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Abstract
The genetically encoded fluorescent sensors convert chemical and physical signals into light. They are powerful tools for the visualisation of physiological processes in living cells and freely moving animals. The fluorescent protein is the reporter module of a genetically encoded biosensor. In this study, we first review the history of the fluorescent protein in full emission spectra on a structural basis. Then, we discuss the design of the genetically encoded biosensor. Finally, we briefly review several major types of genetically encoded biosensors that are currently widely used based on their design and molecular targets, which may be useful for the future design of fluorescent biosensors.
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Affiliation(s)
- Minji Wang
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, No. 3663 Zhong Shan Road North, Shanghai, 200062, China
| | - Yifan Da
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, No. 3663 Zhong Shan Road North, Shanghai, 200062, China
| | - Yang Tian
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, No. 3663 Zhong Shan Road North, Shanghai, 200062, China
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2
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Waldeck-Weiermair M, Alam MR, Khan MJ, Deak AT, Vishnu N, Karsten F, Imamura H, Graier WF, Malli R. Spatiotemporal correlations between cytosolic and mitochondrial Ca(2+) signals using a novel red-shifted mitochondrial targeted cameleon. PLoS One 2012; 7:e45917. [PMID: 23029314 PMCID: PMC3448721 DOI: 10.1371/journal.pone.0045917] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Accepted: 08/23/2012] [Indexed: 01/11/2023] Open
Abstract
The transfer of Ca2+ from the cytosol into the lumen of mitochondria is a crucial process that impacts cell signaling in multiple ways. Cytosolic Ca2+ ([Ca2+]cyto) can be excellently quantified with the ratiometric Ca2+ probe fura-2, while genetically encoded Förster resonance energy transfer (FRET)-based fluorescent Ca2+ sensors, the cameleons, are efficiently used to specifically measure Ca2+ within organelles. However, because of a significant overlap of the fura-2 emission with the spectra of the cyan and yellow fluorescent protein of most of the existing cameleons, the measurement of fura-2 and cameleons within one given cell is a complex task. In this study, we introduce a novel approach to simultaneously assess [Ca2+]cyto and mitochondrial Ca2+ ([Ca2+]mito) signals at the single cell level. In order to eliminate the spectral overlap we developed a novel red-shifted cameleon, D1GO-Cam, in which the green and orange fluorescent proteins were used as the FRET pair. This ratiometric Ca2+ probe could be successfully targeted to mitochondria and was suitable to be used simultaneously with fura-2 to correlate [Ca2+]cyto and [Ca2+]mito within same individual cells. Our data indicate that depending on the kinetics of [Ca2+]cyto rises there is a significant lag between onset of [Ca2+]cyto and [Ca2+]mito signals, pointing to a certain threshold of [Ca2+]cyto necessary to activate mitochondrial Ca2+ uptake. The temporal correlation between [Ca2+]mito and [Ca2+]cyto as well as the efficiency of the transfer of Ca2+ from the cytosol into mitochondria varies between different cell types. Moreover, slow mitochondrial Ca2+ extrusion and a desensitization of mitochondrial Ca2+ uptake cause a clear difference in patterns of mitochondrial and cytosolic Ca2+ oscillations of pancreatic beta-cells in response to D-glucose.
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Affiliation(s)
- Markus Waldeck-Weiermair
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Muhammad Rizwan Alam
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Muhammad Jadoon Khan
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Andras T. Deak
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Neelanjan Vishnu
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Felix Karsten
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Hiromi Imamura
- Precursory Research for Embryonic Science, Japan Science and Technology Agency, Tokyo, Japan
| | - Wolfgang F. Graier
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Roland Malli
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
- * E-mail:
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3
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Strachotová D, Holoubek A, Kučerová H, Benda A, Humpolíčková J, Váchová L, Palková Z. Ato protein interactions in yeast plasma membrane revealed by fluorescence lifetime imaging (FLIM). BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2126-34. [PMID: 22579979 DOI: 10.1016/j.bbamem.2012.05.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Revised: 04/29/2012] [Accepted: 05/04/2012] [Indexed: 12/27/2022]
Abstract
Each of the three plasma membrane Ato proteins is involved in ammonium signalling and the development of yeast colonies. This suggests that although these proteins are homologous, they do not functionally substitute for each other, but may form a functional complex. Here, we present a detailed combined FRET, FLIM and photobleaching study, which enabled us to detect interactions between Ato proteins found in distinct compartments of yeast cells. We thus show that the proteins Ato1p and Ato2p interact and can form complexes when present in the plasma membrane. No interaction was detected between Ato1p and Ato3p or Ato2p and Ato3p. In addition, using specially prepared strains, we were able to detect an interaction between molecules of the same Ato protein, namely Ato1p-Ato1p and Ato3p-Ato3p, but not Ato2p-Ato2p.
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4
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Abraham BG, Tkachenko NV, Santala V, Lemmetyinen H, Karp M. Bidirectional Fluorescence Resonance Energy Transfer (FRET) in Mutated and Chemically Modified Yellow Fluorescent Protein (YFP). Bioconjug Chem 2011; 22:227-34. [DOI: 10.1021/bc100372u] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Bobin George Abraham
- Department of Chemistry and Bioengineering, Tampere University of Technology, 541, 33101 Tampere, Finland
| | - Nikolai V. Tkachenko
- Department of Chemistry and Bioengineering, Tampere University of Technology, 541, 33101 Tampere, Finland
| | - Ville Santala
- Department of Chemistry and Bioengineering, Tampere University of Technology, 541, 33101 Tampere, Finland
| | - Helge Lemmetyinen
- Department of Chemistry and Bioengineering, Tampere University of Technology, 541, 33101 Tampere, Finland
| | - Matti Karp
- Department of Chemistry and Bioengineering, Tampere University of Technology, 541, 33101 Tampere, Finland
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5
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Abstract
Small, fluorescent, calcium-sensing molecules have been enormously useful in mapping intracellular calcium signals in time and space, as chapters in this volume attest. Despite their widespread adoption and utility, they suffer some disadvantages. Genetically encoded calcium sensors that can be expressed inside cells by transfection or transgenesis are desirable. The last 10 years have been marked by a rapid evolution in the laboratory of genetically encoded calcium sensors both figuratively and literally, resulting in 11 distinct configurations of fluorescent proteins and their attendant calcium sensor modules. Here, the design logic and performance of this abundant collection of sensors and their in vitro and in vivo use and performance are described. Genetically encoded calcium sensors have proved valuable in the measurement of calcium concentration in cellular organelles, for the most part in single cells in vitro. Their success as quantitative calcium sensors in tissues in vitro and in vivo is qualified, but they have proved valuable in imaging the pattern of calcium signals within tissues in whole animals. Some branches of the calcium sensor evolutionary tree continue to evolve rapidly and the steady progress in optimizing sensor parameters leads to the certain hope that these drawbacks will eventually be overcome by further genetic engineering.
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Affiliation(s)
- Michael Whitaker
- Institute of Cell and Molecular Biosciences Medical School, Newcastle University, Framlington Place Newcastle upon Tyne, United Kingdom
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6
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Liu B, Gan L, Sun X, Zhu Y, Tong Z, Xu H, Yang X. Enhancement of BK(Ca) channel activity induced by hydrogen peroxide: involvement of lipid phosphatase activity of PTEN. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:2174-82. [PMID: 19646416 DOI: 10.1016/j.bbamem.2009.07.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Revised: 07/01/2009] [Accepted: 07/22/2009] [Indexed: 02/06/2023]
Abstract
Large-conductance calcium and voltage-dependent potassium (BK(Ca)) channel is an important determinant of vascular tone. It is activated by hydrogen peroxide (H(2)O(2)) which occurs in various physiological and pathological processes. However, the regulation mechanism is not fully understood. In the present study, the mSlo in the presence or absence of hbeta1 were cotransfected with the PTEN(wt), PTEN(C124S), PTEN(G129E) in HEK 293 cells. Typical BK(Ca) channel currents could be recorded in cell-attached configurations. We found that PTEN(wt) reduced the H(2)O(2)-induced BK(Ca) channel activation during the initial 10 min treatment. In contrast, coexpression with catalytically inactive PTEN(C124S)/PTEN(G129E) mutants that lack lipid phosphatase activity produced no regulation on the H(2)O(2)-induced BK(Ca) channel activation. These results demonstrated that PTEN regulated the H(2)O(2)-induced BK(Ca) channel activation through phosphatidylinositol 3-phosphatse. However, the inhibitory effect of PTEN on the H(2)O(2)-induced BK(Ca) channel activation was attenuated when cells were treated with H(2)O(2) at concentrations higher than 100 microM or at 100 microM for long-term treatment. In addition, the p-AKT expression level in PTEN(wt) overexpressing cells was lower than that in control cells, and the increase of cytoplasmic free calcium concentration ([Ca(2+)](i)) induced by H(2)O(2) was also inhibited. These findings may elucidate a new mechanism for H(2)O(2)-induced BK(Ca) channel activation and provide some evidences for the role of PTEN on vasodilation induced by H(2)O(2).
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Affiliation(s)
- Bo Liu
- College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, 430074, China
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7
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Abstract
Fluorescence-based assays are widely used in high-throughput screening due to their high sensitivity, diverse selection of fluorophores, ease of operation, and various readout modes. As a result, fluorescence-based assays have been applied to monitor a broad range of activities in life-science research such as molecular dynamics and interactions, enzymatic activities, signal transduction, cell health, and distribution of molecules, organelles, or cells. This chapter describes two fluorescence-based techniques: total intensity measurement as an indication of cell viability, and fluorescence resonance energy transfer as an indication of protein folding and interactions, to illustrate in detail applications suitable for cell-based high-throughput screening in plate-reader and automated microscope-based formats, respectively.
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8
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Roda A, Guardigli M, Michelini E, Mirasoli M. Nanobioanalytical luminescence: Förster-type energy transfer methods. Anal Bioanal Chem 2008; 393:109-23. [DOI: 10.1007/s00216-008-2435-8] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 09/22/2008] [Accepted: 09/23/2008] [Indexed: 12/21/2022]
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9
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Karpova T, McNally JG. Detecting protein-protein interactions with CFP-YFP FRET by acceptor photobleaching. ACTA ACUST UNITED AC 2008; Chapter 12:Unit12.7. [PMID: 18770833 DOI: 10.1002/0471142956.cy1207s35] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
FRET is a light microscopy method for detecting protein-protein interactions within intact cells. The FRET protocol presented here is for CFP- and YFP-tagged proteins examined with an argon laser on a scanning confocal microscope. FRET is assayed by one of the most straightforward approaches available, namely, acceptor photobleaching. In this procedure, the YFP-tagged protein (the FRET "acceptor") is photobleached at a cellular site of interest, and then the intensity of the CFP-tagged protein (the FRET "donor") at that same site is measured. In principle, FRET is detected when the CFP intensity increases after the photobleaching of YFP. This unit describes the appropriate steps to perform this measurement, as well as the necessary controls to ensure that an increase in CFP intensity, if detected, in fact reflects bona fide FRET. Successful application of the protocol will support the conclusion that the CFP- and YFP-tagged proteins directly interact at the site of the photobleaching.
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10
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Neumann D, Kollewe C, Pich A, Cao P, Resch K, Martin MU. Threonine 66 in the death domain of IRAK-1 is critical for interaction with signaling molecules but is not a target site for autophosphorylation. J Leukoc Biol 2008; 84:807-13. [DOI: 10.1189/jlb.0507290] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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11
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Fretwell JF, K. Ismail SM, Cummings JM, Selby TL. Characterization of a randomized FRET library for protease specificity determination. MOLECULAR BIOSYSTEMS 2008; 4:862-70. [DOI: 10.1039/b709290c] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Okumoto S, Takanaga H, Frommer WB. Quantitative imaging for discovery and assembly of the metabo-regulome. THE NEW PHYTOLOGIST 2008; 180:271-295. [PMID: 19138219 PMCID: PMC2663047 DOI: 10.1111/j.1469-8137.2008.02611.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Little is known about regulatory networks that control metabolic flux in plant cells. Detailed understanding of regulation is crucial for synthetic biology. The difficulty of measuring metabolites with cellular and subcellular precision is a major roadblock. New tools have been developed for monitoring extracellular, cytosolic, organellar and vacuolar ion and metabolite concentrations with a time resolution of milliseconds to hours. Genetically encoded sensors allow quantitative measurement of steady-state concentrations of ions, signaling molecules and metabolites and their respective changes over time. Fluorescence resonance energy transfer (FRET) sensors exploit conformational changes in polypeptides as a proxy for analyte concentrations. Subtle effects of analyte binding on the conformation of the recognition element are translated into a FRET change between two fused green fluorescent protein (GFP) variants, enabling simple monitoring of analyte concentrations using fluorimetry or fluorescence microscopy. Fluorimetry provides information averaged over cell populations, while microscopy detects differences between cells or populations of cells. The genetically encoded sensors can be targeted to subcellular compartments or the cell surface. Confocal microscopy ultimately permits observation of gradients or local differences within a compartment. The FRET assays can be adapted to high-throughput analysis to screen mutant populations in order to systematically identify signaling networks that control individual steps in metabolic flux.
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Affiliation(s)
- Sakiko Okumoto
- Plant Pathology, Physiology, and Weed Science Department, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
| | - Hitomi Takanaga
- Carnegie Institution for Science, Department of Plant Biology, 260 Panama St., Stanford, CA 94305, USA
| | - Wolf B. Frommer
- Carnegie Institution for Science, Department of Plant Biology, 260 Panama St., Stanford, CA 94305, USA
- Joint Bioenergy Institute, Feedstocks Division, Emerystation East, 5885 Hollis Street Emeryville, CA 94608, USA
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13
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Jiang L, Fan J, Bai L, Wang Y, Chen Y, Yang L, Chen L, Xu T. Direct quantification of fusion rate reveals a distal role for AS160 in insulin-stimulated fusion of GLUT4 storage vesicles. J Biol Chem 2007; 283:8508-16. [PMID: 18063571 DOI: 10.1074/jbc.m708688200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin-stimulated GLUT4 translocation to the plasma membrane constitutes a key process for blood glucose control. However, convenient and robust assays to monitor this dynamic process in real time are lacking, which hinders current progress toward elucidation of the underlying molecular events as well as screens for drugs targeting this particular pathway. Here, we have developed a novel dual colored probe to monitor the translocation process of GLUT4 based on dual color fluorescence measurement. We demonstrate that this probe is more than an order of magnitude more sensitive than the current technology for detecting fusion events from single GLUT4 storage vesicles (GSVs). A small fraction of fusion events were found to be of the "kiss-and-run" type. For the first time, we show that insulin stimulation evokes a approximately 40-fold increase in the fusion of GSVs in 3T3-L1 adipocytes, compared with basal conditions. The probe can also be used to monitor the prefusion behavior of GSVs. By quantifying both the docking and fusion rates simultaneously, we demonstrate a proportional inhibition in both docking and fusion of GSVs by a dominant negative mutant of AS160, indicating a role for AS160 in the docking of GSVs but not in the regulation of GSV fusion after docking.
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Affiliation(s)
- Li Jiang
- Joint Laboratory of Institute of Biophysics & Huazhong University of Science and Technology, National Laboratory of Biomacromolecules, Chinese Academy of Sciences, Beijing, China
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14
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Dong Y, Wan Q, Yang X, Bai L, Xu P. Interaction of Munc18 and Syntaxin in the regulation of insulin secretion. Biochem Biophys Res Commun 2007; 360:609-14. [PMID: 17617378 DOI: 10.1016/j.bbrc.2007.06.107] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2007] [Accepted: 06/15/2007] [Indexed: 10/23/2022]
Abstract
Syntaxin1A and Munc18-1 play essential roles in exocytosis. However, the molecular mechanism and the functional roles of their interaction in insulin secretion remain to be explored. Using membrane capacitance measurement, we examine effect of overexpressing Munc18-1 on exocytosis in pancreatic beta cells. The results show that Munc18-1 negatively regulates vesicle fusion. To probe the interaction between Munc18-1 and Syntaxin1A, Munc18-1-Tdimer2 and EGFP-Syntaxin1A were co-transfected into INS-1 cells. FRET measurement confirmed that Munc18-1 interacted with wild type Syntaxin 1A, but not the constitutively open form (DM) of Syntaxin1A. Overexpressing DM in primary pancreatic beta cells augmented insulin secretion, and this effect can overcome the inhibitory effect of Munc18-1 overexpression. We propose that Munc18-1 inhibitis the SNARE complex assembly by stabilizing Syntaxin1A in a closed conformation in vesicle priming process, therefore negatively regulates insulin secretion.
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Affiliation(s)
- Yongming Dong
- Joint Laboratory of the Institute of Biophysics & Huazhong University of Science and Technology, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, PR China
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15
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Chowdhury RP, Chatterji D. Estimation of Förster's distance between two ends of Dps protein from mycobacteria: distance heterogeneity as a function of oligomerization and DNA binding. Biophys Chem 2007; 128:19-29. [PMID: 17368913 DOI: 10.1016/j.bpc.2007.02.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Revised: 02/23/2007] [Accepted: 02/27/2007] [Indexed: 10/23/2022]
Abstract
Dps protein (DNA binding Protein from Starved Cells) from Mycobacterium smegmatis (Ms-Dps) is known to undergo an in vitro irreversible oligomeric transition from trimer to dodecamer. This transition helps the protein to provide for bimodal protection to the bacterial DNA from the free radical and Fenton mediated damages in the stationary state. The protein exists as a stable trimer, when purified from E. coli cells transformed with an over-expression plasmid. Both trimer as well as dodecamer are known to exhibit ferroxidation activity, thus removing toxic hydroxyl radicals in vivo, whereas iron accumulation and non-sequence specific DNA binding activity are found in dodecamer only. This seems to be aided by the positively charged long C-terminal tail of the protein. We used frequency domain phase-modulation fluorescence spectroscopy and Förster Resonance Energy Transfer (FRET) to monitor this oligomeric switch from a trimer to a dodecamer and to elucidate the structure of DNA-Dps dodecamer complex. As Ms-Dps is devoid of any Cysteine residues, a Serine is mutated to Cysteine (S169C) at a position adjacent to the putative DNA binding domain. This Cysteine is subsequently labeled with fluorescent probe and another probe is placed at the N-terminus, as crystal structure of the protein reveals several side-chain interactions between these two termini, and both are exposed towards the surface of the protein. Here, we report the Förster's distance distribution in the trimer and the dodecamer in the presence and absence of DNA. Through discrete lifetime analysis of the probes tagged at the respective regions in the macromolecule, coupled with Maximum Entropy Method (MEM) analysis, we show that the dodecamer, upon DNA binding shows conformational heterogeneity in overall structure, perhaps mediated by a non-specific DNA-protein interaction. On the other hand, the nature of DNA-Dps interaction is not known and several models exist in literature. We show here with the help of fluorescence anisotropy measurements of labeled DNA having different length and unlabeled native dodecameric protein that tandem occupation of DNA binding sites by a series of Dps molecules perhaps guide the tight packing of Dps over DNA backbone.
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16
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Li IT, Pham E, Truong K. Protein biosensors based on the principle of fluorescence resonance energy transfer for monitoring cellular dynamics. Biotechnol Lett 2006; 28:1971-82. [PMID: 17021660 DOI: 10.1007/s10529-006-9193-5] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2006] [Revised: 08/01/2006] [Accepted: 08/14/2006] [Indexed: 11/26/2022]
Abstract
Genetically-coded, fluorescence resonance energy transfer (FRET) biosensors are widely used to study molecular events from single cells to whole organisms. They are unique among biosensors because of their spontaneous fluorescence and targeting specificity to both organelles and tissues. In this review, we discuss the theoretical basis of FRET with a focus on key parameters responsible for designing FRET biosensors that have the highest sensitivity. Next, we discuss recent applications that are grouped into four common biosensor design patterns--intermolecular FRET, intramolecular FRET, FRET from substrate cleavage and FRET using multiple colour fluorescent proteins. Lastly, we discuss recent progress in creating fluorescent proteins suitable for FRET purposes. Together these advances in the development of FRET biosensors are beginning to unravel the interconnected and intricate signalling processes as they are occurring in living cells and organisms.
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Affiliation(s)
- Isaac T Li
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, 164 College Street, Toronto, Ont., Canada, M5S 3G9
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17
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Yang X, Xu P, Xiao Y, Xiong X, Xu T. Domain Requirement for the Membrane Trafficking and Targeting of Syntaxin 1A. J Biol Chem 2006; 281:15457-63. [PMID: 16595658 DOI: 10.1074/jbc.m513246200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Syntaxin plays a key role in intracellular membrane fusion in eukaryotic cells. The function of syntaxin relies on its proper trafficking to and targeting at the target membrane. The mechanisms underlying the trafficking and targeting of syntaxin to its physiological sites remain poorly understood. Here we have analyzed the trafficking of syntaxin 1A in INS-1 and CHO cells. We have identified the transmembrane domain together with several flanking positive-charged amino acids as the minimal domain required for the membrane delivery. Interestingly, we found that SNARE motif-exposed syntaxin 1A mutants were retained in endoplasmic reticulum (ER) and failed to transport to the cell surface in the absence of SNAP-25, suggesting that the exposure of the SNARE motif causes ER retention and complexation with SNAP-25 helps the ER escape. Finally, our data propose two key roles for the H(abc) domain: to protect nonspecific interaction by masking the SNARE motif and to participate in the clustering of syntaxin 1A to the fusion sites in the plasma membrane.
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Affiliation(s)
- Xiaofei Yang
- Joint Laboratory of Institute of Biophysics & Huazhong University of Science and Technology, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
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18
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Knöpfel T, Díez-García J, Akemann W. Optical probing of neuronal circuit dynamics: genetically encoded versus classical fluorescent sensors. Trends Neurosci 2006; 29:160-6. [PMID: 16443289 DOI: 10.1016/j.tins.2006.01.004] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2005] [Revised: 11/17/2005] [Accepted: 01/12/2006] [Indexed: 11/25/2022]
Abstract
During the past few decades, optical methods for imaging activity in networks composed of thousands of neurons have been developed. These techniques rely mainly on organic-chemistry-based dyes as indicators of Ca(2+) and membrane potential. However, recently a new generation of probes, genetically encoded fluorescent protein sensors, has emerged for use by physiologists studying the operation of neuronal circuits. We critically review the development of these new probes, and analyze objectives and experimental conditions in which classical probes are likely to prevail and where the fluorescent protein sensors will open paths to previously unexplored territories of functional neuroimaging.
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Affiliation(s)
- Thomas Knöpfel
- Laboratory for Neuronal Circuit Dynamics, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama 351-0198 Japan.
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19
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Prescott M, Battad JM, Wilmann PG, Rossjohn J, Devenish RJ. Recent advances in all-protein chromophore technology. BIOTECHNOLOGY ANNUAL REVIEW 2006; 12:31-66. [PMID: 17045191 DOI: 10.1016/s1387-2656(06)12002-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The green fluorescent protein (GFP) is the foundation of a powerful technology that has revolutionized the way in which the life scientist carries out experiments in the living cell. The technology is continually evolving and improving through the development of existing proteins and discovery of new members of the all-protein chromophore (APC) family. This review gives an overview of the more recent advances in the technology with a particular focus on APCs having optical properties that are significantly red-shifted relative to those variants derived from Aequorea victoria GFP.
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Affiliation(s)
- Mark Prescott
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Clayton, Victoria 3800, Australia.
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20
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Plattner H, Hentschel J. Sub-second cellular dynamics: time-resolved electron microscopy and functional correlation. INTERNATIONAL REVIEW OF CYTOLOGY 2006; 255:133-76. [PMID: 17178466 DOI: 10.1016/s0074-7696(06)55003-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Subcellular processes, from molecular events to organellar responses and cell movement, cover a broad scale in time and space. Clearly the extremes, such as ion channel activation are accessible only by electrophysiology, whereas numerous routine methods exist for relatively slow processes. However, many other processes, from a millisecond time scale on, can be "caught" only by methods providing appropriate time resolution. Fast freezing (cryofixation) is the method of choice in that case. In combination with follow-up methodologies appropriate for electron microscopic (EM) analysis, with all its variations, such technologies can also provide high spatial resolution. Such analyses may include, for example, freeze-fracturing for analyzing restructuring of membrane components, scanning EM and other standard EM techniques, as well as analytical EM analyses. The latter encompass energy-dispersive x-ray microanalysis and electron spectroscopic imaging, all applicable, for instance, to the second messenger, calcium. Most importantly, when conducted in parallel, such analyses can provide a structural background to the functional analyses, such as cyclic nucleotide formation or protein de- or rephosphorylation during cell stimulation. In sum, we discuss many examples of how it is practically possible to achieve strict function-structure correlations in the sub-second time range. We complement this review by discussing alternative methods currently available to analyze fast cellular phenomena occurring in the sub-second time range.
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Affiliation(s)
- Helmut Plattner
- Department of Biology, University of Konstanz, 78457 Konstanz, Germany
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Laser literature watch. Photomed Laser Surg 2005; 23:513-24. [PMID: 16262584 DOI: 10.1089/pho.2005.23.513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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