What Is IGF-1 LR3?
IGF-1 LR3, also written as Long R3 IGF-1 or Long Arg3 IGF-1, is a modified recombinant form of human insulin-like growth factor 1 (IGF-1). Native IGF-1 is a 70-amino-acid peptide hormone produced primarily in the liver in response to growth hormone stimulation. IGF-1 LR3 adds a 13-amino-acid extension to the N-terminus and substitutes an arginine residue at position 3 in place of the native glutamate, producing an 83-amino-acid analog.
These modifications dramatically reduce the analog's affinity for IGF binding proteins (IGFBPs), the circulating proteins that normally sequester endogenous IGF-1 and limit its availability. Because IGF-1 LR3 is largely unable to bind IGFBPs, it remains active in circulation and in cell culture systems for substantially longer than native IGF-1. This property has made IGF-1 LR3 particularly valuable in laboratory research where sustained IGF-1 receptor activation is desired.
Peptide Profile
Full Name: Long R3 Insulin-Like Growth Factor 1
Length: 83 amino acids
Modifications: 13-aa N-terminal extension + Arg3 substitution
Molecular Weight: ~9,111 g/mol
Classification: IGF-1 analog (recombinant growth factor)
Mechanism of Action
IGF-1 LR3 acts through the same receptor system as native IGF-1, primarily the IGF-1 receptor (IGF-1R). The analog retains full activity at this receptor while its reduced IGFBP binding profile alters its pharmacokinetic and pharmacodynamic behavior.
IGF-1 Receptor Activation
Binding of IGF-1 LR3 to the IGF-1 receptor triggers autophosphorylation of the receptor's intracellular tyrosine kinase domains. This initiates two principal downstream signaling pathways: the PI3K-Akt-mTOR cascade, associated with cell growth, protein synthesis, and survival, and the Ras-MAPK cascade, associated with cell proliferation and differentiation.
Reduced IGFBP Binding
In normal physiology, over 95% of circulating IGF-1 is bound to IGF binding proteins, primarily IGFBP-3, which regulate its bioavailability and clearance. The Arg3 substitution in IGF-1 LR3 disrupts the IGFBP binding site, allowing the analog to remain predominantly in free form and extending its biological activity. This property is a defining feature of the compound.
Cell Proliferation and Protein Synthesis
Through IGF-1R-mediated activation of Akt and mTOR, IGF-1 LR3 strongly promotes protein synthesis and cellular growth in responsive tissues. Research has documented pronounced effects on skeletal muscle cells, neuronal cultures, and various other cell types sensitive to IGF-1 signaling.
Anti-apoptotic Signaling
Activation of the PI3K-Akt pathway by IGF-1 LR3 has been associated with suppression of pro-apoptotic signaling, contributing to enhanced cell survival in culture. This property has been widely exploited in research involving sensitive primary cell types.
Research Overview
IGF-1 LR3 is among the most widely used growth factor analogs in laboratory research. It is a standard reagent in cell culture applications, recombinant protein production, and preclinical investigations of tissue growth and repair.
| Research Area | Key Findings | Study Type |
|---|---|---|
| Cell Culture / Bioprocessing | Standard supplement in serum-free media formulations; supports proliferation and productivity of CHO and other production cell lines used in recombinant protein manufacturing | Industrial / in vitro |
| Skeletal Muscle Research | Preclinical studies have examined effects on myoblast proliferation, myotube formation, and hypertrophy signaling | In vitro / in vivo |
| Neuronal Survival | Research has observed neuroprotective and growth-promoting effects in primary neuronal culture models | In vitro |
| Tissue Regeneration | Preclinical investigations have studied effects on wound healing, bone regeneration, and tissue repair | In vivo (rodent) |
| Cardiac Research | Studies have examined IGF-1 signaling in cardiomyocyte growth, survival, and post-ischemic recovery models | In vitro / in vivo |
| Stem Cell Research | Used as a culture-media component in stem cell expansion and differentiation protocols | In vitro |
IGF-1 LR3 is primarily a research and bioprocessing reagent. It has not been developed as a pharmaceutical agent for human use, and there is no clinical indication for which it is approved. Research findings derived from in vitro and animal models do not necessarily translate directly to human outcomes. The compound is sold strictly for laboratory research purposes.
Common Areas of Research Interest
IGF-1 LR3's extended bioavailability and potent IGF-1 receptor activity make it a widely used tool across multiple research domains.
- Serum-free cell culture, Standard supplement for supporting cell proliferation and productivity without animal-derived serum components
- Recombinant protein production, Used industrially in media formulations for CHO and other production cell lines
- Muscle and tissue biology, Investigation of IGF-1 signaling in myogenesis, hypertrophy, and tissue regeneration models
- Neuroscience, Cultured neuron survival, neurite outgrowth, and neuroprotection research
- Stem cell research, Component of many stem cell expansion and differentiation culture systems
- Cardiac research, Preclinical models investigating IGF-1 pathway effects on cardiomyocyte biology and post-injury recovery
Pharmacokinetics
The defining pharmacokinetic feature of IGF-1 LR3 is its extended plasma half-life relative to native IGF-1, a direct consequence of its reduced IGFBP binding.
Native IGF-1 has a plasma half-life of approximately 10 to 20 minutes in free form, extending to several hours when bound to IGFBPs. IGF-1 LR3, with its markedly reduced IGFBP affinity, shows a half-life that can extend into 20 to 30 hours in some reports, a roughly 100-fold increase in free-form biological availability. This extended exposure profile is central to its utility in cell culture and preclinical research.
Comparison to Similar Compounds
IGF-1 LR3 is often considered alongside other peptides and growth factors involved in growth, recovery, and tissue-building research.
| Feature | IGF-1 LR3 | Native IGF-1 | MGF (Mechano Growth Factor) |
|---|---|---|---|
| Class | Modified IGF-1 analog | Endogenous growth factor | IGF-1 splice variant |
| IGFBP Binding | Minimal | High (>95% bound) | Minimal |
| Half-Life | ~20-30 hours | ~10-20 min (free); ~12h (bound) | Short, localized |
| Primary Research Use | Sustained IGF-1R activation; cell culture | Endogenous signaling studies | Local muscle repair signaling |
Frequently Asked Questions
Sources & References
- Francis GL, et al. "Novel recombinant fusion protein analogues of insulin-like growth factor (IGF)-I indicate the relative importance of IGF-binding protein and receptor binding for enhanced biological potency." Journal of Molecular Endocrinology. 1992;8(3):213-223. PubMed
- Tomas FM, et al. "Anabolic effects of insulin-like growth factor-I (IGF-I) and an IGF-I variant in normal female rats." Journal of Endocrinology. 1993;137(3):413-421.
- Clemmons DR. "Insulin-like growth factor binding proteins and their role in controlling IGF actions." Cytokine and Growth Factor Reviews. 1997;8(1):45-62. PubMed
- Barnard R, et al. "Studies of the metabolism of the exons and introns of the insulin-like growth factor-I gene." Molecular and Cellular Endocrinology. 1994;102(1-2):161-167.
- Hill DJ, et al. "The insulin-like growth factors and their binding proteins: Biological functions and clinical applications." Endocrine Reviews. 1995;16(1):3-34.
- Rinderknecht E, Humbel RE. "The amino acid sequence of human insulin-like growth factor I and its structural homology with proinsulin." Journal of Biological Chemistry. 1978;253(8):2769-2776. PubMed
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View IGF-1 LR3 Products — $90This product is intended for research and laboratory use only. It is not intended for human consumption.