Laboratory of Obesity and Aging Research, Genetics and Developmental Biology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Proc Natl Acad Sci U S A. 2013 Jun 11;110(24):9873-8. doi: 10.1073/pnas.1307928110. Epub 2013 May 28.
The ability to sense metabolic stress is critical for successful cellular adaptation. In eukaryotes, the AMP-activated protein kinase (AMPK), a highly conserved serine/threonine kinase, functions as a critical metabolic sensor. AMPK is activated by the rising ADP/ATP and AMP/ATP ratios during conditions of energy depletion and also by increasing intracellular Ca(2+). In response to metabolic stress, AMPK maintains energy homeostasis by phosphorylating and regulating proteins that are involved in many physiological processes including glucose and fatty acid metabolism, transcription, cell growth, mitochondrial biogenesis, and autophagy. Evidence is mounting that AMPK also plays a role in a number of pathways unrelated to energy metabolism. Here, we identify the recombination-activating gene 1 protein (RAG1) as a substrate of AMPK. The RAG1/RAG2 complex is a lymphoid-specific endonuclease that catalyzes specific DNA cleavage during V(D)J recombination, which is required for the assembly of the Ig and T-cell receptor genes of the immune system. AMPK directly phosphorylates RAG1 at serine 528, and the phosphorylation enhances the catalytic activity of the RAG complex, resulting in increased cleavage of oligonucleotide substrates in vitro, or increased recombination of an extrachromosomal substrate in a cellular assay. Our results suggest that V(D)J recombination can be regulated by AMPK activation, providing a potential new link between metabolic stress and development of B and T lymphocytes.
感应代谢应激的能力对于细胞的成功适应至关重要。在真核生物中，AMP 激活的蛋白激酶（AMPK）作为一种关键的代谢传感器，是一种高度保守的丝氨酸/苏氨酸激酶。在能量耗竭的情况下，当 ADP/ATP 和 AMP/ATP 比值升高时，以及通过增加细胞内 Ca(2+)，AMPK 被激活。为了应对代谢应激，AMPK 通过磷酸化和调节涉及许多生理过程的蛋白质来维持能量稳态，包括葡萄糖和脂肪酸代谢、转录、细胞生长、线粒体生物发生和自噬。越来越多的证据表明，AMPK 还在许多与能量代谢无关的途径中发挥作用。在这里，我们确定重组激活基因 1 蛋白（RAG1）是 AMPK 的底物。RAG1/RAG2 复合物是一种淋巴细胞特异性内切酶，在 V(D)J 重组过程中催化特定的 DNA 切割，这是免疫系统中免疫球蛋白和 T 细胞受体基因组装所必需的。AMPK 直接在丝氨酸 528 处磷酸化 RAG1，磷酸化增强了 RAG 复合物的催化活性，导致体外寡核苷酸底物的切割增加，或细胞测定中染色体外底物的重组增加。我们的结果表明，V(D)J 重组可以通过 AMPK 激活来调节，为代谢应激和 B 和 T 淋巴细胞发育之间提供了一个潜在的新联系。
