Name: measuring peptide translocation into large unilamellar vesicles
Uploaded: 2012-01-27T13:00:00
Description: Watch this Scientific Journal Video about Measuring Peptide Translocation into Large Unilamellar Vesicles at JoVE.com

Gli autori desiderano ringraziare Eleonora Fleming e Jessica Chen per le discussioni utili. Il finanziamento è stato fornito da Istituto Nazionale di allergie e malattie infettive (NIAID-NIH) e un Premio R15AI079685 Research Corporation Cottrell Award Science College. Sostegno degli studenti sono state fornite dal Howard Hughes Medical Institute e del fondo Staley.

1. Preparazione di grandi vescicole lipidiche unilamellari (luvs) <ol><li> Preparare luvs a servire come membrana cellulare imita per il dosaggio 19. </li><li> Mix fosfatidilcolina (POPC, 760,10 g / mol), fosfatidilglicerolo (POPG. 770,99 g / mol), 5-dimethylaminonaphthalene-1-sulfonil fosfatidiletanolammina (DNS-PAPA, 994,350 g / mol) (Avanti Polar Lipids) disciolto in cloroformio in un 50 : rapporto 45:5. Come ogni test richiede la gestione separata di luvs sia sperimentale e di controllo, due fiale torta...

<ol>
	<li>Henriques, S. T., Melo, M. N., Castanho, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell-penetrating+peptides+and+antimicrobial+peptides:+how+different+are+they?.">Cell-penetrating peptides and antimicrobial peptides: how different are they?.</a> Biochem. J. 399 (1), 1-1 (2006).</li><li>Trehin, R., Merkle, H. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chances+and+pitfalls+of+cell+penetrating+peptides+for+cellular+drug+delivery.">Chances and pitfalls of cell penetrating peptides for cellular drug delivery.</a> Eur. J. Pharm. Biopharm. 58 (2), 209-209 (2004).</li><li>Temsamani, J., Vidal, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+use+of+cell-penetrating+peptides+for+drug+delivery.">The use of cell-penetrating peptides for drug delivery.</a> Drug Discov. Today. 9 (23), 1012-1012 (2004).</li><li>Hale, J. D., Hancock, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alternative+mechanisms+of+action+of+cationic+antimicrobial+peptides+on+bacteria.">Alternative mechanisms of action of cationic antimicrobial peptides on bacteria.</a> Expert Review of Anti-Infective Therapy. 5 (6), 951-951 (2007).</li><li>Nicolas, P., Rosenstein, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multifunctional+host+defense+peptides.">Multifunctional host defense peptides.</a> FEBS J. 276 (22), 6464-6464 (2009).</li><li>Boman, H. G., Agerberth, B., Boman, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+of+Action+on+Escherichia-Coli+of+Cecropin-P1+and+Pr-39,+2+Antibacterial+Peptides+from+Pig+Intestine.">Mechanisms of Action on Escherichia-Coli of Cecropin-P1 and Pr-39, 2 Antibacterial Peptides from Pig Intestine.</a> Infection and Immunity. 61 (7), 2978-2978 (1993).</li><li>Park, C. B., Kim, H. S., Kim, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanism+of+action+of+the+antimicrobial+peptide+buforin+II:+Buforin+II+kills+microorganisms+by+penetrating+the+cell+membrane+and+inhibiting+cellular+functions.">Mechanism of action of the antimicrobial peptide buforin II: Buforin II kills microorganisms by penetrating the cell membrane and inhibiting cellular functions.</a> Biochemical and Biophysical Research Communications. 244 (1), 253-253 (1998).</li><li>Bobone, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+thin+line+between+cell-penetrating+and+antimicrobial+peptides:+the+case+of+Pep-1+and+Pep-1-K.">The thin line between cell-penetrating and antimicrobial peptides: the case of Pep-1 and Pep-1-K.</a> J. Pept. Sci. 17 (5), 335-335 (2011).</li><li>Marks, J. R., Placone, J., Hristova, K., Wimley, W. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spontaneous+Membrane-Translocating+Peptides+by+Orthogonal+High-throughput+Screening.">Spontaneous Membrane-Translocating Peptides by Orthogonal High-throughput Screening.</a> J. Am. Chem. Soc.. , (2011).</li><li>Rosenbluh, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Translocation+of+histone+proteins+across+lipid+bilayers+and+Mycoplasma+membranes.">Translocation of histone proteins across lipid bilayers and Mycoplasma membranes.</a> J. Mol. Biol. 345 (2), 387-387 (2005).</li><li>Bárány-Wallje, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+critical+reassessment+of+penetratin+translocation+across+lipid+membranes.">A critical reassessment of penetratin translocation across lipid membranes.</a> Biophys. J. 89 (4), 2513-2513 (2005).</li><li>Henriques, S. T., Costa, J., Castanho, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Translocation+of+beta-galactosidase+mediated+by+the+cell-penetrating+peptide+pep-1+into+lipid+vesicles+and+human+HeLa+cells+is+driven+by+membrane+electrostatic+potential.">Translocation of beta-galactosidase mediated by the cell-penetrating peptide pep-1 into lipid vesicles and human HeLa cells is driven by membrane electrostatic potential.</a> Biochemistry. 44 (30), 10189-10189 (2005).</li><li>Orioni, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Membrane+perturbation+by+the+antimicrobial+peptide+PMAP-23:+a+fluorescence+and+molecular+dynamics+study.">Membrane perturbation by the antimicrobial peptide PMAP-23: a fluorescence and molecular dynamics study.</a> Biochim. Biophys. Acta. 1788 (7), 1523-1523 (2009).</li><li>Ladokhin, A. S., Jayasinghe, S., White, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+to+measure+and+analyze+tryptophan+fluorescence+in+membranes+properly,+and+why+bother?.">How to measure and analyze tryptophan fluorescence in membranes properly, and why bother?.</a> Anal. Biochem. 285 (2), 235-235 (2000).</li><li>Epand, R. M., Epand, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liposomes+as+models+for+antimicrobial+peptides.">Liposomes as models for antimicrobial peptides.</a> Methods Enzymol. 372, 124-124 (2003).</li><li>Kobayashi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interactions+of+the+novel+antimicrobial+peptide+buforin+2+with+lipid+bilayers:+Proline+as+a+translocation+promoting+factor.">Interactions of the novel antimicrobial peptide buforin 2 with lipid bilayers: Proline as a translocation promoting factor.</a> Biochemistry. 39 (29), 8648-8648 (2000).</li><li>Matsuzaki, K., Murase, O., Fujii, N., Miyajima, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Translocation+of+a+channel-forming+antimicrobial+peptide,+magainin+2,+across+lipid+bilayers+by+forming+a+pore.">Translocation of a channel-forming antimicrobial peptide, magainin 2, across lipid bilayers by forming a pore.</a> Biochemistry. 34 (19), 6521-6521 (1995).</li><li>Henriques, S. T., Costa, J., Castanho, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Re-evaluating+the+role+of+strongly+charged+sequences+in+amphipathic+cell-penetrating+peptides:+a+fluorescence+study+using+Pep-1.">Re-evaluating the role of strongly charged sequences in amphipathic cell-penetrating peptides: a fluorescence study using Pep-1.</a> FEBS Lett. 579 (20), 4498-4498 (2005).</li><li>Torchilin, V. P., Weissig, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Liposomes. , (2003).</li><li>Almeida, P. F., Pokorny, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Avanti+Polar+Lipids,+Determination+of+Total+Phosphorus.">Avanti Polar Lipids, Determination of Total Phosphorus.</a> Biochemistry. 1686 (34), 8083-8083 (2009).</li><li>Kobayashi, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Membrane+translocation+mechanism+of+the+antimicrobial+peptide+buforin+2.">Membrane translocation mechanism of the antimicrobial peptide buforin 2.</a> Biochemistry. 43 (49), 15610-15610 (2004).</li></ol>

Il protocollo presentato qui può essere utilizzato per valutare la variazione relativa della concentrazione di peptidi all&#39;interno e all&#39;esterno delle vescicole lipidiche. Questi cambiamenti sono legati alla capacità di traslocazione. Questo protocollo può essere utilizzato per identificare cellule penetrante peptidi con potenziale come vettori di consegna della droga. Come interesse nella cella-penetrante peptidi cresce, sarà interessante vedere come i metodi che misurano direttamente l&#39;evento traslocaz...

<table border="1"><tbody><tr><td> Nome del reagente </td><td> Azienda </td><td> Numero di catalogo </td></tr><tr><td> 16:00-18:01 PG </td><td> Lipidi Avanti Polar </td><td> 840457C </td></tr><tr><td> 01:18 Dansyl PE </td><td> Lipidi Avanti Polar </td><td> 810330C </td></tr><tr><td> 16:00-18:01 PC </td><td> Lipidi Avanti Polar </td><td> 850457C </td></tr><tr><td> Suini tripsina </td><td> Sigma </td><td> T-0303 </td></tr><tr><td> Bowman-Birk tripsina / chimotripsina inibitore </td><td> Sigma </td><td> T-9777 </td></tr><tr><td> Mini-estrusore </td><td> Lipidi Avanti Polar </td><td> 610000 </td></tr><tr><td> Ammonio molibdato (para) </td><td> Alfa Aesar </td><td> 10811 </td></tr><tr><td> Acido L-ascorbico </td><td> Sigma </td><td> A1417 </td></tr><tr><td> Perossido di idrogeno, 30% di soluzione </td><td> Mallinckrodt prodotti chimici </td><td> 5240-05 </td></tr><tr><td> HEPES </td><td> Sigma </td><td> H-3375 </td></tr><tr><td> NaCl </td><td> Sigma </td><td> S-9625 &lt;/ Td&gt; </tr><tr><td> EDTA </td><td> Sigma </td><td> E5134 </td></tr><tr><td> NaH 2 PO 4 </td><td> Sigma </td><td> S-0751 </td></tr></tbody></table>

measuring peptide translocation into large unilamellar vesicles

C&#39;è un interesse attivo nel peptidi che attraversano facilmente le membrane cellulari senza l&#39;ausilio di recettori di membrana delle cellule 1. Molti di questi sono indicati come cella penetrante peptidi, che sono spesso noti per il loro potenziale come vettori di consegna della droga 1-3. Inoltre, c&#39;è un interesse crescente in peptidi antimicrobici che operano attraverso meccanismi di membrana non-litica 4,5, in particolare quelli che attraversano le membrane batteriche senza causare la lisi cellulare e uccidere le cellule interferendo con i processi intracellulari 6,7. In realtà, gli autori hanno sempre sottolineato il rapporto tra peptidi cellula-penetrante e antimicrobico 1,8. Una solida conoscenza del processo di traslocazione della membrana e il rapporto tra struttura peptidica e la sua capacità di traslocare devono essere efficaci, i test riproducibili per traslocazione. Diversi gruppi hanno proposto metodi per misurare la traslocazione in unilamel grandeLAR vescicole lipidiche (luvs) 9-13. Luvs servire come modelli utili per le membrane delle cellule batteriche e eucariotiche e sono frequentemente utilizzati in studi peptide fluorescente 14,15. Qui, descriviamo la nostra applicazione del primo metodo sviluppato da Matsuzaki e collaboratori di prendere in considerazione peptidi antimicrobici, come magainin e buforin II 16,17. Oltre a fornire il nostro protocollo per questo metodo, abbiamo anche presentare un approccio diretto per l&#39;analisi dei dati che quantifica la capacità traslocazione da questo test. I vantaggi di questo test traslocazione rispetto ad altri che ha il potenziale per fornire informazioni circa la velocità di traslocazione della membrana e non richiede l&#39;aggiunta di un&#39;etichetta fluorescente, che possono alterare le proprietà del peptide 18, di triptofano contenenti peptidi. In breve, la capacità di traslocazione in vescicole lipidiche è misurata in funzione della Foster Resonance Energy Transfer (FRET) tra i residui di triptofano nativi e dansyl fosfatidiletanolamina quando le proteine ​​sono associate con l&#39;esterno LUV membrana (Figura 1). Cell-penetrante peptidi sono spaccati in quanto incontro tripsina disinibita incapsulato con il luvs, porta alla dissociazione dal LUV membrana e un calo del segnale FRET. Il calo FRET segnale osservato per un peptide translocating è significativamente maggiore di quello osservato per il peptide stesso quando il luvs contengono sia tripsina e inibitore della tripsina, o quando un peptide che non spontaneamente attraversare le membrane lipidiche è esposto a tripsina contenenti luvs. Questo cambiamento di fluorescenza fornisce una quantificazione diretta della traslocazione del peptide nel tempo.

Watch this Scientific Journal Video about Measuring Peptide Translocation into Large Unilamellar Vesicles at JoVE.com

Measuring Peptide Translocation into Large Unilamellar Vesicles

Questa dettagli del protocollo un metodo per la misura quantitativa della traslocazione peptidica in grandi vescicole lipidiche unilamellari. Questo metodo fornisce anche informazioni circa la velocità di traslocazione della membrana e può essere utilizzato per identificare i peptidi che in modo efficiente e spontaneamente croce doppi strati lipidici.

Misurazione Traslocazione Peptide in grandi vescicole unilamellari

There is an active interest in peptides that readily cross cell membranes without the assistance of cell membrane receptors1.  Many of these are referred ...

measuring-peptide-translocation-into-large-unilamellar-vesicles

Research

JoVE Journal

Biology

Large-Scale Screens of Metagenomic Libraries

Metagenomic libraries archive large fragments of contiguous genomic sequences from microorganisms without requiring prior cultivation. Generating a streamlined procedure for creating and screening metagenomic libraries is therefore useful for efficient high-throughput investigations into the genetic and metabolic properties of uncultured microbial assemblages. Here, key protocols are presented on video, which we propose is the most useful format for accurately describing a long process that alternately depends on robotic instrumentation and (human) manual interventions. First, we employed robotics to spot library clones onto high-density macroarray membranes, each of which can contain duplicate colonies from twenty-four 384-well library plates. Automation is essential for this procedure not only for accuracy and speed, but also due to the miniaturization of scale required to fit the large number of library clones into highly dense spatial arrangements. Once generated, we next demonstrated how the macroarray membranes can be screened for genes of interest using modified versions of standard protocols for probe labeling, membrane hybridization, and signal detection. We complemented the visual demonstration of these procedures with detailed written descriptions of the steps involved and the materials required, all of which are available online alongside the video.

Su larga scala Schermi di librerie metagenomiche

Metagenomic libraries archive large fragments of contiguous genomic sequences from microorganisms without requiring prior cultivation.  Generating a ...

Ricerca

Biologia

Large Insert Environmental Genomic Library Production

The vast majority of microbes in nature currently remain inaccessible to traditional cultivation methods. Over the past decade, culture-independent environmental genomic (i.e. metagenomic) approaches have emerged, enabling researchers to bridge this cultivation gap by capturing the genetic content of indigenous microbial communities directly from the environment. To this end, genomic DNA libraries are constructed using standard albeit artful laboratory cloning techniques. Here we describe the construction of a large insert environmental genomic fosmid library with DNA derived from the vertical depth continuum of a seasonally hypoxic fjord. This protocol is directly linked to a series of connected protocols including coastal marine water sampling [1], large volume filtration of microbial biomass [2] and a DNA extraction and purification protocol [3]. At the outset, high quality genomic DNA is end-repaired with the creation of 5 -phosphorylated blunt ends. End-repaired DNA is subjected to pulsed-field gel electrophoresis (PFGE) for size selection and gel extraction is performed to recover DNA fragments between 30 and 60 thousand base pairs (Kb) in length. Size selected DNA is purified away from the PFGE gel matrix and ligated to the phosphatase-treated blunt-end fosmid CopyControl vector pCC1 (EPICENTRE <a href="http://www.epibio.com/item.asp?ID=385">http://www.epibio.com/item.asp?ID=385</a>). Linear concatemers of pCC1 and insert DNA are subsequently headfull packaged into phage particles by lambda terminase, with subsequent infection of phage-resistant E. coli cells. Successfully transduced clones are recovered on LB agar plates under antibiotic selection and archived in 384-well plate format using an automated colony picking robot (Qpix2, GENETIX). The current protocol draws from various sources including the CopyControl Fosmid Library Production Kit from EPICENTRE and the published works of multiple research groups [4-7]. Each step is presented with best practice in mind. Whenever possible we highlight subtleties in execution to improve overall quality and efficiency of library production. The whole process of fosmid library production and automated colony picking takes at least 7-10 days as there are many incubation steps included. However, there are several stopping points possible which are mentioned within the protocol.

Construction of a fosmid library with environmental genomic DNA isolated from the vertical depth continuum of a seasonally hypoxic fjord is described. The resulting clone library is picked into 384-well plates and archived for downstream sequencing and functional screening by the application of an automated colony picking system.

Inserire grande Ambientale Genomic Produzione Biblioteca

The vast majority of microbes in nature currently remain inaccessible to traditional cultivation methods. Over the past decade, culture-independent ...

Mutagenesis and Functional Analysis of Ion Channels Heterologously Expressed in Mammalian Cells

We will demonstrate how to study the functional effects of introducing a point mutation in an ion channel. We study G protein-gated inwardly rectifying potassium (referred to as GIRK) channels, which are important for regulating the excitability of neurons. There are four different mammalian GIRK channel subunits (GIRK1-GIRK4) - we focus on GIRK2 because it forms a homotetramer. Stimulation of different types of G protein-coupled receptors (GPCRs), such as the muscarinic receptor (M2R), leads to activation of GIRK channels. Alcohol also directly activates GIRK channels. We will show how to mutate one amino acid by specifically changing one or more nucleotides in the cDNA for the GIRK channel. This mutated cDNA sequence will be amplified in bacteria, purified, and the presence of the point mutation will be confirmed by DNA sequencing. The cDNAs for the mutated and wild-type GIRK channels will be transfected into human embryonic kidney HEK293T cells cultured in vitro. Lastly, whole-cell patch-clamp electrophysiology will be used to study the macroscopic potassium currents through the ectopically expressed wild-type or mutated GIRK channels. In this experiment, we will examine the effect of a L257W mutation in GIRK2 channels on M2R-dependent and alcohol-dependent activation.

We will demonstrate how to study the effect of a single point mutation on the function of an ion channel.

Mutagenesi e Analisi funzionale dei canali ionici Heterologously Espresso in cellule di mammifero

We will demonstrate how to study the functional effects of introducing a point mutation in an ion channel. We study G protein-gated inwardly rectifying ...

Quantitative Measurement of GLUT4 Translocation to the Plasma Membrane by Flow Cytometry

Glucose is the main source of energy for the body, requiring constant regulation of its blood concentration. Insulin release by the pancreas induces glucose uptake by insulin-sensitive tissues, most notably the brain, skeletal muscle, and adipocytes. Patients suffering from type-2 diabetes and/or obesity often develop insulin resistance and are unable to control their glucose homeostasis. New insights into the mechanisms of insulin resistance may provide new treatment strategies for type-2 diabetes.
The GLUT family of glucose transporters consists of thirteen members distributed on different tissues throughout the body1. Glucose transporter type 4 (GLUT4) is the major transporter that mediates glucose uptake by insulin sensitive tissues, such as the skeletal muscle. Upon binding of insulin to its receptor, vesicles containing GLUT4 translocate from the cytoplasm to the plasma membrane, inducing glucose uptake. Reduced GLUT4 translocation is one of the causes of insulin resistance in type-2 diabetes2,3.
The translocation of GLUT4 from the cytoplasm to the plasma membrane can be visualized by immunocytochemistry, using fluorophore-conjugated GLUT4-specific antibodies.
Here, we describe a technique to quantify total amounts of GLUT4 translocation to the plasma membrane of cells during a chosen duration, using flow cytometry. This protocol is rapid (less than 4 hours, including incubation with insulin) and allows the analysis of as few as 3,000 cells or as many as 1 million cells per condition in a single experiment. It relies on anti-GLUT4 antibodies directed to an external epitope of the transporter that bind to it as soon as it is exposed to the extracellular medium after translocation to the plasma membrane.

This protocol describes a rapid technique to quantify the translocation of GLUT4 from the cytoplasm to the plasma membrane of cells by flow cytometry.

Misurazione quantitativa della traslocazione GLUT4 sulla membrana plasmatica mediante citometria di flusso

Glucose is the main source of energy for the body, requiring constant regulation of its blood concentration. Insulin release by the pancreas induces ...

Polarized Translocation of Fluorescent Proteins in Xenopus Ectoderm in Response to Wnt Signaling

Cell polarity is a fundamental property of eukaryotic cells that is dynamically regulated by both intrinsic and extrinsic factors during embryonic development 1, 2. One of the signaling pathways involved in this regulation is the Wnt pathway, which is used many times during embryogenesis and critical for human disease3, 4, 5. Multiple molecular components of this pathway coordinately regulate signaling in a spatially-restricted manner, but the underlying mechanisms are not fully understood. Xenopus embryonic epithelial cells is an excellent system to study subcellular localization of various signaling proteins. Fluorescent fusion proteins are expressed in Xenopus embryos by RNA microinjection, ectodermal explants are prepared and protein localization is evaluated by epifluorescence. In this experimental protocol we describe how subcellular localization of Diversin, a cytoplasmic protein that has been implicated in signaling and cell polarity determination6, 7 is visualized in Xenopus ectodermal cells to study Wnt signal transduction8. Coexpression of a Wnt ligand or a Frizzled receptor alters the distribution of Diversin fused with red fluorescent protein, RFP, and recruits it to the cell membrane in a polarized fashion 8, 9. This ex vivo protocol should be a useful addition to in vitro studies of cultured mammalian cells, in which spatial control of signaling differs from that of the intact tissue and is much more difficult to analyze.

Polarized Translocation of Fluorescent Proteins in Xenopus Ectoderm in Response to Wnt Signaling

Xenopus embryonic ectoderm has become an attractive model for studies of cell polarity. An assay is described, in which subcellular distribution of fluorescent proteins is assessed in ectoderm cells. This protocol will help address questions related to spatial control of signaling.

Traslocazione polarizzato di proteine ​​fluorescenti in Xenopus</emEctoderma> in risposta alla segnalazione Wnt

Cell polarity is a fundamental property of eukaryotic cells that is dynamically regulated by both intrinsic and extrinsic factors during embryonic ...

Examining BCL-2 Family Function with Large Unilamellar Vesicles

The BCL-2 (B cell CLL/Lymphoma) family is comprised of approximately twenty proteins that collaborate to either maintain cell survival or initiate apoptosis1. Following cellular stress (e.g., DNA damage), the pro-apoptotic BCL-2 family effectors BAK (BCL-2 antagonistic killer 1) and/or BAX (BCL-2 associated X protein) become activated and compromise the integrity of the outer mitochondrial membrane (OMM), though the process referred to as mitochondrial outer membrane permeabilization (MOMP)1. After MOMP occurs, pro-apoptotic proteins (e.g., cytochrome c) gain access to the cytoplasm, promote caspase activation, and apoptosis rapidly ensues2.
In order for BAK/BAX to induce MOMP, they require transient interactions with members of another pro-apoptotic subset of the BCL-2 family, the BCL-2 homology domain 3 (BH3)-only proteins, such as BID (BH3-interacting domain agonist)3-6. Anti-apoptotic BCL-2 family proteins (e.g., BCL-2 related gene, long isoform, BCL-xL; myeloid cell leukemia 1, MCL-1) regulate cellular survival by tightly controlling the interactions between BAK/BAX and the BH3-only proteins capable of directly inducing BAK/BAX activation7,8. In addition, anti-apoptotic BCL-2 protein availability is also dictated by sensitizer/de-repressor BH3-only proteins, such as BAD (BCL-2 antagonist of cell death) or PUMA (p53 upregulated modulator of apoptosis), which bind and inhibit anti-apoptotic members7,9. As most of the anti-apoptotic BCL-2 repertoire is localized to the OMM, the cellular decision to maintain survival or induce MOMP is dictated by multiple BCL-2 family interactions at this membrane.
 Large unilamellar vesicles (LUVs) are a biochemical model to explore relationships between BCL-2 family interactions and membrane permeabilization10. LUVs are comprised of defined lipids that are assembled in ratios identified in lipid composition studies from solvent extracted Xenopus mitochondria (46.5% phosphatidylcholine, 28.5% phosphatidylethanoloamine, 9% phosphatidylinositol, 9% phosphatidylserine, and 7% cardiolipin)10. This is a convenient model system to directly explore BCL-2 family function because the protein and lipid components are completely defined and tractable, which is not always the case with primary mitochondria. While cardiolipin is not usually this high throughout the OMM, this model does faithfully mimic the OMM to promote BCL-2 family function. Furthermore, a more recent modification of the above protocol allows for kinetic analyses of protein interactions and real-time measurements of membrane permeabilization, which is based on LUVs containing a polyanionic dye (ANTS: 8-aminonaphthalene-1,3,6-trisulfonic acid) and cationic quencher (DPX: p-xylene-bis-pyridinium bromide)11. As the LUVs permeabilize, ANTS and DPX diffuse apart, and a gain in fluorescence is detected. Here, commonly used recombinant BCL-2 family protein combinations and controls using the LUVs containing ANTS/DPX are described.

Biochemically-defined large unilamellar vesicles (LUVs) are a convenient model system to analyze BCL-2 family interactions with immediate implications in better understanding the mitochondrial pathway of apoptosis. A method to produce LUVs, along with standard BCL-2 family protein combinations and controls to examine LUV permeabilization, are presented.

Esaminando BCL-2 Funzione Famiglia con grandi vescicole unilamellari

The BCL-2 (B cell CLL/Lymphoma) family is comprised of approximately twenty proteins that collaborate to either maintain cell survival or initiate ...

Reconstitution of a Transmembrane Protein, the Voltage-gated Ion Channel, KvAP, into Giant Unilamellar Vesicles for Microscopy and Patch Clamp Studies

Giant Unilamellar Vesicles (GUVs) are a popular biomimetic system for studying membrane associated phenomena. However, commonly used protocols to grow GUVs must be modified in order to form GUVs containing functional transmembrane proteins. This article describes two dehydration-rehydration methods &#8212; electroformation and gel-assisted swelling &#8212; to form GUVs containing the voltage-gated potassium channel, KvAP. In both methods, a solution of protein-containing small unilamellar vesicles is partially dehydrated to form a stack of membranes, which is then allowed to swell in a rehydration buffer. For the electroformation method, the film is deposited on platinum electrodes so that an AC field can be applied during film rehydration. In contrast, the gel-assisted swelling method uses an agarose gel substrate to enhance film rehydration. Both methods can produce GUVs in low (e.g., 5 mM) and physiological (e.g., 100 mM) salt concentrations. The resulting GUVs are characterized via fluorescence microscopy, and the function of reconstituted channels measured using the inside-out patch-clamp configuration. While swelling in the presence of an alternating electric field (electroformation) gives a high yield of defect-free GUVs, the gel-assisted swelling method produces a more homogeneous protein distribution and requires no special equipment.

The reconstitution of the transmembrane protein, KvAP, into giant unilamellar vesicles (GUVs) is demonstrated for two dehydration-rehydration methods &#8212; electroformation, and gel-assisted swelling. In both methods, small unilamellar vesicles containing the protein are fused together to form GUVs that can then be studied by fluorescence microscopy and patch-clamp electrophysiology.

Ricostituzione di una proteina transmembrana, la tensione gated canali ionici, KvAP, in Giant unilamellari vescicole per la microscopia e Patch Clamp Studies

Giant Unilamellar Vesicles (GUVs) are a popular biomimetic system for studying membrane associated phenomena. However, commonly used protocols to grow ...

Visualization of Surface-tethered Large DNA Molecules with a Fluorescent Protein DNA Binding Peptide

Large DNA molecules tethered on the functionalized glass surface have been utilized in polymer physics and biochemistry particularly for investigating interactions between DNA and its binding proteins. Here, we report a method that uses fluorescent microscopy for visualizing large DNA molecules tethered on the surface. First, glass coverslips are biotinylated and passivated by coating with biotinylated polyethylene glycol, which specifically binds biotinylated DNA via avidin protein linkers and significantly reduces undesirable binding from non-specific interactions of proteins or DNA molecules on the surface. Second, the DNA molecules are biotinylated by two different methods depending on their terminals. The blunt ended DNA is tagged with biotinylated dUTP at its 3' hydroxyl terminus, by terminal transferase, while the sticky ended DNA is hybridized with biotinylated complimentary oligonucleotides by DNA ligase. Finally, a microfluidic shear flow makes single DNA molecules stretch to their full contour lengths after being stained with fluorescent protein-DNA binding peptide (FP-DBP).

We present an approach for visualizing fluorescent protein DNA binding peptide (FP-DBP)-stained large DNA molecules tethered on the polyethylene glycol (PEG) and avidin-coated glass surface and stretched with microfluidic shear flows.

Visualizzazione del Surface-legato Grande DNA molecole con un DNA proteina fluorescente Binding peptide

Large DNA molecules tethered on the functionalized glass surface have been utilized in polymer physics and biochemistry particularly for investigating ...

Pulling Membrane Nanotubes from Giant Unilamellar Vesicles

The reshaping of the cell membrane is an integral part of many cellular phenomena, such as endocytosis, trafficking, the formation of filopodia, etc. Many different proteins associate with curved membranes because of their ability to sense or induce membrane curvature. Typically, these processes involve a multitude of proteins making them too complex to study quantitatively in the cell. We describe a protocol to reconstitute a curved membrane in vitro, mimicking a curved cellular structure, such as the endocytic neck. A giant unilamellar vesicle (GUV) is used as a model of a cell membrane, whose internal pressure and surface tension are controlled with micropipette aspiration. Applying a point pulling force on the GUV using optical tweezers creates a nanotube of high curvature connected to a flat membrane. This method has traditionally been used to measure the fundamental mechanical properties of lipid membranes, such as bending rigidity. In recent years, it has been expanded to study how proteins interact with membrane curvature and the way they affect the shape and the mechanics of membranes. A system combining micromanipulation, microinjection, optical tweezers, and confocal microscopy allows measurement of membrane curvature, membrane tension, and the surface density of proteins, concurrently. From these measurements, many important mechanical and morphological properties of the protein-membrane system can be inferred. In addition, we lay out a protocol of creating GUVs in the presence of physiological salt concentration, and a method of quantifying the surface density of proteins on the membrane from fluorescence intensities of labeled proteins and lipids.

Many proteins in the cell sense and induce membrane curvature. We describe a method to pull membrane nanotubes from lipid vesicles to study the interaction of proteins or any curvature-active molecule with curved membranes in vitro.

Tirando nanotubi di membrana da vescicole unilamellari gigante

The reshaping of the cell membrane is an integral part of many cellular phenomena, such as endocytosis, trafficking, the formation of filopodia, etc. Many ...

Subretinal Transplantation of Human Embryonic Stem Cell Derived-retinal Pigment Epithelial Cells into a Large-eyed Model of Geographic Atrophy

Geographic atrophy (GA), the late stage of dry age-related macular degeneration is characterized by loss of the retinal pigment epithelial (RPE) layer, which leads to subsequent degeneration of vital retinal structures (e.g., photoreceptors) causing severe vision impairment. Similarly, RPE-loss and decrease in visual acuity is seen in long-term follow up of patients with advanced wet age-related macular degeneration (AMD) receiving intravitreal anti-vascular endothelial growth factor (VEGF) treatment. Therefore, on the one hand, it is fundamental to efficiently derive RPE cells from an unlimited source that could serve as replacement therapy. On the other hand, it is important to assess the behavior and integration of the derived cells in a model of the disease entailing surgical and imaging methods as close as possible to those applied in humans. Here, we provide a detailed protocol based on our previous publications that describes the generation of a preclinical model of GA using the albino rabbit eye, for evaluation of the human embryonic stem cell derived retinal pigment epithelial cells (hESC-RPE) in a clinically relevant setting. Differentiated hESC-RPE are transplanted into naive eyes or eyes with NaIO3-induced GA-like retinal degeneration using a 25 G transvitreal pars plana technique. Evaluation of degenerated and transplanted areas is performed by multimodal high-resolution non-invasive real-time imaging.

Retinal pigment epithelial cells could serve as a cell-replacement therapy for the advanced form of dry age-related macular degeneration. This protocol describes the generation of a large-eyed model of geographic atrophy and the subretinal transplantation of human embryonic stem cell-derived retinal pigment epithelial cells into this model of disease.

Subretinal trapianto delle cellule epiteliali del pigmento retinico derivato di cellule staminali embrionali umane in un modello di atrofia geografica gran-eyed

Geographic atrophy (GA), the late stage of dry age-related macular degeneration is characterized by loss of the retinal pigment epithelial (RPE) layer, ...