Advisor(s)
Lori McMahon
John Chatham
Committee Member(s)
Lauren Ball
Lynn Dobrunz
Mark Bevensee
Scott Wilson
School
Joint Health Sciences (Interdisciplinary)
Document Type
Dissertation
Department (new version)
Pathology
Date of Award
9-9-2024
Abstract
Changes in the strength of GABAergic transmission is heavily influenced by posttranslational modifications and allosteric modulators like benzodiazepines and neurosteroids. O-GlcNAcylation (O-GlcNAc) is a post-translational modification that is tightly regulated by O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA), which add or remove the O-GlcNAc moiety of β–N-acetylglucosamine to serine and threonine residues on proteins, respectively. Published reports from our lab have demonstrated that an acute increase in O-GlcNAcylation induces a long-term depression (LTD) of evoked GABAAR mediated IPSCs (eIPSCs) and reduces the amplitude and frequency of spontaneous IPSC (sIPSC) in hippocampal principal cells, however the mechanism in which this occurs is unknown. Numerous studies have shown that serine phosphorylation of GABAAR subunits can increase or decrease GABAAR currents depending on the neuron type and specific subunit. While O-GlcNAcylation modulates inhibitory GABA-gated currents, no studies have examined its interplay with serine phosphorylation on GABAergic transmission. Because the crosstalk between O-GlcNAcylation and phosphorylation affects the regulation of various proteins, the potential exists that O-GlcNAcylation and phosphorylation will interact in the modulation of GABAAR function and the strength of inhibitory transmission. Furthermore, a potential interaction could impact how allosteric modulators affect GABAARs, since serine phosphorylation can either increase or decrease efficacy of these modulators. In this dissertation, I show that pharmacologically increasing O-GlcNAcylation, after increasing serine phosphorylation via the adenylate cyclase activator, forskolin, had no significant effect. However, when increasing O-GlcNAcylation prior to forskolin, the O-GlcNAc induced eIPSC depression is reversed, unmasking a forskolin-dependent increase in eIPSC amplitude. This effect, however, is not due to a serine phosphorylation mechanism because pharmacological inhibition of adenylate cyclase or protein kinase A did not prevent the forskolin-dependent increase in eIPSC amplitude. Additionally, a previous study in carp amacrine-like cells (Li& Yang, 2001) found that forskolin can act directly at the neurosteroid site on GABAARs. I found that increasing O-GlcNAcylation prior to the application of neurosteriods, 5α-pregnane-3α,21-diol-20-one (THDOC) and progesterone, led to a potentiating effect that mimicked forskolin. Altogether, my findings show that in the presence of increased O-GlcNAcylation, access to the neurosteroid site on GABAARs is enhanced leading to an increase in the strength of GABAergic transmission.
ProQuest ID
Recommended Citation
Phillips, Shekinah, "O-Glcnacylation And Modulation Of Gabaergic Transmission" (2024). All ETDs from UAB. 7591.
https://digitalcommons.library.uab.edu/etd-collection/7591
