Regulated redistribution of calretinins in WiDr cells

The calcium-binding protein calretinin and the alternatively spliced form calretinin-22k are expressed in the colon adenocarcinoma cell line WiDr. As calcium-binding proteins have been implicated to play a role in cell cycle control, proliferation and differentiation, the levels and intracellular localisation of these two proteins were investigated. The addition of 1,25-dihydroxy vitamin D3 (10(-8) M) led to a transient translocation of calretinin-22k into the nucleus, while the cell growth was not affected. The addition of sodium butyrate and hexamethylene bisacteamide which induce markers of enterocyte differentiation decreased the levels of both forms of calretinin more than 90%. The agents which induced differentiation also led to a substantial inhibition of 3H-thymidine incorporation (>95%) which was paralleled by the disappearance of calretinins. We conclude that calretinin and calretinin-22k are associated with the proliferative status of WiDr cells and are almost completely absent in differentiated cells.