Biology subjects

Heon-Roberts, R.

Publications and source records attributed to Heon-Roberts, R..

4 recordsLinked to original sources

bioRxiv2025

TFEB and TFE3 have cell-type specific expression in the brain and divergent roles in neurons

Lysosomal dysfunction occurs in many neurodegenerative diseases, including Parkinsons disease, and activating TFEB to enhance lysosomal biogenesis is a promising therapeutic strategy. To understand TFEB physiology in cells of the brain, we characterised TFEB expression using iPSC-derived models, and transcriptomic analysis of human and mouse brain tissue. Surprisingly, TFEB expression at the RNA and protein level was restricted to glia, whereas the related transcription factor, TFE3, was expressed ubiquitously. We identified HDAC1/2/3 as transcriptional repressors of neuronal TFEB and found the brain-penetrant HDAC inhibitor ACY-738 derepressed TFEB expression and enhanced TFE3 nuclear translocation in iPSC-dopaminergic neurons (iPSC-DaNs). We delineated the role of each transcription factor by genetic manipulation in iPSC-DaNs to reveal divergent roles in which TFEB activates mitochondrial biogenesis, whereas TFE3 enhances lysosomal biogenesis. Finally, we show TFE3 activation corrects the lysosomal dysfunction associated with GBA-N370S and SNCA-Triplication mutations in Parkinsons patient-derived iPSC-DaNs, demonstrating therapeutic utility in neurodegeneration.

cell biology↗

bioRxiv2025

USP30 inhibition improves mitochondrial health through both PINK1-dependent and independent mechanisms

Mitochondrial dysfunction is a key feature of many pathologies, including Parkinsons disease. The selective vulnerability of dopaminergic neurons is thought to be influenced by mitochondrial dysfunction and mutations in the mitophagy regulating proteins PINK1 and Parkin that are known to cause early-onset Parkinsonism in an autosomal recessive manner. Augmentation of mitophagy through inhibition of USP30 may be a viable therapeutic strategy for a number of diseases including Parkinsons. USP30 inhibition has been demonstrated to augment PINK1/PRKN mitophagy but also potentiate basal mitophagy to support the removal of dysfunctional mitochondria. Therefore, long-term de-regulation of mitophagy has been proposed to lead to mitochondrial depletion. We have used an integrated approach across cell lines, primary neurons and iPSC-derived dopaminergic neuronal cultures to assess the short and long-term effects of USP30 inhibition on mitochondrial health and neuronal activity. We investigated the dependence of USP30 inhibition phenotypes on the PINK1/Parkin pathway using genetic ablation and in iPSC-derived neurons from Parkinsons patients with PINK1 or PRKN mutations. Loss of USP30 through CRISPR/Cas9-mediated knockout resulted in increased basal and depolarisation-induced mitophagy in SH-SY5Y cells. Loss of USP30 or pharmacological inhibition altered mitochondrial morphology and led to increases in membrane potential and ATP levels with decreased oxygen consumption, suggesting that USP30 loss results in a more efficient mitochondrial network. These changes in morphology were found to be independent of PINK1 or Parkin. Chronic pharmacological inhibition of USP30 or CRISPRi-mediated knockdown of USP30 did not impact dopaminergic neuronal activity, as assessed by electrophysiological profiling, but did potentiate depolarisation-induced mitophagy in primary and iPSC-derived neuronal cultures. We observed minimal changes in mitophagy levels in iPSC-derived dopaminergic neurons from Parkinsons patients with PINK1 or PRKN mutations that were independent of the ability to produce p65Ub. Importantly, within this experimental paradigm, pharmacological USP30 inhibition increased depolarisation-induced mitophagy in both PINK1 and PRKN patients to the same extent as control neurons. These results support a role for USP30 in modulating the trigger threshold for mitophagy and suggest that USP30 inhibitors may be beneficial in patients with impairments in PINK1/Parkin-mediated mitophagy.

neuroscience↗

bioRxiv2024

Secondary deficiency of neuraminidase 1 contributes to CNS pathology in neurological mucopolysaccharidoses via hypersialylation of brain glycoproteins

Mucopolysaccharidoses (MPS) are lysosomal storage diseases caused by defects in catabolism of glycosaminoglycans. MPS I, II, III and VII are associated with lysosomal accumulation of heparan sulphate and manifest with neurological deterioration. Most of these neurological MPS currently lack effective treatments. Here, we report that, compared to controls, neuraminidase 1 (NEU1) activity is drastically reduced in brain tissues of neurological MPS patients and in mouse models of MPS I, II, IIIA, IIIB and IIIC, but not of other neurological lysosomal disorders not presenting with heparan sulphate storage. We further show that accumulated heparan sulphate disrupts the lysosomal multienzyme complex of NEU1 with cathepsin A (CTSA), {beta}-galactosidase (GLB1) and glucosamine-6-sulfate sulfatase (GALNS) necessary to maintain enzyme activity, and that NEU1 deficiency is linked to partial deficiencies of GLB1 and GALNS in cortical tissues and iPSC-derived cortical neurons of neurological MPS patients. Increased sialylation of N-linked glycans in brain samples of human MPS III patients and MPS IIIC mice implicated insufficient processing of brain N-linked sialylated glycans, except for polysialic acid, which was reduced in the brains of MPS IIIC mice. Correction of NEU1 activity in MPS IIIC mice by lentiviral gene transfer ameliorated previously identified hallmarks of the disease, including memory impairment, behavioural traits, and reduced levels of the excitatory synapse markers VGLUT1 and PSD95. Overexpression of NEU1 also restored levels of VGLUT1-/PSD95-positive puncta in cortical neurons derived from iPSC of an MPS IIIA patient. Together, our data demonstrate that heparan sulphate-induced secondary NEU1 deficiency and aberrant sialylation of glycoproteins implicated in synaptogenesis, memory, and behaviour constitute a novel pathological pathway in neurological MPS spectrum crucially contributing to CNS pathology. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=89 SRC="FIGDIR/small/587986v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@3905c3org.highwire.dtl.DTLVardef@1a9672corg.highwire.dtl.DTLVardef@b4911forg.highwire.dtl.DTLVardef@a3b190_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2021

Oral Glucosamine Ameliorates Aggravated Neurological Phenotype in Mucopolysaccharidosis III Type C Mouse Model Expressing Misfolded HGSNAT Variant

ObjectiveOver 55% of mucopolysaccharidosis IIIC (MPS IIIC) patients have at least one allelic missense variant responsible for misfolding of heparan sulfate acetyl-CoA:-glucosaminide N- acetyltransferase (HGSNAT). These variants are potentially treatable with pharmacological chaperones, such as a competitive HGSNAT inhibitor, glucosamine. Since the constitutive HGSNAT knockout mice, we generated previously cannot be used to test such strategy in vivo, we generated a novel model, the HgsnatP304L strain, expressing misfolded mutant HGSNAT with human missense mutation Pro311Leu (Pro304Leu in the mouse enzyme). ResultsHgsnatP304L mice present deficits in short-term (novel object recognition test) and working/spatial (Y-maze test) memory at 4 months of age, 2-4 months earlier than previously described gene-targeted Hgsnat-Geo mice, which lack HGSNAT protein. HgsnatP304L mice also show increased severity of synaptic deficits in CA1 neurons, and accelerated course of CNS pathology including neuronal storage of heparan sulfate, accumulation of misfolded proteins, increase of simple gangliosides, and neuroinflammation as compared with Hgsnat-Geo mice. Expression of misfolded human Pro311Leu HGSNAT protein in cultured hippocampal Hgsnat- Geo neurons aggravated reduction of synaptic proteins. Memory deficits and majority of pathological changes in the brain were rescued in mice receiving daily doses of oral glucosamine. InterpretationAltogether, our data for the first time demonstrate dominant-negative effects of the misfolded HGSNAT Pro304Leu variant and show that these effects are treatable by oral administration of glucosamine, suggesting that patients, affected with missense mutations preventing normal folding of the enzyme, could benefit from chaperone therapy.

animal behavior and cognition↗