Department of Surgery and Center for Engineering in Medicine, Massachusetts General Hospital & Harvard Medical School, 114 16th Street, Charlestown, 02129, MA, USA.
Institute of Biochemistry and Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada.
Biochim Biophys Acta Gen Subj. 2017 Nov;1861(11 Pt A):2811-2821. doi: 10.1016/j.bbagen.2017.07.026. Epub 2017 Aug 2.
The thirteen-lined ground squirrel (I. tridecemlineatus) becomes hypometabolic during hibernation; characterized by reductions in energy expensive processes like transcription during periods of low temperature and starvation. We were interested in elucidating the mechanisms of transcriptional control by studying the MAPK pathway and downstream transcription factors in skeletal muscle. We were also interested in how environmental factors, such as body temperature, that fluctuate during hibernation, can affect transcriptional regulation.
Protein abundance of MAPKs and effectors were quantified using immunoblotting and Luminex® multiplex assays. DNA-protein interaction (DPI)-ELISA was used to quantitatively assess the binding of transcription factors to DNA promoter sequences under environmental conditions which are reflective of those during torpor.
JNK2/3 showed increases in protein abundance during early arousal. The transcription factor, Elk1, showed increases in phosphorylation of S383 (which is indicative of increased activity) during arousal that accompany decreases in total protein levels. Further analysis on the relative binding of this transcription factor to its consensus sequence during euthermia and torpor showed that its binding is significantly different when environmental conditions such as temperature, [urea], and [Ca] were changed.
We show evidence of Elk1 regulation during hibernation, and its activity could be influenced by environmental factors such as temperature, [urea] and [Ca], as well as post-translational modifications via JNK2/3.
I. tridecemlineatus has natural mechanisms of transcriptional regulation during hibernation through phosphorylation and changes to the cellular environment. We identify regulation of JNK and Elk1 in the skeletal muscle of hibernating I. tridecemlineatus.
十三线地松鼠（I. tridecemlineatus）在冬眠期间会出现代谢降低的现象；其特征是在低温和饥饿期间减少转录等能量消耗过程。我们有兴趣通过研究骨骼肌中的 MAPK 途径和下游转录因子来阐明转录控制的机制。我们还对体温等环境因素在冬眠期间波动如何影响转录调节感兴趣。
使用免疫印迹和 Luminex®多重分析测定 MAPK 和效应物的蛋白丰度。DNA-蛋白相互作用（DPI）-ELISA 用于定量评估在反映冬眠期间环境条件下转录因子与 DNA 启动子序列的结合。
JNK2/3 在早期觉醒时蛋白丰度增加。转录因子 Elk1 在觉醒期间 S383 的磷酸化增加（表明活性增加），同时总蛋白水平下降。进一步分析该转录因子在体温和冬眠期间相对结合其共有序列的情况表明，当环境条件如温度、[尿素]和[Ca]发生变化时，其结合明显不同。
我们在冬眠期间证明了 Elk1 的调节作用，其活性可能受到环境因素如温度、[尿素]和[Ca]以及通过 JNK2/3 的翻译后修饰的影响。
I. tridecemlineatus 在冬眠期间通过磷酸化和改变细胞环境具有天然的转录调节机制。我们在冬眠的 I. tridecemlineatus 骨骼肌中鉴定了 JNK 和 Elk1 的调节作用。
