Alternatively spliced EDA segment regulates fibronectin-dependent cell cycle progression and mitogenic signal transduction

Fibronectin (FN) is comprised of multiple isoforms arising from alternative splicing of a single gene transcript. One of the alternatively spliced seg ments, EDA, is expressed prominently in embryonic development, malignant tr ansformation, and wound healing. We showed previously that EDA(+) FN was mo re potent than EDA(-) FN in promoting cell spreading and cell migration bec ause of its enhanced binding affinity to integrin alpha 5 beta 1 (Manabe, R ., Oh-e, N., Maeda, T., Fukuda, T., and Sekiguchi, K. (1997) J. Cell Biol. 139, 295-307). In this study, we compared the cell cycle progression and it s associated signal transduction events induced by FN isoforms with or with out the EDA segment to examine whether the EDA segment modulates the cell p roliferative potential of FN. We found that EDA(+) FN was more potent than EDA- FN in inducing G(1)-S phase transition. Inclusion of the EDA segment p otentiated the ability of FN to induce expression of cyclin D1, hyperphosph orylation of pRb, and activation of mitogen-activated protein kinase extrac ellular signal regulated kinase 2 (ERK2). EDA(+) FN was also more potent th an EDA(-) FN in promoting FN-mediated tyrosine phosphorylation of p130(Cas) , but not focal adhesion kinase, which occurred in parallel with the activa tion of ERK2, suggesting that p130(Cas) may be involved in activation of ER K2, These results indicated that alternative splicing at the EDA region is a novel mechanism that promotes FN-induced cell cycle progression through u p-regulation of integrin-mediated mitogenic signal transduction.