Bu çalışma, Japonya Uehara Memorial Foundation (ES) yanı sıra Whitehall Vakfı, Ulusal Nörolojik Bozukluklar ve İnme ve Stein-Oppenheimer Endowment Ödülü (BSK) Enstitüsü tarafından desteklendi.

DENEYSEL PROSEDÜRLER Deneysel işlemin bir adım daha akıllıca bir şekilde aşağıda açıklanan iki ana bölümden oluşmaktadır. Bölüm 1: HAZIRLAMA hipokampal astrosit KÜLTÜRLER Kısaca, karışık, hipokampal astrosit nöron kültürleri iyi kurulmuş bir protokol 1,2,3 kullanılarak hazırlanmıştır. Prosedürü, sağlıklı kültürlü astrositler verim için optimize edilmiş. Aşağıda listelenen tüm işlemler, steril bir ortamda böyle bir laminer akış kaputu gibi yapılmalıdır. Hazırlanması lamelleri <ul><li> 22 mm lamelleri (VWR, 48.380-068) </li><li> Poly-D-Lizin (PDL, Sigma P0899), alikotları (1 mg / ml) </li><li> Laminin alikotları (20 mg / ml): 1 mg / ml laminin solüsyonu (Sigma L2020) ile 49 ml steril su ekleyin, -20 ° C&#39;de 1.2 ml alikotları ve mağaza </li></ul><ol><li> (50 mg / ml) steril su PDL çözülür </li><li> Lamelleri Otoklav, PDL steril su ve yeri (100 lamelleri için 20 ml) ile durulayın. Gece boyunca oda sıcaklığında bekletin. </li><li> PDL steril su ile (3 geniş yıkar) değiştirin. Sonra 4 lamelleri ve mağaza ° C kuru </li><li> 6 plaka (Steril Bioscience BD Kapaklar multiwell Düz Tabanlı Tabaklar) steril bir kuyu astrositler, bireysel lamelleri kaplama bir gün önce. Her lamel laminin ul 400 koyun ve buharlaşmasını önlemek için inkübatör, gece inkübe edin. </li></ol> Diseksiyon Diseksiyon medya: <ul><li> 500 ml Earle Dengeli Tuz Çözeltisi (EBSS) (1X), sıvı (Invitrogen, 14.155-063) </li><li> 5 ml Hepes solüsyonu (Sigma, H0887) </li></ul> Hipokampal medya: <ul><li> 412,5 ml Minimum Essential Medium (MEM) (1X), sıvı Earle Kullanıcı tuz içerir, ancak hiçbir L-glutamin veya fenol kırmızısı (Invitrogen, 51.200-038) </li><li> 10 ml glikoz (Sigma, D-(+) GLİKOZ susuz SIGMA ULTRA G7528) 1 M MEM </li><li> 5 ml Penisilin-Streptomisin (Invitrogen, 15.140-122) </li><li> 5 ml sodyum piruvat çözüm (Sigma, S8636) </li><li> 12.5 ml Hepes çözüm 1 M (Sigma, H0887) </li><li> 5 ml N-2 Eki (100X), sıvı (Invitrogen, 17.502-048) </li><li> 50 ml At Serum, Isı-İnaktive (Invitrogen, 26.050-088) </li></ul> Papain çözüm: <ul><li> Worthington papain-022 flakon (LK003178; nihai konsantrasyonu, 20 U / ml), diseksiyon medya 5 ml ve 37 ° C 60 dakika inkübe edin. </li></ul><ol><li> P1 (genellikle 2 yavrular) ulusal düzenlemeler ve yerel Kurumsal Hayvan Bakım ve Kullanım Kurulu tarafından onaylanmış ve onaylanan yönergeleri izleyerek yaşlı sıçan yavrular başını kesmek. </li><li> Petri kabındaki soğuk diseksiyon medya ile doldurulmuş deri ve kafatası yer ve beyin çıkarın. </li><li> Meninksler kaldırıldı, her iki yarımkürede incelemek ve hippocampi teşrih. </li><li> Hippocampi ~ 37 ° papain çözüm 1X1 mm parçaları ve hazmı ° C 11-13 dakika süreyle içine doğrayın. </li><li> Doku parçaları yerleştikten sonra, kaldırmak dikkatle papain ve enzim bütün izlerini kaldırmak için 5 ml hipokampal orta eklemek. Hipokampal orta (2 ml) ve bu adımı tekrar süspansiyon tekrarlayın. </li><li> Kümeleri, üç aşamalı olarak küçük delikleri (1000 mm, ~ 500 mm ~ 300 mikron) alev cilalı pipetler sol kalmayana dek hücreleri ~ 5 kez Karışım. </li><li> Triturated sonra, bir hücre süzgeç (gözenek boyutu, 70 mikron, BD Bioscience) aracılığıyla hücrelere geçerler. 10 ul süspansiyon hücreleri saymak. 400.000 hücre / ml sahip amacıyla hipokampal ortamın ses seviyesini ayarlayın. </li><li> Lamelleri kapalı laminin aspire ve lamel başına hücre süspansiyonu kapakları kuru önce, plaka 200 ul. </li><li> Onları inkübatörde 60 dakika ekleyiniz ve sonra iyi ortalama 2 ml hipokampal orta eklemek bırakın. </li><li> Ertesi gün, ölü hücreleri ve enkaz kaldırma ve 2 ml, önceden ısıtılmış taze hipokampal orta eklemek için eski hipokampal orta aspirat. </li></ol> Bakım Neurobasal medya: <ul><li> 500 ml neurobasal (Invitrogen, 12.348-017) </li><li> 10 ml B27 serum serbest eki (Invitrogen, 17.504-044) </li><li> 5 ml Penisilin-Streptomisin (Invitrogen, 15.140-122) </li><li> 1.25 ml L-glutamin (Invitrogen, 25.030-149) </li></ul> Kaplama dört gün sonra başlayan, neurobasal orta astrosit-nöron kültürler haftada iki kez besleyin. Sıcaklık ve CO 2 denge sağlaması için yaklaşık 30 dakika havalandırılan bir balonuna inkübatör medya Preincubate. Bölüm 2: KALSİYUM GÖRÜNTÜLEME Hipokampal kayıt tampon: 110 mM NaCl, 5.4 mMKCl, 1.8 mM CaCl 2, 0.8 mM MgCl 2, 10 mM D-glukoz, 10 mM HEPES (Sigma tüm kimyasallar), pH 7.4 (NaOH ile düzeltilmiş) . Astrositler kalsiyum göstergesi boya yükleme <ol><li> 2 ml hipokampal kayıt tampon DMSO 2.5 mcM Fluo-4, AM (Invitrogen, F-14.217) ve% 0.05 Pluronic ® F-127% 20 çözüm içeren dolu bir 6-plaka (Invitrogen, iyi bir kültür koyun P-3000MP) ve 10-30 dakika süreyle oda sıcaklığında inkübe edin. </li><li> Fluo-4 çözüm çıkarın ve 30 dakika oda sıcaklığında hipokampal kayıt tampon ve inkübe ile lamelleri 3 kere yıkayın. </li><li> Lamel odasına yerleştirin ve lens temizleme sıvı ile lamel diğer tarafında temiz. </li><li> Amaç küçük bir damla immersiyon yağı (Cargille Immersion Yağı TİPİ DF) koyun ve mikroskop (Olympus IX71) sahne odası (25 mm yuvarlak lamel için Warner Instruments Açık odası) koymak. </li><li> Iletim ışık kullanarak hücreleri hücrelerin nasıl göründüğüne bakmak ve onları almak için odak noktası haline bakın. Sonra (Vizyon KADAR Polychrome V) monokromatör gelen 488 nm hücreleri aydınlatmak ve Fluo-4 floresan sinyal üniforma ve astrositler saptanabilir olup olmadığını belirlemek. </li><li> EPI ve TIRF aydınlatma astrositler kalsiyum ölçmek için kullanın. </li></ol> TIRF mikroskopi Kısaca, biz bir Andor IXON DV887DCS EMCCD kamera ile donatılmış bir Olympus IX71 mikroskop kullanıyoruz. Eksitasyon ve görüntü alımı kontrolü TILLVision yazılımı kullanılarak elde edilir. 454/488/515 nm Argon (100 mW) ve 442 nm (45 mW) katı hal lazerleri kirişler kombine ve kontrollü bir KADAR Polyline lazer birleştirici, TIRF çift bağlantı kondansatör ve acoustoptical arasında ayarlanabilir filtre ve denetleyicisi (AOTF tüm TIRF kondenser içine giriş için Kineflex geniş bant fiber içine Fotonik) ve beslenen KADAR. Biz TIRF elde etmek için Olympus 60X 1.45 NA lens kullanın. Kamera kazancı en iyi sinyal-gürültü görüntüleri sağlamak için her astrosit ayarlanır. Arka plan ve TIRF mikroskopi ilkeleri, son zamanlarda, 5 4 gözden geçirilmiştir . Kullandığımız optik bileşenlerin çoğu şimdi Agilent Technologies (http://www.till-photonics.com/) bir parçası Fotonik, KADAR satın alındı. TIR penetrasyon derinliği aşağıdaki denklemler hesaplanabilir. <img style="float:left;" src="/files/ftp_upload/1142/equation.png" alt="Denklem" /> d = penetrasyon derinliği n1 = cam kırılma indisi n2 = kırılma indisi hücre insidansı = açısı NAI = sayısal açıklık insidansı Lazer TIRF için optimal aynı hizada olmasını sağlamak için 100 nm floresan boncuk (Invitrogen, F8803) gözlemlemek için yararlı bulabilirsiniz. Biz hala EPI ve TIRF mikroskopi ile boncuk çerçeveleri ve videoları mevcut. Zaman TIRF, bir sinyal-gürültü dramatik bir artış gözlemlemiştir ve boncuk Brown difüzyon gösterilecek. Kritik açı eşit olmasaydı oluşacak tehlikeye eğik aydınlatma yerine daha optimum TIRF oluşur emin olmak için düzenli olarak (haftada ~ kez) TIRF mikroskobu ile 100 nm boncuk davranışlarını gözlemlemek için yararlı buluyorum α (bkz. Şekil 1). G-protein kenetli reseptör agonistleri Uygulama Astrositler Gq-reseptörler 6, 7 metabotropik glutamat reseptörleri ve P2Y reseptörleri (agonist, ATP, ADP) de dahil olmak üzere çeşitli ifade eder. Bu reseptörlerin aktivasyonu astrositler içinde hücre içi kalsiyum düzeylerinde önemli artışlara yol açar. Örneğin, bir hücre içi kalsiyum yükselmeler astrositler 8-10 ATP (30 mcM) uygulama sırasında kolayca izleyebilirsiniz . Warner Instruments switcher VC-77SP Hızlı Adım Perfüzyon Sistemi (http://www.warneronline.com/index.cfm) olarak adlandırılan hızlı bir çözüm kullanın. ~ 10 ms &#39;den daha az bir süre içinde bu yöntemi çözümleri uygulanabilir. <img src="/files/ftp_upload/1142/Fig 1a.jpg" alt="Şekil 1" /> <img src="/files/ftp_upload/1142/fig1c.jpg" alt="" /> ŞEKİL 1 Karikatür ve fotoğrafları görüntüleme kurdu. A., (B) lazer montaj, kontrolörler ve kiriş kutuları bir fotoğraf gösterir iken, üzerine monte edilmiş bir airtable mikroskop bir fotoğraf gösterir. C. mikroskop aşamasında bir fotoğraf görüntüleme için monte edilen oda gösterir. Hızlı perfüzyon cihazı (step motor ve teta tüp ile birlikte) görülebilir bıraktı. Sağ tarafta bir Axopatch 200A amplifikatör headstage görülür. Karikatür set ışık yolu schematizes ve nasıl TIRF elde edilir. Lazer, kritik açı α immersiyon ortaya çıkar, böylece merkezi ayarlanır 60X 1.45 NA objektif lens ve konumunu arka odak düzlemi üzerinde duruldu. Bu noktada demiri düşük kırılma indisi orta mesafe λ (ana metin denklemi) ile toplam iç yansıma ve bozunur muzdarip. Bu durumda bu kayıt tampon astrositler ve astrositler kendilerini çevreleyen. Sonuç olarak plazma zarı ~ 100 nm içinde moleküllerin optik uyarım (ve dolayısıyla görüntüleme). Hücre içinde veya hücrenin üst yüzeyinde bu heyecanlı ise hücre karikatür, yeşil &quot;heyecan&quot; membran reseptörleri olarak gösterilir. TIRF mikroskopi tam bir hesap Steyer ve Almers 4 tarafından sağlanmıştır. <img src="/files/ftp_upload/1142/fig2.png" alt="Şekil 2" /> ŞEKİL 2 EPI ve TIRF mikroskobu ile elde edilen 100 nm floresan boncuk Görüntüler. A. birkaç düzine 100 nm floresan boncuk manzaralı bir alan EPI görüntüleri gösterir. Mavi ok ucu suya difüzyon. Boncuk noktası ise, cam lamel üzerine yerleşmiş boncuk kırmızı oklar noktası. B. Bu görüşe göre, sadece kırmızı oklarla gösterilen yapışık boncuk görünür A&#39;da gösterildiği gibi aynı alan TIRF bir görüntü gösterir. Bu cam coverlsip üzerine yerleşti ve böylece ~ 100 nm kaybolan saha içinde vardı çünkü. Boncuk mavi oklarla gösterilen bu bölge içinde değildir ve TIRF görüntüleri böylece görünmez. Düşük araziler görüntülerin 3D render göstermektedir. Bu sinyal-gürültü TIRF mikroskopi tarafından gözlemlenen büyük bir artış kaybolan alanı içinde boncuklar oluşur açıktır. Aslında bu görüntüler için TIRF için 20 iken ± 0.7 EPI için sinyal-gürültü, 7.1 ± 0.6 idi. <img src="/files/ftp_upload/1142/fig3.png" alt="Şekil 3" /> ŞEKİL 3 EPI ve TIRF mikroskobu ile elde Fluo-4 kalsiyum gösterge boyası ile yüklü astrositler Görüntüler. Beş astrositler manzaralı bir alan A. EPI görüntüler. B. A, A ve B görüntüleri anlamlı derecede farklı olduğunu B. Not gösterilen bakış aynı alanda TIRF görüntü. Bu TIRF aydınlatma ile cam lamel yakın apozisyon sadece plazma zarı bölgelerde görüntülü çünkü. Alt panelleri göstermek ATP-uyarılmış hücre içi kalsiyum transientler EPI ve TIRF mikroskobu ile görüntülenmiş.

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Astrositler hücre içi kalsiyum yükselmeler görüntüler çok iyi kurulmuştur. Bu, kendiliğinden meydana gelen nöronal aktivite veya 11 astrosit yüzey reseptörleri aktive agonistleri uygulama tarafından tetiklenebilir. Bir önemli ve tartışmalı bir konu olmadığını astrosit hücre içi kalsiyum yükselmeleri, nöronlar 11, 12 reseptörleri aktive sinyal molekülleri serbest bırakılması tetikleyebilir. Yorum Haydon 7, 13 ve McCarthy 11 laboratuvarları tarafından vurgulanan bu g?...

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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>VWR&#174; Micro Cover Slips, Round, No. 1</td>
<td>Tool</td>
<td>VWR</td>
<td>48380-068</td>
<td>&nbsp;</td>
<tr>
<td>Poly-D-lysine hydrobromide</td>
<td>Reagent</td>
<td>Sigma</td>
<td>P0899</td>
<td>&nbsp;</td>
<tr>
<td>Laminin from Engelbreth-Holm-Swarm murine sarcoma basement membrane</td>
<td>Reagent</td>
<td>Sigma</td>
<td>L2020</td>
<td>&nbsp;</td>
<tr>
<td>Earle&#x2019;s Balanced Salt Solution (EBSS) (1X), liquid</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>14155-063</td>
<td>&nbsp;</td>
<tr>
<td>Minimum Essential Medium (MEM) (1X), liquid Contains Earle's salts, but no L-glutamine or phenol red</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>51200-038</td>
<td>&nbsp;</td>
<tr>
<td>Penicillin-Streptomycin liquid</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>15140-122</td>
<td>&nbsp;</td>
<tr>
<td>Sodium pyruvate solution</td>
<td>Reagent</td>
<td>Sigma</td>
<td>S8636</td>
<td>&nbsp;</td>
<tr>
<td>HEPES solution 1 M</td>
<td>Reagent</td>
<td>Sigma</td>
<td>H0887</td>
<td>&nbsp;</td>
<tr>
<td>N-2 Supplement (100X), liquid</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>17502-048</td>
<td>&nbsp;</td>
<tr>
<td>Horse Serum, Heat-Inactivated</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>26050-088</td>
<td>&nbsp;</td>
<tr>
<td>PAPAIN-022</td>
<td>Reagent</td>
<td>Worthington</td>
<td>LK003178</td>
<td>&nbsp;</td>
<tr>
<td>Neurobasal&#x2122; Medium (1X) Liquid without Phenol Red</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>12348-017</td>
<td>&nbsp;</td>
<tr>
<td>B-27 Serum-Free Supplement (50X), liquid</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>17504-044</td>
<td>&nbsp;</td>
<tr>
<td>L-Glutamine-200 mM (100X), liquid</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>25030-149</td>
<td>&nbsp;</td>
<tr>
<td>Cell Strainers</td>
<td>Tool</td>
<td>BD Biosciences</td>
<td>352350</td>
<td>&nbsp;</td>
<tr>
<td>BD Falcon Multiwell Flat-Bottom Plates with Lids, Sterile</td>
<td>Tool</td>
<td>BD Biosciences</td>
<td>353046</td>
<td>&nbsp;</td>
<tr>
<td>NaCl</td>
<td>Reagent</td>
<td>Sigma</td>
<td>S7653</td>
<td>&nbsp;</td>
<tr>
<td>KCl</td>
<td>Reagent</td>
<td>Sigma</td>
<td>P3911</td>
<td>&nbsp;</td>
<tr>
<td>CaCl2 hexahydrate</td>
<td>Reagent</td>
<td>Sigma</td>
<td>21108</td>
<td>&nbsp;</td>
<tr>
<td>MgCl2 hexahydrate</td>
<td>Reagent</td>
<td>Sigma</td>
<td>M2670</td>
<td>&nbsp;</td>
<tr>
<td>HEPES free acid</td>
<td>Reagent</td>
<td>Sigma</td>
<td>H3375</td>
<td>&nbsp;</td>
<tr>
<td>D-(+)-glucose</td>
<td>Reagent</td>
<td>Sigma</td>
<td>G7528</td>
<td>&nbsp;</td>
<tr>
<td>Fluo-4, AM 1 mM solution in DMSO</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>F-14217</td>
<td>&nbsp;</td>
<tr>
<td>Pluronic&#174; F-127 20% solution in DMSO</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>P-3000MP</td>
<td>&nbsp;</td>
<tr>
<td>Immersion Oil TYPE DF</td>
<td>Microscope</td>
<td>Cargille</td>
<td>16242</td>
<td>&nbsp;</td>
<tr>
<td>Open chamber for 25 mm round coverslips, 100 &mu;l volume</td>
<td>Tool</td>
<td>WARNER Instruments</td>
<td>64-0362 (RC-21BDW)</td>
<td>&nbsp;</td>
<tr>
<td>P-2 platform for Series 20 chambers, non-heater</td>
<td>Tool</td>
<td>WARNER Instruments</td>
<td>64-0278 (P-2)</td>
<td>&nbsp;</td>
<tr>
<td>FluoSpheres carboxylate-modified microspheres, 0.1 &mu;m, yellow-green fluorescent (505/515) 2% solids</td>
<td>Reagent</td>
<td>Invitrogen</td>
<td>F8803</td>
<td>&nbsp;</td>		</tbody>
		</table>
		</div>

measuring near plasma membrane and global intracellular calcium dynamics in astrocytes

Beyin glial hücreler içerir. Astrositler, glial hücre tipi, uzun nöronlar için pasif bir destekleyici bir rol sağlamak için bilinmektedir. Ancak, artan kanıtlar astrositler nöronlar ile fonksiyonel etkileşim yoluyla da aktif beyin fonksiyonu katılmak olabileceğini düşündürmektedir. Ancak, birçok temel yönleri astrosit biyoloji, tartışmalı, belirsiz ve / veya deneysel keşfedilmemiş kalır. Bir önemli konu astrositlerde hücre içi kalsiyum Transientlerin dinamikleri. Kalsiyum önemli bir ikinci haberci olarak iyi kurulmuş ve çünkü astrosit kalsiyum yükselmeler astrositler gelen vericileri serbest bırakılması tetikleyebilir ileri sürülmektedir çünkü bu geçerlidir. Ancak, yakın plazma membranı kalsiyum astrositler sinyal herhangi bir ayrıntılı ve tatmin edici bir açıklama olmamıştır. Toplam iç yansıma floresan (TIRF) mikroskopi canlı hücrelerinin plazma membranı yaklaşık 100 nm içinde önemli fizyolojik sinyalleme olaylarını analiz etmek için güçlü bir araçtır. Burada, TIRF mikroskobu kullanımı ve neredeyse aynı anda, plazma membranı ve küresel hücre içi kalsiyum dinamikleri yakın izlemek nasıl tarif. Bu yaklaşımın daha rafine ve sistematik bir uygulama astrosit kalsiyum sinyal kesin detaylar hakkında bilgi potansiyeline sahiptir. Astrosit kalsiyum dinamiklerinin ayrıntılı bir anlayış, nasıl, ne zaman ve neden astrositler ve nöron kalsiyum-bağımlı fonksiyonel etkileşimleri tabi anlamak için bir temel sağlayabilir.

Watch this Scientific Journal Video about Measuring Near Plasma Membrane and Global Intracellular Calcium Dynamics in Astrocytes at JoVE.com

Measuring Near Plasma Membrane and Global Intracellular Calcium Dynamics in Astrocytes

Biz toplam iç yansıma ve Epifloresans mikroskopi kullanılarak kültürlü astrositler membran ve küresel hücre içi kalsiyum dinamikleri yakın ölçmek için nasıl açıklar.

Astrositler Plazma Membran ve Küresel Hücre içi kalsiyum Dynamics civarında Ölçüm

The brain contains glial cells.  Astrocytes, a type of glial cell, have long been known to provide a passive supportive role to neurons. However, ...

measuring-near-plasma-membrane-global-intracellular-calcium-dynamics

Research

JoVE Journal

Biology

13.0K Görüntüleme.  David Geffen School of Medicine, University of California, Los Angeles. Biz toplam iç yansıma ve Epifloresans mikroskopi kullanılarak kültürlü astrositler membran ve küresel hücre içi kalsiyum dinamikleri yakın ölçmek için nasıl açıklar.

Video: Measuring Near Plasma Membrane and Global Intracellular Calcium Dynamics in Astrocytes

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.

Tersinir biyotinilasyon Plazma Membran Protein endositik Oranları Ölçüm

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

Biyoloji

Measuring Fast Calcium Fluxes in Cardiomyocytes

Cardiomyocytes have multiple Ca2+ fluxes of varying duration that work together to optimize function 1,2. Changes in Ca2+ activity in response to extracellular agents is predominantly regulated by the phospholipase C&beta;- G&alpha;q pathway localized on the plasma membrane which is stimulated by agents such as acetylcholine 3,4. We have recently found that plasma membrane protein domains called caveolae5,6 can entrap activated G&alpha;q 7. This entrapment has the effect of stabilizing the activated state of G&alpha;q and resulting in prolonged Ca2+ signals in cardiomyocytes and other cell types8. We uncovered this surprising result by measuring dynamic calcium responses on a fast scale in living cardiomyocytes. Briefly, cells are loaded with a fluorescent Ca2+ indicator. In our studies, we used Ca2+ Green (Invitrogen, Inc.) which exhibits an increase in fluorescence emission intensity upon binding of calcium ions. The fluorescence intensity is then recorded for using a line-scan mode of a laser scanning confocal microscope. This method allows rapid acquisition of the time course of fluorescence intensity in pixels along a selected line, producing several hundreds of time traces on the microsecond time scale. These very fast traces are transferred into excel and then into Sigmaplot for analysis, and are compared to traces obtained for electronic noise, free dye, and other controls. To dissect Ca2+ responses of different flux rates, we performed a histogram analysis that binned pixel intensities with time. Binning allows us to group over 500 traces of scans and visualize the compiled results spatially and temporally on a single plot. Thus, the slow Ca2+ waves that are difficult to discern when the scans are overlaid due to different peak placement and noise, can be readily seen in the binned histograms. Very fast fluxes in the time scale of the measurement show a narrow distribution of intensities in the very short time bins whereas longer Ca2+ waves show binned data with a broad distribution over longer time bins. These different time distributions allow us to dissect the timing of Ca2+fluxes in the cells, and to determine their impact on various cellular events.

We present a method to isolate rapid (microsecond) calcium events from slower fluxes in living cells using laser scanning confocal microscopy. The method measures fluorescence intensity fluctuations of calcium indicators by recording line scans of several hundred pixels in a cell. Histogram analysis allows us to isolate the time scales of different calcium fluxes.

Hızlı Kalsiyum Dekapanları kardiyomiyositlerde Ölçme

Cardiomyocytes have multiple Ca2+ fluxes of varying duration that work together to optimize function 1,2. Changes in Ca2+ activity in response to ...

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.

Çoklu Hedef İzleme (MTT) tarafından Plazma Membran Moleküler Difüzyon Haritalama

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

Intravital Microscopy for Imaging Subcellular Structures in Live Mice Expressing Fluorescent Proteins

Here we describe a procedure to image subcellular structures in live rodents that is based on the use of confocal intravital microscopy. As a model organ, we use the salivary glands of live mice since they provide several advantages. First, they can be easily exposed to enable access to the optics, and stabilized to facilitate the reduction of the motion artifacts due to heartbeat and respiration. This significantly facilitates imaging and tracking small subcellular structures. Second, most of the cell populations of the salivary glands are accessible from the surface of the organ. This permits the use of confocal microscopy that has a higher spatial resolution than other techniques that have been used for in vivo imaging, such as two-photon microscopy. Finally, salivary glands can be easily manipulated pharmacologically and genetically, thus providing a robust system to investigate biological processes at a molecular level.
In this study we focus on a protocol designed to follow the kinetics of the exocytosis of secretory granules in acinar cells and the dynamics of the apical plasma membrane where the secretory granules fuse upon stimulation of the beta-adrenergic receptors. Specifically, we used a transgenic mouse that co-expresses cytosolic GFP and a membrane-targeted peptide fused with the fluorescent protein tandem-Tomato. However, the procedures that we used to stabilize and image the salivary glands can be extended to other mouse models and coupled to other approaches to label in vivo cellular components, enabling the visualization of various subcellular structures, such as endosomes, lysosomes, mitochondria, and the actin cytoskeleton.

Intravital microscopy is a powerful tool that enables imaging various biological processes in live animals. In this article, we present a detailed method for imaging the dynamics of subcellular structures, such as the secretory granules, in the salivary glands of live mice.

Floresan Proteinler ifade Canlı Farelerde Görüntüleme hücrealtı Yapıların Intravital Mikroskopi

Here we describe a procedure to image subcellular structures in live rodents that is based on the use of confocal intravital microscopy. As a model organ, ...

Imaging Plasma Membrane Deformations With pTIRFM

To gain novel insights into the dynamics of exocytosis, our group focuses on the changes in lipid bilayer shape that must be precisely regulated during the fusion of vesicle and plasma membranes. These rapid and localized changes are achieved by dynamic interactions between lipids and specialized proteins that control membrane curvature. The absence of such interactions would not only have devastating consequences for vesicle fusion, but a host of other cellular functions that involve control of membrane shape. In recent years, the identity of a number of proteins with membrane-shaping properties has been determined. What remains missing is a roadmap of when, where, and how they act as fusion and content release progress.
Our understanding of the molecular events that enable membrane remodeling has historically been limited by a lack of analytical methods that are sensitive to membrane curvature or have the temporal resolution to track rapid changes. PTIRFM satisfies both of these criteria. We discuss how pTIRFM is implemented to visualize and interpret rapid, submicron changes in the orientation of chromaffin cell membranes during dense core vesicle (DCV) fusion. The chromaffin cells we use are isolated from bovine adrenal glands. The membrane is stained with a lipophilic carbocyanine dye,1,1&#39;-dioctadecyl-3,3,3&#39;,3&#39;-tetramethylindodicarbocyanine, 4-chlorobenzenesulfonate, or&#160;diD. DiD intercalates in the membrane plane with a &#34;fixed&#34; orientation and is therefore sensitive to the polarization of the evanescent field. The diD-stained cell membrane is sequentially excited with orthogonal polarizations of a 561&#160;nm laser (p-pol, s-pol). A 488&#160;nm laser is used to visualize vesicle constituents and time the moment of fusion. Exocytosis is triggered by locally perfusing cells with a depolarizing KCl solution. Analysis is performed offline using custom-written software to understand how diD emission intensity changes relate to fusion pore dilation.

Polarization-based Total Internal Reflection Fluorescence Microscopy (pTIRFM) enables real-time detection of cell membrane dynamics. This article describes the implementation of pTIRFM for the study of membrane remodeling during regulated exocytosis. The technique is generalizable to other processes in cell biology that directly or indirectly involve changes in membrane shape.

PTIRFM ile görüntüleme Plazma Membran deformasyonlar

To gain novel insights into the dynamics of exocytosis, our group focuses on the changes in lipid bilayer shape that must be precisely regulated during ...

Functional Characterization of Na+/H+ Exchangers of Intracellular Compartments Using Proton-killing Selection to Express Them at the Plasma Membrane

Endosomal acidification is critical for a wide range of processes, such as protein recycling and degradation, receptor desensitization, and neurotransmitter loading in synaptic vesicles. This acidification is described to be mediated by proton ATPases, coupled to ClC chloride transporters. Highly-conserved electroneutral protons transporters, the Na+/H+ exchangers (NHE) 6, 7 and 9 are also expressed in these compartments. Mutations in their genes have been linked with human cognitive and neurodegenerative diseases. Paradoxically, their roles remain elusive, as their intracellular localization has prevented detailed functional characterization. This manuscript shows a method to solve this problem. This consists of the selection of mutant cell lines, capable of surviving acute cytosolic acidification by retaining intracellular NHEs at the plasma membrane. It then depicts two complementary protocols to measure the ion selectivity and activity of these exchangers: (i) one based on intracellular pH measurements using fluorescence video microscopy, and (ii) one based on the fast kinetics of lithium uptake. Such protocols can be extrapolated to measure other non-electrogenic transporters. Furthermore, the selection procedure presented here generates cells with an intracellular retention defective phenotype. Therefore these cells will also express other vesicular membrane proteins at the plasma membrane. The experimental strategy depicted here may therefore constitute a potentially powerful tool to study other intracellular proteins that will be then expressed at the plasma membrane together with the vesicular Na+/H+ exchangers used for the selection.

Functional Characterization of Na+/H+ Exchangers of Intracellular Compartments Using Proton-killing Selection to Express Them at the Plasma Membrane

The first part of this article shows how to select mutant cell lines expressing vesicular Na+/H+ exchangers at their plasma membrane. The second part provides protocols based on intracellular pH measurements and fast ion uptake, which are used to determine the ion selectivity and the kinetic parameters of these exchangers.

Na fonksiyonel karakterizasyonu<sup&gt; +</sup&gt; / H<sup&gt; +</sup&gt; Seçim Proton-öldürme Kullanma hücre içi Bölmeler ve Eşanjörleri Plazma Membran Them Express

Endosomal acidification is critical for a wide range of processes, such as protein recycling and degradation, receptor desensitization, and ...

Determination of Plasma Membrane Partitioning for Peripherally-associated Proteins

This method provides a fast approach for the determination of plasma membrane partitioning of any fluorescently-tagged peripherally-associated protein using the profiles of fluorescence intensity across the plasma membrane. Measured fluorescence profiles are fitted by a model for membrane and cytoplasm fluorescence distribution along a line applied perpendicularly to the cell periphery. This model is constructed from the fluorescence intensity values in reference cells expressing a fluorescently-tagged marker for cytoplasm and with FM 4-64-labeled plasma membrane. The method can be applied to various cell types and organisms; however, only plasma membranes of non-neighboring cells can be evaluated. This fast microscopy-based method is suitable for experiments, where subtle and dynamic changes of plasma membrane-associated markers are expected and need to be quantified, e.g., in the analysis of mutant versions of proteins, inhibitor treatments, and signal transduction observations. The method is implemented in a multi-platform R package that is coupled with an ImageJ macro that serves as a user-friendly interface.

Here, we present a protocol to perform a quantitative analysis of the level of plasma-membrane association for fluorescently-tagged peripherally-associated protein. The method is based on the computational decomposition of membrane and cytoplasmic component of signal observed in cells labeled with plasma membrane fluorescent marker.

Plazma zarı periferik ilişkili proteinler için bölümleme belirlenmesi

This method provides a fast approach for the determination of plasma membrane partitioning of any fluorescently-tagged peripherally-associated protein ...

Characterization of MLKL-mediated Plasma Membrane Rupture in Necroptosis

Necroptosis is a programmed cell death pathway triggered by activation of receptor interacting protein kinase 3 (RIPK3), which phosphorylates and activates the mixed lineage kinase-like domain pseudokinase, MLKL, to rupture or permeabilize the plasma membrane. Necroptosis is an inflammatory pathway associated with multiple pathologies including autoimmunity, infectious and cardiovascular diseases, stroke, neurodegeneration, and cancer. Here, we describe protocols that can be used to characterize MLKL as the executioner of plasma membrane rupture in necroptosis. We visualize the process of necroptosis in cells using live-cell imaging with conventional and confocal fluorescence&#160;microscopy, and in fixed cells using electron microscopy, which together revealed the redistribution of MLKL from the cytosol to the plasma membrane prior to induction of large holes in the plasma membrane. We present in vitro nuclear magnetic resonance (NMR) analysis using lipids to identify putative modulators of MLKL-mediated necroptosis. Based on this method, we identified quantitative lipid-binding preferences and phosphatidyl-inositol phosphates (PIPs) as critical binders of MLKL that are required for plasma membrane targeting and permeabilization in necroptosis.

We report methods for characterization of MLKL-mediated plasma membrane rupture in necroptosis including conventional and confocal live-cell microscopy imaging, scanning electron microscopy, and NMR-based lipid binding.

Necroptosis MLKL-aracılı plazma zarı kopma karakterizasyonu

Necroptosis is a programmed cell death pathway triggered by activation of receptor interacting protein kinase 3 (RIPK3), which phosphorylates and ...

Simultaneous Measurements of Intracellular Calcium and Membrane Potential in Freshly Isolated and Intact Mouse Cerebral Endothelium

Cerebral arteries and their respective microcirculation deliver oxygen and nutrients to the brain via blood flow regulation. Endothelial cells line the lumen of blood vessels and command changes in vascular diameter as needed to meet the metabolic demand of neurons. Primary endothelial-dependent signaling pathways of hyperpolarization of membrane potential (Vm) and nitric oxide typically operate in parallel to mediate vasodilation and thereby increase blood flow. Although integral to coordinating vasodilation over several millimeters of vascular length, components of endothelium-derived hyperpolarization (EDH) have been historically difficult to measure. These components of EDH entail intracellular Ca2+ [Ca2+]i increases and subsequent activation of small- and intermediate conductance Ca2+-activated K+ (SKCa/IKCa) channels.
Here, we present a simplified illustration of the isolation of fresh endothelium from mouse cerebral arteries; simultaneous measurements of endothelial [Ca2+]i and Vm using Fura-2 photometry and intracellular sharp electrodes, respectively; and a continuous superfusion of salt solutions and pharmacological agents under physiological conditions (pH 7.4, 37 &#176;C). Posterior cerebral arteries from the Circle of Willis are removed free of the posterior communicating and the basilar arteries. Enzymatic digestion of cleaned posterior cerebral arterial segments and subsequent trituration facilitates removal of adventitia, perivascular nerves, and smooth muscle cells. Resulting posterior cerebral arterial endothelial &#34;tubes&#34; are then secured under a microscope and examined using a camera, photomultiplier tube, and one to two electrometers while under continuous superfusion. Collectively, this method can simultaneously measure changes in endothelial [Ca2+]i and Vm in discrete cellular locations, in addition to the spreading of EDH through gap junctions up to millimeter distances along the intact endothelium. This method is expected to yield a high-throughput analysis of the cerebral endothelial functions underlying mechanisms of blood flow regulation in the normal and diseased brain.

Demonstrated here are protocols for (1) freshly isolating intact cerebral endothelial "tubes" and (2) simultaneous measurements of endothelial calcium and membrane potential during endothelium-derived hyperpolarization. Further, these methods allow for pharmacological tuning of endothelial cell calcium and electrical signaling as individual or interactive experimental variables.

Hücre içi kalsiyum ve taze izole ve olduğu gibi fare serebral endotel membran potansiyeli eşzamanlı ölçümler

Cerebral arteries and their respective microcirculation deliver oxygen and nutrients to the brain via blood flow regulation. Endothelial cells line the ...

Imaging Calcium Dynamics in Subpopulations of Mouse Pancreatic Islet Cells

Pancreatic islet hormones regulate blood glucose homeostasis. Changes in blood glucose induce oscillations of cytosolic calcium in pancreatic islet cells that trigger secretion of three main hormones: insulin (from &#946;-cells), glucagon (&#945;-cells) and somatostatin (&#948;-cells). &#946;-Cells, which make up the majority of islet cells and are electrically coupled to each other, respond to the glucose stimulus as one single entity. The excitability of the minor subpopulations, &#945;-cells and &#948;-cells (making up around 20% (30%) and 4% (10%) of the total rodent1 (human2) islet cell numbers, respectively) is less predictable and is therefore of special interest.
Calcium sensors are delivered into the peripheral layer of cells within the isolated islet. The islet or a group of islets is then immobilized and imaged using a fluorescence microscope. The choice of the imaging mode is between higher throughput (wide-field) and better spatial resolution (confocal). Conventionally, laser scanning confocal microscopy is used for imaging tissue, as it provides the best separation of the signal between the neighboring cells. A wide-field system can be utilized too, if the contaminating signal from the dominating population of &#946;-cells is minimized.
Once calcium dynamics in response to specific stimuli have been recorded, data are expressed in numerical form as fluorescence intensity vs. time, normalized to the initial fluorescence and baseline-corrected, to remove the effects linked to bleaching of the fluorophore. Changes in the spike frequency or partial area under the curve (pAUC) are computed vs. time, to quantify the observed effects. pAUC is more sensitive and quite robust whereas spiking frequency provides more information on the mechanism of calcium increase.
Minor cell subpopulations can be identified using functional responses to marker compounds, such as adrenaline and ghrelin, that induce changes in cytosolic calcium in a specific populations of islet cells.

Here, we present a protocol for imaging and quantifying calcium dynamics in heterogeneous cell populations, such as pancreatic islet cells. Fluorescent reporters are delivered into the peripheral layer of cells within the islet, which is then immobilized and imaged, and per-cell analysis of the dynamics of fluorescence intensity is performed.

Fare Pankreas Adacık Hücrelerinin Alt Popülasyonlarında Görüntüleme Kalsiyum Dinamiği

Pancreatic islet hormones regulate blood glucose homeostasis. Changes in blood glucose induce oscillations of cytosolic calcium in pancreatic islet cells ...