LeMosy E K, Kemler D, Hashimoto C
Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520-8002, USA.
Development. 1998 Oct;125(20):4045-53. doi: 10.1242/dev.125.20.4045.
The establishment of embryonic dorsoventral polarity in Drosophila depends on a signaling mechanism in which the signal for ventral development is locally produced. This mechanism requires the activity of the nudel gene in ovarian follicle cells, which provide dorsoventral positional information for the embryo. The nudel gene product, a large mosaic protein with a central serine protease domain, has been proposed to function in locally triggering a protease cascade that produces the ventral signal. Here we provide evidence that the serine protease activity of the Nudel protein is essential for embryonic dorsoventral polarity and that the active Nudel protease is generated by autoproteolytic cleavage of a zymogen form. Activation of the Nudel protease is independent of the other known proteases involved in dorsoventral polarity establishment and appears to occur symmetrically on the surface of the embryo. Our findings suggest that Nudel protease activation initiates the protease cascade that produces the ventral signal, but that spatial regulation occurring downstream of Nudel protease activation localizes the cascade to the ventral side of the embryo.
果蝇胚胎背腹极性的建立依赖于一种信号传导机制，其中腹侧发育信号是局部产生的。这种机制需要卵巢滤泡细胞中nudel基因的活性，该基因可为胚胎提供背腹位置信息。nudel基因产物是一种具有中央丝氨酸蛋白酶结构域的大型镶嵌蛋白，有人提出它在局部触发产生腹侧信号的蛋白酶级联反应中发挥作用。在此我们提供证据表明，Nudel蛋白的丝氨酸蛋白酶活性对于胚胎背腹极性至关重要，并且活性Nudel蛋白酶是由酶原形式的自蛋白水解切割产生的。Nudel蛋白酶的激活独立于参与背腹极性建立的其他已知蛋白酶，并且似乎在胚胎表面对称发生。我们的研究结果表明，Nudel蛋白酶激活启动了产生腹侧信号的蛋白酶级联反应，但Nudel蛋白酶激活下游发生的空间调节将该级联反应定位在胚胎的腹侧。
