Protein kinase D-mediated phosphorylation and nuclear export of sphingosine kinase 2
Protein kinase D-mediated phosphorylation and nuclear export of sphingosine kinase 2
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DOI：
10.1074/jbc.m701641200
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发表时间：
2007-09-14
影响因子：
4.8
通讯作者：
Nakamura, Shun-ichi
中科院分区：
文献类型：
--
作者：
Ding, Guo;Sonoda, Hirofumi;Nakamura, Shun-ichi
鞘氨醇激酶（SPHK）是一种关键酶，可产生重要的信使分子1 - 磷酸鞘氨醇，并且与细胞增殖和细胞凋亡抑制有关。由于激动剂诱导的SPHK活化程度适中，通过SPHK的信号传导可能通过其在特定细胞内位点的定位来调节。尽管SPHK1异构体已被广泛研究和表征，但另一种异构体SPHK2的表达和功能调节在很大程度上仍未被探索。在此我们描述了一种重要的翻译后修饰，即由蛋白激酶D（PKD）催化的SPHK2磷酸化，它调节其定位。在用肿瘤促进剂佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯刺激HeLa细胞时，在SPHK2中首次鉴定出的一个新的假定核输出信号中的一个丝氨酸残基被磷酸化，随后SPHK2从细胞核输出。组成型活性PKD在体内和体外均可使核输出信号中的这个丝氨酸残基磷酸化。此外，通过RNA干扰下调PKD会导致基础的以及佛波醇12 - 肉豆蔻酸酯13 - 乙酸酯诱导的磷酸化减弱，随后SPHK2在细胞核中积累，而这种情况可通过PKD过表达来挽救。这些结果表明PKD是一种与SPHK2磷酸化生理相关的酶，它导致SPHK2核输出以进行后续的细胞信号传导。
Sphingosine kinase (SPHK) is a key enzyme producing important messenger sphingosine 1-phosphate and is implicated in cell proliferation and suppression of apoptosis. Because the extent of agonist-induced activation of SPHK is modest, signaling via SPHK may be regulated through its localization at specific intracellular sites. Although the SPHK1 isoform has been extensively studied and characterized, the regulation of expression and function of the other isoform, SPHK2, remain largely unexplored. Here we describe an important post-translational modification, namely, phosphorylation of SPHK2 catalyzed by protein kinase D (PKD), which regulates its localization. Upon stimulation of HeLa cells by tumor promoter phorbol 12-myristate 13-acetate, a serine residue in a novel and putative nuclear export signal, identified for the first time, in SPHK2 was phosphorylated followed by SPHK2 export from the nucleus. Constitutively active PKD phosphorylated this serine residue in the nuclear export signal both in vivo and in vitro. Moreover, down-regulation of PKDs through RNA interference resulted in the attenuation of both basal and phorbol 12-myristate 13-acetateinduced phosphorylation, which was followed by the accumulation of SPHK2 in the nucleus in a manner rescued by PKD overexpression. These results indicate that PKD is a physiologically relevant enzyme for SPHK2 phosphorylation, which leads to its nuclear export for subsequent cellular signaling.