The molecular organization of differentially curved caveolae indicates bendable structural units at the plasma membrane.
Claudia Matthaeus, Kem A. Sochacki, Andrea Dickey, Dmytro Puchkov, Volker Haucke, Martin Lehmann, Justin W. Taraska
Nature-Communications: DOI: 10.1038/s41467-022-34958-3
BioRxiv: https://www.biorxiv.org/content/10.1101/2022.03.31.486578v1.full
Abstract:
Caveolae are small coated inner plasma membrane invaginations found in many cell types. Their diverse functions span from endocytosis to signaling, regulating key cellular processes including lipid uptake, pathogen entry, and membrane tension. Caveolae undergo curvature changes from low to highly curved invaginations into the cytosol. It is unclear which proteins regulate this process. To address this gap, we studied low and highly curved caveolae with platinum replica electron microscopy in six common cell types. Next, we developed a correlative multi-color stimulated emission depletion (STED) fluorescence and platinum replica EM imaging (CLEM) method to directly image caveolae-associated proteins at single caveolae of different curvature shapes at the nanoscale. Caveolins and cavins were found at all caveolae, independent of their curvature. EHD2, a classic caveolar neck protein, was strongly detected at both low and highly curved caveolae. Both pacsin2 and the regulator EHBP1 were found only at a subset of caveolae. Pacsin2 was localized primarily to areas surrounding lower curved caveolae, whereas EHBP1 was mostly detected at highly curved. Contrary to current models, dynamin was absent from caveolae and localized to clathrin-coated structures. Cells lacking dynamin showed no substantial changes to caveolae, suggesting that dynamin is not directly involved in caveolae curvature. Together, we provide a mechanistic map for the molecular control of caveolae curvature by eight of the major caveolae-associated coat and regulatory proteins. We propose a model where caveolins, cavins, and EHD2 assemble as a cohesive structural unit regulated by more intermittent associations with pacsin2 and EHBP1. These complexes can flatten and curve, capturing membrane to enable lipid traffic, signaling, and changes to the exposed surface area of the cell.
Note:
All PREM image datasets in this project are tiled montages acquired on an AMT XR111 ccd at 15000 x magnification (pixel size 1.23 nm).
Detailed methods description can be found in the online article at Nature Communications.
