A chymotrypsin-sensitive step in the development of Dictyostelium discoideum

Abstract

THE cellular slime mould, Dictyostelium discoideum, is an ideal organism with which to study the changes in cell behaviour resulting from the formation of cell–cell contacts (ref. 1 and for review, ref. 2). The role of adhesive interactions in the development of this organism is understood in outline and much is known about the nature and developmental kinetics of the macromolecules thought to be involved in establishing stable cell–cell contacts during aggregation³. There is now good evidence that the formation and maintenance of contact between amoebae is necessary for the synthesis of several developmentally regulated enzymes⁴ and several polypeptides characteristic of post-aggregation cells⁵. Clearly, it is important to understand the molecular mechanisms involved in cell–cell interactions, as they not only make multicellular aggregates structurally coherent, but also induce the synthesis of developmental gene products. In our attempts to identify the cell surface structures responsible for adhesion and developmental triggering, we have allowed starving amoebae to develop in the presence of proteolytic enzymes that might modify accessible cell surface proteins. We report here that in the presence of α-chymotrypsin amoebae are able to undergo normal aggregation and cell–cell adhesion but are unable to differentiate into stalks or spores.