Caveolae couple mechanical stress to integrin recycling and activation

Lolo FN, Pavón DM, Grande A, Elósegui Artola A, Segatori VI, Sánchez S, Trepat X, Roca-Cusachs P, & Del Pozo MA*.

Abstract: Cells are subjected to multiple mechanical inputs throughout their lives. Their ability to detect these environmental cues is called mechanosensing, a process in which integrins play an important role. During cellular mechanosensing, plasma membrane (PM) tension is adjusted to mechanical stress through the buffering action of caveolae; however, little is known about the role of caveolae in early integrin mechanosensing regulation. Here, we show that Cav1KO fibroblasts increase adhesion to FN-coated beads when pulled with magnetic tweezers, as compared to wild type fibroblasts. This phenotype is Rho-independent and mainly derived from increased active β1-integrin content on the surface of Cav1KO fibroblasts. Florescence recovery after photobleaching analysis and endocytosis/recycling assays revealed that active β1-integrin is mostly endocytosed through the clathrin independent carrier/glycosylphosphatidyl inositol (GPI)-enriched endocytic compartment pathway and is more rapidly recycled to the PM in Cav1KO fibroblasts, in a Rab4 and PM tension-dependent manner. Moreover, the threshold for PM tension-driven β1-integrin activation is lower in Cav1KO mouse embryonic fibroblasts (MEFs) than in wild type MEFs, through a mechanism dependent on talin activity. Our findings suggest that caveolae couple mechanical stress to integrin cycling and activation, thereby regulating the early steps of the cellular mechanosensing response.

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Strategies for the Biofunctionalization of Straining Flow Spinning Regenerated Bombyx mori Fibers

Paloma Lozano-Picazo, Cristina Castro-Domínguez, Augusto Luis Bruno, Alejandro Baeza, Adelia S. Martínez, Patricia A. López, Ángela Castro, Yassmin Lakhal, Elena Montero, Luis Colchero, Daniel González-Nieto, Francisco Javier Rojo, Fivos Panetsos, Milagros Ramos, Rafael Daza, Alfonso M. Gañán-Calvo, Manuel Elices, Gustavo Víctor Guinea and José Pérez-Rigueiro.

Abstract: High-performance regenerated silkworm (Bombyx mori) silk fibers can be produced efficiently through the straining flow spinning (SFS) technique. In addition to an enhanced biocompatibility that results from the removal of contaminants during the processing of the material, regenerated silk fibers may be functionalized conveniently by using a range of different strategies. In this work, the possibility of implementing various functionalization techniques is explored, including the production of fluorescent fibers that may be tracked when implanted, the combination of the fibers with enzymes to yield fibers with catalytic properties, and the functionalization of the fibers with cell-adhesion motifs to modulate the adherence of different cell lineages to the material. When considered globally, all these techniques are a strong indication not only of the high versatility offered by the functionalization of regenerated fibers in terms of the different chemistries that can be employed, but also on the wide range of applications that can be covered with these functionalized fibers.

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Classification of the Binding Events between Streptavidin and Biotin-Decorated Activated Vapour Silanized (Avs) Atomic Force Microscopy Tips

Daniel Corregidor, Raquel Tabraue, Luis Colchero, Rafael Daza, Manuel Elices, Gustavo V. Guinea and José Pérez-Rigueiro.

Abstract: AFM tips were functionalized using the activated vapour silanization (AVS) process and its application in affinity atomic force microscopy was assessed by characterizing the interaction between biotin and streptavidin as model system. AVS-functionalized tips can be easily decorated with sensor molecules following well-established cross-linking chemistries as shown by covalently binding biotin molecules to the amine groups of the AFM tip. Force-distance (F-d) curves were recorded to measure the interaction between the biotin-decorated tips and a substrate covered with covalently bound streptavidin. F-d curves were initially recorded with a pristine streptavidin coating and, subsequently, new F-d curves were obtained after blocking the streptavidin binding sites with biotin-albumin. The F-d curves were classified from the intensity of the adhesion force and the number of interaction events (peaks) observed in each curve. It is shown that single molecular biotin-streptavidin interaction events are recorded consistently and no degradation evidence was observed in any of the functionalized tips during the whole two-step experiment.

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