Super Resolution Microscopy Reveals that Caveolin-1 is Required for Antiviral Immune Response

Abstract

Understanding the organization of lipid rafts enhances our knowledge of the dynamic interactions of the receptors that reside in these membrane nanodomains. Caveolin-1 incorporates into lipid rafts and oligomerizes to induce the formation of caveolae, specialized lipid raft domains characterized by their flask-like morphology. Caveolae are integral for numerous signaling events, including immune responses, but their function in antiviral signaling is largely unexplored. Conventional studies of lipid raft association involve fractionation of detergent resistant membranes, which does not provide spatial and quantitative information. Fluorescence Photoactivation Localization Microscopy (FPALM), a super-resolution microscopy method, can be used to examine the organization and dynamics of single molecules underlying biological processes at the nanoscale. Interferon (IFN) plays a pivotal role in the antiviral response and this study shows that the IFN-receptor (IFN-R) co-localizes with Cav-1 and disperses upon Cav-1 knockdown. Expression levels of an IFN-stimulated gene are preserved upon covalent crosslinking of the IFN-R, despite Cav-1 knockdown, suggesting that caveolae corral or cluster the receptor for downstream signaling. To our best knowledge this is the first report of microscopic visualization of an immune receptor colocalizing with a membrane nanodomain, which is necessary for corralling antiviral receptors for the subsequent downstream signal.