Biology subjects

Thomas, A. S.

Publications and source records attributed to Thomas, A. S..

5 recordsLinked to original sources

bioRxiv2026

Metal toxicity contributes to the structuring of bacterial communities in the Arabidopsis leaf phyllosphere

O_LIThe causal factors shaping plant-associated microbiota are incompletely known. Elevated concentrations of the micronutrients zinc (Zn), manganese (Mn) and copper (Cu), and exposure to non-essential trace elements including cadmium (Cd) and arsenic (As), can be toxic. Here we explored whether differences in metal(loid) sensitivity between plants and bacteria influence phyllosphere bacterial community composition. C_LIO_LI224 representative Arabidopsis thaliana phyllosphere bacterial strains were screened on metal(loid) concentration series in synthetic media. We obtained leaf apoplastic fluid ionomes for comparisons with bacteriotoxicity profiles, and tested for relationships between strain-wise metal(loid) tolerances, phylogeny and gene content. C_LIO_LILeaf apoplastic Zn2+ and Cd2+ concentrations were the most likely to arrest growth of metal-sensitive bacteria in planta. Soil bacterial strains were several-fold more sensitive to both these metals than leaf strains, consistent with selection for increased bacterial Zn and Cd tolerance in the phyllosphere. Strains known to govern bacterial community structure were metal-sensitive, with only minor influences of between-metal and between-strain interactions. Bacterial genus explained considerable proportions of the variances in metal(loid)-related gene content and tolerance phenotypes. Bacterial Cd tolerance correlated with the presence and copy number of known Cd-related genes. C_LIO_LIOur results suggest that plant metal homeostasis contributes to structuring bacterial communities in the leaf endosphere. C_LI

plant biology↗

bioRxiv2023

Low frequency optogenetic deep brain stimulation of nucleus accumbens dopamine D1 or D2 receptor-containing neurons attenuates cocaine seeking selectively in male rats in part by reversing synaptic plasticity deficits

BackgroundClinically, deep brain stimulation (DBS) utilizes relatively high frequencies (>100 Hz). In preclinical models, 160 Hz stimulation of the nucleus accumbens in rodents prevents relapse of drug seeking. However, the ability of varied frequencies of accumbens DBS to attenuate drug seeking, and the neuronal subtype specificity of this effect, is unclear. MethodsThe present study examined the effect of DBS in the nucleus accumbens on neuronal plasticity and cocaine-primed reinstatement of cocaine seeking behavior in rats. ResultsElectrical DBS of the accumbens shell attenuated cocaine primed reinstatement across a range of frequencies in male rats, including as low as 12 Hz. The majority of nucleus accumbens neurons are medium spiny neurons (MSNs), which can be differentiated in terms of projections and effects on cocaine-related behaviors by expression of dopamine D1 receptors (D1DRs) or D2DRs. In slice electrophysiology experiments, 12 Hz electrical stimulation evoked long term potentiation (LTP) in eYFP labeled D1DR-MSNs and D2DR-MSNs from cocaine naive male and female rats. However, in rats that self-administered cocaine and underwent extinction training, a paradigm identical to our reinstatement experiments, electrical DBS only elicited LTP in D2DR-MSNs from male rats; this effect was replicated by optical stimulation in rats expressing Cre-dependent ChR2 in D2DR-MSNs. Low-frequency optogenetic-DBS in D1DR-containing or D2DR-containing neurons attenuated cocaine-primed reinstatement of cocaine seeking in male but not female rats. ConclusionsThese results suggest that administering DBS in the nucleus accumbens shell at lower frequencies effectively, but sex-specifically, suppresses cocaine craving, perhaps in part by reversing synaptic plasticity deficits selectively in D2DR-MSNs.

neuroscience↗

bioRxiv2022

High frequency DBS-like optogenetic stimulation of nucleus accumbens dopamine D2 receptor-containing neurons attenuates cocaine reinstatement in male rats

BackgroundPrevious work indicated that deep brain stimulation (DBS) of the nucleus accumbens shell in male rats attenuated reinstatement of cocaine seeking, an animal model of craving. However, the potential differential impact of DBS on specific populations of neurons to drive the suppression of cocaine seeking is unknown. Medium spiny neurons in the nucleus accumbens are differentiated by expression of dopamine D1 receptors (D1DRs) or D2DRs, activation of which promotes or inhibits cocaine-related behaviors, respectively. The advent of transgenic rat lines expressing Cre recombinase selectively in D1DR-containing or D2DR-containing neurons, when coupled with Cre-dependent virally mediated gene transfer of channelrhodopsin (ChR2), enabled mimicry of DBS in a selective subpopulation of neurons during complex tasks. HypothesisWe tested the hypothesis that high frequency DBS-like optogenetic stimulation of D1DR-containing neurons in the accumbens shell would potentiate, whereas stimulation of D2DR-containing neurons in the accumbens shell would attenuate, cocaine-primed reinstatement of cocaine seeking. ResultsResults indicated that high frequency, DBS-like optogenetic stimulation of D2DR-containing neurons attenuated reinstatement of cocaine seeking in male rats, whereas DBS-like optogenetic stimulation of D1DR-containing neurons did not alter cocaine-primed reinstatement. Surprisingly, DBS-like optogenetic stimulation did not alter reinstatement of cocaine seeking in female rats. In rats which only expressed eYFP, intra-accumbens optogenetic stimulation did not alter cocaine reinstatement relative to sham stimulation, indicating that the effect of DBS-like stimulation to attenuate cocaine reinstatement is mediated specifically by ChR2 rather than consequent to prolonged light delivery. ConclusionsThese results suggest that DBS of the accumbens attenuates cocaine-primed reinstatement in male rats through the selective manipulation of D2DR-containing neurons.

neuroscience↗

bioRxiv2020

Co-translational folding of the first transmembrane domain of ABC-transporter CFTR is supported by assembly with the first cytosolic domain

ABC-transporters transport a wealth of molecules across membranes and consist of transmembrane and cytosolic domains. Their activity cycle involves a tightly regulated and concerted domain choreography. Regulation is driven by the cytosolic domains and function by the transmembrane domains. Folding of these polytopic multidomain proteins to their functional state is a challenge for cells, which is mitigated by co-translational and sequential events. We here reveal the first stages of co-translational domain folding and assembly of CFTR, the ABC-transporter defective in the most abundant rare inherited disease cystic fibrosis. We have combined biosynthetic radiolabeling with protease-susceptibility assays and domain-specific antibodies. The most N-terminal domain, TMD1 (transmembrane domain 1), folds both its hydrophobic and soluble helices during translation: the transmembrane helices pack tightly and the cytosolic N- and C-termini assemble with the first cytosolic helical loop ICL1, leaving only ICL2 exposed. This N-C-ICL1 assembly is strengthened by two independent events: i) assembly of ICL1 with the N-terminal subdomain of the next domain, cytosolic NBD1 (nucleotide-binding domain 1); and ii) in the presence of corrector drug VX-809, which rescues cell-surface expression of a range of disease-causing CFTR mutants. Both lead to increased shielding of the CFTR N-terminus, and their additivity implies different modes of action. Early assembly of NBD1 and TMD1 is essential for CFTR folding and positions both domains for the required assembly with TMD2. Altogether, we have gained insights into this first, nucleating, VX-809-enhanced domain-assembly event during and immediately after CFTR translation, involving structures conserved in type-I ABC exporters.

biochemistry↗

bioRxiv2020

NREM consolidation and increased spindle counts improve age-related memory impairments and hippocampal representations

Age-related changes in sleep patterns have been linked to cognitive decline. Specifically, increasing age is associated with increasing fragmentation of sleep and wake cycles. However, it remains unknown if improvements in sleep architecture can ameliorate cellular and cognitive deficits. We evaluated how changes in sleep architecture following sleep restriction affected hippocampal representations and memory in young and old mice. After training in a hippocampus- dependent object/place recognition task, control animals were allowed to sleep ad libitum, while experimental animals underwent 5 hours of sleep restriction (SR). Interestingly, old SR mice exhibited successful object/place learning comparable to young control mice, whereas young SR and old control mice did not. Successful learning correlated with the presence of two hippocampal cell types: 1) "Context" cells, which remained stable throughout training and testing, and 2) "Object" cells, which shifted their preferred firing location when objects were introduced to the context and moved during testing. As expected, EEG analysis revealed more fragmented sleep and fewer spindles in old controls than young controls during the post-training sleep period. However, following the acute SR session, old animals exhibited increased consolidation of NREM and increased spindle count, while young mice only displayed changes in REM bout length. These results indicate that consolidation of NREM sleep and increases in spindle count serve to ameliorate age-related memory deficits and allow hippocampal representations to adapt to changing environments. eTORC BlurbAge-related cognitive decline is associated with poor sleep quality. This study shows that acute sleep restriction serves to improve memory, hippocampal representations, and sleep quality in old mice, having the opposite effect in young animals. These findings indicate that improving sleep quality may mitigate age-related cognitive decline. HighlightsAcute sleep restriction improves memory in old mice, but adversely affects young ones Acute sleep restriction makes hippocampal representations more flexible in old mice Acute sleep restriction improves sleep quality and increases spindle count in old mice Acute sleep restriction decreases hippocampal flexibility in young mice

neuroscience↗