title: Actopaxin (α-parvin) phosphorylation is required for matrix degradation and cancer cell invasion.
abstract: Dysregulation of cell adhesion and motility is known to be an important factor in the development of tumor malignancy. Actopaxin (α-parvin) is a paxillin, integrin-linked kinase, and F-actin binding focal adhesion protein with several serine phosphorylation sites in the amino terminus that contribute to the regulation of cell spreading and migration. Here, phosphorylation of actopaxin is shown to contribute to the regulation of matrix degradation and cell invasion. Osteosarcoma cells stably expressing wild type (WT), nonphosphorylatable (Quint), and phosphomimetic (S4D/S8D) actopaxin demonstrate that actopaxin phosphorylation is necessary for efficient Src and matrix metalloproteinase-driven degradation of extracellular matrix. Rac1 was found to be required for actopaxin-induced matrix degradation whereas inhibition of myosin contractility promoted degradation in the phosphomutant-expressing Quint cells, indicating that a balance of Rho GTPase signaling and regulation of cellular tension are important for the process. Furthermore, actopaxin forms a complex with the Rac1/Cdc42 GEF β-PIX and Rac1/Cdc42 effector PAK1, to regulate actopaxin-dependent matrix degradation. Actopaxin phosphorylation is elevated in the invasive breast cancer cell line MDA-MB-231 compared with normal breast epithelial MCF10A cells. Expression of the nonphosphorylatable Quint actopaxin in MDA-MB-231 cells inhibits cell invasion whereas overexpression of WT actopaxin promotes invasion in MCF10A cells. Taken together, this study demonstrates a new role for actopaxin phosphorylation in matrix degradation and cell invasion via regulation of Rho GTPase signaling.
authors.affiliation: Department of Cell and Developmental Biology, State University of New York, Upstate Medical University, Syracuse, New York 13210, USA.
authors.forename: Jeanine
authors.initials: J
authors.lastname: Pignatelli
authors.forename: Sara E
authors.initials: SE
authors.lastname: LaLonde
authors.forename: David P
authors.initials: DP
authors.lastname: LaLonde
authors.forename: Dominic
authors.initials: D
authors.lastname: Clarke
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Turner
mesh_terms: D045744:Cell Line, Tumor; D002465:Cell Movement; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005109:Extracellular Matrix / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006801:Humans; D053505:Matrix Metalloproteinases, Secreted / Q000037:antagonists & inhibitors / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism*; D009218:Myosins / Q000378:metabolism; D009361:Neoplasm Invasiveness; D009369:Neoplasms / Q000201:enzymology / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D059748:Proteolysis; D064067:Rho Guanine Nucleotide Exchange Factors; D054462:p21-Activated Kinases / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000096985:Calponins
chemical_list: D004791:Enzyme Inhibitors; D020662:Guanine Nucleotide Exchange Factors; D053505:Matrix Metalloproteinases, Secreted; D008840:Microfilament Proteins; D009218:Myosins; D064067:Rho Guanine Nucleotide Exchange Factors; D054462:p21-Activated Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein; D019061:src-Family Kinases; C576606:ARHGEF7 protein, human; C486590:PARVA protein, human; D000096985:Calponins; C107953:RAC1 protein, human