IGFBP4 (Insulin-like Growth Factor-binding Protein 4, IBP-4, IGF-binding Protein 4, IGFBP-4, IBP4)

The insulin like growth factors (IGFs) are the major growth- promoting factors in plasma. IGFs are secreted by a variety of cells and exert a multitude of effects on cellular survival, growth and differentiation. The A and B domains of IGFs are identical to insulin. IGF initiates their biological action through binding to the type IGF receptor (IGF-1R), a heterotrimeric protein complex with a tyrosine kinase activity. The IGF-IIR lacks the kinase activity and is actually identical to the mannose-6-phophate receptor. Unlike most other peptide hormones, IGFs are complexed with specific binding proteins in the plasma known as IGF Binding proteins (IGFBPs). These proteins are present in plasma in high concentration as compared to the membrane IGFRs. Therefore, IGFBPs have the potential to modulate the IGF action. IGFBPs have been shown to either inhibit or stimulate the IGF effects. The primary structures of mammalian IGFBPs appear to contain three distinct domains of roughly equivalent sizes: the conserved N-terminal domain, the highly variable mid region and the conserved C-terminal domain. Human IGFBPs share ~36% identity. IGFBP4 (aa22-237 mature protein, Accession # P22692) is expressed in multiple tissues including adrenal, testis, spleen, heart, lung, kidney, liver, stomach, hypothalamus and brain cortex. High expression levels are found in the non-paranchymal cells of the liver. IGFBP4 is expressed by human osteoblast-like cells and is also expressed in skin fibroblasts.\nApplications:\nSuitable for use in ELISA, Western Blot and Neutralization. Other applications not tested.\nRecommended Dilutions:\nELISA: 1:10,000. Recommended as the capture antibody in sandwich ELISA.\nWestern Blot: 1:1000-1:2000. Concentrated cell serum free culture medium or recombinant protein can be used as positve control.\nNeutralization: 10-100ug/ml is the ND50 for I7661-16P4 in the presence of 0.3ug/ml of recombinant human IGFBP-4 and 14ng/ml of recombinant human IGF-II using prolifereation of the MCF7 cell line as an assay.\nOptimal dilutions to be determined by the researcher.\nStorage and Stability:\nLyophilized powder may be stored at -20 degrees C. Stable for 12 months at -20 degrees C. Reconstitute with sterile PBS. Aliquot to avoid repeated freezing and thawing. Store at -20 degrees C. Reconstituted product is stable for 12 months at -20 degrees C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.

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