RT Journal Article
SR Electronic
T1 Stress-dependent dynamic and reversible formation of cytoskeleton-like filaments and gel-transition by tardigrade tolerance proteins
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 2021.10.02.462891
DO 10.1101/2021.10.02.462891
A1 Akihiro Tanaka
A1 Tomomi Nakano
A1 Kento Watanabe
A1 Kazutoshi Masuda
A1 Shuichi Kamata
A1 Reitaro Yasui
A1 Hiroko Kozuka-Hata
A1 Chiho Watanabe
A1 Takumi Chinen
A1 Daiju Kitagawa
A1 Masaaki Oyama
A1 Miho Yanagisawa
A1 Takekazu Kunieda
YR 2021
UL http://biorxiv.org/content/early/2021/10/03/2021.10.02.462891.abstract
AB Tardigrades are able to tolerate almost complete dehydration by entering a reversible ametabolic state called anhydrobiosis and resume their animation upon rehydration. Dehydrated tardigrades are exceptionally stable and withstand various physical extremes. Although trehalose and late embryogenesis abundant (LEA) proteins have been extensively studied as potent protectants against dehydration in other anhydrobiotic organisms, tardigrades produce high amounts of tardigrade-unique protective cytoplasmic-abundant heat-soluble (CAHS) proteins which are essential for the anhydrobiotic survival of tardigrades. However, the precise mechanisms of their action in this protective role are not fully understood. In the present study, we first postulated the presence of tolerance proteins that form protective condensates via phase separation in a stress-dependent manner and searched for tardigrade proteins that reversibly form condensates upon dehydration-like stress. Through comprehensive analysis, we identified 336 such proteins, collectively dubbed “dehydration-induced reversibly condensing proteins (DRPs)”. Unexpectedly, we rediscovered CAHS proteins as highly enriched in DRPs, 3 of which were major components of DRPs. We revealed that these CAHS proteins reversibly polymerize into many cytoskeleton-like filaments depending on hyperosmotic stress in cultured cells and undergo reversible gel-transition in vitro, which increases the mechanical strength of cell-like microdroplets. The conserved putative helical C-terminal region is necessary and sufficient for filament formation by CAHS proteins, and mutations disrupting the secondary structure of this region impaired both the filament formation and the gel transition. On the basis of these results, we propose that CAHS proteins are novel cytoskeletal proteins that form filamentous networks and undergo gel-transition in a stress-dependent manner to provide on-demand physical stabilization of cell integrity against deformative forces during dehydration and contribute to the exceptional stability of dehydrated tardigrades.Competing Interest StatementThe authors have declared no competing interest.