title: Involvement of the paxillin pathway in JB6 Cl41 cell transformation.
abstract: Paxillin is a substrate of the Src tyrosine onco-kinase and is involved in cell transformation, cell spreading, migration, and cancer development mediated through the mitogen-activated protein kinase signaling cascades. Here, we showed that paxillin plays a key role in skin cell transformation induced by epidermal growth factor (EGF) or 12-O-tetradecanoylphorbol-13-acetate (TPA). To investigate the mechanism of paxillin's role in cell transformation, we established a paxillin knockdown stably transfected cell line by introducing small interfering RNA-paxillin (si-paxillin). The si-paxillin cells displayed a dramatic suppression of cell proliferation and anchorage-independent cell transformation induced by EGF or TPA compared with si-mock control cells. In si-paxillin cells, decreased activator protein-1 (AP-1)-dependent luciferase activity corresponded with suppressed AP-1 DNA binding activity. Importantly, knockdown of paxillin inhibited EGF- or TPA-induced c-Jun phosphorylation at Ser(63) and Ser(73). Furthermore, total c-Jun protein level was dramatically decreased in si-paxillin cells and was dependent on serum deprivation time. The down-regulation of c-Jun was restored in si-paxillin cells by treatment with the proteasome inhibitor lactacystin but not by the lysosome inhibitor leupeptin. These results clearly provided evidence that paxillin regulates c-Jun protein level and plays a key role in cell transformation most likely through the regulation of c-Jun stability.
authors.affiliation: Hormel Institute, University of Minnesota, Austin, Minnesota.
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Tatsumi
authors.forename: Yong-Yeon
authors.initials: YY
authors.lastname: Cho
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: He
authors.forename: Hideya
authors.initials: H
authors.lastname: Mizuno
authors.forename: Hong
authors.initials: H
authors.lastname: Seok Choi
authors.forename: Ann M
authors.initials: AM
authors.lastname: Bode
authors.forename: Zigang
authors.initials: Z
authors.lastname: Dong
mesh_terms: D000818:Animals; D001483:Base Sequence; D048708:Cell Growth Processes / Q000502:physiology; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D004815:Epidermal Growth Factor; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D051419:Paxillin / Q000096:biosynthesis / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D012694:Serine / Q000378:metabolism; D012867:Skin / Q000187:drug effects / Q000378:metabolism; D012878:Skin Neoplasms / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D013755:Tetradecanoylphorbol Acetate; D014162:Transfection
chemical_list: D051419:Paxillin; D016755:Proto-Oncogene Proteins c-jun; D034741:RNA, Small Interfering; D012694:Serine; D004815:Epidermal Growth Factor; D048670:MAP Kinase Kinase 4; D013755:Tetradecanoylphorbol Acetate