Caveolae are specialized invaginations on the plasma membrane of mammalian cells, involved in cell adhesion, signal transduction, and membrane organization. They act as membrane buffers for the local expansion and resorption of the plasma membrane when tension is applied in order to prevent membrane rupture. They are interesting objects for quantitative analysis, since their assembly follows a quantal principle (Pelkmans, Zerial, 2005). The lateral dynamics, formation, internalization, and exocytosis of caveolar structures, as well as their coat assembly, remodelling, and disassembly can be quantitatively followed using photobleaching and total internal reflection fluorescence microscopy (Pelkmans, Zerial, 2005).
Quantal assembly and kiss-and-run of caveolar structures. a, TIR-FM of HeLa cells stably expressing CAV1–GFP. b, Intensity histogram of 396 CAV1–GFP-positive structures in HeLa cells, fitted to 4 gaussian curves (R2 = 0.99). The mean of the first peak is defined as q. c, Plots of intensity over time (17-ms interval) of 12 appearing and 10 disappearing structures in TIR-FM, and sigmoidal curve fits (solid lines) of average values (filled circles) (R2 = 0.82). d, Intensity histograms and gaussian fits of 90 docking/mobile (R2 = 1.00) and 308 fixed/immobile structures (R2 = 0.97). Of the 90 mobile spots, 71 are q1 and 7 are q2. Of the 308 fixed spots, 87 are q1 and 221 are qn>1.
- How and where do caveolae form in the cell?
- Can the architecture and composition of a caveolar coat be altered, and if so, how dynamic is that?
- Are caveolae ‘membrane reservoirs’ to allow membrane blebbing and bleb resorption?
- Are caveolar structures within a single cell heterogeneous, and does such heterogeneity have a functional role?
- Can the caveolar membrane system of a single cell have multiple states, and does this vary between cells?
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