Name: a protocol for using f&#246;rster resonance energy transfer (fret)-force biosensors to measure mechanical forces across the nuclear linc complex
Uploaded: 2017-04-11T12:30:00
Description: Watch this Scientific Journal Video about A Protocol for Using FÃ¶rster Resonance Energy Transfer FRET-force Biosensors to Measure Mechanical Forces across the Nuclear LINC Complex at JoVE.com

Dette arbeid ble støttet av Thomas F. og Kate Miller Jeffress Memoria Trust (DEC) og NIH gi R35GM119617 (DEC). Det konfokale mikroskop avbildning ble utført ved VCU nano Karakterisering Kjerne (NCC) Facility.

1. Få Nesprin-2G Sensor DNA og andre PlasmidDNA <ol><li> Oppnå Nesprin-2G TS (strekksensor), Nesprin-2G HL (hodeløs) kontroll, mTFP1, Venus, og TSmod fra en kommersiell kilde. Forplante alle DNA-plasmider og rense dem ved hjelp av standard E. coli-stammer, slik som DH5-α, som beskrevet tidligere 12, 13. </li></ol> 2. transfektere celler med Nesprin-2G og andre Plasmid DNA <ol><li> Vokse NIH 3T3 fibroblaster celler til 70-...

<ol>
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En fremgangsmåte og demonstrasjon av levende celle avbildning av mekanisk spenning over Nesprin-2G, et protein som i det kjernefysiske LINC-komplekset, ble beskrevet ovenfor. Forut for dette arbeidet, forskjellige teknikker, for eksempel mikropipette aspirasjon, magnetisk-perle-cytometri, og mikroskopisk laser-ablasjon, er blitt benyttet for å påføre belastning på cellekjernen og for å måle dens bulkmaterialegenskaper 16, 17, ...

Kraft-følsomme, har genetisk kodede FRET sensorer nylig dukket opp som et viktig verktøy for å måle strekk-krefter basert på levende celler, gir innsikt i hvordan mekaniske krefter som påføres på tvers av proteiner 1, 2, 3, 4. Med disse verktøyene, kan forskerne ikke-invasiv bilde intracellulære krefter i levende celler ved hjelp av konvensjonelle lysrør mikroskoper. Disse sensorene består av et FRET-par (donor og akseptor fluorescerende proteiner, oftest en blå donor og akseptor gul) adskilt av en elastisk peptid 3. I motsetning til C- eller N-terminal merking, innføres denne sensoren inn i et indre område av et protein for å måle den mekaniske kraft som overføres på tvers av protein, oppfører seg som en molekylær strekklapp. Økt mekanisk spenning over sensoren resulterer i en øket avstand mellom de FRET-pluft, noe som resulterer i redusert FRET 3. Som et resultat, er FRET omvendt relatert til strekkspenning. Disse fluorescerende-baserte sensorer har blitt utviklet for fokale adhesjonsproteiner (vinculin 3 og talin 4), cytoskjelettproteiner (α-aktinin 5), og celle-celle-junction-proteiner (E-cadherin 6, 7, VE-cadherin 8, og PECAM 8). Det mest brukte og godt karakterisert elastisk linker i slike biosensorer er kjent som TSmod og består av en repeterende sekvens av 40 aminosyrer, (GPGGA) 8, som ble avledet fra spideren silke protein flagelliform. TSmod er blitt vist å oppføre seg som en lineær elastisk nano-fjær, med FRET respons på 1 til 5, pN av strekkraft tre. Forskjellige lengder av flagelliform kan brukes til å endre den dynamiske range av TSmod FRET-kraft følsomhet 9. I tillegg til flagelliform, gjentar spektrin 5 og villin headpiece peptid (kjent som HP35) 4 er blitt anvendt som de elastiske peptidene mellom FRET-par i tilsvarende kraft biosensorer 4. Endelig en fersk rapport viste at TSmod kan også brukes til å oppdage kompresjonskrefter 10. Vi har nylig utviklet en kraftsensor for linkeren til den nucleo-cytoskjelettet (LINC) kompleks protein Nesprin2G ved hjelp TSmod innsatt i en tidligere utviklet avkortet Nesprin2G protein som kalles mini-Nesprin2G (figur 2C), som oppfører seg på samme måte som endogent Nesprin-2G 11. Den LINC Komplekset inneholder flere proteiner som fører fra utsiden til innsiden av kjernen, som forbinder den cytoplasmatiske cytoskjelettet på atom lamina. Nesprin-2G er et strukturelt protein å binde seg til bådeaktin cytoskjelettet i cytoplasma og til sol proteiner i perinukleære plass. Ved hjelp av vår biosensor, var vi i stand til å vise at Nesprin-2G er underlagt actomyosin avhengig spenning i NIH3T3 fibroblaster 2. Dette var første gang at styrken ble målt direkte over et protein i den kjernefysiske LINC komplekse, og det er sannsynlig å bli et viktig verktøy for å forstå hvilken rolle kraft på kjernen i mechanobiology. Protokollen nedenfor gir en detaljert metodikk for hvordan man skal bruke Nesprin-2G kraftsensor, inkludert ekspresjonen av Nesprin spenningsføleren (Nesprin-TS) i pattedyrceller, samt innsamling og analyse av FRET bilder av celler som uttrykker Nesprin- TS. Ved hjelp av et invertert konfokalt mikroskop utstyrt med en spektral-detektor, gnage en beskrivelse av hvordan man skal måle sensibiliserte emisjon ved bruk av spektral unmixing og ratiometrisk FRET avbildning er gitt. Utgangs Proporsjonal Bildene kan brukes til å lage relativ quantitative kraft sammenligninger. Selv om denne protokollen er fokusert på ekspresjon av Nesprin-TS i fibroblaster, er det lett tilpasses til andre pattedyrceller, innbefattende begge cellelinjer og primære celler. Videre kan denne protokoll som det er relatert til bildeinnsamling og FRET analyse lett tilpasses andre FRET-baserte kraft biosensorer som er blitt utviklet for andre proteiner.

<table border="0" cellpadding="0" cellspacing="0" width="1183">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">Nesprin-TS DNA</td>
			<td style="width:108px;">Addgene</td>
			<td style="width:119px;">68127</td>
			<td style="width:475px;">Retrieve from https://www.addgene.org/68127/</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">Nesprin-HL DNA</td>
			<td style="width:108px;">Addgene</td>
			<td style="width:119px;">68128</td>
			<td>Retrieve from https://www.addgene.org/68128/</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">mTFP1 DNA</td>
			<td style="width:108px;">Addgene</td>
			<td style="width:119px;">54613</td>
			<td>Retrieve from https://www.addgene.org/54613/</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">mVenus DNA</td>
			<td style="width:108px;">Addgene</td>
			<td style="width:119px;">27793</td>
			<td>Retrieve from https://www.addgene.org/27793/</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">TSmod DNA</td>
			<td style="width:108px;">Addgene</td>
			<td style="width:119px;">26021</td>
			<td>Retrieve from https://www.addgene.org/26021/</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">Competent Cells</td>
			<td style="width:108px;">Bioline</td>
			<td style="width:119px;">BIO-85026</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">Liquid LB Media</td>
			<td style="width:108px;">ThermoFisher</td>
			<td align="right" style="width:119px;">10855001</td>
			<td>https://www.thermofisher.com/order/catalog/product/10855001</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">Solid LB Bacterial Culture Plates</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td style="width:119px;">L5667</td>
			<td>http://www.sigmaaldrich.com/catalog/product/sigma/l5667?lang=en&#38;region=US</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">Ampicillin</td>
			<td style="width:108px;">Sigma</td>
			<td style="width:119px;">A9518</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">Spectrophotometer</td>
			<td style="width:108px;">Biorad</td>
			<td style="width:119px;">273 BR 07335</td>
			<td>SmartSpec Plus</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">quartz cuvette</td>
			<td style="width:108px;">Biorad</td>
			<td align="right" style="width:119px;">1702504</td>
			<td>Cuvette for SmartSpec Plus</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:483px;">&#160;DNA isolation kit</td>
			<td style="width:108px;">Macherey-Nagel</td>
			<td align="right" style="width:119px;">740412.5</td>
			<td>NucleoBond Xtra Midi Plus</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">6-well cell culture dish</td>
			<td style="width:108px;">Falcon-Corning</td>
			<td align="right" style="width:119px;">353046</td>
			<td>Multiwell 6-well Polystrene Culture Dish</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">Dulbecco&#39;s Modified Eagle Medium, (DMEM) cell media</td>
			<td style="width:108px;">Gibco</td>
			<td style="width:119px;">11995-065</td>
			<td>DMEM(1x)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">&#160;Bovine Serum</td>
			<td>Life Technologies</td>
			<td>16170-078</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">reduced serum cell media</td>
			<td style="width:108px;">Gibco</td>
			<td style="width:119px;">31985-070</td>
			<td>Reduced Serum Medium, &#34;optimem&#34;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">Lipid Carrier Solution</td>
			<td style="width:108px;">invitrogen</td>
			<td style="width:119px;">11668-019</td>
			<td>Lipid Reagent, &#34;Lipofectamine 2000&#34;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">1.5mL sterile plastic tube</td>
			<td style="width:108px;">Denville</td>
			<td style="width:119px;">c2170</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">Trypsin</td>
			<td style="width:108px;">Gibco</td>
			<td style="width:119px;">25200-056</td>
			<td>0.25% Trypsin-EDTA (1x)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:483px;">glass-bottom microscope viewing dish</td>
			<td style="width:108px;">In Vitro Scientific</td>
			<td style="width:119px;">D35-20-1.5-N</td>
			<td>35mm Dish with 20mm Bottom Well #1.5 glass</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">Fibronectin</td>
			<td style="width:108px;">ThermoFisher</td>
			<td align="right" style="width:119px;">33016015</td>
			<td>fibronectin human protein,plasma</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">Phosphate Buffered Saline (PBS)</td>
			<td style="width:108px;">Gibco</td>
			<td style="width:119px;">14190-144</td>
			<td>Dulbecco&#39;s Phosphate Buffered Saline</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:483px;">15mL sterile centrifuge tube</td>
			<td style="width:108px;">Greiner bio-one</td>
			<td align="right" style="width:119px;">188261</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:483px;">swinging rotor centrifuge&#160;</td>
			<td style="width:108px;">Thermo electron</td>
			<td style="width:119px;">Centra CL2</td>
			<td>Swinging rotor thermo electron 236</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:483px;">cell culture biosafety hood</td>
			<td style="width:108px;">Forma Scientific</td>
			<td align="right" style="width:119px;">1284</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">&#160;climate controlled cell culture incubator</td>
			<td style="width:108px;">ThermoFisher</td>
			<td align="right" style="width:119px;">3596</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:483px;">inverted LED widefield fluorescent microscope</td>
			<td style="width:108px;">Life technologies</td>
			<td style="width:119px;">EVOS FL</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:483px;">Clear HEPES buffered imaging media</td>
			<td style="width:108px;">Molecular Probes</td>
			<td style="width:119px;">A14291DJ</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:483px;">Fetal bovine Serum</td>
			<td style="width:108px;">Life technologies</td>
			<td style="width:119px;">10437-028</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:483px;">Temperature Controlled-Inverted confocal w/458 and 515nm laser sources&#160;</td>
			<td style="width:108px;">Zeiss</td>
			<td style="width:119px;">&#160;LSM 710-w/spectral META detector</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:483px;">Outgrowth Media</td>
			<td style="width:108px;">Newengland Biolabs</td>
			<td style="width:119px;">B9020s</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:483px;">NIH 3T3 Fibroblasts</td>
			<td style="width:108px;">ATCC</td>
			<td style="width:119px;">CRL-1658</td>
			<td></td>
		</tr>
	</tbody>
</table>

a protocol for using f&#246;rster resonance energy transfer (fret)-force biosensors to measure mechanical forces across the nuclear linc complex

The LINC complex has been hypothesized to be the critical structure that mediates the transfer of mechanical forces from the cytoskeleton to the nucleus. Nesprin-2G is a key component of the LINC complex that connects the actin cytoskeleton to membrane proteins (SUN domain proteins) in the perinuclear space. These membrane proteins connect to lamins inside the nucleus. Recently, a F&#246;rster Resonance Energy Transfer (FRET)-force probe was cloned into mini-Nesprin-2G (Nesprin-TS (tension sensor)) and used to measure tension across Nesprin-2G in live NIH3T3 fibroblasts. This paper describes the process of using Nesprin-TS to measure LINC complex forces in NIH3T3 fibroblasts. To extract FRET information from Nesprin-TS, an outline of how to spectrally unmix raw spectral images into acceptor and donor fluorescent channels is also presented. Using open-source software (ImageJ), images are pre-processed and transformed into ratiometric images. Finally, FRET data of Nesprin-TS is presented, along with strategies for how to compare data across different experimental groups.

Ved å følge protokollen ovenfor, ble plasmid-DNA anskaffet fra DNA-arkivet og transformert inn i E. coli-celler. E. coli som uttrykker sensoren DNA ble valgt fra LB / ampicillinplater og forsterkes i en flytende LB-medium. Etter forsterkning av vektorene, ble DNA-plasmider renset inn i Tris-EDTA-buffer ved bruk av en standard, kommersielt tilgjengelig DNA isolasjonskit. Ved hjelp av et spektrofotometer, ble resten renset DNA kvantifisert i en standard konsentrasjon p?...

Watch this Scientific Journal Video about A Protocol for Using FÃ¶rster Resonance Energy Transfer FRET-force Biosensors to Measure Mechanical Forces across the Nuclear LINC Complex at JoVE.com

A Protocol for Using F&#246;rster Resonance Energy Transfer (FRET)-force Biosensors to Measure Mechanical Forces across the Nuclear LINC Complex

A number of FRET-based force biosensors have recently been developed, enabling the protein-specific resolution of intracellular force. In this protocol, we demonstrate how one of these sensors, designed for the linker of the nucleoskeleton-cytoskeleton (LINC) complex protein Nesprin-2G can be used to measure actomyosin forces on the nuclear LINC complex.

En protokoll for å bruke Förster Resonance Energy Transfer (FRET) -force Biosensorer måle mekaniske krefter over hele Nuclear LINC Complex

The LINC complex has been hypothesized to be the critical structure that mediates the transfer of mechanical forces from the cytoskeleton to the nucleus. ...

The overall goal of this procedure is to determine forces on the linker of the nucleoskeleton cytoskeleton, or LINC complex, through FRET microscopy in living cells via a biosensor designed for the LINC complex protein, nesprin-2G. This method can help answer keys questions in the field of mechanotransduction, such as the forces placed on proteins in the nucleus of living cells, and how these forces change under variant conditions. The main advantage of this technique is its ability to measure very small levels of force on proteins and living cells.Generally, individuals new to this method will struggle with capturing images. Optimizing the microscope laser power and gain to receive a good signal between all experimental groups is difficult. To begin, grow NIH 3T3 fiber blast cells to between 70%and 90%confluence in a six-well cell culture dish in a standard cell culture incubator with temperature and CO2 regulation.In a cell culture hood, remove the medium and rinse each well with approximately 1 milliliter of a reduced serum cell medium. Add 800 microliters of reduced serum cell medium to each well, and place the six-well chamber in the incubator. Then, pipette 700 microliters of reduced serum cell medium into a 1.5 milliliter tube labeled L with 35 microliters of lipid carrier solution to form the lipo mix.Mix the suspension by pipetting. Next, pipette 100 microliters of the reduced serum cell medium into each of six 1.5 milliliter tubes labeled one through six. Pipette the plasma DNA for nesprin tension sensor, nesprin headless zero force control, mTFP1, and venus into tubes one through six, as described in the text protocol.Do not reuse pipette tips when pipetting different types of DNA. Then, pipette 100 microliters of the lipo mix from the L tube into each labeled tube, and mix by repeated pipetting, using a clean pipette for each tube. Incubate the suspension for 10 to 20 minutes.Next, add 200 microliters from each labeled tube to a well of the prepared six-well chamber containing cells. Label the top of each well with the corresponding DNA added. Then, place the six-well chamber in an incubator for four to six hours.Following incubation, aspirate the medium, and add one to two milliliters of reduced serum cell medium to rinse. Aspirate the reduced serum cell medium, and add two milliliters of trypsin to each well before placing the six-well dish in the incubator for five to 15 minutes. While the cells detach in the incubator, coat six glass-bottom viewing dishes with a layer of fibronectin at a concentration of 20 micrograms per milliliter dissolved in phosphate-buffered saline.Allow the dishes to coat the surface in the cell culture hood. Neutralize the trypsin by adding two milliliters of DMEM once the cells are detached. Then, transfer the contents of each well to a labeled 15 milliliter centrifuge tube and spin down at 90 times g for five minutes in a swinging rotor centrifuge.Aspirate the supernatant and re-suspend each cell pellet in 1, 000 microliters of DMEM using a pipette. Aspirate the fibronectin mixture from the glass dishes and pipette 1, 000 microliters of each cell suspension onto the dishes. After the cells settle to the bottom of the glass dishes, add another one milliliter of media to each well.Allow the cells to attach and express sensor in the cell incubator for at least 18 to 24 hours. To verify the transfection efficiency, use a fluorescent microscope equipped with an excitation frequency near 462 nanometers for mTFP1, or 525 nanometers for venus. Use an emission filter centered near 492 nanometers for mTFP1, or 525 nanometers for venus.Roughly 18 to 24 hours after completing the transfection, use an inverted fluorescent microscope to examine the efficiency of transfection by comparing the number of fluorescent cells to the total number of cells in view. If live cells cannot be imaged within 48 hours after transfection, fix the cells in 4%paraformaldehyde for five minutes. Allow cells to express sensor for 24 to 48 hours before fixation.Store the cells in PBS and view after 48 hours. In a cell culture hood, replace the cell medium with imaging medium supplemented with 10%fetal bovine serum. Place the viewing dishes in a temperature controlled confocal microscope stage.Place the glass viewing dish with mTFP1 transfected cells over the oil objective at 60X magnification with a numerical aperture of 1.4. Locate mTFP1-expressing cells in widefield fluorescent mode. With a fluorescent cell in the field of view, select the spectral detection mode and capture the spectral image.Include all frequencies beyond 458 nanometers using 10 nanometer increments. Select a bright fluorescent region on the cell. Add the fluorescent ROI mean as the normalized intensity to the spectral database by clicking Save Spectra to Database.Optimize the laser power and gain such that a good signal to noise ratio is achieved. Settings will vary for different equipment. Repeat the process for venus-expressing cells and remain in spectral mode.Use an excitation frequency of 488 nanometers instead of 458 nanometers. Adjust the power settings as needed, but do not change the emission frequencies. Select a bright fluorescent ROI of around a 20-pixel radius.Add the fluorescent ROI mean as the normalized intensity to the spectral database, by clicking Save Spectra to Database. To capture the unmixed images, first switch the capturing mode to spectral unmixing. Add the spectral fingerprints of venus and mTFP1 to the unmixing channels.Set the excitation laser back to a 458 nanometer argon source. Place the nesprin tension sensor viewing dish above the 60X oil objective. After focusing on a fluorescent cell with sufficiently bright expression, adjust the gain and laser power to optimize the signal to noise ratio.Capture a minimum of 15 to 20 images of nesprin tension sensor cells with relatively similar brightness and avoid excessive pixel saturation. Repeat the image capturing process with nesprin headless cells using identical imaging parameters. A representative 10X magnified image of 3T3 fibroblasts transfected with nesprin tension sensor using a lipid mediated carrier is shown here.Typically, only a fraction of cells are transfected in a given field of view. Shown here is a representative pair of two 3T3 nuclei expressing nesprin-TS in the spectrally unmixed venus and mTFP channels. A merged color image of the two channels is shown in the far right panel.Here is a representative sampling of nesprin-TS masked nuclei from stable expressing MDCK cells on patterned and unpatterned substrates. Ratio images are defined as the ratio of the venus channel divided by the mTFP channel and can be used to make relative quantitative force comparisons. Once mastered, this technique can be done in about eight hours if it's performed properly.While attempting this procedure, it's important to remember to carefully label DNA tubes during the transfection, and keep the imaging parameters constant while capturing spectrally result images. After watching this video, you should have a good understanding of how to transfect cells with the nesprin tension sensor and capture spectrally resolved images to computer FRET index that correlates with force on the tension sensor. Though in this case, a FRET sensor is used for nesprin, it can also be applied to other proteins in the cell where measuring force is desired.

Research

JoVE Journal

Bioengineering

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