scholarly journals Selective Autophagy Maintains the Aryl Hydrocarbon Receptor Levels in HeLa Cells: A Mechanism That Is Dependent on the p23 Co-Chaperone

2020 ◽  
Vol 21 (10) ◽  
pp. 3449
Author(s):  
Yujie Yang ◽  
William K. Chan
Keyword(s):  
Aryl Hydrocarbon Receptor ◽  
Hela Cells ◽  
Stem Cell Differentiation ◽  
26S Proteasome ◽  
Chemical Agent ◽  
Physical Interaction ◽  
Hematopoietic Stem ◽  
Selective Autophagy ◽  
Protein Levels ◽  
Aryl Hydrocarbon

The aryl hydrocarbon receptor (AHR) is an environmental sensing molecule which impacts diverse cellular functions such as immune responses, cell growth, respiratory function, and hematopoietic stem cell differentiation. It is widely accepted that the degradation of AHR by 26S proteasome occurs after ligand activation. Recently, we discovered that HeLa cells can modulate the AHR levels via protein degradation without exogenous treatment of a ligand, and this degradation is particularly apparent when the p23 content is down-regulated. Inhibition of autophagy by a chemical agent (such as chloroquine, bafilomycin A1, or 3-methyladenine) increases the AHR protein levels in HeLa cells whereas activation of autophagy by short-term nutrition deprivation reduces its levels. Treatment of chloroquine retards the degradation of AHR and triggers physical interaction between AHR and LC3B. Knockdown of LC3B suppresses the chloroquine-mediated increase of AHR. Down-regulation of p23 promotes AHR degradation via autophagy with no change of the autophagy-related gene expression. Although most data in this study were derived from HeLa cells, human lung (A549), liver (Hep3B), and breast (T-47D and MDA-MB-468) cells also exhibit AHR levels sensitive to chloroquine treatment and AHR–p62/LC3 interactions. Here we provide evidence supporting that AHR undergoes the p62/LC3-mediated selective autophagy in HeLa cells.

scholarly journals Expression, Localization, and Activity of the Aryl Hydrocarbon Receptor in the Human Placenta

2018 ◽  
Vol 19 (12) ◽  
pp. 3762 ◽  
Author(s):  
Anaïs Wakx ◽  
Margaux Nedder ◽  
Céline Tomkiewicz-Raulet ◽  
Jessica Dalmasso ◽  
Audrey Chissey ◽  
...  
Keyword(s):  
Aryl Hydrocarbon Receptor ◽  
Human Placenta ◽  
Target Genes ◽  
Environmental Pollutants ◽  
Cell Fractionation ◽  
Protein Levels ◽  
Aryl Hydrocarbon ◽  
Epithelial Barriers ◽  
Expression And Activity

The human placenta is an organ between the blood of the mother and the fetus, which is essential for fetal development. It also plays a role as a selective barrier against environmental pollutants that may bypass epithelial barriers and reach the placenta, with implications for the outcome of pregnancy. The aryl hydrocarbon receptor (AhR) is one of the most important environmental-sensor transcription factors and mediates the metabolism of a wide variety of xenobiotics. Nevertheless, the identification of dietary and endogenous ligands of AhR suggest that it may also fulfil physiological functions with which pollutants may interfere. Placental AhR expression and activity is largely unknown. We established the cartography of AhR expression at transcript and protein levels, its cellular distribution, and its transcriptional activity toward the expression of its main target genes. We studied the profile of AhR expression and activity during different pregnancy periods, during trophoblasts differentiation in vitro, and in a trophoblast cell line. Using diverse methods, such as cell fractionation and immunofluorescence microscopy, we found a constitutive nuclear localization of AhR in every placental model, in the absence of any voluntarily-added exogenous activator. Our data suggest an intrinsic activation of AhR due to the presence of endogenous placental ligands.

scholarly journals Down-Regulation of p23 in Normal Lung Epithelial Cells Reduces Toxicities From Exposure to Benzo[a]pyrene and Cigarette Smoke Condensate via an Aryl Hydrocarbon Receptor-Dependent Mechanism

2018 ◽  
Vol 167 (1) ◽  
pp. 239-248 ◽  
Author(s):  
Jinyun Chen ◽  
Poonam Yakkundi ◽  
William K Chan
Keyword(s):  
Epithelial Cells ◽  
Aryl Hydrocarbon Receptor ◽  
Cigarette Smoke ◽  
Lung Epithelial Cells ◽  
Normal Lung ◽  
Cigarette Smoke Condensate ◽  
Down Regulation ◽  
Protein Levels ◽  
Aryl Hydrocarbon ◽  
Lung Epithelial

Abstract The aryl hydrocarbon receptor (AHR) is a ligand-activated signaling molecule which controls tumor growth and metastasis, T cell differentiation, and liver development. Expression levels of this receptor protein is sensitive to the cellular p23 protein levels in immortalized cancer cell lines. As little as 30% reduction of the p23 cellular content can suppress the AHR function. Here we reported that down-regulation of the p23 protein content in normal, untransformed human bronchial/tracheal epithelial cells to 48% of its content also suppresses the AHR protein levels to 54% of its content. This p23-mediated suppression of AHR is responsible for the suppression of (1) the ligand-dependent induction of the cyp1a1 gene transcription; (2) the benzo[a]pyrene- or cigarette smoke condensate-induced CYP1A1 enzyme activity, and (3) the benzo[a]pyrene and cigarette smoke condensate-mediated production of reactive oxygen species. Reduction of the p23 content does not alter expression of oxidative stress genes and production of PGE2. Down regulation of p23 suppresses the AHR protein levels in two other untransformed cell types, namely human breast MCF-10A and mouse immune regulatory Tr1 cells. Collectively, down-regulation of p23 suppresses the AHR protein levels in normal and untransformed cells and can in principle protect our lung epithelial cells from AHR-dependent oxidative damage caused by exposure to agents from environment and cigarette smoking.

scholarly journals Epigenetic Activation of BRCA1 by Genistein In Vivo and Triple Negative Breast Cancer Cells Linked to Antagonism toward Aryl Hydrocarbon Receptor

Nutrients ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2559 ◽  
Author(s):  
Donovan ◽  
Selmin ◽  
Doetschman ◽  
Romagnolo
Keyword(s):  
Aryl Hydrocarbon Receptor ◽  
Triple Negative ◽  
Brca1 Gene ◽  
Cpg Methylation ◽  
Breast Cancers ◽  
Mcf7 Cells ◽  
Brca1 Protein ◽  
Protein Levels ◽  
Aryl Hydrocarbon

Triple negative breast cancers (TNBC) are the most aggressive and lethal breast cancers (BC). The aryl hydrocarbon receptor (AHR) is often overexpressed in TNBC, and its activation results in the epigenetic silencing of BRCA1, which is a necessary factor for the transcriptional activation of estrogen receptor (ER)α. The dietary isoflavone genistein (GEN) modulates BRCA1 CpG methylation in BC cells. The purpose of this study was to investigate the effect of GEN on BRCA1 epigenetic regulation and AHR activity in vivo and TNBC cells. Mice were administered a control or GEN-enriched (4 and 10 ppm) diet from gestation through post-natal day 50. Mammary tissue was analyzed for changes in BRCA1 regulation and AhR activity. TNBC cells with constitutively hypermethylated BRCA1 (HCC38) and MCF7 cells were used. Protein levels and mRNA expression were measured by Western blot and real-time PCR, respectively. BRCA1 promoter occupancy and CpG methylation were analyzed by chromatin immunoprecipitation and methylation-specific PCR, respectively. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. GEN administered in the diet dose-dependently decreased basal Brca1 methylation and AHR activity in the mammary gland of adult mice. HCC38 cells were found to overexpress constitutively active AHR in parallel with BRCA1 hypermethylation. The treatment of HCC38 cells with GEN upregulated BRCA1 protein levels, which was attributable to decreased CpG methylation and AHR binding at BRCA1 exon 1a. In MCF7 cells, GEN prevented the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-dependent localization of AHR at the BRCA1 gene. These effects were consistent with those elicited by control AHR antagonists galangin (GAL), CH-223191, and α-naphthoflavone. The pre-treatment with GEN sensitized HCC38 cells to the antiproliferative effects of 4-hydroxytamoxifen. We conclude that the dietary compound GEN may be effective for the prevention and reversal of AHR-dependent BRCA1 hypermethylation, and the restoration of ERα-mediated response, thus imparting the sensitivity of TNBC to antiestrogen therapy.

Transcriptional regulation of lysophosphatidic acid receptors 2 and 3 regulates myeloid commitment of hematopoietic stem cells

2021 ◽  
Author(s):  
Kuan-Hung Lin ◽  
Jui-Chung Chiang ◽  
Wei-Min Chen ◽  
Ya-Hsuan Ho ◽  
Chao-Ling Yao ◽  
...  
Keyword(s):  
Lysophosphatidic Acid ◽  
Stem Cell Differentiation ◽  
Receptor Subtypes ◽  
Physical Interaction ◽  
Hematopoietic Stem ◽  
Lpa Receptor ◽  
Gata Factors ◽  
Lpa Receptors ◽  
Myeloid Progenitors

Lysophosphatidic acid (LPA) is one of the lipids identified to be involved in stem cell differentiation. It exerts various functions through activation of G protein-coupled LPA receptors (LPARs). In previous studies, we have demonstrated that activation of LPA receptor 3 (LPA3) promotes erythropoiesis in human HSCs and zebrafish using molecular andpharmacological approaches. Our results show that treatment of LPA2 agonist suppressed erythropoiesis, whereas activation of LPA3 by 2S-OMPT promoted it, both in vitro and in vivo. Furthermore, we have demonstrated the inhibitory role of LPA3 during megakaryopoiesis. However, the mechanism underlying these observation remains elusive. In the present study, we suggest that the expression pattern of LPARs may be correlated with the transcriptional factors GATA-1 and GATA-2 at different stages of myeloid progenitors. We determined that manipulation of GATA factors affected the expression levels of LPA2 and LPA3. Using luciferase assays, we demonstrate that the promoter regions of LPAR2 and LPAR3 were regulated by these GATA factors. Mutation of GATA binding sites in these regions abrogated luciferase activity, suggesting that LPA2 and LPA3 are regulated by GATA factors. Moreover, physical interaction between GATA factors and the promoter region of LPA receptors was verified using chromatin immunoprecipitation (ChIP) studies. Taken together, our results suggest that balance between LPA2 and LPA3, which may be determined by GATA factors, is a regulatory switch for lineage commitment in myeloid progenitors. The expression-level balance of LPA receptor subtypes represents a novel mechanism regulating erythropoiesis and megakaryopoiesis.

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