Köln, University, Diss., 2003.

Heidelberg, Universiẗat, Diss., 2003. / Dateien im PDF-Format.

Köln, University, Diss., 2003.

Köln, University, Diss., 2004.

The effect of cyclic adenosine 3', 5' monophosphate (cyclic AMP ) on ionic movement across the cell-membrane of the cellular slime mold Dictyostelium discoideum, strains V-12 and NC4, has been studied by using radioisotopes, Na²² and Ca⁴⁵. D. discoideum was grown on water agar associated with autoclaved radioactive E. coli 281.The experimental amoebae were centrifuged to free them from bacteria. Cyclic AMP was added to the experimental culture every 10 or 20 minutes. The results showed that cyclic AMP has a significant effect on calcium ion movement across the membrane both in the pre-aggregative amoeboid stage and during the aggregating phase. The movement of sodium ion was changed only during aggregation. The addition of phosphodiesterase the enzyme -which inactives cyclic AMP by converting it to 5' AMP, showed no effect on ion transport either in the pre-aggregative stage or the aggregating stage. The ionic contents of sodium, potassium, and calcium, were measured at the slug stage. The relationship of calcium ion and cyclic AMP to amoeboid movement was compared with the role of cyclic AMP in muscular contraction and other function. / Science, Faculty of / Zoology, Department of / Graduate

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Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 172-199). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 172-199). Also available on the Internet.

The transport of material across the plasma membrane and between subcellular compartments is a major trafficking event by which cells communicate, regulate developmental processes and maintain homeostasis. Clathrin-coated vesicles select and traffic proteins to specific compartments in eukaryotic cells. Recently a large number of proteins have been identified that serve as clathrin adaptors and accessory proteins. Information regarding the interaction between individual clathrin adaptors and accessory proteins during coated pit formation is currently lacking. Here we investigated the intracellular role of one clathrin adaptor, Dictyostelium discoideum Hip1r, and identified a functional relationship between Hip1r and a second clathrin adaptor, epsin. Hip1r is phosphorylated and localizes to punctae on the plasma membrane that also contain epsin. Moreover, expression of the NH₂-terminal ENTH domain of epsin alone was sufficient to restore both the phosphorylation and the restricted localization of Hip1r to the plasma membrane. Analysis of the individual Hip1r domains demonstrated the phosphorylation event is also dependent upon the expression of the central coiled-coil region of the Hip1r. During development, Hip1r null cells form mature fruiting bodies that yield defective spores. While the mutant spores contain both cellulose and at least one protein secreted from prespore vesicles, spore coats lack the organized fibrils typical of wild type spores. Moreover, Hip1r spores are round, rather than ovoid, and exhibit decreased viability. Domain analysis of Hip1r in conjunction with investigation of phenotypes associated with a Hip1r/epsin double mutant reveal a requirement for full length Hip1r in the production of robust spores. Results from this study suggest that the Hip1r protein functions with epsin during cellular events in both growing and developing Dictyostelium cells and reveals a previously unidentified interaction between two clathrin adaptors. / text