title: Osmotic Stress Reduces Ca2+ Signals through Deformation of Caveolae.
abstract: Caveolae are membrane invaginations that can sequester various signaling proteins. Caveolae have been shown to provide mechanical strength to cells by flattening to accommodate increased volume when cells are subjected to hypo-osmotic stress. We have previously found that caveolin, the main structural component of caveolae, specifically binds Gαq and stabilizes its activation state resulting in an enhanced Ca(2+) signal upon activation. Here, we show that osmotic stress caused by decreasing the osmolarity in half reversibly changes the configuration of caveolae without releasing a significant portion of caveolin molecules. This change in configuration due to flattening leads to a loss in Cav1-Gαq association. This loss in Gαq/Cav1 association due to osmotic stress results in a significant reduction of Gαq/phospholipase Cβ-mediated Ca(2+) signals. This reduced Ca(2+) response is also seen when caveolae are reduced by treatment with siRNA(Cav1) or by dissolving them by methyl-β-cyclodextran. No change in Ca(2+) release with osmotic swelling can be seen when growth factor pathways are activated. Taken together, these results connect the mechanical deformation of caveolae to Gαq-mediated Ca(2+) signals.
authors.affiliation: From the Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11794-8661.
authors.forename: Yuanjian
authors.initials: Y
authors.lastname: Guo
authors.affiliation: From the Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11794-8661.
authors.forename: Lu
authors.initials: L
authors.lastname: Yang
authors.affiliation: From the Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11794-8661.
authors.forename: Katrina
authors.initials: K
authors.lastname: Haught
authors.affiliation: From the Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York 11794-8661 Suzanne.Scarlata@stonybrook.edu.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Scarlata
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D021941:Caveolae / Q000737:chemistry / Q000378:metabolism*; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics / Q000378:metabolism; D009997:Osmotic Pressure; D051381:Rats
chemical_list: D051242:Caveolin 1; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D002118:Calcium
keywords: G proteins; calcium; caveolae; cell signaling; fluorescence; osmotic swelling