title: Symmetry breaking in spreading RAT2 fibroblasts requires the MAPK/ERK pathway scaffold RACK1 that integrates FAK, p190A-RhoGAP and ERK2 signaling.
abstract: The spreading of adhering cells is a morphogenetic process during which cells break spherical or radial symmetry and adopt migratory polarity with spatially segregated protruding cell front and non-protruding cell rear. The organization and regulation of these symmetry-breaking events, which are both complex and stochastic, are not fully understood. Here we show that in radially spreading cells, symmetry breaking commences with the development of discrete non-protruding regions characterized by large but sparse focal adhesions and long peripheral actin bundles. Establishment of this non-protruding static region specifies the distally oriented protruding cell front and thus determines the polarity axis and the direction of cell migration. The development of non-protruding regions requires ERK2 and the ERK pathway scaffold protein RACK1. RACK1 promotes adhesion-mediated activation of ERK2 that in turn inhibits p190A-RhoGAP signaling by reducing the peripheral localization of p190A-RhoGAP. We propose that sustained ERK signaling at the prospective cell rear induces p190A-RhoGAP depletion from the cell periphery resulting in peripheral actin bundles and cell rear formation. Since cell adhesion activates both ERK and p190A-RhoGAP signaling this constitutes a spatially confined incoherent feed-forward signaling circuit.
authors.affiliation: Institute of Microbiology AS CR, Prague, Czech Republic.
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Klímová
authors.affiliation: Institute of Microbiology AS CR, Prague, Czech Republic.
authors.forename: Vojtěch
authors.initials: V
authors.lastname: Bráborec
authors.affiliation: Institute of Microbiology AS CR, Prague, Czech Republic.
authors.forename: Miloslava
authors.initials: M
authors.lastname: Maninová
authors.affiliation: Institute of Microbiology AS CR, Prague, Czech Republic.
authors.forename: Josef
authors.initials: J
authors.lastname: Čáslavský
authors.affiliation: Department of Microbiology, Immunology, and Cancer Biology, University of Virginia, Charlottesville, VA, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Weber
authors.affiliation: Institute of Microbiology AS CR, Prague, Czech Republic. Electronic address: vomy@biomed.cas.cz.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Vomastek
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002448:Cell Adhesion; D002465:Cell Movement; D048430:Cell Shape; D005347:Fibroblasts / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000172:deficiency / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D020935:MAP Kinase Signaling System; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D008954:Models, Biological; D010641:Phenotype; D051381:Rats; D000075370:Receptors for Activated C Kinase; D012097:Repressor Proteins / Q000378:metabolism*
chemical_list: D000199:Actins; C513040:Arhgap35 protein, rat; C550931:RACK1 protein, rat; D000075370:Receptors for Activated C Kinase; D012097:Repressor Proteins; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D019204:GTP-Binding Proteins
keywords: ERK; FAK; Feed-forward loop; Polarity; RACK1; p190A-RhoGAP