While MARVEL domain-containing protein 1 (MARVELD1) is widely expressed in normal tissue, its expression is decreased in tumor tissue. Importin-β1 is a kind of nucleocytoplasmic transport protein, which participates in protein transportation between the nucleus and cytoplasm. It has been known that MARVELD1 binds importin-β1. To define the biological functions of the binding between MARVELD1 and importin-β1, confocal laser scanning microscopy was applied to confirm the distribution of MARVELD1 in the cells when importin-β1, is knocked down, and the results show that MARVELD1's concentration is decreased in the nucleus and elevated in the cytoplasm. GST-pull down and western blot were applied to test the binding affinity between the normal importin-β1, and several truncations of MARVELD1, and the binding affinity between the normal MARVELD1 and several truncations of importin-β1. These results show that there exist several binding points between MARVELD1 and importin-β1. Basing on these results one can come to a conclusion that importin-β1 mediates the non-classical nucleocytoplasmic transportation of MARVELD1. It was also found that knockdown of importin-β1, leads to an increase in the total density of MARVELD1. Considering the abnormally reduced expression of MARVELD1 in tumor tissue, the results of this study will help gaining a better understanding of the roles of MARVELD1 in the signal network systems during tumorigenesis in cancer cells.
Keywords: MARVELD1; importin-β1; nucleocytoplasmic transportation; protein-protein interaction.