PI(3,4)P-mediated membrane tubulation promotes integrin trafficking and invasive cell migration.

Invadopodia are integrin-mediated adhesions with abundant PI(3,4)P However, the functional role of PI(3,4)P in adhesion signaling remains unclear. Here, we find that the PI(3,4)P biogenesis regulates the integrin endocytosis at invadopodia. PI(3,4)P is locally produced by PIK3CA and SHIP2 and is concentrated at the trailing edge of the invadopodium arc. The PI(3,4)P-rich compartment locally forms small puncta (membrane buds) in a SNX9-dependent manner, recruits dynein activator Hook1 through AKTIP, and rearranges into micrometer-long tubular invaginations (membrane tubes). The uncurving membrane tube extends rapidly, follows the retrograde movement of dynein along microtubule tracks, and disconnects from the plasma membrane. Activated integrin-beta3 is locally internalized through the pathway of PI(3,4)P-mediated membrane invagination and is then actively recycled. Blockages of PI3K, SHIP2, and SNX9 suppress integrin-beta3 endocytosis, delay adhesion turnover, and impede transwell invasion of MEF-Src and MDA-MB-231 cells. Thus, the production of PI(3,4)P promotes invasive cell migration by stimulating the trafficking of integrin receptor at the invadopodium.