It is important to understand the mechanism of endocytic invasion into the host cell by Staphylococcus aureus. Activation of phosphoinositide-3-kinase (PI3K) is essential to S. aureus invasion. In a normal cell, the p85 subunit of PI3K is bound at the Rho GTPase activating protein (RhoGAP) domain to small guanosine triphosphate binding proteins (GTPases), which are attached to the cell membrane by a prenyl group. This association anchors PI3K near the cellular membrane. PI3K must be anchored near the membrane in order to phosphorylate its substrate. The hypothesis for this project is that deletion of the binding domain between PI3K and small GTPases will block endocytic bacterial invasion by sequestering PI3K in the cytosol. To investigate this hypothesis, the RhoGAP binding domain of PI3K p85 was mutated using site-directed mutagenesis and S. aureus invasion was reduced by up to 86% (p<0.05), which shows that this domain is important to bacterial invasion. / Department of Biology

Access to abstract restricted until May 2015 / Access to thesis restricted until May 2015 / Department of Biology

Staphylococcus aureus infections have become a widespread problem. Simvastatin decreases S. aureus invasion. Simvastatin use reduces prenylation of target proteins, including CDC42. Prenylated CDC42 is active at the cell membrane. Our hypothesis is that CDC42 activity at the cell membrane is needed for endocytic S. aureus invasion. The prenylation site on CDC42 was deleted and mutant CDC42 (CDC42C5O7V/V5) was transfected into mammalian cells, which were exposed to S. aureus. Decreased bacterial infection of up to 90% was seen in cells stably expressing CDC42C507V/V5. Mammalian cells were treated with secramine A, an inhibitor of CDC42 activity, and exposed to S. aureus. Decreased bacterial invasion of 70% in these cells was seen. These findings suggest that CDC42 activity at the cell membrane is needed for S. aureus cell invasion. These findings increase understanding of the mechanism of S. aureus cell invasion and could be used to develop new treatment or prevention methods. / Department of Biology

Statins are widely used to treat hypercholesterolemia. Statins inhibit cholesterol biosynthesis, thereby activating genes involved in cholesterol homeostasis, which are under the control of the Sterol Regulatory Element (SRE). Statins also have cholesterol-independent beneficial cardiovascular effects mediated through the phosphoinositide 3-kinase (PI3-K) / Akt signaling pathway and by inhibition of protein prenylation. Because statins inhibit the synthesis of isoprenoids, they can act by inhibiting the small signaling GTPases Ras and Rho, which require post-translational prenylation to become membrane-anchored and functional. We showed that simvastatin-mediated inhibition of protein prenylation does not appear to play a role in activation of SRE transcriptional activity in HepG2 cells. We also found that when isoprenoids were replenished, basal phospho-Akt decreased, suggesting that inhibition of prenylation by simvastatin mediates Akt phosphorylation. Future studies will be needed to investigate the role that inhibition of protein prenylation plays in the activation of the PI3-K/Akt pathway by simvastatin. / Department of Biology

Access to abstract permanently restricted. / Aldol condensation to synthesize substituted chalcones -- Synthesis and testing of substituted 4,5-dihydropyrazoles -- Biological testing of synthesized 4,5-dihydropyrazoles. / Access to thesis permanently restricted. / Department of Chemistry