Este trabajo fue financiado por los NIH R01 EB014869.

1. preparar las células para la proyección de imagen
Nota: La punta de prueba de fuerza directa (DFP) se puede utilizar para cualquier tipo de células adherentes. Aquí, fibroblastos de ratón 3T3 NIH se utilizan como la línea celular de modelo para este protocolo.
<ol><li>Células de fibroblastos 3T3 NIH la cultura en el medio modificado Eagle de Dulbecco (DMEM) suplementado con 10% suero bovino de donante y 1% de penicilina-estreptomicina en un fondo de cristal de 35 mm plato hasta confluencia deseada. Mantener las células a 37 ° C y 5% CO2.<ol>
<li>Asegúrese de cubrir todos platos de fondo de cristal de 35 mm con 5 μg/mL de fibronectina (o proteína similar de ECM), antes de sembrar las células 3T3 de NIH para la proyección de imagen. Nota: Las células deben ser completamente extendidas y adherente en el plato para el experimento. No hay restricciones en cuanto a la confluencia del método DFP trabajar.</li>
	</ol>
</li>
	<li>Inmediatamente antes del experimento, se lavan las células dos veces con PBS, seguido de un lavado solo con medio de cultivo completo.</li>
	<li>Añadir 3 mL de medio de cultivo completo en el plato de fondo de vidrio.</li>
</ol>2. microscopia y adquisición de imágenes
Nota: Un invertido fluorescencia microscopio (o equivalente) con instrumental quirúrgico instalado en el brazo lateral, según las recomendaciones del fabricante. El microscopio también debe ser equipado con una cámara de medio ambiente para mantener la temperatura a 37 ° C y el nivel de CO2 al 5%. También se requiere un instrumental quirúrgico y microinyector conectado al microscopio. Una inmersión de aceite 40 x / 1.3 NA o 60 x / 1.49 NA (u objetivos equivalentes) se recomiendan para los experimentos. El microscopio debe montarse sobre una tabla de aislamiento de vibración.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/58038/58038fig1.jpg"> Figura 1 . Deformación nuclear y enfoque del microscopio A. máxima deformación nuclear y relajación de la deformación nuclear. Antes de calcular la máxima deformación nuclear, los bordes posteriores de las formas nucleares fueron primero coincidió para corregir para la traducción de núcleo deformado. La forma del núcleo en el momento de desprendimiento de la punta de una micropipeta se superpuestos en la forma nuclear inicial antes de tirar. Se midió la diferencia de área entre las dos formas como ΔA1. La máxima deformación nuclear se define como ΔA1 dividido por el área nuclear original. Del mismo modo, un segundo parámetro, ΔA2, puede ser definido por la superposición de la forma nuclear de estado estacionario final después del desprendimiento de la micropipeta en la forma nuclear original. B. centrar el celular en el plano A y luego mover el plano focal hasta plano B para encontrar la punta de la micropipeta. Durante la proyección de imagen, la micropipeta fue traducida a la derecha (dirección de la flecha naranja). Esta figura ha sido modificada de Neelam et al. 15. <a href="https://jove.unicartagenaproxy.elogim.com/files/ftp_upload/58038/58038fig1large.jpg" target="_blank">haga clic aquí para ver una versión más grande de esta figura.</a>
<ol><li>Encienda la microinyectora según el protocolo del fabricante.</li>
	<li>Utilizando un gotero de aceite de inmersión, aplique una sola gota de aceite de inmersión sobre la lente del objetivo.</li>
	<li>Sujete el plato firmemente en el soporte del plato y el soporte de plato en la etapa de carga. Nota: Las células deben mantenerse a 37 ° C y 5% de CO2 durante todo el experimento.</li>
	<li>Ajuste la altura del objetivo para traer las células en el foco (A plano, figura 1B).</li>
	<li>Mover la platina del microscopio para encontrar una célula de interés.</li>
	<li>Gire la palanca de mando en el micromanipulador para mover el soporte de la pipeta a la posición superior. Carga de la micropipeta de punta de 0,5 μm de diámetro en el soporte de pipeta.<ol>
<li>Para evitar la adherencia de la célula a la micropipeta, tratamiento previo de la punta de la micropipeta con 0,3 mg/mL solución de PLL-g-PEG durante 1 h a temperatura ambiente. Prueba de adherencia tocando la micropipeta al núcleo sin ninguna presión de succión, y luego traducir la micropipeta lejos del núcleo. La falta de adherencia se puede discernir de una completa falta de deformación nuclear y traducción. Nota: Por favor, siga las sugerencias de la fabricación para abrir el paquete.</li>
	</ol>
</li>
	<li>Levantar el plano focal objetivo sobre el plano A y la parte superior de la celda al plano B ajustando el control de estabilidad (figura 1B, consulte el paso 2.4).</li>
	<li>Establezca el instrumental quirúrgico para controlar el grueso . Lentamente llevar la micropipeta hasta plano B observando la silueta de la micropipeta, hasta que la micropipeta se quede totalmente enfocada.</li>
	<li>Una vez que la punta de la micropipeta está en foco, establezca el micromanipulador para controlar bien .</li>
	<li>Bajar el objetivo para el plano ecuatorial de la célula (plano A, figura 1B) y baje la micropipeta a alrededor de 15 μm sobre plano A (figura 1B, micropipeta discontinua).</li>
	<li>Ajuste la presión de compensación (Pc) en la microinyectora a presión deseada; Espere unos segundos para estabilizar la presión. Nota: El punto de ajuste de la presión óptima depende de tipo de la célula y los objetivos específicos del experimento. Para la mayoría de los casos, 300 hPa sería un buen punto de partida.</li>
	<li>Asegúrese de que no esté obstruida la micropipeta utilizando el ajuste de limpiar en el panel de instrumental quirúrgico y comprobación para asegurarse de que las burbujas de aire surgen desde la punta de la micropipeta.</li>
	<li>Inserte la punta en la célula reduciendo gradualmente la micropipeta hasta que la punta es tocar ligeramente la superficie nuclear. Nota: Al bajar la micropipeta, la silueta de la punta de la micropipeta se convertirá en clara ya que viene en foco. Antes de la micropipeta toca el núcleo, aumentar el foco objetivo y alinear la punta de la micropipeta con núcleo (misma coordenada de x-y, z-plano superior). Volver la atención hacia el plano ecuatorial del núcleo (A plano, figura 1B) y poco a poco baje la punta de la micropipeta.</li>
	<li>Desconectar el tubo de suministro de presión del sistema de microinyección, abriendo así el extremo del tubo una micropipeta a la atmósfera para crear un sello entre la punta de la micropipeta y la membrana nuclear. Este paso crea una presión negativa igual a Pc en la superficie nuclear.</li>
	<li>Adquisición de imágenes con el software de colección de imágenes de microscopios. Establezca una adquisición de avi (video) o nd-adquisición (imágenes) en el software de colección de la imagen. Nota: Para cualquier adquisición de software de imágenes, crear imágenes de video en tiempo real o adquisiciones de Time-lapse de imágenes con un intervalo de tiempo corto.</li>
	<li>Alternar al fluorescente correspondiente canal la proyección de imagen (es decir, GFP, RFP, etc.) y comienza la proyección de imagen.</li>
	<li>Traducir la punta de la micropipeta lejos del cuerpo de la célula (a la derecha, figura 1B) hasta que el núcleo se desprende de la micropipeta. Nota: Tire de la punta a lo largo de la dirección de x positiva (a la derecha en el campo de visión). El tipo de tracción puede ser programado y controlado por la computadora o el joystick puede ser movido manualmente. No hemos encontrado ninguna correlación entre la tracción velocidad y deformación nuclear15 sugiriendo una respuesta elástica principalmente a la fuerza.</li>
</ol>3. Análisis de los datos
<ol><li>Realizar análisis de imagen con cualquier software de procesamiento de imágenes básica disponible. El grado de deformación nuclear puede cuantificarse por la cepa de longitud (Ɛ) o la deformación de la zona (figura 1A). Cuantificar la tensión longitud utilizando la ecuación 1, donde L y L0 representan las longitudes del núcleo de deformación máxima y la posición inicial, respectivamente. <img alt="Equation 1" src="/files/ftp_upload/58038/58038eq1.jpg">(Ecuación 1)</li>
</ol>

<ol>
	<li>Chow, K. H., Factor, R. E., Ullman, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+nuclear+envelope+environment+and+its+cancer+connections.">The nuclear envelope environment and its cancer connections.</a> Nature Reviews Cancer. 12 (3), 196-209 (2012).</li><li>Zink, D., Fischer, A. H., Nickerson, 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=Nuclear+structure+in+cancer+cells.">Nuclear structure in cancer cells.</a> Nature Reviews Cancer. 4 (9), 677-687 (2004).</li><li>Bank, E. M., Gruenbaum, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+nuclear+lamina+and+heterochromatin:+a+complex+relationship.">The nuclear lamina and heterochromatin: a complex relationship.</a> Biochemical Society Transactions. 39 (6), 1705-1709 (2011).</li><li>Lammerding, 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=Lamins+A+and+C+but+not+lamin+B1+regulate+nuclear+mechanics.">Lamins A and C but not lamin B1 regulate nuclear mechanics.</a> Journal of Biological Chemistry. 281 (35), 25768-25780 (2006).</li><li>Dahl, K. N., Engler, A. J., Pajerowski, J. D., Discher, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Power-law+rheology+of+isolated+nuclei+with+deformation+mapping+of+nuclear+substructures.">Power-law rheology of isolated nuclei with deformation mapping of nuclear substructures.</a> Biophysical Journal. 89 (4), 2855-2864 (2005).</li><li>Crisp, 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=Coupling+of+the+nucleus+and+cytoplasm:+role+of+the+LINC+complex.">Coupling of the nucleus and cytoplasm: role of the LINC complex.</a> Journal of Cell Biology. 172 (1), 41-53 (2006).</li><li>Sosa, B. A., Rothballer, A., Kutay, U., Schwartz, T. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=LINC+complexes+form+by+binding+of+three+KASH+peptides+to+domain+interfaces+of+trimeric+SUN+proteins.">LINC complexes form by binding of three KASH peptides to domain interfaces of trimeric SUN proteins.</a> Cell. 149 (5), 1035-1047 (2012).</li><li>Tapley, E. C., Starr, 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=Connecting+the+nucleus+to+the+cytoskeleton+by+SUN-KASH+bridges+across+the+nuclear+envelope.">Connecting the nucleus to the cytoskeleton by SUN-KASH bridges across the nuclear envelope.</a> Current Opinion in Cell Biology. 25 (1), 57-62 (2013).</li><li>Arsenovic, P. T., 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=Nesprin-2G,+a+Component+of+the+Nuclear+LINC+Complex,+Is+Subject+to+Myosin-Dependent+Tension.">Nesprin-2G, a Component of the Nuclear LINC Complex, Is Subject to Myosin-Dependent Tension.</a> Biophysical Journal. 110 (1), 34-43 (2016).</li><li>Rowat, A. C., Lammerding, J., Ipsen, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+properties+of+the+cell+nucleus+and+the+effect+of+emerin+deficiency.">Mechanical properties of the cell nucleus and the effect of emerin deficiency.</a> Biophysical Journal. 91 (12), 4649-4664 (2006).</li><li>Rowat, A. C., Foster, L. J., Nielsen, M. M., Weiss, M., Ipsen, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+the+elastic+properties+of+the+nuclear+envelope.">Characterization of the elastic properties of the nuclear envelope.</a> Journal of the Royal Society Interface. 2 (2), 63-69 (2005).</li><li>Pagliara, 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=Auxetic+nuclei+in+embryonic+stem+cells+exiting+pluripotency.">Auxetic nuclei in embryonic stem cells exiting pluripotency.</a> Nature Materials. 13 (6), 638-644 (2014).</li><li>Liu, H., 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=In+situ+mechanical+characterization+of+the+cell+nucleus+by+atomic+force+microscopy.">In situ mechanical characterization of the cell nucleus by atomic force microscopy.</a> ACS Nanotechnology. 8 (4), 3821-3828 (2014).</li><li>Krause, M., Te Riet, J., Wolf, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+the+compressibility+of+tumor+cell+nuclei+by+combined+atomic+force-confocal+microscopy.">Probing the compressibility of tumor cell nuclei by combined atomic force-confocal microscopy.</a> Physical Biology. 10 (6), 065002 (2013).</li><li>Neelam, 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=Direct+force+probe+reveals+the+mechanics+of+nuclear+homeostasis+in+the+mammalian+cell.">Direct force probe reveals the mechanics of nuclear homeostasis in the mammalian cell.</a> Proceedings of the National Academy of Sciences of the United States of America. 112 (18), 5720-5725 (2015).</li><li>Pajerowski, J. D., Dahl, K. N., Zhong, F. L., Sammak, P. J., Discher, D. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physical+plasticity+of+the+nucleus+in+stem+cell+differentiation.">Physical plasticity of the nucleus in stem cell differentiation.</a> Proceedings of the National Academy of Sciences of the United States of America. 104 (40), 15619-15624 (2007).</li><li>Lammerding, 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=Lamin+A/C+deficiency+causes+defective+nuclear+mechanics+and+mechanotransduction.">Lamin A/C deficiency causes defective nuclear mechanics and mechanotransduction.</a> Journal of Clinical Investigation. 113 (3), 370-378 (2004).</li><li>Chancellor, T. J., Lee, J., Thodeti, C. K., Lele, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Actomyosin+tension+exerted+on+the+nucleus+through+nesprin-1+connections+influences+endothelial+cell+adhesion,+migration,+and+cyclic+strain-induced+reorientation.">Actomyosin tension exerted on the nucleus through nesprin-1 connections influences endothelial cell adhesion, migration, and cyclic strain-induced reorientation.</a> Biophysical Journal. 99 (1), 115-123 (2010).</li><li>Neelam, S., Dickinson, R. B., Lele, T. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+approaches+for+understanding+the+nuclear+force+balance+in+living,+adherent+cells.">New approaches for understanding the nuclear force balance in living, adherent cells.</a> Methods. 94, 27-32 (2016).</li></ol>

Los autores no tienen nada que revelar.

Medición de la integración mecánica del núcleo con el citoesqueleto es un reto para métodos más actuales, como la micropipeta aspiración16, porque requieren cualquiera de los dos núcleos aislados (donde el núcleo es desacoplado de citoesqueleto) o núcleos en células suspendidas (donde están ausentes las fuerzas extracelulares, tales como las fuerzas de tracción,). Fuerza se ha aplicado al núcleo mediante la aplicación de tensión biaxial a adherente de las células a una membrana<su...

Patologías como el cáncer implican alteraciones nuclear forma y estructura1,2, que generalmente están acompañados por una descalcificación de los núcleo3,4. Nuclear resistencia a la deformación mecánica se ha caracterizado generalmente por aplicación de una fuerza en núcleos aislados5.
El núcleo en las células está conectado molecularmente con el citoesqueleto por el vinculador del nucleoesqueleto y citoesqueleto (LINC) complejo6,7,8,9. Como resultado, el núcleo está integrado mecánicamente con el citoesqueleto y, a través de adherencias de sustrato celular, la matriz extracelular. Mecánicamente el núcleo interior de las células adherentes de sondeo puede proporcionar la penetración en esta integración mecánica. Los métodos para manipular los núcleos en las células vivas incluyen micropipeta aspiración10,11y microscopía de fuerza atómica12,13,14. Recientemente hemos descrito un sondeo de la fuerza directa (DFP) que aplica fuerzas mecánicas directamente sobre el núcleo de una vida celular adherente15.
Aquí describiremos el procedimiento para utilizar un sistema de microinyección que está comúnmente disponible en las instalaciones de microscopía para aplicar una fuerza mecánica de nano-escala conocida, directamente al núcleo en una célula adherente. Un femtotip (punta de micropipeta del diámetro del μm 0,5) es montado y conectado al sistema de microinyección por un tubo. La punta, colocada en un ángulo de 45° con respecto a la superficie de la placa de cultivo, se baja hasta adyacente a la superficie nuclear. El tubo entonces se desconecta y abierto a la atmósfera, que crea una presión negativa de succión en la superficie nuclear y sella la punta de la micropipeta contra la superficie nuclear. A través de la traducción de la punta de una micropipeta, el núcleo es deforme y eventualmente (dependiendo de la magnitud de fuerza aplicada), separado de la micropipeta. Esta separación se produce cuando las fuerzas de restauración (resistencia), ejercidas por el núcleo y la célula, igualan a la fuerza de la succión aplicada por la micropipeta. Análisis se pueden realizar midiendo el desplazamiento del núcleo, la cepa de longitud (ecuación 1), o la deformación de la zona (figura 1A).

<table border="0" cellpadding="0" cellspacing="0" style="width:843px;" width="843">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">FluoroDish</td>
			<td style="width:71px;">WPI</td>
			<td style="width:119px;">FD35</td>
			<td style="width:355px;"></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:299px;">SYTO 59</td>
			<td style="width:71px;">ThermoFisher Scientific</td>
			<td style="width:119px;">S11341</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:299px;">Femtotips&#160;</td>
			<td style="width:71px;">Eppendorf</td>
			<td align="right">930000043</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:299px;">InjectMan NI2</td>
			<td style="width:71px;">Eppendorf</td>
			<td style="width:119px;">NA</td>
			<td>discontinued, current equivalent model: InjectMan 4</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:299px;">FemtoJet</td>
			<td style="width:71px;">Eppendorf</td>
			<td style="width:119px;">NA</td>
			<td>Current model FemtoJet 4i</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">Plan Fluor oil immersion 40x</td>
			<td style="width:71px;">Nikon</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">Apo TIRF oil immersion 60x</td>
			<td style="width:71px;">Nikon</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:299px;">Donor Bovine Serum (DBS)</td>
			<td style="width:71px;">ThermoFisher Scientific</td>
			<td align="right" style="width:119px;">16030074</td>
			<td>NIH 3T3 serum</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Dulbecco&#39;s Modification of Eagle&#39;s (DMEM)</td>
			<td style="width:71px;">Mediatech cellgro</td>
			<td style="width:119px;">MT10013CVRF</td>
			<td>NIH 3T3 medium</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:299px;">Penicillin-Streptomycin&#160;</td>
			<td style="width:71px;">Mediatech</td>
			<td style="width:119px;">MT30004CIRF</td>
			<td>NIH 3T3 medium supplement</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">Immersion Oil Type LDF Non-Fluorescing</td>
			<td style="width:71px;">Nikon</td>
			<td align="right" style="width:119px;">77007</td>
			<td>Immersion oil for objective lens&#160;</td>
		</tr>
	</tbody>
</table>

a direct force probe for measuring mechanical integration between the nucleus and the cytoskeleton

Las propiedades mecánicas del núcleo determinan su respuesta a fuerzas mecánicas generadas en las células. Porque el núcleo es molecularmente continuo con el citoesqueleto, se necesitan métodos para sondear su comportamiento mecánico en las células adherentes. Aquí, discutimos la sonda fuerza directa (DFP) como una herramienta para aplicar la fuerza directamente al núcleo en una célula adherente de viva. Atribuimos una micropipeta estrecha a la superficie nuclear con la succión. La micropipeta es traducida fuera del núcleo, que hace que el núcleo se deforman y traducir. Cuando la fuerza restauradora es igual a la fuerza de succión, el núcleo se separa y elásticamente se relaja. Porque precisamente se conoce la presión de succión, se conoce la fuerza en la superficie nuclear. Este método ha revelado que las fuerzas de la nano-escala son suficientes para deformar y traducir el núcleo de las células adherentes e identificaron elementos citoesqueléticos que permiten el núcleo resistir las fuerzas. El DFP puede utilizarse para analizar las contribuciones de los componentes celulares y nucleares para propiedades mecánicas nucleares en las células vivas.

Figura 2A muestra el forzamiento de un núcleo de fibroblasto de ratón NIH 3T3. Como la punta de la micropipeta es traducida a la derecha, el núcleo se deforma y finalmente se separa de la punta de la micropipeta. La tensión de la longitud del núcleo se considera que aumentan con el aumento de fuerza de la succión (figura 2B). El borde delantero del núcleo (micropipeta tirando borde) forma una protuberancia nuclear y el bor...

Watch this Scientific Journal Video about A Direct Force Probe for Measuring Mechanical Integration Between the Nucleus and the Cytoskeleton at JoVE.com

A Direct Force Probe for Measuring Mechanical Integration Between the Nucleus and the Cytoskeleton

Un sondeo de la fuerza directa para medir la integración mecánica entre el núcleo y el citoesqueleto

En este protocolo, se describe un método de la micropipeta para aplicar directamente una fuerza controlada al núcleo en una célula viva. Este ensayo permite interrogatorio de nucleares propiedades mecánicas en la célula viva, adherente.

The mechanical properties of the nucleus determine its response to mechanical forces generated in cells. Because the nucleus is molecularly continuous ...

a-direct-force-probe-for-measuring-mechanical-integration-between

Universidad de Cartagena UDEC

Research

JoVE Journal

Biochemistry

15.1K vistas.  University of Florida. En este protocolo, se describe un método de la micropipeta para aplicar directamente una fuerza controlada al núcleo en una célula viva. Este ensayo permite interrogatorio de nucleares propiedades mecánicas en la célula viva, adherente.

Video: A Direct Force Probe for Measuring Mechanical Integration Between the Nucleus and the Cytoskeleton

Method for Identifying Small Molecule Inhibitors of the Protein-protein Interaction Between HCN1 and TRIP8b

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed ubiquitously throughout the brain, where they function to regulate the excitability of neurons. The subcellular distribution of these channels in pyramidal neurons of hippocampal area CA1 is regulated by tetratricopeptide repeat-containing Rab8b interacting protein (TRIP8b), an auxiliary subunit. Genetic knockout of HCN pore forming subunits or TRIP8b, both lead to an increase in antidepressant-like behavior, suggesting that limiting the function of HCN channels may be useful as a treatment for Major Depressive Disorder (MDD). Despite significant therapeutic interest, HCN channels are also expressed in the heart, where they regulate rhythmicity. To circumvent off-target issues associated with blocking cardiac HCN channels, our lab has recently proposed targeting the protein-protein interaction between HCN and TRIP8b in order to specifically disrupt HCN channel function in the brain. TRIP8b binds to HCN pore forming subunits at two distinct interaction sites, although here the focus is on the interaction between the tetratricopeptide repeat (TPR) domains of TRIP8b and the C terminal tail of HCN1. In this protocol, an expanded description of a method for purifying TRIP8b and executing a high throughput screen to identify small molecule inhibitors of the interaction between HCN and TRIP8b, is described. The method for high throughput screening utilizes a Fluorescence Polarization (FP) -based assay to monitor the binding of a large TRIP8b fragment to a fluorophore-tagged eleven amino acid peptide corresponding to the HCN1 C terminal tail. This method allows &#39;hit&#39; compounds to be identified based on the change in the polarization of emitted light. Validation assays are then performed to ensure that &#39;hit&#39; compounds are not artifactual.

The interaction between HCN channels and their auxiliary subunit has been identified as a therapeutic target in Major Depressive Disorder. Here, a fluorescence polarization-based method for identifying small molecule inhibitors of this protein-protein interaction, is presented.

Método para la identificación de inhibidores de moléculas pequeñas de la interacción proteína-proteína entre HCN1 y TRIP8b

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are expressed ubiquitously throughout the brain, where they function to regulate the ...

Investigación

Bioquímica

Time-resolved ElectroSpray Ionization Hydrogen-deuterium Exchange Mass Spectrometry for Studying Protein Structure and Dynamics

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. Hydrogen-Deuterium Exchange (HDX) measured at rapid time scales is uniquely suited to detect structures and hydrogen bonding networks that are briefly populated, allowing for the characterization of transient conformers in native ensembles. Coupling of HDX to mass spectrometry offers several key advantages, including high sensitivity, low sample consumption and no restriction on protein size. This technique has advanced greatly in the last several decades, including the ability to monitor HDX labeling times on the millisecond time scale. In addition, by incorporating the HDX workflow onto a microfluidic platform housing an acidic protease microreactor, we are able to localize dynamic properties at the peptide level. In this study, Time-Resolved ElectroSpray Ionization Mass Spectrometry (TRESI-MS) coupled to HDX was used to provide a detailed picture of residual structure in the tau protein, as well as the conformational shifts induced upon hyperphosphorylation.

Conformational flexibility plays a critical role in protein function. Herein, we describe the use of time-resolved electrospray ionization mass spectrometry coupled to hydrogen-deuterium exchange for probing the rapid structural changes that drive function in ordered and disordered proteins.

Resuelta en el tiempo de ionización por electrospray de hidrógeno-deuterio Espectrometría de Masas de cambio para el estudio de la estructura proteica y Dinámica

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. ...

Force Spectroscopy of Single Protein Molecules Using an Atomic Force Microscope

The determination of the folding process of proteins from their amino acid sequence to their native 3D structure is an important problem in biology. Atomic force microscopy (AFM) can address this problem by enabling stretching and relaxation of single protein molecules, which gives direct evidence of specific unfolding and refolding characteristics. AFM-based single-molecule force-spectroscopy (AFM-SMFS) provides a means to consistently measure high-energy conformations in proteins that are not possible in traditional bulk (biochemical) measurements. Although numerous papers were published to show principles of AFM-SMFS, it is not easy to conduct SMFS experiments due to a lack of an exhaustively complete protocol. In this study, we briefly illustrate the principles of AFM and extensively detail the protocols, procedures, and data analysis as a guideline to achieve good results from SMFS experiments. We demonstrate representative SMFS results of single protein mechanical unfolding measurements and we provide troubleshooting strategies for some commonly encountered problems.

We describe the detailed procedures and strategies to measure the mechanical properties and mechanical unfolding pathways of single protein molecules using an atomic force microscope. We also show representative results as a reference for selection and justification of good single protein molecule recordings.

Espectroscopia de la fuerza de las moléculas de proteína sola utilizando un microscopio de fuerza atómica

The determination of the folding process of proteins from their amino acid sequence to their native 3D structure is an important problem in biology. ...

Utilizing a Comprehensive Immunoprecipitation Enrichment System to Identify an Endogenous Post-translational Modification Profile for Target Proteins

It is now well-appreciated that post-translational modifications (PTMs) play an integral role in regulating a protein&#39;s structure and function, which may be essential for a given protein&#39;s role both physiologically and pathologically. Enrichment of PTMs is often necessary when investigating the PTM status of a target protein, because PTMs are often transient and relatively low in abundance. Many pitfalls are encountered when enriching for a PTM of a target protein, such as buffer incompatibility, the target protein antibody is not IP-compatible, loss of PTM signal, and others. The degree of difficulty is magnified when investigating multiple PTMs like acetylation, ubiquitination, SUMOylation 2/3, and tyrosine phosphorylation for a given target protein. Studying a combination of these PTMs may be necessary, as crosstalk between PTMs is prevalent and critical for protein regulation. Often, these PTMs are studied in different lysis buffers and with unique inhibitor compositions. To simplify the process, a unique denaturing lysis system was developed that effectively isolates and preserves these four PTMs; thus, enabling investigation of potential crosstalk in a single lysis system. A unique filter system was engineered to remove contaminating genomic DNA from the lysate, which is a problematic by-product of denaturing buffers. Robust affinity matrices targeting each of the four PTMs were developed in concert with the buffer system to maximize the enrichment and detection of the endogenous states of these four PTMs. This comprehensive PTM detection toolset streamlines the process of obtaining critical information about whether a protein is modified by one or more of these PTMs.

Investigating multiple, endogenous post-translational modifications for a target protein can be extremely challenging. Techniques described here utilize an optimized lysis buffer and filter system developed with specific PTM-targeting, affinity matrices to detect the acetylation, ubiquitination, SUMOylation 2/3, and tyrosine phosphorylation modifications for a target protein using a single, streamlined system.

Utilizando un sistema de enriquecimiento integral inmunoprecipitación para identificar un perfil endógeno modificación poste-de translación de proteínas blanco

It is now well-appreciated that post-translational modifications (PTMs) play an integral role in regulating a protein&#39;s structure and function, which ...

A Colorimetric Method for Measuring Iron Content in Plants

Iron, one of the most important micronutrients in living organisms, is involved in basic processes, such as respiration and photosynthesis. Iron content is rather low in all organisms, amounting in plants to about 0.009% of dry weight. To date, one of the most accurate methods for measuring iron concentration in plant tissues is flame absorption atomic spectroscopy. However, this approach is time-consuming and expensive and requires specific equipment not commonly found in plant laboratories. Therefore, a simpler, yet accurate method that can be routinely used is needed. The colorimetric Prussian Blue method is regularly used for qualitative iron staining in animal and plant histological sections. In this study, we adapted the Prussian Blue method for quantitative measurements of iron in tobacco leaves. We validated the accuracy of this method using both atomic spectroscopy and Prussian Blue staining to measure iron content in the same samples and found a linear regression (R2 = 0.988) between the two procedures. We conclude that the Prussian Blue method for quantitative iron measurement in plant tissues is precise, simple, and inexpensive. However, the linear regression presented here may not be appropriate for other plant species, due to potential interactions between the sample and the reagent. Establishment of a regression curve is thus needed for different plant species.

We present a simple and reliable protocol for measuring iron content in plant tissues using the colorimetric Prussian Blue method.

Un método colorimétrico para medir el contenido de hierro en plantas

Iron, one of the most important micronutrients in living organisms, is involved in basic processes, such as respiration and photosynthesis. Iron content ...

Polysome Profiling in Leishmania, Human Cells and Mouse Testis

Proper protein expression at the right time and in the right amounts is the basis of normal cell function and survival in a fast-changing environment. For a long time, the gene expression studies were dominated by research on the transcriptional level. However, the steady-state levels of mRNAs do not correlate well with protein production, and the translatability of mRNAs varies greatly depending on the conditions. In some organisms, like the parasite Leishmania, the protein expression is regulated mostly at the translational level. Recent studies demonstrated that protein translation dysregulation is associated with cancer, metabolic, neurodegenerative and other human diseases. Polysome profiling is a powerful method to study protein translation regulation. It allows to measure the translational status of individual mRNAs or examine translation on a genome-wide scale. The basis of this technique is the separation of polysomes, ribosomes, their subunits and free mRNAs during centrifugation of a cytoplasmic lysate through a sucrose gradient. Here, we present a universal polysome profiling protocol used on three different models - parasite Leishmania major, cultured human cells and animal tissues. Leishmania cells freely grow in suspension and cultured human cells grow in adherent monolayer, while mouse testis represents an animal tissue sample. Thus, the technique is adapted to all of these sources. The protocol for the analysis of polysomal fractions includes detection of individual mRNA levels by RT-qPCR, proteins by Western blot and analysis of ribosomal RNAs by electrophoresis. The method can be further extended by examination of mRNAs association with the ribosome on a transcriptome level by deep RNA-seq and analysis of ribosome-associated proteins by mass spectroscopy of the fractions. The method can be easily adjusted to other biological models.

Polysome Profiling in Leishmania, Human Cells and Mouse Testis

The overall goal of polysome profiling technique is analysis of translational activity of individual mRNAs or transcriptome mRNAs during protein synthesis. The method is important for studies of protein synthesis regulation, translation activation and repression in health and multiple human diseases.

Polysome perfilado en Leishmania, las células humanas y testículo de ratón

Proper protein expression at the right time and in the right amounts is the basis of normal cell function and survival in a fast-changing environment. For ...

Covalent Immobilization of Proteins for the Single Molecule Force Spectroscopy

In recent years, atomic force microscopy (AFM) based single molecule force spectroscopy (SMFS) extended our understanding of molecular properties and functions. It gave us the opportunity to explore a multiplicity of biophysical mechanisms, e.g., how bacterial adhesins bind to host surface receptors in more detail. Among other factors, the success of SMFS experiments depends on the functional and native immobilization of the biomolecules of interest on solid surfaces and AFM tips. Here, we describe a straightforward protocol for the covalent coupling of proteins to silicon surfaces using silane-PEG-carboxyls and the well-established N-hydroxysuccinimid/1-ethyl-3-(3-dimethyl-aminopropyl)carbodiimid (EDC/NHS) chemistry in order to explore the interaction of pilus-1 adhesin RrgA from the Gram-positive bacterium Streptococcus pneumoniae (S. pneumoniae) with the extracellular matrix protein fibronectin (Fn). Our results show that the surface functionalization leads to a homogenous distribution of Fn on the glass surface and to an appropriate concentration of RrgA on the AFM cantilever tip, apparent by the target value of up to 20% of interaction events during SMFS measurements and revealed that RrgA binds to Fn with a mean force of 52 pN. The protocol can be adjusted to couple via site specific free thiol groups. This results in a predefined protein or molecule orientation and is suitable for other biophysical applications besides the SMFS.

This protocol describes the covalent immobilization of proteins with a heterobifunctional silane coupling agent to silicon-oxide surfaces designed for the atomic force microscopy based single molecule force spectroscopy which is exemplified by the interaction of RrgA (pilus-1 tip adhesin of S. pneumoniae) with fibronectin.

Inmovilización covalente de las proteínas para la espectroscopia de fuerza sola molécula

In recent years, atomic force microscopy (AFM) based single molecule force spectroscopy (SMFS) extended our understanding of molecular properties and ...

Imaging of Extracellular Vesicles by Atomic Force Microscopy

Exosomes and other extracellular vesicles (EVs) are molecular complexes consisting of a lipid membrane vesicle, its surface decoration by membrane proteins and other molecules, and diverse luminal content inherited from a parent cell, which includes RNAs, proteins, and DNAs. The characterization of the hydrodynamic sizes of EVs, which depends on the size of the vesicle and its coronal layer formed by surface decorations, has become routine. For exosomes, the smallest of EVs, the relative difference between the hydrodynamic and vesicles sizes is significant. The characterization of vesicles sizes by the cryogenic transmission electron microscopy (cryo-TEM) imaging, a gold standard technique, remains a challenge due to the cost of the instrument, the expertise required to perform the sample preparation, imaging and data analysis, and a small number of particles often observed in images. A widely available and accessible alternative is the atomic force microscopy (AFM), which can produce versatile data on three-dimensional geometry, size, and other biophysical properties of extracellular vesicles. The developed protocol guides the users in utilizing this analytical tool and outlines the workflow for the analysis of EVs by the AFM, which includes the sample preparation for imaging EVs in hydrated or desiccated form, the electrostatic immobilization of vesicles on a substrate, data acquisition, its analysis, and interpretation. The representative results demonstrate that the fixation of EVs on the modified mica surface is predictable, customizable, and allows the user to obtain sizing results for a large number of vesicles. The vesicle sizing based on the AFM data was found to be consistent with the cryo-TEM imaging.&#160;

A step-by-step procedure is described for label-free immobilization of exosomes and extracellular vesicles from liquid samples and their imaging by atomic force microscopy (AFM). The AFM images are used to estimate the size of the vesicles in the solution and characterize other biophysical properties.&#160;

Imagen de vesículas extracelulares mediante microscopía de fuerza atómica

Exosomes and other extracellular vesicles (EVs) are molecular complexes consisting of a lipid membrane vesicle, its surface decoration by membrane ...

High-Throughput Total Internal Reflection Fluorescence and Direct Stochastic Optical Reconstruction Microscopy Using a Photonic Chip

Total internal reflection fluorescence (TIRF) is commonly used in single molecule localization based super-resolution microscopy as it gives enhanced contrast due to optical sectioning. The conventional approach is to use high numerical aperture microscope TIRF objectives for both excitation and collection, severely limiting the field of view and throughput. We present a novel approach to generating TIRF excitation for imaging with optical waveguides, called chip-based nanoscopy. The aim of this protocol is to demonstrate how chip-based imaging is performed in an already built setup. The main advantage of chip-based nanoscopy is that the excitation and collection pathways are decoupled. Imaging can then be done with a low magnification lens, resulting in large field of view TIRF images, at the price of a small reduction in resolution. Liver sinusoidal endothelial cells (LSECs) were imaged using direct stochastic optical reconstruction microscopy (dSTORM), showing a resolution comparable to traditional super-resolution microscopes. In addition, we demonstrate the high-throughput capabilities by imaging a 500 &#181;m x 500 &#181;m region with a low magnification lens, providing a resolution of 76 nm. Through its compact character, chip-based imaging can be retrofitted into most common microscopes and can be combined with other on-chip optical techniques, such as on-chip sensing, spectroscopy, optical trapping, etc. The technique is thus ideally suited for high throughput 2D super-resolution imaging, but also offers great opportunities for multi-modal analysis.

Chip-based super-resolution optical microscopy is a novel approach to fluorescence microscopy and offers advantages in cost effectiveness and throughput. Here, the protocols for chip preparation and imaging are shown for TIRF microscopy and localization-based super-resolution microscopy.

Fluorescencia de reflexión interna total de alto rendimiento y microscopía de reconstrucción óptica estocástica directa utilizando un chip fotónico

Total internal reflection fluorescence (TIRF) is commonly used in single molecule localization based super-resolution microscopy as it gives enhanced ...

A High-Throughput Enzyme-Coupled Activity Assay to Probe Small Molecule Interaction with the dNTPase SAMHD1

Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) is a pivotal regulator of intracellular deoxynucleoside triphosphate (dNTP) pools, as this enzyme can hydrolyze dNTPs into their corresponding nucleosides and inorganic triphosphates. Due to its critical role in nucleotide metabolism, its association to several pathologies, and its role in therapy resistance, intense research is currently being carried out for a better understanding of both the regulation and cellular function of this enzyme. For this reason, development of simple and inexpensive high-throughput amenable methods to probe small molecule interaction with SAMHD1, such as allosteric regulators, substrates, or inhibitors, is vital. To this purpose, the enzyme-coupled malachite green assay is a simple and robust colorimetric assay that can be deployed in a 384-microwell plate format allowing the indirect measurement of SAMHD1 activity. As SAMHD1 releases the triphosphate group from nucleotide substrates, we can couple a pyrophosphatase activity to this reaction, thereby producing inorganic phosphate, which can be quantified by the malachite green reagent through the formation of a phosphomolybdate malachite green complex. Here, we show the application of this methodology to characterize known inhibitors of SAMHD1 and to decipher the mechanisms involved in SAMHD1 catalysis of non-canonical substrates and regulation by allosteric activators, exemplified by nucleoside-based anticancer drugs. Thus, the enzyme-coupled malachite green assay is a powerful tool to study SAMHD1, and furthermore, could also be utilized in the study of several enzymes which release phosphate species.

SAMHD1 is a deoxynucleoside triphosphate triphosphohydrolase with critical roles in human health and disease. Here we present a versatile enzyme-coupled SAMHD1 activity assay, deployed in a 384-well microplate format, that allows for the evaluation of small molecules and nucleotide analogues as SAMHD1 substrates, activators, and inhibitors.

Un ensayo de actividad acoplada a enzimas de alto rendimiento para sondear la interacción de moléculas pequeñas con la dNTPasa SAMHD1

Sterile alpha motif and HD domain-containing protein 1 (SAMHD1) is a pivotal regulator of intracellular deoxynucleoside triphosphate (dNTP) pools, as this ...