Research Groups
Introduction
Blundell Brindle Broadhurst Brown Carrington Dupree Evan  Head of Dept. Farndale Gay Grace Griffin Hendrich Hesketh Higgins Hollfelder Hong Howe Hyvonen Jackson S Jackson T Jackson R Laue Leadlay Lester Lilley Lipkow	Livesey Luisi Lummis Mata McCafferty Metcalfe Mishima Miska Monie Mott Murzina Nietlispach Owen Oliver Packman Pellegrini Robinson Salmond Scadden Silva Smith A Smith C Standart Thomas Timmers Tolkovsky Welch Zhang
Past members

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G Proteins and their Effectors as Therapeutic Targets in Invasion and Metastasis

Research Grouping: Structural and molecular cell biology

For the majority of cancers the acquisition of invasive and metastatic characteristics leads to incurable disease in the host. A major challenge, therefore, is the elucidation of the underlying molecular changes that lead to the unimpeded ability of tumour cells to invade neighbouring tissue and disperse to secondary sites and the development of therapies to arrest such a progression. Small G proteins, particularly members of the Rho family, are known regulators of the actin cytoskeleton and therefore control the morphology and motility of mammalian cells. It is not surprising therefore, that they are implicated with increasing frequency in the transition to invasive and metastatic forms of cancers. This implies the existence of a therapeutic avenue directed against these proteins and their downstream effectors.

Figure 1. ACK binding 'hotspots' on the surface of Cdc42. Cdc42 is shown as a space-filled model in white, the ACK peptide is shown as a backbone trace in yellow. Residues in Cdc42 that contribute significantly to the binding energy of the complex are highlighted in pink and red. Residues coloured red are also involved in the specificity of the interaction between Cdc42 and ACK (as opposed to other CRIB effectors) and so would indicate possible regions for targeting small molecule therapeutics

Our work addresses the relationship between structure and function in small G proteins and their effector complexes. We have determined the structures (by NMR) of the G protein, Cdc42, in complex with the G protein binding domains of its effector proteins ACK and PAK. ACK is known to function in integrin mediated adhesion pathways, while PAK is involved both in tumourigenicity and adhesion, being particularly identified as active in breast cancer metastasis. Our structures facilitated the design of mutations that selectively inhibited the interaction of Cdc42 with its effectors. Thermodynamic analysis of these mutants led to the identification of 'hotspots' on the G protein surface that define areas which could be targeted by small molecules for therapeutic purposes (figure 1). We have also studied the interaction of PRK1, another kinase with a potential role in invasion, with the Rho and Rac GTPases. We have solved the structure of the HR1b repeat of PRK1 and have used a combination of NMR and mutagenesis to determine the residues important for the interaction between Rac and PRK1 (figure 2).

Figure 2a. The structure of HR1b. An ensemble of 20 structures is shown on the left with the structure closest to the mean on the right, b. HR1b is shown in green with residues that shift on complex formation with Rac highlighted as purple balls, c. A model of HR1b bound to Rac based on the HR1b mapping data and mutagenesis data from Rac. Rac is shown in purple and HR1b in green.

Recently, we have also extended our investigations to include the Ras family member, Ral. Preliminary data indicate that the control of exocytosis by Ral is involved in cell motility and therefore another possible target for anti-metastasis therapies.
First and foremost we hope our work will lead to a more detailed understanding of the protein/protein interactions involved in cell motility. The data generated, however, could also provide regulatory, structural, thermodynamic and in some cases kinetic data to assist rational drug design

Lab members
Louise Campbell, Jose Vicente-Garcia, Catherine Hutchinson, Kadalmani Krishnan, Irina Ogay

References