Mouse/Rat IGF-I/IGF-1 Quantikine ELISA Kit

Mature mouse IGF-1 is a non-glycosylated, 70 amino acid (aa) secreted polypeptide that is derived from either a 153 aa or a 159 aa preproprotein. It shares 99% and 94% aa sequence identity with rat and human IGF-1, respectively. IGF-1 is synthesized in the liver and other tissues. It is found in blood and other body fluids as a complex with specific high affinity IGF binding proteins (IGFBP-1 to -6). The IGFBPs are expressed in specific patterns during development. They are modulators of IGF actions, which control IGF bioavailability to specific cell-surface receptors. Their functions are further regulated by IGFBP proteases, which proteolytically cleave the IGFBPs to lower the affinity with which they bind IGFs and increase IGF bioavailability. Some IGFBPs also have IGF-Independent effects on cell functions. IGF-Independent circulates primarily as a ternary complex with IGFBP-3 or IGFBP-5 and the acid-labile subunit (ALS). Some IGF-1 is also present in binary complexes with other IGFBPs. Whereas the ternary complexes are generally restricted to the vasculature, the binary complexes freely enter the tissues. 

IGF-1 actions are mediated by two ubiquitously expressed receptor tyrosine kinases: IGF-I R and Insulin R/CD220. IGF-I R and Insulin R are disulfide-linked heterotetrameric complexes that consist of two alpha and two beta subunits. For both of these receptors, the prepro proteins are cleaved to produce extracellular alpha subunits which contain a cysteine-rich region and ligand-binding fibronectin type III (FN-III) domains, and beta subunits which contain an extracellular FN-III domain, transmembrane, and cytoplasmic tyrosine kinase domains. A hybrid complex containing one IGF-I R and one Insulin R also serves as a functional high affinity receptor for IGF-1. IGF-I R-Insulin R hybrids respond primarily to IGF-1, potentially downregulating the cellular response to Insulin. IGF signaling is also modulated by IGF binding proteins and the scavenger receptor, IGF-I I R.