Department of Biology, National Museum of Natural Science, 1 Kuan-Chien Road, Taichung, Taiwan 404, ROC.
Department of Biology, National Museum of Natural Science, 1 Kuan-Chien Road, Taichung, Taiwan 404, ROC.
J Insect Physiol. 2023 Sep;149:104548. doi: 10.1016/j.jinsphys.2023.104548. Epub 2023 Jul 21.
In the present study, we investigated downstream pathways of cyclic adenosine monophosphate (cAMP) signaling (which is related to prothoracicotropic hormone (PTTH)-stimulated ecdysteroidogenesis) in Bombyx mori prothoracic glands (PGs). Results showed that treatment with either dibutyryl cAMP (dbcAMP) or 1-methyl-3-isobutylxanthine (MIX) inhibited phosphorylation of adenosine 5'-monophosphate-activated protein kinase (AMPK) and activated phosphorylation of the translational repressor, 4E-binding protein (4E-BP), a marker of target of rapamycin (TOR) signaling. A chemical activator of AMPK (5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside, AICAR) increased dbcAMP-inhibited AMPK phosphorylation and blocked dbcAMP-stimulated phosphorylation of 4E-BP, indicating that inhibition of AMPK phosphorylation lies upstream of dbcAMP-stimulated TOR signaling. Treatment of PGs with dbcAMP and MIX also stimulated phosphorylation of a 37-kDa protein, as recognized by a protein kinase C (PKC) substrate antibody, indicating that cAMP activates PKC signaling. Treatment with either LY294002 or AICAR did not affect dbcAMP-stimulated phosphorylation of the PKC-dependent 37-kDa protein, indicating that cAMP-stimulated PKC signaling is not related to phosphoinositide 3-kinase (PI3K) or AMPK. In addition, dbcAMP-stimulated ecdysteroidogenesis in PGs was partially inhibited by pretreatment with either LY294002, AICAR, or calphostin C. From these results, we concluded that AMPK/TOR/4E-BP and PKC pathways are involved in ecdysteroidogenesis of PGs stimulated by cAMP signaling in B. mori.
在本研究中，我们研究了环腺苷酸 (cAMP) 信号转导（与促前胸腺激素 (PTTH) 刺激蜕皮甾类生成有关）在家蚕前胸腺 (PG) 中的下游途径。结果表明，用二丁酰环腺苷酸 (dbcAMP) 或 1-甲基-3-异丁基黄嘌呤 (MIX) 处理抑制了腺苷 5'-单磷酸激活蛋白激酶 (AMPK) 的磷酸化，并激活了翻译抑制剂 4E 结合蛋白 (4E-BP) 的磷酸化，这是雷帕霉素 (TOR) 信号的标志物。AMPK 的化学激活剂 (5-氨基咪唑-4-羧酰胺-1-β-D-呋喃核糖苷，AICAR) 增加了 dbcAMP 抑制的 AMPK 磷酸化并阻断了 dbcAMP 刺激的 4E-BP 磷酸化，表明 AMPK 磷酸化的抑制位于 dbcAMP 刺激的 TOR 信号之前。用 dbcAMP 和 MIX 处理 PG 也刺激了一种 37 kDa 蛋白的磷酸化，该蛋白被蛋白激酶 C (PKC) 底物抗体识别，表明 cAMP 激活了 PKC 信号转导。用 LY294002 或 AICAR 处理并不影响 dbcAMP 刺激的 PKC 依赖性 37 kDa 蛋白的磷酸化，表明 cAMP 刺激的 PKC 信号与磷酸肌醇 3-激酶 (PI3K) 或 AMPK 无关。此外，用 LY294002、AICAR 或 calphostin C 预处理部分抑制了 dbcAMP 刺激的 PG 中蜕皮甾类的生成。根据这些结果，我们得出结论，AMPK/TOR/4E-BP 和 PKC 途径参与了 cAMP 信号在家蚕 PG 中刺激的蜕皮甾类生成。
