Lehen'kyi V'yacheslav, Beck Benjamin, Polakowska Renata, Charveron Maria, Bordat Pascal, Skryma Roman, Prevarskaya Natalia
Inserm, U-800, Equipe Labellisée par la Ligue Nationale Contre le Cancer, Université des Sciences et Technologies de Lille, F-59655 Villeneuve d'Ascq, France.
J Biol Chem. 2007 Aug 3;282(31):22582-91. doi: 10.1074/jbc.M611398200. Epub 2007 Jun 5.
Ca(2+) is an essential factor inducing keratinocyte differentiation due to the natural Ca(2+) gradient in the skin. However, the membrane mechanisms that mediate calcium entry and trigger keratinocyte differentiation had not previously been elucidated. In this study we demonstrate that Ca(2+)-induced differentiation up-regulates both mRNA and protein expression of a transient receptor potential highly Ca(2+)-selective channel, TRPV6. The latter mediates Ca(2+) uptake and accounts for the basal Ca(2+) in human keratinocytes. Our results show that TRPV6 is a prerequisite for keratinocyte entry into differentiation, because the silencing of TRPV6 in human primary keratinocytes led to the development of impaired differentiated phenotype triggered by Ca(2+). The expression of such differentiation markers as involucrin, transglutaminase-1, and cytokeratin-10 was significantly inhibited by small interfering RNA-TRPV6 as compared with differentiated control cells. TRPV6 silencing affected cell morphology and the development of intercellular contacts, as well as the ability of cells to stratify. 1,25-Dihydroxyvitamin D3, a cofactor of differentiation, dose-dependently increased TRPV6 mRNA and protein expression in human keratinocytes. This TRPV6 up-regulation led to a significant increase in Ca(2+) uptake in both undifferentiated and differentiated keratinocytes. We conclude that TRPV6 mediates, at least in part, the pro-differentiating effects of 1,25-dihydroxyvitamin D3 by increasing Ca(2+) entry, thereby promoting differentiation. Taken together, these data suggest that the TRPV6 channel is a key element in Ca(2+)/1,25-dihydroxyvitamin D3-induced differentiation of human keratinocytes.
由于皮肤中天然存在的钙离子梯度，钙离子是诱导角质形成细胞分化的重要因素。然而，此前尚未阐明介导钙离子内流并触发角质形成细胞分化的膜机制。在本研究中，我们证明钙离子诱导的分化上调了一种瞬时受体电位高钙离子选择性通道TRPV6的mRNA和蛋白表达。后者介导钙离子摄取并决定人角质形成细胞中的基础胞内钙离子浓度。我们的结果表明，TRPV6是角质形成细胞进入分化状态的前提条件，因为在人原代角质形成细胞中沉默TRPV6会导致由钙离子触发的分化表型受损。与分化的对照细胞相比，小干扰RNA-TRPV6显著抑制了诸如兜甲蛋白、转谷氨酰胺酶-1和细胞角蛋白-10等分化标志物的表达。TRPV6沉默影响细胞形态、细胞间连接的形成以及细胞分层的能力。1,25-二羟维生素D3作为分化的辅助因子，剂量依赖性地增加人角质形成细胞中TRPV6的mRNA和蛋白表达。这种TRPV6的上调导致未分化和已分化角质形成细胞中钙离子摄取均显著增加。我们得出结论，TRPV6至少部分地通过增加钙离子内流介导1,25-二羟维生素D3的促分化作用，从而促进分化。综上所述，这些数据表明TRPV6通道是钙离子/1,25-二羟维生素D3诱导人角质形成细胞分化的关键要素。
