Mechanisms of Matrix Metalloproteinase-Mediated p53 Regulation

Cell contraction and membrane blebbing are evolutionarily conserved events that occur during the execution phase of apoptosis. Several members of the TNF-ligand superfamily, which are associated with the promotion of a number of pathological processes, including inflammation and cancer are also capable of inducing membrane blebbing in some cell types. Most of these ligands are transmembrane bound but can be shed from the cell surface through proteolytic processing where soluble ligands can act as antagonists, as in the case of FAS ligand, or agonists, as with TNF-a. Here we provide evidence that the matrix metalloproteinase, MMP-3/stromelysin-1 induces rapid membrane blebbing in serum starved or cyclohexamide-treated MCF1OA human breast epithelial cells. MMP-3-mediated membrane blebbing is associated with reorganization of the actin cytoskeleton, upregulation of both p53 and p38 MAP kinase activity, and loss of cell surface E-cadherin. A broad-spectrum MMP inhibitor completely abolishes these reactions. To understand the signaling cascade initiated by MMP-3, we asked whether factors downstream of TNF-superfamily signaling were involved. We show that inhibitors against JNK and caspase-3, and RNAi reduction of MKK7, a known activator of JNK inhibit membrane blebbing. Moreover, stable expression of a dominant negative FADD (dnFADD), a downstream effector of several TNF superfamily ligands, renders MCF1OA cells resistant to membrane blebbing. Together these findings indicate that MMP-3 induces cell membrane blebbing through a TNF-superfamily signaling pathway and provides an impetus to further explore this protease in inflammation and cancer.