The Role of Late Embryogenesis-Abundant Proteins in Desiccation-Induced Apoptosis

Encysted embryos of the brine shrimp Artemia franciscana survive extreme water loss by expressing the late embryogenesis abundant (LEA) protein AfLEA1.3 and the moss Physcomitrella patens expresses PpDHNA under conditions of dehydration. I investigated the impact of transgenic expression of PpDHNA and AfLEA1.3 on the metabolism of mammalian cells exposed to 0.5 M sucrose. The gene PpDHNA was transgenically expressed in human embryonic kidney (HEK) cells and AfLEA1.3 was cloned into human hepatocellular carcinoma (HepG2) cells. Calorimetry was utilized to measure the metabolic activity of both cell lines. HEK cells showed a metabolic output of -24.1 ± 2.04 (SD) μW per million cells, independent of the presence of the transgene (HEK-PpDHNA: -22.9 ± 2.44 μW). Metabolic heat flow was reduced by 0.5 M sucrose in HEK and HEK-PpDHNA cells to -15.4 ± 2.13 μW and -17.9 ± 1.93 μW, respectively. The average heat flows in HepG2 under control and osmotic stress conditions were -27.2 ± 1.75 μW and -23.3 ± 1.13 μW, respectively. HepG2-AfLEA1.3 cells showed an average heat output of -35.1 ± 4.27 μW in control medium, while HepG2-AfLEA1.3 in sucrose medium was -24.03 ± 1.14 μW. The average output for HepG2-AfLEA 1.3 cells in control medium after gene induction was -24.5 ± 1.86 μW, while heat flow after exposure to 0.5 M sucrose was -24.4 ± 1.65 μW. These results show that PpDHNA did not impact performance of HEK cells under osmotic stress, while AfLEA1.3 might play a role in preservation of cell metabolism under conditions of osmotic stress