Expression of Drosophila Trehalose-Phosphate Synthase in HEK-293 Cells Increases Hypoxia Tolerance*

Increasing hypoxia tolerance in mammalian cells is potentially of major importance, but it has not been feasible thus far. The disaccharide trehalose, which accumulates dramatically during heat shock, enhances thermotolerance and reduces aggregation of denatured proteins. Previous studies from our laboratory showed that over-expression of Drosophila trehalose-phosphate synthase (dtps1) increases the trehalose level and anoxia tolerance in flies. To determine whether trehalose can protect against anoxic injury in mammalian cells, we transfected the dtps1 gene into human HEK-293 cells using the recombinant plasmid pcDNA3.1(–)-dtps1 and obtained more than 20 stable cell strains. Glucose starvation in culture showed that HEK-293 cells transfected with pcDNA3.1(–)-dtps1 (HEK-dtps1) do not metabolize intracellular trehalose, and, interestingly, these cells accumulated intracellular trehalose during hypoxic exposure. In contrast to HEK-293 cells transfected with pcDNA3.1(–) (HEK-v), cells with trehalose were more resistant to low oxygen stress (1% O2). To elucidate how trehalose protects cells from anoxic injury, we assayed protein solubility and the amount of ubiquitinated proteins. There was three times more insoluble protein in HEK-v than in HEK-dtps1 after 3 days of exposure to low O2. The amount of Na+-K+ ATPase present in the insoluble proteins dramatically increased in HEK-v cells after 2 and 3 days of exposure, whereas there was no significant change in HEK-dtps1 cells. Ubiquitinated proteins increased dramatically in HEK-v cells after 2 and 3 days of exposure but not in HEK-dtps1 cells over the same period. Our results indicate that increased trehalose in mammalian cells following transfection by the Drosophila tps1 gene protects cells from hypoxic injury. The mechanism of this protection is likely related to a decrease in protein denaturation, through protein-trehalose interactions, resulting in enhanced cellular recovery from hypoxic stress.