Theses and Dissertations

Issuing Body

Mississippi State University


Donaldson, Janet R.

Committee Member

Wise, Dwayne

Committee Member

Coats, Karen

Committee Member

Hernandez, Rafael

Committee Member

French, Todd William

Date of Degree


Original embargo terms

MSU Only Indefinitely

Document Type

Dissertation - Campus Access Only


Biological Sciences

Degree Name

Doctor of Philosophy


College of Arts and Sciences


Department of Biological Sciences


The Renin Angiotensin System (RAS) plays a vital role in the regulation of blood pressure and fluid homeostasis. RAS is regulated via the hormone Angiotensin II through an association with the Na+/H+ exchanger NHE6. Here, NHE6 was found to be activated by Angiotensin II through the Angiotensin II AT1 receptor. Furthermore, it was shown that NHE6 requires phosphorylation for activation and this phosphorylation signaling mechanism does not involve phospholipase C. The elucidation of the signaling pathway associated with NHE6 and AT1 allows for the greater understanding of function and regulation of the NHE6 protein. The Angiotensin receptor AT2 is a G-coupled protein receptor (GPCR) that is highly expressed in infant neural tissue. The S1 subunit of the pertussis toxin can inhibit GPCR signaling via ADP-ribosylation of the cognate Gi protein, suggesting that the S1 subunit may interfere with AT2 signaling. In order to observe whether S1 associates with AT2, Chinese hamster ovary cells were transfected with plasmids expressing AT2 or mutants of AT2. The lysates of these cells were incubated with His-tagged S1 subunit and it was observed that only the wild-type AT2 co-immunoprecipitated with S1. These results imply that there is a direct interaction between the S1 subunit and AT2. Municipal wastewater can be considered as an effective growth medium for the cultivation of microorganisms due to organic material found in the water. Oleaginous microorganisms produce large amounts of triacylglycerols (TAGs) when cultivated on medium containing high sugar content and low nitrogen. These TAGs can then be converted into biodiesel. To determine if the oleaginous yeast Rhodotorula glutinis could survive and synthesize lipids using wastewater as a cultivation medium, R. glutinis was inoculated into primary effluent wastewater supplemented with glucose. Results indicated that R. glutinis was able to survive and synthesize lipids in the wastewater which is suggestive that R. glutinis can successfully compete with indigenous microorganisms in the wastewater.



Rhodotorula glutinis||Oleaginous Microorganisms||Pertussis Toxin||NHE6||Angiotensin II||AT2||AT1