Malinow Rose Aria, Ying Phoenix, Koorman Thijs, Boxem Mike, Jin Yishi, Kim Kyung Won
Section of Neurobiology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA, United States.
Department of Biology, Utrecht University, Utrecht, Netherlands.
Front Cell Neurosci. 2019 Jul 31;13:348. doi: 10.3389/fncel.2019.00348. eCollection 2019.
The basic leucine-zipper (bZIP) domain transcription factors CCAAT/enhancer-binding proteins (C/EBP) have a variety of roles in cell proliferation, differentiation, and stress response. In the nervous system, several isoforms of C/EBP function in learning and memory, neuronal plasticity, neuroinflammation, and axon regeneration. We previously reported that the C/EBP homolog, CEBP-1, is essential for axon regeneration. CEBP-1 consists of 319 amino acids, with its bZIP domain at the C-terminus and a long N-terminal fragment with no known protein motifs. Here, using forward genetic screening with targeted genome editing, we have identified a unique domain in the N-terminus that is critical for its function. Additionally, we characterized three nuclear localization signals (NLS) in CEBP-1 that act together to mediate CEBP-1's nuclear import. Moreover, the Importin-α, IMA-3, can bind to CEBP-1 via one of the NLS. is ubiquitously expressed in all somatic cells, and null mutants are larval lethal. Using Cre-lox dependent neuron-specific deletion strategy, we show that is not critical for axon development, but is required for axon regeneration in adults. Together, these data advance our understanding of CEBP-1's function, and suggest new regulators that remain to be identified to expand the CEBP-1 protein interactome.
碱性亮氨酸拉链（bZIP）结构域转录因子CCAAT/增强子结合蛋白（C/EBP）在细胞增殖、分化和应激反应中具有多种作用。在神经系统中，C/EBP的几种亚型在学习与记忆、神经元可塑性、神经炎症和轴突再生中发挥作用。我们之前报道过，C/EBP同源物CEBP-1对轴突再生至关重要。CEBP-1由319个氨基酸组成，其bZIP结构域位于C末端，N末端有一个长片段，没有已知的蛋白质基序。在这里，我们通过靶向基因组编辑的正向遗传学筛选，在N末端鉴定出一个对其功能至关重要的独特结构域。此外，我们还对CEBP-1中的三个核定位信号（NLS）进行了表征，它们共同作用介导CEBP-1的核输入。而且，输入蛋白-α，即IMA-3，可以通过其中一个NLS与CEBP-1结合。IMA-3在所有体细胞中普遍表达，其缺失突变体在幼虫期致死。使用依赖Cre-lox的神经元特异性缺失策略，我们发现IMA-3对轴突发育并不关键，但对成年动物的轴突再生是必需的。总之，这些数据增进了我们对CEBP-1功能的理解，并提示仍有待鉴定新的调节因子以扩展CEBP-1蛋白相互作用组。
