Award details

Synthesis and characterisation of amyloid fibre motifs and mimetics participating in cooperative binding with serum amyloid p component.

Reference	BB/H015809/1
Principal Investigator / Supervisor	Professor Stephen Wood
Co-Investigators / Co-Supervisors	Dr Robert Broadbridge
Institution	University College London
Department	Medicine
Funding type	Skills
Value (£)	83,281
Status	Completed
Type	Training Grants
Start date	01/10/2010
End date	30/09/2014
Duration	48 months

Abstract

unavailable

Summary

The plasma glycoprotein, serum amyloid p component (SAP) binds to amyloid fibres wherever they are deposited in diseased tissues. More than twenty different proteins are known to form fibres. SAP does not bind to any of the proteins in their native state. Therefore the fibre recognition motif must arise from the structural transition that takes place during fibre formation. SAP may be involved in promoting fibre deposition and is known to stabilise fibres, protecting them against proteolytic attack and digestion by phagocytic cells. The interaction therefore appears to be a good target for amyloid clearing drugs. SAP is pentameric and each Mr 23500 subunit carries a double calcium site that is believed to be the amyloid recognition site. Small molecules such as phosphoethanolamine or D-proline bind to this site with modest affinity (Kd 20-40 micromolar) via their acidic components binding the calcium ions. The experimental drug CPHPC (Pepys et al Nature 2002) is a bivalent compound comprising two D-proline residues linked through their N termini via a six carbon aliphatic chain. This compound crosslinks pairs of SAP molecules forming a decameric complex where five drug molecules interact with ten SAP subunits. The cooperativity of this mode of binding enhances the affinity of the interaction by three orders (Kd 10 nano-molar). The resulting decamers of SAP are rapidly cleared by the liver in vivo but the compound has insuffient affinity to completely strip all SAP from fibre deposits. The aim of this project is to synthesise cyclic peptides carrying five D-proline arms on one face or ten D-proline arms distributed on both faces. The hypothesis is that these compounds should bind to SAP in a calcium dependent manner with enhanced cooperativity and high affinity, forming pentameric SAP with blocked fibre recognition sites or crosslinked decamers. Dr Broadbridge has extensive experience in preparing a wide spectrum of different cyclic peptides and this phase of thetraining will be carried out in his lab. at Peptide Protein Research Ltd. The binding of these products to SAP will be characterised by calorimetry at UCL and the potential mode of binding investigated by computer graphic investigation of SAP and the binding sites for D-proline head groups. The materials will be co-crystallised with SAP and the detailed structure of the interaction investigated by X-ray analysis. We will also investigate peptide sequences likely to be exposed on the surface of fibres. Structural studies on Abeta 1-42 and H/D exchange measurements on transthyretin and beta2 - microglobulin suggest likely regions that are exposed on fibres. The results of the work will provide new tools for investigating fibre formation and contribute to the design of more effective blockers of this process.

Committee	Not funded via Committee
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	Training Grant - Industrial Case

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