Mouse Osteoactivin/GPNMB Antibody

Osteoactivin (also named GPNMB and DC-HIL) is a 125 kDa, intracellular glycoprotein that is associated with cell endosomal/lysosomal compartments (1, 2). Mouse osteoactivin is synthesized as a type I, transmembrane, 574 amino acid (aa) precursor that contains a 22 aa signal sequence, a 478 aa luminal/extracellular domain, a 23 aa transmembrane segment and a 51 aa cytoplasmic tail. The luminal region contains an N-terminal heparin-binding motif, multiple glycosylation sites, an RGD motif and a 130 aa PKD domain. The intracellular tail also has an RGD motif, plus an ITAM (Y-x-x-I) and lysosomal targeting (L-L) motif. The extracellular/luminal region is 89% and 74% aa identical to the equivalent regions in rat and human, respectively. Cells known to express osteoactivin include osteoblasts, dendritic cells, and melanocytes, plus fetal chondrocytes and stratum basale keratinocytes (2, 3). Osteoactivin is reported to bind to heparan sulfate-proteoglycan, possibly on the surface of fibroblasts and endothelial cells (2). It may also interact with integrins.