Caveolae are specialized membrane domains enriched in Caveolin-1 (Cav1) and Cavin proteins, historically linked to lipid rafts due to their cholesterol sensitivity and their insolubility in nonionic detergents. Cav1 is a membrane protein that assembles into large disk-like structures that embed in the inner plasma membrane leaflet, while Cavins are cytoplasmic proteins that interact with Cav1. Together, Cav1 and Cavins assemble into invaginated structures called caveolae. Here, we describe experimental results exploring the hypothesis that caveolae assemble through the process of prewetting. Prewetting is a phase transition that occurs when proteins condense at a surface while remaining dispersed in the bulk. Recent work has shown that prewetting transitions robustly occur at membrane surfaces when condensate-prone proteins interact with mobile, membrane-bound tethers. We hypothesize that Cavins, which form condensates in reconstitution, prewet membranes through their interactions with Cav1 tethers within caveolae. To test this hypothesis, we are investigating how caveolae assembly and morphology varies with perturbations of membrane composition and thermodynamics. We employ DNA-PAINT super-resolution fluorescence localization microscopy to visualize caveolae in chemically fixed cells. Our findings aim to provide new physical insight into the mechanisms of caveolae formation and their relationship to membrane and cytoplasmic phase transitions.
Nie et al. (Sun,) studied this question.