I. Mookjung et H. Gordon, ACETYLCHOLINE-RECEPTOR CLUSTERING IN C2 MUSCLE-CELLS REQUIRES CHONDROITIN SULFATE, Journal of neurobiology, 28(4), 1995, pp. 482-492
Proteoglycans have been implicated in the clustering of acetylcholine
receptors (AChRs) on cultured myotubes and at the neuromuscular juncti
on. We report that the presence of chondroitin sulfate is associated w
ith the ability of cultured myotubes to form spontaneous clusters of A
ChRs. Three experimental manipulations of wild type C2 cells in cultur
e were found to affect both glycosaminoglycans (GAGs) and AChR cluster
ing in concert. Chlorate was found to have dose-dependent negative eff
ects both on GAG sulfation and on the frequency of AChR clusters. When
extracellular calcium was raised from 1.8 to 6.8 mM in cultures of wi
ld-type C2 myotubes, increases were observed both in the level of cell
layer-associated chondroitin sulfate and in the frequency of AChR clu
sters. Culture of wild-type C2 myotubes in the presence of chondroitin
ase ABC eliminated cell layer-associated chondroitin sulfate while lea
ving heparan sulfate intact and simultaneously prevented the formation
of AChR clusters. Treatment with either chlorate or chondroitinase in
hibited AChR clustering only if begun prior to the spontaneous formati
on of clusters. We propose that chondroitin sulfate plays an essential
role in the initiation of AChR clustering and in the early events of
synapse formation on muscle. (C) 1995 John Wiley & Sons, Inc.