Defense Date
2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Pharmaceutical Sciences
First Advisor
Yana Cen
Abstract
Sirtuins are class III histone deacetylases (HDACs) that utilize nicotinamide adenine dinucleotide (NAD+) as a cofactor to remove lysine acylations from histone and non-histone proteins, thereby influencing gene transcription and protein function. Here, we explored the modulation of two class III sirtuins, Plasmodium falciparum Sir2A (PfSir2A) and human SIRT5.
Plasmodium falciparum causes the most severe form of malaria in humans, maintaining persistent infection by antigenic variation, a mechanism regulated by PfSir2A. Here, we characterized the in vitro activity and steady-state kinetics of PfSir2A. Consistent with previous reports, PfSir2A preferentially removes long-chain fatty-acyl groups rather than acetyl groups from lysine residues. Interestingly, both activities of PfSir2A were activated by DNA supplementation. Through the repurposing of existing human sirtuin modulators, we identified nicotinamide riboside (NR) and 3-TYP as inhibitors of PfSir2A activity. Collectively, the mechanistic insights and inhibitors described in this study will facilitate the future development of PfSir2A inhibitors as antimalarial agents.
The second part of this project aimed at elucidating the basis of SIRT5 activation by NR using X-ray crystallography. SIRT5 is one of seven human sirtuin isoforms primarily localized in the mitochondria and heavily implicated in the regulation of metabolism. In our earlier studies, we showed the selective activation of SIRT5 deacetylase activity by NR. After several attempts to co-crystallize SIRT5 with NR, we only obtained apo-SIRT5 crystals. Nonetheless, this apo-SIRT5 reveals structural features of unliganded SIRT5, which can be further explored to identify druggable pockets to influence the rational development of a more selective and potent SIRT5 modulator.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
12-9-2025