that the diffusion coefficient scales with the mass of the used probes, taking into account the oligomeric state of the proteins, while parameters such as native protein abundance or the number of protein-protein interactions do not correlate with the mobility of the proteins. We argue that our data paint the prokaryotic cytoplasm as a compartment with subdomains in which the diffusion of macromolecules changes with the perceived viscosity.
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Affiliation(s)
- Wojciech M. Śmigiel
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, Netherlands
| | - Luca Mantovanelli
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, Netherlands
| | - Dmitrii S. Linnik
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, Netherlands
| | - Michiel Punter
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, Netherlands
| | - Jakob Silberberg
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, Netherlands
| | - Limin Xiang
- Department of Chemistry, UC Berkeley, Stanley Hall, Berkeley, CA 94720, USA
| | - Ke Xu
- Department of Chemistry, UC Berkeley, Stanley Hall, Berkeley, CA 94720, USA
| | - Bert Poolman
- Department of Biochemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, Netherlands
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40
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Schmitz TC, van Doeselaar M, Tryfonidou MA, Ito K. Detergent-Free Decellularization of Notochordal Cell-Derived Matrix Yields a Regenerative, Injectable, and Swellable Biomaterial. ACS Biomater Sci Eng 2022; 8:3912-3923. [PMID: 35942885 PMCID: PMC9472229 DOI: 10.1021/acsbiomaterials.2c00790] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Porcine notochordal cell-derived matrix (NCM) has anti-inflammatory
and regenerative effects on degenerated intervertebral discs. For
its clinical use, safety must be assured. The porcine DNA is concerning
because of (1) the transmission of endogenous retroviruses and (2)
the inflammatory potential of cell-free DNA. Here, we present a simple,
detergent-free protocol: tissue lyophilization lyses cells, and matrix
integrity is preserved by limiting swelling during decellularization.
DNA is digested quickly by a high nuclease concentration, followed
by a short washout. Ninety-four percent of DNA was removed, and there
was no loss of glycosaminoglycans or collagen. Forty-three percent
of the total proteins remained in the decellularized NCM (dNCM). dNCM
stimulated as much GAG production as NCM in nucleus pulposus cells
but lost some anti-inflammatory effects. Reconstituted pulverized
dNCM yielded a soft, shear-thinning biomaterial with a swelling ratio
of 350% that also acted as an injectable cell carrier (cell viability
>70%). dNCM can therefore be used as the basis for future biomaterials
aimed at disc regeneration on a biological level and may restore joint
mechanics by creating swelling pressure within the intervertebral
disc.
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Affiliation(s)
- Tara C Schmitz
- Orthopaedic Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, Eindhoven 5600 MB, The Netherlands
| | - Marina van Doeselaar
- Orthopaedic Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, Eindhoven 5600 MB, The Netherlands
| | - Marianna A Tryfonidou
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 108, Utrecht 3584 CM, Netherlands
| | - Keita Ito
- Orthopaedic Biomechanics, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, Eindhoven 5600 MB, The Netherlands
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Zhang P, Wang R, Wan Z, Zhou X, Ma G, Kolay J, Jiang J, Wang S. Label-Free Imaging of Single Proteins and Binding Kinetics Using Total Internal Reflection-Based Evanescent Scattering Microscopy. Anal Chem 2022; 94:10781-10787. [PMID: 35852494 PMCID: PMC9467297 DOI: 10.1021/acs.analchem.2c01510] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Single-molecule detection can push beyond ensemble averages and reveal the statistical distributions of molecular properties. Measuring the binding kinetics of single proteins also represents one of the critical and challenging tasks in protein analysis. Here, we report total internal reflection-based evanescent scattering microscopy with label-free single-protein detection capability. Total internal reflection is employed to excite the evanescent field to enhance light-analyte interaction and reduce environmental noise. As a result, the system provides wide-field imaging capability and allows excitation and observation using one objective. In addition, this system quantifies protein binding kinetics by simultaneously counting the binding of individual molecules and recording their binding sites with nanometer precision, providing a digital method to measure binding kinetics with high spatiotemporal resolution. This approach does not employ specially designed microspheres or nanomaterials and may pave a way for label-free single-protein analysis in conventional microscopy.
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Affiliation(s)
- Pengfei Zhang
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
| | - Rui Wang
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
| | - Zijian Wan
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
- School of Electrical, Energy and Computer Engineering, Arizona State University, Tempe, Arizona 85287, United States
| | - Xinyu Zhou
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona 85287, United States
| | - Guangzhong Ma
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
| | - Jayeeta Kolay
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
| | - Jiapei Jiang
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona 85287, United States
| | - Shaopeng Wang
- Biodesign Center for Bioelectronics and Biosensors, Arizona State University, Tempe, Arizona 85287, United States
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, Arizona 85287, United States
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42
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Evanescent scattering imaging of single protein binding kinetics and DNA conformation changes. Nat Commun 2022; 13:2298. [PMID: 35484120 PMCID: PMC9051210 DOI: 10.1038/s41467-022-30046-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 04/04/2022] [Indexed: 11/08/2022] Open
Abstract
Evanescent illumination has been widely used to detect single biological macromolecules because it can notably enhance light-analyte interaction. However, the current evanescent single-molecule detection system usually requires specially designed microspheres or nanomaterials. Here we show that single protein detection and imaging can be realized on a plain glass surface by imaging the interference between the evanescent lights scattered by the single proteins and by the natural roughness of the cover glass. This allows us to quantify the sizes of single proteins, characterize the protein-antibody interactions at the single-molecule level, and analyze the heterogeneity of single protein binding behaviors. In addition, owing to the exponential distribution of evanescent field intensity, the evanescent imaging system can track the analyte axial movement with high resolution, which can be used to analyze the DNA conformation changes, providing one solution for detecting small molecules, such as microRNA. This work demonstrates a label-free single protein imaging method with ordinary consumables and may pave a road for detecting small biological molecules.
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43
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Chong S, Graham TGW, Dugast-Darzacq C, Dailey GM, Darzacq X, Tjian R. Tuning levels of low-complexity domain interactions to modulate endogenous oncogenic transcription. Mol Cell 2022; 82:2084-2097.e5. [PMID: 35483357 DOI: 10.1016/j.molcel.2022.04.007] [Citation(s) in RCA: 94] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Revised: 02/14/2022] [Accepted: 04/01/2022] [Indexed: 01/09/2023]
Abstract
Gene activation by mammalian transcription factors (TFs) requires multivalent interactions of their low-complexity domains (LCDs), but how such interactions regulate transcription remains unclear. It has been proposed that extensive LCD-LCD interactions culminating in liquid-liquid phase separation (LLPS) of TFs is the dominant mechanism underlying transactivation. Here, we investigated how tuning the amount and localization of LCD-LCD interactions in vivo affects transcription of endogenous human genes. Quantitative single-cell and single-molecule imaging reveals that the oncogenic TF EWS::FLI1 requires a narrow optimum of LCD-LCD interactions to activate its target genes associated with GGAA microsatellites. Increasing LCD-LCD interactions toward putative LLPS represses transcription of these genes in patient-derived cells. Likewise, ectopically creating LCD-LCD interactions to sequester EWS::FLI1 into a well-documented LLPS compartment, the nucleolus, inhibits EWS::FLI1-driven transcription and oncogenic transformation. Our findings show how altering the balance of LCD-LCD interactions can influence transcriptional regulation and suggest a potential therapeutic strategy for targeting disease-causing TFs.
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Affiliation(s)
- Shasha Chong
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Thomas G W Graham
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Claire Dugast-Darzacq
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; CIRM Center of Excellence, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Gina M Dailey
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; CIRM Center of Excellence, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Xavier Darzacq
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; CIRM Center of Excellence, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Robert Tjian
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, CA 94720, USA; Li Ka Shing Center for Biomedical & Health Sciences, University of California, Berkeley, Berkeley, CA 94720, USA; CIRM Center of Excellence, University of California, Berkeley, Berkeley, CA 94720, USA.
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44
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Abstract
In-cell structural biology aims at extracting structural information about proteins or nucleic acids in their native, cellular environment. This emerging field holds great promise and is already providing new facts and outlooks of interest at both fundamental and applied levels. NMR spectroscopy has important contributions on this stage: It brings information on a broad variety of nuclei at the atomic scale, which ensures its great versatility and uniqueness. Here, we detail the methods, the fundamental knowledge, and the applications in biomedical engineering related to in-cell structural biology by NMR. We finally propose a brief overview of the main other techniques in the field (EPR, smFRET, cryo-ET, etc.) to draw some advisable developments for in-cell NMR. In the era of large-scale screenings and deep learning, both accurate and qualitative experimental evidence are as essential as ever to understand the interior life of cells. In-cell structural biology by NMR spectroscopy can generate such a knowledge, and it does so at the atomic scale. This review is meant to deliver comprehensive but accessible information, with advanced technical details and reflections on the methods, the nature of the results, and the future of the field.
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Affiliation(s)
- Francois-Xavier Theillet
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
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45
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Choi AA, Park HH, Chen K, Yan R, Li W, Xu K. Displacement Statistics of Unhindered Single Molecules Show no Enhanced Diffusion in Enzymatic Reactions. J Am Chem Soc 2022; 144:4839-4844. [PMID: 35258969 PMCID: PMC8975259 DOI: 10.1021/jacs.1c12328] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Recent studies have sparked debate over whether catalytic reactions enhance the diffusion coefficients D of enzymes. Through high statistics of the transient (600 μs) displacements of unhindered single molecules freely diffusing in common buffers, we here quantify D for four enzymes under catalytic turnovers. We thus formulate how ∼ ±1% precisions may be achieved for D, and show no changes in diffusivity for catalase, urease, aldolase, and alkaline phosphatase under the application of wide concentration ranges of substrates. Our single-molecule approach thus overcomes potential limitations and artifacts underscored by recent studies to show no enhanced diffusion in enzymatic reactions.
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Affiliation(s)
- Alexander A. Choi
- Department of Chemistry, University of California, Berkeley, CA 94720
| | - Ha H. Park
- Department of Chemistry, University of California, Berkeley, CA 94720
| | - Kun Chen
- Department of Chemistry, University of California, Berkeley, CA 94720
| | - Rui Yan
- Department of Chemistry, University of California, Berkeley, CA 94720
| | - Wan Li
- Department of Chemistry, University of California, Berkeley, CA 94720
| | - Ke Xu
- Department of Chemistry, University of California, Berkeley, CA 94720
- Chan Zuckerberg Biohub, San Francisco, CA 94158
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46
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Xu J, Sun X, Kim K, Brand RM, Hartman D, Ma H, Brand RE, Bai M, Liu Y. Ultrastructural visualization of chromatin in cancer pathogenesis using a simple small-molecule fluorescent probe. SCIENCE ADVANCES 2022; 8:eabm8293. [PMID: 35245126 PMCID: PMC8896800 DOI: 10.1126/sciadv.abm8293] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 01/12/2022] [Indexed: 06/14/2023]
Abstract
Imaging chromatin organization at the molecular-scale resolution remains an important endeavor in basic and translational research. Stochastic optical reconstruction microscopy (STORM) is a powerful superresolution imaging technique to visualize nanoscale molecular organization down to the resolution of ~20 to 30 nm. Despite the substantial progress in imaging chromatin organization in cells and model systems, its routine application on assessing pathological tissue remains limited. It is, in part, hampered by the lack of simple labels that consistently generates high-quality STORM images on the highly processed clinical tissue. We developed a fast, simple, and robust small-molecule fluorescent probe-cyanine 5-conjugated Hoechst-for routine superresolution imaging of nanoscale nuclear architecture on clinical tissue. We demonstrated the biological and clinical significance of imaging superresolved chromatin structure in cancer development and its potential clinical utility for cancer risk stratification.
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Affiliation(s)
- Jianquan Xu
- Biomedical Optical Imaging Laboratory, Departments of Medicine and Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Xuejiao Sun
- Biomedical Optical Imaging Laboratory, Departments of Medicine and Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Kwangho Kim
- Department of Chemistry, Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37232, USA
| | - Rhonda M. Brand
- Department of Medicine, Division of Gastroenterology, Hepatology, and Nutrition, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Douglas Hartman
- Department of Pathology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
| | - Hongqiang Ma
- Biomedical Optical Imaging Laboratory, Departments of Medicine and Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Randall E. Brand
- Department of Medicine, Division of Gastroenterology, Hepatology, and Nutrition, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Mingfeng Bai
- Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Yang Liu
- Biomedical Optical Imaging Laboratory, Departments of Medicine and Bioengineering, University of Pittsburgh, Pittsburgh, PA 15213, USA
- Department of Medicine, Division of Gastroenterology, Hepatology, and Nutrition, University of Pittsburgh, Pittsburgh, PA 15213, USA
- University of Pittsburgh Hillman Cancer Center, Pittsburgh, PA 15232, USA
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48
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Jeong D, Kim D. Super‐resolution fluorescence microscopy‐based single‐molecule spectroscopy. B KOREAN CHEM SOC 2022. [DOI: 10.1002/bkcs.12471] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Dokyung Jeong
- Department of Chemistry Hanyang University Seoul Republic of Korea
| | - Doory Kim
- Department of Chemistry Hanyang University Seoul Republic of Korea
- Research Institute for Convergence of Basic Science, Institute of Nano Science and Technology, and Research Institute for Natural Sciences Hanyang University Seoul Republic of Korea
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49
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Directed evolution approaches for optogenetic tool development. Biochem Soc Trans 2021; 49:2737-2748. [PMID: 34783342 DOI: 10.1042/bst20210700] [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: 09/13/2021] [Revised: 10/16/2021] [Accepted: 10/21/2021] [Indexed: 12/30/2022]
Abstract
Photoswitchable proteins enable specific molecular events occurring in complex biological settings to be probed in a rapid and reversible fashion. Recent progress in the development of photoswitchable proteins as components of optogenetic tools has been greatly facilitated by directed evolution approaches in vitro, in bacteria, or in yeast. We review these developments and suggest future directions for this rapidly advancing field.
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50
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Wang Z, Deng W. Dynamic transcription regulation at the single-molecule level. Dev Biol 2021; 482:67-81. [PMID: 34896367 DOI: 10.1016/j.ydbio.2021.11.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 11/14/2021] [Accepted: 11/15/2021] [Indexed: 02/07/2023]
Abstract
Cell fate changes during development, differentiation, and reprogramming are largely controlled at the transcription level. The DNA-binding transcription factors (TFs) often act in a combinatorial fashion to alter chromatin states and drive cell type-specific gene expression. Recent advances in fluorescent microscopy technologies have enabled direct visualization of biomolecules involved in the process of transcription and its regulatory events at the single-molecule level in living cells. Remarkably, imaging and tracking individual TF molecules at high temporal and spatial resolution revealed that they are highly dynamic in searching and binding cognate targets, rather than static and binding constantly. In combination with investigation using techniques from biochemistry, structure biology, genetics, and genomics, a more well-rounded view of transcription regulation is emerging. In this review, we briefly cover the technical aspects of live-cell single-molecule imaging and focus on the biological relevance and interpretation of the single-molecule dynamic features of transcription regulatory events observed in the native chromatin environment of living eukaryotic cells. We also discuss how these dynamic features might shed light on mechanistic understanding of transcription regulation.
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Affiliation(s)
- Zuhui Wang
- Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing, 100871, China; Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China
| | - Wulan Deng
- Biomedical Pioneering Innovation Center (BIOPIC), Peking University, Beijing, 100871, China; Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, 100871, China; Beijing Advanced Innovation Center for Genomics (ICG), Peking University, Beijing, 100871, China; Peking-Tsinghua Center for Life Sciences (CLS), Peking University, Beijing, 100871, China; School of Life Sciences, Peking University, Beijing, 100871, China.
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