title: Osmotic stress-induced remodeling of the cortical cytoskeleton.
abstract: Osmotic stress is known to affect the cytoskeleton; however, this adaptive response has remained poorly characterized, and the underlying signaling pathways are unexplored. Here we show that hypertonicity induces submembranous de novo F-actin assembly concomitant with the peripheral translocation and colocalization of cortactin and the actin-related protein 2/3 (Arp2/3) complex, which are key components of the actin nucleation machinery. Additionally, hyperosmolarity promotes the association of cortactin with Arp2/3 as revealed by coimmunoprecipitation. Using various truncation or phosphorylation-incompetent mutants, we show that cortactin translocation requires the Arp2/3- or the F-actin binding domain, but the process is independent of the shrinkage-induced tyrosine phosphorylation of cortactin. Looking for an alternative signaling mechanism, we found that hypertonicity stimulates Rac and Cdc42. This appears to be a key event in the osmotically triggered cytoskeletal reorganization, because 1) constitutively active small GTPases translocate cortactin, 2) Rac and cortactin colocalize at the periphery of hypertonically challenged cells, and 3) dominant-negative Rac and Cdc42 inhibit the hypertonicity-provoked cortactin and Arp3 translocation. The Rho family-dependent cytoskeleton remodeling may be an important osmoprotective response that reinforces the cell cortex.
authors.affiliation: Department of Surgery, Toronto General Hospital, University Health Network and University of Toronto, Ontario, Canada.
authors.forename: Caterina
authors.initials: C
authors.lastname: Di Ciano
authors.forename: Zilin
authors.initials: Z
authors.lastname: Nie
authors.forename: Katalin
authors.initials: K
authors.lastname: Szászi
authors.forename: Alison
authors.initials: A
authors.lastname: Lewis
authors.forename: Takehito
authors.initials: T
authors.lastname: Uruno
authors.forename: Xi
authors.initials: X
authors.lastname: Zhan
authors.forename: Ori D
authors.initials: OD
authors.lastname: Rotstein
authors.forename: Alan
authors.initials: A
authors.lastname: Mak
authors.forename: András
authors.initials: A
authors.lastname: Kapus
mesh_terms: D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000378:metabolism; D000222:Adaptation, Physiological / Q000187:drug effects; D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D051356:Cortactin; D006224:Cricetinae; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D020536:Enzyme Activators / Q000494:pharmacology; D006982:Hypertonic Solutions / Q000494:pharmacology; D018374:LLC-PK1 Cells; D046911:Macromolecular Substances; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D009997:Osmotic Pressure; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013552:Swine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism
chemical_list: D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; D051356:Cortactin; C495870:Cttn protein, rat; D003598:Cytoskeletal Proteins; D020536:Enzyme Activators; D006982:Hypertonic Solutions; D046911:Macromolecular Substances; D008840:Microfilament Proteins; D011993:Recombinant Fusion Proteins; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate