PLASMINOGEN ACTIVATORS AND THEIR INTERACTION WITH THE EXTRACELLULAR-MATRIX IN NEURAL DEVELOPMENT, PLASTICITY AND REGENERATION

Plasminogen activators are extracellular serine proteases which are ac tively secreted by developing and regenerating neurons. These molecule s, as discussed in this review, have been implicated in cell migration , axonal growth, growth factor activation, and synaptic remodeling ass ociated with learning. Secreted plasminogen activators not only bind t o their specific cell surface receptors, where they retain full proteo lytic activity, but they also associate with extracellular matrix mole cules including fibronectin and laminin. Plasminogen activator associa tion with specific matrix proteins may target these proteins for degra dation, altering the matrix composition and leading to intracellular s ignaling and influencing cell differentiation. The secreted plasminoge n activator can bring about the degradation of matrix molecules either directly, or indirectly via the formation of plasmin.