Date of Award
Doctor of Philosophy (PhD)
Dr. Rennolds S. Ostrom
Dr. Moom Roosan
Dr. Surya Nauli
Dr. Khaled Elsaid
Glucocorticoids (GCs) are steroid hormones that regulate diverse physiological processes. Synthetic versions of GCs are commonly used to treat inflammatory diseases such as asthma by modulating gene expression to suppressing several inflammatory activities. However, it is estimated that 5-10% of asthmatics are unresponsive to GCs, which may be explained by receptor desensitization and/or the presence of a neutrophilic endotype. One understudied phenomenon of GCs is their ability to induce rapid, non-genomic actions. For example, GCs can acutely modulate calcium concentrations levels, induce smooth muscle relaxation and modulate nitric oxide synthase activity, within minutes and sometimes seconds, which is too rapid for genomic actions to account for. Normally, genomic actions are slower and occur on a timescale of hours. Interestingly, when GCs are combined with cAMP elevating agents, many of their beneficial effects are enhanced both in vitro and clinically. However, mechanistic studies elucidating the signaling pathway of non-genomic GC activity are lacking. Moreover, given that cAMP seems to intersect at some level in the GC signaling pathway to augment its effects, perhaps studying the interplay between both components can reveal a novel signaling mechanism. My hypothesis is that GCs can rapidly induce cAMP production in a non-genomic manner, where the effect is mediated by a Gs-coupled GPCR and that GC-induced non-genomic actions contribute to later genomic actions. To carry out the study, I will focus on the following aims a). Demonstrate that GC rapidly stimulate cAMP levels b). Test the involvement of G𝛼s in the signaling pathway c). Determine what role non-genomic signaling plays in the known genomic effects of GCs and d). Identify the GPCR receptor involved. My studies showed that GCs can stimulate cAMP in various live mammalian cells within seconds in a G s-dependent manner, which implies that a GPCR(s) is involved. High throughput screening of GPCRs revealed GPR173 as a hit, however the receptor could not be confidently validated. Finally, RNA sequencing data showed that non-genomic signaling contributes to about 1/3 of its classical genomic effects. Identification of the GC-activated GPCR may help to develop and leverage novel pharmacological interventions for asthma and other inflammatory diseases.
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Nunez, FJ. Identifying a Glucocorticoid-activated GPCR that Rapidly and Non-Genomically Increases cAMP Levels in Mammalian Cells. [dissertation]. Irvine, CA: Chapman University; 2022. https://doi.org/10.36837/chapman.000400
Available for download on Tuesday, August 15, 2023
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