title: A new family of Cdc42 effector proteins, CEPs, function in fibroblast and epithelial cell shape changes.
abstract: Cdc42, a Rho GTPase, regulates the organization of the actin cytoskeleton by its interaction with several distinct families of downstream effector proteins. Here, we report the identification of four new Cdc42-binding proteins that, along with MSE55, constitute a new family of effector proteins. These molecules, designated CEPs, contain three regions of homology, including a Cdc42 binding domain and two unique domains called CI and CII. Experimentally, we have verified that CEP2 and CEP5 bind Cdc42. Expression of CEP2, CEP3, CEP4, and CEP5 in NIH-3T3 fibroblasts induced pseudopodia formation. Fibroblasts coexpressing dominant negative Cdc42 with CEP2 or expressing a Cdc42/Rac interactive binding domain mutant of CEP2 did not induce pseudopodia formation. In primary keratinocytes, CEP2- and CEP5-expressing cells showed reduced F-actin localization at the adherens junctions with an increase in thin stress fibers that extended the length of the cell body. Keratinocytes expressing CEPs also showed an altered vinculin distribution and a loss of E-cadherin from adherens junctions. Similar effects were observed in keratinocytes expressing constitutively active Cdc42, but were not seen with a Cdc42/Rac interactive binding domain mutant of CEP2. These results suggest that CEPs act downstream of Cdc42 to induce actin filament assembly leading to cell shape changes.
authors.affiliation: Department of Oncology, Lombardi Cancer Center, Georgetown University Medical Center, Washington, DC 20007, USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Hirsch
authors.forename: D M
authors.initials: DM
authors.lastname: Pirone
authors.forename: P D
authors.initials: PD
authors.lastname: Burbelo
mesh_terms: D016475:3T3 Cells; D000199:Actins / Q000502:physiology / Q000648:ultrastructure; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015820:Cadherins / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D048429:Cell Size; D003001:Cloning, Molecular; D016384:Consensus Sequence; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology* / Q000502:physiology; D005347:Fibroblasts / Q000166:cytology* / Q000502:physiology; D020549:GTP Phosphohydrolase Activators; D020558:GTP Phosphohydrolases; D020555:GTP-Binding Protein Regulators; D006801:Humans; D018386:Kinetochores; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D020741:rho GTP-Binding Proteins
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; C422984:CDC42EP2 protein, human; C484093:CDC42EP3 protein, human; C422985:CDC42EP4 protein, human; C484094:CDC42EP5 protein, human; C000601180:Cep250 protein, mouse; C092348:CEP3 protein, S cerevisiae; D015820:Cadherins; D002352:Carrier Proteins; C484092:Cdc42ep5 protein, mouse; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D020549:GTP Phosphohydrolase Activators; D020555:GTP-Binding Protein Regulators; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D029701:Saccharomyces cerevisiae Proteins; C075598:CDC42EP1 protein, human; D020558:GTP Phosphohydrolases; D020764:cdc42 GTP-Binding Protein; D020741:rho GTP-Binding Proteins