Biology subjects

Roberts, A. G.

Publications and source records attributed to Roberts, A. G..

6 recordsLinked to original sources

bioRxiv2026

Opposing GIPR brainstem circuits differentially control feeding behaviour

Central glucose-dependent insulinotropic polypeptide receptor (GIPR) signalling is required for the efficacy of GIP-based obesity therapeutics, yet how distinct subpopulations of GIPR neurons shape appetite remains undefined. Here we show that GIPR neurons in adjacent brainstem nuclei, the area postrema (AP) and nucleus tractus solitarius (NTS), exert opposing control over ingestion. We find GIPRAP neurons dampen post-ingestive satiation, permitting hyperphagia, whereas GIPRNTS neurons are anorectic. In line with this model, we show Gipr expression in AP, but not NTS, neurons is necessary for appetite suppression following GIPR antagonism. Additionally, we reveal that GIPR neurons in the AP and NTS occupy distinct gut-brain circuits, and are differentially sensitive to obesity-driven circuit remodelling. These data offer a framework for understanding how current GIPR agonist and antagonist strategies elicit weight loss.

neuroscience↗

bioRxiv2025

NodoMap: a spatio-cellular map of the mouse nodose ganglia

The vagus nerve is a key component of the parasympathetic nervous system, innervating multiple abdominal organs to monitor and regulate their function. It forms the main neural pathway between the gastrointestinal tract and the brain, playing a major role in the regulation of energy homeostasis. The cell bodies for vagal sensory neurons reside in the nodose ganglia, with the left and right ganglia reported to have distinct roles in food intake and reward. Here, we have integrated our own single nucleus RNA sequencing data with multiple publicly available datasets to create a database of 108,482 nuclei and cells, and combined this with spatial transcriptomics to present a spatio-cellular transcriptional map of the mouse nodose ganglia, the NodoMap. Nodose ganglia neuronal cells clustered into twenty-two different subtypes, all found in both left and right nodose ganglia, but with significant differences in gene expression between left and right ganglia across multiple neuronal subtypes. Overnight fasting modulated gene expression across specific neuronal subtypes, including nutrient responsive pathways. Spatial transcriptomics showed that while vagal neuronal types were highly interspersed, patterns of organisation into cellular neighbourhoods could be observed, with neighbourhoods identified of predominantly non-neuronal cells and of different neuronal populations accompanied by glial-like cells. Thus, NodoMap provides a detailed atlas of the mouse nodose ganglia in a spatial context, providing a platform for vagovagal neurocircuit analysis, and serving as an important resource to identify targets for pharmacotherapies for metabolic disease.

physiology↗

bioRxiv2025

Enteropancreatic neurons drive the glucoregulatory response to ingested lipid

Enteropancreatic neurons project from the small intestinal wall to the pancreas. Though well positioned to mediate the effects of ingested nutrients on pancreatic function, the metabolic role of these neurons is unclear. Diets rich in olive oil promote weight loss and improve remission rates in patients with T2DM. Here, we show that olive oil improves acute glucose tolerance by stimulating insulin release via neurotensin receptor type 1 (NTSR1)-expressing enteropancreatic neurons. These neurons are necessary for the effects of olive and neurotensin on glucose tolerance, and their activation is sufficient to improve glucose tolerance. These findings suggest a mechanism by which dietary olive oil regulates blood glucose levels and present a novel functional role for enteropancreatic neurons in regulating glucose homeostasis.

physiology↗

bioRxiv2025

Tying the Knot: In Silico Design of Foldable Lasso Peptides

Lasso peptides are a unique class of natural products with distinctively threaded structures, conferring exceptional stability against thermal and proteolytic degradation. Despite their promising biotechnological and pharmaceutical applications, reported attempts to prepare them by chemical synthesis result in forming the nonthreaded branched-cyclic isomer, rather than the desired lassoed structure. This is likely due to the entropic challenge of folding a short, threaded motif prior to chemically mediated cyclization. Accordingly, this study aims to better understand and enhance the relative stability of pre-lasso conformations--the essential precursor to lasso peptide formation--through sequence optimization, chemical modification, and disulfide incorporation. Using Rosetta fixed backbone design, optimal sequences for several class II lasso peptides are identified. Enhanced sampling with well-tempered metadynamics confirmed that designed sequences derived from the lasso structures of rubrivinodin and microcin J25 exhibit a notable improvement in pre-lasso stability relative to the competing nonthreaded conformations. Chemical modifications to the isopeptide bond-forming residues of microcin J25 further increase the probability of pre-lasso formation, highlighting the beneficial role of non-canonical amino acid residues. Counterintuitively, the introduction of a disulfide cross-link decreased pre-lasso stability. Although cross-linking inherently constrains the peptide structure, decreasing the entropic dominance of unfolded phase space, it hinders the requisite wrapping of the N-terminal end around the tail to adopt the pre-lasso conformation. However, combining chemical modifications with the disulfide cross-link results in further pre-lasso stabilization, indicating that the ring modifications counteract the constraints and provide a cooperative benefit with cross-linking. These findings lay the groundwork for further design efforts to enable synthetic access to the lasso peptide scaffold. SIGNIFICANCELasso peptides are a unique class of ribosomally synthesized and post-translationally modified natural products with diverse biological activities and potential for therapeutic applications. Although direct synthesis would facilitate therapeutic design, it has not yet been possible to fold these short sequences to their threaded architecture without the help of biosynthetic enzyme stabilization. Our work explores strategies to enhance the stability of the pre-lasso structure, the essential precursor to de novo lasso peptide formation. We find that sequence design, incorporating non-canonical amino acid residues, and design-guided cross-linking can augment stability to increase the likelihood of lasso motif accessibility. This work presents several strategies for the continued design of foldable lasso peptides.

biophysics↗

bioRxiv2022

A widespread methylotroph acyl-homoserine lactone synthase produces an atypical quorum sensing signal

Pink pigmented facultative methylotrophs of the genera Methylorubrum and Methylobacterium are omnipresent bacteria often found associated with plants. Despite their widespread occurrence, the molecular details of how these organisms interact with each other and their environment remain understudied. We analyzed genes encoding N-acylhomoserine lactone quorum sensing signal synthases in published genomes of these bacteria and determined that the product of the largest group of signal synthases had not been characterized. We subsequently identified this N-acylhomoserine lactone product using inverse stable isotopic labeling (InverSIL), which revealed an atypical signal. We then demonstrate in one representative strain that this signal activates its cognate LuxR-family transcription factor and is produced in a positive feedback loop. These results reveal a previously undescribed yet widespread signal used by pink pigmented facultative methylotrophs, which helps us understand the chemical ecology of these important bacteria.

microbiology↗

bioRxiv2021

A novel method for producing functionalized vesicles that efficiently deliver oligonucleotides in vitro and in vivo in mice

Nano-based delivery systems have enhanced our ability to administer and target drugs and macromolecules to their targets. Oligonucleotide drugs have great therapeutic potential but often have off-target effects and stability issues. Therefore, they are often encapsulated in vesicles with targeting ligands such as antibodies (Ab) to deliver their cargo. Herein, we describe a novel, scalable and straightforward approach to producing functionalized vesicles called the "Functionalized Lipid Insertion Method," which differs from the older "Detergent-Dialysis Method." The latter method required excess detergent and extensive dialysis over many hours to produce the functionalized vesicles. With our method, only the functionalized lipid is detergent-solubilized during the engineering of the vesicle. The approach reduces the dialysis time, keeps the vesicles intact while orienting the targeting moieties of the functionalized lipid toward the outside of the vesicle. Pilot in vitro and in vivo experiments was performed to show the feasibility of our method. Dynamic light scattering (DLS) experiments suggested that the original vesicular structure was relatively unperturbed, and the functionalized lipid was inserted externally. Our approach efficiently delivered oligonucleotides and affected the function of liver cancer HepG2 cells. Furthermore, functionalized vesicles achieved targeted delivery of oligonucleotides in mice without inducing a significant innate immune response. The industrial and therapeutic significance and implications of functionalized vesicles produced by our method are also discussed. Additional experiments and analyses are recommended to bring out the full potential of this molecular delivery technology.

bioengineering↗