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Published on: October 2, 2017
Expression and purification of an activated orexin receptor 1- G-protein complex
Ioanna Ramou1, Steven Janvier1, Sarah Druwé2
1VIB-VUB Center for Structural Biology, VIB, Pleinlaan 2, Brussels, Belgium; Structural Biology Brussels, Vrije Universiteit Brussel (VUB), Pleinlaan 2, Brussels, Belgium.
Abstract:
Orexin receptors constitute a family of class A G-protein coupled receptors. There are two subtypes of orexin receptors, namely OX1R and OX2R. OX1R and OX2R are widely distributed in the central nervous system and are the targets for the peptide neurotransmitters orexin-A and orexin-B. Orexins are involved in a plethora of key physiological functions such as regulation of the sleep/wake cycle, feeding behavior, energy homeostasis, and cognition. Dysfunction of the orexin system has been linked to various pathological conditions, such as narcolepsy, insomnia, obesity, addiction, cognitive impairment, and depression. The active state structure of OX2R has been elucidated, while the active state structure of OX1R remains unresolved. Here, we describe a method for the expression and purification of an activated OX1R bound to its native peptide ligand, orexin-A, in complex with a Dominant Negative Gsq protein and Nb35. The proteins were expressed in Hi5 insect cells and subsequently purified via two consecutive affinity chromatography steps, followed by a final polishing Size Exclusion Chromatography step. This study could stimulate further research into the activation mechanisms of OX1R and the structural determination of its active state structure.
Insights
Researchers developed a method to express and purify the OX1R receptor bound to orexin-A. This breakthrough facilitates structural studies of OX1R, crucial for understanding its role in sleep, feeding, and neurological disorders.
Area of Science:
- Pharmacology
- Neuroscience
- Structural Biology
Background:
- Orexin receptors (OX1R and OX2R) are Class A G-protein coupled receptors crucial for regulating sleep-wake cycles, feeding, and cognition.
- Orexin system dysfunction is implicated in narcolepsy, insomnia, obesity, addiction, and depression.
- While the active OX2R structure is known, the active OX1R structure remains elusive.
Purpose of the Study:
- To develop a method for expressing and purifying the activated OX1R in complex with its native ligand, orexin-A.
- To facilitate structural determination of the OX1R active state.
Main Methods:
- Expression of activated OX1R-orexin-A complex with a Dominant Negative Gsq protein and Nb35 in Hi5 insect cells.
- Purification using two sequential affinity chromatography steps.
- Final polishing via Size Exclusion Chromatography.
Main Results:
- Successfully expressed and purified the activated OX1R-orexin-A complex.
- Established a robust protocol for obtaining stable, purified receptor-ligand complexes.
Conclusions:
- The developed method provides a pathway for further structural studies of OX1R.
- This research may unlock new insights into orexin receptor activation mechanisms and inform therapeutic strategies for related disorders.
