1
|
Guarra F, Colombo G. Conformational Dynamics, Energetics, and the Divergent Evolution of Allosteric Regulation: The Case of the Yeast MAPK Family. Chembiochem 2024; 25:e202400175. [PMID: 38775368 DOI: 10.1002/cbic.202400175] [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: 02/26/2024] [Revised: 04/24/2024] [Indexed: 07/06/2024]
Abstract
Allosteric mechanisms provide finely-tuned control over signalling proteins. Proteins of the same family may share high sequence identity and structural similarity but show distinct traits of allosteric control and evolutionary divergent regulation. Revealing the determinants of such properties may be important to understand the molecular bases of different regulatory pathways. Herein, we investigate whether and how evolutionarily-divergent traits of allosteric regulation in homologous proteins can be decoded in terms of internal dynamics and interaction networks that support functionally oriented conformations. In this framework, we start from the comparative analysis of the dynamics and energetics of the yeast MAP Kinases (MAPKs) Fus3 and Kss1 in their native basins. Importantly, distinctive dynamic and energetic stabilization features emerge, which can be related to the two proteins' differential ability to be phosphorylated and engage with the allosteric activator Ste5. We then expanded our study to other evolutionarily-related MAPKs. We show that the dynamical and energetical traits defining the distinct regulatory profiles of Fus3 and Kss1 can be traced along their evolutionary tree. Overall, our approach is able to reconnect (latent) allostery with the principal elements of protein structural stabilization and dynamics, showing how allosteric regulation was encrypted in MAPKs structure well before Ste5 appearance.
Collapse
Affiliation(s)
- Federica Guarra
- Department of Chemistry, University of Pavia, Via Taramelli 12, 27100, Pavia, Italia
| | - Giorgio Colombo
- Department of Chemistry, University of Pavia, Via Taramelli 12, 27100, Pavia, Italia
| |
Collapse
|
2
|
Li S, Liu Q, Wang E, Wang J. Global quantitative understanding of non-equilibrium cell fate decision-making in response to pheromone. iScience 2023; 26:107885. [PMID: 37766979 PMCID: PMC10520453 DOI: 10.1016/j.isci.2023.107885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 08/09/2023] [Accepted: 09/07/2023] [Indexed: 09/29/2023] Open
Abstract
Cell-cycle arrest and polarized growth are commonly used to characterize the response of yeast to pheromone. However, the quantitative decision-making processes underlying time-dependent changes in cell fate remain unclear. In this study, we conducted single-cell level experiments to observe multidimensional responses, uncovering diverse fates of yeast cells. Multiple states are revealed, along with the kinetic switching rates and pathways among them, giving rise to a quantitative landscape of mating response. To quantify the experimentally observed cell fates, we developed a theoretical framework based on non-equilibrium landscape and flux theory. Additionally, we performed stochastic simulations of biochemical reactions to elucidate signal transduction and cell growth. Notably, our experimental findings have provided the first global quantitative evidence of the real-time synchronization between intracellular signaling, physiological growth, and morphological functions. These results validate the proposed underlying mechanism governing the emergence of multiple cell fate states. This study introduces an emerging mechanistic approach to understand non-equilibrium cell fate decision-making in response to pheromone.
Collapse
Affiliation(s)
- Sheng Li
- College of Chemistry, Jilin University, Changchun, Jilin 130012, China
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, China
| | - Qiong Liu
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, China
| | - Erkang Wang
- College of Chemistry, Jilin University, Changchun, Jilin 130012, China
- State Key Laboratory of Electroanalytical Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022, China
| | - Jin Wang
- Department of Chemistry and of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, NY 11794-3400, USA
| |
Collapse
|
3
|
Bardwell L, Thorner J. Mitogen-activated protein kinase (MAPK) cascades-A yeast perspective. Enzymes 2023; 54:137-170. [PMID: 37945169 DOI: 10.1016/bs.enz.2023.07.001] [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] [Indexed: 11/12/2023]
Abstract
Discovery of the class of protein kinase now dubbed a mitogen (or messenger)-activated protein kinase (MAPK) is an illustrative example of how disparate lines of investigation can converge and reveal an enzyme family universally conserved among eukaryotes, from single-celled microbes to humans. Moreover, elucidation of the circuitry controlling MAPK function defined a now overarching principle in enzyme regulation-the concept of an activation cascade mediated by sequential phosphorylation events. Particularly ground-breaking for this field of exploration were the contributions of genetic approaches conducted using several model organisms, but especially the budding yeast Saccharomyces cerevisiae. Notably, examination of how haploid yeast cells respond to their secreted peptide mating pheromones was crucial in pinpointing genes encoding MAPKs and their upstream activators. Fully contemporaneous biochemical analysis of the activities elicited upon stimulation of mammalian cells by insulin and other growth- and differentiation-inducing factors lead eventually to the demonstration that components homologous to those in yeast were involved. Continued studies of these pathways in yeast were integral to other foundational discoveries in MAPK signaling, including the roles of tethering, scaffolding and docking interactions.
Collapse
Affiliation(s)
- Lee Bardwell
- Department of Developmental and Cell Biology, School of Biological Sciences, University of California, Irvine, Irvine, CA, United States
| | - Jeremy Thorner
- Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, College of Letters and Science, University of California, Berkeley, Berkeley, CA, United States.
| |
Collapse
|
4
|
Ravindran R, Bacellar IOL, Castellanos-Girouard X, Wahba HM, Zhang Z, Omichinski JG, Kisley L, Michnick SW. Peroxisome biogenesis initiated by protein phase separation. Nature 2023; 617:608-615. [PMID: 37165185 PMCID: PMC10302873 DOI: 10.1038/s41586-023-06044-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 04/03/2023] [Indexed: 05/12/2023]
Abstract
Peroxisomes are organelles that carry out β-oxidation of fatty acids and amino acids. Both rare and prevalent diseases are caused by their dysfunction1. Among disease-causing variant genes are those required for protein transport into peroxisomes. The peroxisomal protein import machinery, which also shares similarities with chloroplasts2, is unique in transporting folded and large, up to 10 nm in diameter, protein complexes into peroxisomes3. Current models postulate a large pore formed by transmembrane proteins4; however, so far, no pore structure has been observed. In the budding yeast Saccharomyces cerevisiae, the minimum transport machinery includes the membrane proteins Pex13 and Pex14 and the cargo-protein-binding transport receptor, Pex5. Here we show that Pex13 undergoes liquid-liquid phase separation (LLPS) with Pex5-cargo. Intrinsically disordered regions in Pex13 and Pex5 resemble those found in nuclear pore complex proteins. Peroxisomal protein import depends on both the number and pattern of aromatic residues in these intrinsically disordered regions, consistent with their roles as 'stickers' in associative polymer models of LLPS5,6. Finally, imaging fluorescence cross-correlation spectroscopy shows that cargo import correlates with transient focusing of GFP-Pex13 and GFP-Pex14 on the peroxisome membrane. Pex13 and Pex14 form foci in distinct time frames, suggesting that they may form channels at different saturating concentrations of Pex5-cargo. Our findings lead us to suggest a model in which LLPS of Pex5-cargo with Pex13 and Pex14 results in transient protein transport channels7.
Collapse
Affiliation(s)
- Rini Ravindran
- Département de Biochimie, Université de Montréal, Montreal, Quebec, Canada
| | - Isabel O L Bacellar
- Département de Biochimie, Université de Montréal, Montreal, Quebec, Canada
- Douglas Research Centre, Montreal, Quebec, Canada
| | | | - Haytham M Wahba
- Département de Biochimie, Université de Montréal, Montreal, Quebec, Canada
- Department of Biochemistry, Faculty of Pharmacy, Beni-Suef University, Beni-Suef, Egypt
| | - Zhenghao Zhang
- Department of Physics, Case Western Reserve University, Cleveland, OH, USA
- Mitchell Physics Building (MPHY), College Station, TX, USA
| | - James G Omichinski
- Département de Biochimie, Université de Montréal, Montreal, Quebec, Canada
| | - Lydia Kisley
- Department of Physics, Case Western Reserve University, Cleveland, OH, USA
- Department of Chemistry, Case Western Reserve University, Cleveland, OH, USA
| | - Stephen W Michnick
- Département de Biochimie, Université de Montréal, Montreal, Quebec, Canada.
| |
Collapse
|
5
|
Protein–Protein Interaction Prediction for Targeted Protein Degradation. Int J Mol Sci 2022; 23:ijms23137033. [PMID: 35806036 PMCID: PMC9266413 DOI: 10.3390/ijms23137033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 06/17/2022] [Accepted: 06/18/2022] [Indexed: 02/04/2023] Open
Abstract
Protein–protein interactions (PPIs) play a fundamental role in various biological functions; thus, detecting PPI sites is essential for understanding diseases and developing new drugs. PPI prediction is of particular relevance for the development of drugs employing targeted protein degradation, as their efficacy relies on the formation of a stable ternary complex involving two proteins. However, experimental methods to detect PPI sites are both costly and time-intensive. In recent years, machine learning-based methods have been developed as screening tools. While they are computationally more efficient than traditional docking methods and thus allow rapid execution, these tools have so far primarily been based on sequence information, and they are therefore limited in their ability to address spatial requirements. In addition, they have to date not been applied to targeted protein degradation. Here, we present a new deep learning architecture based on the concept of graph representation learning that can predict interaction sites and interactions of proteins based on their surface representations. We demonstrate that our model reaches state-of-the-art performance using AUROC scores on the established MaSIF dataset. We furthermore introduce a new dataset with more diverse protein interactions and show that our model generalizes well to this new data. These generalization capabilities allow our model to predict the PPIs relevant for targeted protein degradation, which we show by demonstrating the high accuracy of our model for PPI prediction on the available ternary complex data. Our results suggest that PPI prediction models can be a valuable tool for screening protein pairs while developing new drugs for targeted protein degradation.
Collapse
|
6
|
Pócsi I, Szigeti ZM, Emri T, Boczonádi I, Vereb G, Szöllősi J. Use of red, far-red, and near-infrared light in imaging of yeasts and filamentous fungi. Appl Microbiol Biotechnol 2022; 106:3895-3912. [PMID: 35599256 PMCID: PMC9200671 DOI: 10.1007/s00253-022-11967-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 05/02/2022] [Accepted: 05/07/2022] [Indexed: 11/30/2022]
Abstract
Abstract While phototoxicity can be a useful therapeutic modality not only for eliminating malignant cells but also in treating fungal infections, mycologists aiming to observe morphological changes or molecular events in fungi, especially when long observation periods or high light fluxes are warranted, encounter problems owed to altered regulatory pathways or even cell death caused by various photosensing mechanisms. Consequently, the ever expanding repertoire of visible fluorescent protein toolboxes and high-resolution microscopy methods designed to investigate fungi in vitro and in vivo need to comply with an additional requirement: to decrease the unwanted side effects of illumination. In addition to optimizing exposure, an obvious solution is red-shifted illumination, which, however, does not come without compromises. This review summarizes the interactions of fungi with light and the various molecular biology and technology approaches developed for exploring their functions on the molecular, cellular, and in vivo microscopic levels, and outlines the progress towards reducing phototoxicity through applying far-red and near-infrared light. Key points • Fungal biological processes alter upon illumination, also under the microscope • Red shifted fluorescent protein toolboxes decrease interference by illumination • Innovations like two-photon, lightsheet, and near IR microscopy reduce phototoxicity
Collapse
Affiliation(s)
- István Pócsi
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Egyetem tér 1, 4032, Debrecen, Hungary.
| | - Zsuzsa M Szigeti
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Egyetem tér 1, 4032, Debrecen, Hungary
| | - Tamás Emri
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Egyetem tér 1, 4032, Debrecen, Hungary
| | - Imre Boczonádi
- Department of Molecular Biotechnology and Microbiology, Institute of Biotechnology, Faculty of Science and Technology, University of Debrecen, Egyetem tér 1, 4032, Debrecen, Hungary
| | - György Vereb
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem tér 1, 4032, Debrecen, Hungary.,MTA-DE Cell Biology and Signaling Research Group, Faculty of Medicine, University of Debrecen, Egyetem tér 1, 4032, Debrecen, Hungary.,Faculty of Pharmacy, University of Debrecen, Egyetem tér 1, 4032, Debrecen, Hungary
| | - János Szöllősi
- Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem tér 1, 4032, Debrecen, Hungary.,MTA-DE Cell Biology and Signaling Research Group, Faculty of Medicine, University of Debrecen, Egyetem tér 1, 4032, Debrecen, Hungary
| |
Collapse
|
7
|
Yao J, Huang X, Ren J. Selective analysis of newly synthesized proteins by combining fluorescence correlation spectroscopy with bioorthogonal non-canonical amino acid tagging. Analyst 2021; 146:478-486. [DOI: 10.1039/d0an01697g] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
FCS with the BONCAT strategy is a promising approach for analysis of newly synthesized proteins and also be extended to further application for studying physiological or pathological processes related to proteins or other metabolic molecular changes.
Collapse
Affiliation(s)
- Jun Yao
- School of Chemistry and Chemical Engineering
- Frontiers Science Center for Transformative Molecules
- State Key Laboratory of Metal Matrix Composites
- Shanghai Jiao Tong University
- Shanghai 200240
| | - Xiangyi Huang
- School of Chemistry and Chemical Engineering
- Frontiers Science Center for Transformative Molecules
- State Key Laboratory of Metal Matrix Composites
- Shanghai Jiao Tong University
- Shanghai 200240
| | - Jicun Ren
- School of Chemistry and Chemical Engineering
- Frontiers Science Center for Transformative Molecules
- State Key Laboratory of Metal Matrix Composites
- Shanghai Jiao Tong University
- Shanghai 200240
| |
Collapse
|
8
|
Sreenivasan VKA, Graus MS, Pillai RR, Yang Z, Goyette J, Gaus K. Influence of FRET and fluorescent protein maturation on the quantification of binding affinity with dual-channel fluorescence cross-correlation spectroscopy. BIOMEDICAL OPTICS EXPRESS 2020; 11:6137-6153. [PMID: 33282480 PMCID: PMC7687962 DOI: 10.1364/boe.401056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 09/08/2020] [Accepted: 09/08/2020] [Indexed: 06/12/2023]
Abstract
Protein-protein interactions at the plasma membrane mediate transmembrane signaling. Dual-channel fluorescence cross-correlation spectroscopy (dc-FCCS) is a method with which these interactions can be quantified in a cellular context. However, factors such as incomplete maturation of fluorescent proteins, spectral crosstalk, and fluorescence resonance energy transfer (FRET) affect quantification. Some of these can be corrected or accounted for during data analysis and/or interpretation. Here, we experimentally and analytically demonstrate that it is difficult to correct the error caused due to FRET when applying dc-FCCS to measure binding affinity or bound molecular concentrations. Additionally, the presence of dark fluorescent proteins due to incomplete maturation introduces further errors, which too cannot be corrected in the presence of FRET. Based on simulations, we find that modalities such as pulse-interleaved excitation FCCS do not eliminate FRET-induced errors. Finally, we demonstrate that the detrimental effect of FRET can be eliminated with careful experimental design when applying dc-FCCS to quantify protein-protein interactions at the plasma membrane of living cells.
Collapse
Affiliation(s)
- Varun K A Sreenivasan
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney 2052, Australia
| | - Matthew S Graus
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney 2052, Australia
| | - Rashmi R Pillai
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney 2052, Australia
| | - Zhengmin Yang
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney 2052, Australia
| | - Jesse Goyette
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney 2052, Australia
| | - Katharina Gaus
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney 2052, Australia
| |
Collapse
|
9
|
Chen J, Yu Z, Unruh JR, Slaughter BD, Jaspersen SL. Super-resolution Microscopy-based Bimolecular Fluorescence Complementation to Study Protein Complex Assembly and Co-localization. Bio Protoc 2020; 10:e3524. [PMID: 33654748 DOI: 10.21769/bioprotoc.3524] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 12/26/2019] [Accepted: 01/13/2020] [Indexed: 11/02/2022] Open
Abstract
Numerous experimental approaches exist to study interactions between two subunits of a large macromolecular complex. However, most methods do not provide spatial and temporal information about binding, which are critical for dissecting the mechanism of assembly of nanosized complexes in vivo. While recent advances in super-resolution microscopy techniques have provided insights into biological structures beyond the diffraction limit, most require extensive expertise and/or special sample preparation, and it is a challenge to extend beyond binary, two color experiments. Using HyVolution, a super-resolution technique that combines confocal microscopy at sub-airy unit pinhole sizes with computational deconvolution, we achieved 140 nm resolution in both live and fixed samples with three colors, including two fluorescent proteins (mTurquoise2 and GFP) with significant spectral overlap that were distinguished by means of shifting the excitation wavelength away from common wavelengths. By combining HyVolution super-resolution fluorescence microscopy with bimolecular fluorescence complementation (SRM-BiFC), we describe a new assay capable of visualizing protein-protein interactions in vivo at sub-diffraction resolution. This method was used to improve our understanding of the ordered assembly of the Saccharomyces cerevisiae spindle pole body (SPB), a ~1 giga-Dalton heteromeric protein complex formed from 18 structural components present in multiple copies. We propose that SRM-BiFC is a powerful tool for examination of direct interactions between protein complex subunits at sub-diffraction resolution in live cells.
Collapse
Affiliation(s)
- Jingjing Chen
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Zulin Yu
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Jay R Unruh
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | | | - Sue L Jaspersen
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA.,Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| |
Collapse
|
10
|
Scales N, Swain PS. Resolving fluorescent species by their brightness and diffusion using correlated photon-counting histograms. PLoS One 2019; 14:e0226063. [PMID: 31887113 PMCID: PMC6936799 DOI: 10.1371/journal.pone.0226063] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Accepted: 11/19/2019] [Indexed: 12/27/2022] Open
Abstract
Fluorescence fluctuation spectroscopy (FFS) refers to techniques that analyze fluctuations in the fluorescence emitted by fluorophores diffusing in a small volume and can be used to distinguish between populations of molecules that exhibit differences in brightness or diffusion. For example, fluorescence correlation spectroscopy (FCS) resolves species through their diffusion by analyzing correlations in the fluorescence over time; photon counting histograms (PCH) and related methods based on moment analysis resolve species through their brightness by analyzing fluctuations in the photon counts. Here we introduce correlated photon counting histograms (cPCH), which uses both types of information to simultaneously resolve fluorescent species by their brightness and diffusion. We define the cPCH distribution by the probability to detect both a particular number of photons at the current time and another number at a later time. FCS and moment analysis are special cases of the moments of the cPCH distribution, and PCH is obtained by summing over the photon counts in either channel. cPCH is inherently a dual channel technique, and the expressions we develop apply to the dual colour case. Using simulations, we demonstrate that two species differing in both their diffusion and brightness can be better resolved with cPCH than with either FCS or PCH. Further, we show that cPCH can be extended both to longer dwell times to improve the signal-to-noise and to the analysis of images. By better exploiting the information available in fluorescence fluctuation spectroscopy, cPCH will be an enabling methodology for quantitative biology.
Collapse
Affiliation(s)
- Nathan Scales
- Department of Physiology, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec H3G 1Y6, Canada
| | - Peter S. Swain
- Department of Physiology, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec H3G 1Y6, Canada
- School of Biological Sciences, University of Edinburgh, Mayfield Road, Edinburgh EH9 3BF, United Kingdom
| |
Collapse
|
11
|
Derrer CP, Mancini R, Vallotton P, Huet S, Weis K, Dultz E. The RNA export factor Mex67 functions as a mobile nucleoporin. J Cell Biol 2019; 218:3967-3976. [PMID: 31753862 PMCID: PMC6891080 DOI: 10.1083/jcb.201909028] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 11/01/2019] [Accepted: 11/04/2019] [Indexed: 01/09/2023] Open
Abstract
Derrer et al. show that the mRNA export factor Mex67 can perform its essential function when stably tethered to the nuclear pore complex. The RNA export factor Mex67 is essential for the transport of mRNA through the nuclear pore complex (NPC) in yeast, but the molecular mechanism of this export process remains poorly understood. Here, we use quantitative fluorescence microscopy techniques in live budding yeast cells to investigate how Mex67 facilitates mRNA export. We show that Mex67 exhibits little interaction with mRNA in the nucleus and localizes to the NPC independently of mRNA, occupying a set of binding sites offered by FG repeats in the NPC. The ATPase Dbp5, which is thought to remove Mex67 from transcripts, does not affect the interaction of Mex67 with the NPC. Strikingly, we find that the essential function of Mex67 is spatially restricted to the NPC since a fusion of Mex67 to the nucleoporin Nup116 rescues a deletion of MEX67. Thus, Mex67 functions as a mobile NPC component, which receives mRNA export substrates in the central channel of the NPC to facilitate their translocation to the cytoplasm.
Collapse
Affiliation(s)
| | | | | | - Sébastien Huet
- Université de Rennes, Centre National de la Recherche Scientifique, Institut de génétique et développement de Rennes - UMR 6290, Rennes, France
| | - Karsten Weis
- Institute of Biochemistry, ETH Zürich, Zurich, Switzerland
| | - Elisa Dultz
- Institute of Biochemistry, ETH Zürich, Zurich, Switzerland
| |
Collapse
|
12
|
Skruzny M, Pohl E, Abella M. FRET Microscopy in Yeast. BIOSENSORS 2019; 9:E122. [PMID: 31614546 PMCID: PMC6956097 DOI: 10.3390/bios9040122] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Revised: 09/19/2019] [Accepted: 09/30/2019] [Indexed: 02/06/2023]
Abstract
Förster resonance energy transfer (FRET) microscopy is a powerful fluorescence microscopy method to study the nanoscale organization of multiprotein assemblies in vivo. Moreover, many biochemical and biophysical processes can be followed by employing sophisticated FRET biosensors directly in living cells. Here, we summarize existing FRET experiments and biosensors applied in yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe, two important models of fundamental biomedical research and efficient platforms for analyses of bioactive molecules. We aim to provide a practical guide on suitable FRET techniques, fluorescent proteins, and experimental setups available for successful FRET experiments in yeasts.
Collapse
Affiliation(s)
- Michal Skruzny
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany.
- LOEWE Center for Synthetic Microbiology (SYNMIKRO), 35043 Marburg, Germany.
| | - Emma Pohl
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
- LOEWE Center for Synthetic Microbiology (SYNMIKRO), 35043 Marburg, Germany
| | - Marc Abella
- Department of Systems and Synthetic Microbiology, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
- LOEWE Center for Synthetic Microbiology (SYNMIKRO), 35043 Marburg, Germany
| |
Collapse
|
13
|
Komatsubara AT, Goto Y, Kondo Y, Matsuda M, Aoki K. Single-cell quantification of the concentrations and dissociation constants of endogenous proteins. J Biol Chem 2019; 294:6062-6072. [PMID: 30739083 DOI: 10.1074/jbc.ra119.007685] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Revised: 01/30/2019] [Indexed: 01/23/2023] Open
Abstract
Kinetic simulation is a useful approach for elucidating complex cell-signaling systems. The numerical simulations required for kinetic modeling in live cells critically require parameters such as protein concentrations and dissociation constants (Kd ). However, only a limited number of parameters have been measured experimentally in living cells. Here we describe an approach for quantifying the concentration and Kd of endogenous proteins at the single-cell level with CRISPR/Cas9-mediated knock-in and fluorescence cross-correlation spectroscopy. First, the mEGFP gene was knocked in at the end of the mitogen-activated protein kinase 1 (MAPK1) gene, encoding extracellular signal-regulated kinase 2 (ERK2), through homology-directed repair or microhomology-mediated end joining. Next, the HaloTag gene was knocked in at the end of the ribosomal S6 kinase 2 (RSK2) gene. We then used fluorescence correlation spectroscopy to measure the protein concentrations of endogenous ERK2-mEGFP and RSK2-HaloTag fusion constructs in living cells, revealing substantial heterogeneities. Moreover, fluorescence cross-correlation spectroscopy analyses revealed temporal changes in the apparent Kd values of the binding between ERK2-mEGFP and RSK2-HaloTag in response to epidermal growth factor stimulation. Our approach presented here provides a robust and efficient method for quantifying endogenous protein concentrations and dissociation constants in living cells.
Collapse
Affiliation(s)
- Akira T Komatsubara
- From the Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan; the Division of Quantitative Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan
| | - Yuhei Goto
- the Division of Quantitative Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan; the Quantitative Biology Research Group, Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan
| | - Yohei Kondo
- the Division of Quantitative Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan; the Quantitative Biology Research Group, Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan; the Imaging Platform for Spatio-Temporal Information, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan; the Department of Basic Biology, Faculty of Life Science, SOKENDAI (Graduate University for Advanced Studies), Myodaiji, Okazaki, Aichi 444-8787, Japan
| | - Michiyuki Matsuda
- From the Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan; the Department of Pathology and Biology of Diseases, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Kazuhiro Aoki
- the Division of Quantitative Biology, National Institute for Basic Biology, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan; the Quantitative Biology Research Group, Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji-cho, Okazaki, Aichi 444-8787, Japan; the Imaging Platform for Spatio-Temporal Information, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan; the Department of Basic Biology, Faculty of Life Science, SOKENDAI (Graduate University for Advanced Studies), Myodaiji, Okazaki, Aichi 444-8787, Japan.
| |
Collapse
|
14
|
Cdc48/VCP Promotes Chromosome Morphogenesis by Releasing Condensin from Self-Entrapment in Chromatin. Mol Cell 2019; 69:664-676.e5. [PMID: 29452641 DOI: 10.1016/j.molcel.2018.01.030] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2017] [Revised: 11/04/2017] [Accepted: 01/22/2018] [Indexed: 01/26/2023]
Abstract
The morphological transformation of amorphous chromatin into distinct chromosomes is a hallmark of mitosis. To achieve this, chromatin must be compacted and remodeled by a ring-shaped enzyme complex known as condensin. However, the mechanistic basis underpinning condensin's role in chromosome remodeling has remained elusive. Here we show that condensin has a strong tendency to trap itself in its own reaction product during chromatin compaction and yet is capable of interacting with chromatin in a highly dynamic manner in vivo. To resolve this apparent paradox, we identified specific chromatin remodelers and AAA-class ATPases that act in a coordinated manner to release condensin from chromatin entrapment. The Cdc48 segregase is the central linchpin of this regulatory mechanism and promotes ubiquitin-dependent cycling of condensin on mitotic chromatin as well as effective chromosome condensation. Collectively, our results show that condensin inhibition by its own reaction product is relieved by forceful enzyme extraction from chromatin.
Collapse
|
15
|
Unsay JD, Murad F, Hermann E, Ries J, García-Sáez AJ. Scanning Fluorescence Correlation Spectroscopy for Quantification of the Dynamics and Interactions in Tube Organelles of Living Cells. Chemphyschem 2018; 19:3273-3278. [PMID: 30335213 DOI: 10.1002/cphc.201800705] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Indexed: 01/03/2023]
Abstract
Single-molecule spectroscopic quantification of protein-protein interactions directly in the organelles of living cells is highly desirable but remains challenging. Bulk methods, such as Förster resonance energy transfer (FRET), currently only give a relative quantification of the strength of protein-protein interactions. Here, we introduce tube scanning fluorescence cross-correlation spectroscopy (tubeSFCCS) for the absolute quantification of diffusion and complex formation of fluorescently labeled molecules in the mitochondrial compartments. We determined the extent of association between the apoptosis regulators Bcl-xL and tBid at the mitochondrial outer membrane of living cells and discovered that practically all mitochondria-bound Bcl-xL and tBid are associated with each other, in contrast to undetectable association in the cytosol. Furthermore, we show further applicability of our method to other mitochondrial proteins, as well as to proteins in the endoplasmic reticulum (ER) membrane.
Collapse
Affiliation(s)
- Joseph D Unsay
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076, Tübingen, Germany
- Max Planck Insitute for Intteligen Systems, Heisenbergstrasse 3, 70569, Stuttgart, Germany
- German Cancer Research Center, Im Neuenheimer Feld 280, 62120, Heidelberg, Germany
| | - Fabronia Murad
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076, Tübingen, Germany
| | - Eduard Hermann
- Max Planck Insitute for Intteligen Systems, Heisenbergstrasse 3, 70569, Stuttgart, Germany
| | - Jonas Ries
- European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117, Heidelberg, Germany
| | - Ana J García-Sáez
- Interfaculty Institute of Biochemistry, University of Tübingen, Hoppe-Seyler-Str. 4, 72076, Tübingen, Germany
- Max Planck Insitute for Intteligen Systems, Heisenbergstrasse 3, 70569, Stuttgart, Germany
| |
Collapse
|
16
|
Masters TA, Marsh RJ, Blacker TS, Armoogum DA, Larijani B, Bain AJ. Polarized two-photon photoselection in EGFP: Theory and experiment. J Chem Phys 2018; 148:134311. [PMID: 29626864 DOI: 10.1063/1.5011642] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
In this work, we present a complete theoretical description of the excited state order created by two-photon photoselection from an isotropic ground state; this encompasses both the conventionally measured quadrupolar (K = 2) and the "hidden" degree of hexadecapolar (K = 4) transition dipole alignment, their dependence on the two-photon transition tensor and emission transition dipole moment orientation. Linearly and circularly polarized two-photon absorption (TPA) and time-resolved single- and two-photon fluorescence anisotropy measurements are used to determine the structure of the transition tensor in the deprotonated form of enhanced green fluorescent protein. For excitation wavelengths between 800 nm and 900 nm, TPA is best described by a single element, almost completely diagonal, two-dimensional (planar) transition tensor whose principal axis is collinear to that of the single-photon S0 → S1 transition moment. These observations are in accordance with assignments of the near-infrared two-photon absorption band in fluorescent proteins to a vibronically enhanced S0 → S1 transition.
Collapse
Affiliation(s)
- T A Masters
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - R J Marsh
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - T S Blacker
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - D A Armoogum
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| | - B Larijani
- Cell Biophysics Laboratory, Ikerbasque, Basque Foundation for Science and Unidad de Biofisica (CSIC-UPV/EHU), Bilbao, Spain
| | - A J Bain
- Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
| |
Collapse
|
17
|
Delarue M, Brittingham GP, Pfeffer S, Surovtsev IV, Pinglay S, Kennedy KJ, Schaffer M, Gutierrez JI, Sang D, Poterewicz G, Chung JK, Plitzko JM, Groves JT, Jacobs-Wagner C, Engel BD, Holt LJ. mTORC1 Controls Phase Separation and the Biophysical Properties of the Cytoplasm by Tuning Crowding. Cell 2018. [PMID: 29937223 DOI: 10.1016/j.cell.2018.1005.1042] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
Macromolecular crowding has a profound impact on reaction rates and the physical properties of the cell interior, but the mechanisms that regulate crowding are poorly understood. We developed genetically encoded multimeric nanoparticles (GEMs) to dissect these mechanisms. GEMs are homomultimeric scaffolds fused to a fluorescent protein that self-assemble into bright, stable particles of defined size and shape. By combining tracking of GEMs with genetic and pharmacological approaches, we discovered that the mTORC1 pathway can modulate the effective diffusion coefficient of particles ≥20 nm in diameter more than 2-fold by tuning ribosome concentration, without any discernable effect on the motion of molecules ≤5 nm. This change in ribosome concentration affected phase separation both in vitro and in vivo. Together, these results establish a role for mTORC1 in controlling both the mesoscale biophysical properties of the cytoplasm and biomolecular condensation.
Collapse
Affiliation(s)
- M Delarue
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA
| | - G P Brittingham
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA
| | - S Pfeffer
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - I V Surovtsev
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06511, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA; Microbial Sciences Institute, Yale West Campus, West Haven, CT 06516, USA
| | - S Pinglay
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA
| | - K J Kennedy
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 95720, USA
| | - M Schaffer
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - J I Gutierrez
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 95720, USA
| | - D Sang
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA
| | - G Poterewicz
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA
| | - J K Chung
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 95720, USA
| | - J M Plitzko
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - J T Groves
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 95720, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - C Jacobs-Wagner
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06511, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA; Microbial Sciences Institute, Yale West Campus, West Haven, CT 06516, USA; Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06511, USA
| | - B D Engel
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
| | - L J Holt
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA.
| |
Collapse
|
18
|
Delarue M, Brittingham GP, Pfeffer S, Surovtsev IV, Pinglay S, Kennedy KJ, Schaffer M, Gutierrez JI, Sang D, Poterewicz G, Chung JK, Plitzko JM, Groves JT, Jacobs-Wagner C, Engel BD, Holt LJ. mTORC1 Controls Phase Separation and the Biophysical Properties of the Cytoplasm by Tuning Crowding. Cell 2018; 174:338-349.e20. [PMID: 29937223 PMCID: PMC10080728 DOI: 10.1016/j.cell.2018.05.042] [Citation(s) in RCA: 260] [Impact Index Per Article: 43.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 03/26/2018] [Accepted: 05/17/2018] [Indexed: 12/14/2022]
Abstract
Macromolecular crowding has a profound impact on reaction rates and the physical properties of the cell interior, but the mechanisms that regulate crowding are poorly understood. We developed genetically encoded multimeric nanoparticles (GEMs) to dissect these mechanisms. GEMs are homomultimeric scaffolds fused to a fluorescent protein that self-assemble into bright, stable particles of defined size and shape. By combining tracking of GEMs with genetic and pharmacological approaches, we discovered that the mTORC1 pathway can modulate the effective diffusion coefficient of particles ≥20 nm in diameter more than 2-fold by tuning ribosome concentration, without any discernable effect on the motion of molecules ≤5 nm. This change in ribosome concentration affected phase separation both in vitro and in vivo. Together, these results establish a role for mTORC1 in controlling both the mesoscale biophysical properties of the cytoplasm and biomolecular condensation.
Collapse
Affiliation(s)
- M Delarue
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA
| | - G P Brittingham
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA
| | - S Pfeffer
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - I V Surovtsev
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06511, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA; Microbial Sciences Institute, Yale West Campus, West Haven, CT 06516, USA
| | - S Pinglay
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA
| | - K J Kennedy
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 95720, USA
| | - M Schaffer
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - J I Gutierrez
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 95720, USA
| | - D Sang
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA
| | - G Poterewicz
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA
| | - J K Chung
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 95720, USA
| | - J M Plitzko
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - J T Groves
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 95720, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA
| | - C Jacobs-Wagner
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06511, USA; Howard Hughes Medical Institute, Chevy Chase, MD 20815, USA; Microbial Sciences Institute, Yale West Campus, West Haven, CT 06516, USA; Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06511, USA
| | - B D Engel
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
| | - L J Holt
- Institute for Systems Genetics, New York University Langone Health, New York, NY 10016, USA.
| |
Collapse
|
19
|
Trogdon M, Drawert B, Gomez C, Banavar SP, Yi TM, Campàs O, Petzold LR. The effect of cell geometry on polarization in budding yeast. PLoS Comput Biol 2018; 14:e1006241. [PMID: 29889845 PMCID: PMC6013239 DOI: 10.1371/journal.pcbi.1006241] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 06/21/2018] [Accepted: 05/29/2018] [Indexed: 11/19/2022] Open
Abstract
The localization (or polarization) of proteins on the membrane during the mating of budding yeast (Saccharomyces cerevisiae) is an important model system for understanding simple pattern formation within cells. While there are many existing mathematical models of polarization, for both budding and mating, there are still many aspects of this process that are not well understood. In this paper we set out to elucidate the effect that the geometry of the cell can have on the dynamics of certain models of polarization. Specifically, we look at several spatial stochastic models of Cdc42 polarization that have been adapted from published models, on a variety of tip-shaped geometries, to replicate the shape change that occurs during the growth of the mating projection. We show here that there is a complex interplay between the dynamics of polarization and the shape of the cell. Our results show that while models of polarization can generate a stable polarization cap, its localization at the tip of mating projections is unstable, with the polarization cap drifting away from the tip of the projection in a geometry dependent manner. We also compare predictions from our computational results to experiments that observe cells with projections of varying lengths, and track the stability of the polarization cap. Lastly, we examine one model of actin polarization and show that it is unlikely, at least for the models studied here, that actin dynamics and vesicle traffic are able to overcome this effect of geometry.
Collapse
Affiliation(s)
- Michael Trogdon
- Department of Mechanical Engineering, University of California, Santa Barbara, Santa Barbara, California, United States of America
- * E-mail:
| | - Brian Drawert
- Department of Computer Science, University of North Carolina, Asheville, Asheville, North Carolina, United States of America
| | - Carlos Gomez
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, United States of America
- California NanoSystems Institute, University of California, Santa Barbara, Santa Barbara, California, United States of America
| | - Samhita P. Banavar
- California NanoSystems Institute, University of California, Santa Barbara, Santa Barbara, California, United States of America
- Department of Physics, University of California, Santa Barbara, Santa Barbara, California, United States of America
| | - Tau-Mu Yi
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, United States of America
| | - Otger Campàs
- Department of Mechanical Engineering, University of California, Santa Barbara, Santa Barbara, California, United States of America
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California, United States of America
- California NanoSystems Institute, University of California, Santa Barbara, Santa Barbara, California, United States of America
- Center for Bioengineering, University of California, Santa Barbara, Santa Barbara, California, United States of America
| | - Linda R. Petzold
- Department of Mechanical Engineering, University of California, Santa Barbara, Santa Barbara, California, United States of America
- Center for Bioengineering, University of California, Santa Barbara, Santa Barbara, California, United States of America
- Department of Computer Science, University of California, Santa Barbara, Santa Barbara, California, United States of America
| |
Collapse
|
20
|
Miao Y, Tipakornsaowapak T, Zheng L, Mu Y, Lewellyn E. Phospho-regulation of intrinsically disordered proteins for actin assembly and endocytosis. FEBS J 2018; 285:2762-2784. [PMID: 29722136 DOI: 10.1111/febs.14493] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Revised: 04/04/2018] [Accepted: 04/26/2018] [Indexed: 12/13/2022]
Abstract
Actin filament assembly contributes to the endocytic pathway pleiotropically, with active roles in clathrin-dependent and clathrin-independent endocytosis as well as subsequent endosomal trafficking. Endocytosis comprises a series of dynamic events, including the initiation of membrane curvature, bud invagination, vesicle abscission and subsequent vesicular transport. The ultimate success of endocytosis requires the coordinated activities of proteins that trigger actin polymerization, recruit actin-binding proteins (ABPs) and organize endocytic proteins (EPs) that promote membrane curvature through molecular crowding or scaffolding mechanisms. A particularly interesting phenomenon is that multiple EPs and ABPs contain a substantial percentage of intrinsically disordered regions (IDRs), which can contribute to protein coacervation and phase separation. In addition, intrinsically disordered proteins (IDPs) frequently contain sites for post-translational modifications (PTMs) such as phosphorylation, and these modifications exhibit a high preference for IDR residues [Groban ES et al. (2006) PLoS Comput Biol 2, e32]. PTMs are implicated in regulating protein function by modulating the protein conformation, protein-protein interactions and the transition between order and disorder states of IDPs. The molecular mechanisms by which IDRs of ABPs and EPs fine-tune actin assembly and endocytosis remain mostly unexplored and elusive. In this review, we analyze protein sequences of budding yeast EPs and ABPs, and discuss the potential underlying mechanisms for regulating endocytosis and actin assembly through the emerging concept of IDR-mediated protein multivalency, coacervation, and phase transition, with an emphasis on the phospho-regulation of IDRs. Finally, we summarize the current understanding of how these mechanisms coordinate actin cytoskeleton assembly and membrane curvature formation during endocytosis in budding yeast.
Collapse
Affiliation(s)
- Yansong Miao
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.,School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore, Singapore
| | | | - Liangzhen Zheng
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Yuguang Mu
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Eric Lewellyn
- Department of Biology, Division of Natural Sciences, St Norbert College, De Pere, WI, USA
| |
Collapse
|
21
|
Kaliszewski MJ, Shi X, Hou Y, Lingerak R, Kim S, Mallory P, Smith AW. Quantifying membrane protein oligomerization with fluorescence cross-correlation spectroscopy. Methods 2018; 140-141:40-51. [PMID: 29448037 DOI: 10.1016/j.ymeth.2018.02.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Revised: 12/17/2017] [Accepted: 02/07/2018] [Indexed: 01/27/2023] Open
Abstract
Fluorescence cross-correlation spectroscopy (FCCS) is an advanced fluorescence technique that can quantify protein-protein interactions in vivo. Due to the dynamic, heterogeneous nature of the membrane, special considerations must be made to interpret FCCS data accurately. In this study, we describe a method to quantify the oligomerization of membrane proteins tagged with two commonly used fluorescent probes, mCherry (mCH) and enhanced green (eGFP) fluorescent proteins. A mathematical model is described that relates the relative cross-correlation value (fc) to the degree of oligomerization. This treatment accounts for mismatch in the confocal volumes, combinatoric effects of using two fluorescent probes, and the presence of non-fluorescent probes. Using this model, we calculate a ladder of fc values which can be used to determine the oligomer state of membrane proteins from live-cell experimental data. Additionally, a probabilistic mathematical simulation is described to resolve the affinity of different dimeric and oligomeric protein controls.
Collapse
Affiliation(s)
| | - Xiaojun Shi
- Department of Chemistry, University of Akron, Akron, OH 44325, USA
| | - Yixuan Hou
- Food Animal Health Research Program, Ohio Agriculture Research and Development Center, Department of Veterinary Preventive Medicine, The Ohio State University, Wooster, OH 44691, USA
| | - Ryan Lingerak
- Department of Biology, University of Akron, Akron, OH 44325, USA
| | - Soyeon Kim
- Department of Chemistry, University of Akron, Akron, OH 44325, USA
| | - Paul Mallory
- Department of Chemistry, University of Akron, Akron, OH 44325, USA
| | - Adam W Smith
- Department of Chemistry, University of Akron, Akron, OH 44325, USA.
| |
Collapse
|
22
|
Papini C, Royer CA. Scanning number and brightness yields absolute protein concentrations in live cells: a crucial parameter controlling functional bio-molecular interaction networks. Biophys Rev 2018; 10:87-96. [PMID: 29383593 DOI: 10.1007/s12551-017-0394-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 12/29/2017] [Indexed: 12/27/2022] Open
Abstract
Biological function results from properly timed bio-molecular interactions that transduce external or internal signals, resulting in any number of cellular fates, including triggering of cell-state transitions (division, differentiation, transformation, apoptosis), metabolic homeostasis and adjustment to changing physical or nutritional environments, amongst many more. These bio-molecular interactions can be modulated by chemical modifications of proteins, nucleic acids, lipids and other small molecules. They can result in bio-molecular transport from one cellular compartment to the other and often trigger specific enzyme activities involved in bio-molecular synthesis, modification or degradation. Clearly, a mechanistic understanding of any given high level biological function requires a quantitative characterization of the principal bio-molecular interactions involved and how these may change dynamically. Such information can be obtained using fluctation analysis, in particular scanning number and brightness, and used to build and test mechanistic models of the functional network to define which characteristics are the most important for its regulation.
Collapse
Affiliation(s)
- Christina Papini
- Program in Biochemistry and Biophysics, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA
| | - Catherine A Royer
- Program in Biochemistry and Biophysics, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA.
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA.
| |
Collapse
|
23
|
Elson EL. Introduction to fluorescence correlation Spectroscopy-Brief and simple. Methods 2017; 140-141:3-9. [PMID: 29155128 DOI: 10.1016/j.ymeth.2017.11.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 11/13/2017] [Indexed: 02/04/2023] Open
Affiliation(s)
- Elliot L Elson
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
| |
Collapse
|
24
|
Tavakoli M, Taylor JN, Li CB, Komatsuzaki T, Pressé S. Single Molecule Data Analysis: An Introduction. ADVANCES IN CHEMICAL PHYSICS 2017. [DOI: 10.1002/9781119324560.ch4] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Meysam Tavakoli
- Physics Department; Indiana University-Purdue University Indianapolis; Indianapolis IN 46202 USA
| | - J. Nicholas Taylor
- Research Institute for Electronic Science; Hokkaido University; Kita 20 Nishi 10 Kita-Ku Sapporo 001-0020 Japan
| | - Chun-Biu Li
- Research Institute for Electronic Science; Hokkaido University; Kita 20 Nishi 10 Kita-Ku Sapporo 001-0020 Japan
- Department of Mathematics; Stockholm University; 106 91 Stockholm Sweden
| | - Tamiki Komatsuzaki
- Research Institute for Electronic Science; Hokkaido University; Kita 20 Nishi 10 Kita-Ku Sapporo 001-0020 Japan
| | - Steve Pressé
- Physics Department; Indiana University-Purdue University Indianapolis; Indianapolis IN 46202 USA
- Department of Chemistry and Chemical Biology; Indiana University-Purdue University Indianapolis; Indianapolis IN 46202 USA
- Department of Cell and Integrative Physiology; Indiana University School of Medicine; Indianapolis IN 46202 USA
- Department of Physics and School of Molecular Sciences; Arizona State University; Tempe AZ 85287 USA
| |
Collapse
|
25
|
Dopamine Receptor Signaling in MIN6 β-Cells Revealed by Fluorescence Fluctuation Spectroscopy. Biophys J 2017; 111:609-618. [PMID: 27508444 DOI: 10.1016/j.bpj.2016.06.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 06/21/2016] [Accepted: 06/23/2016] [Indexed: 11/22/2022] Open
Abstract
Insulin secretion defects are central to the development of type II diabetes mellitus. Glucose stimulation of insulin secretion has been extensively studied, but its regulation by other stimuli such as incretins and neurotransmitters is not as well understood. We investigated the mechanisms underlying the inhibition of insulin secretion by dopamine, which is synthesized in pancreatic β-cells from circulating L-dopa. Previous research has shown that this inhibition is mediated primarily by activation of the dopamine receptor D3 subtype (DRD3), even though both DRD2 and DRD3 are expressed in β-cells. To understand this dichotomy, we investigated the dynamic interactions between the dopamine receptor subtypes and their G-proteins using two-color fluorescence fluctuation spectroscopy (FFS) of mouse MIN6 β-cells. We show that proper membrane localization of exogenous G-proteins depends on both the Gβ and Gγ subunits being overexpressed in the cell. Triple transfections of the dopamine receptor subtype and Gβ and Gγ subunits, each labeled with a different-colored fluorescent protein (FP), yielded plasma membrane expression of all three FPs and permitted an FFS evaluation of interactions between the dopamine receptors and the Gβγ complex. Upon dopamine stimulation, we measured a significant decrease in interactions between DRD3 and the Gβγ complex, which is consistent with receptor activation. In contrast, dopamine stimulation did not cause significant changes in the interactions between DRD2 and the Gβγ complex. These results demonstrate that two-color FFS is a powerful tool for measuring dynamic protein interactions in living cells, and show that preferential DRD3 signaling in β-cells occurs at the level of G-protein release.
Collapse
|
26
|
Phosphatidylserine Lateral Organization Influences the Interaction of Influenza Virus Matrix Protein 1 with Lipid Membranes. J Virol 2017; 91:JVI.00267-17. [PMID: 28356535 DOI: 10.1128/jvi.00267-17] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 03/21/2017] [Indexed: 01/21/2023] Open
Abstract
Influenza A virus matrix protein 1 (M1) is an essential component involved in the structural stability of the virus and in the budding of new virions from infected cells. A deeper understanding of the molecular basis of virion formation and the budding process is required in order to devise new therapeutic approaches. We performed a detailed investigation of the interaction between M1 and phosphatidylserine (PS) (i.e., its main binding target at the plasma membrane [PM]), as well as the distribution of PS itself, both in model membranes and in living cells. To this end, we used a combination of techniques, including Förster resonance energy transfer (FRET), confocal microscopy imaging, raster image correlation spectroscopy, and number and brightness (N&B) analysis. Our results show that PS can cluster in segregated regions in the plane of the lipid bilayer, both in model bilayers constituted of PS and phosphatidylcholine and in living cells. The viral protein M1 interacts specifically with PS-enriched domains, and such interaction in turn affects its oligomerization process. Furthermore, M1 can stabilize PS domains, as observed in model membranes. For living cells, the presence of PS clusters is suggested by N&B experiments monitoring the clustering of the PS sensor lactadherin. Also, colocalization between M1 and a fluorescent PS probe suggest that, in infected cells, the matrix protein can specifically bind to the regions of PM in which PS is clustered. Taken together, our observations provide novel evidence regarding the role of PS-rich domains in tuning M1-lipid and M1-M1 interactions at the PM of infected cells.IMPORTANCE Influenza virus particles assemble at the plasma membranes (PM) of infected cells. This process is orchestrated by the matrix protein M1, which interacts with membrane lipids while binding to the other proteins and genetic material of the virus. Despite its importance, the initial step in virus assembly (i.e., M1-lipid interaction) is still not well understood. In this work, we show that phosphatidylserine can form lipid domains in physical models of the inner leaflet of the PM. Furthermore, the spatial organization of PS in the plane of the bilayer modulates M1-M1 interactions. Finally, we show that PS domains appear to be present in the PM of living cells and that M1 seems to display a high affinity for them.
Collapse
|
27
|
Chattoraj S, Saha S, Halder D, Jana SS, Bhattacharyya K. Structural Oscillations of Non-muscle Myosin II-C2: Time Resolved Confocal Microscopy. ChemistrySelect 2017. [DOI: 10.1002/slct.201601963] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Shyamtanu Chattoraj
- Department of Physical Chemistry; Indian Association for the Cultivation of Science; Jadavpur; Kolkata-32 INDIA
| | - Shekhar Saha
- Department of Biological Chemistry; Indian Association for the Cultivation of Science; Jadavpur; Kolkata-32 INDIA
- Department of Biochemistry and Molecular Genetics; University of Virginia; Charlottesville, VA USA
| | - Debdatta Halder
- Department of Biological Chemistry; Indian Association for the Cultivation of Science; Jadavpur; Kolkata-32 INDIA
| | - Siddhartha S. Jana
- Department of Biological Chemistry; Indian Association for the Cultivation of Science; Jadavpur; Kolkata-32 INDIA
| | - Kankan Bhattacharyya
- Department of Physical Chemistry; Indian Association for the Cultivation of Science; Jadavpur; Kolkata-32 INDIA
- Department of Chemistry; Indian Institute of Science Education and Research (IISER); Bhopal, Madhya Pradesh 462030 INDIA
| |
Collapse
|
28
|
Hur KH, Chen Y, Mueller JD. Characterization of Ternary Protein Systems In Vivo with Tricolor Heterospecies Partition Analysis. Biophys J 2016; 110:1158-67. [PMID: 26958892 DOI: 10.1016/j.bpj.2016.01.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 12/24/2015] [Accepted: 01/04/2016] [Indexed: 11/16/2022] Open
Abstract
Tools and assays that characterize protein-protein interactions are of fundamental importance to biology, because protein assemblies play a critical role in the control and regulation of nearly every cellular process. The availability of fluorescent proteins has facilitated the direct and real-time observation of protein-protein interactions inside living cells, but existing methods are mostly limited to binary interactions between two proteins. Because of the scarcity of techniques capable of identifying ternary interactions, we developed tricolor heterospecies partition analysis. The technique is based on brightness analysis of fluorescence fluctuations from three fluorescent proteins that serve as protein labels. We identified three fluorescent proteins suitable for tricolor brightness experiments. In addition, we developed the theory of identifying interactions in a ternary protein system using tricolor heterospecies partition analysis. The theory was verified by experiments on well-characterized protein systems. A graphical representation of the heterospecies partition data was introduced to visualize interactions in ternary protein systems. Lastly, we performed fluorescence fluctuation experiments on cells expressing a coactivator and two nuclear receptors and applied heterospecies partition analysis to explore the interactions of this ternary protein system.
Collapse
Affiliation(s)
- Kwang-Ho Hur
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota
| | - Yan Chen
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota; Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota
| | - Joachim D Mueller
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota; Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota; Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota.
| |
Collapse
|
29
|
Single-cell dynamics and variability of MAPK activity in a yeast differentiation pathway. Proc Natl Acad Sci U S A 2016; 113:E5896-E5905. [PMID: 27651485 DOI: 10.1073/pnas.1610081113] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In response to pheromones, yeast cells activate a MAPK pathway to direct processes important for mating, including gene induction, cell-cycle arrest, and polarized cell growth. Although a variety of assays have been able to elucidate signaling activities at multiple steps in the pathway, measurements of MAPK activity during the pheromone response have remained elusive, and our understanding of single-cell signaling behavior is incomplete. Using a yeast-optimized FRET-based mammalian Erk-activity reporter to monitor Fus3 and Kss1 activity in live yeast cells, we demonstrate that overall mating MAPK activity exhibits distinct temporal dynamics, rapid reversibility, and a graded dose dependence around the KD of the receptor, where phenotypic transitions occur. The complex dose response was found to be largely a consequence of two feedbacks involving cyclin-mediated scaffold phosphorylation and Fus3 autoregulation. Distinct cell cycle-dependent response patterns comprised a large portion of the cell-to-cell variability at each dose, constituting the major source of extrinsic noise in coupling activity to downstream gene-expression responses. Additionally, we found diverse spatial MAPK activity patterns to emerge over time in cells undergoing default, gradient, and true mating responses. Furthermore, ramping up and rapid loss of activity were closely associated with zygote formation in mating-cell pairs, supporting a role for elevated MAPK activity in successful cell fusion and morphogenic reorganization. Altogether, these findings present a detailed view of spatiotemporal MAPK activity during the pheromone response, elucidating its role in mediating complex long-term developmental fates in a unicellular differentiation system.
Collapse
|
30
|
Feng S, Ollivier JF, Soyer OS. Enzyme Sequestration as a Tuning Point in Controlling Response Dynamics of Signalling Networks. PLoS Comput Biol 2016; 12:e1004918. [PMID: 27163612 PMCID: PMC4862689 DOI: 10.1371/journal.pcbi.1004918] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Accepted: 04/17/2016] [Indexed: 11/18/2022] Open
Abstract
Signalling networks result from combinatorial interactions among many enzymes and scaffolding proteins. These complex systems generate response dynamics that are often essential for correct decision-making in cells. Uncovering biochemical design principles that underpin such response dynamics is a prerequisite to understand evolved signalling networks and to design synthetic ones. Here, we use in silico evolution to explore the possible biochemical design space for signalling networks displaying ultrasensitive and adaptive response dynamics. By running evolutionary simulations mimicking different biochemical scenarios, we find that enzyme sequestration emerges as a key mechanism for enabling such dynamics. Inspired by these findings, and to test the role of sequestration, we design a generic, minimalist model of a signalling cycle, featuring two enzymes and a single scaffolding protein. We show that this simple system is capable of displaying both ultrasensitive and adaptive response dynamics. Furthermore, we find that tuning the concentration or kinetics of the sequestering protein can shift system dynamics between these two response types. These empirical results suggest that enzyme sequestration through scaffolding proteins is exploited by evolution to generate diverse response dynamics in signalling networks and could provide an engineering point in synthetic biology applications.
Collapse
Affiliation(s)
- Song Feng
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | | | - Orkun S. Soyer
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
- * E-mail:
| |
Collapse
|
31
|
Hu Z, Wang Y, Yu L, Mahanty SK, Mendoza N, Elion EA. Mapping regions in Ste5 that support Msn5-dependent and -independent nuclear export. Biochem Cell Biol 2016; 94:109-28. [PMID: 26824509 DOI: 10.1139/bcb-2015-0101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Careful control of the available pool of the MAPK scaffold Ste5 is important for mating-pathway activation and the prevention of inappropriate mating differentiation in haploid Saccharomyces cerevisiae. Ste5 shuttles constitutively through the nucleus, where it is degraded by a ubiquitin-dependent mechanism triggered by G1 CDK phosphorylation. Here we narrow-down regions of Ste5 that mediate nuclear export. Four regions in Ste5 relocalize SV40-TAgNLS-GFP-GFP from nucleus to cytoplasm. One region is N-terminal, dependent on exportin Msn5/Ste21/Kap142, and interacts with Msn5 in 2 hybrid assays independently of mating pheromone, Fus3, Kss1, Ptc1, the NLS/PM, and RING-H2. A second region overlaps the PH domain and Ste11 binding site and 2 others are on the vWA domain and include residues essential for MAPK activation. We find no evidence for dependence on Crm1/Xpo1, despite numerous potential nuclear export sequences (NESs) detected by LocNES and NetNES1.1 predictors. Thus, Msn5 (homolog of human Exportin-5) and one or more exportins or adaptor molecules besides Crm1/Xpo1 may regulate Ste5 through multiple recognition sites.
Collapse
Affiliation(s)
- Zhenhua Hu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Yunmei Wang
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Lu Yu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Sanjoy K Mahanty
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Natalia Mendoza
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Elaine A Elion
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.,Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| |
Collapse
|
32
|
Olivera-Couto A, Salzman V, Mailhos M, Digman MA, Gratton E, Aguilar PS. Eisosomes are dynamic plasma membrane domains showing pil1-lsp1 heteroligomer binding equilibrium. Biophys J 2016; 108:1633-1644. [PMID: 25863055 PMCID: PMC4390835 DOI: 10.1016/j.bpj.2015.02.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Revised: 01/28/2015] [Accepted: 02/12/2015] [Indexed: 12/11/2022] Open
Abstract
Eisosomes are plasma membrane domains concentrating lipids, transporters, and signaling molecules. In the budding yeast Saccharomyces cerevisiae, these domains are structured by scaffolds composed mainly by two cytoplasmic proteins Pil1 and Lsp1. Eisosomes are immobile domains, have relatively uniform size, and encompass thousands of units of the core proteins Pil1 and Lsp1. In this work we used fluorescence fluctuation analytical methods to determine the dynamics of eisosome core proteins at different subcellular locations. Using a combination of scanning techniques with autocorrelation analysis, we show that Pil1 and Lsp1 cytoplasmic pools freely diffuse whereas an eisosome-associated fraction of these proteins exhibits slow dynamics that fit with a binding-unbinding equilibrium. Number and brightness analysis shows that the eisosome-associated fraction is oligomeric, while cytoplasmic pools have lower aggregation states. Fluorescence lifetime imaging results indicate that Pil1 and Lsp1 directly interact in the cytoplasm and within the eisosomes. These results support a model where Pil1-Lsp1 heterodimers are the minimal eisosomes building blocks. Moreover, individual-eisosome fluorescence fluctuation analysis shows that eisosomes in the same cell are not equal domains: while roughly half of them are mostly static, the other half is actively exchanging core protein subunits.
Collapse
Affiliation(s)
- Agustina Olivera-Couto
- Laboratorio de Biología Celular de Membranas, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Valentina Salzman
- Laboratorio de Biología Celular de Membranas, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Milagros Mailhos
- Laboratorio de Biología Celular de Membranas, Institut Pasteur de Montevideo, Montevideo, Uruguay
| | - Michelle A Digman
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California-Irvine, Irvine, California; Centre for Bioactive Discovery in Health and Ageing, School of Science and Technology, University of New England, Armidale, Australia
| | - Enrico Gratton
- Laboratory for Fluorescence Dynamics, Department of Biomedical Engineering, University of California-Irvine, Irvine, California.
| | - Pablo S Aguilar
- Laboratorio de Biología Celular de Membranas, Institut Pasteur de Montevideo, Montevideo, Uruguay.
| |
Collapse
|
33
|
Georgieva MV, Yahya G, Codó L, Ortiz R, Teixidó L, Claros J, Jara R, Jara M, Iborra A, Gelpí JL, Gallego C, Orozco M, Aldea M. Inntags: small self-structured epitopes for innocuous protein tagging. Nat Methods 2015; 12:955-8. [PMID: 26322837 DOI: 10.1038/nmeth.3556] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 07/06/2015] [Indexed: 11/09/2022]
Abstract
Protein tagging is widely used in approaches ranging from affinity purification to fluorescence-based detection in live cells. However, an intrinsic limitation of tagging is that the native function of the protein may be compromised or even abolished by the presence of the tag. Here we describe and characterize a set of small, innocuous protein tags (inntags) that we anticipate will find application in a variety of biological techniques.
Collapse
Affiliation(s)
- Maya V Georgieva
- Molecular Biology Institute of Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Galal Yahya
- Molecular Biology Institute of Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain.,Department of Microbiology and Immunology, School of Pharmacy, Zagazig University, Zagazig, Egypt
| | - Laia Codó
- Barcelona Supercomputing Center (BSC), Barcelona, Spain.,Joint BSC-CRG-IRB Programme in Computational Biology, Barcelona, Spain
| | - Raúl Ortiz
- Molecular Biology Institute of Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | | | | | | | | | | | - Josep Lluís Gelpí
- Barcelona Supercomputing Center (BSC), Barcelona, Spain.,Joint BSC-CRG-IRB Programme in Computational Biology, Barcelona, Spain.,Departament de Bioquimica, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain
| | - Carme Gallego
- Molecular Biology Institute of Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| | - Modesto Orozco
- Joint BSC-CRG-IRB Programme in Computational Biology, Barcelona, Spain.,Departament de Bioquimica, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain.,Institute for Research in Biomedicine (IRB Barcelona), Barcelona, Spain
| | - Martí Aldea
- Molecular Biology Institute of Barcelona (IBMB), Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain
| |
Collapse
|
34
|
Mikuni S, Kodama K, Sasaki A, Kohira N, Maki H, Munetomo M, Maenaka K, Kinjo M. Screening for FtsZ Dimerization Inhibitors Using Fluorescence Cross-Correlation Spectroscopy and Surface Resonance Plasmon Analysis. PLoS One 2015; 10:e0130933. [PMID: 26154290 PMCID: PMC4496089 DOI: 10.1371/journal.pone.0130933] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 05/01/2015] [Indexed: 01/16/2023] Open
Abstract
FtsZ is an attractive target for antibiotic research because it is an essential bacterial cell division protein that polymerizes in a GTP-dependent manner. To find the seed chemical structure, we established a high-throughput, quantitative screening method combining fluorescence cross-correlation spectroscopy (FCCS) and surface plasmon resonance (SPR). As a new concept for the application of FCCS to polymerization-prone protein, Staphylococcus aureus FtsZ was fragmented into the N-terminal and C-terminal, which were fused with GFP and mCherry (red fluorescent protein), respectively. By this fragmentation, the GTP-dependent head-to-tail dimerization of each fluorescent labeled fragment of FtsZ could be observed, and the inhibitory processes of chemicals could be monitored by FCCS. In the first round of screening by FCCS, 28 candidates were quantitatively and statistically selected from 495 chemicals determined by in silico screening. Subsequently, in the second round of screening by FCCS, 71 candidates were also chosen from 888 chemicals selected via an in silico structural similarity search of the chemicals screened in the first round of screening. Moreover, the dissociation constants between the highest inhibitory chemicals and Staphylococcus aureus FtsZ were determined by SPR. Finally, by measuring the minimum inhibitory concentration, it was confirmed that the screened chemical had antibacterial activity against Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus (MRSA).
Collapse
Affiliation(s)
- Shintaro Mikuni
- Laboratory of Molecular Cell Dynamics, Faculty of Advanced Life Science, Hokkaido University, Sapporo, Japan
| | - Kota Kodama
- Creative Research Institution, Hokkaido University, Sapporo, Japan
| | - Akira Sasaki
- Bio-Analytical Research Group, Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki, Japan
| | - Naoki Kohira
- Discovery Research Laboratory for Core Therapeutic Areas, Shionogi & Co., Ltd., Toyonaka, Osaka, Japan
| | - Hideki Maki
- Discovery Research Laboratory for Core Therapeutic Areas, Shionogi & Co., Ltd., Toyonaka, Osaka, Japan
| | - Masaharu Munetomo
- Information Initiative Center and Graduate School of Information Science and Technology, Hokkaido University, Sapporo, Japan
| | - Katsumi Maenaka
- Laboratory of Biomolecular Science, Faculty of Pharmaceutical Science, Hokkaido University, Sapporo, Japan
| | - Masataka Kinjo
- Laboratory of Molecular Cell Dynamics, Faculty of Advanced Life Science, Hokkaido University, Sapporo, Japan
- * E-mail:
| |
Collapse
|
35
|
Tsekouras K, Siegel AP, Day RN, Pressé S. Inferring diffusion dynamics from FCS in heterogeneous nuclear environments. Biophys J 2015; 109:7-17. [PMID: 26153697 PMCID: PMC4572512 DOI: 10.1016/j.bpj.2015.05.035] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 05/20/2015] [Accepted: 05/28/2015] [Indexed: 01/08/2023] Open
Abstract
Fluorescence correlation spectroscopy (FCS) is a noninvasive technique that probes the diffusion dynamics of proteins down to single-molecule sensitivity in living cells. Critical mechanistic insight is often drawn from FCS experiments by fitting the resulting time-intensity correlation function, G(t), to known diffusion models. When simple models fail, the complex diffusion dynamics of proteins within heterogeneous cellular environments can be fit to anomalous diffusion models with adjustable anomalous exponents. Here, we take a different approach. We use the maximum entropy method to show-first using synthetic data-that a model for proteins diffusing while stochastically binding/unbinding to various affinity sites in living cells gives rise to a G(t) that could otherwise be equally well fit using anomalous diffusion models. We explain the mechanistic insight derived from our method. In particular, using real FCS data, we describe how the effects of cell crowding and binding to affinity sites manifest themselves in the behavior of G(t). Our focus is on the diffusive behavior of an engineered protein in 1) the heterochromatin region of the cell's nucleus as well as 2) in the cell's cytoplasm and 3) in solution. The protein consists of the basic region-leucine zipper (BZip) domain of the CCAAT/enhancer-binding protein (C/EBP) fused to fluorescent proteins.
Collapse
Affiliation(s)
| | - Amanda P Siegel
- Integrated Nanosystems Development Institute, IUPUI, Indianapolis Indiana
| | - Richard N Day
- Department of Cellular & Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Steve Pressé
- Department of Physics, IUPUI, Indianapolis Indiana; Department of Cellular & Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana.
| |
Collapse
|
36
|
Feng S, Ollivier JF, Swain PS, Soyer OS. BioJazz: in silico evolution of cellular networks with unbounded complexity using rule-based modeling. Nucleic Acids Res 2015; 43:e123. [PMID: 26101250 PMCID: PMC4627059 DOI: 10.1093/nar/gkv595] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 05/26/2015] [Indexed: 11/13/2022] Open
Abstract
Systems biologists aim to decipher the structure and dynamics of signaling and regulatory networks underpinning cellular responses; synthetic biologists can use this insight to alter existing networks or engineer de novo ones. Both tasks will benefit from an understanding of which structural and dynamic features of networks can emerge from evolutionary processes, through which intermediary steps these arise, and whether they embody general design principles. As natural evolution at the level of network dynamics is difficult to study, in silico evolution of network models can provide important insights. However, current tools used for in silico evolution of network dynamics are limited to ad hoc computer simulations and models. Here we introduce BioJazz, an extendable, user-friendly tool for simulating the evolution of dynamic biochemical networks. Unlike previous tools for in silico evolution, BioJazz allows for the evolution of cellular networks with unbounded complexity by combining rule-based modeling with an encoding of networks that is akin to a genome. We show that BioJazz can be used to implement biologically realistic selective pressures and allows exploration of the space of network architectures and dynamics that implement prescribed physiological functions. BioJazz is provided as an open-source tool to facilitate its further development and use. Source code and user manuals are available at: http://oss-lab.github.io/biojazz and http://osslab.lifesci.warwick.ac.uk/BioJazz.aspx.
Collapse
Affiliation(s)
- Song Feng
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | | | - Peter S Swain
- SynthSys, The University of Edinburgh, Edinburgh, United Kingdom
| | - Orkun S Soyer
- School of Life Sciences, University of Warwick, Coventry, United Kingdom
| |
Collapse
|
37
|
Hur KH, Mueller JD. Quantitative Brightness Analysis of Fluorescence Intensity Fluctuations in E. Coli. PLoS One 2015; 10:e0130063. [PMID: 26099032 PMCID: PMC4476568 DOI: 10.1371/journal.pone.0130063] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2015] [Accepted: 05/15/2015] [Indexed: 11/18/2022] Open
Abstract
The brightness measured by fluorescence fluctuation spectroscopy specifies the average stoichiometry of a labeled protein in a sample. Here we extended brightness analysis, which has been mainly applied in eukaryotic cells, to prokaryotic cells with E. coli serving as a model system. The small size of the E. coli cell introduces unique challenges for applying brightness analysis that are addressed in this work. Photobleaching leads to a depletion of fluorophores and a reduction of the brightness of protein complexes. In addition, the E. coli cell and the point spread function of the instrument only partially overlap, which influences intensity fluctuations. To address these challenges we developed MSQ analysis, which is based on the mean Q-value of segmented photon count data, and combined it with the analysis of axial scans through the E. coli cell. The MSQ method recovers brightness, concentration, and diffusion time of soluble proteins in E. coli. We applied MSQ to measure the brightness of EGFP in E. coli and compared it to solution measurements. We further used MSQ analysis to determine the oligomeric state of nuclear transport factor 2 labeled with EGFP expressed in E. coli cells. The results obtained demonstrate the feasibility of quantifying the stoichiometry of proteins by brightness analysis in a prokaryotic cell.
Collapse
Affiliation(s)
- Kwang-Ho Hur
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Joachim D. Mueller
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota, United States of America
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota, United States of America
- * E-mail:
| |
Collapse
|
38
|
Robellet X, Thattikota Y, Wang F, Wee TL, Pascariu M, Shankar S, Bonneil É, Brown CM, D'Amours D. A high-sensitivity phospho-switch triggered by Cdk1 governs chromosome morphogenesis during cell division. Genes Dev 2015; 29:426-39. [PMID: 25691469 PMCID: PMC4335297 DOI: 10.1101/gad.253294.114] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The initiation of chromosome morphogenesis marks the beginning of mitosis in eukaryotic cells. Robellet et al. found that multisite phosphorylation of the chromatin-binding sensor Smc4 integrates the activation state of Cdk1 with the dynamic binding of the condensation machinery to chromatin. Abrogation of this event leads to chromosome segregation defects and lethality, while moderate reduction reveals the existence of a novel chromatin transition state specific to mitosis, the intertwist configuration. The initiation of chromosome morphogenesis marks the beginning of mitosis in all eukaryotic cells. Although many effectors of chromatin compaction have been reported, the nature and design of the essential trigger for global chromosome assembly remain unknown. Here we reveal the identity of the core mechanism responsible for chromosome morphogenesis in early mitosis. We show that the unique sensitivity of the chromosome condensation machinery for the kinase activity of Cdk1 acts as a major driving force for the compaction of chromatin at mitotic entry. This sensitivity is imparted by multisite phosphorylation of a conserved chromatin-binding sensor, the Smc4 protein. The multisite phosphorylation of this sensor integrates the activation state of Cdk1 with the dynamic binding of the condensation machinery to chromatin. Abrogation of this event leads to chromosome segregation defects and lethality, while moderate reduction reveals the existence of a novel chromatin transition state specific to mitosis, the intertwist configuration. Collectively, our results identify the mechanistic basis governing chromosome morphogenesis in early mitosis and how distinct chromatin compaction states can be established via specific thresholds of Cdk1 kinase activity.
Collapse
Affiliation(s)
- Xavier Robellet
- Institute for Research in Immunology and Cancer (IRIC), Département de Pathologie et Biologie Cellulaire, Université de Montréal, Montréal, Quebec H3C 3J7, Canada
| | - Yogitha Thattikota
- Institute for Research in Immunology and Cancer (IRIC), Département de Pathologie et Biologie Cellulaire, Université de Montréal, Montréal, Quebec H3C 3J7, Canada
| | - Fang Wang
- Institute for Research in Immunology and Cancer (IRIC), Département de Pathologie et Biologie Cellulaire, Université de Montréal, Montréal, Quebec H3C 3J7, Canada
| | - Tse-Luen Wee
- Advanced BioImaging Facility (ABIF), Department of Physiology, McGill University, Montréal, Quebec H3G 0B1, Canada
| | - Mirela Pascariu
- Institute for Research in Immunology and Cancer (IRIC), Département de Pathologie et Biologie Cellulaire, Université de Montréal, Montréal, Quebec H3C 3J7, Canada
| | - Sahana Shankar
- Institute for Research in Immunology and Cancer (IRIC), Département de Pathologie et Biologie Cellulaire, Université de Montréal, Montréal, Quebec H3C 3J7, Canada
| | - Éric Bonneil
- Institute for Research in Immunology and Cancer (IRIC)
| | - Claire M Brown
- Advanced BioImaging Facility (ABIF), Department of Physiology, McGill University, Montréal, Quebec H3G 0B1, Canada
| | - Damien D'Amours
- Institute for Research in Immunology and Cancer (IRIC), Département de Pathologie et Biologie Cellulaire, Université de Montréal, Montréal, Quebec H3C 3J7, Canada
| |
Collapse
|
39
|
Cui Y, Naz A, Thompson DH, Irudayaraj J. Decitabine nanoconjugate sensitizes human glioblastoma cells to temozolomide. Mol Pharm 2015; 12:1279-88. [PMID: 25751281 DOI: 10.1021/mp500815b] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
In this study, we developed and characterized a delivery system for the epigenetic demethylating drug, decitabine, to sensitize temozolomide-resistant human glioblastoma multiforme (GBM) cells to alkylating chemotherapy. A poly(lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) based nanoconjugate was fabricated to encapsulate decitabine and achieved a better therapeutic response in GBM cells than that with the free drug. After synthesis, the highly efficient uptake process and intracellular dynamics of this nanoconjugate were monitored by single-molecule fluorescence tools. Our experiments demonstrated that, under an acidic pH due to active glycolysis in cancer cells, the PLGA-PEG nanovector could release the conjugated decitabine at a faster rate, after which the hydrolyzed lactic acid and glycolic acid would further acidify the intracellular microenvironment, thus providing positive feedback to increase the effective drug concentration and realize growth inhibition. In temozolomide-resistant GBM cells, decitabine can potentiate the cytotoxic DNA alkylation by counteracting cytosine methylation and reactivating tumor suppressor genes, such as p53 and p21. Owing to the excellent internalization and endolysosomal escape enabled by the PLGA-PEG backbone, the encapsulated decitabine exhibited a better anti-GBM potential than that of free drug molecules. Hence, the synthesized nanoconjugate and temozolomide could act in synergy to deliver a more potent and long-term antiproliferative effect against malignant GBM cells.
Collapse
Affiliation(s)
| | - Asia Naz
- ‡Department of Pharmaceutical Chemistry, University of Karachi, Karachi 75270, Pakistan
| | | | | |
Collapse
|
40
|
Cui Y, Irudayaraj J. Dissecting the behavior and function of MBD3 in DNA methylation homeostasis by single-molecule spectroscopy and microscopy. Nucleic Acids Res 2015; 43:3046-55. [PMID: 25753672 PMCID: PMC4381056 DOI: 10.1093/nar/gkv098] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Accepted: 01/29/2015] [Indexed: 12/14/2022] Open
Abstract
The detailed mechanism for DNA methylation homeostasis relies on an intricate regulatory network with a possible contribution from methyl-CpG-binding domain protein 3 (MBD3). In this study we examine the single-molecule behavior of MBD3 and its functional implication in balancing the activity of DNA methyltransferases (DNMTs). Besides a localization tendency to DNA demethylating sites, MBD3 experiences a concurrent transcription with DNMTs in cell cycle. Fluorescence lifetime correlation spectroscopy (FLCS) and photon counting histogram (PCH) were applied to characterize the chromatin binding kinetics and stoichiometry of MBD3 in different cell phases. In the G1-phase, MBD3, in the context of the Mi-2/NuRD (nucleosome remodeling deacetylase) complex, could adopt a salt-dependent homodimeric association with its target epigenomic loci. Along with cell cycle progression, utilizing fluorescence lifetime imaging microscopy-based Förster resonance energy transfer (FLIM-FRET) we revealed that a proportion of MBD3 and MBD2 would co-localize with DNMT1 during DNA maintenance methylation, providing a proofreading and protective mechanism against a possible excessive methylation by DNMT1. In accordance with our hypothesis, insufficient MBD3 induced by small interfering RNA (siRNA) was found to result in a global DNA hypermethylation as well as increased methylation in the promoter CpG islands (CGIs) of a number of cell cycle related genes.
Collapse
Affiliation(s)
- Yi Cui
- Department of Agricultural and Biological Engineering, 225 S. University Street, Purdue University, West Lafayette, IN 47907, USA Bindley Bioscience Center, 1203 W. State Street, Purdue University, West Lafayette, IN 47907, USA
| | - Joseph Irudayaraj
- Department of Agricultural and Biological Engineering, 225 S. University Street, Purdue University, West Lafayette, IN 47907, USA Bindley Bioscience Center, 1203 W. State Street, Purdue University, West Lafayette, IN 47907, USA
| |
Collapse
|
41
|
Monillas ES, Caplan JL, Thévenin AF, Bahnson BJ. Oligomeric state regulated trafficking of human platelet-activating factor acetylhydrolase type-II. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:469-75. [PMID: 25707358 DOI: 10.1016/j.bbapap.2015.02.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 02/06/2015] [Accepted: 02/12/2015] [Indexed: 01/19/2023]
Abstract
The intracellular enzyme platelet-activating factor acetylhydrolase type-II (PAFAH-II) hydrolyzes platelet-activating factor and oxidatively fragmented phospholipids. PAFAH-II in its resting state is mainly cytoplasmic, and it responds to oxidative stress by becoming increasingly bound to endoplasmic reticulum and Golgi membranes. Numerous studies have indicated that this enzyme is essential for protecting cells from oxidative stress induced apoptosis. However, the regulatory mechanism of the oxidative stress response by PAFAH-II has not been fully resolved. Here, changes to the oligomeric state of human PAFAH-II were investigated as a potential regulatory mechanism toward enzyme trafficking. Native PAGE analysis in vitro and photon counting histogram within live cells showed that PAFAH-II is both monomeric and dimeric. A Gly-2-Ala site-directed mutation of PAFAH-II demonstrated that the N-terminal myristoyl group is required for homodimerization. Additionally, the distribution of oligomeric PAFAH-II is distinct within the cell; homodimers of PAFAH-II were localized to the cytoplasm while monomers were associated to the membranes of the endoplasmic reticulum and Golgi. We propose that the oligomeric state of PAFAH-II drives functional protein trafficking. PAFAH-II localization to the membrane is critical for substrate acquisition and effective oxidative stress protection. It is hypothesized that the balance between monomer and dimer serves as a regulatory mechanism of a PAFAH-II oxidative stress response.
Collapse
Affiliation(s)
- Elizabeth S Monillas
- Department of Chemistry & Biochemistry, University of Delaware, Newark, DE 19716, USA
| | - Jeffrey L Caplan
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Anastasia F Thévenin
- Department of Chemistry & Biochemistry, University of Delaware, Newark, DE 19716, USA
| | - Brian J Bahnson
- Department of Chemistry & Biochemistry, University of Delaware, Newark, DE 19716, USA.
| |
Collapse
|
42
|
Pelassa I, Zhao C, Pasche M, Odermatt B, Lagnado L. Synaptic vesicles are "primed" for fast clathrin-mediated endocytosis at the ribbon synapse. Front Mol Neurosci 2014; 7:91. [PMID: 25520613 PMCID: PMC4248811 DOI: 10.3389/fnmol.2014.00091] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 11/03/2014] [Indexed: 11/13/2022] Open
Abstract
Retrieval of synaptic vesicles can occur 1-10 s after fusion, but the role of clathrin during this process has been unclear because the classical mode of clathrin-mediated endocytosis (CME) is an order of magnitude slower, as during retrieval of surface receptors. Classical CME is thought to be rate-limited by the recruitment of clathrin, which raises the question: how is clathrin recruited during synaptic vesicle recycling? To investigate this question we applied total internal reflection fluorescence microscopy (TIRFM) to the synaptic terminal of retinal bipolar cells expressing fluorescent constructs of clathrin light-chain A. Upon calcium influx we observed a fast accumulation of clathrin within 100 ms at the periphery of the active zone. The subsequent loss of clathrin from these regions reflected endocytosis because the application of a potent clathrin inhibitor Pitstop2 dramatically slowed down this phase by ~3 fold. These results indicate that clathrin-dependent retrieval of synaptic vesicles is unusually fast, most probably because of a "priming" step involving a state of association of clathrin with the docked vesicle and with the endosomes and cisternae surrounding the ribbons. Fluorescence correlation spectroscopy (FCS) and fluorescence recovery after photobleaching (FRAP) showed that the majority of clathrin is moving with the same kinetics as synaptic vesicle proteins. Together, these results indicate that the fast endocytic mechanism operating to retrieve synaptic vesicles differs substantially from the classical mode of CME operating via formation of a coated pit.
Collapse
Affiliation(s)
| | | | | | | | - Leon Lagnado
- Medical Research Council Laboratory of Molecular Biology, Neurobiology DivisionCambridge, UK
| |
Collapse
|
43
|
Cui Y, Irudayaraj J. Inside single cells: quantitative analysis with advanced optics and nanomaterials. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2014; 7:387-407. [PMID: 25430077 DOI: 10.1002/wnan.1321] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 10/17/2014] [Accepted: 10/29/2014] [Indexed: 01/08/2023]
Abstract
Single-cell explorations offer a unique window to inspect molecules and events relevant to mechanisms and heterogeneity constituting the central dogma of biology. A large number of nucleic acids, proteins, metabolites, and small molecules are involved in determining and fine-tuning the state and function of a single cell at a given time point. Advanced optical platforms and nanotools provide tremendous opportunities to probe intracellular components with single-molecule accuracy, as well as promising tools to adjust single-cell activity. To obtain quantitative information (e.g., molecular quantity, kinetics, and stoichiometry) within an intact cell, achieving the observation with comparable spatiotemporal resolution is a challenge. For single-cell studies, both the method of detection and the biocompatibility are critical factors as they determine the feasibility, especially when considering live-cell analysis. Although a considerable proportion of single-cell methodologies depend on specialized expertise and expensive instruments, it is our expectation that the information content and implication will outweigh the costs given the impact on life science enabled by single-cell analysis.
Collapse
Affiliation(s)
- Yi Cui
- Department of Agricultural and Biological Engineering, Bindley Bioscience Center and Birck Nanotechnology Center, Purdue University, West Lafayette, IN, USA
| | | |
Collapse
|
44
|
Boeke D, Trautmann S, Meurer M, Wachsmuth M, Godlee C, Knop M, Kaksonen M. Quantification of cytosolic interactions identifies Ede1 oligomers as key organizers of endocytosis. Mol Syst Biol 2014; 10:756. [PMID: 25366307 PMCID: PMC4299599 DOI: 10.15252/msb.20145422] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 09/11/2014] [Accepted: 10/01/2014] [Indexed: 01/08/2023] Open
Abstract
Clathrin-mediated endocytosis is a highly conserved intracellular trafficking pathway that depends on dynamic protein-protein interactions between up to 60 different proteins. However, little is known about the spatio-temporal regulation of these interactions. Using fluorescence (cross)-correlation spectroscopy in yeast, we tested 41 previously reported interactions in vivo and found 16 to exist in the cytoplasm. These detected cytoplasmic interactions included the self-interaction of Ede1, homolog of mammalian Eps15. Ede1 is the crucial scaffold for the organization of the early stages of endocytosis. We show that oligomerization of Ede1 through its central coiled coil domain is necessary for its localization to the endocytic site and we link the oligomerization of Ede1 to its function in locally concentrating endocytic adaptors and organizing the endocytic machinery. Our study sheds light on the importance of the regulation of protein-protein interactions in the cytoplasm for the assembly of the endocytic machinery in vivo.
Collapse
Affiliation(s)
- Dominik Boeke
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) Deutsches Krebsforschungszentrum (DKFZ) DKFZ-ZMBH-Allianz, Heidelberg, Germany
| | - Susanne Trautmann
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) Deutsches Krebsforschungszentrum (DKFZ) DKFZ-ZMBH-Allianz, Heidelberg, Germany
| | - Matthias Meurer
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) Deutsches Krebsforschungszentrum (DKFZ) DKFZ-ZMBH-Allianz, Heidelberg, Germany
| | - Malte Wachsmuth
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | - Camilla Godlee
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | - Michael Knop
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH) Deutsches Krebsforschungszentrum (DKFZ) DKFZ-ZMBH-Allianz, Heidelberg, Germany
| | - Marko Kaksonen
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| |
Collapse
|
45
|
Youker RT, Teng H. Measuring protein dynamics in live cells: protocols and practical considerations for fluorescence fluctuation microscopy. JOURNAL OF BIOMEDICAL OPTICS 2014; 19:90801. [PMID: 25260867 PMCID: PMC4183152 DOI: 10.1117/1.jbo.19.9.090801] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Revised: 08/12/2014] [Accepted: 07/31/2014] [Indexed: 06/03/2023]
Abstract
Quantitative analysis of protein complex stoichiometries and mobilities are critical for elucidating the mechanisms that regulate cellular pathways. Fluorescence fluctuation spectroscopy (FFS) techniques can measure protein dynamics, such as diffusion coefficients and formation of complexes, with extraordinary precision and sensitivity. Complete calibration and characterization of the microscope instrument is necessary in order to avoid artifacts during data acquisition and to capitalize on the full capabilities of FFS techniques. We provide an overview of the theory behind FFS techniques, discuss calibration procedures, provide protocols, and give practical considerations for performing FFS experiments. One important parameter recovered from FFS measurements is the relative molecular brightness that can correlate with oligomerization. Three methods for measuring molecular brightness (fluorescence correlation spectroscopy, photon-counting histogram, and number and brightness analysis) recover similar values when measuring samples under ideal conditions in vitro. However, examples are given illustrating that these different methods used for calculating molecular brightness of fluorescent molecules in cells are not always equivalent. Methods relying on spot measurements are more prone to bleaching and movement artifacts that can lead to underestimation of brightness values. We advocate for the use of multiple FFS techniques to study molecular brightnesses to overcome and compliment limitations of individual techniques.
Collapse
Affiliation(s)
- Robert T. Youker
- University of Pittsburgh School of
Medicine, Renal-Electrolyte Division, Pittsburgh, Pennsylvania
15261, United States
- Western Carolina University,
Department of Biology, Cullowhee, North Carolina 28723, United
States
| | - Haibing Teng
- Carnegie Mellon University,
Molecular Biosensor and Imaging Center (MBIC), Pittsburgh, Pennsylvania 15213,
United States
| |
Collapse
|
46
|
Quantitative in vivo fluorescence cross-correlation analyses highlight the importance of competitive effects in the regulation of protein-protein interactions. Mol Cell Biol 2014; 34:3272-90. [PMID: 24958104 DOI: 10.1128/mcb.00087-14] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Computer-assisted simulation is a promising approach for clarifying complicated signaling networks. However, this approach is currently limited by a deficiency of kinetic parameters determined in living cells. To overcome this problem, we applied fluorescence cross-correlation spectrometry (FCCS) to measure dissociation constant (Kd) values of signaling molecule complexes in living cells (in vivo Kd). Among the pairs of fluorescent molecules tested, that of monomerized enhanced green fluorescent protein (mEGFP) and HaloTag-tetramethylrhodamine was most suitable for the measurement of in vivo Kd by FCCS. Using this pair, we determined 22 in vivo Kd values of signaling molecule complexes comprising the epidermal growth factor receptor (EGFR)-Ras-extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase pathway. With these parameters, we developed a kinetic simulation model of the EGFR-Ras-ERK MAP kinase pathway and uncovered a potential role played by stoichiometry in Shc binding to EGFR during the peak activations of Ras, MEK, and ERK. Intriguingly, most of the in vivo Kd values determined in this study were higher than the in vitro Kd values reported previously, suggesting the significance of competitive bindings inside cells. These in vivo Kd values will provide a sound basis for the quantitative understanding of signal transduction.
Collapse
|
47
|
Caculitan N, Kai H, Liu EY, Fay N, Yu Y, Lohmüller T, O’Donoghue G, Groves JT. Size-based chromatography of signaling clusters in a living cell membrane. NANO LETTERS 2014; 14:2293-8. [PMID: 24655064 PMCID: PMC4025576 DOI: 10.1021/nl404514e] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Revised: 03/13/2014] [Indexed: 05/05/2023]
Abstract
Here we introduce a form of chromatography that can be imposed on the membrane of a living cell. A cell-cell signaling interaction is reconstituted in a hybrid live cell-supported membrane junction. The chromatographic material consists of a hexagonally ordered array of gold nanoparticles (nanodot array), which is fabricated onto the underlying substrate. While individual membrane components move freely throughout the array, the movement of larger assemblies is impeded if they exceed the physical dimensions of the array. This tactile approach to probing membrane structures in living cells reveals organizational aspects of the membrane environment unobservable by other techniques.
Collapse
Affiliation(s)
- Niña
G. Caculitan
- Howard
Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Hiroyuki Kai
- Howard
Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Eulanca Y. Liu
- Howard
Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Nicole Fay
- Howard
Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Yan Yu
- Howard
Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California 94720, United States
- Physical
Biosciences and Materials Sciences Divisions, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Theobald Lohmüller
- Howard
Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California 94720, United States
- Physical
Biosciences and Materials Sciences Divisions, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Geoff
P. O’Donoghue
- Howard
Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California 94720, United States
| | - Jay T. Groves
- Howard
Hughes Medical Institute, Department of Chemistry, University of California, Berkeley, California 94720, United States
- Physical
Biosciences and Materials Sciences Divisions, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| |
Collapse
|
48
|
Hur KH, Macdonald PJ, Berk S, Angert CI, Chen Y, Mueller JD. Quantitative measurement of brightness from living cells in the presence of photodepletion. PLoS One 2014; 9:e97440. [PMID: 24820174 PMCID: PMC4018325 DOI: 10.1371/journal.pone.0097440] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 04/10/2014] [Indexed: 11/21/2022] Open
Abstract
The brightness of fluorescently labeled proteins provides an excellent marker for identifying protein interactions in living cells. Quantitative interpretation of brightness, however, hinges on a detailed understanding of the processes that affect the signal fluctuation of the fluorescent label. Here, we focus on the cumulative influence of photobleaching on brightness measurements in cells. Photobleaching within the finite volume of the cell leads to a depletion of the population of fluorescently labeled proteins with time. The process of photodepletion reduces the fluorescence signal which biases the analysis of brightness data. Our data show that even small reductions in the signal can introduce significant bias into the analysis of the data. We develop a model that quantifies the bias and introduce an analysis method that accurately determines brightness in the presence of photodepletion as verified by experiments with mammalian and yeast cells. In addition, photodepletion experiments with the fluorescent protein EGFP reveal the presence of a photoconversion process, which leads to a marked decrease in the brightness of the EGFP protein. We also identify conditions where the effect of EGFP's photoconversion on brightness experiments can be safely ignored.
Collapse
Affiliation(s)
- Kwang-Ho Hur
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Patrick J Macdonald
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Serkan Berk
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - C Isaac Angert
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Yan Chen
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Joachim D Mueller
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota, United States of America
| |
Collapse
|
49
|
McCormick CD, Akamatsu MS, Ti SC, Pollard TD. Measuring affinities of fission yeast spindle pole body proteins in live cells across the cell cycle. Biophys J 2014; 105:1324-35. [PMID: 24047983 DOI: 10.1016/j.bpj.2013.08.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 08/12/2013] [Accepted: 08/14/2013] [Indexed: 12/22/2022] Open
Abstract
Characterizing protein-protein interactions is essential for understanding molecular mechanisms, although reproducing cellular conditions in vitro is challenging and some proteins are difficult to purify. We developed a method to measure binding to cellular structures using fission yeast cells as reaction vessels. We varied the concentrations of Sid2p and Mob1p (proteins of the septation initiation network) and measured their binding to spindle pole bodies (SPBs), the centrosome equivalent of yeast. From our measurements we infer that Sid2p and Mob1p both exist as monomeric, heterodimeric, and homodimeric species throughout the cell cycle. During interphase these species have widely different affinities for their common receptor Cdc11p on the SPB. The data support a model with a subset of Cdc11p binding the heterodimeric species with a Kd < 0.1 μM when Sid2p binds Mob1p-Cdc11p and Kd in the micromolar range when Mob1p binds Sid2p-Cdc11p. During mitosis an additional species presumed to be the phosphorylated Sid2p-Mob1p heterodimer binds SPBs with a lower affinity. Homodimers of Sid2p or Mob1p bind to the rest of Cdc11p at SPBs with lower affinity: Kds > 10 μM during interphase and somewhat stronger during mitosis. These measurements allowed us to account for the fluctuations in Sid2p binding to SPBs throughout the cell cycle.
Collapse
Affiliation(s)
- Chad D McCormick
- Departments of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut
| | | | | | | |
Collapse
|
50
|
Pack CG, Yukii H, Toh-e A, Kudo T, Tsuchiya H, Kaiho A, Sakata E, Murata S, Yokosawa H, Sako Y, Baumeister W, Tanaka K, Saeki Y. Quantitative live-cell imaging reveals spatio-temporal dynamics and cytoplasmic assembly of the 26S proteasome. Nat Commun 2014; 5:3396. [PMID: 24598877 DOI: 10.1038/ncomms4396] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Accepted: 02/06/2014] [Indexed: 01/15/2023] Open
Abstract
The 26S proteasome is a 2.5-MDa multisubunit protease complex that degrades polyubiquitylated proteins. Although its functions and structure have been extensively characterized, little is known about its dynamics in living cells. Here, we investigate the absolute concentration, spatio-temporal dynamics and complex formation of the proteasome in living cells using fluorescence correlation spectroscopy. We find that the 26S proteasome complex is highly mobile, and that almost all proteasome subunits throughout the cell are stably incorporated into 26S proteasomes. The interaction between 19S and 20S particles is stable even in an importin-α mutant, suggesting that the 26S proteasome is assembled in the cytoplasm. Furthermore, a genetically stabilized 26S proteasome mutant is able to enter the nucleus. These results suggest that the 26S proteasome completes its assembly process in the cytoplasm and translocates into the nucleus through the nuclear pore complex as a holoenzyme.
Collapse
Affiliation(s)
- Chan-Gi Pack
- Cellular Informatics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Haruka Yukii
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Akio Toh-e
- Medical Mycology Center, Chiba University, 1-8-1 Inohana, Chiba 260-8673, Japan
| | - Tai Kudo
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Hikaru Tsuchiya
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Ai Kaiho
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Eri Sakata
- Department of Molecular Structural Biology, Max-Planck-Institute of Biochemistry, 82152 Martinsried, Germany
| | - Shigeo Murata
- Laboratory of Protein Metabolism, Graduate School of Pharmaceutical Sciences, the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hideyoshi Yokosawa
- Department of Medicinal Biochemistry, School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya 464-8650, Japan
| | - Yasushi Sako
- Cellular Informatics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Wolfgang Baumeister
- Department of Molecular Structural Biology, Max-Planck-Institute of Biochemistry, 82152 Martinsried, Germany
| | - Keiji Tanaka
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Yasushi Saeki
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| |
Collapse
|