Transcription factor Creb3l1 regulates the synthesis of prohormone convertase enzyme PC1/3 in endocrine cells

Abstract

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.

Gsα-dependent signaling is required for postnatal establishment of a functional β-cell mass

“…At p28, β-GsαKO islets contained less Creb protein and displayed lower Creb phosphorylation (relative to total Creb) than controls ( Figure 4 C). Our prior results showing downregulation of Ccna2 , Mafa, and Pcsk1 in p28 β-GsαKO islets (see Figure 2 , Figure 3 A) reinforce this finding, as these genes have been reported to be direct Creb targets [ 15 , 36 , 37 ]. Therefore, these results support the reduction of PKA/Creb signaling in p28 β-GsαKO islets.…”

Osmoregulation of the transcriptome of the hypothalamic supraoptic nucleus: A resource for the community

“…Thus, we used GeneChip™ (Affymetrix, Santa Clara, CA, USA) analysis 17‐21 to document the transcriptomes of the adult male and female Sprague‐Dawley rat SON and PVN, and to describe how these change following the chronic osmotic challenge of 72 hours of complete fluid deprivation (dehydration). Some of the novel differentially expressed genes (DEGs) identified have been subjected to detailed functional investigation, for example Creb3l1 , 23‐27 Azin1 , 28 Slc12a1 , 29 Caprin2 30,31 and Rasd1 32 . We have thus demonstrated that the SON is a tractable model that enables sustained progress from transcriptome datasets to novel physiological understanding 33 .…”

Transcription factor Creb3l1 maintains proteostasis in neuroendocrine cells

“…Creb3l1 and non-targeting short hairpin RNAs (shRNAs) were cloned into pGFP-A-shAAV (OriGene, TR30034) as previously described [ 20 ]. We generated adeno-associated viruses (AAVs) expressing GFP and Creb3l1CA directed by a 2 kb fragment of the rat Avp promoter.…”

“…We were the first to describe expression of ER stress sensor cAMP responsive element-binding protein 3 like 1 (Creb3l1) in MCNs of the hypothalamus [ 17 ]. We have gone on to characterise its mechanism of activation and functions in MCNs in the regulation of vasopressin (AVP) and oxytocin (OXT) synthesis in response to increased physiological demand [ [16] , [17] , [18] , [19] , [20] , [21] ]. Creb3l1 is a TF of the CREB/ATF family that, like ATF6, is activated by regulated intramembrane proteolysis (RIP) [ 22 ].…”