DLC3 suppresses MT1-MMP-dependent matrix degradation by controlling RhoB and actin remodeling at endosomal membranes

Abstract

Cancer cells degrade the extracellular matrix through actin-rich protrusions termed invadopodia. The formation of functional invadopodia requires polarized membrane trafficking driven by Rho GTPase-mediated cytoskeletal remodeling. We identify the Rho GTPase-activating protein deleted in liver cancer 3 (DLC3; also known as STARD8) as an integral component of the endosomal transport and sortingmachinery. We provide evidence for the direct regulation ofRhoB by DLC3 at endosomal membranes to which DLC3 is recruited by interacting with the sorting nexin SNX27. In TGF-β-treated MCF10A breast epithelial cells, DLC3 knockdown enhanced metalloproteinasedependent matrix degradation, which was partially rescued by RhoB co-depletion. Thiswas recapitulated inMDA-MB-231 breast cancer cells in which earlyendosomes demonstrated aberrantly enriched F-actin and accumulated the metalloproteinaseMT1-MMP (also known as MMP14) upon DLC3 knockdown. Remarkably, Rab4 (herein referring to Rab4A) downregulation fully rescued the enhanced matrix degradation of TGF-β-treated MCF10A and MDA-MB-231 cells. In summary, our findings establish a novel role for DLC3 in the suppression of MT1-MMP-dependent matrix degradation by inactivating RhoB signaling at endosomal membranes. We propose that DLC3 function is required to limit endosomal actin polymerization, Rab4-dependent recycling ofMT1-MMP and, consequently, matrix degradation mediated by invadopodial activity.