Inagaki Yuichi, Li Pei-Yun, Wada Atsushi, Mitsutake Susumu, Igarashi Yasuyuki
Department of Biomembrane and Biofunctional Chemistry, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Biochem Biophys Res Commun. 2003 Nov 7;311(1):168-73. doi: 10.1016/j.bbrc.2003.09.194.
Sphingosine kinase (SPHK) is an enzyme that phosphorylates sphingosine to form sphingosine 1-phosphate (S1P). Human SPHK1 (hSPHK1) was localized predominantly in the cytoplasm when transiently expressed in Cos7 cells. In this study, we have found two functional nuclear export signal (NES) sequences in the middle region of hSPHK1. Deletion and mutagenesis studies revealed that the cytoplasmic localization of SPHK1 depends on its nuclear export, directed by the NES. Furthermore, upon treatment with leptomycin B, a specific inhibitor of the nuclear export receptor CRM1, a marked nuclear accumulation of hSPHK1 was observed, indicating that hSPHK1 shuttles between the cytoplasm and the nucleus. Our results provide the first evidence of the active nuclear export of SPHK1 and suggest it is mediated by a CRM1-dependent pathway.
鞘氨醇激酶（SPHK）是一种将鞘氨醇磷酸化形成1-磷酸鞘氨醇（S1P）的酶。人SPHK1（hSPHK1）在Cos7细胞中瞬时表达时主要定位于细胞质中。在本研究中，我们在hSPHK1的中间区域发现了两个功能性核输出信号（NES）序列。缺失和诱变研究表明，SPHK1的细胞质定位依赖于由NES介导的核输出。此外，在用核输出受体CRM1的特异性抑制剂 leptomycin B处理后，观察到hSPHK1明显在细胞核中积累，表明hSPHK1在细胞质和细胞核之间穿梭。我们的结果提供了SPHK1主动核输出的首个证据，并表明它是由CRM1依赖性途径介导的。
