Laminin-10/11 and fibronectin differentially prevent apoptosis induced by serum removal via phosphatidylinositol 3-kinase/Akt- and MEK1/ERK-dependent pathways

Cell adhesion to the extracellular matrix inhibits apoptosis, but the molecular mechanisms underlying the signals transduced by different matrix components are not well understood. Here, we examined integrin-mediated antiapoptotic signals from laminin-10/11 in comparison with those from fibronectin, the best characterized extracellular adhesive ligand. We found that the activation of protein kinase B/Akt in cells adhering to laminin-10/11 can rescue cell apoptosis induced by serum removal. Consistent with this, wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase, or ectopic expression of a dominant-negative mutant of Akt selectively accelerated cell death upon serum removal. In contrast to laminin-10/11, fibronectin rescued cells from serum depletion-induced apoptosis mainly through the extracellular signal-regulated kinase pathway. Cell survival on fibronectin but not laminin was significantly reduced by treatment with PD98059, a specific inhibitor of mitogen- or extracellular signal-regulated kinase kinase-1 (MEK1) and by expression of a dominant-negative mutant of MEK1. Laminin-10/11 was more potent than fibronectin in preventing apoptosis induced by serum depletion. These results, taken together, demonstrate laminin-10/11 potency as a survival factor and demonstrate that different extracellular matrix components can transduce distinct survival signals through preferential activation of subsets of multiple integrin-mediated signaling pathways.