Gosselet Fabien P, Magnaldo Thierry, Culerrier Raphaël M, Sarasin Alain, Ehrhart Jean-Claude
Laboratory of Genomes and Cancers, FRE 2939 CNRS, Institut Gustave Roussy-PR2, 39 rue Camille Desmoulins, 94805 Villejuif, France.
Cell Signal. 2007 Apr;19(4):731-9. doi: 10.1016/j.cellsig.2006.09.006. Epub 2006 Oct 4.
Functional studies of the canonical Bone Morphogenetic Protein (BMP) signalling pathway in human epidermal keratinocytes have been limited to the immortalized and p53-mutated HaCaT cells and are primarily dependent on BMP6 treatment in mouse epidermal keratinocytes. Despite these insightful analyses, the molecular mechanism underlying the role of BMP signalling in the precise balance between growth arrest and terminal differentiation of keratinocytes still remains not clearly defined. The current study first investigated the hitherto uncharacterized status and functions of BMP signalling in normal human keratinocytes by using three independent strains of primary interfollicular epidermal keratinocytes. Then we provided data demonstrating the role of BMP2 compared to BMP6 in the inhibition of growth and induction of subsequent terminal differentiation of these cells. A second relevant finding is based on the clonal analysis of colony types present in untreated and BMP2/6-treated cultures in absence of EGF. BMP treatment results in the clonal transition from proliferative to abortive colonies, suggesting that BMP signalling most likely inhibits stem cell proliferation and triggers cell cycle exit from transit amplifying cells. Third, we showed evidence that, of the three members of the Cip/Kip family of cyclin-dependent kinase inhibitors, only p57(Kip2) and p21(Cip1) have a BMP2/6-induced expression. One mechanism of inhibition of cell proliferation involves p57(Kip2) as an immediate early response, in contradistinction with p21(Cip1) which largely depends on de novo protein synthesis for its effect to proceed. All together, these results clarify the BMP signalling status in normal primary human keratinocytes and support a new mechanism of inhibition of the proliferation of interfollicular epidermal keratinocytes coupled with induction of their terminal differentiation following BMP2 or BMP6 addition.
对人表皮角质形成细胞中经典骨形态发生蛋白（BMP）信号通路的功能研究仅限于永生化且p53突变的HaCaT细胞，并且主要依赖于对小鼠表皮角质形成细胞的BMP6处理。尽管有这些深入的分析，但BMP信号在角质形成细胞生长停滞和终末分化的精确平衡中所起作用的分子机制仍未明确界定。本研究首先通过使用三株独立的初级毛囊间表皮角质形成细胞，研究了BMP信号在正常人角质形成细胞中迄今未被描述的状态和功能。然后我们提供的数据表明，与BMP6相比，BMP2在抑制这些细胞生长和诱导其随后的终末分化方面的作用。第二个相关发现基于在无表皮生长因子（EGF）的情况下，对未处理和BMP2/6处理的培养物中存在的菌落类型进行克隆分析。BMP处理导致从增殖性菌落向流产菌落的克隆转变，这表明BMP信号很可能抑制干细胞增殖并触发过渡增殖细胞退出细胞周期。第三，我们证明，在细胞周期蛋白依赖性激酶抑制剂Cip/Kip家族的三个成员中，只有p57（Kip2）和p21（Cip1）具有BMP2/6诱导的表达。抑制细胞增殖的一种机制涉及p57（Kip2）作为即时早期反应，这与p21（Cip1）相反，后者在很大程度上依赖于从头合成蛋白质来发挥其作用。总之，这些结果阐明了正常人原代角质形成细胞中的BMP信号状态，并支持一种新的机制，即添加BMP2或BMP6后抑制毛囊间表皮角质形成细胞的增殖并诱导其终末分化。
