TNFRSF 11 B ( tumor necrosis factor receptor superfamily , member 11 b )

Note RefSeq NP-002537.3; Size: 401 amino acids; 46040 Da; Subunit: Homodimer; Subcellular location: Secreted. Osteoprotegerin (OPG) was isolated independently by two laboratories in 1997 (Tsuda et al., 1997; Simonet et al., 1997), as being a protein that exhibits a protective effect on bone. OPG is a member of the TNF-receptor superfamily, which consists of proteins that evoke different signal transduction, mediating several biological responses, such as cytotoxicity, apoptosis and cell survival, proliferation and differentiation. OPG has two known TNF family ligands: receptor activator of NF-kB ligand (RANKL) (Yasuda et al., 1998b) and TRAIL (Emery et al., 1998) (Diagram 1). RANKL normally binds to its membrane receptor RANK inducing differentiation, activation, and survival of osteoclasts. By binding to RANKL, OPG acts as a soluble inhibitor that prevents RANKL/RANK interaction and subsequent osteoclastogenesis (Yasuda et al., 1998b) (Diagram 1). However, it has been reported that also OPG binding to TRAIL inhibits TRAIL/TRAIL-receptors (TR-R1/R2) interaction, as revealed by the inhibition of TRAIL-induced apoptosis (Emery et al., 1998) (Diagram 1). Vice-versa, TRAIL can block the inhibitory activity of OPG on osteoclastogenesis (Emery et al., 1998).