IGF-1 LR3

Research Benefits

• Extended Half-Life — IGF-1 LR3 (Long R3 IGF-1) is an 83-amino acid analog with a 13-amino acid extension and an Arg→Glu substitution at position 3, reducing IGF-binding protein affinity and extending biological half-life.
• Cell Proliferation Research — IGF-1 LR3 is a potent mitogen in cell culture, enhancing proliferation of many cell types including myoblasts, fibroblasts, and stem cells.
• Muscle Biology — IGF-1R activation by LR3 promotes satellite cell activation, myoblast differentiation, and myotube hypertrophy in skeletal muscle research models.
• Cell Culture Supplement — LR3 is widely used as a serum-free culture supplement, reducing serum dependency in cell line maintenance and stem cell expansion protocols.

Mechanism of Action

IGF-1 LR3 is a modified form of insulin-like growth factor-1 with enhanced potency due to reduced binding to IGF-binding proteins (IGFBPs).

IGF-1 Receptor Activation: LR3 binds the IGF-1 receptor (IGF-1R), a receptor tyrosine kinase. Ligand binding triggers autophosphorylation of the intracellular kinase domain and recruitment of IRS-1 (insulin receptor substrate-1).

PI3K/Akt Pathway: IRS-1 activates PI3K, generating PIP3 and activating Akt/PKB. This pathway promotes cell survival (BAD phosphorylation), protein synthesis (mTORC1 activation), and glucose uptake (GLUT4 translocation).

MAPK/ERK Pathway: IGF-1R activation also recruits Grb2/SOS, activating the Ras-Raf-MEK-ERK cascade, which drives cell proliferation and differentiation.

Reduced IGFBP Binding: The Arg3→Glu substitution and N-terminal extension dramatically reduce binding to IGFBPs (1-6), leaving more free IGF-1 LR3 available for receptor activation. This results in ~3x greater potency than native IGF-1 in many bioassays.

Research Protocol

For research use only.

Reconstitution

Reconstitute in 10 mM HCl or sterile water. Stock: 100 μg/mL. Add 0.1% BSA as carrier to prevent adsorption.

Research Applications

• Cell culture supplement: 10-100 ng/mL in serum-free or reduced-serum media.
• Myoblast differentiation: 50-100 ng/mL in C2C12 or primary myoblast cultures.
• In vivo (murine): 20-100 mcg/kg SC or IP daily for muscle and growth studies.

Storage

Lyophilized at -20°C. Reconstituted: aliquot and store at -20°C or -80°C. Avoid repeated freeze-thaw. Working dilutions at 2-8°C, use within 7 days.

Safety & Handling

Research Use Only.

Known Considerations

• IGF-1 LR3 is a potent mitogen; handle with care in cancer research contexts as it can promote proliferation of transformed cells.
• Hypoglycemia risk exists due to cross-reactivity with the insulin receptor at high concentrations.
• Monitor blood glucose in in vivo studies with chronic administration.

Frequently Asked Questions

What makes LR3 different from native IGF-1?

IGF-1 LR3 has a 13-amino acid N-terminal extension and an Arg3→Glu substitution that dramatically reduces binding to IGF-binding proteins. This results in greater free peptide availability and ~3x higher potency in bioassays.

Can LR3 replace serum in cell culture?

LR3 is commonly used as a serum supplement (10-100 ng/mL) to reduce serum dependency. It is typically combined with transferrin and other growth factors for complete serum-free formulations.

What purity is this product?

BeaCapra IGF-1 LR3 is ≥99% pure by HPLC with COA documentation.