Abstract 17543: DMPK E Disrupts Sarcomere Structure by Inhibition of SRF Transcriptional Activity

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Ies Elzenaar ◽  
Amin Damanafshan ◽  
Inge van der Made ◽  
Yigal M Pinto ◽  
Ralph J van Oort
Keyword(s):  
Heart Failure ◽  
Transcription Factor ◽  
Transcriptional Activity ◽  
Structural Changes ◽  
Target Genes ◽  
Serum Response Factor ◽  
Splice Variants ◽  
Fold Increase ◽  
Mrna Levels ◽  
Qpcr Analysis

Background: Heart failure is associated with elongation of cardiomyocytes and loss of sarcomeres. Although the transcription factor myocyte enhancer factor-2 (MEF2) has an important role in this adverse remodeling, the mechanism underlying the structural changes of cardiomyocytes remains to be elucidated. In a screen for MEF2 target genes, we have recently identified myotonic dystrophy protein kinase (DMPK) as a potential mediator of adverse cardiomyocyte remodeling. However, it remains to be determined whether DMPK levels are increased in failing hearts and if DMPK is sufficient to induce structural remodeling of cardiomyocytes. Methods and Results: Since the DMPK gene is subject to extensive alternative splicing, we performed RT-PCR and QPCR analysis of known DMPK splice variants in hearts from mice subjected to transverse aortic constriction (TAC) or sham surgery. This demonstrated a 1.6 fold increase in the DMPK E isoform in failing mouse hearts compared to controls (P<0.05). To test the role of this specific splice isoform, we generated adenoviruses expressing DMPK E or a kinase dead mutant DMPK E. Overexpression of wildtype DMPK E, but not of the kinase dead mutant, in cardiomyocytes resulted in severe loss of sarcomeric structure. Moreover, QPCR analysis showed a decrease in mRNA levels for several sarcomeric genes after overexpression of DMPK E. Since these genes are known targets of the transcription factor serum response factor (SRF) and DMPK is known to phosphorylate SRF, we tested the effect of DMPK E on SRF activity. Luciferase experiments demonstrated that DMPK E is an inhibitor of SRF transcriptional activity. Finally, immunostaining revealed a translocation of SRF from the nucleus to the cytosol upon DMPK E overexpression. Conclusion: Our data indicate that the expression of DMPK E is increased in heart failure. Moreover, increased expression of this DMPK splice variant results in a decrease in sarcomeric gene expression by translocation and inhibition of SRF. Together, these results assign a novel function to DMPK in adverse cardiomyocyte remodeling during heart failure development.

Abstract 066: MEF2-induced Loss of Sarcomeres is Mediated by an Alternative Splice Variant of DMPK

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Ies Elzenaar ◽  
Inge van der Made ◽  
Wino J Wijnen ◽  
Elisabeth Ehler ◽  
Leon J De Windt ◽  
...  
Keyword(s):  
Heart Failure ◽  
Transcription Factor ◽  
Microarray Analysis ◽  
Splice Variant ◽  
Transcriptional Activity ◽  
Target Genes ◽  
Neonatal Rat ◽  
Pcr Analysis ◽  
Mrna Levels ◽  
Rat Cardiomyocytes

The pathology of heart failure is characterized by poorly contracting and dilated ventricles. Although this is associated with lengthening of individual cardiomyocytes and loss of sarcomeres, the mechanism underlying these changes in cardiomyocyte structure remains to be elucidated. We have previously identified the transcription factor myocyte enhancer factor-2 (MEF2) as important trigger for adverse cardiomyocyte remodeling. Here, we use microarray analysis and gain- and loss- of function approaches to identify MEF2 target genes involved in structural remodeling of the cardiomyocyte. Isolated neonatal rat cardiomyocytes infected with adenoviruses expressing MEF2 underwent cellular elongation associated with loss of sarcomeric structure. Microarray analysis revealed myotonic dystrophy protein kinase (DMPK) as MEF2 target gene, which we verified by chromatin immunoprecipitation experiments. siRNA mediated knockdown of DMPK prevented MEF2-induced cardiomyocyte elongation and loss of sarcomeres. Interestingly, RT-PCR analysis of known DMPK splice variants demonstrated a relative increase of the DMPK E isoform in failing mouse hearts. To test the role of this specific splice isoform, we generated adenoviruses expressing DMPK E or a kinase dead mutant DMPK E. Overexpression of wildtype DMPK E, but not of the kinase dead mutant, in cardiomyocytes resulted in severe loss of sarcomeric structure. Moreover, quantitative PCR analysis showed a decrease in mRNA levels for several sarcomeric genes after overexpression of DMPK E. These genes are known targets of the transcription factor serum response factor (SRF) and DMPK is known to phosphorylate SRF. Therefore, we tested the effect of DMPK on SRF activity in luciferase experiments, which demonstrated that DMPK E is an inhibitor of SRF transcriptional activity. Our data indicate that MEF2 induces loss of sarcomeres, which is mediated by at least one specific splice variant of DMPK. Moreover, increased expression of this DMPK splice variant results in a decrease in sarcomeric gene expression, which possibly involves inhibition of SRF transcriptional activity. Together, these results assign a novel function to MEF2 and DMPK in adverse cardiomyocyte remodeling during heart failure development.

Transcriptional activity of the zinc finger protein NGFI-A is influenced by its interaction with a cellular factor

1993 ◽  
Vol 13 (11) ◽  
pp. 6858-6865
Author(s):  
M W Russo ◽  
C Matheny ◽  
J Milbrandt
Keyword(s):  
Transcription Factor ◽  
Dna Binding ◽  
Transcriptional Activity ◽  
Zinc Fingers ◽  
Fold Increase ◽  
Binding Domain ◽  
Dna Binding Domain ◽  
Activation Domains ◽  
Cellular Factor ◽  
Inhibitory Domain

NGFI-A is an immediate-early gene that encodes a transcription factor whose DNA-binding domain is composed of three zinc fingers. To define the domains responsible for its transcriptional activity, a mutational analysis was conducted with an NGFI-A molecule in which the zinc fingers were replaced by the GAL4 DNA-binding domain. In a cotransfection assay, four activation domains were found within NGFI-A. Three of the activation domains are similar to those characterized previously: one contains a large number of acidic residues, another is enriched in proline and glutamine residues, and another has some sequence homology to a domain found in Krox-20. The fourth bears no resemblance to previously described activation domains. NGFI-A also contains an inhibitory domain whose removal resulted in a 15-fold increase in NGFI-A activity. This increase in activity occurred in all mammalian cell types tested but not in Drosophila S2 cells. Competition experiments in which increasing amounts of the inhibitory domain were cotransfected along with NGFI-A demonstrated a dose-dependent increase in NGFI-A activity. A point mutation within the inhibitory domain of the competitor (I293F) abolished this property. When the analogous mutation was introduced into native NGFI-A, a 17-fold increase in activity was observed. The inhibitory effect therefore appears to be the result of an interaction between this domain and a titratable cellular factor which is weakened by this mutation. Downmodulation of transcription factor activity through interaction with a cellular factor has been observed in several other systems, including the regulation of transcription factor E2F by retinoblastoma protein, and in studies of c-Jun.

scholarly journals MRTFA augments megakaryocyte maturation by enhancing the SRF regulatory axis

2018 ◽  
Vol 2 (20) ◽  
pp. 2691-2703 ◽  
Author(s):  
Nur-Taz Rahman ◽  
Vincent P. Schulz ◽  
Lin Wang ◽  
Patrick G. Gallagher ◽  
Oleg Denisenko ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Target Genes ◽  
Serum Response Factor ◽  
Sequencing Data ◽  
Binding Motifs ◽  
Ets Proteins ◽  
Human Cd34 ◽  
Genomic Association ◽  
Hel Cells ◽  
Related Transcription Factor

Abstract Serum response factor (SRF) is a ubiquitously expressed transcription factor that binds DNA at CArG (CC[A/T]6GG) domains in association with myocardin-family proteins (eg, myocardin-related transcription factor A [MRTFA]) or the ternary complex factor family of E26 transformation-specific (ETS) proteins. In primary hematopoietic cells, knockout of either SRF or MRTFA decreases megakaryocyte (Mk) maturation causing thrombocytopenia. The human erythroleukemia (HEL) cell line mimics the effects of MRTFA on Mk maturation, and MRTFA overexpression (MRTFAOE) in HEL cells enhances megakaryopoiesis. To identify the mechanisms underlying these effects, we performed integrated analyses of anti-SRF chromatin immunoprecipitation (ChIP) and RNA-sequencing data from noninduced and phorbol ester (12-O-tetradecanoylphorbol-13-acetate [TPA])–induced HEL cells, with and without MRTFAOE. We found that 11% of genes were upregulated with TPA induction, which was enhanced by MRTFAOE, resulting in an upregulation of 25% of genes. MRTFAOE increased binding of SRF to genomic sites and enhanced TPA-induced expression of SRF target genes. The TPA-induced genes are predicted to be regulated by SRF and ETS factors, whereas those upregulated by TPA plus MRTFAOE lack ETS binding motifs, and MRTFAOE skews SRF binding to genomic regions with CArG sites in regions relatively lacking in ETS binding motifs. Finally, ChIP–polymerase chain reaction using HEL cells and primary human CD34+ cell–derived subpopulations confirms that both SRF and MRTFA have increased binding during megakaryopoiesis at upregulated target genes (eg, CORO1A). We show for the first time that MRTFA increases both the genomic association and activity of SRF and upregulates genes that enhance primary human megakaryopoiesis.

scholarly journals TGF-β regulates the expression of transcription factor KLF6 and its splice variants and promotes co-operative transactivation of common target genes through a Smad3–Sp1–KLF6 interaction

2009 ◽  
Vol 419 (2) ◽  
pp. 485-495 ◽  
Author(s):  
Luisa M. Botella ◽  
Francisco Sanz-Rodriguez ◽  
Yusuke Komi ◽  
Africa Fernandez-L ◽  
Elisa Varela ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Target Genes ◽  
Transforming Growth Factor ◽  
Splice Variants ◽  
Biological Activities ◽  
Resonance Energy ◽  
Transforming Growth Factor Β1 ◽  
Full Length ◽  
Specific Cell ◽  
Tgf Β1

KLF6 (Krüppel-like factor 6) is a transcription factor and tumour suppressor with a growing range of biological activities and transcriptional targets. Among these, KLF6 suppresses growth through transactivation of TGF-β1 (transforming growth factor-β1). KLF6 can be alternatively spliced, generating lower-molecular-mass isoforms that antagonize the full-length WT (wild-type) protein and promote growth. A key target gene of full-length KLF6 is endoglin, which is induced in vascular injury. Endoglin, a homodimeric cell membrane glycoprotein and TGF-β auxiliary receptor, has a pro-angiogenic role in endothelial cells and is also involved in malignant progression. The aim of the present work was to explore the effect of TGF-β on KLF6 expression and splicing, and to define the contribution of TGF-β on promoters regulated by co-operation between KLF6 and Sp1 (specificity protein 1). Using co-transfection, co-immunoprecipitation and fluorescence resonance energy transfer, our data demonstrate that KLF6 co-operates with Sp1 in transcriptionally regulating KLF6-responsive genes and that this co-operation is further enhanced by TGF-β1 through at least two mechanisms. First, in specific cell types, TGF-β1 may decrease KLF6 alternative splicing, resulting in a net increase in full-length, growth-suppressive KLF6 activity. Secondly, KLF6–Sp1 co-operation is further enhanced by the TGF-β–Smad (similar to mothers against decapentaplegic) pathway via the likely formation of a tripartite KLF6–Sp1–Smad3 complex in which KLF6 interacts indirectly with Smad3 through Sp1, which may serve as a bridging molecule to co-ordinate this interaction. These findings unveil a finely tuned network of interactions between KLF6, Sp1 and TGF-β to regulate target genes.

Abnormally High Levels of E- and N-Cadherin Expression Add to Altered Regulation of b-Catenin In Multiple Myeloma

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2982-2982
Author(s):  
Ya-Wei Qiang ◽  
Peter Stewart ◽  
Yu Chen ◽  
Bo Hu ◽  
John Shaughnessy ◽  
...  
Keyword(s):  
Transcriptional Activity ◽  
Target Genes ◽  
Plasma Cells ◽  
Expression System ◽  
Mrna Levels ◽  
Hematopoietic Stem ◽  
Mesenchymal Transition ◽  
Protein Levels ◽  
Elevated Expression ◽  
E Cadherin

Abstract Abstract 2982 Gene expression profiling (GEP) of normal and malignant plasma cells and B-cells, revealed that MM is uniquely characterized by elevated expression of E- or N-cadherin. Classical cadherins are integral plasma membrane proteins, that together with a- and b-catenin form calcium-dependent adherent junctions. Homotypic interaction of N-cadherin+ hematopoietic stem cells and N-cadherin+ bone lining cells in the endosteal niche regulates HSC function. Adherent junctions contribute to the regulation of Wnt/b-catenin signaling by modulating the balance between membrane-bound and free cytosolic b-catenin, the latter of which is required for TCF transcriptional activity. Overexpression of DKK1 and suppression of Wnt/b-catenin osteoblasts causes a loss in self-renewal of HSC and only stromal cells with active nuclear b-catenin can support hematopoiesis in-vitro. On the other hand, disruption of adherent junctions and release of b-catenin contributes to epithelial-to-mesenchymal transition and solid tumor metastases. We, and others, have demonstrated that Wnt/β-catenin signaling is active in MM. However, emerging evidence suggests that loss of Wnt/b-catenin activity, rather than its activation, is central to MM pathogenesis. Nearly 90% of primary MM cells express and secrete DKK1 and/or SFRP3 or SFRP2, potent inhibitors of Wnt/b-catenin signaling. Moreover, loss-of-function mutations of APC or axin genes or gain-of-function mutations in the β-catenin gene common in colon cancer have not been found in MM. We therefore hypothesized that elevated expression of N/E-cadherin in MM cells contributes to the abnormally increase of b-catenin in MM. We first assessed the steady-state levels of β-catenin protein in MMCL with immunoblotting analysis. β-Catenin protein was expressed in all tested MMCL, with variable levels in individual lines. Interestingly, relative levels of β-catenin protein were comparable to N-cadherin expression in all eight tested myeloma cell lines. CD138-enriched plasma cells from the BM of 72 patients newly diagnosed MM revealed β-catenin protein levels are highly variable. After normalization of β-catenin with β-tubulin levels we segregated cases into three groups: 39% had low, 23% moderate, and 38% high levels of β-catenin. Analysis of correlation of b-catenin protein levels with U133Plus microarray data revealed there are striking positive correlations between N- or E-cadherin mRNA levels with levels of b-catenin protein. Importantly, b-catenin levels were not correlated with known Wnt/b-catenin target genes. To evaluate the role of N-cadherin in regulating β-catenin signaling in MM, we used a lentiviral expression system to express wild-type N-cadherin (NCadW/MMS1) or empty vector (EV/MMS1) in MMS1 cells. Significant increases in total and free b-catenin correlated with N-cadherin protein expression. These results indicate that N-cadherin protein modulates b-catenin levels MM cells. Results of experiments to determine whether N-cadherin-mediated regulation of b-catenin translates into altered TCF/b-catenin transcriptional activity in MM cells will be reported. Disclosures: Shaughnessy: Myeloma Health LLC: Consultancy, Equity Ownership, Patents & Royalties; Novartis: Membership on an entity's Board of Directors or advisory committees, Patents & Royalties; Genzyme: Patents & Royalties; Millennium: Honoraria; Celgene: Honoraria; OrthoBiotech: Honoraria; Array BioPharma: Honoraria.

First-in-human clinical, pharmacokinetic (PK), and pharmacodynamic (PD) phase I study of the first-in-class spliceosome inhibitor E7107 administered IV (bolus) on days 1, 8, and 15 every 28 days to patients with solid tumors

2009 ◽  
Vol 27 (15_suppl) ◽  
pp. 3508-3508
Author(s):  
F. A. Eskens ◽  
F. J. Ramos ◽  
H. Burger ◽  
M. J. de Jonge ◽  
J. Wanders ◽  
...  
Keyword(s):  
Target Genes ◽  
Expression Profiles ◽  
Systemic Exposure ◽  
Fold Increase ◽  
Pharmacokinetic Analysis ◽  
Base Line ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Grade 3 ◽  
Dose Dependent

3508 Background: E7107 is a potent first-in-class inhibitor of the spliceosome, most likely by interacting with spliceosome-associated protein-130 (SAP 130). Splicing removes intron sequences from pre-mRNA and exons are fused resulting in the formation of mature mRNA. Alternative splicing frequently encodes oncoproteins. E7107 interferes the maturation process of pre-mRNA to mRNA, with consequent changes in protein expression profiles. Methods: Objectives of this study were to explore (1) tolerability and safety profile, (2) PK, (3) PD effects on pre-mRNA splicing, and (4) anti tumor activity of E7107 administered as bolus infusion on days 1, 8, 15 of a 28-day schedule Results: 36 patients (21M/15F, median age 61yrs (45–79)) received E7107 doses of 0.6 mg/m2 (n=4), 0.9 mg/m2 (n=3), 1.3 mg/m2 (n=3), 2.0 mg/m2 (n=3), 3.0 mg/m2 (n=4), 4.5 mg/m2 (n=3) and 4.0 mg/m2 (n=16). At 4.5 mg/m2 two episodes of DLT (grade 3 and 4 diarrhea) and at 4.0 mg/m2 one episode of DLT (a combination of grade 3 nausea, vomiting and abdominal cramps) were observed. Other frequently occurring side effects were mainly gastrointestinal. The maximum tolerable dose (MTD) is 4.0 mg/m2. No complete or partial responses were observed. Pharmacokinetic analysis revealed large volume of distribution (Vss: 279 to 1369 L), high systemic clearance (CL: 111 to 253 L/hr), and moderate elimination half-life (t1/2: 5.3 to 15.1 hr). Systemic exposure on Days 1 and 15 (Cmax, AUC0-∞) increased in a dose-dependent manner. At the MTD, mRNA levels of selected target genes (TRAPPC4, SLC25A19, GTF2H1), monitored in PBMC's, showed a 15–25-fold decrease, whereas unspliced pre-mRNA levels of DNAJB1 and EIF4A1 showed a 10–25-fold increase. Notably, at days 1 and 15, modulations generally peaked at 2–6 hr after end of the infusion and almost completely recovered to base-line levels at 24–48 hr. Conclusions: The MTD for E7107 using this schedule is 4.0 mg/m2. PK is dose-dependent and reproducible within subjects. PD analysis revealed dose-dependent reversible inhibition of pre-mRNA processing of target genes, confirming proof-of-principle activity of E7107. [Table: see text]

scholarly journals The Polymorphism in ADORA3 Decreases Transcriptional Activity and Influences the Chronic Heart Failure Risk in the Chinese

2018 ◽  
Vol 2018 ◽  
pp. 1-9
Author(s):  
Hai-Rong He ◽  
Yuan-Jie Li ◽  
Gong-Hao He ◽  
Hua Qiang ◽  
Ya-Jing Zhai ◽  
...  
Keyword(s):  
Heart Failure ◽  
Chronic Heart Failure ◽  
Transcriptional Activity ◽  
Case Control Study ◽  
Southern China ◽  
Case Control ◽  
Luciferase Reporter ◽  
Mrna Levels ◽  
Chinese Han ◽  
Control Study

Aim. To investigate the genetic contribution of adenosine A3 receptor (ADORA3) gene polymorphisms in the pathogenesis of chronic heart failure (CHF). Methods. Firstly, a case-control study was performed to investigate the association of ADORA3 polymorphisms with CHF risk. Three hundred northern Chinese Han CHF patients and 400 ethnicity-matched healthy controls were included. Four polymorphisms were genotyped. This case-control study was also replicated in 304 CHF patients and 402 controls from southern China. Finally, the functional variability of positive polymorphism was analyzed using luciferase reporter assay and real-time PCR. Results. Overall, the rs1544223 was significantly associated with CHF risk under the dominant model (P=0.046, OR = 1.662, 95% CI = 1.009–2.738). But it did not affect disease severity. These results were also consistent in replicated population. In addition, the transcriptional activity for promoter with the A allele was lower than that with the G allele (n=3, 4.501±0.308 versus 0.571±0.114, P<0.01) and ADORA3 mRNA levels were significantly higher in GG homozygotes than subjects carrying GA (n=6, 0.058±0.01 versus 0.143±0.068, P=0.004) or AA genotypes (n=6, 0.065±0.01 versus 0.143±0.068, P=0.008). Conclusions. Should the findings be validated by further studies with larger patient samples and in different ethnicities, they may provide novel insight into the pathogenesis of CHF.

scholarly journals Adipocyte expression of PU.1 transcription factor causes insulin resistance through upregulation of inflammatory cytokine gene expression and ROS production

2012 ◽  
Vol 302 (12) ◽  
pp. E1550-E1559 ◽  
Author(s):  
Ligen Lin ◽  
Weijun Pang ◽  
Keyun Chen ◽  
Fei Wang ◽  
Jon Gengler ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Transcription Factor ◽  
Nadph Oxidase ◽  
Proinflammatory Cytokines ◽  
Target Genes ◽  
Cytokine Gene Expression ◽  
Ros Generation ◽  
Mrna Levels ◽  
Ets Family ◽  
Adipose Inflammation

We have reported previously that ETS family transcription factor PU.1 is expressed in mature adipocytes of white adipose tissue. PU.1 expression is increased greatly in mouse models of genetic or diet-induced obesity. Here, we show that PU.1 expression is increased only in visceral but not subcutaneous adipose tissues of obese mice, and the adipocytes are responsible for this increase in PU.1 expression. To further address PU.1's physiological function in mature adipocytes, PU.1 was knocked down in 3T3-L1 cells using retroviral-mediated expression of PU.1-targeting shRNA. Consistent with previous findings that PU.1 regulates its target genes, such as NADPH oxidase subunits and proinflammatory cytokines in myeloid cells, the mRNA levels of proinflammatory cytokines (TNFα, IL-1β, and IL-6) and cytosolic components of NADPH oxidase (p47phox and p40phox) were downregulated significantly in PU.1-silenced adipocytes. NADPH oxidase is a main source for reactive oxygen species (ROS) generation. Indeed, silencing PU.1 suppressed NADPH oxidase activity and attenuated ROS in basal or hydrogen peroxide-treated adipocytes. Silencing PU.1 in adipocytes suppressed JNK1 activation and IRS-1 phosphorylation at Ser307. Consequently, PU.1 knockdown improved insulin signaling and increased glucose uptake in basal and insulin-stimulated conditions. Furthermore, knocking down PU.1 suppressed basal lipolysis but activated stimulated lipolysis. Collectively, these findings indicate that obesity induces PU.1 expression in adipocytes to upregulate the production of ROS and proinflammatory cytokines, both of which lead to JNK1 activation, insulin resistance, and dysregulation of lipolysis. Therefore, PU.1 might be a mediator for obesity-induced adipose inflammation and insulin resistance.

scholarly journals Sorcin stimulates Activation Transcription Factor 6α (ATF6) transcriptional activity

2020 ◽  
Author(s):  
Steven Parks ◽  
Tian Gao ◽  
Natalia Jimenez Awuapura ◽  
Joseph Ayathamattam ◽  
Pauline L. Chabosseau ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Transcription Factor ◽  
Beta Cell ◽  
Er Stress ◽  
Transcriptional Activity ◽  
Pancreatic Beta Cell ◽  
Mrna Levels ◽  
High Fat ◽  
Insulin Promoter

ABSTRACTLevels of the transcription factor ATF6α, a key mediator of the unfolded protein response, that provides cellular protection during the progression endoplasmic reticulum (ER) stress, are markedly reduced in the pancreatic islet of patients with type 2 diabetes and in rodent models of the disease, including ob/ob and high fat-fed mice. Sorcin (gene name SRI) is a calcium (Ca2+) binding protein involved in maintaining ER Ca2+ homeostasis.We have previously shown that overexpressing sorcin under the rat insulin promoter in transgenic mice was protective against high fat diet-induced pancreatic beta cell dysfunction, namely preserving intracellular Ca2+ homeostasis and glucose-stimulated insulin secretion during lipotoxic stress. Additionally, sorcin overexpression was apparently activating ATF6 signalling in MIN6 cells despite lowering ER stress.Here, in order to investigate further the relationship between sorcin and ATF6, we describe changes in sorcin expression during ER and lipotoxic stress and changes in ATF6 signalling after sorcin overexpression or inactivation, both in excitable and non-excitable cells.Sorcin mRNA levels were significantly increased in response to the ER stress-inducing agents thapsigargin and tunicamycin, but not by palmitate. On the contrary, palmitate caused a significant decrease in sorcin expression as assessed by both qRT-PCR and Western blotting despite inducing ER stress. Moreover, palmitate prevented the increase in sorcin expression induced by thapsigargin. In addition, sorcin overexpression significantly increased ATF6 transcriptional activity, whereas sorcin inactivation decreased ATF6 signalling. Finally, sorcin overexpression increased levels of ATF6 immunoreactivity and FRET imaging experiments following ER stress induction by thapsigargin showed a direct sorcin-ATF6 interaction.Altogether, our data suggest that sorcin down-regulation during lipotoxicity may prevent full ATF6 activation and a normal UPR during the progression of obesity and insulin resistance, contributing to beta cell failure and type 2 diabetes.

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