Translational Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK.
Health Care Center, Kochi University, Kochi, Japan.
J Neuroendocrinol. 2020 Apr;32(4):e12851. doi: 10.1111/jne.12851. Epub 2020 Apr 21.
Transcription factor cAMP responsive element-binding protein 3 like 1 (Creb3l1) is a non-classical endoplasmic reticulum stress molecule that is emerging as an important component for cellular homeostasis, particularly within cell types with high peptide secretory capabilities. We have previously shown that Creb3l1 serves an important role in body fluid homeostasis through its transcriptional control of the gene coding for antidiuretic hormone arginine vasopressin in the neuropeptide-rich magnocellular neurones of the supraoptic nucleus. In response to osmotic stimuli such as dehydration, vasopressin magnocellular neurones undergo remarkable transcriptome changes, including increased Creb3l1 expression, to ensure that the supply of vasopressin meets demand. To determine where else Creb3l1 fits into the secretory cell supply chain, we performed RNA-sequencing of Creb3l1 knockdown anterior pituitary mouse corticotroph cell line AtT20. The target chosen for further investigation was Pcsk1, which encodes proprotein convertase enzyme 1 (PC1/3). PC1/3 is crucial for processing of neuropeptides and peptide hormones such as pro-opiomelanocortin (POMC), proinsulin, proglucagon, vasopressin and oxytocin. Viral manipulations in supraoptic nuclei by over-expression of Creb3l1 increased Pcsk1, whereas Creb3l1 knockdown decreased Pcsk1 expression. In vitro promoter activity and binding studies showed that Creb3l1 was a transcription factor of the Pcsk1 gene binding directly to a G-box motif in the promoter. In the dehydrated rat anterior pituitary, Creb3l1 and Pcsk1 expression decreased in parallel compared to control, supporting our findings from manipulations in AtT20 cells and the supraoptic nucleus. No relationship was observed between Creb3l1 and Pcsk1 expression in the neurointermediate lobe of the pituitary, indicating a different mechanism of PC1/3 synthesis by these POMC-synthesising cells. Therefore, Creb3l1, by regulating the expression of Pcsk1, does not control the processing of POMC peptides in the intermediate lobe.
转录因子 cAMP 反应元件结合蛋白 3 样 1（Creb3l1）是一种非经典内质网应激分子，作为细胞内稳态的重要组成部分，特别是在具有高肽分泌能力的细胞类型中。我们之前已经表明，Creb3l1 通过其对神经垂体富含神经肽的大细胞神经元中编码抗利尿激素精氨酸血管加压素的基因的转录控制，在体液内稳态中发挥重要作用。响应于渗透压刺激，如脱水，血管加压素大细胞神经元经历显著的转录组变化，包括增加 Creb3l1 表达，以确保血管加压素的供应满足需求。为了确定 Creb3l1 还适合分泌细胞供应链的哪个位置，我们对 Creb3l1 敲低的垂体前叶小鼠 corticotroph 细胞系 AtT20 进行了 RNA 测序。选择进一步研究的目标是 Pcsk1，它编码蛋白水解酶 1（PC1/3）的前蛋白转化酶。PC1/3 对于神经肽和肽激素如 pro-opiomelanocortin (POMC)、胰岛素原、胰高血糖素原、血管加压素和催产素的加工至关重要。通过过度表达 Creb3l1 在神经垂体中进行病毒操作增加了 Pcsk1，而 Creb3l1 敲低降低了 Pcsk1 的表达。体外启动子活性和结合研究表明，Creb3l1 是 Pcsk1 基因的转录因子，直接结合到启动子中的 G 框基序上。在脱水大鼠垂体前叶中，与对照相比，Creb3l1 和 Pcsk1 的表达呈平行下降，这支持了我们在 AtT20 细胞和神经垂体中进行的操作的发现。在垂体中间叶中未观察到 Creb3l1 和 Pcsk1 表达之间的关系，表明这些 POMC 合成细胞中 PC1/3 合成的不同机制。因此，Creb3l1 通过调节 Pcsk1 的表达，不控制中间叶中 POMC 肽的加工。
