title: B-50/GAP-43-induced formation of filopodia depends on Rho-GTPase.
abstract: In the present study we show that expression of the neural PKC-substrate B-50 (growth-associated protein [GAP-43]) in Rat-1 fibroblasts induced the formation of filopodial extensions during spreading. This morphological change was accompanied by an enhanced formation of peripheral actin filaments and by accumulation of vinculin immunoreactivity in filopodial focal adhesions, colocalizing with B-50. In time lapse experiments, the B-50-induced filopodial extensions were shown to stay in close contact with the substratum and appeared remarkably stable, resulting in a delayed lamellar spreading of the fibroblasts. The morphogenetic effects of the B-50 protein were entirely dependent on the integrity of the two N-terminal cysteines involved in membrane association (C3C4), but were not significantly affected by mutations of the PKC-phosphorylation site (S41) or deletion of the C terminus (177-226). Cotransfection of B-50 with dominant negative Cdc42 or Rac did not prevent B-50-induced formation of filopodial cells, whereas this process could be completely blocked by cotransfection with dominant negative Rho or Clostridium botulinum C3-transferase. Conversely, constitutively active Rho induced a similar filopodial phenotype as B-50. We therefore propose that the induction of surface extensions by B-50 in spreading Rat-1 fibroblasts depends on Rho-guanosine triphosphatase function.
authors.affiliation: Department of Physiological Chemistry, Utrecht University, 3584 CG, Utrecht, The Netherlands.
authors.forename: L H
authors.initials: LH
authors.lastname: Aarts
authors.forename: L H
authors.initials: LH
authors.lastname: Schrama
authors.forename: W J
authors.initials: WJ
authors.lastname: Hage
authors.forename: J L
authors.initials: JL
authors.lastname: Bos
authors.forename: W H
authors.initials: WH
authors.lastname: Gispen
authors.forename: P
authors.initials: P
authors.lastname: Schotman
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002465:Cell Movement; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism; D019922:GAP-43 Protein / Q000235:genetics / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D009024:Morphogenesis; D016296:Mutagenesis; D015388:Organelles / Q000378:metabolism*; D010641:Phenotype; D051381:Rats; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins
chemical_list: D018797:Cell Cycle Proteins; D019922:GAP-43 Protein; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins