IGFBP5 is a secreted protein that is a critical member of the IGF axis. It binds IGF-1 and restricts it from accessing its cell-surface receptor (IGF-1R). This aids in regulation of cell growth, differentiation, and apoptosis. IGFBP5 also displays IGF-1 independent transactivational activity in the nucleus. Some tissues and cell types with higher levels of this protein include kidney, heart, placenta, and skeletal cells. Expression has also been reported in a variety of cancers, including mammary gland and neuroblastoma. IGFBP5 (272 amino acids) has a calculated molecular weight of 30.6 kDa. Reported glycosylation and phosphorylation sites may explain the band migration to 33 kDa. Cayman’s IGFBP5 polyclonal antibody is directed against a synthetic peptide sequence that partially overlaps the IGFBP5 region identified as a nuclear localization signal.
