ANNEXIN-I REGULATION IN HUMAN EPIDERMAL-CELLS

Annexin 1 (named p35, lipocortin I or calpactin II), initially describ ed as a glucocorticoid induced protein, belongs to a new characterized family of intracellular proteins. In the skin, the role of annexins h as still not been elucidated. In a previous study, we reported the loc alization of annexin 1 in both freshly isolated human epidermal cells and in cultured keratinocytes using immunofluorescence, FACS analysis and immunoblotting techniques. The protein was characterized by Wester n blot and immunoprecipitation as a 35 kDa protein. Results from in vi vo studies confirmed the presence of annexin 1 in basal and suprabasal layers of normal human skin with modified reactivity patterns in hype rproliferative lesions. In the present study, the role of glucocortico ids in annexin 1 regulation was investigated in epidermal cells by Wes tern blot and immunoprecipation assays. In contrast to other studies, we found that glucocorticoid treatment of epidermal cells led to a dec rease in annexin 1 content in the cytoplasm and the membranes of cells . As annexin 1 was not detected in the nucleus of cells, we conclude t hat there was a down regulation of annexin 1 after glucocorticoid trea tments rather than a translocation of the protein to the nucleus. Desp ite the absence of the signal peptide sequence necessary for protein s ecretion, annexin 1 was released in the keratinocyte culture medium. W e found that the protein was secreted only in low Ca2+ medium (0.15 mM ), this process required an active metabolism.