Anillin tunes contractility and regulates barrier function during Rho flare-mediated tight junction remodeling

Abstract

To preserve barrier function, cell-cell junctions must dynamically remodel during cell shape changes. We have previously described a rapid tight junction repair pathway characterized by local, transient activation of RhoA, termed Rho flares, which repair leaks in tight junctions via promoting local actomyosin-mediated junction remodeling. In this pathway, junction elongation is a mechanical trigger that initiates RhoA activation through an influx of intracellular calcium and recruitment of p115RhoGEF. However, mechanisms that tune the level of RhoA activation and Myosin II contractility during the process remain uncharacterized. Here, we show that the scaffolding protein Anillin localizes to Rho flares and regulates RhoA activity and actomyosin contraction at flares. Knocking down Anillin results in Rho flares with increased intensity but shorter duration. These changes in active RhoA dynamics weaken downstream F-actin and Myosin II accumulation at the site of Rho flares, resulting in decreased junction contraction. Consequently, tight junction breaks are not reinforced following Rho flares. We show that Anillin-driven RhoA regulation is necessary for successfully repairing tight junction leaks and protecting junctions from repeated barrier damage. Together, these results uncover a novel regulatory role for Anillin during tight junction repair and barrier function maintenance. Significance StatementO_LIBarrier function is critical for epithelial tissues. Epithelial cells maintain barrier function via tight junctions, which must be remodeled to allow for cell- and tissue-scale shape changes. How barrier function is maintained and remodeled as epithelial cells change shape remains unclear. C_LIO_LIThe scaffolding protein Anillin is required for generating effective actomyosin contraction to reinforce damaged tight junctions; lack of reinforcement leads to repeated barrier leaks. C_LIO_LIThese findings highlight a novel role for Anillin in tight junction remodeling and suggest that Anillins ability to tune the level and duration of local Rho activation affects the contractile output. C_LI