Towards subunit specific proteasome inhibitors

Abstract

This Thesis aims at the development of novel subunit selective inhibitors of the proteasome. -Three vinyl sulfone analogues of three epoxyketone containing inhibitors described in literature are synthesised and characterised. The nature of the electrophile determines subunit selectivity of the inhibitor. -Ten Michael acceptors are coupled to three peptoid tails yielding thirty peptide-like compounds. None of the peptoid Michael acceptors are efficient proteasome inhibitors. Using the Staudinger-Bertozzi ligation followed by affinity purification, tryptic digestion of the isolated proteins and LC/MS/MS identification, the targets of two compounds in HEK293T and RAW264.7 cells are determined. -Syringolins are potent proteasome inhibitors found in nature. A syringolin structural motif was built in peptoid epoxyketones and vinyl sulfones yielding a 16-membered library of proteasome inhibitors. The distance between the urea and electrophile dictates subunit selectivity. -Three cyclooctynes are compared to the Staudinger-Bertozzi two-step labelling strategy. Cyclooctynes quantitatively convert azide labelled proteasomes at a lower concentration than the Staudinger-Bertozzi phosphane but cyclooctyne two-step labelling is associated with tremendous background labelling. -A library of peptoid vinyl sulfones with basic amino acid side chains is synthesised. A compound with two benzylamine residues is a potent and _2 selective proteasome inhibitor. Attachment of a BODIPY fluorophore yielded a _2 selective probe.