title: Actin depolymerization-induced tyrosine phosphorylation of cortactin: the role of Fer kinase.
abstract: The F-actin-binding protein cortactin is an important regulator of cytoskeletal dynamics, and a prominent target of various tyrosine kinases. Tyrosine phosphorylation of cortactin has been suggested to reduce its F-actin cross-linking capability. In the present study, we investigated whether a reciprocal relationship exists, i.e. whether the polymerization state of actin impacts on the cortactin tyrosine phosphorylation. Actin depolymerization by LB (latrunculin B) induced robust phosphorylation of C-terminal tyrosine residues of cortactin. In contrast, F-actin stabilization by jasplakinolide, which redistributed cortactin to F-actin-containing patches, prevented cortactin phosphorylation triggered by hypertonic stress or LB. Using cell lines deficient in candidate tyrosine kinases, we found that the F-actin depolymerization-induced cortactin phosphorylation was mediated by the Fyn/Fer kinase pathway, independent of Src and c-Abl. LB caused modest Fer activation and strongly facilitated the association between Fer and cortactin. Interestingly, the F-actin-binding region within the cortactin N-terminus was essential for the efficient phosphorylation of C-terminal tyrosine residues. Investigating the structural requirements for the Fer-cortactin association, we found that (i) phosphorylation-incompetent cortactin still bound to Fer; (ii) the isolated N-terminus associated with Fer; and (iii) the C-terminus alone was insufficient for binding. Thus the cortactin N-terminus participates in the Fer-cortactin interaction, which cannot be fully due to the binding of the Fer Src homology 2 domain to C-terminal tyrosine residues of cortactin. Taken together, F-actin stabilization prevents cortactin tyrosine phosphorylation, whereas depolymerization promotes it. Depolymerization-induced phosphorylation is mediated by Fer, and requires the actin-binding domain of cortactin. These results define a novel F-actin-dependent pathway that may serve as a feedback mechanism during cytoskeleton remodelling.
authors.affiliation: Department of Surgery, The Toronto General Hospital and University Health Network, 200 Elizabeth Street, Toronto, ON, Canada M5G 2C4.
authors.forename: Lingzhi
authors.initials: L
authors.lastname: Fan
authors.forename: Caterina
authors.initials: C
authors.lastname: Di Ciano-Oliveira
authors.forename: Scott A
authors.initials: SA
authors.lastname: Weed
authors.forename: Andrew W B
authors.initials: AW
authors.lastname: Craig
authors.forename: Peter A
authors.initials: PA
authors.lastname: Greer
authors.forename: Ori D
authors.initials: OD
authors.lastname: Rotstein
authors.forename: András
authors.initials: A
authors.lastname: Kapus
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D016466:CHO Cells; D051356:Cortactin; D006224:Cricetinae; D004789:Enzyme Activation / Q000187:drug effects; D008840:Microfilament Proteins / Q000378:metabolism*; D009997:Osmotic Pressure; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine; D011108:Polymers / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D051076:Proto-Oncogene Proteins c-fyn; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D014162:Transfection / Q000379:methods; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D051356:Cortactin; D008840:Microfilament Proteins; D010455:Peptides; D011108:Polymers; D011518:Proto-Oncogene Proteins; D013844:Thiazoles; D053778:Thiazolidines; C052602:proto-oncogene protein c-fes-fps; D019000:Phosphotyrosine; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051076:Proto-Oncogene Proteins c-fyn; C037068:latrunculin B