Biology subjects

Herinckx, G.

Publications and source records attributed to Herinckx, G..

5 recordsLinked to original sources

bioRxiv2026

Stage-dependent tau post-translational modifications map the spatiotemporal progression of Alzheimer's disease

Alzheimers disease (AD) is defined by progressive tau aggregation, yet the molecular events driving this process remain poorly understood. Post-translational modifications (PTMs) are key regulators of tau biology and potential biomarkers of disease progression. Using immunoprecipitation-mass spectrometry and absolute quantification of tau isoforms, we profiled tau PTMs in soluble and insoluble brain fractions. We studied multiple brain regions (hippocampus, inferior temporal and frontal gyri), representing regions affected at different stages of pathology, from human donors spanning the AD spectrum and staged by ABC neuropathological scoring. We uncovered a stage-dependent PTM landscape across AD progression: early phosphorylation changes, including pT217 and pS262, precede later ubiquitination events, such as uK311, associated with tau aggregation. We also identified PTMs negatively correlated with aggregation, including mK258, suggesting potential protective roles. These findings refine our understanding of the spatiotemporal evolution of tau biochemistry and offer mechanistic and translational insights into AD tauopathy.

neuroscience↗

bioRxiv2025

Conserved phosphorylatable residues in motif G of positive-stranded virus RdRps regulate polymerase activity and suggest targets for drug design.

RNA viruses rely on an RNA-dependent RNA polymerase (RdRp) to replicate their genome. RdRps share a conserved core replicase structure described as a right hand within which RNA replication occurs. RNA polymerases contain a series of conserved motifs (A-G) that are essential for catalysis. Motif G, located at the RNA entry channel, guides the incoming RNA into the catalytic centre and and holds it in place during catalysis. Although RdRp phosphorylation has been reported, it has been scarcely studied. In most studied cases, phosphomimetic mutations reduced viral replication. In this study, we identified Theilers murine encephalomyelitis virus (TMEV) polymerase (3Dpol) residues that undergo some extent of phosphorylation in infected cells. Among these residues, Thr109 and Ser110 located in motif G are highly conserved in the sequences of picornavirus polymerases and in the structure of many positive-stranded virus polymerases, including nsp12 of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Using mutagenesis and reporter viruses, we show that phosphomimetic mutation of either residue abrogates viral replication, for both TMEV and SARS-CoV-2. Mutations of 3Dpol residues 109 and 110 into all other possible residues shows that, besides negatively charged phosphomimetic residues, bulky residues strongly inhibit replication, suggesting that phosphorylation inhibits polymerase activity by steric hindrance and/or through charge repulsion with RNA entering the catalytic core. Because these phosphorylatable residues are surface-exposed and conserved among viral polymerases, they represent promising targets for the rational design of broad-spectrum antiviral agents. ImportanceRNA viruses require an RNA-dependent RNA polymerase to replicate their genome. We identified in Theilers murine encephalomyelitis virus polymerase (TMEV 3Dpol) residues that undergo some extent of phosphorylation in infected cells. Among these residues, Thr109 and Ser110 are located in the entry channel of the polymerase, a region important for directing the RNA into the polymerase and locking it in place during catalysis. Incidentally, Thr109 and Ser110 are highly conserved in the sequences of picornavirus polymerases and in the structures of many positive-stranded virus polymerases including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nsp12. Our study revealed that, in both TMEV 3Dpol and SARS-CoV-2 nsp12, mutation of either residue into a negatively charged amino acid that mimics phosphorylation abrogates viral replication, suggesting phosphorylation would block polymerase activity. As these phosphorylated residues are accessible and conserved, they provide important candidate targets for the design of antiviral molecules.

microbiology↗

bioRxiv2025

The Circadian Clock Controls Hepatic Stellate Cell Activation in Liver Fibrosis via a BMAL1/CK1ϵ/REV-ERBα/Transgelin Signaling Pathway.

Liver fibrosis is a progressive and life-threatening condition with no effective targeted treatments. Growing evidence indicates a two-way relationship between circadian rhythm and fibrogenesis, although the specific molecular signaling pathways involved are still not well understood. The molecular clock, which governs circadian rhythms, regulates metabolic and cellular functions, and its pharmacological manipulation has shown potential as a therapy for organ fibrosis. Although the livers molecular clock appeared resilient to the progression of chronic liver disease in humans from steatosis to fibrosis, detectable changes in the daily amplitude of clock genes were observed in a cohort of people living with obesity. We discovered a clock-controlled signaling pathway that drives hepatic stellate cell (HSC) activation, a key event in fibrosis progression. Interfering with this pathway, either by disrupting the core regulator CLOCK:BMAL1 or activating the nuclear receptors REV-ERBs, significantly reduced HSC activation. We also identified transgelin as the downstream effector of clock-regulated HSC contractility, a characteristic of HSC activation. Transgelin is regulated indirectly by a BMAL1-CK1{varepsilon} signaling pathway and directly by REV-ERB. Our findings identify a previously unknown circadian-controlled mechanism that links the molecular clock to HSC activation and cell contractile function, which is relevant to human diseases. This pathway provides several entry points for drugs to target and disrupt fibrogenic signaling. By connecting clock biology to the cellular processes that cause fibrosis, our work also offers a mechanistic basis for chronotherapeutic strategies against chronic liver disease.

molecular biology↗

bioRxiv2025

Cardiovirus-Mediated PKR Inhibition Results from Nucleocytoplasmic Trafficking Disruption

Eukaryotic translation initiation factor 2 alpha kinase 2 (EIF2AK2), know as PKR, is a key antiviral kinase activated by double-stranded RNA (dsRNA) typically produced during viral replication. Upon activation, PKR phosphorylates eIF2, leading to the inhibition of translation and viral replication. However, many viruses have evolved mechanisms to counteract PKR activity. In Cardioviruses, the Leader protein (L), a short peptide cleaved from the N-terminus of the viral polyprotein, not only inhibits PKR but also blocks interferon production and disrupts nucleocytoplasmic trafficking (NCT). L disrupts NCT by recruiting host RSK kinases to the nuclear pore complex (NPC), where RSK phosphorylates FG-nucleoporins, thereby impairing NCT. L mutations that affect NCT disruption also impact its ability to inhibit PKR, suggesting a mechanistic link. Recombinant TMEV and EMCV viruses designed to disrupt NCT through different mechanisms exhibited some extent of PKR inhibition, supporting the link between NCT disruption and PKR inhibition. Immunostaining and live-cell imaging revealed that L-induced NCT disruption redistributes a fraction of PKR to the nucleoli, where PKR remains inactive. This suggests that nucleolar sequestration contributes to PKR inhibition. Additionally, L-mediated NCT disruption leads to the release of nuclear RNA-binding proteins (nRBPs) into the cytosol, which may bind or modify viral dsRNA, further preventing PKR activation. Collectively, these results highlight nucleocytoplasmic trafficking as a critical regulatory mechanism governing PKR activation. Thus, beyond the specific action of cardiovirus L protein, our study reveals that interference with host nucleocytoplasmic transport can significantly impact the subcellular localization and functional regulation of immune effectors such as PKR. Author SummaryProtein kinase R (PKR) is a crucial component of the host innate immune response. It is activated by double-stranded RNA (dsRNA) typically produced during viral replication and triggers a shutdown of mRNA translation. This antiviral mechanism limits viral propagation by inhibiting both host and viral protein synthesis. However, many viruses have developed mechanisms to inhibit PKR, allowing them to escape immune detection. PKR downregulation facilitates viral replication whereas uncontrolled PKR activation can lead to autoimmune disorders. Therefore, PKR activity must be tightly regulated to maintain immune homeostasis. Using recombinant viruses which target the nuclear pore complex, we show that nucleocytoplasmic trafficking of cellular components is critical for regulation of PKR activity. Infection of cells with Theilers murine encephalomyelitis virus triggers an efflux of nuclear RNA binding proteins which likely compete with PKR for dsRNA binding and thereby block PKR activity. Moreover, upon TMEV infection as well as during mitosis, PKR is detected in the nucleoli where it is thought to interact with structured RNAs without being activated. Our data highlight an important link between nucleocytoplasmic trafficking and PKR activity.

immunology↗

bioRxiv2022

Cardiovirus leader proteins retarget RSK kinases toward alternative substrates to perturb nucleocytoplasmic traffic

Proteins from some unrelated pathogens, including viruses and bacteria can recruit and activate cellular p90-ribosomal protein S6 kinases (RSKs) through a common linear motif. Our data suggested that such pathogens proteins might act as adapters to dock the kinase toward specific substrates. We explored this hypothesis using the Cardiovirus leader protein (L) as a paradigm. L is known to trigger phenylalanine-glycine nucleoporins (FG-NUPs) hyperphosphorylation and nucleocytoplasmic trafficking perturbation. Using a biotin ligase fused to either RSK or to L, we identified FG-NUPs as primary partners of the L-RSK complex in infected cells. Mutant analysis shows that L uses distinct motifs to recruit RSK and to dock the L-RSK complex toward the FG-NUPs. Using an analog-sensitive RSK2 mutant kinase, we show that, in infected cells, L can trigger RSK to use NUP98 and NUP214 as direct substrates. Our data illustrate a novel virulence mechanism where pathogens proteins retarget cellular protein kinases toward specific substrates.

microbiology↗