Î±7Î²2 Nicotinic Acetylcholine Receptors Assemble Function And Are Activated Primarily Via Their Î±7-Î±7 Interfaces
We investigated assembly and function of nicotinic acetylcholine receptors (nAChRs) composed of Î±7 and Î²2 subunits. We measured optical and electrophysiological properties of wildtype and mutant subunits expressed in cell lines and Xenopus laevis oocytes. Laser scanning confocal microscopy indicated that fluorescently tagged Î±7 and Î²2 subunits colocalize. FÃ¶rster resonance energy transfer between fluorescently tagged subunits strongly suggested that Î±7 and Î²2 subunits coassemble. Total internal reflection fluorescence microscopy revealed that assemblies localized to filopodia-like processes of SH-EP1 cells. Gain-of-function Î±7 and Î²2 subunits confirmed that these subunits coassemble within functional receptors. Moreover, Î±7Î²2 nAChRs composed of wild-type subunits or fluorescently tagged subunits had pharmacological properties similar to those of Î±7 nAChRs, although amplitudes of Î±7Î²2 nAChR-mediated, agonist-evoked currents were generally âˆ¼2-fold lower than those for Î±7 nAChRs. It is noteworthy that Î±7Î²2 nAChRs displayed sensitivity to low concentrations of the antagonist dihydro-Î²-erythroidine that was not observed for Î±7 nAChRs at comparable concentrations. In addition, cysteine mutants revealed that the Î±7-Î²2 subunit interface does not bind ligand in a functionally productive manner, partly explaining lower Î±7Î²2 nAChR current amplitudes and challenges in identifying the function of native Î±7Î²2 nAChRs. On the basis of our findings, we have constructed a model predicting receptor function that is based on stoichiometry and position of Î²2 subunits within the Î±7Î²2 nAChRs. Copyright Â© 2012 The American Society for Pharmacology and Experimental Therapeutics.
Digital Object Identifier (DOI)
Murray, Teresa A.; Bertrand, Daniel; Papke, Roger L.; George, Andrew A.; Pantoja, Rigo; Srinivasan, Rahul; Liu, Qiang; Wu, Jie; Whiteaker, Paul; Lester, Henry A.; and Lukas, Ronald J., "Î±7Î²2 Nicotinic Acetylcholine Receptors Assemble Function And Are Activated Primarily Via Their Î±7-Î±7 Interfaces" (2012). Neurobiology. 74.