We thank Barbara Windschiegl for her help in establishing SOPs; Dennis Remme for his work on the NanoCalcFX software and Alina Kollmannsperger, Markus Braner and Milan Gerovac for helpful suggestions on the manuscript. The German-Israeli Project Cooperation (DIP) provided by the DFG and the Federal Ministry of Education and Research to R.T., as well as the Federal Ministry of Economics and Technology (ZIM R&amp;D Project) to R.T. and Nanospot GmbH supported this work.

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The authors declare no competing financial interests.

Die hier vorgestellte Technik ermöglicht eine hochparallele Analyse von Membranproteintransport. Rekonstituierten Membranprotein-Systeme können direkt auf dem Biochip aufgebracht werden, so dass die Anpassung der theoretisch jeder Membrantransporter oder möglichen Kanal. Transport-Analyse wird durch die Einrichtung eines fluoreszierenden Auslesesystem, entweder durch direkte Fluoreszenzänderung (Translokation von Fluorophore oder fluoreszenzmarkierte Substrate) oder indirekte Fluoreszenzänderung (pH-sensitiven Farb...

Die Analyse von Membranproteinen ist von Interesse in den letzten 20 Jahren für die Grund- und pharmazeutischen Forschung erhöht werden. Die Entwicklung neuer Medikamente ist abhängig von der Identifizierung und detaillierte Charakterisierung neuer Ziele, die derzeit einer der limitierenden Faktoren zu sein. Die Tatsache , dass etwa 60% aller drug targets sind Membranproteine ​​1, macht die Entwicklung von Techniken , um ihre Funktion wichtigsten aufzuklären. 4 - In der Vergangenheit wurden in 2 Vielzahl entwickelten Techniken für die Untersuchung von elektrogenen Kanäle und Transporter. Nicht elektrogener Substrate im Gegensatz eine schwierige Aufgabe darstellen. Sie sind jedoch von besonderem Interesse als Hauptangriffspunkte für Medikamente, da sie den Fluss von gelösten Stoffen und Nährstoffen durch die Zellmembran und die Funktion als Schlüsselrezeptoren in Signalkaskaden 5 steuern. Beträchtliche Anstrengungen wurden in die Entwicklung von t gesetztechniques die Funktion von Membrantransportproteinen 6, 7 zu untersuchen. 10, darunter auch feste unterstützten Lipid - Doppelschichten, tethered Bilayer 11, 12, microblack Lipidmembranen 13, 14 und nativen Vesikel - Arrays 15, 16 ein paar zu nennen - Systeme festen Träger unter Verwendung von Membranen wurden als vielversprechendsten Instrumente auf diesem Gebiet 8 entstanden. Einige von ihnen sind sogar als Handelsaufbauten 17, 18. Einige Beispiele wurden veröffentlicht Kombination die Fähigkeit einzelne Membranproteine ​​in einer hochparallelen Weise 14 zu studieren, 19, Voraussetzung für Screening - Anwendungen. Allerdings überbrücken diese Methoden nur selten aus der Grundlagenforschung zur industriellen Umfeld. Die Schwierigkeiten liegen oft in der Fähigkeit des Systems, automatisierbar zu sein, die kostenintensive Herstellung und / oder aufwendige Vorbereitung. Ein Ansatz overcoming alle oben erwähnten Hindernisse ist das Endziel. Die Technik , die hier vorgestellt wurde entwickelt Membrankanäle und Transporter in vitro in einer kontrollierten Umgebung auf dem einzelnen Protein - Ebene 20 zu studieren - 22. Die Rekonstitution von gereinigten Membranproteinen in LUVs ist viel mehr etabliert als vergleichbare Ansätze für GUVs 23-26 oder schwarzen Lipidmembranen 27. Sie können direkt auf die Chipoberfläche aufgebracht werden, in dem Doppelschichtbildung erfolgt über eine Selbstorganisationsprozess stattfindet. Der Glasboden Design des nanoporösen Chip (Fig. 1) ermöglicht eine Luft Mikroskopie, die die einfache Automatisierung des Systems ermöglicht. In Kombination mit einer motorisierten Stufe kann mehrere Chips gleichzeitig gemessen werden, wobei jedes Sichtfeld Tausende von abgedichteten Hohlräumen zur Analyse enthält. Abbildung 1. Design von gemultiplexten Nanopore Biochips. A) A silicon-on-insulator (SOI) Wafers durch reaktives Ionenätzen strukturiert. Ungefähr 1.150 einzelne Chips werden von jedem Wafer hergestellt mit identischen Eigenschaften und Qualität. B) Jeder Chip umfasst 250.000 einzelne Mikrokavitäten mit Nano - Öffnungen. Maßstabsbalken:. 200 &amp; mgr; m C) Jeder Hohlraum ist adressierbar über multispektrale Fluoreszenz ausgelesen. Eine undurchsichtige Deckschicht blockiert die Fluoreszenzsignale aus dem Pufferspeicher, so dass der Biochip kompatibel mit invertierten Fluoreszenzmikroskop. D) Rasterkraftmikroskopie (AFM) Bildgebung Porenöffnungen und Oberflächenrauhigkeit der Siliziumdioxid - Schicht von 3,6 nm gleichmäßig angeordnet enthüllt (n = 40) optimal für Vesikelfusion. Maßstabsbalken:. 5 um E) Rasterelektronen microscopy (SEM) Aufnahme zeigt einen Querschnitt durch die Nanopore die den Zugang zu den Femtoliter Hohlräume innerhalb des Siliziumchips. Diese Zahl wurde mit Erlaubnis wiederverwendet werden von 21. <a href="https://www.jove.com/files/ftp_upload/53373/53373fig1large.jpg" target="_blank">Bitte klicken Sie hier</a> , um <a href="https://www.jove.com/files/ftp_upload/53373/53373fig1large.jpg" target="_blank">eine größere Version dieser Figur zu sehen.</a> Alle Datenanalyse wird mit Freeware durchgeführt uneingeschränkten Zugriff für Endanwender zu gewährleisten. Zeitreihen sind mit dem kostenlosen Bildverarbeitungssoftware analysiert und eine benutzerdefinierte Build-Kurvenanalyse-Software ermöglicht die Stapelverarbeitung und einfache Korrelation von großen Datensätzen mit mehreren Fluoreszenzkanälen und Tausende von Kurven. Das Modellprotein in diesem Protokoll wird die mechanosensitive Kanal von großer Leitfähigkeit (MscL) Kanalproteins von E. abgeleitet coli. Es fungiert als ein Ventil in der Natur osmotischen Schock freizusetzen, wurde aber derart modifiziert, dass synt rational entworfenhetic Funktionalitäten können kovalent an die Kanäle Einschnürung Seite angebracht werden. Via Ladungs ​​Abstoßung des kovalent gebundenen Aktivator (MTSET) der Kanal ausgelöst wird, zu öffnen, die Schaffung eines Nano-Ventil. Kleine Moleküle, wie Ionen, Wasser, kleine Proteine, aber auch kleine Fluorophore können durch den Kanal zu durchdringen. Hierbei wird das Protein als ein Modell verwendet, um die Fähigkeit des Systems zu demonstrieren Protein-vermittelte Translokation zu detektieren.

<table border="0" cellpadding="0" cellspacing="0" width="1093">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Reagent</td>
			<td style="width:232px;"></td>
			<td style="width:305px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">[2-(Trimethylammonium)ethyl] 
			methanethiosulfonate</td>
			<td style="width:232px;">Toronto Research Chemicals Inc.</td>
			<td style="width:305px;">T792900</td>
			<td>MTSET; hydrolized by water. Keep as dry pouder aliquot at -80 &#176;C. Use immediately (30 minutes) after solubilization in buffer.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">1 ml gas-tight syringe</td>
			<td style="width:232px;">Hamilton</td>
			<td style="width:305px;">#1001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">10 ml round flask</td>
			<td style="width:232px;">Schott Duran</td>
			<td style="width:305px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">2.7 mm glas beads</td>
			<td style="width:232px;">Roth</td>
			<td style="width:305px;">N032.1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">2-Propanole</td>
			<td style="width:232px;">Roth</td>
			<td style="width:305px;">9866.5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">30 cm Luer-Lock Extension Tube</td>
			<td style="width:232px;">Sarstedt</td>
			<td style="width:305px;">744304</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Acetone</td>
			<td style="width:232px;">Roth</td>
			<td style="width:305px;">5025.5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Bio-Beads SM-2 Adsorbent</td>
			<td style="width:232px;">Bio-Rad</td>
			<td style="width:305px;">152-3920</td>
			<td>need to be activated before first use</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:389px;">CaCl2 Dihydrat</td>
			<td style="width:232px;">Roth</td>
			<td style="width:305px;">HN04.3</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Calcein</td>
			<td style="width:232px;">Sigma</td>
			<td style="width:305px;">C0875</td>
			<td>store dark at -20 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Chloroform reagent grade</td>
			<td style="width:232px;">VWR Chemicals</td>
			<td style="width:305px;">22711324</td>
			<td></td>
		</tr>
		<tr height="24">
			<td height="24" style="height:24px;width:389px;">DOPEATTO390</td>
			<td style="width:232px;">ATTO-TEC</td>
			<td style="width:305px;">AD 390-165</td>
			<td>store dark at -20 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Ethanol absolute</td>
			<td style="width:232px;">Sigma-Aldrich</td>
			<td style="width:305px;">32205</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Injekt Single-use syringe</td>
			<td style="width:232px;">Braun</td>
			<td style="width:305px;">460 60 51V</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Injekt-F single-use syringe</td>
			<td style="width:232px;">Braun</td>
			<td style="width:305px;">91 66 017V</td>
			<td></td>
		</tr>
		<tr height="27">
			<td height="27" style="height:27px;width:389px;">Keck clips</td>
			<td style="width:232px;">Schott</td>
			<td style="width:305px;">KC29</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">L-&#945;-Phosphatidylcholine, 20% (Soy)</td>
			<td style="width:232px;">Avanti Polar Lipids</td>
			<td style="width:305px;">5416016</td>
			<td>store under inert gas at -20 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">NaCl 99.5% p.a.</td>
			<td style="width:232px;">Roth</td>
			<td style="width:305px;">3957.2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Nanopore E100 wafer/chips</td>
			<td style="width:232px;">Micromotive (Mainz/Germany)</td>
			<td style="width:305px;"></td>
			<td>available on request</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Nucleopore Track-Etch Membrane 0.4 &#181;m</td>
			<td style="width:232px;">Whatman</td>
			<td style="width:305px;">800282</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Oregon Green Dextran 488 (70 kDa)</td>
			<td style="width:232px;">life Technologies</td>
			<td style="width:305px;">D-7173</td>
			<td>store dark at -20 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Oy647</td>
			<td style="width:232px;">Luminartis (M&#252;nster/Germany)</td>
			<td style="width:305px;">OY-647-T-1mg</td>
			<td>store dark at -20 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Rotilabo-syringe filtration, unsterile, pore-size 0.22 &#181;m</td>
			<td style="width:232px;">Roth</td>
			<td style="width:305px;">P 818.1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Sephadex G-50</td>
			<td style="width:232px;">Sigma-Aldrich</td>
			<td style="width:305px;">G5080</td>
			<td>column material for size exclusion chromatography</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Silastic MDX4-4210</td>
			<td style="width:232px;">Dow Corning</td>
			<td style="width:305px;"></td>
			<td>curing agent for chip fixation onto cover glass support</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">sticky-Slide 8-well</td>
			<td style="width:232px;">ibidi</td>
			<td style="width:305px;">80828</td>
			<td>multi-well chamber for the mounting onto glass slides (chip holder)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Three-way stopcock blue</td>
			<td style="width:232px;">Sarstedt</td>
			<td style="width:305px;">744410001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Tris Pufferan 99.9% Ultra Quality</td>
			<td style="width:232px;">Roth</td>
			<td style="width:305px;">5429.2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Triton-X 100</td>
			<td style="width:232px;">Roth</td>
			<td style="width:305px;">6683.1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Whatman 0.2 &#181;m cellulose nitrate membrane filter</td>
			<td style="width:232px;">Roth</td>
			<td style="width:305px;">NH69.1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Name</td>
			<td style="width:232px;">Company</td>
			<td style="width:305px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Equipment</td>
			<td style="width:232px;"></td>
			<td style="width:305px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">B&#252;chi 461 water bath</td>
			<td style="width:232px;">B&#252;chi</td>
			<td style="width:305px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">B&#252;chi Rotavapor RE 111</td>
			<td style="width:232px;">B&#252;chi</td>
			<td style="width:305px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Cary Eclipse Fluorescence Spectrophtometer&#160;</td>
			<td style="width:232px;">Varian</td>
			<td style="width:305px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">LiposoFast Mini Extruder</td>
			<td style="width:232px;">Avestin</td>
			<td style="width:305px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Membrane pump&#160;</td>
			<td style="width:232px;">Vaccubrand</td>
			<td style="width:305px;">15430</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Nanosight Nanoparticle Tracking Microscope</td>
			<td style="width:232px;">Malvern / Nanosight</td>
			<td style="width:305px;">LM 14C</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">NyONE microscope</td>
			<td style="width:232px;">Synentec</td>
			<td style="width:305px;"></td>
			<td>available on request</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Pump control</td>
			<td style="width:232px;">Vaccubrand</td>
			<td style="width:305px;">CVC 2II</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Sonicator bath Sonorex RK100H</td>
			<td style="width:232px;">Brandelin electronic</td>
			<td style="width:305px;">31200001107477</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Vaccum pump RC5</td>
			<td style="width:232px;">Vaccubrand</td>
			<td style="width:305px;">1805400204</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Water bath W13</td>
			<td style="width:232px;">Haake</td>
			<td style="width:305px;">002-9910</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Plasma Cleaner PDC-37G</td>
			<td style="width:232px;">Harrick Plasma</td>
			<td style="width:305px;">PDC-37G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Name</td>
			<td style="width:232px;">Company</td>
			<td style="width:305px;">Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">Software</td>
			<td style="width:232px;"></td>
			<td style="width:305px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">ImageJ</td>
			<td style="width:232px;">Open Source</td>
			<td style="width:305px;">http://imagej.nih.gov/ij/</td>
			<td>scientific image processing software</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">NanoCalcFX</td>
			<td style="width:232px;">Freeware</td>
			<td style="width:305px;">http://sourceforge.net/projects/nanocalc/</td>
			<td>data analysis/evaluation software for massive transport kinetic datasets</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">NTA 2.3 Analytical Software</td>
			<td style="width:232px;">Nanosight</td>
			<td style="width:305px;"></td>
			<td>data acquisition and analysis software for nanoparticle tracking microscope</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:389px;">NTA 2.3 Temperature Comms</td>
			<td style="width:232px;">Nanosight</td>
			<td style="width:305px;"></td>
			<td>temperature controle software for nanoparticle tracking microscope</td>
		</tr>
	</tbody>
</table>

membrane transport processes analyzed by a highly parallel nanopore chip system at single protein resolution

Membranproteintransport auf dem einzelnen Proteinebene ausweicht noch detaillierte Analyse, wenn das transloziert Substrat nicht elektrogener ist. Erhebliche Anstrengungen wurden in diesem Bereich, sondern Techniken ermöglicht automatisierte Hochdurchsatz-Transport-Analyse in Kombination mit lösemittelfreien Techniken Lipid-Doppelschicht für die Analyse von Membrantransportern sind erforderlich selten. Diese Klasse von Transportern ist jedoch von entscheidender Bedeutung in der Zelle Homöostase und daher ein zentrales Ziel in der Medikamentenentwicklung und Methoden neue Erkenntnisse dringend benötigt zu gewinnen. Die hier präsentierten Handschrift beschreibt den Aufbau und die Handhabung eines neuartigen Biochips für die Analyse von Membranprotein-vermittelte Transportprozesse auf Einzel transporter Auflösung. Der Biochip besteht aus Mikrokavitäten durch Nanoporen eingeschlossen, die stark parallel in seiner Gestaltung und kann in Industriequalität und Menge hergestellt werden. Protein-tragende Liposomen können direkt angewendet werdendie Chipoberfläche bilden selbstorganisierende poren Spanning Lipid-Doppelschichten SSM-Techniken (feste Lipidmembranen unterstützt). Pore-Spanning Teile der Membran sind freistehend, Bereitstellen der Schnittstelle für das Substrat Translokation in den oder aus dem Hohlraum, die durch multispektrale Fluoreszenzanzeige in Echtzeit verfolgt werden können. Die Einrichtung von Standard Operating Procedures (SOPs) ermöglicht die einfache Einrichtung von Protein-tragenden Lipid-Doppelschichten auf der Chipoberfläche praktisch jeder Membranprotein, das funktionell wiederhergestellt werden kann. Einzige Voraussetzung ist die Schaffung eines Fluoreszenzlesesystem für Nicht-elektrogener Transportgründen. High-Content-Screening-Anwendungen sind erfüllbar durch den Einsatz von automatisierten inversen Fluoreszenzmikroskope mehrere Chips parallel aufzuzeichnen. Große Datenmengen können mit dem frei verfügbaren anwendungsspezifische Analyse-Software analysiert werden. Drei-Farben-Mehrspektrale FluoreszenzAuslesen erlaubt darüber hinaus für unvoreingenommene Daten Diskriminierung in verschiedenen Ereignisklassen, falsch positive Ergebnisse zu beseitigen. Die Chip - Technologie basiert derzeit auf SiO 2 -Oberflächen, aber weitere Funktionalisierung goldbeschichteten Spanflächen ist ebenfalls möglich.

Pore-Spanning Membranen können leicht auf der Oberfläche nanostrukturierten Chip in einer selbstorganisierenden Weise erstellt werden. Doch der zugrunde liegende Prozess ist noch zart und von vielen Parametern wie Liposomgröße, Monodispersität der Liposomen-Population, Lamellarität, Lipid- und Salz-Konzentration und chemischen Oberflächeneigenschaften beeinflusst. Die meisten dieser Parameter sind in dem obigen Protokoll sorgfältig charakterisiert und standardisiert. Andere Param...

Watch this Scientific Journal Video about Membrane Transport Processes Analyzed by a Highly Parallel Nanopore Chip System at Single Protein Resolution at JoVE.com

Membrane Transport Processes Analyzed by a Highly Parallel Nanopore Chip System at Single Protein Resolution

The presented protocol describes the analysis of membrane protein mediated transport on the single transporter level using pore-spanning solvent-free lipid bilayers. This is achieved by the creation of bulk produced nanopore array chips, combined with highly parallel data acquisition and analysis, enabling the future establishment of membrane protein effector screenings.

Membrantransportprozesse durch eine hochparallele Nanopore Chip-System bei Einzel Protein Resolution Analysierte

Membrane protein transport on the single protein level still evades detailed analysis, if the substrate translocated is non-electrogenic. Considerable ...

membrane-transport-processes-analyzed-highly-parallel-nanopore-chip

Research

JoVE Journal

Biology

11.6K Aufrufe.  Goethe University Frankfurt. The presented protocol describes the analysis of membrane protein mediated transport on the single transporter level using pore-spanning solvent-free lipid bilayers. This is achieved by the creation of bulk produced nanopore array chips, combined with highly parallel data acquisition and analysis, enabling the future establishment of membrane protein effector screenings.

Serie: Membrane Transport Processes Analyzed by a Highly Parallel Nanopore Chip System at Single Protein Resolution

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.

Mess-Plasmamembranprotein endocytischen Preise von Reversible Biotinylierung

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

Forschung

Biologie

Split-Ubiquitin Based Membrane Yeast Two-Hybrid (MYTH) System: A Powerful Tool For Identifying Protein-Protein Interactions

The fundamental biological and clinical importance of integral membrane proteins prompted the development of a yeast-based system for the high-throughput identification of protein-protein interactions (PPI) for full-length transmembrane proteins. To this end, our lab developed the split-ubiquitin based Membrane Yeast Two-Hybrid (MYTH) system. This technology allows for the sensitive detection of transient and stable protein interactions using Saccharomyces cerevisiae as a host organism. MYTH takes advantage of the observation that ubiquitin can be separated into two stable moieties: the C-terminal half of yeast ubiquitin (Cub) and the N-terminal half of the ubiquitin moiety (Nub). In MYTH, this principle is adapted for use as a 'sensor' of protein-protein interactions. Briefly, the integral membrane bait protein is fused to Cub which is linked to an artificial transcription factor. Prey proteins, either in individual or library format, are fused to the Nub moiety. Protein interaction between the bait and prey leads to reconstitution of the ubiquitin moieties, forming a full-length 'pseudo-ubiquitin' molecule. This molecule is in turn recognized by cytosolic deubiquitinating enzymes, resulting in cleavage of the transcription factor, and subsequent induction of reporter gene expression. The system is highly adaptable, and is particularly well-suited to high-throughput screening. It has been successfully employed to investigate interactions using integral membrane proteins from both yeast and other organisms.

Split-Ubiquitin Based Membrane Yeast Two-Hybrid MYTH System: A Powerful Tool For Identifying Protein-Protein Interactions

MYTH allows the sensitive detection of transient and stable interactions between proteins that are expressed in the model organism Saccharomyces cerevisiae. It has been successfully applied to study exogenous and yeast integral membrane proteins in order to identify their interacting partners in a high throughput manner.

Split-Ubiquitin Basierend Membrane Yeast Two-Hybrid (Mythos) System: Ein wirksames Instrument zur Ermittlung von Protein-Protein-Wechselwirkungen

The fundamental biological and clinical importance of integral membrane proteins prompted the development of a yeast-based system for the high-throughput ...

Using the GELFREE 8100 Fractionation System for Molecular Weight-Based Fractionation with Liquid Phase Recovery

The GELFREE 8100 Fractionation System is a novel protein fractionation system designed to maximize protein recovery during molecular weight based fractionation. The system is comprised of single-use, 8-sample capacity cartridges and a benchtop GELFREE Fractionation Instrument. During separation, a constant voltage is applied between the anode and cathode reservoirs, and each protein mixture is electrophoretically driven from a loading chamber into a specially designed gel column gel. Proteins are concentrated into a tight band in a stacking gel, and separated based on their respective electrophoretic mobilities in a resolving gel. As proteins elute from the column, they are trapped and concentrated in liquid phase in the collection chamber, free of the gel. The instrument is then paused at specific time intervals, and fractions are collected using a pipette. This process is repeated until all desired fractions have been collected. If fewer than 8 samples are run on a cartridge, any unused chambers can be used in subsequent separations.
This novel technology facilitates the quick and simple separation of up to 8 complex protein mixtures simultaneously, and offers several advantages when compared to previously available fractionation methods. This system is capable of fractionating up to 1mg of total protein per channel, for a total of 8mg per cartridge. Intact proteins over a broad mass range are separated on the basis of molecular weight, retaining important physiochemical properties of the analyte. The liquid phase entrapment provides for high recovery while eliminating the need for band or spot cutting, making the fractionation process highly reproducible1.

The accompanying video describes the use of the GELFREE 8100 Fractionation System, which partitions complex protein samples on the basis of molecular weight and recovers the fractions in liquid phase. The video describes how the technology works, how it is used, and provides resultant data, with polyacrylamide gel electrophoresis analysis of fractionated bovine liver homogenate.

Mit dem GELFREE 8100 Fraktionierung System für Molecular Weight-Based Fraktionierung mit Liquid Phase Wiederherstellung

The GELFREE 8100 Fractionation System is a novel protein fractionation system designed to maximize protein recovery during molecular weight based ...

Single-Molecule Imaging of Nuclear Transport

The utility of single molecule fluorescence microscopy approaches has been proven to be of a great avail in understanding biological reactions over the last decade. The investigation of molecular interactions with high temporal and spatial resolutions deep within cells has remained challenging due to the inherently weak signals arising from individual molecules. Recent works by Yang et al. demonstrated that narrow-field epifluorescence microscopy allows visualization of nucleocytoplasmic transport at the single molecule level. By the single molecule approach, important kinetics, such as nuclear transport time and efficiency, for signal-dependent and independent cargo molecules have been obtained. Here we described a protocol for the methodological approach with an improved spatiotemporal resolution of 0.4 ms and 12 nm. The improved resolution enabled us to capture transient active transport and passive diffusion events through the nuclear pore complexes (NPC) in semi-intact cells. We expect this method to be used in elucidating other binding and trafficking events within cells.

Single molecule microscopy approch provided novel insights into nuclear transport.

The utility of single molecule fluorescence microscopy approaches has been proven to be of a great avail in understanding biological reactions over the ...

Direct Analysis of Single Cells by Mass Spectrometry at Atmospheric Pressure

Analysis of biochemicals in single cells is important for understanding cell metabolism, cell cycle, adaptation, disease states, etc. Even the same cell types exhibit heterogeneous biochemical makeup depending on their physiological conditions and interactions with the environment. Conventional methods of mass spectrometry (MS) used for the analysis of biomolecules in single cells rely on extensive sample preparation. Removing the cells from their natural environment and extensive sample processing could lead to changes in the cellular composition. Ambient ionization methods enable the analysis of samples in their native environment and without extensive sample preparation.1 The techniques based on the mid infrared (mid-IR) laser ablation of biological materials at 2.94 &mu;m wavelength utilize the sudden excitation of water that results in phase explosion.2 Ambient ionization techniques based on mid-IR laser radiation, such as laser ablation electrospray ionization (LAESI) and atmospheric pressure infrared matrix-assisted laser desorption ionization (AP IR-MALDI), have successfully demonstrated the ability to directly analyze water-rich tissues and biofluids at atmospheric pressure.3-11 In LAESI the mid-IR laser ablation plume that mostly consists of neutral particulate matter from the sample coalesces with highly charged electrospray droplets to produce ions. Recently, mid-IR ablation of single cells was performed by delivering the mid-IR radiation through an etched fiber. The plume generated from this ablation was postionized by an electrospray enabling the analysis of diverse metabolites in single cells by LAESI-MS.12 This article describes the detailed protocol for single cell analysis using LAESI-MS. The presented video demonstrates the analysis of a single epidermal cell from the skin of an Allium cepa bulb. The schematic of the system is shown in Figure 1. A representative example of single cell ablation and a LAESI mass spectrum from the cell are provided in Figure 2.

Single cell analysis is performed by mass spectrometry on plant and animal cells at atmospheric pressure by using a sharpened optical fiber to sample the cells for laser ablation electrospray ionization (LAESI) mass spectrometry.

Direkte Analyse von Einzelzellen durch Massenspektrometrie bei Atmosphärendruck

Analysis of biochemicals in single cells is important for understanding cell metabolism, cell cycle, adaptation, disease states, etc. Even the same cell ...

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.

Real-time Analyse von Retinol Transport durch die Membran-Rezeptor von 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 ...

Visualizing Clathrin-mediated Endocytosis of G Protein-coupled Receptors at Single-event Resolution via TIRF Microscopy

Many important signaling receptors are internalized through the well-studied process of clathrin-mediated endocytosis (CME). Traditional cell biological assays, measuring global changes in endocytosis, have identified over 30 known components participating in CME, and biochemical studies have generated an interaction map of many of these components. It is becoming increasingly clear, however, that CME is a highly dynamic process whose regulation is complex and delicate. In this manuscript, we describe the use of Total Internal Reflection Fluorescence (TIRF) microscopy to directly visualize the dynamics of components of the clathrin-mediated endocytic machinery, in real time in living cells, at the level of individual events that mediate this process. This approach is essential to elucidate the subtle changes that can alter endocytosis without globally blocking it, as is seen with physiological regulation. We will focus on using this technique to analyze an area of emerging interest, the role of cargo composition in modulating the dynamics of distinct clathrin-coated pits (CCPs). This protocol is compatible with a variety of widely available fluorescence probes, and may be applied to visualizing the dynamics of many cargo molecules that are internalized from the cell surface.

Clathrin-mediated endocytosis, a rapid and highly dynamic process internalizes many proteins, including signaling receptors. The protocol described here directly visualizes the kinetics of individual endocytic events. This is essential for understanding how core members of the endocytic machinery coordinate with each other, and how protein cargo influence this process.

Visualisierung Clathrin-vermittelte Endozytose von G-Protein-gekoppelten Rezeptoren an Einzelereignis Resolution über TIRF-Mikroskopie

Many important signaling receptors are internalized through the well-studied process of clathrin-mediated endocytosis (CME). Traditional cell biological ...

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

The production of recombinant membrane proteins for structural and functional studies remains technically challenging due to low levels of expression and the inherent instability of many membrane proteins once solubilized in detergents. A protocol is described that combines ligation independent cloning of membrane proteins as GFP fusions with expression in Escherichia coli detected by GFP fluorescence. This enables the construction and expression screening of multiple membrane protein/variants to identify candidates suitable for further investment of time and effort. The GFP reporter is used in a primary screen of expression by visualizing GFP fluorescence following SDS polyacrylamide gel electrophoresis (SDS-PAGE). Membrane proteins that show both a high expression level with minimum degradation as indicated by the absence of free GFP, are selected for a secondary screen. These constructs are scaled and a total membrane fraction prepared and solubilized in four different detergents. Following ultracentrifugation to remove detergent-insoluble material, lysates are analyzed by fluorescence detection size exclusion chromatography (FSEC). Monitoring the size exclusion profile by GFP fluorescence provides information about the mono-dispersity and integrity of the membrane proteins in different detergents. Protein: detergent combinations that elute with a symmetrical peak with little or no free GFP and minimum aggregation are candidates for subsequent purification. Using the above methodology, the heterologous expression in E. coli of SED (shape, elongation, division, and sporulation) proteins from 47 different species of bacteria was analyzed. These proteins typically have ten transmembrane domains and are essential for cell division. The results show that the production of the SEDs orthologues in E. coli was highly variable with respect to the expression levels and integrity of the GFP fusion proteins. The experiment identified a subset for further investigation.

Green Fluorescent Protein-based Expression Screening of Membrane Proteins in Escherichia coli

A streamlined approach to screening for the expression of recombinant membrane proteins in Escherichia coli based on fusion to green fluorescent protein is presented.

Green Fluorescent Protein-basierte Screening Expression von Membranproteinen in<em&gt; Escherichia coli</em

The production of recombinant membrane proteins for structural and functional studies remains technically challenging due to low levels of expression and ...

CUBIC Protocol Visualizes Protein Expression at Single Cell Resolution in Whole Mount Skin Preparations

The skin is essential for our survival. The outer epidermal layer consists of the interfollicular epidermis, which is a stratified squamous epithelium covering most of our body, and epidermal appendages such as the hair follicles and sweat glands. The epidermis undergoes regeneration throughout life and in response to injury. This is enabled by K14-expressing basal epidermal stem/progenitor cell populations that are tightly regulated by multiple regulatory mechanisms active within the epidermis and between epidermis and dermis. This article describes a simple method to clarify full thickness mouse skin biopsies, and visualize K14 protein expression patterns, Ki67 labeled proliferating cells, Nile Red labeled sebocytes, and DAPI nuclear labeling at single cell resolution in 3D. This method enables accurate assessment and quantification of skin anatomy and pathology, and of abnormal epidermal phenotypes in genetically modified mouse lines. The CUBIC protocol is the best method available to date to investigate molecular and cellular interactions in full thickness skin biopsies at single cell resolution.

This report describes a CUBIC protocol to clarify full thickness mouse skin biopsies, and visualize protein expression patterns, proliferating cells, and sebocytes at the single cell resolution in 3D. This method enables accurate assessment of skin anatomy and pathology, and of abnormal epidermal phenotypes in genetically modified mouse lines.

CUBIC Protokoll Visualisiert Expression Protein bei Single Cell Resolution in Ganze Berge Vorbereitung der Haut

The skin is essential for our survival. The outer epidermal layer consists of the interfollicular epidermis, which is a stratified squamous epithelium ...

Methods to Study Epithelial Transport Protein Function and Expression in Native Intestine and Caco-2 Cells Grown in 3D

The intestinal epithelium has important transport and barrier functions that play key roles in normal physiological functions of the body while providing a barrier to foreign particles. Impaired epithelial transport (ion, nutrient, or drugs) has been associated with many diseases and can have consequences that extend beyond the normal physiological functions of the transporters, such as by influencing epithelial integrity and the gut microbiome. Understanding the function and regulation of transport proteins is critical for the development of improved therapeutic interventions. The biggest challenge in the study of epithelial transport is developing a suitable model system that recapitulates important features of the native intestinal epithelial cells. Several in vitro cell culture models, such as Caco-2, T-84, and HT-29-Cl.19A cells are typically used in epithelial transport research. These cell lines represent a reductionist approach to modeling the epithelium and have been used in many mechanistic studies, including their examination of epithelial-microbial interactions. However, cell monolayers do not accurately reflect cell-cell interactions and the in vivo microenvironment. Cells grown in 3D have shown to be promising models for drug permeability studies. We show that Caco-2 cells in 3D can be used to study epithelial transporters. It is also important that studies in Caco-2 cells are complemented with other models to rule out cell specific effects and to take into account the complexity of the native intestine. Several methods have been previously used to assess the functionality of transporters, such as everted sac and uptake in isolated epithelial cells or in isolated plasma membrane vesicles. Taking into consideration the challenges in the field with respect to models and the measurement of transport function, we demonstrate here a protocol to grow Caco-2 cells in 3D and describe the use of an Ussing chamber as an effective approach to measure serotonin transport, such as in intact polarized intestinal epithelia.

We describe simple methods to study the regulation of intestinal serotonin transporter (SERT) function and expression using an in vitro cell culture model of Caco-2 cells grown in 3D&#160;and an ex vivo model of mouse intestines. These methods are applicable to the study of other epithelial transporters.

Methoden Epithelial Transportprotein Funktion und Expression in Mutterdarm und Caco-2-Zellen gezüchtet in 3D zu studieren

The intestinal epithelium has important transport and barrier functions that play key roles in normal physiological functions of the body while providing ...