The membrane-tethered membrane type 1-matrix metalloproteinase (MT1-MMP) mediates proteolysis-based invasive tumor

The membrane-tethered membrane type 1-matrix metalloproteinase (MT1-MMP) mediates proteolysis-based invasive tumor growth. 1-matrix metalloproteinase (MT1-MMP) as a key enzyme in the regulation of localized ECM breakdown (Itoh 2015 MT1-MMP contains a transmembrane domain name and can thus be embedded in the RAF1 plasma membrane of malignancy cells (Itoh 2015 Once uncovered on the surface MT1-MMP can also be reinternalized (Remacle et al. 2003 initiating a complex cycle of intracellular trafficking that results in either degradation of the proteinase or recycling back to the cell surface. As only surface-exposed MT1-MMP can contact ECM material malignancy cells must spatiotemporally change their levels of surface-localized MT1-MMP depending on the pericellular environment. Invadopodia-ECM-degrading protrusions of malignancy cells-are important sites of local MT1-MMP accumulation (Linder et al. 2011 Murphy and Courtneidge 2011 and thus the molecular details of MT1-MMP delivery to invadopodia are Roxadustat the focus of intensive research efforts. Identification of pathways regulating MT1-MMP delivery is usually of fundamental interest to both cell biologists and clinicians interested in identifying prognostic markers of malignancy progression Roxadustat or developing therapies targeted against metastatic cells. In this issue Marchesin et al. (2015) describe a mechanism for the localized delivery of MT1-MMP from endosomes to the surface of Roxadustat invadopodia in breast cancer cells promoting invasiveness. Moreover this study reveals a novel set of potential prognostic markers for aggressive breast malignancy. As the GTPase ARF6 was previously associated with tumor invasion and metastasis the experts analyzed its contribution to MT1-MMP trafficking. siRNA-mediated knockdown of ARF6 or its effectors JNK interactor protein 3 and 4 (JIP3 and JIP4) in MT1-MMP-expressing breast cancer cells reduced MT1-MMP exocytosis and tumor cell invasion. Prior work showed that ARF6-JIP3/JIP4 and motor proteins associate on endosomes (Montagnac et al. 2009 so the authors postulated that these proteins regulate MT1-MMP-positive endosome movement. Depletion of ARF6 or JIP3/JIP4 indeed impaired endosome positioning Roxadustat and image analysis of endosome position combined with ARF6 or JIP3/JIP4 silencing revealed that endosomes are docked at invadopodia through membrane-localized ARF6 associated with JIP3/JIP4. Searching for the motors contributing to endosome docking and movement the experts depleted crucial subunits of various motors including p150Glued (dynein-dynactin) KIF5B (kinesin-1) or KIF3A (kinesin-2) and observed that lack of any of these motors prevented normal MT1-MMP-positive endosome motility. Immunofluorescence analysis as well as coimmunoprecipitations confirmed the conversation between MT1-MMP and each of the three motor proteins. Interestingly silencing of JIP3/JIP4 affected the association of MT1-MMP with kinesin-1/KIF5B and dynein-dynactin-p150Glued but not with kinesin-2/KIF3A suggesting that JIP3/JIP4 controls the transport of MT1-MMP endosomes through the association of kinesin-1/KIF5B and dynein-dynactin with these endosomes while having no effect on kinesin-2/KIF3A recruitment. Furthermore MT1-MMP exocytosis may involve the forming of tubular cable connections between endosomes as well as the plasma membrane in colaboration with ECM fibers. To investigate the contribution of ARF6 JIP3/JIP4 and motor proteins to MT1-MMP-containing endosome exocytosis Marchesin et al. (2015) used time-lapse microscopy in cells overexpressing or silenced for p150Glued KIF5B or KIF3A. These experiments showed that ARF6 JIP3/JIP4 the dynein-dynactin-p150Glued complex and kinesin-1/KIF5B are required for tubulogenesis Roxadustat from MT1-MMP-positive compartments. Furthermore tubulation is known to require WASH (Wiskott-Aldrich syndrome protein and scar homologue) an activator of the Arp2/3 complex and the experts found via knockdown experiments that WASH fulfills a dual function by recruiting JIP3/JIP4 to endosomes and promoting the F-actin remodeling necessary for endosome tubulation. Overall the authors propose that activated ARF6 through JIP3/JIP4 maintains dynein-dynactin anchored in place.