Transcriptional Effector Research Articles

The role of MYB proto-oncogene like 2 in tamoxifen resistance in breast cancer.

Despite the efficacy of tamoxifen in preventing disease relapse, a large portion of breast cancer patients show intrinsic or acquired resistance to tamoxifen, leading to treatment failure and unfavorable clinical outcome. MYB proto-oncogene like 2 (MYBL2) is a transcription factor implicated in the initiation and progression of various human cancers. However, its role in tamoxifen resistance in breast cancer remained largely unknown. In the present study, by analyzing public transcriptome dataset, we found that MYBL2 is overexpressed in breast cancer and is associated with the poor prognosis of breast cancer patients. By establishing tamoxifen-resistant breast cancer cell lines, we also provided evidence that MYBL2 overexpression contributes to tamoxifen resistance by up-regulating its downstream transcriptional effectors involved in cell proliferation (PLK1, PRC1), survival (BIRC5) and metastasis (HMMR). In contrast, inhibiting those genes via MYBL2 depletion suppresses cancer progression, restores tamoxifen and eventually reduces the risk of disease recurrence. All these findings revealed a critical role of MYBL2 in promoting tamoxifen resistance and exacerbating the progression of breast cancer, which may serve as a novel therapeutic target to overcome drug resistance and improve the prognosis of breast cancer patients.

E3 ubiquitin ligase PARK2, an inhibitor of melanoma cell growth, is repressed by the oncogenic ERK1/2-ELK1 transcriptional axis

Malignant melanoma, the most aggressive form of skin cancer, is characterized by high prevalence of BRAF/NRAS mutations and hyperactivation of extracellular signal-regulated kinase 1 and 2 (ERK1/2), mitogen-activated protein kinases (MAPK), leading to uncontrolled melanoma growth. Efficacy of current targeted therapies against mutant BRAF or MEK1/2 have been hindered by existence of innate or development of acquired resistance. Therefore, a better understanding of the mechanisms controlled by MAPK pathway driving melanogenesis will help develop new treatment approaches targeting this oncogenic cascade. Here, we identify E3 ubiquitin ligase PARK2 as a direct target of ELK1, a known transcriptional effector of MAPK signaling in melanoma cells. We show that pharmacological inhibition of BRAF-V600E or ERK1/2 in melanoma cells increases PARK2 expression. PARK2 overexpression reduces melanoma cell growth in vitro and in vivo and induces apoptosis. Conversely, its genetic silencing increases melanoma cell proliferation and reduces cell death. Further, we demonstrate that ELK1 is required by the BRAF-ERK1/2 pathway to repress PARK2 expression and promoter activity in melanoma cells. Clinically, PARK2 is highly expressed in WT BRAF and NRAS melanomas, but it is expressed at low levels in melanomas carrying BRAF/NRAS mutations. Overall, our data provide new insights into the tumor suppressive role of PARK2 in malignant melanoma and uncover a novel mechanism for the negative regulation of PARK2 via the ERK1/2-ELK1 axis. These findings suggest that reactivation of PARK2 may be a promising therapeutic approach to counteract melanoma growth.

Tead1 Reciprocally Regulates Adult β-Cell Proliferation and Function to Maintain Glucose Homeostasis

The low proliferative rate of adult β-cells presents a challenge for diabetes therapy to increase β-cell numbers while maintaining mature function. Although proliferative quiescence in β-cells is required to maintain functional competence, exemplified by glucose stimulated insulin secretion, the molecular underpinnings of this reciprocal relationship remain enigmatic. Here, we demonstrate that Tead1, the transcription effector of the mammalian-Hippo pathway drives developmental stage-specific β-cell proliferative capacity in conjunction with its functional maturation. Tead1 promotes adult β-cell mature identity by direct transcriptional control of a network of critical β-cell transcription factors, including, Pdx1, Nkx6.1 and MafA, while its regulation of Cdkn2a maintains proliferative quiescence. Consequently, mice with either constitutive or inducible genetic deletion of Tead1 in β-cells developed overt diabetes due to a severe loss of secretory function despite induction of proliferation. Furthermore, we show that Tead1 has a similar regulatory role in human β-cells. We propose that Tead1 is an essential intrinsic molecular switch coordinating adult β-cell proliferative quiescence with mature identity and functional competence to maintain glucose homeostasis.

Transcriptomic Profiling of Human Effector and Regulatory T Cell Subsets Identifies Predictive Population Signatures.

After activation, CD4+ Th cells differentiate into functionally specialized populations that coordinate distinct immune responses and protect against different types of pathogens. In humans, these effector and memory Th cell subsets can be readily identified in peripheral blood based on their differential expression of chemokine receptors that govern their homeostatic and inflammatory trafficking. Foxp3+ regulatory T (Treg) cells can also be divided into subsets that phenotypically mirror each of these effector populations and share expression of key transcription factors and effector cytokines. In this study, we performed comprehensive transcriptional profiling of 11 phenotypically distinct Th and Treg cell subsets sorted from peripheral blood of healthy individuals. Despite their shared phenotypes, we found that mirror Th and Treg subsets were transcriptionally dissimilar and that Treg cell populations showed limited transcriptional diversity compared with Th cells. We identified core transcriptional signatures shared across all Th and Treg cell populations and unique signatures that define each of the Th or Treg populations. Finally, we applied these signatures to bulk Th and Treg RNA-sequencing data and found enrichment of specific Th and Treg cell populations in different human tissues. These results further define the molecular basis for the functional specialization and differentiation of Th and Treg cell populations and provide a new resource for examining Th and Treg specialization in RNA-sequencing data.

YAP vs. TAZ: differences in expression revealed through rigorous validation of target-specific monoclonal antibodies

ABSTRACT The ability to reproduce scientific findings is foundational in research; yet, it is compromised in part by poorly characterized reagents, including antibodies. In this report, we describe the application of complementary validation strategies tailored for use in immunohistochemical assays in the characterization of rabbit monoclonal antibodies against YAP and TAZ, homologous and sequentially similar transcriptional effectors of the Hippo signaling pathway. A lack of antibody reagents rigorously validated for immunohistochemistry has limited the Hippo signaling research community’s ability to interrogate YAP and TAZ independently in tissue. In a series of normal and diseased human tissues, we were able to demonstrate differential expression patterns of YAP and TAZ, suggesting the potential for functional differences of these proteins. These differences can now be studied in greater detail with these highly validated tools.

Postnatal Deletion of Bmal1 in Mice Protects Against Obstructive Renal Fibrosis Via Suppressing Gli2 Transcription

Background: Circadian clock is involved in regulating most renal physiological functions, including water and electrolyte balance and blood pressure homeostasis. However, the role of circadian clock in renal pathophysiology remains largely unknown. Methods: The inducible postnatal Bmal1 knockout mice (iKO) were used in the study. The diurnal oscillation of blood pressure and urinary water and electrolyte excretion was compared between iKO and controls. Unilateral ureteral obstruction (UUO) was performed to induce renal fibrosis. ChIP, luciferase reporter assay, and the in vitro cell culture experiments were used to elucidate the transcriptional activation of Bmal1 on Gli2. Findings: The iKO mice exhibit increased urinary volume and electrolyte excretion but abolished diurnal variation. Upon UUO, the iKO mice displayed significantly attenuated tubulointerstitial fibrosis and decreased expression of the hedgehog pathway transcriptional effectors Gli1 and Gli2. ChIP and luciferase reporter assays revealed that BMAL1 bound to the promoter of and activate the transcription of Gli2, but not Gli1, suggesting that the involvement of Bmal1 in renal fibrosis was possibly mediated via Gli2-dependent mechanisms. Furthermore, treatment with TGF-β increased Bmal1 in cultured murine proximal tubular cells, and knockdown of Bmal1 abolished, while overexpression of Bmal1 increased, Gli2 and the expression of fibrosis related genes. Interpretation: Our results revealed a prominent role of the circadian clock in renal fibrosis. Moreover, we identified Gli2 as a novel target of Bmal1, which may mediate the adverse effect of Bmal1 in obstructive nephropathy.

Pharmacological Inhibition of PPARy Boosts HIV Reactivation and Th17 Effector Functions, While Preventing Progeny Virion Release and de novo Infection.

The frequency and functions of Th17-polarized CCR6+RORyt+CD4+ T cells are rapidly compromised upon HIV infection and are not restored with long-term viral suppressive antiretroviral therapy (ART). In line with this, Th17 cells represent selective HIV-1 infection targets mainly at mucosal sites, with long-lived Th17 subsets carrying replication-competent HIV-DNA during ART. Therefore, novel Th17-specific therapeutic interventions are needed as a supplement of ART to reach the goal of HIV remission/cure. Th17 cells express high levels of peroxisome proliferator-activated receptor gamma (PPARy), which acts as a transcriptional repressor of the HIV provirus and the rorc gene, which encodes for the Th17-specific master regulator RORyt. Thus, we hypothesized that the pharmacological inhibition of PPARy will facilitate HIV reservoir reactivation while enhancing Th17 effector functions. Consistent with this prediction, the PPARy antagonist T0070907 significantly increased HIV transcription (cell-associated HIV-RNA) and RORyt-mediated Th17 effector functions (IL-17A). Unexpectedly, the PPARy antagonism limited HIV outgrowth from cells of ART-treated people living with HIV (PLWH), as well as HIV replication in vitro. Mechanistically, PPARy inhibition in CCR6+CD4+ T cells induced the upregulation of transcripts linked to Th17-polarisation (RORyt, STAT3, BCL6 IL-17A/F, IL-21) and HIV transcription (NCOA1-3, CDK9, HTATIP2). Interestingly, several transcripts involved in HIV-restriction were upregulated (Caveolin-1, TRIM22, TRIM5α, BST2, miR-29), whereas HIV permissiveness transcripts were downregulated (CCR5, furin), consistent with the decrease in HIV outgrowth/replication. Finally, PPARy inhibition increased intracellular HIV-p24 expression and prevented BST-2 downregulation on infected T cells, suggesting that progeny virion release is restricted by BST-2-dependent mechanisms. These results provide a strong rationale for considering PPARy antagonism as a novel strategy for HIV-reservoir purging and restoring Th17-mediated mucosal immunity in ART-treated PLWH.

IL-10 production by ILC2s requires Blimp-1 and cMaf, modulates cellular metabolism, and ameliorates airway hyperreactivity

Group 2 innate lymphoid cells (ILC2s) are the dominant innate lymphoid cell population in the lungs at steady state, and their release of type 2 cytokines is a central driver in responding eosinophil infiltration and increased airway hyperreactivity. Our laboratory has identified a unique subset of ILC2s in the lungs that actively produce IL-10 (ILC210s). Our aim was to characterize the effector functions of ILC210s in the development and pathology of allergic asthma. IL-4-stimulated ILC210s were isolated to evaluate cytokine secretion, transcription factor signaling, metabolic dependence, and effector functions invitro. ILC210s were also adoptively transferred into Rag2-/-γc-/- mice, which were then challenged with IL-33 and assessed for airway hyperreactivity and lung inflammation. We have determined that the transcription factors cMaf and Blimp-1 regulate IL-10 expression in ILC210s. Strikingly, our results demonstrate that ILC210s can utilize both autocrine and paracrine signaling to suppress proinflammatory ILC2 effector functions invitro. Further, this subset dampens airway hyperreactivity and significantly reduces lung inflammation invivo. Interestingly, ILC210s demonstrated a metabolic dependency on the glycolytic pathway for IL-10 production, shifting from the fatty acid oxidation pathway conventionally utilized for proinflammatory effector functions. These findings provide an important and previously unrecognized role of ILC210s in diseases associated with ILC2s such as allergic lung inflammation and asthma. They also provide new insights into the metabolism dependency of proinflammatory and anti-inflammatory ILC2 phenotypes.

Bacteria-induced IMD-Relish-AMPs pathway activation in Chinese mitten crab

The innate immune response is an important line of defense against invading pathogens in invertebrates. Signaling pathways, including the IMD pathway, play critical roles in the production of antimicrobial peptides (AMPs), which induce the transcription of immune effectors that protect against bacterial invasion. In the present study, the cDNA of IMD from Eriocheir sinensis was cloned (designated EsIMD) and shown to be significantly upregulated following Gram-positive and Gram-negative bacterial infection. In vivo and in vitro studies collectively suggested that both the Gram-negative bacterium Vibrio parahemolyticus and the Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis elicit the translocation of Relish. Moreover, EsIMD positively regulated EsRelish translocation from the cytoplasm to the nucleus following stimulation with both Gram-positive and Gram-negative bacteria. EsRelish knockdown in hemocytes significantly suppressed AMPs’ expression. Furthermore, both Lys-type and DAP-type peptidoglycan-containing bacteria activated the IMD pathway and elicited antibacterial responses in crab. Conclusively, these findings demonstrate that both Gram-positive and Gram-negative bacteria activate IMD signaling, via a mechanism that is distinct with that by which Gram-negative bacteria activate IMD signaling in Drosophila. These findings might pave the way for a better understanding of the innate immune system and the fundamental network of the IMD signaling pathway in crustacean.

Endothelin 1-induced retinal ganglion cell death is largely mediated by JUN activation

Glaucoma is a neurodegenerative disease characterized by loss of retinal ganglion cells (RGCs), the output neurons of the retina. Multiple lines of evidence show the endothelin (EDN, also known as ET) system is important in glaucomatous neurodegeneration. To date, the molecular mechanisms within RGCs driving EDN-induced RGC death have not been clarified. The pro-apoptotic transcription factor JUN (the canonical target of JNK signaling) and the endoplasmic reticulum stress effector and transcription factor DNA damage inducible transcript 3 (DDIT3, also known as CHOP) have been shown to act downstream of EDN receptors. Previous studies demonstrated that JUN and DDIT3 were important regulators of RGC death after glaucoma-relevant injures. Here, we characterized EDN insult in vivo and investigated the role of JUN and DDIT3 in EDN-induced RGC death. To accomplish this, EDN1 ligand was intravitreally injected into the eyes of wildtype, Six3-cre+Junfl/fl (Jun−/−), Ddit3 null (Ddit3−/−), and Ddit3−/−Jun−/− mice. Intravitreal EDN1 was sufficient to drive RGC death in vivo. EDN1 insult caused JUN activation in RGCs, and deletion of Jun from the neural retina attenuated RGC death after EDN insult. However, deletion of Ddit3 did not confer significant protection to RGCs after EDN1 insult. These results indicate that EDN caused RGC death via a JUN-dependent mechanism. In addition, EDN signaling is known to elicit potent vasoconstriction. JUN signaling was shown to drive neuronal death after ischemic insult. Therefore, the effects of intravitreal EDN1 on retinal vessel diameter and hypoxia were explored. Intravitreal EDN1 caused transient retinal vasoconstriction and regions of RGC and Müller glia hypoxia. Thus, it remains a possibility that EDN elicits a hypoxic insult to RGCs, causing apoptosis via JNK-JUN signaling. The importance of EDN-induced vasoconstriction and hypoxia in causing RGC death after EDN insult and in models of glaucoma requires further investigation.

THE YAP INHIBITOR VERTEPORFIN REGULATES ACTIVIN-A/SMAD SIGNALING AND MECHANOTRANSDUCTION IN UTERINE FIBROID CELLS

Uterine fibroids are mechanically stiff fibrotic tumors of the uterus. Activin A, a member of the TGF-β superfamily, is overexpressed in fibroids and is known to increase expression of extracellular matrix (ECM) proteins. The increased stiffness of ECM in fibroids leads to activation of mechanotransduction signaling. Hippo is a key pathway that regulates cell growth and fibrosis in response to stiffness of ECM. YAP (yes-associated protein), a transcriptional effector of Hippo signaling, is also overexpressed in fibroids.

Analysis of Glucocorticoid-Related Genes Reveal CCHCR1 as a New Candidate Gene for Type 2 Diabetes.

Glucocorticoids have multiple therapeutic benefits and are used both for immunosuppression and treatment purposes. Notwithstanding their benefits, glucocorticoid use often leads to hyperglycemia. Owing to the pathophysiologic overlap in glucocorticoid-induced hyperglycemia (GIH) and type 2 diabetes (T2D), we hypothesized that genetic variation in glucocorticoid pathways contributes to T2D risk. To determine the genetic contribution of glucocorticoid action on T2D risk, we conducted multiple genetic studies. First, we performed gene-set enrichment analyses on 3 collated glucocorticoid-related gene sets using publicly available genome-wide association and whole-exome data and demonstrated that genetic variants in glucocorticoid-related genes are associated with T2D and related glycemic traits. To identify which genes are driving this association, we performed gene burden tests using whole-exome sequence data. We identified 20 genes within the glucocorticoid-related gene sets that are nominally enriched for T2D-associated protein-coding variants. The most significant association was found in coding variants in coiled-coil α-helical rod protein 1 (CCHCR1) in the HLA region (P = .001). Further analyses revealed that noncoding variants near CCHCR1 are also associated with T2D at genome-wide significance (P = 7.70 × 10–14), independent of type 1 diabetes HLA risk. Finally, gene expression and colocalization analyses demonstrate that variants associated with increased T2D risk are also associated with decreased expression of CCHCR1 in multiple tissues, implicating this gene as a potential effector transcript at this locus. Our discovery of a genetic link between glucocorticoids and T2D findings support the hypothesis that T2D and GIH may have shared underlying mechanisms.

Abstract A04: Genetic and pharmacologic inhibition of HES1 reduces YAP1 expression, impairing rhabdomyosarcoma cell growth

Abstract Rhabdomyosarcoma (RMS) is a mesenchymal cancer with skeletal muscle histogenesis and the most common soft-tissue sarcoma of childhood. High-risk patient groups continue to have a poor survival (<30%) and novel therapeutic targets are needed. In our studies of Hippo signaling in RMS, we found that expression of YAP1 in a human myoblast-based model of RMS is permissive for bypass of senescence, tolerance of oncogenic RAS expression, and full transformation to cells able to grow as xenografts mimicking the embryonal variant of RMS (ERMS). In parallel, we found that YAP1 engages in a positive feedback loop with the Notch signaling pathway, suggesting that Notch effectors must impact downstream YAP1. Here we show that shRNA-mediated suppression of the basic helix-loop-helix transcriptional repressor and Notch effector, HES1, inhibits ERMS cell growth in vitro. Mechanistically, HES1 suppression causes decreased levels of YAP1 mRNA and protein, and increased mRNA and protein levels of the cell cycle regulator and tumor suppressor CDKN1C (P57kip2) across three different cell lines. Additionally, HES1 suppression results in cell line-specific increases in the myogenic markers MYOD1, MYOG, and MYF6. Recently, Perron et al. reported that the small molecule JI051 inhibits HES1 by stabilizing its interaction (doi:10.1074/jbc.RA118.002316) with the protein chaperone prohibitin-2, thus sequestering HES1 outside the nucleus. We demonstrate that JI051 inhibits ERMS cell growth in vitro with EC50 values in the low nanomolar range. Preclinical in vivo studies combining HES1 inhibition and YAP1 inhibition are planned, with the hypothesis that their coinhibition could prove effective in mitigating treatment resistance. A full understanding of the relationship between HES1 and YAP1 signaling will be paramount in moving compounds such as JI051 from the laboratory to the clinic. Citation Format: Alexander R. Kovach, Corinne M. Linardic. Genetic and pharmacologic inhibition of HES1 reduces YAP1 expression, impairing rhabdomyosarcoma cell growth [abstract]. In: Proceedings of the AACR Special Conference on the Hippo Pathway: Signaling, Cancer, and Beyond; 2019 May 8-11; San Diego, CA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(8_Suppl):Abstract nr A04.

Maf1 regulates dendritic morphogenesis and influences learning and memory

Maf1, a general transcriptional regulator and mTOR downstream effector, is highly expressed in the hippocampus and cortex, but the function of Maf1 in neurons is not well elucidated. Here, we first demonstrate that Maf1 plays a central role in the inhibition of dendritic morphogenesis and the growth of dendritic spines both in vitro and in vivo. Furthermore, Maf1 downregulation paradoxically leads to activation of AKT-mTOR signaling, which is mediated by decreased PTEN expression. Moreover, we confirmed that Maf1 could regulate the activity of PTEN promoter by luciferase reporter assay, and proved that Maf1 could bind to the promoter of PTEN by ChIP-PCR experiment. We also demonstrate that expression of Maf1 in the hippocampus affects learning and memory in mice. Taken together, we show for the first time that Maf1 inhibits dendritic morphogenesis and the growth of dendritic spines through AKT-mTOR signaling by increasing PTEN expression.

Targeting Rad51 as a strategy for the treatment of melanoma cells resistant to MAPK pathway inhibition

Rad51 is an essential factor of the homologous recombination DNA repair pathway and therefore plays an important role in maintaining genomic stability. We show that RAD51 and other homologous recombination repair genes are overexpressed in metastatic melanoma cell lines and in melanoma patient samples, which correlates with reduced survival of melanoma patients. In addition, Rad51 expression in melanoma cells was regulated on a transcriptional level by the MAPK signaling pathway with Elk1 as the main downstream transcriptional effector. Most strikingly, melanoma cells which developed resistance towards MAPK inhibitors could be efficiently targeted by Rad51 inhibitors similar to their sensitive counterparts, leading to DNA damage, G2/M arrest and apoptosis. Furthermore, the treatment of MAPK inhibitor resistant cells with Rad51 inhibitors enhances the susceptibility of these cells for MAPK inhibitor treatment in vitro and in vivo. These data indicate that Rad51 plays a critical role in the survival of metastatic melanoma cells and is a promising target for the therapy of melanoma irrespective of its MAPK inhibitor resistance status.

The Histone Chaperone FACT Induces Cas9 Multi-turnover Behavior and Modifies Genome Manipulation in Human Cells

Cas9 is a prokaryotic RNA-guided DNA endonuclease that binds substrates tightly invitro but turns over rapidly when used to manipulate genomes in eukaryotic cells. Little is known about the factors responsible for dislodging Cas9 or how they influence genome engineering. Unbiased detection through proximity labeling of transient protein interactions in cell-free Xenopus laevis egg extract identified the dimeric histone chaperone facilitates chromatin transcription (FACT) as an interactor of substrate-bound Cas9. FACT is both necessary and sufficient to displace dCas9, and FACT immunodepletion converts Cas9's activity from multi-turnover to single turnover. In human cells, FACT depletion extends dCas9 residence times, delays genome editing, and alters the balance between indel formation and homology-directed repair. FACT knockdown also increases epigenetic marking by dCas9-based transcriptional effectors with a concomitant enhancement of transcriptional modulation. FACT thus shapes the intrinsic cellular response to Cas9-based genome manipulation most likely by determining Cas9 residence times.

Targeting the Hippo pathway in cancer, fibrosis, wound healing and regenerative medicine.

The Hippo pathway is an evolutionarily conserved signalling pathway with key roles in organ development, epithelial homeostasis, tissue regeneration, wound healing and immune modulation. Many of these roles are mediated by the transcriptional effectors YAP and TAZ, which direct gene expression via control of the TEAD family of transcription factors. Dysregulated Hippo pathway and YAP/TAZ-TEAD activity is associated with various diseases, most notably cancer, making this pathway an attractive target for therapeutic intervention. This Review highlights the key findings from studies of Hippo pathway signalling across biological processes and diseases, and discusses new strategies and therapeutic implications of targeting this pathway.

Shaping Microglial Phenotypes Through Estrogen Receptors: Relevance to Sex-Specific Neuroinflammatory Responses to Brain Injury and Disease.

In mammals, 17β-estradiol (E2), the primary endogenous estrogen, maintains normal central nervous system (CNS) function throughout life and influences brain responses to injury and disease. Estradiol-induced cellular changes are mediated through the activation of nuclear and extranuclear estrogen receptors (ERs), which include ERα, ERβ, and the G-protein coupled receptor, GPER1. ERs are widely expressed throughout the brain, acting as transcriptional effectors or rapidly initiating membrane and cytoplasmic signaling cascades in practically all brain cells including microglia, the resident immune cells of the CNS. Activation of ERs by E2 exerts potent anti-inflammatory effects through mechanisms involving the modification of microglial cell responses to acute or chronic brain injury. Recent studies suggest that microglial maturation is influenced by the internal gonadal hormone milieu and that their functions in the normal and diseased brain are sex specific. However, the role that each ER subtype plays in microglial development or in determining microglial function as the primary cellular defense mechanism against pathogens and injury remains unclear. This is partly due to the fact that most studies investigating the mechanisms by which E2-ER signaling modifies microglial cellular phenotypes have been restricted to one sex or age. This review examines the different in vivo and in vitro models used to study the direct and indirect regulation of microglial cell function by E2 through ERs. Ischemic stroke will be used as an example of a neurologic disease in which activation of ERs shapes microglial phenotypes in response to injury in a sex- and age-specific fashion. SIGNIFICANCE STATEMENT: As the primary immune sensors of central nervous system damage, microglia are important potential therapeutic targets. Estrogen receptor signaling modulates microglial responses to brain injury and disease in a sex- and age-specific fashion. Hence, investigating the molecular mechanisms by which estrogen receptors regulate and shape microglial functions throughout life may result in novel and effective therapeutic opportunities that are tailored for each sex and age.

Tead1 is essential for mitochondrial function in cardiomyocytes.

Mitochondrial dysfunction occurs in most forms of heart failure. We have previously reported that Tead1, the transcriptional effector of Hippo pathway, is critical for maintaining adult cardiomyocyte function, and its deletion in adult heart results in lethal acute dilated cardiomyopathy. Growing lines of evidence indicate that Hippo pathway plays a role in regulating mitochondrial function, although its role in cardiomyocytes is unknown. Here, we show that Tead1 plays a critical role in regulating mitochondrial OXPHOS in cardiomyocytes. Assessment of mitochondrial bioenergetics in isolated mitochondria from adult hearts showed that loss of Tead1 led to a significant decrease in respiratory rates, with both palmitoylcarnitine and pyruvate/malate substrates, and was associated with reduced electron transport chain complex I activity and expression. Transcriptomic analysis from Tead1-knockout myocardium revealed genes encoding oxidative phosphorylation, TCA cycle, and fatty acid oxidation proteins as the top differentially enriched gene sets. Ex vivo loss of function of Tead1 in primary cardiomyocytes also showed diminished aerobic respiration and maximal mitochondrial oxygen consumption capacity, demonstrating that Tead1 regulation of OXPHOS in cardiomyocytes is cell autonomous. Taken together, our data demonstrate that Tead1 is a crucial transcriptional node that is a cell-autonomous regulator, a large network of mitochondrial function and biogenesis related genes essential for maintaining mitochondrial function and adult cardiomyocyte homeostasis.NEW & NOTEWORTHY Mitochondrial dysfunction constitutes an important aspect of heart failure etiopathogenesis and progression. However, the molecular mechanisms are still largely unknown. Growing lines of evidence indicate that Hippo-Tead pathway plays a role in cellular bioenergetics. This study reveals the novel role of Tead1, the downstream transcriptional effector of Hippo pathway, as a novel regulator of mitochondrial oxidative phosphorylation and in vivo cardiomyocyte energy metabolism, thus providing a potential therapeutic target for modulating mitochondrial function and enhancing cytoprotection of cardiomyocytes.

Syringaresinol Inhibits UVA-Induced MMP-1 Expression by Suppression of MAPK/AP-1 Signaling in HaCaT Keratinocytes and Human Dermal Fibroblasts.

Ultraviolet (UV) irradiation induces detrimental changes in human skin which result in photoaging. UV-induced intracellular changes cause degradation of extracellular matrix (ECM). UV-stimulated cleavage of collagen in ECM occurs via matrix metalloproteinases (MMPs). (±)-syringaresinol (SYR), a phytochemical which belongs to the lignan group of polyphenols, was investigated for its ability to reverse the UVA-induced changes in human HaCaT keratinocytes and dermal fibroblasts (HDFs) in vitro. Effect of SYR on UVA-induced changes was investigated by production and activation of MMPs and its transcriptional upstream effectors; mitogen-activated protein kinases (MAPKs) and pro-inflammatory mediators. Levels of expression were determined using ELISA, RT-PCR and immunoblotting. UVA irradiation stimulated the production of MMP-1 and inhibited collagen production. SYR treatment suppressed MMP-1 and enhanced collagen production in UVA-irradiated HaCaT keratinocytes and HDFs. SYR repressed the UV-induced phosphorylation of p38, ERK and JNK MAPKs in HaCaT keratinocytes while only suppressing JNK phosphorylation in HDFs. In addition, SYR was able to inhibit UVA-induced production of inflammatory cytokines; TNF-α, COX-2, IL-1β and IL-6. Moreover, SYR suppressed the activator protein-1 (AP-1), a heterodimer of phosphorylated transcription factors c-Jun and c-Fos. SYR-treatment decreased nuclear levels of activated c-Fos and c-Jun as a mechanism to inhibit UVA-induced transcriptional activities leading to MMP-1 production. In conclusion, current results demonstrated that SYR could inhibit UVA-induced upregulation of MMP-1 by suppressing MAPK/AP-1 signaling in HaCaT keratinocytes and HDFs. Therefore, SYR was suggested as a potential compound with antiphotoaging properties against UVA-induced skin aging.