Regulation of acetylcholine receptors in the mouse muscle cell line, C2.
The effects of culture age, muscle activity, and cell fusion on the metabolism of acetylcholine receptors in the mouse muscle cell line, C2, were determined. Receptor degradation followed complex kinetics and was dependent on culture age. One or two day old myotubes degraded receptors rapidly (t50 = 7-8 h) in a nearly single exponential process. Four or five day old myotubes, however, degraded receptors more slowly (t50 = 12-16 h) in a process that deviated substantially from single exponential kinetics. A similar complex pattern of receptor degradation was seen with the L6 cell line, but receptor degradation followed single exponential kinetics and was independent of culture age in primary rat myotubes and the BC3H-1 cell line. Acetylcholine receptors on C2 myotubes were immunologically similar to the extrajunctional receptors of denervated mouse muscle. Clustered receptors were degraded at approximately the same rate as the total receptor population and receptor turnover was not changed when spontaneous contractions of the C2 myotubes were inhibited. Newly synthesized receptors were more rapidly degraded than older receptors. Finally, receptors on fusion-arrested C2 myoblasts were degraded at the same rate (t50 = 16 h) regardless of culture age.
D000818:Animals; D001345:Autoradiography; D002038:Bungarotoxins / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D007118:Immunoassay; D007457:Iodine Radioisotopes; D007700:Kinetics; D009132:Muscles / Q000196:embryology / Q000378:metabolism*; D009157:Myasthenia Gravis / Q000097:blood; D051381:Rats; D011950:Receptors, Cholinergic / Q000378:metabolism*
D002038:Bungarotoxins; D007457:Iodine Radioisotopes; D011950:Receptors, Cholinergic