A 33 kDa protein band is enhanced during long-term adaptation of EUE cells to a hypertonic medium

A cell line derived from human embryonic epithelium (EUE cells) shows an enhanced expression of a 33 kDa protein when adapted to grow in a hypertonic medium containing 0.246 M NaCl (1.8 x the isotonic concentration). The maximum amount of this protein, followed by SDS-PAGE electrophoresis, was found after 4 days of adaptation; thereafter, the protein band remained fairly constant up to 30 days. When the cells were transferred back to a medium containing 0.137 M NaCl (isotonic medium), the protein pattern reverted to that of control cells. This protein is mainly localized in the cytosol, although a small part is associated with the 150,000 g pellet and needs detergents to be extracted. The molecular weight and the cellular location suggest a possible analogy with the so-called amphitropic proteins, that are known to interact with both the epidermal growth factor receptor and hydrophobic structures, such as the membrane phospholipids and the cytoskeletal components.