PROTEASES IN CELLULAR SLIME-MOLD DEVELOPMENT - EVIDENCE FOR THEIR INVOLVEMENT

Protein degradation appears to be essential for normal differentiation in the cellular slime mold D. discoideum. Several protease inhibitors block normal differentiation, and in most cases this inhibition can be reversed by addition of amino acids. For example, chloroquine, which inhibits slime mold cathepsin B activity, interfered with development by blocking sorocarp formation, and this inhibition was reversed by the addition of amino acids. Tosyllysyl chloromethyl ketone also blocked development, and this inhibition was reversed by simultaneous additions of amino acids and glutathione. Moreover, the addition of antipain and leupeptin delayed sorocarp formation. Since cathepsin B activity is differentially localized in the prestalk-prespore zones of the migrating slugs, proteolysis apparently plays a regulatory role in cellular slime mold differentiation.