Specific decrease in the level of Hic-5, a focal adhesion protein, during immortalization of mouse embryonic fibroblasts, and its association with focal adhesion kinase

Hic-5 is a paxillin homologue with four LIM domains in its C-terminal regio n, localized mainly in focal adhesions in normal fibroblasts. Hic-5 is also known to associate with focal adhesion kinase (FAK) or the related CAK bet a, and with vinculin. In the present study, we examined changes in Hic-5 an d paxillin protein levels in primary mouse embryo fibroblasts (MEF) during mortal and immortal stages. The Hic-5 level was markedly decreased when cel ls became immortalized, whereas that of paxillin was increased. The vinculi n level was not changed significantly. Hic-5 was mainly localized in focal adhesion plaques of mortal MEF but was localized in the nuclear periphery i n the immortalized MEF; the number of focal adhesion plaques was decreased in these cells. Mouse Hic-5 contains three LD domains in its N-terminal hal f, and the first LD domain (LD1) appears to be involved in interaction with FAK. However, this interaction was not essential for recruitment of Hic-5 to focal adhesions, since its subcellular localization was similar in FAK-/ - cells. Forced expression of Hic-5 decreased colony forming ability of MEF from FAK(+/+) mice, but not of FAK(-/-) cells. These observations suggeste d the involvement of Hic-5 in determination of cellular proliferative capac ity in collaboration with other cytoskeletal components. (C) 2000 Wiley-Lis s, Inc.