title: Novel mitochondria-targeted heat-soluble proteins identified in the anhydrobiotic Tardigrade improve osmotic tolerance of human cells.
abstract: Tardigrades are able to tolerate almost complete dehydration through transition to a metabolically inactive state, called "anhydrobiosis". Late Embryogenesis Abundant (LEA) proteins are heat-soluble proteins involved in the desiccation tolerance of many anhydrobiotic organisms. Tardigrades, Ramazzottius varieornatus, however, express predominantly tardigrade-unique heat-soluble proteins: CAHS (Cytoplasmic Abundant Heat Soluble) and SAHS (Secretory Abundant Heat Soluble) proteins, which are secreted or localized in most intracellular compartments, except the mitochondria. Although mitochondrial integrity is crucial to ensure cellular survival, protective molecules for mitochondria have remained elusive. Here, we identified two novel mitochondrial heat-soluble proteins, RvLEAM and MAHS (Mitochondrial Abundant Heat Soluble), as potent mitochondrial protectants from Ramazzottius varieornatus. RvLEAM is a group3 LEA protein and immunohistochemistry confirmed its mitochondrial localization in tardigrade cells. MAHS-green fluorescent protein fusion protein localized in human mitochondria and was heat-soluble in vitro, though no sequence similarity with other known proteins was found, and one region was conserved among tardigrades. Furthermore, we demonstrated that RvLEAM protein as well as MAHS protein improved the hyperosmotic tolerance of human cells. The findings of the present study revealed that tardigrade mitochondria contain at least two types of heat-soluble proteins that might have protective roles in water-deficient environments.
authors: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, Japan.
authors: Sae
authors: S
authors: Tanaka
authors: Faculty of Medicine, University of Tsukuba, 1-1-1 Ten-noudai, Tsukuba, Japan.
authors: Junko
authors: J
authors: Tanaka
authors: Faculty of Medicine, University of Tsukuba, 1-1-1 Ten-noudai, Tsukuba, Japan.
authors: Yoshihiro
authors: Y
authors: Miwa
authors: Institute for Advanced Biosciences, Keio University, Endo 5322, Fujisawa, Kanagawa, Japan.
authors: Daiki D
authors: DD
authors: Horikawa
authors: Database Center for Life Science, 178-4-4 Wakashiba, Kashiwa-shi, Chiba, Japan.
authors: Toshiaki
authors: T
authors: Katayama
authors: Institute for Advanced Biosciences, Keio University, Endo 5322, Fujisawa, Kanagawa, Japan.
authors: Kazuharu
authors: K
authors: Arakawa
authors: Comparative Genomics Laboratory, Center for Information Biology, National institute of genetics, Yata 1111, Mishima, Shizuoka, Japan; Advanced Genomics Center, National institute of genetics, Yata 1111, Mishima, Shizuoka, Japan.
authors: Atsushi
authors: A
authors: Toyoda
authors: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, Japan.
authors: Takeo
authors: T
authors: Kubo
authors: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, Japan.
authors: Takekazu
authors: T
authors: Kunieda
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D006358:Hot Temperature; D006801:Humans; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D064587:Osmoregulation / Q000235:genetics; D009997:Osmotic Pressure; D021381:Protein Transport; D012995:Solubility; D058467:Tardigrada / Q000502:physiology*
chemical_list: D024101:Mitochondrial Proteins