We work on perforins, perforin-like proteins (PLPs) and the related bacterial cholesterol-dependent cytolysins (CDCs) [Gilbert et al., 2014; Ni and Gilbert, 2017]. These are mostly pore-forming proteins which target membranes either to allow the entry or exit of pathogens, or mechanisms of immune defence (Figure 1). However, some members of this membrane attack complex-perforin (MACPF)/CDC family have also been adapted to enable quite different processes, such as neural cell mechanisms of migration [Ni et al., 2016] (Figure 2).
There are three particular focuses of current work on MACPF/CDCs: (i) PLPs in Apicomplexan parasites like Plasmodium (PPLPs) and Toxoplasma (TgPLPs) and essential for infection and disease; (ii) mammalian perforin-2; (iii) proteins controlling neurodevelopmental processes.
(i) We have solved the structure of part of PPLP1 and are working on that of PPLP2; we are collaborating with a vaccine research group in London on the application of PPLP2. The next challenge is to understand the mechanism of the PPLPs and their pore structure. We have already solved the structure of TgPLP1, as a monomer and as an oligomer – a paper describing this work has been submitted.
(ii) Mammalian perforin-2 was only recently discovered, by a group in Miami with whom we collaborate [Podack and Munson, 2017]. We solved the structure of part of perforin-2 already but need to solve its pore structure and understand its activation. Perforin-2 is the essential frontline defence in humans against intracellular bacteria and differs in important ways from perforin-1 (e.g. it is a transmembrane protein).
(iii) We solved a structure of the soluble region of astrotactin-2, which guides cerebellar granule neurons along glial cells and is implicated in a host of neurodevelopmental diseases and early-onset Alzheimer’s [Ni et al., 2016] (Figure 3). We are now working on the structure of the full-length protein, as well as towards an improved understanding of its role using live cell imaging.