Neuronal nicotinic α7 subunits assemble into cell-surface complexes that neither function nor bind α-bungarotoxin when expressed in tsA201 cells. Functional α-bungarotoxin receptors are expressed if the membrane-spanning and cytoplasmic domains of the α7 subunit are replaced by the homologous regions of the serotonin-3 receptor subunit. Bgt-binding surface receptors assembled from chimeric α7/serotonin-3 subunits contain subunits in two different conformations as shown by differences in redox state and other features of the subunits. In contrast, α7 subunit complexes in the same cell line contain subunits in a single conformation. The appearance of a second α7/serotonin-3 subunit conformation coincides with the formation of α-bungarotoxin–binding sites and intrasubunit disulfide bonding, apparently within the α7 domain of the α7/serotonin-3 chimera. In cell lines of neuronal origin that produce functional α7 receptors, α7 subunits undergo a conformational change similar to α7/serotonin-3 subunits. α7 subunits, thus, can fold and assemble by two different pathways. Subunits in a single conformation assemble into nonfunctional receptors, or subunits expressed in specialized cells undergo additional processing to produce functional, α-bungarotoxin–binding receptors with two α7 conformations. Our results suggest that α7 subunit diversity can be achieved postranslationally and is required for functional homomeric receptors.
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12 July 1999
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July 12 1999
α-Bungarotoxin Receptors Contain α7 Subunits in Two Different Disulfide-Bonded Conformations
Daniel S. McGehee,
Daniel S. McGehee
aDepartment of Pharmacological and Physiological Sciences, Department of Anesthesia and Critical Care, University of Chicago, Chicago, Illinois 60637
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Sergey Rakhilin
Renaldo C. Drisdel
Daphna Sagher
Daniel S. McGehee
aDepartment of Pharmacological and Physiological Sciences, Department of Anesthesia and Critical Care, University of Chicago, Chicago, Illinois 60637
Yolanda Vallejo
William N. Green
1.used in this paper: 5HT, 5-hydroxytryptamine (serotonin); ACh, acetylcholine; AChR, acetylcholine receptor; Bgt, α-bungarotoxin; BgtR, α-bungarotoxin receptor; HA, hemagglutinin; NEM, N-ethylmaleimide; TMR-Bgt, α-bungarotoxin tetramethylrhodamine
Sergey Rakhilin's present address is Laboratory of Molecular and Cellular Neuroscience, The Rockefeller University, New York, NY 10021.
Received:
November 20 1998
Revision Requested:
June 01 1999
Accepted:
June 07 1999
Online ISSN: 1540-8140
Print ISSN: 0021-9525
© 1999 The Rockefeller University Press
1999
The Rockefeller University Press
J Cell Biol (1999) 146 (1): 203–218.
Article history
Received:
November 20 1998
Revision Requested:
June 01 1999
Accepted:
June 07 1999
Citation
Sergey Rakhilin, Renaldo C. Drisdel, Daphna Sagher, Daniel S. McGehee, Yolanda Vallejo, William N. Green; α-Bungarotoxin Receptors Contain α7 Subunits in Two Different Disulfide-Bonded Conformations. J Cell Biol 12 July 1999; 146 (1): 203–218. doi: https://doi.org/10.1083/jcb.146.1.203
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