Regulated exocytosis in neuroendocrine cells: a role for subplasmalemmal Cdc42/N-WASP-induced actin filaments.
In neuroendocrine cells, actin reorganization is a prerequisite for regulated exocytosis. Small GTPases, Rho proteins, represent potential candidates coupling actin dynamics to membrane trafficking events. We previously reported that Cdc42 plays an active role in regulated exocytosis in chromaffin cells. The aim of the present work was to dissect the molecular effector pathway integrating Cdc42 to the actin architecture required for the secretory reaction in neuroendocrine cells. Using PC12 cells as a secretory model, we show that Cdc42 is activated at the plasma membrane during exocytosis. Expression of the constitutively active Cdc42(L61) mutant increases the secretory response, recruits neural Wiskott-Aldrich syndrome protein (N-WASP), and enhances actin polymerization in the subplasmalemmal region. Moreover, expression of N-WASP stimulates secretion by a mechanism dependent on its ability to induce actin polymerization at the cell periphery. Finally, we observed that actin-related protein-2/3 (Arp2/3) is associated with secretory granules and that it accompanies granules to the docking sites at the plasma membrane upon cell activation. Our results demonstrate for the first time that secretagogue-evoked stimulation induces the sequential ordering of Cdc42, N-WASP, and Arp2/3 at the interface between granules and the plasma membrane, thereby providing an actin structure that makes the exocytotic machinery more efficient.
Gasman
Stéphane
S
Centre National de la Recherche Scientifique Unité Propre de Recherche 2356, Institut Fédératif de Recherche 37, 67084 Strasbourg, France. gasman@neurochem.u-strasbg.fr
Chasserot-Golaz
Sylvette
S
Malacombe
Magali
M
Way
Michael
M
Bader
Marie-France
MF
D008841:Actin Cytoskeleton / Q000378:metabolism*; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000818:Animals; D002451:Cell Compartmentation / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D005089:Exocytosis / Q000502:physiology*; D013006:Growth Hormone / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D016716:PC12 Cells; D051381:Rats; D022142:Secretory Vesicles / Q000378:metabolism; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*
D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D003598:Cytoskeletal Proteins; D009419:Nerve Tissue Proteins; C495770:Wasl protein, rat; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D013006:Growth Hormone; D020764:cdc42 GTP-Binding Protein