Multiparametric analysis of cell shape demonstrates that β-PIX directly couples YAP activation to extracellular matrix adhesion

Mechanical signals from the extracellular matrix and cellular geometry regulate the nuclear translocation of transcriptional regulators such as Yes-Associated Protein (YAP). Elucidating how physical signals control the activity of mechanosensitive proteins poses a technical challenge, because perturbations that affect cell shape may also affect protein localization indirectly. Here we present an approach that mitigates confounding effects of cell shape changes, allowing us to identify direct regulators of YAP localization. This method uses single cell image analysis and statistical models that exploit the naturally occurring heterogeneity of cellular populations. Through systematic depletion of all human kinases, Rho family GTPases, GEFs, and GAPs, and targeted chemical perturbations we found that β-PIX, a Rac1/Ccd42 GEF, and PAK2, a Rac1/Cdc42 effector, drive both YAP activation and cell-ECM adhesion turnover during cell spreading. Our observations suggest that coupling YAP to adhesion dynamics acts as a mechano-timer, allowing cells to rapidly tune gene expression in response to physical signals.