F1-Adenosine Triphosphatase Displays Properties Characteristic of an Antigen Presentation Molecule for Vγ9Vδ2 T Cells

Abstract

Human Vγ9Vδ2 T lymphocytes are activated by phosphoantigens provided exogenously or produced by tumors and infected cells. Activation requires a contact between Vγ9Vδ2 cells and neighboring cells. We previously reported a role for cell surface F1-adenosine triphosphatase (ATPase) in T cell activation by tumors and specific interactions between Vγ9Vδ2 TCRs and purified F1-ATPase. 721.221 cells do not express surface F1-ATPase and do not support phosphoantigen responses unless they are rendered apoptotic by high doses of zoledronate, a treatment that promotes F1-expression as well as endogenous phosphoantigen production. By monitoring calcium flux in single cells, we show in this study that contact of T cells with F1-ATPase on polystyrene beads can partially replace the cell-cell contact stimulus during phosphoantigen responses. Triphosphoric acid 1-adenosin-5′-yl ester 3-(3-methylbut-3-enyl) ester, an adenylated derivative of isopentenyl pyrophosphate, can stably bind to F1-ATPase–coated beads and promotes TCR aggregation, lymphokine secretion, and activation of the cytolytic process provided that nucleotide pyrophosphatase activity is present. It also acts as an allosteric activator of F1-ATPase. In the absence of Vγ9Vδ2 cells, triphosphoric acid 1-adenosin-5′-yl ester 3-(3-methylbut-3-enyl) ester immobilized on F1-ATPase is protected from nucleotide pyrophosphatase activity, as is the antigenic activity of stimulatory target cells. Our experiments support the notion that Vγ9Vδ2 T cells are dedicated to the recognition of phosphoantigens on cell membranes in the form of nucleotide derivatives that can bind to F1-ATPase acting as a presentation molecule.