Eye Center of the Second Affiliated Hospital of Zhejiang University, School of Medicine, Hangzhou 310009, China; Zhejiang Provincial Key Lab of Ophthalmology, Hangzhou, Zhejiang Province 310009, China.
Ninghai First Hospital, Ningbo 315600, China.
Gene. 2021 Jun 20;786:145621. doi: 10.1016/j.gene.2021.145621. Epub 2021 Mar 31.
KPNA4 (also called importin-α3) belongs to the importin α adaptor proteins family, which orchestrates classical nuclear transport processes, importin-α/importin-β1 pathway, and involves in cellular homeostasis. Disruption of balanced transport pathways may result in ectopic nuclear proteins and eventually cause diseases, mainly under the situation of cellular stress, such as oxidative stress. Little evidence is available on its cellular functions for high specific expression in lens. We firstly studied the role of KPNA4 in cataract formation. Lens defects were observed at an early age in kpna4 gene knockout zebrafish, generated by the CRISPR/Cas9 system. Those phenotype, including cloudy center part of the lens, via bright field microscopy, and the thinning of the LE layer, wider space between the adjacent LE and LF cells, irregular cells morphology and the increased number of holes inside the LE cells, which were detected by transmission electron microscopy, recapitulate the clinical features of cataract patients. As the p53-specific adaptor of the nuclear import, KPNA4 upregulated with the same pattern of p53 in hydrogen peroxide-induced apoptosis in human lens epithelia cells. Furthermore, the loss of Kpna4 resulted in the accumulation of p53 in the center of lens. Taken together, we showed that KPNA4 was involved in the formation of cataract, likely by mediating p53 nuclear transport.
KPNA4（也称为 importin-α3）属于 importin-α 衔接蛋白家族，该家族协调经典核转运过程、importin-α/importin-β1 途径，并参与细胞内稳态。平衡转运途径的破坏可能导致核内蛋白异位，最终导致疾病，主要是在细胞应激（如氧化应激）的情况下。KPNA4 在晶状体中高特异性表达的细胞功能的证据很少。我们首先研究了 KPNA4 在白内障形成中的作用。通过 CRISPR/Cas9 系统生成的 kpna4 基因敲除斑马鱼在早期就观察到晶状体缺陷。这些表型包括通过明场显微镜观察到晶状体中心混浊部分，以及 LE 层变薄、相邻 LE 和 LF 细胞之间的空间变宽、细胞形态不规则以及 LE 细胞内孔增多，透射电镜检测到这些表型，重现了白内障患者的临床特征。作为核输入的 p53 特异性衔接物，KPNA4 在人晶状体上皮细胞中过氧化氢诱导的细胞凋亡中与 p53 呈相同模式上调。此外，Kpna4 的缺失导致 p53 在晶状体中心的积累。综上所述，我们表明 KPNA4 参与白内障的形成，可能通过介导 p53 核转运。
