This work was supported by NIH grant GM085232 and an Irma T. Hirschl/ Monique Weill-Caulier Scholar Award (to A.A.).

1.脂質の準備<ol><li>透明なガラス管に所望量の脂質を分注し。 E.を使用してください大腸菌極性脂質抽出物が、ほとんどの脂質組成物を用いることができる。脂質は粉末形態である場合は、20 mg / mlの濃度のクロロホルムで再懸濁。すべての溶媒が蒸発するまでN 2ガ ​​ス下、RTで脂質を乾燥させる。 </li><li>ペンタン中の脂質を再懸濁し、クロロホルムの残り痕跡を除去するために再びガスN 2の安定した流れを、それを乾燥させてください。乾燥した全ての溶媒が蒸発するまで。乾燥しながら脂質をチューブの底に三分の一をカバーする均一な膜に分布してではなく、一番下に密な塊を形成されるように、静かにチューブを回転させる。 </li><li>脂質を溶解する界面活性剤（300mMの塩化カリウム、50mMのクエン酸、25mMのK 2 HPO 4、pH4.5で、35mMのCHAPS）を含有する再構成バッファを追加する。タンパク質がCHAPSにはあまり寛容である場合は、このステップのために他の中性洗剤を使用してください。 </li><li> Resuspen水浴超音波処理を使用して明瞭に脂質をdは。短い（30秒-1分）一時停止（30秒-1分）短いパルスの最大電力で水超音波処理槽の中心にチューブを浸し。溶液は透明になるはず。 注：達成明確化の最終的な程度は、使用される特定の脂質組成に依存します。この段階で、いくつかのバッチ間の変動があっても、名目上同一の脂質の中でも可能である。残留ヘイズは遠心分離により除去することができる懸濁液中の大きな粒子による光の散乱によるものである。 </li><li> 20〜60分間、室温で再懸濁脂質をインキュベートする。 </li></ol> 2.プロテオリポソー​​ムの形成注：いくつかの戦略は、リポソーム内に界面活性剤で可溶化タンパク質を挿入するために使用することができる。 CLC-EC1のために透析がうまく機能し、そのために選択6,9,10の方法です。 <ol><li> μgのOで表され、所望のタンパク質対脂質（P / L）比（に精製タンパク質を追加します。<html> Fタンパク質/ mg脂質）。 P / L比の選択は、実験の目的に依存する。 <ol><li>目標は、関心対象のタンパク質の活性を評価することである場合には、各リポソームは、タンパク質の複数のコピーが含まれるように、信号を最大化するために高いP / L&#39;sで再構成する。各小胞は、平均1タンパク質に含まれるように、活性および/またはタンパク質の単一の輸送速度を定量化するために、低いP / L&#39;sのポアソン希釈領域で再構成する。各政権をどのような場合に使用するのより深い分析のための手順7と議論を参照してください。 </li></ol></li><li>様々なレジメンのための最適なP / L値を決定するには、タンパク質濃度8,11-13の関数として活性の完全な滴定を行う。しかし、活性単位の分子量（MWは、kDaので表す）する任意のタンパク質について、以下のP / Lの値が初期guesstimatesとして使用することができる知られている。 pgの &quot;/&gt; <img alt="式2" fo:content-width="1.5in" src="/files/ftp_upload/52369/52369eq2.jpg" /></li><li>予め湿らせた透析チューブまたはカセットにタンパク質と脂質混合物をロードします。 500-1,000x脂質再構成バッファのボリュームを含むビーカーに透析装置を配置（ すなわち 、脂質の再懸濁の1ミリリットルのため1 Lバッファ）穏やかに撹拌しながら。 <ol><li> &gt; 3時間間隔で変更バッファ3〜4回。すべてのソリューションの変更では、蒸留水でカセット/チューブ、ビーカーを洗浄し、新鮮な再構成緩衝液でビーカーを埋める。溶液交換のための1-2のO / N間隔を含めます。ソリューションの変更の正確な数と期間は、使用される正確な脂質や洗剤に依存します。 </li></ol></li><li>最後のステップが完了した後、-80℃で液体N 2又は凍結で、透析容器からリポソームを除去するチューブでそれらをアリコートし、フラッシュ、それらを凍結する。 </li></ol> 3.録音セットアップ &lt;Pクラス= &quot;jove_content&quot;&gt;注： - （下記参照）電極、アナログとpH計記録のセットアップ（ 図2A）は、二つのチャンバー（平底シリンダー、〜3,4容）、Clから構成されていまたはデジタル電気出力、デジタイザ、および適切な取得ソフトウェアを備えたコンピュータ。 <ol><li> pH計の電極、コンピュータに接続されているデジタイザにpH計の出力-はClを接続します。 1チャンバー内の参照電極と他の（ 図2B）で再コーディングワイヤーを配置します。 注：ΔV カルが正である（ステップ6.4および7.2参照）がワイヤの極性が正しい。 </li><li>記録チャンバー（ 図1B）で撹拌棒で撹拌プレート上室を置きます。撹拌棒が電極に接触していないことを確認してください。 </li><li>寒天橋（ 図2B）（100 mMのKClおよび2％アガロース）を使用してチャンバーを接続します。 100のKClに寒天ブリッジを保管してください。 </LI&gt; </ol>のCl 4.準備-電極<ol><li>古いものと-possibly-非機能pH電極を取る。完全に銀線を明らかにするためにガラスコーティングを破る。 </li><li>慎重に手術用メスの刃を使用して銀ワイヤからコーティングを除去。 H 2 OおよびEtOH大量のを使用して、ワイヤを清掃してください。 </li><li>ワイヤまでのFeCl 3（または漂白剤）の飽和溶液の代わりに塩化銀の均一な暗い被膜で覆われている。 </li></ol>単ラメラ小胞の5準備<ol><li>実験前の夜は、のために（攪拌しないでください）穏やかに振盪しながら外部バッファ（1のKCl、150mMのK 2 SO 4、25mMのクエン酸、pH4.5）中の15ミリリットルでセファデックスG-50ビーズの1グラムを膨潤使用前に室温で少なくとも3時間。各実験は、膨潤したビーズの〜3ミリリットルが必要です。せいぜい数日、4℃で膨張したビーズにしてください。 </li><li>リポソームは、室温で解凍している間、各列〜3メートルに注ぐ膨潤したG-50ビーズリットル。 RTで重力流によってそれらが乾燥してみましょう。これは通常、1〜2分かかります。 </li><li> 0.4メートルテフロンカットオフを使用したミニ押出機を通してテオを11回押し出して単ラメラ小胞を準備します。 </li><li>プラスチック製の丸底チューブ内の列を配置します。過剰な溶液を除去するためのカラムをスピン。臨床遠心機で1400×gで20〜30秒間遠心する。 </li><li>フロースルーを捨て、13×100mmのガラス管内の場所の列と列に押し出された小胞の100μlを添加する。臨床遠心機で500×gで1分間コラムスピン。 </li><li>ステップ6.5で記録チャンバーに追加され、フロースルーの〜200μlのを収集します。 </li></ol> 6.流出測定<ol><li>記録チャンバーに置き参照2mlの100mMのKClを（接地）チャンバと外部バッファ1.8mlの（1のKCl、150mMのK 2 SO 4、25mMのクエン酸、pH4.5中）。内部の間のわずかな浸透圧の不均衡と外部のソリューションは影響しません</li><li>取得プログラムを起動します。これは数分かかることがあり、ベースラインが平衡化しましょう​​。 </li><li>信号が安定したベースラインを（リポソームは準備ができていると列を乾燥）に達すると、（ 図3A）の記録を開始。 </li><li>システム（ 図2A）を校正するために10 mMのKCl溶液の15μlのを追加します。 </li><li>リポソームを追加します。プロテオリポソーム（ 図3A）から-小さなジャンプは、外部のClの除去が不完全に見えるかもしれません。ベースラインが安定するまで待ちます。 </li><li>流出（ 図3A）を開始するためにバリノマイシン（EtOH中で1mg / mlで1μl）を追加します。 </li><li>流出がそれプラトー（ 図3A）までの時間経過を実行してみましょう。 </li><li>すべてのリポソーム（ 図3A）を溶解するために、外部緩衝液中で調製1.5 Mβオクチルグルコシド（β-OG）の40μlを添加する。録音を終了します。 </li></ol> 7.データAnalysis <ol><li> ASCIIまたはテキスト形式でのトレースファイルをエクスポートし、選択した解析プログラムにインポート。 </li><li>以下の点（ 図3A）の電圧を測定します。 記録の開始時（V 0）。 較正パルス（V 校正 ）を添加した後、 リポソーム（V リポ ）を添加した後、 流出（V フィン ）の終わりに、 洗剤（V totは ）を添加した後、 ベースラインV 0 = 0となるよう電圧。 </li><li>の実験値を決定するために、ネルンスト - プランク方程式を使用して、 <img alt="式3" fo:content-width=".3in" src="/files/ftp_upload/52369/52369eq3.jpg" />測定することにより、 <img alt="式4" fo:content-width="3in" src="/files/ftp_upload/52369/52369eq4.jpg" /> 巻カルは、実験開始時の室容積はでμL、1800での校正パルスのボリューム表現されている場合1; L、[Clで] CAL /中 Clである-校正パルスのとMMとΔVCALで外部バッファの濃度は、校正パルス後に測定mV単位のジャンプです。 注：αのこの経験的な決定は、3の目的があります。それは、システムが適切に応答していることを保証し、実験間の機器の応答の一貫性の尺度を提供していますだけでなく、間違いが解製作に行われなかったことを確認する。 </li><li>次のように各ステップの後のCl濃度を計算します。 <img alt="式5" fo:content-width="3.5in" src="/files/ftp_upload/52369/52369eq5.jpg" /> <img alt="式6" fo:content-width="3.5in" src="/files/ftp_upload/52369/52369eq6.jpg" /> <img alt="式7" fo:content-width="3.5in" src="/files/ftp_upload/52369/52369eq7.jpg" /> 要因400分の3は、2000μlの最終容量に15μlの校正パルスの希釈から来ている。 </li><li>計算学会各ステップで[CL &#39;の変化、ΔCL リポ/フィン/ TOTを食べました。 </li><li>とはCl（t）がV（t）を変換する <img alt="式8" fo:content-width="3.5in" src="/files/ftp_upload/52369/52369eq8.jpg" /> 直接の重要なポイントで &#39;CL値を決定し、内部統制などの計算値と比較します。 </li><li>トレースを正規のCl 相対 リポ = 0とCl REL TOT = 1となるよう <img alt="式9" fo:content-width="3.5in" src="/files/ftp_upload/52369/52369eq9.jpg" /></li><li>次式に流出時間経過をフィット： <img alt="式10" fo:content-width="3.5in" src="/files/ftp_upload/52369/52369eq10.jpg" /> 実験的にはClを測定することによって決定される漏れ- - Lは、Clの割合である場合、同じ条件及びτで製造したタンパク質を含まないリポソームからの流出は、プロセスの時定数である。 </li><li> V、初期速度を計算します。 ここΔCL フィンはミリモルで発現され、Vはμlのチャンバの容積である。 </li><li>輸送速度/コンダクタンスを計算します <img alt="式12" fo:content-width="3.5in" src="/files/ftp_upload/52369/52369eq12.jpg" /> pがP / Lであり、MWは、活性複合体の分子量は、kDaの中で発現され</li></ol>

<ol>
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L., Kolmakova-Partensky, L., Miller, 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+family+of+fluoride-specific+ion+channels+with+dual-topology+architecture.">A family of fluoride-specific ion channels with dual-topology architecture.</a> Elife. 2, e01084 (2013).</li><li>Nimigean, C., Shane, T., Miller, 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+cyclic+nucleotide+modulated+prokaryotic+K++channel.">A cyclic nucleotide modulated prokaryotic K+ channel.</a> J Gen Physiol. 124, 7 (2004).</li><li>Brohawn, S. G., del M&#225;rmol, ., J, R., MacKinnon, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crystal+Structure+of+the+Human+K2P+TRAAK,+a+Lipid-+and+Mechano-Sensitive+K++Ion+Channel.">Crystal Structure of the Human K2P TRAAK, a Lipid- and Mechano-Sensitive K+ Ion Channel.</a> Science. 335, 436-441 (2012).</li><li>Jayaram, H., Robertson, J. L., Wu, F., Williams, C., Miller, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+of+a+slow+CLC+Cl-/H++antiporter+from+a+cyanobacterium.">Structure of a slow CLC Cl-/H+ antiporter from a cyanobacterium.</a> Biochemistry. 50, 788-794 (2011).</li></ol>

The authors declare no competing financial interests.

精製された陰イオン選択的チャネルまたはリポソーム中に再構成トランスポーターによって媒介輸送-私たちは、詳細はClを測定するためのプロトコルを記載している。交換CLC-EC1 -使用例は、原核生物のH + / CLだった。検討中のイオンに適したものでAgCl電極ただし、方法論は、容易にリガンド12,13,15、電圧11,12、またはAgを交換することによって、異なる...

最後の二つの過剰発現および膜輸送タンパク質を精製する能力が劇的に増加している数十年：イオンチャネル、プライマリとセカンダリのトランスポーターは、現在日常的に異種発現系、ならびに天然の供給源から精製される。これらのタンパク質の安定性を、発現をモニタリング改善し、抽出を容易にし、強化するための新しいアプローチが常に1-5開発されている。これらの技術革新は、順番に、その機能の構造的な拠点の我々の理解を高め、膜タンパク質上の原子レベルの構造情報の爆発をトリガーに尽力している。対照的に、我々の能力は、いくつかの場合において、高分解能の構造情報をこのように定量的構造に基づいた予測をテストする我々の能力を制限する、定性機能的データが付随するように、同じ割合で増加しなかった精製されたタンパク質の機能的特性をプローブする。したがって、developmen定量的および一般化機能アッセイのtは膜タンパク質機能のメカニズムの基盤の解明に向けた重要なステップである。 チャネルおよびトランスポーター-ここでは、定量的に精製され、再構成されたCl -の主要な機能的特性を決定するために用いることができる流出アッセイを記載する。アッセイの基礎となる原理は、輸送システムの様々な、ならびに非イオン輸送タンパク質に一般化することができる。チャネル/大型のClの存在下でのトランス- -リポソームは、精製されたClで再構成する勾配（ 図1A、B）。のCl -の流出は、我々の場合K +イオノフォアバリノマイシンに、対イオン流束を可能にするために、イオノフォアを添加することによって開始のClによって確立された電圧をシャントれている-勾配及びKの平衡電位に初期の膜電位を設定する+ 6,7。トンなしそれは膜電位の発生により阻止されるように流出が発生し、 -彼は有意な正味のClをイオノフォアん。 -流出、およびf 0、活性タンパク質を含有しないリポソームの割合τ、Cl -の時定数：データは、定量的に2測定可能なパラメータ（ 図1C）によって記載されている。 τおよびf 0から一体のCl -輸送速度、活性タンパク質の画分と活性複合体の分子量は8導出することができる。既知の構造および機能の交換-技術はCLC-EC1、よく特徴付けCLC型H + / Clで再構成されたプロテオリポソームを用いて、ここに示されている。このアッセイは、容易に又は活性電圧および/またはリガンドの存在に依存して異なるイオン選択性チャネルまたは輸送体に一般化される。さらに、このアッセイは、小分子は、直接再構成タンパク質に影響を与えるかどうかを決定するために用いることができるこれらの化合物の効果を定量する方法、および膜組成物又は脂質修飾試薬は、再構成されたチャネルおよび輸送体の機能に影響を与える。

<table><tbody><tr><td>Liposomicator, Avanti Polar Lipids Inc.</td><td>&amp;nbsp;Avanti Polar Lipids Inc.</td><td>610200</td><td></td></tr><tr><td>IEC Centra CL2 Benchtop</td><td>Thermo Scientific</td><td></td><td></td></tr><tr><td>Orion Research Model 701A Digital pH-mV meter</td><td></td><td></td><td>These can be found on Ebay.</td></tr><tr><td>Non-functional pH probe</td><td></td><td></td><td>Any pH meter probe with silver wires will work. The glass/plastic coating needs to be removed and the wires cleaned.</td></tr><tr><td>DI-710 Data Logger</td><td>DATAQ instruments</td><td></td><td></td></tr><tr><td>WinDAQ acquisition software</td><td>DATAQ instruments</td><td></td><td></td></tr><tr><td>Pierce Disposable Plastic Columns, Gravity-flow, 2ml</td><td>Pierce (Thermo Scientific)</td><td>29922</td><td></td></tr><tr><td>KIMAX Culture Tubes, Disposable, Borosilicate Glass</td><td>Kimble Chase</td><td>73500-13100</td><td></td></tr><tr><td>Extruder Set With Holder/Heating Block</td><td>Avanti Polar Lipids Inc.</td><td>610000</td><td></td></tr><tr><td>Computer</td><td></td><td></td><td></td></tr></tbody></table>

a proteoliposome-based efflux assay to determine single-molecule properties of cl- channels and transporters

The last 15 years have been characterized by an explosion in the ability to overexpress and purify membrane proteins from prokaryotic organisms as well as from eukaryotes. This increase has been largely driven by the successful push to obtain structural information on membrane proteins. However, the ability to functionally interrogate these proteins has not advanced at the same rate and is often limited to qualitative assays of limited quantitative value, thereby limiting the mechanistic insights that they can provide. An assay to quantitatively investigate the transport activity of reconstituted Cl- channels or transporters is described. The assay is based on the measure of the efflux rate of Cl- from proteoliposomes following the addition of the K+ ionophore valinomycin to shunt the membrane potential. An ion sensitive electrode is used to follow the time-course of ion efflux from proteoliposomes reconstituted with the desired protein. The method is highly suited for mechanistic studies, as it allows for the quantitative determination of key properties of the reconstituted protein, such as its unitary transport rate, the fraction of active protein and the molecular mass of the functional unit. The assay can also be utilized to determine the effect of small molecule compounds that directly inhibit/activate the reconstituted protein, as well as to test the modulatory effects of the membrane composition or lipid-modifying reagents. Where possible, direct comparison between results obtained using this method were found to be in good agreement with those obtained using electrophysiological approaches. The technique is illustrated using CLC-ec1, a CLC-type H+/Cl- exchanger, as a model system. The efflux assay can be utilized to study any Cl- conducting channel/transporter and, with minimal changes, can be adapted to study any ion-transporting protein.

交換器、リポソーム中に再構成-精製されたCLC-EC1、原核生物CLC型H + / CLにより媒介輸送-私たちは、詳細かつ堅牢なのClを測定するためのプロトコルについて説明します。実験の概略図を図3に示されている精製されたCLC-EC1及び高い内部のClを含有する再構成されたプロテオリポソームは、 -低のClを含有する浴溶液に浸漬されている- 。これ?...

Watch this Scientific Journal Video about A Proteoliposome-Based Efflux Assay to Determine Single-molecule Properties of Cl- Channels and Transporters at JoVE.com

A Proteoliposome-Based Efflux Assay to Determine Single-molecule Properties of Cl- Channels and Transporters

Proteoliposomes are used to study purified channels and transporters reconstituted in a well-defined biochemical environment. An experimental procedure to measure efflux mediated by these proteins is illustrated. The steps to prepare proteoliposomes, perform the recordings, and analyze data to quantitatively determine the functional properties of the reconstituted protein are described.

プロテオリポソー​​ムベースの流出アッセイのClの単一分子特性を決定する<sup&gt; -</sup&gt;チャネルとトランスポーター

The last 15 years have been characterized by an explosion in the ability to overexpress and purify membrane proteins from prokaryotic organisms as well as ...

a-proteoliposome-based-efflux-assay-to-determine-single-molecule

Research

JoVE Journal

Biology

A Proteoliposome-Based Efflux Assay to Determine Single-molecule Properties of Cl- Channels and Transporters

9.8K ビュー.  Weill Cornell Medical College. Proteoliposomes are used to study purified channels and transporters reconstituted in a well-defined biochemical environment. An experimental procedure to measure efflux mediated by these proteins is illustrated. The steps to prepare proteoliposomes, perform the recordings, and analyze data to quantitatively determine the functional properties of the reconstituted protein are described.

ビデオ: A Proteoliposome-Based Efflux Assay to Determine Single-molecule Properties of Cl- Channels and Transporters

Cholesterol Efflux Assay

Cholesterol content of cells must be maintained within the very tight limits, too much or too little cholesterol in a cell results in disruption of cellular membranes, apoptosis and necrosis 1. Cells can source cholesterol from intracellular synthesis and from plasma lipoproteins, both sources are sufficient to fully satisfy cells' requirements for cholesterol. The processes of cholesterol synthesis and uptake are tightly regulated and deficiencies of cholesterol are rare 2. Excessive cholesterol is more common problem 3. With the exception of hepatocytes and to some degree adrenocortical cells, cells are unable to degrade cholesterol. Cells have two options to reduce their cholesterol content: to convert cholesterol into cholesteryl esters, an option with limited capacity as overloading cells with cholesteryl esters is also toxic, and cholesterol efflux, an option with potentially unlimited capacity. Cholesterol efflux is a specific process that is regulated by a number of intracellular transporters, such as ATP binding cassette transporter proteins A1 (ABCA1) and G1 (ABCG1) and scavenger receptor type B1. The natural acceptor of cholesterol in plasma is high density lipoprotein (HDL) and apolipoprotein A-I. 
The cholesterol efflux assay is designed to quantitate the rate of cholesterol efflux from cultured cells. It measures the capacity of cells to maintain cholesterol efflux and/or the capacity of plasma acceptors to accept cholesterol released from cells. The assay consists of the following steps. Step 1: labelling cellular cholesterol by adding labelled cholesterol to serum-containing medium and incubating with cells for 24-48 h. This step may be combined with loading of cells with cholesterol. Step 2: incubation of cells in serum-free medium to equilibrate labelled cholesterol among all intracellular cholesterol pools. This stage may be combined with activation of cellular cholesterol transporters. Step 3: incubation of cells with extracellular acceptor and quantitation of movement of labelled cholesterol from cells to the acceptor. If cholesterol precursors were used to label newly synthesized cholesterol, a fourth step, purification of cholesterol, may be required.
The assay delivers the following information: (i) how a particular treatment (a mutation, a knock-down, an overexpression or a treatment) affects the capacity of cell to efflux cholesterol and (ii) how the capacity of plasma acceptors to accept cholesterol is affected by a disease or a treatment. This method is often used in context of cardiovascular research, metabolic and neurodegenerative disorders, infectious and reproductive diseases.

The cholesterol assay is designed to quantitate the rate of cholesterol efflux from cultured cells and the capacity of plasma acceptors to accept cholesterol released from cells. The assay consists of labelling cells with cholesterol, equilibration of cholesterol among intracellular pools and release of cholesterol to an extracellular acceptor.

コレステロール流出アッセイ

Cholesterol content of cells must be maintained within the very tight limits, too much or too little cholesterol in a cell results in disruption of ...

医学

Models and Methods to Evaluate Transport of Drug Delivery Systems Across Cellular Barriers

Sub-micrometer carriers (nanocarriers; NCs) enhance efficacy of drugs by improving solubility, stability, circulation time, targeting, and release. Additionally, traversing cellular barriers in the body is crucial for both oral delivery of therapeutic NCs into the circulation and transport from the blood into tissues, where intervention is needed. NC transport across cellular barriers is achieved by: (i) the paracellular route, via transient disruption of the junctions that interlock adjacent cells, or (ii) the transcellular route, where materials are internalized by endocytosis, transported across the cell body, and secreted at the opposite cell surface (transyctosis). Delivery across cellular barriers can be facilitated by coupling therapeutics or their carriers with targeting agents that bind specifically to cell-surface markers involved in transport. Here, we provide methods to measure the extent and mechanism of NC transport across a model cell barrier, which consists of a monolayer of gastrointestinal (GI) epithelial cells grown on a porous membrane located in a transwell insert. Formation of a permeability barrier is confirmed by measuring transepithelial electrical resistance (TEER), transepithelial transport of a control substance, and immunostaining of tight junctions. As an example, ~200&#160;nm polymer NCs are used, which carry a therapeutic cargo and are coated with an antibody that targets a cell-surface determinant. The antibody or therapeutic cargo is labeled with 125I for radioisotope tracing and labeled NCs are added to the upper chamber over the cell monolayer for varying periods of time. NCs associated to the cells and/or transported to the underlying chamber can be detected. Measurement of free 125I allows subtraction of the degraded fraction. The paracellular route is assessed by determining potential changes caused by NC transport to the barrier parameters described above. Transcellular transport is determined by addressing the effect of modulating endocytosis and transcytosis pathways.

Many therapeutic applications require safe and efficient transport of drug carriers and their cargoes across cellular barriers in the body. This article describes an adaptation of established methods to evaluate the rate and mechanism of transport of drug nanocarriers (NCs) across cellular barriers, such as the gastrointestinal (GI) epithelium.

携帯の障壁を通過する薬物送達システムの輸送を評価するためのモデルと方法

Sub-micrometer carriers (nanocarriers; NCs) enhance efficacy of drugs by improving solubility, stability, circulation time, targeting, and release. ...

生物工学

Single Liposome Measurements for the Study of Proton-Pumping Membrane Enzymes Using Electrochemistry and Fluorescent Microscopy

Proton-pumping enzymes of electron transfer chains couple redox reactions to proton translocation across the membrane, creating a proton-motive force used for ATP production. The amphiphilic nature of membrane proteins requires particular attention to their handling, and reconstitution into the natural lipid environment is indispensable when studying membrane transport processes like proton translocation. Here, we detail a method that has been used for the investigation of the proton-pumping mechanism of membrane redox enzymes, taking cytochrome bo3 from Escherichia coli as an example. A combination of electrochemistry and fluorescence microscopy is used to control the redox state of the quinone pool and monitor pH changes in the lumen. Due to the spatial resolution of fluorescent microscopy, hundreds of liposomes can be measured simultaneously while the enzyme content can be scaled down to a single enzyme or transporter per liposome. The respective single enzyme analysis can reveal patterns in the enzyme functional dynamics that might be otherwise hidden by the behavior of the whole population. We include a description of a script for automated image analysis.

Here, we present a protocol to study the molecular mechanism of proton translocation across lipid membranes of single liposomes, using cytochrome bo3 as an example. Combining electrochemistry and fluorescence microscopy, pH changes in the lumen of single vesicles, containing single or multiple enzyme, can be detected and analyzed individually.

電気化学と蛍光顕微鏡を用いたプロトン ポンプ膜酵素の研究のための単一リポソーム測定

Proton-pumping enzymes of electron transfer chains couple redox reactions to proton translocation across the membrane, creating a proton-motive force used ...

生化学

Selection of Transporter-Targeted Inhibitory Nanobodies by Solid-Supported-Membrane (SSM)-Based Electrophysiology

Single domain antibodies (nanobodies) have been extensively used in mechanistic and structural studies of proteins and they pose an enormous potential as tools for developing clinical therapies, many of which depend on the inhibition of membrane proteins such as transporters. However, most of the methods used to determine the inhibition of transport activity are difficult to perform in high-throughput routines and depend on labeled substrates availability thereby complicating the screening of large nanobody libraries. Solid-supported membrane (SSM) electrophysiology is a high-throughput method, used for characterizing electrogenic transporters and measuring their transport kinetics and inhibition. Here we show the implementation of SSM-based electrophysiology to select inhibitory and non-inhibitory nanobodies targeting an electrogenic secondary transporter and to calculate nanobodies inhibitory constants. This technique may be especially useful for selecting inhibitory nanobodies targeting transporters for which labeled substrates are not available.

Selection of Transporter-Targeted Inhibitory Nanobodies by Solid-Supported-Membrane SSM-Based Electrophysiology

Nanobodies are important tools in structural biology and pose a great potential for the development of therapies. However, the selection of nanobodies with inhibitory properties can be challenging. Here we demonstrate the use of solid-supported-membrane (SSM)-based electrophysiology for the classification of inhibitory and non-inhibitory nanobodies targeting electrogenic membrane transporters.

固体支持膜(SSM)ベースの電気生理学によるトランスポーター標的阻害ナノボディの選択

Single domain antibodies (nanobodies) have been extensively used in mechanistic and structural studies of proteins and they pose an enormous potential as ...

Gramicidin-based Fluorescence Assay; for Determining Small Molecules Potential for Modifying Lipid Bilayer Properties

Many drugs and other small molecules used to modulate biological function are amphiphiles that adsorb at the bilayer/solution interface and thereby alter lipid bilayer properties. This is important because membrane proteins are energetically coupled to their host bilayer by hydrophobic interactions. Changes in bilayer properties thus alter membrane protein function, which provides an indirect way for amphiphiles to modulate protein function and a possible mechanism for "off-target" drug effects. We have previously developed an electrophysiological assay for detecting changes in lipid bilayer properties using linear gramicidin channels as probes 3,12. Gramicidin channels are mini-proteins formed by the transbilayer dimerization of two non-conducting subunits. They are sensitive to changes in their membrane environment, which makes them powerful probes for monitoring changes in lipid bilayer properties as sensed by bilayer spanning proteins. We now demonstrate a fluorescence assay for detecting changes in bilayer properties using the same channels as probes. The assay is based on measuring the time-course of fluorescence quenching from fluorophore-loaded large unilamellar vesicles due to the entry of a quencher through the gramicidin channels. We use the fluorescence indicator/quencher pair 8-aminonaphthalene-1,3,6-trisulfonate (ANTS)/Tl+ that has been successfully used in other fluorescence quenching assays 5,13. Tl+ permeates the lipid bilayer slowly 8 but passes readily through conducting gramicidin channels 1,14. The method is scalable and suitable for both mechanistic studies and high-throughput screening of small molecules for bilayer-perturbing, and potential "off-target", effects. We find that results using this method are in good agreement with previous electrophysiological results 12.

We introduce a fast fluorescence-based assay that monitors the rate of fluorescence quenching as a measure of gramicidin channel activity. The gramicidin channels are used as molecular force transducers to monitor changes in lipid bilayer properties as sensed by bilayer spanning proteins.

グラミシジンベースの蛍光アッセイ、脂質二重層のプロパティの変更の可能性小分子を決定するための

Many drugs and other small molecules used to modulate biological function are amphiphiles that adsorb at the bilayer/solution interface and thereby alter ...

生物学

A Quantitative Fluorescence Microscopy-based Single Liposome Assay for Detecting the Compositional Inhomogeneity Between Individual Liposomes

Most research employing liposomes as membrane model systems or drug delivery carriers relies on bulk read-out techniques and thus intrinsically assumes all liposomes of the ensemble to be identical. However, new experimental platforms able to observe liposomes at the single-particle level have made it possible to perform highly sophisticated and quantitative studies on protein-membrane interactions or drug carrier properties on individual liposomes, thus avoiding errors from ensemble averaging. Here we present a protocol for preparing, detecting, and analyzing single liposomes using a fluorescence-based microscopy assay, facilitating such single-particle measurements. The setup allows for imaging individual liposomes in a massive parallel manner and is employed to reveal intra-sample size and compositional inhomogeneities. Additionally, the protocol describes the advantages of studying liposomes at the single liposome level, the limitations of the assay, and the important features to be considered when modifying it to study other research questions.

This protocol describes the fabrication of liposomes and how these can be immobilized on a surface and imaged individually in a massive parallel manner using fluorescence microscopy. This allows for the quantification of the size and compositional inhomogeneity between single liposomes of the population.

個々のリポソーム間の組成不均一性を検出するための定量的蛍光顕微鏡ベースの単一リポソームアッセイ

Most research employing liposomes as membrane model systems or drug delivery carriers relies on bulk read-out techniques and thus intrinsically assumes ...

High-throughput Screening for Small-molecule Modulators of Inward Rectifier Potassium Channels

Specific members of the inward rectifier potassium (Kir) channel family are postulated drug targets for a variety of disorders, including hypertension, atrial fibrillation, and pain1,2. For the most part, however, progress toward understanding their therapeutic potential or even basic physiological functions has been slowed by the lack of good pharmacological tools. Indeed, the molecular pharmacology of the inward rectifier family has lagged far behind that of the S4 superfamily of voltage-gated potassium (Kv) channels, for which a number of nanomolar-affinity and highly selective peptide toxin modulators have been discovered3. The bee venom toxin tertiapin and its derivatives are potent inhibitors of Kir1.1 and Kir3 channels4,5, but peptides are of limited use therapeutically as well as experimentally due to their antigenic properties and poor bioavailability, metabolic stability and tissue penetrance. The development of potent and selective small-molecule probes with improved pharmacological properties will be a key to fully understanding the physiology and therapeutic potential of Kir channels.
The Molecular Libraries Probes Production Center Network (MLPCN) supported by the National Institutes of Health (NIH) Common Fund has created opportunities for academic scientists to initiate probe discovery campaigns for molecular targets and signaling pathways in need of better pharmacology6. The MLPCN provides researchers access to industry-scale screening centers and medicinal chemistry and informatics support to develop small-molecule probes to elucidate the function of genes and gene networks. The critical step in gaining entry to the MLPCN is the development of a robust target- or pathway-specific assay that is amenable for high-throughput screening (HTS).
Here, we describe how to develop a fluorescence-based thallium (Tl+) flux assay of Kir channel function for high-throughput compound screening7,8,9,10.The assay is based on the permeability of the K+ channel pore to the K+ congener Tl+. A commercially available fluorescent Tl+ reporter dye is used to detect transmembrane flux of Tl+ through the pore. There are at least three commercially available dyes that are suitable for Tl+ flux assays: BTC, FluoZin-2, and FluxOR7,8. This protocol describes assay development using FluoZin-2. Although originally developed and marketed as a zinc indicator, FluoZin-2 exhibits a robust and dose-dependent increase in fluorescence emission upon Tl+ binding. We began working with FluoZin-2 before FluxOR was available7,8 and have continued to do so9,10. However, the steps in assay development are essentially identical for all three dyes, and users should determine which dye is most appropriate for their specific needs. We also discuss the assay's performance benchmarks that must be reached to be considered for entry to the MLPCN. Since Tl+ readily permeates most K+ channels, the assay should be adaptable to most K+ channel targets.

Methods for developing and validating a quantitative fluorescence assay for measuring the activity of inward rectifier potassium (Kir) channels for high-throughput compound screening is presented.

内向き整流カリウムチャネルの小分子モジュレーターのためのハイスループットスクリーニング

Specific members of the inward rectifier potassium (Kir) channel family are postulated drug targets for a variety of disorders, including hypertension, ...

In vitro Investigation of the MexAB Efflux Pump From Pseudomonas aeruginosa

There is an emerging scientific need for reliable tools for monitoring membrane protein transport. We present a methodology leading to the reconstitution of efflux pumps from the Gram-negative bacteria Pseudomonas aeruginosa in a biomimetic environment that allows for an accurate investigation of their activity of transport. Three prerequisites are fulfilled: compartmentation in a lipidic environment, use of a relevant index for transport, and generation of a proton gradient. The membrane protein transporter is reconstituted into liposomes together with bacteriorhodopsin, a light-activated proton pump that generates a proton gradient that is robust as well as reversible and tunable. The activity of the protein is deduced from the pH variations occurring within the liposome, using pyranin, a pH-dependent fluorescent probe. We describe a step-by-step procedure where membrane protein purification, liposome formation, protein reconstitution, and transport analysis are addressed. Although they were specifically designed for an RND transporter, the described methods could potentially be adapted for use with any other membrane protein transporter energized by a proton gradient.

In vitro Investigation of the MexAB Efflux Pump From Pseudomonas aeruginosa

We present a protocol for the in vitro investigation of efflux pumps from Pseudomonas aeruginosa. This protocol allows for the generation of a robust, reversible, and tunable proton gradient within the liposome membrane and hence should be adaptable to any membrane protein energized by the protomotive force.

緑膿菌からの MexAB排出ポンプの体外調査に

There is an emerging scientific need for reliable tools for monitoring membrane protein transport. We present a methodology leading to the reconstitution ...

Functional Reconstitution and Channel Activity Measurements of Purified Wildtype and Mutant CFTR Protein

The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a unique channel-forming member of the ATP Binding Cassette (ABC) superfamily of transporters. The phosphorylation and nucleotide dependent chloride channel activity of CFTR has been frequently studied in whole cell systems and as single channels in excised membrane patches. Many Cystic Fibrosis-causing mutations have been shown to alter this activity. While a small number of purification protocols have been published, a fast reconstitution method that retains channel activity and a suitable method for studying population channel activity in a purified system have been lacking. Here rapid methods are described for purification and functional reconstitution of the full-length CFTR protein into proteoliposomes of defined lipid composition that retains activity as a regulated halide channel. This reconstitution method together with a novel flux-based assay of channel activity is a suitable system for studying the population channel properties of wild type CFTR and the disease-causing mutants F508del- and G551D-CFTR. Specifically, the method has utility in studying the direct effects of phosphorylation, nucleotides and small molecules such as potentiators and inhibitors on CFTR channel activity. The methods are also amenable to the study of other membrane channels/transporters for anionic substrates.

Described here is a rapid and effective procedure for functional reconstitution of purified wild-type and mutant CFTR protein that preserves activity for this chloride channel, which is defective in Cystic Fibrosis. Iodide efflux from reconstituted proteoliposomes mediated by CFTR allows studies of channel activity and the effects of small molecules.

精製された野生型および変異型CFTRタンパク質の機能的再構成とチャネル活性の測定

The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a unique channel-forming member of the ATP Binding Cassette (ABC) superfamily of ...

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

Membrane protein transport on the single protein level still evades detailed analysis, if the substrate translocated is non-electrogenic. Considerable efforts have been made in this field, but techniques enabling automated high-throughput transport analysis in combination with solvent-free lipid bilayer techniques required for the analysis of membrane transporters are rare. This class of transporters however is crucial in cell homeostasis and therefore a key target in drug development and methodologies to gain new insights desperately needed.
The here presented manuscript describes the establishment and handling of a novel biochip for the analysis of membrane protein mediated transport processes at single transporter resolution. The biochip is composed of microcavities enclosed by nanopores that is highly parallel in its design and can be produced in industrial grade and quantity. Protein-harboring liposomes can directly be applied to the chip surface forming self-assembled pore-spanning lipid bilayers using SSM-techniques (solid supported lipid membranes). Pore-spanning parts of the membrane are freestanding, providing the interface for substrate translocation into or out of the cavity space, which can be followed by multi-spectral fluorescent readout in real-time. The establishment of standard operating procedures (SOPs) allows the straightforward establishment of protein-harboring lipid bilayers on the chip surface of virtually every membrane protein that can be reconstituted functionally. The sole prerequisite is the establishment of a fluorescent read-out system for non-electrogenic transport substrates.
High-content screening applications are accomplishable by the use of automated inverted fluorescent microscopes recording multiple chips in parallel. Large data sets can be analyzed using the freely available custom-designed analysis software. Three-color multi spectral fluorescent read-out furthermore allows for unbiased data discrimination into different event classes, eliminating false positive results.
The chip technology is currently based on SiO2 surfaces, but further functionalization using gold-coated chip surfaces is also possible.

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.

単一のタンパク質解像度で高並列ナノ細孔チップシステムにより分析膜輸送プロセス

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

プロテオリポソームベースの流出アッセイのClの単一分子特性を決定する

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この動画の章

コレステロール流出アッセイ

携帯の障壁を通過する薬物送達システムの輸送を評価するためのモデルと方法

電気化学と蛍光顕微鏡を用いたプロトンポンプ膜酵素の研究のための単一リポソーム測定

固体支持膜(SSM)ベースの電気生理学によるトランスポーター標的阻害ナノボディの選択

グラミシジンベースの蛍光アッセイ、脂質二重層のプロパティの変更の可能性小分子を決定するための

個々のリポソーム間の組成不均一性を検出するための定量的蛍光顕微鏡ベースの単一リポソームアッセイ

内向き整流カリウムチャネルの小分子モジュレーターのためのハイスループットスクリーニング

緑膿菌からの MexAB排出ポンプの体外調査に

精製された野生型および変異型CFTRタンパク質の機能的再構成とチャネル活性の測定

単一のタンパク質解像度で高並列ナノ細孔チップシステムにより分析膜輸送プロセス

プロテオリポソー​​ムベースの流出アッセイのClの単一分子特性を決定する

要約

さらに動画を探す

この動画の章

コレステロール流出アッセイ

携帯の障壁を通過する薬物送達システムの輸送を評価するためのモデルと方法

電気化学と蛍光顕微鏡を用いたプロトン ポンプ膜酵素の研究のための単一リポソーム測定

固体支持膜(SSM)ベースの電気生理学によるトランスポーター標的阻害ナノボディの選択

グラミシジンベースの蛍光アッセイ、脂質二重層のプロパティの変更の可能性小分子を決定するための

個々のリポソーム間の組成不均一性を検出するための定量的蛍光顕微鏡ベースの単一リポソームアッセイ

内向き整流カリウムチャネルの小分子モジュレーターのためのハイスループットスクリーニング

緑膿菌からの MexAB排出ポンプの体外調査に

精製された野生型および変異型CFTRタンパク質の機能的再構成とチャネル活性の測定

単一のタンパク質解像度で高並列ナノ細孔チップシステムにより分析膜輸送プロセス

プロテオリポソームベースの流出アッセイのClの単一分子特性を決定する

電気化学と蛍光顕微鏡を用いたプロトンポンプ膜酵素の研究のための単一リポソーム測定