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Stangherlin A. Ion dynamics and the regulation of circadian cellular physiology. Am J Physiol Cell Physiol 2023; 324:C632-C643. [PMID: 36689675 DOI: 10.1152/ajpcell.00378.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Circadian rhythms in physiology and behavior allow organisms to anticipate the daily environmental changes imposed by the rotation of our planet around its axis. Although these rhythms eventually manifest at the organismal level, a cellular basis for circadian rhythms has been demonstrated. Significant contributors to these cell-autonomous rhythms are daily cycles in gene expression and protein translation. However, recent data revealed cellular rhythms in other biological processes, including ionic currents, ion transport, and cytosolic ion abundance. Circadian rhythms in ion currents sustain circadian variation in action potential firing rate, which coordinates neuronal behavior and activity. Circadian regulation of metal ions abundance and dynamics is implicated in distinct cellular processes, from protein translation to membrane activity and osmotic homeostasis. In turn, studies showed that manipulating ion abundance affects the expression of core clock genes and proteins, suggestive of a close interplay. However, the relationship between gene expression cycles, ion dynamics, and cellular function is still poorly characterized. In this review, I will discuss the mechanisms that generate ion rhythms, the cellular functions they govern, and how they feed back to regulate the core clock machinery.
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Affiliation(s)
- Alessandra Stangherlin
- Faculty of Medicine and University Hospital Cologne, Cluster of Excellence Cellular Stress Responses in Aging-associated Diseases (CECAD), Institute for Mitochondrial Diseases and Ageing, University of Cologne, Cologne, Germany
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Baruah D, Marak CNK, Roy A, Gohain D, Kumar A, Das P, Borkovich KA, Tamuli R. Multiple calcium signaling genes play a role in the circadian period of Neurospora crassa. FEMS Microbiol Lett 2023; 370:fnad044. [PMID: 37193664 PMCID: PMC10237334 DOI: 10.1093/femsle/fnad044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 04/12/2023] [Accepted: 05/15/2023] [Indexed: 05/18/2023] Open
Abstract
The Ca2+ signaling genes cpe-1, plc-1, ncs-1, splA2, camk-1, camk-2, camk-3, camk-4, cmd, and cnb-1 are necessary for a normal circadian period length in Neurospora crassa. In addition, the Q10 values ranged between 0.8 and 1.2 for the single mutants lacking cpe-1, splA2, camk-1, camk-2, camk-3, camk-4, and cnb-1, suggesting that the circadian clock exhibits standard temperature compensation. However, the Q10 value for the ∆plc-1 mutant was 1.41 at 25 and 30 °C, 1.53 and 1.40 for the ∆ncs-1 mutant at 20 and 25 °C, and at 20 and 30 °C, respectively, suggesting a partial loss of temperature compensation in these two mutants. Moreover, expression of frq, a regulator of the circadian period, and the blue light receptor wc-1, were increased >2-fold in the Δplc-1, ∆plc-1; ∆cpe-1, and the ∆plc-1; ∆splA2 mutants at 20 °C. The frq mRNA level was increased >2-fold in the Δncs-1 mutant compared to the ras-1bd strain at 20 °C. Therefore, multiple Ca2+ signaling genes regulate the circadian period, by influencing expression of the frq and wc-1 genes that are critical for maintaining the normal circadian period length in N. crassa.
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Affiliation(s)
- Darshana Baruah
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Christy Noche K Marak
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Avishek Roy
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Dibakar Gohain
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Ajeet Kumar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Pallavi Das
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
| | - Katherine A Borkovich
- Department of Microbiology and Plant Pathology, Institute for Integrative Genome Biology, College of Natural and Agricultural Sciences, University of California Riverside, Riverside 92521, CA, USA
| | - Ranjan Tamuli
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India
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Cavieres-Lepe J, Ewer J. Reciprocal Relationship Between Calcium Signaling and Circadian Clocks: Implications for Calcium Homeostasis, Clock Function, and Therapeutics. Front Mol Neurosci 2021; 14:666673. [PMID: 34045944 PMCID: PMC8144308 DOI: 10.3389/fnmol.2021.666673] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 04/09/2021] [Indexed: 12/03/2022] Open
Abstract
In animals, circadian clocks impose a daily rhythmicity to many behaviors and physiological processes. At the molecular level, circadian rhythms are driven by intracellular transcriptional/translational feedback loops (TTFL). Interestingly, emerging evidence indicates that they can also be modulated by multiple signaling pathways. Among these, Ca2+ signaling plays a key role in regulating the molecular rhythms of clock genes and of the resulting circadian behavior. In addition, the application of in vivo imaging approaches has revealed that Ca2+ is fundamental to the synchronization of the neuronal networks that make up circadian pacemakers. Conversely, the activity of circadian clocks may influence Ca2+ signaling. For instance, several genes that encode Ca2+ channels and Ca2+-binding proteins display a rhythmic expression, and a disruption of this cycling affects circadian function, underscoring their reciprocal relationship. Here, we review recent advances in our understanding of how Ca2+ signaling both modulates and is modulated by circadian clocks, focusing on the regulatory mechanisms described in Drosophila and mice. In particular, we examine findings related to the oscillations in intracellular Ca2+ levels in circadian pacemakers and how they are regulated by canonical clock genes, neuropeptides, and light stimuli. In addition, we discuss how Ca2+ rhythms and their associated signaling pathways modulate clock gene expression at the transcriptional and post-translational levels. We also review evidence based on transcriptomic analyzes that suggests that mammalian Ca2+ channels and transporters (e.g., ryanodine receptor, ip3r, serca, L- and T-type Ca2+ channels) as well as Ca2+-binding proteins (e.g., camk, cask, and calcineurin) show rhythmic expression in the central brain clock and in peripheral tissues such as the heart and skeletal muscles. Finally, we discuss how the discovery that Ca2+ signaling is regulated by the circadian clock could influence the efficacy of pharmacotherapy and the outcomes of clinical interventions.
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Affiliation(s)
- Javier Cavieres-Lepe
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile.,Programa de Doctorado en Ciencias, Mención Neurociencia, Universidad de Valparaíso, Valparaíso, Chile
| | - John Ewer
- Centro Interdisciplinario de Neurociencia de Valparaíso, Instituto de Neurociencias, Universidad de Valparaíso, Valparaíso, Chile
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Aguilar-Roblero R, Quinto D, Báez-Ruíz A, Chávez JL, Belin AC, Díaz-Muñoz M, Michel S, Lundkvist G. Ryanodine-sensitive intracellular Ca 2+ channels are involved in the output from the SCN circadian clock. Eur J Neurosci 2016; 44:2504-2514. [PMID: 27529310 PMCID: PMC5053303 DOI: 10.1111/ejn.13368] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 08/03/2016] [Accepted: 08/09/2016] [Indexed: 01/07/2023]
Abstract
The suprachiasmatic nuclei (SCN) contain the major circadian clock responsible for generation of circadian rhythms in mammals. The time measured by the molecular circadian clock must eventually be translated into a neuronal firing rate pattern to transmit a meaningful signal to other tissues and organs in the animal. Previous observations suggest that circadian modulation of ryanodine receptors (RyR) is a key element of the output pathway from the molecular circadian clock. To directly test this hypothesis, we studied the effects of RyR activation and inhibition on real time expression of PERIOD2::LUCIFERASE, intracellular calcium levels and spontaneous firing frequency in mouse SCN neurons. Furthermore, we determined whether the RyR-2 mRNA is expressed with a daily variation in SCN neurons. We provide evidence that pharmacological manipulation of RyR in mice SCN neurons alters the free [Ca2+ ]i in the cytoplasm and the spontaneous firing without affecting the molecular clock mechanism. Our data also show a daily variation in RyR-2 mRNA from single mouse SCN neurons with highest levels during the day. Together, these results confirm the hypothesis that RyR-2 is a key element of the circadian clock output from SCN neurons.
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Affiliation(s)
- Raúl Aguilar-Roblero
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacan, Mexico City D.F, 04510, México.
| | - Daniel Quinto
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacan, Mexico City D.F, 04510, México
| | - Adrian Báez-Ruíz
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla Querétaro, México
| | - José Luis Chávez
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, Coyoacan, Mexico City D.F, 04510, México
| | | | - Mauricio Díaz-Muñoz
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, Juriquilla Querétaro, México
| | - Stephan Michel
- Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands
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Vanderlinden LA, Saba LM, Bennett B, Hoffman PL, Tabakoff B. Influence of sex on genetic regulation of "drinking in the dark" alcohol consumption. Mamm Genome 2015; 26:43-56. [PMID: 25559016 DOI: 10.1007/s00335-014-9553-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 12/17/2014] [Indexed: 10/24/2022]
Abstract
The ILSXISS (LXS) recombinant inbred (RI) panel of mice is a valuable resource for genetic mapping studies of complex traits, due to its genetic diversity and large number of strains. Male and female mice from this panel were used to investigate genetic influences on alcohol consumption in the "drinking in the dark" (DID) model. Male mice (38 strains) and female mice (36 strains) were given access to 20% ethanol during the early phase of their circadian dark cycle for four consecutive days. The first principal component of alcohol consumption measures on days 2, 3, and 4 was used as a phenotype (DID phenotype) to calculate QTLs, using a SNP marker set for the LXS RI panel. Five QTLs were identified, three of which included a significant genotype by sex interaction, i.e., a significant genotype effect in males and not females. To investigate candidate genes associated with the DID phenotype, data from brain microarray analysis (Affymetrix Mouse Exon 1.0 ST Arrays) of male LXS RI strains were combined with RNA-Seq data (mouse brain transcriptome reconstruction) from the parental ILS and ISS strains in order to identify expressed mouse brain transcripts. Candidate genes were determined based on common eQTL and DID phenotype QTL regions and correlation of transcript expression levels with the DID phenotype. The resulting candidate genes (in particular, Arntl/Bmal1) focused attention on the influence of circadian regulation on the variation in the DID phenotype in this population of mice.
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Affiliation(s)
- Lauren A Vanderlinden
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy & Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, 12850 E. Montview Blvd., Campus Box: C238, Aurora, CO, 80045, USA,
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Narishige S, Kuwahara M, Shinozaki A, Okada S, Ikeda Y, Kamagata M, Tahara Y, Shibata S. Effects of caffeine on circadian phase, amplitude and period evaluated in cells in vitro and peripheral organs in vivo in PER2::LUCIFERASE mice. Br J Pharmacol 2014; 171:5858-69. [PMID: 25160990 DOI: 10.1111/bph.12890] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 06/27/2014] [Accepted: 08/16/2014] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND AND PURPOSE Caffeine is one of the most commonly used psychoactive substances. Circadian rhythms consist of the main suprachiasmatic nucleus (SCN) clocks and peripheral clocks. Although caffeine lengthens circadian rhythms and modifies phase changes in SCN-operated rhythms, the effects on caffeine on the phase, period and amplitude of peripheral organ clocks are not known. In addition, the role of cAMP/Ca(2+) signalling in effects of caffeine on rhythm has not been fully elucidated. EXPERIMENTAL APPROACH We examined whether chronic or transient application of caffeine affects circadian period/amplitude and phase by evaluating bioluminescence rhythm in PER2::LUCIFERASE knock-in mice. Circadian rhythms were monitored in vitro using fibroblasts and ex vivo and in vivo for monitoring of peripheral clocks. KEY RESULTS Chronic application of caffeine (0.1-10 mM) increased period and amplitude in vitro. Transient application of caffeine (10 mM) near the bottom of the decreasing phase of bioluminescence rhythm caused phase advance in vitro. Caffeine (0.1%) intake caused a phase delay under light-dark or constant dark conditions, suggesting a period-lengthening effect in vivo. Caffeine (20 mg·kg(-1) ) at daytime or at late night-time caused phase advance or delay in bioluminescence rhythm in the liver and kidney respectively. The complicated roles of cAMP/Ca(2+) signalling may be involved in the caffeine-induced increase of period and amplitude in vitro. CONCLUSIONS AND IMPLICATIONS Caffeine affects circadian rhythm in mice by lengthening the period and causing a phase shift of peripheral clocks. These results suggest that caffeine intake with food/drink may help with food-induced resetting of peripheral circadian clocks.
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Affiliation(s)
- Seira Narishige
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Shinjuku-ku, Tokyo, Japan
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Pluquet O, Dejeans N, Chevet E. Watching the clock: endoplasmic reticulum-mediated control of circadian rhythms in cancer. Ann Med 2014; 46:233-43. [PMID: 24491143 DOI: 10.3109/07853890.2013.874664] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In the past 20 years both the circadian clock and endoplasmic reticulum (ER) stress signaling have emerged as major players in oncogenesis and cancer development. Although several lines of evidence have established functional links between these two molecular pathways, their interconnection and the subsequent functional implications in cancer development remain to be fully characterized. Herein, we provide an extensive review of the literature depicting the molecular connectivity linking ER stress signaling and the circadian clock and elaborate on the potential use of these functional interactions in cancer therapeutics.
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Affiliation(s)
- Olivier Pluquet
- Institut de Biologie de Lille, CNRS UMR8161/Universités Lille 1 et Lille 2/Institut Pasteur de Lille , 1, rue du Pr. Calmette, BP 447, 59021 Lille , France
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Nagane M, Suge R, Watanabe SI. Psychosomatic disorder may be related to circadian rhythms in physically healthy students. BIOL RHYTHM RES 2013. [DOI: 10.1080/09291016.2013.842380] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Báez-Ruiz A, Cázares-Gómez K, Vázquez-Martínez O, Aguilar-Roblero R, Díaz-Muñoz M. Diurnal and nutritional adjustments of intracellular Ca2+ release channels and Ca2+ ATPases associated with restricted feeding schedules in the rat liver. J Circadian Rhythms 2013; 11:8. [PMID: 23962056 PMCID: PMC3850936 DOI: 10.1186/1740-3391-11-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2013] [Accepted: 08/07/2013] [Indexed: 01/18/2023] Open
Abstract
Background Intracellular calcium is a biochemical messenger that regulates part of the metabolic adaptations in the daily fed-fast cycle. The aim of this study was to characterize the 24-h variations of the liver ryanodine and IP3 receptors (RyR and IP3R) as well as of the endoplasmic-reticulum and plasma-membrane Ca2+-ATPases (SERCA and PMCA) in daytime restricted feeding protocol. Methods A biochemical and immunohistochemical approach was implemented in this study: specific ligand-binding for RyR and IP3R, enzymatic activity (SERCA and PMCA), and protein levels and zonational hepatic-distribution were determined by immunoblot and immunohistochemistry respectively under conditions of fasting, feeding, and temporal food-restriction. Results Binding assays and immunoblots for IP3R1 and 2 showed a peak at the light/dark transition in the ad-libitum (AL) group, whereas in the restricted-feeding (RF) group the peak shifted towards the food-access time. In the case of RyR binding experiments, both AL and RF groups showed a modest elevation during the dark period, with the RF rats exhibiting increased binding in response to feeding. The AL group showed 24-h rhythmicity in SERCA level; in contrast, RF group showed a pronounced amplitude elevation and a peak phase-shift during the light-period in SERCA level and activity. The activity of PMCA was constant along day in both groups; PMCA1 levels showed a 24-h rhythmicity in the RF rats (with a peak in the light period), meanwhile PMCA4 protein levels showed rhythmicity in both groups. The fasted condition promoted an increase in IP3R binding and protein level; re-feeding increased the amount of RyR; neither the activity nor expression of SERCA and PMCA protein was affected by fasting–re-feeding conditions. Histochemical experiments showed that the distribution of the Ca2+-handling proteins, between periportal and pericentral zones of the liver, varied with the time of day and the feeding protocol. Conclusions Our findings show that RF influences mainly the phase and amplitude of hepatic IP3R and SERCA rhythms as well as discrete zonational distribution for RyR, IP3Rs, SERCA, and PMCA within the liver acinus, suggesting that intracellular calcium dynamics could be part of the rheostatic adaptation of the liver due to diurnal meal entrainment/food entrained oscillator expression.
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Affiliation(s)
- Adrián Báez-Ruiz
- Departamento de Neurobiología Molecular y Celular, Instituto de Neurobiología, UNAM-Juriquilla, Boulevard Juriquilla #3001, Apdo, Postal 1-1141, Querétaro, QRO 76230, México.
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Metabolic regulation of circadian clocks. Semin Cell Dev Biol 2013; 24:414-21. [DOI: 10.1016/j.semcdb.2013.03.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Revised: 03/14/2013] [Accepted: 03/19/2013] [Indexed: 01/09/2023]
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O'Neill JS, Maywood ES, Hastings MH. Cellular mechanisms of circadian pacemaking: beyond transcriptional loops. Handb Exp Pharmacol 2013:67-103. [PMID: 23604476 DOI: 10.1007/978-3-642-25950-0_4] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Circadian clocks drive the daily rhythms in our physiology and behaviour that adapt us to the 24-h solar and social worlds. Because they impinge upon every facet of metabolism, their acute or chronic disruption compromises performance (both physical and mental) and systemic health, respectively. Equally, the presence of such rhythms has significant implications for pharmacological dynamics and efficacy, because the fate of a drug and the state of its therapeutic target will vary as a function of time of day. Improved understanding of the cellular and molecular biology of circadian clocks therefore offers novel approaches for therapeutic development, for both clock-related and other conditions. At the cellular level, circadian clocks are pivoted around a transcriptional/post-translational delayed feedback loop (TTFL) in which the activation of Period and Cryptochrome genes is negatively regulated by their cognate protein products. Synchrony between these, literally countless, cellular clocks across the organism is maintained by the principal circadian pacemaker, the suprachiasmatic nucleus (SCN) of the hypothalamus. Notwithstanding the success of the TTFL model, a diverse range of experimental studies has shown that it is insufficient to account for all properties of cellular pacemaking. Most strikingly, circadian cycles of metabolic status can continue in human red blood cells, devoid of nuclei and thus incompetent to sustain a TTFL. Recent interest has therefore focused on the role of oscillatory cytosolic mechanisms as partners to the TTFL. In particular, cAMP- and Ca²⁺-dependent signalling are important components of the clock, whilst timekeeping activity is also sensitive to a series of highly conserved kinases and phosphatases. This has led to the view that the 'proto-clock' may have been a cytosolic, metabolic oscillation onto which evolution has bolted TTFLs to provide robustness and amplify circadian outputs in the form of rhythmic gene expression. This evolutionary ascent of the clock has culminated in the SCN, a true pacemaker to the innumerable clock cells distributed across the body. On the basis of findings from our own and other laboratories, we propose a model of the SCN pacemaker that synthesises the themes of TTFLs, intracellular signalling, metabolic flux and interneuronal coupling that can account for its unique circadian properties and pre-eminence.
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Affiliation(s)
- John S O'Neill
- Department of Clinical Neurosciences, University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Addenbrooke's Hospital, UK.
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Sancho-Martínez SM, Prieto-García L, Prieto M, López-Novoa JM, López-Hernández FJ. Subcellular targets of cisplatin cytotoxicity: An integrated view. Pharmacol Ther 2012; 136:35-55. [DOI: 10.1016/j.pharmthera.2012.07.003] [Citation(s) in RCA: 128] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 06/28/2012] [Indexed: 12/29/2022]
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Daytime restricted feeding modifies 24 h rhythmicity and subcellular distribution of liver glucocorticoid receptor and the urea cycle in rat liver. Br J Nutr 2012; 108:2002-13. [DOI: 10.1017/s0007114512000268] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The timing system in mammals is formed by a set of peripheral biological clocks coordinated by a light-entrainable pacemaker located in the suprachiasmatic nucleus. Daytime restricted feeding (DRF) modifies the circadian control and uncouples the light-dependent physiological rhythmicity, food access becoming the principal external time cue. In these conditions, an alternative biological clock is expressed, the food-entrainable oscillator (FEO). Glucocorticoid hormones are an important part of the humoral mechanisms in the daily synchronisation of the metabolic response of peripheral oscillators by the timing system. A peak of circulating corticosterone has been reported before food access in DRF protocols. In the present study we explored in the liver the 24 h variations of: (1) the subcellular distribution of glucocorticoid receptor (GCR), (2) the activities of the corticosterone-forming and NADPH-generating enzymes (11β-hydroxysteroid dehydrogenase type 1 (11β-HSD-1) and hexose-6-phosphate dehydrogenase (H6PDH)), and, (3) parameters related with the urea cycle (circulating urea and activities of carbamoyl phosphate synthetase and ornithine transcarbamylase) elicited by DRF. The results showed that DRF promoted an increase of more than two times of the hepatic GCR, but exclusively in the cytosolic compartment, since the GCR in the nuclear fraction showed a reduction. No changes were observed in the activities of 11β-HSD-1 and H6PDH, but the rhythmicity of all of the urea cycle-related parameters was modified. It is concluded that liver glucocorticoid signalling and the urea cycle are responsive to feeding-restricted schedules and could be part of the FEO.
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O'Neill JS, Reddy AB. The essential role of cAMP/Ca2+ signalling in mammalian circadian timekeeping. Biochem Soc Trans 2012; 40:44-50. [PMID: 22260664 PMCID: PMC3399769 DOI: 10.1042/bst20110691] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Approximately daily, or circadian, rhythms are ubiquitous across eukaryotes. They are manifest in the temporal co-ordination of metabolism, physiology and behaviour, thereby allowing organisms to anticipate and synchronize with daily environmental cycles. Although cellular rhythms are self-sustained and cell-intrinsic, in mammals, the master regulator of timekeeping is localized within the hypothalamic SCN (suprachiasmatic nucleus). Molecular models for mammalian circadian rhythms have focused largely on transcriptional-translational feedback loops, but recent data have revealed essential contributions by intracellular signalling mechanisms. cAMP and Ca2+ signalling are not only regulated by the cellular clock, but also contribute directly to the timekeeping mechanism, in that appropriate manipulations determine the canonical pacemaker properties of amplitude, phase and period. It is proposed that daily auto-amplification of second messenger activity, through paracrine neuropeptidergic coupling, is necessary and sufficient to account for the increased amplitude, accuracy and robustness of SCN timekeeping.
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Affiliation(s)
- John S O'Neill
- Department of Clinical Neurosciences, University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 0QQ, UK.
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