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Updated: Sep 22, 2025
10:24
Detection of Ligand-activated G Protein-coupled Receptor Internalization by Confocal Microscopy
Published on: April 9, 2017
10.9K
Structural insights into galanin receptor signaling
Wentong Jiang1,2, Sanduo Zheng1,2,3
1Sanduo Zheng Laboratory, National Institute of Biological Sciences, Beijing 102206, China.
Summary
Structural insights into galanin receptor (GALR) function reveal how these G protein–coupled receptors (GPCRs) bind galanin and select G proteins. These findings clarify GPCR signaling mechanisms and zinc ion modulation.
Area of Science:
- Neuroscience
- Structural Biology
- Biochemistry
Background:
- Galanin is a neuropeptide that signals through three G protein–coupled receptors (GPCRs): GALR1, GALR2, and GALR3.
- GALR signaling influences energy metabolism, pain, epilepsy, and sleep, with different receptors coupling to distinct G protein pathways (Gi/o for GALR1/3, Gq/11 for GALR2).
- The molecular mechanisms of galanin recognition and G protein selectivity by GALRs are not fully understood.
Purpose of the Study:
- To determine the structural basis of galanin recognition and G protein selectivity for GALR1 and GALR2.
- To investigate the role of zinc ions in modulating GALR activity.
Main Methods:
- Cryoelectron microscopy (cryo-EM) was used to determine the structures of GALR1-Go and GALR2-Gq complexes.
- Functional assays were performed to validate structural findings and assess G protein selectivity.
- Allosteric modulation by zinc ions was investigated.
Main Results:
- The structures reveal how galanin binds to the extracellular vestibule of GALRs, adopting an alpha-helical conformation.
- Key structural determinants for G protein selectivity were identified for GALRs and other class A GPCRs.
- Zinc ions were found to be negative allosteric regulators of GALR1 but not GALR2.
Conclusions:
- This study provides atomic-level insights into galanin receptor activation and G protein coupling.
- The findings elucidate mechanisms of GPCR G protein selectivity and highlight zinc as a potential neuromodulator of GPCR signaling in the central nervous system.
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