title: Palladin binds to Eps8 and enhances the formation of dorsal ruffles and podosomes in vascular smooth muscle cells.
abstract: Palladin is a widely expressed phosphoprotein that plays an important role in organizing the actin cytoskeleton. Palladin is concentrated in multiple actin-based structures involved in cell motility and adhesion, including stress fibers, focal adhesions, cell-cell junctions, growth cones and Z-discs. Here, we show that palladin also localizes to the dorsal, circular ruffles that form transiently in response to growth factor stimulation. More importantly, palladin knockdown results in decreased ruffle formation and decreased Rac activation following PDGF treatment. In addition, we describe a novel interaction between palladin and Eps8, a receptor tyrosine kinase (RTK) substrate that participates in the activation of the Rac-specific guanine nucleotide-exchange function of Sos-1. Eps8 was identified as a molecular partner for palladin in a yeast two-hybrid screen, and the interaction was confirmed biochemically in co-immunoprecipitation assays. The two proteins were found to colocalize extensively in dorsal ruffles. Palladin also localizes to podosomes after phorbol ester stimulation, and palladin knockdown results in decreased podosome formation in response to PDBu. Together, these data provide strong evidence for a direct and specific interaction between palladin and Eps8, and suggest that they act together in the rapid and transient remodeling of the actin cytoskeleton, which promotes the formation of highly dynamic membrane protrusions in response to PDGF and phorbol ester treatment.
authors.affiliation: Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, NC, USA.
authors.forename: Silvia
authors.initials: S
authors.lastname: Goicoechea
authors.forename: Daniel
authors.initials: D
authors.lastname: Arneman
authors.forename: Andrea
authors.initials: A
authors.lastname: Disanza
authors.forename: Rafael
authors.initials: R
authors.lastname: Garcia-Mata
authors.forename: Giorgio
authors.initials: G
authors.lastname: Scita
authors.forename: Carol A
authors.initials: CA
authors.lastname: Otey
mesh_terms: D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000502:physiology; D000818:Animals; D022081:Cell Surface Extensions / Q000502:physiology* / Q000648:ultrastructure; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D003599:Cytoskeleton / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D010703:Phorbol Esters / Q000494:pharmacology; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D020837:SOS1 Protein / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D020798:Two-Hybrid System Techniques; D020744:rac GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; C489989:EPS8 protein, human; C083430:Eps8 protein, mouse; C498142:Eps8 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; C485874:LOC103693936; C412722:PALLD protein, human; D010703:Phorbol Esters; D010750:Phosphoproteins; D010982:Platelet-Derived Growth Factor; D011506:Proteins; D020837:SOS1 Protein; C485873:palladin protein, mouse; D020744:rac GTP-Binding Proteins