Biology subjects

Crockett, S. L.

Publications and source records attributed to Crockett, S. L..

4 recordsLinked to original sources

bioRxiv2025

Trim47 inhibits murine norovirus replication in a strain-dependent manner

Human norovirus is the leading cause of gastroenteritis worldwide. Norovirus exhibits remarkable genetic diversity. Understanding the impact of genetic diversity on infection and immunity has been challenging due to the difficulties of in vitro cultivation and the current lack of a small animal model. Murine norovirus (MNV) has emerged as a premier model system to investigate norovirus biology. Here, we identify Trim47 as a host restriction factor that potently inhibits MNV infection in a strain dependent manner. We determine that Trim47 expression inhibits an early stage of the viral life cycle for the MNV strain CR6, while the replication of the closely related strain CW3 is not restricted by Trim47. Using a forward genetic screen we determine that genetic variation within the nonstructural gene NS1 accounts for this differential sensitivity to Trim47. While most TRIM containing proteins promote the ubiquitination and degradation of its targets, Trim47 does neither. Instead, Trim47 promotes the deubiquitination of the NS1/2 precursor protein. Our data provide new insight into a potential antiviral gene and mechanistic insight into norovirus evolution that may impact viral tropism. ImportanceViruses exist as genetically heterogeneous populations. Understanding the contribution of viral genetic variation on infection outcomes is critical in predicting emerging viruses and their variants. Noroviruses are genetically diverse but human norovirus has been technically challenging to study. In this study we use the model system murine norovirus to identify a viral strain specific restriction mechanism where a host gene can specifically restrict one strain of the virus but has no impact on a closely related strain. Dissecting the mechanism of this specificity provides insight into viral diversity and possible host restriction pathways.

microbiology↗

bioRxiv2024

Gene regulation of infection-associated L-tartrate metabolism in Salmonella enterica serovar Typhimurium

Enteric pathogens such as Salmonella enterica serovar Typhimurium experience spatial and temporal changes to the metabolic landscape throughout infection. Host reactive oxygen and nitrogen species non-enzymatically convert monosaccharides to alpha hydroxy acids, including L-tartrate. Salmonella utilizes L-tartrate early during infection to support fumarate respiration, while L-tartrate utilization ceases at later time points due to the increased availability of exogenous electron acceptors such as tetrathionate, nitrate, and oxygen. It remains unknown how Salmonella regulates its gene expression to metabolically adapt to changing nutritional environments. Here, we investigated how the transcriptional regulation for L-tartrate metabolism in Salmonella is influenced by infection-relevant cues. L-tartrate induces the transcription of ttdBAU, genes involved in L-tartrate utilization. L-tartrate metabolism is negatively regulated by two previously uncharacterized transcriptional regulators TtdV (STM3357) and TtdW (STM3358), and both TtdV and TtdW are required for sensing of L-tartrate. The electron acceptors nitrate, tetrathionate, and oxygen repress ttdBAU transcription via the two-component system ArcAB. Furthermore, regulation of L-tartrate metabolism is required for optimal fitness in a mouse model of Salmonella-induced colitis. TtdV, TtdW, and ArcAB allow for the integration of two cues, substrate availability and availability of exogenous electron acceptors, to control L-tartrate metabolism. Our findings provide novel insights into how Salmonella prioritizes utilization of different electron acceptors for respiration as it experiences transitional nutrient availability throughout infection. IMPORTANCEBacterial pathogens must adapt their gene expression profiles to cope with diverse environments encountered during infection. This coordinated process is carried out by the integration of cues that the pathogen senses to fine-tune gene expression in a spatiotemporal manner. Many studies have elucidated the regulatory mechanisms on how Salmonella sense metabolites in the gut to activate or repress its virulence program, however our understanding of how Salmonella coordinates its gene expression to maximize the utilization of carbon and energy sources found in transitional nutrient niches is not well understood. In this study, we discovered how Salmonella integrates two infection-relevant cues, substrate availability and exogenous electron acceptors, to control L-tartrate metabolism. From our experiments, we propose a model for how L-tartrate metabolism is regulated in response to different metabolic cues in addition to characterizing two previously unknown transcriptional regulators. This study expands our understanding of how microbes combine metabolic cues to enhance fitness during infection.

microbiology↗

bioRxiv2023

Arrest of mouse preterm labor until term delivery by combination therapy with atosiban and mundulone, a natural product with tocolytic efficacy

Currently, there is a lack of FDA-approved tocolytics for the management of preterm labor (PL). In prior drug discovery efforts, we identified mundulone and its analog mundulone acetate (MA) as inhibitors of in vitro intracellular Ca2+-regulated myometrial contractility. In this study, we probed the tocolytic and therapeutic potential of these small molecules using myometrial cells and tissues obtained from patients receiving cesarean deliveries, as well as a mouse model of PL resulting in preterm birth. In a phenotypic assay, mundulone displayed greater efficacy in the inhibition of intracellular-Ca2+ from myometrial cells; however, MA showed greater potency and uterine-selectivity, based IC50 and Emax values between myometrial cells compared to aorta vascular smooth muscle cells, a major maternal off-target site of current tocolytics. Cell viability assays revealed that MA was significantly less cytotoxic. Organ bath and vessel myography studies showed that only mundulone exerted concentration-dependent inhibition of ex vivo myometrial contractions and that neither mundulone or MA affected vasoreactivity of ductus arteriosus, a major fetal off-target of current tocolytics. A high-throughput combination screen of in vitro intracellular Ca2+-mobilization identified that mundulone exhibits synergism with two clinical-tocolytics (atosiban and nifedipine), and MA displayed synergistic efficacy with nifedipine. Of these synergistic combinations, mundulone + atosiban demonstrated a favorable in vitro therapeutic index (TI)=10, a substantial improvement compared to TI=0.8 for mundulone alone. The ex vivo and in vivo synergism of mundulone and atosiban was substantiated, yielding greater tocolytic efficacy and potency on isolated mouse and human myometrial tissue and reduced preterm birth rates in a mouse model of PL compared to each single agent. Treatment with mundulone 5hrs after mifepristone administration (and PL induction) dose-dependently delayed the timing of delivery. Importantly, mundulone in combination with atosiban (FR 3.7:1, 6.5mg/kg + 1.75mg/kg) permitted long-term management of PL after induction with 30 g mifepristone, allowing 71% dams to deliver viable pups at term (> day 19, 4-5 days post-mifepristone exposure) without any visible maternal and fetal consequences. Collectively, these studies provide a strong foundation for the future development of mundulone as a stand-alone single- and/or combination-tocolytic therapy for management of PL.

pharmacology and toxicology↗

bioRxiv2021

Identification of mundulone and mundulone acetate as natural products with tocolytic efficacy in mono- and combination-therapy with current tocolytics

Currently, there are a lack of FDA-approved tocolytics for the management of preterm labor. We previously observed that the isoflavones mundulone and mundulone acetate (MA) inhibit intracellular Ca2+-regulated myometrial contractility. Here, we further probed the potential of these natural products to be small molecule leads for discovery of novel tocolytics by: (1) examining uterine-selectivity by comparing concentration-response between human primary myometrial cells and a major off-target site, aortic vascular smooth muscle cells (VSMCs), (2) identifying synergistic combinations with current clinical tocolytics to increase efficacy or and reduce off-target side effects, (3) determining cytotoxic effects and (4) investigating the efficacy, potency and tissue-selectivity between myometrial contractility and constriction of fetal ductus arteriosus (DA), a major off-target of current tocolytics. Mundulone displayed significantly greater efficacy (Emax = 80.5% vs. 44.5%, p=0.0005) and potency (IC50 = 27 M and 14 M, p=0.007) compared to MA in the inhibition of intracellular-Ca2+ from myometrial cells. MA showed greater uterine-selectivity, compared to mundulone, based on greater differences in the IC50 (4.3 vs. 2.3 fold) and Emax (70% vs. 0%) between myometrial cells compared to aorta VSMCs. Moreover, MA demonstrated a favorable in vitro therapeutic index of 8.8, compared to TI = 0.8 of mundulone, due to its significantly (p<0.0005) smaller effect on the viability of myometrial (hTERT-HM), liver (HepG2) and kidney (RPTEC) cells. However, mundulone exhibited synergism with two current tocolytics (atosiban and nifedipine), while MA only displayed synergistic efficacy with only nifedipine. Of these synergistic combinations, only mundulone + atosiban demonstrated a favorable TI = 10 compared to TI=0.8 for mundulone alone. While only mundulone showed concentration-dependent inhibition of ex vivo mouse myometrial contractions, neither mundulone or MA affected mouse fetal DA vasoreactivity. The combination of mundulone and atosiban yielded greater tocolytic efficacy and potency on term pregnant mouse and human myometrial tissue compared to single-drugs. Collectively, these data highlight the difference in uterine-selectivity of Ca2+-mobilization, effects on cell viability and tocolytic efficacy between mundulone and MA. These natural products could benefit from medicinal chemistry efforts to study the structural activity relationship for further development into a promising single- and/or combination-tocolytic therapy for management of preterm labor. Chemical compounds studied in this articleatosiban (Pubchem CID: 5311010); indomethacin (Pubchem CID: 3715); mundulone (Pubchem CID: 4587968); mundulone acetate (Pubchem CID: 6857790); nifedipine (Pubchem CID: 4485); oxytocin acetate (Pubchem CID: 5771); U46619 (Pubchem CID: 5311493)

pharmacology and toxicology↗