Abstract Fri158: PIP5K-Ras bistability initiates plasma membrane symmetry breaking to regulate cell polarity and migration

Symmetry breaking, polarity establishment, and spontaneous cell protrusion formation are fundamental yet poorly understood cellular behaviors. Here, we demonstrate that a biochemical network centered on the mutually inhibitory localization of phosphatidylinositol-4-phosphate 5-kinase (PIP5K) and Ras activity governs these processes. In resting cells, PIP5K is uniformly elevated on the plasma membrane, while Ras activity remains minimal. Symmetry breaking arises from local PIP5K displacements, triggering Ras activation and downstream signaling events, including phosphoinositide 3-kinase (PI3K) activation. PIP5K knockout dramatically increases Ras-PI3K activation patches, leading to enhanced F-actin assembly, cortical wave formation, and increased protrusive activity, shifting the mode of migration. Conversely, high inducible PIP5K overexpression abolishes Ras-PI3K signaling, cytoskeletal activity, and migration, while acute PIP5K recruitment to the membrane induces contraction and blebbing—phenotypes reversed by myosin II inhibition, suggesting myosin’s involvement in this regulatory network. Strikingly, low PIP5K overexpression unexpectedly facilitates polarity establishment, underscoring its role as a master regulator of cell dynamics. Computational modeling integrating an excitable system, cytoskeletal feedback, and dynamic PIP5K partitioning recapitulates these findings. These mechanisms have profound implications for cardiovascular biology, as cell migration and polarity are essential for endothelial function, vascular development, and tissue repair. Endothelial and smooth muscle cells rely on tightly regulated migration to form and remodel blood vessels, and disruptions in these pathways can contribute to atherosclerosis, aneurysm formation, and impaired wound healing. Moreover, actomyosin dynamics linked to PIP5K-Ras interactions may regulate vascular contractility and endothelial barrier integrity. Understanding these core principles offers novel insights into cardiovascular pathophysiology and potential therapeutic strategies targeting cell migration in vascular disease and regenerative medicine. By elucidating a fundamental signaling network that drives symmetry breaking and polarity establishment, this study advances our knowledge of cellular behavior in both normal and diseased cardiovascular systems, highlighting PIP5K as a key molecular switch in migration and contractility.