Greenwood Mingkwan, Greenwood Michael Paul, Paton Julian F R, Murphy David
School of Clinical Sciences, University of Bristol, Bristol, England.
School of Physiology and Pharmacology, University of Bristol, Bristol, England.
PLoS One. 2015 Apr 27;10(4):e0124956. doi: 10.1371/journal.pone.0124956. eCollection 2015.
Arginine vasopressin (AVP) is synthesised in magnocellular neurons (MCNs) of supraoptic nucleus (SON) and paraventricular nucleus (PVN) of the hypothalamus. In response to the hyperosmotic stressors of dehydration (complete fluid deprivation, DH) or salt loading (drinking 2% salt solution, SL), AVP synthesis increases in MCNs, which over-burdens the protein folding machinery in the endoplasmic reticulum (ER). ER stress and the unfolded protein response (UPR) are signaling pathways that improve ER function in response to the accumulation of misfold/unfold protein. We asked whether an ER stress response was activated in the SON and PVN of DH and SL rats. We observed increased mRNA expression for the immunoglobulin heavy chain binding protein (BiP), activating transcription factor 4 (Atf4), C/EBP-homologous protein (Chop), and cAMP responsive element binding protein 3 like 1 (Creb3l1) in both SON and PVN of DH and SL rats. Although we found no changes in the splicing pattern of X box-binding protein 1 (Xbp1), an increase in the level of the unspliced form of Xbp1 (Xbp1U) was observed in DH and SL rats. CREB3L1, a novel ER stress inducer, has been shown to be activated by ER stress to regulate the expression of target genes. We have previously shown that CREB3L1 is a transcriptional regulator of the AVP gene; however, a role for CREB3L1 in the response to ER stress has yet to be investigated in MCNs. Here, we used lentiviral vectors to introduce a dominant negative form of CREB3L1 (CREB3L1DN) in the rat SON. Expression of CREB3L1DN in the SON decreased Chop and Xbp1U mRNA levels, but not BiP and Atf4 transcript expression. CREB3L1 is thus implicated as a transcriptional mediator of the ER stress response in the osmotically stimulated SON.
精氨酸加压素（AVP）在下丘脑视上核（SON）和室旁核（PVN）的大细胞神经元（MCNs）中合成。响应脱水（完全禁水，DH）或盐负荷（饮用2%盐溶液，SL）等高渗应激源时，MCNs中AVP的合成增加，这使内质网（ER）中的蛋白质折叠机制负担过重。内质网应激和未折叠蛋白反应（UPR）是响应错误折叠/未折叠蛋白积累而改善内质网功能的信号通路。我们研究了DH和SL大鼠的SON和PVN中是否激活了内质网应激反应。我们观察到，DH和SL大鼠的SON和PVN中免疫球蛋白重链结合蛋白（BiP）、激活转录因子4（Atf4）、C/EBP同源蛋白（Chop）和cAMP反应元件结合蛋白3样1（Creb3l1）的mRNA表达均增加。虽然我们未发现X盒结合蛋白1（Xbp1）的剪接模式有变化，但在DH和SL大鼠中观察到未剪接形式的Xbp1（Xbp1U）水平升高。CREB3L1是一种新型内质网应激诱导剂，已证明它可被内质网应激激活以调节靶基因的表达。我们之前已表明CREB3L1是AVP基因的转录调节因子；然而，CREB3L1在MCNs对内质网应激反应中的作用尚未得到研究。在此，我们使用慢病毒载体在大鼠SON中导入显性负性形式的CREB3L1（CREB3L1DN）。SON中CREB3L1DN的表达降低了Chop和Xbp1U的mRNA水平，但未降低BiP和Atf4的转录本表达。因此，CREB3L1被认为是渗透压刺激的SON中内质网应激反应的转录介质。
