Jnk-mediated regulation of adherens junctions and lentiviral infection
Lee, Meng Horng
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Cell-cell adhesion is dynamically regulated under different biological circumstances such as the establishment of epithelial cell polarity, wound healing, cell scattering and tumorigenesis. However, the mechanism of adherens junction regulation is not completely understood. The current work led to the discovery that c-Jun N-terminal kinase (JNK) is associated with adherens junctions and regulates cell-cell adhesion. Specifically, we indentified that JNK phosphorylated β-catenin at serine 33/37 and threonine 41. Blocking JNK led to the release of a-catenin from the adherens junction complex and promoted translocation of E-cadherin and β-catenin to the cell-cell contact sites and formation of compact colonies. In addition, the domains of a-catenin that are necessary for these interactions have been identified by expressing several a-catenin mutants in epithelial cells lacking a-catenin and monitoring adherens junction formation using confocal microscopy. These results suggest that JNK acts as a switch that regulates adherens junctions by controlling binding of alpha-catenin to beta-catenin. These finding may have wide implications in understanding the process of cell-cell communication, formation of epithelial tissues and cancer metastasis. Recombinant lentivirus is widely used as a gene transfer vehicle for gene therapy and tissue engineering due to high transduction efficiency and its ability to infect non-dividing cells and stem cells in vitro and in vivo. However, the interactions between lentivirus and the target cells during transduction process are only partially understood. Here we show that transduction with recombinant lentivirus activated the c-jun-N-terminal kinase (JNK) pathway by phosphorylating JNK in primary epidermal cells and several epithelial cell lines. Blocking JNK phosphorylation with chemical inhibitors and siRNA decreased gene transfer in a dose dependent manner. Similar results were observed with actively growing as well as non-proliferating cells indicating that JNK may affect gene transfer independent of cell cycle status of target cells. In addition, we found that inhibition of JNK affected early events in the gene transfer process. Specifically, activation of JNK was necessary of internalization of viral particles in the cell cytoplasm as evidenced by measurements of internalized viral proteins using western blots. Immunostaining results further indicated that JNK affected viral internalization may through regulating filopodia formation of the target cells. These results suggest activation of JNK may be necessary for lentivirus to gain entry into the target cells.