PI(4,5)P2-dependent microdomain assemblies capture microtubules to promote and control leading edge motility

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Abstract
The lipid second messenger PI(4,5)P2 modulates actin dynamics, and its local accumulation at plasmalemmal microdomains (rafts) might mediate regulation of protrusive motility. However, how PI(4,5)P2-rich rafts regulate surface motility is not well understood. Here, we show that upon signals promoting cell surface motility, PI(4,5)P2 directs the assembly of dynamic raft-rich plasmalemmal patches, which promote and sustain protrusive motility. The accumulation of PI(4,5)P2 at rafts, together with Cdc42, promotes patch assembly through N-WASP. The patches exhibit locally regulated PI(4,5)P2 turnover and reduced diffusion-mediated exchange with their environment. Patches capture microtubules (MTs) through patch IQGAP1, to stabilize MTs at the leading edge. Captured MTs in turn deliver PKA to patches to promote patch clustering through further PI(4,5)P2 accumulation in response to cAMP. Patch clustering restricts, spatially confines, and polarizes protrusive motility. Thus, PI(4,5)P2-dependent raft-rich patches enhance local signaling for motility, and their assembly into clusters is regulated through captured MTs and PKA, coupling local regulation of motility to cell polarity, and organization.