Actin-dependent recruitment of Ago2 to the zonula adherens

Abstract

Adherens junctions are cadherin-based structures critical for cellular architecture. E-cadherin junctions in mature epithelial cell monolayers tether to an apical actomyosin ring to form the zonula adherens (ZA). We have previously shown that the adherens junction protein PLEKHA7 associates with and regulates the function of the core RNA interference (RNAi) component AGO2 specifically at the ZA. However, the mechanism mediating Ago2 recruitment to the ZA remained unexplored. Here, we reveal that this ZA-specific recruitment of AGO2 depends on both the structural and tensile integrity of the actomyosin cytoskeleton. We found that depletion of not only PLEKHA7, but also either of three PLEKHA7-interacting, LIM-domain family proteins, namely LMO7, LIMCH1, and PDLIM1, results in disruption of actomyosin organization and tension, as well as disruption of AGO2 junctional localization and of its miRNA-binding ability. We also show that AGO2 binds Myosin IIB and that PLEKHA7, LMO7, LIMCH1, and PDLIM1 all disrupt interaction of AGO2 with Myosin IIB at the ZA. These results demonstrate that recruitment of Ago2 to the ZA is sensitive to actomyosin perturbations, introducing the concept of a mechanosensitive RNAi machinery, with potential implications in tissue remodeling and in disease. SummaryRecruitment and miRNA-binding activity of the key RNA interference (RNAi) component AGO2 to epithelial zonula adherens depends on apical actomyosin integrity and tension, revealing the existence of a mechanosensitive RNAi machinery at the zonula adherens. Significance StatementO_LIPrevious work has shown that PLEKHA7 recruits core RNAi components, including AGO2, to regulate tumor-suppressing miRNAs specifically at the zonula adherens (ZA), through an unknown mechanism. C_LIO_LIHere, the authors show that three LIM domain-containing proteins, LMO7, LIMCH1, and PDLIM1, are also responsible for AGO2s recruitment and miRNA activity at the ZA and that all four PLEKHA7, LMO7, LIMCH1, PDLIM1 mediate AGO2 recruitment to the ZA not due to their protein-protein interactions, but through stabilizing actomyosin structure and tension. C_LIO_LIThese findings introduce a mechanosensitive RNAi machinery responsive to actomyosin perturbations, with potentially broad implications in regulation of cellular plasticity. C_LI