126
|
Abstract
MG and SRB aptamers, which are short RNA sequences originally selected only for binding to malachite green or sulforhodamine B, can greatly enhance the fluorescence of normally nonfluorescent triphenylmethane dyes. MG aptamer enhances the quantum yields of malachite green (MG) and a novel rigidized derivative, indolinyl malachite green (IMG) by >2000-fold. SRB aptamer brightens patent blue V and VF by >90-fold. These enhancements are specific because MG aptamer has no effect on patent blue dyes and SRB aptamer has little or no effect on MG and IMG. Such sequence-specific fluorescence labeling of short RNA motifs is a first step toward genetically encodable fusion tags for imaging selected RNAs in vitro and in cells.
Collapse
|
127
|
Hasegawa S, Jackson WC, Tsien RY, Rao J. Imaging Tetrahymena ribozyme splicing activity in single live mammalian cells. Proc Natl Acad Sci U S A 2003; 100:14892-6. [PMID: 14645710 PMCID: PMC299846 DOI: 10.1073/pnas.2036553100] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Tetrahymena ribozymes hold promise for repairing genetic disorders but are largely limited by their modest splicing efficiency and low production of final therapeutic proteins. Ribozyme evolution in intact living mammalian cells would greatly facilitate the discovery of new ribozyme variants with high in vivo activity, but no such strategies have been reported. Here we present a study using a new reporter enzyme, beta-lactamase, to report splicing activity in single living cells and perform high-throughput screening with flow cytometry. The reporter ribozyme constructs consist of the self-splicing Tetrahymena thermophila group I intron ribozyme that is inserted into the ORF of the mRNA of beta-lactamase. The splicing activity in single living cells can be readily detected quantitatively and visualized. Individual cells have shown considerable heterogeneity in ribozyme activity. Screening of Tetrahymena ribozymes with insertions in the middle of the L1 loop led to identification of better variants with at least 4-fold more final in vivo activity than the native sequence. Our work has provided a new reporter system that allows high-throughput screening with flow cytometry of single living mammalian cells for a direct and facile in vivo selection of desired ribozyme variants.
Collapse
|
128
|
Tour O, Meijer RM, Zacharias DA, Adams SR, Tsien RY. Genetically targeted chromophore-assisted light inactivation. Nat Biotechnol 2003; 21:1505-8. [PMID: 14625562 DOI: 10.1038/nbt914] [Citation(s) in RCA: 173] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2003] [Accepted: 09/10/2003] [Indexed: 11/08/2022]
Abstract
Studies of protein function would be facilitated by a general method to inactivate selected proteins in living cells noninvasively with high spatial and temporal precision. Chromophore-assisted light inactivation (CALI) uses photochemically generated, reactive oxygen species to inactivate proteins acutely, but its use has been limited by the need to microinject dye-labeled nonfunction-blocking antibodies. We now demonstrate CALI of connexin43 (Cx43) and alpha1C L-type calcium channels, each tagged with one or two small tetracysteine (TC) motifs that specifically bind the membrane-permeant, red biarsenical dye, ReAsH. ReAsH-based CALI is genetically targeted, requires no antibodies or microinjection, and inactivates each protein by approximately 90% in <30 s of widefield illumination. Similar light doses applied to Cx43 or alpha1C tagged with green fluorescent protein (GFP) had negligible to slight effects with or without ReAsH exposure, showing the expected molecular specificity. ReAsH-mediated CALI acts largely via singlet oxygen because quenchers or enhancers of singlet oxygen respectively inhibit or enhance CALI.
Collapse
|
129
|
Gao W, Xing B, Tsien RY, Rao J. Novel Fluorogenic Substrates for Imaging β-Lactamase Gene Expression. J Am Chem Soc 2003; 125:11146-7. [PMID: 16220906 DOI: 10.1021/ja036126o] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A new class of small nonfluorescent fluorogenic substrates becomes brightly fluorescent after beta-lactamase hydrolysis with up to 153-fold enhancement in the fluorescence intensity. Less than 500 fM of beta-lactamase in cell lysates can be readily detected, and beta-lactamase expression in living cells can be imaged with a red fluorescence derivative. These new fluorogenic substrates should find uses in clinical diagnostics and facilitate the applications of beta-lactamase as a biosensor.
Collapse
|
130
|
Tsien RY. Imagining imaging's future. Nat Rev Mol Cell Biol 2003; Suppl:SS16-21. [PMID: 14587522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023]
Abstract
Imaging specific molecules and their interactions in space and time will be essential to understand how genomes create cells, how cells constitute organisms and how errant cells cause disease. Molecular imaging must be extended and applied from nanometre to metre scales and from milliseconds to days. This quest will require input from physics, chemistry, and the genetics and biochemistry of diverse organisms with useful talents.
Collapse
|
131
|
Tsai PS, Friedman B, Ifarraguerri AI, Thompson BD, Lev-Ram V, Schaffer CB, Xiong Q, Tsien RY, Squier JA, Kleinfeld D. All-optical histology using ultrashort laser pulses. Neuron 2003; 39:27-41. [PMID: 12848930 DOI: 10.1016/s0896-6273(03)00370-2] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
As a means to automate the three-dimensional histological analysis of brain tissue, we demonstrate the use of femtosecond laser pulses to iteratively cut and image fixed as well as fresh tissue. Cuts are accomplished with 1 to 10 microJ pulses to ablate tissue with micron precision. We show that the permeability, immunoreactivity, and optical clarity of the tissue is retained after pulsed laser cutting. Further, samples from transgenic mice that express fluorescent proteins retained their fluorescence to within microns of the cut surface. Imaging of exogenous or endogenous fluorescent labels down to 100 microm or more below the cut surface is accomplished with 0.1 to 1 nJ pulses and conventional two-photon laser scanning microscopy. In one example, labeled projection neurons within the full extent of a neocortical column were visualized with micron resolution. In a second example, the microvasculature within a block of neocortex was measured and reconstructed with micron resolution.
Collapse
|
132
|
Violin JD, Zhang J, Tsien RY, Newton AC. A genetically encoded fluorescent reporter reveals oscillatory phosphorylation by protein kinase C. J Cell Biol 2003; 161:899-909. [PMID: 12782683 PMCID: PMC2172956 DOI: 10.1083/jcb.200302125] [Citation(s) in RCA: 432] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Signals transduced by kinases depend on the extent and duration of substrate phosphorylation. We generated genetically encoded fluorescent reporters for PKC activity that reversibly respond to stimuli activating PKC. Specifically, phosphorylation of the reporter expressed in mammalian cells causes changes in fluorescence resonance energy transfer (FRET), allowing real time imaging of phosphorylation resulting from PKC activation. Targeting of the reporter to the plasma membrane, where PKC is activated, reveals oscillatory phosphorylation in HeLa cells in response to histamine. Each oscillation in substrate phosphorylation follows a calcium oscillation with a lag of approximately 10 s. Novel FRET-based reporters for PKC translocation, phosphoinositide bisphosphate conversion to IP3, and diacylglycerol show that in HeLa cells the oscillatory phosphorylations correlate with Ca2+-controlled translocation of conventional PKC to the membrane without oscillations of PLC activity or diacylglycerol. However, in MDCK cells stimulated with ATP, PLC and diacylglycerol fluctuate together with Ca2+ and phosphorylation. Thus, specificity of PKC signaling depends on the local second messenger-controlled equilibrium between kinase and phosphatase activities to result in strict calcium-controlled temporal regulation of substrate phosphorylation.
Collapse
|
133
|
Yu D, Baird GS, Tsien RY, Davis RL. Detection of calcium transients in Drosophila mushroom body neurons with camgaroo reporters. J Neurosci 2003; 23:64-72. [PMID: 12514202 PMCID: PMC6742124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023] Open
Abstract
Camgaroos are yellow fluorescent protein derivatives that hold promise as transgenically encoded calcium sensors in behaving animals. We expressed two versions of camgaroo in Drosophila mushroom bodies using the galactosidase-4 (GAL4) system. Potassium depolarization of brains expressing the reporters produces a robust increase in fluorescence that is blocked by removing extracellular calcium or by antagonists of voltage-dependent calcium channels. The fluorescence increase is not attributable to cytoplasmic alkalization; depolarization induces a slight acidification of the cytoplasm of mushroom body neurons. Acetylcholine applied near the dendrites of the mushroom body neurons induces a rapid and ipsilateral-specific fluorescence increase in the mushroom body axons that is blocked by antagonists of calcium channels or nicotinic acetylcholine receptors. Fluorescence was observed to increase in all three classes of mushroom body neurons, indicating that all types respond to cholinergic innervation.
Collapse
|
134
|
Zhang J, Campbell RE, Ting AY, Tsien RY. Erratum: Creating new fluorescent probes for cell biology. Nat Rev Mol Cell Biol 2003. [DOI: 10.1038/nrm1031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
135
|
Gilman AG, Simon MI, Bourne HR, Harris BA, Long R, Ross EM, Stull JT, Taussig R, Bourne HR, Arkin AP, Cobb MH, Cyster JG, Devreotes PN, Ferrell JE, Fruman D, Gold M, Weiss A, Stull JT, Berridge MJ, Cantley LC, Catterall WA, Coughlin SR, Olson EN, Smith TF, Brugge JS, Botstein D, Dixon JE, Hunter T, Lefkowitz RJ, Pawson AJ, Sternberg PW, Varmus H, Subramaniam S, Sinkovits RS, Li J, Mock D, Ning Y, Saunders B, Sternweis PC, Hilgemann D, Scheuermann RH, DeCamp D, Hsueh R, Lin KM, Ni Y, Seaman WE, Simpson PC, O'Connell TD, Roach T, Simon MI, Choi S, Eversole-Cire P, Fraser I, Mumby MC, Zhao Y, Brekken D, Shu H, Meyer T, Chandy G, Heo WD, Liou J, O'Rourke N, Verghese M, Mumby SM, Han H, Brown HA, Forrester JS, Ivanova P, Milne SB, Casey PJ, Harden TK, Arkin AP, Doyle J, Gray ML, Meyer T, Michnick S, Schmidt MA, Toner M, Tsien RY, Natarajan M, Ranganathan R, Sambrano GR. Overview of the Alliance for Cellular Signaling. Nature 2002; 420:703-6. [PMID: 12478301 DOI: 10.1038/nature01304] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The Alliance for Cellular Signaling is a large-scale collaboration designed to answer global questions about signalling networks. Pathways will be studied intensively in two cells--B lymphocytes (the cells of the immune system) and cardiac myocytes--to facilitate quantitative modelling. One goal is to catalyse complementary research in individual laboratories; to facilitate this, all alliance data are freely available for use by the entire research community.
Collapse
|
136
|
Zhang J, Campbell RE, Ting AY, Tsien RY. Creating new fluorescent probes for cell biology. Nat Rev Mol Cell Biol 2002; 3:906-18. [PMID: 12461557 DOI: 10.1038/nrm976] [Citation(s) in RCA: 1418] [Impact Index Per Article: 64.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Fluorescent probes are one of the cornerstones of real-time imaging of live cells and a powerful tool for cell biologists. They provide high sensitivity and great versatility while minimally perturbing the cell under investigation. Genetically-encoded reporter constructs that are derived from fluorescent proteins are leading a revolution in the real-time visualization and tracking of various cellular events. Recent advances include the continued development of 'passive' markers for the measurement of biomolecule expression and localization in live cells, and 'active' indicators for monitoring more complex cellular processes such as small-molecule-messenger dynamics, enzyme activation and protein-protein interactions.
Collapse
|
137
|
Campbell RE, Tour O, Palmer AE, Steinbach PA, Baird GS, Zacharias DA, Tsien RY. A monomeric red fluorescent protein. Proc Natl Acad Sci U S A 2002; 99:7877-82. [PMID: 12060735 PMCID: PMC122988 DOI: 10.1073/pnas.082243699] [Citation(s) in RCA: 1857] [Impact Index Per Article: 84.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/23/2002] [Indexed: 11/18/2022] Open
Abstract
All coelenterate fluorescent proteins cloned to date display some form of quaternary structure, including the weak tendency of Aequorea green fluorescent protein (GFP) to dimerize, the obligate dimerization of Renilla GFP, and the obligate tetramerization of the red fluorescent protein from Discosoma (DsRed). Although the weak dimerization of Aequorea GFP has not impeded its acceptance as an indispensable tool of cell biology, the obligate tetramerization of DsRed has greatly hindered its use as a genetically encoded fusion tag. We present here the stepwise evolution of DsRed to a dimer and then either to a genetic fusion of two copies of the protein, i.e., a tandem dimer, or to a true monomer designated mRFP1 (monomeric red fluorescent protein). Each subunit interface was disrupted by insertion of arginines, which initially crippled the resulting protein, but red fluorescence could be rescued by random and directed mutagenesis totaling 17 substitutions in the dimer and 33 in mRFP1. Fusions of the gap junction protein connexin43 to mRFP1 formed fully functional junctions, whereas analogous fusions to the tetramer and dimer failed. Although mRFP1 has somewhat lower extinction coefficient, quantum yield, and photostability than DsRed, mRFP1 matures >10 times faster, so that it shows similar brightness in living cells. In addition, the excitation and emission peaks of mRFP1, 584 and 607 nm, are approximately 25 nm red-shifted from DsRed, which should confer greater tissue penetration and spectral separation from autofluorescence and other fluorescent proteins.
Collapse
|
138
|
Lev-Ram V, Wong ST, Storm DR, Tsien RY. A new form of cerebellar long-term potentiation is postsynaptic and depends on nitric oxide but not cAMP. Proc Natl Acad Sci U S A 2002; 99:8389-93. [PMID: 12048250 PMCID: PMC123077 DOI: 10.1073/pnas.122206399] [Citation(s) in RCA: 250] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Long-term depression (LTD) at cerebellar parallel fiber (PF)-Purkinje cell synapses must be balanced by long-term potentiation (LTP) to prevent saturation and allow reversal of motor learning. The only previously analyzed form of cerebellar LTP is induced by 4-8 Hz PF stimulation and requires cAMP but not nitric oxide. It is a poor candidate to reverse LTD because it is presynaptically expressed whereas LTD is postsynaptic. We now characterize a new form of LTP induced by 1 Hz PF stimulation for at least 300 s. This LTP is postsynaptically expressed, enhanced by chelating postsynaptic Ca(2+), and depends on nitric oxide but not cAMP or cGMP, making it a plausible anti-Hebbian counterpart to Hebbian LTD.
Collapse
|
139
|
Adams SR, Campbell RE, Gross LA, Martin BR, Walkup GK, Yao Y, Llopis J, Tsien RY. New biarsenical ligands and tetracysteine motifs for protein labeling in vitro and in vivo: synthesis and biological applications. J Am Chem Soc 2002; 124:6063-76. [PMID: 12022841 DOI: 10.1021/ja017687n] [Citation(s) in RCA: 701] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We recently introduced a method (Griffin, B. A.; Adams, S. R.; Tsien, R. Y. Science 1998, 281, 269-272 and Griffin, B. A.; Adams, S. R.; Jones, J.; Tsien, R. Y. Methods Enzymol. 2000, 327, 565-578) for site-specific fluorescent labeling of recombinant proteins in living cells. The sequence Cys-Cys-Xaa-Xaa-Cys-Cys, where Xaa is an noncysteine amino acid, is genetically fused to or inserted within the protein, where it can be specifically recognized by a membrane-permeant fluorescein derivative with two As(III) substituents, FlAsH, which fluoresces only after the arsenics bind to the cysteine thiols. We now report kinetics and dissociation constants ( approximately 10(-11) M) for FlAsH binding to model tetracysteine peptides. Affinities in vitro and detection limits in living cells are optimized with Xaa-Xaa = Pro-Gly, suggesting that the preferred peptide conformation is a hairpin rather than the previously proposed alpha-helix. Many analogues of FlAsH have been synthesized, including ReAsH, a resorufin derivative excitable at 590 nm and fluorescing in the red. Analogous biarsenicals enable affinity chromatography, fluorescence anisotropy measurements, and electron-microscopic localization of tetracysteine-tagged proteins.
Collapse
|
140
|
Zacharias DA, Violin JD, Newton AC, Tsien RY. Partitioning of lipid-modified monomeric GFPs into membrane microdomains of live cells. Science 2002; 296:913-6. [PMID: 11988576 DOI: 10.1126/science.1068539] [Citation(s) in RCA: 1736] [Impact Index Per Article: 78.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Many proteins associated with the plasma membrane are known to partition into submicroscopic sphingolipid- and cholesterol-rich domains called lipid rafts, but the determinants dictating this segregation of proteins in the membrane are poorly understood. We suppressed the tendency of Aequorea fluorescent proteins to dimerize and targeted these variants to the plasma membrane using several different types of lipid anchors. Fluorescence resonance energy transfer measurements in living cells revealed that acyl but not prenyl modifications promote clustering in lipid rafts. Thus the nature of the lipid anchor on a protein is sufficient to determine submicroscopic localization within the plasma membrane.
Collapse
|
141
|
Gaietta G, Deerinck TJ, Adams SR, Bouwer J, Tour O, Laird DW, Sosinsky GE, Tsien RY, Ellisman MH. Multicolor and electron microscopic imaging of connexin trafficking. Science 2002; 296:503-7. [PMID: 11964472 DOI: 10.1126/science.1068793] [Citation(s) in RCA: 763] [Impact Index Per Article: 34.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Recombinant proteins containing tetracysteine tags can be successively labeled in living cells with different colors of biarsenical fluorophores so that older and younger protein molecules can be sharply distinguished by both fluorescence and electron microscopy. Here we used this approach to show that newly synthesized connexin43 was transported predominantly in 100- to 150-nanometer vesicles to the plasma membrane and incorporated at the periphery of existing gap junctions, whereas older connexins were removed from the center of the plaques into pleiomorphic vesicles of widely varying sizes. Selective imaging by correlated optical and electron microscopy of protein molecules of known ages will clarify fundamental processes of protein trafficking in situ.
Collapse
|
142
|
Zhang J, Ma Y, Taylor SS, Tsien RY. Genetically encoded reporters of protein kinase A activity reveal impact of substrate tethering. Proc Natl Acad Sci U S A 2001; 98:14997-5002. [PMID: 11752448 PMCID: PMC64972 DOI: 10.1073/pnas.211566798] [Citation(s) in RCA: 457] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The complexity and specificity of many forms of signal transduction are widely suspected to require spatial microcompartmentation of protein kinase and phosphatase activities, yet current relevant imaging methods such as phosphorylation-specific antibodies or fluorescent peptide substrates require fixation or microinjection and lack temporal or spatial resolution. We present a genetically encoded fluorescent reporter for protein kinase A (PKA) consisting of fusions of cyan fluorescent protein, a phosphoamino acid binding domain (14-3-3tau), a consensus substrate for PKA, and yellow fluorescent protein. cAMP elevations cause 25-50% changes in the ratios of yellow to cyan emissions in live cells caused by phosphorylation-induced changes in fluorescence resonance energy transfer. The reporter response was accelerated by tethering to PKA holoenzyme and slowed by localization to the nucleus. We demonstrate that deliberate redistribution of a substrate or colocalizing a substrate and PKA can modulate its susceptibility to phosphorylation by the kinase. The successful design of a fluorescent reporter of PKA activity and its application for studying compartmentalized and dynamic modulation of kinases lays a foundation for studying targeting and compartmentation of PKA and other kinases and phosphatases.
Collapse
|
143
|
Ting AY, Kain KH, Klemke RL, Tsien RY. Genetically encoded fluorescent reporters of protein tyrosine kinase activities in living cells. Proc Natl Acad Sci U S A 2001; 98:15003-8. [PMID: 11752449 PMCID: PMC64973 DOI: 10.1073/pnas.211564598] [Citation(s) in RCA: 379] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The complexity and specificity of many forms of signal transduction are widely believed to require spatial compartmentation of protein kinase and phosphatase activities, yet existing methods for measuring kinase activities in cells lack generality or spatial or temporal resolution. We present three genetically encoded fluorescent reporters for the tyrosine kinases Src, Abl, and epidermal growth factor (EGF) receptor. The reporters consist of fusions of cyan fluorescent protein (CFP), a phosphotyrosine binding domain, a consensus substrate for the relevant kinase, and yellow fluorescent protein (YFP). Stimulation of kinase activities in living cells with addition of growth factors causes 20-35% changes in the ratios of yellow to cyan emissions because of phosphorylation-induced changes in fluorescence resonance energy transfer (FRET). Platelet-derived growth factor (PDGF) stimulated Abl activity most strongly in actin-rich membrane ruffles, supporting the importance of this tyrosine kinase in the regulation of cell morphology. These results establish a general strategy for nondestructively imaging dynamic protein tyrosine kinase activities with high spatial and temporal resolution in single living cells.
Collapse
|
144
|
Wu MM, Grabe M, Adams S, Tsien RY, Moore HP, Machen TE. Mechanisms of pH regulation in the regulated secretory pathway. J Biol Chem 2001; 276:33027-35. [PMID: 11402049 DOI: 10.1074/jbc.m103917200] [Citation(s) in RCA: 199] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A precise pH gradient between organelles of the regulated secretory pathway is required for sorting and processing of prohormones. We studied pH regulation in live endocrine cells by targeting biotin-based pH indicators to cellular organelles expressing avidin-chimera proteins. In AtT-20 cells, we found that steady-state pH decreased from the endoplasmic reticulum (ER) (pH(ER) = 7.4 +/- 0.2, mean +/- S.D.) to Golgi (pH(G) = 6.2 +/- 0.4) to mature secretory granules (MSGs) (pH(MSG) = 5.5 +/- 0.4). Golgi and MSGs required active H(+) v-ATPases for acidification. ER, Golgi, and MSG steady-state pH values were also dependent upon the different H(+) leak rates across each membrane. However, neither steady-state pH(MSG) nor rates of passive H(+) leak were affected by Cl(-)-free solutions or valinomycin, indicating that MSG membrane potential was small and not a determinant of pH(MSG). Therefore, our data do not support earlier suggestions that organelle acidification is primarily regulated by Cl(-) conductances. Measurements of H(+) leak rates, buffer capacities, and estimates of surface areas and volumes of these organelles were applied to a mathematical model to determine the H(+) permeability (P(H+)) of each organelle membrane. We found that P(H+) decreased progressively from ER to Golgi to MSGs, and proper acidification of Golgi and MSGs required gradual decreases in P(H+) and successive increases in the active H(+) pump density.
Collapse
|
145
|
Burdette SC, Walkup GK, Spingler B, Tsien RY, Lippard SJ. Fluorescent sensors for Zn(2+) based on a fluorescein platform: synthesis, properties and intracellular distribution. J Am Chem Soc 2001; 123:7831-41. [PMID: 11493056 DOI: 10.1021/ja010059l] [Citation(s) in RCA: 560] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two new fluorescent sensors for Zn(2+) that utilize fluorescein as a reporting group, Zinpyr-1 and Zinpyr-2, have been synthesized and characterized. Zinpyr-1 is prepared in one step via a Mannich reaction, and Zinpyr-2 is obtained in a multistep synthesis that utilizes 4',5'-fluorescein dicarboxaldehyde as a key intermediate. Both Zinpyr sensors have excitation and emission wavelengths in the visible range ( approximately 500 nm), dissociation constants (K(d1)) for Zn(2+) of <1 nM, quantum yields approaching unity (Phi = approximately 0.9), and cell permeability, making them well-suited for intracellular applications. A 3- to 5-fold fluorescent enhancement is observed under simulated physiological conditions corresponding to the binding of the Zn(2+) cation to the sensor, which inhibits a photoinduced electron transfer (PET) quenching pathway. The X-ray crystal structure of a 2:1 Zn(2+):Zinpyr-1 complex has also been solved, and is the first structurally characterized example of a complex of fluorescein substituted with metal binding ligands.
Collapse
|
146
|
Griesbeck O, Baird GS, Campbell RE, Zacharias DA, Tsien RY. Reducing the environmental sensitivity of yellow fluorescent protein. Mechanism and applications. J Biol Chem 2001; 276:29188-94. [PMID: 11387331 DOI: 10.1074/jbc.m102815200] [Citation(s) in RCA: 791] [Impact Index Per Article: 34.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Yellow mutants of the green fluorescent protein (YFP) are crucial constituents of genetically encoded indicators of signal transduction and fusions to monitor protein-protein interactions. However, previous YFPs show excessive pH sensitivity, chloride interference, poor photostability, or poor expression at 37 degrees C. Protein evolution in Escherichia coli has produced a new YFP named Citrine, in which the mutation Q69M confers a much lower pK(a) (5.7) than for previous YFPs, indifference to chloride, twice the photostability of previous YFPs, and much better expression at 37 degrees C and in organelles. The halide resistance is explained by a 2.2-A x-ray crystal structure of Citrine, showing that the methionine side chain fills what was once a large halide-binding cavity adjacent to the chromophore. Insertion of calmodulin within Citrine or fusion of cyan fluorescent protein, calmodulin, a calmodulin-binding peptide and Citrine has generated improved calcium indicators. These chimeras can be targeted to multiple cellular locations and have permitted the first single-cell imaging of free [Ca(2+)] in the Golgi. Citrine is superior to all previous YFPs except when pH or halide sensitivity is desired and is particularly advantageous within genetically encoded fluorescent indicators of physiological signals.
Collapse
|
147
|
Chan FK, Siegel RM, Zacharias D, Swofford R, Holmes KL, Tsien RY, Lenardo MJ. Fluorescence resonance energy transfer analysis of cell surface receptor interactions and signaling using spectral variants of the green fluorescent protein. CYTOMETRY 2001; 44:361-8. [PMID: 11500853 DOI: 10.1002/1097-0320(20010801)44:4<361::aid-cyto1128>3.0.co;2-3] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
BACKGROUND Fluorescence resonance energy transfer (FRET) is a powerful technique for measuring molecular interactions at Angstrom distances. We present a new method for FRET that utilizes the unique spectral properties of variants of the green fluorescent protein (GFP) for large-scale analysis by flow cytometry. METHODS The proteins of interest are fused in frame separately to the cyan fluorescent protein (CFP) or the yellow fluorescent protein (YFP). FRET between these differentially tagged fusion proteins is analyzed using a dual-laser FACSVantage cytometer. RESULTS We show that homotypic interactions between individual receptor chains of tumor necrosis factor receptor (TNFR) family members can be detected as FRET from CFP-tagged receptor chains to YFP-tagged receptor chains. Noncovalent molecular complexation can be detected as FRET between fusions of CFP and YFP to either the intracellular or extracellular regions of the receptor chains. The specificity of the assay is demonstrated by the absence of FRET between heterologous receptor pairs that do not biochemically associate with each other. Interaction between a TNFR-like receptor (Fas/CD95/Apo-1) and a downstream cytoplasmic signaling component (FADD) can also be demonstrated by flow cytometric FRET analysis. CONCLUSIONS The utility of spectral variants of GFP in flow cytometric FRET analysis of membrane receptors is demonstrated. This method of analyzing FRET allows probing of noncovalent molecular interactions that involve both the intracellular and extracellular regions of membrane proteins as well as proteins within the cells. Unlike biochemical methods, FRET allows the quantitative determination of noncovalent molecular associations at Angstrom level in living cells. Moreover, flow cytometry allows quantitative analyses to be carried out on a cell-by-cell basis on large number of cells. Published 2001 Wiley-Liss, Inc.
Collapse
|
148
|
Ando H, Furuta T, Tsien RY, Okamoto H. Photo-mediated gene activation using caged RNA/DNA in zebrafish embryos. Nat Genet 2001; 28:317-25. [PMID: 11479592 DOI: 10.1038/ng583] [Citation(s) in RCA: 317] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We report a new and simple technique for photo-mediated temporal and spatial control of gene activation in zebrafish embryos as an alternative to the gene 'knockdown' approach using antisense, morpholino-modified oligonucleotides (morpholinos). The synthetic compound 6-bromo-4-diazomethyl-7-hydroxycoumarin (Bhc-diazo) forms a covalent bond with the phosphate moiety of the sugar-phosphate backbone of RNA, a process known as caging. The 6-bromo-7-hydroxycoumarin-4-ylmethyl (Bhc) group binds to approximately 30 sites on the phosphate moieties per 1 kb of RNA sequence. Bhc-caged mRNA undergoes photolysis (uncaging) when exposed to long-wave ultraviolet light (350 to 365 nm). We show that Bhc-caged green fluorescent protein (Gfp) mRNA has severely reduced translational activity in vitro, whereas illumination of Bhc-caged mRNA with ultraviolet light leads to partial recovery of translational activity. Bhc-caged mRNA is highly stable in zebrafish embryos. In embryos injected with Bhc-caged Gfp mRNA at the one-cell stage, GFP protein expression and fluorescence is specifically induced by ultraviolet light. We also show that, consistent with results obtained using other methods, uncaging eng2a (which encodes the transcription factor Engrailed2a) in the head region during early development causes a severe reduction in the size of the eye and enhanced development of the midbrain and the midbrain-hindbrain boundary at the expense of the forebrain.
Collapse
|
149
|
Griffin BA, Adams SR, Jones J, Tsien RY. Fluorescent labeling of recombinant proteins in living cells with FlAsH. Methods Enzymol 2001; 327:565-78. [PMID: 11045009 DOI: 10.1016/s0076-6879(00)27302-3] [Citation(s) in RCA: 200] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
|
150
|
Wu MM, Llopis J, Adams SR, McCaffery JM, Teter K, Kulomaa MS, Machen TE, Moore HP, Tsien RY. Studying organelle physiology with fusion protein-targeted avidin and fluorescent biotin conjugates. Methods Enzymol 2001; 327:546-64. [PMID: 11045008 DOI: 10.1016/s0076-6879(00)27301-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
|