EASTBIO: Using protein engineering to understand the role of CD180 in immunity

Innate and adaptive immunity are essential for the mammalian host’s response to infection and tissue damage, and as such are closely regulated via a range of cellular receptors. Toll like receptors (TLRs) are one such group of receptors and are critical to both macrophage and B cell function. CD180 is a poorly understood receptor with homology to TLRs that is thought to play an activating role on B cells but an inhibitory role on macrophages.  In B cells, we have shown that it can promote proliferation and synergise with other receptors (including TLRs) to promote antibody isotype switching. It also modules type I interferon responses in B cells and, via this mechanism, may contribute to the production of pathogenic autoantibodies in Lupus. The project will have 3 main aims, to characterise CD180 signalling in isolated cells, to develop novel nanobody based reagents for CD180 and to use these to look at the effect of acute CD180 inhibition or activation on antibody responses in vivo.

While the extracellular domain of CD180 is similar to that of TLRs, it has an atypical intracellular tail and the mechanism by which it signals is poorly understood. We have shown that signalling via CD180 is dependent on the tyrosine kinase Syk and most likely depends on the assembly of an active receptor complex requiring several co-receptors. The project will use a number of techniques, such as proximity labelling and mass spectrometry, to isolate and characterise the active CD180 receptor complex. We will also screen for and characterise novel nanobody reagents for CD180, and use antibody engineering to develop activating and inhibitory nanobody dimers to module CD180 function. These will also be linked to nanobodies against TLR2 to investigate how creating TLR2/CD180 complexes on the cell surface modulates signalling and isotype switching in activated B cells. Finally, selected nanobody reagents will be used to look at the acute effects of modulating CD180 on antibody responses in vivo, focusing on models with a known type I interferon component.

Together these experiments will greatly advance our understanding of CD180 and how it regulates immune function. It addition to a range of cell biology and biochemical techniques it provide training in a range of cutting edge methods including mass spectrometry, proteomics and antibody engineering.

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