title: Mutual regulation between metabotropic glutamate type 1alpha receptor and caveolin proteins: from traffick to constitutive activity.
abstract: In this paper, a molecular and functional interaction between metabotropic glutamate receptor type 1alpha (mGlu1alpha receptor) and caveolin-1 or caveolin-2beta is described. An overlapping pattern of staining for mGlu1alpha receptor with caveolin-1 and caveolin-2 by confocal laser microscopy in transiently transfected HEK-293 cells is observed. The presence of mGlu1alpha receptor in caveolin-enriched membrane fractions was demonstrated by flotation gradient analysis in the absence of detergents and the interaction between mGlu1alpha receptor with caveolin-1 and with caveolin-2beta was demonstrated by coimmunoprecipitation experiments. In HEK-293 cells, caveolin-2beta accumulates surrounding lipid droplets when single expressed but coexpression with mGlu1alpha receptor changed dramatically the subcellular localization of caveolin-2beta, directing it from lipid droplets to the cell surface. At the membrane level, the interaction between caveolin-1 and mGlu1alpha receptor could abrogate the constitutive activity exhibited by mGlu1alpha receptor. Overall, these results show that mGlu1alpha receptor interacts with caveolins and that this interaction is physiologically relevant for receptor function. Interestingly, we provide evidence that caveolin-1 is not just acting as a scaffolding protein for the mGlu1alpha receptor but that also regulates mGlu1alpha receptor constitutive activity.
authors.affiliation: Department of Biochemistry and Molecular Biology. University of Barcelona. Barcelona, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Burgueño
authors.forename: Enric I
authors.initials: EI
authors.lastname: Canela
authors.forename: Josefa
authors.initials: J
authors.lastname: Mallol
authors.forename: Carmen
authors.initials: C
authors.lastname: Lluis
authors.forename: Rafael
authors.initials: R
authors.lastname: Franco
authors.forename: Francisco
authors.initials: F
authors.lastname: Ciruela
mesh_terms: D021941:Caveolae / Q000378:metabolism* / Q000648:ultrastructure; D051242:Caveolin 1; D051243:Caveolin 2; D022461:Caveolins / Q000378:metabolism*; D002460:Cell Line; D025461:Feedback, Physiological / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D050356:Lipid Metabolism; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure; D020033:Protein Isoforms / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*
chemical_list: C495540:CAV1 protein, human; D051242:Caveolin 1; D051243:Caveolin 2; D022461:Caveolins; D020033:Protein Isoforms; D018094:Receptors, Metabotropic Glutamate; C104077:metabotropic glutamate receptor type 1; D018698:Glutamic Acid