title: Downregulated AP-1 activity is associated with inhibition of Protein-Kinase-C-dependent CD44 and ezrin localisation and upregulation of PKC theta in A431 cells.
abstract: Progression to an invasive, metastatic tumour requires the coordinated expression and function of a number of gene products, as well as their regulation in the context of invasion. The transcription factor AP-1 regulates expression of many of those genes necessary for implementation of the invasion programme. Two such gene products, CD44 and ezrin, are both upregulated in fibroblasts transformed by v-fos and are commonly implicated in cell motility and invasion. Here we report that CD44 and ezrin colocalise to membrane ruffles and microvilli of A431 cells after treatment with EGF. However, A431 cells expressing dominant-negative c-Jun (TAM67), and which as a consequence fail to invade in response to EGF, also fail to correctly localise CD44 and ezrin. CD44 and ezrin are both substrates for Protein Kinase C, and we show that their EGF-dependent colocalisation requires Protein Kinase C activity. Associated with TAM67 expression and disrupted CD44 and ezrin colocalisation is the increased expression and activation of the novel PKC theta isoform. Expression of PKC theta in A431 cells results in the inhibition of cell motility and disrupted localisation of CD44 and ezrin. We propose that AP-1 regulates the integrity of Protein Kinase C signalling and identifies PKC theta as a potential suppressor of the invasion programme.
authors.affiliation: Cancer Research UK Beatson Laboratories, Garscube Estate, Switchback Road, Glasgow, G61 1BD Scotland. g.stapleton@beatson.gla.ac.uk
authors.forename: Genevieve
authors.initials: G
authors.lastname: Stapleton
authors.forename: Angeliki
authors.initials: A
authors.lastname: Malliri
authors.forename: Bradford W
authors.initials: BW
authors.lastname: Ozanne
mesh_terms: D000818:Animals; D002451:Cell Compartmentation / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor; D005455:Fluorescent Antibody Technique; D006801:Humans; D018960:Hyaluronan Receptors / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis; D009369:Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000503:physiopathology; D010641:Phenotype; D010703:Phorbol Esters / Q000494:pharmacology; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D018808:Transcription Factor AP-1 / Q000172:deficiency* / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology*; D000099149:Ezrin
chemical_list: D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; D004815:Epidermal Growth Factor; D018960:Hyaluronan Receptors; D007527:Isoenzymes; D010703:Phorbol Esters; D010750:Phosphoproteins; D020033:Protein Isoforms; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta; D016755:Proto-Oncogene Proteins c-jun; D018808:Transcription Factor AP-1; D000099149:Ezrin; C076233:PRKCQ protein, human