Function and dynamics of early acidic endosomes in Dictyostelium discoideum

• Applicant: Professor Dr. Markus Maniak
• Subject Area: Biochemistry
• Term: from 2002 to 2004
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5367018

Cells take up material form their environment by endocytosis and release material by secretion. Within the cell, this material is transported by the means of vesicles, which traffic between compartments such as the endoplasmic reticulum, the golgi apparatus and endosomes. As a consequence, compartments that are connected by vesicle flow exist in a dynamic equilibrium. Therefore, many proteins are distributed over more than one compartment in the cell. To analyse the morphology, dynamics and function of a single compartment, specific makers are required. Our preliminary results have shown that two proteins could serve to study the obscure early endosomal compartment in Dictyostelium. Lysozyme could provide a marker for the lumen of these vesicles and the long-chain-fatty-acyl-CoA synthetase (LC-FACS) associates with the cytoplasmic side of the early endosomal membrane. We propose to study the localisation of these proteins in living cells to obtain information on the dynamics of endosomal compartments. We further propose to analyse their respective functions. We hypothesise that lysozyme will play a role in the degradation of phagocytosed bacteria, whereas the LC-FACS will probably modify the lipids of endosomal membranes, and could influence their function in vesicle trafficking. Kinetic analysis of individual steps in endocytic trafficking in lysozyme-deficient cells and LC-FACS mutants will provide information on the organsisation and regulation of the endocytic pathway in Dictyostelium that may influence the understanding of homologous processes in mammalian cells.

• DFG Programme: Research Grants