title: Involvement of myosin II in dopamine-induced reorganization of the lactotroph cell's actin cytoskeleton.
abstract: We have shown that dopamine (DA), an inhibitor of prolactin secretion from anterior pituitary lactotrophs, stabilizes the cortical actin cytoskeleton. DA-induced cortical actin stabilization is accompanied by cytoplasmic actin cable disassembly and cell rounding up. Our aim was to identify the mechanisms involved in DA-induced stabilization of the lactotroph's actin cytoskeleton. Here we show that DA increased the association of myosin II with the cell cortex, suggesting that DA facilitates actin-myosin interaction to stabilize cortical actin filaments. This notion was supported by the finding that inhibitors of actin-myosin interaction blocked DA-evoked morphological responses. In addition, our results showed that DA-induced myosin association with the cell periphery may be mediated by inhibition of Rac1/Cdc42-dependent pathways, whereas, DA-induced cytoplasmic actin filament disassembly may be mediated by the inhibition of MLCK- and RhoA-dependent pathways. In conclusion, the present results provide evidence that myosin II is involved in the DA-induced remodeling of actin filaments in lactotrophs, and that DA-induced cortical actin filament assembly and stabilization involve the translocation of myosin II to the cell cortex. This effect requires, among other things, inhibition of the Rac1/Cdc42-dependent signaling pathway.
authors.affiliation: Département de Pathologie et Biologie Cellulaire, Faculté de Médecine, Université de Montréal, Montréal, QC, Canada. maria.leiza.vitale@umontreal.ca
authors.forename: María L
authors.initials: ML
authors.lastname: Vitale
authors.forename: M Eloísa
authors.initials: ME
authors.lastname: Carbajal
mesh_terms: D000199:Actins / Q000502:physiology / Q000648:ultrastructure*; D000818:Animals; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000648:ultrastructure*; D004298:Dopamine / Q000378:metabolism* / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D024462:Myosin Type II / Q000502:physiology*; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D020764:cdc42 GTP-Binding Protein / Q000502:physiology; D020830:rac1 GTP-Binding Protein / Q000502:physiology
chemical_list: D000199:Actins; D024462:Myosin Type II; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D004298:Dopamine