Alternative signaling in the presence of cyclosporine A. In normal, signaling calcineurin binds to and dephosphorylates NFAT, allowing it to enter the nucleus where it induces IL-2 expression. In the presence of cyclosporine this pathway is blocked by the binding of the cyclosporine/cyclophilin complex to calcineurin, which prevents the subsequent binding to NFAT. Alternative signaling occurs via the induction of a MAPK cascade, resulting in the expression of IL-2.
