251
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Weinreis SA, Ellis JP, Cavagnero S. Dynamic fluorescence depolarization: a powerful tool to explore protein folding on the ribosome. Methods 2010; 52:57-73. [PMID: 20685617 PMCID: PMC2934862 DOI: 10.1016/j.ymeth.2010.06.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Revised: 05/28/2010] [Accepted: 06/01/2010] [Indexed: 11/25/2022] Open
Abstract
Protein folding is a fundamental biological process of great significance for cell function and life-related processes. Surprisingly, very little is presently known about how proteins fold in vivo. The influence of the cellular environment is of paramount importance, as molecular chaperones, the ribosome, and the crowded medium affect both folding pathways and potentially even equilibrium structures. Studying protein folding in physiologically relevant environments, however, poses a number of technical challenges due to slow tumbling rates, low concentrations and potentially non-homogenous populations. Early work in this area relied on biological assays based on antibody recognition, proteolysis, and activity studies. More recently, it has been possible to directly observe the structure and dynamics of nascent polypeptides at high resolution by spectroscopic and microscopic techniques. The fluorescence depolarization decay of nascent polypeptides labeled with a small extrinsic fluorophore is a particularly powerful tool to gain insights into the dynamics of newly synthesized proteins. The fluorophore label senses both its own local mobility and the motions of the macromolecule to which it is attached. Fluorescence anisotropy decays can be measured both in the time and frequency domains. The latter mode of data collection is extremely convenient to capture the nanosecond motions in ribosome-bound nascent proteins, indicative of the development of independent structure and folding on the ribosome. In this review, we discuss the theory of fluorescence depolarization and its exciting applications to the study of the dynamics of nascent proteins in the cellular environment.
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Affiliation(s)
- Sarah A. Weinreis
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA
| | | | - Silvia Cavagnero
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA
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252
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Ambrosio M, Zürn A, Lohse MJ. Sensing G protein-coupled receptor activation. Neuropharmacology 2010; 60:45-51. [PMID: 20727363 DOI: 10.1016/j.neuropharm.2010.08.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 08/07/2010] [Indexed: 11/25/2022]
Abstract
G protein-coupled receptors (GPCRs) are the key elements of a highly regulated transduction machinery that generates different signaling outcomes to hormones and neurotransmitters. Until recently, it was assumed that diverse ligands of a given GPCR differ only in their ability to alter the balance between the OFF and the ON state of the receptor. However, it has now become evident that their activation mechanisms are more complex and that receptors presumably display distinguishable active conformational states, which are induced by different agonists and correlate to specific signaling outputs. The use of different labeling strategies to insert fluorescent labels into purified, reconstituted receptors, or into receptors in intact cells, has made it possible to sense receptor activation via changes in their fluorescence. Here, we summarize recent progress in the analysis of agonist-dependent activation mechanisms of GPCRs acquired using modern spectroscopic and crystallographic techniques.
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Affiliation(s)
- Manuela Ambrosio
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany
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253
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Dieterich DC. Chemical reporters for the illumination of protein and cell dynamics. Curr Opin Neurobiol 2010; 20:623-30. [PMID: 20650631 DOI: 10.1016/j.conb.2010.06.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Revised: 06/09/2010] [Accepted: 06/28/2010] [Indexed: 10/19/2022]
Abstract
Fluorescent proteins have revolutionized cell biology and, therefore, our understanding of the complex molecular and cellular mechanisms that wire the brain together and enable its plasticity throughout life. The ability to visualize cell biological processes has inspired the development of alternative protein labeling strategies by both chemists and biologists. Among those approaches are the introduction of small bioorthogonal chemical reporters and new fluorescent probes by either genetic encoding or by utilizing the cell's own biosynthesis machinery in live cells. This review will highlight recent advances in approaches to track discrete proteins or whole subpopulations of a proteome including post-translational modifications with spatiotemporal resolution.
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Affiliation(s)
- Daniela C Dieterich
- Emmy Noether Research Group Neuralomics, Leibniz Institute for Neurobiology, Brenneckestr. 6, 39118 Magdeburg, Germany.
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254
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Van Engelenburg SB, Nahreini T, Palmer AE. FACS-based selection of tandem tetracysteine peptides with improved ReAsH brightness in live cells. Chembiochem 2010; 11:489-93. [PMID: 20099291 DOI: 10.1002/cbic.200900689] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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255
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Abstract
Macromolecules drive the complex behavior of neurons. For example, channels and transporters control the movements of ions across membranes, SNAREs direct the fusion of vesicles at the synapse, and motors move cargo throughout the cell. Understanding the structure, assembly, and conformational movements of these and other neuronal proteins is essential to understanding the brain. Developments in fluorescence have allowed the architecture and dynamics of proteins to be studied in real time and in a cellular context with great accuracy. In this review, we cover classic and recent methods for studying protein structure, assembly, and dynamics with fluorescence. These methods include fluorescence and luminescence resonance energy transfer, single-molecule bleaching analysis, intensity measurements, colocalization microscopy, electron transfer, and bimolecular complementation analysis. We present the principles of these methods, highlight recent work that uses the methods, and discuss a framework for interpreting results as they apply to molecular neurobiology.
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256
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Zürn A, Klenk C, Zabel U, Reiner S, Lohse MJ, Hoffmann C. Site-Specific, Orthogonal Labeling of Proteins in Intact Cells with Two Small Biarsenical Fluorophores. Bioconjug Chem 2010; 21:853-9. [DOI: 10.1021/bc900394j] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alexander Zürn
- Institute of Pharmacology and Toxicology, Rudolf Virchow Center University of Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany
| | - Christoph Klenk
- Institute of Pharmacology and Toxicology, Rudolf Virchow Center University of Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany
| | - Ulrike Zabel
- Institute of Pharmacology and Toxicology, Rudolf Virchow Center University of Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany
| | - Susanne Reiner
- Institute of Pharmacology and Toxicology, Rudolf Virchow Center University of Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany
| | - Martin J. Lohse
- Institute of Pharmacology and Toxicology, Rudolf Virchow Center University of Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany
| | - Carsten Hoffmann
- Institute of Pharmacology and Toxicology, Rudolf Virchow Center University of Würzburg, Versbacher Strasse 9, 97078 Würzburg, Germany
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257
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Kim SH, Gunther JR, Katzenellenbogen JA. Monitoring a coordinated exchange process in a four-component biological interaction system: development of a time-resolved terbium-based one-donor/three-acceptor multicolor FRET system. J Am Chem Soc 2010; 132:4685-92. [PMID: 20230029 PMCID: PMC2860875 DOI: 10.1021/ja100248q] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hormonal regulation of cellular function involves the binding of small molecules with receptors that then coordinate subsequent interactions with other signal transduction proteins. These dynamic, multicomponent processes are difficult to track in cells and even in reconstituted in vitro systems, and most methods can monitor only two-component interactions, often with limited capacity to follow dynamic changes. Through a judicious choice of three organic acceptor fluorophores paired with a terbium donor fluorophore, we have developed the first example of a one-donor/three-acceptor multicolor time-resolved fluorescence energy transfer (TR-FRET) system, and we have exemplified its use by monitoring a ligand-regulated protein-protein exchange process in a four-component biological system. By careful quantification of the emission from each of the three acceptors at the four channels for terbium donor emission, we demonstrate that any of these donor channels can be used to estimate the magnitude of the three FRET signals in this terbium-donor triple-acceptor system with minimal bleedthrough. Using this three-channel terbium-based, TR-FRET assay system, we show in one experiment that the addition of a fluorescein-labeled estrogen agonist displaces a SNAPFL-labeled antiestrogen from the ligand binding pocket of a terbium-labeled estrogen receptor, at the same time causing a Cy5-labeled coactivator to be recruited to the estrogen receptor. This experiment demonstrates the power of a four-color TR-FRET experiment, and it shows that the overall process of estrogen receptor ligand exchange and coactivator binding is a dynamic but precisely coordinated process.
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Affiliation(s)
- Sung Hoon Kim
- Department of Chemistry, University of Illinois, 600 S. Mathews Ave., Urbana, IL 61801
| | - Jillian R. Gunther
- Department of Chemistry, University of Illinois, 600 S. Mathews Ave., Urbana, IL 61801
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258
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Falkenburger BH, Jensen JB, Hille B. Kinetics of M1 muscarinic receptor and G protein signaling to phospholipase C in living cells. ACTA ACUST UNITED AC 2010; 135:81-97. [PMID: 20100890 PMCID: PMC2812500 DOI: 10.1085/jgp.200910344] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
G protein-coupled receptors (GPCRs) mediate responses to external stimuli in various cell types. Early events, such as the binding of ligand and G proteins to the receptor, nucleotide exchange (NX), and GTPase activity at the Galpha subunit, are common for many different GPCRs. For G(q)-coupled M(1) muscarinic (acetylcholine) receptors (M(1)Rs), we recently measured time courses of intermediate steps in the signaling cascade using Förster resonance energy transfer (FRET). The expression of FRET probes changes the density of signaling molecules. To provide a full quantitative description of M(1)R signaling that includes a simulation of kinetics in native (tsA201) cells, we now determine the density of FRET probes and construct a kinetic model of M(1)R signaling through G(q) to activation of phospholipase C (PLC). Downstream effects on the trace membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP(2)) and PIP(2)-dependent KCNQ2/3 current are considered in our companion paper in this issue (Falkenburger et al. 2010. J. Gen. Physiol. doi:10.1085/jgp.200910345). By calibrating their fluorescence intensity, we found that we selected transfected cells for our experiments with approximately 3,000 fluorescently labeled receptors, G proteins, or PLC molecules per microm(2) of plasma membrane. Endogenous levels are much lower, 1-40 per microm(2). Our kinetic model reproduces the time courses and concentration-response relationships measured by FRET and explains observed delays. It predicts affinities and rate constants that align well with literature values. In native tsA201 cells, much of the delay between ligand binding and PLC activation reflects slow binding of G proteins to receptors. With M(1)R and Gbeta FRET probes overexpressed, 10% of receptors have G proteins bound at rest, rising to 73% in the presence of agonist. In agreement with previous work, the model suggests that binding of PLC to Galpha(q) greatly speeds up NX and GTPase activity, and that PLC is maintained in the active state by cycles of rapid GTP hydrolysis and NX on Galpha(q) subunits bound to PLC.
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Affiliation(s)
- Björn H Falkenburger
- Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA
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259
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Gaspersic J, Hafner-Bratkovic I, Stephan M, Veranic P, Bencina M, Vorberg I, Jerala R. Tetracysteine-tagged prion protein allows discrimination between the native and converted forms. FEBS J 2010; 277:2038-50. [PMID: 20345906 DOI: 10.1111/j.1742-4658.2010.07619.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The conformational conversion of prion protein (PrP) from a native conformation to the amyloid form is a hallmark of transmissible spongiform encephalopathies. Conversion is usually monitored by fluorescent dyes, which bind generic amyloids and are less suited for living cell imaging. We report a new method for the synthesis of membrane-permeable and membrane-impermeable biarsenical reagents, which are then used to monitor murine PrP (mPrP) misfolding. We introduced tetracysteine (TC) tags into three different positions of mPrP, which folded into a native-like structure. Whereas mPrPs with a TC tag inserted at the N-terminus or C-terminus supported fibril formation, insertion into the helix 2-helix 3 loop inhibited conversion. We devised a quantitative protease-free method to determine the fraction of converted PrP, based on the ability of the fluorescein arsenical helix binder reagent to differentiate between the monomeric and fibrilized form of TC-tagged PrP, and showed that TC-tagged mPrP could be detected on transfected cells, thereby expanding the potential use of this method for the detection and study of conformational diseases.
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Affiliation(s)
- Jernej Gaspersic
- Department of Biotechnology, National Institute of Chemistry, Ljubljana, Slovenia
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260
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Tikhonova IG, Costanzi S. Unraveling the structure and function of G protein-coupled receptors through NMR spectroscopy. Curr Pharm Des 2010; 15:4003-16. [PMID: 20028318 DOI: 10.2174/138161209789824803] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
G protein-coupled receptors (GPCRs) are a large superfamily of signaling proteins expressed on the plasma membrane. They are involved in a wide range of physiological processes and, therefore, are exploited as drug targets in a multitude of therapeutic areas. In this extent, knowledge of structural and functional properties of GPCRs may greatly facilitate rational design of modulator compounds. Solution and solid-state nuclear magnetic resonance (NMR) spectroscopy represents a powerful method to gather atomistic insights into protein structure and dynamics. In spite of the difficulties inherent the solution of the structure of membrane proteins through NMR, these methods have been successfully applied, sometimes in combination with molecular modeling, to the determination of the structure of GPCR fragments, the mapping of receptor-ligand interactions, and the study of the conformational changes associated with the activation of the receptors. In this review, we provide a summary of the NMR contributions to the study of the structure and function of GPCRs, also in light of the published crystal structures.
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Affiliation(s)
- Irina G Tikhonova
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, MD 20892, USA
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261
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Molecular Biomechanics: The Molecular Basis of How Forces Regulate Cellular Function. Cell Mol Bioeng 2010; 3:91-105. [PMID: 20700472 DOI: 10.1007/s12195-010-0109-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Recent advances have led to the emergence of molecular biomechanics as an essential element of modern biology. These efforts focus on theoretical and experimental studies of the mechanics of proteins and nucleic acids, and the understanding of the molecular mechanisms of stress transmission, mechanosensing and mechanotransduction in living cells. In particular, single-molecule biomechanics studies of proteins and DNA, and mechanochemical coupling in biomolecular motors have demonstrated the critical importance of molecular mechanics as a new frontier in bioengineering and life sciences. To stimulate a more systematic study of the basic issues in molecular biomechanics, and attract a broader range of researchers to enter this emerging field, here we discuss its significance and relevance, describe the important issues to be addressed and the most critical questions to be answered, summarize both experimental and theoretical/computational challenges, and identify some short-term and long-term goals for the field. The needs to train young researchers in molecular biomechanics with a broader knowledge base, and to bridge and integrate molecular, subcellular and cellular level studies of biomechanics are articulated.
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262
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Tsien RY. Nobel lecture: constructing and exploiting the fluorescent protein paintbox. Integr Biol (Camb) 2010; 2:77-93. [DOI: 10.1039/b926500g] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Roger Y. Tsien
- Howard Hughes Medical Institute and Departments of Pharmacology and Chemistry & Biochemistry, University of California, San Diego 9500 Gilman Drive, La Jolla, CA 92093-0647, USA
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263
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Jensen JB, Lyssand JS, Hague C, Hille B. Fluorescence changes reveal kinetic steps of muscarinic receptor-mediated modulation of phosphoinositides and Kv7.2/7.3 K+ channels. ACTA ACUST UNITED AC 2010; 133:347-59. [PMID: 19332618 PMCID: PMC2699104 DOI: 10.1085/jgp.200810075] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
G protein–coupled receptors initiate signaling cascades. M1 muscarinic receptor (M1R) activation couples through Gαq to stimulate phospholipase C (PLC), which cleaves phosphatidylinositol 4,5-bisphosphate (PIP2). Depletion of PIP2 closes PIP2-requiring Kv7.2/7.3 potassium channels (M current), thereby increasing neuronal excitability. This modulation of M current is relatively slow (6.4 s to reach within 1/e of the steady-state value). To identify the rate-limiting steps, we investigated the kinetics of each step using pairwise optical interactions likely to represent fluorescence resonance energy transfer for M1R activation, M1R/Gβ interaction, Gαq/Gβ separation, Gαq/PLC interaction, and PIP2 hydrolysis. Electrophysiology was used to monitor channel closure. Time constants for M1R activation (<100 ms) and M1R/Gβ interaction (200 ms) are both fast, suggesting that neither of them is rate limiting during muscarinic suppression of M current. Gαq/Gβ separation and Gαq/PLC interaction have intermediate 1/e times (2.9 and 1.7 s, respectively), and PIP2 hydrolysis (6.7 s) occurs on the timescale of M current suppression. Overexpression of PLC accelerates the rate of M current suppression threefold (to 2.0 s) to become nearly contemporaneous with Gαq/PLC interaction. Evidently, channel release of PIP2 and closure are rapid, and the availability of active PLC limits the rate of M current suppression.
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Affiliation(s)
- Jill B Jensen
- Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, WA 98195, USA
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264
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Matsushita S, Nakata H, Kubo Y, Tateyama M. Ligand-induced rearrangements of the GABA(B) receptor revealed by fluorescence resonance energy transfer. J Biol Chem 2010; 285:10291-9. [PMID: 20129919 DOI: 10.1074/jbc.m109.077990] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The gamma-aminobutyric acid type B receptor (GABA(B)R), one of the family C G-protein-coupled receptor members, exists as a heterodimer comprised of subunits GB1 and GB2. To clarify the ligand-induced activation mechanism of the GABA(B)R, each subunit was fused with either Cerulean or enhanced yellow fluorescent protein at its intracellular loop, and fluorescence resonance energy transfer (FRET) changes upon agonist application were monitored. As a result, FRET decreases were observed between GB1a loop 2 and GB2 loop 2 and between GB1a loop 2 and GB2 loop 1, suggesting the dissociation of intracellular domains during the receptor activation. Both intersubunit FRET pairs were expected to faithfully capture the activation of the original receptor as their pharmacological properties were highly similar to that of the wild-type receptor. However, the intrasubunit data suggest that the receptor activation does not involve major structural changes within the transmembrane domain of each subunit. By combining the results obtained from two different levels, it was concluded that the GABA(B)R activation by agonist is associated with an asymmetrical intersubunit rearrangement of GB1a and GB2 on the membrane. This type of activation mode, an intersubunit rearrangement without apparent intrahelical structural changes, appears commonly shared by the GABA(B)R and the metabotropic glutamate receptor 1alpha, another family C G-protein-coupled receptor previously studied by our group. Nevertheless, the directions of intracellular domain movements and its asymmetry observed here highlight the qualitative difference between the two receptors.
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Affiliation(s)
- Shinichi Matsushita
- Division of Biophysics and Neurobiology, Department of Molecular Physiology, National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan
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265
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Maier-Peuschel M, Frölich N, Dees C, Hommers LG, Hoffmann C, Nikolaev VO, Lohse MJ. A fluorescence resonance energy transfer-based M2 muscarinic receptor sensor reveals rapid kinetics of allosteric modulation. J Biol Chem 2010; 285:8793-800. [PMID: 20083608 DOI: 10.1074/jbc.m109.098517] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Allosteric modulators have been identified for several G protein-coupled receptors, most notably muscarinic receptors. To study their mechanism of action, we made use of a recently developed technique to generate fluorescence resonance energy transfer (FRET)-based sensors to monitor G protein-coupled receptor activation. Cyan fluorescent protein was fused to the C terminus of the M(2) muscarinic receptor, and a specific binding sequence for the small fluorescent compound fluorescein arsenical hairpin binder, FlAsH, was inserted into the third intracellular loop; the latter site was labeled in intact cells by incubation with FlAsH. We then measured FRET between the donor cyan fluorescent protein and the acceptor FlAsH in intact cells and monitored its changes in real time. Agonists such as acetylcholine and carbachol induced rapid changes in FRET, indicative of agonist-induced conformational changes. Removal of the agonists or addition of an antagonist caused a reversal of this signal with rate constants between 400 and 1100 ms. The allosteric ligands gallamine and dimethyl-W84 caused no changes in FRET when given alone, but increased FRET when given in the presence of an agonist, compatible with an inactivation of the receptors. The kinetics of these effects were very rapid, with rate constants of 80-100 ms and approximately 200 ms for saturating concentrations of gallamine and dimethyl-W84, respectively. Because these speeds are significantly faster than the responses to antagonists, these data indicate that gallamine and dimethyl-W84 are allosteric ligands and actively induce a conformation of the M(2) receptor with a reduced affinity for its agonists.
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Affiliation(s)
- Monika Maier-Peuschel
- Institute of Pharmacology and Toxicology and the Rudolf Virchow Center, University of Würzburg, 97078 Würzburg, Germany
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266
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267
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Sadhu KK, Mizukami S, Watanabe S, Kikuchi K. Turn-on fluorescence switch involving aggregation and elimination processes for β-lactamase-tag. Chem Commun (Camb) 2010; 46:7403-5. [DOI: 10.1039/c0cc02432e] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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268
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Tracking single proteins in live cells using single-chain antibody fragment-fluorescent quantum dot affinity pair. Methods Enzymol 2010; 475:61-79. [PMID: 20627153 DOI: 10.1016/s0076-6879(10)75003-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Quantum dots (QDs) are extremely bright fluorescent imaging probes that are particularly useful for tracking individual molecules in living cells. Here, we show how a two-component system composed of a high-affinity single-chain fragment antibody and its cognate hapten (fluorescein) can be utilized for tracking individual proteins in various cell types. The single-chain fragment antibody against fluorescein is genetically appended to the protein of interest, while the hapten fluorescein is attached to the end of the peptide that is used to coat the QDs. We describe (i) the method used to functionalize QDs with fluorescein peptides; (ii) the method used to control the stoichiometry of the hapten on the surface of the QD; and (iii) the technical details necessary to observe single molecules in living cells.
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269
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Studying the dynamics of flagella in multicellular communities of Escherichia coli by using biarsenical dyes. Appl Environ Microbiol 2009; 76:1241-50. [PMID: 20023074 DOI: 10.1128/aem.02153-09] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This paper describes a new approach for labeling intact flagella using the biarsenical dyes FlAsH and ReAsH and imaging their spatial and temporal dynamics on live Escherichia coli cells in swarming communities of bacteria by using epifluorescence microscopy. Using this approach, we observed that (i) bundles of flagella on swarmer cells remain cohesive during frequent collisions with neighboring cells, (ii) flagella on nonmotile swarmer cells at the leading edge of the colony protrude in the direction of the uncolonized agar surface and are actively rotated in a thin layer of fluid that extends outward from the colony, and (iii) flagella form transient interactions with the flagella of other swarmer cells that are in close proximity. This approach opens a window for observing the dynamics of cells in communities that are relevant to ecology, industry, and biomedicine.
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270
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Tsien RY. Constructing and exploiting the fluorescent protein paintbox (Nobel Lecture). Angew Chem Int Ed Engl 2009; 48:5612-26. [PMID: 19565590 DOI: 10.1002/anie.200901916] [Citation(s) in RCA: 307] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Roger Y Tsien
- Howard Hughes Medical Institute and Department of Pharmacology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0647, USA.
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271
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Balla T. Green light to illuminate signal transduction events. Trends Cell Biol 2009; 19:575-86. [PMID: 19818623 DOI: 10.1016/j.tcb.2009.08.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Revised: 08/03/2009] [Accepted: 08/11/2009] [Indexed: 11/17/2022]
Abstract
When cells are exposed to hormones that act on cell surface receptors, information is processed through the plasma membrane into the cell interior via second messengers generated in the inner leaflet of the plasma membrane. Individual biochemical steps along this cascade have been characterized from ligand binding to receptors through to activation of guanine nucleotide binding proteins and their downstream effectors such as adenylate cyclase or phospholipase C. However, the complexity of temporal and spatial integration of these molecular events requires that they are studied in intact cells. The great expansion of fluorescent techniques and improved imaging technologies such as confocal and TIRF microscopy combined with genetically-engineered protein modules has provided a completely new approach to signal transduction research. Spatial definition of biochemical events followed with real-time temporal resolution has become a standard goal, and several new techniques are now breaking the resolution barrier of light microscopy.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program on Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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272
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Yano Y, Matsuzaki K. Tag–probe labeling methods for live-cell imaging of membrane proteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:2124-31. [DOI: 10.1016/j.bbamem.2009.07.017] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2009] [Revised: 07/16/2009] [Accepted: 07/23/2009] [Indexed: 11/28/2022]
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273
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Reiner S, Ziegler N, Leon C, Lorenz K, von Hayn K, Gachet C, Lohse MJ, Hoffmann C. beta-Arrestin-2 interaction and internalization of the human P2Y1 receptor are dependent on C-terminal phosphorylation sites. Mol Pharmacol 2009; 76:1162-71. [PMID: 19741005 DOI: 10.1124/mol.109.060467] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The nucleotide receptor P2Y(1) regulates a variety of physiological processes and is involved in platelet aggregation. Using human P2Y(1)-receptors C-terminally fused with a fluorescent protein, we studied the role of potential receptor phosphorylation sites in receptor internalization and beta-arrestin-2 translocation by means of confocal microscopy. Three receptor constructs were generated that lacked potential phosphorylation sites in the third intracellular loop, the proximal C terminus, or the distal C terminus. The corresponding receptor constructs were expressed in human embryonic kidney (HEK)-293 cells and stimulated with 100 muM ADP. Rapid receptor internalization was observed for the wild-type receptor and from those constructs mutated in the third intracellular loop and the proximal C terminus. However, the construct lacking phosphorylation sites at the distal C terminus did not show receptor internalization upon stimulation. The microscopic data were validated by HA-tagged receptor constructs using a cell surface enzyme-linked immunosorbent assay. P2Y(1)-receptor stimulated beta-arrestin-2-yellow fluorescent protein (YFP) translocation followed the same pattern as receptor internalization. Hence, no beta-arrestin-2-YFP translocation was observed when the distal C-terminal phosphorylation sites were mutated. Individual mutations indicate that residues Ser352 and Thr358 are essential for receptor internalization and beta-arrestin-2-YFP translocation. In contrast, protein kinase C (PKC)-mediated receptor desensitization was not affected by mutation of potential phosphorylation sites in the distal C terminus but was prevented by mutation of potential phosphorylation sites in the proximal C terminus. P2Y(1)-receptor internalization in HEK-293 cells was not blocked by inhibitors of PKC and calmodulin-dependent protein kinase. Thus, we conclude that P2Y(1)-receptor desensitization and internalization are mediated by different phosphorylation sites and kinases.
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Affiliation(s)
- Susanne Reiner
- Department of Pharmacology and Toxicology, University of Wuerzburg, Versbacher Str. 9, 97078 Wuerzburg, Germany
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274
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Sletten E, Bertozzi C. Bioorthogonale Chemie - oder: in einem Meer aus Funktionalität nach Selektivität fischen. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200900942] [Citation(s) in RCA: 522] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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275
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276
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Böhme I, Beck-Sickinger AG. Illuminating the life of GPCRs. Cell Commun Signal 2009; 7:16. [PMID: 19602276 PMCID: PMC2726148 DOI: 10.1186/1478-811x-7-16] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Accepted: 07/14/2009] [Indexed: 01/19/2023] Open
Abstract
The investigation of biological systems highly depends on the possibilities that allow scientists to visualize and quantify biomolecules and their related activities in real-time and non-invasively. G-protein coupled receptors represent a family of very dynamic and highly regulated transmembrane proteins that are involved in various important physiological processes. Since their localization is not confined to the cell surface they have been a very attractive "moving target" and the understanding of their intracellular pathways as well as the identified protein-protein-interactions has had implications for therapeutic interventions. Recent and ongoing advances in both the establishment of a variety of labeling methods and the improvement of measuring and analyzing instrumentation, have made fluorescence techniques to an indispensable tool for GPCR imaging. The illumination of their complex life cycle, which includes receptor biosynthesis, membrane targeting, ligand binding, signaling, internalization, recycling and degradation, will provide new insights into the relationship between spatial receptor distribution and function. This review covers the existing technologies to track GPCRs in living cells. Fluorescent ligands, antibodies, auto-fluorescent proteins as well as the evolving technologies for chemical labeling with peptide- and protein-tags are described and their major applications concerning the GPCR life cycle are presented.
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Affiliation(s)
- Ilka Böhme
- Institute of Biochemistry, Faculty of Biosciences, Pharmacy and Psychology, Leipzig University, Brüderstr, 34, 04103 Leipzig, Germany.
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277
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Madani F, Lind J, Damberg P, Adams SR, Tsien RY, Gräslund AO. Hairpin structure of a biarsenical-tetracysteine motif determined by NMR spectroscopy. J Am Chem Soc 2009; 131:4613-5. [PMID: 19281235 DOI: 10.1021/ja809315x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The biarsenical-tetracysteine motif is a useful tag for genetic labeling of proteins with small molecules in living cells. The present study concerns the structure of a 12 amino acid peptide FLNCCPGCCMEP bound to the fluorophore ReAsH based on resorufin. (1)H NMR spectroscopy was used to determine the solution structure of the complex formed between the peptide and the ReAsH moiety. Structure calculations based on the NMR results showed that the backbone structure of the peptide is fairly well defined, with a hairpinlike turn, similar to a type-II beta-turn, formed by the central CPGC segment. The most stable complex was formed when As2 was bonded to C4 and C5 and As1 to C8 and C9. Two clear NOESY cross-peaks between the Phe1 side chain and ReAsH confirmed the close positioning of the phenyl ring of Phe1 and ReAsH. Phe1 was found to have an edge-face geometry relative to ReAsH. The close interaction between Phe1 and ReAsH may be highly significant for the fluorescence properties of the ReAsH complex.
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Affiliation(s)
- Fatemeh Madani
- Department of Biochemistry and Biophysics, Arrhenius Laboratories, Stockholm University, SE-106 91 Stockholm, Sweden
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278
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Optical measurement of mGluR1 conformational changes reveals fast activation, slow deactivation, and sensitization. Proc Natl Acad Sci U S A 2009; 106:11388-93. [PMID: 19549872 DOI: 10.1073/pnas.0901290106] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Metabotropic glutamate receptor (mGluR) activation has been extensively studied under steady-state conditions. However, at central synapses, mGluRs are exposed to brief submillisecond glutamate transients and may not reach steady-state. The lack of information on the kinetics of mGluR activation impairs accurate predictions of their operation during synaptic transmission. Here, we report experiments designed to investigate mGluR kinetics in real-time. We inserted either CFP or YFP into the second intracellular loop of mGluR1beta. When these constructs were coexpressed in PC12 cells, glutamate application induced a conformational change that could be monitored, using fluorescence resonance energy transfer (FRET), with an EC(50) of 7.5 microM. The FRET response was mimicked by the agonist DHPG, abolished by the competitive antagonist MCPG, and partially inhibited by mGluR1-selective allosteric modulators. These results suggest that the FRET response reports active conformations of mGluR1 dimers. The solution exchange at the cell membrane was optimized for voltage-clamped cells by recording the current induced by co-application of 30 mM potassium. When glutamate was applied at increasing concentrations up to 2 mM, the activation time course decreased to a minimum of approximately 10 ms, whereas the deactivation time course remained constant (approximately 50 ms). During long-lasting applications, no desensitization was observed. In contrast, we observed a robust sensitization of the FRET response that developed over approximately 400 ms. Activation, deactivation, and sensitization time courses and amplitudes were used to derive a kinetic scheme and rate constants, from which we inferred the EC(50) and frequency dependence of mGluR1 activation under non-steady-state conditions, as occurs during synaptic transmission.
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279
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Optical reporters for the conformation of alpha-synuclein reveal a specific interaction with mitochondria. J Neurosci 2009; 28:12305-17. [PMID: 19020024 DOI: 10.1523/jneurosci.3088-08.2008] [Citation(s) in RCA: 158] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The aggregation of abnormally folded proteins is a defining feature of neurodegenerative disease, but it has not previously been possible to assess the conformation of these proteins in a physiologically relevant context, before they form morphologically recognizable aggregates. We now describe FRET-based reporters for the conformation of alpha-synuclein, a protein central to the pathogenesis of Parkinson's disease (PD). Characterization in vitro shows that alpha-synuclein adopts a relatively "closed" conformation in solution that converts to "open" on membrane binding. In living cells, the closed conformation predominates. In neurons, however, cell bodies contain a much larger proportion of the open conformation than synaptic boutons. To account for these differences, we also used the reporters to characterize the interaction with native membranes. We find that the conformation of alpha-synuclein responds selectively to mitochondria, indicating a direct link between alpha-synuclein and an organelle strongly implicated in the pathogenesis of PD.
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280
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Conformational detection of p53's oligomeric state by FlAsH Fluorescence. Biochem Biophys Res Commun 2009; 384:66-70. [PMID: 19393630 DOI: 10.1016/j.bbrc.2009.04.073] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Accepted: 04/16/2009] [Indexed: 12/24/2022]
Abstract
The p53 tumor suppressor protein is a critical checkpoint in prevention of tumor formation, and the function of p53 is dependent on proper formation of the active tetramer. In vitro studies have shown that p53 binds DNA most efficiently as a tetramer, though inactive p53 is predicted to be monomeric in vivo. We demonstrate that FlAsH binding can be used to distinguish between oligomeric states of p53, providing a potential tool to explore p53 oligomerization in vivo. The FlAsH tetra-cysteine binding motif has been incorporated along the dimer and tetramer interfaces in the p53 tetramerization domain to create reporters for the dimeric and tetrameric states of p53, though the geometry of the four cysteines is critical for efficient FlAsH binding. Furthermore, we demonstrate that FlAsH binding can be used to monitor tetramer formation in real-time. These results demonstrate the potential for using FlAsH fluorescence to monitor protein-protein interactions in vivo.
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281
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Brain receptor mosaics and their intramembrane receptor-receptor interactions: molecular integration in transmission and novel targets for drug development. J Acupunct Meridian Stud 2009; 2:1-25. [PMID: 20633470 DOI: 10.1016/s2005-2901(09)60011-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2008] [Accepted: 01/06/2009] [Indexed: 11/21/2022] Open
Abstract
The concept of intramembrane receptor-receptor interactions and evidence for their existence was introduced by Agnati and Fuxe in 1980/81 suggesting the existence of heteromerization of receptors. In 1982, they proposed the existence of aggregates of multiple receptors in the plasma membrane and coined the term receptor mosaics (RM). In this way, cell signaling becomes a branched process beginning at the level of receptor recognition at the plasma membrane where receptors can directly modify the ligand recognition and signaling capacity of the receptors within a RM. Receptor-receptor interactions in RM are classified as operating either with classical cooperativity, when consisting of homomers or heteromers of similar receptor subtypes having the same transmitter, or non-classical cooperativity, when consisting of heteromers. It has been shown that information processing within a RM depends not only on its receptor composition, but also on the topology and the order of receptor activation determined by the concentrations of the ligands and the receptor properties. The general function of RM has also been demonstrated to depend on allosteric regulators (e.g., homocysteine) of the receptor subtypes present. RM as integrative nodes for receptor-receptor interactions in conjunction with membrane associated proteins may form horizontal molecular networks in the plasma membrane coordinating the activity of multiple effector systems modulating the excitability and gene expression of the cells. The key role of electrostatic epitope-epitope interactions will be discussed for the formation of the RM. These interactions probably represent a general molecular mechanism for receptor-receptor interactions and, without a doubt, indicate a role for phosphorylation-dephosphorylation events in these interactions. The novel therapeutic aspects given by the RMs will be discussed in the frame of molecular neurology and psychiatry and combined drug therapy appears as the future way to go.
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282
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Ahles A, Engelhardt S. Polymorphisms determine beta-adrenoceptor conformation: implications for cardiovascular disease and therapy. Trends Pharmacol Sci 2009; 30:188-93. [PMID: 19272658 DOI: 10.1016/j.tips.2009.02.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2008] [Revised: 02/02/2009] [Accepted: 02/03/2009] [Indexed: 11/16/2022]
Abstract
Beta(1)- and beta(2)-adrenoceptors are crucial regulators of cardiovascular function. Agonists and antagonists at these receptor subtypes are cornerstones in the treatment of cardiovascular disease. In humans, both of the genes encoding the beta(1)- and beta(2)-adrenoceptors carry frequent polymorphisms resulting in different variants of the receptor proteins. Whether the polymorphic nature of the receptors causes the clinically observed differences with respect to the response of the patients to therapeutic drugs is currently a matter of intense discussion. Here, we discuss recent progress regarding the determination of beta-adrenoceptor conformational changes and how these can help to clarify this issue. Specifically, novel optical methods enable us to directly assess the functional importance of beta-adrenoceptor polymorphisms on ligand-induced changes of receptor conformation. The ability to determine polymorphism-dependent differences in drug efficacy directly on the receptor level might develop into an important approach to establish individualized drug therapies based on the genetic determinants of the patients.
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Affiliation(s)
- Andrea Ahles
- Rudolf Virchow Center, Deutsche Forschungsgemeinschaft Research Center for Experimental Biomedicine, Universitaet Wuerzburg, 97078 Wuerzburg, Germany
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283
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Orun O, Rasmussen S, Gether U. Introducing tetraCys motifs at two different sites results in a functional dopamine transporter. ACTA BIOLOGICA HUNGARICA 2009; 60:15-25. [PMID: 19378920 DOI: 10.1556/abiol.60.2009.1.2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have introduced tetracysteine motifs into different positions of the dopamine transporter (DAT) for specific FlAsH labeling. Two of the constructs expressed at the cell surface and were functional as determined by [3H] dopamine uptake experiments. The N-terminally modified transporter showed uptake levels comparable to the wild-type DAT, while the construct with tetracysteine motif at position 511 displayed an uptake level about 1/3 of its wild-type counterpart. In addition, these two transporter constructs were visualized on the cell surface following labeling with a fluorescent cocaine analog. YFP introduced into the same N-terminal position was also shown to have surface staining in agreement with activity tests. We propose that these two sites are suitable targets for tetracysteine labeling to be used in FlAsH staining studies, while p134, p342, p427, p433 and p517 sites are not.
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Affiliation(s)
- Oya Orun
- Dept. of Biophysics, Marmara Univ. School of Medicine, Istanbul, Turkey.
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284
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Narayanaswamy R, Moradi EK, Niu W, Hart GT, Davis M, McGary KL, Ellington AD, Marcotte EM. Systematic definition of protein constituents along the major polarization axis reveals an adaptive reuse of the polarization machinery in pheromone-treated budding yeast. J Proteome Res 2009; 8:6-19. [PMID: 19053807 PMCID: PMC2651748 DOI: 10.1021/pr800524g] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
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Polarizing cells extensively restructure cellular components in a spatially and temporally coupled manner along the major axis of cellular extension. Budding yeast are a useful model of polarized growth, helping to define many molecular components of this conserved process. Besides budding, yeast cells also differentiate upon treatment with pheromone from the opposite mating type, forming a mating projection (the ‘shmoo’) by directional restructuring of the cytoskeleton, localized vesicular transport and overall reorganization of the cytosol. To characterize the proteomic localization changes accompanying polarized growth, we developed and implemented a novel cell microarray-based imaging assay for measuring the spatial redistribution of a large fraction of the yeast proteome, and applied this assay to identify proteins localized along the mating projection following pheromone treatment. We further trained a machine learning algorithm to refine the cell imaging screen, identifying additional shmoo-localized proteins. In all, we identified 74 proteins that specifically localize to the mating projection, including previously uncharacterized proteins (Ycr043c, Ydr348c, Yer071c, Ymr295c, and Yor304c-a) and known polarization complexes such as the exocyst. Functional analysis of these proteins, coupled with quantitative analysis of individual organelle movements during shmoo formation, suggests a model in which the basic machinery for cell polarization is generally conserved between processes forming the bud and the shmoo, with a distinct subset of proteins used only for shmoo formation. The net effect is a defined ordering of major organelles along the polarization axis, with specific proteins implicated at the proximal growth tip. Upon sensing mating pheromone, budding yeast cells form a mating projection (the ‘shmoo’) that serves as a model for polarized cell growth, involving cytoskeletal/cytosolic restructuring and directed vesicular transport. We developed a cell microarray-based imaging assay for measuring localization of the yeast proteome during polarized growth. We find major organelles ordered along the polarization axis, localize 74 proteins to the growth tip, and observe adaptive reuse of general polarization machinery.
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Affiliation(s)
- Rammohan Narayanaswamy
- Center for Systems and Synthetic Biology, Departments of Chemistry and Biochemistry, University of Texas, Austin, Texas 78712
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285
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Picchietti S, Belardinelli M, Taddei AR, Fausto AM, Pellegrino M, Maggio R, Rossi M, Giorgi F. Thyroid disruptor 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) prevents internalization of TSH receptor. Cell Tissue Res 2009; 336:31-40. [DOI: 10.1007/s00441-008-0749-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Accepted: 12/19/2008] [Indexed: 11/30/2022]
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286
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Abstract
Autofluorescent proteins have become indispensable in our quest to visualize molecular events in living cells. Further progress in the visualization and quantification of all biochemical activities of the cell will require the introduction of additional and complementary methods for sensing and probing biomolecules. Here I highlight some of the areas where the development of new probes and labeling methods is eagerly awaited and where chemical biologists could make important contributions.
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Affiliation(s)
- Kai Johnsson
- Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
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287
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288
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Xie H, Guo XM, Chen H. Making the most of fusion tags technology in structural characterization of membrane proteins. Mol Biotechnol 2009; 42:135-45. [PMID: 19199085 DOI: 10.1007/s12033-009-9148-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Accepted: 01/19/2009] [Indexed: 11/24/2022]
Abstract
Membrane proteins can be investigated at various structural levels, including the topological structure, the high-resolution three-dimensional structure, and the organization and assembly of membrane protein complexes. Gene fusion technology makes it possible to insert a polynucleotide encoding a protein or polypeptide tag into the gene encoding a membrane protein of interest. Resultant recombinant proteins may possess the functions of the original membrane proteins, together with the biochemical properties of the imported fusion tag, greatly enhancing functional and structural studies of membrane proteins. In this article, the latest literature is reviewed in relation to types, applications, strategies, and approaches to fusion tag technology for structural investigations of membrane proteins.
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Affiliation(s)
- Hao Xie
- Department of Biological Science and Biotechnology, Institute of Science, Wuhan University of Technology, People's Republic of China.
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289
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Vilardaga JP, Bünemann M, Feinstein TN, Lambert N, Nikolaev VO, Engelhardt S, Lohse MJ, Hoffmann C. GPCR and G proteins: drug efficacy and activation in live cells. Mol Endocrinol 2009; 23:590-9. [PMID: 19196832 DOI: 10.1210/me.2008-0204] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Many biochemical pathways are driven by G protein-coupled receptors, cell surface proteins that convert the binding of extracellular chemical, sensory, and mechanical stimuli into cellular signals. Their interaction with various ligands triggers receptor activation that typically couples to and activates heterotrimeric G proteins, which in turn control the propagation of secondary messenger molecules (e.g. cAMP) involved in critically important physiological processes (e.g. heart beat). Successful transfer of information from ligand binding events to intracellular signaling cascades involves a dynamic interplay between ligands, receptors, and G proteins. The development of Förster resonance energy transfer and bioluminescence resonance energy transfer-based methods has now permitted the kinetic analysis of initial steps involved in G protein-coupled receptor-mediated signaling in live cells and in systems as diverse as neurotransmitter and hormone signaling. The direct measurement of ligand efficacy at the level of the receptor by Förster resonance energy transfer is also now possible and allows intrinsic efficacies of clinical drugs to be linked with the effect of receptor polymorphisms.
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Affiliation(s)
- Jean-Pierre Vilardaga
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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290
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Yamamoto T, Nagamune T. Expansion of the sortase-mediated labeling method for site-specific N-terminal labeling of cell surface proteins on living cells. Chem Commun (Camb) 2009:1022-4. [PMID: 19225623 DOI: 10.1039/b818792d] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The sortase-mediated labeling method, whose applications have been limited to C-terminal labeling of cell surface proteins, has been expanded for site-specific N-terminal labeling of cell surface proteins.
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Affiliation(s)
- Teruyasu Yamamoto
- Department of Chemistry and Biotechnology, Graduate School of Engineering, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan
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291
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Sletten EM, Bertozzi CR. Bioorthogonal chemistry: fishing for selectivity in a sea of functionality. Angew Chem Int Ed Engl 2009; 48:6974-98. [PMID: 19714693 PMCID: PMC2864149 DOI: 10.1002/anie.200900942] [Citation(s) in RCA: 2343] [Impact Index Per Article: 156.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The study of biomolecules in their native environments is a challenging task because of the vast complexity of cellular systems. Technologies developed in the last few years for the selective modification of biological species in living systems have yielded new insights into cellular processes. Key to these new techniques are bioorthogonal chemical reactions, whose components must react rapidly and selectively with each other under physiological conditions in the presence of the plethora of functionality necessary to sustain life. Herein we describe the bioorthogonal chemical reactions developed to date and how they can be used to study biomolecules.
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Affiliation(s)
- Ellen M. Sletten
- Department of Chemistry, University of California, Berkeley, CA 94720 (USA)
| | - Carolyn R. Bertozzi
- Departments of Chemistry and Molecular and Cell Biology and Howard Hughes Medical Institute, University of California and The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (USA), Fax: (+1)510-643-2628
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292
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Dynamic visualization of cellular signaling. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2009; 119:79-97. [PMID: 19499207 DOI: 10.1007/10_2008_48] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Our understanding of cellular signaling is critically dependent on our ability to visualize and quantify specific signaling events with high spatial and temporal resolution in the cellular context. Over the past decade or so, biosensors based on fluorescent proteins and fluorescence resonance energy transfer (FRET) have emerged as one major class of fluorescent probes that are capable of tracking a variety of cellular signaling events, such as second messenger dynamics and enzyme activation/activity, in time and space. Here we review recent advances in the development of such biosensors and some biological insights revealed by these biosensors in living cells, tissue, and organisms.
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293
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Chapter 5 Visible fluorescent proteins for FRET. ACTA ACUST UNITED AC 2009. [DOI: 10.1016/s0075-7535(08)00005-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
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294
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Copik AJ, Ma C, Kosaka A, Sahdeo S, Trane A, Ho H, Dietrich PS, Yu H, Ford APDW, Button D, Milla ME. Facilitatory interplay in alpha 1a and beta 2 adrenoceptor function reveals a non-Gq signaling mode: implications for diversification of intracellular signal transduction. Mol Pharmacol 2008; 75:713-28. [PMID: 19109357 DOI: 10.1124/mol.108.050765] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Agonist occupied alpha(1)-adrenoceptors (alpha(1)-ARs) engage several signaling pathways, including phosphatidylinositol hydrolysis, calcium mobilization, arachidonic acid release, mitogen-activated protein (MAP) kinase activation, and cAMP accumulation. The natural agonist norepinephrine (NE) activates with variable affinity and intrinsic efficacy all adrenoceptors, and in cells that coexpress alpha(1)- and beta-AR subtypes, such as cardiomyocytes, this leads to coactivation of multiple downstream pathways. This may result in pathway cross-talk with significant consequences to heart physiology and pathologic state. To dissect signaling components involved specifically in alpha(1A)- and beta(2)-AR signal interplay, we have developed a recombinant model system that mimics the levels of receptor expression observed in native cells. We followed intracellular Ca(2+) mobilization to monitor in real time the activation of both G(q) and G(s) pathways. We found that coactivation of alpha(1A)- and beta(2)-AR by the nonselective agonist NE or via a combination of the highly selective alpha(1A)-AR agonist A61603 and the beta-selective agonist isoproterenol led to increases in Ca(2+) influx from the extracellular compartment relative to stimulation with A61603 alone, with no effect on the associated transient release of Ca(2+) from intracellular stores. This effect became more evident upon examination of an alpha(1A)-AR variant exhibiting a partial defect in coupling to G(q), and we attribute it to potentiation of a non G(q)-pathway, uncovered by application of a combination of xestospongin C, an endoplasmic reticulum inositol 1,4,5-triphosphate receptor blocker, and 2-aminoethoxydiphenyl borate, a nonselective storeoperated Ca(2+) entry channel blocker. We also found that stimulation with A61603 of a second alpha(1A)-AR variant entirely unable to signal induced no Ca(2+) unless beta(2)-AR was concomitantly activated. These results may be accounted for by the presence of alpha(1A)/beta(2)-AR heterodimers or alternatively by specific adrenoceptor signal cross-talk resulting in distinct pharmacological behavior. Finally, our findings provide a new conceptual framework to rationalize outcomes from clinical studies targeting alpha- and beta-adrenoceptors.
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Affiliation(s)
- Alicja J Copik
- Inflammation Discovery, Roche Palo Alto, Palo Alto, California, USA
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295
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Zürn A, Zabel U, Vilardaga JP, Schindelin H, Lohse MJ, Hoffmann C. Fluorescence Resonance Energy Transfer Analysis of α2a-Adrenergic Receptor Activation Reveals Distinct Agonist-Specific Conformational Changes. Mol Pharmacol 2008; 75:534-41. [DOI: 10.1124/mol.108.052399] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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296
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Hausch F, Becker CFW. EMBL conference on Chemical Biology 2008. Chembiochem 2008; 9:3083-6. [PMID: 19006153 DOI: 10.1002/cbic.200800711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Felix Hausch
- Chemical Genomics Research Group, Max Planck Institute of Psychiatry, Munich, Germany.
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297
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Preparation of the membrane-permeant biarsenicals FlAsH-EDT2 and ReAsH-EDT2 for fluorescent labeling of tetracysteine-tagged proteins. Nat Protoc 2008; 3:1527-34. [PMID: 18772880 DOI: 10.1038/nprot.2008.144] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The membrane-permeant fluorogenic biarsenicals FlAsH-EDT(2) and ReAsH-EDT(2) can be prepared in good yields by a straightforward two-step procedure from the inexpensive precursor dyes fluorescein and resorufin, respectively. Handling of toxic reagents such as arsenic trichloride is minimized so the synthesis can be carried out in a typical chemistry laboratory, usually taking about 2-3 d. A wide range of other biarsenical reagents and intermediates that also bind to tetracysteine-tagged (CysCysProGlyCysCys) proteins can be prepared similarly using this general procedure.
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298
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Huber T, Menon S, Sakmar TP. Structural basis for ligand binding and specificity in adrenergic receptors: implications for GPCR-targeted drug discovery. Biochemistry 2008; 47:11013-23. [PMID: 18821775 DOI: 10.1021/bi800891r] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Crystal structures of engineered human beta 2-adrenergic receptors (ARs) in complex with an inverse agonist ligand, carazolol, provide three-dimensional snapshots of the disposition of seven transmembrane helices and the ligand-binding site of an important G protein-coupled receptor (GPCR). As expected, beta 2-AR shares substantial structural similarities with rhodopsin, the dim-light photoreceptor of the rod cell. However, although carazolol and the 11- cis-retinylidene moiety of rhodopsin are situated in the same general binding pocket, the second extracellular (E2) loop structures are quite distinct. E2 in rhodopsin shows beta-sheet structure and forms part of the chromophore-binding site. In the beta 2-AR, E2 is alpha-helical and seems to be distinct from the receptor's active site, allowing a potential entry pathway for diffusible ligands. The structures, together with extensive structure-activity relationship (SAR) data from earlier studies, provide insight about possible structural determinants of ligand specificity and how the binding of agonist ligands might alter receptor conformation. We review key features of the new beta 2-AR structures in the context of recent complementary work on the conformational dynamics of GPCRs. We also report 600 ns molecular dynamics simulations that quantified beta 2-AR receptor mobility in a membrane bilayer environment and show how the binding of an agonist ligand, adrenaline (epinephrine), causes conformational changes to the ligand-binding pocket and neighboring helices.
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Affiliation(s)
- Thomas Huber
- Laboratory of Molecular Biology and Biochemistry, The Rockefeller University, 1230 York Avenue, New York, New York 10065, USA.
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299
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Bishop AC, Chen VL. Brought to life: targeted activation of enzyme function with small molecules. J Chem Biol 2008; 2:1-9. [PMID: 19568788 DOI: 10.1007/s12154-008-0012-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2008] [Accepted: 09/04/2008] [Indexed: 11/30/2022] Open
Abstract
Cell-permeable small molecules that are capable of activating particular enzymes would be invaluable tools for studying protein function in complex cell-signaling cascades. But, is it feasible to identify compounds that allow chemical-biology researchers to activate specific enzymes in a cellular context? In this review, we describe some recent advances in achieving targeted enzyme activation with small molecules. In addition to surveying progress in the identification and targeting of enzymes that contain natural allosteric-activation sites, we focus on recently developed protein-engineering strategies that allow researchers to render an enzyme of interest "activatable" by a pre-chosen compound. Three distinct strategies for targeting an engineered enzyme are discussed: direct chemical "rescue" of an intentionally inactivated enzyme, activation of an enzyme by targeting a de novo small-molecule-binding site, and the generation of activatable enzymes via fusion of target enzymes to previously characterized small-molecule-binding domains.
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Affiliation(s)
- Anthony C Bishop
- Department of Chemistry, Amherst College, Amherst, MA, 01002, USA,
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300
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Faron-Górecka A, Górecki A, Kuśmider M, Wasylewski Z, Dziedzicka-Wasylewska M. The role of D1-D2 receptor hetero-dimerization in the mechanism of action of clozapine. Eur Neuropsychopharmacol 2008; 18:682-91. [PMID: 18550344 DOI: 10.1016/j.euroneuro.2008.05.001] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2008] [Revised: 04/21/2008] [Accepted: 05/01/2008] [Indexed: 01/24/2023]
Abstract
Clozapine is effective although still not perfect drug used to treat schizophrenia. The precise mechanism of its action is not known. Here we show that there are two binding sites for clozapine at the dopamine D1 and D2 receptors, and the affinity of D1R strongly depended on whether the receptor was present alone or together with D2R (or its genetic variant D2Ser311Cys) in the cell membrane, pointing to the role of receptor hetero-dimerization in the observed phenomenon. The use of fluorescence resonance energy transfer (FRET) technology, observed via fluorescence lifetime microscopy of the single cell, indicated that low concentration of clozapine (10(-9) M), sufficient to saturate the high affinity site, uncoupled the D1R-D2R hetero-dimers. Therefore it has been concluded that clozapine might antagonize the effect of concomitant stimulation of both dopamine receptors, which has been shown previously to enhance the formation of hetero-dimers and to stimulate the calcium signaling pathway.
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Affiliation(s)
- Agata Faron-Górecka
- Department of Pharmacology, Institute of Pharmacology, Polish Academy of Sciences, Kraków, Poland
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