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Distinct regulation of mitochondrial localization and stability of two human Sirt5 isoforms
Author(s) -
Matsushita Nobuko,
Yonashiro Ryo,
Ogata Yoshinobu,
Sugiura Ayumu,
Nagashima Shun,
Fukuda Toshifumi,
Inatome Ryoko,
Yanagi Shigeru
Publication year - 2011
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1111/j.1365-2443.2010.01475.x
Subject(s) - gene isoform , biology , subcellular localization , mitochondrion , cytoplasm , cycloheximide , biochemistry , sirtuin , microbiology and biotechnology , n terminus , peptide sequence , gene , protein biosynthesis , acetylation
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., SIRT5 iso1 and SIRT5 iso2 ) 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 SIRT5 iso2 was localized mainly in mitochondria, whereas the cleaved SIRT5 iso1 was localized in both mitochondria and cytoplasm. SIRT5ΔC, which is composed of only the common domain, showed the same mitochondrial localization as that of SIRT5 iso2 . These results suggest that the cytoplasmic localization of cleaved SIRT5 iso1 is dependent on the SIRT5 iso1 ‐specific C‐terminus. Further analysis showed that the C‐terminus of SIRT5 iso2 , 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 SIRT5 iso1 ‐specific C‐terminus is necessary for maintaining the stability of SIRT5 iso1 . Moreover, genome sequence analysis from each organism examined indicated that SIRT5 iso2 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.