Ce travail a été soutenu par des subventions de la Mme Clifford Elder Graham White Doté Fonds de recherche et le NIH (AR059838) à CB, du NIH (AR052791, AR044387-ARRA, &amp; NS063298) pour LTT, et par le Baylor College of Medicine de cytométrie et de tri cellulaire de base avec un financement du NIH (NCRR S10RR024574, le NIAID AI036211, &amp; NCI P30CA125123). Le contenu est uniquement la responsabilité de leurs auteurs et ne représentent pas nécessairement les vues officielles de la NIH.

1. Coloration des cellules <ol><li> Préparer les cellules. Les cellules doivent être utilisées tout en pleine croissance (60 - 80% de confluence). Sérum affamer les cellules pendant la nuit, les cellules de la plaque à 0,1 million par puits dans 0,5 ml milieu sans sérum dans une plaque de 24 puits et les placer dans l&#39;incubateur (37 ° C, 5% CO 2) pendant 30 min - 2 heures pour récupérer à partir trypsinisation. </li><li> Mélanger les anticorps primaires et secondaires. Mélanger (5 pi de primaire anti-GLUT4 anticorps avec 1 poulet uL secondaire anti-chèvre anticorps IgG conjugué à AlexaFluor 488) x nombre de puits. Incuber 10 minutes à température ambiante, dans l&#39;obscurité. </li><li> Préparer un stock de travail de l&#39;insuline 2X en le diluant dans le milieu. </li><li> Vérifiez si les cellules ont adhéré ou non. </li><li> Ajouter délicatement 6 mélange d&#39;anticorps uL et 0,5 mL de votre stock de travail 2X de l&#39;insuline dans les puits contenant les cellules. Évitez toute turbulence du milieu. Incuber (37 ° C, 5% CO 2) pendant 30 minutes, dans l&#39;obscurité. </li><li> Fixer les cellules en ajoutant 0,5 ml de PBS + 1% PFA dans chaque puits, sans secouer les cellules. Incuber pendant 20 minutes à température ambiante, dans l&#39;obscurité. </li><li> Si vos cellules ont adhéré aux puits, délicatement les soulever avec un lifter cellule. Transférer les cellules (1 mL au total) dans des tubes qui correspondent à votre cytomètre en flux et centrifuger pour sédimenter les cellules. </li><li> Laver le culot à deux reprises avec 1 ml de PBS et remettre en suspension dans 0,4 ml de PBS + 1% PFA. À ce stade, les cellules peuvent être enveloppés dans une feuille et de les conserver au réfrigérateur (4-8 ° C) ou prises pour le cytomètre en flux pour l&#39;acquisition de données immédiates. </li></ol> 2. Acquisition de données <ol><li> Régler une porte large autour des cellules vivantes dans la diffusion latérale (SSC) par rapport à l&#39;avant de dispersion (FCS) du panneau. Utiliser un tube négatif (cellules non traitées à l&#39;insuline ou des cellules &quot;taché&quot; avec un contrôle isotypique) pour définir votre paramètre FL1. Assurez-vous de pointe est complètement dans le panneau, pas couper sur le côté inférieur. </li><li> Acquérir des données provenant d&#39;au moins 10 000 cellules par tube. </li></ol> 3. Analyse des données <ol><li> Dessinez une porte autour des cellules vivent dans le panneau CSS vs FSC (figure 1A). Tracer les histogrammes de 488 AlexaFluor intensité de fluorescence en fonction du nombre de cellules dans la porte des cellules vivantes (figure 1B). Vous pouvez superposer des histogrammes différents de visualiser les différences, mais pour la quantification, de déterminer l&#39;intensité moyenne et la médiane de fluorescence pour chaque population de cellules et d&#39;utiliser ces numéros pour vos comparaisons (figure 1C). </li><li> Normaliser les données de la valeur obtenue en l&#39;absence d&#39;insuline, comme indiqué dans les figures 1C et 1D. </li></ol> 4. Les résultats représentatifs Dans les myoblastes isolés d&#39;un individu sain (pas de résistance à l&#39;insuline), l&#39;insuline induit une translocation dose-dépendante de GLUT4 du cytoplasme vers la membrane plasmique (Figure 1, gauche). En revanche, l&#39;insuline ne pas provoquer la translocation de GLUT4 à la membrane plasmique des myoblastes isolés à partir d&#39;un patient avec résistance à l&#39;insuline (Figure 1, droite). <img src="/files/ftp_upload/2429/2429fig1.jpg" alt="Figure 1" /> Figure 1. Exemple d&#39;une expérience de coloration. Myoblastes ont été isolés à partir d&#39;un donneur sans résistance à l&#39;insuline (à gauche) et chez un patient insulino-résistance (à droite). A, SSC (Side Scatter) versus FCS (forward scatter) parcelle avec une porte autour des cellules vivantes. B, les cellules fermées en Un, colorées avec l&#39;anticorps contre un épitope externe de GLUT4, et de gauche non stimulées (rouge) ou stimulées par l&#39;insuline 1 nm (bleu), 10 nm (orange), ou 100 nm (vert). Pour plus de clarté la figure, nous ne montrons données sans et avec 100 nM d&#39;insuline pour les cellules insulino-résistance. C, les intensités moyennes de fluorescence (MFI) des histogrammes montré en B ont été normalisées à l&#39;IMF des cellules non stimulées gauche (pas d&#39;insuline). D, tracés des données normalisées de l&#39;IMF histogrammes montré en B.

<ol>
	<li>Zhao, F. Q., Keating, A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+properties+and+genomics+of+glucose+transporters.">Functional properties and genomics of glucose transporters.</a> Curr. Genomics. 8, 113-128 (2007).</li><li>Karnieli, E., Armoni, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcriptional+regulation+of+the+insulin-responsive+glucose+transporter+GLUT4+gene:+from+physiology+to+pathology.">Transcriptional regulation of the insulin-responsive glucose transporter GLUT4 gene: from physiology to pathology.</a> Am. J. Endocrinol. Metab. 295, 38-45 (2008).</li><li>Graham, T. E., Kahn, B. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tissue-specific+alterations+of+glucose+transport+and+molecular+mechanisms+of+intertissue+communication+in+obesity+and+type+2+diabetes.">Tissue-specific alterations of glucose transport and molecular mechanisms of intertissue communication in obesity and type 2 diabetes.</a> Horm. Metab. Res. 39, 717-721 (2007).</li><li>Alter, G., Malenfant, J. M., Altfeld, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CD107a+as+a+functional+marker+for+the+identification+of+natural+killer+cell+activity.">CD107a as a functional marker for the identification of natural killer cell activity.</a> J. Immunol. Methods. 294, 15-22 (2004).</li><li>Vermes, I., Haanen, C., Steffens-Nakken, H., Reutellingsperger, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+assay+for+apoptosis.+Flow+cytometric+detection+of+phosphatidylserine+expression+on+early+apoptotic+cells+using+fluorescein+labeled+Annexin+V.">A novel assay for apoptosis. Flow cytometric detection of phosphatidylserine expression on early apoptotic cells using fluorescein labeled Annexin V.</a> J. Immunol. Methods. 184, 39-51 (1995).</li><li>Lugli, E., Roederer, M., Cossarizza, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Data+analysis+in+flow+cytometry:+the+future+just+started.">Data analysis in flow cytometry: the future just started.</a> Cytometry A. 77, 705-713 (2010).</li></ol>

Nous avons démontré une technique rapide pour quantifier la translocation de GLUT4 du cytoplasme vers la membrane plasmique des cellules par cytométrie en flux. GLUT4 est seulement transitoirement exprimé à la membrane plasmique des cellules et est endocytose. Depuis les anticorps liés restent attachés à la GLUT4, même pendant l&#39;endocytose, le signal de fluorescence donne le montant total de GLUT4 qui a été exposée à la membrane plasmique pendant la durée choisie d&#39;incubation en présence d&#39;insuline. Cette technique peut également être appliquée à l&#39;étude de la translocation d&#39;autres protéines à partir d&#39;un compartiment intracellulaire à la membrane plasmique, a fourni un bon anticorps dirigé contre un épitope externe de la protéine d&#39;intérêt est disponible. Par exemple, un test similaire est maintenant couramment utilisé pour évaluer le taux de la dégranulation des lymphocytes T cytotoxiques et lymphocytes natural killer en mesurant la translocation de CD107a à leur membrane plasmique 4,5. La translocation de la phosphatidylsérine du côté intérieur de la membrane plasmique à la face externe lors de l&#39;apoptose cellulaire ou une nécrose peut également être détectée par cytométrie en flux, en utilisant un fluorophore étiquetés annexine V 6. Outre la rapidité de l&#39;essai, la cytométrie en flux présente l&#39;avantage de permettre l&#39;étude de la translocation de la protéine à la membrane plasmique dans les populations de cellules mixtes. En effet, on peut combiner coloration pour les marqueurs de sous-ensemble de cellules et pour la protéine d&#39;intérêt, suivie par l&#39;acquisition de données sur un cytomètre en flux multi-laser 7. Les quantités d&#39;anticorps donnée au paragraphe 1.2 du protocole sont un point de départ; nous vous conseillons de titrer vos anticorps avec les cellules de votre intérêt pour déterminer la concentration d&#39;anticorps minimum qui vous donne un maximum de signal. Une bonne gamme de départ pour le premier anticorps anti-humain GLUT4, nous avons utilisé ici serait uL 10-10 par tube (anticorps-dire 0,2 à 2 mg par tube), chaque tube contenant pas plus de 1 million de cellules. Pour les autres anticorps primaires, se reporter aux instructions du fournisseur. La normalisation des données est nécessaire que l&#39;autofluorescence des cellules varie d&#39;un donneur à et d&#39;une expérience à.

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		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
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<tr>
<td>Anti-human GLUT4 antibodies</td>
<td>&nbsp;</td>
<td>Santa Cruz Biotechnologies</td>
<td>sc-1606</td>
<td>Against an external epitope of GLUT4</td>
</tr>
<tr>
<td>Chicken anti-goat IgG conjugated to AlexaFluor 488</td>
<td>&nbsp;</td>
<td>Invitrogen</td>
<td>A-21467</td>
<td>&nbsp;</td>
<tr>
<td>Recombinant human insulin</td>
<td>&nbsp;</td>
<td>Sigma</td>
<td>I2643</td>
<td>&nbsp;</td>
<tr>
<td>Cell lifters</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>29942-118</td>
<td>Cut to fit the wells</td>
</tr>
<tr>
<td>5 ml tubes for FACS</td>
<td>&nbsp;</td>
<td>VWR</td>
<td>60819-138</td>
<td>Fit all BD machines</td>
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quantitative measurement of glut4 translocation to the plasma membrane by flow cytometry

Le glucose est la source principale d&#39;énergie pour le corps, nécessitant une régulation constante de sa concentration sanguine. Libération d&#39;insuline par le pancréas provoque l&#39;absorption du glucose par l&#39;insuline tissus sensibles, notamment le cerveau, les muscles squelettiques et les adipocytes. Les patients souffrant de diabète de type 2 et / ou l&#39;obésité se développent souvent une résistance de l&#39;insuline et sont incapables de contrôler leur homéostasie du glucose. Nouveaux éclairages sur les mécanismes de résistance à l&#39;insuline peuvent fournir de nouvelles stratégies thérapeutiques pour le diabète de type 2. La famille des transporteurs de glucose GLUT compose de treize membres répartis sur les différents tissus dans le corps 1. Type de transporteur du glucose 4 (GLUT4) est le transporteur de glucose majeurs qui médie l&#39;absorption par les tissus sensibles à l&#39;insuline, tels que le muscle squelettique. Lors de la liaison de l&#39;insuline à son récepteur, la translocation des vésicules contenant GLUT4 du cytoplasme vers la membrane plasmique, provoquant la captation du glucose. Réduction GLUT4 translocation est l&#39;une des causes de la résistance à l&#39;insuline dans le diabète de type 2 2,3. La translocation de GLUT4 du cytoplasme vers la membrane plasmique peut être visualisée par immunocytochimie en utilisant un fluorophore conjugué GLUT4 anticorps spécifiques. Ici, nous décrivons une technique pour quantifier montant total de GLUT4 translocation vers la membrane plasmique des cellules pendant une durée choisie, en utilisant la cytométrie de flux. Ce protocole est rapide (moins de 4 heures, y compris d&#39;incubation avec de l&#39;insuline) et permet l&#39;analyse d&#39;aussi peu que 3000 cellules ou autant que 1 million de cellules par condition dans une expérience unique. Elle s&#39;appuie sur l&#39;anti-GLUT4 anticorps dirigé contre un épitope externes du transporteur qui se lient à elle dès qu&#39;elle est exposée dans le milieu extracellulaire après la translocation vers la membrane plasmique.

Watch this Scientific Journal Video about Quantitative Measurement of GLUT4 Translocation to the Plasma Membrane by Flow Cytometry at JoVE.com

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

Ce protocole décrit une technique rapide pour quantifier la translocation de GLUT4 du cytoplasme vers la membrane plasmique des cellules par cytométrie en flux.

Mesure quantitative de GLUT4 Translocation à la membrane plasmique par cytométrie en flux

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

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26.3K vues.  Baylor College of Medicine. Ce protocole décrit une technique rapide pour quantifier la translocation de GLUT4 du cytoplasme vers la membrane plasmique des cellules par cytométrie en flux.

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

Measuring Plasma Membrane Protein Endocytic Rates by Reversible Biotinylation

Plasma membrane proteins are a large, diverse group of proteins comprised of receptors, ion channels, transporters and pumps.  Activity of these proteins is responsible for a variety of key cellular events, including nutrient delivery, cellular excitability, and chemical signaling.  Many plasma membrane proteins are dynamically regulated by endocytic trafficking, which modulates protein function by altering protein surface expression.  The mechanisms that facilitate protein endocytosis are complex and are not fully understood for many membrane proteins.  In order to fully understand the mechanisms that control the endocytic trafficking of a given protein, it is critical that the protein s endocytic rate be precisely measured.  For many receptors, direct endocytic rate measurements are frequently achieved utilizing labeled receptor ligands.  However, for many classes of membrane proteins, such as transporters, pumps and ion channels, there is no convenient ligand that can be used to measure the endocytic rate.  In the present report, we describe a reversible biotinylation method that we employ to measure the dopamine transporter (DAT) endocytic rate.  This method provides a straightforward approach to measuring internalization rates, and can be easily employed for trafficking studies of most membrane proteins.

Regulated endocytosis governs the cell surface expression levels of the majority of membrane proteins. Here we utilize reducible, membrane impermeant biotinylation reagents to measure the endocytic rate of the dopamine transporter (DAT), a polytopic membrane protein. The method facilitates a straightforward approach to measuring the endocytic rate of most plasma membrane proteins.

Mesure du taux plasmatique des protéines membranaires par endocytique Biotinylation réversible

Plasma membrane proteins are a large, diverse group of proteins comprised of receptors, ion channels, transporters and pumps.  Activity of these proteins ...

Recherche

Biologie

IP-FCM:  Immunoprecipitation Detected by Flow Cytometry

Immunoprecipitation detected by flow cytometry (IP-FCM) is an efficient method for detecting and quantifying protein-protein interactions. The basic principle extends that of sandwich ELISA, wherein the captured primary analyte can be detected together with other molecules physically associated within multiprotein complexes. The procedure involves covalent coupling of polystyrene latex microbeads with immunoprecipitating monoclonal antibodies (mAb) specific for a protein of interest, incubating these beads with cell lysates, probing captured protein complexes with fluorochrome-conjugated probes, and analyzing bead-associated fluorescence by flow cytometry. IP-FCM is extremely sensitive, allows analysis of proteins in their native (non-denatured) state, and is amenable to either semi-quantitative or quantitative analysis. As additional advantages, IP-FCM requires no genetic engineering or specialized equipment, other than a flow cytometer, and it can be readily adapted for high-throughput applications.

The IP-FCM method is presented, which allows a sensitive, robust, biochemical assessment of native protein-protein interactions, without requiring genetic engineering or large sample sizes.

IP-FCM: immunoprécipitation détectée par cytométrie en flux

Immunoprecipitation detected by flow cytometry (IP-FCM) is an efficient method for detecting and quantifying protein-protein interactions. The basic ...

Flow Cytometry Purification of Mouse Meiotic Cells

The heterogeneous nature of cell types in the testis and the absence of meiotic cell culture models have been significant hurdles to the study of the unique differentiation programs that are manifest during meiosis. Two principal methods have been developed to purify, to varying degrees, various meiotic fractions from both adult and immature animals: elutriation or Staput (sedimentation) using BSA and/or percoll gradients. Both of these methods rely on cell size and density to separate meiotic cells1-5. Overall, except for few cell populations6, these protocols fail to yield sufficient purity of the numerous meiotic cell populations that are necessary for detailed molecular analyses. Moreover, with such methods usually one type of meiotic cells can be purified at a given time, which adds an extra level of complexity regarding the reproducibility and homogeneity when comparing meiotic cell samples.
Here, we describe a refined method that allows one to easily visualize, identify, and purify meiotic cells, from germ cells to round spermatids, using FACS combined with Hoechst 33342 staining7,8. This method provides an overall snapshot of the entire meiotic process and allows one to highly purify viable cells from most stage of meiosis. These purified cells can then be analyzed in detail for molecular changes that accompany progression through meiosis, for example changes in gene expression9,10and the dynamics of nucleosome occupancy at hotspots of meiotic recombination11.

An efficient method to obtain highly purified viable meiotic fractions from mouse testis is described, which combines a refined cell dissociation protocol with fluorescent activated cell sorting (FACS). This method takes advantage of differences in the DNA content and nuclear density of discrete meiotic fractions.

Purification cytométrie en flux des cellules de souris méiotique

The heterogeneous nature of cell types in the testis and the absence of meiotic cell culture models have been significant hurdles to the study of the ...

Mapping Molecular Diffusion in the Plasma Membrane by Multiple-Target Tracing (MTT)

Our goal is to obtain a comprehensive description of molecular processes occurring at cellular membranes in different biological functions. We aim at characterizing the complex organization and dynamics of the plasma membrane at single-molecule level, by developing analytic tools dedicated to Single-Particle Tracking (SPT) at high density: Multiple-Target Tracing (MTT)1. Single-molecule videomicroscopy, offering millisecond and nanometric resolution1-11, allows a detailed representation of membrane organization12-14 by accurately mapping descriptors such as cell receptors localization, mobility, confinement or interactions.
We revisited SPT, both experimentally and algorithmically. Experimental aspects included optimizing setup and cell labeling, with a particular emphasis on reaching the highest possible labeling density, in order to provide a dynamic snapshot of molecular dynamics as it occurs within the membrane. Algorithmic issues concerned each step used for rebuilding trajectories: peaks detection, estimation and reconnection, addressed by specific tools from image analysis15,16. Implementing deflation after detection allows rescuing peaks initially hidden by neighboring, stronger peaks. Of note, improving detection directly impacts reconnection, by reducing gaps within trajectories. Performances have been evaluated using Monte-Carlo simulations for various labeling density and noise values, which typically represent the two major limitations for parallel measurements at high spatiotemporal resolution.
The nanometric accuracy17 obtained for single molecules, using either successive on/off photoswitching or non-linear optics, can deliver exhaustive observations. This is the basis of nanoscopy methods17 such as STORM18, PALM19,20, RESOLFT21 or STED22,23, which may often require imaging fixed samples. The central task is the detection and estimation of diffraction-limited peaks emanating from single-molecules. Hence, providing adequate assumptions such as handling a constant positional accuracy instead of Brownian motion, MTT is straightforwardly suited for nanoscopic analyses. Furthermore, MTT can fundamentally be used at any scale: not only for molecules, but also for cells or animals, for instance. Hence, MTT is a powerful tracking algorithm that finds applications at molecular and cellular scales.

Mapping Molecular Diffusion in the Plasma Membrane by Multiple-Target Tracing MTT

Multiple-Target Tracing is a homemade algorithm developed for tracking individually labeled molecules within the plasma membrane of living cells. Efficiently detecting, estimating and tracing molecules over time at high-density provide a user-friendly, comprehensive tool to investigate nanoscale membrane dynamics.

Cartographie Diffusion moléculaire dans la membrane plasmique par multiple-cible de Recherches (MTT)

Our goal is to obtain a comprehensive description of molecular processes occurring at cellular membranes in different biological functions. We aim at ...

Optimized Staining and Proliferation Modeling Methods for Cell Division Monitoring using Cell Tracking Dyes

Fluorescent cell tracking dyes, in combination with flow and image cytometry, are powerful tools with which to study the interactions and fates of different cell types in vitro and in vivo.1-5 Although there are literally thousands of publications using such dyes, some of the most commonly encountered cell tracking applications include monitoring of:
<ol>
	<li>stem and progenitor cell quiescence, proliferation and/or differentiation6-8</li>
	<li>antigen-driven membrane transfer9 and/or precursor cell proliferation3,4,10-18 and</li>
	<li>immune regulatory and effector cell function1,18-21.</li>
</ol>
Commercially available cell tracking dyes vary widely in their chemistries and fluorescence properties but the great majority fall into one of two classes based on their mechanism of cell labeling. "Membrane dyes", typified by PKH26, are highly lipophilic dyes that partition stably but non-covalently into cell membranes1,2,11. "Protein dyes", typified by CFSE, are amino-reactive dyes that form stable covalent bonds with cell proteins4,16,18. Each class has its own advantages and limitations. The key to their successful use, particularly in multicolor studies where multiple dyes are used to track different cell types, is therefore to understand the critical issues enabling optimal use of each class2-4,16,18,24.
The protocols included here highlight three common causes of poor or variable results when using cell-tracking dyes. These are:
<ol>
	<li>Failure to achieve bright, uniform, reproducible labeling. This is a necessary starting point for any cell tracking study but requires attention to different variables when using membrane dyes than when using protein dyes or equilibrium binding reagents such as antibodies.</li>
	<li>Suboptimal fluorochrome combinations and/or failure to include critical compensation controls. Tracking dye fluorescence is typically 102 - 103 times brighter than antibody fluorescence. It is therefore essential to verify that the presence of tracking dye does not compromise the ability to detect other probes being used.</li>
	<li>Failure to obtain a good fit with peak modeling software. Such software allows quantitative comparison of proliferative responses across different populations or stimuli based on precursor frequency or other metrics. Obtaining a good fit, however, requires exclusion of dead/dying cells that can distort dye dilution profiles and matching of the assumptions underlying the model with characteristics of the observed dye dilution profile.</li>
</ol>
Examples given here illustrate how these variables can affect results when using membrane and/or protein dyes to monitor cell proliferation.

Successful use of cell tracking dyes to monitor immune cell function and proliferation involves several critical steps. We describe methods for: 1) obtaining bright, uniform, reproducible label-ing with membrane dyes; 2) selecting fluorochromes and data acquisition conditions; and 3) choosing a model to quantify cell proliferation based on dye dilution.

Optimisé méthodes de modélisation de coloration et de prolifération pour la surveillance division cellulaire en utilisant des colorants Suivi cellulaires

Fluorescent cell tracking dyes, in combination with flow and image cytometry, are powerful tools with which to study the interactions and fates of ...

Real-time Analyses of Retinol Transport by the Membrane Receptor of Plasma Retinol Binding Protein

Vitamin A is essential for vision and the growth/differentiation of almost all human organs. Plasma retinol binding protein (RBP) is the principle and specific carrier of vitamin A in the blood. Here we describe an optimized technique to produce and purify holo-RBP and two real-time monitoring techniques to study the transport of vitamin A by the high-affinity RBP receptor STRA6. The first technique makes it possible to produce a large quantity of high quality holo-RBP (100%-loaded with retinol) for vitamin A transport assays. High quality RBP is essential for functional assays because misfolded RBP releases vitamin A readily and bacterial contamination in RBP preparation can cause artifacts. Real-time monitoring techniques like electrophysiology have made critical contributions to the studies of membrane transport. The RBP receptor-mediated retinol transport has not been analyzed in real time until recently. The second technique described here is the real-time analysis of STRA6-catalyzed retinol release or loading. The third technique is real-time analysis of STRA6-catalyzed retinol transport from holo-RBP to cellular retinol binding protein I (CRBP-I). These techniques provide high sensitivity and resolution in revealing RBP receptor's vitamin A uptake mechanism.

Here we describe an optimized technique to produce high-quality vitamin A/RBP complex and two real-time monitoring techniques to study vitamin A transport by STRA6, the RBP receptor.

Les analyses en temps réel des Transports rétinol par le récepteur membranaire de plasma Retinol Binding Protein

Vitamin A is essential for vision and the growth/differentiation of almost all human organs.  Plasma retinol binding protein (RBP) is the principle and ...

Immunodetection of Outer Membrane Proteins by Flow Cytometry of Isolated Mitochondria

Methods to detect and monitor mitochondrial outer membrane protein components in animal tissues are vital to study mitochondrial physiology and pathophysiology. This protocol describes a technique where mitochondria isolated from rodent tissue are immunolabeled and analyzed by flow cytometry. Mitochondria are isolated from rodent spinal cords and subjected to a rapid enrichment step so as to remove myelin, a major contaminant of mitochondrial fractions prepared from nervous tissue. Isolated mitochondria are then labeled with an antibody of choice and a fluorescently conjugated secondary antibody. Analysis by flow cytometry verifies the relative purity of mitochondrial preparations by staining with a mitochondrial specific dye, followed by detection and quantification of immunolabeled protein. This technique is rapid, quantifiable and high-throughput, allowing for the analysis of hundreds of thousands of mitochondria per sample. It is applicable to assess novel proteins at the mitochondrial surface under normal physiological conditions as well as the proteins that may become mislocalized to this organelle during pathology. Importantly, this method can be coupled to fluorescent indicator dyes to report on certain activities of mitochondrial subpopulations and is feasible for mitochondria from the central nervous system (brain and spinal cord) as well as liver.

Described here is a method to detect and quantify mitochondrial outer membrane proteins by immunolabeling of mitochondria isolated from rodent tissue and analysis by flow cytometry. This method can be extended to assess functional aspects of mitochondrial subpopulations.

Immunodétection de la membrane externe de protéines par cytométrie en flux de mitochondries isolées

Methods to detect and monitor mitochondrial outer membrane protein components in animal tissues are vital to study mitochondrial physiology and ...

Measuring Endoreduplication by Flow Cytometry of Isolated Tuber Protoplasts

Endoreduplication, the replication of a cell's nuclear genome without subsequent cytokinesis, yields cells with increased DNA content and is associated with specialization, development and increase in cellular size. In plants, endoreduplication seems to facilitate the growth and expansion of certain tissues and organs. Among them is the tuber of potato (Solanum tuberosum), which undergoes considerable cellular expansion in fulfilling its function of carbohydrate storage. Thus, endoreduplication may play an important role in how tubers are able to accommodate this abundance of carbon. However, the cellular debris resulting from crude nuclear isolation methods of tubers, methods that can be used effectively with leaves, precludes the estimation of the tuber endoreduplication index (EI). This article presents a technique for assessing tuber endoreduplication through the isolation of protoplasts while demonstrating representative results obtained from different genotypes and compartmentalized tuber tissues. The major limitations of the protocol are the time and reagent costs required for sample preparation as well as relatively short lifespan of samples after lysis of protoplasts. While the protocol is sensitive to technical variation, it represents an improvement over traditional methods of nuclear isolation from these large specialized cells. Possibilities for improvements to the protocol such as recycling enzyme, the use of fixatives, and other alterations are proposed.

The protocol described herein is a method for measuring endoreduplication within tubers of potato (Solanum tuberosum). It includes plasmolysis and protoplast extraction steps to decrease the noise and debris in downstream flow cytometric analysis.

Mesurer d’endoréduplication par cytométrie de flux des protoplastes isolés Tuber

Endoreduplication, the replication of a cell's nuclear genome without subsequent cytokinesis, yields cells with increased DNA content and is associated ...

Sensitive Measurement of Mitophagy by Flow Cytometry Using the pH-dependent Fluorescent Reporter mt-Keima

Mitophagy is a process of selective removal of damaged or unnecessary mitochondria using autophagy machinery. Close links have been found between defective mitophagy and various human diseases, including neurodegenerative diseases, cancer, and metabolic diseases. In addition, recent studies have shown that mitophagy is involved in normal cellular processes, such as differentiation and development. However, the precise role of and molecular mechanisms underlying mitophagy require further study. Therefore, it is critical to develop a robust and convenient method for measuring changes in mitophagy activity. Here, we describe a detailed protocol for quantitatively assessing mitophagy activity through flow cytometry using the mitochondria-targeted fluorescent protein Keima (mt-Keima). This flow cytometry assay can analyze mitophagy activity more rapidly and sensitively than conventional microscopy- or immunoblotting-based methods. This protocol can be applied to analyze mitophagy activity in various cell types.

Mitophagy, the selective degradation of mitochondria, has been implicated in mitochondrial homeostasis and is deregulated in various human diseases. However, convenient experimental methods for measuring mitophagy activity are very limited. Here, we provide a sensitive assay for measuring mitophagy activity using flow cytometry.

Mesure sensible des Mitophagy par Flow Cytometry à l’aide de la fonction du pH Fluorescent journaliste mt-Keima

Mitophagy is a process of selective removal of damaged or unnecessary mitochondria using autophagy machinery. Close links have been found between ...

High-throughput Measurement of Dictyostelium discoideum Macropinocytosis by Flow Cytometry

Large-scale non-specific fluid uptake by macropinocytosis is important for the proliferation of certain cancer cells, antigen sampling, host cell invasion and the spread of neurodegenerative diseases. The commonly used laboratory strains of the amoeba Dictyostelium discoideum have extremely high fluid uptake rates when grown in nutrient medium, over 90% of which is due to macropinocytosis. In addition, many of the known core components of mammalian macropinocytosis are also present, making it an excellent model system for studying macropinocytosis. Here, the standard technique to measure internalized fluid using fluorescent dextran as a label is adapted to a 96-well plate format, with the samples analyzed by flow cytometry using a high-throughput sampling (HTS) attachment.
Cells are fed non-quenchable fluorescent dextran for a pre-determined length of time, washed by immersion in ice-cold buffer and detached using 5 mM sodium azide, which also stops exocytosis. Cells in each well are then analyzed by flow cytometry. The method can also be adapted to measure membrane uptake and phagocytosis of fluorescent beads or bacteria.
This method was designed to allow measurement of fluid uptake by Dictyostelium in a high-throughput, labor and resource efficient manner. It allows simultaneous comparison of multiple strains (e.g. knockout mutants of a gene) and conditions (e.g. cells in different media or treated with different concentrations of inhibitor) in parallel and simplifies time-courses.

High-throughput Measurement of Dictyostelium discoideum Macropinocytosis by Flow Cytometry

Macropinocytosis, large-scale non-specific fluid uptake, is important in many areas of clinical biology including immunology, infection, cancer, and neurodegenerative diseases. Here, existing techniques have been adapted to allow high-throughput, single-cell resolution measurement of macropinocytosis in the macropinocytosis model organism Dictyostelium discoideum using flow cytometry.

Haut débit mesure de Dictyostelium discoideum macropinocytose par cytométrie en flux

Large-scale non-specific fluid uptake by macropinocytosis is important for the proliferation of certain cancer cells, antigen sampling, host cell invasion ...