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  • Structure and superorganization of acetylcholine receptor-rapsyn complexes.

Structure and superorganization of acetylcholine receptor-rapsyn complexes.

Proceedings of the National Academy of Sciences of the United States of America (2013-06-12)
Benoît Zuber, Nigel Unwin
ABSTRACT

The scaffolding protein at the neuromuscular junction, rapsyn, enables clustering of nicotinic acetylcholine receptors in high concentration and is critical for muscle function. Patients with insufficient receptor clustering suffer from muscle weakness. However, the detailed organization of the receptor-rapsyn network is poorly understood: it is unclear whether rapsyn first forms a wide meshwork to which receptors can subsequently dock or whether it only forms short bridges linking receptors together to make a large cluster. Furthermore, the number of rapsyn-binding sites per receptor (a heteropentamer) has been controversial. Here, we show by cryoelectron tomography and subtomogram averaging of Torpedo postsynaptic membrane that receptors are connected by up to three rapsyn bridges, the minimum number required to form a 2D network. Half of the receptors belong to rapsyn-connected groups comprising between two and fourteen receptors. Our results provide a structural basis for explaining the stability and low diffusion of receptors within clusters.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Monoclonal Anti-Rapsyn antibody produced in mouse, 1 mg/mL, clone 1234, purified immunoglobulin, buffered aqueous solution
Sigma-Aldrich
Anti-Mouse IgG (whole molecule)–Gold antibody produced in goat, affinity isolated antibody, aqueous glycerol suspension, 5 nm (colloidal gold)