Anhydrobiosis is an extremely dehydrated state in which organisms show no detectable metabolism but retain the ability to revive after rehydration. Thus far, two hypotheses have been proposed to explain how cells are protected during dehydration: (i) water replacement by compatible solutes and (ii) vitrification. The present study provides direct physiological and physicochemical evidence for these hypotheses in an African chironomid, Polypedilum vanderplanki, which is the largest multicellular animal capable of anhydrobiosis. Differential scanning calorimetry measurements and Fourier-transform infrared (FTIR) analyses indicated that the anhydrobiotic larvae were in a glassy state up to as high as 65°C. Changing from the glassy to the rubbery state by either heating or allowing slight moisture uptake greatly decreased the survival rate of dehydrated larvae. In addition, FTIR spectra showed that sugars formed hydrogen bonds with phospholipids and that membranes remained in the liquid-crystalline state in the anhydrobiotic larvae. These results indicate that larvae of P. vanderplanki survive extreme dehydration by replacing the normal intracellular medium with a biological glass. When entering anhydrobiosis, P. vanderplanki accumulated nonreducing disaccharide trehalose that was uniformly distributed throughout the dehydrated body by FTIR microscopic mapping image. Therefore, we assume that trehalose plays important roles in water replacement and intracellular glass formation, although other compounds are surely involved in these phenomena.trehalose ͉ water replacement ͉ Fourier-transform infrared microspectroscopy ͉ biological glass ͉ cryptobiosis

Anhydrobiotic (i.e., life without water) organisms are known to produce group 3 late embryogenesis abundant (G3LEA) proteins during adaptation to severely water-deficient conditions. Their primary amino acid sequences are composed largely of loosely conserved 11-mer repeat units. However, little information has been obtained for the structural and functional roles of these repeat units. In this study, we first explore the consensus sequences of the 11-mer repeat units for several native G3LEA proteins originating from anhydrobiotic organisms among insects (Polypedilum vanderplanki), nematodes, and plants. Next, we synthesize four kinds of model peptides (LEA models), each of which consists of four or two repeats of the 11-mer consensus sequences for each of the three organisms. The structural and thermodynamic properties of the LEA models were examined in solution, in dehydrated and rehydrated states, and furthermore in the presence of trehalose, since a great quantity of this sugar is known to be produced in the dried cells of most anhydrobiotic organisms. The results of Fourier transform infrared (FTIR) spectroscopic measurements indicate that all of the LEA models transform from random coils to alpha-helical coiled coils on dehydration and return to random coils again on rehydration, both with and without trehalose. In contrast, such structural changes were never observed for a control peptide with a randomized amino acid sequence. Furthermore, our differential scanning calorimetry (DSC) measurements provide the first evidence that the above 11-mer motif-containing peptides themselves vitrify with a high glass transition temperature (>100 degrees C) and a low enthalpy relaxation rate. In addition, they play a role in reinforcing the glassy matrix of the coexisting trehalose. On the basis of these results, we discuss the underlying mechanism of G3LEA proteins as desiccation stress protectants.

LEA proteins are found in anhydrobiotes and are thought to be associated with the acquisition of desiccation tolerance. The sleeping chironomid Polypedilum vanderplanki, which can survive in an almost completely desiccated state throughout the larval stage, accumulates LEA proteins in response to desiccation and high salinity conditions. However, the biochemical functions of these proteins remain unclear. Here, we report the characterization of a novel chironomid LEA protein, PvLEA4, which is the most highly accumulated LEA protein in desiccated larvae. Cytoplasmic-soluble PvLEA4 showed many typical characteristics of group 3 LEA proteins (G3LEAs), such as desiccation-inducible accumulation, high hydrophilicity, folding into α-helices on drying, and the ability to reduce aggregation of dehydration-sensitive proteins. This last property of LEA proteins has been termed molecular shield function. To further investigate the molecular shield activity of PvLEA4, we introduced two distinct methods, turbidity measurement and dynamic light scattering (DLS). Turbidity measurements demonstrated that both PvLEA4, and BSA as a positive control, reduced aggregation in α-casein subjected to desiccation and rehydration. However, DLS experiments showed that a small amount of BSA relative to α-casein increased aggregate particle size, whereas PvLEA4 decreased particle size in a dose-dependent manner. Trehalose, which is the main heamolymph sugar in most insects but also a protectant as a chemical chaperone in the sleeping chironomid, has less effect on the limitation of aggregate formation. This analysis suggests that molecular shield proteins function by limiting the growth of protein aggregates during drying and that PvLEA4 counteracts protein aggregation in the desiccation-tolerant larvae of the sleeping chironomid.

No abstract

Type 1 diabetes (T1D) is an autoimmune disease in which insulin-producing pancreatic β-cells are destroyed. Intestinal helminths can cause asymptomatic chronic and immunosuppressive infections and suppress disease in rodent models of T1D. However, the underlying regulatory mechanisms for this protection are unclear. Here, we report that CD8 + regulatory T (Treg) cells prevent the onset of streptozotocin -induced diabetes by a rodent intestinal nematode. Trehalose derived from nematodes affects the intestinal microbiota and increases the abundance of Ruminococcus spp., resulting in the induction of CD8 + Treg cells. Furthermore, trehalose has therapeutic effects on both streptozotocin-induced diabetes and in the NOD mouse model of T1D. In addition, compared with healthy volunteers, patients with T1D have fewer CD8 + Treg cells, and the abundance of intestinal Ruminococcus positively correlates with the number of CD8 + Treg cells in humans.