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Updated: Jun 25, 2025
Method for Identifying Small Molecule Inhibitors of the Protein-protein Interaction Between HCN1 and TRIP8b
Published on: November 11, 2016
Structural basis for inhibition of the lysosomal two-pore channel TPC2 by a small molecule antagonist
Gamma Chi1, Dawid Jaślan2, Veronika Kudrina2
1Centre for Medicines Discovery, Nuffield Department of Medicine, University of Oxford, Nuffield Department of Medicine Research Building, Oxford OX3 7FZ, UK; Structural Genomics Consortium, Nuffield Department of Medicine, University of Oxford, Nuffield Department of Medicine Research Building, Oxford OX3 7FZ, UK.
Abstract:
Two pore channels are lysosomal cation channels with crucial roles in tumor angiogenesis and viral release from endosomes. Inhibition of the two-pore channel 2 (TPC2) has emerged as potential therapeutic strategy for the treatment of cancers and viral infections, including Ebola and COVID-19. Here, we demonstrate that antagonist SG-094, a synthetic analog of the Chinese alkaloid medicine tetrandrine with increased potency and reduced toxicity, induces asymmetrical structural changes leading to a single binding pocket at only one intersubunit interface within the asymmetrical dimer. Supported by functional characterization of mutants by Ca2+ imaging and patch clamp experiments, we identify key residues in S1 and S4 involved in compound binding to the voltage sensing domain II. SG-094 arrests IIS4 in a downward shifted state which prevents pore opening via the IIS4/S5 linker, hence resembling gating modifiers of canonical VGICs. These findings may guide the rational development of new therapeutics antagonizing TPC2 activity.
Insights
The drug SG-094, a potent two-pore channel 2 (TPC2) inhibitor, binds asymmetrically to TPC2, blocking channel function. This discovery offers a new therapeutic strategy for cancers and viral diseases like Ebola and COVID-19.
Area of Science:
- Molecular biology
- Biophysics
- Pharmacology
Background:
- Two pore channels (TPCs) are lysosomal cation channels vital for tumor angiogenesis and viral release.
- Inhibiting the two-pore channel 2 (TPC2) presents a therapeutic avenue for cancers and viral infections (e.g., Ebola, COVID-19).
Purpose of the Study:
- To investigate the mechanism of action of SG-094, a novel TPC2 antagonist.
- To identify key residues and structural changes underlying TPC2 inhibition by SG-094.
Main Methods:
- Structural analysis of TPC2 inhibition by SG-094.
- Functional characterization using Ca2+ imaging and patch clamp experiments on mutant TPC2 channels.
- Identification of key residues in voltage-sensing domains involved in binding.
Main Results:
- SG-094 induces asymmetrical structural changes in TPC2, creating a single binding pocket.
- Key residues in S1 and S4 of voltage-sensing domain II are crucial for SG-094 binding.
- SG-094 traps the IIS4 segment in a downward-shifted state, inhibiting pore opening.
Conclusions:
- SG-094 functions as a gating modifier by stabilizing an inactive TPC2 conformation.
- These findings provide a structural basis for developing novel TPC2-targeting therapeutics.
- The mechanism resembles that of canonical voltage-gated ion channel (VGIC) modifiers.
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