α7β2 nicotinic acetylcholine receptors assemble, function, and are activated primarily via their α7-α7 interfaces

Area of Science:

• Neuroscience
• Molecular Biology
• Biophysics

Background:

• Nicotinic acetylcholine receptors (nAChRs) are crucial ion channels involved in neurotransmission.
• The α7 and β2 subunits are known to form functional nAChRs, but their assembly and properties require further investigation.

Purpose of the Study:

• To investigate the assembly and functional properties of nicotinic acetylcholine receptors (nAChRs) composed of α7 and β2 subunits.
• To elucidate the structural basis for the function of α7β2 nAChRs.

Main Methods:

• Utilized laser scanning confocal microscopy and Förster resonance energy transfer (FRET) to assess subunit colocalization and coassembly.
• Employed total internal reflection fluorescence microscopy to determine the localization of receptor assemblies.
• Measured optical and electrophysiological properties of wild-type and mutant subunits expressed in cell lines and Xenopus laevis oocytes.

Main Results:

• Fluorescently tagged α7 and β2 subunits were found to colocalize and coassemble, forming functional α7β2 nAChRs.
• α7β2 nAChRs exhibited pharmacological properties similar to α7 nAChRs but with approximately 2-fold lower agonist-evoked current amplitudes.
• These receptors showed sensitivity to dihydro-β-erythroidine, a characteristic not observed for α7 nAChRs.
• Cysteine mutant analysis indicated that the α7-β2 subunit interface is not functionally productive for ligand binding.

Conclusions:

• α7 and β2 subunits coassemble to form functional nAChRs with distinct pharmacological profiles.
• The α7-β2 subunit interface contributes to lower current amplitudes and presents challenges in identifying native α7β2 nAChR function.
• A model was developed to predict α7β2 nAChR function based on subunit stoichiometry and position.