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Relax, Cool Down and Scaffold: How to Restore Surface Expression of Folding-Deficient Mutant GPCRs and SLC6
H M Mazhar Asjad1, Shahrooz Nasrollahi-Shirazi2, Sonja Sucic3
1Institute of Pharmacology and the Gaston H. Glock Research Laboratories for Exploratory Drug Development, Center of Physiology and Pharmacology, Medical University of Vienna, A-1090 Vienna, Austria. n1442638@students.meduniwien.ac.at.
Abstract:
Many diseases arise from mutations, which impair protein folding. The study of folding-deficient variants of G protein-coupled receptors and solute carrier 6 (SLC6) transporters has shed light on the folding trajectory, how it is monitored and how misfolding can be remedied. Reducing the temperature lowers the energy barrier between folding intermediates and thereby eliminates stalling along the folding trajectory. For obvious reasons, cooling down is not a therapeutic option. One approach to rescue misfolded variants is to use membrane-permeable orthosteric ligands. Antagonists of GPCRs are-in many instances-effective pharmacochaperones: they restore cell surface expression provided that they enter cells and bind to folding intermediates. Pharmacochaperoning of SLC6 transporters is less readily achieved because the ionic conditions in the endoplasmic reticulum (ER) are not conducive to binding of typical inhibitors. The second approach is to target the heat-shock protein (HSP) relay, which monitors the folding trajectory on the cytosolic side. Importantly, orthosteric ligands and HSP-inhibitors are not mutually exclusive. In fact, pharmacochaperones and HSP-inhibitors can act in an additive or synergistic manner. This was exemplified by rescuing disease-causing, folding-deficient variants of the human dopamine transporters with the HSP70 inhibitor pifithrin-micro and the pharmacochaperone noribogaine in Drosophila melanogaster.
Insights
Misfolded proteins, like those causing disease, can be rescued using pharmacochaperones or heat-shock protein (HSP) inhibitors. These approaches, targeting protein folding and monitoring, can work together to restore normal function.
Area of Science:
- Biochemistry
- Molecular Biology
- Pharmacology
Background:
- Protein misfolding due to mutations is a cause of many diseases.
- G protein-coupled receptors (GPCRs) and solute carrier 6 (SLC6) transporters are examples of proteins whose folding can be impaired.
- Understanding protein folding trajectories, monitoring, and correction is crucial for disease research.
Purpose of the Study:
- To investigate methods for rescuing misfolded protein variants.
- To explore the therapeutic potential of pharmacochaperones and heat-shock protein (HSP) inhibitors.
- To determine if these two approaches can be combined for enhanced therapeutic effects.
Main Methods:
- Studied folding-deficient variants of GPCRs and SLC6 transporters.
- Investigated the use of membrane-permeable orthosteric ligands as pharmacochaperones.
- Examined targeting the HSP relay system for protein folding monitoring.
- Tested the combined effects of pharmacochaperones and HSP inhibitors in a disease model.
Main Results:
- Orthosteric ligands can act as pharmacochaperones, restoring cell surface expression of GPCRs.
- Pharmacochaperoning of SLC6 transporters is challenging due to endoplasmic reticulum (ER) conditions.
- HSP inhibitors can target the cytosolic monitoring of protein folding.
- Pharmacochaperones and HSP inhibitors demonstrated additive or synergistic effects in rescuing misfolded variants.
Conclusions:
- Pharmacochaperones and HSP inhibitors represent viable strategies for correcting protein misfolding.
- Combining these approaches offers a promising therapeutic avenue for diseases caused by misfolded proteins.
- The study successfully rescued disease-causing variants of human dopamine transporters using a combined approach in a model organism.
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