Extracellular protease production by Drosophila imaginal discs.

We are investigating the role of extracellular proteases in imaginal disc eversion to understand the mechanism that controls cell rearrangements within epithelia. We have identified three cation-dependent neutral proteases released by Drosophila leg discs everting in culture. Serine protease inhibitors block disc eversion and inhibit activity of disc proteases. The pattern of extracellular proteases changes when eversion is blocked with added protease inhibitors. Changes in protease activity occur when released disc proteases are treated with trypsin. Trypsin treatment of intact imaginal discs releases protease and inhibitor activities to the medium, indicating their presence on the cell surface before release. Our results suggest that extracellular proteases are required for imaginal disc morphogenesis and are regulated by more than one mechanism.