IGF-1 LR3 Peptide

IGF-1 LR3 (Long R3 Insulin-like Growth Factor-1) is a synthetic 83-amino acid analog of human IGF-1. The modification involves substitution of Arginine for Glutamic acid at position 3 and an N-terminal extension peptide of 13 amino acids. These modifications were specifically engineered to dramatically reduce binding to IGF binding proteins (IGFBPs). Native IGF-1 circulates primarily bound to IGFBPs (particularly IGFBP-3), which regulate its bioavailability and half-life. By reducing IGFBP binding, IGF-1 LR3 maintains significantly higher free-form concentrations and extended biological activity compared to native IGF-1. For laboratory research use only.

IGF-1 Receptor Signaling IGF-1 LR3 binds to and activates the IGF-1 receptor (IGF-1R), a receptor tyrosine kinase. Upon ligand binding, IGF-1R undergoes autophosphorylation, recruiting insulin receptor substrate (IRS) proteins. This triggers two major downstream cascades: the PI3K/Akt/mTOR pathway (promoting protein synthesis and cell survival) and the Ras/Raf/MEK/ERK pathway (promoting cell proliferation). Reduced IGFBP Binding The key advantage of the LR3 modification is a ~100-fold reduction in affinity for IGFBPs compared to native IGF-1. In standard culture media containing IGFBPs, this translates to dramatically enhanced potency since nearly all IGF-1 LR3 remains in the free, receptor-active form rather than being sequestered by binding proteins. mTOR Pathway Activation Through PI3K/Akt signaling, IGF-1 LR3 activates the mechanistic target of rapamycin (mTOR), specifically mTORC1. This complex phosphorylates p70S6K and 4E-BP1, promoting ribosomal biogenesis and cap-dependent translation initiation — key steps in protein synthesis.