Cholesterol modification is necessary for controlled planar long-range activity of Hedgehog in Drosophila epithelia
Cholesterol modification is necessary for controlled planar long-range activity of Hedgehog in Drosophila epithelia
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DOI：
10.1242/dev.02212
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发表时间：
2006-02-01
期刊：
影响因子：
4.6
通讯作者：
Thérond, PR
中科院分区：
文献类型：
--
作者：
Gallet, A;Ruel, L;Thérond, PR
Hedgehog形态原是一种主要的发育调节因子，在短期和长期内起作用，指导无脊椎动物和脊椎动物组织中细胞命运的决定。Hedgehog是已知的唯一具有共价连接胆固醇部分的后生动物蛋白质。虽然刺猬的胆固醇基团的作用尚不清楚，但它在果蝇中的长期活动被认为是可有可无的。在这里，我们提供了三种不同的上皮-腹侧和背侧胚胎外胚层以及幼虫想象盘组织的数据-表明胆固醇修饰实际上是果蝇刺猬受控长期活动所必需的。我们通过显示未经修饰的HH只有在鳞状细胞中表达时才能在远距离发挥作用，尽管是以一种不受控制的方式，从而解释了我们的结果与以前的报告之间的差异。我们的数据显示，胆固醇修饰在多个水平上控制着远程HH活动。首先，胆固醇增加了HH对质膜的亲和力，从而增强了其在体外和体内的表观内在活性。此外，活性HH的多聚体需要胆固醇的存在。这些多聚体与体内活性HH梯度中存在的HH组装成位于顶端的大的点状结构相关。通过比较胆固醇修饰的HH在柱状上皮细胞和足周鳞状细胞中的活性，我们发现上皮细胞为HH的受控平面运动提供了必要的机械，从而防止了蛋白质在上皮细胞三维空间内的不受限制的扩散。我们的结论是，与脊椎动物一样，胆固醇修饰对于果蝇受控的远程HH信号是必不可少的。
The Hedgehog morphogen is a major developmental regulator that acts at short and long range to direct cell fate decisions in invertebrate and vertebrate tissues. Hedgehog is the only known metazoan protein to possess a covalently linked cholesterol moiety. Although the role of the cholesterol group of Hedgehog remains unclear, it has been suggested to be dispensable for the its long-range activity in Drosophila. Here, we provide data in three different epithelia-ventral and dorsal embryonic ectoderm, and larval imaginal disc tissue-showing that cholesterol modification is in fact necessary for the controlled long-range activity of Drosophila Hedgehog. We provide an explanation for the discrepancy between our results and previous reports by showing that unmodified Hh can act at long range, albeit in an uncontrolled manner, only when expressed in squamous cells. Our data show that cholesterol modification controls long-range Hh activity at multiple levels. First, cholesterol increases the affinity of Hh for the plasma membrane, and consequently enhances its apparent intrinsic activity, both in vitro and in vivo. In addition, multimerisation of active Hh requires the presence of cholesterol. These multimers are correlated with the assembly of Hh into apically located, large punctate structures present in active Hh gradients in vivo. By comparing the activity of cholesterol-modified Hh in columnar epithelial cells and peripodial squamous cells, we show that epithelial cells provide the machinery necessary for the controlled planar movement of Hh, thereby preventing the unrestricted spreading of the protein within the three-dimensional space of the epithelium. We conclude that, as in vertebrates, cholesterol modification is essential for controlled long-range Hh signalling in Drosophila.