title: Super-resolution Visualization of Caveola Deformation in Response to Osmotic Stress.
abstract: Caveolae are protein-dense plasma membrane domains structurally composed of caveolin-1 or -3 along with other proteins. Our previous studies have shown that caveolae enhance calcium signals generated through the Gαq/phospholipase Cβ signaling pathway and that subjecting cells to hypo-osmotic stress reverses this enhancement. In this study, we have used super-resolution fluorescence microscopy supplemented by fluorescence correlation studies to determine the structural factors that underlie this behavior. We find similar and significant population of Gαqand one of its receptors, bradykinin type 2 receptor (B2R), as well as a significant population of Gαiand its coupled β2-adrenergic receptor (βAR), are localized to caveola domains. Although mild osmotic stress deforms caveolae and alters interactions between the caveolae and these proteins, the general structure and the localization of caveola components remain largely unchanged. This deformation eliminates the ability of caveolae to stabilize calcium signals mediated through Gαq-B2R, but does not affect cAMP signals mediated through Gαiand βAR. Structurally, we find that mild osmotic stress corresponding roughly to a pressure of 3.82 newtons/m2increases the domain diameter by ∼30% and increases the fluorescence intensity in the center of the domain mouth suggesting a flattening of the invagination. Approximate calculations show that caveolae in muscle tissue have the strength to handle the stress of muscle movement.
authors.affiliation: From the Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, Massachusetts 01609.
authors.forename: Lu
authors.initials: L
authors.lastname: Yang
authors.affiliation: From the Department of Chemistry and Biochemistry, Worcester Polytechnic Institute, Worcester, Massachusetts 01609 sfscarlata@wpi.edu.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Scarlata
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling; D021941:Caveolae / Q000473:pathology*; D051242:Caveolin 1 / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009130:Muscle, Smooth / Q000378:metabolism; D009995:Osmosis; D009997:Osmotic Pressure; D011485:Protein Binding; D000072417:Protein Domains; D051381:Rats; D043782:Receptor, Bradykinin B2 / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000378:metabolism
chemical_list: D051242:Caveolin 1; D043782:Receptor, Bradykinin B2; D018343:Receptors, Adrenergic, beta-2; D000242:Cyclic AMP; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D002118:Calcium
keywords: G protein; caveolae; fluorescence; membrane structure; osmotic swelling