The Study On The Function Of Gp150 And Caspase-3 During Dictyostelium Discoideum Cell Differentiation

The social amoeba Dictyostelium discoideum which phagocytes soil bacteria for food is a unicellular eukaryote. When food is plentiful, it multiples by equal mitotic division. Cells are triggered to undergo multicellular development under starvation conditions. The development is similar to mutilcellular embryogenesis regulated strictly by spatial-temporal process. Cells gather to form a mound under cAMP concentration, and begin to express some genes regulating cell differentiation and related proteins involving many cellular components, such as adhesion molecule, differentiation inducing factor, cytoskeleton proteins and so on. They transfer signals between cells, and cells differentiate into two distinct cell-types, prestalk and prespore cells. Eventually, cells form a fruiting body consisting of spores and a stalk. The latter is a result of cell death. Therefore, the cell differentiation is actually a process of apoptosis. We don't know clearly that the difference of protein components between these two types and whether Caspase is necessary for apoptosis.We took Kax-3 (wild type) cell as experiment material and collected cells every two hours during slug stage. Prestalk and prespore cells obtained from mechanically dissociated slugs were separated by the centrifugation on preformed Percoll density gradients. Proteins were separated using SDS-PAGE and scanned by BIO-PROFILE of VILBER LOURMAT. The datum showed the lands 101.2kD, 85.9kD, 68.2kD, 49.8kD, 42.4kD, 40.6kD, 33.0kD, 24.4kD and 21.5kD were shared by prestalk and prespore cells. Among these proteins, 101.2kkD, 68.2kD, 49.8kD, 42.4kD and 33.0kD were the most stable. 101.2kD may be gp100, which is required for the cell-cell adhesion. 68.2kD may be actin-link protein, whose function strengthens the adhesion of cells. 49.2kD is close to tubulin, which is involved in maintain of cell morphogenesis and movement. 42.4kD may be actin, which plays an important role in cell migration. The most different existed in some proteins, for example, 37.5kD and 31.5kD, these proteins were only expressed in prestalk cells, whose content were raised with the cell differentiation. This result indicated these proteins had a relationship with apoptosis. Moreover, 31.5kD is close to Caspase-3, whether it is or not, should be proved in further research. 36.7kD was only existed during mound stage, which showed that was required for early development. And the functions of 33.0kD, 24.4kD and 21.5kD should be further investigated.