Study On The Effect Of Mitochondria And Cytochrome C During Dictyostelium Discoideum Apoptosis

The social amoeba Dictyostelium discoideum which phagocytosis soil bacteria for food is a unicellular eukaryote. Under favorable condition, it multiplies as a unicellular organism. Upon starvation, a pathway involving aggregation, mound, slug, culmination stages induces the formation of a fruiting body consisting of a head of spores supported on a stalk of vacuolated cells. Spores await dispersal and germinate in favourable conditions for amoeboid growth. However, the formation of stalk cells is a process of cell death. Current evidences suggest that the mitochondria not only provide energy for the cell, but also play a crucial role in cell differentiation and cell apoptosis. The change of mitochondrial membrane permeability may cause the start of apoptosis. The opening of permeability transition pore (PTP) would induce the decline of membrane potential and the release of some apoptosis inducing factors (such as cytochrome c, AIF) and the decrease of ATP production. The differences of mitochondria components, the variety of transmembrane potential during the development and the role of cytochrome c in the process of apoptosis were not clear yet.Kax-3 cells (wild type) and AK127 cells (mutant type) were taken as experimental materials and the mitochondria were got at different developmental stages. Prestalk and prespore cells obtained from mechanically dissociated slugs were separated by the centrifugation on preformed percoll density gradients. Proteins of mitochondria and cytoplasm were separated by SDS-PAGE. Proteins during differentiation of prestalk cells and prespore cells were investigated and some different proteins were found in mitochondria and cytoplasm between prestalk and prespore cells. Different mitochondrial proteins were found in the development of Kax-3 cells. During the whole development, 54kD, 47kD, 41.21kD, 38.4kD proteins were shared consistent change. The content of 83.0kD protein ascended at aggregation and culmination stages, and declined at mound and slug stages. The content of 75kD and 19.5kD rose at aggregation stage, but decreased obviously at mound stage. So 75kD and 19.5kD may be mitochondrial membrane proteins, and participate in cell differentiation and movement at aggregation stage. The content of 65.6kD protein increased at cell mound stage, but other protein kept changeless. 50kD protein and 26kD protein only occurred in prespore mitochondria, they might be prespore mitochondrial specific proteins. 79kD protein wasn't found in prespore cytoplasm, but there was a little amount in prestalk cytoplasm. 53kD protein wasn't found in prestalk...