pr-39 and Cell-Transformation--Neoplastic

PR-39, which is an endogenous antimicrobial peptide, can bind to Src homology 3 domains of the NADPH complex protein p47(phox) and the signaling adapter protein p130(Cas). Recently, we have reported that PR-39 gene transduction altered invasive activity and actin structure of human hepatocellular carcinoma cells, suggesting that this peptide affects cellular signaling due to its proline-rich motif. In order to clarify the mechanism of the PR-39 functions, we transfected the PR-39 gene into mouse NIH3T3 cells which had already been transformed with human activated k-ras gene. The PR-39 gene transfectant showed a reorganization of actin structure and suppression of cell proliferation both in vitro and in vivo. Decreases of MAP (mitogen-activated protein) kinase activity, cyclin D1 expression and JNK activity were observed in the PR-39 gene transfectant. Co-immunoprecipitation analysis revealed that PR-39 binds to PI3-kinase p85alpha, which is a regulatory subunit of PI3-kinase and one of the effectors by which ras induces cytoskeletal changes and stimulates mitogenesis. The PI3-kinase activity of the PR-39 gene transfectant was decreased compared with that of the ras transformant. These results suggest that PR-39 alters actin structure and cell proliferation rate by binding to PI3-kinase p85alpha and suppressing the PI3-kinase activity.

Topics: 3T3 Cells; Actin Cytoskeleton; Amino Acid Motifs; Animals; Antimicrobial Cationic Peptides; Cell Division; Cell Line, Transformed; Cell Transformation, Neoplastic; Cyclin D1; Cytoskeleton; Enzyme Induction; Genes, ras; Humans; JNK Mitogen-Activated Protein Kinases; MAP Kinase Signaling System; Mice; Mitogen-Activated Protein Kinases; Neoplasm Proteins; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Protein Binding; Protein Interaction Mapping; Recombinant Fusion Proteins; src Homology Domains; Swine; Transfection