Biology subjects

Mohammed, S.

Publications and source records attributed to Mohammed, S..

At least 37 records · Page 2Linked to original sources

bioRxiv2025

Isostere 18F-protein post-translational editing enables dynamic tracking of neurodegeneration biomarkers

The neurofilament light chain protein (NfL) is a suggested general marker for neuronal loss. Its release from brain parenchyma into cerebral spinal fluid, and presumed detection in blood has seen it established as a first blood-based marker of disease activity and drug efficacy in multiple sclerosis (MS) and in the presymptomatic diagnosis and assessment of disease course for other neurodegenerative disorders.1 However, the lack of characterisation of its behaviour in circulation, largely due to its antibody-dependent measurement, have hampered the biological interpretation of these measurements, especially after acute injury such as in MS relapse or head trauma.2 Here, we describe a strategy for exploiting positron emission tomography (PET) imaging using isosteric protein mimics following the installation of a fluorine-18 label that is benign enough to provide sensitive, real-time information on the dynamics and trafficking of NfL protein. This circumvents the limits of current methods that integrate 18F into proteins through the bio-conjugation of bulky, unnatural groups, which we show perturb NfLs assembly and functional properties from those in the natural state. We use a visible-light-driven reaction to access radioactive isostere proteins that are unperturbed and so closely resemble their native form. In this way, generation of [18F]fluoroalkyl radicals that can be rapidly reacted at pre-defined sites on proteins creates mimics of proteinogenic side chains bearing near-zero-size labels to probe proteins in functionally true form. These prosthetic-free, protein radiotracers can be generated in excellent radiochemical yield (up to 67%) via a semi-automated protocol in just 15 mins. High associated molar activities (precursor up to 102 GBq mol-1) allowed high sensitivity dynamic observations in blood, brain and cerebrospinal fluid, enabling even the first unambiguous observations of spinal flow kinetics using proteins. These dynamics, including the high rate of spinal flow (on the order of mm per min) and drainage of NfL from CSF into sacral lymph nodes, now provides evidence that the slow fall rate of antibody-detected markers that is observed after acute neural insults is not due to a long half-life, but rather reflects sustained neuronal loss. This discovery will now help to better correlate clinical and radiological features of disease with NfL blood levels. Our methodology now demonstrates the broad potential of a near-zero-size labelling method for the functional study of proteins in whole organisms without interfering with their biological activity and native assembly.

synthetic biology↗

bioRxiv2025

SERUM AND PLASMA SPHINGOLIPIDS AS BIOMARKERS OFANTHRACYCLINE-INDUCED CARDIOTOXICITY

Although effective as a chemotherapy, the utility of Doxorubicin (Dox) is hampered by cardiotoxicity. Despite this, the ability to predict and guide monitoring of patients receiving Dox or other anthracyclines is hampered by a lack of effective biomarkers to identify susceptible patients, and to detect early signs of subclinical cardiotoxicity. Based on their well-established roles in the response to Dox and other chemotherapies, we performed a retrospective analysis of serum and plasma sphingolipids (SLs) from patients undergoing anthracycline-containing therapy, correlating with cardiac parameters assessed by echocardiography. Results showed there were substantial changes in both plasma and serum SL species during therapy including ceramide (Cer), deoxydihydroCer, and dihydrosphingosine with reversion towards baseline following treatment. Linear mixed-effects model analysis revealed that at baseline, a number of SLs correlated with adverse cardiac outcomes with serum sphingosine-1-phosphate (S1P) and dihydroS1P, and plasma Cer performing comparably to the prognostic value of pro-NT-BNP, an established biomarker of cardiotoxicity. Intriguingly, while pro-NT-BNP had no predictive value at mid- and post-therapy timepoints, serum S1P and dhS1P and plasma Cer levels showed correlation with adverse outcomes, particularly at the post-therapy timepoint. Finally, analysis of plasma and serum C16:C24- Cer ratios - previously reported as predictive of adverse cardiac outcomes - showed no correlation in the context of anthracycline treatment. Taken together, this pilot study provides supporting evidence that plasma and serum SLs may have benefit as both prognostic and diagnostic biomarkers for patients undergoing anthracycline-containing therapy. This suggests that diagnostic SL measurements - recently implemented for metabolic-associated cardiac disorders - could have wider utility.

physiology↗

bioRxiv2024

XRN1 supplies free nucleotides to feed alphavirus replication

Several RNA viruses induce widespread degradation of cellular mRNAs upon infection; however, the biological significance and mechanistic details of this phenomenon remain unknown. Here, we make use of a model alphavirus, Sindbis virus (SINV), to fill this knowledge gap. We found that SINV triggers cellular RNA decay through the exonuclease XRN1 and the 5-to-3 degradation machinery (5-3DM). These proteins accumulate at viral replication organelles (VROs) and interact with the non-structural protein 1 (nsP1), bringing mRNA degradation into proximity with vRNA synthesis. Our data suggest that monophosphate nucleotides released by cellular RNA decay are recycled through the salvage pathway to feed viral replications. Our work thus reveals a fundamental connection between cellular mRNA degradation and viral replication via nucleotides repurposing. Research highlightsO_LI5-3 RNA decay is essential for the replication of a wide range of viruses. C_LIO_LIXRN1 directly interacts with transcripts which are degraded during infection. C_LIO_LIRNA decay factors and salvage pathway members localise to viral factories. C_LIO_LISupplying nucleosides to several 5-3DM deficient cells facilitates SINV infection. C_LI

biochemistry↗

bioRxiv2024

Netupitant Exhibits Potent Activity on Mycobacterium tuberculosis Persisters

In Mycobacterium tuberculosis (Mtb), persisters are genotypically drug-sensitive bacteria that nonetheless survive antibiotic treatment. Persisters represent a significant challenge to shortening TB treatment and preventing relapse, underscoring the need for new therapeutic strategies. In this study, we screened 2,336 FDA-approved compounds to identify agents that enhance the sterilizing activity of standard anti-TB drugs and prevent the regrowth of persisters. Netupitant (NTP), an FDA-approved antiemetic, emerged as a promising candidate with bacteriostatic activity on its own. However, in combination with isoniazid (INH) and rifampicin (RIF), NTP eliminated viable Mtb cells within 7 days, achieving a >6-log reduction in colony-forming units (CFUs) compared to the 2.5-log reduction observed with INH-RIF alone. NTP also demonstrated broad-spectrum efficacy, enhancing the activity of multiple TB drugs, including ethambutol, moxifloxacin, amikacin, and bedaquiline. Notably, NTP retained its potency under hypoxic and caseum-mimicking conditions, both of which are known to enrich for non-replicating, drug-tolerant cells. Interestingly, under hypoxic conditions, NTP demonstrated strong tuberculocidal activity, achieving an approximate 4-log CFU reduction, whereas high-dose INH-RIF was ineffective. Transcriptomic analysis revealed that NTP primarily disrupts cellular bioenergetics, with significant downregulation observed in activities associated with the electron transport chain, oxidative phosphorylation, NADH-ubiquinone oxidoreductase, succinate dehydrogenase, and ATP synthesis. While further studies are required to decipher the mechanism of action and resistance profile of NTP, and to assess its in vivo efficacy, these findings underscore its potential as a promising adjunct to existing TB therapies.

microbiology↗

bioRxiv2024

Uukuniemi virus infection causes a pervasive remodelling of the RNA-binding proteome in tick cell cultures

Cellular RNA-binding proteins (RBPs) are pivotal for the viral lifecycle, mediating key host-virus interactions that promote or repress virus infection. While these interactions have been largely studied in the vertebrate host, no comprehensive analyses of protein-RNA interactions occurring in cells of arbovirus vectors, in particular ticks, have been performed to date. Here we systematically identified the responses of the RNA-binding proteome (RBPome) to infection with a prototype bunyavirus (Uukuniemi virus; UUKV) in tick cells and discovered changes in RNA-binding activity for 283 proteins. In an orthogonal approach, we analysed the composition of the viral ribonucleoprotein by immunoprecipitation of UUKV nucleocapsid protein (N) in infected cells. We found many tick RBPs that are regulated by UUKV infection and associate with viral nucleocapsid protein complexes. We confirmed experimentally that these RBPs impact UUKV infection. This includes the tick homolog of topoisomerase 3B (TOP3B), a protein able to manipulate the topology of RNA, which showed an effect on viral particle production. Our data thus reveals the first protein-RNA interaction map for infected tick cells. Research highlightsO_LIUUKV RNAs interact with nearly three hundred tick cell RBPs. C_LIO_LIDemonstrated an enrichment of N protein interactors within the upregulated RIC data suggesting a direct involvement in viral RNA metabolism and translation. C_LIO_LIDeveloped a robust methodology to silence gene expression in tick cell cultures. C_LIO_LIThe TOP3B complex facilitates efficient packaging of UUKV virions. C_LI

microbiology↗

bioRxiv2024

Multi-omics analysis of virus-permissive versus hostile cellular states reveals protein networks controlling virus infection

The capacity of host cells to sustain or restrict virus infection is influenced by their proteome. Understanding the compendium of proteins defining cellular permissiveness is key to many questions in fundamental virology. Here, we apply a multiomic approach to determine the proteins that are associated with highly permissive, intermediate, and hostile cellular states. We observed two groups of differentially regulated genes: i) with robust changes in mRNA and protein levels, and ii) with protein/RNA discordances. Many of the latter are classified as interferon stimulated genes (ISGs) but have no reported antiviral activity. This suggests that IFN-dependent changes in mRNA levels do not imply antiviral function. Phosphoproteomics revealed an additional regulatory layer involving non-signalling proteins with altered phosphorylation. Indeed, we confirmed that several permissiveness-associated proteins with changes in abundance or phosphorylation regulate infection fitness. Altogether, our study provides a comprehensive and systematic map of the cellular alterations driving virus susceptibility.

pathology↗

bioRxiv2024

Removal of NHS-labelling by-products in Proteomic Samples

N-Hydroxysuccinimide (NHS) ester chemistry is used extensively across proteomics sample preparation. One of its increasingly prevalent applications is in isobaric reagent-based quantitation such as the iTRAQ (isobaric tags for relative and absolute quantitation) and TMT (tandem mass tag) approaches. In these methods, labelling on the primary amines of lysine residues and N-termini of tryptic peptides via amide formation (N-derivatives) from corresponding NHS ester reagents is the intended reactive outcome. However, the role of NHS esters as activated carboxyls can also drive the formation of serine-, tyrosine-, and threonine-derived esters (O-derivatives). These O-derivative peptides are typically classed as over-labelled and are disregarded for quantification, leading to loss of information and hence potential sensitivity. Their presence also unnecessarily increases sample complexity, which reduces the overall identification rates. One common approach for removing these unwanted labelling events has involved a quench with hydroxylamine. We show here that this approach is not fully efficient and can still leave substantial levels of unwanted over-labelled peptides. Through systematic screening of nucleophilic aminolysis reagents and reaction conditions, we have now developed a robust method to efficiently remove over-labelled peptides. The new method reduces the proportion of over-labelled peptides in the sample to less than 1% without affecting the labelling rate or introducing other modifications, leading to superior identification rates and quantitation precision.

systems biology↗

bioRxiv2024

Cheap, Robust and Versatile Two-Dimensional Chromatography system for Proteomics of Nanogram Scale Samples

In this work we describe a low loss fractionation system comprised of a reconfigured Evosep One LC system for the first dimension and a repurposed 3D-printer as a fraction collector. The setup operates as a high-pH fractionation system capable of effectively working with nanogram scales of lysate digests. The 2D RP-RP system demonstrated superior proteome coverage over single-shot data-dependent acquisition (DDA) analysis using only 5 ng of human cell lysate digest with performance increasing with increasing amounts of material. We found that the fractionation system allowed over 70% signal recovery at the peptide level and, more importantly, we observed over 30% increase on protein level intensity which indicates the complexity reduction afforded by the system outweighs the sample losses endured. The application of data-independent acquisition (DIA) and wide window acquisition (WWA) to fractionated samples allowed more than 8,000 proteins to be identified from 50 ng of material. The utility of the 2D system was further investigated for phosphoproteomics (>21,000 phosphosites from 50 g starting material) and pull-down type experiments and showed substantial improvements over single-shot experiments. We show that the 2D RP-RP system is highly versatile and powerful tool for many proteomics workflows.

systems biology↗

bioRxiv2024

Non-Necroptotic Roles of MLKL in Diet-Induced Obesity, Liver Pathology, and Insulin Sensitivity: Insights from a High Fat, High Fructose, High Cholesterol Diet Mouse Model

Chronic inflammation is a key player in metabolic dysfunction-associated fatty liver disease (MAFLD) progression. Necroptosis, an inflammatory cell death pathway, is elevated in MAFLD patients and mouse models, yet its role is unclear due to diverse mouse models and inhibition strategies. In our study, we inhibited necroptosis by targeting mixed lineage kinase domain like pseudokinase (MLKL), the terminal effector of necroptosis, in a high-fat, high-fructose, high-cholesterol (HFHFrHC) mouse model of diet-induced MAFLD mouse model. Despite HFHFrHC diet upregulating MLKL (2.5-fold), WT mice livers showed no increase in necroptosis markers or associated proinflammatory cytokines. Surprisingly, Mlkl-/-mice experienced exacerbated liver inflammation without protection from diet-induced liver damage, steatosis, or fibrosis. In contrast, Mlkl+/- mice showed significant reduction in these parameters that was associated with elevated Ppar and Ppar{gamma} levels. Both Mlkl-/-and Mlkl+/- mice on HFHFrHC diet resisted diet-induced obesity, attributed to increased beiging, enhanced oxygen consumption and energy expenditure due to adipose tissue, and exhibited improved insulin sensitivity. These findings highlight the tissue specific effects of MLKL on the liver and adipose tissue, and suggest a dose-dependent effect of MLKL on liver pathology.

biochemistry↗

bioRxiv2024

A basally active cGAS-STING pathway limits SARS-CoV-2 replication in a subset of ACE2 positive airway cell models

Host factors that define the cellular tropism of SARS-CoV-2 beyond the cognate ACE2 receptor are poorly defined. Here we report that SARS-CoV-2 replication is restricted at a post-entry step in a number of ACE2-positive airway-derived cell lines due to tonic activation of the cGAS-STING pathway mediated by mitochondrial DNA leakage and naturally occurring cGAS and STING variants. Genetic and pharmacological inhibition of the cGAS-STING and type I/III IFN pathways as well as ACE2 overexpression overcome these blocks. SARS-CoV-2 replication in STING knockout cell lines and primary airway cultures induces ISG expression but only in uninfected bystander cells, demonstrating efficient antagonism of the type I/III IFN-pathway in productively infected cells. Pharmacological inhibition of STING in primary airway cells enhances SARS-CoV-2 replication and reduces virus-induced innate immune activation. Together, our study highlights that tonic activation of the cGAS-STING and IFN pathways can impact SARS-CoV-2 cellular tropism in a manner dependent on ACE2 expression levels.

microbiology↗

bioRxiv2023

Mapping glymphatic solute transportation through the perivascular space of hippocampal arterioles with 14 Tesla MRI

The perivascular space (PVS) plays a crucial role in facilitating the clearance of waste products and the exchange of cerebrospinal fluid and interstitial fluid in the central nervous system. While optical imaging methods identify the glymphatic transport of fluorescent tracers through PVS of surface-diving arteries, their limited depth penetration impedes the study of glymphatic dynamics in deep brain regions. In this study, we introduced a novel high-resolution dynamic contrast-enhanced MRI mapping approach based on single-vessel multi-gradient-echo methods. This technique allowed the differentiation of penetrating arterioles and venules from adjacent parenchymal tissue voxels and enabled the detection of Gd-enhanced signals coupled to PVS of penetrating arterioles in the deep cortex and hippocampus. By directly infusing Gd into the lateral ventricle, we eliminated delays in cerebrospinal fluid flow and focused on PVS Gd transport through PVS of hippocampal arterioles. The study revealed significant PVS-specific Gd signal enhancements, shedding light on glymphatic function in deep brain regions. These findings advance our understanding of brain-wide glymphatic dynamics and hold potential implications for neurological conditions characterized by impaired waste clearance, warranting further exploration of their clinical relevance and therapeutic applications.

neuroscience↗

bioRxiv2023

Spatial single-cell isotope tracing reveals heterogeneity of de novo fatty acid synthesis in cancer cells

Metabolism has emerged as a key factor in homeostasis and disease including cancer. Yet, little is known about the heterogeneity of metabolic activity of cancer cells due to the lack of tools to directly probe it. Here, we present a novel method, 13C-SpaceM for spatial single-cell isotope tracing of glucose-dependent de novo lipogenesis. The method combines imaging mass spectrometry for spatially-resolved detection of 13C6-glucose-derived 13C label incorporated into esterified fatty acids with microscopy and computational methods for data integration and analysis. We validated 13C-SpaceM on a spatially-heterogeneous normoxia-hypoxia model of liver cancer cells. Investigating cultured cells, we revealed single-cell heterogeneity of lipogenic acetyl-CoA pool labelling degree upon ACLY knockdown that is hidden in the bulk analysis and its effect on synthesis of individual fatty acids. Next, we adapted 13C-SpaceM to analyze tissue sections of mice harboring isocitrate dehydrogenase (IDH)-mutant gliomas. We found a strong induction of de novo fatty acid synthesis in the tumor tissue compared to the surrounding brain. Comparison of fatty acid isotopologue patterns revealed elevated uptake of mono-unsaturated and essential fatty acids in the tumor. Furthermore, our analysis uncovered substantial spatial heterogeneity in the labelling of the lipogenic acetyl-CoA pool indicative of metabolic reprogramming during microenvironmental adaptation. Overall, 13C-SpaceM enables novel ways for spatial probing of metabolic activity at the single cell level. Additionally, this methodology provides unprecedented insight into fatty acid uptake, synthesis and modification in normal and cancerous tissues.

biochemistry↗

bioRxiv2023

Entanglement of AGE-RAGE axis in cardiac pathosis

Cardiovascular diseases are the major cause of death globally. Acute coronary syndrome is one of numerous cardiovascular illnesses, including advanced glycation end products (AGEs), which play an instrumental part in their development and progression. A substance with multiple pleiotropic characteristics is rosuvastatin. This study examined the cardioprotective effects of rosuvastatin in isoproterenol-induced myocardial injury, as well as the alterations in advanced glycation end products and their roles in cardiac damage. Rosuvastatin (10 mg/kg, orally) was given to male rats daily for 4 weeks, and on the 29th and 30th days, isoproterenol (85 mg/kg, subcutaneously) was administered to cause cardiac damage. Rats were euthanised on the 31st day, and various samples were collected for examination. Administration of isoproterenol increased cardiac mass, levels of cardiac damage markers, lipid oxidation, and collagen content in the heart. Additionally, it reduced the activities of SOD, CAT, GST, GR, and all other antioxidants. Additionally, isoproterenol raises levels of inflammatory markers including TNF- and IL-6. It has been observed that advanced glycation end products rise along with heart injury. The AGE-RAGE cascade also messes with the injured hearts echocardiogram. Additionally, histopathological alterations were noticed. According to the study, rosuvastatin has cardioprotective effects on the experimental model, which were supported by an array of physical, biochemical, and histological characteristics. SummaryThis study examined the cardioprotective effects of rosuvastatin in isoproterenol-induced myocardial injury, as well as the alterations in advanced glycation end products and their roles in cardiac damage. According to the study, rosuvastatin has cardioprotective effects on the experimental model, which were supported by a number of physiological, biochemical, and histological characteristics. By showing how the functional AGE/RAGE axis is inhibited following rosuvastatin medication, this work provides an etiologic theory involving rosuvastatin therapy in heart injury. These findings may also have practical significance since they highlight the intriguing possibility that rosuvastatin-induced modulation of AGE-RAGE signalling may represent a unique therapeutic approach for the prevention and treatment of other cardiovascular diseases.

pharmacology and toxicology↗

bioRxiv2023

Incorporation of genome-bound cellular proteins into HIV-1 particles regulates viral infection

The initial steps of the human immunodeficiency virus 1 (HIV-1) lifecycle are regulated by cellular RNA-binding proteins (RBPs). To understand the scope of these early host-virus interactions, we developed in virion RNA interactome capture (ivRIC), which allowed the comprehensive and systematic profiling of the proteins that interact with the HIV-1 genomic (g)RNA inside viral particles. ivRIC identified 104 cellular RBPs within the encapsidated HIV-1 ribonucleoprotein, many of which are typically found in the cellular nucleus. Notably, these nuclear RBPs interact with the HIV-1 RBP Rev, suggesting that they associate with HIV-1 gRNA during its nuclear life. Functional assays show that ivRBPs are important for HIV-1, including PURA and PURB, which control viral gene expression and infectivity through interaction with critical sequences in the gRNA. Our characterisation of the composition of the encapsidated ribonucleoprotein of HIV-1 uncovers new host-virus interactions that invokes new mechanisms for controlling HIV-1 infection.

molecular biology↗

bioRxiv2023

Characterisation of an Omnitrap-Orbitrap platform equipped with IRMPD, UVPD and ExD for the analysis of peptides and proteins

We describe an instrument configuration based on the Orbitrap Exploris 480 mass spectrometer that has been coupled to an Omnitrap platform. The Omnitrap possesses three distinct ion-activation regions, that can be used to perform resonant based collision induced dissociation, several forms of electron associated fragmentation, and ultraviolet photodissociation. Each section can also be combined with infrared multiphoton dissociation. In this work, we demonstrate all these modes of operation on a range of peptides and proteins. The results show that this instrument configuration produces similar data to previous implementations of each activation technique and at similar efficiency levels. We demonstrate that this unique instrument configuration is extremely versatile for the interrogation of polypeptides.

systems biology↗

bioRxiv2022

Stereoretentive Post-Translational Protein Editing

Chemical post-translational methods now allow convergent side-chain editing of proteins as a form of direct chemical mutagenesis without needing to resort to genetic intervention. Current approaches that allow the creation of constitutionally native side-chains via C-C formation using off-protein carbon-centred C* radicals added to unnatural amino acid radical acceptor SOMOphile tags such as dehydroalanine are benign and wide-ranging. However, they also typically create epimeric mixtures of D-/L-residues. Here we describe a light-mediated desulfurative method that, through the creation and reaction of stereoretained on-protein L-alanyl C{beta}* radicals, allows C{beta}-H{gamma}, C{beta}-O{gamma}, C{beta}-Se{gamma}, C{beta}-B{gamma} and C{beta}-C{gamma} bond formation to flexibly generate site-selectively edited proteins with full retention of native stereochemistry under mild conditions from a natural amino acid. This methodology shows great potential to explore protein side-chain diversity and construct useful bioconjugates. Table of Contents Image O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=32 SRC="FIGDIR/small/504816v1_ufig1.gif" ALT="Figure 1"> View larger version (7K): org.highwire.dtl.DTLVardef@1ccd60corg.highwire.dtl.DTLVardef@f8ca72org.highwire.dtl.DTLVardef@1b33835org.highwire.dtl.DTLVardef@12f32e9_HPS_FORMAT_FIGEXP M_FIG C_FIG

synthetic biology↗

bioRxiv2022

Blocking necroptosis reduces inflammation and tumor incidence in a mouse model of diet-induced hepatocellular carcinoma

Background & AimsNonalcoholic fatty liver disease (NAFLD) is one of the etiologies that contribute to hepatocellular carcinoma (HCC), and chronic inflammation is one of the proposed mediators of HCC. As necroptosis is a cell death pathway that induces inflammation, we tested whether necroptosis- induced inflammation contributes to the progression of NAFLD to HCC in a mouse model of diet- induced HCC. MethodsMale and female wild-type (WT) mice or mouse models where necroptosis is blocked (Ripk3-/- or Mlkl-/- mice) were fed a control diet or choline-deficient low fat diet (CD-LFD) or CD-high fat diet (CD-HFD) for 6 months. Changes in inflammation, immune cell infiltration, activation of oncogenic pathways, and tumor incidence were assessed by gene expression analysis, western blotting, and flow cytometry. RNA sequencing (RNA-seq) was performed to assess the changes in liver transcriptome. ResultsBlocking necroptosis by deleting either Ripk3 or Mlkl reduced markers of inflammation [proinflammatory cytokines (TNF, IL-6, and IL-1{beta}), F4/80+ve macrophages, CCR2+ve infiltrating monocytes], inflammation associated oncogenic pathways (JNK, PD-L1/PD-1, {beta}-catenin), and HCC in male mice. In female mice, blocking necroptosis reduced HCC independent of inflammation. Blocking necroptosis reduced cell senescence markers in males and females, suggesting a novel cross-talk between necroptosis and cell senescence. ConclusionsOur data show that hepatic necroptosis promotes recruitment and activation of liver macrophages leading to chronic inflammation, which in turn trigger oncogenic pathways leading to the progression of NAFLD to HCC in male mice. In female mice necroptosis contributes to HCC independent of inflammation. Thus, our study suggests that necroptosis is a valid target for NAFLD-mediated HCC. SynopsisNecroptosis is a cell death pathway that mediate inflammation. Blocking necroptosis attenuated chronic inflammation by reducing recruitment and activation of liver macrophages, which in turn reduced activation of oncogenic pathways and progression of NAFLD to HCC in mice. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=142 SRC="FIGDIR/small/502666v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@1bf82d7org.highwire.dtl.DTLVardef@26fc68org.highwire.dtl.DTLVardef@18538f4org.highwire.dtl.DTLVardef@15e338b_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2022

Ubiquitin-based pathway acts inside chloroplasts to regulate photosynthesis

Photosynthesis is the energetic basis for most life on Earth, and in plants it operates inside double-membrane-bound organelles called chloroplasts. The photosynthetic apparatus comprises numerous proteins encoded by the nuclear and organellar genomes. Maintenance of this apparatus requires the action of internal chloroplast proteases, but a role for the nucleocytosolic ubiquitin-proteasome system (UPS) was not expected owing to the barrier presented by the double-membrane envelope. Here, we show that photosynthesis proteins (including those encoded internally by chloroplast genes) are ubiquitinated, and processed via the CHLORAD pathway: they are degraded by the 26S proteasome following CDC48-dependent retrotranslocation to the cytosol. This demonstrates that the reach of the UPS extends to the interior of endosymbiotically-derived chloroplasts, where it acts to regulate one of the most fundamental processes of life. One Sentence SummaryThe ubiquitin-proteasome system targets proteins inside chloroplasts, including chloroplast-encoded photosynthesis subunits.

plant biology↗