A sodium-dependent trehalose transporter contributes to anhydrobiosis in insect cell line, Pv11

Significance

Pv11 is the only animal cell line with extreme desiccation tolerance, called anhydrobiosis, induced by pretreatment with high concentrations of trehalose. Heterologous expression systems revealed that an identified transporter (STRT1), which is up-regulated upon rehydration, exhibits Na ⁺-dependent trehalose import and export activities. This study reports a trehalose transporter belonging to the solute carrier family 5 (SLC5). Knockout of Strt1 significantly reduced the viability of desiccated Pv11 cells after rehydration. Further gene knockout experiments revealed that STRT1 effectively effluxes excess trehalose during rehydration, which likely contributes to the alleviation of deleterious morphological changes caused by osmotic shock. These results suggest that STRT1 plays an important role in the recovery of Pv11 cells from the state of anhydrobiosis.

Abstract

Pv11 is the only animal cell line that, when preconditioned with a high concentration of trehalose, can be preserved in the dry state at room temperature for more than one year while retaining the ability to resume proliferation. This extreme desiccation tolerance is referred to as anhydrobiosis. Here, we identified a transporter that contributes to the recovery of Pv11 cells from anhydrobiosis. In general, the solute carrier 5 (SLC5)-type secondary active transporters cotransport Na ⁺ and carbohydrates including glucose. The heterologous expression systems showed that the transporter belonging to the SLC5 family, whose expression increases upon rehydration, exhibits Na ⁺-dependent trehalose transport activity. Therefore, we named it STRT1 (sodium-ion trehalose transporter 1). We report an SLC5 family member that transports a naturally occurring disaccharide, such as trehalose. Knockout of the Strt1 gene significantly reduced the viability of Pv11 cells upon rehydration after desiccation. During rehydration, when intracellular trehalose is no longer needed, Strt1-knockout cells released the disaccharide more slowly than the parental cell line. During rehydration, Pv11 cells became roughly spherical due to osmotic pressure changes, but then returned to their original spindle shape after about 30 min. Strt1-knockout cells, however, required about 50 min to adopt their normal morphology. STRT1 probably regulates intracellular osmolality by releasing unwanted intracellular trehalose with Na ⁺, thereby facilitating the recovery of normal cell morphology during rehydration. STRT1 likely improves the viability of dried Pv11 cells by rapidly alleviating the significant physical stresses that arise during rehydration.