Angi-17. Regulation of Plasma Membrane Tension by Plexin Receptors Facilitates Invasion of GBM Through Confined Space

Invading Glioblastoma (GBM) cells experience strong physical constraints and face severe mechanical challenges when they squeeze through tight, confined interstitial space. How GBM cells adapt to confined space to achieve the typical diffuse, invasive migration is not well understood. Our recent microchannel migration assays have revealed that GBM cells usurp the guidance receptor Plexin-B2 to gain increased biomechanical plasticity for polarized migration through confined space. Plexins have been long known as receptors for semaphorins to direct axon guidance. Our studies add a new biomechanical paradigm of glioma cell migration, with Plexins taking a key role in adjusting the membrane tension of GBM cells invading through confined space. We demonstrated with a series of biomechanical measurements and imaging assays, including atomic force microscopy, optical tweezers, and Flipper-TR fluorescence lifetime imaging, a key role of Plexin-B2 in controlling membrane tension and cortical actin contractility of GBM cells, which was associated with changes of the inner membrane electrical surface charge. Using live-cell imaging to track GBM cells negotiating microchannels, we revealed active endocytosis at cell front and filamentous actin assembly at rear to propel GBM cells through constrictions, and that these two processes are interconnected and governed by Plexin-B2 that orchestrates cortical actin and membrane tension. Our studies also indicate that Plexin-B2 has an intrinsic mechanosensitive function, responding to lateral membrane compression forces. Blocking the bendability of the extracellular ring-shaped domain by point mutations affected membrane internalization, permeability, phospholipid composition, as well as inner membrane surface charge. Together, our studies unveil Plexins as key players in regulation of membrane tension that enables GBM cells to adapt to physical constraints and achieve polarized confined migration. As such, Plexins represent a potential novel therapeutic target to curb the invasiveness of GBM, which we are currently investigating with novel function blocking nanobodies.