Novel peptide inhibitors targeting the TGF-β receptor I/II complex modulate SMAD and ERK signaling in vitro

Area of Science:

• Molecular Biology
• Cell Signaling
• Drug Discovery

Background:

• Transforming growth factor-β (TGF-β) drives fibrosis, immunosuppression, and tumor progression.
• Systemic TGF-β inhibition faces challenges due to toxicity and lack of selectivity.
• Targeting the TGF-β receptor complex offers a potential strategy for more precise therapeutic intervention.

Purpose of the Study:

• To evaluate novel peptides designed to inhibit the TGF-β receptor I/II complex.
• To assess the effects of these peptides on canonical (SMAD) and noncanonical (ERK, JNK) TGF-β signaling pathways in vitro.
• To explore the potential for selective modulation of TGF-β signaling by novel peptide inhibitors.

Main Methods:

• In silico docking was used to select peptides targeting the TGF-β receptor interface.
• Peptides 2_5 and 2_6 were tested in HEK293T cells at varying concentrations (20 and 50 μM).
• Western blotting and densitometry were employed to quantify total and phosphorylated SMAD2, SMAD3, ERK1/2, and JNK levels, with SD-208 as a reference inhibitor.

Main Results:

• Peptide 2_5 significantly reduced total ERK1/2 (65% at 50 μM) and phosphorylated ERK1/2 (up to 90.4% at 20 μM).
• Peptide 2_5 also decreased total SMAD2 by 81% at 50 μM, though SMAD2 phosphorylation effects were inconsistent.
• Peptide 2_6 exhibited minimal effects, JNK remained largely unaffected, and SMAD3 signaling was inconclusive.

Conclusions:

• Preliminary findings indicate that peptide 2_5 may differentially modulate TGF-β signaling pathways.
• Peptide 2_5 shows a more pronounced effect on ERK1/2 signaling compared to SMAD2.
• Further quantitative studies are required to confirm receptor targeting and pathway selectivity of peptide 2_5.