γ9δ2 T cells detect mevalonate diphosphate via BTN3A3

Area of Science:

• Immunology
• Molecular Biology
• Biochemistry

Background:

• Butyrophilins (BTNs) are key sensors of phosphoantigens (pAgs) involved in immune responses.
• BTN3A1 recognizes exogenous HMBPP and endogenous DMAPP/IPP, activating γ9δ2 T cells.
• The function and ligands of the related BTN3A3 remain largely unknown.

Purpose of the Study:

• To investigate the potential ligands and functions of Butyrophilin-3A3 (BTN3A3).
• To explore the role of Mevalonate diphosphate (MPP) in γ9δ2 T cell activation.
• To elucidate the interaction between BTN3A3, MPP, and immune cell activation.

Main Methods:

• Computational docking to assess ligand binding affinity to BTN3A1 and BTN3A3.
• Functional assays measuring γ9δ2 T cell activation by various compounds.
• ³¹P NMR and LC-MS to confirm molecular interactions and metabolic changes.
• Cell-based co-culture experiments with transfected cells.

Main Results:

• Mevalonate diphosphate (MPP) exhibited high docking scores with both BTN3A1 and BTN3A3.
• MPP activated γ9δ2 T cells, confirming it as a functional ligand.
• ³¹P NMR confirmed MPP binding to BTN3A1 and BTN3A3 internal domains.
• 6-Fluoromevalonate (6-FM), an MPP-related compound, also activated γ9δ2 T cells.
• Transfected cells expressing BTN2A1 with BTN3A1 or BTN3A3 responded to 6-FM.

Conclusions:

• Mevalonate diphosphate (MPP) is identified as a natural ligand for Butyrophilin-3A3 (BTN3A3).
• This finding expands the known repertoire of phosphoantigen sensors and their ligands.
• The study provides a foundation for understanding BTN3A3's biological roles in immunity.