Biology subjects

Peter, K.

Publications and source records attributed to Peter, K..

10 recordsLinked to original sources

bioRxiv2026

Phenotypic characterization of an Arabidopsis stn7 stn8 pck2 triple mutant reveals only minor effects on chloroplast functions

Reversible protein phosphorylation is a key regulator of chloroplast function. Although chloroplast kinases STN7, STN8, and plastid casein kinase 2 (pCK2) regulate photosynthetic acclimation and other chloroplast processes, their functional interplay remains poorly understood. We generated and characterized the first Arabidopsis thaliana stn7 stn8 pck2 triple knockout mutant. Biochemical analyses confirmed the loss of all three kinase activities on established substrates. Growth resembled the pck2 single mutant, whereas photosynthetic fluorescence parameters reflected the stn7 stn8 double mutant. Thus, simultaneous disruption of all three kinases primarily combined the parental phenotypes, with little evidence of additive or synergistic effects under standard growth conditions. This triple mutant enables studies of chloroplast phosphorylation networks and demonstrates the remarkable resilience of chloroplast physiology to combined kinase loss.

plant biology↗

bioRxiv2026

Phosphoproteomics profiling of the monocytes uncovers the mechanosensory pathways regulating monocytes responses to pathologic level of shear stress

Background: Calcific aortic valve disease (CAVD) is the most common valvular heart disease in older adults and currently has no approved pharmacological therapy to prevent or slow disease progression. Aortic valve replacement, either surgically or by transcatheter aortic valve implantation (TAVI), therefore remains the only effective treatment for severe CAVD. Monocytes play an important role in driving inflammation and disease progression in CAVD. As the disease progresses and the aortic valve becomes increasingly stenotic, circulating monocytes passing through the narrowed valve are repeatedly exposed to pathological haemodynamic forces, including markedly elevated shear stress, before their recruitment into the valve tissue. However, how exposure to these mechanical forces reprograms circulating monocytes influences their subsequent responses within the valve remain poorly understood. Methods and Results: In this study, we used an engineered model of aortic valve stenosis combined with phosphoproteomic profiling to investigate how prolonged exposure to pathological shear stress reprograms circulating monocytes and influences their subsequent phenotype and function following recruitment into the valve matrix. We further used TAVI as a unique clinical model to determine whether restoration of physiological haemodynamics in patients with severe aortic stenosis reverses the shear-induced monocyte phenotype observed in our experimental model. We found that prolonged exposure of monocytes to pathological shear stress induced extensive remodelling of the proteomic and phosphoproteomic landscape, with enrichment of pathways associated with cellular metabolism, cytoskeletal organisation, and inflammatory signalling. Kinase activity analysis further identified increased protein kinase C (PKC) activity accompanied by suppression of AKT signalling. Consistent with these molecular changes, pathological shear stress increased actin polymerisation, mitochondrial membrane potential, intracellular calcium signalling, and PKC activity. Using a bioengineered extracellular matrix model that recapitulates the glycosaminoglycan-rich microenvironment of the stenotic aortic valve we found that prior exposure to pathological shear stress altered monocyte-to-macrophage differentiation, reducing oxidised LDL uptake and foam-cell formation while promoting co-expression of CD80 and CD163, indicative of a mixed macrophage phenotype. Finally, using a myeloid-specific Piezo1 knockout mouse model, we identified Piezo1 as a key mechanosensor linking pathological shear stress to PKC activation, mitochondrial responses, and persistent changes in monocyte phenotype following migration into the extracellular matrix. Conclusions: These findings establish a mechanistic link between abnormal valve haemodynamics, metabolic and inflammatory reprogramming of circulating monocytes, extracellular matrix remodelling, and immune dysregulation during CAVD progression, highlighting monocyte mechanotransduction and downstream PKC/Piezo1 signalling as potential therapeutic targets.

cell biology↗

bioRxiv2026

Immune-Mediated Necrotic Cell Death Initiated by Stressed Cardiomyocytes is a Major Contributor to Cardiomyocyte Loss Following Myocardial Infarction

AimsPercutaneous coronary intervention has improved survival following myocardial infarction, yet strategies to further reduce infarct size are limited. This study investigates the role of cytotoxic {gamma}{delta}-T cells in ischemic cardiomyocyte death and potential therapeutic interventions to reduce infarct size. MethodsGenetic and pharmacological approaches were used to delete {gamma}{delta}-T cells and their specific proteins to assess their involvement in cardiomyocyte death using mouse models of permanent ligation (PL) and ischemia/reperfusion (IR). Results{gamma}{delta}-T cells accumulated in infarct zones within 6h post-PL, expressing IFN-{gamma}, TNF-, granzyme B, and perforin. Their deletion reduced infarct size by 73% (PL) and 64% (IR). They induced cardiomyocyte death via apoptosis, gasdermin E-dependent pyroptosis, and MLKL-dependent necroptosis; {gamma}{delta}-T cell depletion reduced apoptosis by 80% and pyroptosis by 38%, with perforin deletion yielding similar effects. Necroptosis, attributed to combined IFN-{gamma}/TNF- cytotoxicity, decreased by 67%. Cytoplasmic DNA (cDNA) in stressed cardiomyocytes activated the cGAS/STING pathway, inducing expression of chemoattractant MCP-1 and death signal RAE-1. These signals recruited and activated {gamma}{delta}-T cells, which then triggered the death of the stressed cardiomyocytes. STING inhibition suppressed these expressions, reducing {gamma}{delta}-T cell accumulation and infarct size. NKG2D-deficient {gamma}{delta}-T cells prevented activation and reduced infarct size. Administration of an anti-IFNAR antibody at PL onset markedly reduced infarct size. ConclusionEarly activation of cytotoxic {gamma}{delta}-T cells via cardiomyocyte stress signals contributes significantly to immunogenic cardiomyocyte death. Targeting the STING pathway and type I interferon signalling presents a promising therapeutic avenue to mitigate infarct size and improve outcomes.

immunology↗

bioRxiv2025

Endothelial-targeted CD39 prevents Toxin-induced Pulmonary Hypertension Mice.

Disruption of the pulmonary endothelium by drugs, toxins, viruses (e.g., COVID-19), or bacterial sepsis can cause acute pulmonary vasculopathy leading to pulmonary hypertension and consequential heart failure. CD39 is a membrane-anchored ecto-enzyme expressed on endothelial cells (EC), integral in maintaining the antithrombotic profile of the endothelium. This ecto-enzyme works in concert with CD73 to hydrolyze both eATP (pro-inflammatory) and ADP (pro-thrombotic) ultimately to adenosine, which is anti-inflammatory, vasodilatory, and antithrombotic. CD39 activity and adenosine signalling are disrupted in idiopathic pulmonary arterial hypertension (PAH). In this work, we explored the efficacy of endothelial cell-targeted delivery of CD39 to prevent the development of acute toxin-induced PAH in a mouse model. We generated a novel therapeutic anti-VCAM-CD39 containing an scFv recognising VCAM-1 (a receptor expressed on activated EC) fused to the soluble form of extracellular human CD39. In a mouse model of endothelial cell-toxin-induced PAH, we show that a single administration of anti-VCAM-CD39 (0.4 mg/kg IV) prevented the development of PAH-- as reflected in the preservation of right ventricular systolic pressures and the absence of right ventricular hypertrophy at day 10 when compared with controls. This protection is conferred by multiple mechanisms: IL-10-driven potentiation of heme oxygenase (HO)-1, a known inhibitor of smooth muscle proliferation; VCAM-1 blockade reduces leukocyte adhesion to the endothelium; and cytoprotective effects through adenosine signalling. Thus, anti-VCAM-CD39 is a novel bifunctional therapeutic strategy for PAH.

physiology↗

bioRxiv2025

Human Fcγ-receptors selectively respond to C-reactive protein (CRP) isoforms

The pentameric C-reactive protein (pCRP), an acute-phase protein, binds to lysophosphatidylcholine (LPC) displayed on the surface of dying cells and microorganisms to activate the complement system and to opsonize immune cells via Fc{gamma}-receptors (Fc{gamma}Rs). Members of the Fc{gamma}R family are characterized by the recognition of the Fc part of IgG antibodies. We utilized a mouse thymoma BW5147 reporter cell panel stably expressing chimeric human Fc{gamma}R-CD3{zeta}-chain receptors to define the molecular requirements for Fc{gamma}R crosslinking by C-reactive protein (CRP). Applying this approach, we show a robust activation of CD64/Fc{gamma}RI and CD32a/Fc{gamma}RIIa by immobilized CRP isoforms as well as triggering of inhibitory CD32b/Fc{gamma}RIIb. Of note, activation of Fc{gamma}RIIa was restricted to the 131R allelic variant but not observed with 131H. In contrast, Fc{gamma}RIII isoforms CD16aF, CD16aV and CD16b were not activated by pCRP, although binding of CRP isoforms to Fc{gamma}RIII was detectable. Activation of Fc{gamma}Rs by free pCRP in solution phase was considerably lower than with immobilized pCRP on hydrophilic plastic surfaces and readily abolished by IgG at serum level concentrations, whereas it was enhanced by the addition of streptococci. The types of Fc{gamma}Rs mainly responding to pCRP in solution phase (CD64/Fc{gamma}RI and CD32aR/Fc{gamma}RIIaR) clearly differed from Fc{gamma}Rs responding to soluble multimeric IgG complexes (i.e., CD16aV/Fc{gamma}RIIIaV and CD32aH/Fc{gamma}RIIaH). Compared to pCRP, monomeric CRP (mCRP) showed lower levels of activation in those selective Fc{gamma}Rs. Fc{gamma}R activation was linked to recognition by conformation-dependent CRP antibodies. Unmasking of the mAb 9C9-defined neoepitope in pCRP* correlated with the triggering of Fc{gamma}Rs, indicating that pCRP* is the major Fc{gamma}R-activating CRP conformation. The assay provides a novel, scalable approach to determine the molecular properties of CRP as a physiological ligand of Fc{gamma}R-mediated bioactivities. Scope statementFc{gamma} receptors (Fc{gamma}Rs) are important immune regulators that come in different variants and combinations, making it difficult to predict which components will ultimately lead to immunological effector functions. Classical Fc{gamma}Rs are defined by their recognition of IgG-Fc, while other ligands, such as C-reactive protein (CRP), are often neglected. Circulating concentrations of CRP, an acute phase protein, are elevated during inflammatory responses. As a pattern recognition receptor, CRP binds to lysophosphatidylcholine expressed on the surface of dying cells and microbes in order to activate the complement system via C1q. We have established a reporter cell assay platform that goes beyond ligand binding and takes a deeper look at the activation outcome(s) by CRP compared with IgG-Fc. This is the first comprehensive study defining CRP-responsive vs non-responsive Fc{gamma}Rs and investigating the interaction of Fc{gamma}Rs with CRP isoforms (pCRP/pCRP*/mCRP). We distinguish binding from receptor triggering using reporter cells stably expressing a chimeric Fc{gamma}R-CD3{zeta} chain, thereby defining the molecular requirements for Fc{gamma}R cross-linking by CRP. The assay provides a novel, sensitive and scalable approach to the properties of CRP as a ligand inducing Fc{gamma}R-mediated bioactivities.

immunology↗

bioRxiv2024

Multifunctional biomimetic porphyrin-lipid nanoparticles - novel nanoscale theranostics for atherosclerotic cardiovascular disease

BackgroundHigh-density lipoprotein (HDL) nanoagents have unrealized potential for atherosclerosis theranostics. Porphyrin-lipid HDL mimetic nanoparticles (Por-HDL-NPs) incorporate porphyrin-lipid which permits near infrared fluorescence imaging and positron emission tomography (PET) through chelation of Copper-64 (64Cu). The outer shell contains apolipoprotein A-I mimetic peptide R4F that interacts with scavenger receptor SR-BI, enabling macrophage targeting and therapeutic effects. We leveraged the theranostic properties of Por-HDL-NPs for testing in atherosclerosis. Methods and ResultsIn vitro, Por-HDL-NPs were internalised by immortalised bone marrow-derived macrophages (iBMDMs), visualised via fluorescence microscopy and flow cytometry. Por-HDL-NPs increased cholesterol efflux from [3H]-cholesterol-loaded iBMDMs, (49%, P<0.05), compared to reconstituted HDL. Incubation of iBMDMs with Por-HDL-NPs reduced mRNA levels of inflammatory mediators Il-1{beta} (88%), Il-18 (54%) and Ccl5 (75%), and protein secretion of IL-1{beta} (69%) and CCL5 (82%), P<0.05. Por-HDL-NPs suppressed inflammasome components Nlrp3 (69%) and Asc (36%), P<0.05. Studies using siRNA deletion of SR-B1 and methyl-{beta}-cyclodextrin, revealed the anti-inflammatory properties of Por-HDL-NPs were independent of SR-B1 and cholesterol efflux. However, Por-HDL-NPs suppressed activation of inflammatory transcription factor NF-{kappa}B (53%, P<0.05). In Apoe-/- mice, PET imaging showed 64Cu-Por-HDL-NPs localised in hearts and detected increases in plaque over time with high-cholesterol diet. Por-HDL-NP fluorescence was visualised in aortic sinus plaques, co-localised with CD68+ macrophages, and by fluorescence IVIS imaging in aortic arch plaque. Por-HDL-NP-treated mice had smaller early-stage (22%) and unstable plaques (52%) and fewer circulating monocytes (32%) than control PBS-treated mice, P<0.05 for all. ConclusionsPor-HDL-NPs have theranostic properties, exhibiting both multi-modal imaging capabilities for identifying plaque and athero-protective therapeutic effects. Clinical PerspectiveO_ST_ABSWhat is new?C_ST_ABSO_LIPorphyrin high-density lipoprotein (HDL) mimetic nanoparticles (Por-HDL-NPs) have theranostic application in atherosclerosis. C_LIO_LIPor-HDL-NPs are internalized by macrophages in vitro and plaque macrophages in vivo, enabling the visualization of atherosclerosis by both positron emission tomography and multiple fluorescence imaging modalities. C_LIO_LIPor-HDL-NPs exhibit atheroprotective effects and suppress inflammation, promote cholesterol efflux, reduce atherosclerotic plaque development and lower the number of circulating monocytes. C_LI What are the clinical implications?O_LIThe PET imaging and plaque targeting capabilities of Por-HDL-NPs have implications for improved non-invasive tracking of human atherosclerosis development. C_LIO_LIThe excellent fluorescence imaging and plaque targeting properties of Por-HDL-NPs have clinical significance for improved detection of early-stage plaque using intravascular imaging strategies. C_LIO_LIPor-HDL-NPs provide therapeutic capabilities that target plaque directly, independent of lipid-lowering, suggestive of their potential to provide benefit on top of current lipid-lowering strategies. C_LI

cell biology↗

bioRxiv2023

Development of endothelial-targeted CD39 as a therapy for ischaemic stroke

BackgroundIschaemic stroke is characterized by a necrotic lesion in the brain surrounded by an area of dying cells termed the penumbra. Salvaging the penumbra either with thrombolysis or mechanical retrieval is the cornerstone of stroke management. At-risk neuronal cells release extracellular adenosine triphosphate (eATP) triggering microglial activation and causing a thromboinflammatory response culminating in endothelial activation and vascular disruption. This is further aggravated by ischaemia-reperfusion (I/R) injury that follows all reperfusion therapies. The ecto-enzyme CD39 regulates eATP by hydrolysing to adenosine which has anti-thrombotic and anti-inflammatory properties and reverses I/R injury. MethodsWe developed anti-VCAM-CD39 that targets the antithrombotic and anti-inflammatory properties of recombinant CD39 to the activated endothelium of the penumbra by binding to vascular cell adhesion molecule (VCAM)-1. Mice were subjected to 30 minutes of middle cerebral artery occlusion (MCAo) and analysed at 24h. Anti-VCAM-CD39 or control agents (saline, non-targeted CD39, or anti-VCAM-inactive CD39) were given at 3h post-MCAo. ResultsAnti-VCAM-CD39 treatment reduced neurological deficit; MRI confirmed significantly smaller infarcts together with an increase in cerebrovascular perfusion. Anti-VCAM-CD39 also restored blood brain barrier (BBB) integrity and reduced microglial activation. Coadministration of anti-VCAM-CD39 with thrombolytics (tPA) further reduced infarct volumes and attenuated BBB permeability with no associated increase in intracranial haemorrhage. ConclusionAnti-VCAM-CD39, uniquely targeted to endothelial cells, could be a new stroke therapy even when administered 3 h post ischaemia and may further synergise with thrombolytic therapy to improve stroke outcomes.

neuroscience↗

bioRxiv2022

Transcriptional Profiles Analysis of COVID-19 and Malaria Patients Reveals Potential Biomarkers in Children

The clinical presentation overlap between malaria and COVID-19 poses special challenges for rapid diagnosis in febrile children. In this study, we collected RNA-seq data of children with malaria and COVID-19 infection from the public databases as raw data in fastq format paired end files. A group of six, five and two biological replicates of malaria, COVID-19 and healthy donors respectively were used for the study. We conducted differential gene expression analysis to visualize differences in the expression profiles. Using edgeR, we explored particularly gene expression levels in different phenotype groups and found that 1084 genes and 2495 genes were differentially expressed in the malaria samples and COVID-19 samples respectively when compared to healthy controls. The highly expressed gene in the COVID-19 group we found CD151 gene which is facilitates in T cell proliferation, while in the malaria group, among the highly expressed gene we identified GBP5 gene which involved in inflammatory response and response to bacterium. By comparing both malaria and COVID-19 infections, the overlap of 62 differentially expressed genes patterns were identified. Among them, three genes (ENSG00000234998, H2AC19 and TXNDC5) were highly upregulated in both infections. Strikingly, we observed 13 genes such as HBQ1, HBM, SLC7A5, SERINC2, ATP6V0C, ST6GALNAC4, RAD23A, PNPLA2, GAS2L1, TMEM86B, SLC6A8, UBALD1, RNF187 were downregulated in children with malaria and uniquely upregulated in children with COVID-19, thus may be further validated as potential biomarkers to delineate COVID-19 from malaria-related febrile infection. The hemoglobin complexes and lipid metabolism biological pathways are highly expressed in both infections. Our study provided new insights for further investigation of the biological pattern in hosts with malaria and COVID-19 coinfection.

bioinformatics↗

bioRxiv2022

Systemic RNA interference-defective (SID) genes modulate dopaminergic neurodegeneration in C. elegans

The fine-tuning of gene expression is critical for all cellular processes; aberrations in this activity can lead to pathology, and conversely, resilience. As their role in coordinating organismal responses to both internal and external factors have increasingly come into focus, small non-coding RNAs have emerged as an essential component to disease etiology. Using Systemic RNA interference Defective (SID) mutants of the nematode Caenorhabditis elegans, deficient in endogenous gene silencing, we examined the potential consequences of dysfunctional epigenomic regulation in the context of Parkinsons disease (PD). Specifically, the loss of either the sid-1 or sid-3 genes, which encode a dsRNA transporter and an endocytic regulatory non-receptor tyrosine kinase, respectively, conferred neuroprotection to dopaminergic neurons in an established transgenic C. elegans strain wherein overexpression of human -synuclein (-syn) from a chromosomally integrated multicopy transgene causes neurodegeneration. We further show that knockout of a specific microRNA, mir-2, attenuates -syn neurotoxicity; suggesting that the native targets of mir-2-dependent gene silencing represent putative neuroprotective modulators. In support of this, we demonstrated that RNAi knockdown of multiple mir-2 targets enhanced -syn-induced dopaminergic neurodegeneration. Moreover, we demonstrate that mir-2 overexpression originating in the intestine can induce neurodegeneration of dopaminergic neurons, an effect that was reversed by pharmacological inhibition of SID-3 activity. Interestingly, sid-1 mutants retained mir-2-induced enhancement of neurodegeneration. Transcriptomic analysis of -syn animals with and without a sid-1 mutation revealed 27 differentially expressed genes with human orthologs related to a variety of diseases, including PD. Among these was pgp-8, encoding a P-glycoprotein-related ABC transporter. Notably, sid-1; pgp-8 double mutants abolished the neurodegeneration resulting from intestinal mir-2 overexpression. This research positions known regulators of small RNA-dependent gene silencing within a framework that facilitates mechanistic evaluation of epigenetic responses to exogenous and endogenous factors influencing dopaminergic neurodegeneration, revealing a path toward new targets for therapeutic intervention of PD. Author SummaryThe progressive death of neurons that produce the neurotransmitter dopamine is a clinical hallmark of Parkinsons disease (PD). An integrated response to environmental and genetic factors leads to expression changes in specific genes and non-protein-coding regulatory molecules called dsRNAs that influence the pathology underlying PD. Here we report, for the first time in an animal model of PD, that mutations in genes encoding proteins which function in the cellular import of dsRNA protect dopamine neurons from degeneration. By generating a profile of individual genes affected when dsRNA transport is incapacitated, we established a foundation for the systematic analysis of their distinct contributions to neuroprotection. One subclass of dsRNAs, termed microRNAs, function analogously to a conductor of an orchestra by controlling hundreds of genes, simultaneously, to coordinate cellular processes. We identified a single microRNA that suppresses the activity of numerous genes in dopamine neurons and contributes to neurodegeneration. Genomic knockout of this deleterious microRNA, or prevention of its transport into dopamine neurons, unmasked a set of previously unreported neuroprotective proteins. This study supports a hypothesis whereby mechanisms that "fine tune" dopamine availability intersect with regulators of dsRNA transport to cooperatively maintain an optimal balance between neuronal activity, survival, and neurodegeneration.

genetics↗

bioRxiv2018

Inhibition of platelet function by targeting the platelet cytoskeleton via the LIMK-signaling pathway.

Actin is highly abundant in platelets, and platelet function is dependent on actin structures. Actin filaments are dynamic structures involved in many cellular processes including platelet shape changes and adhesion. The actin cytoskeleton is tightly regulated by actin-binding proteins, which include the members of the actin depolymerising factor (ADF)/cofilin family. LIM kinase (LIMK) and slingshot phosphatase (SSH-1L) regulate actin dynamics by controlling the binding affinity of ADF/cofilin towards actin. We hypothesised that inhibition of LIMK activity may prevent the changes in platelet shape during their activation and therefore their function by controlling the dynamics of Factin. Therefore, inhibition of LIMK activity may represent an attractive new strategy to control and inhibit platelet function; particularly the formation of stable platelet aggregates and thus stable thrombi.

cell biology↗