scholarly journals Phosphorylation and Circadian Molecular Timing

2020 ◽  
Vol 11 ◽  
Author(s):  
Andrea Brenna ◽  
Urs Albrecht
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Environmental Changes ◽  
Circadian System ◽  
Post Translational Modifications ◽  
Physiological Processes ◽  
Clock Proteins ◽  
Protein Components ◽  
Response To Environmental Change ◽  
External Stimuli

Endogenous circadian rhythms are biological processes generated by an internal body clock. They are self-sustaining, and they govern biochemical and physiological processes. However, circadian rhythms are influenced by many external stimuli to reprogram the phase in response to environmental change. Through their adaptability to environmental changes, they synchronize physiological responses to environmental challenges that occur within a sidereal day. The precision of this circadian system is assured by many post-translational modifications (PTMs) that occur on the protein components of the circadian clock mechanism. The most ancient example of circadian rhythmicity driven by phosphorylation of clock proteins was observed in cyanobacteria. The influence of phosphorylation on the circadian system is observed through different kingdoms, from plants to humans. Here, we discuss how phosphorylation modulates the mammalian circadian clock, and we give a detailed overview of the most critical discoveries in the field.

Abstract P199: Circadian Contributions To Blood Pressure Variation Under Constant Conditions

Hypertension ◽  
2021 ◽  
Vol 78 (Suppl_1) ◽  
Author(s):  
Gabrielle F Gloston ◽  
Annie E Ensor ◽  
Samarth Patel ◽  
Rebecca Williams ◽  
Courtney M Peterson ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Body Temperature ◽  
Circadian Clock ◽  
Environmental Changes ◽  
Core Body Temperature ◽  
Circadian System ◽  
External Factors ◽  
Future Research ◽  
Physiological Processes ◽  
Core Body

The circadian clock is an endogenous biological timekeeper that responds to environmental changes and governs various physiological processes over a 24-hour cycle. Blood pressure (BP) variation is thought to be controlled by the circadian clock, but few studies have examined circadian control of BP in humans. Moreover, it is unknown whether nighttime BP dipping is driven by the circadian system or by external factors. We investigated whether the circadian system drives 24-hour rhythms in BP, including nighttime BP dipping, using a 30-hour constant routine (CR) protocol. The CR protocol controls for external factors, allowing circadian rhythms to be isolated and measured, by having participants lie in a semi-recumbent posture in dim light (<10 lux) at a constant temperature, consume isocaloric snacks every 2 hours, and maintain wakefulness. To measure the BP rhythm, ambulatory BP was measured every 30 minutes (SpaceLabs 90227), and to measure the central circadian rhythm, core body temperature was measured every 10 seconds using an ingestible, wireless sensor (HQInc Core Body Temperature Wireless Data Record and Sensor). To date, 17 normotensive African American participants (13 females and 4 males), with a mean age of 37 (± 11.3) years and body mass index (BMI) of 32.5 kg/m 2 , have completed the study. Approximately 59% of participants (10 of 17) had non-dipping systolic BP at screening, defined as a <10% decrease in mean systolic BP from daytime to nighttime. Under constant conditions, 94% of participants (16 of 17) had a non-dipping BP phenotype. Median systolic BP dipping was 0.8% for females and 2.2% for males. There was a robust rhythm in participants’ core body temperature but not BP, suggesting that the circadian clock may not contribute substantially to a nighttime decrease in BP in normotensive African Americans. Instead, the non-dipping BP phenotype is likely more so a result of behavioral and/or physiological sleep-related processes. Future research and interventions for non-dipping BP may need to target these underlying behavioral and physiological processes.

scholarly journals Circadian Rhythm: Potential Therapeutic Target for Atherosclerosis and Thrombosis

2021 ◽  
Vol 22 (2) ◽  
pp. 676
Author(s):  
Andy W. C. Man ◽  
Huige Li ◽  
Ning Xia
Keyword(s):  
Circadian Rhythm ◽  
Cardiovascular Diseases ◽  
Circadian Rhythms ◽  
Circadian Clock ◽  
Therapeutic Target ◽  
Environmental Changes ◽  
Clock Genes ◽  
Vascular System ◽  
Peripheral Tissues ◽  
Inflammatory Processes

Every organism has an intrinsic biological rhythm that orchestrates biological processes in adjusting to daily environmental changes. Circadian rhythms are maintained by networks of molecular clocks throughout the core and peripheral tissues, including immune cells, blood vessels, and perivascular adipose tissues. Recent findings have suggested strong correlations between the circadian clock and cardiovascular diseases. Desynchronization between the circadian rhythm and body metabolism contributes to the development of cardiovascular diseases including arteriosclerosis and thrombosis. Circadian rhythms are involved in controlling inflammatory processes and metabolisms, which can influence the pathology of arteriosclerosis and thrombosis. Circadian clock genes are critical in maintaining the robust relationship between diurnal variation and the cardiovascular system. The circadian machinery in the vascular system may be a novel therapeutic target for the prevention and treatment of cardiovascular diseases. The research on circadian rhythms in cardiovascular diseases is still progressing. In this review, we briefly summarize recent studies on circadian rhythms and cardiovascular homeostasis, focusing on the circadian control of inflammatory processes and metabolisms. Based on the recent findings, we discuss the potential target molecules for future therapeutic strategies against cardiovascular diseases by targeting the circadian clock.

scholarly journals Interaction between photoperiod and variation in circadian rhythms in tomato

2022 ◽  
Author(s):  
Yanli Xiang ◽  
Thomas Sapir ◽  
Pauline Rouillard ◽  
Marina Ferrand ◽  
Jose M Jimenez-Gomez
Keyword(s):  
Seasonal Variation ◽  
Circadian Rhythms ◽  
Phase Shift ◽  
Circadian Clock ◽  
Environmental Changes ◽  
Circadian Clocks ◽  
Biological Processes ◽  
Near Isogenic Lines ◽  
Transcriptomic Profiling ◽  
Isogenic Lines

Many biological processes follow circadian rhythmicity and are controlled by the circadian clock. Predictable environmental changes such as seasonal variation in photoperiod can modulate circadian rhythms, allowing organisms to adjust to the time of the year. Modification of circadian clocks is especially relevant in crops to enhance their cultivability in specific regions by changing their sensibility to photoperiod. In tomato, the appearance of mutations in EMPFINDLICHER IM DUNKELROTEN LICHT 1 (EID1, Solyc09g075080) and NIGHT LIGHT-INDUCIBLE AND CLOCK-REGULATED GENE 2 (LNK2, Solyc01g068560) during domestication delayed its circadian rhythms, and allowed its expansion outside its equatorial origin. Here we study how variation in circadian rhythms in tomato affects its perception of photoperiod. To do this, we create near isogenic lines carrying combinations of wild alleles of EID1 and LNK2 and perform transcriptomic profiling under two different photoperiods. We observe that EID1, but not LNK2, has a large effect on the tomato transcriptome and its response to photoperiod. This large effect of EID1 is likely a consequence of the global phase shift elicited by this gene in tomato's circadian rhythms.

Evolution Analysis of the Circadian Clock Protein KaiB

2013 ◽  
Vol 647 ◽  
pp. 391-395
Author(s):  
Liu Sen ◽  
Song Liu
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Feedback Loop ◽  
Circadian System ◽  
Circadian Rhythmicity ◽  
Physiological Functions ◽  
Clock System ◽  
Evolution Analysis ◽  
Clock Protein

Regulation of daily physiological functions with approximate a 24-hour periodicity, or circadian rhythms, is a characteristic of eukaryotes. So far, cyanobacteria are only known prokaryotes reported to possess circadian rhythmicity. The circadian system in cyanobacteria comprises both a post-translational oscillator (PTO) and a transcriptional/translational feedback loop (TTFL). The PTO can be reconstituted in vitro with three purified proteins (KaiA, KaiB, and KaiC) with the existence of ATP. Phase of the nanoclockwork has been associated with the phosphorylation states of KaiC, with KaiA promoting the phosphorylation of KaiC, and KaiB de-phosphorylating KaiC. Here we studied the evolution of the KaiB protein. The result will be helpful in understanding the evolution of the circadian clock system.

scholarly journals Roles of Neuropeptides, VIP and AVP, in the Mammalian Central Circadian Clock

2021 ◽  
Vol 15 ◽  
Author(s):  
Daisuke Ono ◽  
Ken-ichi Honma ◽  
Sato Honma
Keyword(s):  
Transcription Factors ◽  
Circadian Rhythms ◽  
Circadian Clock ◽  
Cellular Networks ◽  
Clock Genes ◽  
Circadian System ◽  
Developmental Changes ◽  
Circadian Period ◽  
Functional Roles ◽  
Environmental Light

In mammals, the central circadian clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Individual SCN cells exhibit intrinsic oscillations, and their circadian period and robustness are different cell by cell in the absence of cellular coupling, indicating that cellular coupling is important for coherent circadian rhythms in the SCN. Several neuropeptides such as arginine vasopressin (AVP) and vasoactive intestinal polypeptide (VIP) are expressed in the SCN, where these neuropeptides function as synchronizers and are important for entrainment to environmental light and for determining the circadian period. These neuropeptides are also related to developmental changes of the circadian system of the SCN. Transcription factors are required for the formation of neuropeptide-related neuronal networks. Although VIP is critical for synchrony of circadian rhythms in the neonatal SCN, it is not required for synchrony in the embryonic SCN. During postnatal development, the clock genes cryptochrome (Cry)1 and Cry2 are involved in the maturation of cellular networks, and AVP is involved in SCN networks. This mini-review focuses on the functional roles of neuropeptides in the SCN based on recent findings in the literature.

scholarly journals Clock proteins regulate spatiotemporal organization of clock genes to control circadian rhythms

2020 ◽  
Author(s):  
Yangbo Xiao ◽  
Ye Yuan ◽  
Mariana Jimenez ◽  
Neeraj Soni ◽  
Swathi Yadlapalli
Keyword(s):  
Gene Expression ◽  
Circadian Rhythms ◽  
Nuclear Envelope ◽  
Circadian Clock ◽  
Clock Genes ◽  
Circadian Clocks ◽  
Spatiotemporal Organization ◽  
Clock Proteins ◽  
Expression Behavior ◽  
Clock Protein

ABSTRACTCircadian clocks regulate ∼24 hour oscillations in gene expression, behavior, and physiology. While the molecular and neural mechanisms of circadian rhythms are well characterized, how cellular organization of clock components controls circadian clock regulation remains poorly understood. Here, we elucidate how clock proteins regulate circadian rhythms by controlling the spatiotemporal organization of clock genes. Using high-resolution live imaging techniques we demonstrate that Drosophila clock proteins are concentrated in a few discrete foci and are organized at the nuclear envelope; these results are in contrast to longstanding expectations that clock proteins are diffusely distributed in the nucleus. We also show that clock protein foci are highly dynamic and change in number, size, and localization over the circadian cycle. Further, we demonstrate that clock genes are positioned at the nuclear periphery by the clock proteins precisely during the circadian repression phase, suggesting that subnuclear localization of clock genes plays an important role in the control of rhythmic gene expression. Finally, we show that Lamin B receptor, a nuclear envelope protein, is required for peripheral localization of clock protein foci and clock genes and for normal circadian rhythms. These results reveal that clock proteins form dynamic nuclear foci and play a hitherto unexpected role in the subnuclear reorganization of clock genes to control circadian rhythms, identifying a novel mechanism of circadian regulation. Our results further suggest a new role for clock protein foci in the clustering of clock-regulated genes during the repression phase to control gene co-regulation and circadian rhythms.SIGNIFICANCEAlmost all living organisms have evolved circadian clocks to tell time. Circadian clocks regulate ∼24-hour oscillations in gene expression, behavior and physiology. Here, we reveal the surprisingly sophisticated spatiotemporal organization of clock proteins and clock genes and its critical role in circadian clock function. We show, in contrast to current expectations, that clock proteins are concentrated in a few discrete, dynamic nuclear foci at the nuclear envelope during the repression phase. Further, we uncovered several unexpected features of clock protein foci, including their role in positioning the clock genes at the nuclear envelope precisely during the repression phase to enable circadian rhythms. These studies provide fundamental new insights into the cellular mechanisms of circadian rhythms and establish direct links between nuclear organization and circadian clocks.

Analysis of the Sequence Conservation of the Circadian Clock Protein KaiC

2013 ◽  
Vol 699 ◽  
pp. 184-188
Author(s):  
Liu Sen ◽  
Song Liu ◽  
Fei Yun Chen
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Feedback Loop ◽  
Sequence Variation ◽  
Protein Sequences ◽  
Circadian System ◽  
Site Variation ◽  
Key Residues ◽  
Clock Protein

Regulation of daily physiological functions with approximate a 24-hour periodicity, or circadian rhythms, is a characteristic of eukaryotes. So far, cyanobacteria are only known prokaryotes reported to possess circadian rhythmicity. The circadian system in cyanobacteria comprises both a post-translational oscillator (PTO) and a transcriptional/translational feedback loop (TTFL). The PTO can be reconstituted in vitro with three purified proteins (KaiA, KaiB, and KaiC) with the existence of ATP. Phase of the nanoclockwork has been associated with the phosphorylation states of KaiC, with KaiA promoting the phosphorylation of KaiC, and KaiB de-phosphorylating KaiC. Here we studied the sequence variation of 65 KaiC proteins in evolution, and determined some key residues in KaiC by analyzing the site variation rates of the protein sequences. These key residues could be used to study the key interactions of KaiC with KaiA and KaiB.

scholarly journals Nutrition and the circadian system

2016 ◽  
Vol 116 (3) ◽  
pp. 434-442 ◽  
Author(s):  
Gregory D. M. Potter ◽  
Janet E. Cade ◽  
Peter J. Grant ◽  
Laura J. Hardie
Keyword(s):  
Environmental Changes ◽  
Time Of Day ◽  
Circadian System ◽  
Suprachiasmatic Nuclei ◽  
Peripheral Tissues ◽  
Physiological Processes ◽  
Nutritional Science ◽  
High Fat Diets ◽  
Nutritional Compounds ◽  
Fat Diets

AbstractThe human circadian system anticipates and adapts to daily environmental changes to optimise behaviour according to time of day and temporally partitions incompatible physiological processes. At the helm of this system is a master clock in the suprachiasmatic nuclei (SCN) of the anterior hypothalamus. The SCN are primarily synchronised to the 24-h day by the light/dark cycle; however, feeding/fasting cycles are the primary time cues for clocks in peripheral tissues. Aligning feeding/fasting cycles with clock-regulated metabolic changes optimises metabolism, and studies of other animals suggest that feeding at inappropriate times disrupts circadian system organisation, and thereby contributes to adverse metabolic consequences and chronic disease development. ‘High-fat diets’ (HFD) produce particularly deleterious effects on circadian system organisation in rodents by blunting feeding/fasting cycles. Time-of-day-restricted feeding, where food availability is restricted to a period of several hours, offsets many adverse consequences of HFD in these animals; however, further evidence is required to assess whether the same is true in humans. Several nutritional compounds have robust effects on the circadian system. Caffeine, for example, can speed synchronisation to new time zones after jetlag. An appreciation of the circadian system has many implications for nutritional science and may ultimately help reduce the burden of chronic diseases.

Plant circadian networks and responses to the environment

2018 ◽  
Vol 45 (4) ◽  
pp. 393 ◽  
Author(s):  
Chenjerai I. Muchapirei ◽  
Shannon-Leigh Valentine ◽  
Laura C. Roden
Keyword(s):  
Stress Response ◽  
Circadian Clock ◽  
Environmental Changes ◽  
Hierarchical Control ◽  
Metabolic Efficiency ◽  
The Sun ◽  
Biological Processes ◽  
Post Translational Modifications ◽  
Biological Time ◽  
Reciprocal Interactions

There are regular, and therefore predictable, environmental changes on Earth due to the rotation of the planet on its axis and its orbit around the sun. Thus organisms have adapted their metabolism, physiology and behaviour to minimise stresses caused by unfavourable conditions and maximise efficiency of growth. Additionally, most organisms are able to anticipate these changes and accordingly maximise metabolic efficiency and growth, because they have a complex biological time-keeping system commonly referred to as the circadian clock. Multiple pathways in plants are organised in a temporal manner through circadian clock-regulation of gene transcription and post-translational modifications. What is becoming more apparent is the bidirectional nature of interactions between the clock and stress response pathways. Until recently, the focus of many studies had been on the unidirectional, hierarchical control of biological processes by the circadian clock, and impacts on the clock in response to environmental stress had been largely ignored. Studies of interactions of the circadian clock with the environment have primarily been to understand mechanisms of entrainment. We review the evidence and implications of the reciprocal interactions between the clock and the environment.

scholarly journals Circadian rhythms in mitochondrial respiration

2018 ◽  
Vol 60 (3) ◽  
pp. R115-R130 ◽  
Author(s):  
Paul de Goede ◽  
Jakob Wefers ◽  
Eline Constance Brombacher ◽  
Patrick Schrauwen ◽  
Andries Kalsbeek
Keyword(s):  
Circadian Rhythms ◽  
Circadian Clock ◽  
Mitochondrial Respiration ◽  
Metabolic Diseases ◽  
Environmental Changes ◽  
Morphological Changes ◽  
Active Phase ◽  
Whole Body ◽  
Mitochondrial Morphology ◽  
Diurnal Changes

Many physiological processes are regulated with a 24-h periodicity to anticipate the environmental changes of daytime to nighttime and vice versa. These 24-h regulations, commonly termed circadian rhythms, among others control the sleep–wake cycle, locomotor activity and preparation for food availability during the active phase (daytime for humans and nighttime for nocturnal animals). Disturbing circadian rhythms at the organ or whole-body level by social jetlag or shift work, increases the risk to develop chronic metabolic diseases such as type 2 diabetes mellitus. The molecular basis of this risk is a topic of increasing interest. Mitochondria are essential organelles that produce the majority of energy in eukaryotes by converting lipids and carbohydrates into ATP through oxidative phosphorylation. To adapt to the ever-changing environment, mitochondria are highly dynamic in form and function and a loss of this flexibility is linked to metabolic diseases. Interestingly, recent studies have indicated that changes in mitochondrial morphology (i.e., fusion and fission) as well as generation of new mitochondria are dependent on a viable circadian clock. In addition, fission and fusion processes display diurnal changes that are aligned to the light/darkness cycle. Besides morphological changes, mitochondrial respiration also displays diurnal changes. Disturbing the molecular clock in animal models leads to abrogated mitochondrial rhythmicity and altered respiration. Moreover, mitochondrial-dependent production of reactive oxygen species, which plays a role in cellular signaling, has also been linked to the circadian clock. In this review, we will summarize recent advances in the study of circadian rhythms of mitochondria and how this is linked to the molecular circadian clock.

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