51
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Ghale G, Kuhnert N, Nau WM. Monitoring Stepwise Proteolytic Degradation of Peptides by Supramolecular Domino Tandem Assays and Mass Spectrometry for Trypsin and Leucine Aminopeptidase. Nat Prod Commun 2012. [DOI: 10.1177/1934578x1200700315] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
A label-free optical detection method has been designed that allows direct monitoring of enzymatic peptide digestion in vitro. The method is based on the addition of a reporter pair, composed of the macrocyclic host cucurbit[7]uril (CB7) and the fluorescent dye acridine orange (AO), to detect the proteolytic degradation of peptides. The enzymatic activity of trypsin and leucine aminopeptidase (LAP) was investigated using H-LSRFSWGA-OH as a substrate. The substrate as well as the intermediary and final products (i.e., H-FSWGA-OH and phenylalanine) formed during its enzymatic hydrolysis differ in their binding affinity to the receptor CB7, which results in varying degrees of dye displacement and, therefore, different fluorescence intensities. CB7 showed a relatively weak binding constant of K ≈ 104 M–1 with the substrate, a relatively strong binding constant of K ≥ 106 M–1 with H-FSWGA-OH (which is a final product formed by trypsin digestion and the intermediary product formed during the enzymatic activity of LAP), and a moderate binding constant of K ≤ 105 M–1 with phenylalanine. Owing to this differential binding affinity of CB7 with the substrate and the corresponding products, the digestion of a peptide by trypsin was followed as a decrease in fluorescence signal, while the complete degradation of the peptide by LAP was monitored as a decrease and a subsequent increase in fluorescence signal. The kcat/ KM value for trypsin (2.0 × 107 min–1M–1) was derived from the change in fluorescence signal with time. Additionally, the complete degradation of the peptide by LAP was also followed by mass spectrometry. The use of a supramolecular sensing ensemble (macrocyclic host and dye) as a fluorescent reporter pair gives this method the flexibility to adapt for monitoring the stepwise degradation of different biologically relevant peptides by other proteases.
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Affiliation(s)
- Garima Ghale
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Nikolai Kuhnert
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
| | - Werner M. Nau
- School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany
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52
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Savitsky AP, Rusanov AL, Zherdeva VV, Gorodnicheva TV, Khrenova MG, Nemukhin AV. FLIM-FRET Imaging of Caspase-3 Activity in Live Cells Using Pair of Red Fluorescent Proteins. Theranostics 2012; 2:215-26. [PMID: 22375160 PMCID: PMC3287422 DOI: 10.7150/thno.3885] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Accepted: 01/18/2012] [Indexed: 11/05/2022] Open
Abstract
We report a new technique to detect enzyme activity inside cells. The method based on Fluorescence Lifetime Imaging (FLIM) technology allows one to follow sensor cleavage by proteolytic enzyme caspase-3. Specifically, we use the FLIM FRET of living cells via the confocal fluorescence microscopy. A specially designed lentivector pLVT with the DNA fragment of TagRFP-23-KFP was applied for transduction of A549 cell lines. Computer simulations are carried out to estimate FRET efficiency and to analyze possible steric restrictions of the reaction between the substrate TagRFP-23-KFP and caspase-3 dimer. Successful use of the fuse protein TagRFP-23-KFP to register the caspase-3 activation based on average life-time measurements is demonstrated. We show that the average life-time distribution is dramatically changed for cells with the modified morphology that is typical for apoptosis. Namely, the short-lived component at 1.8-2.1 ns completely disappears and the long-lived component appears at 2.4-2.6 ns. The latter is a fingerprint of the TagRFP molecule released after cleavage of the TagRFP-23-KFP complex by caspase-3. Analysis of life-time distributions for population of cells allows us to discriminate apoptotic and surviving cells within single frame and to peform statistical analysis of drug efficiency. This system can be adjusted for HTS by using special readers oriented on measurements of fluorescence life-time.
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53
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Won YJ, Han WT, Kim DY. Precision and accuracy of the analog mean-delay method for high-speed fluorescence lifetime measurement. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2011; 28:2026-32. [PMID: 21979507 DOI: 10.1364/josaa.28.002026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The analog mean-delay (AMD) method is a new alternative method to measure the lifetime of a fluorescence molecule. Because of its powerful advantages of accurate lifetime determination, good photon economy, and a high photon detection rate, the AMD method is considered to be very suitable for high-speed confocal fluorescence lifetime imaging microscopy (FLIM). For the practical usage of the AMD method in FLIM (AMD-FLIM), detailed study on various experimental conditions and parameters that affect the precision and the accuracy of the AMD method is required. In this paper, we present the relation between the precision and accuracy of the lifetime versus iteration number in the AMD method, the best cutoff frequency of a low-pass filter used in the AMD-FLIM system for a given fluorophore, and the optimum position and width of the integration window by using Monte Carlo simulations and a series of AMD-FLIM experiments.
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Affiliation(s)
- Young Jae Won
- Department of Information and Communications, Gwangju Institute of Science and Technology, Gwangju, Korea
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54
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How ClpX Unfolds GFP in Stages by Pulling. J Mol Biol 2011; 413:1-3. [DOI: 10.1016/j.jmb.2011.08.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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55
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Watson DS, Jambunathan K, Askew DS, Kodukula K, Galande AK. Robust substrate profiling method reveals striking differences in specificities of serum and lung fluid proteases. Biotechniques 2011; 51:95-104. [PMID: 21806553 PMCID: PMC3159512 DOI: 10.2144/000113717] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Accepted: 05/10/2011] [Indexed: 11/23/2022] Open
Abstract
Proteases are candidate biomarkers and therapeutic targets for many diseases. Sensitive and robust techniques are needed to quantify proteolytic activities within the complex biological milieu. We hypothesized that a combinatorial protease substrate library could be used effectively to identify similarities and differences between serum and bronchoalveolar lavage fluid (BALF), two body fluids that are clinically important for developing targeted therapies and diagnostics. We used a concise library of fluorogenic probes to map the protease substrate specificities of serum and BALF from guinea pigs. Differences in the proteolytic fingerprints of the two fluids were striking: serum proteases cleaved substrates containing cationic residues and proline, whereas BALF proteases cleaved substrates containing aliphatic and aromatic residues. Notably, cleavage of proline-containing substrates dominated all other protease activities in both human and guinea pig serum. This substrate profiling approach provides a foundation for quantitative comparisons of protease specificities between complex biological samples.
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Affiliation(s)
- Douglas S. Watson
- Center for Advanced Drug Research, Biosciences Division, SRI International, Harrisonburg, VA, USA
| | - Kalyani Jambunathan
- Center for Advanced Drug Research, Biosciences Division, SRI International, Harrisonburg, VA, USA
| | - David S. Askew
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Krishna Kodukula
- Center for Advanced Drug Research, Biosciences Division, SRI International, Harrisonburg, VA, USA
| | - Amit K. Galande
- Center for Advanced Drug Research, Biosciences Division, SRI International, Harrisonburg, VA, USA
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56
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Abstract
We report a bacterial system for the evolution of cyclic peptides that makes use of an expanded set of amino acid building blocks. Orthogonal aminoacyl-tRNA synthetase/tRNA(CUA) pairs, together with a split intein system were used to biosynthesize a library of ribosomal peptides containing amino acids with unique structures and reactivities. This peptide library was subsequently used to evolve an inhibitor of HIV protease using a selection based on cellular viability. Two of three cyclic peptides isolated after two rounds of selection contained the keto amino acid p-benzoylphenylalanine (pBzF). The most potent peptide (G12: GIXVSL; X=pBzF) inhibited HIV protease through the formation of a covalent Schiff base adduct of the pBzF residue with the ε-amino group of Lys 14 on the protease. This result suggests that an expanded genetic code can confer an evolutionary advantage in response to selective pressure. Moreover, the combination of natural evolutionary processes with chemically biased building blocks provides another strategy for the generation of biologically active peptides using microbial systems.
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57
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Sisoula C, Gonos ES. CHIP E3 ligase regulates mammalian senescence by modulating the levels of oxidized proteins. Mech Ageing Dev 2011; 132:269-72. [PMID: 21510971 DOI: 10.1016/j.mad.2011.04.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 03/15/2011] [Accepted: 04/04/2011] [Indexed: 01/03/2023]
Abstract
Senescence can be induced by various stressors including oxidative stress. It has been reported that CHIP (C-terminus of Hsp70-interacting protein) ligase is induced during senescence while CHIP(-/-) mice exhibit accelerated aging. Here, we explore the effects of modulating CHIP expression on mammalian senescence. We demonstrate that CHIP silencing induces premature senescence that is accompanied by elevated levels of oxidized proteins. On the contrary, ectopic expression of CHIP leads to oxidized proteins levels reduction. Moreover, we reveal that CHIP(-/-) mouse fibroblasts have an impaired ubiquitin proteasome system. Taken together, we propose that CHIP influences cellular senescence by modulating the oxidative load.
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Affiliation(s)
- Christina Sisoula
- National Hellenic Research Foundation, Institute of Biological Research and Biotechnology, Athens, Greece
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58
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Won Y, Moon S, Yang W, Kim D, Han WT, Kim DY. High-speed confocal fluorescence lifetime imaging microscopy (FLIM) with the analog mean delay (AMD) method. OPTICS EXPRESS 2011; 19:3396-405. [PMID: 21369162 DOI: 10.1364/oe.19.003396] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
We demonstrate a high-speed confocal fluorescence lifetime imaging microscopy (FLIM) whose accuracy and photon economy are as good as that of a time-correlated single photon counting (TCSPC). It is based on a new lifetime determination scheme, the analog mean delay (AMD) method. Due to the technical advantages of multiple fluorescence photon detection capability, accurate lifetime determination scheme and high photon detection efficiency, the AMD method can be the most effective method for high-speed confocal FLIM. The feasibility of real-time confocal FLIM with the AMD method has been demonstrated by observing the dynamic reaction of calcium channels in a RBL-2H3 cell with respect to 4αPDD stimulus. We have achieved the photon detection rate of 125 times faster than a conventional TCSPC based system in this experiment.
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Affiliation(s)
- Youngjae Won
- Department of Information and Communications, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712, South Korea
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59
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Gabriel D, Zuluaga MF, Lange N. On the cutting edge: protease-sensitive prodrugs for the delivery of photoactive compounds. Photochem Photobiol Sci 2011; 10:689-703. [DOI: 10.1039/c0pp00341g] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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60
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Breurken M, Lempens EHM, Merkx M. Protease-activatable collagen targeting based on protein cyclization. Chembiochem 2010; 11:1665-8. [PMID: 20589824 DOI: 10.1002/cbic.201000223] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Monika Breurken
- Laboratory for Chemical Biology, Department of Biomedical Engineering, Eindhoven University of Technology, 5600 MB, Eindhoven, the Netherlands
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61
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Urru SAM, Veglianese P, De Luigi A, Fumagalli E, Erba E, Gonella Diaza R, Carrà A, Davoli E, Borsello T, Forloni G, Pengo N, Monzani E, Cascio P, Cenci S, Sitia R, Salmona M. A new fluorogenic peptide determines proteasome activity in single cells. J Med Chem 2010; 53:7452-60. [PMID: 20883027 DOI: 10.1021/jm100362x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ubiquitin-proteasome system plays a critical role in many diseases, making it an attractive biomarker and therapeutic target. However, the impact of results obtained in vitro using purified proteasome particles or whole cell extracts is limited by the lack of efficient methods to assess proteasome activity in living cells. We have engineered an internally quenched fluorogenic peptide with a proteasome-specific cleavage motif fused to TAT and linked to the fluorophores DABCYL and EDANS. This peptide penetrates cell membranes and is rapidly cleaved by the proteasomal chymotrypsin-like activity, generating a quantitative fluorescent reporter of in vivo proteasome activity as assessed by time-lapse or flow cytometry fluorescence analysis. This reporter is an innovative tool for monitoring proteasomal proteolytic activities in physiological and pathological conditions.
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Affiliation(s)
- Silvana A M Urru
- Istituto di Ricerche Farmacologiche Mario Negri, Via La Masa 19, Milan 20156, Italy
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62
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Abstract
Since the first schematic illustrations of dividing cells, we have come a long way in characterising eukaryotic cells and defining their cell-cycle status thanks to a number of complementary approaches. Although most of these approaches rely on cell-fixation procedures to identify molecular components in cell lysates, cultured cells or tissues, the development of GFP technology has enabled visualisation of virtually any fusion protein in cellulo and in vivo, and the exploitation of functional elements with well-defined spatiotemporal characteristics has enabled the development of genetically encoded fluorescent markers of cell-cycle phases, thus providing novel means of characterising the status of living cells in real time with high resolution. Together with technological advances in fluorescence chemistry and imaging approaches, the more recent development of fluorescent biosensors has provided direct means of probing cell-cycle regulators and of studying their dynamics with high spatial and temporal resolution. Here we review classical approaches that rely on cell fixation to characterise the cell-cycle status and its regulatory enzymes, and we describe the more recent development of cell-cycle markers based on genetically encoded fusions of fluorescent proteins with characteristic cell-cycle features, and of fluorescent biosensor technology to probe cell-cycle regulators in living cells. Biosensors not only provide a means of characterising the behaviour of cell-cycle regulators in their natural environment, they are also very useful for comparative studies of biological processes in healthy and pathological conditions, and can be further applied to diagnostic approaches to assess the status of a specific target, and to monitor response to therapeutic intervention.
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63
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Morris MC. Fluorescent biosensors of intracellular targets from genetically encoded reporters to modular polypeptide probes. Cell Biochem Biophys 2010; 56:19-37. [PMID: 19921468 DOI: 10.1007/s12013-009-9070-7] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
With the escalation of drug discovery programmes, it has become essential to visualize and monitor biological activities in healthy and pathological cells, with high spatial and temporal resolution. To this aim, the development of probes and sensors, which can report on the levels and activities of specific intracellular targets, has become essential. Together with the discovery of the Green Fluorescent Protein (GFP), and the development of GFP-based reporters, recent advances in the synthesis of small molecule fluorescent probes, and the explosion of fluorescence-based imaging technologies, the biosensor field has witnessed a dramatic expansion of fluorescence-based reporters which can be applied to complex biological samples, living cells and tissues to probe protein/protein interactions, conformational changes and posttranslational modifications. Here, we review recent developments in the field of fluorescent biosensor technology. We describe different varieties and categories of fluorescent biosensors together with an overview of the technologies commonly employed to image biosensors in cellulo and in vivo. We discuss issues and strategies related to the choice of synthetic fluorescent probes, labelling, quenching, caging and intracellular delivery of biosensors. Finally, we provide examples of some well-characterized genetically encoded FRET reporter systems, peptide and protein biosensors and describe biosensor applications in a wide variety of fields.
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Affiliation(s)
- May C Morris
- Interactions and Molecular Mechanisms regulating Cell Cycle Progression, Université de Montpellier, CRBM-CNRS UMR5237, 1919 Route de Mende, IFR122, 34293, Montpellier, France.
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64
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Salomons FA, Acs K, Dantuma NP. Illuminating the ubiquitin/proteasome system. Exp Cell Res 2010; 316:1289-95. [PMID: 20149791 DOI: 10.1016/j.yexcr.2010.02.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Accepted: 02/01/2010] [Indexed: 12/01/2022]
Abstract
The ubiquitin/proteasome system (UPS) is responsible for the regulated processive degradation of proteins residing in the cytosol, nucleus, and endoplasmic reticulum. The two central players are ubiquitin, a small protein that is conjugated to substrates, and the proteasome, a large multi-subunit proteolytic complex that executes degradation of ubiquitylated proteins. Ubiquitylation and proteasomal degradation are highly dynamic processes. During the last decade, many researchers have started taking advantage of fluorescent proteins, which allow studying the dynamic nature of this system in the context of its natural environment: the living cell. In this review, we will summarize studies that have implemented this approach to examine the UPS and discuss novel insights in the dynamic organization of the UPS.
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Affiliation(s)
- Florian A Salomons
- Department of Cell and Molecular Biology, Karolinska Institutet, S-17177 Stockholm, Sweden
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65
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Alvarez-Castelao B, Martín-Guerrero I, García-Orad Á, Castaño JG. Cytomegalovirus promoter up-regulation is the major cause of increased protein levels of unstable reporter proteins after treatment of living cells with proteasome inhibitors. J Biol Chem 2009; 284:28253-28262. [PMID: 19679666 DOI: 10.1074/jbc.m109.004101] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Fluorescent unstable proteins obtained by the fusion of a fluorescent protein coding sequence with specific amino acid sequences that promote its fast degradation have become popular to gauge the activity of the ubiquitin/proteasome system in living cells. The steady-state levels of expression of these unstable proteins is low in agreement with their short half-lives, and they accumulate in the cell upon treatment with proteasome inhibitors. We show here that this accumulation is mainly due to transcriptional up-regulation of the cytomegalovirus promoter by proteasome inhibitors and mediated, at least in part, by AP1 transactivation. These simple facts put under quarantine conclusions reached about the activity of the ubiquitin/proteasome pathway in animal cells in culture or in transgenic mice, where popular cytomegalovirus-driven constructs are used, as transcriptional regulation of the expression of the reporter protein construct and not degradation of the unstable protein by the ubiquitin/proteasome system may contribute significantly to the interpretation of the results observed.
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Affiliation(s)
- Beatriz Alvarez-Castelao
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas "Alberto Sols," Universidad Autónoma de Madrid y Consejo Superior de Investigaciones Científicas (UAM-CSIC) y Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Facultad de Medicina UAM, 28029 Madrid, Spain
| | - Idoia Martín-Guerrero
- Departamento de Genética, Antropología Física y Fisiología Animal, Facultad de Medicina, Universidad del País Vasco (UPV/EHU), 48940 Leioa, Spain
| | - África García-Orad
- Departamento de Genética, Antropología Física y Fisiología Animal, Facultad de Medicina, Universidad del País Vasco (UPV/EHU), 48940 Leioa, Spain
| | - José G Castaño
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas "Alberto Sols," Universidad Autónoma de Madrid y Consejo Superior de Investigaciones Científicas (UAM-CSIC) y Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Facultad de Medicina UAM, 28029 Madrid, Spain.
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66
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Chaudhari AJ, Ahn S, Levenson R, Badawi RD, Cherry SR, Leahy RM. Excitation spectroscopy in multispectral optical fluorescence tomography: methodology, feasibility and computer simulation studies. Phys Med Biol 2009; 54:4687-704. [PMID: 19590118 DOI: 10.1088/0031-9155/54/15/004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Molecular probes used for in vivo optical fluorescence tomography (OFT) studies in small animals are typically chosen such that their emission spectra lie in the 680-850 nm wavelength range. This is because tissue attenuation in this spectral band is relatively low, allowing optical photons even from deep sites in tissue to reach the animal surface and consequently be detected by a CCD camera. The wavelength dependence of tissue optical properties within the 680-850 nm band can be exploited for emitted light by measuring fluorescent data via multispectral approaches and incorporating the spectral dependence of these optical properties into the OFT inverse problem-that of reconstructing underlying 3D fluorescent probe distributions from optical data collected on the animal surface. However, in the aforementioned spectral band, due to only small variations in the tissue optical properties, multispectral emission data, though superior for image reconstruction compared to achromatic data, tend to be somewhat redundant. A different spectral approach for OFT is to capitalize on the larger variations in the optical properties of tissue for excitation photons than for the emission photons by using excitation at multiple wavelengths as a means of decoding source depth in tissue. The full potential of spectral approaches in OFT can be realized by a synergistic combination of these two approaches, that is, exciting the underlying fluorescent probe at multiple wavelengths and measuring emission data multispectrally. In this paper, we describe a method that incorporates both excitation and emission spectral information into the OFT inverse problem. We describe a linear algebraic formulation of the multiple wavelength illumination-multispectral detection forward model for OFT and compare it to models that use only excitation at multiple wavelengths or those that use only multispectral detection techniques. This study is carried out in a realistic inhomogeneous mouse atlas using singular value decomposition and analysis of reconstructed spatial resolution versus noise. For simplicity, quantitative results have been shown for one representative fluorescent probe (Alexa 700) and effects due to tissue autofluorescence have not been taken into account. We also demonstrate the performance of our method for 3D reconstruction of tumors in a simulated mouse model of metastatic human hepatocellular carcinoma.
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Affiliation(s)
- Abhijit J Chaudhari
- Department of Biomedical Engineering, University of California-Davis, Davis, CA 95616, USA.
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67
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Saxena SK, Mishra N, Saxena R. Advances in antiviral drug discovery and development: Part II: Advancements in antiviral drug development. Future Virol 2009. [DOI: 10.2217/fvl.09.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Shailendra K Saxena
- Centre for Cellular & Molecular Biology, Uppal Road, Hyderabad 500 007 (AP), India
| | - Niraj Mishra
- Centre for Cellular & Molecular Biology, Uppal Road, Hyderabad 500 007 (AP), India
| | - Rakhi Saxena
- Centre for Cellular & Molecular Biology, Uppal Road, Hyderabad 500 007 (AP), India
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68
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The proteasome load versus capacity balance determines apoptotic sensitivity of multiple myeloma cells to proteasome inhibition. Blood 2009; 113:3040-9. [PMID: 19164601 DOI: 10.1182/blood-2008-08-172734] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Abstract
Proteasome inhibitors (PIs) are effective against multiple myeloma (MM), but the mechanisms of action and bases of individual susceptibility remain unclear. Recent work linked PI sensitivity to protein synthesis and proteasome activity, raising the question whether different levels of proteasome expression and workload underlie PI sensitivity in MM cells (MMCs). Exploiting human MM lines characterized by differential PI sensitivity, we report that highly sensitive MMCs express lower proteasome levels and higher proteasomal workload than relatively PI-resistant MMCs, resulting in the accumulation of polyubiquitinated proteins at the expense of free ubiquitin (proteasome stress). Manipulating proteasome expression or workload alters apoptotic sensitivity to PI, demonstrating a cause-effect relationship between proteasome stress and apoptotic responses in MMCs. Intracellular immunostaining in primary, patient-derived MMCs reveals that polyubiquitinated proteins hallmark neoplastic plasma cells, in positive correlation with immunoglobulin (Ig) content, both intra- and interpatient. Moreover, overall proteasome activity of primary MMCs inversely correlates with apoptotic sensitivity to PI. Altogether, our data indicate that the balance between proteasome workload and degradative capacity represents a critical determinant of apoptotic sensitivity of MMCs to PI, potentially providing a framework for identifying indicators of responsiveness and designing novel combination therapies.
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69
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Selective accumulation of aggregation-prone proteasome substrates in response to proteotoxic stress. Mol Cell Biol 2009; 29:1774-85. [PMID: 19158272 DOI: 10.1128/mcb.01485-08] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Conditions causing an increase in misfolded or aberrant proteins can impair the activity of the ubiquitin/proteasome system (UPS). This observation is of particular interest, given the fact that proteotoxic stress is closely associated with a large variety of disorders. Although impairment of the UPS appears to be a general consequence of proteotoxic insults, the underlying mechanisms remain enigmatic. Here, we show that heat shock-induced proteotoxic stress resulted in conjugation of ubiquitin to detergent-insoluble protein aggregates, which coincided with reduced levels of free ubiquitin and impediment of ubiquitin-dependent proteasomal degradation. Interestingly, whereas soluble proteasome substrates returned to normal levels after a transient accumulation, the levels of an aggregation-prone substrate remained high even when the free ubiquitin levels were restored. Consistently, overexpression of ubiquitin prevented accumulation of soluble but not aggregation-prone substrates in thermally stressed cells. Notably, cells were also unable to resume degradation of aggregation-prone substrates after treatment with the translation inhibitor puromycin, indicating that selective accumulation of aggregation-prone proteins is a consistent feature of proteotoxic stress. Our data suggest that the failure of the UPS to clear aggregated proteins in the aftermath of proteotoxic stress episodes may contribute to the selective deposition of aggregation-prone proteins in conformational diseases.
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70
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Li J, Yao SQ. “Singapore Green”: A New Fluorescent Dye for Microarray and Bioimaging Applications. Org Lett 2008; 11:405-8. [DOI: 10.1021/ol802700w] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Junqi Li
- Departments of Chemistry and Biological Sciences, NUS MedChem Program of the Office of Life Sciences, National University of Singapore, Singapore 117543
| | - Shao Q. Yao
- Departments of Chemistry and Biological Sciences, NUS MedChem Program of the Office of Life Sciences, National University of Singapore, Singapore 117543
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71
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Cheroni C, Marino M, Tortarolo M, Veglianese P, De Biasi S, Fontana E, Zuccarello LV, Maynard CJ, Dantuma NP, Bendotti C. Functional alterations of the ubiquitin-proteasome system in motor neurons of a mouse model of familial amyotrophic lateral sclerosis. Hum Mol Genet 2008; 18:82-96. [PMID: 18826962 DOI: 10.1093/hmg/ddn319] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In familial and sporadic amyotrophic lateral sclerosis (ALS) and in rodent models of the disease, alterations in the ubiquitin-proteasome system (UPS) may be responsible for the accumulation of potentially harmful ubiquitinated proteins, leading to motor neuron death. In the spinal cord of transgenic mice expressing the familial ALS superoxide dismutase 1 (SOD1) gene mutation G93A (SOD1G93A), we found a decrease in constitutive proteasome subunits during disease progression, as assessed by real-time PCR and immunohistochemistry. In parallel, an increased immunoproteasome expression was observed, which correlated with a local inflammatory response due to glial activation. These findings support the existence of proteasome modifications in ALS vulnerable tissues. To functionally investigate the UPS in ALS motor neurons in vivo, we crossed SOD1G93A mice with transgenic mice that express a fluorescently tagged reporter substrate of the UPS. In double-transgenic Ub(G76V)-GFP /SOD1G93A mice an increase in Ub(G76V)-GFP reporter, indicative of UPS impairment, was detectable in a few spinal motor neurons and not in reactive astrocytes or microglia, at symptomatic stage but not before symptoms onset. The levels of reporter transcript were unaltered, suggesting that the accumulation of Ub(G76V)-GFP was due to deficient reporter degradation. In some motor neurons the increase of Ub(G76V)-GFP was accompanied by the accumulation of ubiquitin and phosphorylated neurofilaments, both markers of ALS pathology. These data suggest that UPS impairment occurs in motor neurons of mutant SOD1-linked ALS mice and may play a role in the disease progression.
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Affiliation(s)
- Cristina Cheroni
- Laboratory of Molecular Neurobiology, Department of Neuroscience, Mario Negri Institute for Pharmacological Research, Via La Masa, 19, 20156 Milan, Italy
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72
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The neuronal ubiquitin-proteasome system: Murine models and their neurological phenotype. Prog Neurobiol 2008; 85:176-93. [DOI: 10.1016/j.pneurobio.2008.03.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Revised: 12/12/2007] [Accepted: 03/11/2008] [Indexed: 02/03/2023]
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73
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Abstract
Photodynamic therapy (PDT) is a treatment modality for the selective destruction of cancerous and nonneoplastic pathologies that involves the simultaneous presence of light, oxygen and a light-activatable chemical called a photosensitizer (PS) to achieve a cytotoxic effect. The photophysics and mechanisms of cell killing by PDT have been extensively studied in recent years, and PDT has received regulatory approval for the treatment of a number of diseases worldwide. As the application of this treatment modality expands with regard to both anatomical sites and disease stages, it will be important to develop strategies for enhancing PDT outcomes. This article focuses on two broad approaches for PDT enhancement: (1) mechanism-based combination treatments in which PDT and a second modality can be designed to either increase the susceptibility of tumor cells to PDT or nullify the treatment outcome-mitigating molecular responses triggered by PDT of tumors, and (2) the more recent approaches of PS targeting, either by specific cellular function-sensitive linkages or via conjugation to macromolecules.
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Affiliation(s)
- Sarika Verma
- Wellman Center for Photomedicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
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74
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Kanno A, Yamanaka Y, Hirano H, Umezawa Y, Ozawa T. Cyclic luciferase for real-time sensing of caspase-3 activities in living mammals. Angew Chem Int Ed Engl 2007; 46:7595-9. [PMID: 17722214 DOI: 10.1002/anie.200700538] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Akira Kanno
- Department of Chemistry, School of Science, The University of Tokyo, Japan Science and Technology Agency, Tokyo 113-0033, Japan
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75
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Kanno A, Yamanaka Y, Hirano H, Umezawa Y, Ozawa T. Cyclic Luciferase for Real-Time Sensing of Caspase-3 Activities in Living Mammals. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200700538] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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76
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Pandey UB, Nie Z, Batlevi Y, McCray BA, Ritson GP, Nedelsky NB, Schwartz SL, DiProspero NA, Knight MA, Schuldiner O, Padmanabhan R, Hild M, Berry DL, Garza D, Hubbert CC, Yao TP, Baehrecke EH, Taylor JP. HDAC6 rescues neurodegeneration and provides an essential link between autophagy and the UPS. Nature 2007; 447:859-63. [PMID: 17568747 DOI: 10.1038/nature05853] [Citation(s) in RCA: 929] [Impact Index Per Article: 54.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2006] [Accepted: 04/16/2007] [Indexed: 12/31/2022]
Abstract
A prominent feature of late-onset neurodegenerative diseases is accumulation of misfolded protein in vulnerable neurons. When levels of misfolded protein overwhelm degradative pathways, the result is cellular toxicity and neurodegeneration. Cellular mechanisms for degrading misfolded protein include the ubiquitin-proteasome system (UPS), the main non-lysosomal degradative pathway for ubiquitinated proteins, and autophagy, a lysosome-mediated degradative pathway. The UPS and autophagy have long been viewed as complementary degradation systems with no point of intersection. This view has been challenged by two observations suggesting an apparent interaction: impairment of the UPS induces autophagy in vitro, and conditional knockout of autophagy in the mouse brain leads to neurodegeneration with ubiquitin-positive pathology. It is not known whether autophagy is strictly a parallel degradation system, or whether it is a compensatory degradation system when the UPS is impaired; furthermore, if there is a compensatory interaction between these systems, the molecular link is not known. Here we show that autophagy acts as a compensatory degradation system when the UPS is impaired in Drosophila melanogaster, and that histone deacetylase 6 (HDAC6), a microtubule-associated deacetylase that interacts with polyubiquitinated proteins, is an essential mechanistic link in this compensatory interaction. We found that compensatory autophagy was induced in response to mutations affecting the proteasome and in response to UPS impairment in a fly model of the neurodegenerative disease spinobulbar muscular atrophy. Autophagy compensated for impaired UPS function in an HDAC6-dependent manner. Furthermore, expression of HDAC6 was sufficient to rescue degeneration associated with UPS dysfunction in vivo in an autophagy-dependent manner. This study suggests that impairment of autophagy (for example, associated with ageing or genetic variation) might predispose to neurodegeneration. Morover, these findings suggest that it may be possible to intervene in neurodegeneration by augmenting HDAC6 to enhance autophagy.
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Affiliation(s)
- Udai Bhan Pandey
- Department of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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77
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Amon M, Ligneau X, Camelin JC, Berrebi-Bertrand I, Schwartz JC, Stark H. Highly Potent Fluorescence-Tagged Nonimidazole Histamine H3 Receptor Ligands. ChemMedChem 2007; 2:708-16. [PMID: 17361979 DOI: 10.1002/cmdc.200600270] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Different (3-phenoxypropyl)piperidine derivatives have been coupled to fluorescent moieties (5-dimethylaminonaphthalene-1-sulfonyl, carbazol-9-ylcarbonyl, 2-cyanoisoindol-1-yl, 2-cyanobenzo[f]isoindol-1-yl, 2,4-dinitrobenzen-1-yl, 2,4-diaminophenyl, 7-nitrobenzofurazan-4-yl, 7-aminosulfonylbenzofurazan-4-yl, 4-methylcoumarin-6-yl) as novel histamine H(3) receptor ligands. They have been synthesised starting from piperidine in a few steps. The compounds display good to excellent histamine hH(3) receptor affinities with K(i) values ranging from 13.4 to 0.048 nM. Some of the new compounds belong to the most potent ligands known so far and may act as tools for identification and understanding of the binding site on the histamine H(3) receptor. In vivo screening on selected derivatives of Sanger's reagent showed antagonist potencies with ED(50) values from 7.9 to 0.39 mg kg(-1), p.o.
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Affiliation(s)
- Michael Amon
- Institut für Pharmazeutische Chemie, Johann Wolfgang Goethe-Universität, ZAFES/CMP, Biozentrum, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
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78
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Hennig A, Florea M, Roth D, Enderle T, Nau WM. Design of peptide substrates for nanosecond time-resolved fluorescence assays of proteases: 2,3-Diazabicyclo[2.2.2]oct-2-ene as a noninvasive fluorophore. Anal Biochem 2007; 360:255-65. [PMID: 17134673 DOI: 10.1016/j.ab.2006.09.015] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2006] [Revised: 09/15/2006] [Accepted: 09/17/2006] [Indexed: 11/26/2022]
Abstract
Fluorescence protease assays were investigated with peptide substrates containing a 2,3-diazabicyclo[2.2.2]oct-2-ene-labeled asparagine (Dbo) as a fluorescent amino acid. The special characteristic of the fluorophore Dbo is its exceedingly long fluorescence lifetime (ca. 300 ns in water under air), which allows the use of nanosecond time-resolved fluorescence (Nano-TRF) detection to efficiently suppress shorter-lived background emission. In addition, the natural amino acids tryptophan and tyrosine can be employed as intramolecular fluorescence quenchers, which facilitates substrate design. Fourteen synthetic peptide substrates (composed of 2-19 amino acids) and five enzymes (trypsin, pepsin, carboxypeptidase A, leucine aminopeptidase, and chymotrypsin) were investigated and, in all 28 examined combinations, enzymatic activity was detected by monitoring the increase in steady state fluorescence with time and determining the reaction rates as kcat/Km values, which ranged from 0.2 to 80x10(6) M-1 min-1. The results suggest an excellent compatibility of the very small and hydrophilic fluorescent probe Dbo with solid-phase peptide synthesis and the investigated proteases. For all 14 peptides the fluorescence lifetimes before and after enzymatic cleavage were measured and Nano-TRF measurements were performed in 384-well microplates. The fluorescence lifetimes of the different peptides provide the basis for the rational design of Dbo-based fluorescent substrates for protease assays. Measurements in Nano-TRF mode revealed, in addition to efficient suppression of background fluorescence, an increased differentiation between cleaved and uncleaved substrate. The Dbo-based assays can be adapted for high-throughput screening.
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Affiliation(s)
- Andreas Hennig
- School of Engineering and Science, International University Bremen, Campus Ring 1, D-28759 Bremen, Germany
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79
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Tanabe K, Zhang Z, Ito T, Hatta H, Nishimoto SI. Current molecular design of intelligent drugs and imaging probes targeting tumor-specific microenvironments. Org Biomol Chem 2007; 5:3745-57. [DOI: 10.1039/b711244k] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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80
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Abstract
Until fairly recently, proteases were considered primarily to be protein-degrading enzymes. However, this view has dramatically changed and proteases are now seen as extremely important signalling molecules that are involved in numerous vital processes. Protease signalling pathways are strictly regulated, and the dysregulation of protease activity can lead to pathologies such as cardiovascular and inflammatory diseases, cancer, osteoporosis and neurological disorders. Several small-molecule drugs targeting proteases are already on the market and many more are in development. The status of human protease research and prospects for future protease-targeted drugs are reviewed here, with reference to some key examples where protease drugs have succeeded or failed.
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Affiliation(s)
- Boris Turk
- Department of Biochemistry and Molecular Biology, J. Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
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81
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Amon M, Ligneau X, Schwartz JC, Stark H. Fluorescent non-imidazole histamine H3 receptor ligands with nanomolar affinities. Bioorg Med Chem Lett 2006; 16:1938-40. [PMID: 16434192 DOI: 10.1016/j.bmcl.2005.12.084] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2005] [Revised: 12/21/2005] [Accepted: 12/21/2005] [Indexed: 11/24/2022]
Abstract
Omega-piperidinoalkanamine derivatives with fluorescent moieties (2-cyanoisoindol-1-yl, 7-nitrobenzofurazan-4-yl) have been synthesized starting from piperidine in three steps. The compounds display moderate to good histamine hH(3) receptor affinities with K(i) values ranging from 178 to 11nM. The new compounds may act as tools for identification and understanding of the binding site on the histamine H(3) receptor.
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Affiliation(s)
- Michael Amon
- Johann Wolfgang Goethe-Universität, ZAFES, Biozentrum, Institut für Pharmazeutische Chemie, 60431 Frankfurt, Germany
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82
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Affiliation(s)
- Andreas Hennig
- School of Engineering and Science, International University Bremen, Campus Ring 1, 28759 Bremen, Germany
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83
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Lin J, Zhang Z, Yang J, Zeng S, Liu BF, Luo Q. Real-time detection of caspase-2 activation in a single living HeLa cell during cisplatin-induced apoptosis. JOURNAL OF BIOMEDICAL OPTICS 2006; 11:024011. [PMID: 16674201 DOI: 10.1117/1.2187013] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Caspase-2 is important for the mitochondrial apoptotic pathway, however, the mechanism by which caspase-2 executes apoptosis remains obscure. We carry out the first measurements of the dynamics of caspase-2 activation in a single living cell by a FRET (fluorescence resonance energy transfer) probe. Two FRET probes are constructed that each encoded a CRS (caspase-2 or caspase-3 recognition site) fused with a cyan fluorescent protein (CFP) and a red fluorescent protein (DsRed) (CFP-CRS-DsRed). Using these probes, we found that during cisplatin-induced apoptosis, caspase-2 activation occurred more slowly than did activation of caspase-3; additionally, caspase-2 activation was initiated much earlier than that of caspase-3.
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Affiliation(s)
- Juqiang Lin
- Huazhong University of Science and Technology, Key Laboratory of Biomedical Photonics of Ministry of Education-Hubei, Bioinformatics and Molecular Imaging Key Laboratory, Wuhan 430074 China
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84
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Mitra S, Barrios AM. Highly sensitive peptide-based probes for protein tyrosine phosphatase activity utilizing a fluorogenic mimic of phosphotyrosine. Bioorg Med Chem Lett 2005; 15:5142-5. [PMID: 16203147 DOI: 10.1016/j.bmcl.2005.08.054] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2005] [Revised: 08/18/2005] [Accepted: 08/22/2005] [Indexed: 11/20/2022]
Abstract
Fluorescent probes that can be incorporated into peptides and proteins are in high demand, with applications ranging from cellular imaging to binding and activity assays. Here, we report the high yielding synthesis of an enantiomerically pure phosphocoumarin-based amino acid and its incorporation into peptides via standard solid-phase peptide synthesis methodologies. Peptides containing this new amino acid serve as highly sensitive fluorogenic probes for protein tyrosine phosphatase activity.
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Affiliation(s)
- Sayantan Mitra
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA
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85
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Abstract
Regulated turnover of proteins in the cytosol and nucleus of eukaryotic cells is primarily performed by the ubiquitin–proteasome system (UPS). The UPS is involved in many essential cellular processes. Alterations in this proteolytic system are associated with a variety of human pathologies, such as neurodegenerative diseases, cancer, immunological disorders and inflammation. The precise role of the UPS in the pathophysiology of these diseases, however, remains poorly understood. Detection of UPS aberrations has been a major challenge because of the complexity of the system. Most studies focus on various aspects of the UPS, such as substrate recognition, ubiquitination, deubiquitination or proteasome activity, and do not provide a complete picture of the UPS as an integral system. To monitor the efficacy of the UPS, a number of reporter substrates have been developed based on fluorescent proteins, such as the green fluorescent protein and its spectral variants. These fluorescent UPS reporters contain specific degradation signals that target them with high efficiency and accuracy for proteasomal degradation. Several studies have shown that these reporters can probe the functionality of the UPS in cellular and animal models and provide us with important information on the status of the UPS under various conditions. Moreover, these reporters can aid the identification and development of novel anti-cancer and anti-inflammatory drugs based on UPS inhibition.
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86
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Menéndez-Benito V, Heessen S, Dantuma NP. Monitoring of ubiquitin-dependent proteolysis with green fluorescent protein substrates. Methods Enzymol 2005; 399:490-511. [PMID: 16338378 DOI: 10.1016/s0076-6879(05)99034-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A reliable and robust means of evaluating the functional status of ubiquitin-dependent proteolysis in living cells is to follow the turnover of readily detectable reporter substrates. During the past few years, several reporter substrates have been generated by use of the green fluorescent protein (GFP), which is converted for this purpose from a normally very stable protein into a short-lived substrate of the ubiquitin/proteasome system. These short-lived substrates are valuable tools providing researchers with unique information about the absence or presence of blockades in this system in living cells. We have recently generated the first transgenic mouse model for monitoring the ubiquitin/proteasome system based on the ubiquitous expression of a GFP-based proteasome substrate. Together these models can be used to study ubiquitin-dependent degradation in health and disease and for the identification of small synthetic compounds or proteins capable of modifying the activity of the system. In this chapter, we describe the basic principles of GFP-based reporter substrates, their strengths and weaknesses, and a number of protocols that can be used to study the ubiquitin/proteasome system in yeast, cell lines, and transgenic mice.
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87
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Bence NF, Bennett EJ, Kopito RR. Application and analysis of the GFPu family of ubiquitin-proteasome system reporters. Methods Enzymol 2005; 399:481-90. [PMID: 16338377 DOI: 10.1016/s0076-6879(05)99033-2] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
The relevance of the ubiquitin proteasome system (UPS) to disease and fundamental cellular processes has generated a demand for methods to monitor the activity of this system in living cells and organisms. Here we describe the GFP(u) family of UPS reporters. These reporters are constitutively degraded, ubiquitin-dependent proteasome substrates that can be used to monitor UPS function in the living cell. The GFP(u) reporter family consists of three variants that can report on global, nuclear, and cytoplasmic UPS function. This article focuses on the properties and design of these reporters and highlights appropriate techniques and applications for their use.
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Affiliation(s)
- Neil F Bence
- Department of Biological Sciences, Stanford University, Stanford, California, USA
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