The HOPS Complex is Required for Matrix Degradation through Late Endosomal Recycling of MT1-MMP

Abstract

MT1-MMP is a type I transmembrane proteinase that plays a key role in cancer metastasis through degradation of the extracellular matrix (ECM) and activation of other proteases. Recycling of MT1-MMP is essential for its function in cellular invasion. During its recycling, theHOPS complex is involved in late endosomal trafficking of MT1-MMP. Here, we investigate the role of HOPS in recycling of MT1-MMPin more detail. Depletion ofHOPS subunitsVPS18 and VPS39 results in accumulation of MT1-MMP in mixed endolysosomal compartments. Migrationassaysof these lines revealed that cell motility in 2D was unaffected. However, cell motility in 3D, for which ECM degradation is crucial, was significantly decreasedin the VPS39 knockouts. Further analysis of the degradative capacity in a gelatin degradation assay revealedthat knockout of VPS18and, more strongly, VPS39inhibits matrix degradation. By total internal reflection microscopy (TIRF) of MT1-MMP exocytic events, wedescribeimpaired lysosomal trafficking in the HOPS knockouts.We demonstrate that MT1-MMP mislocalises and its trafficking is impaired upon depletion of the HOPScomplex.Furthermore, the HOPS complex and VPS39 specifically are required for ECM degradation and invasion.Taken together, this indicates an indispensable role for HOPS in recycling of MT1-MMPand cancer cell invasion.