Green Stuart R, Al-Attar Rasha, McKechnie Andrew E, Naidoo Samantha, Storey Kenneth B
Institute of Biochemistry & Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa K1S 5B6, Ontario, Canada.
South African Research Chair in Conservation Physiology, National Zoological Garden, South African National Biodiversity Institute, Pretoria, South Africa; DST-NRF Centre of Excellence, FitzPatrick Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
Cell Signal. 2020 Nov;75:109763. doi: 10.1016/j.cellsig.2020.109763. Epub 2020 Aug 29.
Pronounced heterothermic responses are relatively rare among birds. Along with taxa such as hummingbirds and caprimulgids, the order Coliiformes (mousebirds) is known to possess the physiological capacity for torpor. During torpor, body temperature is greatly reduced and a bird becomes unresponsive to external stimuli until ambient temperatures return to more favorable conditions. Under such conditions, these birds are forced to rely only on their internal fuel storage for energy and show great reduction in metabolic rates by decreasing energy-expensive processes. This study investigated the role of the key insulin-Akt signaling kinase pathway involved in regulating energy metabolism and protein translation in the liver, kidney, heart, skeletal muscle, and brain of the speckled mousebird (Colius striatus). The degree of phosphorylation of well-conserved target residues with important regulatory function was examined in both the euthermic control and torpid birds. The results demonstrated marked differences in responses between the tissues with decreases in RPS6 S235/236 phosphorylation in the kidney (0.52 fold of euthermic) and muscle (0.29 fold of euthermic) as well as decreases in GS3K3β S9 in muscle (0.60 fold of euthermic) and GSK3α S21 (0.71 fold of euthermic) phosphorylation in kidney during torpor, suggesting a downregulation of this pathway. Interestingly, the liver demonstrated an increase in RPS6 S235/236 (2.89 fold increase) and P70S6K T412 (1.44 fold increase) phosphorylation in the torpor group suggesting that protein translation is maintained in this tissue. This study demonstrates that avian torpor is a complex phenomenon and alterations in this signaling pathway follow a tissue specific pattern.
明显的异温反应在鸟类中相对少见。与蜂鸟和夜鹰等类群一样，鼠鸟目（鼠鸟）已知具有进入蛰伏状态的生理能力。在蛰伏期间，体温会大幅降低，鸟类对外界刺激变得无反应，直到环境温度恢复到更适宜的条件。在这种情况下，这些鸟类被迫仅依靠体内的能量储备来获取能量，并通过减少耗能过程使代谢率大幅降低。本研究调查了关键的胰岛素 - Akt信号激酶途径在调节斑纹鼠鸟（Colius striatus）的肝脏、肾脏、心脏、骨骼肌和大脑中的能量代谢及蛋白质翻译方面所起的作用。在正常体温的对照鸟和蛰伏鸟中，均检测了具有重要调节功能的保守靶位点的磷酸化程度。结果表明，各组织之间的反应存在显著差异，蛰伏期间肾脏中RPS6 S235/236磷酸化水平降低（为正常体温时的0.52倍），肌肉中也降低（为正常体温时的0.29倍），肌肉中GS3K3β S9磷酸化水平降低（为正常体温时的0.60倍），肾脏中GSK3α S21磷酸化水平降低（为正常体温时的0.71倍），这表明该途径下调。有趣的是，蛰伏组肝脏中RPS6 S235/236磷酸化水平升高（增加2.89倍），P70S6K T412磷酸化水平升高（增加1.44倍），这表明该组织中蛋白质翻译得以维持。本研究表明，鸟类蛰伏是一种复杂的现象，且该信号通路的变化遵循组织特异性模式。
