Extracellular serine proteases are required in several signal transduction systems in order to generate extracellular ligands. These include some relatively well characterized systems involving EGF, TGF-a, CSF-1, and KL-1. The proteases involved in these systems, however, have not been extensively characterized. A newly described signal transduction system is one which specifies the dorsal- ventral axis during the embryonic development of Drosophila melanogaster. The available data suggest that at least three serine proteases are required in this signaling pathway. This investigator is interested in elucidating the role of these proteases and understanding how their activities are regulated. These serine proteases are encoded by the maternal effect genes snake, easter, and gastrulation defective. These proteases are secreted into an extracellular compartment called the perivitelline space as inactive proenzymes (zymogens). Activation of the zymogens involves a protease cascade and the end product of the cascade is proteolytic cleavage of the spaetzle protein into a ligand for the Toll receptor. This investigator has developed a method of producing biologically active recombinant proteases; he has set up several in vivo and in vitro assays for the activities of these enzymes. The biochemical interactions of these components are fundamental to the mechanism by which a signal is produced in the perivitelline space.
