Department of Anatomy and Cell Biology, Yamagata University School of Medicine, Yamagata 990-9585, Japan.
Exp Cell Res. 2011 Dec 10;317(20):2853-63. doi: 10.1016/j.yexcr.2011.09.014. Epub 2011 Oct 5.
Diacylglycerol kinase (DGK) is involved in the regulation of lipid-mediated signal transduction through the metabolism of a second messenger diacylglycerol. Of the DGK family, DGKζ, which contains a nuclear localization signal, localizes mainly to the nucleus but translocates to the cytoplasm under pathological conditions. However, the detailed mechanism of translocation and its functional significance remain unclear. To elucidate these issues, we used a proteomic approach to search for protein targets that interact with DGKζ. Results show that nucleosome assembly protein (NAP) 1-like 1 (NAP1L1) and NAP1-like 4 (NAP1L4) are identified as novel DGKζ binding partners. NAP1Ls constitutively shuttle between the nucleus and the cytoplasm in transfected HEK293 cells. The molecular interaction of DGKζ and NAP1Ls prohibits nuclear import of DGKζ because binding of NAP1Ls to DGKζ blocks import carrier proteins, Qip1 and NPI1, to interact with DGKζ, leading to cytoplasmic tethering of DGKζ. In addition, overexpression of NAP1Ls exerts a protective effect against doxorubicin-induced cytotoxicity. These findings suggest that NAP1Ls are involved in a novel molecular basis for the regulation of nucleocytoplasmic shuttling of DGKζ and provide a clue to examine functional significance of its translocation under pathological conditions.
二酰基甘油激酶 (DGK) 通过代谢第二信使二酰基甘油参与脂质介导的信号转导的调节。DGK 家族中的 DGKζ 含有核定位信号，主要定位于核内，但在病理条件下易位到细胞质。然而，易位的详细机制及其功能意义仍不清楚。为了阐明这些问题，我们使用蛋白质组学方法来搜索与 DGKζ 相互作用的蛋白质靶标。结果表明，核小体组装蛋白 (NAP) 1 样 1 (NAP1L1) 和 NAP1 样 4 (NAP1L4) 被鉴定为 DGKζ 的新结合伴侣。NAP1Ls 在转染的 HEK293 细胞中在核内和细胞质之间持续穿梭。DGKζ 和 NAP1Ls 的分子相互作用阻止了 DGKζ 的核内输入，因为 NAP1Ls 与 DGKζ 的结合阻止了输入载体蛋白 Qip1 和 NPI1 与 DGKζ 的相互作用，导致 DGKζ 的细胞质束缚。此外，NAP1Ls 的过表达对阿霉素诱导的细胞毒性具有保护作用。这些发现表明，NAP1Ls 参与了 DGKζ 核质穿梭的调控的新分子基础，并为研究其在病理条件下易位的功能意义提供了线索。
