title: Activation of rho GTPases by cytotoxic necrotizing factor 1 induces macropinocytosis and scavenging activity in epithelial cells.
abstract: Macropinocytosis, a ruffling-driven process that allows the capture of large material, is an essential aspect of normal cell function. It can be either constitutive, as in professional phagocytes where it ends with the digestion of captured material, or induced, as in epithelial cells stimulated by growth factors. In this case, the internalized material recycles back to the cell surface. We herein show that activation of Rho GTPases by a bacterial protein toxin, the Escherichia coli cytotoxic necrotizing factor 1 (CNF1), allowed epithelial cells to engulf and digest apoptotic cells in a manner similar to that of professional phagocytes. In particular, we have demonstrated that 1) the activation of all Rho, Rac, and Cdc42 by CNF1 was essential for the capture and internalization of apoptotic cells; and 2) such activation allowed the discharge of macropinosomal content into Rab7 and lysosomal associated membrane protein-1 acidic lysosomal vesicles where the ingested particles underwent degradation. Taken together, these findings indicate that CNF1-induced "switching on" of Rho GTPases may induce in epithelial cells a scavenging activity, comparable to that exerted by professional phagocytes. The activation of such activity in epithelial cells may be relevant, in mucosal tissues, in supporting or integrating the scavenging activity of resident macrophages.
authors.affiliation: Department of Ultrastructures, Istituto Superiore di Sanità, 00161, Rome, Italy. carla.fiorentini@iss.it
authors.forename: C
authors.initials: C
authors.lastname: Fiorentini
authors.forename: L
authors.initials: L
authors.lastname: Falzano
authors.forename: A
authors.initials: A
authors.lastname: Fabbri
authors.forename: A
authors.initials: A
authors.lastname: Stringaro
authors.forename: M
authors.initials: M
authors.lastname: Logozzi
authors.forename: S
authors.initials: S
authors.lastname: Travaglione
authors.forename: S
authors.initials: S
authors.lastname: Contamin
authors.forename: G
authors.initials: G
authors.lastname: Arancia
authors.forename: W
authors.initials: W
authors.lastname: Malorni
authors.forename: S
authors.initials: S
authors.lastname: Fais
mesh_terms: D017209:Apoptosis; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D002451:Cell Compartmentation; D002478:Cells, Cultured; D003603:Cytotoxins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D011992:Endosomes; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000187:drug effects* / Q000502:physiology; D029968:Escherichia coli Proteins; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000502:physiology; D010873:Pinocytosis / Q000502:physiology*; D014407:Tumor Cells, Cultured; D020298:U937 Cells; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000378:metabolism; D000090802:rab7 GTP-Binding Proteins; D020744:rac GTP-Binding Proteins / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D001427:Bacterial Toxins; D003603:Cytotoxins; D029968:Escherichia coli Proteins; D000090802:rab7 GTP-Binding Proteins; C000716463:rab7 GTP-binding proteins, human; C060296:cytotoxic necrotizing factor type 1; D020764:cdc42 GTP-Binding Protein; D020691:rab GTP-Binding Proteins; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins