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Structure-function relationship of dynorphin B variants using naturally occurring amino acid substitutions
Luca Zangrandi1,2, Barbara Fogli1, Anna Mutti1
1Institute of Pharmacology, Medical University of Innsbruck, Innsbruck, Austria.
Frontiers in Pharmacology
|November 14, 2024
Summary
Researchers developed novel dynorphin B (DynB) variants with enhanced selectivity for kappa opioid receptors (KOPrs). These DynB derivatives show potential for targeted therapeutic effects by minimizing unwanted interactions with other opioid receptors.
Area of Science:
- Pharmacology and Medicinal Chemistry
- Neuroscience
- Molecular Biology
Background:
- Dynorphins (Dyn) are endogenous opioid peptides with high affinity for kappa opioid receptors (KOPrs), mediating anticonvulsant effects.
- Dyn also interact with mu (MOPrs) and delta opioid receptors (DOPrs), potentially leading to unwanted side effects.
- Optimizing dynorphin therapy requires enhanced KOPr selectivity and reduced mTOR pathway activation.
Purpose of the Study:
- To design and characterize dynorphin B (DynB) variants with improved selectivity for KOPrs over MOPrs and DOPrs.
- To investigate the impact of specific amino acid substitutions on opioid receptor binding affinity and signal transduction.
- To evaluate functional selectivity and mTOR pathway activation of novel DynB derivatives.
Main Methods:
- Synthesis of DynB variants with single or double amino acid substitutions.
- Competitive radio binding assays to determine receptor affinity.
- GTPγS assays, PRESTO-Tango, and Western blotting to assess G-protein and β-arrestin pathway activation and mTOR signaling.
Main Results:
- Seven DynB derivatives exhibited at least 10-fold greater selectivity for KOPrs compared to MOPrs or DOPrs.
- DynB_G3M/Q8H showed highest selectivity for KOPrs over MOPrs; DynB_L5S demonstrated highest selectivity for KOPrs over DOPrs.
- Selectivity gains resulted from reduced affinity/potency at MOPrs/DOPrs, not increased affinity at KOPrs; no DynB variants showed increased potency or functional selectivity.
Conclusions:
- Amino acid substitutions at positions 3, 5, and 8 significantly influence MOPr and DOPr binding and activation.
- Dynorphin B variants with enhanced KOPr selectivity were successfully generated.
- Receptor affinity alone is insufficient for predicting peptidergic agonist potency or efficacy; downstream pathway assessment is crucial for predicting in vivo effects.
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