Abstract
We have characterized the oligosaccharide chains of the alpha subunit of acetylcholine receptor of the clonal mouse muscle cell line BC3H-1 by their sensitivity to end-beta-N-acetylglucosaminidase H and by comparison of the native glycosylated polypeptide with the nonglycosylated form made in tunicamycin-treated cells. These studies indicate that the native alpha subunit has a single N-asparagine-linked oligosaccharide chain of the "high mannose" or "simple" type. Furthermore, these results considered in light of our previous characterization of the alpha subunit synthesized in vitro suggest that the alpha subunit contains no "complex"-type N-linked oligosaccharide chains. We have investigated the role of glycosylation in the biogenesis of the acetylcholine receptor. Receptor biogenesis in normal cells involves the assembly of newly synthesized alpha subunits into a form active for binding alpha-bungarotoxin. This process is only 30% efficient and is complete by 30 min postsynthesis. When glycosylation is inhibited by tunicamycin, alpha subunit synthesis is inhibited only slightly but assembly into an alpha-bungarotoxin binding species is reduced dramatically.
Highlights
We have characterized the oligosaccharide chainosf Contractile and electrical activity are themselves normally the a subunit of acetylcholine receptor of the clonal controlled by the frequency of ACh receptor activation by mouse muscle cell line BC3H-1 by their sensitivity to ACh released from motor neurons
From polysome fractionation and in vitro run-off experiments, we have determined that atleast 1ACh receptor subunit (a) glycosylation inthe biogenesis of the acetylcholine rei-s synthesized on membrane-bound polyribosomes and is glyceptor.Receptor biogenesis in normal cells involves cosylated during translation [4].More recent experiments the assembly of newly synthesized a subunits into a using messenger-dependent reticulocyte lysates to translate form active for binding a-bungarotoxTinh.is process is purified RNA indicate that thea subunit is synthesized as a only 30% efficient and is complete by 30 min postsyn- preprotein containing approximately 2000 daltons of NH2
When glycosylation is inhibited by tunicamycin, terminal amino acid sequence not found in the native polya subunit synthesisis inhibited only slightly but assemp-eptide.2Pulse-chase labeling in vivo has identified an early bly into an a-bungarotoxin binding speciesis reduced stage in the biogenesis of functional ACh receptor molecules
Summary
We have characterized the oligosaccharide chainosf Contractile and electrical activity are themselves normally the a subunit of acetylcholine receptor of the clonal controlled by the frequency of ACh receptor activation by mouse muscle cell line BC3H-1 by their sensitivity to ACh released from motor neurons. This is a system endo-/?-N-acetylglucosaminidasHe and by comparison in which receptor content is autoregulated, a phenomenon of the native glycosylated polypeptide with the nongwlyhi-ch may be common among transmitter and hormone recosylatedformmade in tunicamycin-treatedcells. GranttotheUniversity of Pittsburgh, by fundsprovidedby the Mental Health Clinical Research Center for the Study of Affective
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
