Characterisation of a novel therapeutic peptide derived from Syndecan-2

Abstract

Angiogenesis, the formation of new blood vessels from pre-existing vasculature, is a feature of a number of pathologies, including neovascular eye diseases such as diabetic retinopathy. A key pro-angiogenic signalling pathway is the vascular endothelial growth factor (VEGF) system and current therapeutic options for the treatment of pathological angiogenesis target VEGF, blocking its binding and subsequent activation of VEGF receptors to prevent downstream pro-angiogenic signalling. These therapies have significant drawbacks and so in this thesis, we propose an alternative treatment option, in the form of a therapeutic peptide derived from human syndecan-2 (SDC2). Previous work by our group has provided evidence of an inhibitory role for SDC2 in angiogenesis, a signalling pathway in which the protein tyrosine phosphatase receptor (PTPR), CD148, has been implicated as a binding target of SDC2. Angiogenesis is inhibited upon SDC2 interaction with CD148. Building on this, I have produced a body of work that characterises our therapeutic peptide, regarding its stability and detectability, through novel in vitro stability assays. Furthermore, I have accumulated preliminary evidence for its inhibition of angiogenesis and, for the first time, provided insight into its mode of action. This was completed primarily through optimisation of solid phase binding assays, with miniaturisation of binding proteins to determine the specific site responsible for the interaction. In addition, we have explored the anti-angiogenic activity of CD148 short form (CD148SF), an endogenous protein translated from a CD148 splice variant. The data in this thesis provides evidence that CD148SF inhibits angiogenesis, demonstrated across a variety of in vitro and ex vivo angiogenesis models. As well as using established angiogenesis assays, I developed a novel angiogenesis model and used it to show CD148SF inhibitory effects. Together, the work contained in this thesis provides novel understanding into the activity of our therapeutic peptide, specifically regarding its binding and stability, and delivers preliminary insight into the role of CD148SF.