Function and dynamics of early acidic endosomes in Dictyostelium discoideum

细胞通过内吞作用从环境中摄取物质，通过分泌作用释放物质。在细胞内，这种物质通过囊泡的方式运输，囊泡在诸如内质网、高尔基体和内体的隔室之间运输。因此，由囊泡流连接的隔室存在于动态平衡中。因此，许多蛋白质分布在细胞中的一个以上的隔室中。为了分析单个室的形态、动力学和功能，需要特定的标记。我们的初步结果表明，两个蛋白质可以用来研究模糊的早期内体区室在网骨藻。溶菌酶可以为这些囊泡的内腔提供标记，并且长链脂肪酰辅酶A合成酶（LC-FACS）与早期内体膜的细胞质侧相关联。我们建议研究这些蛋白质在活细胞中的定位，以获得有关内体区室动力学的信息。我们还建议分析它们各自的职能。我们假设溶菌酶将在吞噬细菌的降解中发挥作用，而LC-FACS可能会改变内体膜的脂质，并可能影响它们在囊泡运输中的功能。在溶菌酶缺陷细胞和LC-FACS突变体的内吞运输的各个步骤的动力学分析将提供信息的organisisation和调控的内吞途径在Dictyosteoprotein，可能会影响在哺乳动物细胞中的同源过程的理解。

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.