The invention relates to the discovery and characterization of Tango-63d, Tango-63e genes and the polypeptides they encode. Tango-63d and Tango-63e are two novel polypeptides within the tumor necrosis factor (TNF) receptor superfamily. The invention encompasses nucleic acid molecules encoding nucleic acids and polypeptides of the invention, or mutant forms thereof that encode dysfunctional receptor polypeptides, vectors containing these nucleic acid molecules, cells harboring recombinant DNA molecules encoding nucleic acids or polypeptides of the invention, or mutant forms thereof, host fusion proteins that include functional or dysfunctional polypeptides of the invention, transgenic animals that express nucleic acids or polypeptides of the invention, screening methods and therapeutic methods employing the nucleic acid molecules and polypeptides described above, substantially purified nucleic acids and polypeptides of the invention, and therapeutic compositions containing these nucleic acid molecules and polypeptides.