Journal of Neuroscience, Vol 10, 1711-1718, Copyright © 1990 by Society for Neuroscience
Subunit composition of nicotinic acetylcholine receptors from chick ciliary ganglia
SW Halvorsen and DK Berg
Department of Biology, University of California, San Diego, La Jolla 92093.
Nicotinic ACh receptors were immunoaffinity-purified from chick ciliary
ganglia, radioiodinated, and examined by SDS-PAGE. Components with Mr's of
49, 52, and 60 kDa were obtained. Limited proteolysis produced different
peptide maps from the components, confirming the 3 as distinct species. All
are glycoproteins since treatment with glycopeptidase F altered their
migration during electrophoresis. The 60 kDa component appears to be
encoded by the AChR alpha 3 gene since it was selectively
immunoprecipitated by an antiserum to a fusion protein containing a
putative cytoplasmic region of the predicted alpha 3 gene product. The 49
kDa component selectively cross-reacted on immunoblots with 4 monoclonal
antibodies that recognize a component of similar size in AChR preparations
from chicken brain. The 52 kDa component is a novel species not previously
identified in preparations of brain AChRs. If all 3 components represent
integral AChR subunits, they may compose 2 receptor subtypes in the
ganglion, e.g., one containing 49 and 60 kDa subunits and another
containing 52 and 60 kDa subunits. This is supported by the finding that a
receptor preparation can be obtained containing only the 49 and 60 kDa
components and is consistent with reports of brain AChRs having only 2
types of subunits. Alternatively, ganglionic AChRs may contain 3 or more
types of subunits, with at least one being selectively lost under certain
conditions.