RhoA Mediates Epithelial Cell Shape Changes via Mechanosensitive Endocytosis

Epithelial remodeling involves ratcheting behavior whereby periodic contractility produces transient changes in cell-cell contact lengths, which stabilize to produce lasting morphogenetic changes. Pulsatile RhoA activity is thought to underlie morphogenetic ratchets, but how RhoA governs transient changes in junction length, and how these changes are rectified to produce irreversible deformation, remains poorly understood. Here, we use optogenetics to characterize responses to pulsatile RhoA in model epithelium. Short RhoA pulses drive reversible junction contractions, while longer pulses produce irreversible junction length changes that saturate with prolonged pulse durations. Using an enhanced vertex model, we show this is explained by two effects: thresholded tension remodeling and continuous strain relaxation. Our model predicts that structuring RhoA into multiple pulses overcomes the saturation of contractility and confirms this experimentally. Junction remodeling also requires formin-mediated E-cadherin clustering and dynamin-dependent endocytosis. Thus, irreversible junction deformations are regulated by RhoA-mediated contractility, membrane trafficking, and adhesion receptor remodeling. •Short RhoA pulses reversibly shorten junction length, and long pulses stabilize shortening•Threshold-dependent tension remodeling and strain relaxation explain length changes•Endocytosis stabilizes junction length remodeling•Ratcheting RhoA produces more junction length change than one equivalent pulse Cavanaugh et al. use optogenetic control of RhoA to discover a mechanosensitive endocytic pathway that stabilizes cell-cell junction lengths in model epithelia. This pathway likely represents a homeostatic mechanism to regulate junction lengths, where small fluctuations in exogenous RhoA are buffered but longer patterned RhoA activity directs morphogenetic change.