AMPK activity is required for the induction of anhydrobiosis in a tardigrade Hypsibius exemplaris, and its potential up‐regulator is PP2A

Abstract

The anhydrobiotic tardigrade, Hypsibius exemplaris, was previously considered to require de novo gene expression and protein phosphatase 1 (PP1) and protein phosphatase 2A (PP2A) activity for successful anhydrobiosis. These indicate that H. exemplaris has signal transduction systems responding to desiccation stress, with the involvement of phosphorylation events. To this end, we carried out time‐series phosphoproteomics of H. exemplaris exposed to mild desiccation stress and detected 48 phosphoproteins with significant differential regulations. Among them, immediate and successive reduction of phosphorylation levels of AMP‐activated protein kinase (AMPK) was observed. The subsequent chemical genetic approach showed that AMPK was activated during the preconditioning stage for anhydrobiosis, and inhibition of its activity impaired successful anhydrobiosis. As PP2A is known to dephosphorylate AMPK in other organisms, we suggested that decreased phosphorylation levels of AMPK upon mild desiccation stress were caused by dephosphorylation by PP2A. Accordingly, phosphoproteomics of animals pre‐treated with the PP1/PP2A inhibitor cantharidic acid (CA) lacked the decrease in phosphorylation levels of AMPK. These observations suggest that AMPK activity is required for successful anhydrobiosis in H. exemplaris, and its phosphorylation state is possibly regulated by PP2A.

Deciphering the Biological Enigma—Genomic Evolution Underlying Anhydrobiosis in the Phylum Tardigrada and the Chironomid Polypedilum vanderplanki

“…Several signaling and transcription factors have been implicated in the regulation of anhydrobiosis machinery so far, including heat shock factor (HSF) and nuclear transcription factor Y subunit gamma-like (NF-YC) in Pol. vanderplanki [ 125 , 126 ], and AMP-activated protein kinase (AMPK), protein phosphatase 1 (PP1), and protein phosphatase 2A (PP2A) in H. exemplaris [ 24 , 127 ]. Trehalose secretion from fat body tissue is also seemingly a key signal of systemic anhydrobiosis in Pol.…”

Tardigrades and Their Emergence as Model Organisms

“…Methods for transgenesis and CRISPR in tardigrades would be valuable for accelerating discovery of mechanisms used to survive extremes as well as a variety of other discoveries. RNA interference allows some studies of gene function, as discussed above, and chemical inhibitors have also been used to discover genes or pathways of interest from tardigrades (Kondo et al, 2015(Kondo et al, , 2019(Kondo et al, , 2020Wojciechowska et al, 2021). To date, forward genetic screening using mutagenesis has not been reported.…”

How long can tardigrades survive in anhydrobiotic state? Searching on tardigrade anhydrobiosis patterns

“…To date, experiments on anhydrobiosis under controlled conditions have been conducted for several species, including Acutuncus antarcticus (Richters, [33]) [34], Bertolanius volubilis (Durante Pasa & Maucci, [35]) [36], Echiniscus testudo (Doyère, [37]) [38], Hypsibius exemplaris Gasiorek, Stec, Morek & Michalczyk, [39] (formerly Hys. dujardini (Doyère, [37]) [32, 40, 41, 42, 43, 44, 45, 46, 47, 48]), Milnesium inceptum Morek, Suzuki, Schill, Georgiev, Yankova, Marley & Michalczyk, [49] (formerly Mil. tardigradum Doyère, [37] [25, 38, 47, 50, 51, 52], Paramacrobiotus richtersi (Murray, [53]) [54, 55], Pam.…”