Membrane Dynamics Induced by a Phosphatidylinositol 3,4,5-Trisphosphate Optogenetic Tool

Membrane dynamic structures such as filopodia, lamellipodia, and ruffles have important cellular functions in phagocytosis and cell motility, and in pathological states, such as cancer metastasis. Phosphatidylinositol 3,4,5-trisphosphate (PIP₃) is a crucial lipid that regulates PIP₃ dynamics. Investigations of how PIP₃ is involved in these functions have mainly relied on pharmacological interventions, and therefore have not generated detailed spatiotemporal information concerning membrane dynamics upon PIP₃ production. In the present study, we applied an optogenetic approach using the CRY2-CIBN system. Using this system, we revealed that local PIP₃ generation induced directional cell motility and membrane ruffles in COS7 cells. Furthermore, combined with structured illumination microscopy (SIM), membrane dynamics were investigated with high spatial resolution. We observed PIP₃-induced apical ruffles and unique actin fiber behavior in that a single actin fiber protruded from the plasma membrane was taken up into the plasma membrane without depolymerization. This system has the potential to investigate other high-level cell motility and dynamic behaviors, such as cancer cell invasion and wound healing with high spatiotemporal resolution, and could provide new insights of biological sciences for membrane dynamics.