Biology subjects

Beale, A. D.

Publications and source records attributed to Beale, A. D..

10 recordsLinked to original sources

bioRxiv2026

Post-transcriptional glucocorticoid receptor signalling synchronises circadian rhythms

Keeping cellular circadian clocks synchronised is critical for cellular and physiological health. Glucocorticoid (GC) hormones are the most potent systemic timing signal for cellular clocks, acting via the glucocorticoid receptor (GR), a transcription factor conventionally thought to synchronise cells by translocating into the nucleus and activating the transcription of clock genes. Our findings overturn this model: acute changes in GR translocation and nascent transcription are both dispensable for GC-resetting of the circadian clock. Instead, physiological GC pulses act post-transcriptionally to rapidly increase Period1 mRNA through enhanced RNA processing, not synthesis. This elevates PER1 protein production which, alone, is sufficient to reset the clock. Yet each pulse resets only a subset of cells, explaining why, in vivo, repeated daily hormonal cues are required for full re-entrainment after jet lag or shift work. We propose a new model for hormonal signalling to the circadian clock and identify RNA processing kinetics as a general regulatory lever for nuclear receptor signalling.

molecular biology↗

bioRxiv2026

High sensitivity imaging of intracellular Cl- reveals the spatiotemporal evolution of GABAergic chloride fluxes in vitro and in vivo

Fast GABAergic inhibition in the brain is mediated by chloride currents whose driving force depends on intracellular Chloride concentration ([Cl-]i). Resolving the spatiotemporal dynamics of [Cl-]i in neurons requires a sensor combining high Cl- affinity, pH independence, and photostability - properties no existing tool achieves simultaneously. Here we introduce iClima (improved Chloride Imaging), a ratiometric genetically encoded sensor with high Cl- affinity (Kd=3.5 mM at pH 7.2), pH-insensitive under physiological conditions, and markedly improved photostability compared to existing sensors. These properties enable dynamic Cl- imaging without simultaneous pH correction. We demonstrate that iClima resolves GABAA-driven Cl- transients in cultured neurons, detects discrete Cl- hotspots along dendrites, and captures sensory-evoked Cl- transients in vivo. Finally, exploiting the spectral compatibility of iClima with GCaMP6f, we measure in interleaved trials Cl- and Ca2+ transients in the same neurons in vivo, revealing a divergence between the somatic inhibitory drive and the neuronal excitation state as reported by Ca2+ dynamics.

neuroscience↗

bioRxiv2024

Potassium rhythms couple the circadian clock to the cell cycle

Circadian ([~]24 h) rhythms are a fundamental feature of life, and their disruption increases the risk of infectious diseases, metabolic disorders, and cancer1-6. Circadian rhythms couple to the cell cycle across eukaryotes7,8 but the underlying mechanism is unknown. We previously identified an evolutionarily conserved circadian oscillation in intracellular potassium concentration, [K+]i9,10. As critical events in the cell cycle are regulated by intracellular potassium11,12, an enticing hypothesis is that circadian rhythms in [K+]i form the basis of this coupling. We used a minimal model cell, the alga Ostreococcus tauri, to uncover the role of potassium in linking these two cycles. We found direct reciprocal feedback between [K+]i and circadian gene expression. Inhibition of proliferation by manipulating potassium rhythms was dependent on the phase of the circadian cycle. Furthermore, we observed a total inhibition of cell proliferation when circadian gene expression is inhibited. Strikingly, under these conditions a sudden enforced gradient of extracellular potassium was sufficient to induce a round of cell division. Finally, we provide evidence that interactions between potassium and circadian rhythms also influence proliferation in mammalian cells. These results establish circadian regulation of intracellular potassium levels as a primary factor coupling the cell- and circadian cycles across diverse organisms.

cell biology↗

bioRxiv2024

Circadian clocks in human cerebral organoids

Circadian rhythms result from cell-intrinsic timing mechanisms that impact health and disease1,2. To date, however, neural circadian research has largely focused on the hypothalamic circuitry of nocturnal rodents3. Whether circadian rhythms exist in human brain cells is unknown. Here we show bona fide circadian rhythms in human neurons, glia, cerebral organoids, and cerebral organoid slices (ALI-COs)4-8. Human neural circadian rhythms are synchronised by physiological timing cues such as glucocorticoids and daily temperature cycles, and these rhythms are temperature-compensated across the range of normal human brain temperatures9. Astrocyte rhythms are phase-advanced relative to other cultures and they modulate neuronal clock responses to temperature shift. Cerebral organoid rhythms are more robust at physiological brain temperatures; the relative amplitude of these rhythms increases over time in culture and their resetting capacity recapitulates key neurodevelopmental transitions in glucocorticoid signalling10-14. Remarkably, organoid post-transcriptional bioluminescent clock reporter rhythms are retained even when those of their putative transcriptional drivers are indiscernible15, and electrophysiology recordings confirm circadian rhythms in functional activity of monocultures, organoids, and ALI-COs. Around one third of the cerebral organoid proteome and phosphoproteome are circadian-rhythmic, with temporal consolidation of disease-relevant neural processes. Finally, we show that human brain organoid rhythms can be modulated and disrupted by commonly used brain-permeant drugs and mistimed cortisol exposure, respectively. Our results demonstrate that human brain cells and tissues develop their own circadian oscillations and that canonical mechanisms of the circadian clockwork may be inadequate to explain these rhythmic phenomena. 2D and 3D human neural cultures represent complementary and tractable models for exploring the emergence, disruption, and mechanics of the circadian neural clockwork, with important implications for chronobiology, brain function, and brain health.

neuroscience↗

bioRxiv2023

Thermosensitivity of translation underlies the mammalian nocturnal-diurnal switch

Early mammals were nocturnal until the Cretaceous-Paleogene extinction enabled diurnal niche expansion. Diurnality evolved multiple times independently, but the mechanisms driving this shift remain unclear. We identify a conserved cell-intrinsic signal inversion that facilitates the transition from nocturnality to diurnality. Diurnal and nocturnal mammalian cells respond oppositely to temperature and osmotic cycles, mirroring species activity patterns. Cells exhibit differential global responses to temperature changes, including the phosphoproteome and protein synthesis. mTOR signaling is identified as a central mediator of this inversion, with diurnal mammals converging on modifications to mTOR and WNK pathways during evolution. Reducing mTOR activity induces nocturnal-to-diurnal shifting at cellular, tissue, and organismal levels. Therefore, the mTOR pathway is a cellular nexus that integrates energetic state and environmental signals to determine activity niche.

cell biology↗

bioRxiv2022

Circadian regulation of protein turnover and proteome renewal

Although costly to maintain, protein homeostasis is indispensable for normal cellular function and long-term health. In mammalian cells and tissues, daily variation in global protein synthesis has been observed, but its utility and consequences for proteome integrity are not fully understood. Using several different pulse-labelling strategies, here we gain direct insight into the relationship between protein synthesis and abundance proteome-wide. We show that protein degradation varies in-phase with protein synthesis, facilitating rhythms in turnover rather than abundance. This results in daily consolidation of proteome renewal whilst minimising changes in composition. Coupled rhythms in synthesis and turnover are especially salient to the assembly of macromolecular protein complexes, particularly the ribosome, the most abundant species of complex in the cell. Daily turnover and proteasomal degradation rhythms render cells and mice more sensitive to proteotoxic stress at specific times of day, potentially contributing to daily rhythms in the efficacy of proteasomal inhibitors against cancer. Our findings suggest that circadian rhythms function to minimise the bioenergetic cost of protein homeostasis through temporal consolidation of protein turnover.

cell biology↗

bioRxiv2021

Clock gene-independent daily regulation of haemoglobin oxidation in red blood cells

Cellular circadian rhythms confer temporal organisation upon physiology that is fundamental to human health. Rhythms are present in red blood cells (RBCs), the most abundant cell type in the body, but their physiological function is poorly understood. Here, we present a novel biochemical assay for haemoglobin (Hb) oxidation status which relies on a redox-sensitive covalent haem-Hb linkage that forms during SDS-mediated cell lysis. Formation of this linkage is lowest when ferrous Hb is oxidised, in the form of ferric metHb. Daily haemoglobin oxidation rhythms are observed in RBCs cultured in vitro or taken from freely behaving mice or humans exhibit and are unaffected by mutations that affect circadian rhythms in nucleated cells. These rhythms correlate with daily rhythms in core body temperature, with temperature lowest when metHb levels are highest. Raising metHb levels with dietary sodium nitrite can further decrease daytime core body temperature in mice via NO signaling. These results extend our molecular understanding of RBC circadian rhythms and suggest they contribute to the regulation of body temperature.

cell biology↗

bioRxiv2020

Compensatory ion transport buffers daily protein rhythms to regulate osmotic balance and cellular physiology

Between 6-20% of the cellular proteome is under circadian control to tune cell function with cycles of environmental change. For cell viability, and to maintain volume within narrow limits, the osmotic pressure exerted by changes in the soluble proteome must be compensated. The mechanisms and consequences underlying compensation are not known. Here, we show in cultured mammalian cells and in vivo that compensation requires electroneutral active transport of Na+, K+, and Cl- through differential activity of SLC12A family cotransporters. In cardiomyocytes ex vivo and in vivo, compensatory ion fluxes alter their electrical activity at different times of the day. Perturbation of soluble protein abundance has commensurate effects on ion composition and cellular function across the circadian cycle. Thus, circadian regulation of the proteome impacts ion homeostasis with substantial consequences for the physiology of electrically active cells such as cardiomyocytes.

cell biology↗

bioRxiv2020

Eukaryotic cell biology is temporally coordinated to support the energetic demands of protein homeostasis

Every aspect of yeast physiology is subject to robust temporal regulation, this becomes apparent under nutrient-limiting conditions 1-6 and results in biological oscillations whose function and mechanism is poorly resolved7. These yeast metabolic oscillations share features with circadian rhythms and typically interact with, but are independent of, the cell division cycle. Here we show that these cellular rhythms act to minimise energy expenditure by temporally restricting protein synthesis until sufficient cellular resources are present, whilst maintaining osmotic homeostasis and protein quality control. Although nutrient supply is constant, cells initially sequester and store metabolic resources such as carbohydrates, amino acids, K+ and other osmolytes; which accumulate via increased synthesis, transport, autophagy and biomolecular condensation that is stimulated by low glucose and cytosolic acidification. Replete stores trigger increased H+ export to elevate cytosolic pH, thereby stimulating TORC1 and liberating proteasomes, ribosomes, chaperones and metabolic enzymes from non-membrane bound compartments. This facilitates a burst of increased protein synthesis, the liquidation of storage carbohydrates to sustain higher respiration rates and increased ATP turnover, and the export of osmolytes to maintain osmotic potential. As the duration of translational bursting is determined by cell-intrinsic factors, the period of oscillation is determined by the time cells take to store sufficient resources to license passage through the pH-dependent metabolic checkpoint that initiates translational bursting. We propose that dynamic regulation of ion transport and metabolic plasticity are required to maintain osmotic and protein homeostasis during remodelling of eukaryotic proteomes, and that bioenergetic constraints have selected for temporal organisation that promotes oscillatory behaviour.

molecular biology↗

bioRxiv2020

CRYPTOCHROME suppresses the circadian proteome and promotes protein homeostasis

The daily organisation of most mammalian cellular functions is attributed to circadian regulation of clock-controlled protein expression, driven by daily cycles of CRYPTOCHROME-dependent transcriptional feedback repression. To test this, we compared the circadian proteome and phosphoproteome of wild type and CRY-deficient fibroblast cells. Strikingly, CRY-deficient cells showed a two-fold increase in circadian-regulated proteins, phosphopeptides, and K+ transport. This was accompanied by extensive remodelling of the cellular proteome overall, including reduced phosphatase and proteasome subunit expression. These adaptations rendered CRY-deficient cells more sensitive to stress, which may account for their reduced circadian robustness and contribute to the wide-ranging phenotypes of CRY-deficient mice. We suggest that CRY ultimately functions to suppress, rather than generate, daily rhythms in cellular protein abundance, thereby maintaining protein and osmotic homeostasis.

cell biology↗