Questo lavoro è stato sostenuto dalla Fondazione Memorial Uehara del Giappone (ES) e la Fondazione Whitehall, del National Institute of Neurological Disorder and Stroke e un Stein-Oppenheimer Premio Endowment (a BSK).

Procedure sperimentali La procedura sperimentale consiste di due parti principali che sono descritti in maniera saggia passo sotto. Parte 1: PREPARAZIONE CULTURE astrociti dell&#39;ippocampo In breve, misto astrociti-neuroni dell&#39;ippocampo culture sono state preparate utilizzando un protocollo ben definito 1,2,3. Abbiamo ottimizzato il procedimento per produrre sano astrociti in coltura. Tutte le procedure di seguito elencati deve essere effettuata in un ambiente sterile come una cappa a flusso laminare. Coprioggetto preparazione <ul><li> Coprioggetto 22 mm (VWR, 48380-068) </li><li> Poli-D-lisina (PDL, Sigma P0899), aliquote (1 mg / ml) </li><li> Laminina aliquote (20 mg / ml): aggiungere 49 ml di acqua sterile a 1 mg / ml soluzione laminina (Sigma L2020), fanno aliquote da 1,2 ml e conservare a -20 ° C </li></ul><ol><li> Sciogliere PDL in acqua sterile (50 mg / ml) </li><li> Autoclave i coprioggetti, sciacquare con acqua sterile e posto in PDL (20 ml per 100 lamelle). Lasciare a temperatura ambiente per una notte. </li><li> Sostituire il PDL con acqua sterile (3 lavaggi estensiva). Poi asciugare i coprioggetti e conservare a 4 ° C. </li><li> Il giorno prima della placcatura astrociti, coprioggetto posto individuale in un pozzo sterile su un 6-pozzetti (pozzetti a fondo piatto Piatti con coperchio, sterile da BD Bioscience). Mettere 400 ml di laminina su ogni coprioggetto e incubare una notte, in incubatrice per evitare l&#39;evaporazione. </li></ol> Dissezione Dissezione dei media: <ul><li> 500 ml di Earle soluzione salina bilanciata (EBSS) (1X), liquido (Invitrogen, 14155-063) </li><li> HEPES 5 ml di soluzione (Sigma, H0887) </li></ul> Mezzi di comunicazione dell&#39;ippocampo: <ul><li> 412,5 ml di media minima essenziale (MEM) (1X), liquido Contiene sali di Earle, ma non rosso L-glutammina o fenolo (Invitrogen, 51200-038) </li><li> 10 ml di glucosio (Sigma, D-(+)-glucosio anidro SIGMA ULTRA G7528) 1 M a MEM </li><li> 5 ml di penicillina-streptomicina (Invitrogen, 15140-122) </li><li> 5 ml di soluzione di sodio piruvato (Sigma, S8636) </li><li> 12,5 ml HEPES soluzione 1 M (Sigma, H0887) </li><li> 5 ml N-2 Supplement (100X), liquido (Invitrogen, 17502-048) </li><li> 50 ml di siero di cavallo, inattivato per calore (Invitrogen, 26050-088) </li></ul> Papaina soluzione: <ul><li> Aggiungere 5 ml di dissezione dei media in Worthington papaina-022 flaconcino (LK003178; concentrazione finale, 20 U / ml) e incubare a 37 ° C per 60 min. </li></ul><ol><li> Decapitare ratti di età compresa tra P1 (in genere 2 cuccioli) le linee guida controllati e approvati dalla normativa nazionale e Cura il tuo locale degli animali e del Comitato Istituzionale Usa. </li><li> Togliere la pelle e il cranio e il cervello posto nella piastra di Petri riempite con i media dissezione a freddo. </li><li> Rimosso meningi, sezionare entrambi gli emisferi e sezionare dell&#39;ippocampo. </li><li> Tritate la dell&#39;ippocampo in ~ 1X1 pezzi mm e digerire in soluzione papaina a 37 ° C per 11-13 minuti. </li><li> Una volta che i pezzi di tessuto sono insediati, rimuovere la papaina con cura e aggiungere 5 ml di terreno dell&#39;ippocampo a rimuovere tutte le tracce di un enzima. Ripetere questo passaggio e risospendere in media dell&#39;ippocampo (2 ml). </li><li> Triturare le cellule ~ 5 volte fino a quando non ci sono grumi sinistra, con tre fiamma lucido pipette di fori progressivamente più piccoli (1000 micron, ~ 500 micron e ~ 300 micron). </li><li> Una volta triturato, le cellule passano attraverso un filtro cella (dimensione dei pori, 70 micron, BD Bioscience). Contare le cellule in 10 ml di sospensione. Regolare il volume di terreno dell&#39;ippocampo in modo da avere 400000 cellule / ml. </li><li> Aspirare il laminina fuori i coprioggetti, e prima che le coperture possono asciutto, piatto 200 microlitri della sospensione cellulare per coprioggetto. </li><li> Lasciateli per attaccare per 60 minuti in incubatrice, e poi aggiungere 2 ml di terreno dell&#39;ippocampo per bene. </li><li> Il giorno successivo, aspirare vecchi media dell&#39;ippocampo per rimuovere le cellule morte e detriti e aggiungere 2 ml di pre-riscaldato terreno fresco dell&#39;ippocampo. </li></ol> Manutenzione Mezzi di comunicazione Neurobasal: <ul><li> 500 ml neurobasal (Invitrogen, 12348-017) </li><li> 10 ml di siero B27 supplemento gratuito (Invitrogen, 17504-044) </li><li> 5 ml di penicillina-streptomicina (Invitrogen, 15140-122) </li><li> 1,25 ml L-glutamina (Invitrogen, 25030-149) </li></ul> Feed the culture astrociti-neuroni due volte alla settimana con il mezzo neurobasal, a partire da quattro giorni dopo la placcatura. Preincubare i media di circa 30 minuti in incubatrice in un pallone ventilato per equilibrare la temperatura e CO 2. Parte 2: IMAGING DI CALCIO Registrazione dell&#39;ippocampo tampone: 110 mM NaCl, 5.4 mMKCl, 1,8 mM CaCl 2, 0,8 mM MgCl 2, 10 mM D-glucosio, 10 mM HEPES (Tutti i prodotti chimici da Sigma), pH 7.4 (corretto con NaOH). Caricamento indicatore colorante calcio in astrociti <ol><li> Posizionare la cultura in un bene su un 6-pozzetti riempiti con 2 ml di buffer di registrazione dell&#39;ippocampo contenente 2,5 mM Fluo-4, AM (Invitrogen, F-14217) e 0,05% Pluronic soluzione ® F-127, il 20% in DMSO (Invitrogen, P-3000MP) e incubare a temperatura ambiente per 10-30 min. </li><li> Rimuovere Fluo-4 soluzione e lavare coprioggetto 3 volte con buffer di registrazione dell&#39;ippocampo e incubare a temperatura ambiente per 30 min. </li><li> Posizionare il coprioggetto sulla camera, e pulire il lato del vetrino con il liquido per pulire le lenti. </li><li> Metti una piccola goccia di olio da immersione (olio DF immersione TIPO da Cargille) l&#39;obiettivo e mettere da camera (camera aperta per 25 coprioggetto tondo mm dalla Warner Instruments) sul palco del microscopio (Olympus IX71). </li><li> Guarda le cellule usando la luce di trasmissione per vedere come le cellule aspetto, e portarli a fuoco. Poi illuminare le cellule con 488 nm da un monocromatore (policroma V da TILL Vision) e determinare se il segnale di fluorescenza di Fluo-4 è uniforme e rilevabile negli astrociti. </li><li> Usa EPI e TIRF illuminazione per misurare il calcio negli astrociti. </li></ol> Microscopia TIRF In breve, usiamo un microscopio Olympus IX71 dotato di una fotocamera IXON Andor DV887DCS EMCCD. Il controllo di eccitazione e di acquisizione delle immagini è ottenuta utilizzando un software TILLVision. Le travi di 454/488/515 nm Argon (100 mW) e 442 nm allo stato solido (45 mW) i laser sono combinati e controllati con una FINO Polilinea laser combinatore, TIRF porta a condensatore a doppio e acoustoptical filtro sintonizzabile e controller (AOTF; tutto da FINO Photonics) e inseriti in una fibra Kineflex a banda larga per l&#39;ingresso nel condensatore TIRF. Usiamo un Olympus 60X 1,45 lente NA per raggiungere TIRF. Il guadagno della telecamera è adeguato, per ogni astrociti per fornire il miglior segnale al rumore delle immagini. Lo sfondo ed i principi della microscopia TIRF sono state recentemente recensione 4, 5. La maggior parte dei componenti ottici che utilizziamo sono stati acquistati da TILL Photonics, che ora fa parte di Agilent Technologies (http://www.till-photonics.com/). La profondità di penetrazione TIR può essere calcolato dalle equazioni di seguito. <img style="float:left;" src="/files/ftp_upload/1142/equation.png" alt="Equazione" /> d = profondità di penetrazione n1 = indice di rifrazione del vetro n2 = indice di rifrazione di cellule un angolo di incidenza = NAi = apertura numerica di incidenza Al fine di garantire il laser è allineato in modo ottimale per TIRF riteniamo utile osservare 100 nm perline fluorescenti (Invitrogen, F8803). Vi presentiamo fotogrammi e video di perline con EPI e microscopia TIRF. Quando nel TIRF, si osserva un aumento drammatico nel rapporto segnale-rumore e le perline visualizzazione diffusione browniano. Per noi è utile osservare il comportamento di 100 nm con perline microscopia TIRF su base regolare (~ una volta a settimana) per essere sicuri che TIRF ottimale si verifica, piuttosto che l&#39;illuminazione compromessa obliqua che si verificherebbe se l&#39;angolo critici non sono stati pari a α (vedi Fig. 1). Applicazione di agonisti accoppiata G-proteina recettore Astrociti esprimono una varietà di Gq recettori accoppiati 6, 7 tra cui i recettori metabotropici del glutammato e recettori P2Y (agonista, ATP, ADP). L&#39;attivazione di questi recettori porta ad un aumento significativo dei livelli intracellulari di calcio in astrociti. Per esempio, si può facilmente osservare prospetti del calcio intracellulare durante l&#39;applicazione di ATP (30 mM) a 8-10 astrociti. Usiamo una soluzione rapida switcher da Warner Instruments chiamato VC-77SP Fast-Passo del sistema di perfusione (http://www.warneronline.com/index.cfm). Con questo metodo le soluzioni possono essere applicate in meno di ~ 10 ms. <img src="/files/ftp_upload/1142/Fig 1a.jpg" alt="Figura 1" /> <img src="/files/ftp_upload/1142/fig1c.jpg" alt="" /> Cartoon FIGURA 1. Fotografie e immagini del set up. A. mostra una fotografia del microscopio montato su un airtable, mentre (B) mostra una fotografia del gruppo laser, controllori e scatole fascio. C. Mostra una fotografia della scena microscopio con la camera montata per l&#39;imaging. A sinistra il dispositivo di perfusione veloce può essere visto (insieme con il motore passo-passo e tubi theta). Sulla destra il headstage di un amplificatore Axopatch 200A è visto. Il fumetto schematizza il percorso della luce nel set up e come TIRF è raggiunto. Il laser viene focalizzato sul piano focale posteriore della lente dell&#39;obiettivo 60X 1,45 NA e la sua posizione viene regolata fuori centro in modo che emerge in olio da immersione al α angolo critico. A questo punto il fascio soffre di riflessione interna totale e decade con una distanza λ (vedi equazione nel testo principale) nel mezzo di indice di rifrazione più basso. In questo caso, questo è il buffer di registrazione che circonda la astrociti e gli astrociti stessi. Il risultato è eccitazione ottica (e quindi immagini) di molecole all&#39;interno di ~ 100 nm della membrana plasmatica. Nel cartone animato della cellula, viene visualizzato come verde &quot;eccitato&quot; recettori di membrana, mentre quelli all&#39;interno della cellula o sulla superficie superiore della cella non sono entusiasti. Un resoconto completo di microscopia TIRF è stata fornita da Steyer e Almers 4. <img src="/files/ftp_upload/1142/fig2.png" alt="Figura 2" /> FIGURA 2. Immagini di 100 nm perline fluorescenti acquisito con EPI e microscopia TIRF. A. mostra le immagini EPI di un campo di vista con diverse decine di 100 nm perline fluorescenti. Il punto rosso frecce per perline che si sono insediati sul vetrino di vetro, mentre le frecce blu indicano che sono perle di diffusione in acqua. B. mostra un&#39;immagine TIRF dello stesso campo di vista, come mostrato in A. In questa visione solo le perle aderente mostrato dalle frecce rosse sono visibili. Questo perché questi si erano stabiliti sulla coverlsip vetro e sono stati pertanto nel campo 100 nm ~ evanescente. Le perle mostrato in A con frecce blu non sono in questa regione e sono quindi invisibili nelle immagini TIRF. I grafici mostrano inferiore rendering 3D delle immagini. E &#39;chiaro che un forte aumento del rapporto segnale-rumore si verifica per perline all&#39;interno del campo evanescente quando osservate al microscopio TIRF. Infatti per queste immagini il rapporto segnale-rumore per EPI è stato 7,1 ± 0,6, mentre per TIRF era 20 ± 0,7. <img src="/files/ftp_upload/1142/fig3.png" alt="Figura 3" /> FIGURA 3. Immagini di astrociti caricato con Fluo-4 colorante indicatore di calcio acquisito con EPI e microscopia TIRF. A. EPI immagini di un campo di vista con cinque astrociti. B. Una immagine TIRF dello stesso campo di vista mostrato in B. Nota che le immagini in A e B sono significativamente differenti. Questo perché con TIRF illuminazione solo le regioni membrana plasmatica in apposizione vicino al coprioggetto di vetro sono ripreso. I pannelli inferiori mostrano ATP-evocate transienti di calcio intracellulare ripreso con EPI e microscopia TIRF.

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E &#39;ben dimostrato che gli astrociti visualizzare prospetti del calcio intracellulare. Questi si verificano spontaneamente, può essere attivato da un&#39;attività neuronale o mediante l&#39;applicazione di agonisti per attivare i recettori sulla superficie astrociti 11. Un tema importante e controverso è se astrociti prospetti del calcio intracellulare può innescare il rilascio di molecole di segnalazione che attivano i recettori sui neuroni 11, 12. Questo è controversa perché c&#39;è stata la prova a favore ...

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		<thead>
		<tr>
		<th>Material Name</th>
		<th>Type</th>
		<th>Company</th>
		<th>Catalogue Number</th>
		<th>Comment</th>
		</tr>
		</thead>
		<tbody>
		
<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

Il cervello contiene cellule gliali. Astrociti, un tipo di cellule gliali, sono da tempo noti per fornire un ruolo passivo di supporto ai neuroni. Tuttavia, una crescente evidenza suggerisce che gli astrociti possono anche partecipare attivamente nella funzione del cervello attraverso le interazioni funzionali con i neuroni. Tuttavia, molti aspetti fondamentali della biologia astrociti rimangono controversi, chiari e / o sperimentale inesplorati. Una questione importante è la dinamica dei transitori calcio intracellulare negli astrociti. Questo è importante perché il calcio è così affermato come un importante messaggero secondo e perché è stato proposto che elevazioni di calcio astrociti possono innescare il rilascio di trasmettitori da astrociti. Tuttavia, non vi è stata alcuna descrizione dettagliata e soddisfacente di calcio vicino a membrana plasmatica di segnalazione negli astrociti. Fluorescenza di riflessione interna totale (TIRF) microscopia è un potente strumento per analizzare gli eventi di segnalazione fisiologicamente rilevanti all&#39;interno di circa 100 nm della membrana plasmatica delle cellule vive. Qui, usiamo microscopia TIRF e descrivono come monitor vicino membrana plasmatica e globale dinamiche di calcio intracellulare quasi simultaneamente. L&#39;ulteriore perfezionamento e l&#39;applicazione sistematica di questo approccio ha il potenziale per informare sui dettagli precisi della segnalazione calcio astrociti. Una comprensione dettagliata delle dinamiche di calcio astrociti possono fornire una base per capire se, come, quando e perché astrociti e neuroni subiscono interazioni funzionali calcio-dipendente.

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

Noi descriviamo come misurare vicino a membrana e globale dinamiche di calcio intracellulare negli astrociti in coltura utilizzando riflessione interna totale e epifluorescenza.

Misura Vicino membrana plasmatica e Global Dynamics calcio intracellulare negli astrociti

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 Views.  David Geffen School of Medicine, University of California, Los Angeles. Noi descriviamo come misurare vicino a membrana e globale dinamiche di calcio intracellulare negli astrociti in coltura utilizzando riflessione interna totale e epifluorescenza.

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.

Misurazione delle proteine ​​plasmatiche Tariffe endocitico membrana da biotinilazione reversibile

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

Ricerca

Biologia

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.

Misurare flussi di calcio veloce in cardiomiociti

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.

Mappatura diffusione molecolare nella membrana plasmatica da parte di più-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 ...

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.

Intravitale Microscopia per le strutture Imaging subcellulari in topi vivi Esprimere proteine ​​fluorescenti

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.

Imaging Plasma membrana Deformazioni Con 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 ...

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.

Caratterizzazione funzionale di Na<sup&gt; +</sup&gt; / H<sup&gt; +</sup&gt; Scambiatori di intracellulare compartimenti, utilizzando Proton-uccidere selezione di esprimerle livello della membrana plasmatica

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.

Determinazione della membrana plasmatica di partizionamento per marginalmente-associated Proteins

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.

Caratterizzazione della rottura della membrana plasmatica MLKL-mediata in Necroptosis

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.

Misurazioni simultanee di calcio intracellulare e potenziale di membrana nell'endotelio cerebrale Mouse appena isolato ed intatto

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.

Imaging calcio Dynamics in sottopopolazioni di cellule di islet pancreatica del topo

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