Biology subjects

Nunn, F.

Publications and source records attributed to Nunn, F..

3 recordsLinked to original sources

bioRxiv2025

The c-Src inhibitor eCF506 diminishes opioid tolerance creating bias against β-arrestin2 recruitment

Opioids reduce severe pain, but persistent use is compromised by tolerance, attenuated by either {beta}-arrestin2 depletion, prompting development of biased opioids limited by partial efficacy, or c-Src kinase inhibitors, potentially acting through off-target effects. We tested eCF506, a conformationally selective c-Src inhibitor, on morphine antinociception and examined its effect on receptor signaling and {beta}-arrestin2 recruitment. Oral eCF506 inhibited morphine tolerance in C57BL/6J mice. Exposure of PathHunter CHO cells to eCF506 did not affect inhibition of cAMP accumulation by the agonist, DAMGO, but reduced {beta}-arrestin2 recruitment. This effect, mimicked by targeted degradation of c-Src, occurred through inhibition of c-Src catalytic function as evidenced by its diminution by the catalytically inactive Src250-536(K298M) construct. This mutant also restricted the effect of c-Src inhibitors on {beta}-arrestin2 recruitment. eCF506 additionally increased surface expression of receptors and limited their internalization by endomorphin-2 but did not alter DAMGO-evoked GRK-mediated receptor phosphorylation. These findings suggest that eCF506 prolongs opioid antinociception by inducing signalling bias, diminishing {beta}-arrestin2-mediated receptor regulation.

neuroscience↗

bioRxiv2021

A Rickettsiella endosymbiont is a potential source of essential B-vitamins for the poultry red mite, Dermanyssus gallinae

Obligate blood-sucking arthropods rely on symbiotic bacteria to provision essential B vitamins that are either missing or at sub-optimal amounts in their nutritionally challenging blood diet. The poultry red mite Dermanyssus gallinae, an obligate blood-feeding ectoparasite, is primarily associated with poultry and a serious threat to the hen egg industry. Thus far, the identity and biological role of nutrient provisioning bacterial mutualists from D. gallinae are little understood. Here, we demonstrate that a Rickettsiella Gammaproteobacteria in maternally transmitted in D. gallinae and universally present in D. gallinae mites collected at different sites throughout Europe. In addition, we report the genome sequence of uncultivable endosymbiont "Candidatus Rickettsiella rubrum" from D. gallinae eggs. The endosymbiont has a circular 1. 89 Mbp genome that encodes 1973 protein. Phylogenetic analysis confirms the placement R. rubrum within the Rickettsiella genus, closely related to a facultative endosymbiont from the pea aphid and Coxiella-like endosymbionts from blood feeding ticks. Analysis of the R. rubrum genome reveals many protein-coding sequences are either pseudogenized or lost, but R. rubrum has retained several B vitamin biosynthesis pathways, confirming the importance of these pathways in evolution of its nutritional symbiosis with D. gallinae. In silico metabolic pathway reconstruction revealed that R. rubrum is unable to synthesise protein amino acids and therefore these nutrients are likely provisioned by the host. In contrast R. rubrum retains biosynthetic pathways for B vitamins: thiamine (vitamin B1) via the salvage pathway; riboflavin (vitamin B2) and pyridoxine (vitamin B6) and the cofactors: flavin adenine dinucleotide (FAD) and coenzyme A (CoA) that likely provision these nutrients to the host. We propose that bacterial symbionts which are essential to blood-feeding arthropod survival provide attractive targets for the development of novel control methods.

microbiology↗

bioRxiv2020

RNAi gene knockdown in the poultry red mite, Dermanyssus gallinae (De Geer 1778), a tool for functional genomics

BackgroundThe avian haematophagous ectoparasite, Dermanyssus gallinae or the poultry red mite, causes significant economic losses to the egg laying industry worldwide and also represents a significant welfare threat. Current acaricide-based controls are unsustainable due to the mites ability to rapidly develop resistance, thus developing a novel sustainable means of control for D. gallinae is a priority. RNA interference (RNAi) mediated gene silencing is a valuable tool for studying gene function in non-model organisms, but is also emerging as a novel tool for parasite control. MethodsHere we use an in silico approach to identify core RNAi pathway genes in the recently sequenced D. gallinae genome. In addition we utilise an in vitro feeding device to deliver dsRNA to D. gallinae targeting the D. gallinae vATPase subunit A (Dg vATPase A) gene and monitor gene knockdown using quantitive PCR (qPCR). ResultsWe identified core components of the small interfering RNA (siRNA) and micro RNA (miRNA) pathways in D. gallinae, which indicate these gene silencing pathways are likely functional. Strikingly, the Piwi-interacting RNA (piRNA) pathway was absent in D. gallinae. In addition, we demonstrate that feeding Dg vATPase A dsRNA to adult female D. gallinae results in silencing of the targeted gene compared to control mites fed non-specific lacZ dsRNA. In D. gallinae, dsRNA mediated gene knockdown is rapid, detectable 24 hours after oral delivery of dsRNA and persisted for at least 120 hours. ConclusionsThis study has shown the presence of core RNAi machinery components in the D. gallinae genome. In addition, we have developed a robust RNAi methodology for targeting genes in D. gallinae, which will be of value for studying genes of unknown function and validating potential control targets in D. gallinae.

genomics↗