title: Gangliosides GM1 and GM3 in the living cell membrane form clusters susceptible to cholesterol depletion and chilling.
abstract: Presence of microdomains has been postulated in the cell membrane, but two-dimensional distribution of lipid molecules has been difficult to determine in the submicrometer scale. In the present paper, we examined the distribution of gangliosides GM1 and GM3, putative raft molecules in the cell membrane, by immunoelectron microscopy using quick-frozen and freeze-fractured specimens. This method physically immobilized molecules in situ and thus minimized the possibility of artifactual perturbation. By point pattern analysis of immunogold labeling, GM1 was shown to make clusters of <100 nm in diameter in normal mouse fibroblasts. GM1-null fibroblasts were not labeled, but developed a similar clustered pattern when GM1 was administered. On cholesterol depletion or chilling, the clustering of both endogenous and exogenously-loaded GM1 decreased significantly, but the distribution showed marked regional heterogeneity in the cells. GM3 also showed cholesterol-dependent clustering, and although clusters of GM1 and GM3 were found to occasionally coincide, these aggregates were separated in most cases, suggesting the presence of heterogeneous microdomains. The present method enabled to capture the molecular distribution of lipids in the cell membrane, and demonstrated that GM1 and GM3 form clusters that are susceptible to cholesterol depletion and chilling.
authors: Department of Anatomy and Molecular Cell Biology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan.
authors: Akikazu
authors: A
authors: Fujita
authors: Jinglei
authors: J
authors: Cheng
authors: Minako
authors: M
authors: Hirakawa
authors: Koichi
authors: K
authors: Furukawa
authors: Susumu
authors: S
authors: Kusunoki
authors: Toyoshi
authors: T
authors: Fujimoto
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D003080:Cold Temperature; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D005614:Freeze Fracturing; D005677:G(M1) Ganglioside / Q000378:metabolism*; D005679:G(M3) Ganglioside / Q000378:metabolism*; D007150:Immunohistochemistry; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism; D021962:Membrane Microdomains / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D018345:Mice, Knockout; D016253:Microscopy, Immunoelectron; D017350:N-Acetylgalactosaminyltransferases / Q000235:genetics / Q000378:metabolism; D047392:beta-Cyclodextrins / Q000378:metabolism
chemical_list: D005679:G(M3) Ganglioside; D008563:Membrane Lipids; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D005677:G(M1) Ganglioside; D002784:Cholesterol; D017350:N-Acetylgalactosaminyltransferases