A TRPV4-dependent calcium signaling axis regulates lamellipodial actin architecture to promote cell migration

Cell migration is crucial for development and tissue homeostasis, while its dysregulation leads to severe pathologies. Cell migration is driven by the extension of actin-based lamellipodial protrusions powered by actin polymerization, which is tightly regulated by signaling pathways, including Rho GTPases and calcium (Ca²⁺) signaling. While the importance of Ca²⁺ signaling in lamellipodial protrusions has been established, the molecular mechanisms linking Ca²⁺ to lamellipodia assembly are unknown. Here, we identify a novel Ca²⁺ signaling axis involving the mechano-gated channel transient receptor potential vanilloid 4 (TRPV4), which regulates lamellipodial protrusions in various cell types. Using Ca²⁺ and Förster resonance energy transfer (FRET) imaging, we demonstrate that TRPV4-mediated Ca²⁺ influx upregulates RhoA activity within lamellipodia, which then facilitates formin-mediated actin assembly. Mechanistically, we identify Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and tumor endothelial marker 4 (TEM4) as key mediators relaying the TRPV4-mediated Ca²⁺ signal to RhoA. These data define a molecular pathway by which Ca²⁺ influx regulates small GTPase activity within a specific cellular domain-lamellipodia-and demonstrate its critical role in organizing the actin machinery and promoting cell migration in diverse biological contexts.