Structural organization of developing acetylcholine receptor aggregates.
We report the first quantitative ultrastructural analysis of newly formed acetylcholine receptor aggregates. Aggregates were induced in Xenopus muscle cell cultures with agrin, labeled with gold particles, and detected using high resolution scanning electron microscopy. Aggregates are readily discernible at the ultrastructural level within 2 h of stimulation by agrin. The size and density profiles of the developing aggregates show that receptors reach maximal density very quickly in small "nano-aggregates" and that the aggregation process is not limited by the diffusion rate of the receptor. Quantitative analysis of label locations indicates that the receptor distribution within aggregates is nonrandom. Instead, the newly aggregated receptors appear to be bound to a localized scaffold conforming to a hexagonal (close-packed) geometry with a spacing of approximately 9.9 nm.
Kunkel
D D
DD
Békésy Laboratory of Neurobiology, University of Hawaii at Manoa, Honolulu 96822, USA.
Stollberg
J
J
D018171:Agrin / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000502:physiology / Q000648:ultrastructure; D002478:Cells, Cultured; D004625:Embryo, Nonmammalian; D007700:Kinetics; D008855:Microscopy, Electron, Scanning; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D011950:Receptors, Cholinergic / Q000096:biosynthesis* / Q000187:drug effects / Q000648:ultrastructure; D013997:Time Factors; D014982:Xenopus laevis / Q000196:embryology
D018171:Agrin; D011950:Receptors, Cholinergic