Mediator complex subunit 1 promotes oral squamous cell carcinoma progression by activating MMP9 transcription and suppressing CD8+ T cell antitumor immunity.

BACKGROUND: The role of Mediator complex subunit 1 (MED1), a pivotal transcriptional coactivator implicated in diverse biological pathways, remains unexplored in the context of oral squamous cell carcinoma (OSCC). This study aims to elucidate the contributory mechanisms and potential impact of MED1 on the progression of OSCC. METHODS: The expression and clinical significance of MED1 in OSCC tissues were evaluated through the bioinformatics analyses. The effects of MED1 on the biological behavior of OSCC cancer cells were assessed both in vitro and in vivo. Dual-luciferase reporter assay, chromatin immunoprecipitation (ChIP) assay, bioinformatic analysis, CD8+ T cell isolation experiment, coculture experiment, enzyme-linked immunosorbent assay (ELISA), and flow cytometric analysis were employed to elucidate the underlying mechanism through which MED1 operates in the progression of OSCC. RESULTS: MED1 exhibited upregulation in both OSCC tissues and multiple OSCC cell lines, which correlated with decreased overall survival in patients. In vitro experiments demonstrated that knockdown of MED1 in metastatic OSCC cell lines SCC-9 and UPCI-SCC-154 hindered cell migration and invasion, while overexpression of MED1 promoted these processes. Whereas, MED1 knockdown had no impact on proliferation of cell lines mentioned above. In vivo studies further revealed that downregulation of MED1 effectively suppressed distant metastasis in OSCC. Mechanistically, MED1 enhanced the binding of transcription factors c-Jun and c-Fos to the matrix metalloprotein 9 (MMP9) promoters, resulting in a significant upregulation of MMP9 transcription. This process contributes to the migration and invasion of SCC-9 and UPCI-SCC-154 cells. Furthermore, MED1 modulated the expression of programmed death-ligand 1 (PD-L1) through the Notch signaling pathway, consequently impacting the tumor-killing capacity of CD8+ T cells in the tumor microenvironment. CONCLUSIONS: Our findings indicate that MED1 plays a pivotal role in OSCC progression through the activation of MMP9 transcription and suppression of CD8+ T cell antitumor immunity, suggesting that MED1 may serve as a novel prognostic marker and therapeutic target in OSCC.

BET degrader exhibits lower antiproliferative activity than its inhibitor via EGR1 recruiting septins to promote E2F1-3 transcription in triple-negative breast cancer.

The bromodomain and extraterminal domain (BET) family proteins serve as primary readers of acetylated lysine residues and play crucial roles in cell proliferation and differentiation. Dysregulation of BET proteins has been implicated in tumorigenesis, making them important therapeutic targets. BET-bromodomain (BD) inhibitors and BET-targeting degraders have been developed to inhibit BET proteins. In this study, we found that the BET inhibitor MS645 exhibited superior antiproliferative activity than BET degraders including ARV771, AT1, MZ1 and dBET1 in triple-negative breast cancer (TNBC) cells. Treatment with MS645 led to the dissociation of BETs, MED1 and RNA polymerase II from the E2F1-3 promoter, resulting in the suppression of E2F1-3 transcription and subsequent inhibition of cell growth in TNBC. In contrast, while ARV771 displaced BET proteins from chromatin, it did not significantly alter E2F1-3 expression. Mechanistically, ARV771 induced BRD4 depletion at protein level, which markedly increased EGR1 expression. This elevation of EGR1 subsequently recruited septin 2 and septin 9 to E2F1-3 promoters, enhancing E2F1-3 transcription and promoting cell proliferation rate in vitro and in vivo. Our findings provide valuable insights into differential mechanisms of BET inhibition and highlight potential of developing BET-targeting molecules as therapeutic strategies for TNBC.

Med1 controls thymic T-cell migration into lymph node through enhancer-based Foxo1-Klf2 transcription program.

The migration is the key step for thymic T cells to enter circulation and then lymph nodes (LNs), essential for future immune surveillance. Although promoter-based transcriptional regulation through Foxo1, Klf2, Ccr7, and Sell regulates T-cell migration, it remains largely unexplored whether and how enhancers are involved in this process. Here we found that the conditional deletion of Med1, a component of the mediator complex and a mediator between enhancers and RNA polymerase II, caused a reduction of both CD4+ and CD8+ T cells in LNs, as well as a decrease of CD8+ T cells in the spleen. Importantly, Med1 deletion hindered the migration of thymic αßT cells into the circulation and then into LNs, accompanied by the downregulation of KLF2, CCR7, and CD62L. Mechanistically, Med1 promotes Klf2 transcription by facilitating Foxo1 binding to the Klf2 enhancer. Furthermore, forced expression of Klf2 rescued Ccr7 and Sell expression, as well as αßT-cell migration into LNs. Collectively, our study unveils a crucial role for Med1 in regulating the enhancer-based Foxo1-Klf2 transcriptional program and the migration of αßT cells into LNs, providing valuable insights into the molecular mechanisms underlying T-cell migration.

Mediator complex subunit 1 architects a tumorigenic Treg cell program independent of inflammation.

While immunotherapy has revolutionized cancer treatment, its safety has been hampered by immunotherapy-related adverse events. Unexpectedly, we show that Mediator complex subunit 1 (MED1) is required for T regulatory (Treg) cell function specifically in the tumor microenvironment. Treg cell-specific MED1 deletion does not predispose mice to autoimmunity or excessive inflammation. In contrast, MED1 is required for Treg cell promotion of tumor growth because MED1 is required for the terminal differentiation of effector Treg cells in the tumor. Suppression of these terminally differentiated Treg cells is sufficient for eliciting antitumor immunity. Both human and murine Treg cells experience divergent paths of differentiation in tumors and matched tissues with non-malignant inflammation. Collectively, we identify a pathway promoting the differentiation of a Treg cell effector subset specific to tumors and demonstrate that suppression of a subset of Treg cells is sufficient for promoting antitumor immunity in the absence of autoimmune consequences.

Effect of Med1 on T cell development and CD4+ T cell differentiation in immune response. / Med1对T细胞发育及CD4+ Tç»†èƒžåœ¨å ç–«åº”ç­”ä¸­åˆ†åŒ–çš„å½±å“.

OBJECTIVES: The differentiation of CD4+ T cells is regulated by a complex and fine signaling pathway composed of many molecules during immune response, and the molecular mechanism for regulating T-bet expression is unclear. Mediator complex subunit 1 (Med1) can combine with a variety of co-factors to regulate gene transcription, promote cell proliferation and survival, and affect invariant natural killer T cell (iNKT) development. This study aims to investigate the effect of Med1 on T cell development and CD4+ T cell differentiation in immune response. METHODS: Mice with T cell-specific knockout of Med1 gene (Med1F/FCD4cre+, KO) were constructed and verified. The percentage and number of CD4+ and CD8+ T cells in thymus, spleen, and lymph nodes of KO mice and control (Con) mice (Med1F/FCD4cre-) were detected by flow cytometry. After 8 days of infection with lymphocytic choriomeningitis virus (LCMV), the percentage and number of CD4+ T cells or antigen-specific (GP66+) CD4+ T cells, the percentage and number of Th1 cells (Ly6c+PSGL1+) in CD4+ T cells or antigen-specific CD4+ T cells were examined in the spleen of mice. Moreover, the fluorescence intensity of T-bet in CD4+ T cells or antigen-specific CD4+ T cells was analyzed. RESULTS: Compared with the Con group, the percentage and number of CD4+ T cells and CD8+ T cells in the thymus, CD4+ T cells in the spleen and lymph nodes of the KO group showed no significant differences (all P>0.05), but the percentage and number of CD8+ T cells in the spleen and lymph nodes of the KO group were diminished significantly (all P<0.05). After 8 days of infection with LCMV, there was no significant difference in the percentage and number of CD4+ T cells or antigen-specific CD4+ T cells in the spleen between the KO group and the Con group (all P>0.05), while in comparison with the Con group, the percentage and number of Th1 cells in CD4+ T cells or antigen-specific CD4+ T cells, and the expression of T-bet in CD4+ T cells or antigen-specific CD4+ T cells were significantly reduced in the spleen of the KO group (all P<0.05). CONCLUSIONS: Specific knockout of Med1 in T cells does not affect the development of CD4+ and CD8+ T cells in the thymus, but does affect the maintenance of peripheral CD8+ T cells. In the immune response, Med1 gene deletion affects the expression of transcription factor T-bet, which in turn to reduce Th1 cell differentiation.

Interactions between BRD4S, LOXL2, and MED1 drive cell cycle transcription in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) often develops resistance to single-agent treatment, which can be circumvented using targeted combinatorial approaches. Here, we demonstrate that the simultaneous inhibition of LOXL2 and BRD4 synergistically limits TNBC proliferation in vitro and in vivo. Mechanistically, LOXL2 interacts in the nucleus with the short isoform of BRD4 (BRD4S), MED1, and the cell cycle transcriptional regulator B-MyB. These interactions sustain the formation of BRD4 and MED1 nuclear transcriptional foci and control cell cycle progression at the gene expression level. The pharmacological co-inhibition of LOXL2 and BRD4 reduces BRD4 nuclear foci, BRD4-MED1 colocalization, and the transcription of cell cycle genes, thus suppressing TNBC cell proliferation. Targeting the interaction between BRD4S and LOXL2 could be a starting point for the development of new anticancer strategies for the treatment of TNBC.

Mediator subunit MED1 deficiency prevents carbon tetrachloride-induced hepatic fibrosis in mice.

Mediator subunit mediator 1 (MED1) mediates ligand-dependent binding of the mediator coactivator complex to various nuclear receptors and plays a critical role in embryonic development, lipid and glucose metabolism, liver regeneration, and tumorigenesis. However, the precise role of MED1 in the development of liver fibrosis has been unclear. Here, we showed that MED1 expression was increased in livers from nonalcoholic steatohepatitis (NASH) patients and mice and positively correlated with transforming growth factor ß (TGF-ß) signaling and profibrotic factors. Upon treatment with carbon tetrachloride (CCl4), hepatic fibrosis was much less in liver-specific MED1 deletion (MED1ΔLiv) mice than in MED1fl/fl littermates. TGF-ß/Smad2/3 signaling pathway was inhibited, and gene expression of fibrotic markers, including α-smooth muscle actin (α-SMA), collagen type 1 α 1 (Col1a1), matrix metalloproteinase-2 (Mmp2), and metallopeptidase inhibitor 1 (Timp1) were decreased in livers of MED1ΔLiv mice with CCl4 injection. Transcriptomic analysis revealed that the differentially expressed genes in livers of CCl4-administered MED1ΔLiv mice were enriched in the pathway of oxidoreductase activity, followed by robustly reduced oxidoreductase activity-related genes, such as Gm4756, Txnrd3, and Etfbkmt. More importantly, we found that the reduction of reactive oxygen species (ROS) in MED1 knockdown hepatocytes blocked the activation of TGF-ß/Smad2/3 pathway and the expression of fibrotic genes in LX2 cells. These results indicate that MED1 is a positive regulator for hepatic fibrogenesis, and MED1 may be considered as a potential therapeutic target for the regression of liver fibrosis.NEW & NOTEWORTHY In this study, we present the first evidence that liver mediator 1 (MED1) deficiency attenuated carbon tetrachloride-induced hepatic fibrosis in mouse. The underlying mechanism is that MED1 deficiency reduces reactive oxygen species (ROS) production in hepatocytes, thus restricts the activation of TGF-ß/Smad2/3 signaling pathway and fibrogenic genes expression in hepatic stellate cells (HSCs). These data suggest that MED1 is an essential regulator for hepatic fibrogenesis, and MED1 may be considered as a potential therapeutic target for liver fibrosis.

MED1 induces M2 polarization of tumor-associated macrophages to aggravate breast cancer.

BACKGROUND: Breast cancer is a common malignant tumor in female, and its 5-year survival rate remains low. The correlation between mediator subunit 1 (MED1) gene and macrophage phenotypic transformation may be a key factor affecting the therapeutic effect on cancer. OBJECTIVE: The present study intended to explore the role of MED1 in macrophage polarization and its further influence on the malignant behaviors of breast cancer. METHODS: Bioinformatics analysis was carried out to predict the expression pattern of MED1 in breast cancer. Flow cytometry was conducted to detect the effect of MED1 overexpression or silencing on macrophage polarization. ELISA was applied to analyze the effect of abnormal MED1 expression on cytokine secretion of macrophages. CCK-8, colony formation, Transwell and scratch healing assays were applied to investigate the effects of macrophage conditioned medium on the malignant behaviors of breast cancer cells. RESULTS: MED1 expression was prominently increased in M2 macrophages, and overexpression of MED1 significantly increased M2 polarization of tumor-associated macrophages (TAMs) and IL-10 cytokine level. Meanwhile, M2 macrophages with MED1 overexpression could significantly promote the malignant behaviors of breast cancer cells. Dasatinib rescue experiment further confirmed that MED1-induced M2 macrophage polarization could facilitate the malignant progression of breast cancer cells. CONCLUSION: In summary, MED1 could induce M2 macrophage polarization and thus regulate the malignant behaviors of breast cancer cells.

Retrospective analysis of dissemination of the 2.MED1 phylogenetic branch of Yersinia pestis in the Caucasus.

The 2.MED1 phylogenetic branch of Yersinia pestis of the medieval biovar became widespread in the Caspian Sea region, the Caucasus, and the Northern Aral Sea region in the 20th century, causing outbreaks and epizootics of plague there. Some of the formed natural foci of 2.MED1 still show epizootic activity and retain their epidemic potential. In this work, we carried out a phylogenetic analysis of 46 Y. pestis strains of the medieval biovar isolated in the Caucasus, the Caspian Sea, and the Northern Aral Sea regions during epidemic outbreaks and epizootics from 1922-2014. The obtained phylogenetic data, together with epidemiological and epizootological data accumulated over a period of about a hundred years, indicate the presence of two waves of penetration of the 2.MED1 branch into the Caucasus. The first occurred, apparently, in the first half of the 20th century as a result of the penetration of 2.MED1 from the foci of the Northern and North-Western Caspian Sea. The second wave was caused by the spread of 2.MED1 from the Northern Aral to the foci of the North-Western, Northern and Eastern Caspian Sea regions at the beginning of the second half of the 20th century, followed by introduction into the Pre-Caucasus and Transcaucasia. The rapid spread of 2.MED1 could be associated with the transfer of the pathogen by land and sea transport in the process of economic activity of the population.

Mediator subunit MED1 differentially modulates mutant thyroid hormone receptor intracellular dynamics in Resistance to Thyroid Hormone syndrome.

Thyroid hormone receptor (TR) controls the expression of thyroid hormone (T3)-responsive genes, while undergoing rapid nucleocytoplasmic shuttling. In Resistance to Thyroid Hormone syndrome (RTH), mutant TR fails to activate T3-dependent transcription. Previously, we showed that Mediator subunit 1 (MED1) plays a role in TR nuclear retention. Here, we investigated MED1's effect on RTH mutants using nucleocytoplasmic scoring and fluorescence recovery after photobleaching in transfected cells. MED1 overexpression and knockout did not change the nucleocytoplasmic distribution or intranuclear mobility of C392X and P398R TRα1 at physiological T3 levels. At elevated T3 levels, however, overexpression increased P398R's nuclear retention and MED1 knockout decreased P398R's and A263V's intranuclear mobility, while not impacting C392X. Although A263V TRα1-transfected cells had a high percentage of aggregates, MED1 rescued A263V's impaired intranuclear mobility, suggesting that MED1 ameliorates nonfunctional aggregates. Results correlate with clinical severity, suggesting that altered interaction between MED1 and TRα1 mutants contributes to RTH pathology.

MED1 Ablation Promotes Oral Mucosal Wound Healing via JNK Signaling Pathway.

Mediator complex subunit 1 (MED1) is a coactivator of multiple transcription factors and plays a key role in regulating epidermal homeostasis as well as skin wound healing. It is unknown, however, whether it plays a role in healing oral mucosal wounds. In this study, we investigate MED1's functional effects on oral mucosal wound healing and its underlying mechanism. The epithelial-specific MED1 null (Med1epi-/-) mice were established using the Cre-loxP system with C57/BL6 background. A 3 mm diameter wound was made in the cheek mucosa of the 8-week-old mice. In vivo experiments were conducted using HE staining and immunostaining with Ki67 and uPAR antibodies. The in vitro study used lentiviral transduction, scratch assays, qRT-PCR, and Western blotting to reveal the underlying mechanisms. The results showed that ablation of MED1 accelerated oral mucosal wound healing in 8-week-old mice. As a result of ablation of MED1, Activin A/Follistatin expression was altered, resulting in an activation of the JNK/c-Jun pathway. Similarly, knockdown of MED1 enhanced the proliferation and migration of keratinocytes in vitro, promoting re-epithelialization, which accelerates the healing of oral mucosal wounds. Our study reveals a novel role for MED1 in oral keratinocytes, providing a new molecular therapeutic target for accelerated wound healing.

MED1 Regulates BMP/TGF-ß in Endothelium: Implication for Pulmonary Hypertension.

BACKGROUND: Dysregulated BMP (bone morphogenetic protein) or TGF-ß (transforming growth factor beta) signaling pathways are imperative in idiopathic and familial pulmonary arterial hypertension (PAH) as well as experimental pulmonary hypertension (PH) in rodent models. MED1 (mediator complex subunit 1) is a key transcriptional co-activator and KLF4 (Krüppel-like factor 4) is a master transcription factor in endothelium. However, MED1 and KLF4 epigenetic and transcriptional regulations of the BMP/TGF-ß axes in pulmonary endothelium and their dysregulations leading to PAH remain elusive. We investigate the MED1/KLF4 co-regulation of the BMP/TGF-ß axes in endothelium by studying the epigenetic regulation of BMPR2 (BMP receptor type II), ETS-related gene (ERG), and TGFBR2 (TGF-ß receptor 2) and their involvement in the PH. METHODS: High-throughput screening involving data from RNA-seq, MED1 ChIP-seq, H3K27ac ChIP-seq, ATAC-seq, and high-throughput chromosome conformation capture together with in silico computations were used to explore the epigenetic and transcriptional regulation of BMPR2, ERG, and TGFBR2 by MED1 and KLF4. In vitro experiments with cultured pulmonary arterial endothelial cells (ECs) and bulk assays were used to validate results from these in silico analyses. Lung tissue from patients with idiopathic PAH, animals with experimental PH, and mice with endothelial ablation of MED1 (EC-MED1-/-) were used to study the PH-protective effect of MED1. RESULTS: Levels of MED1 were decreased in lung tissue or pulmonary arterial endothelial cells from idiopathic PAH patients and rodent PH models. Mechanistically, MED1 acted synergistically with KLF4 to transactivate BMPR2, ERG, and TGFBR2 via chromatin remodeling and enhancer-promoter interactions. EC-MED1-/- mice showed PH susceptibility. In contrast, MED1 overexpression mitigated the PH phenotype in rodents. CONCLUSIONS: A homeostatic regulation of BMPR2, ERG, and TGFBR2 in ECs by MED1 synergistic with KLF4 is essential for the normal function of the pulmonary endothelium. Dysregulation of MED1 and the resulting impairment of the BMP/TGF-ß signaling is implicated in the disease progression of PAH in humans and PH in rodent models.

MED1, a novel binding partner of BRCA1, regulates homologous recombination and R-loop processing.

Homologous recombination (HR) is a major repair pathway of DNA double-strand breaks and is closely related to carcinogenesis. HR deficiency has been established as a therapeutic target. The aim of this study was to elucidate the functions of a novel HR factor, Mediator complex subunit 1 (MED1), and its association with BRCA1. Formation of the MED1/BRCA1 complex was examined by immunoprecipitation and GST-pull down assays. The transcription cofactor role of BRCA1 was evaluated using luciferase assays. The roles of MED1 on DNA damage response and HR were analyzed by immunofluorescence and HR assays. R-loop accumulation was analyzed using immunofluorescence. R-loop-induced DNA damage was analyzed by comet assays. Immunoprecipitation and GST-pull down assays demonstrated that MED1 is a novel binding partner of BRCA1 and binds to the BRCT domain. Luciferase assays showed that MED1 potentiated the transcription ability of BRCT by two-fold. In MED1-depleted cells, recruitment of HR genes, such as RPA and γH2AX, to DNA damage sites was severely impaired. HR assays showed that MED1 knockdown significantly decreased HR activity. R-loop nuclear accumulation and R-loop-induced comet tails were observed in MED1-depleted cells. We conclude that the transcription factor MED1 contributes to the regulation of the HR pathway and R-loop processing.

Med1 Controls Effector CD8+ T Cell Differentiation and Survival through C/EBPß-Mediated Transcriptional Control of T-bet.

Effector CD8+ T cells are crucial players in adaptive immunity for effective protection against invading pathogens. The regulatory mechanisms underlying CD8+ T cell effector differentiation are incompletely understood. In this study, we defined a critical role of mediator complex subunit 1 (Med1) in controlling effector CD8+ T cell differentiation and survival during acute bacterial infection. Mice with Med1-deficient CD8+ T cells exhibited significantly impaired expansion with evidently reduced killer cell lectin-like receptor G1+ terminally differentiated and Ly6c+ effector cell populations. Moreover, Med1 deficiency led to enhanced cell apoptosis and expression of multiple inhibitory receptors (programmed cell death 1, T cell Ig and mucin domain-containing-3, and T cell immunoreceptor with Ig and ITIM domains). RNA-sequencing analysis revealed that T-bet- and Zeb2-mediated transcriptional programs were impaired in Med1-deficient CD8+ T cells. Overexpression of T-bet could rescue the differentiation and survival of Med1-deficient CD8+ effector T cells. Mechanistically, the transcription factor C/EBPß promoted T-bet expression through interacting with Med1 in effector T cells. Collectively, our findings revealed a novel role of Med1 in regulating effector CD8+ T cell differentiation and survival in response to bacterial infection.

Overexpression of circFNDC3B promotes the progression of oral tongue squamous cell carcinoma through the miR-1322/MED1 axis.

BACKGROUND: The potential role of circFNDC3B in regulating oral tongue squamous cell carcinoma development (OTSCC) remains unknown. METHODS: The level of circFNDC3B in OTSCC tissues or cell lines was measured and its function in vitro and in vivo was analyzed. Interactions among circFNDC3B, miR-1322, and MED1 were verified by luciferase reporter and RNA pull-down assays. RESULTS: The level of circFNDC3B in tissues or cell lines of OTSCC was higher than that in control groups. siRNA-mediated circFNDC3B inhibition resulted in weakened proliferation, migration, and invasion, which was reversed by miR-1322. Overexpression of MED1 in OTSCC cells partially reversed the tumor suppression functions of si-circFNDC3B or miR-1322 mimics in vitro. circFNDC3B overexpression dramatically promoted tumor growth in vivo. circFNDC3B directly bound with miR-1322 and consequently promoted the MED1 expression in OTSCC cells. CONCLUSIONS: The circFNDC3B/miR-1322/MED1 axis participates in OTSCC progression, which may provide novel therapeutic targets for OTSCC.

Targeting cyclin-dependent kinase 7-association between CDK7 and pMED1 expression in prostate cancer tissue.

Cyclin-dependent kinase (CDK) 7-mediated phosphorylation of Mediator-complex subunit 1 (MED1) enhances androgen receptor (AR) activity in prostate cancer (PCa). Hyperactive AR-signalling plays a key role for the development of castration resistance. Several CDK7 inhibitors are currently under investigation in Phase I/II trials addressing solid tumours, including PCa. Aim of this study was to characterize the CDK7/phospho-(p)MED1 axis in human tissue. Immunohistochemistry was performed on 595 PCa samples including 394 primary tumour foci obtained by radical prostatectomy (RP), 64 advanced or recurrent tumours obtained by palliative transurethral resection of the prostate (pTUR), 65 lymph node metastases (LNM), 35 distant metastases (DM) and 36 benign samples. CDK7 is expressed in 79.3% of PCa tissues and protein levels are significantly higher in LNM, pTUR and DM and lower in benign tissues compared to primary tumours. CDK7 and pMED1 expression show strong positive correlation. High expression of CDK7 associated with shorter 5-year biochemical recurrence-free-survival (63.0% vs. 85.0%) and reduced survival persists when adjusted for T-Stage, nodal status, resection boundaries, grade group and pre-operative prostate-specific antigen in multivariate Cox-regression (hazard ratio 4.30; 95% CI, 1.43 to 12,40, P = 0.007). High CDK7 and pMED1 levels correlate with nuclear AR expression. CDK7 positive tumours harbour higher Ki67 expression indices and show more frequently positive ERG (ETS-related gene)-status. In conclusion, CDK7 is frequently expressed in human PCa and predicts disease recurrence after RP. Therapeutical inhibition of CDK7 might be a promising approach in treatment of advanced PCa.

MED1 Deficiency in Macrophages Aggravates Isoproterenol-Induced Cardiac Fibrosis in Mice.

Mediator 1 (MED1), a key subunit of the mediator complex, interacts with various nuclear receptors and functions in lipid metabolism and energy homeostasis. Dilated cardiomyopathy-related ventricular dilatation and heart failure have been reported in mice with cardiomyocyte-specific Med1 deficiency. However, the contribution of macrophage-specific MED1 in cardiac remodeling remains unclear. In this study, macrophage-specific Med1 knockout (Med1ΔMac) mice were generated and exposed to isoproterenol (ISO) to induce cardiac fibrosis; these mice showed aggravated cardiac fibrosis compared with Med1fl/fl mice. The levels of expression of marker genes for myofibroblast transdifferentiation [α-smooth muscle actin (SMA)] and of profibrotic genes, including Col1a1, Col3a1, Postn, Mmp2, Timp1, and Fn1, were significantly increased in the cardiac tissues of Med1ΔMac mice with ISO-induced myocardial fibrosis. In particular, the transforming growth factor (TGF)-ß-Smad2/3 signaling pathway was activated. In bone marrow-derived and peritoneal macrophages, Med1 deficiency was also associated with elevated levels of expression of proinflammatory genes, including Il6, Tnfa, and Il1b. These findings indicate that macrophage-specific MED1 deficiency may aggravate ISO-induced cardiac fibrosis via the regulation of the TGF-ß-SMAD2/3 pathway, and the underlying mechanism may involve MED1 deficiency triggering the activation of inflammatory cytokines in macrophages, which in turn may stimulate phenotypic switch of cardiac fibroblasts and accelerate cardiac fibrosis. Thus, MED1 is a potential therapeutic target for cardiac fibrosis.

Phosphorylated MED1 links transcription recycling and cancer growth.

Mediator activates RNA polymerase II (Pol II) function during transcription, but it remains unclear whether Mediator is able to travel with Pol II and regulate Pol II transcription beyond the initiation and early elongation steps. By using in vitro and in vivo transcription recycling assays, we find that human Mediator 1 (MED1), when phosphorylated at the mammal-specific threonine 1032 by cyclin-dependent kinase 9 (CDK9), dynamically moves along with Pol II throughout the transcribed genes to drive Pol II recycling after the initial round of transcription. Mechanistically, MED31 mediates the recycling of phosphorylated MED1 and Pol II, enhancing mRNA output during the transcription recycling process. Importantly, MED1 phosphorylation increases during prostate cancer progression to the lethal phase, and pharmacological inhibition of CDK9 decreases prostate tumor growth by decreasing MED1 phosphorylation and Pol II recycling. Our results reveal a novel role of MED1 in Pol II transcription and identify phosphorylated MED1 as a targetable driver of dysregulated Pol II recycling in cancer.

MED1 Downregulation Contributes to TGFß-Induced Metastasis by Inhibiting SMAD2 Ubiquitination Degradation in Cutaneous Melanoma.

Metastasis is the main reason for the high mortality of patients and indeed a difficult task in the treatment of cutaneous melanoma. Therefore, it is of great clinical value to explore the molecular mechanism of cutaneous metastatic melanoma and develop novel therapies. MED1, acting as a factor required for activator-dependent transcription, is reported to be involved in carcinogenesis and progression. In this study, we found that MED1 was highly expressed in patients with cutaneous melanoma. MED1 downregulation could induce cellular epithelial-to-mesenchymal transition and promote migration, invasion, and metastasis of cutaneous melanoma in vivo and in vitro. Further analysis showed that in Med1 knockdown cells, the TGFß/SMAD2 signaling pathway mediated an increase in epithelial-to-mesenchymal transition phenotype and migration. The opposite results were observed after treatment with TGFß inhibitors. To further explore the mechanism, we found that MED1 interacted with SMAD2, and MED1 downregulation could protect SMAD2 from degradation by inhibiting SMAD2 ubiquitination. Together, these results suggest that MED1 inhibited TGFß signaling pathway to reduce cell epithelial-to-mesenchymal transition phenotype and migration through SMAD2 ubiquitination in the metastasis of cutaneous melanoma. Our findings elucidated the role of MED1 in the metastasis of cutaneous melanoma and provided a target for the therapeutic strategies of cutaneous melanoma.

MED1/BDNF/TrkB pathway is involved in thalamic hemorrhage-induced pain and depression by regulating microglia.

Central post-stroke pain (CPSP) and associated depression remain poorly understood and pharmacological treatments are unsatisfactory. Recently, microglia activation was suggested to be involved in CPSP pathophysiology. The goal of this study was to investigate the effectiveness of a co-ultramicronized combination of N-palmitoylethanolamide and luteolin (PEALut) in a mouse model of thalamic hemorrhage (TH)-induced CPSP. TH was established through the collagenase-IV injection in thalamic ventral-posterolateral-nucleus. PEALut effects in CPSP-associated behaviors were evaluated during a 28-days observation period. We found that repeated administrations of co-ultra PEALut significantly reduced mechanical hypersensitivity after TH, as compared to vehicle, by reducing the early microglial activation in the perilesional site. Moreover, PEALut prevented the development of depressive-like behavior (21 days post-TH). These effects were associated with the restoration of synaptic plasticity in LEC-DG pathway and monoamines levels found impaired in TH mice. Hippocampal MED1 and TrkB expressions were significantly increased in TH compared to sham mice 21 days post-TH, whereas BDNF levels were decreased. PEALut restored MED1/TrkB/BDNF expression in mice. Remarkably, we found significant overexpression of MED1 in the human autoptic brain specimens after stroke, indicating a translational potential of our findings. These results pave the way for better-investigating depression in TH- induced CPSP, together with the involvement of MED1/TrkB/BDNF pathway, proposing PEALut as an adjuvant treatment.