Belt-like localisation of caveolin in deep caveolae and its re-distribution after cholesterol depletion.
Caveolae are specialised vesicular microdomains of the plasma membrane. Using freeze-fracture immunogold labelling and stereoscopic imaging, the distribution of labelled caveolin 1 in caveolae of 3T3-L1 mouse fibroblast cells was shown. Immunogold-labelled caveolin structures surrounded the basolateral region of deeply invaginated caveolae like a belt whereas in the apical region distal to the plasma membrane, the caveolin labelling was nearly absent. Shallow caveolar membranes showed a dispersed caveolin labelling. After membrane cholesterol reduction by methyl-beta-cyclodextrin treatment, a dynamic re-distribution of labelled caveolin 1 and a flattening of caveolar structures was found. The highly curved caveolar membrane got totally flat, and the initial belt-like caveolin labelling disintegrated to a ring-like structure and later to a dispersed order. Intramembrane particle-free domains were still observable after cholesterol depletion and caveolin re-distribution. These results indicate that cholesterol interacting with caveolin structures at the basolateral part of caveolae is necessary for the maintenance of the deeply invaginated caveolar membranes.
Westermann
Martin
M
Elektronenmikroskopisches Zentrum am Klinikum der Friedrich-Schiller-Universität Jena, Ziegelmühlenweg 1, 07740, Jena, Germany. martin.westermann@uni-jena.de
Steiniger
Frank
F
Richter
Walter
W
D041721:3T3-L1 Cells; D000818:Animals; D021941:Caveolae / Q000737:chemistry* / Q000187:drug effects / Q000648:ultrastructure; D051242:Caveolin 1; D022461:Caveolins / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism*; D005614:Freeze Fracturing; D051379:Mice; D008854:Microscopy, Electron / Q000379:methods; D013997:Time Factors; D047392:beta-Cyclodextrins / Q000494:pharmacology
C495541:Cav1 protein, mouse; D051242:Caveolin 1; D022461:Caveolins; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; D002784:Cholesterol