Huang Jie-Xin, Wang Chun-I, Kuo Chia-Yu, Chang Ting-Wei, Liu Yu-Chin, Hsiao Ting-Feng, Wang Chih-Liang, Yu Chia-Jung
Graduate Institute of Biomedical Sciences, College of Medicine Chang Gung University Taoyuan Taiwan.
Department of Biochemistry, School of Medicine China Medical University Taichung Taiwan.
FASEB Bioadv. 2024 Jul 5;6(8):276-288. doi: 10.1096/fba.2024-00078. eCollection 2024 Aug.
Karyopherin α 2 (KPNA2, importin α1), a transport factor shuttling between the nuclear and cytoplasmic compartments, is involved in the nuclear import of proteins and participates in cellular processes such as cell cycle regulation, apoptosis, and transcriptional regulation. However, it is still unclear which signaling regulates the nucleocytoplasmic distribution of KPNA2 in response to cellular stress. In this study, we report that oxidative stress increases nuclear retention of KPNA2 through alpha serine/threonine-protein kinase (AKT1)-mediated reduction of serine 62 (S62) phosphorylation. We first found that AKT1 activation was required for HO-induced nuclear accumulation of KPNA2. Immunoprecipitation and quantitative proteomic analysis revealed that the phosphorylation of KPNA2 at S62 was decreased under HO-induced oxidative stress. We showed that cyclin-dependent kinase 1 (CDK1), a kinase responsible for KPNA2 S62 phosphorylation, contributes to the localization of KPNA2 in the cytoplasm. AKT1 knockdown increased KPNA2 S62 phosphorylation and inhibited CDK1 activation. Furthermore, HO-induced AKT1 activation promoted nuclear KPNA2 interaction with nucleophosmin 1 (NPM1), resulting in attenuation of NPM1-mediated cyclin D1 gene transcription. Thus, we infer that the AKT1-CDK1 axis regulates the nucleocytoplasmic shuttling and function of KPNA2 through spatiotemporal regulation of KPNA2 S62 phosphorylation under oxidative stress conditions.
核转运蛋白α2（KPNA2，输入蛋白α1）是一种在细胞核和细胞质区室之间穿梭的转运因子，参与蛋白质的核输入，并参与细胞周期调控、细胞凋亡和转录调控等细胞过程。然而，尚不清楚哪种信号传导在细胞应激反应中调节KPNA2的核质分布。在本研究中，我们报告氧化应激通过α丝氨酸/苏氨酸蛋白激酶（AKT1）介导的丝氨酸62（S62）磷酸化减少增加了KPNA2的核滞留。我们首先发现HO诱导的KPNA2核积累需要AKT1激活。免疫沉淀和定量蛋白质组学分析显示，在HO诱导的氧化应激下，KPNA2在S62处的磷酸化降低。我们表明，细胞周期蛋白依赖性激酶1（CDK1）是负责KPNA2 S62磷酸化的激酶，有助于KPNA2在细胞质中的定位。AKT1敲低增加了KPNA2 S62磷酸化并抑制了CDK1激活。此外，HO诱导的AKT1激活促进了核KPNA2与核仁磷酸蛋白1（NPM1）的相互作用，导致NPM1介导的细胞周期蛋白D1基因转录减弱。因此，我们推断AKT1-CDK1轴在氧化应激条件下通过对KPNA2 S62磷酸化的时空调节来调节KPNA2的核质穿梭和功能。
