Distinct regulation of mitochondrial localization and stability of two human Sirt5 isoforms

作者：Matsushita Nobuko; Yonashiro Ryo; Ogata Yoshinobu; Sugiura Ayumu; Nagashima Shun; Fukuda Toshifumi; Inatome Ryoko; Yanagi Shigeru^*

来源：Genes to Cells, 2011, 16(2): 190-202.

DOI：10.1111/j.1365-2443.2010.01475.x

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.

• 出版日期2011-2