Membrane clustering and bungarotoxin binding by the nicotinic acetylcholine receptor: role of the ? subunit

Wheeler, Susan V., Jane, Steven D., Cross, Kathryn M.L., Chad, John E. and Foreman, Richard C. (1994) Membrane clustering and bungarotoxin binding by the nicotinic acetylcholine receptor: role of the ? subunit. Journal of Neurochemistry, 63 (5), 1891-1899. (doi:10.1046/j.1471-4159.1994.63051891.x).

Abstract

Nicotinic acetylcholine receptors (nAChRs) are localised at morphologically distinct regions of the postsynaptic membrane by interactions between the receptor subunits and cytoskeletal proteins, such as the 43-kDa protein. We have used Xenopus oocytes to examine the localisation and pharmacological properties of muscle nAChRs associated with 43-kDa protein and to compare them with hybrid muscle nAChRs containing a ? subunit derived from a neuronal source. Receptors expressed on the oocyte outer membrane were visualised using confocal scanning laser microscopy. Coexpression of mouse muscle subunit ?1?1?? and 43-kDa protein transcripts produced discrete receptor aggregates with a diameter of 1–5 µm whose function was partially blocked by application of neuronal bungarotoxin (NBT) at 100 nM. Substitution of the ?1 subunit by the neuronal ?2 protein produced a functioning receptor that did not aggregate in the presence of 43-kDa protein and was substantially blocked by the same concentration of NBT. Hybrid ?1?4?? receptors exhibited a combination of characteristics in that they clustered like normal muscle subunits in the presence of 43-kDa protein, but showed a sensitivity to NBT intermediate between that of muscle receptors and that of hybrids containing ?2. These results suggest that the ? subunit is an important determinant in receptor localisation and sensitivity to NBT.

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Contributors

Author: John E. Chad

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