综述: 植物蛋白O-GlcNAc糖基化及生物学功能

蛋白质的O-GlcNAc糖基化现象发现迄今已有30多年历史．动物中,O-GlcNAc糖基化在调控细胞信号转导、基因转录、表观遗传和新陈代谢等方面发挥重要作用．而植物中,O-GlcNAc糖基化在近几年才得到关注并进行初步研究．本文对植物中O-GlcNAc修饰的糖供体合成途径、O-GlcNAc修饰关键酶、O-GlcNAc修饰蛋白的检测及功能等方面的研究工作进行归纳总结,发现O-GlcNAc糖基化在植物的生长发育、激素网络调控、信号转导、植物病毒侵染等过程均发挥重要作用,为进一步研究植物中O-GlcNAc糖基化的生物学功能提供参考．     

O-乙酰氨基葡萄糖(O-GlcNAc)修饰及其生物学功能研究进展

O-GlcNAc修饰系发生在蛋白质丝氨酸、苏氨酸羟基末端连接的乙酰氨基葡萄糖上的单糖基修饰。自1984年以来,针对O-GlcNAc糖基化修饰的研究日益升温。O-GlcNAc修饰是动态变化、可调控的,满足蛋白质翻译后修饰参与信号通路的必要条件。在多数情况下,O-GlcNAc修饰与磷酸化修饰发生在蛋白质的相同氨基酸残基上,故两种修饰之间常存在竞争性抑制,亦被称之为"阴阳"制衡。O-GlcNAc修饰参与细胞内多种信号通路的调控,调节着生长、增殖、激素响应等过程,在糖尿病、神经退行性疾病和肿瘤等代谢性疾病中扮演重要角色。探究O-GlcNAc修饰及其在生理、病理状态中的作用具有极为重要的意义。     

昼夜节律与能量代谢

地球上大多数生物存在内源性的昼夜节律生物钟,它使得生物个体能够预知环境中由于地球自转产生的周期性昼夜变化。这种预知性使得生物个体的内在生理节律与周围环境的变化周期保持一致,从而能够更有效地从周围环境中摄取能量,在体内更高效地利用能量,亦即更好的适应环境以获得进化上的优势。生物钟能够广泛调控哺乳动物的睡眠、进食和代谢等多个方面的行为和生理功能,生物钟的破坏与多种代谢疾病相关;同时代谢过程和进食行为也能反过来调控生物钟。近年来对生物钟的不断研究加深了人们对肥胖和糖尿病等代谢疾病的理解,为这些疾病的治疗提供了新的思路和方法。本文主要综述哺乳动物生物钟与能量代谢之间的关系及研究进展。     

Diurnal variation of physiological rhythms in a patient with sleepwalking

The association between sleepwalking, a non-rapid-eye-movement parasomnia, and biological rhythms has not been subject of research in the past, although shift work is a known risk factor of the disorder. We present the case of a 36-year-old policeman who suffered for years from sleepwalking and was referred to the hospital for polysomnography. All standard investigations including multiple sleep latency or maintenance wakeful test were normal. On the contrary, chronobiological assessment revealed phase delay of vital functions and body temperature, whereas acrophases of melatonin and cortisol remained stable. We postulate an increase in sleep fragmentation due to shift work, but further research is needed to substantiate the hypothesis.     

Circadian rhythms of indoleamines and serotonin N-acetyltransferase activity in the pineal gland

Conclusion The circadian rhythm of melatonin synthesis in the pineal glands of various species has been summarized. The night-time elevation of melatonin content is in most if not all cases regulated by the change of N-acetyltransferase activity. In mammals, the N-acetyltransferase rhythm is controlled by the central nervous system, presumably by suprachiasmatic nuclei in hypothalamus through the superior cervical ganglion. In birds, the circadian oscillator that regulates the N-acetyltransferase rhythm is located in the pineal glands. The avian pineal gland may play a biological clock function to control the circadian rhythms in physiological, endocrinological and biochemical processes via pineal hormone melatonin.     

The daily rhythms of mitochondrial gene expression and oxidative stress regulation are altered by aging in the mouse liver

The circadian clock regulates many cellular processes, notably including the cell cycle, metabolism and aging. Mitochondria play essential roles in metabolism and are the major sites of reactive oxygen species (ROS) production in the cell. The clock regulates mitochondrial functions by driving daily changes in NAD⁺ levels and Sirt3 activity. In addition to this central route, in the present study, we find that the expression of some mitochondrial genes is also rhythmic in the liver, and that there rhythms are disrupted by the Clock^Δ19 mutation in young mice, suggesting that they are regulated by the core circadian oscillator. Related to this observation, we also find that the regulation of oxidative stress is rhythmic in the liver. Since mitochondria and ROS play important roles in aging, and mitochondrial functions are also disturbed by aging, these related observations prompt the compelling hypothesis that circadian oscillators influence aging by regulating ROS in mitochondria. During aging, the expression rhythms of some mitochondrial genes were altered in the liver and the temporal regulation over the dynamics of mitochondrial oxidative stress was disrupted. However, the expression of clock genes was not affected. Our results suggested that mitochondrial functions are combinatorially regulated by the clock and other age-dependent mechanism(s), and that aging disrupts mitochondrial rhythms through mechanisms downstream of the clock.     

Temperature-induced phase shifting of circadian rhythms in cotton seedlings as related to variations in chilling resistance

The relationship between the degree of chilling resistance and phase shifting caused by low-temperature pulses was examined in two circadian rhythms in cotton (Gossypium hirsutum L. cv. Deltapine 50) seedlings grown under light-dark cycles of 1212 h at 33° C. The seedlings showed a circadian rhythm of chilling resistance and of cotyledon movement. A pulse of 19° C for 12 h during the chilling-sensitive phase (light period) caused a phase delay of 6 h, while a similar temperature pulse during the chilling-resistant phase (dark period) did not cause any phase shift. Exposure to 19° C, 85% RH (relative humidity) for 12 h during the dark period induced chilling resistance in the following otherwise chilling-sensitive light period. In this light period a 12-h 19° C pulse did not cause a phase shift of chilling resistance. Pulses of low temperatures (5–19° C) were more effective in causing phase delays in the rhythm of cotyledon movement when given during the chilling-sensitive phase than when given during the chilling-resistant phase. A 12-h pulse of 5° C, 100% RH during the light period caused a phase delay of cotyledon movement of 12 h. However, when that pulse had been preceded by a chill-acclimating exposure to 19° C, 85% RH for 12 h during the dark period the phase delay was shortened to 6 h. The correlation between higher degree of chilling resistance and the prevention or shortening of the phase delay caused by low temperatures indicates that the mechanism that increases chilling resistance directly or indirectly confers greater ability for prevention of phase shifting by low temperatures in circadian rhythms.Abbreviations CT circadian time - LDC light-dark cycle of 24 h - RH relative humidity     

Sleep,daily activity rhythms and postpartum mood: A longitudinal study across the perinatal period

Women with a diagnosis of bipolar and major depressive disorders are at higher risk to develop postpartum depression. The primary objective of this longitudinal study was to determine whether daily activity rhythms and sleep parameters differ between women with and without a history of a mood disorder across the perinatal period. A secondary objective was to determine whether changes in these parameters were associated with postpartum mood. In total, 33 women were included in this study, 15 of which had a history of a mood disorder (high-risk group) and 18 who did not (low-risk group). Sleep and daily rhythms were assessed subjectively and objectively during the third trimester (≥26 weeks gestation) and again at 6–12 weeks postpartum. Mood was also assessed at both time points. Women in the high-risk group showed greater subjective daily rhythms and sleep disturbances across the perinatal period. Objective sleep efficiency was worse in the high-risk group in the postpartum period. Changes in both subjective daily rhythms and objective sleep efficiency were predictive of changes in depressive symptoms across the perinatal period. These findings encourage the development of preventative therapeutics to ensure circadian rhythm and sleep stability throughout the perinatal period.     

Effect of different lighting conditions on circadian developmental rhythms and behaviour in Ephestia kuehniella Zell

Abstract

A study was made on the developmental rhythms of Ephestia kuehniella during different photoperiods: constant lighting (L/L), under conditions of 12 hours light per day (L/D) and in constant darkness (D/D). Observations were made every 2 hrs, for 3 successive 24‐hr periods, of the number of wandering larvae emerging from food, the number of pupations and of imaginai moults. Emergence of wandering larvae is rhythmic only under L/D conditions, and in addition this is also affected by the density of the larvae. Rhythm is least apparent with greatest density of the larvae. Pupation in E. kuehniella is a non‐rhythmic process with each of the photoperiods examined, whereas the imaginai moult is characterized by an endogenous (existing under D/D conditions) rhythm. Emergence of imagines is non‐rhythmic under L/L, and also when pupae under L/D fail to receive the final period of darkness. The rhythm of the imaginai moult is possibly controlled by the biological clock, which stops under conditions of constant light.     

Daily rhythms of locomotor and demand-feeding activities in Schizothorax pelzami (Kessler, 1870)

A study was carried out to investigate the daily rhythms of locomotor and feeding activity of Khajoo, Schizothorax pelzami, a candidate species for freshwater aquaculture. Using self-feeder juvenile Khajoo were exposed to a 12/12 LD cycle to determine the rhythms of locomotor and feeding activity. The effects of feeding on locomotor and feeding activity of fish were also examined. Finally, the endogenous rhythmicity under different lighting condition tested. Fish displayed a strictly diurnal feeding and locomotor activities with 98% and 84% of the total activity occurred in the photophase, respectively. In scheduled feeding, both the L-group (fed in light) and the D-group (fed in the dark) showed a diurnal locomotor activity pattern. However, the L-group had a peak of locomotor activity near the feeding time, but the D-group had a scarce locomotor activity in the scatophase with no significant change at the mealtime. Most of the individuals display free-running rhythms when exposed to different lighting condition including, constant darkness, ultradian 45:45 min LD cycle and reversed DL photo cycle. Taken together the results of this study showed that both locomotor and feeding activity have diurnal rhythms in Khajoo S. pelzami, even fish feeding had taken place at night. Additionally, the free-running locomotor activity of the fish in the absence of external light stimuli, suggests the existence of an endogenous timing mechanism in this fish species.     

类胡萝卜素的生物合成途径及生物学功能研究进展

类胡萝卜素具有重要的生物学功能,一直是研究的热点。综述近十年来对植物类胡萝卜素的生物合成途径,并对其生物学功能参与光系统的组装、非光化学猝灭、基因表达、抗氧化性和维持膜的稳定性等五个方面的研究进展作一介绍。     

Activity patterns of rodents: the physiological ecology of biological rhythms

To date, most research in the field of biological rhythms has been performed on nocturnal rodents under laboratory conditions. This research has made much progress in recent years. It is now time to investigate the adaptive value of the studied molecular mechanisms under natural conditions. Here we review relevant studies of rodent activity patterns. We also review a case study of temporal partitioning between spiny mice. We conclude that the response to environmental stimuli, using a system composed of a rigid master circadian oscillator and more flexible mechanisms such as peripheral oscillators with weak coupling, masking responses, and downstream switching mechanisms, is adaptive since it enables an animal to reset its activity phase without the cost of shifting the phase of the entire circadian system. We suggest that these mechanisms play a significant role in determining activity patterns under natural conditions, and are important for understanding the ecology and evolution of activity rhythms.     

Emergence rhythms and protandry in relation to daily patterns of locomotor activity inTrichogramma species

Summary In insect parasitoids, the mating structure of the population depends on the emergence pattern of adults and on their behaviour after emergence. In order to study some aspects of these characteristics in four species of egg parasitoid of the genusTrichogramma, laboratory experiments using automatic video analysis are performed. Adult emergence is concentrated in the morning, with an earlier time for males. The variability of the time of emergence is under genetic control. The relationships between the emergence pattern and the locomotor activity are considered by measuring individually: first, the delay between the emergence and the first locomotion which is significantly greater in females than in males and, second, the activity of newly emerged males, which is maximum at the time of the emergence of females. The locomotor activity is influenced by mating; mated females are much more active than virgin ones, mated males are less active than virgin ones. The adaptive values of the rhythmicity of emergence and of protandry are discussed together with their relationship with the patterns of locomotor activity. The results are also considered with respect to mating strategies in insect parasitoids; they actually support the hypothesis of mating occurring principally among individuals native to the same host patch inTrichogramma species.     

The effects of biological rhythms and sleep quality on benign paroxysmal positional vertigo and reflux symptom severity

Recently, there has been increased interest in chronotypes and clinical differences between them. However, there is limited information about the potential influence of the chronotypes on clinical manifestations and symptom intensity of somatic diseases. The aim of this study is to evaluate the impact of biological rhythm differences and sleep quality on benign paroxysmal positional vertigo (BPPV) and larengo pharyngeal reflux (LPR) severity. Forty-four LPR patients, 43 BBPV patients and 42 controls were included in the study. The morningness–eveningness questionnaire was used to determine chronotypes, and the Pittsburgh Sleep Quality Index was used to assess subjective sleep quality. Both patient groups reported a significantly greater tendency to eveningness diurnal preferences compared to healthy controls. As with the circadian preferences, patients with BPPV or LPR characterized by poorer sleep quality and worse insomnia than non-patient individuals. It can be concluded that the circadian rhythm and sleep quality are related to the severity of LPR and BPPV.     

Systematic analysis of the impact of phosphorylation and O-GlcNAcylation on protein subcellular localization

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