Tri M. Bui-Nguyen

Regulation of NF-κB Circuitry by a Component of the Nucleosome Remodeling and Deacetylase Complex Controls Inflammatory Response Homeostasis

The MTA1 coregulator (metastatic tumor antigen 1), a component of the nucleosome remodeling and deacetylase (NuRD) complex, has been intimately linked with human cancer, but its role in inflammatory responses remains unknown. Here, we discovered that MTA1 is a target of inflammation, and stimulation of macrophages with Escherichia coli lipopolysaccharide (LPS) stimulates MTA1 transcription via the NF-κB pathway. Unexpectedly, we found that MTA1 depletion in LPS-stimulated macrophages impairs NF-κB signaling and expression of inflammatory molecules. MTA1 itself acts as a transcriptional coactivator of inflammatory cytokines in LPS-stimulated macrophages, and in contrast, it acts as a corepressor in resting primary macrophages as its depletion induced cytokine expression. LPS stimulates S-nitrosylation of histone deacetylase 2 (HDAC2) and interferes with its binding to MTA1, which, in turn, resulted in the loss of corepressor behavior of MTA1·HDAC complex in activated macrophages. Consequently, the net levels of inflammatory cytokines in LPS-stimulated macrophages from MTA1−/− mice were high compared with wild-type mice. Accordingly, MTA1−/− mice were much more susceptible than control mice to septic shock induced by LPS, revealing that MTA1 protects mice from deregulated host inflammatory response. These findings reveal a previously unrecognized, critical homeostatic role of MTA1, both as a target and as a component of the NF-κB circuitry, in the regulation of inflammatory responses.

NF-κB SIGNALING MEDIATES THE INDUCTION OF MTA1 BY HEPATITIS B VIRUS TRANSACTIVATOR PROTEIN HBx

Metastasis-associated protein 1 (MTA1), a master chromatin modifier, has been shown to regulate cancer progression and is widely upregulated in human cancer, including hepatitis B virus-associated hepatocellular carcinomas (HCCs). Here we provide evidence that hepatitis B virus transactivator protein HBx stimulates the expression of MTA1 but not of MTA2 or MTA3. The underlying mechanism of HBx stimulation of MTA1 involves HBx targeting of transcription factor nuclear factor (NF)-κB and the recruitment of HBx/p65 complex to the NF-κB consensus motif on the relaxed MTA1 gene chromatin. We also discovered that MTA1 depletion in HBx-expressing cells severely impairs the ability of HBx to stimulate NF-κB signaling and the expression of target proinflammatory molecules. Furthermore, the presence of HBx in HBx-infected HCCs correlated well with increased MTA1 and NF-κB-p65. Collectively, these findings revealed a previously unrecognized integral role of MTA1 in HBx stimulation of NF-κB signaling and consequently, the expression of NF-κB targets gene products with functions in inflammation and tumorigenesis.

Stimulation of Inducible Nitric Oxide by Hepatitis B Virus Transactivator Protein HBx Requires MTA1 Coregulator

Nitric oxide has been implicated in the pathogenesis of inflammatory disorders, including hepatitis B virus-associated hepatocellular carcinoma. Transactivator protein HBx, a major regulator of cellular responses of hepatitis B virus, is known to induce the expression of MTA1 (metastasis-associated protein 1) coregulator via NF-κB signaling in hepatic cells. However, the underlying mechanism of HBx regulation of the inducible nitric-oxide synthase (iNOS) pathway remains unknown. Here we provide evidence that MTA1 is a positive regulator of iNOS transcription and plays a mechanistic role in HBx stimulation of iNOS expression and activity. We found that the HBx-MTA1 complex is recruited onto the human iNOS promoter in an NF-κB-dependent manner. Pharmacological inhibition of the NF-κB signaling prevented the ability of HBx to stimulate the transcription, the expression, and the activity of iNOS; nevertheless, these effects could be substantially rescued by MTA1 dysregulation. We further discovered that HBx-mediated stimulation of MTA1 is paralleled by the suppression of miR-661, a member of the small noncoding RNAs, recently shown to target MTA1. We observed that miR-661 controls of MTA1 expression contributed to the expression and activity of iNOS in HBx-expressing HepG2 cells. Accordingly, depletion of MTA1 by either miR-661 or siRNA in HBx-expressing cells severely impaired the ability of HBx to modulate the endogenous levels of iNOS and nitrite production. Together, these findings reveal an inherent role of MTA1 in HBx regulation of iNOS expression and consequently its function in the liver cancer cells.

MTA1 Coregulator Regulates LPS Response via MyD88-dependent Signaling

Although metastasis tumor antigen 1 (MTA1) contributes to the responsiveness of macrophages to LPS, the underlying mechanism remains unknown. Here, we investigated the role of MTA1 in the regulation of expression and function of MyD88, a proximal component of NF-κB signaling. We discovered that MTA1 targets MyD88 and that MyD88 is a NF-κB-responsive gene in LPS-stimulated macrophages. We found that MTA1 is required for MyD88-dependent stimulation of NF-κB signaling and expression of proinflammatory cytokines such as IL-1β, MIP2, and TNF-α as MTA1 depletion leads to a substantial reduction in the expression of NF-κB target genes. In addition, LPS-mediated stimulation of MyD88 transcription was accompanied by an enhanced recruitment of MTA1, RNA polymerase II, and p65RelA complex to the NF-κB consensus sites in the MyD88 promoter. Interestingly, the recruitment of both MTA1 and MyD88 expression is effectively blocked by NF-κB inhibitor parthenolide. Selective knockdown of MyD88 by a dominant negative mutant of MyD88 or selective siRNA also impairs the ability of LPS to stimulate the NF-κB target genes. These findings reveal an inherent coregulatory role of MTA1 upon the expression of MyD88 and suggest that MTA1 regulation of MyD88 may constitute at least one of the mechanisms by which MTA1 stimulates LPS-induced NF-κB signaling in stimulated macrophages.

Thrombin stimulation of inflammatory breast cancer cells leads to aggressiveness via the EGFR-PAR1-Pak1 pathway

Inflammatory breast cancer (IBC) accounts for a small fraction but aggressive form of epithelial breast cancer. Although the role of thrombin in cancer is beginning to be unfolded, its impact on the biology of IBC remains unknown. The purpose of this study was to establish the role of thrombin on the invasiveness of IBC cells. The IBC SUM149 cell line was treated with thrombin in the absence or presence of the epidermal growth factor receptor (EGFR) inhibitor erlotinib and protease-activated receptor 1 (PAR1) inhibitor. The effects of pharmacological inhibitors on the ability of thrombin to stimulate the growth rate and invasiveness were examined. We found that the inhibition of putative cellular targets of thrombin action suppresses both the growth and invasiveness of SUM149 cells in a concentration-dependent manner. In addition, thrombin-mediated increased invasion of SUM149 cells was routed through EGFR phosphorylation, and in turn, stimulation of the p21-activated kinase (Pak1) activity in a EGFR-sensitive manner. Interestingly, thrombin-mediated activation of the Pak1 pathway stimulation was blocked by erlotinib and PAR1 inhibitor. For proof-of-principle studies, we found immunohistochemical evidence of Pak1 activation as well as expression of PAR1 in IBC. Thrombin utilizes EGFR to relay signals promoting SUM149 cell growth and invasion via the Pak1 pathway. The study provides the rationale for future therapeutic approaches in mitigating the invasive nature of IBC by targeting Pak1 and/or EGFR.

Anti-NMDA-receptor encephalitis during pregnancy: A case report and literature review

Anti‐N‐methyl‐d‐aspartate receptor (anti‐NMDA‐R) encephalitis is an autoimmune disorder that was first described by Dr Vitaliani in 2005. In 2007, Dalmau et al. found anti‐NMDA‐R antibody expressed both in the hippocampus and prefrontal nerve cell membrane, finally proposing the diagnosis of autoimmune anti‐NMDA‐R encephalitis. Most of the patients are female (91%), with ages ranging from 4 to 76 years. The average age is 23 years, a birth peak age, although anti‐NMDA‐R encephalitis is rare during pregnancy. The disorder is characterized by prominent psychosis, dyskinesias, seizures, autonomic disturbance, and central hypoventilation. We report a 24‐year‐old woman hospitalized at 28 gestational weeks with acute‐onset psychosis. Over the course of 3 weeks, her mental status worsened until she fell into a coma. Both serum and cerebrospinal fluid anti‐NMDA‐R antibodies were found to be positive. At cesarean section, a healthy baby boy was born and a wedge‐shaped bilateral ovarian resection was performed. Treatment with corticosteroids, intravenous immunoglobulin, and plasmapheresis can lead to improved outcomes for both mother and baby.

Erratum: Stimulation of inducible nitric oxide by hepatitis B virus transactivator protein-HBx requires MTA1 coregulator (Journal of Biological Chemistry (2010) 285 (6980-6986) DOI: 10.1074/jbc.M109.065987)

Tri M. Bui-Nguyen, Suresh B. Pakala, Divijendranatha Reddy Sirigiri, Emil Martin, Ferid Murad, and Rakesh Kumar This article has been withdrawn by the authors. Upon becoming aware of concerns raised regarding errors with respect to Fig. 3B, the authors are withdrawing the paper and apologize for these errors. The senior author states that the experiments and the final assembly of Fig. 3B were performed by specific co-authors from his laboratory. The authors state that the potential issues raised with Fig. 3B do not affect the scientific conclusions of this work. THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 292, NO. 11, p. 4765, March 17, 2017

Erratum: Regulation of NF-κB circuitry by a component of the nucleosome remodeling and deacetylase complex controls inflammatory response homeostasis (Journal of Biological Chemistry (2010) 285 (23590-23597) DOI: 10.1074/jbc.A110.139469)

Suresh B. Pakala, Tri M. Bui-Nguyen, Sirigiri Divijendra Natha Reddy, Da-Qiang Li, Shaohua Peng, Suresh K. Rayala, Richard R. Behringer, and Rakesh Kumar This article has been withdrawn by the authors. Upon becoming aware of concerns raised regarding errors with respect to Fig. 4B, the authors are withdrawing the paper and apologize for these errors. The senior author states that the experiments and the final assembly of Fig. 4B were performed by specific co-authors from his laboratory. The authors state that the potential issues raised with Fig. 4B do not affect the scientific conclusions of this work. THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 292, NO. 11, p. 4764, March 17, 2017

Erratum: Regulation of NF-κB circuitry by a component of the nucleosome remodeling and deacetylase complex controls inflammatory response homeostasis (Journal of Biological Chemistry (2010) 285 (23590-23597)

Tri M. Bui-Nguyen, Suresh B. Pakala, Divijendranatha Reddy Sirigiri, Emil Martin, Ferid Murad, and Rakesh Kumar The publisher of the Journal of Biological Chemistry is issuing an Expression of Concern to inform readers that questions have been raised with the corresponding author’s institution regarding some of the data and conclusions in the articles listed above. This Expression of Concern is solely intended to notify readers for informational purposes. It is not a statement regarding the validity of the data. The Journal of Biological Chemistry will provide additional information as it becomes available. THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 291, NO. 3, p. 1198, January 15, 2016