title: Annexin 2 promotes the formation of lipid microdomains required for calcium-regulated exocytosis of dense-core vesicles.
abstract: Annexin 2 is a calcium-dependent phospholipid-binding protein that has been implicated in a number of membrane-related events, including regulated exocytosis. In chromaffin cells, we previously reported that catecholamine secretion requires the translocation and formation of the annexin 2 tetramer near the exocytotic sites. Here, to obtain direct evidence for a role of annexin 2 in exocytosis, we modified its expression level in chromaffin cells by using the Semliki Forest virus expression system. Using a real-time assay for individual cells, we found that the reduction of cytosolic annexin 2, and the consequent decrease of annexin 2 tetramer at the cell periphery, strongly inhibited exocytosis, most likely at an early stage before membrane fusion. Secretion also was severely impaired in cells expressing a chimera that sequestered annexin 2 into cytosolic aggregates. Moreover, we demonstrate that secretagogue-evoked stimulation triggers the formation of lipid rafts in the plasma membrane, essential for exocytosis, and which can be attributed to the annexin 2 tetramer. We propose that annexin 2 acts as a calcium-dependent promoter of lipid microdomains required for structural and spatial organization of the exocytotic machinery.
authors.affiliation: Centre National de la Recherche Scientifique, Unité Propre de Recherche 2356, IFR 37 des Neurosciences, 67084 Strasbourg Cedex, France.
authors.forename: Sylvette
authors.initials: S
authors.lastname: Chasserot-Golaz
authors.forename: Nicolas
authors.initials: N
authors.lastname: Vitale
authors.forename: Emeline
authors.initials: E
authors.lastname: Umbrecht-Jenck
authors.forename: Derek
authors.initials: D
authors.lastname: Knight
authors.forename: Volker
authors.initials: V
authors.lastname: Gerke
authors.forename: Marie-France
authors.initials: MF
authors.lastname: Bader
mesh_terms: D000199:Actins / Q000378:metabolism; D000311:Adrenal Glands / Q000378:metabolism; D000818:Animals; D017306:Annexin A2 / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D019439:Chromaffin Cells / Q000378:metabolism; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D005089:Exocytosis; D005372:Filipin / Q000494:pharmacology; D015151:Immunoblotting; D008055:Lipids / Q000737:chemistry*; D021962:Membrane Microdomains / Q000378:metabolism*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009638:Norepinephrine / Q000494:pharmacology; D022142:Secretory Vesicles / Q000378:metabolism; D012672:Semliki forest virus / Q000235:genetics; D013347:Subcellular Fractions; D013997:Time Factors
chemical_list: D000199:Actins; D017306:Annexin A2; D002395:Catecholamines; D008055:Lipids; D005372:Filipin; D002784:Cholesterol; D002118:Calcium; D009638:Norepinephrine