Ribbon molecular model of RANKL (Receptor Activator for Nuclear Factor kappa B Ligand), also known as TNF-related activation-induced cytokine (TRANCE), osteoprotegerin ligand (OPGL), and ODF (osteoclast differentiation factor). RANKL is a molecule important in bone metabolism. This natural and necessary surface-bound molecule activates osteoclasts, cells involved in bone resorption. Overproduction of RANKL is implicated in a variety of degenerative bone diseases, such as rheumatoid arthritis and osteomyelitis. The image shows the 3 protein chains of the molecule.