Abstract
The nicotinic acetylcholine receptor (AChR) is in intimate contact with the lipids in its native membrane. Here we analyze the possibility that it is the intrinsic properties of the AChR that determine its partition into a given lipid domain. Torpedo AChR or a synthetic peptide corresponding to the AChR M4 segment (the one in closer contact with lipids) was reconstituted into "raft"-containing model membranes. The distribution of the AChR was assessed by Triton X-100 extraction in combination with fluorescence studies, and lipid analyses were performed on each sample. The influence of rapsyn, a peripheral protein involved in AChR aggregation, was studied. Raft-like domain aggregation was also studied using membranes containing the ganglioside GM1 followed by GM1 crosslinking. The gammaM4 peptide displays a marked preference for raft-like domains. In contrast, AChR alone or in the presence of rapsyn or ganglioside aggregation exhibits no such preference for raft-like domains, but it does cause a significant reduction in the total amount of these domains. The results indicate that the distribution of the AChR in lipid domains cannot be due exclusively to the intrinsic physicochemical properties of the protein and that there must be an external signal in native cell membranes that directs the AChR to a specific membrane domain.
Highlights
The nicotinic acetylcholine receptor (AChR) is in intimate contact with the lipids in its native membrane
The sample was submitted to Triton X-100 treatment at 4°C and subsequently separated into detergent-soluble membrane (DSM) and detergent-resistant membrane (DRM) fractions by centrifugation
The aim of this study was to characterize the relationship between the AChR/PC:SM:Chol (1:1:1) (AChR) protein and its lipid environment with regard to the possible occurrence of the receptor in laterally segregated lipid domains in the membrane
Summary
The nicotinic acetylcholine receptor (AChR) is in intimate contact with the lipids in its native membrane. Raft-like domain aggregation was studied using membranes containing the ganglioside GM1 followed by GM1 crosslinking. AChR alone or in the presence of rapsyn or ganglioside aggregation exhibits no such preference for raft-like domains, but it does cause a significant reduction in the total amount of these domains. The results indicate that the distribution of the AChR in lipid domains cannot be due exclusively to the intrinsic physicochemical properties of the protein and that there must be an external signal in native cell membranes that directs the AChR to a specific membrane domain.—Bermúdez, V., S. Partition profile of the nicotinic acetylcholine receptor in lipid domains upon reconstitution.
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