Differential effects of light and heat on the Drosophila circadian clock proteins PER and TIM.
Differential effects of light and heat on the Drosophila circadian clock proteins PER and TIM.
复制标题
光和热对果蝇生物钟蛋白 PER 和 TIM 的不同影响。
DOI：
10.1128/mcb.18.4.2004
复制
发表时间：
1998
影响因子：
5.3
通讯作者：
Edery,I
中科院分区：
文献类型：
--
作者：
Sidote,D;Majercak,J;Parikh,V;Edery,I
昼夜节律（24小时）由内源性生化振荡器（时钟）控制，在各种各样的生物体中，通过短暂暴露于光和温度变化，可以相移（即延迟或提前）。然而，温度变化如何重置昼夜节律计时机制尚不清楚。为了开始解决这个问题，我们测量了短时间热脉冲对果蝇生物钟基因周期（per）和时间（tim）的蛋白质和mRNA产物的影响。在每天的循环中，任何时候的热脉冲都会引起PER和TIM蛋白水平的急剧下降。PER对热敏感，但对光不敏感，这表明单个时钟组件对环境刺激的敏感性有显著差异。类似的重置机制涉及到转录-翻译反馈回路的延迟，这可能是观察到的基础，即当热和光信号在夜间早期给予时，它们都会引起行为节律的相位延迟。然而，尽管先前的研究表明，在深夜，光诱导的TIM降解伴随着PER和TIM生化节律的时间调节的稳定阶段进展，但在每日周期的这些时间，热诱导的PER和TIM降解对这些时钟蛋白的周期几乎没有长期扰动。相反，PER和TIM在深夜的初始热诱导降解之后，PER-TIM时间程序的速度会短暂而迅速地增加。这些热诱导变化的净效应导致振荡机制具有与无扰动控制情况相似的稳态相。这些发现可以解释为什么在深夜施加热脉冲时果蝇的行为节律缺乏明显的稳态变化，并强烈表明刺激引起的生物钟速度变化可以促进相移反应。
Circadian (≅24-h) rhythms are governed by endogenous biochemical oscillators (clocks) that in a wide variety of organisms can be phase shifted (i.e., delayed or advanced) by brief exposure to light and changes in temperature. However, how changes in temperature reset circadian timekeeping mechanisms is not known. To begin to address this issue, we measured the effects of short-duration heat pulses on the protein and mRNA products from theDrosophilacircadian clock genesperiod(per) andtimeless(tim). Heat pulses at all times in a daily cycle elicited dramatic and rapid decreases in the levels of PER and TIM proteins. PER is sensitive to heat but not light, indicating that individual clock components can markedly differ in sensitivity to environmental stimuli. A similar resetting mechanism involving delays in theper-timtranscriptional-translational feedback loop likely underlies the observation that when heat and light signals are administered in the early night, they both evoke phase delays in behavioral rhythms. However, whereas previous studies showed that the light-induced degradation of TIM in the late night is accompanied by stable phase advances in the temporal regulation of the PER and TIM biochemical rhythms, the heat-induced degradation of PER and TIM at these times in a daily cycle results in little, if any, long-term perturbation in the cycles of these clock proteins. Rather, the initial heat-induced degradation of PER and TIM in the late night is followed by a transient and rapid increase in the speed of the PER-TIM temporal program. The net effect of these heat-induced changes results in an oscillatory mechanism with a steady-state phase similar to that of the unperturbed control situation. These findings can account for the lack of apparent steady-state shifts inDrosophilabehavioral rhythms by heat pulses applied in the late night and strongly suggest that stimulus-induced changes in the speed of circadian clocks can contribute to phase-shifting responses.