BTN3A1 Discriminates γδ T Cell Phosphoantigens from Nonantigenic Small Molecules via a Conformational Sensor in Its B30.2 Domain

5 years ago

BTN3A1 Discriminates γδ T Cell Phosphoantigens from Nonantigenic Small Molecules via a Conformational Sensor in Its B30.2 Domain

Carrie R. Willcox, Pooja Sridhar, Fiyaz Mohammed, Mahboob Salim, Mark Jeeves, Timothy J Knowles, Youcef Mehellou, Taher E. Taher, John Wilkie, Martin S. Davey, Adrian Hayday, Benjamin E. Willcox, Pierre Vantourout, Hachemi Kadri, Alfie T. Baker

Human Vγ9/Vδ2 T-cells detect tumor cells and microbial infections by recognizing small phosphorylated prenyl metabolites termed phosphoantigens (P–Ag). The type-1 transmembrane protein Butyrophilin 3A1 (BTN3A1) is critical to the P–Ag-mediated activation of Vγ9/Vδ2 T-cells; however, the molecular mechanisms involved in BTN3A1-mediated metabolite sensing are unclear, including how P–Ag’s are discriminated from nonantigenic small molecules. Here, we utilized NMR and X-ray crystallography to probe P–Ag sensing by BTN3A1. Whereas the BTN3A1 immunoglobulin variable domain failed to bind P–Ag, the intracellular B30.2 domain bound a range of negatively charged small molecules, including P–Ag, in a positively charged surface pocket. However, NMR chemical shift perturbations indicated BTN3A1 discriminated P–Ag from nonantigenic small molecules by their ability to induce a specific conformational change in the B30.2 domain that propagated from the P–Ag binding site to distal parts of the domain. These results suggest BTN3A1 selectively detects P–Ag intracellularly via a conformational antigenic sensor in its B30.2 domain and have implications for rational design of antigens for Vγ9/Vδ2-based T-cell immunotherapies.

Publisher URL: http://dx.doi.org/10.1021/acschembio.7b00694

DOI: 10.1021/acschembio.7b00694