Targeting a designer TIMP-1 to the cell surface for effective MT1-MMP inhibition: A potential role for the prion protein in renal carcinoma therapy

Renal carcinoma cells express Membrane Type 1-Matrix Metalloproteinase (MT1-MMP, MMP-14) to degrade extracellular matrix components and a range of bioactive molecules to allow metastasis and cell proliferation. The activity of MT1-MMP is modulated by the endogenous inhibitors, Tissue Inhibitor of Metalloproteinases (TIMPs). In this study, we describe a novel strategy that would enable a “designer” TIMP-1 tailored specifically for MT1-MMP inhibition (V4A/P6V/T98L; K_i^app 1.66 nM) to be targeted to the plasma membrane for more effective MT1-MMP inhibition. To achieve this, we fuse the designer TIMP-1 to the glycosyl-phosphatidyl inositol (GPI) anchor of the prion protein to create a membrane-tethered, high-affinity TIMP variant named “T1^Pr α^MT1” that is predominantly located on the cell surface and co-localised with MT1-MMP. Confocal microscopy shows that T1^Pr α^MT1 is found throughout the cell surface in particular the membrane ruffles where MT1-MMP is most abundant. Expression of T1^Pr α^MT1 brings about a complete abrogation of the gelatinolytic activity of cellular MT1-MMP in HT1080 fibrosarcoma cells whilst in renal carcinoma cells CaKi-1, the GPI-TIMP causes a disruption in MMP-mediated proteolysis of ECM components such as fibronectin, collagen I and laminin that consequently triggers a downstream senescence response. Moreover, the transduced cells also suffer from an impairment in proliferation and survival in vitro as well as in NOD/SCID mouse xenograft. Taken together, our findings demonstrate that the GPI anchor of prion could be exploited as a targeting device in TIMP engineering for MT1-MMP inhibition with a potential in renal carcinoma therapy.