Department of Biology, National Museum of Natural Science, Taichung, Taiwan.
Chung Hwa University of Medical Technology, Tainan, Taiwan.
Insect Mol Biol. 2021 Oct;30(5):497-507. doi: 10.1111/imb.12720. Epub 2021 Jun 14.
It is well known that phosphorylation of extracellular signal-regulated kinase (ERK) is involved in prothoracicotropic hormone (PTTH)-stimulated ecdysteroidogenesis in insect prothoracic glands (PGs). In the present study, we further investigated the downstream signalling pathways. Our results showed that PTTH stimulated p90 ribosomal S6 kinase (RSK) phosphorylation at Thr573 in Bombyx mori PGs both in vitro and in vivo. The in vitro PTTH stimulation was stage- and dose-dependent. The absence of Ca reduced PTTH-stimulated RSK phosphorylation. Stimulation of RSK phosphorylation was also observed after treatment with either A23187 or thapsigargin. A phospholipase C (PLC) inhibitor, U73122, blocked PTTH-stimulated RSK phosphorylation. These results indicate the involvement of Ca and PLC. Treatment with diphenylene iodonium (DPI), a mitochondrial oxidative phosphorylation inhibitor, blocked PTTH-regulated RSK phosphorylation, indicating its redox regulation. A mitogen-activated protein kinase (MAPK)/ERK kinase (MEK) inhibitor, U0126, but not a phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002, decreased PTTH-stimulated RSK phosphorylation, indicating that ERK is an upstream signalling. A protein kinase C (PKC) inhibitor, chelerythrine C, inhibited PTTH-stimulated RSK phosphorylation, and a PKC activator, phorbol 12-myristate acetate (PMA) stimulated RSK phosphorylation, indicating the involvement of PKC. BI-D1870, a specific RSK inhibitor, partly prevented PTTH-stimulated RSK phosphorylation and significantly inhibited PTTH-stimulated ecdysteroid secretion, indicating that PTTH-stimulated RSK phosphorylation is involved in ecdysteroidogenesis. Taken together, these data indicate that PTTH activates RSK phosphorylation which plays important roles in PTTH-stimulated ecdysteroidogenesis.
众所周知，细胞外信号调节激酶（ERK）的磷酸化参与了昆虫前胸腺（PG）中促前胸腺激素（PTTH）刺激的蜕皮甾酮生成。在本研究中，我们进一步研究了下游信号通路。我们的结果表明，PTTH 在体外和体内均刺激家蚕 PG 中 p90 核糖体 S6 激酶（RSK）在 Thr573 处的磷酸化。体外 PTTH 刺激具有阶段和剂量依赖性。Ca 的缺失减少了 PTTH 刺激的 RSK 磷酸化。在用 A23187 或 thapsigargin 处理后，也观察到 RSK 磷酸化的刺激。PLC 抑制剂 U73122 阻断了 PTTH 刺激的 RSK 磷酸化。这些结果表明 Ca 和 PLC 的参与。用二苯基碘鎓（DPI）处理，一种线粒体氧化磷酸化抑制剂，阻断了 PTTH 调节的 RSK 磷酸化，表明其氧化还原调节。丝裂原活化蛋白激酶（MAPK）/ERK 激酶（MEK）抑制剂 U0126，但不是磷脂酰肌醇 3-激酶（PI3K）抑制剂 LY294002，降低了 PTTH 刺激的 RSK 磷酸化，表明 ERK 是上游信号。蛋白激酶 C（PKC）抑制剂 Chelerythrine C 抑制了 PTTH 刺激的 RSK 磷酸化，而 PKC 激活剂佛波醇 12-肉豆蔻酸酯（PMA）刺激了 RSK 磷酸化，表明 PKC 的参与。特异性 RSK 抑制剂 BI-D1870 部分阻止了 PTTH 刺激的 RSK 磷酸化，并显著抑制了 PTTH 刺激的蜕皮甾酮分泌，表明 PTTH 刺激的 RSK 磷酸化参与了蜕皮甾酮生成。综上所述，这些数据表明，PTTH 激活了 RSK 磷酸化，这在家蚕 PG 中发挥了重要作用。PTTH 刺激的蜕皮甾酮生成。
