Kuwahara Hiroshi, Nakamura Norihiro, Kanazawa Hiroshi
Department of Biological Sciences, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
Biol Pharm Bull. 2006 Feb;29(2):225-33. doi: 10.1248/bpb.29.225.
DAP kinase-related apoptosis-inducing kinase 2 (DRAK2), a member of the DAP kinase family, is a serine/threonine kinase capable of inducing apoptosis. Here we studied the relationship between DRAK2 intracellular localization and apoptosis, and found that UV light acts as a stimulus for apoptosis induced by DRAK2. The intracellular location of DRAK2 depended on the cell line: DRAK2 was found primarily in the nuclei of NRK, NIH3T3, and Caco-2 cells while it was present primarily in the cytoplasm of ACL-15, HeLa, and WI-38 cells. Overexpression of Myc-tagged DRAK2 led to apoptosis-like cell death in NRK cells, but not in ACL-15 cells. A GFP fusion protein of DRAK2 was spontaneously localized to the nucleus of ACL-15 cells and resulted in cell death. Nuclear localization and cell death were also observed with DRAK2(1-293) fused to the NLS of SV40 but not with DRAK2(1-293) alone. These results suggested that nuclear accumulation of DRAK2 and the resulting increase in the endogenous level of its kinase activity are required for cell death. UV irradiation caused nuclear accumulation of endogenous DRAK2 in ACL-15 cells, which was followed by apoptosis-like cell death. Knockdown of DRAK2 expression by siRNA partially suppressed UV-induced apoptosis. These results suggest that DRAK2 plays a role in UV induced apoptosis.
死亡相关蛋白激酶相关凋亡诱导激酶2(DRAK2)是死亡相关蛋白激酶家族的成员之一,是一种能够诱导细胞凋亡的丝氨酸/苏氨酸激酶。在此,我们研究了DRAK2细胞内定位与细胞凋亡之间的关系,发现紫外线是DRAK2诱导细胞凋亡的刺激因素。DRAK2的细胞内定位取决于细胞系:在NRK、NIH3T3和Caco-2细胞中,DRAK2主要位于细胞核中,而在ACL-15、HeLa和WI-38细胞中,它主要存在于细胞质中。Myc标签的DRAK2过表达导致NRK细胞发生类似凋亡的细胞死亡,但在ACL-15细胞中则不然。DRAK2的绿色荧光蛋白融合蛋白自发定位于ACL-15细胞的细胞核并导致细胞死亡。与SV40核定位信号融合的DRAK2(1-293)也观察到核定位和细胞死亡,但单独的DRAK2(1-293)则未观察到。这些结果表明,DRAK2的核积累及其激酶活性内源性水平的增加是细胞死亡所必需的。紫外线照射导致ACL-15细胞内源性DRAK2的核积累,随后发生类似凋亡的细胞死亡。用小干扰RNA敲低DRAK2表达可部分抑制紫外线诱导的细胞凋亡。这些结果表明,DRAK2在紫外线诱导的细胞凋亡中起作用。
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