HSP27 regulates force-coordinated DDR1 condensate disassembly and liquid-to-gel phase transition.

Endothelial cell (EC) mechanosensing is essential for vascular homeostasis and atherosclerosis development, though the influence of blood flow patterns on EC signaling is not fully understood. Discoidin domain receptor 1 (DDR1), a tyrosine kinase receptor, acts as a mechanosensor linking shear force to endothelial responses. Atheroprotective laminar shear flow induces rapid, transient DDR1 activation and condensation through liquid-liquid phase separation without harmful effects, while atherogenic shear causes delayed, sustained condensation, leading to Yes-associated protein (YAP) activation and downstream pathological signaling. We show that heat shock protein 27 (HSP27) regulates shear-dependent DDR1 condensation and phase transition. Specifically, the interaction between DDR1 and HSP27, mediated by their respective domains, is crucial for DDR1 condensate disassembly. Atherogenic shear, unlike atheroprotective shear, triggers prolonged DDR1-mediated HSP27 phosphorylation, promoting DDR1 gel transition and activating YAP signaling. The DDR1-HSP27 axis is key in endothelial YAP activation and atherogenesis in vivo. Targeting this pathway may offer therapeutic potential for preventing endothelial dysfunction and atherosclerosis.