Protease activity during cell differentiation of the cellular slime mold Dictyostelium discoideum

Abstract

Individual aggregates, migrating pseudoplasmodia and sorocarps of D. discoideum were assayed for proteolytic activities by colorimetric and fluorometric techniques. Cathepsin D-like and cathepsin B-like acid protease activities were found to decrease thoughout development, but the patterns of decrease were different for the 2 enzymes. A gradual decrease was found for cathepsin D; a sharp decrease between aggregates and migrating pseudoplasmodia was detected for cathepsin B. By using microdissection techniques and fluorometric assays for amino acids and peptides, prestalk cells and prespore cells exhibited no difference in cathepsin D activity; cathepsin B activity was higher in the prestalk cells. Stalk cells and spores in the sorocarps showed no difference in cathepsin D activity, but showed a 5-fold higher cathepsin B activity in the stalk cells. A possible role for cathepsin B in stalk cell differentiation was suggested.