Name: fabricating multi-component lipid nanotube networks using the gliding kinesin motility assay
Uploaded: 2021-07-26T13:00:00
Description: Watch this Scientific Journal Video about Fabricating Multi-Component Lipid Nanotube Networks Using the Gliding Kinesin Motility Assay at JoVE.com

This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering (BES-MSE). Kinesin synthesis and fluorescence microscopy were performed through a user project (ZIM) at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science.

1. Preparation of stock microtubule solutions
CAUTION: Safety goggles, gloves and a lab coat should always be worn throughout the protocol.
<ol>
	<li>Prepare 5x BRB80 buffer: add 24.19 g of PIPES (piperazine-N,N&#8242;-bis[2-ethanesulfonic acid]) and 0.38 g of EGTA (ethylene glycol-bis[&#946;-aminoethyl ether]-N,N,N&#8242;,N&#8242;-tetraacetic acid) to a 1 L glass bottle. Add 1 mL of 1 M MgCl2 and adjust the pH to 6.9 with KOH. Add deionized water to bring the solution to a 500 mL...

<ol>
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LNT networks are a useful tool for in vitro studies to membrane properties and the transport of biomolecules such as transmembrane proteins. Moreover, using complex lipid formulations to fabricate LNT networks enables more biologically relevant studies. Other fabrication studies have used either 1) simple lipid formulations and multilamellar vesicles or 2) more cumbersome motility techniques to fabricate networks from GUVs comprised of complex lipid formulations. The method described here enables the efficient fabricatio...

The fabrication of lipid nanotube (LNT) networks is of increasing interest for in vitro examination of nonequilibrium lipid structures1,2,3. Cells use lipid tubules for the diffusive transport of proteins4 and nucleic acids5 as well as cell-to-cell communication6,7. The endoplasmic reticulum and Golgi apparatus are particularly interesting, as these membrane-bound organelles are the primary locations for lipid and protein synthesis as well as transport of these integral biomolecules within the cytoplasm of a cell8,9. The membranes of these organelles are comprised of multiple lipid species including sphingolipids, cholesterol, and phospholipids10 that ultimately help define their functionality. Thus, to more closely replicate and study these organelles, in vitro LNTs must be fabricated from vesicles with increasingly complex lipid formulations11.
Giant unilamellar vesicles (GUVs) are used pervasively for studying lipid membrane behavior because they can be reliably synthesized with complex formulations that include cholesterol, phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), and phosphatidylinositol (PI)12,13. Described here is a method to fabricate LNTs from GUVs with varying lipid formulations using the gliding motility assay (GMA), in which LNTs are extruded based on the work performed by kinesin motors and microtubule filaments acting on GUVs. In this system, kinesin motor proteins adsorbed to a surface propel biotinylated microtubules, converting chemical energy from the hydrolysis of ATP into useful work (specifically, the extrusion of LNTs from biotinylated vesicles)11. The resulting LNT network provides a model platform to study effects of the differences in lipid phases on changes in LNT morphology.
Briefly, kinesin motor proteins are introduced into a flow chamber in a solution containing casein, which enables the adsorption of the motors onto the glass surface of the chamber. Next, biotinylated microtubules in a solution containing ATP flow through the chamber and are allowed to bind to the kinesin motors and begin motility. A streptavidin solution is then introduced into the chamber and allowed to bind non-covalently to the microtubules. Finally, GUVs containing a biotinylated lipid are introduced into the chamber and bind to the streptavidin-coated microtubules, then extrude LNTs to form large-scale networks over the course of 15&#8211;30 min. This method produces large, branched LNT networks using standard laboratory equipment and reagents at a low cost11.

<table border="0" cellpadding="0" cellspacing="0" style="width:1071px;" width="1071">
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	</colgroup>
	<tbody>
		<tr height="64">
			<td height="64" style="height:65px;width:328px;">100x/1.4 Numerical Aperture Oil Immersion Objective</td>
			<td style="width:104px;">Olympus</td>
			<td style="width:119px;">1-U2B836</td>
			<td style="width:520px;">Olympus UPlanSApo 100x/1.40 Oil Objective Infinity Corrected, RMS Thread 
			Working Distance 0.12mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">3.0 ND Filter</td>
			<td style="width:104px;">Olympus</td>
			<td style="width:119px;"></td>
			<td>Neutral Density Filter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">AMP-PNP</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td style="width:119px;">A2647</td>
			<td>(&#946;,&#947;-imidoadenosine 5&#8242;-triphosphate)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">ATP</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td style="width:119px;">A7699</td>
			<td>Adenosine 5&#39;-triphosphate disodium salt hydrate BioXtra</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:328px;">Brightline Pinkel DA/FI/TR/Cy5/Cy7-5X-A000 filter set</td>
			<td style="width:104px;">Semrock</td>
			<td style="width:119px;">LED-DA/FI/TR/Cy5/Cy7-5X-A-000</td>
			<td style="width:520px;"> 
			BrightLine Pinkel filter set, optimized for DAPI, FITC, TRITC, Cy5 &#38; Cy7 and other like fluorophores, illuminated with LED-based light sources</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Casein</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">22090</td>
			<td>Casein hydrolysate for microbiology</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Catalase</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td style="width:119px;">C9322</td>
			<td>Catalase from Bovine Liver</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Chloroform</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">288306</td>
			<td>Chloroform anhydrous contains 0.5-1.0% ethanol as stabilizer</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Cholesterol</td>
			<td style="width:104px;">Avanti</td>
			<td style="width:119px;">700000P</td>
			<td>cholesterol (ovine wool, &#62;98%) (powder)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:328px;">D-Glucose</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td style="width:119px;">G7021</td>
			<td style="width:520px;">D-(+)-Glucose powder, BioReagent, suitable for cell culture, suitable for insect cell culture, suitable for plant cell culture, &#8805;99.5%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">DOPC</td>
			<td style="width:104px;">Avanti</td>
			<td style="width:119px;">850375C</td>
			<td>1,2-Dioleoyl-sn-glycero-3-phosphocholine (in chloroform)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">DOPE-Biotin</td>
			<td style="width:104px;">Avanti</td>
			<td style="width:119px;">870282C</td>
			<td>1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(biotinyl) (sodium salt)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">DPPC</td>
			<td style="width:104px;">Avanti</td>
			<td style="width:119px;">850355P</td>
			<td>1,2-dipalmitoyl-sn-glycero-3-phosphocholine (powder)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">DPPE-Biotin</td>
			<td style="width:104px;">Avanti</td>
			<td style="width:119px;">870285P</td>
			<td>1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-(biotinyl) (sodium salt)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">DTT</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">43816</td>
			<td>DL-Dithiothreitol solution 1 M</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:328px;">EGTA</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td style="width:119px;">E4378</td>
			<td style="width:520px;">EGTA, Egtazic acid, Ethylene-bis(oxyethylenenitrilo)tetraacetic acid, Glycol ether diamine tetraacetic acid</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:328px;">Glucose Oxidase</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td style="width:119px;">G6125</td>
			<td style="width:520px;">Glucose Oxidase from Aspergillus niger 
			Type II, &#8805;10,000 units/g solid (without added oxygen)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Glycerol</td>
			<td style="width:104px;">Fisher</td>
			<td style="width:119px;">G33</td>
			<td>Glycerol (Certified ACS), Fisher Chemical</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">GTP</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td style="width:119px;">G8877</td>
			<td>Guanosine 5&#8242;-triphosphate sodium salt hydrate</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">IX-81 Olympus Microscope</td>
			<td style="width:104px;">Olympus</td>
			<td style="width:119px;">N/A</td>
			<td>IX81 Inverted Microscope from Olympus</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">KOH</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">1050121000</td>
			<td>Potassium Hydroxide</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Magnesium Chloride</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td style="width:119px;">M1028</td>
			<td>1.00 M magnesium chloride solution</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Orca Flash 4.0 Digital Camera</td>
			<td style="width:104px;">Hamamatsu</td>
			<td style="width:119px;">C13440-20CU</td>
			<td>ORCA-Flash 4.0 V3 Digital CMOS camera</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Oregon Green-DHPE</td>
			<td style="width:104px;">Invitrogen</td>
			<td style="width:119px;">O12650</td>
			<td>Oregon Green 488 1,2-Dihexadecanoyl-sn-Glycero-3-Phosphoethanolamine</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Paclitaxel</td>
			<td style="width:104px;">ThermoFisher</td>
			<td style="width:119px;">P3456</td>
			<td>Paclitaxel (Taxol Equivalent) - for use in research only</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:328px;">PIPES</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td style="width:119px;">P6757</td>
			<td style="width:520px;">1,4-Piperazinediethanesulfonic acid, Piperazine-1,4-bis(2-ethanesulfonic acid), Piperazine-N,N&#8242;-bis(2-ethanesulfonic acid)</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:328px;">Texas Red-DHPE</td>
			<td style="width:104px;">Invitrogen</td>
			<td style="width:119px;">T1395MP</td>
			<td style="width:520px;">Texas Red 1,2-Dihexadecanoyl-sn-Glycero-3-Phosphoethanolamine, 
			Triethylammonium Salt</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Trolox</td>
			<td style="width:104px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">238813</td>
			<td>(&#177;)-6-Hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Tubulin, Biotin</td>
			<td style="width:104px;">Cytoskeleton</td>
			<td style="width:119px;">T333P</td>
			<td>Tubulin protein (biotin) porcine brain</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Tubulin, Hy-Lite 488</td>
			<td style="width:104px;">Cytoskeleton</td>
			<td style="width:119px;">TL488M</td>
			<td>Tubulin protein (fluorescent HiLyte 488) porcine brain</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:328px;">Tubulin, Unlabeled</td>
			<td style="width:104px;">Cytoskeleton</td>
			<td style="width:119px;">T240</td>
			<td>Tubulin protein porcine brain</td>
		</tr>
	</tbody>
</table>

fabricating multi-component lipid nanotube networks using the gliding kinesin motility assay

Lipid nanotube (LNT) networks represent an in vitro model system for studying molecular transport and lipid biophysics with relevance to the ubiquitous lipid tubules found in eukaryotic cells. However, in vivo LNTs are highly non-equilibrium structures that require chemical energy and molecular motors to be assembled, maintained, and reorganized. Furthermore, the composition of in vivo LNTs is complex, comprising of multiple different lipid species. Typical methods to extrude LNTs are both time- and labor-intensive, and they require optical tweezers, microbeads, and micropipettes to forcibly pull nanotubes from giant lipid vesicles. Presented here is a protocol for the gliding motility assay (GMA), in which large scale LNT networks are rapidly generated from giant unilamellar vesicles (GUVs) using kinesin-powered microtubule motility. Using this method, LNT networks are formed from a wide array of lipid formulations that mimic the complexity of biological LNTs, making them increasingly useful for in vitro studies of lipid biophysics and membrane-associated transport. Additionally, this method is capable of reliably producing LNT networks in a short time (&#60;30 min) using commonly used laboratory equipment. LNT network characteristics such as length, width, and lipid partitioning are also tunable by altering the lipid composition of the GUVs used for fabricating the networks.

LNT networks (Figure 4) were fabricated using the described protocol, which uses the work performed by kinesin transport of microtubules to extrude LNTs from GUVs. Briefly, GUVs were prepared using agarose gel rehydration using sucrose solution, and microtubules were polymerized in GPEM solution and stabilized in BRB80T. Next, kinesin motors were introduced into a flow cell forming an active layer&#160;of motors on the surface of the coverslip. Microtubules were then introduced and a strepta...

Watch this Scientific Journal Video about Fabricating Multi-Component Lipid Nanotube Networks Using the Gliding Kinesin Motility Assay at JoVE.com

Fabricating Multi-Component Lipid Nanotube Networks Using the Gliding Kinesin Motility Assay

This protocol describes a process for fabricating lipid nanotube networks using gliding kinesin motility in conjunction with giant unilamellar lipid vesicles.

Lipid nanotube (LNT) networks represent an in vitro model system for studying molecular transport and lipid biophysics with relevance to the ubiquitous ...

This protocol allows for the simple generation of large-scale lipid nanotube networks in which the individual nanotubes display phase separation behavior similar to that of parent vesicle. The key advantage of this approach is that we co-opt the work done by the molecular motors to self-assemble the lipid nanotubes in a highly parallel manner and without human intervention. To set up a gliding motility assay, first, affix three sets of double-sided tape strips onto a glass slide five millimeters apart.Gently press a cover slip onto the tape and add 30 microliters of a one-micromolar kinesin solution into the prepared flow cell. After five minutes, add 30 microliters of a 10-microgram/milliliter microtubule solution into the cell, pressing a laboratory wipe gently against the opposite end of the flow channel to facilitate the solution exchange. After another five minute incubation, wash the cell one to three times with 50 microliters of room-temperature motility solution per wash before adding 30 microliters of 10-microgram/milliliter streptavidin solution to the flow cell.After 10 minutes, add 30 microliters of a 10X GUV solution for a 30 minute incubation at room temperature. Then, add two microliters of a 100-millimolar AMP-PNP solution and close the chamber with sealant. Transfer the flow chamber to an inverted microscope for imaging and select the appropriate filter set.Use a 100X oil objective to focus first the surface of the cover slip before acquiring an image of a network of interest. Then open the image in ImageJ and click Image, Color, and Composite to overlay the red and green channels to create a composite image. After imaging, open the image of interest and click Analyze and Set scale to calibrate the scale for the microscope.Fill in the pixels to the micrometer conversion factor and click OK.Use the multi-point line tool to trace the nanotubes starting from the parent GUV and press and hold Control and M to measure the length. The image processing tool will save each new measurement in the results window. When all of the tubes have been measured, select Image, Adjust, and Threshold and click Apply to apply the threshold.Then, draw a rectangle of known length over the desired tube. To measure the integrated density of the area, click Analyze and Measure To determine the lipid partitioning in the liquid nanotube nodes, use the line tool to draw a line over the node of interest and measure the node intensity in both the green and red channels. In this representative analysis, liquid nanotube networks were fabricated as demonstrated to generate liquid-disordered and ordered phases, as well as phase-separated vesicles.For example, vesicles synthesized with 45%saturated lipid and 55%unsaturated lipid results in vesicles that separate into coexisting liquid-disordered and solid phases. If cholesterol is included, however, liquid-liquid coexistence can then be observed, creating GUVs that separate into coexisting liquid-ordered and liquid-disordered phases. Moreover, nodes can be observed within the phase-separated mixtures.The most important thing to remember is to pick the appropriate exposure time and ND filter set to be able to visualize the lipid nanotubes without photo-bleaching the fluorophores. Tailoring the composition of phase behavior of the lipid nanotubes allows us to use a minimalistic model system to begin studying the biophysics of the tunneling nanotubes that connect cells.

Research

JoVE Journal

Bioengineering

Plasma Lithography Surface Patterning for Creation of Cell Networks

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Biomembrane Fabrication by the Solvent-assisted Lipid Bilayer (SALB) Method

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Solid Lipid Nanoparticles (SLNs) for Intracellular Targeting Applications

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Fabricating Cotton Analytical Devices

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