Rearick J I, Albro P W, Jetten A M
Laboratory Pulmonary Pathobiology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
J Biol Chem. 1987 Sep 25;262(27):13069-74.
It has previously been demonstrated that rabbit tracheal epithelial cells in primary culture undergo terminal differentiation at confluence to yield cornified cells much in analogy to epidermal keratinocytes and that one biochemical marker of this process seems to be the accumulation of cholesterol sulfate by the cells. The current work addresses the possible causes of this accumulation. Our studies show that the stimulation of cholesterol sulfate is paralleled by an increased activity of the biosynthetic enzyme cholesterol sulfotransferase. Squamous differentiated cells exhibited 20- to 30- fold higher levels of this enzyme activity than that in undifferentiated cells. As with other markers of squamous cell differentiation, the increase in cholesterol sulfotransferase can be prevented by the inclusion of retinoids in the cell culture medium. Inhibition of sulfotransferase levels can be observed at concentration of retinoic acid as low as 10(-11) M. The enzyme activity is optimal at pH 7 in buffers containing 0.2 M NaCl and 0.01% Triton X-100. Apparent Michaelis constants for the substrates 3'-phosphoadenosine-5'-phosphosulfate and cholesterol are 1 microM and 0.6 mM, respectively. Our results indicate that the increase in cholesterol sulfotransferase is the proximate cause for the accumulation of cholesterol sulfate in rabbit tracheal epithelial cells during squamous cell differentiation.
先前已经证明，原代培养的兔气管上皮细胞在汇合时会经历终末分化，产生角质化细胞，这与表皮角质形成细胞非常相似，并且这个过程的一个生化标志物似乎是细胞内硫酸胆固醇的积累。目前的工作探讨了这种积累的可能原因。我们的研究表明，硫酸胆固醇的积累伴随着生物合成酶胆固醇硫酸转移酶活性的增加。鳞状分化细胞中这种酶的活性水平比未分化细胞高20到30倍。与鳞状细胞分化的其他标志物一样，在细胞培养基中加入视黄醇可以阻止胆固醇硫酸转移酶的增加。在低至10(-11)M的视黄酸浓度下即可观察到硫酸转移酶水平的抑制。在含有0.2M NaCl和0.01% Triton X-100的缓冲液中，该酶的活性在pH 7时最佳。底物3'-磷酸腺苷-5'-磷酸硫酸酯和胆固醇的表观米氏常数分别为1 microM和0.6 mM。我们的结果表明，胆固醇硫酸转移酶的增加是兔气管上皮细胞在鳞状细胞分化过程中硫酸胆固醇积累的直接原因。
