Clustering and immobilization of acetylcholine receptors by the 43-kD protein: a possible role for dystrophin-related protein.
Recombinant acetylcholine receptors (AChRs) expressed on the surface of cultured fibroblasts become organized into discrete membrane domains when the 43-kD postsynaptic protein (43k) is co-expressed in the same cells (Froehner, S.C., C. W. Luetje, P. B. Scotland, and J. Patrick, 1990. Neuron. 5:403-410; Phillips, W. D., M. C. Kopta, P. Blount, P. D. Gardner, J. H. Steinbach, and J. P. Merlie. 1991. Science (Wash. DC). 251:568-570). Here we show that AChRs present on the fibroblast cell surface prior to transfection of 43k are recruited into 43k-rich membrane domains. Aggregated AChRs show increased resistance to extraction with Triton X-100, suggesting a 43k-dependent linkage to the cytoskeleton. Myotubes of the mouse cell line C2 spontaneously display occasional AChR/43k-rich membrane domains that ranged in diameter up to 15 microns, but expressed many more when 43k was overexpressed following transfection of 43k cDNA. However, the membrane domains induced by recombinant 43k were predominantly small (< or = 2 microns). We were then interested in whether the cytoskeletal component, dystrophin related protein (DRP; Tinsley, J. M., D. J. Blake, A. Roche, U. Fairbrother, J. Riss, B. C. Byth, A. E. Knight, J. Kendrick-Jones, G. K. Suthers, D. R. Love, Y. H. Edwards, and K. E. Davis, 1992. Nature (Lond.). 360:591-593) contributed to the development of AChR clusters. Immunofluorescent anti-DRP staining was present at the earliest stages of AChR clustering at the neuromuscular synapse in mouse embryos and was also concentrated at the large AChR-rich domains on nontransfected C2 myotubes. Surprisingly, anti-DRP staining was concentrated mainly at the large, but not the small AChR clusters on C2 myotubes suggesting that DRP may be principally involved in permitting the growth of AChR clusters.
Phillips
W D
WD
Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110.
Noakes
P G
PG
Roberds
S L
SL
Campbell
K P
KP
Merlie
J P
JP
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000032:analysis / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D046911:Macromolecular Substances; D008565:Membrane Proteins; D051379:Mice; D009132:Muscles / Q000378:metabolism*; D011485:Protein Binding; D011784:Quail; D011950:Receptors, Cholinergic / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*; D011994:Recombinant Proteins / Q000032:analysis / Q000378:metabolism; D013569:Synapses / Q000378:metabolism; D014162:Transfection; D049411:Utrophin
D003598:Cytoskeletal Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D011950:Receptors, Cholinergic; D011994:Recombinant Proteins; C483600:Utrn protein, mouse; D049411:Utrophin