Biology subjects

Hudson, B. D.

Publications and source records attributed to Hudson, B. D..

5 recordsLinked to original sources

bioRxiv2025

Inverse Agonism of the FFA4 free fatty acid receptor controls both adipogenesis and mature adipocyte function

Adipocyte disfunction is an important component of many metabolic disorders and there is a need for pharmacological approaches that can restore normal adipocyte function. The FFA4 receptor is a G protein coupled receptor (GPCR), activated by long chain free fatty acids (FFAs), that controls adipocyte function. Importantly, adipocytes produce FFAs, which may directly activate FFA4 and there is a need to better understand how FFAs produced by adipocytes interact with FFA4 signalling. In this study we have employed human and mouse adipocyte cell models to determine how pharmacological agonism or antagonism of FFA4 affects adipogenesis, lipolysis and glucose uptake. We show that a commonly used FFA4 antagonist, AH7614, is an inverse agonist and that treating adipocytes with this compound suppressed adipogenesis, inhibits glucose uptake and enhances isoprenaline stimulated lipolysis. In contrast, treatment with a synthetic FFA4 agonist, TUG-891, has only modest effects on adipogenesis and lipolysis, while showing no effect on glucose uptake. To explore the mechanism for why AH7614 but not TUG-891 affects adipocyte function, we demonstrate that during adipogenic differentiation sufficient FFAs are released into the culture medium to activate FFA4, suggesting AH7614 inhibits an autocrine feedback loop to suppress adipogenesis. In contrast, during lipolysis experiments, insufficient FFAs were released to activate the receptor, suggesting that AH7614 must enhance lipolysis by either inhibiting ligand independent FFA4 signalling, or FFA signalling that does not require the FFAs to be released from the cell. This study will help establish how FFA4 targeting therapeutics could be used to treat adipocyte dysfunction.

pharmacology and toxicology↗

bioRxiv2024

Multi-Coloured Sequential Resonance Energy Transfer for Simultaneous Ligand Binding at G Protein-Coupled Receptors

G protein coupled receptors (GPCRs) are the largest family of signalling proteins and highly successful drug targets. Most GPCR drugs interact with a binding pocket for the natural ligand, typically near the extracellular region of the transmembrane domains. Advancements in structural biology have identified additional allosteric binding sites in other parts of these receptors. Allosteric sites provide theoretical advantages, including the ability to modulate natural ligand function, and there is a need for better ways to study how ligands interact with these binding sites. We have developed an approach to study multiple ligands binding to the same receptor at the same time based on sequential resonance energy transfer between two fluorescent ligands bound to a GPCR. We use this approach to identify novel ligand pharmacology and understand binding kinetics to the FFA1 free fatty acid receptor, a clinically relevant receptor. This novel method will aid development of new GPCR drugs.

pharmacology and toxicology↗

bioRxiv2023

A new paradigm of intracrine free fatty acid receptor 4 signaling at lipid droplets

G protein-coupled receptors (GPCRs), once thought to be active exclusively at the plasma membrane, have been shown to signal from multiple intracellular membrane compartments, including endosomes and the Golgi. However, the potential occurrence and functional relevance of intracellular signaling for the emerging family of metabolite-sensing GPCRs is largely unknown. Here, we used live-cell imaging, bioluminescence resonance energy transfer (BRET) measurements, and functional readouts to investigate signal compartmentalization of the free fatty acid receptor 4 (FFA4), a prototypical metabolite-sensing GPCR that is activated by medium- and long-chain free fatty acids (FFAs). Unexpectedly, we show that FFA4 largely resides on intracellular membranes that are intimately associated with lipid droplets in adipocytes. Upon lipolysis induction, the released FFAs rapidly bind to and activate this intracellular pool of FFA4, leading to local Gi/o coupling and inhibition of cAMP production in the vicinity of lipid droplets. This provides a spatiotemporally confined negative feedback mechanism allowing individual lipid droplets to rapidly adjust their lipolysis rate. Our results reveal a novel intracrine signaling modality by a prototypical metabolite-sensing GPCR and identify a new lipid-droplet-associated signaling hub implicated in the rapid regulation of lipid metabolism, with important implications for adipocyte physiology and pharmacology.

pharmacology and toxicology↗

bioRxiv2021

Phosphorylation of the M1 muscarinic acetylcholine receptor mediates protection in neurodegenerative disease

There are currently no treatments that can slow the progression of neurodegenerative diseases such as Alzheimers disease (AD). There is, however, a growing body of evidence that activation of the M1 muscarinic acetylcholine receptor (M1-receptor) can not only restore memory loss in AD patients, but in preclinical animal models can also slow neurodegenerative disease progression. The generation of an effective medicine targeting the M1-receptor has however been severely hampered by associated cholinergic adverse responses. By using genetically engineered mouse models that express a G protein-biased M1-receptor, we recently established that M1-receptor mediated adverse responses can be minimised by ensuring activating ligands maintain receptor phosphorylation/arrestin-dependent signalling. Here, we use these same genetic models in concert with murine prion disease, a terminal neurodegenerative disease showing key hallmarks of AD, to establish that phosphorylation/arrestin-dependent signalling delivers neuroprotection that both extends normal animal behaviour and prolongs the life span of prion diseased mice. Our data point to an important neuroprotective property inherent to the M1-receptor and indicate that next generation M1-receptor ligands designed to drive receptor phosphorylation/arrestin-dependent signalling would potentially show low adverse responses whilst delivering neuroprotection that will slow disease progression.

pharmacology and toxicology↗

bioRxiv2020

Chemogenetic analysis of how receptors for short chain fatty acids regulate the gut-brain axis

The gut-brain axis allows bi-directional communication between the enteric and central nervous systems. Short chain fatty acids (SCFAs) generated by the gut microbiota are important regulators of this interface. However, defining mechanisms by which SCFAs do so has been challenging because, amongst various roles, they co-activate both of a pair of closely related and poorly characterized G protein-coupled receptors, FFA2 and FFA3. Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) can provide an important approach in defining receptor-specific functions. By screening a library of carboxylate-containing small molecules we identified 4-methoxy-3-methyl-benzoic acid (MOMBA) as a specific agonist of a DREADD variant of FFA2 which is not activated by SCFAs. Using mice engineered to replace FFA2 with this FFA2-DREADD, whilst retaining FFA3 expression, combinations of MOMBA and the now FFA3 receptor selective SCFAs defined key, but distinct, roles of FFA2 and FFA3 in each of gut transit time, secretion of entero-endocrine hormones, and communication from the gut to each of autonomic and somatic sensory ganglion cells and the spinal cord. These studies map mechanisms and signalling pathways by which each of FFA2 and FFA3 act to link the gut and the brain and provide both animal models and novel tool compounds to further explore this interface.

pharmacology and toxicology↗