NRF2 Exerts Anti-Inflammatory Effects in LPS-Induced gEECs by Inhibiting the Activation of the NF-κB

Nuclear factor E2-related factor 2 (NRF2) plays an anti-inflammatory role in several pathological processes, but its function in lipopolysaccharide- (LPS-) induced goat endometrial epithelial cells (gEECs) is still unknown. We designed a study to investigate the function of NRF2 in LPS-induced gEECs. LPS was found to increase the NRF2 expression and the nuclear abundance of NRF2 in gEECs in a dose-dependent manner. NRF2 knockout (KO) not only increased the expression of LPS-induced proinflammatory cytokines (TNF-α, IL-1β, IL-6 and IL-8) but also increased the expression of TLR4, p-IκBα/IκBα, and p-p65/p65 proteins. Immunoprecipitation experiments showed that NRF2 directly binds to p65 in the nucleus and inhibits the binding of p65 to downstream target genes (TNF-α, IL-1β, IL-6, and IL-8). Even though a NF-κB/p65 inhibitor (PDTC) reduced the LPS-induced NRF2 expression and nuclear abundance of NRF2, overexpressing TNF-α reversed the inhibitory effects of PDTC on the NRF2 expression and on its abundance in the nucleus. Similarly, knockdown of the proinflammatory cytokines (TNF-α, IL-1β, IL-6, or IL-8) significantly decreased the LPS-induced NRF2 expression and NRF2 in the nucleus. In conclusion, our data suggest that proinflammatory cytokines induced by LPS through the TLR4/NF-κB pathway promote the NRF2 expression and its translocation into the nucleus. Our work also suggests that NRF2 inhibits the expression of proinflammatory cytokines by directly binding to p65.

Nuclear RNA binding regulates TDP-43 nuclear localization and passive nuclear export

Nuclear clearance of the DNA/RNA-binding protein TDP-43 is a pathologic hallmark of amyotrophic lateral sclerosis and frontotemporal dementia that remains unexplained. Moreover, our current understanding of TDP-43 nucleocytoplasmic shuttling does not fully explain the predominantly nuclear localization of TDP-43 in healthy cells. Here, we used permeabilized and live-cell models to investigate TDP-43 nuclear export and the role of RNA in TDP-43 localization. We show that TDP-43 nuclear efflux occurs in low-ATP conditions and independent of active mRNA export, consistent with export by passive diffusion through nuclear pore channels. TDP-43 nuclear residence requires binding to GU-rich nuclear intronic pre-mRNAs, based on the induction of TDP-43 nuclear efflux by RNase and GU-rich oligomers and TDP-43 nuclear retention conferred by pre-mRNA splicing inhibitors. Mutation of TDP-43 RNA recognition motifs disrupts TDP-43 nuclear accumulation and abolishes transcriptional blockade-induced TDP-43 nuclear efflux, demonstrating strict dependence of TDP-43 nuclear localization on RNA binding. Thus, the nuclear abundance of GU-rich intronic pre-mRNAs, as dictated by the balance of transcription and pre-mRNA processing, regulates TDP-43 nuclear sequestration and availability for passive nuclear export.

Cytokines Stimulated by IL-33 in Human Skin Mast Cells: Involvement of NF-κB and p38 at Distinct Levels and Potent Co-Operation with FcεRI and MRGPRX2

The IL-1 family cytokine IL-33 activates and re-shapes mast cells (MCs), but whether and by what mechanisms it elicits cytokines in MCs from human skin remains poorly understood. The current study found that IL-33 activates CCL1, CCL2, IL-5, IL-8, IL-13, and TNF-α, while IL-1β, IL-6, IL-31, and VEGFA remain unaffected in cutaneous MCs, highlighting that each MC subset responds to IL-33 with a unique cytokine profile. Mechanistically, IL-33 induced the rapid (1–2 min) and durable (2 h) phosphorylation of p38, whereas the phosphorylation of JNK was weaker and more transient. Moreover, the NF-κB pathway was potently activated, as revealed by IκB degradation, increased nuclear abundance of p50/p65, and vigorous phosphorylation of p65. The activation of NF-κB occurred independently of p38 or JNK. The induced transcription of the cytokines selected for further study (CCL1, CCL2, IL-8, TNF-α) was abolished by interference with NF-κB, while p38/JNK had only some cytokine-selective effects. Surprisingly, at the level of the secreted protein products, p38 was nearly as effective as NF-κB for all entities, suggesting post-transcriptional involvement. IL-33 did not only instruct skin MCs to produce selected cytokines, but it also efficiently co-operated with the allergic and pseudo-allergic/neurogenic activation networks in the production of IL-8, TNF-α, CCL1, and CCL2. Synergism was more pronounced at the protein than at the mRNA level and appeared stronger for MRGPRX2 ligands than for FcεRI. Our results underscore the pro-inflammatory nature of an acute IL-33 stimulus and imply that especially in combination with allergens or MRGPRX2 agonists, IL-33 will efficiently amplify skin inflammation and thereby aggravate inflammatory dermatoses.

An aberrant cytoplasmic intron retention programme is a blueprint for ALS-related RBP mislocalization

SUMMARYWe recently described aberrant cytoplasmic SFPQ intron-retaining transcripts (IRTs) and concurrent SFPQ protein mislocalization as a new hallmark of amyotrophic lateral sclerosis (ALS). However the generalizability and potential roles of cytoplasmic IRTs in health and disease remain unclear. Here, using time-resolved deep-sequencing of nuclear and cytoplasmic fractions of hiPSCs undergoing motor neurogenesis, we reveal that ALS-causing VCP gene mutations lead to compartment-specific aberrant accumulation of IRTs. Specifically, we identify >100 IRTs with increased cytoplasmic (but not nuclear) abundance in ALS samples. Furthermore, these aberrant cytoplasmic IRTs possess sequence-specific attributes and differential predicted binding affinity to RNA binding proteins (RBPs). Remarkably, TDP-43, SFPQ and FUS – RBPs known for nuclear-to-cytoplasmic mislocalization in ALS – avidly and specifically bind to this aberrant cytoplasmic pool of IRTs, as opposed to any individual IRT. Our data are therefore consistent with a novel role for cytoplasmic IRTs in regulating compartment-specific protein abundance. This study provides new molecular insight into potential pathomechanisms underlying ALS and highlights aberrant cytoplasmic IRTs as potential therapeutic targets.Abstract Figure

The Fanconi Anemia-Associated Protein NIPA Is Essential for the Nuclear Abundance of FANCD2

Inherited bone marrow failure syndromes (IBMFS) are a heterogeneous group of disorders characterized by impaired stem cell function resulting in pancytopenia. Diagnosis of IBMFS presents a major challenge due to limited diagnostic tests and overlapping phenotypes. For that reason, novel and clinical relevant biomarkers and possible targets are urgently needed. Our study defines NIPA as an IBMFS gene, which is significantly downregulated in a distinct subset of MDS-type refractory cytopenia of childhood patients. Mechanistically, NIPA binds FANCD2 and regulates its nuclear abundance. The stabilization of both non- and monoubiquitinated FANCD2 identifies NIPA as an essential player in the Fanconi Anemia (FA) pathway. NIPA thereby prevents MMC hypersensitivity visualized by increased numbers of chromosome radials and reduced cell survival after induction of interstrand crosslinks. To provide proof of principle, re-expression of FANCD2 in Nipa deficient cells restores MMC sensitivity. In a knockout mouse model, Nipa deficiency leads to major cell intrinsic long-term repopulation defects of hematopoietic stem cells (HSCs), with impaired self-renewal in serial transplantations and a bias towards myeloid differentiation. Unresolved DNA damage in Nipa deficient HSCs causes increased sensitivity to cell death and leads to progressive, age-related loss of the HSC pool. Induction of replication stress triggers the phenotypic reduction and functional decline of murine HSCs, resulting in complete bone marrow failure and death of the mice thereby mimicing Fanconi Anemia. Taken together, our study adds NIPA to the short list of FA-associated proteins being essential for a functional DNA repair/FA/BRCA axis and thereby emphasizing its impact as potential diagnostic marker and/or possible target in bone marrow failure syndromes. Disclosures Niemeyer: Celgene: Consultancy.

PIN-LIKES coordinate brassinosteroid signalling with nuclear auxin input in Arabidopsis thaliana

Auxin and brassinosteroids (BR) are crucial growth regulators and display overlapping functions during plant development. Here, we reveal an alternative phytohormone crosstalk mechanism, revealing that brassinosteroid signaling controls nuclear abundance of auxin. We performed a forward genetic screen for imperial pils (imp) mutants that enhance the overexpression phenotypes of PIN-LIKES (PILS) putative intracellular auxin transport facilitator. Here we report that the imp1 mutant is defective in the brassinosteroid-receptor BRI1. Our data reveals that BR signaling transcriptionally and posttranslationally represses accumulation of PILS proteins at the endoplasmic reticulum, thereby increasing nuclear abundance and signaling of auxin. We demonstrate that this alternative phytohormonal crosstalk mechanism integrates BR signaling into auxin-dependent organ growth rates and likely has widespread importance for plant development.

DEAD-box protein family member DDX28 is a negative regulator of HIF-2α and eIF4E2-directed hypoxic translation

ABSTRACTHypoxia occurs when there is a deficiency in oxygen delivery to tissues and is connected to physiological and pathophysiological processes such as embryonic development, wound healing, heart disease and cancer. The master regulators of oxygen homeostasis in mammalian cells are the heterodimeric hypoxia-inducible transcription factors HIF-1 and HIF-2. The oxygen-labile HIF-2α subunit has not only been implicated in transcription, but also as a regulator of eIF4E2-directed hypoxic translation. Here, we have identified the DEAD-box protein family member DDX28 as a novel interactor and negative regulator of HIF-2α that suppresses its ability to activate eIF4E2-directed translation. We demonstrate that stable silencing of DDX28 via shRNA in hypoxic human U87MG glioblastoma cells caused an increase, relative to control, to: HIF-2α protein levels, the ability of eIF4E2 to bind the m7GTP cap structure, and the translation of select eIF4E2 target mRNAs. DDX28 depletion elevated both nuclear and cytoplasmic HIF-2α, but HIF-2α transcriptional activity did not increase possibly due to its already high nuclear abundance in hypoxic control cells. Depletion of DDX28 conferred a proliferative advantage to hypoxic, but not normoxic cells, which is likely a consequence of the translational upregulation of a subset of hypoxia-response mRNAs. DDX28 protein levels are reduced in several cancers, including glioma, relative to normal tissue. Therefore, we uncover a regulatory mechanism for this potential tumor suppressor in the repression of HIF-2α- and eIF4E2-mediated translation activation of oncogenic mRNAs.

An acute bout of high-intensity interval training increases the nuclear abundance of PGC-1α and activates mitochondrial biogenesis in human skeletal muscle

Low-volume, high-intensity interval training (HIT) increases skeletal muscle mitochondrial capacity, yet little is known regarding potential mechanisms promoting this adaptive response. Our purpose was to examine molecular processes involved in mitochondrial biogenesis in human skeletal muscle in response to an acute bout of HIT. Eight healthy men performed 4 × 30-s bursts of all-out maximal intensity cycling interspersed with 4 min of rest. Muscle biopsy samples (vastus lateralis) were obtained immediately before and after exercise, and after 3 and 24 h of recovery. At rest, the majority of peroxisome proliferator-activated receptor γ coactivator (PGC)-1α, a master regulator of mitochondrial biogenesis, was detected in cytosolic fractions. Exercise activated p38 MAPK and AMPK in the cytosol. Nuclear PGC-1α protein increased 3 h into recovery from exercise, a time point that coincided with increased mRNA expression of mitochondrial genes. This was followed by an increase in mitochondrial protein content and enzyme activity after 24 h of recovery. These findings support the hypothesis that an acute bout of low-volume HIT activates mitochondrial biogenesis through a mechanism involving increased nuclear abundance of PGC-1α.