RESUMEN
Cadherin-mediated cell-cell adhesion is required for epithelial tissue integrity in homeostasis, during development, and in tissue repair. E-cadherin stability depends on F-actin, but the mechanisms regulating actin polymerization at cell-cell junctions remain poorly understood. Here we investigated a role for formin-mediated actin polymerization at cell-cell junctions. We identify mDia1 and Fmnl3 as major factors enhancing actin polymerization and stabilizing E-cadherin at epithelial junctions. Fmnl3 localizes to adherens junctions downstream of Src and Cdc42 and its depletion leads to a reduction in F-actin and E-cadherin at junctions and a weakening of cell-cell adhesion. Of importance, Fmnl3 expression is up-regulated and junctional localization increases during collective cell migration. Depletion of Fmnl3 or mDia1 in migrating monolayers results in dissociation of leader cells and impaired wound repair. In summary, our results show that formin activity at epithelial cell-cell junctions is important for adhesion and the maintenance of epithelial cohesion during dynamic processes, such as wound repair.
Asunto(s)
Cadherinas/metabolismo , Proteínas/metabolismo , Citoesqueleto de Actina/metabolismo , Actinas/metabolismo , Uniones Adherentes/metabolismo , Animales , Cadherinas/fisiología , Proteínas Portadoras/metabolismo , Adhesión Celular , Línea Celular , Movimiento Celular , Células Epiteliales/metabolismo , Epitelio/metabolismo , Proteínas Fetales/metabolismo , Forminas , Uniones Intercelulares/metabolismo , Ratones , Proteínas de Microfilamentos/metabolismo , Proteínas Nucleares/metabolismo , Polimerizacion , Cicatrización de Heridas/fisiología , Heridas y Lesiones/metabolismoRESUMEN
Adherens junctions, broadly defined as attachment sites in which cadherin adhesion receptors connect the actin cytoskeletons of neighboring animal cells, are multi-tasking by nature. In addition to mediating cell-cell adhesion and providing the tissue with mechanical continuity and barrier function, they maintain polarity, are sites of mechanosensing and signaling, and they regulate actomyosin dynamics and can thus generate forces to drive morphogenesis. Here we propose that the key to performing such diverse tasks is the integration within the cadherin adhesome of functional modules that evolved independently to perform other duties within the cell, and we discuss three such functional modules: force transmission, actin dynamics regulation, and contractile force generation. We compare each module to a more ancient cellular structure with similar function, identify shared components, and speculate on how the module was integrated into the cadherin adhesome.
Asunto(s)
Uniones Adherentes/metabolismo , Citoesqueleto de Actina/metabolismo , Actomiosina/metabolismo , Animales , Cadherinas/metabolismo , Adhesión Celular , Humanos , Transducción de SeñalRESUMEN
We have developed an optogenetic technique for the activation of diaphanous-related formins. Our approach is based on fusion of the light-oxygen-voltage 2 domain of Avena sativa Phototrophin1 to an isolated Diaphanous Autoregulatory Domain from mDia1. This "caged" diaphanous auto-regulatory domain was inactive in the dark but in the presence of blue light rapidly activated endogenous diaphanous-related formins. Using an F-actin reporter, we observed filopodia and lamellipodia formation as well as a steady increase in F-actin along existing stress fibers, starting within minutes of photo-activation. Interestingly, we did not observe the formation of new stress fibers. Remarkably, a 1.9-fold increase in F-actin was not paralleled by an increase in myosin II along stress fibers and the amount of tension generated by the fibers, as judged by focal adhesion size, appeared unchanged. Our results suggest a decoupling between F-actin accumulation and contractility in stress fibers and demonstrate the utility of photoactivatable diaphanous autoregulatory domain for the study of diaphanous-related formin function in cells.