title: The role of the exocyst in matrix metalloproteinase secretion and actin dynamics during tumor cell invadopodia formation.
abstract: Invadopodia are actin-rich membrane protrusions formed by tumor cells that degrade the extracellular matrix for invasion. Invadopodia formation involves membrane protrusions driven by Arp2/3-mediated actin polymerization and secretion of matrix metalloproteinases (MMPs) at the focal degrading sites. The exocyst mediates the tethering of post-Golgi secretory vesicles at the plasma membrane for exocytosis and has recently been implicated in regulating actin dynamics during cell migration. Here, we report that the exocyst plays a pivotal role in invadopodial activity. With RNAi knockdown of the exocyst component Exo70 or Sec8, MDA-MB-231 cells expressing constitutively active c-Src failed to form invadopodia. On the other hand, overexpression of Exo70 promoted invadopodia formation. Disrupting the exocyst function by siEXO70 or siSEC8 treatment or by expression of a dominant negative fragment of Exo70 inhibited the secretion of MMPs. We have also found that the exocyst interacts with the Arp2/3 complex in cells with high invasion potential; blocking the exocyst-Arp2/3 interaction inhibited Arp2/3-mediated actin polymerization and invadopodia formation. Together, our results suggest that the exocyst plays important roles in cell invasion by mediating the secretion of MMPs at focal degrading sites and regulating Arp2/3-mediated actin dynamics.
authors.affiliation: Department of Biology, University of Pennsylvania, Philadelphia, 19104-6018, USA.
authors.forename: Jianglan
authors.initials: J
authors.lastname: Liu
authors.forename: Peng
authors.initials: P
authors.lastname: Yue
authors.forename: Vira V
authors.initials: VV
authors.lastname: Artym
authors.forename: Susette C
authors.initials: SC
authors.lastname: Mueller
authors.forename: Wei
authors.initials: W
authors.lastname: Guo
mesh_terms: D051376:Actin-Related Protein 2-3 Complex / Q000235:genetics / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D000818:Animals; D022081:Cell Surface Extensions / Q000378:metabolism*; D053505:Matrix Metalloproteinases, Secreted / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D009369:Neoplasms / Q000378:metabolism / Q000473:pathology; D034622:RNA Interference; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; C489607:EXOC4 protein, human; C109901:Exoc7 protein, rat; D011993:Recombinant Fusion Proteins; D033921:Vesicular Transport Proteins; D053505:Matrix Metalloproteinases, Secreted