Oka Chio, Tsujimoto Rumi, Kajikawa Miwa, Koshiba-Takeuchi Kazuko, Ina Junko, Yano Masato, Tsuchiya Akiho, Ueta Yoshihumi, Soma Akinobu, Kanda Hidenobu, Matsumoto Michio, Kawaichi Masashi
Division of Gene Function in Animals, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan.
Development. 2004 Mar;131(5):1041-53. doi: 10.1242/dev.00999.
HtrA1, a member of the mammalian HtrA serine protease family, has a highly conserved protease domain followed by a PDZ domain. Because HtrA1 is a secretory protein and has another functional domain with homology to follistatin, we examined whether HtrA1 functions as an antagonist of Tgfbeta family proteins. During embryo development, mouse HtrA1 was expressed in specific areas where signaling by Tgfbeta family proteins plays important regulatory roles. The GST-pulldown assay showed that HtrA1 binds to a broad range of Tgfbeta family proteins, including Bmp4, Gdf5, Tgfbetas and activin. HtrA1 inhibited signaling by Bmp4, Bmp2, and Tgfbeta1 in C2C12 cells, presumably by preventing receptor activation. Experiments using a series of deletion mutants indicated that the binding activity of HtrA1 required the protease domain and a small linker region preceding it, and that inhibition of Tgfbeta signaling is dependent on the proteolytic activity of HtrA1. Misexpression of HtrA1 near the developing chick eye led to suppression of eye development that was indistinguishable from the effects of noggin. Taken together, these data indicate that HtrA1 protease is a novel inhibitor of Tgfbeta family members.
HtrA1是哺乳动物HtrA丝氨酸蛋白酶家族的成员，具有一个高度保守的蛋白酶结构域，其后是一个PDZ结构域。由于HtrA1是一种分泌蛋白，并且具有与卵泡抑素同源的另一个功能结构域，我们研究了HtrA1是否作为转化生长因子β（Tgfbeta）家族蛋白的拮抗剂发挥作用。在胚胎发育过程中，小鼠HtrA1在Tgfbeta家族蛋白信号传导起重要调节作用的特定区域表达。谷胱甘肽-S-转移酶（GST）下拉试验表明，HtrA1与多种Tgfbeta家族蛋白结合，包括骨形态发生蛋白4（Bmp4）、生长分化因子5（Gdf5）、转化生长因子β（Tgfbetas）和激活素。HtrA1可能通过阻止受体激活来抑制C2C12细胞中Bmp4、Bmp2和转化生长因子β1（Tgfbeta1）的信号传导。使用一系列缺失突变体的实验表明，HtrA1的结合活性需要蛋白酶结构域及其前面的一个小连接区域，并且对Tgfbeta信号的抑制取决于HtrA1的蛋白水解活性。在发育中的鸡眼附近错误表达HtrA1会导致眼发育受到抑制，这与头蛋白的作用难以区分。综上所述，这些数据表明HtrA1蛋白酶是Tgfbeta家族成员的一种新型抑制剂。
