Biology subjects

Blacker, T. S.

Publications and source records attributed to Blacker, T. S..

5 recordsLinked to original sources

bioRxiv2025

Targeting Lysosomal pH Restores Mitochondrial Quality Control in GBA1-Mutant Parkinsons Disease

BackgroundHeterozygous mutations in the Glucocerebrosidase gene (GBA1), which encodes the lysosomal enzyme {beta}-glucocerebrosidase (GCase), are a genetic risk factor for Parkinsons disease (PD). The pathophysiological consequences of GBA1 mutations on dopaminergic neuronal function, especially their impact on lysosomal function, mitophagy, and mitochondrial bioenergetics, remain unclear. MethodsFibroblasts and dopaminergic neurons generated from induced pluripotent stem cells (iPSCs) derived from patients with GBA1-PD were used in the study. Live-cell imaging was performed to measure lysosomal acidification, protease activity, mitochondrial membrane potential, and mitophagy. Mitochondrial morphology and autophagic vesicles were examined using transmission electron microscopy. Oxygen consumption rate was measured by Seahorse assay. V-ATPase assembly was quantified using FLIM-FRET, and pharmacological interventions included rapamycin and acidic nanoparticles. Statistical analyses involved unpaired t-tests, one-way ANOVA, and two-way ANOVA. ResultsGCase activity, lysosomal acidification, protease activity, mitophagy and mitochondrial bioenergetic function were all impaired. Mitochondria were fragmented, with reduced membrane potential and oxygen consumption. MTORC1 was constitutively phosphorylated and FLIM-FRET measurements confirmed impaired lysosomal V-ATPase assembly, which was reversed following rapamycin treatment. Rapamycin and lysosome-targeted acidic nanoparticles rescued lysosomal pH, restored mitophagy, mitochondrial membrane potential and mitochondrial OXPHOS complex levels in GBA1 mutant dopaminergic neurons. ConclusionsWe reveal a novel mechanistic link between GBA1 mutations and mitochondrial dysfunction, as disruption of V-ATPase assembly driven by MTORC1 activation impairs lysosomal acidification. Mitophagy is therefore impaired leading to mitochondrial dysfunction, undermining dopaminergic cell function and fate. Pharmacological intervention with rapamycin or acidic nanoparticles restore lysosomal pH and rescue mitochondrial function, signposting a novel therapeutic approach for GBA1-PD.

neuroscience↗

bioRxiv2025

Pathological mutation in SMN impairs modulation of GAR1 phase separation linking condensate dysfunction to Spinal Muscular Atrophy

Pathological mutations in liquid-liquid phase separation (LLPS) scaffold proteins have been linked to biomolecular condensate dysfunction in neurodegenerative diseases, while the possible impact of client protein mutations remains unclear. In spinal muscular atrophy (SMA), the disease-associated E134K mutation in the Tudor domain (TD) of the survival motor neuron (SMN) protein disrupts its interaction with GAR1, an RGG-rich protein within the H/ACA small nucleolar ribonucleoprotein complex. The consequences of this impaired interaction have not been elucidated. Here, we identified GAR1 as an LLPS scaffold protein that is phase separated in nuclear compartments and forms gel-like condensates via complex coacervation with RNA in vitro. In cells, we reveal that SMN co-localizes with GAR1 in Cajal bodies and modulates its dynamics. Using confocal microscopy and NMR spectroscopy, we further show that SMN TD is a client protein that regulates the architecture and dynamics of GAR1 condensates through competitive RNA interactions, implicating GAR1 phase separation in RNA accumulation and release processes regulated by SMN. Notably, the SMA-associated E134K variant of SMN exhibits a reduced affinity for GAR1, impairing the modulation of GAR1 condensates and displacement RNA. Our findings suggest a mechanistic link between phase separation dysregulation and SMA, driven by disrupted scaffold-client interactions, that highlights the therapeutic potential of targeting SMN-dependent condensate regulation in SMA.

biochemistry↗

bioRxiv2024

Redox-dependent binding and conformational equilibria govern the fluorescence decay of NAD(P)H in living cells

When probed using fluorescence lifetime imaging microscopy (FLIM), the emission from reduced nicotinamide adenine dinucleotide (NADH) and its phosphorylated form NADPH have shown promise as sensitive intrinsic reporters of metabolism in living systems. However, an incomplete understanding of the biochemical processes controlling their fluorescence decay makes it difficult to draw unambiguous conclusions from NAD(P)H FLIM data. Here we utilised time-resolved fluorescence anisotropy imaging to identify multiple enzyme binding configurations in live cells associated with lifetimes both longer and shorter than unbound NAD(P)H. FLIM, combined with mathematical and computational modelling, revealed that the redox states of the NAD and NADP pools control the steady-state equilibrium of binding configurations, which in-turn determines the observed fluorescence decay. This knowledge will be foundational to developing the accurate interpretation of NAD(P)H FLIM.

biochemistry↗

bioRxiv2022

Gradients in cellular metabolism regulate development of tonotopy along the chick cochlea.

In vertebrates with elongated auditory organs, mechanosensory hair cells (HCs) are organised such that complex sounds are broken down into their component frequencies along the proximal-to-distal long (tonotopic) axis. Acquisition of frequency-specific morphologies at the appropriate positions along the chick cochlea, the basilar papilla (BP), requires that nascent HCs determine their tonotopic positions during development. The complex signalling within the auditory organ between the developing HC and its local niche along the axis is currently poorly understood. Here we apply NAD(P)H fluorescence lifetime imaging (FLIM) to reveal metabolic gradients along the tonotopic axis of the developing BP. Re-shaping these gradients during development, by inhibiting different branch points of cytosolic glucose catabolism, alters normal morphogen signalling and abolishes tonotopic patterning, normalising the graded differences in hair cell morphology along the BP. These findings highlight a causal link between morphogen signalling and metabolic reprogramming in specifying tonotopic identity in developing auditory HCs.

developmental biology↗

bioRxiv2019

CHCHD4 regulates a proliferation-EMT switch in tumour cells, through respiratory complex I mediated metabolism.

BACKGROUNDMitochondrial metabolism involves oxidative phosphorylation (OXPHOS) via the respiratory chain and is required for the maintenance of tumour cell proliferation and regulation of epithelial-mesenchymal transition (EMT)-related phenotypes through mechanisms that are not fully understood. The essential mitochondrial import protein coiled-coil helix coiled-coil helix domain-containing protein 4 (CHCHD4) controls respiratory chain complex activity and oxygen consumption, and regulates the growth of tumours in vivo. In this study we interrogate the role of CHCHD4-regulated respiratory chain activity and metabolism in tumour cell proliferation and EMT-related phenotypes.\n\nRESULTSWe show that CHCHD4 is essential for the proliferation of tumour cells irrespective of their aetiology. In human tumours, elevated CHCHD4 expression is correlated with a mitochondrial OXPHOS gene signature and with a proliferative gene signature associated with the mTORC1 signalling pathway. Elevated CHCHD4 increases tumour cell proliferation, in a manner that is dependent on complex I (CI) activity, glutamine consumption and mTORC1 activation. CHCHD4 expression is inversely correlated with EMT gene expression both in vitro and in vivo. Finally, we show CHCHD4 regulates the intracellular distribution of the EMT marker vimentin, in a CI-mediated manner.\n\nCONCLUSIONSCHCHD4 regulates tumour cell proliferation and metastatic (EMT-related) phenotypes through its control of CI-mediated mitochondrial metabolism.

cell biology↗