title: Actopaxin interacts with TESK1 to regulate cell spreading on fibronectin.
abstract: The focal adhesion protein actopaxin contributes to integrin-actin associations and is involved in cell adhesion, spreading, and motility. Herein, we identify and characterize an association between actopaxin and the serine/threonine kinase testicular protein kinase 1 (TESK1), a ubiquitously expressed protein previously reported to regulate cellular spreading and focal adhesion formation via phosphorylation of cofilin. The interaction between actopaxin and TESK1 is direct and the binding sites were mapped to the carboxyl terminus of both proteins. The association between actopaxin and TESK1 is negatively regulated by adhesion to fibronectin, and a phosphomimetic actopaxin mutant that promotes cell spreading also exhibits impaired binding to TESK1. Binding of actopaxin to TESK1 inhibits TESK1 kinase activity in vitro. Expression of the carboxyl terminus of actopaxin has previously been reported to retard cell spreading. This effect was reversed following overexpression of TESK1 and was found to be dependent on an inability of actopaxin carboxyl terminus expressing cells to promote cofilin phosphorylation upon matrix adhesion and caused by retention of TESK1 by this actopaxin mutant. Thus, the association between actopaxin and TESK1, which is likely regulated by phosphorylation of actopaxin, regulates TESK1 activity and subsequent cellular spreading on fibronectin.
authors.affiliation: Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, New York 13210, USA.
authors.forename: David P
authors.initials: DP
authors.lastname: LaLonde
authors.forename: Michael C
authors.initials: MC
authors.lastname: Brown
authors.forename: Brian P
authors.initials: BP
authors.lastname: Bouverat
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Turner
mesh_terms: D051339:Actin Depolymerizing Factors; D000185:Actinin; D002448:Cell Adhesion; D002460:Cell Line; D002465:Cell Movement; D017931:DNA Primers / Q000737:chemistry; D005353:Fibronectins / Q000737:chemistry* / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009154:Mutation; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D014162:Transfection; D020798:Two-Hybrid System Techniques; D001616:beta-Galactosidase / Q000378:metabolism; D000096985:Calponins
chemical_list: D051339:Actin Depolymerizing Factors; D000185:Actinin; D017931:DNA Primers; D005353:Fibronectins; D005982:Glutathione Transferase; D049452:Green Fluorescent Proteins; D008840:Microfilament Proteins; D017346:Protein Serine-Threonine Kinases; D001616:beta-Galactosidase; C486590:PARVA protein, human; D000096985:Calponins; C097507:testis-specific protein kinase 1