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Significant advancements in cardiovascular and metabolic disease research have been made with the CREB3 protein family. Studies have revealed that members of this family are crucial in the development of these diseases, contributing to the regulation of lipid metabolism, inflammation, and vascular function. These studies provide useful information for future therapeutic strategies in cardiovascular and metabolic diseases. [ABSTRACT FROM AUTHOR]

Lipid metabolism hinges on a balance between lipogenesis and fatty acid oxidation (FAO). Disruptions in this balance can induce endoplasmic reticulum (ER) stress triggering the unfolded protein response (UPR) and contribute to metabolic diseases. The UPR protein, Luman or CREB3, has recently been implicated in metabolic regulation–CREB3 knockout mice exhibit resistance to diet‐induced obesity and altered insulin sensitivity. Here, we show that CREB3 activated PPARGC1A transcription from a 1 kb promoter region. An increase in CREB3 expression correlated inversely with endogenous PPARGC1A mRNA levels and genes involved in FAO. As PGC‐1α encoded by PPARGC1A is a master regulator of mitochondrial biogenesis and energy homeostasis, these findings demonstrate that CREB3 is a transcriptional regulator of PGC‐1α, underlining the potential role of CREB3 in energy metabolism. [ABSTRACT FROM AUTHOR]

OSW-1, a steroidal saponin isolated from the bulbs of Ornithogalum saundersiae, is a promising compound for an anticancer drug; however, its cytotoxic mechanisms have not been fully elucidated. Therefore, we analyzed the stress responses triggered by OSW-1 in the mouse neuroblastoma cell line Neuro2a by comparing it with brefeldin A (BFA), a Golgi apparatus-disrupting reagent. Among the Golgi stress sensors TFE3/TFEB and CREB3, OSW-1 induced dephosphorylation of TFE3/TFEB but not cleavage of CREB3, and induction of the ER stress-inducible genes GADD153 and GADD34 was slight. On the other hand, the induction of LC3-II, an autophagy marker, was more pronounced than the BFA stimulation. To elucidate OSW-1-induced gene expression, we performed a comprehensive gene analysis using a microarray method and observed changes in numerous genes involved in lipid metabolism, such as cholesterol, and in the regulation of the ER–Golgi apparatus. Abnormalities in ER–Golgi transport were also evident in the examination of secretory activity using NanoLuc-tag genes. Finally, we established Neuro2a cells lacking oxysterol-binding protein (OSBP), which were severely reduced by OSW-1, but found OSBP deficiency had little effect on OSW-1-induced cell death and the LC3-II/LC3-I ratio in Neuro2a cells. Future work to elucidate the relationship between OSW-1-induced atypical Golgi stress responses and autophagy induction may lead to the development of new anticancer agents. [ABSTRACT FROM AUTHOR]

• Knockout of Creb3 in MEF cells results in increased susceptibility to H 2 O 2 and higher basal ROS levels. • Creb3 -knockout MEFs have increased ER-Ca2+ efflux and mitochondrial [Ca2+]. • Creb3 -knockout in MEF cells leads to an increase in mitochondrial respiration/ATP production and spare respiratory capacity. • CREB3 is essential for maintaining normal cellular Ca2+-ATP-ROS homeostasis in MEF cells. In mammalian cells, mitochondrial respiration produces reactive oxygen species (ROS) such as superoxide (O 2 –), which is then converted by the SOD1 enzyme into hydrogen peroxide (H 2 O 2), the predominant form of cytosolic ROS. ROS at high levels can be toxic, but below this threshold are important for physiological processes acting as a second messenger similar to Ca2+. Mitochondrial Ca2+ influx from the ER increases ATP and ROS production, while ATP and ROS can regulate Ca2+ homeostasis, leading to an intricate interplay between Ca2+, ROS, and ATP synthesis. The Unfolded Protein Response (UPR) proteins ATF6α and XBP1 contribute to protection from oxidative stress through upregulation of Sod1 and Catalase genes. Here, UPR-associated protein CREB3 is shown to play a role in balancing Ca2+, ROS, and ATP homeostasis. Creb3 -deficient mouse embryonic fibroblast cells (MEF-/-) were susceptible to H 2 O 2 -induced oxidative stress while having a functioning antioxidant gene expression response compared to MEF+/+. MEF-/- cells also contained elevated basal cytosolic ROS levels, which was attributed to drastically increased basal mitochondrial respiration and spare respiratory capacity relative to MEF+/+. MEF-/- cells also showed an increase in endoplasmic reticulum Ca2+ release and mitochondrial Ca2+ levels hinting at a potential cause for MEF-/- cell mitochondrial dysfunction. These results suggest that CREB3 is essential for maintaining proper Ca2+, ATP, and ROS homeostasis in mammalian cells. [ABSTRACT FROM AUTHOR]

Backgrounds: The endoplasmic reticulum (ER) is a crucial organelle that regulates both the folding, modification and transport of many proteins and senses certain stimuli inside and outside of cells. ER-associated degradation (ERAD), including SEL1L is a crucial mechanism to maintain homeostasis. In this study, we performed comparative proteome analysis in wild-type (wt) and SEL1L-deficient cells. Methods and results: We found constitutively high expression of thioredoxin domain-containing protein 11 (TXNDC11) mRNA and protein in our SEL1L-deficient HEK293 cells by RT-PCR and Western blot analysis. The TXNDC11 gene possesses a well-conserved unfolded protein response element (UPRE) around its transcription start site, and ER stress increased TXNDC11 mRNA and luciferase reporter activity via this putative UPRE in HEK293 cells. The amounts of TXNDC11 protein in wild-type and SEL1L-deficient cells with or without thapsigargin (Tg) treatment were parallel to their mRNAs in these cells, which was almost proportional to spliced XBP1 (sXBP1) mRNA expression. The establishment and characterization of TXNDC11-deficient HEK293 cells revealed that the expression of three different ER resident stress sensors, ATF6α, CREB3 and CREB3L2, is regulated by TXNDC11. The rate of disappearance of the three proteins by CHX treatment in wt cells was remarkably different, and the full-length CREB3L2 protein was almost completely degraded within 15 min after CHX treatment. TXNDC11 deficiency increased the expression of each full-length form under resting conditions and delayed their disappearance by CHX treatment. Interestingly, the degree of increase in full-length CREB3/CREB3L2 by TXNDC11 deficiency was apparently higher than that in full-length ATF6α. The increase in these proteins by TXNDC11 deficiency was hardly correlated with the expression of each mRNA. Treatment with ER stress inducers influenced each full-length mature form, and the difference in each full-length form observed in wt and TXNDC11-deficient cells was smaller. Conclusion: This study demonstrated that TXNDC11 is an ER stress-inducible gene regulated by the IRE1-sXBP1 pathway. In addition, TXNDC11 is involved in the regulation of ATF6α, CREB3 and CREB3L2 protein expression, although the contribution to the stability of these proteins is quite variable. Therefore, its further characterization will provide new insights for understanding protein homeostasis in ER physiology and pathology. [ABSTRACT FROM AUTHOR]

Herpes Simplex Virus 1 (HSV-1) is a neurotropic human virus that belongs to the Alphaherpesvirinae subfamily of Herpesviridae. Establishment of its productive infection and progression of disease pathologies depend largely on successful release of virions from the virus-producing cells. HSV-1 is known to exploit many host factors for its release. Recent studies have shown that heparanase (HPSE) is one such host enzyme that is recruited for this purpose. It is an endoglycosidase that cleaves heparan sulfate (HS) from the surface of infected cells. HS is a virus attachment coreceptor that is commonly found on cell surfaces as HS proteoglycans e.g., syndecan-1 (SDC-1). The current model suggests that HSV-1 during the late stage of infection upregulates HPSE, which in turn enhances viral release by removing the virus-trapping HS moieties. In addition to its role in directly enabling viral release, HPSE accelerates the shedding of HS-containing ectodomains of SDC-1, which enhances HSV-1 release via a similar mechanism by upregulating CREB3 and COPII proteins. This review outlines the role of HPSE and SDC-1 as newly assigned host factors that facilitate HSV-1 release during a lytic infection cycle. [ABSTRACT FROM AUTHOR]

Herpes simplex virus type-1 (HSV-1) exploits several host factors to enhance its replication and release from infected cells. It induces the production of host enzyme heparanase (HPSE) to aid in egress. While the mechanism by which HPSE assists in viral release is well-characterized, other host factors that are recruited along with HPSE for viral release are less well understood. In this study, we identify cyclic-AMP-responsive element-binding protein3 (CREB3) as a key player in HPSE-facilitated HSV-1 egress. When CREB3 is transiently upregulated in human corneal epithelial cells, HSV-1 release from the infected cells is correspondingly enhanced. This activity is linked to HPSE expression such that HPSE-transfected corneal epithelial (HCE) cells more highly express CREB3 than wild-type cells while the cells knocked out for HPSE show very little CREB3 expression. CREB3-transfected HCE cells showed significantly higher export of HPSE upon infection than wild-type cells. Our data suggests that coat protein complex II (COPII), which mediates HPSE trafficking, is also upregulated via a CREB3-dependent pathway during HSV-1 infection. Finally, the co-transfection of CREB3 and HPSE in HCE cells shows the highest viral release compared to either treatment alone, establishing CREB3 as a key player in HPSE-facilitated HSV-1 egress. [ABSTRACT FROM AUTHOR]

Alteration of the lipid composition of biological membranes interferes with their function and can cause tissue damage by triggering apoptosis. Upon lipid bilayer stress, the endoplasmic reticulum mounts a stress response similar to the unfolded protein response. However, only a few genes are known to regulate lipid bilayer stress. We performed a suppressor screen that combined the auxin-inducible degradation (AID) system with conventional RNAi in C. elegans to identify members of the lipid bilayer stress response. AID-mediated degradation of the mediator MDT-15, a protein required for the upregulation of fatty acid desaturases, induced the activation of lipid bilayer stress-sensitive reporters. We screened through most C. elegans kinases and transcription factors by feeding RNAi. We discovered nine genes that suppressed the lipid bilayer stress response in C. elegans. These suppressor genes included drl-1/MAP3K3, gsk-3/GSK3, let-607/CREB3, ire-1/IRE1, and skn-1/NRF1,2,3. Our candidate suppressor genes suggest a network of transcription factors and the integration of multiple tissues for a centralized lipotoxicity response in the intestine. Thus, we demonstrated proof-of-concept for combining AID and RNAi as a new screening strategy and identified eight conserved genes that had not previously been implicated in the lipid bilayer stress response.

Karyoptosis is a type of regulated cell death (RCD) characterized by explosive nuclear rupture caused by a loss of nuclear membrane integrity, resulting in the release of genomic DNA and other nuclear components into the cytosol and extracellular environment. The mechanism underlying karyoptosis involves a delicate balance between the following forces: the expansion force exerted by the tightly packed DNA in the nucleus, the resistance provided by the nuclear lamina at the inner nuclear membrane (INM), and the tensile force from the cytoskeleton that helps position the nucleus at the center of the cytoplasm, allowing it to remain maximally expanded. In addition, CREB3, a type II integral membrane protein with DNA-binding ability, tethers chromatin to the INM, providing a tightening force through chromatin interactions that prevent nuclear membrane rupture. UVB radiation can trigger this process, inducing CREB3-FL cleavage and producing CREB3-CF. Therefore, UVB acts as an intrinsic factor in the induction of karyoptosis. Importantly, biochemical analysis of RCD markers shows that karyoptosis is distinct from other forms of cell death, such as apoptosis, autophagy, necroptosis, and pyroptosis. This review explores the mechanisms involved in maintaining nuclear membrane integrity and the role of CREB3 in triggering karyoptosis and provides brief suggestions on the potential implications for targeting cancer cells.

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Copyright of Canadian Journal of Animal Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The organelle of eukaryotes is a finely regulated system. Once disturbed, it activates the specific autoregulatory systems, namely, organelle autoregulation. Among which, the Golgi stress response accounts for one. When the abundance and capacity of the Golgi apparatus are insufficient compared with cellular demand, the Golgi stress response is activated to enhance the function of the Golgi apparatus. Although the molecular mechanism of the Golgi stress response has not been well characterized yet, it seems to be an important part of the mammalian stress response. In this review, we discuss the current status of research on the six pathways of the mammalian Golgi stress response (the TFE3, heat shock protein 47, CREB3, E26 transformation specific, proteoglycan, and mucin pathways), which regulate the general function of the Golgi apparatus, anti‐apoptosis, pro‐apoptosis, proteoglycan glycosylation, and mucin glycosylation, respectively. [ABSTRACT FROM AUTHOR]

Brefeldin A (BFA) disrupts the structure of the Golgi apparatus to trigger ER stress signaling pathways. On the other hand, treatment with BFA induces the activation of CREB3, the protein structure of which is similar to that of ATF6. In this study, we established Neuro2a cells in which three different transcription factors, namely, ATF4, ATF3 and CREB3, were deficient using the CRISPR/Cas9 approach, and we investigated the BFA-induced ER and Golgi stress response in these cells. BFA treatment rapidly induced ATF4, ATF3, Herp and GADD153 protein expression in Neuro2a cells. ATF4-deficient Neuro2a cells exhibited significantly decreased mRNA and protein expression of ATF3 and Herp but not GADD153; however, cells deficient in ATF3 exhibited minimal effects on GADD34, GADD153 and Herp expression. The cleavage of CREB3 in Neuro2a cells was triggered by BFA; however, the expression of several ER and Golgi stress-related factors was hardly influenced by the CREB3 deficiency in these Neuro2a cells. This study shows that CREB3 minimally associates with typical ER stress-inducible responses in Neuro2a cells. Therefore, identification and characterization of the downstream transcriptional targets of CREB3 is required to clarify not only Golgi stress response but also its relationship with ER stress signaling pathways. [ABSTRACT FROM AUTHOR]

Abstract Background As a subclass of noncoding RNAs, circular RNAs (circRNAs) have been demonstrated to play a critical role in regulating gene expression in eukaryotes. Recent studies have revealed the pivotal functions of circRNAs in cancer progression. However, little is known about the role of circTADA2A, also named hsa_circ_0043278, in osteosarcoma (OS). Methods CircTADA2A was selected from a previously reported circRNA microarray comparing OS cell lines and normal bone cells. QRT-PCR was used to detect the expression of circTADA2A in OS tissue and cell lines. Luciferase reporter, RNA immunoprecipitation (RIP), RNA pull-down and fluorescence in situ hybridization (FISH) assays were performed to confirm the binding of circTADA2A with miR-203a-3p. OS cells were stably transfected with lentiviruses, and Transwell migration, Matrigel invasion, colony formation, proliferation, apoptosis, Western blotting, and in vivo tumorigenesis and metastasis assays were employed to evaluate the roles of circTADA2A, miR-203a-3p and CREB3. Results Our findings demonstrated that circTADA2A was highly expressed in both OS tissue and cell lines, and circTADA2A inhibition attenuated the migration, invasion and proliferation of OS cells in vitro as well as tumorigenesis and metastasis in vivo. A mechanistic study revealed that circTADA2A could readily sponge miR-203a-3p to upregulate the expression of CREB3, which was identified as a driver gene in OS. Furthermore, miR-203a-3p inhibition or CREB3 overexpression could reverse the circTADA2A silencing-induced impairment of malignant tumor behavior. Conclusions CircTADA2A functions as a tumor promoter in OS to increase malignant tumor behavior through the miR-203a-3p/CREB3 axis, which could be a novel target for OS therapy.

Nerve growth factor (NGF) stimulates numerous cellular physiological processes, including growth, differentiation, and survival, and maintains the phenotype of several neuronal types. Most of these NGF-induced processes require adaptation of the secretory pathway since they involve extensive remodeling of membranes and protein redistribution along newly formed neuritic processes. CREB3 transcription factors have emerged as signaling hubs for the regulation of numerous genes involved in the secretory pathway and Golgi homeostasis, integrating stimuli from multiple sources to control secretion, posttranslational modifications and trafficking of proteins. Although recent studies have focused on their role in the central nervous system, little is known about their participation in cell differentiation. Therefore, we aimed to analyze the expression and signaling mechanism of CREB3 transcription factor family members, using the NGF-induced PC12 cell differentiation model. Results show that NGF treatment causes Golgi enlargement and a parallel increased expression of proteins and mRNAs encoding for proteins required for membrane transport (transport factors). Additionally, a significant increase in CREB3L2 protein and mRNA levels is detected in response to NGF. Both MAPK and cAMP signaling pathways are required for this response. Interestingly, CREB3L2 overexpression hampers the NGF-induced neurite outgrowth while its inhibition enhances the morphological changes driven by NGF. In agreement, CREB3L2 overexpressing cells display higher immunofluorescence intensity of Rab5 GTPase (a negative regulator of PC12 differentiation) than control cells. Also, Rab5 immunofluorescence levels decrease in CREB3L2-depleted cells. Taken together, our findings imply that CREB3L2 is an important downstream effector of NGF-activated pathways, leading to neuronal differentiation.

Nerve growth factor (NGF) stimulates numerous cellular physiological processes, including growth, differentiation, and survival, and maintains the phenotype of several neuronal types. Most of these NGF-induced processes require adaptation of the secretory pathway since they involve extensive remodeling of membranes and protein redistribution along newly formed neuritic processes. CREB3 transcription factors have emerged as signaling hubs for the regulation of numerous genes involved in the secretory pathway and Golgi homeostasis, integrating stimuli from multiple sources to control secretion, posttranslational modifications and trafficking of proteins. Although recent studies have focused on their role in the central nervous system, little is known about their participation in cell differentiation. Therefore, we aimed to analyze the expression and signaling mechanism of CREB3 transcription factor family members, using the NGF-induced PC12 cell differentiation model. Results show that NGF treatment causes Golgi enlargement and a parallel increased expression of proteins and mRNAs encoding for proteins required for membrane transport (transport factors). Additionally, a significant increase in CREB3L2 protein and mRNA levels is detected in response to NGF. Both MAPK and cAMP signaling pathways are required for this response. Interestingly, CREB3L2 overexpression hampers the NGF-induced neurite outgrowth while its inhibition enhances the morphological changes driven by NGF. In agreement, CREB3L2 overexpressing cells display higher immunofluorescence intensity of Rab5 GTPase (a negative regulator of PC12 differentiation) than control cells. Also, Rab5 immunofluorescence levels decrease in CREB3L2-depleted cells. Taken together, our findings imply that CREB3L2 is an important downstream effector of NGF-activated pathways, leading to neuronal differentiation. [ABSTRACT FROM AUTHOR]

We performed expression and functional analysis of mouse CREB3 regulatory factor (CREBRF) in Neuro2a cells by constructing several expression vectors. Overexpressed full-length (FL) CREBRF protein was stabilized by MG132; however, the intrinsic CREBRF expression in Neuro2a cells was negligible under all conditions. On the other hand, N- or C-terminal deletion of CREBRF influenced its stability. Cotransfection of CREBRF together with GAL4-tagged FL CREB3 increased luciferase reporter activity, and only the N-terminal region of CREBRF was sufficient to potentiate luciferase activity. Furthermore, this positive effect of CREBRF was also observed in cells expressing GAL4-tagged cleaved CREB3, although CREBRF hardly influenced the protein stability of NanoLuc-tagged cleaved CREB3 or intracellular localization of EGFP-tagged one. In conclusion, this study suggests that CREBRF, a quite unstable proteasome substrate, positively regulates the CREB3 pathway, which is distinct from the canonical ER stress pathway in Neuro2a cells. [ABSTRACT FROM AUTHOR]

Objective: Drug resistance greatly limits the therapeutic effect of a drug. This study aimed to explore the role of long noncoding RNA ZFAS1 in Donafenib resistance of hepatocellular carcinoma (HCC) cells., Methods: The expression of CREB3, ZFAS1, and p65 in HCC cell lines was measured by RT-qPCR and western blotting. After transfection with sh-ZFAS1, sh-CREB3, or sh-CREB3 + oe-p65 in Donafenib-resistent (DR) HCC cell lines, the transfection efficiency was evaluated by RT-qPCR and western blotting. The proliferation and IC 50 to Donafenib of HCC cell lines was examined by MTT assay. Cell proliferation and apoptosis were examined by colony formation and flow cytometry assays. Then, the correlation amongst CREB3, ZFAS1, LSD1/CoREST, and p65 was analysed by ChIP, dual-luciferase reporter gene, and RIP assays., Results: ZFAS1, CREB3, and p65 were upregulated in HepG2-DR and Huh7-DR cells. Silencing of ZFAS1 or CREB3 enhanced the sensitivity of HCC cells to Donafenib, inhibited cell proliferation and IC 50 , and increased cell apoptosis, which were reversed by p65 overexpression. Mechanistically, CREB3 bound to ZFAS1 promoter to augment ZFAS1 transcriptional expression, and ZFAS1 recruited LSD1/CoREST to the p65 promoter region to decrease H3K4 methylation and elevate p65 transcriptional expression., Conclusion: CREB3 overexpression contributed to Donafenib resistance in HCC cells by activating the ZFAS1/p65 axis., Competing Interests: Declaration of competing interest The authors declare there is no conflict of interests., (Copyright © 2023. Published by Elsevier Inc.)

Our ability to overcome the challenges behind metabolic disorders will require a detailed understanding of the regulation of responses to nutrition. The Creb3 transcription factor family appears to have a unique regulatory role that links cellular secretory capacity with development, nutritional state, infection, and other stresses. This role in regulating individual secretory capacity genes could place this family of transcription factors at an important regulatory intersection mediating an animal’s responses to nutrients and other environmental challenges. Interestingly, in both humans and mice, individuals with mutations in Creb3L3/CrebH, one of the Creb3 family members, exhibit hypertriglyceridemia (HTG) thus linking this transcription factor to lipid metabolism. We are beginning to understand how Creb3L3 and related family members are regulated and to dissect the potential redundancy and cross talk between distinct family members, thereby mediating both healthy and pathological responses to the environment. Here, we review the current knowledge on the regulation of Creb3 family transcription factor activity, their target genes, and their role in metabolic disease.

CREB3 is a transcription factor localized to the ER. Here, we investigated endogenous CREB3 expression in HEK293 cells using pharmacological and genome editing approaches. Full‐length CREB3 detected under resting conditions disappeared following treatment with tunicamycin, brefeldin A and nigericin. Treatment with cycloheximide and MG132 indicated that endogenous CREB3 is a proteasome substrate. Using cells deficient for the ER‐associated protein degradation (ERAD) factors SEL1L and Herp, we demonstrate that SEL1L, but not Herp, plays a crucial role in the posttranslational regulation of full‐length CREB3 expression. In addition, kifunensine, an α‐mannosidase inhibitor, remarkably increased full‐length CREB3 expression. Our study suggests that endogenous full‐length CREB3 is a novel substrate for ERAD and identifies unique cellular signals distinct from those in canonical ER stress. [ABSTRACT FROM AUTHOR]

Organelles have been studied traditionally as single units, but a novel concept is now emerging: each organelle has distinct functional zones that regulate specific functions. The Golgi apparatus seems to have various zones, including zones for: glycosylphosphatidylinositol‐anchored proteins; proteoglycan, mucin and lipid glycosylation; transport of cholesterol and ceramides; protein degradation (Golgi membrane‐associated degradation); and signalling for apoptosis. The capacity for these specific functions and the size of the corresponding zones appear to be tightly regulated by the Golgi stress response to accommodate cellular demands. For instance, the proteoglycan and mucin zones seem to be separately augmented during the differentiation of chondrocytes and goblet cells, respectively. The mammalian Golgi stress response consists of several response pathways. The TFE3 pathway regulates the general function of the Golgi, such as structural maintenance, N‐glycosylation and vesicular transport, whereas the proteoglycan pathway increases the expression of glycosylation enzymes for proteoglycans. The CREB3 and HSP47 pathways regulate pro‐ and anti‐apoptotic functions, respectively. These observations indicate that the Golgi is a dynamic organelle, the capacity of which is upregulated according to cellular needs. [ABSTRACT FROM AUTHOR]

Our ability to overcome the challenges behind metabolic disorders will require a detailed understanding of the regulation of responses to nutrition. The Creb3 transcription factor family appears to have a unique regulatory role that links cellular secretory capacity with development, nutritional state, infection, and other stresses. This role in regulating individual secretory capacity genes could place this family of transcription factors at an important regulatory intersection mediating an animal's responses to nutrients and other environmental challenges. Interestingly, in both humans and mice, individuals with mutations in Creb3L3/CrebH, one of the Creb3 family members, exhibit hypertriglyceridemia (HTG) thus linking this transcription factor to lipid metabolism. We are beginning to understand how Creb3L3 and related family members are regulated and to dissect the potential redundancy and cross talk between distinct family members, thereby mediating both healthy and pathological responses to the environment. Here, we review the current knowledge on the regulation of Creb3 family transcription factor activity, their target genes, and their role in metabolic disease. [ABSTRACT FROM AUTHOR]

cAMP response element binding Protein 3 (CREB3) is an endoplasmic reticulum (ER) membrane‐bound transcription factor, which belongs to the basic leucine zipper (bZIP) superfamily of eukaryotic transcription factors. CREB3 plays a role in the ER‐stress induced unfolded protein response (UPR) and is a multifunctional cellular factor implicated in a number of biological processes including cell proliferation and migration, tumor suppression, and immune‐related gene expression. To gain structural insights into the transcription factor, we determined the crystal structure of the conserved bZIP domain of chicken CREB3 (chCREB3) to a resolution of 3.95 Å. The X‐ray structure provides evidence that chCREB3 can form a stable homodimer. The chCREB3 bZIP has a structured, pre‐formed DNA binding region, even in the absence of DNA, a feature that could potentially enhance both the DNA binding specificity and affinity of chCREB3. Significantly, the homodimeric bZIP possesses an intermolecular disulfide bond that connects equivalent cysteine residues of the parallel helices in the leucine zipper region. This disulfide bond in the hydrophobic core of the bZIP may increase the stability of the homodimer under oxidizing conditions. Moreover, sequence alignment of bZIP sequences from chicken, human, and mouse reveals that only members of the CREB3 subfamily contain this cysteine residue, indicating that it could act as a redox‐sensor. Taken together, these results suggest that the activity of these transcription factors may be redox‐regulated and they may be activated in response to oxidative stress. PDB Code(s): 6IAK [ABSTRACT FROM AUTHOR]

CREB3 is an ER membrane-bound transcription factor; however, post-translational regulation of CREB3, including expression, processing, and activation, is not fully characterized. We therefore constructed several types of mouse CREB3 expression genes and elucidated their expression in Neuro2a cells by treatment with stimuli and co-transfection with genes associated with ER-Golgi homeostasis, such as mutant Sar1 [H79G], GRP78, and KDEL receptor 1 (KDELR1). Interestingly, treatment of Neuro2a cells expressing Flag-tagged full-length CREB3 with monensin and nigericin induced the expression of the approximately 50 kDa N-terminal fragment; however, its cleavage was not parallel to the levels of GADD153 and LC3-II. Co-transfection of full-length CREB3 together with Sar1 [H79G], GRP78, or KDELR1 showed that only Sar1 [H79G] induced expression of the cleaved form, and KDELR1 dramatically decreased the expression of the full-length form. Accordingly, Sar1 [H79G]- and KDELR1-overexpression influenced GAL4-CREB3-dependent luciferase activities. To understand the activation of CREB3 under more pathophysiological conditions, we focused on the effect of metal ions on CREB3 cleavage in Neuro2a cells. Among the six metal ions we tested, only copper ion stabilized full-length CREB3 expression. Copper ion also increased its N-terminal form and GAL4-CREB3-dependent luciferase activity, which was accompanied by the increase in the ubiquitinated proteins in Neuro2a cells. Taken together, CREB3 expression is regulated by multiple ER-Golgi resident factors in a post-translational manner, but its processing is not directly associated with ER stress and autophagic dysfunction. This finding is especially true for the unique action of the copper ion on CREB3 stabilization and processing in parallel to aberration of ubiquitin-proteasome system, which might provide new insights into understanding the mechanisms of intractable disorders. [ABSTRACT FROM AUTHOR]

Hypertensive myocardial hypertrophy produces a hostile microenvironment characterized by cardiomyocyte hypertrophy, inflammation and oxidative stress, which also leads to endothelial progenitor cells (EPCs) dysfunction, preventing EPC migration, adhesion and angiogenesis. Heme oxygenase-1 (HO-1) is an intracellular protein that plays an important role in angiogenesis and cell survival. The upregulation of cAMP response element-binding protein 3 (CREB3) is closely related to the formation of endothelial cells. The purpose of this study was to evaluate the role of HO-1 and CREB3 in EPCs and their effects on hypertensive myocardial hypertrophy. EPCs were transfected with HO-1 adenoviral overexpression vector (Ad–HO–1) or together with CREB3 siRNA (si-CREB3), or transfected with CREB3 adenoviral overexpression vector (Ad-CREB3) or together with HO-1 siRNA, and then treated with 100 nM Ang Ⅱ for 12 h. Overexpressing HO-1 or CREB3 promoted adhesion to extracellular matrix, cell migration, and angiogenesis, inhibited the secretion of inflammatory factors TNF-α and IL-6, and reduced ROS level, ICAM-1 and MCP-1 mRNA expression levels in EPCs treated with Ang Ⅱ. Online prediction and Co-IP assay showed that HO-1 interacts with CREB3, and they promote expression of each other. EPC-conditioned medium supplemented with CREB3 recombinant protein decreased the levels of ANP and BNP mRNA in H9C2 cells treated with Ang Ⅱ and alleviated oxidative stress. Ad-CREB3 transfected EPCs promoted the phosphorylation of AKT in vivo and in vitro , thereby improving myocardial swelling and dysfunction in SHR rats. Taken together, transplantation of CREB3 overexpressing EPCs alleviates myocardial hypertrophy in spontaneously hypertensive rats by promoting HO-1 protein expression and AKT phosphorylation. [Display omitted] • Overexpressing HO-1 or CREB3 improved adhesion to extracellular matrix, promoted cell migration, angiogenesis, and inhibited inflammatory and oxidative stress in Ang Ⅱ-induced EPCs. • HO-1 promotes the expression level of CREB3 by interacting with CREB3. • Overexpression of CREB3 promotes the phosphorylation of AKT. • EPC-conditioned medium supplemented with CREB3 recombinant protein alleviated Ang Ⅱ-induced oxidative stress in H9C2 cells. • Transplantation of CREB3 overexpressing EPCs alleviates myocardial hypertrophy in spontaneously hypertensive rats. [ABSTRACT FROM AUTHOR]

Abstract: Regulated intramembrane proteolysis (RIP) is a signaling mechanism through which transmembrane precursor proteins are cleaved to liberate their cytoplasmic and/or luminal/extracellular fragments from membranes so that these fragments are able to function at a new location. Recent studies have indicated that this proteolytic reaction plays an important role in host–virus interaction. On one hand, RIP transfers the signal from the endoplasmic reticulum (ER) to nucleus to activate antiviral genes in response to alteration of the ER caused by viral infection. On the other hand, RIP can be hijacked by virus to process transmembrane viral protein precursors and to destroy transmembrane antiviral proteins. Understanding this Yin and Yang side of RIP may lead to new strategies to combat viral infection. This article is part of a Special Issue entitled: Intramembrane Proteases. [Copyright &y& Elsevier]

The minor allele (A) of the rs373863828 variant (p.Arg457Gln) in CREBRF is restricted to indigenous peoples of the Pacific islands (including New Zealand Māori and peoples of Polynesia), with a frequency of up to 25% in these populations. This allele associates with a large increase in body mass index (BMI) but with significantly lower risk of type-2 diabetes (T2D). It remains unclear whether the increased BMI is driven by increased adiposity or by increased lean mass. We undertook body composition analysis using DXA in 189 young men of Māori and Pacific descent living in Aotearoa New Zealand. Further investigation was carried out in two orthologous Arg458Gln knockin mouse models on FVB/NJ and C57BL/6j backgrounds. The rs373863828 A allele was associated with lower fat mass when adjusted for BMI (p < 0.05) and was associated with significantly lower circulating levels of the muscle inhibitory hormone myostatin (p < 0.05). Supporting the human data, significant reductions in adipose tissue mass were observed in the knockin mice. This was more significant in older mice in both backgrounds and appeared to be the result of reduced age-associated increases in fat mass. The older male knockin mice on C57BL/6j background also had increased grip strength (p < 0.01) and lower levels of myostatin (p < 0.05). Overall, these results prove that the rs373863828 A-allele is associated with a reduction of myostatin levels which likely contribute to an age-dependent lowering of fat mass, at least in males. • The CREBRF p.457Gln variant associates with decreased fat mass in males. • Consistent with this CREBRF p.457Gln associates with decreased myostatin levels. • These effects are more obvious with age. [ABSTRACT FROM AUTHOR]

Anorexia Nervosa (AN) is a chronic psychiatric disorder whose pathophysiology is largely unknown but has a significant genetic component. The objective of this work was to identify rare genetic variants of predisposition for anorexia nervosa. We studied 10 families of 15 affected women, 11 cases of restrictive ANR (ANR) and 4 cases of binge-purging AN, and analyzed in trio by new generation sequencing. The variants were filtered by quality controls (blanket, IGV viewer), segregation in familial forms, deleterious in silico prediction of variants (Cadd> 15), and absence or rarity in unaffected controls and in the databases (Gnomad, "Déjà vu" Paris Descartes) (< 1%). The analysis of the de novo variants did not make it possible to identify deleterious candidate variants (with the exception of p.L206 V, deleterious in the LUMAN/CREB3 gene) and recurrent ones. In index cases of familial forms, potential de novo variants have been identified. Dominant model analysis identified 349 potential variants distributed in 110 genes. Analysis of this list of genes by String, David and GeneOntology has identified several biological pathways that may be altered. Three major KEGG pathways could be identified: "neuroactive ligand-receptor interaction" 9 genes, "cholinergic synapse" 6 genes, and "dopaminergic synapse" 6 genes. In addition, the literature analysis identified 24 variants in genes contributing to neuropsychiatric disorders. We identified specific damaging variant in several genes than can play a role in AN. Targeted analyzes of a large cohort of patients should be conducted to confirm our results. This study was supported by Fondation Maladies Rares (#11632) Program high throughput sequencing and rare diseases. [ABSTRACT FROM AUTHOR]

We performed a comparative analysis of two ER-resident CREB3 family proteins, CREB3 and CREB3L2, in HEK293 cells using pharmacological and genome editing approaches and identified several differences between the two. Treatment with brefeldin A (BFA) and monensin induced the cleavage of full-length CREB3 and CREB3L2; however, the level of the full-length CREB3 protein, but not CREB3L2 protein, was not noticeably reduced by the monensin treatment. On the other hand, treatment with tunicamycin (Tm) shifted the molecular weight of the full-length CREB3L2 protein downward but abolished CREB3 protein expression. Thapsigargin (Tg) significantly increased the expression of only full-length CREB3L2 protein concomitant with a slight increase in the level of its cleaved form. Treatment with cycloheximide and MG132 revealed that both endogenous CREB3 and CREB3L2 are proteasome substrates. In addition, kifunensine, an α-mannosidase inhibitor, significantly increased the levels of both full-length forms. Consistent with these findings, cells lacking SEL1L, a crucial ER-associated protein degradation (ERAD) component, showed increased expression of both full-length CREB3 and CREB3L2; however, cycloheximide treatment downregulated full-length CREB3L2 protein expression more rapidly in SEL1L-deficient cells than the full-length CREB3 protein. Finally, we investigated the induction of the expression of several CREB3 and CREB3L2 target genes by Tg and BFA treatments and SEL1L deficiency. In conclusion, this study suggests that both endogenous full-length CREB3 and CREB3L2 are substrates for ER-associated protein degradation but are partially regulated by distinct mechanisms, each of which contributes to unique cellular responses that are distinct from canonical ER signals. [ABSTRACT FROM AUTHOR]

Background: As a subclass of noncoding RNAs, circular RNAs (circRNAs) have been demonstrated to play a critical role in regulating gene expression in eukaryotes. Recent studies have revealed the pivotal functions of circRNAs in cancer progression. However, little is known about the role of circTADA2A, also named hsa_circ_0043278, in osteosarcoma (OS). Methods: CircTADA2A was selected from a previously reported circRNA microarray comparing OS cell lines and normal bone cells. QRT-PCR was used to detect the expression of circTADA2A in OS tissue and cell lines. Luciferase reporter, RNA immunoprecipitation (RIP), RNA pull-down and fluorescence in situ hybridization (FISH) assays were performed to confirm the binding of circTADA2A with miR-203a-3p. OS cells were stably transfected with lentiviruses, and Transwell migration, Matrigel invasion, colony formation, proliferation, apoptosis, Western blotting, and in vivo tumorigenesis and metastasis assays were employed to evaluate the roles of circTADA2A, miR-203a-3p and CREB3. Results: Our findings demonstrated that circTADA2A was highly expressed in both OS tissue and cell lines, and circTADA2A inhibition attenuated the migration, invasion and proliferation of OS cells in vitro as well as tumorigenesis and metastasis in vivo. A mechanistic study revealed that circTADA2A could readily sponge miR-203a-3p to upregulate the expression of CREB3, which was identified as a driver gene in OS. Furthermore, miR-203a-3p inhibition or CREB3 overexpression could reverse the circTADA2A silencing-induced impairment of malignant tumor behavior. Conclusions: CircTADA2A functions as a tumor promoter in OS to increase malignant tumor behavior through the miR-203a-3p/CREB3 axis, which could be a novel target for OS therapy. [ABSTRACT FROM AUTHOR]