Biology subjects

Eden, E. R.

Publications and source records attributed to Eden, E. R..

6 recordsLinked to original sources

bioRxiv2026

HKDC1 contributes to aberrant lysosome-mitochondria contact in Niemann-Pick disease type C

Niemann-Pick disease type C (NPC) is a neurovisceral lysosomal storage disorder comprising two clinically indistinguishable but genetically distinct subtypes caused by mutations in NPC1, or NPC2. The specific impact of each deficiency on cellular homeostasis remains poorly defined due to the phenotypic heterogeneity of patient-derived models and a lack of isogenic platforms for comparative study. Here we established isogenic ARPE19 models of NPC1 and NPC2 deficiency that faithfully recapitulate hallmark pathologies, including homogeneous lysosomal expansion and lipid sequestration. Direct comparison of these isogenic lines revealed a fundamental divergence in organelle crosstalk: while both genotypes exhibit comparable lipid accumulation, expanded mitochondria-lysosome contact sites (MLCs) are observed exclusively in NPC1-/- cells. Using StARD3-targeted proximity labelling and quantitative proteomics, we identified the mitochondrial protein HKDC1 as an MLC regulator. We demonstrate that HKDC1 is markedly upregulated in NPC1-/- cells and that its overexpression drives MLC expansion in wild-type cells. Thus our study uncovers a homeostatic role for HKDC1-mediated organelle remodelling and demonstrates the power of isogenic modelling for identifying novel regulators of organelle architecture and potential therapeutic targets.

cell biology↗

bioRxiv2026

HRS dephosphorylation at membrane contact sites promotes sorting within multivesicular endosomes

HRS is a receptor tyrosine kinase substrate and component of the ESCRT machinery. It enables sorting of ubiquitylated cargo into multivesicular endosomes (MVEs) for lysosomal degradation but also functions in receptor recycling. We show that co-depletion of its ESCRT-0 binding partners, STAM1 and STAM2, recapitulates defects in EGF receptor (EGFR) sorting onto intraluminal vesicles (ILVs) but does not mirror the increased MVE size evident after HRS depletion. Using mutagenesis of the endogenous gene or introduction of APEX2-tagged HRS variants, we find that HRS Y329/334 phosphorylation is dispensable for EGFR sorting and MVE size control. AnnexinA1 mediates endosomal contact with the ER and promotes EGF-stimulated ILV formation. We show that reduced ILV formation on AnnexinA1 depletion is accompanied by increased HRS phosphorylation, likely through reduced HRS dephosphorylation by ER-localised PTP1B. Conversely, Y329/334 mutation renders ILV formation insensitive to AnnexinA1 depletion. Our data suggest that rapid HRS dephosphorylation at ER:MVE contacts promotes efficient ILV formation.

cell biology↗

bioRxiv2025

Alternate Splicing Directs PMCA2 to Lysosomes and is Linked to Neurodegeneration

Plasma membrane calcium ATPases (PMCAs) are believed to function exclusively at the plasma membrane where they expel calcium from the cytosol. We have unexpectedly identified a splice variant-dependent localisation of the PMCA isoform PMCA2 to the lysosome, where it forms an evolutionarily conserved complex with NPC1, the lysosomal membrane protein defective in the rare lysosomal storage disease Niemann-Pick disease type C (NPC). This interaction is required for lysosomal Ca2+ homeostasis and implicates PMCA2 as a mediator of Ca2+ uptake into lysosomes. Disruption of the NPC1-PMCA2 complex contributes to the pathophysiology of both Niemann-Pick disease type C and Parkinsons disease, revealing an unrecognised intracellular function for PMCA2 and a shared mechanism linking lysosomal Ca2+ and lipid regulation in neurodegeneration.

cell biology↗

bioRxiv2025

Antisense oligonucleotide allele-specific targeting of EFEMP1 in a patient-derived model of Doyne honeycomb retinal dystrophy

Doyne honeycomb retinal dystrophy is an incurable juvenile macular dystrophy that leads to visual impairment by early to mid-adulthood. It is an autosomal dominant disorder caused by a c.1033C>T, p.Arg(345Trp) variant in EFEMP1, and is characterised by the early onset extracellular deposition of drusen between the retinal pigment epithelium basement membrane and underlying layers of Bruchs membrane. In this study, we developed an antisense oligonucleotide approach to target EFEMP1. We reprogrammed patient-derived renal epithelial cells to induced pluripotent stem cells followed by directed differentiation to retinal pigment epithelium and compared the phenotype to gene-corrected and EFEMP1 knockout patient-derived retinal pigment epithelium. In the patient-derived disease model, remodelling of the extracellular matrix occurred with progressive accumulation of extracellular deposits containing the drusen-associated proteins apolipoprotein E and collagen IV, in addition to EFEMP1. Moreover, the intracellular accumulation of neutral lipids was evident. We developed an allele-specific antisense oligonucleotide which specifically and effectively promoted the clearance of the EFEMP1 c.1033C>T transcript in the patient-derived disease model following assisted or gymnotic delivery. In this disease model, gymnotic delivery led to a decrease in extracellular deposits and cleared the intracellular accumulation of lipids, even after the onset of this disease phenotype, suggesting this could be a practical and effective therapeutic approach.

molecular biology↗

bioRxiv2025

N-Acetyl-l-Leucine (NALL) rescues inter-organelle communication in Niemann-Pick disease type-C patient cells.

Niemann-Pick disease type-C (NPC) is a progressive neurodegenerative disease caused by loss-of-function mutations in NPC1 or NPC2. In NPC patient cells lacking functional NPC proteins, lipids accumulate in lysosomes causing severe lysosomal storage disease. Surprisingly, lipid accumulation caused by defects in the lysosomal membrane protein NPC1 is strongly associated with mitochondrial dysfunction. The mechanism of this coupled dysfunction is not fully understood, but a recently approved NPC therapeutic, N-Acetyl-l-Leucine (NALL), reverses both lysosomal and mitochondrial phenotypes in NPC patient cells. Our data indicate that direct inter-organelle communication through lysosome membrane contact sites with mitochondria contribute to the coupled organelle dysfunction in NPC. We find that mitochondria:lysosome contact sites are expanded in NPC, dependent on accumulation of lysosomal cholesterol and that NALL rescues the aberrant contact sites. We further identify a direct correlation between mitochondria:lysosome contact site expansion and mitochondrial dysfunction and propose that normalisation of contacts sites contributes to the coupled restoration of lysosome and mitochondrial function by NALL. We further find that NALL-mediated normalisation of lysosomal contact sites also correlates with restoration of autophagic flux and lysosome repair in NPC patient cells.

cell biology↗

bioRxiv2025

Identification of ER:melanosome membrane contact sites in the retinal pigment epithelium.

The retinal pigment epithelium (RPE) forms a monolayer of cells at the blood:retina interface that plays important roles for photoreceptor renewal and function and is central to retinal health. RPE pigment is provided by melanin-containing melanosomes which offer protection against light and oxidative stress. Melanosome migration into the apical processes of the RPE following light onset is thought to contribute to preventing retinal degeneration with age, though the mechanism is not yet clear. Melanosomes are transported along microtubules to the apical surface where they are transferred to actin filaments within the apical processes. Melanosomes are lysosome-related organelles derived from endosomes and endosome transport along microtubules is heavily influenced by the endoplasmic reticulum (ER) through ER:endosome contact sites. Here we describe extensive connection between the ER and melanosomes in the RPE. We further show, in skin melanocytes, that the ER forms contact sites with all stages of melanosome maturation, but ER contact is reduced as melanosomes mature. Finally, we identify tripartite contact sites between the ER, melanosomes and mitochondria in both RPE tissue and cellular models, suggesting that the ER may influence melanosome biogenesis, maturation and interaction with mitochondria.

cell biology↗