Date of Award
Doctor of Philosophy (PhD)
Susanna Fletcher Greer
Major histocompatibility complex molecules (MHCII) are cell surface glycoproteins that present extracellular antigens to CD4+ T lymphocytes and initiate adaptive immune responses. Apart from their protective role, overexpression of MHCII contributes to autoimmune disorders where the immune system attacks our own tissues. Autoimmune diseases are characterized by self-reactive responses to autoantigens, promoting tissue damage, inflammation mediated by proinflammatory cytokines, autoreactive lymphocytes, and autoantibodies. MHCII molecules are tightly regulated at the level of transcription by Class II transactivator (CIITA). CIITA associates with an enhanceosome complex at MHCII promoters and regulates the expression of MHCII. It is thus crucial to understand the regulation of CIITA expression in order to regulate MHCII in autoimmune diseases. Our lab has shown that the 19S ATPases of the 26S proteasome associate with MHCII and CIITA promoters and play important roles in gene transcription, regulate covalent modifications to histones, and are involved in the assembly of activator complexes in mammalian cells. The mechanisms by which the proteasome influences transcription remain unclear. Here, we define novel roles of the 19S ATPases Sug1, S7, and S6a in expression of CIITApIV genes. These ATPases are recruited to CIITApIV promoters and coding regions, interact with the elongation factor PTEFb, and with Ser5 phosphorylated RNA Pol II. Both the generation of CIITApIV transcripts and efficient recruitment of RNA Pol II to CIITApIV are negatively impacted by knockdown of 19S ATPases.
Alternatively, inflammation is also suppressed via the Regulator of G-protein signaling 10 (RGS10) in microglial cells which express high levels of RGS10 and promote homeostasis in the central nervous system. However, chronic activation of microglial cells leads to release of cytokines which cause neuroinflammation. Our investigation of roles played by RGS10 in chronically activated microglial cells indicates that RGS10 binds to promoters of IL-1β, and TNF-α and regulates these genes, while the molecular mechanism remains to be investigated. Together, our observations indicate roles for the UPS in modulating gene expression and for RGS10 in regulating proinflammatory cytokines in microglial cells, each of which provides novel therapeutic targets to combat inflammation in autoimmune and neurodegenerative diseases.
Maganti, Nagini, "Role of 26S Proteasome and Regulator of G-Protein Signaling 10 in Regulating Neuroinflammation in the Central Nervous System." Dissertation, Georgia State University, 2015.