Juno (egg Izumo receptor) (Juno)

Juno (formerly folate receptor 4, FOLR4) is a GPI-anchored cell-surface protein essential for the recognition and fusion of sperm and egg in mammals. It acts as the egg receptor for Izumo1, the corresponding sperm surface protein. Despite sequence homology with classical folate receptors, Juno does not bind folate and cannot mediate folate uptake. Its function is critical for female fertility, and genetic ablation results in infertility due to failed sperm-egg fusion[3][5]. In mouse, Folr4/Juno is also expressed on regulatory T cells and explored for tumor immunotherapy, though these roles are not established in humans. Juno (Folate receptor 4, FOLR4) is an essential receptor for sperm-egg fusion in mammals, but it does not perform typical folate transport. Its main biological role is in reproduction, making it a unique receptor outside classical folate receptor family functions[3][5].

Other names

Folate receptor 4Folate receptor deltaIZUMO1RJuno

For targeting fertility, Juno functions as the receptor for sperm protein Izumo1; modulating the Juno-Izumo1 interaction could hypothetically impact fertilization. As an immunotherapy target, mechanisms relate to cell-surface recognition in mouse regulatory T cells.