Membrane expression of annexin I is enhanced by calcium and TPA in cultured human keratinocytes |
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Authors: | K. C. Sato-Matsumura T. Matsumura H. Nakamura H. Sawa K. Nagashima H. Koizumi |
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Affiliation: | (1) Department of Dermatology, Hokkaido University School of Medicine, Kita 15, Nishi 7, Kita-ku, Sapporo, 060-8638, Japan Tel.: +81-11-7161161, Fax: +81-11-7067820, JP;(2) Department of Pathology, Hokkaido University School of Medicine, Kita 15, Nishi 7, Kita-ku, Sapporo, 060-8638, Japan, JP |
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Abstract: | Abstract Annexin I plays an important role in the process of keratinization as a component of the cornified envelope. To elucidate the function of annexin I in keratinization, we investigated the effects of calcium, epinephrine, hydrocortisone, and 12-O-tetradecanoyl phorbol 13-acetate (TPA) on the expression and localization of annexin I in cultured human keratinocytes. Normal human keratinocytes were cultured in serum-free culture medium (0.15 mM calcium) until 70% confluence. After incubation with a higher concentration of calcium (1.8 mM), TPA (100 nM), epinephrine (50 ìM), or hydrocortisone (10 ìM) for 24 h, the expression of annexin I protein and mRNA was examined using immunofluorescence, Western blot, and Northern blot techniques. Immunofluorescence microscopy showed increased membrane staining of annexin I by calcium, which was inhibited by the addition of epinephrine or hydrocortisone. Western blotting confirmed elevated annexin I on the cell membrane. It was increased in the cell membrane fraction, but not in the cytosol fraction. Interestingly, the mRNA level of annexin I was slightly reduced after incubation with calcium, whereas TPA upregulated both membrane expression and the mRNA level. Secretion of annexin I was increased by TPA but inhibited by calcium. Because calcium and TPA are known to promote keratinization, our data suggest that annexin I expression on the cell membrane is involved in the process of keratinization. Received: 23 March 2000 / Revised: 14 June 2000 / Accepted: 21 July 2000 |
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Keywords: | Keratinization Cornified envelope 12-O-Tetradecanoyl phorbol 13-acetate (TPA) Epinephrine |
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