RESUMO
Actomyosin-undercoated adherens junctions are critical for epithelial cell integrity and remodeling. Actomyosin associates with adherens junctions through αE-catenin complexed with ß-catenin and E-cadherin in vivo; however, in vitro biochemical studies in solution showed that αE-catenin complexed with ß-catenin binds to F-actin less efficiently than αE-catenin that is not complexed with ß-catenin. Although a "catch-bond model" partly explains this inconsistency, the mechanism for this inconsistency between the in vivo and in vitro results remains elusive. We herein demonstrate that afadin binds to αE-catenin complexed with ß-catenin and enhances its F-actin-binding activity in a novel mechanism, eventually inducing the proper actomyosin organization through αE-catenin complexed with ß-catenin and E-cadherin at adherens junctions.
Assuntos
Junções Aderentes/genética , Caderinas/genética , Proteínas dos Microfilamentos/genética , beta Catenina/genética , Citoesqueleto de Actina/genética , Citoesqueleto de Actina/ultraestrutura , Actinas/genética , Actomiosina/genética , Actomiosina/ultraestrutura , Junções Aderentes/ultraestrutura , Animais , Humanos , Camundongos , Camundongos Knockout , Complexos Multiproteicos/genética , Complexos Multiproteicos/ultraestrutura , Ligação Proteica/genética , Vinculina/genética , alfa Catenina/genética , alfa Catenina/ultraestruturaRESUMO
The N-cadherin (N-cad) complex plays a crucial role in cardiac cell structure and function. Cadherins are adhesion proteins linking adjacent cardiac cells and, like integrin adhesions, are sensitive to force transmission. Forces through these adhesions are capable of eliciting structural and functional changes in myocytes. Compared to integrins, the mechanisms of force transduction through cadherins are less explored. α-catenin is a major component of the cadherin-catenin complex, thought to provide a link to the cell actin cytoskeleton. Using N-cad micropatterned substrates in an adhesion constrainment model, the results from this study show that α-catenin localizes to regions of highest internal stress in myocytes. This localization suggests that α-catenin acts as an adaptor protein associated with the cadherin mechanosensory apparatus, which is distinct from mechanosensing through integrins. Myosin inhibition in cells bound by integrins to fibronectin-coated patterns disrupts myofibiril organization, whereas on N-cad coated patterns, myosin inhibition leads to better organized myofibrils. This result indicates that the two adhesion systems provide independent mechanisms for regulating myocyte structural organization.
