Distinct regulation of mitochondrial localization and stability of two human Sirt5 isoforms
Distinct regulation of mitochondrial localization and stability of two human Sirt5 isoforms
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DOI：
10.1111/j.1365-2443.2010.01475.x
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发表时间：
2011-02-01
期刊：
影响因子：
2.1
通讯作者：
Yanagi, Shigeru
中科院分区：
文献类型：
--
作者：
Matsushita, Nobuko;Yonashiro, Ryo;Yanagi, Shigeru
迄今为止已鉴定出7种人类sirr2同源物（sirtuin）。在本研究中，我们明确了人类SIRT5基因编码的两个SIRT5亚型（SIRT5iso1和SIRT5iso2）的亚细胞定位机制，这两个亚型的c端略有不同。尽管这两种同工异构体在其n端都含有可切割的线粒体靶向信号，但我们发现，被切割的SIRT5iso2主要定位于线粒体，而被切割的SIRT5iso1则定位于线粒体和细胞质。SIRT5 δ C仅由共同结构域组成，其线粒体定位与SIRT5iso2相同。这些结果表明，被切割的SIRT5iso1的细胞质定位依赖于SIRT5iso1特异性的c端。进一步分析表明，SIRT5iso2的c端富含疏水氨基酸残基，具有线粒体膜插入信号的功能。此外，利用环己亚胺进行的从头蛋白合成抑制实验表明，SIRT5iso1特异性的c端对于维持SIRT5iso1的稳定性是必要的。此外，对每一种生物的基因组序列分析表明，SIRT5iso2是灵长类特有的同种异构体。综上所述，这些结果表明，人类SIRT5可能通过两种具有不同细胞内定位或稳定性的同种异构体来控制各种灵长类特异性功能。
Seven human Sir2 homologues (sirtuin) have been identified to date. In this study, we clarified the mechanism of subcellular localization of two SIRT5 isoforms (i.e., SIRT5iso1 and SIRT5iso2) encoded by the human SIRT5 gene and whose C-termini slightly differ from each other. Although both isoforms contain cleavable mitochondrial targeting signals at their N-termini, we found that the cleaved SIRT5iso2 was localized mainly in mitochondria, whereas the cleaved SIRT5iso1 was localized in both mitochondria and cytoplasm. SIRT5 delta C, which is composed of only the common domain, showed the same mitochondrial localization as that of SIRT5iso2. These results suggest that the cytoplasmic localization of cleaved SIRT5iso1 is dependent on the SIRT5iso1-specific C-terminus. Further analysis showed that the C-terminus of SIRT5iso2, which is rich in hydrophobic amino acid residues, functions as a mitochondrial membrane insertion signal. In addition, a de novo protein synthesis inhibition experiment using cycloheximide showed that the SIRT5iso1-specific C-terminus is necessary for maintaining the stability of SIRT5iso1. Moreover, genome sequence analysis from each organism examined indicated that SIRT5iso2 is a primate-specific isoform. Taken together, these results indicate that human SIRT5 potentially controls various primate-specific functions via two isoforms with different intracellular localizations or stabilities.