Designer TIMPs: Therapeutic applications against TACE-related diseases

TNF-alpha is a key protein produced by our body as part of the self-defense machinery. Excessive levels of TNF-alpha are known to lead to many common inflammatory diseases such as rheumatoid arthritis and Crohn's disease. The agent responsible for the release of TNF-alpha is an enzyme called TACE. Medications that slow down or partially destroy the activity of TACE have been shown to prevent the destruction of vital organs and subsequently lead to a better clinical prognosis. In the human body, TACE is controlled by a group of natural inhibitors - the TIMPs. Given the significance of TACE and its impact on human health, it is importance for us to learn to control the activity of the enzyme, and should it be necessary, know how to destroy it. In this project, we aim to unlock the secret of TACE regulation by the TIMPs. We have created a new generation of 'designer TIMPs' that are highly potent against TACE and wish to investigate their inhibitory behaviours under physiological conditions. Furthermore we are interested in developing these designer TIMPs into therapeutic agents against TACE-related diseases. Strategies will be developed to enhance the potency as well as the delivery efficiency of the TIMPs to the sites where their remedial effects are most required. It is our hope that this project will lead to the creation of a novel class of safe drugs that could be used to treat patients suffering from disorders caused by inappropriate activity of TACE enzyme.

TNF-alpha converting enzyme (TACE, ADAM-17) is a zinc-dependent ADAM metalloproteinase of the metzincin superfamily. The enzyme regulates the shedding of a variety of cell surface-anchored molecules such as cytokines, growth factors and receptors. The main physiological regulators of TACE are the tissue inhibitors of matrix metalloproteinases (TIMPs), notably TIMP-3 that to which the enzyme is most sensitive. We have recently delineated the molecular basis that underpins TIMP-3/TACE selectivity and created a generation of 'designer' TIMPs that are highly effective against TACE in vitro. This proposal is tailored towards understanding the mechanism of TACE regulation by TIMP-3 under cell-based conditions. This apart, we also intend to develop a panel of designer TIMPs supplemented with anti-TACE capability into 'smart' inhibitory agents that could selectively modulate the proteolytic environments of native TACE. The designer TIMPs will be rendered ADAM-specific by the abrogation of their matrix metalloproteinase (MMP)-inhibiting abilities. Other biological effects typically associated with the TIMPs, e.g. growth-inducing activity, apoptotic activity will be closely monitored throughout the studies. TIMP-3 is associated with the extracellular matrix (ECM) but the mechanism is hitherto unknown. Here, we will endeavour to unlock the molecular basis of TIMP-3/ECM binding by transplanting the hypothetical ECM-binding motif of C-TIMP-3 onto C-TIMP-1, -2 and -4 scaffolds. To further enhance the targeting efficiency, different strategies will be employed to deliver the TIMPs to the cell surface where TACE enzyme resides; plausible tactics include tagging the TIMPs with GPI anchors and/or expressing the TIMPs in fusion with the ECM-binding motif of C-TIMP-3. It is hoped that the findings derived from this study will ultimately lead to the development of selective TIMPs as alternative therapeutic agents against TACE-related diseases.