Malcolm Walkinshaw

Lab members

Tsabieh Bilal, Liz Blackburn, Sandra Bruce, Yiyuan Chen, Jaqueline Dornan, Peter Fernandes, James Kinkead, Divya Malik, Iain McNae, Paul Michels, Rosie Mitchell, Jia Ning, Matthew Nowicki, Paul Taylor, Martin Wear, Andromachi Xipnitou, Li-Hsuan Yen

Drug discovery and molecular recognition in biological systems

A major project over the last two years has been sponsored by the Wellcome Trust Seeding Drug Discovery scheme to develop a drug to cure Human African Trypanomiasis (HAT), more commonly known as Sleeping Sickness. The unicellular trypanosome parasite that causes the disease is transferred to the mammalian host by the bite of the tsetse fly. It lives and proliferates in the blood (stage 1 HAT) until eventually making its way into the CNS and brain (stage 2 HAT) ultimately causing death. In the nutrient-rich environment of the blood the parasite relies solely on the breakdown of glucose (glycolysis) for the production of ATP. Our approach to kill the parasite has been to block the glycolytic pathway in the parasite by developing small molecule inhibitors. We have used a high-throughput screen of a large library of chemical compounds followed by a ‘structure-based approach’ to identify drug-like molecules that will only affect the parasite enzymes and not the mammalian hosts. One of the ten conserved enzymes in the pathway is the allosteric enzyme phosphofructokinase which adds a phospho group to fructose 6-phosphate. We have solved a series of protein X-ray structures of this protein in different active and inactive conformations. With chemists at the company Selcia we have designed and synthesised a series of compounds that sit in an ‘allosteric pocket’ near the active site of the parasite enzyme and prevent the protein from adopting its active conformation thus blocking enzyme activity. These molecules kill cultured parasites and also cure mice infected with the parasite (Figure 1). The most recently synthesised compounds can be given to the mice orally and a one-day dosing regimen will cure Stage 1 infection (meaning that there is no resurgence of parasites for at least 30 days). Another important feature of this drug family is the very fast killing-time. As expected with this biochemical mode of action, once the glycolytic pathway is blocked there is no alternative biochemical route for the production of ATP, leading to immediate cell death. This contrasts with the other drugs currently used in the treatment of trypanosomiasis infection (Figure 1B) which all take at least several hours compared to the phosphofructokinase inhibitors which kill over 99% of the parasites within 30 minutes

Selected publications:

Naithani, A., Taylor, P., Erman, B., and Walkinshaw, M. D. (2015) A Molecular Dynamics Study of Allosteric Transitions in Leishmania mexicana Pyruvate Kinase. Biophys J 109, 1149-1156
Blackburn, E. A., Wear, M. A., Landre, V., Narayan, V., Ning, J., Erman, B., Ball, K. L., and Walkinshaw, M. D. (2015) Cyclophilin40 isomerase activity is regulated by a temperature-dependent allosteric interaction with Hsp90. Biosci Rep 35
Shave,S.,Blackburn,E.A.,Adie,J.,Houston,D.R.,Auer,M.,Webster,S.P.,Taylor, P. and Walkinshaw, M.D., UFSRAT: Ultra-Fast Shape Recognition with Atom Types–The Discovery of Novel Bioactive Small Molecular Scaffolds for FKBP12 and 11βHSD1 (2015),PloS one 10 (2), e0116570