Chemically stapled peptides targeting the protein-protein interaction between calcium channel subunits selectively inhibited channel function in an isoform-specific manner, demonstrating a new approach to ion channel drug development.
First PPI inhibitors to control ion channel functionStapled peptides targeting CaV subunit assembly achieved isoform-selective channel modulation — a new paradigm for ion channel drug development
What the researchers found
Meta-xylyl stapled peptides targeting the CaV α-interaction domain (AID) were developed and characterized:
- Structural: Staples enhanced helical structure (CD spectroscopy) and maintained native-like AID:CaVβ binding geometry (X-ray crystallography)
- Thermodynamic: Stapling reduced the entropic penalty of binding (ITC), improving affinity
- Functional: Stapled AID peptides effectively inhibited the CaVα1:CaVβ protein-protein interaction
- Selectivity: Modulation was CaVβ isoform-selective, demonstrating that different beta subunits can be preferentially targeted
This represents the first proof-of-concept for using protein-protein interaction inhibitors to control voltage-gated ion channel function.
Why it matters
Voltage-gated calcium channels are drug targets for heart disease (arrhythmias, hypertension), pain, epilepsy, and more. Current calcium channel blockers (like amlodipine, verapamil) block the channel pore non-selectively. Targeting the protein-protein interactions that assemble the channel offers a completely new approach: you could selectively disable specific channel subtypes in specific tissues. Stapled peptides provide the structural rigidity needed to effectively disrupt these large protein interfaces, which small molecule drugs struggle to do.
How the study worked
Stapled peptides were designed based on the AID helix that mediates CaVα-CaVβ interaction. Meta-xylyl chemical staples were incorporated to stabilize helical structure. Structural characterization used circular dichroism spectroscopy and X-ray crystallography. Binding thermodynamics were measured by isothermal titration calorimetry. Functional effects on calcium channel activity were assessed by electrophysiological recordings, testing selectivity across CaVβ isoforms.
What this study cannot tell us
This is a proof-of-concept study demonstrating feasibility, not a drug development study. The peptides were tested in controlled in vitro and cellular electrophysiology systems that don't recapitulate in vivo pharmacology. Cell permeability, metabolic stability, and in vivo efficacy of the stapled peptides were not assessed. The selectivity between CaVβ isoforms, while demonstrated, may not be sufficient for therapeutic selectivity between tissues. Translation from stapled peptides to practical therapeutics faces significant drug delivery challenges.
How to read the evidence
This is a rigorous proof-of-concept study combining four complementary techniques (CD, X-ray crystallography, ITC, electrophysiology). The structural and functional data are compelling for establishing feasibility, but the approach is entirely in vitro with no in vivo or therapeutic validation.
When this study was published
Published in 2017, this study represents foundational work in applying stapled peptide technology to ion channel targets. The approach continues to be explored as stapled peptide drug development advances.
The bigger picture
This study sits at the intersection of two important trends: stapled peptide technology and protein-protein interaction (PPI) drug development. PPIs are notoriously difficult drug targets for small molecules because the interaction surfaces are large and flat. Stapled peptides solve this by mimicking the natural helical binding motif with enhanced stability. Applying this approach to ion channels — a massive drug target class — is novel and could yield a new generation of selective channel modulators for neurological and cardiac diseases.
Questions still open
- Can these stapled AID peptides be delivered to cardiac or neuronal cells in vivo to achieve tissue-specific calcium channel modulation?
- Would isoform-selective CaV disruption produce better therapeutic profiles than current non-selective calcium channel blockers?
- Could this PPI-targeting approach be extended to other voltage-gated ion channels like sodium or potassium channels?
Common questions
What are stapled peptides and why are they useful for drug development?
Why target calcium channel assembly instead of blocking the channel directly?
Read the original research
Stapled Voltage-Gated Calcium Channel (CaV) α-Interaction Domain (AID) Peptides Act As Selective Protein-Protein Interaction Inhibitors of CaV Function.
ACS chemical neuroscience, 8(6), 1313-1326
Citation
Findeisen, Felix; Campiglio, Marta; Jo, Hyunil; Abderemane-Ali, Fayal; Rumpf, Christine H; Pope, Lianne; Rossen, Nathan D; Flucher, Bernhard E; DeGrado, William F; Minor, Daniel L. (2017). Stapled Voltage-Gated Calcium Channel (CaV) α-Interaction Domain (AID) Peptides Act As Selective Protein-Protein Interaction Inhibitors of CaV Function.. ACS chemical neuroscience, 8(6), 1313-1326. https://doi.org/10.1021/acschemneuro.6b00454