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The recombinant proregion of transforming growth factor beta1 (latency-associated peptide) inhibits active
E P Böttinger1, V M Factor, M L Tsang
1Laboratory of Chemoprevention, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-5055, USA.
Abstract:
All three isoforms of transforming growth factors beta (TGF-betal, TGF-beta2, and TGF-beta3) are secreted as latent complexes and activated extracellularly, leading to the release of the mature cytokines from their noncovalently associated proregions, also known as latency-associated peptides (LAPs). The LAP region of TGF-beta1 was expressed in a baculovirus expression system and purified to homogeneity. In vitro assays of growth inhibition and gene induction mediated by TGF-beta3 demonstrate that recombinant TGF-beta1 LAP is a potent inhibitor of the activities of TGF-betal, -beta2, and -beta3. Effective dosages of LAP for 50% neutralization of TGF-beta activities range from 4.7- to 80-fold molar excess depending on the TGF-beta isoform and activity examined. Using 125I-labeled LAP, we show that the intraperitoneal application route is effective for systemic administration of LAP. Comparison of concentrations of LAP in tissues shows a homogenous pattern in most organs with the exception of heart and muscle, in which levels of LAP are 4- to 8-fold lower. In transgenic mice with elevated hepatic levels of bioactive TGF-betal, treatment with recombinant LAP completely reverses suppression of the early proliferative response induced by TGF-beta1 in remnant livers after partial hepatectomy. The results suggest that recombinant LAP is a potent inhibitor of bioactive TGF-beta both in vitro and in vivo, after intraperitoneal administration. Recombinant LAP should be a useful tool for novel approaches to study and therapeutically modulate pathophysiological processes mediated by TGF-beta3.
Insights
Recombinant latency-associated peptide (LAP) effectively inhibits all three transforming growth factor-beta (TGF-beta) isoforms. This potent LAP inhibitor demonstrates therapeutic potential for TGF-beta-mediated diseases.
Area of Science:
- Biochemistry
- Molecular Biology
- Immunology
Background:
- Transforming growth factors beta (TGF-beta) are secreted as latent complexes.
- Extracellular activation releases mature cytokines from latency-associated peptides (LAPs).
- TGF-beta signaling plays critical roles in cellular processes and disease pathogenesis.
Purpose of the Study:
- To investigate the inhibitory potential of recombinant TGF-beta1 LAP against all TGF-beta isoforms.
- To evaluate the efficacy of LAP for in vitro and in vivo applications.
- To explore LAP as a potential therapeutic agent for TGF-beta-mediated conditions.
Main Methods:
- Expression and purification of recombinant TGF-beta1 LAP using a baculovirus system.
- In vitro assays measuring growth inhibition and gene induction by TGF-beta isoforms.
- Systemic administration of 125I-labeled LAP in mice and tissue distribution analysis.
- Assessment of LAP's efficacy in a transgenic mouse model of TGF-beta1-induced liver suppression.
Main Results:
- Recombinant TGF-beta1 LAP potently inhibited TGF-beta1, TGF-beta2, and TGF-beta3 activities in vitro.
- Effective LAP dosages for 50% neutralization ranged from 4.7- to 80-fold molar excess.
- Intraperitoneal administration of LAP resulted in systemic distribution, with lower concentrations in heart and muscle.
- LAP treatment reversed TGF-beta1-induced suppression in a mouse model of partial hepatectomy.
Conclusions:
- Recombinant LAP is a potent inhibitor of bioactive TGF-beta isoforms, effective both in vitro and in vivo.
- Intraperitoneal administration of LAP allows for systemic delivery and therapeutic modulation.
- Recombinant LAP represents a promising tool for studying and treating TGF-beta-mediated pathophysiological processes.