This work was supported by National Institutes of Health grants R01-DK080834 and R01-DK093045. We thank J. Denise Wetzel, CCHMC Medical Writer, for editing of the manuscript.

1. Ingenuity Pathway Analysis
<ol>
	<li>Uploading Protein-interactome Dataset
	<ol>
		<li>Insert the proteins/genes of interest in a spreadsheet with their unique gene identifiers (preferably gene symbols and gene identifier numbers as obtained with mass spectrometric data).</li>
		<li>Assign one column in the spreadsheet for Gene identifier number and one column for observational value (e.g., Fold-change or p-value). Select the &#39;contains column header&#39; option to view the column headings.</li>
		<li>Upload the dataset on the IPA by clicking on the upload dataset tab and selecting the spreadsheet mentioned above. Choose the flexible format tab, and select the appropriate category of gene identifier. 
		Note: A flexible format of the dataset overcomes the formatting specifications for uploading.</li>
		<li>After the dataset appears, select ID and observation columns. Ensure that all of the proteins (MRP4 interactome as identified by mass-spectrometry) are mapped by checking on the dataset summary tab. The dataset is now ready for the desired analysis.</li>
	</ol>
	</li>
	<li>Data Analysis 
	Note: Described are the partial uses of IPA features that were utilized for this study.
	<ol>
		<li>After uploading MRP4 interactome with their gene names as the unique identifiers, click on new and choose core analysis in the top left menu of IPA software.</li>
		<li>Set the expression cutoffs value for intensity in accordance with the experiment type (Intensity value of 100 is recommended for analysis).</li>
		<li>Calculate the fold-change in expression while preparing the dataset if control and experimental conditions are involved and include it as part of the dataset file if a comparison analysis needs to be performed (A cut-off value of 1.5 fold change is usually recommended for analysis). 
		Note: After completion of the core analysis, multiple sections of analyses can be obtained. The first tab shows the summary of the total analyses and suggests top canonical pathways, upstream regulators, molecular and cellular functions, and networks among others; all calculated based on the confidence level (p value) and arranged in ascending order of p value.</li>
		<li>Open the major canonical pathways (using the open pathway option) as large molecular networks that pictorially show cross talking, overlapping, and affected signaling pathways. 
		Look at the list of the canonical pathways that are majorly involved based on the p-value (p &#60;0.05 is considered as significant). 
		Note: The significance values for the canonical pathways are calculated by Fisher&#39;s exact test right-tailed. The significance indicates the probability of association of molecules from the dataset with the canonical pathway by random chance alone.</li>
		<li>Confirm the input proteins (MRP4 interactome as identified by mass-spectrometry) among the list of proteins involved in each pathway. 
		Note: Using this option, it was observed that the cellular actin cytoskeleton signaling network is the major affected pathway and how the input proteins fit into it (Figure 1). This approach helps identify which molecular networks would be closely associated and affected by the test proteins.</li>
		<li>Use the network tab in the analyses to identify the top diseases and functions that are potentially linked to a particular protein network based on the number of focus molecules. 
		Note: A score value is given based on the known proteins that are determined as part of a network e.g., cellular assembly and organization network, through literature knowledge and experimental evidences and focus molecules that are identified from the dataset and become part of the network. Henceforth, the network gets filtered in the first place based on the number of focus molecules.</li>
	</ol>
	</li>
</ol>
2. High-content Microscopy
<ol>
	<li>Preparation of Cells 
	Note: All cell culture work was done under the horizontal-flow cell culture hood.
	<ol>
		<li>Use 96-well microplates for the wound-healing assay.</li>
		<li>Coat the microplate with 1% fibronectin solution (reconstituted in PBS), and keep the plate in a standard CO2 incubator at 37 &#176;C for 2 hr.</li>
		<li>Remove Mrp4-/- and Mrp4+/+ mouse embryonic fibroblast (MEFs) grown in 25 cm&#178; cell culture flasks from the incubator, wash 1 time with PBS, and trypsinize the cells for 5 min using 1 ml of 4x trypsin-EDTA solution.</li>
		<li>Wash the cells with complete medium (DMEM containing 10% FBS and 1% penicillin/streptomycin) and resuspend them in 5 ml of complete medium.</li>
		<li>Aspirate the fibronectin solution from the wells. Count cells using a hemocytometer and seed 30,000 cells (cell number needs to be optimized based on cell type) into each well.</li>
		<li>Grow the cells to 100% confluence in a standard CO2 incubator at 37 &#176;C for 24 hr.</li>
	</ol>
	</li>
	<li>Creating Wound
	<ol>
		<li>Ensure all the wells are filled with solution. Fill unused wells with PBS to prevent damage to the wound making tool (e.g., WoundMaker).</li>
		<li>After confirming 100% cell confluence, place the 96-well plate inside the wound making tool on the metal base plate and press the 96-well pin block down.</li>
		<li>Wash the cells three-times with PBS to remove any dislodged cells and add 100 &#181;l of complete medium.</li>
		<li>Add the test compounds - H-89 (50 &#181;M; 1:1,000 dilution with complete media using 50 mM stock in DMSO) or Latrunculin B (1 &#181;M; 1:1,000 dilution with complete media using 1 mM stock in DMSO) at this stage.</li>
		<li>Place the assay plate inside the reader at 37 &#176;C and monitor migration over the experimental period.</li>
	</ol>
	</li>
	<li>Monitoring Cell Migration 
	Note: Cell migration was monitored using the microscope and software provided with high-content microscopy system. The use of 96-well microplates ensures that the wounds are automatically monitored by the microscope and registered by the software.
	<ol>
		<li>Set the software to scan the assay plate every hour for migration assays using the schedule scan tab . Select a start time at least 15 min after placing the assay plate inside the reader to allow equilibration prior to imaging.</li>
		<li>Select the tray and choose vessel type (96-well microplate) and experiment type (Scratch Wound).</li>
		<li>Select 10X objective and choose phase-contrast imaging parameters. Select the wells that need to be scanned using the edit scan pattern option.</li>
		<li>Specify the treatments groups and any replicates by selecting the properties tab and setting up a plate map. Scanning can be stopped at any time based on the experimental condition.</li>
	</ol>
	</li>
	<li>Data Analysis
	<ol>
		<li>After the scanning is done, select the vessel view tab for the assay plate. Go to the analysis job utilities and select launch new analysis job.</li>
		<li>Set scratch wound as job type and select the time range for the analysis (0 time point to 24 hr time point).</li>
		<li>Select the wells to be chosen for analysis by a single click on the well and click &#39;OK&#39; to initiate the analysis. Once the analysis is done, graphically visualize relative wound density (RWD) data for each well at each time point using export to the graph option.</li>
		<li>View the phase-contrast image set of each well corresponding to different time-points using the view image tab. Select a specific well by clicking on the plate map, select a specific time point from the time range tab and click on the view image tab.</li>
	</ol>
	</li>
</ol>
3. F&#246;rster Resonance Energy Transfer (FRET)
<ol>
	<li>Preparation of Cells
	<ol>
		<li>Coat 35 mm glass-bottomed dishes with 100 &#181;l of 1% fibronectin solution (as described in section 2.1) and keep them in a standard CO2 incubator at 37 &#176;C for 2 hr.</li>
		<li>Aspirate the fibronectin solution from the plates and seed equal numbers of HEK293 cells (10,000 cells/plate) in complete medium.</li>
		<li>Grow the cells to 60-70% confluence in the fibronectin coated glass-bottomed dishes in a standard CO2 incubator at 37 &#176;C for 24 hr.</li>
	</ol>
	</li>
	<li>Transfection
	<ol>
		<li>Perform all transient transfections using a commercial transfection reagent according to manufacturer&#39;s instructions.</li>
		<li>Aliquot 250 &#181;l of complete medium into two separate 1.5 ml&#160;sterile centrifuge tubes for each 35 mm dish.</li>
		<li>Add 2 &#181;g of DNA (pmAKAR3 or pmAKAR3-TA) in one tube and 5 &#181;l (2.5 fold the DNA concentration) of transfection reagent in another tube.</li>
		<li>Incubate the tubes for 20 min at room temperature and then transfer the diluted DNA into the transfection reagent-containing tube.</li>
		<li>Mix thoroughly and incubate at 37 &#176;C for another 30 min.</li>
		<li>Aspirate the medium off the cells and wash them once with PBS. Add 1 ml of antibiotic-free DMEM F-12 medium containing 10% FBS to the cells.</li>
		<li>Add 507 &#181;l of DNA-lipid conjugate with media to the cells in each plate, mix gently, and keep in the CO2 incubator at 37 &#176;C for 48 hr. Use 2 &#181;g of DNA (1 &#181;g/&#181;l stock) and 5 &#181;l lipid for 10,000-50,000 cells in each plate.</li>
	</ol>
	</li>
	<li>Live-cell Imaging
	<ol>
		<li>After 48 hr of transfection, remove growth medium and wash the cells 2 times with Hank&#39;s Balanced Salt Solution (HBSS, pre-warmed at 37 &#176;C). Add a final volume of 1.9 ml HBSS to the washed cells and mount them on an inverted wide-field microscope system for FRET imaging inside a custom-made 37 &#176;C maintained chamber. 
		Note: In this system, the excitation light is provided by a 300 W Xenon lamp attenuated with a Neutral Density filter with 50% light transmission.</li>
		<li>Use 60X objective. Manually focus on the cells and set an optimal field of view using the microscope. Activate the selected field of view on the computer screen using the Focus &#34;F&#34; option on the software. For performing FRET measurements, select the proper filter set (CFP/YFP filter set with a 430/25 nm excitation filter, a double dichroic beam splitter, and two emission filters (470/30 nm for CFP and 535/30 nm for FRET) manually.</li>
		<li>Visualize fluorescence by first checking on the channel option CFP/YFP/FRET followed by clicking open fluor tab. Improve the signal intensity by using the intensification tool in the camera tab.</li>
		<li>Select cells expressing pmAKAR3 or pmAKAR3-TA avoiding saturation of the signal intensity. Use the capture window to initiate FRET measurement.</li>
		<li>Select the time-lapse option and setup a time-scan for 30 min with 30 sec interval. Check the FRET option and set the exposure time at 100 msec. Enter the image label and press start to initiate the measurement.</li>
		<li>After five time points and establishment of a baseline, add 25 &#181;M of forskolin (5 &#181;l of 10 &#181;M stock in ethanol, diluted with 100 &#181;l of HBSS) to the cells without disturbing the plate and monitor the cells for a total of 30 min.</li>
	</ol>
	</li>
	<li>Data Analysis 
	Note: Use ratiometric calculation module for data analysis.
	<ol>
		<li>Click on the select tool on the left-hand side of the image window and choose a solid rectangle from the drop down menu. Drag the rectangle on the image field in a cell free area and right click on it to set it as background for the purpose of background subtraction.</li>
		<li>Go to the mask and use &#39;create a new mask&#39; option. Go to the select tool and choose a pen from the drop down menu to manually draw a mask around the cell to select it for a measurement. Select at least 4-6 cells per condition.</li>
		<li>Select the Mask tab and perform mask statistics.</li>
		<li>Check &#39;Entire mask&#39;, expand cross-channel option and select donor normalized FRET (N-FRET) (FRET/CFP). The N-FRET value is representative of PKA activity at the plasma membrane.</li>
		<li>Add time-stamps, look-up table and scale bar using the annotations.</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Ridley, A. 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=Cell+migration:+integrating+signals+from+front+to+back.">Cell migration: integrating signals from front to back.</a> Science. 302 (5651), 1704-1709 (2003).</li><li>Lauffenburger, D. A., Horwitz, A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+migration:+a+physically+integrated+molecular+process.">Cell migration: a physically integrated molecular process.</a> Cell. 84 (3), 359-369 (1996).</li><li>Arora, K., 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=Compartmentalization+of+cyclic+nucleotide+signaling:+a+question+of+when,+where,+and+why?.">Compartmentalization of cyclic nucleotide signaling: a question of when, where, and why?.</a> Pflugers Arch. 465 (10), 1397-1407 (2013).</li><li>Howe, A. K., Baldor, L. C., Hogan, B. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatial+regulation+of+the+cAMP-dependent+protein+kinase+during+chemotactic+cell+migration.">Spatial regulation of the cAMP-dependent protein kinase during chemotactic cell migration.</a> Proc Natl Acad Sci U S A. 102 (40), 14320-14325 (2005).</li><li>Lim, C. 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=Integrin-mediated+protein+kinase+A+activation+at+the+leading+edge+of+migrating+cells.">Integrin-mediated protein kinase A activation at the leading edge of migrating cells.</a> Mol Biol Cell. 19 (11), 4930-4941 (2008).</li><li>Paulucci-Holthauzen, A. A., 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=Spatial+distribution+of+protein+kinase+A+activity+during+cell+migration+is+mediated+by+A-kinase+anchoring+protein+AKAP+Lbc.">Spatial distribution of protein kinase A activity during cell migration is mediated by A-kinase anchoring protein AKAP Lbc.</a> J Biol Chem. 284 (9), 5956-5967 (2009).</li><li>Weaver, A. M., Young, M. E., Lee, W. L., Cooper, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integration+of+signals+to+the+Arp2/3+complex.">Integration of signals to the Arp2/3 complex.</a> Curr Opin Cell Biol. 15 (1), 23-30 (2003).</li><li>Le Clainche, C., Carlier, M. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+actin+assembly+associated+with+protrusion+and+adhesion+in+cell+migration.">Regulation of actin assembly associated with protrusion and adhesion in cell migration.</a> Physiol Rev. 88 (2), 489-513 (2008).</li><li>Raftopoulou, M., Hall, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+migration:+Rho+GTPases+lead+the+way.">Cell migration: Rho GTPases lead the way.</a> Dev Biol. 265 (1), 23-32 (2004).</li><li>Krause, M., Dent, E. W., Bear, J. E., Loureiro, J. J., Gertler, F. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ena/VASP+proteins:+regulators+of+the+actin+cytoskeleton+and+cell+migration.">Ena/VASP proteins: regulators of the actin cytoskeleton and cell migration.</a> Annu Rev Cell Dev Biol. 19, 541-564 (2003).</li><li>Hara, Y., 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=Inhibition+of+MRP4+prevents+and+reverses+pulmonary+hypertension+in+mice.">Inhibition of MRP4 prevents and reverses pulmonary hypertension in mice.</a> J Clin Invest. 121 (7), (2011).</li><li>Russel, F. G., Koenderink, J. B., Masereeuw, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multidrug+resistance+protein+4+(MRP4/ABCC4):+a+versatile+efflux+tra+(7),+2888-289nsporter+for+drugs+and+signalling+molecules.">Multidrug resistance protein 4 (MRP4/ABCC4): a versatile efflux tra (7), 2888-289nsporter for drugs and signalling molecules.</a> Trends Pharmacol Sci. 29 (4), 200-207 (2008).</li><li>Cheepala, S., 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=Cyclic+nucleotide+compartmentalization:+contributions+of+phosphodiesterases+and+ATP-binding+cassette+transporters.">Cyclic nucleotide compartmentalization: contributions of phosphodiesterases and ATP-binding cassette transporters.</a> Annu Rev Pharmacol Toxicol. 53, 231-253 (2013).</li><li>Sinha, C., 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=Multi-drug+resistance+protein+4+(MRP4)-mediated+regulation+of+fibroblast+cell+migration+reflects+a+dichotomous+role+of+intracellular+cyclic+nucleotides.">Multi-drug resistance protein 4 (MRP4)-mediated regulation of fibroblast cell migration reflects a dichotomous role of intracellular cyclic nucleotides.</a> J Biol Chem. 288 (6), 3786-3794 (2013).</li><li>Popovici, C., 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=Direct+and+heterologous+approaches+to+identify+the+LET-756/FGF+interactome.">Direct and heterologous approaches to identify the LET-756/FGF interactome.</a> BMC Genomics. 7 (105), (2006).</li><li>Soler-Lopez, M., Zanzoni, A., Lluis, R., Stelzl, U., Aloy, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interactome+mapping+suggests+new+mechanistic+details+underlying+Alzheimer's+disease.">Interactome mapping suggests new mechanistic details underlying Alzheimer's disease.</a> Genome Res. 21 (3), 364-376 (2011).</li><li>Sinha, C., 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=PKA+and+actin+play+critical+roles+as+downstream+effectors+in+MRP4-mediated+regulation+of+fibroblast+migration.">PKA and actin play critical roles as downstream effectors in MRP4-mediated regulation of fibroblast migration.</a> Cell Signal. 27 (7), 1345-1355 (2015).</li><li>Liu, L., Wang, Y. D., Wu, J., Cui, J., Chen, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carnitine+palmitoyltransferase+1A+(CPT1A):+a+transcriptional+target+of+PAX3-FKHR+and+mediates+PAX3-FKHR-dependent+motility+in+alveolar+rhabdomyosarcoma+cells.">Carnitine palmitoyltransferase 1A (CPT1A): a transcriptional target of PAX3-FKHR and mediates PAX3-FKHR-dependent motility in alveolar rhabdomyosarcoma cells.</a> BMC Cancer. 12 (154), (2012).</li><li>Zhang, J., Ma, Y., Taylor, S. S., Tsien, R. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetically+encoded+reporters+of+protein+kinase+A+activity+reveal+impact+of+substrate+tethering.">Genetically encoded reporters of protein kinase A activity reveal impact of substrate tethering.</a> Proc Natl Acad Sci U S A. 98 (26), 14997-15002 (2001).</li><li>Sinha, C., 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=Forster+resonance+energy+transfer+-+an+approach+to+visualize+the+spatiotemporal+regulation+of+macromolecular+complex+formation+and+compartmentalized+cell+signaling.">Forster resonance energy transfer - an approach to visualize the spatiotemporal regulation of macromolecular complex formation and compartmentalized cell signaling.</a> Biochim Biophys Acta. 1840 (10), 3067-3072 (2014).</li><li>Sato, M., Ozawa, T., Inukai, K., Asano, T., Umezawa, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescent+indicators+for+imaging+protein+phosphorylation+in+single+living+cells.">Fluorescent indicators for imaging protein phosphorylation in single living cells.</a> Nat Biotechnol. 20 (3), 287-294 (2002).</li><li>Allen, M. D., Zhang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Subcellular+dynamics+of+protein+kinase+A+activity+visualized+by+FRET-based+reporters.">Subcellular dynamics of protein kinase A activity visualized by FRET-based reporters.</a> Biochem Biophys Res Commun. 348 (2), 716-721 (2006).</li><li>Ananthanarayanan, B., Ni, Q., Zhang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Signal+propagation+from+membrane+messengers+to+nuclear+effectors+revealed+by+reporters+of+phosphoinositide+dynamics+and+Akt+activity.">Signal propagation from membrane messengers to nuclear effectors revealed by reporters of phosphoinositide dynamics and Akt activity.</a> Proc Natl Acad Sci U S A. 102 (42), 15081-15086 (2005).</li><li>Yamaguchi, H., Condeelis, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+the+actin+cytoskeleton+in+cancer+cell+migration+and+invasion.">Regulation of the actin cytoskeleton in cancer cell migration and invasion.</a> Biochim Biophys Acta. 1773 (5), 642-652 (2007).</li><li>Lamalice, L., Le Boeuf, F., Huot, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+cell+migration+during+angiogenesis.">Endothelial cell migration during angiogenesis.</a> Circ Res. 100 (6), 782-794 (2007).</li><li>Ghosh, M. C., Makena, P. S., Gorantla, V., Sinclair, S. E., Waters, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CXCR4+regulates+migration+of+lung+alveolar+epithelial+cells+through+activation+of+Rac1+and+matrix+metalloproteinase-2.">CXCR4 regulates migration of lung alveolar epithelial cells through activation of Rac1 and matrix metalloproteinase-2.</a> Am J Physiol Lung Cell Mol Physiol. 302 (9), L846-L856 (2012).</li><li>Vicente-Manzanares, M., Webb, D. J., Horwitz, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+migration+at+a+glance.">Cell migration at a glance.</a> J Cell Sci. 118 (Pt 21), 4917-4919 (2005).</li><li>Zaccolo, M., 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=A+genetically+encoded,+fluorescent+indicator+for+cyclic+AMP+in+living+cells.">A genetically encoded, fluorescent indicator for cyclic AMP in living cells.</a> Nat Cell Biol. 2 (1), 25-29 (2000).</li></ol>

The authors have nothing to disclose.

Cell migration is an intricate process that plays indispensable roles in many important physiological events including wound healing1,2. Aberrant cell migrations may cause catastrophic events, such as tumor metastasis and angiogenesis24,25. Therefore, fine-tuned regulation of cell migration is required to maintain normal body function.
Using high-content microscopy18, we demonstrated that MRP4-deficient MEFs migrate faster compared to wild-type fibroblasts...

Cell migration is a complicated multi-step process. Studies have shown that during migration cells are polarized into leading and trailing edges. By adhering to the extracellular matrix, the leading edge provides the traction necessary for the cell body to move forward. Finally, the trailing edge releases rear attachments and completes the migration cycle1,2.
Cell polarization for efficient cell migration is regulated by spatial segregation of intracellular signaling. Cellular second messengers, such as cAMP, mediate the compartmentalization of the signaling events required for fine-tuned directional cell migration3,4. Preferential accumulations of cAMP and cAMP-dependent kinase PKA activity at the leading edge play key roles in directional cell migration5,6. By phosphorylating small GTPases such as Ras-related C3 botulinum toxin substrate (Rac) and cell division control protein 42 homolog or Cdc42, PKA activates actin-related protein 2/3 (Arp 2/3) at the leading edge and induces the formation of lamellipodia7-9. PKA also phosphorylates an anti-capping agent, vasodilator stimulated phosphoprotein (VASP), thereby regulates the oscillatory cycles of membrane extension and retraction10,11.
In cells, cAMP levels are regulated by three major processes: i) synthesis by adenylate cyclase, ii) degradation by phosphodiesterases, and iii) transportation by membrane-bound efflux transporters3. Multidrug resistance protein 4 (MRP4), a member of ATP-binding cassette (ABC) family of membrane transporters, functions as an endogenous efflux transporter of cyclic nucleotides. Therefore, MRP4 can regulate intracellular cAMP levels and cAMP-dependent cellular signaling11-13. We have previously shown that in Mrp4-/-, fibroblasts contain relatively higher levels of cyclic nucleotides and migrate faster compared to Mrp4+/+ fibroblasts14. We also reported a biphasic effect of cyclic nucleotides on fibroblast migration. Based on previous studies and our finding that Mrp4-/- fibroblasts contain more polarized cAMP during the course of migration, we hypothesized that this MRP4-mediated regulation of fibroblast migration is cAMP dependent. In order to understand the downstream mechanism, we took a direct yet multifaceted approach.
To identify the proteins associated and in interplay with MRP4, we immunoprecipitated MRP4-containing macromolecular complexes from HEK293 cells that over express MRP4. Using mass-spectrometry, we identified multiple MRP4-interacting proteins and analyzed their interconnectivity using Ingenuity Pathway Analysis (IPA). IPA is a useful tool to analyze protein-protein interactions (both structural and functional) and explore their contributions in particular physiological and pathological events based on the literature and experimental evidences15,16. IPA indicated that F-actin is a major downstream target of MRP4 in the context of cell migration where cAMP and cGMP are the key signaling molecules17. These data were further confirmed by high-content microscopy. High-content microscopy can capture and analyze cell behaviors such as cell migration in a more convenient, accurate and high-throughput manner18. The high-content microscopy data demonstrated that the effect of MRP4 on fibroblast migration is completely abolished upon disruption of the actin cytoskeleton or inhibition of PKA17.
Additionally, we used a F&#246;rster resonance energy transfer (FRET)-based PKA sensor to monitor the PKA dynamics in migrating cells in real time. FRET-based kinase sensors usually consist of specific phosphorylation substrate peptides flanked by CFP and YFP fluorophores19-21. pmAKAR3 is an improved and membrane targeted FRET-based PKA sensor that contains forkhead-associated domain 1 (FHA1) and the PKA substrate sequence LRRATLVD5,22. Phosphorylation of pmAKAR3 by the PKA catalytic subunit increases FRET signal between CFP and YFP19. Insertion of a lipid modification domain into the sensor targets it to the plasma membrane for monitoring PKA dynamics, specifically at the membrane compartment23.
Using pmAKAR3, we demonstrated that the leading edge of migrating Mrp4-/- fibroblasts exhibited more polarized PKA activity than Mrp4+/+ fibroblasts, which in turn increased the cortical actin formation at the cell&#39;s leading edge17. Together, these events resulted in better cellular polarization and faster directional cell migration in the absence of MRP4. Our specific and direct approach identified key downstream targets for MRP4 and provides an important, but as of yet unexplored mechanism for MRP4-dependent regulation of fibroblast migration.

<table><tbody><tr><td>Lipofectamine 2000</td><td>Invitrogen(Carlsbad, CA)&amp;nbsp;</td><td>11668-027</td><td></td></tr><tr><td>DMEM</td><td>Invitrogen (Carlsbad, CA)&amp;nbsp;</td><td>11965-092</td><td></td></tr><tr><td>IncuCyte Zoom</td><td>Essen BioScience</td><td></td><td></td></tr><tr><td>96-well IncuCyte Image-Lock microplates&amp;nbsp;</td><td>Essen BioScience</td><td>4493</td><td></td></tr><tr><td>Latrunculin B</td><td>Sigma-Aldrich (St. Louis, MO).</td><td>L5288</td><td>Stock in DMSO</td></tr><tr><td>H-89</td><td>Enzo Life Sciences (Farmingdale, NY)</td><td>BML-EI196</td><td>Stock in DMSO</td></tr><tr><td>35 mm glass-bottomed dishes&amp;nbsp;</td><td>(MatTek Corporation; Ashland, MA)</td><td>P35G-1.5-20-C&amp;nbsp;</td><td></td></tr><tr><td>Fibronectin</td><td>Sigma-Aldrich (St. Louis, MO).</td><td>F1141</td><td></td></tr><tr><td>Opti-MEM Reduced Serum Media</td><td>Invitrogen (Carlsbad, CA)&amp;nbsp;</td><td>31985-088</td><td></td></tr><tr><td>FRET microscopy system</td><td>Olympus inverted microscope (IX51)</td><td></td><td></td></tr><tr><td>CCD camera&amp;nbsp;</td><td>Hamamatsu, Japan</td><td>ORCA285</td><td></td></tr><tr><td>SlideBook software 5.5</td><td>Intelligent Imaging Innovation ( Denver, CO)</td><td></td><td></td></tr><tr><td>Ingenuity Pathway Analysis software</td><td>IPA, QIAGEN Redwood City,</td><td></td><td></td></tr><tr><td>Forskolin</td><td>Tocris (Ellisville, MO).&amp;nbsp;</td><td>1099</td><td>Stock in 100% EtOH</td></tr><tr><td>DMEM F-12&amp;nbsp;&amp;nbsp;</td><td>Invitrogen (Carlsbad, CA)&amp;nbsp;</td><td>11330-057</td><td></td></tr><tr><td>HBSS</td><td>Invitrogen (Carlsbad, CA)&amp;nbsp;</td><td>14025-134</td><td></td></tr><tr><td>Excel</td><td>Microsoft</td><td></td><td></td></tr><tr><td>PBS</td><td>Invitrogen(Carlsbad, CA)&amp;nbsp;</td><td>10010-023</td><td></td></tr><tr><td>Trypsin/EDTA Solution (TE)</td><td>Invitrogen(Carlsbad, CA)&amp;nbsp;</td><td>R-001-100</td><td></td></tr><tr><td>Penicillin-Streptomycin</td><td>Invitrogen(Carlsbad, CA)&amp;nbsp;</td><td>15140-122</td><td></td></tr></tbody></table>

methods to study mrp4-containing macromolecular complexes in the regulation of fibroblast migration

Multidrug resistance protein 4 (MRP4) is a member of the ATP-binding cassette family of membrane transporters and is an endogenous efflux transporter of cyclic nucleotides. By modulating intracellular cyclic nucleotide concentration, MRP4 can regulate multiple cyclic nucleotide-dependent cellular events including cell migration. Previously, we demonstrated that in the absence of MRP4, fibroblast cells contain higher levels of intracellular cyclic nucleotides and can migrate faster. To understand the underlying mechanisms of this finding, we adopted a direct yet multifaceted approach. First, we isolated potential interacting protein complexes of MRP4 from a MRP4 over-expression cell system using immunoprecipitation followed by mass-spectrometry. After identifying unique proteins in the MRP4 interactome, we utilized Ingenuity Pathway Analysis (IPA) to explore the role of these protein-protein interactions in the context of signal transduction. We elucidated the potential role of the MRP4 protein complex in cell migration and identified F-actin as a major mediator of the effect of MRP4 on cell migration. This study also emphasized the role of cAMP and cGMP as key players in the migratory phenomena. Using high-content microscopy, we performed cell-migration assays and observed that the effect of MRP4 on fibroblast migration is completely abolished by disruption of the actin cytoskeleton or inhibition of cAMP-dependent kinase A (PKA). To visualize signaling modulations in a migrating cell in real time, we utilized a FRET-based sensor for measuring PKA activity and found, the presence of more polarized PKA activity near the leading edge of migrating Mrp4-/- fibroblast, compared to Mrp4+/+fibroblasts. This in turn increased cortical actin formation and augmented the process of migration. Our approach enables identification of the proteins acting downstream to MRP4 and provides us with an overview of the mechanism involved in MRP4-dependent regulation of fibroblast migration.

To study the effect of MRP4 on fibroblast migration, we used a wound-healing assay utilizing high-content microscopy14. Precise wounds were made on confluent monolayers of MEFs isolated from either Mrp4-/- or Mrp4+/+ mice, and images were taken at 1 hr intervals for 24 hr. We observed a higher migration rate for Mrp4-/- MEFs compared to Mrp4+/+ MEFs (Figur...

Watch this Scientific Journal Video about Methods to Study Mrp4-containing Macromolecular Complexes in the Regulation of Fibroblast Migration at JoVE.com

Methods to Study Mrp4-containing Macromolecular Complexes in the Regulation of Fibroblast Migration

MRP4 regulates various cyclic nucleotide-dependent signaling events including a recently elucidated role in cell migration. We describe a direct, but multifaceted approach to unravel the downstream molecular targets of MRP4 resulting in identification of a unique MRP4 interactome that plays key roles in the fine-tuned regulation of fibroblast migration.

Multidrug resistance protein 4 (MRP4) is a member of the ATP-binding cassette family of membrane transporters and is an endogenous efflux transporter of ...

methods-to-study-mrp4-containing-macromolecular-complexes-regulation

Research

JoVE Journal

Developmental Biology

6.7K Views.  Cincinnati Children’s Hospital Medical Center. MRP4 regulates various cyclic nucleotide-dependent signaling events including a recently elucidated role in cell migration. We describe a direct, but multifaceted approach to unravel the downstream molecular targets of MRP4 resulting in identification of a unique MRP4 interactome that plays key roles in the fine-tuned regulation of fibroblast migration.

Video: Methods to Study Mrp4-containing Macromolecular Complexes in the Regulation of Fibroblast Migration

Real-time Imaging of Leukotriene B4 Mediated Cell Migration and BLT1 Interactions with &beta;-arrestin

G-protein coupled receptors (GPCRs) belong to the seven transmembrane protein family and mediate the transduction of extracellular signals to intracellular responses. GPCRs control diverse biological functions such as chemotaxis, intracellular calcium release, gene regulation in a ligand dependent manner via heterotrimeric G-proteins1-2. Ligand binding induces a series of conformational changes leading to activation of heterotrimeric G-proteins that modulate levels of second messengers such as cyclic adenosine monophosphate (cAMP), inositol triphosphate (IP3) and diacyl glycerol (DG). Concomitant with activation of the receptor ligand binding also initiates a series of events to attenuate the receptor signaling via desensitization, sequestration and/or internalization. The desensitization process of GPCRs occurs via receptor phosphorylation by G-protein receptor kinases (GRKs) and subsequent binding of &beta;-arrestins3. &beta;-arrestins are cytosolic proteins and translocate to membrane upon GPCR activation, binding to phosphorylated receptors (most cases) there by facilitating receptor internalization 4-6.
Leukotriene B4 (LTB4) is a pro-inflammatory lipid molecule derived from arachidonic acid pathway and mediates its actions via GPCRs, LTB4 receptor 1 (BLT1; a high affinity receptor) and LTB4 receptor 2 (BLT2; a low affinity receptor)7-9. The LTB4-BLT1 pathway has been shown to be critical in several inflammatory diseases including, asthma, arthritis and atherosclerosis10-17. The current paper describes the methodologies developed to monitor LTB4-induced leukocyte migration and the interactions of BLT1 with &beta;-arrestin and , receptor translocation in live cells using microscopy imaging techniques18-19.
Bone marrow derived dendritic cells from C57BL/6 mice were isolated and cultured as previously described 20-21. These cells were tested in live cell imaging methods to demonstrate LTB4 induced cell migration. The human BLT1 was tagged with red fluorescent protein (BLT1-RFP) at C-terminus and &beta;-arrestin1 tagged with green fluorescent protein (&beta;-arr-GFP) and transfected the both plasmids into Rat Basophilic Leukomia (RBL-2H3) cell lines18-19. The kinetics of interaction between these proteins and localization were monitored using live cell video microscopy. The methodologies in the current paper describe the use of microscopic techniques to investigate the functional responses of G-protein coupled receptors in live cells. The current paper also describes the use of Metamorph software to quantify the fluorescence intensities to determine the kinetics of receptor and cytosolic protein interactions.

Real-time Imaging of Leukotriene B4 Mediated Cell Migration and BLT1 Interactions with &#946;-arrestin

This paper describes the methodology to determine the chemotactic response of leukocytes to specific ligands and identify interactions between the cell surface receptors and cytosolic proteins using live cell imaging techniques.

G-protein coupled receptors (GPCRs) belong to the seven transmembrane protein family and mediate the transduction of extracellular signals to ...

Immunology and Infection

Live-cell Imaging of Migrating Cells Expressing Fluorescently-tagged Proteins in a Three-dimensional Matrix

Traditionally, cell migration has been studied on two-dimensional, stiff plastic surfaces. However, during important biological processes such as wound healing, tissue regeneration, and cancer metastasis, cells must navigate through complex, three-dimensional extracellular tissue. To better understand the mechanisms behind these biological processes, it is important to examine the roles of the proteins responsible for driving cell migration. Here, we outline a protocol to study the mechanisms of cell migration using the epithelial cell line (MDCK), and a three-dimensional, fibrous, self-polymerizing matrix as a model system. This optically clear extracellular matrix is easily amenable to live-cell imaging studies and better mimics the physiological, soft tissue environment. This report demonstrates a technique for directly visualizing protein localization and dynamics, and deformation of the surrounding three-dimensional matrix. 
Examination of protein localization and dynamics during cellular processes provides key insight into protein functions. Genetically encoded fluorescent tags provide a unique method for observing protein localization and dynamics. Using this technique, we can analyze the subcellular accumulation of key, force-generating cytoskeletal components in real-time as the cell maneuvers through the matrix. In addition, using multiple fluorescent tags with different wavelengths, we can examine the localization of multiple proteins simultaneously, thus allowing us to test, for example, whether different proteins have similar or divergent roles. Furthermore, the dynamics of fluorescently tagged proteins can be quantified using Fluorescent Recovery After Photobleaching (FRAP) analysis. This measurement assays the protein mobility and how stably bound the proteins are to the cytoskeletal network.
By combining live-cell imaging with the treatment of protein function inhibitors, we can examine in real-time the changes in the distribution of proteins and morphology of migrating cells. Furthermore, we also combine live-cell imaging with the use of fluorescent tracer particles embedded within the matrix to visualize the matrix deformation during cell migration. Thus, we can visualize how a migrating cell distributes force-generating proteins, and where the traction forces are exerted to the surrounding matrix. Through these techniques, we can gain valuable insight into the roles of specific proteins and their contributions to the mechanisms of cell migration.

Cellular processes such as cell migration have traditionally been studied on two-dimensional, stiff plastic surfaces. This report describes a technique for directly visualizing protein localization and analyzing protein dynamics in cells migrating in a more physiologically relevant, three-dimensional matrix.

Traditionally, cell migration has been studied on two-dimensional, stiff plastic surfaces. However, during important biological processes such as wound ...

Bioengineering

Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells

Dynamic regulation of the Rho family of small guanosine triphosphatases (GTPases) with great spatiotemporal precision is essential for various cellular functions and events1, 2. Their spatiotemporally dynamic nature has been revealed by visualization of their activity and localization in real time3. In order to gain deeper understanding of their roles in diverse cellular functions at the molecular level, the next step should be perturbation of protein activities at a precise subcellular location and timing. 
To achieve this goal, we have developed a method for light-induced, spatio-temporally controlled activation of small GTPases by combining two techniques: (1) rapamycin-induced FKBP-FRB heterodimerization and (2) a photo-caging method of rapamycin. With the use of rapamycin-mediated FKBP-FRB heterodimerization, we have developed a method for rapidly inducible activation or inactivation of small GTPases including Rac4, Cdc424, RhoA4 and Ras5, in which rapamycin induces translocation of FKBP-fused GTPases, or their activators, to the plasma membrane where FRB is anchored. For coupling with this heterodimerization system, we have also developed a photo-caging system of rapamycin analogs. A photo-caged compound is a small molecule whose activity is suppressed with a photocleavable protecting group known as a caging group. To suppress heterodimerization activity completely, we designed a caged rapamycin that is tethered to a macromolecule such that the resulting large complex cannot cross the plasma membrane, leading to virtually no background activity as a chemical dimerizer inside cells6. Figure 1 illustrates a scheme of our system. With the combination of these two systems, we locally recruited a Rac activator to the plasma membrane on a timescale of seconds and achieved light-induced Rac activation at the subcellular level6.

A method for spatio-temporal control of small GTPase activity by light is described. This method is based on rapamycin-induced FKBP-FRB heterodimerization and photo-caging systems. Optimization of light-irradiation enables the spatio-temporally controlled activation of small GTPases at the subcellular level.

Dynamic regulation of the Rho family of small guanosine triphosphatases (GTPases) with great spatiotemporal precision is essential for various cellular ...

Observing and Quantifying Fibroblast-mediated Fibrin Gel Compaction

Cells embedded in collagen and fibrin gels attach and exert traction forces on the fibers of the gel. These forces can lead to local and global reorganization and realignment of the gel microstructure. This process proceeds in a complex manner that is dependent in part on the interplay between the location of the cells, the geometry of the gel, and the mechanical constraints on the gel. To better understand how these variables produce global fiber alignment patterns, we use time-lapse differential interference contrast (DIC) microscopy coupled with an environmentally controlled bioreactor to observe the compaction process between geometrically spaced explants (clusters of fibroblasts). The images are then analyzed with a custom image processing algorithm to obtain maps of the strain. The information obtained from this technique can be used to probe the mechanobiology of various cell-matrix interactions, which has important implications for understanding processes in wound healing, disease development, and tissue engineering applications.

Time-lapse microscopy and image processing techniques were used to observe and analyze fibroblast-mediated gel compaction and fibrin fiber realignment in an environmentally controlled bioreactor over a 48 hr&#160;period.

Cells embedded in collagen and fibrin gels attach and exert traction forces on the fibers of the gel. These forces can lead to local and global ...

Study of Cell Migration in Microfabricated Channels

The method described here allows the study of cell migration under confinement in one dimension. It is based on the use of microfabricated channels, which impose a polarized phenotype to cells by physical constraints. Once inside channels, cells have only two possibilities: move forward or backward. This simplified migration in which directionality is restricted facilitates the automatic tracking of cells and the extraction of quantitative parameters to describe cell movement. These parameters include cell velocity, changes in direction, and pauses during motion. Microchannels are also compatible with the use of fluorescent markers and are therefore suitable to study localization of intracellular organelles and structures during cell migration at high resolution. Finally, the surface of the channels can be functionalized with different substrates, allowing the control of the adhesive properties of the channels or the study of haptotaxis. In summary, the system here described is intended to analyze the migration of large cell numbers in conditions in which both the geometry and the biochemical nature of the environment are controlled, facilitating the normalization and reproducibility of independent experiments.

A quantitative method to study spontaneous migration of cells in a one-dimensional confined microenvironment is described. This method takes advantage of microfabricated channels and can be used to study migration of large number of cells under different conditions in single experiments.

The method described here allows the study of cell migration under confinement in one dimension. It is based on the use of microfabricated channels, which ...

Concentric Gel System to Study the Biophysical Role of Matrix Microenvironment on 3D Cell Migration

The ability of cells to migrate is crucial in a wide variety of cell functions throughout life&#160;from embryonic development and wound healing&#160;to tumor and cancer metastasis. Despite intense research efforts, the basic biochemical and biophysical principles of cell migration are still not fully understood, especially in the physiologically relevant three-dimensional (3D) microenvironments. Here, we describe an in vitro assay designed to allow quantitative examination of 3D cell migration behaviors. The method exploits the cell&#8217;s mechanosensing ability and propensity to migrate into previously unoccupied extracellular matrix (ECM). We use the invasion of highly invasive breast cancer cells, MDA-MB-231, in collagen gels as a model system. The spread of cell population and the migration dynamics of individual cells over weeks of culture can be monitored using live-cell imaging and analyzed to extract spatiotemporally-resolved data. Furthermore, the method is easily adaptable for diverse extracellular matrices, thus offering a simple yet powerful way to investigate the role of biophysical factors in the microenvironment on cell migration.

The mechanical properties and microstructure of the extracellular matrix strongly affect 3D migration of cells. An in vitro method to study the spatiotemporal cell migration behavior in biophysically variable environments, at both population and individual cell levels, is described.

The ability of cells to migrate is crucial in a wide variety of cell functions throughout life&#160;from embryonic development and wound healing&#160;to ...

Characterizing Cell Migration Within Three-dimensional In Vitro Wound Environments

Currently, most in vitro models of wound healing, such as well-established scratch assays, involve studying cell migration and wound closure on two-dimensional surfaces. However, the physiological environment in which in vivo wound healing takes place is three-dimensional rather than two-dimensional. It is becoming increasingly clear that cell behavior differs greatly in two-dimensional vs. three-dimensional environments; therefore, there is a need for more physiologically relevant in vitro models for studying cell migration behaviors in wound closure. The method described herein allows for the study of cell migration in a three-dimensional model that better reflects physiological conditions than previously established two-dimensional scratch assays. The purpose of this model is to evaluate cell outgrowth via the examination of cell migration away from a spheroid body embedded within a fibrin matrix in the presence of pro- or anti-migratory factors. Using this method, cell outgrowth from the spheroid body in a three-dimensional matrix can be observed and is easily quantifiable over time via brightfield microscopy and analysis of spheroid body area. The effect of pro-migratory and/or inhibitory factors on cell migration can also be evaluated in this system. This method provides researchers with a simple method of analyzing cell migration in three-dimensional wound associated matrices in vitro, thus increasing the relevance of in vitro cell studies prior to the use of in vivo animal models.

Characterizing Cell Migration Within Three-dimensional In Vitro Wound Environments

The goal of this protocol is to evaluate the effect of pro- and anti-migratory factors on cell migration within a three-dimensional fibrin matrix.

Currently, most in vitro models of wound healing, such as well-established scratch assays, involve studying cell migration and wound closure on ...

In vitro Cell Migration and Invasion Assays

Migration is a key property of live cells and critical for normal development, immune response, and disease processes such as cancer metastasis and inflammation. Methods to examine cell migration are very useful and important for a wide range of biomedical research such as cancer biology, immunology, vascular biology, cell biology and developmental biology. Here we use tumor cell migration and invasion as an example and describe two related assays to illustrate the commonly used, easily accessible methods to measure these processes. The first method is the cell culture wound closure assay in which a scratch is generated on a confluent cell monolayer. The speed of wound closure and cell migration can be quantified by taking snapshot pictures with a regular inverted microscope at several time intervals. More detailed cell migratory behavior can be documented using the time-lapse microscopy system. The second method described in this paper is the transwell cell migration and invasion assay that measures the capacity of cell motility and invasiveness toward a chemo-attractant gradient. It is our goal to describe these methods in a highly accessible manner so that the procedures can be successfully performed in research laboratories even just with basic cell biology setup.

In vitro Cell Migration and Invasion Assays

Commonly used, highly accessible methods for examining cell migration and invasion in vitro are described. The first method is the cell wound closure assay that measures cell motility. The second method is the transwell migration and invasion assay that assesses the chemotactic and invasive capacity of cells.

Migration is a key property of live cells and critical for normal development, immune response, and disease processes such as cancer metastasis and ...

Biology

High-resolution Time-lapse Imaging and Automated Analysis of Microtubule Dynamics in Living Human Umbilical Vein Endothelial Cells

The physiological process by which new vasculature forms from existing vasculature requires specific signaling events that trigger morphological changes within individual endothelial cells (ECs). These processes are critical for homeostatic maintenance such as wound healing, and are also crucial in promoting tumor growth and metastasis. EC morphology is defined by the organization of the cytoskeleton, a tightly regulated system of actin and microtubule (MT) dynamics that is known to control EC branching, polarity and directional migration, essential components of angiogenesis. To study MT dynamics, we used high-resolution fluorescence microscopy coupled with computational image analysis of fluorescently-labeled MT plus-ends to investigate MT growth dynamics and the regulation of EC branching morphology and directional migration. Time-lapse imaging of living Human Umbilical Vein Endothelial Cells (HUVECs) was performed following transfection with fluorescently-labeled MT End Binding protein 3 (EB3) and Mitotic Centromere Associated Kinesin (MCAK)-specific cDNA constructs to evaluate effects on MT dynamics. PlusTipTracker software was used to track EB3-labeled MT plus ends in order to measure MT growth speeds and MT growth lifetimes in time-lapse images. This methodology allows for the study of MT dynamics and the identification of how localized regulation of MT dynamics within sub-cellular regions contributes to the angiogenic processes of EC branching and migration.

Protocols for Human Umbilical Vein Endothelial Cell (HUVEC) culture, transient transfection of fluorescently-labeled markers of microtubule growth, live-cell imaging and automated analysis of interphase microtubule growth dynamics are detailed.

The physiological process by which new vasculature forms from existing vasculature requires specific signaling events that trigger morphological changes ...

Micromanipulation Techniques Allowing Analysis of Morphogenetic Dynamics and Turnover of Cytoskeletal Regulators

Examining the spatiotemporal dynamics of proteins can reveal their functional importance in various contexts. In this article, it is discussed how fluorescent recovery after photobleaching (FRAP) and photoactivation techniques can be used to study the spatiotemporal dynamics of proteins in subcellular locations. We also show how these techniques enable straightforward determination of various parameters linked to actin cytoskeletal regulation and cell motility. Moreover, the microinjection of cells is additionally described as an alternative treatment (potentially preceding or complementing the aforementioned photomanipulation techniques) to trigger instantaneous effects of translocated proteins on cell morphology and function. Micromanipulation such as protein injection or local application of plasma membrane-permeable drugs or cytoskeletal inhibitors can serve as powerful tool to record immediate consequences of a given treatment on cell behavior at the single cell and subcellular level. This is exemplified here by immediate induction of lamellipodial cell edge protrusion by the injection of recombinant Rac1 protein, as established a quarter-century ago. In addition, we provide a protocol for determining the turnover of enhanced green fluorescent protein (EGFP)-VASP, an actin filament polymerase prominently accumulating at lamellipodial tips of B16-F1 cells, employing FRAP and including associated data analysis and curve fitting. We also present guidelines for estimating the rates of lamellipodial actin network polymerization, as exemplified by cells expressing EGFP-tagged &#946;-actin. Finally, instructions are given for how to investigate the rates of actin monomer mobility within the cell cytoplasm, followed by actin incorporation at sites of rapid filament assembly, such as the tips of protruding lamellipodia, using photoactivation approaches. None of these protocols is&#160;restricted to components or regulators of the actin cytoskeleton, but can easily be extended to explore in analogous fashion the spatiotemporal dynamics and function of proteins in various different subcellular structures or functional contexts.

We describe how micro- and photomanipulation techniques such as FRAP and photoactivation enable the determination of motility parameters and the spatiotemporal dynamics of proteins within migrating cells. Experimental readouts include subcellular dynamics and turnover of motility regulators or of the underlying actin cytoskeleton.

Methods to Study Mrp4-containing Macromolecular Complexes in the Regulation of Fibroblast Migration

Summary

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Chapters in this video

Real-time Imaging of Leukotriene B₄ Mediated Cell Migration and BLT1 Interactions with β-arrestin

Live-cell Imaging of Migrating Cells Expressing Fluorescently-tagged Proteins in a Three-dimensional Matrix

Spatio-Temporal Manipulation of Small GTPase Activity at Subcellular Level and on Timescale of Seconds in Living Cells

Observing and Quantifying Fibroblast-mediated Fibrin Gel Compaction

Study of Cell Migration in Microfabricated Channels

Concentric Gel System to Study the Biophysical Role of Matrix Microenvironment on 3D Cell Migration

Characterizing Cell Migration Within Three-dimensional In Vitro Wound Environments

In vitro Cell Migration and Invasion Assays

High-resolution Time-lapse Imaging and Automated Analysis of Microtubule Dynamics in Living Human Umbilical Vein Endothelial Cells

Micromanipulation Techniques Allowing Analysis of Morphogenetic Dynamics and Turnover of Cytoskeletal Regulators