Date of Award
4-27-2012
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Biology
First Advisor
John Bush
Abstract
Functional analysis and localization of the small GTPase RabS in the slime mold, Dictyostelium discoideum, was explored using cell lines that over-express a GFP tagged RabS protein. Based on homology to Rab1, Golgi association was explored. Immunofluoresence analysis of the intracellular localization of this GFP tagged protein revealed that this GFP-Rab had a partial co-localization with the contractile vacuole organelle system. Additionally, when the over-expressed RabS cell lines were exposed to selective biochemical inhibitors, the GFP-Tagged Rab localized with what can be assumed is the Golgi network. This dual localization of Golgi and CV may support a previously proposed connection between these organellar systems. Functional testing was also performed by exposing the over-expression cells to osmotic stress conditions in a hypotonic and hypertonic environment in the presence of Brefeldin A Golgi inhibitor. Analysis of the resulting data suggests that BFA caused a Golgi displacement and the previously diffuse GFP-RabS protein was now localized to a structure thought to be the Golgi. Additional functional analysis looked at the processes of endocytosis, exocytosis, and recycling of fluid phase markers. The RabS over-expressing cell lines had more visible endosomes than control cell lines and the rate of fluid phase endocytosis was higher in these cells as compared to wild-type cells. Exocytosis was not significantly altered in these cells but the recycling of a large fluid phase marker may have been slowed by the RabS over-expression. Given the known connections between the Golgi and endosomal system in numerous other organisms these results may not be surprising. This work provides the first evidence of a Golgi localized Rab protein in D. discoideum and supports a model of a CV and Golgi organelle membrane transport pathway.
Recommended Citation
Maringer, Katherine V., "Molecular Analysis and Localization of a Novel Dictyostelium discoideum Rab Protein, RabS" (2012). Theses and Dissertations. 343.
https://research.ualr.edu/etd/343
