Biology subjects

Moore, M. D.

Publications and source records attributed to Moore, M. D..

3 recordsLinked to original sources

bioRxiv2025

NUDT5 regulates purine metabolism and thiopurine sensitivity by interacting with PPAT

Cells generate purine nucleotides through both de novo purine biosynthesis (DNPB) and purine salvage. Purine accumulation represses energetically costly DNPB through feedback inhibition of the enzymatic steps that produce the precursor phosphoribosylamine. Excessive DNPB is associated with human diseases including neurological dysfunction and hyperuricemia. However, the mechanisms explaining how cells balance DNPB and purine salvage are incompletely understood. Data from a genome-wide CRISPR loss-of-function screen and extensive stable isotope tracing identified Nudix hydrolase 5 (NUDT5) as a suppressor of DNPB during purine salvage. NUDT5 ablation allows DNPB to persist in the presence of either native purines or thiopurine drugs; this renders NUDT5-deficient cells insensitive to thiopurine treatment. Surprisingly, this regulation occurs independently of NUDT5s known function in hydrolyzing ADP-ribose to AMP and ribose-5-phosphate. Rather, NUDT5 interacts with phosphoribosyl pyrophosphate amidotransferase (PPAT), the rate-limiting enzyme in DNPB that generates phosphoribosylamine. Upon induction of purine salvage, the PPAT-NUDT5 interaction is required to trigger disassembly of the purinosome, a cytosolic metabolon involved in efficient DNPB. Mutations that disrupt NUDT5s interaction with PPAT but leave its catalytic activity intact permit excessive DNPB during purine salvage, inducing thiopurine resistance. Collectively, our findings identify NUDT5 as a regulator governing the balance between DNPB and purine salvage, underscoring its impact on nucleotide metabolism and efficacy of thiopurine treatment.

biochemistry↗

bioRxiv2022

SAMHD1 controls nucleoside-based cancer therapeutics, deoxyguanosine toxicity, and inflammation

SAMHD1 is a key regulator of dNTP metabolism, being activated by dGTP and converting dNTPs into their respective nucleosides. As a result, it plays a significant role in several distinct diseases. Not only is SAMHD1 a restriction factor for HIV-1 replication, which requires dNTPs for replication, but it is also required for genome stability, is mutated in multiple cancers, and loss of function mutations cause Acardi-Goutieres Syndrome, an early-onset inherited encephalopathy. In this paper we knock out the SAMHD1 gene in pluripotent stem cells, and show that it also affects nucleoside analogue sensitivity of dividing cells and deoxyguanosine toxicity in a cell cycle-independent manner. Comparing wild type and gene-edited macrophages, we also show that deoxyguanosine toxicity is associated with pro-inflammatory cell death, modifications in uric acid production and the formation of monosodium urate crystals within the macrophages. These novel features of the SAMHD1-/- phenotype provide unique insights into the aetiology of Acardi-Goutieres Syndrome, and have implications for certain chemotherapeutic agents.

pharmacology and toxicology↗

bioRxiv2018

HIV-1 evasion of restriction factors: cyclophilin A and cell fusion provide a helping hand.

Retroviral restriction factors are important regulators of viral infection, targeting vulnerable steps of the virus lifecycle; steps that are also targeted by antiviral drugs. It has become clear that the route of cellular infection can alter the sensitivity of HIV-1 to these agents. Using CRISPR-Cas9 edited pluripotent stem cell-derived macrophages, we have explored the potential of a modified restriction factor (human TRIMCyp) to inhibit HIV-1 replication in both cell free and cell-cell infection models. We show that the expression of TRIMCyp from the endogenous TRIM5 locus potently restricts infection by cell-free HIV-1. Our results also show the importance of the human cyclophilin A-HIV-1 capsid interaction for viral escape from restriction by native human TRIM5, highlighting the evolutionary interplay between virus and this host restriction factor. However, when co-cultured with infected T cells, stem cell-derived macrophages are primarily infected by fusion between the cells. We have termed infected cells that result from these fusions heterocytia, and show that their formation overcomes multiple restriction factors and the reverse transcriptase inhibitor AZT.\n\nImportanceAs sentinels of the immune system, macrophages are relatively resistant to infection by pathogens such as HIV-1. However, infected macrophages are found in infected patients and they play key roles in the pathogenesis of the disease as well as being a component of the viral reservoir that must be targeted before treatment can become cure. In this article, we show that some of the mechanisms by which macrophages restrict HIV-1 can be overcome through a recently described cell-cell interaction leading to cell-cell fusion. We also highlight an evolutionary battle between virus and host and show how the virus has co-opted a host protein to protect it from destruction by an antiviral mechanism. These two key findings suggest potential novel treatment strategies that may reduce the viral reservoir and help our natural defences take back control from the virus.

microbiology↗