Biology subjects

Nathan, J. A.

Publications and source records attributed to Nathan, J. A..

17 recordsLinked to original sources

bioRxiv2026

Regulation of proteasome activation by a ubiquitin-independent feedback mechanism

The ubiquitin-proteasome system is the major pathway for selective protein degradation in eukaryotic cells. Some proteins are degraded by the proteasome without ubiquitination, but the prevalence and underlying mechanisms remain poorly understood. Here, we use pulsed-SILAC proteomics to systematically identify proteins undergoing ubiquitin-independent proteasomal degradation (UbInPD). We identify the paralogous proteasome activation factors ZFAND5 and ZFAND6 (ZFAND5/6) and show that ZFAND5 contains a ubiquitin-independent degron that can both promote its rapid turnover and allosterically activate the proteasome. These findings support a model in which proteasome activation and activator degradation are coupled through a ubiquitin-independent feedback mechanism. We further show that ZFAND5/6, together with the scaffold protein p62, restrain NF-{kappa}B activation in the TLR4 pathway. We link this regulation to the degradation of UBCH5c, an abundant E2 ubiquitin-conjugating enzyme that can initiate or prime ubiquitin chain synthesis. Our findings expand the known landscape of UbInPD and reveal unexpected links between proteasome activation, E2 enzyme regulation, and inflammatory signalling.

biochemistry↗

bioRxiv2025

Protein-protein interactions drive differences in the spatiotemporal dynamics of transcription factors NANOG and SOX2 in naïve pluripotent cells

Maintenance of naive pluripotency requires core transcription factors (TFs) like SOX2 and auxiliary TFs like NANOG, yet molecular mechanisms governing their intra-nuclear dynamics and DNA binding interactions remain unclear. Here, using high-density 3D single-molecule light-field microscopy combined with novel spatiotemporal analysis pipelines, we track SOX2 and NANOG dynamics in live cells. Despite lower protein abundance, NANOG displays a similar chromatin-bound fraction to SOX2. This arises partially because, while both TFs undergo frequent transient non-specific binding interactions ([~]0.5-0.7s), NANOG exhibits more stable specific binding ([~]25s vs [~]16s). Both TFs also assemble into phase-separated domains of [~]400 nm containing both freely diffusing and chromatin-bound proteins, which further influences their dynamics. Strikingly, NANOGs protein-protein interaction domain markedly increases chromatin residence time (>5-fold) and the size of these phase-separated domains. Our work uncovers how NANOG and SOX2 stabilise gene regulatory networks that maintain naive pluripotency while providing quantitative pipelines for dissecting spatiotemporal TF dynamics.

cell biology↗

bioRxiv2025

Developmental changes in the carotid body transcriptome accompanying the maturation of chemosensitivity

The carotid body (CB) chemoreceptors mediate rapid cardiorespiratory reflexes to hypoxia, which mature peri-natally and are vital for fetal hypoxia tolerance and post-natal ventilatory control. This maturation is associated with an increase in the sensitivity of the CB electrophysiological response to hypoxia (chemosensitivity): a process that is incompletely understood but critical to systemic oxygen homeostasis. Hypothesizing that perinatal CB gene expression changes would reveal candidate mechanisms for oxygen chemosensitivity, we studied the CB transcriptome in sheep, where peri-natal CB physiology is well-characterised. CB-mediated cardiovascular reflexes are detectable at fetal day 120, and robust by term (day 145), while hypoxic ventilatory responses are established by post-natal day 15. We performed RNA sequencing on sheep CBs at each of these stages, and adults, along with the superior cervical ganglion (SCG) as an oxygen-insensitive control. This allowed us to define tissue-specific changes in the CB transcriptome correlating with chemosensitivity maturation. Striking, progressive CB enrichment is observed in genes implicated in murine CB chemosensitivity, including potassium channels (KCNK9), mitochondrial complex IV regulators (NDUFA4L2, HIGD1C), and HIF-2 (EPAS1). Genes with this expression pattern are also enriched for regulators of diacylglycerol (DAG), particularly the DAG kinase DGKH: one of the most abundant CB transcripts increasing in parallel with chemosensitivity. Across developmental stages, the CB also exhibits marked down-regulation of metabolic pathways and ATP/GTP consuming processes, potentially providing a state permissive to metabolic signal detection. Together, this builds a detailed picture of the CB transcriptional signature, with core features established in fetal life and conserved across species. Key pointsO_LIThe carotid body (CB) chemoreceptors mediate rapid cardiorespiratory responses to hypoxia, which maintain systemic oxygen homeostasis, but CB dysfunction is also implicated in pathologies including hypertension, heart failure and sudden infant death. C_LIO_LICB-mediated chemoreflexes mature during the peri-natal period, with increasing sensitivity of the oxygen chemosensory response. C_LIO_LIWe performed RNA-seq of CBs from sheep across 3 peri-natal stages and adults, enabling us to identify gene expression changes that correlate with functional state. C_LIO_LIWe describe a CB transcriptomic signature that is conserved across species, established in fetal life, and correlates with maturation. This includes features of a unique metabolic phenotype, and up-regulation of genes encoding the extracellular matrix and diacylglycerol signalling. The top transcription factor correlating with functional maturation is EPAS1/ HIF-2. C_LIO_LIWe anticipate that this data set will be a valuable resource in generating novel hypotheses on mechanisms of oxygen chemosensory function, development and CB-associated pathologies. C_LI

physiology↗

bioRxiv2025

SET1B drives sustained HIF activity and disease progression in clear cell renal cell carcinoma.

The cellular response to hypoxia is driven by hypoxia-inducible factors (HIFs), which regulate genes involved in glycolysis, angiogenesis, and cell proliferation, as well as inflammation and tumour progression. HIF activation is well-characterised and is primarily regulated by oxygen-dependent prolyl hydroxylation and subsequent degradation. However, how transcription of individual HIF target genes is regulated at the chromatin level is less clear. SET1B, a histone H3 lysine 4 (H3K4) methyltransferase, has emerged as a key modulator of HIF target gene transcription. Our study reveals that SET1B interacts with RNA Polymerase II to coordinate sustained HIF-mediated transcriptional activity through multiple functional domains. We also show that in clear cell renal cell carcinoma (ccRCC), SET1B is critical for sustained HIF activity, and SET1B expression correlates with disease progression and metastasis in patient samples. Moreover, SET1B depletion enhances the efficacy of HIF-2 inhibitors, establishing SET1B as a potential therapeutic target in ccRCC.

cancer biology↗

bioRxiv2025

ABHD11 inhibition drives sterol metabolism to modulate T cell effector function and alleviate autoimmunity

Chronic inflammation in autoimmunity is driven by T cell hyperactivation. This unregulated response to self is fuelled by heightened metabolic programmes, which offers a promising new direction to uncover novel treatment strategies. /{beta}-hydrolase domain-containing protein 11 (ABHD11) is a mitochondrial hydrolase that maintains the catalytic function of -ketoglutarate dehydrogenase (-KGDH), and its expression in CD4+ T cells has been linked to remission status in rheumatoid arthritis (RA). However, the importance of ABHD11 in regulating T cell metabolism and function - and thus, the downstream implication for autoimmunity - is yet to be explored. Here, we show that pharmacological inhibition of ABHD11 dampens cytokine production by human and mouse T cells. Mechanistically, the anti-inflammatory effects of ABHD11 inhibition are attributed to increased 24,25-epoxycholesterol (24,25-EC) biosynthesis and subsequent liver X receptor (LXR) activation, which arise from a compromised TCA cycle. The impaired cytokine profile established by ABHD11 inhibition is extended to two patient cohorts of autoimmunity. Importantly, using a murine model of accelerated type 1 diabetes (T1D), we show that targeting ABHD11 suppresses cytokine production in antigen-specific T cells and delays the onset of diabetes in vivo. Collectively, our work provides pre-clinical evidence that ABHD11 is an encouraging drug target in T cell-mediated autoimmunity. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/643996v1_ufig1.gif" ALT="Figure 1"> View larger version (59K): org.highwire.dtl.DTLVardef@bb3fcborg.highwire.dtl.DTLVardef@1594fc8org.highwire.dtl.DTLVardef@84e078org.highwire.dtl.DTLVardef@1ad023e_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2025

Mapping the genetic landscape of iron metabolism uncovers the SETD2 methyltransferase as a modulator of iron flux.

Cellular iron levels must be tightly regulated to ensure sufficient iron for essential enzymatic functions whilst avoiding the harmful generation of toxic species. Here, to better understand how iron levels are controlled, we carry out genome-wide mutagenesis screens in human cells. Alongside mapping known components of iron-sensing, we determine the relative contributions of iron uptake, iron recycling, ferritin breakdown, and mitochondrial flux in controlling the labile iron pool. We also identify SETD2, a histone methyltransferase, as a chromatin modifying enzyme that controls intracellular iron availability through ferritin breakdown. Functionally, we show that SETD2 inhibition or cancer-associated SETD2 mutations render cells iron deficient, thereby driving resistance to ferroptosis, and potentially explaining how some tumours evade anti-tumoural immunity.

cell biology↗

bioRxiv2024

ABHD11 mediated deglutarylation regulates the TCA cycle and T cell metabolism

Glutarate is an intermediate of amino acid catabolism and an important metabolite for reprogramming T cell immunity, exerting its effects by inhibition of histone demethylase enzymes or through glutarylation. However, how distinct glutarate modifications are regulated is unclear. Here, we uncover a deglutarylation pathway that couples amino acid catabolism to tricarboxylic acid (TCA) cycle function. By examining how glutarate can form conjugates with lipoate, an essential mitochondrial modification for the TCA cycle, we find that Alpha Beta Hydrolase Domain 11 (ABHD11) protects against the formation of glutaryl-lipoyl adducts. Mechanistically, ABHD11 acts as a thioesterase to selectively remove glutaryl adducts from lipoate, maintaining integrity of the TCA cycle. Functionally, ABHD11 influences the metabolic reprogramming of human T cells, increasing central memory T cell formation and attenuating oxidative phosphorylation. These results uncover ABHD11 as a selective deglutarylating enzyme and highlight that targeting ABHD11 offers a potential approach to metabolically reprogramme cytotoxic T cells.

cell biology↗

bioRxiv2024

VHL synthetic lethality screens uncover CBF-beta as a negative regulator of STING

Clear cell renal cell carcinoma (ccRCC) represents the most common form of kidney cancer and is typified by biallelic inactivation of the von Hippel-Lindau (VHL) tumour suppressor gene. Here, we undertake genome-wide CRISPR/Cas9 screening to reveal synthetic lethal interactors of VHL, and uncover that loss of Core Binding Factor {beta} (CBF-{beta}) causes cell death in VHL-null ccRCC cell lines and impairs tumour establishment and growth in vivo. This synthetic relationship is independent of the elevated activity of hypoxia inducible factors (HIFs) in VHL-null cells, but does involve the RUNX transcription factors that are known binding partners of CBF-{beta}. Mechanistically, CBF-{beta} loss leads to upregulation of type I interferon signalling, and we uncover a direct inhibitory role for CBF-{beta} at the STING locus controlling Interferon Stimulated Gene expression. Targeting CBF-{beta} in kidney cancer both selectively induces tumour cell lethality and promotes activation of type I interferon signalling.

cancer biology↗

bioRxiv2024

Hypoxia promotes airway differentiation in the human lung epithelium

Human early embryos develop under physiological hypoxia, but how hypoxia regulates human organogenesis remains little known. We have investigated oxygen availability effects on the human lung epithelium using organoids. We find first-trimester lung epithelial progenitors remain undifferentiated under normoxia, but spontaneously differentiate towards multiple airway cell types and inhibit alveolar differentiation under hypoxia. Using chemical and genetic tools, we demonstrate that hypoxia-induced airway differentiation is dependent on HIF (Hypoxia-Inducible Factor) pathways, with HIF1 and HIF2 differentially regulating fate decisions. Transcription factors KLF4 and KLF5 are direct targets of the HIF pathway and promote progenitor differentiation to basal and secretory cells. Chronic hypoxia also induces transdifferentiation of human alveolar type 2 cells to airway cells via the HIF pathway, mimicking alveolar bronchiolization processes in lung disease. Our results reveal roles for hypoxia and HIF signalling during human lung development and have implications for aberrant cell fate decisions in chronic lung diseases.

developmental biology↗

bioRxiv2024

Deubiquitinating enzyme mutagenesis screens identify a USP43 driven HIF-1 transcriptional response

The ubiquitination and proteasome-mediated degradation of Hypoxia Inducible Factors (HIFs) is central to metazoan oxygen-sensing, but the involvement of deubiquitinating enzymes (DUBs) in HIF signalling is less clear. Here, using a bespoke DUBs sgRNA library we conduct CRISPR/Cas9 mutagenesis screens to determine how DUBs are involved in HIF signalling. Alongside defining DUBs involved in HIF activation or suppression, we identify USP43 as a DUB required for efficient activation of a HIF response. USP43 is hypoxia regulated and selectively associates with the HIF-1 isoform, and while USP43 does not alter HIF-1 stability, it facilitates HIF-1 nuclear accumulation and binding to its target genes. Mechanistically, USP43 associates with 14-3-3 proteins in a hypoxia and phosphorylation dependent manner to increase the nuclear pool of HIF-1. Together, our results unveil the DUB landscape in HIF signalling, and highlight the multifunctionality of DUBs, illustrating that they can provide important signalling functions alongside their catalytic roles.

cell biology↗

bioRxiv2022

Glutarate regulates T cell function and metabolism

T cell function is influenced by several metabolites; some acting through enzymatic inhibition of -KG-dependent dioxygenases (KGDDs), others, through post-translational modification of lysines in important targets. We show here that glutarate, a product of amino acid catabolism, has the capacity to do both, with effects on T cell function and differentiation. Glutarate exerts those effects through KGDD inhibition and through direct regulation of T cell metabolism via post-translational modification of the pyruvate dehydrogenase E2 subunit. Diethyl-glutarate, a cell-permeable form of glutarate, alters CD8+ T cell differentiation and increases cytotoxicity against target cells. In vivo administration of the compound reduces tumor growth and is correlated with increased levels of both peripheral and intratumoral cytotoxic CD8+ T cells. These results demonstrate that glutarate regulates both T cell metabolism and differentiation, with a potential role in the improvement of T cell immunotherapy.

immunology↗

bioRxiv2021

LRRC15 mediates an accessory interaction with the SARS-CoV-2 spike protein

The interactions between severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) and human host factors enable the virus to propagate infections that lead to COVID-19. The spike protein is the largest structural component of the virus and mediates interactions essential for infection, including with the primary ACE2 receptor. We performed two independent cell-based systematic screens to determine whether there are additional proteins by which the spike protein of SARS-CoV-2 can interact with human cells. We discovered that in addition to ACE2, expression of LRRC15 also causes spike protein binding. This interaction is distinct from other known spike attachment mechanisms such as heparan sulfates or lectin receptors. Measurements of orthologous coronavirus spike proteins implied the interaction was restricted to SARS-CoV-2, suggesting LRRC15 represents a novel class of spike binding interaction. We localized the interaction to the C-terminus of the S1 domain, and showed that LRRC15 shares recognition of the ACE2 receptor binding domain. From analyzing proteomics and single-cell transcriptomics, we identify LRRC15 expression as being common in human lung vasculature cells and fibroblasts. Although infection assays demonstrated that LRRC15 alone is not sufficient to permit viral entry, we present evidence it can modulate infection of human cells. This unexpected interaction merits further investigation to determine how SARS-CoV-2 exploits host LRRC15 and whether it could account for any of the distinctive features of COVID-19. In briefWe present evidence from genome-wide screening that the spike protein of SARS-CoV-2 interacts with human cells expressing LRRC15. The interaction is distinct from previously known classes of spike attachment factors, and appears to have emerged recently within the coronavirus family. Although not sufficient for cell invasion, this interaction can modulate viral infection. Our data point to an unappreciated host factor for SARS-CoV-2, with potential relevance to COVID-19. Highlights- Two systematic cell-based screens for SARS-CoV-2 spike protein binding identify LRRC15 as a human host factor - Interaction with LRRC15 is reproducible in different human cell lines and independent of known glycan or ACE2 binding pathways - The C-terminal S1 domain of SARS-CoV-2 spike binds LRRC15 with sub-micromolar affinity, while related coronavirus spikes do not - LRRC15 is expressed in tissues with high ACE2 levels and may modulate infection

biochemistry↗

bioRxiv2021

Cigarette smoke preferentially induces full length ACE2 exposure in primary human airway cells but does not alter susceptibility to SARS-CoV-2 infection

Cigarette smoking has multiple serious negative health consequences. However, the epidemiological relationship between cigarette smoking and SARS-CoV-2 infection is controversial; and the interaction between cigarette smoking, airway expression of the ACE2 receptor and the susceptibility of airway cells to infection is unclear. We exposed differentiated air-liquid interface cultures derived from primary human airway stem cells to cigarette smoke extract (CSE) and infected them with SARS-CoV-2. We found that CSE increased expression of full-length ACE2 (flACE2) but did not alter the expression of a Type I-interferon sensitive truncated ACE2 that lacks the capacity to bind SARS-CoV-2 or a panel of interferon-sensitive genes. Importantly, exposure to CSE did not increase viral infectivity despite the increase in flACE2. Our data are consistent with epidemiological data suggesting current smokers are not at excess risk of SARS-CoV-2 infection. This does not detract from public health messaging emphasising the excess risk of severe COVID-19 associated with smoking-related cardiopulmonary disease.

microbiology↗

bioRxiv2021

Topical TMPRSS2 inhibition prevents SARS-CoV-2 infection in differentiated primary human airway cells

BackgroundThere are limited effective prophylactic treatments for SARS-CoV-2 infection, and limited early treatment options. Viral cell entry requires spike protein binding to the ACE2 receptor and spike cleavage by TMPRSS2, a cell surface serine protease. Targeting of TMPRSS2 by either androgen blockade or direct inhibition is already in clinical trials in early SARS-CoV-2 infection. MethodsThe likely initial cells of SARS-CoV-2 entry are the ciliated cells of the upper airway. We therefore used differentiated primary human airway epithelial cells maintained at the air-liquid interface (ALI) to test the impact of targeting TMPRSS2 on the prevention of SARS-CoV-2 infection. ResultsWe first modelled the systemic delivery of compounds. Enzalutamide, an oral androgen receptor antagonist, had no impact on SARS-Cov-2 infection. By contrast, camostat mesylate, an orally available serine protease inhibitor, blocked SARS-CoV-2 entry. However, camostat is rapidly metabolised in the circulation in vivo, and systemic bioavailability after oral dosing is low. We therefore modelled local airway administration by applying camostat to the apical surface of the differentiated ALI cultures. We demonstrated that a brief exposure to topical camostat is effective at restricting SARS-CoV-2 viral infection. ConclusionThese experiments demonstrate a potential therapeutic role for topical camostat for pre- or post-exposure prophylaxis of SARS-CoV-2, which can now be evaluated in a clinical trial.

microbiology↗

bioRxiv2020

A thermostable, closed, SARS-CoV-2 spike protein trimer.

The spike (S) protein of SARS-CoV-2 mediates receptor binding and cell entry and is the dominant target of the immune system. S exhibits substantial conformational flexibility. It transitions from closed to open conformations to expose its receptor binding site, and subsequently from prefusion to postfusion conformations to mediate fusion of viral and cellular membranes. S protein derivatives are components of vaccine candidates and diagnostic assays, as well as tools for research into the biology and immunology of SARS-CoV-2. Here we have designed mutations in S which allow production of thermostable, crosslinked, S protein trimers that are trapped in the closed, pre-fusion, state. We have determined the structures of crosslinked and non-crosslinked proteins, identifying two distinct closed conformations of the S trimer. We demonstrate that the designed, thermostable, closed S trimer can be used in serological assays. This protein has potential applications as a reagent for serology, virology and as an immunogen.

biochemistry↗

bioRxiv2020

ABHD11 regulates 2-oxoglutarate abundance by protecting mitochondrial lipoylated proteins from lipid peroxidation damage

2-oxoglutarate (2-OG or -ketoglutarate) relates mitochondrial metabolism to cell function by modulating the activity of 2-OG dependent dioxygenases (2-OG DDs) involved in the hypoxia response and DNA/histone modifications. However, metabolic pathways that regulate these oxygen and 2-OG sensitive enzymes remain poorly understood. Here, using CRISPR Cas9 genome-wide mutagenesis to screen for genetic determinants of 2-OG levels, we uncover a redox sensitive mitochondrial lipoylation pathway, dependent on the mitochondrial hydrolase ABHD11, that signals changes in mitochondrial 2-OG metabolism to 2-OG DD function. ABHD11 loss or inhibition drives a rapid increase in 2-OG levels by impairing lipoylation of the 2-OG dehydrogenase complex (OGDHc) - the rate limiting step for mitochondrial 2-OG metabolism. Rather than facilitating lipoate conjugation, ABHD11 protects the catalytic lipoyl domain from lipid peroxidation products formed by oxidative damage, demonstrating a requirement for a lipoyl repair pathway in human cells, and highlighting how the redox sensitivity of lipoylation modulates 2-OG metabolism.

cell biology↗

bioRxiv2018

The sterol-responsive RNF145 E3 ubiquitin ligase mediates the degradation of HMG-CoA reductase together with gp78 and Hrd1

HMG-CoA reductase (HMGCR), the rate-limiting enzyme of the cholesterol biosynthetic pathway and the therapeutic target of statins, is post-transcriptionally regulated by sterol-accelerated degradation. Under cholesterol-replete conditions, HMGCR is ubiquitinated and degraded, but the identity of the E3 ubiquitin ligase(s) responsible for mammalian HMGCR turnover remains controversial. Using systematic, unbiased CRISPR/Cas9 genome-wide screens with a sterol-sensitive endogenous HMGCR reporter, we comprehensively map the E3 ligase landscape required for sterol-accelerated HMGCR degradation. We find that RNF145 and gp78, independently co-ordinate HMGCR ubiquitination and degradation. RNF145, a sterol-responsive ER-resident E3 ligase, is unstable but accumulates following sterol depletion. Sterol addition triggers RNF145 recruitment to HMGCR and Insig-1, promoting HMGCR ubiquitination and proteasome-mediated degradation. In the absence of both RNF145 and gp78, Hrd1, a third UBE2G2-dependent ligase partially regulates HMGCR activity. Our findings reveal a critical role for the sterol-responsive RNF145 in HMGCR regulation and elucidate the complexity of sterol-accelerated HMGCR degradation.

cell biology↗