Biology subjects

Nicholson, A. S.

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

6 recordsLinked to original sources

bioRxiv2026

Herpes simplex virus pUL56 abolishes neuronal activity by removing voltage-gated ion channels from the plasma membrane

Herpes simplex virus 1 (HSV-1) infections of the central nervous system cause encephalitis and are associated with increased risk of neurodegeneration, yet the molecular consequences of lytic infection in human neurones remain incompletely defined. We map the transcriptomic, proteomic and surface-proteome changes induced by HSV-1 across the lytic infection cycle in human iPSC-derived cortical glutamatergic neurones. HSV-1 drives extensive plasma-membrane remodelling, including the removal of voltage-gated sodium, potassium and calcium channels, resulting in a profound loss of synchronous calcium signalling. We identify the viral ubiquitin-ligase adaptor pUL56 as the principal effector of this process: pUL56-dependent depletion of ion channels abolishes coordinated calcium signalling, whereas deletion or mutation of its E3-ligase binding motifs preserves synchrony. Furthermore, expression of pUL56 alone is sufficient to abolish neuronal electrical activity. These findings establish pUL56 as a potent viral suppressor of neuronal excitability and provide potential mechanistic links between HSV-1 infection and neurodegenerative pathology.

microbiology↗

bioRxiv2026

Human iPSC Models of Ganglioside Deficiency Reveal a Sialylated Lipid Requirement for Plasma-Membrane Organization and Neuronal Activity

Gangliosides are abundant neuronal glycosphingolipids, yet their roles in organizing the plasma membrane and supporting neuronal function remain poorly defined. Mutations in the biosynthetic enzymes ST3GAL5 or B4GALNT1 cause severe neurodevelopmental disorders, yet their cellular consequences are unclear. Using isogenic human iPSC-derived cortical neurons, we show that loss of these enzymes eliminates major neuronal gangliosides but produces strikingly divergent outcomes. ST3GAL5 deficiency reprograms the glycosphingolipid repertoire toward non-neuronal species and abolishes network-level electrical activity. In contrast, B4GALNT1-deficient neurons retain near-normal excitability, supported by accumulation of simple sialylated precursors (GM3/GD3). Quantitative proteomics reveals a profound loss of plasma membrane proteins, including ion channels and synaptic organizers, only in ST3GAL5-deficient neurons. These findings identify sialylated glycosphingolipids as essential scaffolds for plasma membrane organization and neuronal excitability, providing a mechanistic basis for the severe phenotype caused by loss of GM3 synthase in humans. TEASERHuman neuronal models reveal why loss of GM3 synthase causes severe neurodevelopmental disease

cell biology↗

bioRxiv2025

Optimisation of lytic herpes simplex virus infection in human induced pluripotent stem cell derived cortical neurones

Herpes simplex virus (HSV)-1 infection of cortical neurones is a leading cause of encephalitis. While we have substantial knowledge about the molecular virology of HSV-1 lytic infection in cells of the periphery, like keratinocytes or fibroblasts, we know much less about infection of human neurones owing to the challenges of working with neuronal cell-based models. Here we demonstrate the use of a human induced pluripotent stem cell (iPSC)-derived cortical neurone model (i3Neurones) for HSV-1 infection. i3Neurones are highly scalable and can be rapidly and efficiently differentiated into an isogenic population of cortical glutamatergic neurones. We show that i3Neurones support the full HSV-1 lytic replication cycle. We present an optimised protocol for the infection of i3Neurones with HSV-1 that allows their synchronous infection at near-100% efficiency, and optimised fixation methods that preserves organelle and neurite structure for immunocytochemistry analysis. Our study highlights i3Neurones as a robust, scalable platform for microscopy and biochemical studies of HSV-1 and other neurotropic pathogens. Data summaryThe authors confirm all supporting data, code and protocols have been provided within the article or through supplementary data files.

microbiology↗

bioRxiv2024

Molecular Insights into Neuronal Dysfunction in GM2 Gangliosidoses

Glycosphingolipids (GSL) are important bioactive components of cellular membranes. Complex GSLs, containing sialic acid residues are known as gangliosides and are highly abundant in the brain. Diseases of ganglioside metabolism often result in severe, early-onset neurodegeneration. The ganglioside GM2 is the substrate of the hydrolytic lysosomal {beta}- hexosaminidase A (HexA) enzyme and when subunits of this enzyme are non-functional, GM2 lipid accumulates in cells leading to the GM2 gangliosidoses, Tay-Sachs and Sandhoff diseases. We have developed high-quality i3Neuron-based models of Tay-Sachs and Sandhoff diseases, that demonstrate storage of GM2, formation of membrane whorls and accumulation of endolysosomal proteins consistent with disease phenotypes. Importantly, in addition to lysosomal dysfunction, the composition of the plasma membrane (PM) is significantly impacted in these diseases with changes in the abundance of both lipids and proteins. The changes to the PM proteome are driven in part by exocytosis of lysosomal material resulting in the aberrant accumulation of lysosomal proteins and lipids on the cell surface. The altered abundance of GM2 at the PM was striking, bringing the abundance of this precursor lipid up to that of the common neuronal gangliosides. Furthermore, the PM profiling identifies significant changes in synaptic protein abundances with direct functional impact on neuronal activity including rapid electrical firing consistent with neuronal hyperactivity. This work provides mechanistic insights into neuronal dysfunction in the GM2 gangliosidoses and highlights that these are also severe PM disorders. This work has broad implications for other lysosomal storage disorders and late-onset neurodegenerative diseases involving sphingolipid dysregulation.

neuroscience↗

bioRxiv2022

Altered plasma membrane abundance of the sulfatide-binding protein NF155 links glycosphingolipid imbalances to demyelination

Myelin is a multi-layered membrane that tightly wraps neuronal axons enabling efficient, high-speed signal propagation. The axon and myelin sheath form tight contacts, mediated by specific plasma membrane proteins and lipids, and disruption of these contacts causes devastating demyelinating diseases. Using two cell-based models of demyelinating sphingolipidoses, we demonstrate that altered lipid metabolism changes the abundance of specific plasma membrane proteins. These altered membrane proteins have known roles in cell adhesion and signalling, with several implicated in neurological diseases. The cell surface abundance of the adhesion molecule Neurofascin, a protein critical for the maintenance of myelin-axon contacts, changes following disruption to sphingolipid metabolism. This provides a direct molecular link between altered lipid abundance and myelin stability. We show that the Neurofascin isoform NF155, but not NF186, interacts directly and specifically with the sphingolipid sulfatide via multiple binding sites and that this interaction requires the full-length extracellular domain of NF155. We demonstrate that NF155 adopts an S-shaped conformation and preferrentially binds sulfatide-containing membranes in cis, with important implications for protein arrangement in the tight axon-myelin space. Our work links glycosphingolipid imbalances to disturbance of membrane protein abundance and demonstrates how this may be driven by direct protein-lipid interactions, providing a mechanistic framework to understand the pathogenesis of galactosphingolipidoses.

neuroscience↗

bioRxiv2022

Attenuation hotspots in neurotropic human astroviruses

During the last decade, the detection of neurotropic astroviruses has increased dramatically. The MLB genogroup of astroviruses represents a genetically distinct group of zoonotic astroviruses associated with gastroenteritis and severe neurological complications in young children, the immunocompromised and the elderly. Using different virus evolution approaches, we identified dispensable regions in the 3' end of the capsid-coding region responsible for attenuation of MLB astroviruses in susceptible cell lines. To create recombinant viruses with identified deletions, MLB reverse genetics and replicon systems were developed. Recombinant truncated MLB viruses had wild type-like or enhanced growth and replication properties in permissive cells but were strongly attenuated in iPSC-derived neuronal cultures confirming the location of neurotropism determinants. This approach can be used for the development of vaccine candidates using attenuated astroviruses that infect humans, livestock animals and poultry.

microbiology↗