Biology subjects

Ofori, S.

Publications and source records attributed to Ofori, S..

7 recordsLinked to original sources

bioRxiv2026

Longitudinal fMRI reveals altered developmental trajectories of functional network organisation associated with adolescent cannabis use

Adolescence is a critical period of brain development during which the endocannabinoid system continues to mature. These developmental changes may contribute to age-related differences in the association between cannabis use and large-scale functional network organisation, yet this association remains incompletely characterised. We hypothesised that regular cannabis use would be associated with differential one-year changes in resting-state functional connectivity between adolescents and adults. Resting-state fMRI data at two time points, one year apart, were analysed from 66 participants (31 aged 16-17 years; 35 aged 26-29 years) including 29 with regular cannabis use and 37 age-matched cannabis-naive controls. Seed-to-voxel analyses examined longitudinal changes in functional connectivity across age and cannabis-use groups. Year change, age by user-group interactions were identified in salience and default mode network connectivity, including divergent changes in anticorrelations with medial prefrontal, thalamic, cerebellar and juxtapositional regions. Directionality of effects differed by network and region. Additional main effects of user group were observed for executive control and associative striatal connectivity, with the cannabis-use group showing decreased positive connectivity and reduced anticorrelation, respectively. Changes in functional connectivity were developmentally dissociable and predominantly observed in regions contributing to attentional and transmodal processing. These findings suggest that cannabis may be associated with alterations in the maturational refinement of higher-order neural systems, potentially reflecting age-related differences in neurobiological sensitivity to cannabis exposure. Considering developmental stage may therefore be important for characterising cannabis-related neurobiological differences and may have implications for understanding age-dependent vulnerability to cannabis-related psychiatric outcomes.

neuroscience↗

bioRxiv2025

Receptor-enriched analysis of functional connectivity (REACT) for understanding cannabinoid neuropsychopharmacology

BackgroundCannabis is one of the most widely used psychoactive substances in the world and is increasingly investigated as a treatment for neuropsychiatric conditions. Cannabis contains delta-9-tetrahydrocannabinol (THC), which is thought to underlie its main psychoactive effects, and cannabidiol (CBD), which has been proposed to modulate the effects of THC on the brain. Both have activity at CB1 receptors, whilst THC also binds to CB2 receptors. However, it is unclear how THCs effects on brain function are related to cannabinoid receptors, or how CBD co-administration affects this. We aimed to investigate the effects of vaporised THC and the moderating effects of CBD on CB1 and CB2 receptor- enriched functional connectivity. MethodsForty-eight participants (24 adolescents and 24 adults) who used cannabis 0.5-3 days/week (mean=1.5 days/week) participated in a randomised, crossover, placebo- controlled, double-blind experiment where they inhaled vaporised cannabis containing either THC-only (8mg/75kg person), THC+CBD (8 mg THC + 24 mg CBD/75 kg person) or no psychoactive compounds (placebo). Resting-state functional MRI data were collected approximately 50 minutes post-administration. Receptor distribution maps were derived from positron emission tomography (PET) imaging for CB1 receptors and the Allen Human Brain Atlas (AHBA) for CB2 receptors. Receptor-Enriched Analysis of Connectivity by Targets (REACT) analytical methodology was used to investigate changes in functional connectivity related to specific receptor targets. ResultsInhalation of both THC-only and THC+CBD cannabis induced significant decreases in CB1 and CB2 receptor-enriched functional connectivity compared to placebo. The THC+CBD condition showed more extensive reductions than THC-only cannabis for both CB1- and CB2- enriched functional connectivity, affecting regions including the dorsolateral prefrontal cortex, cingulate cortex, insula, hippocampus, amygdala, and putamen. Higher THC plasma levels were associated with greater decreases in functional connectivity in the THC+CBD condition. Exploratory analyses identified significant positive and negative relationships between subjective drug effects and receptor-enriched functional connectivity in a region- dependent manner. ConclusionsCannabis with and without CBD decreased resting-state functional connectivity in networks associated with CB1 and CB2 receptor distribution. Co-administration of CBD with THC appears to enhance these effects. The REACT analytical methodology identified changes in CB1- and CB2-enriched functional connectivity are related to THC and CBD plasma levels as well as subjective drug effects across a range of regions.

neuroscience↗

bioRxiv2024

An activation-based high throughput screen identifies caspase-10 inhibitors

Caspases are a family of highly homologous cysteine proteases that play critical roles in inflammation and apoptosis. Small molecule inhibitors are useful tools for studying caspase biology, complementary to genetic approaches. However, achieving inhibitor selectivity for individual members of this highly homologous enzyme family remains a major challenge in developing such tool compounds. Prior studies have revealed that one strategy to tackle this selectivity gap is to target the precursor or zymogen forms of individual caspases, which share reduced structural homology when compared to active proteases. To establish a screening assay that favors the discovery of zymogen-directed caspase-10 selective inhibitors, we engineered a low-background and high-activity tobacco etch virus (TEV)--activated caspase-10 protein. We then subjected this turn-on protease to a high-throughput screen of approximately 100,000 compounds, with an average Z value of 0.58 across all plates analyzed. Counter screening, including against TEV protease, delineated bona fide procaspase-10 inhibitors. Confirmatory studies identified a class of low-pH activatable caspase-10 inhibitors. In parallel, mode-of-action studies revealed that pifithrin-{micro} (PFT{micro}), a reported TP53 inhibitor, also functions as a promiscuous caspase inhibitor. Both inhibitor classes showed preferential zymogen inhibition. Given the generalized utility of activation assays, we expect our screening platform to have widespread applications in identifying state-specific protease inhibitors.

biochemistry↗

bioRxiv2024

A system for functional studies of the major virulence factor of malaria parasites

PfEMP1 is a variable antigen displayed on erythrocytes infected with the malaria parasite Plasmodium falciparum. PfEMP1 mediates binding of the infected cell to the endothelium of blood vessels, a cause of severe malaria. Each parasite encodes [~]60 different PfEMP1 variants but only one is expressed at a time. Switching between variants underlies immune evasion in the host and variant-specific severity of disease. PfEMP1 is difficult to study due to expression heterogeneity between parasites which also renders genetic modification approaches ineffective. Here, we used selection linked integration (SLI) to generate parasites all expressing the same PfEMP1 variant and genome edit the expressed locus. Moving this system from the reference strain 3D7 to IT4 resulted in PfEMP1 expressor parasites with effective receptor binding capacities. We also introduce a second version of SLI (SLI2) to introduce additional genome edits. Using these systems, we study PfEMP1 trafficking, generate cell lines binding to the most common endothelial receptors, survey the protein environment from functional PfEMP1 in the host cell and identify new proteins needed for PfEMP1 mediated sequestration. These findings show the usefulness of the system to study the key virulence factor of malaria parasites.

microbiology↗

bioRxiv2023

Chemoproteomics identifies proteoform-selective caspase-2 inhibitors

Caspases are a highly conserved family of cysteine-aspartyl proteases known for their essential roles in regulating apoptosis, inflammation, cell differentiation, and proliferation. Complementary to genetic approaches, small-molecule probes have emerged as useful tools for modulating caspase activity. However, due to the high sequence and structure homology of all twelve human caspases, achieving selectivity remains a central challenge for caspase-directed small-molecule inhibitor development efforts. Here, using mass spectrometry-based chemoproteomics, we first identify a highly reactive non-catalytic cysteine that is unique to caspase-2. By combining both gel-based activity-based protein profiling (ABPP) and a tobacco etch virus (TEV) protease activation assay, we then identify covalent lead compounds that react preferentially with this cysteine and afford a complete blockade of caspase-2 activity. Inhibitory activity is restricted to the zymogen or precursor form of monomeric caspase-2. Focused analogue synthesis combined with chemoproteomic target engagement analysis in cellular lysates and in cells yielded both pan-caspase reactive molecules and caspase-2 selective lead compounds together with a structurally matched inactive control. Application of this focused set of tool compounds to stratify caspase contributions to initiation of intrinsic apoptosis, supports compensatory caspase-9 activity in the context of caspase-2 inactivation. More broadly, our study highlights future opportunities for the development of proteoform-selective caspase inhibitors that target non-conserved and non-catalytic cysteine residues.

biochemistry↗

bioRxiv2023

Multi-omic stratification of the missense variant cysteinome

Cancer genomes are rife with genetic variants; one key outcome of this variation is gain-of-cysteine, which is the most frequently acquired amino acid due to missense variants in COSMIC. Acquired cysteines are both driver mutations and sites targeted by precision therapies. However, despite their ubiquity, nearly all acquired cysteines remain uncharacterized. Here, we pair cysteine chemoproteomics--a technique that enables proteome-wide pinpointing of functional, redox sensitive, and potentially druggable residues--with genomics to reveal the hidden landscape of cysteine acquisition. For both cancer and healthy genomes, we find that cysteine acquisition is a ubiquitous consequence of genetic variation that is further elevated in the context of decreased DNA repair. Our chemoproteogenomics platform integrates chemoproteomic, whole exome, and RNA-seq data, with a customized 2-stage false discovery rate (FDR) error controlled proteomic search, further enhanced with a user-friendly FragPipe interface. Integration of CADD predictions of deleteriousness revealed marked enrichment for likely damaging variants that result in acquisition of cysteine. By deploying chemoproteogenomics across eleven cell lines, we identify 116 gain-of-cysteines, of which 10 were liganded by electrophilic druglike molecules. Reference cysteines proximal to missense variants were also found to be pervasive, 791 in total, supporting heretofore untapped opportunities for proteoform-specific chemical probe development campaigns. As chemoproteogenomics is further distinguished by sample-matched combinatorial variant databases and compatible with redox proteomics and small molecule screening, we expect widespread utility in guiding proteoform-specific biology and therapeutic discovery.

biochemistry↗

bioRxiv2022

Associations between regular cannabis use and brain resting-state functional connectivity in adolescents and adults

Cannabis use is highly prevalent in adolescents however little is known about its effects on adolescent brain function. Resting-state functional Magnetic Resonance Imaging was used in matched groups of cannabis users (N=70, 35 adolescents16-17 years old, 35 adults 26-29 years old) and non-users (N=70, 35 adolescents/35 adults). Pre-registered analyses examined the connectivity of seven major cortical and sub-cortical brain networks (default mode network, executive control network, salience network, hippocampal network, and three striatal networks) using seed-based analysis methods with cross-sectional comparisons between user groups, and age groups. Cannabis users (across both age-groups), relative to controls, showed localised increases in connectivity only in the executive control network analysis. All networks showed localised connectivity differences based on age group, with the adolescents generally showing weaker connectivity than adults; consistent with developmental effects. Mean connectivity across entire network regions of interest (ROIs) was also significantly decreased in the executive control network in adolescents. However, there were no significant interactions found between age-group and user-group in any of the seed-based or ROI analyses. There were also no associations found between cannabis use frequency and any of the derived connectivity measures. Chronic cannabis use is associated with changes to connectivity of the executive control network, which may reflect allostatic or compensatory changes in response to regular cannabis intoxication. However, these associations were not significantly different in adolescents compared to adults.

neuroscience↗