RhoB-Rab1A forms a mechanobiology module that couples cytoskeletal organization to nuclear mechanics and β-catenin access in epithelial cells.

Metastatic competence in epithelia emerges from the coupling of cytoskeletal mechanics to nuclear transcriptional control. Here, using colorectal epithelial cell models, we define a RhoB-Rab1A module that links actin organization to β-catenin nuclear access and thereby tunes EMT programs. Transcriptomic and nuclear proteomic profiling of RhoB-competent versus RhoB-deficient cells indicated enrichment of EMT and Wnt/β-catenin pathways. Loss of RhoB attenuated F-actin polymerization, stress fibers, and lamellipodia, increased whole-cell and nuclear stiffness (AFM), reduced nuclear β-catenin with a shift toward epithelial markers, and impaired migration, invasion, and lung colonization in vivo. Co-immunoprecipitation/mass spectrometry and imaging identified Rab1A as a RhoB interactor; dual RhoB-Rab1A perturbation potentiated effects on mechanics, β-catenin compartmentalization, EMT markers, and motility. These data support a mechanics-to-nucleus route in which a Rho GTPase interfaces with a Rab trafficking GTPase to regulate β-catenin availability in the absence of exogenous Wnt cues. We propose that the RhoB-Rab1A complex functions as a molecular clutch that modulate epithelial plasticity, suggesting generalizable principles for mechanically informed control of epithelial behavior.