Bombyx orcokinins are brain-gut peptides involved in the neuronal regulation of ecdysteroidogenesis.
Bombyx orcokinins are brain-gut peptides involved in the neuronal regulation of ecdysteroidogenesis.
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DOI：
10.1002/cne.22517
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发表时间：
2011-02-01
期刊：
影响因子：
--
通讯作者：
Tanaka Y
中科院分区：
文献类型：
--
作者：
Yamanaka N;Roller L;Zitňan D;Satake H;Mizoguchi A;Kataoka H;Tanaka Y
蜕皮激素是昆虫蜕皮和变态过程中控制基因表达的类固醇激素，其生物合成主要发生在前胸腺（PG）。PG的活性受多种神经肽的调节。在家蚕中，这些神经肽利用激素和神经元途径来调节PG的活性，使昆虫成为研究控制蜕皮甾体生物合成的复杂信号网络的极好模型系统。在这里，我们报告另一组神经肽，orcokinins，作为神经元prothoracotropic因子。使用与PG相关的轴突的直接质谱分析，我们检测到几个肽峰对应于orcokinin基因产物除了先前描述的Bommo-FMRFamides（BRFas）。原位杂交和免疫组织化学显示，orcokinins产生于腹神经节中突出的神经分泌细胞，以及在整个中枢神经系统和中肠内分泌细胞中的许多小神经元。前胸神经节中两对表达BRFa的神经分泌细胞之一共表达orcokinin，这些神经元通过横神经投射轴突并终止于PG表面。使用体外PG生物测定，我们表明orcokinins具有明确的prothoracotropic活性，并且能够取消BRFas对蜕皮激素生物合成的静态作用，而BRFas对cAMP产生的抑制作用在orcokinins存在下保持不变。在这些神经元中发现PG活性的第二个调节因子进一步说明了PG神经支配在昆虫发育调节中的潜在重要性。
Biosynthesis of ecdysteroids, the insect steroid hormones controlling gene expression during molting and metamorphosis, takes place primarily in the prothoracic gland (PG). The activity of the PG is regulated by various neuropeptides. In the silkworm Bombyx mori, these neuropeptides utilize both hormonal and neuronal pathways to regulate the activity of the PG, making the insect an excellent model system to investigate the complex signaling network controlling ecdysteroid biosynthesis. Here we report another group of neuropeptides, orcokinins, as neuronal prothoracicotropic factors. Using direct mass spectrometric profiling of the axons associated with the PG, we detected several peptide peaks which correspond to orcokinin gene products in addition to the previously described Bommo-FMRFamides (BRFas). In situ hybridization and immunohistochemistry revealed that orcokinins are produced in the prominent neurosecretory cells in the ventral ganglia, as well as in numerous small neurons throughout the central nervous system and in midgut endocrine cells. One of the two pairs of BRFa-expressing neurosecretory cells in the prothoracic ganglion coexpresses orcokinin, and these neurons project axons through the transverse nerve and terminate on the surface of the PG. Using an in vitro PG bioassay, we show that orcokinins have a clear prothoracicotropic activity and are able to cancel the static effect of BRFas on ecdysteroid biosynthesis, whereas the suppressive effect of BRFas on cAMP production remained unchanged in the presence of orcokinins. The discovery of a second regulator of PG activity in these neurons further illustrates the potential importance of the PG innervation in the regulation of insect development.