title: Association of the Ste20-like kinase (SLK) with the microtubule. Role in Rac1-mediated regulation of actin dynamics during cell adhesion and spreading.
abstract: Cytoskeletal remodeling events are tightly regulated by signal transduction systems that impinge on adhesion components and modulators of cellular architecture. We have previously shown that the Ste20-like kinase (SLK) can induce apoptosis through the induction of actin disassembly and cellular retraction (Sabourin, L. A., Tamai, K., Seale, P., Wagner, J., and Rudnicki, M. A. (2000) Mol. Cell. Biol. 20, 684-696). Using immunofluorescence studies, we report that SLK is redistributed with adhesion components at large podosome-like adhesion sites in fibronectin-stimulated fibroblasts. However, in vitro kinase assays demonstrate that its activity is not modulated following fibronectin stimulation. Double immunofluorescence studies in exponentially growing or spreading fibroblasts show that SLK is associated with the microtubule network and can be coprecipitated with alpha-tubulin. Furthermore, the stimulation of adhesion site formation by microtubule-disrupting agents induces the relocalization of SLK with unpolymerized alpha-tubulin to large vinculin-containing adhesion complexes. Using microinjection studies, we show that ectopic expression of activated SLK induces the disassembly of actin stress fibers, a process that can be inhibited by dominant negative Rac1. Significantly, endogenous SLK can be colocalized with Rac1 in spreading cells on FN. Finally, the overexpression of SLK by adenoviral infection inhibits cell spreading on fibronectin. These results suggest that SLK is part of a microtubule-associated complex that is targeted to adhesion sites and implicated in the regulation of cytoskeletal dynamics.
authors.affiliation: Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.
authors.forename: Simona
authors.initials: S
authors.lastname: Wagner
authors.forename: Trevor A
authors.initials: TA
authors.lastname: Flood
authors.forename: Paul
authors.initials: P
authors.lastname: O'Reilly
authors.forename: Karri
authors.initials: K
authors.lastname: Hume
authors.forename: Luc A
authors.initials: LA
authors.lastname: Sabourin
mesh_terms: D016475:3T3 Cells; D000199:Actins / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001665:Binding Sites; D002448:Cell Adhesion / Q000502:physiology*; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology; D002478:Cells, Cultured; D004789:Enzyme Activation; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D005353:Fibronectins / Q000494:pharmacology / Q000502:physiology; D051379:Mice; D008870:Microtubules / Q000201:enzymology* / Q000502:physiology; D008954:Models, Biological; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D000099317:Hippo Kinases
chemical_list: D000199:Actins; D005353:Fibronectins; D017346:Protein Serine-Threonine Kinases; D020830:rac1 GTP-Binding Protein; C402650:SLK protein, mouse; D000099317:Hippo Kinases