Biology subjects

Burel, S.

Publications and source records attributed to Burel, S..

6 recordsLinked to original sources

bioRxiv2025

Reversable Acute Sedation Response of Phosphorothioate Antisense Oligonucleotides Following Local Delivery to the Central Nervous System

Antisense oligonucleotides (ASOs) locally delivered to the central nervous system (CNS) are being approved as therapies for neurological diseases. After intrathecal injection of some ASOs, transient toxicities have been reported, but considerable inconsistencies remain in classifying them and their underlying mechanisms. Here, we characterize an acute sedation response that can include loss of lower spinal reflexes, hypoactivity, paresis, sedation and ataxia, peaking [~]3 hours post-intrathecal injection of some phosphorothioate ASOs and reversing by 24 hours with no sequelae. Acute sedation is distinct from acute activation, which is hyperactivity and muscle cramping that occurs immediately after administering oligonucleotides. Acute sedation translates across species from rodents to non-human primates and is sequence-, dose-, and chemistry-dependent. Acute sedation can be mitigated by strategic placement of phosphorothioate backbone linkages in ASOs and by avoiding G-rich sequences. The acute sedation response can be modeled in primary neural cultures, with good predictability of in vivo response. Mechanistically, we demonstrate that acute sedation is caused by high extracellular ASO concentrations inhibiting synaptic transmission, which reverses as ASO is cleared from the extracellular space and taken up into cells. Our results provide a comprehensive framework for quantifying and mitigating acute sedation caused by some phosphorothioate ASOs. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=79 SRC="FIGDIR/small/638136v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@c3c957org.highwire.dtl.DTLVardef@1d7a062org.highwire.dtl.DTLVardef@162adf5org.highwire.dtl.DTLVardef@18ad055_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Transient Acute Neuronal Activation Response Caused by High Concentrations of Oligonucleotides in the Cerebral Spinal Fluid

Oligonucleotide (ON) therapeutics are promising as a disease-modifying therapy for central nervous system disorders. Intrathecal ON administration into the cerebral spinal fluid is a safe and effective delivery mode to the CNS. However, preclinical studies have shown acute toxicities following high-dose central ON delivery. Here we characterize a transient neurobehavioral change peaking 15 minutes after ON dosing and resolving after 120 minutes. Symptoms include shaking, muscle twitching, cramping, hyperactivity, stereotypic movements, hyperreactivity, vocalizations, tremors, convulsions, and seizures. These are collectively referred here as the acute neuronal activation response. Acute neuronal activation is observed in rats, mice, and non-human primates and is quantifiable using a simple scoring system. It is distinct from acute sedation seen with some phosphorothioate-modified antisense oligonucleotides, characterized by loss of spinal reflexes, ataxia, and sedation. The acute neuronal activation response is largely sequence-independent and is driven by ON chelation of divalent cations, particularly influenced by the divalent cations-to-ON ratio in the dosing solution. Acute neuronal activation can be safely mitigated by adjusting this ratio through magnesium supplementation in the ON formulation. We provide a comprehensive framework for quantifying and mitigating the acute neuronal activation response caused by high concentrations of centrally delivered ON therapeutics in preclinical species. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=79 SRC="FIGDIR/small/638138v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@b18796org.highwire.dtl.DTLVardef@13c9898org.highwire.dtl.DTLVardef@1463019org.highwire.dtl.DTLVardef@ffe719_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2024

Endogenous LRRK2 and PINK1 function in a convergent neuroprotective ciliogenesis pathway in the brain

Mutations in LRRK2 and PINK1 are associated with familial Parkinsons disease (PD). LRRK2 phosphorylates Rab GTPases within the Switch II domain whilst PINK1 directly phosphorylates Parkin and ubiquitin and indirectly induces phosphorylation of a subset of Rab GTPases. Herein we have crossed LRRK2 [R1441C] mutant knock-in mice with PINK1 knock-out (KO) mice and report that loss of PINK1 does not impact endogenous LRRK2-mediated Rab phosphorylation nor do we see significant effect of mutant LRRK2 on PINK1-mediated Rab and ubiquitin phosphorylation. In addition, we observe that a pool of the Rab-specific, PPM1H phosphatase, is transcriptionally up-regulated and recruited to damaged mitochondria, independent of PINK1 or LRRK2 activity. Parallel signalling of LRRK2 and PINK1 pathways is supported by assessment of motor behavioural studies that show no evidence of genetic interaction in crossed mouse lines. Previously we showed loss of cilia in LRRK2 R1441C mice and herein we show that PINK1 KO mice exhibit a ciliogenesis defect in striatal cholinergic interneurons and astrocytes that interferes with Hedgehog induction of glial derived-neurotrophic factor (GDNF) transcription. This is not exacerbated in double mutant LRRK2 and PINK1 mice. Overall, our analysis indicates that LRRK2 activation and/or loss of PINK1 function along parallel pathways to impair ciliogenesis, suggesting a convergent mechanism towards PD. Our data suggests that reversal of defects downstream of ciliogenesis offers a common therapeutic strategy for LRRK2 or PINK1 PD patients whereas LRRK2 inhibitors that are currently in clinical trials are unlikely to benefit PINK1 PD patients.

biochemistry↗

bioRxiv2023

FHF2 phosphorylation and regulation of native myocardial NaV1.5 channels

Phosphorylation of the cardiac NaV1.5 channel pore-forming subunit is extensive and critical in modulating channel expression and function, yet the regulation of NaV1.5 by phosphorylation of its accessory proteins remains elusive. Using a phosphoproteomic analysis of NaV channel complexes purified from mouse left ventricles, we identified nine phosphorylation sites on Fibroblast growth factor Homologous Factor 2 (FHF2). To determine the roles of phosphosites in regulating NaV1.5, we developed two models from neonatal and adult mouse ventricular cardiomyocytes in which FHF2 expression is knockdown and rescued by WT, phosphosilent or phosphomimetic FHF2-VY. While the increased rates of closed-state and open-state inactivation of NaV channels induced by the FHF2 knockdown are completely restored by the FHF2-VY isoform in adult cardiomyocytes, sole a partial rescue is obtained in neonatal cardiomyocytes. The FHF2 knockdown also shifts the voltage-dependence of activation towards hyperpolarized potentials in neonatal cardiomyocytes, which is not rescued by FHF2-VY. Parallel investigations showed that the FHF2-VY isoform is predominant in adult cardiomyocytes, while expression of FHF2-VY and FHF2-A is comparable in neonatal cardiomyocytes. Similar to WT FHF2-VY, however, each FHF2-VY phosphomutant restores the NaV channel inactivation properties in both models, preventing identification of FHF2 phosphosite roles. FHF2 knockdown also increases the late Na+ current in adult cardiomyocytes, which is restored similarly by WT and phosphosilent FHF2-VY. Together, our results demonstrate that ventricular FHF2 is highly phosphorylated, implicate differential roles for FHF2 in regulating neonatal and adult mouse ventricular NaV1.5, and suggest that the regulation of NaV1.5 by FHF2 phosphorylation is highly complex. eTOC SummaryLesage et al. identify the phosphorylation sites of FHF2 from mouse left ventricular NaV1.5 channel complexes. While no roles for FHF2 phosphosites could be recognized yet, the findings demonstrate differential FHF2-dependent regulation of neonatal and adult mouse ventricular NaV1.5 channels.

physiology↗

bioRxiv2021

Mapping of a N-terminal α-helix domain required for human PINK1 stabilisation, Serine228 autophosphorylation and activation in cells

Human autosomal recessive mutations in the PINK1 gene are causal for Parkinsons disease (PD). PINK1 encodes a mitochondrial localised protein kinase that is a master-regulator of mitochondrial quality control pathways. Structural studies to date have elaborated the mechanism of how mutations located within the kinase domain disrupt PINK1 function, however, the molecular mechanism of PINK1 mutations located upstream and downstream of the kinase domain are unknown. We have employed mutagenesis studies of human PINK1 in cells to define the minimal region of PINK1, required for optimal ubiquitin phosphorylation, beginning at residue Ile111. Bioinformatic analysis of the region spanning Ile111 to the kinase domain and inspection of the AlphaFold human PINK1 structure model predicts a conserved N-terminal -helical domain extension (NTE domain) within this region corroborated by hydrogen/deuterium exchange mass spectrometry (HDX-MS) of recombinant insect PINK1 protein. The AlphaFold structure also predicts the NTE domain forms an intramolecular interaction with the C-terminal extension (CTE). Cell-based analysis of human PINK1 reveals that PD-associated mutations (e.g. Q126P), located within the NTE:CTE interface, markedly inhibit stabilization of PINK1; autophosphorylation at Serine228 (Ser228); and Ubiquitin Serine65 (Ser65) phosphorylation. Furthermore, we provide evidence that NTE domain mutants do not affect intrinsic catalytic kinase activity but do disrupt PINK1 stabilisation at the mitochondrial Translocase of outer membrane (TOM) complex. The clinical relevance of our findings is supported by the demonstration of defective stabilization and activation of endogenous PINK1 in human fibroblasts of a patient with early-onset PD due to homozygous PINK1 Q126P mutations. Overall, we define a functional role of the NTE:CTE interface towards PINK1 stabilisation and activation and show that loss of NTE:CTE interactions is a major mechanism of PINK1-associated mutations linked to PD.

biochemistry↗

bioRxiv2020

Proteomic and functional mapping of cardiac NaV1.5 channel phosphorylation reveals multisite regulation of surface expression and gating

Phosphorylation of NaV1.5 channels regulates cardiac excitability, yet the phosphorylation sites regulating channel function and the underlying mechanisms remain largely unknown. Using a systematic quantitative phosphoproteomic approach, we analyzed NaV1.5 channel complexes purified from non-failing and failing mouse left ventricles, and we identified 42 phosphorylation sites on NaV1.5. Most sites are clustered, and three of these clusters are highly phosphorylated. Analyses of phosphosilent and phosphomimetic NaV1.5 mutants revealed the roles of three phosphosites in regulating NaV1.5 channel expression and gating. The phosphorylated serines-664 and -667 regulate the voltage-dependence of channel activation in a cumulative manner, whereas phosphorylation of the nearby serine-671, which is increased in failing hearts, decreases cell surface NaV1.5 expression and peak Na+ current. No additional roles could be assigned to the other clusters of phosphosites. Taken together, the results demonstrate that ventricular NaV1.5 is highly phosphorylated, and that the phosphorylation-dependent regulation of NaV1.5-encoded channels is highly complex, site-specific and dynamic. AbbreviationsA, alanine; E, glutamate; HEK-293, Human Embryonic Kidney 293 cells; INa, peak Na+ current; INaL, late Na+ current; IP, immunoprecipitation; mNaVPAN, anti-NaV channel subunit mouse monoclonal antibody; MS, Mass Spectrometry; MS1, mass spectrum of peptide precursors; MS2 or MS/MS, fragmentation mass spectrum of peptides selected in narrow mass range (2 Da) from MS1 scan; NaV, voltage-gated Na+ channel; pS, phosphoserine; pT, phosphothreonine; S, serine; T, threonine; TAC, Transverse Aortic Constriction; TMT, Tandem Mass Tag.

physiology↗