Annexin A2-dependent actin bundling promotes secretory granule docking to the plasma membrane and exocytosis.
Annexin A2, a calcium-, actin-, and lipid-binding protein involved in exocytosis, mediates the formation of lipid microdomains required for the structural and spatial organization of fusion sites at the plasma membrane. To understand how annexin A2 promotes this membrane remodeling, the involvement of cortical actin filaments in lipid domain organization was investigated. 3D electron tomography showed that cortical actin bundled by annexin A2 connected docked secretory granules to the plasma membrane and contributed to the formation of GM1-enriched lipid microdomains at the exocytotic sites in chromaffin cells. When an annexin A2 mutant with impaired actin filament-bundling activity was expressed, the formation of plasma membrane lipid microdomains and the number of exocytotic events were decreased and the fusion kinetics were slower, whereas the pharmacological activation of the intrinsic actin-bundling activity of endogenous annexin A2 had the opposite effects. Thus, annexin A2-induced actin bundling is apparently essential for generating active exocytotic sites.
Institut des Neurosciences Cellulaires et Intégratives, UPR3212 Centre National de la Recherche Scientifique, Université de Strasbourg, F-67084 Strasbourg, France.
Marion
M
Gabel
Laboratoire de Biologie Moléculaire Eucaryote, UMR5099 Centre National de la Recherche Scientifique-Université de Toulouse III Paul Sabatier, F-31000 Toulouse, France.
Franck
F
Delavoie
Plateforme Imagerie In Vitro, Neuropôle de Strasbourg, F-67084 Strasbourg, France.
Valérie
V
Demais
Plateforme Imagerie In Vitro, Neuropôle de Strasbourg, F-67084 Strasbourg, France.
Cathy
C
Royer
Institut des Neurosciences Cellulaires et Intégratives, UPR3212 Centre National de la Recherche Scientifique, Université de Strasbourg, F-67084 Strasbourg, France.
Yannick
Y
Bailly
Institut des Neurosciences Cellulaires et Intégratives, UPR3212 Centre National de la Recherche Scientifique, Université de Strasbourg, F-67084 Strasbourg, France.
Nicolas
N
Vitale
Institut des Neurosciences Cellulaires et Intégratives, UPR3212 Centre National de la Recherche Scientifique, Université de Strasbourg, F-67084 Strasbourg, France.
Marie-France
MF
Bader
Institut des Neurosciences Cellulaires et Intégratives, UPR3212 Centre National de la Recherche Scientifique, Université de Strasbourg, F-67084 Strasbourg, France chasserot@inci-cnrs.unistra.fr.
Sylvette
S
Chasserot-Golaz
D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D000818:Animals; D017306:Annexin A2 / Q000235:genetics / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000502:physiology*; D055032:Electron Microscope Tomography; D005089:Exocytosis / Q000502:physiology*; D008561:Membrane Fusion / Q000502:physiology; D021962:Membrane Microdomains / Q000378:metabolism; D009538:Nicotine / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D022142:Secretory Vesicles / Q000378:metabolism*; D001616:beta-Galactosidase / Q000378:metabolism
D000199:Actins; D017306:Annexin A2; D002395:Catecholamines; D009538:Nicotine; D001616:beta-Galactosidase