Oral Presentation 2014 Cutaneous Biology Meeting

The surface Q-SNARE complex Stx4/SNAP23 regulates delivery of MMP9 and MMP14 to the plasma membrane from the classical transport pathway in macrophages. (#51)

Joan Rohl 1 , Rachael Murray 1
  1. Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, QLD, Australia

Matrix metalloproteinases (MMPs) degrade the extracellular matrix (ECM) and thus play an important role during wound healing. Degradation of the ECM during the repair process is tightly controlled as high levels of MMPs contribute to tissue damage and prolong inflammation as seen in non-healing wounds. Macrophage tissue infiltration depends on MMPs and increased macrophage numbers in wounds amplify inflammation due to their ability to secrete large volumes of MMPs. Current treatments for chronic wounds targeting secreted MMPs have not proven to be very effective. Inhibiting the surface delivery/secretion of MMPs from macrophages could lead to better therapeutics. We have investigated the intracellular trafficking routes and identified transport machinery for two of the key MMPs (MMP14 and MMP9) thought to play a role in wound chronicity. Much work has been undertaken looking at the membrane anchored MMP14 in tumour cells, where pools of MMP14 are typically recycled and delivered to the cell surface to regulate tissue infiltration. We show here that in macrophages MMP14 is newly synthesised then incorporated into the plasma membrane upon LPS activation. By inhibiting intracellular trafficking pathways with drugs, such as bredfeldin A, we show that MMP14 is transported through the classical trafficking pathway via the Golgi complex to the plasma membrane. SNARE proteins are intracellular trafficking machinery proteins that regulate the fusion of intracellular vesicles with their target membranes. We show, using siRNA knockdown, that the surface Q-SNARE complex Stx4/SNAP23 controls fusion of vesicles containing MMP14 with the plasma membrane. MMP9 is a soluble MMP secreted by macrophages and we show that it is newly synthesised by activated macrophages, traffics through a similar pathway and that the surface Q-SNARE Stx4/SNAP23 complex also regulates the secretion of MMP9. Thus, targeting the Q-SNARE complex Stx4/SNAP23 could potentially reduced MMP surface delivery and improve wound healing.