Figure 5. The cavins form part of the striated caveola coat and cavin2 and cavin3 localize to the same caveola while remaining spatially distinct.
(A) High magnification images of immuno-EM labeled 3T3-L1 fibroblasts expressing cavin1 (top row), cavin2 (middle row) and cavin3 (lower row) and their predicted three-dimensional orientation (right hand columns, red line = predicted orientation based on a model of cytoplasmic caveolar striations, yellow box = field of view from electron micrograph of 60 nm section). Scale bars, 100 nm. (B) High magnification images of cavin1-Cherry (3 nm gold–colored red) and cavin3-GFP (7 nm gold–colored green) label the same caveolae and have significant overlap. Scale bars, 100 nm. (C) Cavin-2-GFP (7 nm gold) and cavin-3-Cherry (3 nm gold) demonstrates the spatial separation between both proteins within individual caveolae, consistent with the formation of separate striations. Black circles in the low magnification image denote the spatial limit of the individual caveola and its associated coat of caveolae that are positive for both cavin2 and cavin3. Scale bars, 100 nm. (D) Bivariate clustering analysis of different plasma membrane lawns expressing various combinations of cavin proteins. Significantly higher co-clustering of cavin1-cavin3 was observed when compared to cavin2-cavin3 (CI = confidence interval). Scale bars, 100 nm. (E) Model of association and disassociation of the cavin1-cavin2 and cavin1-cavin3 subcomplexes.