Name: imaging molecular adhesion in cell rolling by adhesion footprint assay
Uploaded: 2021-09-27T15:00:00
Description: Watch this Scientific Journal Video about Imaging Molecular Adhesion in Cell Rolling by Adhesion Footprint Assay at JoVE.com

Dette arbeidet ble støttet av Canada Foundation of Innovation (CFI 35492), Natural Sciences and Engineering Research Council of Canada Discovery Grant (RGPIN-2017-04407), New Frontiers in Research Fund (NFRFE-2018-00969), Michael Smith Foundation for Health Research (SCH-2020-0559) og University of British Columbia Eminence Fund.

1. Oligonukleotid merking og hybridisering
<ol><li>Reduksjon av protein G disulfidbindinger<ol>
<li>Løs opp 10 mg Protein G (ProtG) i 1 ml ultrarent vann. MERK: Protein G her er modifisert med en enkelt cysteinrester ved C-terminus og en N-terminus poly-histidin tag.</li>
		<li>Bufferutveksling ≥20 μL ProtG (10 mg/ml) til 1x PBS (pH 7,2) med en P6-kolonne.</li>
		<li>Mål proteinkonsentrasjonen etter bufferutveksling. MERK: Typisk konsentrasjon på 7-8 mg/ml.</li>
		<li>Forbered 120 mM Tris(2...

<ol>
	<li>McEver, R. P., Zhu, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rolling+cell+adhesion.">Rolling cell adhesion.</a> Annual Review of Cell and Developmental Biology. 26 (1), 363-396 (2010).</li><li>Ley, K., Laudanna, C., Cybulsky, M. I., Nourshargh, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Getting+to+the+site+of+inflammation:+The+leukocyte+adhesion+cascade+updated.">Getting to the site of inflammation: The leukocyte adhesion cascade updated.</a> Nature Reviews Immunology. 7 (9), 678-689 (2007).</li><li>Zarbock, A., Ley, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+adhesion+and+activation+under+flow.">Neutrophil adhesion and activation under flow.</a> Microcirculation. 16 (1), 31-42 (2009).</li><li>Etzioni, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adhesion+molecules+-+Their+role+in+health+and+disease.">Adhesion molecules - Their role in health and disease.</a> Pediatric Research. 39 (2), 191-198 (1996).</li><li>van de Vijver, E., vanden Berg, T. K., Kuijpers, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leukocyte+adhesion+deficiencies.">Leukocyte adhesion deficiencies.</a> Hematology/Oncology Clinics of North America. 27 (1), 101-116 (2013).</li><li>Hanna, S., Etzioni, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leukocyte+adhesion+deficiencies.">Leukocyte adhesion deficiencies.</a> Annals of the New York Academy of Sciences. 1250 (1), 50-55 (2012).</li><li>Geng, Y., Marshall, J. R., King, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glycomechanics+of+the+metastatic+cascade:+Tumor+cell-endothelial+cell+interactions+in+the+circulation.">Glycomechanics of the metastatic cascade: Tumor cell-endothelial cell interactions in the circulation.</a> Annals of Biomedical Engineering. 40 (4), 790-805 (2012).</li><li>Yasmin-Karim, S., King, M. R., Messing, E. M., Lee, Y. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=E-selectin+ligand-1+controls+circulating+prostate+cancer+cell+rolling/adhesion+and+metastasis.">E-selectin ligand-1 controls circulating prostate cancer cell rolling/adhesion and metastasis.</a> Oncotarget. 5 (23), 12097-12110 (2014).</li><li>Marshall, B. T., Long, M., Piper, J. W., Yago, T., McEver, R. P., Zhu, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+observation+of+catch+bonds+involving+cell-adhesion+molecules.">Direct observation of catch bonds involving cell-adhesion molecules.</a> Nature. 423 (6936), 190-193 (2003).</li><li>Hammer, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adhesive+dynamics.">Adhesive dynamics.</a> Journal of Biomechanical Engineering. 136 (2), 021006 (2014).</li><li>Yasunaga, A. B., Murad, Y., Kapras, V., Menard, F., Li, I. T. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+interpretation+of+cell+rolling+velocity+distribution.">Quantitative interpretation of cell rolling velocity distribution.</a> Biophysical Journal. 120 (12), 2511-2520 (2021).</li><li>Li, I. T. S., Ha, T., Chemla, Y. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+cell+surface+adhesion+by+rotation+tracking+and+adhesion+footprinting.">Mapping cell surface adhesion by rotation tracking and adhesion footprinting.</a> Scientific Reports. 7 (1), 44502 (2017).</li><li>Yasunaga, A. B., Li, I. T. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+fast+molecular+adhesion+by+fluorescence+footprinting.">Quantification of fast molecular adhesion by fluorescence footprinting.</a> Science Advances. 7 (34), (2021).</li><li>Dempsey, G. T., Vaughan, J. C., Chen, K. H., Bates, M., Zhuang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+fluorophores+for+optimal+performance+in+localization-based+super-resolution+imaging.">Evaluation of fluorophores for optimal performance in localization-based super-resolution imaging.</a> Nature Methods. 8 (12), 1027-1040 (2011).</li><li>Zhu, M., Lerum, M. Z., Chen, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+to+prepare+reproducible,+homogeneous,+and+hydrolytically+stable+aminosilane-derived+layers+on+silica.">How to prepare reproducible, homogeneous, and hydrolytically stable aminosilane-derived layers on silica.</a> Langmuir. 28 (1), 416-423 (2012).</li><li>Chandradoss, S. D., Haagsma, A. C., Lee, Y. K., Hwang, J. H., Nam, J. M., Joo, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+passivation+for+single-molecule+protein+studies.">Surface passivation for single-molecule protein studies.</a> Journal of Visualized Experiments: JoVE. (86), e50549 (2014).</li><li>Schnitzbauer, J., Strauss, M. T., Schlichthaerle, T., Schueder, F., Jungmann, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Super-resolution+microscopy+with+DNA-PAINT.">Super-resolution microscopy with DNA-PAINT.</a> Nature Protocols. 12 (6), 1198-1228 (2017).</li><li>Chalfoun, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MIST:+Accurate+and+scalable+microscopy+image+stitching+tool+with+stage+modeling+and+error+minimization.">MIST: Accurate and scalable microscopy image stitching tool with stage modeling and error minimization.</a> Scientific Reports. 7 (1), 4988 (2017).</li><li>Wang, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Constructing+modular+and+universal+single+molecule+tension+sensor+using+protein+G+to+study+mechano-sensitive+receptors.">Constructing modular and universal single molecule tension sensor using protein G to study mechano-sensitive receptors.</a> Scientific Reports. 6, 1-10 (2016).</li><li>Crockett-Torabi, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selectins+and+mechanisms+of+signal+transduction.">Selectins and mechanisms of signal transduction.</a> Journal of Leukocyte Biology. 63 (1), 1-14 (1998).</li><li>Ye, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+P-selectin+and+PSGL-1+axis+accelerates+atherosclerosis+via+activation+of+dendritic+cells+by+the+TLR4+signaling+pathway.">The P-selectin and PSGL-1 axis accelerates atherosclerosis via activation of dendritic cells by the TLR4 signaling pathway.</a> Cell Death and Disease. 10 (7), 507 (2019).</li><li>Saha, K., Bender, F., Gizeli, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+study+of+IgG+binding+to+proteins+G+and+A:+Nonequilibrium+kinetic+and+binding+constant+determination+with+the+acoustic+waveguide+device.">Comparative study of IgG binding to proteins G and A: Nonequilibrium kinetic and binding constant determination with the acoustic waveguide device.</a> Analytical Chemistry. 75 (4), 835-842 (2003).</li><li>Murad, Y., Li, I. T. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantifying+molecular+forces+with+serially+connected+force+sensors.">Quantifying molecular forces with serially connected force sensors.</a> Biophysical Journal. 116 (7), 1282-1291 (2019).</li><li>Yasunaga, A. B., Murad, Y., Li, I. T. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantifying+molecular+tension-classifications,+interpretations+and+limitations+of+force+sensors.">Quantifying molecular tension-classifications, interpretations and limitations of force sensors.</a> Physical Biology. 17 (1), 011001 (2020).</li></ol>

Adhesjonsfotavtrykksanalysen muliggjør visualisering av molekylære vedheftshendelser mellom PSGL-1 og P-selectin under cellerulling. Denne prosessen er initiert av P-selectin-mediert fangst etterfulgt av rullende under fluidisk skjær stress. Potensielle problemer under eksperimentet innebærer vanligvis dårlig cellerulling eller manglende fluorescerende spor selv når cellene ruller godt. Disse problemene skyldes ofte kvalitetskontroller ved de kritiske trinnene i protokollen, som oppført i feilsøkingstabellen (<st...

Den rullende vedheftkaskaden beskriver hvordan sirkulerende celler tether til og ruller langs blodkarveggen1. Passiv rulling formidles primært av selectins, en stor klasse av cellulære vedheftsmolekyler (CAMs)1. Under skjærstrømmen av blod danner leukocytter som uttrykker P-selectin glykoprotein ligand-1 (PSGL-1) svært forbigående bindinger med P-selectin, som kan uttrykkes på overflaten av betente endotelceller. Denne prosessen er kritisk for leukocytter å migrere til et sted med betennelse2. I tillegg er PSGL-1 også en mekanosensitiv reseptor som er i stand til å utløse det påfølgende faste vedheftsstadiet av den rullende vedheftkaskaden ved sitt engasjement med P-selectin3.
Genetiske mutasjoner som påvirker CAM-funksjonen kan ha stor innvirkning på immunforsvaret, for eksempel ved den sjeldne sykdommen leukocyttadhesjonsmangel (LAD), der funksjonsfeil i vedheftmolekyler som formidler rullende fører til alvorlig immunkompromitterte individer4,5,6. I tillegg har sirkulerende tumorceller vist seg å migrere etter en lignende rulleprosess, noe som fører til metastase7,8. Men fordi cellerulling er rask og dynamisk, er konvensjonelle eksperimentelle mekanobiologimetoder uegnet til å studere molekylære interaksjoner under cellerulling. Mens enkeltcellede og enkeltmolekylelle manipulasjonsmetoder som atomkraftmikroskopi og optisk pinsett var i stand til å studere molekylære interaksjoner som P-selectins kraftavhengige interaksjon med PSGL-1 på enkeltmolekylnivå9, er de uegnet til å undersøke levende vedheftshendelser under cellerulling. I tillegg kan interaksjonen karakterisert in vitro ikke svare direkte på spørsmålet om molekylær vedheft in vivo. For eksempel, hvilket molekylært spenningsområde er biologisk relevant når celler fungerer i sitt opprinnelige miljø? Beregningsmetoder som limdynamikksimulering10 eller enkel steady-state model11 har fanget visse molekylære detaljer og hvordan de påvirker rullende oppførsel, men er svært avhengige av nøyaktigheten av modelleringsparametrene og antagelsene. Andre teknikker som trekkraftmikroskopi kan oppdage krefter under cellemigrering, men gir ikke tilstrekkelig romlig oppløsning eller kvantitativ informasjon om molekylær spenning. Ingen av disse teknikkene kan gi direkte eksperimentelle observasjoner av den tidsmessige dynamikken, romlig fordeling og størrelsen heterogenitet av molekylære krefter, som direkte relaterer seg til cellefunksjon og oppførsel i sitt opprinnelige miljø.
Derfor er implementering av en molekylær kraftsensor som er i stand til nøyaktig måling av selectin-medierte interaksjoner avgjørende for å forbedre vår forståelse av rullende vedheft. Her beskriver vi protokollen for adhesjonsfotavtrykket assay12 der PSGL-1 belagte perler rulles på en overflate som presenterer p-selectin funksjonaliserte spenningsmålerte tthers (TGTs)13. Disse TGTene er irreversible DNA-baserte kraftsensorer som resulterer i en permanent historie med bruddhendelser i form av fluorescensavlesning. Dette oppnås gjennom rupturing av TGT (dsDNA) og deretter etterfølgende merking av ruptured TGT (ssDNA) med en fluorescerende merket komplementær tråd. En stor fordel med dette systemet er kompatibiliteten med både diffraksjonsbegrenset og superoppløsningsavbildning. Den fluorescerende merkede komplementære tråden kan enten være permanent bundet (>12 bp) for diffraksjonsbegrenset avbildning eller forbigående bundet (7-9 bp) for bildebehandling med superoppløsning gjennom DNA PAINT. Dette er et ideelt system for å studere rullende vedheft da TGT-ene brister under aktiv rulling, men fluorescensavlesningen analyseres etter rulling. De to avbildningsmetodene gir også brukeren mer frihet til å undersøke rullende vedheft. Vanligvis er diffraksjonsbegrenset avbildning nyttig for å trekke ut molekylær bruddkraft gjennom fluorescensintensitet13, mens superoppløsningsavbildning gir kvantitativ analyse av reseptortetthet. Med evnen til å undersøke disse egenskapene til rullende vedheft, gir denne tilnærmingen en lovende plattform for å forstå kraftreguleringsmekanismen på molekylær vedheft av rullende celler under skjærstrøm.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>4-channel drill guide</td>
			<td>Custom made</td>
			<td></td>
			<td>3D printed with ABS filament</td>
		</tr>
		<tr>
			<td>4-holes slide</td>
			<td>Custom made</td>
			<td></td>
			<td>Drill clean microscope slide using a Dremel with diamond coated drill bits on a 4-channels drill guide which has a layout that matches with the centers of the 8-32 threaded holes on the aluminum clamp.</td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>VWR</td>
			<td>BDH1101-4LP</td>
			<td></td>
		</tr>
		<tr>
			<td>Acrylic spacer</td>
			<td>Custom made</td>
			<td></td>
			<td>Cut two blocks of acrylic sheets with the dimension of 40 mm x 30 mm x 2.5 mm. On each block, drill two 3 mm holes that are precisely aligned with the 4-40 holes on the aluminium holder.</td>
		</tr>
		<tr>
			<td>Aluminium chip holder</td>
			<td>Custom made</td>
			<td></td>
			<td>Machine anodized aluminium block into a C-shaped holder with the outer dimension of 640 mm x 500 mm x 65 mm and the opening dimension of 400 mm x 380 mm x 65 mm. Inlets and outlets are tapped with 8-32 thread.</td>
		</tr>
		<tr>
			<td>Aminosilane</td>
			<td>AlfaAesar</td>
			<td>L14043</td>
			<td>CAS 1760-24-3</td>
		</tr>
		<tr>
			<td>Antibiotic/antimycotic solution</td>
			<td>Cytiva HyClone</td>
			<td>SV3007901</td>
			<td>Pen/Strep/Fungiezone</td>
		</tr>
		<tr>
			<td>Beads, ProtG coated polystyrene</td>
			<td>Spherotech</td>
			<td>PGP-60-5</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine serum albumin</td>
			<td>VWR</td>
			<td>332</td>
			<td></td>
		</tr>
		<tr>
			<td>Buffer, DNA PAINT</td>
			<td></td>
			<td></td>
			<td>0.05% Tween-20, 5 mM Tris, 75 mM MgCl2, 1 mM EDTA</td>
		</tr>
		<tr>
			<td>Buffer, T50M5</td>
			<td></td>
			<td></td>
			<td>10mM Tris, 50 mM NaCl, 5 mM MgCl2</td>
		</tr>
		<tr>
			<td>Buffer, Rolling</td>
			<td></td>
			<td></td>
			<td>HBSS with 2mM CaCl2, 2 mM MgCl2, 10 mM Hepes, 0.1% BSA</td>
		</tr>
		<tr>
			<td>Buffer, Wash</td>
			<td></td>
			<td></td>
			<td>10 mM Tris, 50 mM NaCl, 5 mM MgCl2 and 2 mM CaCl2, 0.05% Tween 20</td>
		</tr>
		<tr>
			<td>Calcium chloride</td>
			<td>VWR</td>
			<td>BDH9224</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell culture flasks</td>
			<td>VWR</td>
			<td>10062-868</td>
			<td></td>
		</tr>
		<tr>
			<td>Concentrated sulfuric acid</td>
			<td>VWR</td>
			<td>BDH3072-2.5LG</td>
			<td>95-98%</td>
		</tr>
		<tr>
			<td>Coverslip holding tweezers</td>
			<td>Techni-Tool</td>
			<td>758TW150</td>
			<td></td>
		</tr>
		<tr>
			<td>Diamond-coated drill bits</td>
			<td>Abrasive technology</td>
			<td>C5250510</td>
			<td>0.75 mm diamond drill</td>
		</tr>
		<tr>
			<td>DNA, amine-ssDNA (top strand)</td>
			<td>IDT DNA</td>
			<td>Custom oligo</td>
			<td>CCGGGCGACGCAGGAGGG /3AmMO/</td>
		</tr>
		<tr>
			<td>DNA, biotin-ssDNA (bottom strand)</td>
			<td>IDT DNA</td>
			<td>Custom oligo</td>
			<td>/5BiotinTEG/ TTTTT CCCTCCTGCGTCGCCCGG</td>
		</tr>
		<tr>
			<td>DNA, imager strand for DNA-PAINT</td>
			<td>IDT DNA</td>
			<td>Custom oligo</td>
			<td>GAGGGAAA TT/3Cy3Sp/</td>
		</tr>
		<tr>
			<td>DNA, imager strand for permanent labelling</td>
			<td>IDT DNA</td>
			<td>Custom oligo</td>
			<td>CCGGGCGACGCAGG /3Cy3Sp/</td>
		</tr>
		<tr>
			<td>Double-sided tape</td>
			<td>Scotch</td>
			<td>237</td>
			<td>3/4 inch width, permanent double-sided tape</td>
		</tr>
		<tr>
			<td>EDTA</td>
			<td>Thermofisher</td>
			<td>15575020</td>
			<td>0.5 M EDTA, pH 8.0</td>
		</tr>
		<tr>
			<td>Epoxy</td>
			<td>Gorilla</td>
			<td>42001</td>
			<td>5 minute curing time</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS)</td>
			<td>Avantor</td>
			<td>97068-085</td>
			<td></td>
		</tr>
		<tr>
			<td>GelGreen</td>
			<td>Biotium</td>
			<td>41005</td>
			<td></td>
		</tr>
		<tr>
			<td>Glacial acetic acid</td>
			<td>VWR</td>
			<td>BDH3094-2.5LG</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass, Coverslips</td>
			<td>Fisher Scientific</td>
			<td>12-548-5P</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass, Microscope slide</td>
			<td>VWR</td>
			<td>48300-026</td>
			<td>75 mm x 25 mm x 1 mm</td>
		</tr>
		<tr>
			<td>Glass, Staining jar</td>
			<td>VWR</td>
			<td>74830-150</td>
			<td>Wheaton Staining Jar (900620)</td>
		</tr>
		<tr>
			<td>Hanks&#39; Balanced Salt solution (HBSS)</td>
			<td>Lonza</td>
			<td>04-315Q</td>
			<td></td>
		</tr>
		<tr>
			<td>Hemocytometer</td>
			<td>Sigma-Aldrich</td>
			<td>Z359629-1EA</td>
			<td></td>
		</tr>
		<tr>
			<td>HL-60 cells</td>
			<td>ATCC</td>
			<td>CCL-240</td>
			<td></td>
		</tr>
		<tr>
			<td>Humidity chamber slide support</td>
			<td>Custom made</td>
			<td></td>
			<td>3D printed with ABS filament</td>
		</tr>
		<tr>
			<td>Hydrogen peroxide</td>
			<td>VWR</td>
			<td>BDH7690-1</td>
			<td>30%</td>
		</tr>
		<tr>
			<td>Imidazole</td>
			<td>Sigma-Aldrich</td>
			<td>I2399</td>
			<td></td>
		</tr>
		<tr>
			<td>Inlets/outlets</td>
			<td>Custom made</td>
			<td></td>
			<td>Drill through eight 8-32 set screws using cobalt drill bits. Insert 1.5 cm&#160; polyethylene tubing (Tygon, I.D. 1/32&#8221; O.D. 3/32&#8221;) into each hollow setscrew</td>
		</tr>
		<tr>
			<td>Iscove Modified Dulbecco Media (IMDM)</td>
			<td>Lonza</td>
			<td>12-722F</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium chloride</td>
			<td>VWR</td>
			<td>BDH9244</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic Ni-NTA beads</td>
			<td>Invitrogen</td>
			<td>10103D</td>
			<td></td>
		</tr>
		<tr>
			<td>Mailer tubes</td>
			<td>EMS</td>
			<td>EMS71406-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>VWR</td>
			<td>BDH1135-4LP</td>
			<td></td>
		</tr>
		<tr>
			<td>Micro Bio-Spin P-6 Gel Columns</td>
			<td>Biorad</td>
			<td>7326200</td>
			<td>In SSC Buffer</td>
		</tr>
		<tr>
			<td>PEG</td>
			<td>Laysan Bio</td>
			<td>MPEG-SVA-5000</td>
			<td></td>
		</tr>
		<tr>
			<td>PEG-biotin</td>
			<td>Laysan Bio</td>
			<td>Biotin-PEG-SVA-5000</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium hydroxide</td>
			<td>VWR</td>
			<td>470302-132</td>
			<td></td>
		</tr>
		<tr>
			<td>Protein, Protein G</td>
			<td>Abcam</td>
			<td>ab155724</td>
			<td>N-terminal His-Tag and C-terminal cysteine</td>
		</tr>
		<tr>
			<td>Protein, P-selectin-Fc</td>
			<td>R&#38;D System</td>
			<td>137-PS</td>
			<td>Recombinant Human P-Selectin/CD62P Fc Chimera Protein, CF</td>
		</tr>
		<tr>
			<td>Protein, Streptavidin</td>
			<td>Cedarlane</td>
			<td>CL1005-01-5MG</td>
			<td></td>
		</tr>
		<tr>
			<td>Pump Syringe</td>
			<td>Harvard Apparatus</td>
			<td>704801</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium bicarbonate</td>
			<td>Ward&#8217;s Science</td>
			<td>470302-444</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>VWR</td>
			<td>97061-274</td>
			<td></td>
		</tr>
		<tr>
			<td>Sulfo-SMCC</td>
			<td>Thermofisher</td>
			<td>22322</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe</td>
			<td>Hamilton</td>
			<td>81520</td>
			<td>Syringes with PTFE luer lock, 5 mL</td>
		</tr>
		<tr>
			<td>Syringe needles</td>
			<td>BD</td>
			<td>305115</td>
			<td>Precision Glide 26 G, 5/8 Inch Length</td>
		</tr>
		<tr>
			<td>TCEP</td>
			<td>Sigma-Aldrich</td>
			<td>C4706-2G</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris</td>
			<td>VWR</td>
			<td>BDH4502-500GP</td>
			<td></td>
		</tr>
		<tr>
			<td>Tubing, Adaptor</td>
			<td>Tygon</td>
			<td>ABW00001</td>
			<td>Formulation 3350, I.D. 1/32&#8221;; O.D. 3/32&#8221;</td>
		</tr>
		<tr>
			<td>Tubing, Polyethylene</td>
			<td>BD Intramedic</td>
			<td>427406</td>
			<td>Intramedic (PE20) I.D. 0.38mm; O.D. 1.09mm</td>
		</tr>
		<tr>
			<td>Tween-20</td>
			<td>Sigma-Aldrich</td>
			<td>93773</td>
			<td></td>
		</tr>
	</tbody>
</table>

imaging molecular adhesion in cell rolling by adhesion footprint assay

Rullende vedheft, tilrettelagt av selectin-medierte interaksjoner, er en svært dynamisk, passiv motilitet i å rekruttere leukocytter til betennelsesstedet. Dette fenomenet forekommer i postkapillære venuler, hvor blodstrømmen skyver leukocytter i en rullende bevegelse på endotelcellene. Stabil rulling krever en delikat balanse mellom vedheftsbindingsdannelse og deres mekanisk drevne dissosiasjon, slik at cellen forblir festet til overflaten mens den ruller i strømningsretningen. I motsetning til andre vedheftsprosesser som forekommer i relativt statiske miljøer, er rullende vedheft svært dynamisk når rullecellene beveger seg over tusenvis av mikroner ved titalls mikron per sekund. Følgelig er konvensjonelle mekanobiologimetoder som trekkraftmikroskopi uegnet til å måle de enkelte vedheftshendelsene og de tilknyttede molekylære kreftene på grunn av den korte tidsskalaen og høy følsomhet som kreves. Her beskriver vi vår siste implementering av adhesjonsfotavtrykkanalysen for å avbilde P-selectin: PSGL-1-interaksjoner i rullende vedheft på molekylært nivå. Denne metoden benytter irreversible DNA-baserte spenningsmålere for å produsere en permanent historie med molekylære vedheftshendelser i form av fluorescensspor. Disse sporene kan avbildet på to måter: (1) sy sammen tusenvis av diffraksjonsbegrensede bilder for å produsere et stort synsfelt, noe som muliggjør utvinning av vedheftsfotavtrykk for hver rullende celle over tusenvis av mikroner i lengde, (2) utfører DNA-PAINT for å rekonstruere superoppløselige bilder av fluorescenssporene innenfor et lite synsfelt. I denne studien ble adhesjonsfotavtrykksanalysen brukt til å studere HL-60-celler som rullet på forskjellige skjærspenninger. Ved å gjøre det var vi i stand til å se for oss den romlige fordelingen av P-selectin: PSGL-1-interaksjonen og få innsikt i deres molekylære krefter gjennom fluorescensintensitet. Dermed gir denne metoden grunnlaget for den kvantitative undersøkelsen av de ulike celleoverflateinteraksjonene som er involvert i rullende vedheft på molekylært nivå.

Protokollen ovenfor beskriver den eksperimentelle prosedyren for adhesjonsfotavtrykkanalysen. Den generelle eksperimentarbeidsflyten er illustrert i figur 1, fra strømningskammerenheten (figur 1A) til overflatefunksjonaliseringen (figur 1B) og eksperiment- og bildetrinn (figur 1C).
Figur 2 er et representativt resultat for protG-ssDNA biokonjuge...

Watch this Scientific Journal Video about Imaging Molecular Adhesion in Cell Rolling by Adhesion Footprint Assay at JoVE.com

Imaging Molecular Adhesion in Cell Rolling by Adhesion Footprint Assay

Denne protokollen presenterer eksperimentelle prosedyrer for å utføre vedheft fotavtrykk analysen for å avbilde vedheft hendelser under rask celle rullende vedheft.

Bildemolekylær vedheft i cellerulling ved adhesjonsfotavtrykkanalyse

Rolling adhesion, facilitated by selectin-mediated interactions, is a highly dynamic, passive motility in recruiting leukocytes to the site of ...

Denne protokollen bidrar til å etablere sammenhengen mellom molekylær kraft og cellerullingsatferd i tillegg til å tillate romlig kart og kvantifisere rullende vedheft på molekylært nivå. Denne teknikken gjør det mulig å studere individuelle vedheftshendelser under selve cellerullingen, slik at vi kan måle den fysiologiske relevante molekylære vedheftskraften direkte. Overflateforberedelse ved hjelp av riktig konsentrasjons- og inkubasjonstid i hvert trinn er avgjørende for å oppnå overflatefunksjonalisering av høy kvalitet.Kvaliteten på biokonjugasjoner og riktige forhold er også avgjørende. Visuell demonstrasjon er avgjørende for å hjelpe forskere med å gjenskape denne protokollen. Spesielt vil trinnene som flytkammermontering og etterbehandlingsbilder ha stor nytte av en visuell demonstrasjon.Begynn med å spre en liten mengde epoksy på begge sider av det dobbeltsidige båndet med et barberblad. Bruk en laser til å kutte det epoksybelagte båndet for å lage fire kanaler. Lag strømningsbrikken ved å smøre epoksytapen mellom en firehulls skyve og PEG-deksler.Bruk en pipettespiss, bruk forsiktig trykk langs lengden på kanalene for å skape en god forsegling, og herd deretter epoksyen i minst en time. Juster brikken slik at åpningen på hver kanal plasseres midt på adapteren. Plasser deretter to gjennomsiktige akryl avstandsstykker på toppen av brikken.Påfør fast trykk midt på blokken og skru i enden av hver avstandsstykke. Skru innløpene inn i de gjengede hullene på den andre siden av braketten og overvåk tetningsforholdet gjennom den gjennomsiktige akrylblokken. Strømning 200 mikroliter vaskebuffer inn i kammeret for å se etter lekkasje.Hvis det dannes bobler i kanalen, skyver du aggressivt ytterligere 200 mikroliter vaskebuffer for å fjerne boblene. Tilsett 40 mikroliter BSA i strømningskammeret for å forhindre ikke-spesifikk binding og inkubere i 10 minutter i fuktighetskammeret. Etter inkubasjon, tilsett 40 mikroliter ved Tween 20 til strømningskammeret og inkuber igjen i 10 minutter for å ytterligere redusere den uspesifiserte bindingen.Vask deretter kanalen med 200 mikroliter vaskebuffer for å fjerne alle passivasjonsmidler. For kammeroverflatefunksjonalisering, tilsett 40 mikroliter Streptavidin til strømningskammeret og inkuber i 20 minutter, vask deretter kammeret med 200 mikroliter vaskebuffer. Tilsett nå 40 mikroliter hybridisert protein G-TGT i strømningskammeret og inkuber i 20 minutter.Etter vask med vaskebuffer, tilsett 40 mikroliter protein G-TGT toppstreng og inkuber i 20 minutter for å fullføre en ukybridert TGT bunnstreng på overflaten og vask deretter med vaskebuffer. Til slutt legger du til 40 mikroliter P-selectin-Fc i strømningskammeret og inkuberer i 60 minutter før vask med vaskebuffer. Fyll en fem milliliter glasssprøyte med rullebufferen og trykk på sidene av sprøyten for å løsne og skyve boblene ut mens de flyter mot spissen.Etter å ha satt inn en steril nål i et 200 millimeter stykke polyetylenrør, koble nålen til glasssprøyten. Fest sprøyten på sprøytepumpen og vipp sprøytepumpen slik at stempelsiden er forhøyet for å forhindre at luftbobler kommer inn i kanalen. Sett enden av røret inn i strømningskammerets innløp.Sett den ene enden av et annet 200 millimeter stykke polyetylenrør inn i utløpet og senk den andre enden i et avfallsbeger. Ta en til to milliliter av cellefjæringsprøven og sentrifugen for å pellet cellene. Fjern mediet og resuspender cellene forsiktig i 500 mikroliter av rullebufferen.Koble slangen forsiktig fra innløpene og utløpet og pipetten 40 mikroliter av cellefjæringen inn i strømningskammeret. Koble til slangen igjen som beskrevet tidligere, slik at bobler ikke blir introdusert i strømningskanalen. Start cellerullingseksperimentet ved å starte sprøytepumpen ved ønsket strømningshastighet.Observer cellerulling ved hjelp av et mørkt feltmikroskop med et 10X mål. Når eksperimentet er fullført, fjerner du cellene fra kanalen ved å infundere rullebufferen ved 100 milliliter per time til overflaten er cellefri. For avbildning av de lokale sporene med DNA-PAINT, tilsett 40 mikroliter DNA-PAINT imager strand fremstilt i DNA-PAINT buffer til kanalen.Utfør total intern refleksjon fluorescensmikroskopi ved hjelp av forholdene som er nevnt i tekstmanuskriptet. Lokaliser og gjengi superoppløsningsbildene. For å forestille seg de lange sporene ved permanent merking, legg til den permanente imagerstrengen og inkuber i 120 sekunder i T50M5-bufferen.Vask deretter kanalen ved å infundere 200 mikroliter vaskebuffer. Ta opp et bilde med eksitasjonslaseren av for å få bakgrunnskamerastøy. Bilde et stort område i et rutenett mønster av TIRF mikroskopi.Programmer mikroskopet til å skanne over området på 400 x 50 bilder og dele rådataene i individuelle TIP-filer som hver inneholder maksimalt 10 000 bilder ved hjelp av ImageJ-programmet. Slå sammen alle bildene ved hjelp av belysningsprofilen og bruk MIST-plugin-modulen til å sy bildene. Resultatet for proteinet G ssDNA biokonjugering karakterisering viste at en nesten en er til ett forhold mellom protein G og ssDNA der proteinet G Maleimide ssDNA og imidazol elution buffer spektra fra ortogonalt grunnlag for montering til biokonjugering produktspekteret.Native PAGE ble brukt til å bekrefte biokonjugasjonen som viser de lyse grønne båndene som sammenfaller med det monomeriske proteinet G-båndet som indikerer vellykket konjugering og godt utbytte. TIRF-belysningsprofilen introdusert fra en enkeltmodusfiber er generelt lysere midt i synsfeltet og dimmer rundt kantene. For å kompensere for ujevn belysning og slå sammen bildene for kvantitativ analyse, ble belysningsprofilen bestemt ved å beregne gjennomsnittet av tusenvis av individuelle rammer.Sammenslåtte bilder ble produsert ved å trekke kamerastøyen fra både rå- og belysningsprofiler og deretter normalisere av belysningsprofilen. Rå søm viste klare periodiske mønstre som tilsvarer de ukorrekte bildene, mens det samme synsfeltet sydd sammen fra sammenslåtte bilder ga en flat bakgrunn. En rampe opp strømningsprofil ble brukt til å bestemme omfanget av skjærspenning som resulterte i cellerulling og gi fluorescensspor der et typisk encellet vedheftsfotavtrykk kunne sees.Suboptimale og optimale resultater av fluorescerende spor med utilstrekkelig kontrast, overdreven sportetthet, optimal sportetthet og kontrast, og diffraksjonsbegrenset og DNA-PAINT-avbildning vises. inkubasjonstid på mer enn 60 minutter sikrer overflatefunksjonalisering og riktig kammerkonstruksjon forhindrer passasje av bobler som skader funksjonalisert overflate. Denne prosedyren gjelder for kvantitativ analyse av molekylær kraft involvert i rullende vedheft og lar forskere forstå den rullende oppførselen til de forskjellige celletypene.Denne teknikken gjør det mulig for forskere å utforske nye spørsmål om raske vedheftshendelser som fører til videreutvikling av enkeltmolekyl- og mekanobiologiforskning.

imaging-molecular-adhesion-in-cell-rolling-by-adhesion-footprint-assay

Research

JoVE Journal

Biology

Assay for Adhesion and Agar Invasion in S. cerevisiae

Yeasts are found in natural biofilms, where many microorganisms colonize surfaces. In artificial environments, such as surfaces of man-made objects, biofilms can reduce industrial productivity, destroy structures, and threaten human life. 1-3 On the other hand, harnessing the power of biofilms can help clean the environment and generate sustainable energy. 4-8
The ability of S. cerevisiae to colonize surfaces and participate in complex biofilms was mostly ignored until the rediscovery of the differentiation programs triggered by various signaling pathways and environmental cues in this organism. 9, 10 The continuing interest in using S. cerevisiae as a model organism to understand the interaction and convergence of signaling pathways, such as the Ras-PKA, Kss1 MAPK, and Hog1 osmolarity pathways, quickly placed S. cerevisiae in the junction of biofilm biology and signal transduction research. 11-20 To this end, differentiation of yeast cells into long, adhesive, pseudohyphal filaments became a convenient readout for the activation of signal transduction pathways upon various environmental changes. However, filamentation is a complex collection of phenotypes, which makes assaying for it as if it were a simple phenotype misleading. In the past decade, several assays were successfully adopted from bacterial biofilm studies to yeast research, such as MAT formation assays to measure colony spread on soft agar and crystal violet staining to quantitatively measure cell-surface adherence. 12, 21 However, there has been some confusion in assays developed to qualitatively assess the adhesive and invasive phenotypes of yeast in agar.
Here, we present a simple and reliable method for assessing the adhesive and invasive quality of yeast strains with easy-to-understand steps to isolate the adhesion assessment from invasion assessment. Our method, adopted from previous studies, 10, 16 involves growing cells in liquid media and plating on differential nutrient conditions for growth of large spots, which we then wash with water to assess adhesion and rub cells completely off the agar surface to assess invasion into the agar. We eliminate the need for streaking cells onto agar, which affects the invasion of cells into the agar. In general, we observed that haploid strains that invade agar are always adhesive, yet not all adhesive strains can invade agar medium. Our approach can be used in conjunction with other assays to carefully dissect the differentiation steps and requirements of yeast signal transduction, differentiation, quorum sensing, and biofilm formation.

We describe a qualitative assay for yeast adhesion and agar invasion as a measure of invasive and pseudohyphal differentiation. This simple assay can be used to assess the invasive phenotype of various mutants as well as the effects environmental cues and signaling pathways on yeast differentiation.

Yeasts are found in natural biofilms, where many microorganisms colonize surfaces. In artificial environments, such as surfaces of man-made objects, ...

Dissection of Organizer and Animal Pole Explants from Xenopus laevis Embryos and Assembly of a Cell Adhesion Assay

This video demonstrates the technique used for preparation of organizer and animal pole explants from Xenopus laevis embryos, including the use of the eyebrow knife - a specialized dissection tool made of one's eyebrow. The protocol for assembling an adhesion assay is also given, which probes for the presence of key adhesion molecules present on the surface organizer or animal pole cells that are critical for proper development.

Title Cell Encapsulation by Droplets

A Behavioral Assay to Measure Responsiveness of Zebrafish to Changes in Light Intensities 

The optokinetic reflex (OKR) is a basic visual reflex exhibited by most vertebrates and plays an important role in stabilizing the eye relative to the visual scene. However, the OKR requires that an animal detect moving stripes and it is possible that fish that fail to exhibit an OKR may not be completely blind. One zebrafish mutant, the no optokinetic response c (nrc) has no OKR under any light conditions tested and was reported to be completely blind. Previously, we have shown that OFF-ganglion cell activity can be recorded in these mutants. To determine whether mutant fish with no OKR such as the nrc mutant can detect simple light increments and decrements we developed the visual motor behavioral assay (VMR). In this assay, single zebrafish larvae are placed in each well of a 96-well plate allowing the simultaneous monitoring of larvae using an automated video-tracking system. The locomotor responses of each larva to 30 minutes light ON and 30 minutes light OFF were recorded and quantified. WT fish have a brief spike of motor activity upon lights ON, known as the startle response, followed by return to lower-than baseline activity, called a freeze. WT fish also sharply increase their locomotor activity immediately following lights OFF and only gradually (over several minutes) return to baseline locomotor activity. The nrc mutants respond similarly to light OFF as WT fish, but exhibit a slight reduction in their average activity as compared to WT fish. Motor activity in response to light ON in nrc mutants is delayed and sluggish. There is a slow rise time of the nrc mutant response to light ON as compared to WT light ON response. The results indicate that nrc fish are not completely blind. Because teleosts can detect light through non-retinal tissues, we confirmed that the immediate behavioral responses to light-intensity changes require intact eyes by using the chokh (chk) mutants, which completely lack eyes from the earliest stages of development. In our VMR assay, the chk mutants exhibit no startle response to either light ON or OFF, showing that the lateral eyes mediate this behavior. The VMR assay described here complements the well-established OKR assay, which does not test the ability of zebrafish larvae to respond to changes in light intensities. Additionally, the automation of the VMR assay lends itself to high-throughput screening for defects in light-intensity driven visual responses.

A Behavioral Assay to Measure Responsiveness of Zebrafish to Changes in Light Intensities

We developed the Visual-Motor Response to quantitate the motor output of larval zebrafish in response to light increments and decrements. We also examined zebrafish vision mutants, including the no optokinetic response (nrc) mutants, which were thought to be completely blind when tested by another vision assay, the optokinetic reflex.

The optokinetic reflex (OKR) is a basic visual reflex exhibited by most vertebrates and plays an important role in stabilizing the eye relative to the ...

Platelet Adhesion and Aggregation Under Flow using Microfluidic Flow Cells

Platelet aggregation occurs in response to vascular injury where the extracellular matrix below the endothelium has been exposed. The platelet adhesion cascade takes place in the presence of shear flow, a factor not accounted for in conventional (static) well-plate assays. This article reports on a platelet-aggregation assay utilizing a microfluidic well-plate format to emulate physiological shear flow conditions. Extracellular proteins, collagen I or von Willebrand factor are deposited within the microfluidic channel using active perfusion with a pneumatic pump. The matrix proteins are then washed with buffer and blocked to prepare the microfluidic channel for platelet interactions. Whole blood labeled with fluorescent dye is perfused through the channel at various flow rates in order to achieve platelet activation and aggregation. Inhibitors of platelet aggregation can be added prior to the flow cell experiment to generate IC50 dose response data.

The platelet adhesion cascade takes place in the presence of shear flow, a factor not accounted for in conventional (static) well-plate assays. This article reports on a platelet-aggregation assay utilizing a microfluidic well-plate format to emulate physiological shear flow conditions.

Platelet aggregation occurs in response to vascular injury where the extracellular matrix below the endothelium has been exposed. The platelet adhesion ...

Imaging Cell Shape Change in Living Drosophila Embryos

The developing Drosophila melanogaster embryo undergoes a number of cell shape changes that are highly amenable to live confocal imaging. Cell shape changes in the fly are analogous to those in higher organisms, and they drive tissue morphogenesis. So, in many cases, their study has direct implications for understanding human disease (Table 1)1-5. On the sub-cellular scale, these cell shape changes are the product of activities ranging from gene expression to signal transduction, cell polarity, cytoskeletal remodeling and membrane trafficking. Thus, the Drosophila embryo provides not only the context to evaluate cell shape changes as they relate to tissue morphogenesis, but also offers a completely physiological environment to study the sub-cellular activities that shape cells.
The protocol described here is designed to image a specific cell shape change called cellularization. Cellularization is a process of dramatic plasma membrane growth, and it ultimately converts the syncytial embryo into the cellular blastoderm. That is, at interphase of mitotic cycle 14, the plasma membrane simultaneously invaginates around each of ~6000 cortically anchored nuclei to generate a sheet of primary epithelial cells. Counter to previous suggestions, cellularization is not driven by Myosin-2 contractility6, but is instead fueled largely by exocytosis of membrane from internal stores7. Thus, cellularization is an excellent system for studying membrane trafficking during cell shape changes that require plasma membrane invagination or expansion, such as cytokinesis or transverse-tubule (T-tubule) morphogenesis in muscle.
Note that this protocol is easily applied to the imaging of other cell shape changes in the fly embryo, and only requires slight adaptations such as changing the stage of embryo collection, or using "embryo glue" to mount the embryo in a specific orientation (Table 1)8-19. In all cases, the workflow is basically the same (Figure 1). Standard methods for cloning and Drosophila transgenesis are used to prepare stable fly stocks that express a protein of interest, fused to Green Fluorescent Protein (GFP) or its variants, and these flies provide a renewable source of embryos. Alternatively, fluorescent proteins/probes are directly introduced into fly embryos via straightforward micro-injection techniques9-10. Then, depending on the developmental event and cell shape change to be imaged, embryos are collected and staged by morphology on a dissecting microscope, and finally positioned and mounted for time-lapse imaging on a confocal microscope.

Imaging Cell Shape Change in Living Drosophila Embryos

Early development of the fruit fly, Drosophila melanogaster, is characterized by a number of cell shape changes that are well suited for imaging approaches. This article will describe basic tools and methods required for live confocal imaging of Drosophila embryos, and will focus on a cell shape change called cellularization.

The developing Drosophila melanogaster embryo undergoes a number of cell shape changes that are highly amenable to live confocal imaging.  Cell shape ...

Live Imaging Assay for Assessing the Roles of Ca2+ and Sphingomyelinase in the Repair of Pore-forming Toxin Wounds

Plasma membrane injury is a frequent event, and wounds have to be rapidly repaired to ensure cellular survival. Influx of Ca2+ is a key signaling event that triggers the repair of mechanical wounds on the plasma membrane within ~30 sec. Recent studies revealed that mammalian cells also reseal their plasma membrane after permeabilization with pore forming toxins in a Ca2+-dependent process that involves exocytosis of the lysosomal enzyme acid sphingomyelinase followed by pore endocytosis. Here, we describe the methodology used to demonstrate that the resealing of cells permeabilized by the toxin streptolysin O is also rapid and dependent on Ca2+ influx. The assay design allows synchronization of the injury event and a precise kinetic measurement of the ability of cells to restore plasma membrane integrity by imaging and quantifying the extent by which the liphophilic dye FM1-43 reaches intracellular membranes. This live assay also allows a sensitive assessment of the ability of exogenously added soluble factors such as sphingomyelinase to inhibit FM1-43 influx, reflecting the ability of cells to repair their plasma membrane. This assay allowed us to show for the first time that sphingomyelinase acts downstream of Ca2+-dependent exocytosis, since extracellular addition of the enzyme promotes resealing of cells permeabilized in the absence of Ca2+.

Live Imaging Assay for Assessing the Roles of Ca2+ and Sphingomyelinase in the Repair of Pore-forming Toxin Wounds

Live imaging of cells exposed to the lipophilic dye FM1-43 allows precise determination of the kinetics by which pore-forming toxins are removed from the plasma membrane. This is a sensitive assay that can be used to assess requirements for Ca2+, sphingomyelinase and other factors on plasma membrane repair.

Lev Imaging analysen for vurdering av roller av Ca<sup&gt; 2 +</sup&gt; Og Sphingomyelinase i Reparasjon av poredannende Gift Wounds

Plasma membrane injury is a frequent event, and wounds have to be rapidly repaired to ensure cellular survival. Influx of Ca2+ is a key signaling event ...

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) maintain the turnover of all mature blood cell lineages. The coordination of the complex signals leading to specific HSC fates relies upon the interaction between HSCs and the intricate bone marrow microenvironment, which is still poorly understood[1-2].
We describe how by combining a newly developed specimen holder for stable animal positioning with multi-step confocal and two-photon in vivo imaging techniques, it is possible to obtain high-resolution 3D stacks containing HSPCs and their surrounding niches and to monitor them over time through multi-point time-lapse imaging. High definition imaging allows detecting ex vivo labeled hematopoietic stem and progenitor cells (HSPCs) residing within the bone marrow. Moreover, multi-point time-lapse 3D imaging, obtained with faster acquisition settings, provides accurate information about HSPC movement and the reciprocal interactions between HSPCs and stroma cells.
Tracking of HSPCs in relation to GFP positive osteoblastic cells is shown as an exemplary application of this method. This technique can be utilized to track any appropriately labeled hematopoietic or stromal cell of interest within the mouse calvarium bone marrow space.

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

The nature of the interactions between hematopoietic stem and progenitor cells (HSPCs) and bone marrow niches is poorly understood. Custom hardware modifications and a multi-step acquisition protocol allow the use of two-photon and confocal microscopy to image ex vivo labeled HSPCs homed within bone marrow areas, tracking interactions and movement.

In Vivo 4-Dimensional Sporing av Hematopoietiske Stem og stamceller i Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) ...

Activating Autophagy by Aerobic Exercise in Mice

Autophagy is a lysosomal degradation pathway essential for cell homeostasis, function and differentiation. Under stress conditions, autophagy is induced and targets various cargos, such as bulk cytosol, damaged organelles and misfolded proteins, for degradation in lysosomes. Resulting nutrient molecules are recycled back to the cytosol for new protein synthesis and ATP production. Upregulation of autophagy has beneficial effects against the pathogenesis of many diseases, and pharmacological and physiological strategies to activate autophagy have been reported. Aerobic exercise is recently identified as an efficient autophagy inducer in multiple organs in mice, including muscle, liver, heart and brain. Here we show procedures to induce autophagy in vivo by either forced treadmill exercise or voluntary wheel running. We also demonstrate microscopic and biochemical methods to quantitatively analyze autophagy levels in mouse tissues, using the marker proteins LC3 and p62 that are transported to and degraded in lysosomes along with autophagosomes.

Autophagy activation is beneficial in the prevention of a number of diseases. One of the physiological approaches to induce autophagy in vivo is physical exercise. Here we show how to activate autophagy by aerobic exercise and measure autophagy levels in mice.

Aktivering Autophagy av Aerobic Exercise i Mus

Autophagy is a lysosomal degradation pathway essential for cell homeostasis, function and differentiation. Under stress conditions, autophagy is induced ...

Analyzing Cell Surface Adhesion Remodeling in Response to Mechanical Tension Using Magnetic Beads

Mechanosensitive cell surface adhesion complexes allow cells to sense the mechanical properties of their surroundings. Recent studies have identified both force-sensing molecules at adhesion sites, and force-dependent transcription factors that regulate lineage-specific gene expression and drive phenotypic outputs. However, the signaling networks converting mechanical tension into biochemical pathways have remained elusive. To explore the signaling pathways engaged upon mechanical tension applied to cell surface receptor, superparamagnetic microbeads can be used. Here we present a protocol for using magnetic beads to apply forces to cell surface adhesion proteins. Using this approach, it is possible to investigate not only force-dependent cytoplasmic signaling pathways by various biochemical approaches, but also adhesion remodeling by magnetic isolation of adhesion complexes attached to the ligand-coated beads. This protocol includes the preparation of ligand-coated superparamagnetic beads, and the application of define tensile forces followed by biochemical analyses. Additionally, we provide a representative sample of data demonstrating that tension applied to integrin-based adhesion triggers adhesion remodeling and alters protein tyrosine phosphorylation.

Cell surface adhesions are central in mechanotransduction, as they transmit mechanical tension and initiate the signaling pathways involved in tissue homeostasis and development. Here, we present a protocol for dissecting the biochemical pathways that are activated in response to tension, using ligand-coated magnetic microbeads and force application to adhesion receptors.

Analysere Cell Surface Adhesjon Ombygging i Response til Mekanisk Tension Bruke magnetiske kuler

Mechanosensitive cell surface adhesion complexes allow cells to sense the mechanical properties of their surroundings. Recent studies have identified both ...