How VASP enhances actin-based motility

The function of vasodilator-stimulated phosphoprotein (VASP) in motility is analyzed using a biomimetic motility assay in which ActA-coated microspheres propel themselves in a medium containing actin, the Arp2/3 complex, and three regulatory proteins in the absence or presence of VASP. Propulsion is linked to cycles of filament barbed end attachment-branching-detachment-growth in which the ActA-activated Arp2/3 complex incorporates at the junctions of branched filaments. VASP increases the velocity of beads. VASP increases branch spacing of filaments in the actin tail, as it does in lamellipodia in living cells. The effect of VASP on branch spacing of Arp2/3-induced branched actin arrays is opposed to the effect of capping proteins. However, VASP does not compete with capping proteins for binding barbed ends of actin filaments. VASP enhances branched actin polymerization only when ActA is immobilized on beads or on Listeria. VASP increases the rate of dissociation of the branch junction from immobilized ActA, which is the rate-limiting step in the catalytic cycle of site-directed filament branching

A biomimetic motility assay provides insight into the mechanism of actin-based motility

Abiomimetic motility assay is used to analyze the mechanism of force production by site-directed polymerization of actin. Polystyrene microspheres, functionalized in a controlled fashion by the N-WASP protein, the ubiquitous activator of Arp2/3 complex, undergo actin-based propulsion in a medium that consists of five pure proteins. We have analyzed the dependence of velocity on N-WASP surface density, on the concentration of capping protein, and on external force. Movement was not slowed down by increasing the diameter of the beads (0.2 to 3 μm) nor by increasing the viscosity of the medium by 105-fold. This important result shows that forces due to actin polymerization are balanced by internal forces due to transient attachment of filament ends at the surface. These forces are greater than the viscous drag. Using Alexa®488-labeled Arp2/3, we show that Arp2/3 is incorporated in the actin tail like G-actin by barbed end branching of filaments at the bead surface, not by side branching, and that filaments are more densely branched upon increasing gelsolin concentration. These data support models in which the rates of filament branching and capping control velocity, and autocatalytic branching of filament ends, rather than filament nucleation, occurs at the particle surface

Individual Actin Filaments in a Microfluidic Flow Reveal the Mechanism of ATP Hydrolysis and Give Insight Into the Properties of Profilin

A novel microfluidic approach allows the analysis of the dynamics of individual actin filaments, revealing both their local ADP/ADP-Pi-actin composition and that Pi release is a random mechanism

Les "darons" en festival électro : choc des générations à Tomorrowland ?

International audienceMême si l’origine de la musique électronique remonte aux années 1950 et 1960, c’est véritablement dans les années 80 et 90 avec les mouvements house et techno et le développement de la rave culture, qu’elle a conquis un large public. La génération des fans d’électro qui avaient 20 ans dans les années 80-90 en ont maintenant 50 ou plus encore. Néanmoins, l’électro garde une image associée à un public jeune, notamment du fait que les festivals, dont Tomorrowland, créé en Belgique en 2003 et qui a depuis essaimé dans le monde entier, véhicule cette idée au travers de sa communication ne mettant en scène que des festivaliers de 20-30 ans. Or, la communauté électro et donc celle des festivaliers s’est élargie. Nombre de quadragénaires et quinquagénaires souhaitent fréquenter les festivals électro, de la même manière qu’ils fréquentent les festivals de musiques actuelles (35 ans de moyenne d’âge). Une récente étude menée aux États-Unis montre que 67 % des gens pensent qu’on n’est jamais trop vieux pour faire la fête, et même 72 % pour aller dans voir des concerts durant plusieurs jours. Comment se passe cette cohabitation entre différentes générations ? Se sent-on légitime dans un festival électro quand on est quadragénaire ou quinquagénaire ? Nous avons essayé de le découvrir au festival "Tomorrowland Winter"

Les « darons » en festival électro : choc des générations à Tomorrowland ?

Disponible : https://theconversation.com/economie-durable-la-location-cela-peut-aussi-profiter-aux-entreprises-218661Article publié dans The Conversation : https://theconversation.com/les-darons-en-festival-electro-choc-des-generations-a-tomorrowland-20103

“Music makes the people come together”: intergenerational interactions at electro festivals

This paper aims to investigate how different festival goers of different age groups can feel at ease in an Electro Dance Music event. While those events are primarily aimed at a younger public, older festival goers are also part of participants and keen electronic music enthusiasts. Using an ethnographic approach by immersion in the Tomorrowland Winter edition Festival (TMLW), the study shows that the cohabitation between those two public targets is efficient: for each generation, the presence of the other is not only well perceived but also brings another dimension to their own experience. The results demonstrate that there is a clear positive emotional atmosphere throughout the festival and that age differences are not perceived as a limiting factor. The intergenerational dynamics can be seen as a strength in this leisure experience